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Schleh MW, Ahn C, Ryan BJ, Chugh OK, Luker AT, Luker KE, Gillen JB, Ludzki AC, Van Pelt DW, Pitchford LM, Zhang T, Rode T, Howton SM, Burant CF, Horowitz JF. Both moderate- and high-intensity exercise training increase intramyocellular lipid droplet abundance and modify myocellular distribution in adults with obesity. Am J Physiol Endocrinol Metab 2023; 325:E466-E479. [PMID: 37729021 PMCID: PMC10864005 DOI: 10.1152/ajpendo.00093.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 09/12/2023] [Accepted: 09/12/2023] [Indexed: 09/22/2023]
Abstract
Exercise training modifies lipid metabolism in skeletal muscle, but the effect of exercise training on intramyocellular lipid droplet (LD) abundance, size, and intracellular distribution in adults with obesity remains elusive. This study compared high-intensity interval training (HIIT) with more conventional moderate-intensity continuous training (MICT) on intramyocellular lipid content, as well as LD characteristics (size and number) and abundance within the intramyofibrillar (IMF) and subsarcolemmal (SS) regions of type I and type II skeletal muscle fibers in adults with obesity. Thirty-six adults with obesity [body mass index (BMI) = 33 ± 3 kg/m2] completed 12 wk (4 days/wk) of either HIIT (10 × 1 min, 90% HRmax + 1-min active recovery; n = 19) or MICT (45-min steady-state exercise, 70% HRmax; n = 17), while on a weight-maintaining diet throughout training. Skeletal muscle biopsies were collected from the vastus lateralis before and after training, and intramyocellular lipid content and intracellular LD distribution were measured by immunofluorescence microscopy. Both MICT and HIIT increased total intramyocellular lipid content by more than 50% (P < 0.01), which was attributed to a greater LD number per µm2 in the IMF region of both type I and type II muscle fibers (P < 0.01). Our findings also suggest that LD lipophagy (autophagy-mediated LD degradation) may be transiently upregulated the day after the last exercise training session (P < 0.02 for both MICT and HIIT). In summary, exercise programs for adults with obesity involving either MICT or HIIT increased skeletal muscle LD abundance via a greater number of LDs in the IMF region of the myocyte, thereby providing more lipid in close proximity to the site of energy production during exercise.NEW & NOTEWORTHY In this study, 12 wk of either moderate-intensity continuous training (MICT) or high-intensity interval training (HIIT) enhanced skeletal muscle lipid abundance by increasing lipid droplet number within the intramyofibrillar (IMF) region of muscle. Because the IMF associates with high energy production during muscle contraction, this adaptation may enhance lipid oxidation during exercise. Despite differences in training intensity and energy expenditure between MICT and HIIT, their effects on muscle lipid abundance and metabolism were remarkably similar.
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Affiliation(s)
- Michael W Schleh
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Cheehoon Ahn
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Olivia K Chugh
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Austin T Luker
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Kathryn E Luker
- Department of Radiology, Center for Molecular Imaging, University of Michigan, Ann Arbor, Michigan, United States
- Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan, United States
| | - Jenna B Gillen
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | - Alison C Ludzki
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Douglas W Van Pelt
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Lisa M Pitchford
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Tao Zhang
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Thomas Rode
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Suzette M Howton
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
| | - Charles F Burant
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, United States
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States
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Schleh MW, Ryan BJ, Ahn C, Ludzki AC, Varshney P, Gillen JB, Van Pelt DW, Pitchford LM, Howton SM, Rode T, Chenevert TL, Hummel SL, Burant CF, Horowitz JF. Metabolic dysfunction in obesity is related to impaired suppression of fatty acid release from adipose tissue by insulin. Obesity (Silver Spring) 2023; 31:1347-1361. [PMID: 36988872 PMCID: PMC10192005 DOI: 10.1002/oby.23734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 12/02/2022] [Accepted: 01/01/2023] [Indexed: 03/30/2023]
Abstract
OBJECTIVE The aims of this study were: 1) to assess relationships among insulin-mediated glucose uptake with standard clinical outcomes and deep-phenotyping measures (including fatty acid [FA] rate of appearance [FA Ra] into the systemic circulation); and 2) to examine the contribution of adipocyte size, fibrosis, and proteomic profile to FA Ra regulation. METHODS A total of 66 adults with obesity (BMI = 34 [SD 3] kg/m2 ) were assessed for insulin sensitivity (hyperinsulinemic-euglycemic clamp), and stable isotope dilution methods quantified glucose, FA, and glycerol kinetics in vivo. Abdominal subcutaneous adipose tissue (aSAT) and skeletal muscle biopsies were collected, and magnetic resonance imaging quantified liver and visceral fat content. RESULTS Insulin-mediated FA Ra suppression associated with insulin-mediated glucose uptake (r = 0.51; p < 0.01) and negatively correlated with liver (r = -0.36; p < 0.01) and visceral fat (r = -0.42; p < 0.01). aSAT proteomics from subcohorts of participants with low FA Ra suppression (n = 8) versus high FA Ra suppression (n = 8) demonstrated greater extracellular matrix collagen protein in low versus high FA Ra suppression. Skeletal muscle lipidomics (n = 18) revealed inverse correlations of FA Ra suppression with acyl-chain length of acylcarnitine (r = -0.42; p = 0.02) and triacylglycerol (r = -0.51; p < 0.01), in addition to insulin-mediated glucose uptake (acylcarnitine: r = -0.49; p < 0.01, triacylglycerol: r = -0.40; p < 0.01). CONCLUSIONS Insulin's ability to suppress FA release from aSAT in obesity is related to enhanced insulin-mediated glucose uptake and metabolic health in peripheral tissues.
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Affiliation(s)
- Michael W Schleh
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Cheehoon Ahn
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Alison C Ludzki
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Pallavi Varshney
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jenna B Gillen
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | - Douglas W Van Pelt
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Lisa M Pitchford
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Suzette M Howton
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Thomas Rode
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Thomas L Chenevert
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Scott L Hummel
- Division of Cardiology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
- Veterans Affairs Health System, Ann Arbor, Michigan, USA
| | - Charles F Burant
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
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Ludzki AC, Krueger EM, Gillen JB, Taylor NM, Middlebrook DO, Baldwin TC, Karabetsos KC, Schleh MW, Horowitz JF. One week of overeating upregulates angiogenic and lipolytic gene expression in human subcutaneous adipose tissue from exercise trained and untrained adults. Appl Physiol Nutr Metab 2022; 47:992-1004. [PMID: 35816737 PMCID: PMC10127504 DOI: 10.1139/apnm-2022-0078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Effective storage of excess energy in abdominal subcutaneous adipose tissue during periods of overeating may help attenuate weight-gain-related insulin resistance. The objective of this study was to assess changes in the expression of factors regulating abdominal subcutaneous adipose tissue storage capacity in response to a brief exposure to overeating in nonobese adults. Because exercise can alter the expression of genes involved in regulating adipose tissue storage capacity, we compared the responses to overeating in regular exercisers (EX, n = 11) and nonexercisers (nonEX, n = 11). Abdominal subcutaneous adipose tissue samples and oral glucose tolerance tests were performed before and after participants ate 30% above their estimated daily energy requirements for 1 week. Both EX and nonEX gained ∼1 kg (P < 0.01), and Matsuda insulin sensitivity index was reduced ∼15% (P = 0.04) in both groups. Gene expression of factors involved in lipid metabolism (HSL, ATGL, DGAT, and PPARγ) and angiogenesis (HIF1α and KDR) were increased (P < 0.05), with no differences observed between EX and nonEX. In contrast, protein abundance of these factors did not change. The modest overeating stimulus did not increase markers of inflammation in the systemic circulation or adipose tissue. Overall, our findings indicate that a brief and modest overeating stimulus can impair insulin sensitivity and upregulate genes involved in abdominal adipose tissue storage capacity similarly in exercisers and nonexercisers. ClinicalTrials.gov ID#: NCT02701738.
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Affiliation(s)
- Alison C Ludzki
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Emily M Krueger
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Jenna B Gillen
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON, Canada
| | - Natalie M Taylor
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | | | - Toree C Baldwin
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | | | - Michael W Schleh
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
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Ahn C, Ryan BJ, Schleh MW, Varshney P, Ludzki AC, Gillen JB, Van Pelt DW, Pitchford LM, Howton SM, Rode T, Hummel SL, Burant CF, Little JP, Horowitz JF. Exercise training remodels subcutaneous adipose tissue in adults with obesity even without weight loss. J Physiol 2022; 600:2127-2146. [PMID: 35249225 PMCID: PMC9058215 DOI: 10.1113/jp282371] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 03/01/2022] [Indexed: 11/08/2022] Open
Abstract
Excessive adipose tissue mass underlies much of the metabolic health complications in obesity. Although exercise training is known to improve metabolic health in individuals with obesity, the effects of exercise training without weight loss on adipose tissue structure and metabolic function remain unclear. Thirty-six adults with obesity (body mass index = 33 ± 3 kg · m-2 ) were assigned to 12 weeks (4 days week-1 ) of either moderate-intensity continuous training (MICT; 70% maximal heart rate, 45 min; n = 17) or high-intensity interval training (HIIT; 90% maximal heart rate, 10 × 1 min; n = 19), maintaining their body weight throughout. Abdominal subcutaneous adipose tissue (aSAT) biopsy samples were collected once before and twice after training (1 day after last exercise and again 4 days later). Exercise training modified aSAT morphology (i.e. reduced fat cell size, increased collagen type 5a3, both P ≤ 0.05, increased capillary density, P = 0.05) and altered protein abundance of factors that regulate aSAT remodelling (i.e. reduced matrix metallopeptidase 9; P = 0.02; increased angiopoietin-2; P < 0.01). Exercise training also increased protein abundance of factors that regulate lipid metabolism (e.g. hormone sensitive lipase and fatty acid translocase; P ≤ 0.03) and key proteins involved in the mitogen-activated protein kinase pathway when measured the day after the last exercise session. However, most of these exercise-mediated changes were no longer significant 4 days after exercise. Importantly, MICT and HIIT induced remarkably similar adaptations in aSAT. Collectively, even in the absence of weight loss, 12 weeks of exercise training induced changes in aSAT structure, as well as factors that regulate metabolism and the inflammatory signal pathway in adults with obesity. KEY POINTS: Exercise training is well-known to improve metabolic health in obesity, although how exercise modifies the structure and metabolic function of adipose tissue, in the absence of weight loss, remains unclear. We report that both 12 weeks of moderate-intensity continuous training (MICT) and 12 weeks of high-intensity interval training (HIIT) induced modifications in adipose tissue structure and factors that regulate adipose tissue remodelling, metabolism and the inflammatory signal pathway in adults with obesity, even without weight loss (with no meaningful differences between MICT and HIIT). The modest modifications in adipose tissue structure in response to 12 weeks of MICT or HIIT did not lead to changes in the rate of fatty acid release from adipose tissue. These results expand our understanding about the effects of two commonly used exercise training prescriptions (MICT and HIIT) on adipose tissue remodelling that may lead to advanced strategies for improving metabolic health outcomes in adults with obesity.
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Affiliation(s)
- Cheehoon Ahn
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Benjamin J. Ryan
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Michael W. Schleh
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Pallavi Varshney
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Alison C. Ludzki
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Jenna B. Gillen
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
- Faculty of Kinesiology and Physical Education University of Toronto Toronto Ontario M5S 2C9 Canada
| | - Douglas W. Van Pelt
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Lisa M. Pitchford
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Suzette M. Howton
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Thomas Rode
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
| | - Scott L. Hummel
- Division of Cardiology Department of Internal Medicine University of Michigan Ann Arbor Michigan 48109
- Ann Arbor Veterans Affairs Health System Ann Arbor Michigan 48109
| | - Charles F. Burant
- Division of Metabolism, Endocrinology, and Diabetes Department of Internal Medicine University of Michigan Ann Arbor MI 48109
| | - Jonathan P. Little
- School of Health and Exercise Sciences University of British Columbia Okanagan Campus Kelowna British Columbia V1V 1V7 Canada
| | - Jeffrey F. Horowitz
- Substrate Metabolism Laboratory School of Kinesiology University of Michigan Ann Arbor Michigan 48109
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5
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Wang Q, Qiu X, Liu T, Ahn C, Horowitz JF, Lin JD. The hepatokine TSK maintains myofiber integrity and exercise endurance and contributes to muscle regeneration. JCI Insight 2022; 7:154746. [PMID: 35025761 PMCID: PMC8876464 DOI: 10.1172/jci.insight.154746] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 01/12/2022] [Indexed: 11/17/2022] Open
Abstract
Mammalian skeletal muscle contains heterogenous myofibers with different contractile and metabolic properties that sustain muscle mass and endurance capacity. The transcriptional regulators that govern these myofiber gene programs have been elucidated. However, the hormonal cues that direct the specification of myofiber types and muscle endurance remain largely unknown. Here we uncover the secreted factor Tsukushi (TSK) as an extracellular signal that is required for maintaining muscle mass, strength, and endurance capacity, and contributes to muscle regeneration. Mice lacking TSK exhibited reduced grip strength and impaired exercise capacity. Muscle transcriptomic analysis revealed that TSK deficiency results in a remarkably selective impairment in the expression of myofibrillar genes characteristic of slow-twitch muscle fibers that is associated with abnormal neuromuscular junction formation. AAV-mediated overexpression of TSK failed to rescue these myofiber defects in adult mice, suggesting that the effects of TSK on myofibers are likely restricted to certain developmental stages. Finally, mice lacking TSK exhibited diminished muscle regeneration following cardiotoxin-induced muscle injury. These findings support a crucial role of TSK as a hormonal cue in the regulation of contractile gene expression, endurance capacity, and muscle regeneration.
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Affiliation(s)
- Qiuyu Wang
- Department of Cell & Developmental Biology, University of Michigan, Ann Arbor, United States of America
| | - Xiaoxue Qiu
- Department of Cell & Developmental Biology, University of Michigan, Ann Arbor, United States of America
| | - Tongyu Liu
- Department of Cell & Developmental Biology, University of Michigan, Ann Arbor, United States of America
| | - Cheehoon Ahn
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, United States of America
| | | | - Jiandie D Lin
- University of Michigan, Ann Arbor, United States of America
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6
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Ludzki AC, Schleh MW, Krueger EM, Taylor NM, Ryan BJ, Baldwin TC, Gillen JB, Ahn C, Varshney P, Horowitz JF. Inflammation and metabolism gene sets in subcutaneous abdominal adipose tissue are altered 1 hour after exercise in adults with obesity. J Appl Physiol (1985) 2021; 131:1380-1389. [PMID: 34410849 DOI: 10.1152/japplphysiol.00943.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the health benefits of exercise in adults with obesity are well described, the direct effects of exercise on adipose tissue that may lead to improved metabolic health are poorly understood. The primary aims of this study were to perform an unbiased analysis of the subcutaneous abdominal adipose tissue transcriptomic response to acute exercise in adults with obesity, and to compare the effects of moderate-intensity continuous exercise versus high-intensity interval exercise on this response. Twenty-nine adults with obesity performed a session of either high-intensity interval exercise (HI; 10 × 1 min at 90%HRpeak, 1 min recovery between intervals; n = 14) or moderate-intensity continuous exercise (MI; 45 min at 70%HRpeak; n = 15). Groups were well matched for BMI (HI 33 ± 3 vs. MI 33 ± 4 kg/m2), sex (HI: 9 women vs. MI: 10 women), and age (HI: 32 ± 6 vs. MI: 29 ± 5). Subcutaneous adipose tissue was collected before and 1 h after the session of HI or MI, and samples were processed for RNA sequencing. Gene set enrichment analysis revealed 7 of 21 gene sets enriched postexercise overlapped between HI and MI. Interestingly, both HI and MI upregulated gene sets involved in inflammation (IL6-JAK-STAT3 signaling, allograft rejection, TNFα signaling via NFκB, and inflammatory response; FDR q value < 0.25). Exercise also downregulated adipogenic and oxidative metabolism gene sets in both groups. Overall, these data suggest genes involved in subcutaneous adipose tissue metabolism and inflammation may be an important part of the initial response after a session of exercise.NEW & NOTEWORTHY This study compared the effects of a single session of high-intensity interval exercise versus moderate-intensity continuous exercise on transcriptional changes in subcutaneous abdominal adipose tissue collected from adults with obesity. Our novel findings indicate exercise upregulated inflammation-related gene sets, while it downregulated metabolism-related gene sets - after both high-intensity and moderate-intensity exercise. These data suggest exercise can alter the adipose tissue transcriptome 1 h after exercise in ways that may impact inflammation and metabolism.
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Affiliation(s)
- A C Ludzki
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - M W Schleh
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - E M Krueger
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - N M Taylor
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - B J Ryan
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - T C Baldwin
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - J B Gillen
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan.,Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | - C Ahn
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - P Varshney
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - J F Horowitz
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan
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Akinci EY, Boutros S, Ryan BJ, Sargin P, Akinci B, Neidert AH, Hench R, Horowitz JF, Oral EA. Iron parameters in patients with partial lipodystrophy and impact of exogenous leptin therapy. BMJ Open Diabetes Res Care 2021; 9:9/1/e002385. [PMID: 34373262 PMCID: PMC8354259 DOI: 10.1136/bmjdrc-2021-002385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 06/19/2021] [Indexed: 11/26/2022] Open
Affiliation(s)
- Efe Y Akinci
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan, USA
| | - Sabine Boutros
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan, USA
| | - Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Pinar Sargin
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan, USA
| | - Baris Akinci
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan, USA
| | - Adam H Neidert
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan, USA
| | - Rita Hench
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan, USA
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Elif A Oral
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan, USA
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8
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Ryan BJ, Foug KL, Gioscia-Ryan RA, Varshney P, Ludzki AC, Ahn C, Schleh MW, Gillen JB, Chenevert TL, Horowitz JF. Exercise training decreases whole-body and tissue iron storage in adults with obesity. Exp Physiol 2021; 106:820-827. [PMID: 33559926 DOI: 10.1113/ep089272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 01/29/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Does exercise training modify tissue iron storage in adults with obesity? What is the main finding and its importance? Twelve weeks of moderate-intensity exercise or high-intensity interval training lowered whole-body iron stores, decreased the abundance of the key iron storage protein in skeletal muscle (ferritin) and tended to lower hepatic iron content. These findings show that exercise training can reduce tissue iron storage in adults with obesity and might have important implications for obese individuals with dysregulated iron homeostasis. ABSTRACT The regulation of iron storage is crucial to human health, because both excess and deficient iron storage have adverse consequences. Recent studies suggest altered iron storage in adults with obesity, with increased iron accumulation in their liver and skeletal muscle. Exercise training increases iron use for processes such as red blood cell production and can lower whole-body iron stores in humans. However, the effects of exercise training on liver and muscle iron stores in adults with obesity have not been assessed. The aim of this study was to determine the effects of 12 weeks of exercise training on whole-body iron stores, liver iron content and the abundance of ferritin (the key iron storage protein) in skeletal muscle in adults with obesity. Twenty-two inactive adults (11 women and 11 men; age, 31 ± 6 years; body mass index, 33 ± 3 kg/m2 ) completed 12 weeks (four sessions/week) of either moderate-intensity continuous training (MICT; 45 min at 70% of maximal heart rate; n = 11) or high-intensity interval training (HIIT; 10 × 1 min at 90% of maximal heart rate, interspersed with 1 min active recovery; n = 11). Whole-body iron stores were lower after training, as indicated by decreased plasma concentrations of ferritin (P = 3 × 10-5 ) and hepcidin (P = 0.02), without any change in C-reactive protein. Hepatic R2*, an index of liver iron content, was 6% lower after training (P = 0.06). Training reduced the skeletal muscle abundance of ferritin by 10% (P = 0.03), suggesting lower muscle iron storage. Interestingly, these adaptations were similar in MICT and HIIT groups. Our findings indicate that exercise training decreased iron storage in adults with obesity, which might have important implications for obese individuals with dysregulated iron homeostasis.
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Affiliation(s)
- Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Katherine L Foug
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Rachel A Gioscia-Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Pallavi Varshney
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Alison C Ludzki
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Cheehoon Ahn
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Michael W Schleh
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jenna B Gillen
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA.,Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | - Thomas L Chenevert
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
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Schleh MW, Pitchford LM, Gillen JB, Horowitz JF. Energy Deficit Required for Exercise-induced Improvements in Glycemia the Next Day. Med Sci Sports Exerc 2020; 52:976-982. [PMID: 31809409 DOI: 10.1249/mss.0000000000002211] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
PURPOSE This study determined the impact of an exercise-induced energy deficit on postprandial and 24 h glycemic control the day after a session of exercise. METHODS Fifteen healthy participants (m/f = 5/10, 27 ± 6 yr, body mass index = 24 ± 3 kg·m, peak oxygen consumption [V˙O2peak] = 36 ± 9 mL·kg·min) completed two separate 5-d experimental trials performed under "free-living" conditions. On day 1 of each trial, participants were fitted with a continuous glucose monitor and abstained from exercise. Day 2 served as a nonexercise control (NoEx). On day 3, participants exercised at 3:00 PM (65% V˙O2peak) until they expended 350 kcals (~45 min). The diet during both experimental trials was identical with the exception of meals after this exercise session. During one trial, the dinner after exercise did not replenish the 350 kcal expended during exercise, thereby establishing an exercise energy deficit (ExDEF). During the other experimental trial, the dinner after exercise contained an additional 350 kcal to compensate for the energy expended during exercise, and thereby maintained energy balance after exercise (ExBAL). Free-living glycemia was measured the day before exercise (NoEx) and the day after exercise under ExDEF and ExBAL conditions. RESULTS The day after exercise, 3 h postprandial area under the curve was lower after breakfast in ExDEF compared with ExBAL (16.0 ± 1.8 vs 17.0 ± 1.6 mmol·L·h per 3 h, P = 0.01), but did not differ between groups after lunch (P = 0.24), dinner (P = 0.39), or evening snack (P = 0.45). Despite differences in the glycemic response to breakfast, 24 h glycemia did not differ between ExDEF and ExBAL (area under the curve = 128 ± 10 vs 131 ± 10 mmol·L·h per 24 h, respectively; P = 0.54). CONCLUSIONS An exercise-induced energy deficit lowered the glycemic response to breakfast the next day-but this energy deficit did not impact total 24 h glycemia, the day after exercise in metabolically healthy adults.
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Affiliation(s)
- Michael W Schleh
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI
| | - Lisa M Pitchford
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI
| | | | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI
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10
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Ryan BJ, Foug KL, Gioscia-Ryan RA, Ludzki AC, Ahn C, Schleh MW, Gillen JB, Chenevert TL, Horowitz JF. Skeletal muscle ferritin abundance is tightly related to plasma ferritin concentration in adults with obesity. Exp Physiol 2020; 105:1808-1814. [PMID: 32888323 DOI: 10.1113/ep089010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 09/02/2020] [Indexed: 01/01/2023]
Abstract
NEW FINDINGS What is the central question of this study? Obesity is associated with complex perturbations to iron homeostasis: is plasma ferritin concentration (a biomarker of whole-body iron stores) related to the abundance of ferritin (the key tissue iron storage protein) in skeletal muscle in adults with obesity? What is the main finding and its importance? Plasma ferritin concentration was tightly correlated with the abundance of ferritin in skeletal muscle, and this relationship persisted when accounting for sex, age, body mass index and plasma C-reactive protein concentration. Our findings suggest that skeletal muscle may be an important iron store. ABSTRACT Obesity is associated with complex perturbations to whole-body and tissue iron homeostasis. Recent evidence suggests a potentially important influence of iron storage in skeletal muscle on whole-body iron homeostasis, but this association is not clearly resolved. The primary aim of this study was to assess the relationship between whole-body and skeletal muscle iron stores by measuring the abundance of the key iron storage (ferritin) and import (transferrin receptor) proteins in skeletal muscle, as well as markers of whole-body iron homeostasis in men (n = 19) and women (n = 43) with obesity. Plasma ferritin concentration (a marker of whole-body iron stores) was highly correlated with muscle ferritin abundance (r = 0.77, P = 2 × 10-13 ) and negatively associated with muscle transferrin receptor abundance (r = -0.76, P = 1 × 10-12 ). These relationships persisted when accounting for sex, age, BMI and plasma C-reactive protein concentration. In parallel with higher whole-body iron stores in our male versus female participants, men had 2.2-fold higher muscle ferritin abundance (P = 1 × 10-4 ) compared with women. In accordance with lower muscle iron storage, women had 2.7-fold higher transferrin receptor abundance (P = 7 × 10-10 ) compared with men. We conclude that muscle iron storage and import proteins are tightly and independently related to plasma ferritin concentration in adults with obesity, suggesting that skeletal muscle may be an underappreciated iron store.
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Affiliation(s)
- Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Katherine L Foug
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Rachel A Gioscia-Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Alison C Ludzki
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Cheehoon Ahn
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Michael W Schleh
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Jenna B Gillen
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA.,Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | | | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
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11
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Ryan BJ, Schleh MW, Ahn C, Ludzki AC, Gillen JB, Varshney P, Van Pelt DW, Pitchford LM, Chenevert TL, Gioscia-Ryan RA, Howton SM, Rode T, Hummel SL, Burant CF, Little JP, Horowitz JF. Moderate-Intensity Exercise and High-Intensity Interval Training Affect Insulin Sensitivity Similarly in Obese Adults. J Clin Endocrinol Metab 2020; 105:5850995. [PMID: 32492705 PMCID: PMC7347288 DOI: 10.1210/clinem/dgaa345] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Accepted: 05/28/2020] [Indexed: 01/25/2023]
Abstract
OBJECTIVE We compared the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on insulin sensitivity and other important metabolic adaptations in adults with obesity. METHODS Thirty-one inactive adults with obesity (age: 31 ± 6 years; body mass index: 33 ± 3 kg/m2) completed 12 weeks (4 sessions/week) of either HIIT (10 × 1-minute at 90%HRmax, 1-minute active recovery; n = 16) or MICT (45 minutes at 70%HRmax; n = 15). To assess the direct effects of exercise independent of weight/fat loss, participants were required to maintain body mass. RESULTS Training increased peak oxygen uptake by ~10% in both HIIT and MICT (P < 0.0001), and body weight/fat mass were unchanged. Peripheral insulin sensitivity (hyperinsulinemic-euglycemic clamp) was ~20% greater the day after the final exercise session compared to pretraining (P < 0.01), with no difference between HIIT and MICT. When trained participants abstained from exercise for 4 days, insulin sensitivity returned to pretraining levels in both groups. HIIT and MICT also induced similar increases in abundance of many skeletal muscle proteins involved in mitochondrial respiration and lipid and carbohydrate metabolism. Training-induced alterations in muscle lipid profile were also similar between groups. CONCLUSION Despite large differences in training intensity and exercise time, 12 weeks of HIIT and MICT induce similar acute improvements in peripheral insulin sensitivity the day after exercise, and similar longer term metabolic adaptations in skeletal muscle in adults with obesity. These findings support the notion that the insulin-sensitizing effects of both HIIT and MICT are mediated by factors stemming from the most recent exercise session(s) rather than adaptations that accrue with training.
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Affiliation(s)
- Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Michael W Schleh
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Cheehoon Ahn
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Alison C Ludzki
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Jenna B Gillen
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
| | - Pallavi Varshney
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Douglas W Van Pelt
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Lisa M Pitchford
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | | | - Rachel A Gioscia-Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Suzette M Howton
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Thomas Rode
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Scott L Hummel
- Division of Cardiology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
- Ann Arbor Veterans Affairs Health System, Ann Arbor, Michigan
| | - Charles F Burant
- Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI
| | - Jonathan P Little
- School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
- Correspondence and Reprint Requests: Jeffrey F. Horowitz, PhD, School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI, USA 48109-2214.
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12
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Ludzki AC, Krueger EM, Baldwin TC, Schleh MW, Porsche CE, Ryan BJ, Muir LA, Singer K, Lumeng CN, Horowitz JF. Acute Aerobic Exercise Remodels the Adipose Tissue Progenitor Cell Phenotype in Obese Adults. Front Physiol 2020; 11:903. [PMID: 32848853 PMCID: PMC7399179 DOI: 10.3389/fphys.2020.00903] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 07/06/2020] [Indexed: 12/19/2022] Open
Abstract
Adipose tissue pathology in obese patients often features impaired adipogenesis, angiogenesis, and chronic low-grade inflammation, all of which are regulated in large part by adipose tissue stromal vascular cells [SVC; i.e., non-adipocyte cells within adipose tissue including preadipocytes, endothelial cells (ECs), and immune cells]. Exercise is known to increase subcutaneous adipose tissue lipolysis, but the impact of exercise on SVCs in adipose tissue has not been explored. The purpose of this study was to assess the effects of a session of exercise on preadipocyte, EC, macrophage, and T cell content in human subcutaneous adipose tissue. We collected abdominal subcutaneous adipose tissue samples from 10 obese adults (BMI 33 ± 3 kg/m2, body fat 41 ± 7%) 12 h after a 60 min acute session of endurance exercise (80 ± 3%HRpeak) vs. no acute exercise session. SVCs were isolated by collagenase digestion and stained for flow cytometry. We found that acute exercise reduced preadipocyte content (38 ± 7 vs. 30 ± 13%SVC; p = 0.04). The reduction was driven by a decrease in CD34hi preadipocytes (18 ± 5 vs. 13 ± 6%SVC; p = 0.002), a subset of preadipocytes that generates high lipolytic rate adipocytes ex vivo. Acute exercise did not alter EC content. Acute exercise also did not change total immune cell, macrophage, or T cell content, and future work should assess the effects of exercise on subpopulations of these cells. We conclude that exercise may rapidly regulate the subcutaneous adipose tissue preadipocyte pool in ways that may help attenuate the high lipolytic rates that are commonly found in obesity.
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Affiliation(s)
- Alison C Ludzki
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, United States
| | - Emily M Krueger
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, United States
| | - Toree C Baldwin
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, United States
| | - Michael W Schleh
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, United States
| | - Cara E Porsche
- Department of Pediatrics, Medical School, University of Michigan, Ann Arbor, MI, United States.,Graduate Program in Immunology, Medical School, University of Michigan, Ann Arbor, MI, United States
| | - Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, United States
| | - Lindsey A Muir
- Department of Computational Medicine and Bioinformatics, Medical School, University of Michigan, Ann Arbor, MI, United States
| | - Kanakadurga Singer
- Department of Pediatrics, Medical School, University of Michigan, Ann Arbor, MI, United States.,Graduate Program in Immunology, Medical School, University of Michigan, Ann Arbor, MI, United States.,Department of Molecular and Integrative Physiology, Medical School, University of Michigan, Ann Arbor, MI, United States
| | - Carey N Lumeng
- Department of Pediatrics, Medical School, University of Michigan, Ann Arbor, MI, United States.,Graduate Program in Immunology, Medical School, University of Michigan, Ann Arbor, MI, United States.,Department of Molecular and Integrative Physiology, Medical School, University of Michigan, Ann Arbor, MI, United States
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, United States
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13
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Rothberg AE, Herman WH, Wu C, IglayReger HB, Horowitz JF, Burant CF, Galecki AT, Halter JB. Weight Loss Improves β-Cell Function in People With Severe Obesity and Impaired Fasting Glucose: A Window of Opportunity. J Clin Endocrinol Metab 2020; 105:5624076. [PMID: 31720686 PMCID: PMC7059991 DOI: 10.1210/clinem/dgz189] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 11/11/2019] [Indexed: 11/19/2022]
Abstract
BACKGROUND In people with obesity, β-cell function may adapt to insulin resistance. We describe β-cell function in people with severe obesity and normal fasting glucose (NFG), impaired fasting glucose (IFG), and type 2 diabetes (T2DM), as assessed before, 3 to 6 months after, and 2 years after medical weight loss to describe its effects on insulin sensitivity, insulin secretion, and β-cell function. METHODS Fifty-eight participants with body mass index (BMI) ≥ 35 kg/m2 (14 with NFG, 24 with IFG, and 20 with T2DM) and 13 normal weight participants with NFG underwent mixed meal tolerance tests to estimate insulin sensitivity (S[I]), insulin secretion (Φ), and β-cell function assessed as model-based Φ adjusted for S(I). All 58 obese participants were restudied at 3 to 6 months and 27 were restudied at 2 years. RESULTS At 3 to 6 months, after a 20-kg weight loss and a decrease in BMI of 6 kg/m2, S(I) improved in all obese participants, Φ decreased in obese participants with NFG and IFG and tended to decrease in obese participants with T2DM, and β-cell function improved in obese participants with NFG and tended to improve in obese participants with IFG. At 2 years, β-cell function deteriorated in participants with NFG and T2DM but remained significantly better in participants with IFG compared to baseline. CONCLUSIONS Short-term weight loss improves β-cell function in participants with NFG and IFG, but β-cell function tends to deteriorate over 2 years. In participants with IFG, weight loss improves longer-term β-cell function relative to baseline and likely relative to no intervention, suggesting that obese people with IFG are a subpopulation whose β-cell function is most likely to benefit from weight loss.
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Affiliation(s)
- Amy E Rothberg
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
- Department of Nutritional Sciences, University of Michigan, Ann Arbor, Michigan
- Correspondence: Amy E. Rothberg, MD, PhD, University of Michigan, Department of Internal Medicine, Domino’s Farms - Lobby G, 24 Frank Lloyd Wright Drive, Ann Arbor, MI 48106.
| | - William H Herman
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
- Department of Epidemiology, University of Michigan, Ann Arbor, Michigan
| | - Chunyi Wu
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
| | - Heidi B IglayReger
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
| | | | - Charles F Burant
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
- Department of Nutritional Sciences, University of Michigan, Ann Arbor, Michigan
| | - Andrzej T Galecki
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
- Department of Biostatistics, University of Michigan, Ann Arbor, Michigan
| | - Jeffrey B Halter
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
- Institute of Gerontology, University of Michigan, Ann Arbor, Michigan
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14
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Ryan BJ, Van Pelt DW, Guth LM, Ludzki AC, Gioscia-Ryan RA, Ahn C, Foug KL, Horowitz JF. Plasma ferritin concentration is positively associated with in vivo fatty acid mobilization and insulin resistance in obese women. Exp Physiol 2018; 103:1443-1447. [PMID: 30178895 DOI: 10.1113/ep087283] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 08/31/2018] [Indexed: 01/27/2023]
Abstract
NEW FINDINGS What is the central question of this study? Do obese women with relatively high whole-body iron stores exhibit elevated in vivo rates of fatty acid (FA) release from adipose tissue compared with a well-matched cohort of obese women with relatively low iron stores? What is the main finding and its importance? Obese women with high plasma [ferritin] (a marker of whole-body iron stores) had greater FA mobilization, lipolytic activation in adipose tissue and insulin resistance (IR) compared with obese women with lower plasma [ferritin]. Given that elevated FA mobilization is intimately linked with the development of IR, these findings suggest that elevated iron stores might contribute to IR in obesity by increasing systemic FA availability. ABSTRACT High rates of fatty acid (FA) mobilization from adipose tissue are associated with insulin resistance (IR) in obesity. In vitro evidence suggests that iron stimulates lipolysis in adipocytes, but whether iron is related to in vivo FA mobilization is unknown. We hypothesized that plasma ferritin concentration ([ferritin]), a marker of body iron stores, would be positively associated with FA mobilization. We measured [ferritin], the rate of appearance of FA in the systemic circulation (FA Ra; stable isotope dilution), key adipose tissue lipolytic proteins and IR (hyperinsulinaemic-euglycaemic clamp) in 20 obese, premenopausal women. [Ferritin] was correlated with FA Ra (r = 0.65; P = 0.002) and IR (r = 0.57; P = 0.008); these relationships remained significant after controlling for body mass index and plasma [C-reactive protein] (a marker of systemic inflammation) in multiple regression analyses. We then stratified subjects into tertiles based on [ferritin] to compare subjects with 'High-ferritin' versus 'Low-ferritin'. Plasma [hepcidin] was more than fivefold greater (P < 0.05) in the High-ferritin versus Low-ferritin group, but there was no difference in plasma [C-reactive protein] between groups, indicating that the large difference in plasma [ferritin] reflects a difference in iron stores, not systemic inflammation. We found that FA Ra, adipose protein abundance of hormone-sensitive lipase and adipose triglyceride lipase, and IR were significantly greater in subjects with High-ferritin versus Low-ferritin (all P < 0.05). These data provide the first evidence linking iron and in vivo FA mobilization and suggest that elevated iron stores might contribute to IR in obesity by increasing systemic FA availability.
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Affiliation(s)
- Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Douglas W Van Pelt
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Lisa M Guth
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Alison C Ludzki
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Rachel A Gioscia-Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Chiwoon Ahn
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Katherine L Foug
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
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15
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Meral R, Ryan BJ, Malandrino N, Jalal A, Neidert AH, Muniyappa R, Akıncı B, Horowitz JF, Brown RJ, Oral EA. "Fat Shadows" From DXA for the Qualitative Assessment of Lipodystrophy: When a Picture Is Worth a Thousand Numbers. Diabetes Care 2018; 41:2255-2258. [PMID: 30237235 PMCID: PMC6150431 DOI: 10.2337/dc18-0978] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 07/09/2018] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Lipodystrophy syndromes are a heterogeneous group of disorders associated with selective absence of fat. Currently, the diagnosis is established only clinically. RESEARCH DESIGN AND METHODS We developed a new method from DXA scans called a "fat shadow," which is a color-coded representation highlighting only the fat tissue. We conducted a blinded retrospective validation study to assess its usefulness for the diagnosis of lipodystrophy syndromes. RESULTS We evaluated the fat shadows from 16 patients (11 female and 5 male) with generalized lipodystrophy (GL), 57 (50 female and 7 male) with familial partial lipodystrophy (FPLD), 2 (1 female and 1 male) with acquired partial lipodystrophy, and 126 (90 female and 36 male) control subjects. FPLD was differentiated from control subjects with 85% sensitivity and 96% specificity (95% CIs 72-93 and 91-99, respectively). GL was differentiated from nonobese control subjects with 100% sensitivity and specificity (95% CIs 79-100 and 92-100, respectively). CONCLUSIONS Fat shadows provided sufficient qualitative information to infer clinical phenotype and differentiate these patients from appropriate control subjects. We propose that this method could be used to support the diagnosis.
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Affiliation(s)
- Rasimcan Meral
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
| | - Benjamin J Ryan
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI
| | - Noemi Malandrino
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Abdelwahab Jalal
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
| | - Adam H Neidert
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
| | - Ranganath Muniyappa
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD.,Inter-Institute Endocrinology Training Program, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Barış Akıncı
- Division of Endocrinology, Dokuz Eylül University, Izmir, Turkey
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI
| | - Rebecca J Brown
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Elif A Oral
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
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Horowitz JF, Ortega JF, Hinko A, Li M, Nelson RK, Mora-Rodriguez R. Changes in markers for cardio-metabolic disease risk after only 1-2 weeks of a high saturated fat diet in overweight adults. PLoS One 2018; 13:e0198372. [PMID: 29949578 PMCID: PMC6021040 DOI: 10.1371/journal.pone.0198372] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 05/17/2018] [Indexed: 12/30/2022] Open
Abstract
Purpose Diets high in saturated fat acids (SFA) have been linked with cardio-metabolic disease risk. The purpose of this study was to determine whether only 1–2 weeks of a high SFA diet could impact disease risk factors in overweight adults who normally eat a relatively low proportion of SFA (i.e., <40% of dietary fat). Methods Twelve overweight (BMI: 27±1 kg/m2) young adults were studied before and after a 2-week diet that increased the proportion of SFA (<40% to 60% of dietary fat), while maintaining their daily intake of total fat, carbohydrate, protein, and calories. Insulin resistance, blood pressure, plasma markers of liver damage, total plasma cholesterol concentrations, and fatty acid profile within plasma and skeletal muscle lipid pools were assessed before and after the intervention. Results Total plasma cholesterol concentration increased (148±5 vs. 164±8 mg/dl; P<0.05) after only one week, due exclusively to an increase in LDL-cholesterol (78±4 vs. 95±7 mg/dl; P<0.05). After two weeks, plasma aspartate amino transferase (AST) concentration increased (P<0.05) but we found no change in insulin resistance, or resting blood pressure. The diet increase the proportion of SFA in plasma (35±1% vs. 39±2%; P<0.05) and the intramyocellular triglyceride pool (32±1% vs. 37±1%; P<0.05) suggesting the fatty acids in these pools may readily exchange. Conclusions Although blood lipids remain within normal clinical range, increasing saturated fat in diet for only 2 weeks raises plasma markers of cardiovascular risk (LDL-cholesterol) and liver damage (AST). In overweight, but healthy-young adults SFA accumulate in plasma and muscle after only 1–2 weeks of dietary increase.
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Affiliation(s)
- Jeffrey F. Horowitz
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
| | - Juan F. Ortega
- Exercise Physiology Lab, University of Castilla-La Mancha, Toledo, Spain
| | - Alexander Hinko
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Minghua Li
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Rachael K. Nelson
- College Health Professions, Health Sciences Department, Central Michigan University, Mt. Pleasant, Michigan, United States of America
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17
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Schleh M, Guth L, Jing H, Horowitz JF. Exercise-induced Energy Deficit Lowers Glycemia At Breakfast The Next Day, But Not Over 24-hours. Med Sci Sports Exerc 2018. [DOI: 10.1249/01.mss.0000537152.73919.80] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Ludzki AC, Pataky MW, Cartee GD, Horowitz JF. Acute endurance exercise increases Vegfa mRNA expression in adipose tissue of rats during the early stages of weight gain. Appl Physiol Nutr Metab 2018; 43:751-754. [PMID: 29486133 DOI: 10.1139/apnm-2017-0434] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The aim of this study was to determine the effects of acute exercise on key factors regulating angiogenesis in adipose tissue. Adipose tissue Vegf-a messenger RNA expression was upregulated immediately after acute exercise (p < 0.05) in rats consuming a high-fat diet, but was lower after exercise (p < 0.05) in rats consuming a low-fat diet. Our working hypothesis is that acute exercise augments angiogenic signaling under conditions when adipose tissue is expanding, and with repeated exercise sessions these signals can accrue to enhance vascularization.
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Affiliation(s)
- Alison C Ludzki
- School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109, USA.,School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109, USA
| | - Mark W Pataky
- School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109, USA.,School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109, USA
| | - Gregory D Cartee
- School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109, USA.,School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109, USA
| | - Jeffrey F Horowitz
- School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109, USA.,School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109, USA
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19
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Liu D, Morales FE, IglayReger HB, Treutelaar MK, Rothberg AE, Hubal MJ, Nadler EP, Robidoux J, Barakat H, Horowitz JF, Hoffman EP, Burant CF, Gordon PM. Expression of macrophage genes within skeletal muscle correlates inversely with adiposity and insulin resistance in humans. Appl Physiol Nutr Metab 2017; 43:187-193. [PMID: 29035695 DOI: 10.1139/apnm-2017-0228] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Local inflammation in obese adipose tissue has been shown to contribute to insulin resistance; however, the role of macrophage infiltration within skeletal muscle is still debatable. This study aimed to evaluate the association of skeletal muscle macrophage gene expression with adiposity levels and insulin sensitivity in obese patients. Twenty-two nondiabetic obese patients and 23 healthy lean controls were included. Obese patients underwent a 3-month weight loss intervention. Macrophage gene expression in skeletal muscle (quantitative real-time polymerase chain reaction), body composition (dual-energy X-ray absorptiometry), and insulin sensitivity (homeostatic model assessment (HOMA) and oral glucose tolerance test) were compared between groups and their associations were analyzed. To validate skeletal muscle findings, we repeated the analyses with macrophage gene expression in adipose tissue. Expression levels of macrophage genes (CD68, CD11b, CD206, CD16, CD40, and CD163) were lower in skeletal muscle tissue of obese versus lean participants. Macrophage gene expression was also found to be inversely associated with adiposity, fasting insulin, and HOMA (r = -0.4 ∼ -0.6, p < 0.05), as well as positively associated with insulin sensitivity (r = 0.4 ∼ 0.8, p < 0.05). On the other hand, adipose tissue macrophage gene expression showed higher levels in obese versus lean participants, presenting a positive association with adiposity levels. Macrophage gene expression, in both skeletal and adipose tissue samples, was only minimally affected by the weight loss intervention. In contrast with the established positive relationship between adiposity and macrophage gene expression, an unexpected inverse correlation between these 2 variables was observed in skeletal muscle tissue. Additionally, muscle macrophage gene expression was inversely correlated with insulin resistance.
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Affiliation(s)
- Dongmei Liu
- a Department of Physical Medicine & Rehabilitation, University of Michigan, Ann Arbor, MI 48108, USA.,b School of Kinesiology, Shanghai University of Sports, Shanghai 200433, China
| | - Flor Elisa Morales
- c Department of Health, Human Performance and Recreation, Baylor University, Waco, TX 76798, USA
| | - Heidi B IglayReger
- a Department of Physical Medicine & Rehabilitation, University of Michigan, Ann Arbor, MI 48108, USA.,d Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48105, USA
| | - Mary K Treutelaar
- d Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48105, USA
| | - Amy E Rothberg
- d Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48105, USA
| | - Monica J Hubal
- e Children's National Medical Center, Washington, DC 20010, USA
| | - Evan P Nadler
- e Children's National Medical Center, Washington, DC 20010, USA
| | - Jacques Robidoux
- f Department of Pharmacology and Toxicology, East Carolina University, Greenville, NC 27858, USA
| | - Hisham Barakat
- f Department of Pharmacology and Toxicology, East Carolina University, Greenville, NC 27858, USA
| | - Jeffrey F Horowitz
- g School of Kinesiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Eric P Hoffman
- e Children's National Medical Center, Washington, DC 20010, USA
| | - Charles F Burant
- d Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48105, USA
| | - Paul M Gordon
- a Department of Physical Medicine & Rehabilitation, University of Michigan, Ann Arbor, MI 48108, USA.,c Department of Health, Human Performance and Recreation, Baylor University, Waco, TX 76798, USA
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20
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Van Pelt DW, Guth LM, Wang AY, Horowitz JF. Factors regulating subcutaneous adipose tissue storage, fibrosis, and inflammation may underlie low fatty acid mobilization in insulin-sensitive obese adults. Am J Physiol Endocrinol Metab 2017; 313:E429-E439. [PMID: 28679624 PMCID: PMC5668599 DOI: 10.1152/ajpendo.00084.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 06/01/2017] [Accepted: 06/30/2017] [Indexed: 11/22/2022]
Abstract
Although the rate of fatty acid release from adipose tissue into the systemic circulation is very high in most obese adults, some obese adults maintain relatively low rates of fatty acid release, which helps protect them against the development of systemic insulin resistance. The primary aim of this study was to identify factors in adipose tissue that may underlie low vs. high rates of fatty acid mobilization in a relatively homogeneous cohort of obese adults. We measured systemic fatty acid rate of appearance (FA Ra) via 13C-palmitate isotope dilution, and we obtained subcutaneous abdominal adipose tissue samples from 30 obese adults (BMI: 38 ± 1 kg/m2, age: 30 ± 2 yr) after an overnight fast. We then measured insulin sensitivity using a hyperinsulinemic-euglycemic clamp. Confirming our previous work, insulin sensitivity was inversely proportional to FA Ra (R2 = 0.50; P < 0.001). Immunoblot analysis of subcutaneous adipose tissue samples revealed that, compared with obese adults with high FA Ra, those with low FA Ra had lower markers of lipase activation and higher abundance of glycerol-3-phosphate acyltransferase, which is a primary enzyme for fatty acid esterification. Microarray and pathway analysis provided evidence of lower fibrosis and lower SAPK/JNK pathway activation in obese adults with low FA Ra compared with those with high FA Ra. Our findings suggest that alterations in factors regulating triglyceride storage in adipose tissue, along with lower fibrosis and inflammatory pathway activation, may underlie maintenance of a relatively low FA Ra in obesity, which may help protect against the development of insulin resistance.
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Affiliation(s)
- Douglas W Van Pelt
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Lisa M Guth
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Abigail Y Wang
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
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21
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Van Pelt DW, Guth LM, Horowitz JF. Aerobic exercise elevates markers of angiogenesis and macrophage IL-6 gene expression in the subcutaneous adipose tissue of overweight-to-obese adults. J Appl Physiol (1985) 2017; 123:1150-1159. [PMID: 28798202 DOI: 10.1152/japplphysiol.00614.2017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 07/28/2017] [Accepted: 08/07/2017] [Indexed: 01/04/2023] Open
Abstract
Alterations in the inflammatory state, metabolic function, and structure of subcutaneous adipose tissue (SAT) can impact the development of insulin resistance in obesity. Exercise can improve metabolic health in obesity, but the effects of exercise on SAT are not well known. The purpose of this study was to examine the effects of acute exercise and habitual exercise training on mRNA expression of markers of lipid metabolism, inflammation, fibrosis, and hypoxia/angiogenesis in SAT, as well as adipocyte cell size. We recruited overweight-to-obese adults who exercised regularly (ACTIVE: n = 8) or were sedentary (SED: n = 12). The groups were well matched for age (27 ± 1 vs. 24 ± 2 yr), body mass index (29 ± 1 vs. 27 ± 1 kg/m2), and body composition (30 ± 1 vs. 29 ± 1% body fat), but as expected, cardiorespiratory fitness was greater in ACTIVE vs. SED (V̇o2peak: 51 ± 3 vs. 42 ± 1 ml·kg fat-free mass-1·min-1; P = 0.01). Abdominal SAT biopsy samples were obtained before and 1 h after a single session of aerobic exercise (60 min at ~65% V̇o2peak). The exercise session increased SAT mRNA expression of VEGFA, an important regulator of angiogenic processes, in both groups. In addition, SAT from ACTIVE subjects had greater mRNA expression of the endothelial cell marker CD31 compared with SED, which may be a cumulative effect of the transient increases in VEGFA with regular exercise. We also magnetically sorted CD14+ immune cells from SAT samples and found that IL-6 expression was elevated in ACTIVE compared with SED. In conclusion, exercise initiates increases in factors related to angiogenic processes and may promote alterations in macrophage inflammation in SAT.NEW & NOTEWORTHY Acute exercise in overweight/obese adults increased subcutaneous adipose tissue (SAT) mRNA expression of VEGFA, an important regulator of angiogenesis and capillary growth. In addition, subjects that regularly exercise had elevated SAT CD31 mRNA expression and elevated IL-6 mRNA in adipose tissue macrophages compared with nonexercisers. This study demonstrates that aerobic exercise may alter processes related to whole body metabolic outcomes in obesity, such as angiogenesis and immune response, in the SAT of overweight/obese adults.
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Affiliation(s)
- Douglas W Van Pelt
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Lisa M Guth
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
| | - Jeffrey F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan
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22
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Ajluni N, Meral R, Neidert AH, Brady GF, Buras E, McKenna B, DiPaola F, Chenevert TL, Horowitz JF, Buggs-Saxton C, Rupani AR, Thomas PE, Tayeh MK, Innis JW, Omary MB, Conjeevaram H, Oral EA. Spectrum of disease associated with partial lipodystrophy: lessons from a trial cohort. Clin Endocrinol (Oxf) 2017; 86:698-707. [PMID: 28199729 PMCID: PMC5395301 DOI: 10.1111/cen.13311] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 01/18/2017] [Accepted: 02/10/2017] [Indexed: 12/29/2022]
Abstract
CONTEXT Partial lipodystrophy (PL) is associated with metabolic co-morbidities but may go undiagnosed as the disease spectrum is not fully described. OBJECTIVE The objective of the study was to define disease spectrum in PL using genetic, clinical (historical, morphometric) and laboratory characteristics. DESIGN Cross-sectional evaluation. PARTICIPANTS Twenty-three patients (22 with familial, one acquired, 78·3% female, aged 12-64 years) with PL and non-alcoholic fatty liver disease (NAFLD). MEASUREMENTS Genetic, clinical and laboratory characteristics, body composition indices, liver fat content by magnetic resonance imaging (MRI), histopathological and immunofluorescence examinations of liver biopsies. RESULTS Seven patients displayed heterozygous pathogenic variants in LMNA. Two related patients had a heterozygous, likely pathogenic novel variant of POLD1 (NM002691·3: c.3199 G>A; p.E1067K). Most patients had high ratios (>1·5) of percentage fat trunk to percentage fat legs (FMR) when compared to reference normals. Liver fat quantified using MR Dixon method was high (11·3 ± 6·3%) and correlated positively with haemoglobin A1c and triglycerides while leg fat by dual-energy X-ray absorptiometry (DEXA) correlated negatively with triglycerides. In addition to known metabolic comorbidities; chronic pain (78·3%), hypertension (56·5%) and mood disorders (52·2%) were highly prevalent. Mean NAFLD Activity Score (NAS) was 5 ± 1 and 78·3% had fibrosis. LMNA-immunofluorescence staining from select patients (including one with the novel POLD1 variant) showed a high degree of nuclear atypia and disorganization. CONCLUSIONS Partial lipodystrophy is a complex multi-system disorder. Metabolic parameters correlate negatively with extremity fat and positively with liver fat. DEXA-based FMR may prove useful as a diagnostic tool. Nuclear disorganization and atypia may be a common biomarker even in the absence of pathogenic variants in LMNA.
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Affiliation(s)
- Nevin Ajluni
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Rasimcan Meral
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Adam H. Neidert
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Graham F. Brady
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Eric Buras
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Barbara McKenna
- Department of Pathology, University of Michigan, Ann Arbor, MI, USA
| | - Frank DiPaola
- Division of Pediatric Gastroenterology, University of Michigan, Ann Arbor, MI, USA
| | | | | | - Colleen Buggs-Saxton
- Pediatric Endocrinology, Children’s Hospital of Michigan, Wayne School of Medicine, Detroit, MI, USA
| | - Amit R. Rupani
- Departments of Pediatrics and Communicable Diseases and Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Peedikayil E. Thomas
- Departments of Pediatrics and Communicable Diseases and Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Marwan K. Tayeh
- Departments of Pediatrics and Communicable Diseases and Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Jeffrey W. Innis
- Departments of Pediatrics and Communicable Diseases and Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - M. Bishr Omary
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Hari Conjeevaram
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Elif A. Oral
- Brehm Center for Diabetes Research and Division of Metabolism, Endocrinology & Diabetes, University of Michigan, Ann Arbor, MI, USA
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23
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Ortega JF, Morales-Palomo F, Fernandez-Elias V, Hamouti N, Bernardo FJ, Martin-Doimeadios RC, Nelson RK, Horowitz JF, Mora-Rodriguez R. Dietary supplementation with omega-3 fatty acids and oleate enhances exercise training effects in patients with metabolic syndrome. Obesity (Silver Spring) 2016; 24:1704-11. [PMID: 27356240 DOI: 10.1002/oby.21552] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 04/11/2016] [Accepted: 04/12/2016] [Indexed: 11/06/2022]
Abstract
OBJECTIVE We studied the effects of exercise training alone or combined with dietary supplementation of omega-3 polyunsaturated fatty acids (Ω-3PUFA) and oleate on metabolic syndrome (MSyn) components and other markers of cardiometabolic health. METHODS Thirty-six patients with MSyn underwent 24 weeks of high-intensity interval training. In a double-blind randomized design, half of the group ingested 500 mL/day of semi-skim milk (8 g of fat; placebo milk) whereas the other half ingested 500 mL/day of skim milk enriched with 275 mg of Ω-3PUFA and 7.5 g of oleate (Ω-3 + OLE). RESULTS Ω-3 + OLE treatment elevated 30% plasma Ω-3PUFA but not significantly (P = 0.286). Improvements in VO2peak (12.8%), mean blood pressure (-7.1%), waist circumference (-1.8%), body fat mass (-2.9%), and trunk fat mass (-3.3%) were similar between groups. However, insulin sensitivity (measured by intravenous glucose tolerance test), serum concentration of C-reactive protein, and high-density lipoprotein improved only in the Ω-3 + OLE group by 31.5%, 32.1%, and 10.3%, respectively (all P < 0.05). Fasting serum triacylglycerol, glucose, and plasma fibrinogen concentrations did not improve in either group after 24 weeks of intervention. CONCLUSIONS Diet supplementation with Ω-3PUFA and oleate enhanced cardiometabolic benefits of intense aerobic exercise training in patients with MSyn.
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Affiliation(s)
- Juan F Ortega
- Exercise Physiology Lab, University of Castilla-La Mancha, Toledo, Spain
| | | | | | - Nassim Hamouti
- Exercise Physiology Lab, University of Castilla-La Mancha, Toledo, Spain
| | - Francisco J Bernardo
- Environmental Sciences and Biochemistry, University of Castilla-La Mancha, Toledo, Spain
| | | | - Rachael K Nelson
- College Health Professions, Health Sciences Department, Central Michigan University, Mt. Pleasant, Michigan, USA
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24
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Caruso M, Ma D, Msallaty Z, Lewis M, Seyoum B, Al-janabi W, Diamond M, Abou-Samra AB, Højlund K, Tagett R, Draghici S, Zhang X, Horowitz JF, Yi Z. Increased interaction with insulin receptor substrate 1, a novel abnormality in insulin resistance and type 2 diabetes. Diabetes 2014; 63:1933-47. [PMID: 24584551 PMCID: PMC4030113 DOI: 10.2337/db13-1872] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Insulin receptor substrate 1 (IRS1) is a key mediator of insulin signal transduction. Perturbations involving IRS1 complexes may lead to the development of insulin resistance and type 2 diabetes (T2D). Surprisingly little is known about the proteins that interact with IRS1 in humans under health and disease conditions. We used a proteomic approach to assess IRS1 interaction partners in skeletal muscle from lean healthy control subjects (LCs), obese insulin-resistant nondiabetic control subjects (OCs), and participants with T2D before and after insulin infusion. We identified 113 novel endogenous IRS1 interaction partners, which represents the largest IRS1 interactome in humans and provides new targets for studies of IRS1 complexes in various diseases. Furthermore, we generated the first global picture of IRS1 interaction partners in LCs, and how they differ in OCs and T2D patients. Interestingly, dozens of proteins in OCs and/or T2D patients exhibited increased associations with IRS1 compared with LCs under the basal and/or insulin-stimulated conditions, revealing multiple new dysfunctional IRS1 pathways in OCs and T2D patients. This novel abnormality, increased interaction of multiple proteins with IRS1 in obesity and T2D in humans, provides new insights into the molecular mechanism of insulin resistance and identifies new targets for T2D drug development.
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Affiliation(s)
- Michael Caruso
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, Detroit, MI
| | - Danjun Ma
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, Detroit, MI
| | - Zaher Msallaty
- Division of Endocrinology, Wayne State University School of Medicine, Wayne State University, Detroit, MI
| | - Monique Lewis
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, Detroit, MI
| | - Berhane Seyoum
- Division of Endocrinology, Wayne State University School of Medicine, Wayne State University, Detroit, MI
| | - Wissam Al-janabi
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, Detroit, MI
| | - Michael Diamond
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MIDepartment of Obstetrics and Gynecology, Georgia Regents University, Augusta, GA
| | - Abdul B Abou-Samra
- Division of Endocrinology, Wayne State University School of Medicine, Wayne State University, Detroit, MIDepartment of Medicine, Hamad Medical Corporation, Doha, Qatar
| | - Kurt Højlund
- Diabetes Research Centre, Department of Endocrinology, Odense University Hospital, Odense, Denmark
| | - Rebecca Tagett
- Department of Computer Science, College of Engineering, Wayne State University, Detroit, MI
| | - Sorin Draghici
- Department of Computer Science, College of Engineering, Wayne State University, Detroit, MI
| | - Xiangmin Zhang
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, Detroit, MI
| | | | - Zhengping Yi
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, Detroit, MI
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Van Pelt DW, Newsom SA, Schenk S, Horowitz JF. Relatively low endogenous fatty acid mobilization and uptake helps preserve insulin sensitivity in obese women. Int J Obes (Lond) 2014; 39:149-55. [PMID: 24785103 PMCID: PMC4216778 DOI: 10.1038/ijo.2014.70] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 03/15/2014] [Accepted: 04/14/2014] [Indexed: 12/15/2022]
Abstract
Background Although obesity is commonly linked with metabolic disease risk, some obese adults do not develop metabolic abnormalities, such as insulin resistance. Objectives The primary aim of this study was to determine whether alterations in fatty acid mobilization and uptake underlie differences in insulin sensitivity (Si) among a seemingly homogeneous cohort of obese women. Methods Insulin sensitivity (FSIVGTT), basal fatty acid rate of disappearance from plasma (Rd), resting whole-body fat oxidation, intramyocellular triacylglycerol (IMTG) concentration, and markers of skeletal muscle inflammation were measured in 21 obese women. Participants were divided into tertiles based on their Si. The subset of participants with the lowest Si (LOW-Si; Si ≤2.1 (mU/L)−1·min−1; n=7) was compared with the subset of participants with the highest Si, who exhibited relatively normal insulin sensitivity (NORM-Si; Si ≥3.4 (mU/L)−1·min−1; n=8). Results Despite nearly identical physical characteristics in LOW-Sivs. NORM-Si (BMI: 34±2 vs. 34±1 kg/m2; %body fat: 48±1% vs. 47±1%; waist circumference: 104±2 vs. 104±2 cm; VO2max: 2.2±0.2 vs. 2.3±0.1 L/min), fatty acid Rd was nearly 30% lower in NORM (P=0.02). Importantly, the greater rate of fatty acid uptake in LOW-Sivs. NORMSi did not translate to higher rate of fat oxidation (3.5±0.2 vs. 3.7±0.2 μmol/kg/min) or to a measureable difference in IMTG content, (68.3±12.7 vs. 63.7±6.7 μmol/g dry weight). In conjunction with the lower fatty acid Rd in NORM-Sivs. LOW-Si, activation of inflammatory pathways known to impair insulin action in skeletal muscle was also lower (i.e. lower phosphorylated JNK, higher IκBα abundance). In contrast, LOW-Si and NORM-Si exhibited no differences in plasma markers of inflammation (i.e. TNFα, IL-6, MCP-1). Conclusion These findings suggest that obese women who maintain a relatively low rate of endogenous fatty acid uptake may be somewhat “protected” against the development of insulin resistance potentially by less activation of inflammatory pathways within skeletal muscle.
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Affiliation(s)
- D W Van Pelt
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - S A Newsom
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - S Schenk
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - J F Horowitz
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
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26
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Nelson RK, Van Pelt DW, Horowitz JF. Improvements in Insulin Action Only After Adding Weight-loss to a Mild-intensity Exercise Training Program. Med Sci Sports Exerc 2014. [DOI: 10.1249/01.mss.0000495114.51884.33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Nelson RK, Horowitz JF. Acute exercise ameliorates differences in insulin resistance between physically active and sedentary overweight adults. Appl Physiol Nutr Metab 2014; 39:811-8. [PMID: 24773370 DOI: 10.1139/apnm-2013-0525] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Although regular exercise is associated with reduced cardiometabolic disease risk among overweight adults, it remains unclear whether much of the health benefits of exercise are derived from the most recent session(s) of exercise or if they are the result of adaptations stemming from weeks, months, or even years of training. The purpose of this study was to compare the effects of habitual and acute exercise on key markers of cardiometabolic disease risk in overweight adults. We compared insulin sensitivity index (ISI) using an oral glucose tolerance test, blood pressure (BP), blood lipids, and systemic inflammatory cytokines in 12 overweight to mildly obese adults (BMI: 27-34 kg/m(2)) who exercise regularly (EX; >2.5 h exercise per week) with a well-matched cohort of 12 nonexercisers (Non-EX). Baseline measurements in EX were performed exactly 3 days after exercise, whereas Non-EX remained sedentary. We repeated these measurements the day after a session of exercise in both groups. At baseline, ISI was significantly greater in EX versus Non-EX (3.1 ± 0.2 vs. 2.3 ± 0.2; p = 0.02), but BP, blood lipids, and plasma concentration of the systemic inflammatory cytokines we measured were not different between groups. Acute exercise increased ISI the next morning in Non-EX (2.3 ± 0.2 vs. 2.8 ± 0.3; p = 0.03) but not EX. As a result, ISI was similar between groups the morning after exercise. In summary, exercising regularly was accompanied by a persistent improvement in insulin sensitivity that lasted at least 3 days after exercise in overweight adults, but just one session of exercise increased insulin sensitivity among sedentary overweight adults to levels equivalent to the regular exercisers.
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Affiliation(s)
- Rachael K Nelson
- School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI, USA
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28
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Newsom SA, Everett AC, Hinko A, Horowitz JF. A single session of low-intensity exercise is sufficient to enhance insulin sensitivity into the next day in obese adults. Diabetes Care 2013; 36:2516-22. [PMID: 23757424 PMCID: PMC3747878 DOI: 10.2337/dc12-2606] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE The purpose of this study was to determine the effect of a relatively modest session of exercise on insulin sensitivity and fatty acid uptake the next day in obese adults. RESEARCH DESIGN AND METHODS Eleven sedentary obese adults (male/female: 3/8; BMI 37 ± 1 kg/m(2); peak oxygen uptake [VO2peak] 20 ± 1 mL/kg/min) completed three experimental trials. On two of these occasions, subjects exercised to expend 350 kcal in the afternoon. These two exercise trials were identical except for the exercise intensity (50% VO2peak [EX50] and 65% VO2peak [EX65]) and the duration of exercise necessary to expend 350 kcal (EX50 = ≈ 70 min; EX65 = ≈ 55 min). Subjects also completed a control trial (CON), without exercise. The next morning, we measured insulin sensitivity (hyperinsulinemic-euglycemic clamp) and whole-body fatty acid uptake (palmitate rate of disappearance from plasma [Rd]). RESULTS Exercise increased insulin sensitivity the next day, but whereas the 35% improvement after EX50 compared with CON was statistically significant (P = 0.01), the 20% improvement after EX65 was not (P = 0.17). Despite nearly identical values between CON and EX65 (P = 0.88), systemic fatty acid uptake was lower after EX50 compared with EX65 (P = 0.02), but not quite significant compared with CON (P = 0.07). Importantly, the change in fatty acid uptake after exercise compared with CON was negatively correlated with the change in insulin sensitivity for all trials (r = -0.60, P = 0.003). CONCLUSIONS A relatively modest single session of exercise in obese adults improved insulin sensitivity the next day, and a reduction in systemic fatty acid uptake in the several hours after exercise may be important for this effect.
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Affiliation(s)
- Sean A Newsom
- Substrate Metabolism Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA
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Van Pelt DW, Newsom SA, Schenk S, Horowitz JF. Systemic fatty acid uptake and skeletal muscle inflammatory pathway activation may contribute to the variability in insulin sensitivity found in obesity. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.855.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Douglas W. Van Pelt
- Substrate Metabolism LaboratorySchool of KinesiologyUniversity of MichiganAnn ArborMI
| | - Sean A. Newsom
- Substrate Metabolism LaboratorySchool of KinesiologyUniversity of MichiganAnn ArborMI
| | - Simon Schenk
- Substrate Metabolism LaboratorySchool of KinesiologyUniversity of MichiganAnn ArborMI
| | - Jeffrey F. Horowitz
- Substrate Metabolism LaboratorySchool of KinesiologyUniversity of MichiganAnn ArborMI
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Boon J, Hoy AJ, Stark R, Brown RD, Meex RC, Henstridge DC, Schenk S, Meikle PJ, Horowitz JF, Kingwell BA, Bruce CR, Watt MJ. Ceramides contained in LDL are elevated in type 2 diabetes and promote inflammation and skeletal muscle insulin resistance. Diabetes 2013; 62:401-10. [PMID: 23139352 PMCID: PMC3554351 DOI: 10.2337/db12-0686] [Citation(s) in RCA: 223] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Dysregulated lipid metabolism and inflammation are linked to the development of insulin resistance in obesity, and the intracellular accumulation of the sphingolipid ceramide has been implicated in these processes. Here, we explored the role of circulating ceramide on the pathogenesis of insulin resistance. Ceramide transported in LDL is elevated in the plasma of obese patients with type 2 diabetes and correlated with insulin resistance but not with the degree of obesity. Treating cultured myotubes with LDL containing ceramide promoted ceramide accrual in cells and was accompanied by reduced insulin-stimulated glucose uptake, Akt phosphorylation, and GLUT4 translocation compared with LDL deficient in ceramide. LDL-ceramide induced a proinflammatory response in cultured macrophages via toll-like receptor-dependent and -independent mechanisms. Finally, infusing LDL-ceramide into lean mice reduced insulin-stimulated glucose uptake, and this was due to impaired insulin action specifically in skeletal muscle. These newly identified roles of LDL-ceramide suggest that strategies aimed at reducing hepatic ceramide production or reducing ceramide packaging into lipoproteins may improve skeletal muscle insulin action.
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MESH Headings
- Animals
- Cells, Cultured
- Ceramides/blood
- Ceramides/pharmacology
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/metabolism
- Female
- Glucose/metabolism
- Glucose Transporter Type 4/metabolism
- Humans
- Inflammation/blood
- Inflammation/metabolism
- Insulin/metabolism
- Insulin Resistance/physiology
- Lipoproteins, LDL/blood
- Lipoproteins, LDL/pharmacology
- Macrophages/drug effects
- Macrophages/metabolism
- Male
- Mice
- Mice, Inbred C57BL
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Obesity/blood
- Obesity/metabolism
- Phosphorylation
- Proto-Oncogene Proteins c-akt/metabolism
- Toll-Like Receptors/metabolism
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Affiliation(s)
- James Boon
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Andrew J. Hoy
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Romana Stark
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Russell D. Brown
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | - Ruth C. Meex
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
| | | | - Simon Schenk
- Department of Orthopaedic Surgery, University of California, San Diego, California
| | - Peter J. Meikle
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | | | | | - Clinton R. Bruce
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Matthew J. Watt
- Biology of Lipid Metabolism Laboratory, Department of Physiology, Monash University, Clayton, Victoria, Australia
- Corresponding author: Matthew J. Watt,
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Nelson RK, Horowitz JF, Holleman RG, Swartz AM, Strath SJ, Kriska AM, Richardson CR. Daily physical activity predicts degree of insulin resistance: a cross-sectional observational study using the 2003-2004 National Health and Nutrition Examination Survey. Int J Behav Nutr Phys Act 2013; 10:10. [PMID: 23351329 PMCID: PMC3575359 DOI: 10.1186/1479-5868-10-10] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 01/15/2013] [Indexed: 11/10/2022] Open
Abstract
Background This study examined the independent association of objectively measured physical activity on insulin resistance while controlling for confounding variables including: cardiorespiratory fitness, adiposity, sex, age, and smoking status. Methods Data were obtained from National Health and Nutrition Examination Survey 2003–2004, a cross-sectional observational study conducted by the National Center for Health Statistics of the Centers for Disease Control that uses a stratified, multistage probability design to obtain a nationally representative sample of the U.S. population. The analysis included 402 healthy U.S. adults with valid accelerometer, cardiorespiratory fitness, and fasting plasma glucose and insulin concentrations. After controlling for relevant confounding variables we performed a multiple linear regression to predict homeostatic model of insulin resistance (HOMA-IR) based on average daily minutes of moderate-to-vigorous physical activity (MVPA). Results In our bivariate models, MVPA, cardiorespiratory fitness and body fat percentage were all significantly correlated with log HOMA-IR. In the complete model including MVPA and relevant confounding variables, there were strong and significant associations between MVPA and log HOMA-IR (β= −0.1607, P=0.004). In contrast the association between cardiorespiratory fitness and log HOMA-IR was not significant. Conclusion When using an objective measure of physical activity the amount of time engaged in daily physical activity was associated with lower insulin resistance, whereas higher cardiorespiratory fitness was not. These results suggest that the amount of time engaged in physical activity may be an important determinant for improving glucose metabolism.
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Affiliation(s)
- Rachael K Nelson
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
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32
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Cornford AS, Hinko A, Nelson RK, Barkan AL, Horowitz JF. Rapid development of systemic insulin resistance with overeating is not accompanied by robust changes in skeletal muscle glucose and lipid metabolism. Appl Physiol Nutr Metab 2012; 38:512-9. [PMID: 23668758 DOI: 10.1139/apnm-2012-0266] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Prolonged overeating and the resultant weight gain are clearly linked with the development of insulin resistance and other cardiometabolic abnormalities, but adaptations that occur after relatively short periods of overeating are not completely understood. The purpose of this study was to characterize metabolic adaptations that may accompany the development of insulin resistance after 2 weeks of overeating. Healthy, nonobese subjects (n = 9) were admitted to the hospital for 2 weeks, during which time they ate ∼4000 kcals·day(-1) (70 kcal·kg(-1) fat free mass·day(-1)). Insulin sensitivity was estimated during a meal tolerance test, and a muscle biopsy was obtained to assess muscle lipid accumulation and protein markers associated with insulin resistance, inflammation, and the regulation of lipid metabolism. Whole-body insulin sensitivity declined markedly after 2 weeks of overeating (Matsuda composite index: 8.3 ± 1.3 vs. 4.6 ± 0.7, p < 0.05). However, muscle markers of insulin resistance and inflammation (i.e., phosphorylation of IRS-1-Ser(312), Akt-Ser(473), and c-Jun N-terminal kinase) were not altered by overeating. Intramyocellular lipids tended to increase after 2 weeks of overeating (triacylglyceride: 7.6 ± 1.6 vs. 10.0 ± 1.8 nmol·mg(-1) wet weight; diacylglyceride: 104 ± 10 vs. 142 ± 23 pmol·mg(-1) wet weight) but these changes did not reach statistical significance. Overeating induced a 2-fold increase in 24-h insulin response (area under the curve (AUC); p < 0.05), with a resultant ∼35% reduction in 24-h plasma fatty acid AUC (p < 0.05). This chronic reduction in circulating fatty acids may help explain the lack of a robust increase in muscle lipid accumulation. In summary, our findings suggest alterations in skeletal muscle metabolism may not contribute meaningfully to the marked whole-body insulin resistance observed after 2 weeks of overeating.
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Affiliation(s)
- Andrea S Cornford
- a School of Kinesiology, University of Michigan, 401 Washtenaw Avenue, Ann Arbor, MI 48109, USA
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Cornford AS, Barkan AL, Hinko A, Horowitz JF. Suppression in growth hormone during overeating ameliorates the increase in insulin resistance and cardiovascular disease risk. Am J Physiol Endocrinol Metab 2012; 303:E1264-72. [PMID: 23011065 PMCID: PMC3517632 DOI: 10.1152/ajpendo.00320.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Previously, we reported that overeating for only a few days markedly suppressed the secretion of growth hormone (GH). The purpose of the present study was to determine the role of this reduction in GH concentration on key metabolic adaptations that occur during 2 wk of overeating. Nine nonobese, healthy adults were admitted to the hospital for 2 wk, during which time they ate ∼4,000 kcal/day (70 kcal·kg fat-free mass(-1)·day(-1); 50% carbohydrate, 35% fat, and 15% protein), and their plasma GH concentration was allowed to decline naturally (control). An additional eight subjects underwent the same overeating intervention and received exogenous GH treatment (GHT) administered in four daily injections to mimic physiological GH secretion throughout the 2-wk overeating period. We measured plasma insulin and glucose concentrations in the fasting and postprandial state as well as fasting lipolytic rate, proteolytic rate, and fractional synthetic rate (FSR) using stable-isotope tracer methods. GHT prevented the fall in plasma GH concentration, maintaining plasma GH concentration at baseline levels (1.2 ± 0.2 ng/ml), which increased fasting and postprandial assessments of insulin resistance (P < 0.05) and increased fasting lipidemia (all P < 0.05 vs. control). In addition, preventing the suppression in GH with overeating also blunted the increase in systemic proteolysis (P < 0.05 GHT vs. control). However, GHT did not alter lipolysis or FSR in response to overeating. In conclusion, our main findings suggest that the suppression in GH secretion that naturally occurs during the early stages of overeating may help attenuate the insulin resistance and hyperlipidemia that typically accompany overeating.
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Affiliation(s)
- Andrea S Cornford
- School of Kinesiology, Univ. of Michigan, Ann Arbor, MI 48109-2214, USA
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Watt MJ, Barnett AC, Bruce CR, Schenk S, Horowitz JF, Hoy AJ. Regulation of plasma ceramide levels with fatty acid oversupply: evidence that the liver detects and secretes de novo synthesised ceramide. Diabetologia 2012; 55:2741-2746. [PMID: 22854889 PMCID: PMC3576922 DOI: 10.1007/s00125-012-2649-3] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 06/21/2012] [Indexed: 01/12/2023]
Abstract
AIMS/HYPOTHESIS Plasma ceramide concentrations correlate with insulin sensitivity, inflammation and atherosclerotic risk. We hypothesised that plasma ceramide concentrations are increased in the presence of elevated fatty acid levels and are regulated by increased liver serine C-palmitoyltransferase (SPT) activity. METHODS Lean humans and rats underwent an acute lipid infusion and plasma ceramide levels were determined. One group of lipid-infused rats was administered myriocin to inhibit SPT activity. Liver SPT activity was determined in lipid-infused rats, and obese, insulin resistant mice. The time and palmitate dose-dependent synthesis of intracellular and secreted ceramide was determined in HepG2 liver cells. RESULTS Plasma ceramide levels were increased during lipid infusion in humans and rats, and in obese, insulin-resistant mice. The increase in plasma ceramide was not associated with changes in liver SPT activity, and inhibiting SPT activity by ~50% did not alter plasma ceramide levels in lipid-infused rats. In HepG2 liver cells, palmitate incorporation into extracellular ceramide was both dose- and time-dependent, suggesting the liver cells rapidly secreted the newly synthesised ceramide. CONCLUSIONS/INTERPRETATION Elevated systemic fatty acid availability increased plasma ceramide but this was not associated with changes in hepatic SPT activity, suggesting that liver ceramide synthesis is driven by substrate availability rather than increased SPT activity. This report also provides evidence that the liver is sensitive to the intracellular ceramide concentration, and an increase in liver ceramide secretion may help protect the liver from the deleterious effects of intracellular ceramide accumulation.
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Affiliation(s)
- M J Watt
- Department of Physiology, Monash University, Building 13F, Clayton, VIC, 3800, Australia.
| | - A C Barnett
- Department of Physiology, Monash University, Building 13F, Clayton, VIC, 3800, Australia
| | - C R Bruce
- Department of Physiology, Monash University, Building 13F, Clayton, VIC, 3800, Australia
- Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - S Schenk
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
- Department of Orthopaedic Surgery, University of California, San Diego, CA, USA
| | - J F Horowitz
- School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
| | - A J Hoy
- Department of Physiology, Monash University, Building 13F, Clayton, VIC, 3800, Australia.
- Discipline of Physiology, University of Sydney, Anderson Stuart Building (F13), Sydney, NSW, 2006, Australia.
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35
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Claflin DR, Larkin LM, Cederna PS, Horowitz JF, Alexander NB, Cole NM, Galecki AT, Chen S, Nyquist LV, Carlson BM, Faulkner JA, Ashton-Miller JA. Effects of high- and low-velocity resistance training on the contractile properties of skeletal muscle fibers from young and older humans. J Appl Physiol (1985) 2011; 111:1021-30. [PMID: 21799130 PMCID: PMC3191797 DOI: 10.1152/japplphysiol.01119.2010] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 07/23/2011] [Indexed: 11/22/2022] Open
Abstract
A two-arm, prospective, randomized, controlled trial study was conducted to investigate the effects of movement velocity during progressive resistance training (PRT) on the size and contractile properties of individual fibers from human vastus lateralis muscles. The effects of age and sex were examined by a design that included 63 subjects organized into four groups: young (20-30 yr) men and women, and older (65-80 yr) men and women. In each group, one-half of the subjects underwent a traditional PRT protocol that involved shortening contractions at low velocities against high loads, while the other half performed a modified PRT protocol that involved contractions at 3.5 times higher velocity against reduced loads. Muscles were sampled by needle biopsy before and after the 14-wk PRT program, and functional tests were performed on permeabilized individual fiber segments isolated from the biopsies. We tested the hypothesis that, compared with low-velocity PRT, high-velocity PRT results in a greater increase in the cross-sectional area, force, and power of type 2 fibers. Both types of PRT increased the cross-sectional area, force, and power of type 2 fibers by 8-12%, independent of the sex or age of the subject. Contrary to our hypothesis, the velocity at which the PRT was performed did not affect the fiber-level outcomes substantially. We conclude that, compared with low-velocity PRT, resistance training performed at velocities up to 3.5 times higher against reduced loads is equally effective for eliciting an adaptive response in type 2 fibers from human skeletal muscle.
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Affiliation(s)
- Dennis R Claflin
- Department of Surgery, Section of Plastic Surgery, Univ. of Michigan, BSRB, Rm. 2023, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA.
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Newsom SA, Schenk S, Li M, Everett AC, Horowitz JF. High fatty acid availability after exercise alters the regulation of muscle lipid metabolism. Metabolism 2011; 60:852-9. [PMID: 20870251 PMCID: PMC3011035 DOI: 10.1016/j.metabol.2010.08.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 08/11/2010] [Accepted: 08/11/2010] [Indexed: 01/22/2023]
Abstract
We previously reported that a single exercise session protects against fatty acid (FA)-induced insulin resistance, perhaps in part through augmented intramyocellular triacylglycerol (IMTG) synthesis. The aim of this study was to examine the effect of elevated FA availability after exercise on factors regulating IMTG metabolism. After exercise (90 minutes, 65% peak oxygen uptake), 7 healthy women (body mass index, 23 ± 1 kg/m(2)) were infused overnight (16 hours) with either a lipid and heparin solution (LIPID, 0.11 g fat per kilogram per hour) or saline (SALINE). We measured resting FA oxidation (indirect calorimetry) and obtained a skeletal muscle biopsy sample the next morning. The 4-fold increase in overnight plasma FA concentration during LIPID increased IMTG by approximately 30% during LIPID vs SALINE. This was accompanied by an approximately 25% greater membrane-associated abundance of the FA transporter FAT/CD36 (P < .01) and an approximately 8% increase in the activity of the IMTG synthesis enzyme glycerol-3-phosphate acyltransferase (GPAT, P < .01). In contrast, resting FA oxidation was not affected. We also found no difference in the protein abundance of GPAT1 and diacylglycerol acyltransferase-1, diacylglycerol acyltransferase activity, or the abundance of the lipid droplet coat proteins (perilipins 2, 3, 4, and 5) between treatments. Our findings suggest that augmented capacity for FA flux into muscle (ie, via membrane-associated FAT/CD36), perhaps together with a slight yet significant increase in activity of a key IMTG synthesis enzyme (GPAT), may enhance IMTG storage when FA availability is high after exercise. The importance of the absence of a change in perilipin protein abundance despite increased muscle lipid storage remains to be determined.
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Affiliation(s)
| | | | | | | | - Jeffrey F. Horowitz
- Corresponding Author: Jeffrey F. Horowitz, School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI, 48109-2214, Phone: (734) 647-1076, Fax: (734) 936-1925,
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Newsom SA, Everett AC, Horowitz JF. A Single Session of Exercise Improves Insulin Sensitivity in Obese Adults: Effects of Exercise Intensity. Med Sci Sports Exerc 2011. [DOI: 10.1249/01.mss.0000402847.02364.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Mittendorfer B, Horowitz JF, DePaoli AM, McCamish MA, Patterson BW, Klein S. Recombinant human leptin treatment does not improve insulin action in obese subjects with type 2 diabetes. Diabetes 2011; 60:1474-7. [PMID: 21411512 PMCID: PMC3292320 DOI: 10.2337/db10-1302] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
OBJECTIVE Leptin therapy improves insulin sensitivity in people with leptin deficiency, but it is not known whether it improves insulin action in people who are not leptin deficient. The purpose of the current study was to determine whether leptin treatment has weight loss-independent effects on insulin action in obese subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS We conducted a randomized, placebo-controlled trial in obese subjects (BMI: 35.4 ± 0.6 kg/m(2); mean ± SE) with newly diagnosed type 2 diabetes. Subjects were randomized to treatment with placebo (saline), low-dose (30 mg/day), or high-dose (80 mg/day) recombinant methionyl human (r-Met hu) leptin for 14 days. Multiorgan insulin sensitivity before and after treatment was evaluated by using the hyperinsulinemic-euglycemic clamp procedure in conjunction with stable isotopically labeled tracer infusions to measure glucose, glycerol, and fatty acid kinetics. RESULTS Low-dose and high-dose leptin treatment resulted in a threefold (P < 0.01) and 150-fold (P < 0.001) increase in basal plasma leptin concentrations, respectively. However, neither low-dose nor high-dose therapy had an effect on insulin-mediated suppression of glucose, glycerol, or palmitate rates of appearance into plasma compared with placebo. In addition, leptin treatment did not increase insulin-mediated stimulation of glucose disposal compared with placebo (14.3 ± 3.1, 18.4 ± 3.6, 16.7 ± 2.4 vs. 17.5 ± 2.5, 20.7 ± 3.0, 19.1 ± 3.3 μmol/kg body wt/min before vs. after treatment in the placebo, low-dose, and high-dose leptin groups, respectively). CONCLUSIONS r-Met hu leptin does not have weight loss-independent, clinically important effects on insulin sensitivity in obese people with type 2 diabetes.
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Affiliation(s)
- Bettina Mittendorfer
- Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Jeffrey F. Horowitz
- Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, Missouri
| | | | | | - Bruce W. Patterson
- Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Samuel Klein
- Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, Missouri
- Corresponding author: Samuel Klein,
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Li M, Paran C, Wolins NE, Horowitz JF. High muscle lipid content in obesity is not due to enhanced activation of key triglyceride esterification enzymes or the suppression of lipolytic proteins. Am J Physiol Endocrinol Metab 2011; 300:E699-707. [PMID: 21285405 PMCID: PMC3074947 DOI: 10.1152/ajpendo.00316.2010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mechanisms underlying alterations in muscle lipid metabolism in obesity are poorly understood. The primary aim of this study was to compare the abundance and/or activities of key proteins that regulate intramyocellular triglyceride (IMTG) concentration in the skeletal muscle obtained from obese (OB; n = 8, BMI 38 ± 1 kg/m(2)) and nonobese (NOB; n = 9, BMI 23 ± 1 kg/m(2)) women. IMTG concentration was nearly twofold greater in OB vs. NOB subjects (75 ± 15 vs. 40 ± 8 μmol/g dry wt, P < 0.05). In contrast, the activity and protein abundance of key enzymes that regulate the esterification of IMTG (i.e., glycerol-3-phosphate acyltransferase and diacylglycerol acyltransferase) were not elevated. We also found no differences between groups in muscle adipose triglyceride lipase and hormone-sensitive lipase (HSL) protein abundance and no differences in phosphorylation of specific sites known to affect HSL activity. However, we did find the elevated IMTG in obesity to be accompanied by a greater abundance of the fatty acid transporter FAT/CD36 in the membrane fraction of muscle from OB vs. NOB subjects (P < 0.05), suggestive of an elevated fatty acid transport capacity. Additionally, protein abundance of the lipid-trafficking protein perilipin 3 was lower (P < 0.05) in muscle from OB vs. NOB when expressed relative to IMTG content. Our findings indicate that the elevated IMTG content found in obese women was not due to an upregulation of key lipogenic proteins or to the suppression of lipolytic proteins. The impact of a low perilipin protein abundance relative to the amount of IMTG in obesity remains to be clarified.
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Affiliation(s)
- Minghua Li
- School of Kinesiology, Univ. of Michigan, Ann Arbor, 48109-2214, USA
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Abstract
CONTEXT The very low GH concentration in obesity is commonly attributed to high body fat mass; however, the influence of overeating on GH secretion is not clear. OBJECTIVE The aim of the study was to examine the effects of 2 wk of overeating on changes in GH secretion. SETTING Subjects were admitted to the hospital and stayed within the Michigan Clinical Research Unit throughout the entire 2-wk overeating period. PARTICIPANTS We studied seven healthy, nonobese men (body mass index, 24 ± 1 kg/m(2); age, 25 ± 1 yr). INTERVENTION Subjects ate standardized meals containing 70 kcal/kg fat free mass/d (∼4000 kcal/d) for 2 wk. MAIN OUTCOME MEASURES Twenty-four-hour plasma concentrations of GH (every 20 min) and insulin (every 2 h) were measured before overeating (baseline), on d 3, and after 2 wk of overeating. RESULTS Compared with baseline, average 24-h plasma GH concentration declined nearly 80% by d 3 of overeating (1.30 ± 0.18 vs. 0.36 ± 0.09 ng/ml; P = 0.01). This marked suppression of GH secretion occurred in the absence of an increase in body weight (77.0 ± 2.2 vs. 76.4 ± 2.4 kg). At the same time, average 24-h insulin concentration doubled (16.6 ± 2.1 vs. 31.7 ± 5.8 μU/ml; P = 0.009). After 2 wk, body weight significantly increased (79.0 ± 2.1 kg; P < 0.001), and body fat increased by more than 10% (P = 0.002). However, this did not induce a further suppression in plasma GH concentration (0.33 ± 0.08 ng/ml). CONCLUSION Only a few days of overeating markedly suppressed GH secretion before any measurable weight gain and was accompanied by chronic hyperinsulinemia. Increased body weight and body fat by 2 wk of overeating did not further suppress GH secretion.
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Affiliation(s)
- Andrea S Cornford
- School of Kinesiology, University of Michigan, 401 Washtenaw Avenue, Ann Arbor, Michigan 48109-2214, USA
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Newsom SA, Schenk S, Harber MP, Burant CF, Horowitz JF. Insulin Sensitivity is Lowest in Obese Women with High Rates of Fatty Acid Uptake. Med Sci Sports Exerc 2010. [DOI: 10.1249/01.mss.0000389482.54563.82] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Cornford A, Barkan AL, Horowitz JF. Suppression in Growth Hormone Secretion with Overeating Contributes to a Higher Whole-body Proteolytic Rate. Med Sci Sports Exerc 2010. [DOI: 10.1249/01.mss.0000389563.27228.40] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Nelson RK, Horowitz JF, Holleman RG, Strath SJ, Kriska AM, Swartz AM, Richardson CR. Physical Activity is a Better Predictor of Insulin Resistance than Cardiorespiratory Fitness. Med Sci Sports Exerc 2010. [DOI: 10.1249/01.mss.0000389346.97213.39] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Newsom SA, Schenk S, Li M, Everett AC, Horowitz JF. Elevated fatty acid availability after exercise increases intramyocellular triglyceride content by enhancing capacity for fatty acid flux into skeletal muscle. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.1045.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Minghua Li
- KinesiologyUniversity of MichiganAnn ArborMI
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Li M, Paran C, Wolins NE, Horowitz JF. High muscle triglyceride content in obesity is not due to elevated lipogenic enzyme activity or to the suppression of lipolytic proteins. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.1045.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Minghua Li
- School of KinesiologyUniversity of MichiganAnn ArborMI
| | | | - Nathan E Wolins
- Center for Human NutritionWashington University School of MedicineSt. LouisMO
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Newsom SA, Schenk S, Thomas KM, Harber MP, Knuth ND, Goldenberg N, Horowitz JF. Energy deficit after exercise augments lipid mobilization but does not contribute to the exercise-induced increase in insulin sensitivity. J Appl Physiol (1985) 2009; 108:554-60. [PMID: 20044472 DOI: 10.1152/japplphysiol.01106.2009] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The content of meals consumed after exercise can impact metabolic responses for hours and even days after the exercise session. The purpose of this study was to compare the effect of low dietary carbohydrate (CHO) vs. low energy intake in meals after exercise on insulin sensitivity and lipid metabolism the next day. Nine healthy men participated in four randomized trials. During the control trial (CON) subjects remained sedentary. During the other three trials, subjects exercised [65% peak oxygen consumption (Vo(2 peak)); cycle ergometer and treadmill exercise] until they expended approximately 800 kcal. Dietary intake during CON and one exercise trial (BAL) was designed to provide sufficient energy and carbohydrate to maintain nutrient balance. In contrast, the diets after the other two exercise trials were low in either CHO (LOW-CHO) or energy (LOW-EN). The morning after exercise we obtained a muscle biopsy, assessed insulin sensitivity (S(i); intravenous glucose tolerance test) and measured lipid kinetics (isotope tracers). Although subjects were in energy balance during both LOW-CHO and CON, the lower muscle glycogen concentration during LOW-CHO vs. CON (402 +/- 29 vs. 540 +/- 33 mmol/kg dry wt, P < 0.01) coincided with a significant increase in S(i) [5.2 +/- 0.7 vs. 3.8 +/- 0.7 (mU/l)(-1) x min(-1); P < 0.05]. Conversely, despite ingesting several hundred fewer kilocalories after exercise during LOW-EN compared with BAL, this energy deficit did not affect S(i) the next day [4.9 +/- 0.9, and 5.0 +/- 0.8 (mU/l)(-1) x min(-1)]. Maintaining an energy deficit after exercise had the most potent effect on lipid metabolism, as measured by a higher plasma triacylglycerol concentration, and increased plasma fatty acid mobilization and oxidation compared with when in nutrient balance. Carbohydrate deficit after exercise, but not energy deficit, contributed to the insulin-sensitizing effects of acute aerobic exercise, whereas maintaining an energy deficit after exercise augmented lipid mobilization.
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Affiliation(s)
- Sean A Newsom
- School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109-2214, USA
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Schenk S, Harber MP, Shrivastava CR, Burant CF, Horowitz JF. Improved insulin sensitivity after weight loss and exercise training is mediated by a reduction in plasma fatty acid mobilization, not enhanced oxidative capacity. J Physiol 2009; 587:4949-61. [PMID: 19723783 PMCID: PMC2770158 DOI: 10.1113/jphysiol.2009.175489] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Accepted: 08/24/2009] [Indexed: 12/22/2022] Open
Abstract
Obesity is characterized by excessive rates of plasma fatty acid mobilization and uptake, which play a key role in mediating insulin resistance. While weight loss via diet-only or a diet + exercise program clearly improves insulin sensitivity, the precise mechanisms modulating this improvement are not completely understood. The purpose of the present study was to determine the role of the reduced fatty acid mobilization and uptake after weight loss in obese women who were randomly assigned to lifestyle interventions of either weight loss without exercise (WL) (n = 7) or a weight loss + exercise program (WL + EX) (n = 10). Before and after losing 12% of their body weight, we measured insulin sensitivity (S(I)), systemic fatty acid rate of appearance (Ra) and disappearance (Rd), oxidative capacity, and markers for pro-inflammatory pathways in skeletal muscle. Fatty acid Ra and Rd were reduced by 30% after both interventions (P < 0.05). While oxidative capacity increased 25% in WL + EX (compared with no increase after WL), the improvement in S(I) was identical in both groups (60%; P < 0.05), and skeletal muscle pro-inflammatory pathways were reduced (P < 0.05) similarly in both groups. When we artificially increased fatty acid mobilization after weight loss to pre-weight-loss levels via an overnight lipid infusion, the improvement in S(I) was almost completely reversed. Importantly, WL + EX did not protect against this lipid-induced reversal in S(I) despite a significant increase in resting whole-body fat oxidation and a marked increase in skeletal muscle oxidative capacity. In conclusion, reduced fatty acid mobilization and uptake appears to be a primary mediator of improved insulin sensitivity after weight loss. Moreover, enhancing fatty acid oxidative capacity via exercise training is not sufficient to prevent the insulin resistance caused by high fatty acid mobilization, such as that found in obesity.
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Affiliation(s)
- Simon Schenk
- School of Kinesiology, The University of Michigan, Ann Arbor, MI 48109-2214, USA
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Surya S, Horowitz JF, Goldenberg N, Sakharova A, Harber M, Cornford AS, Symons K, Barkan AL. The pattern of growth hormone delivery to peripheral tissues determines insulin-like growth factor-1 and lipolytic responses in obese subjects. J Clin Endocrinol Metab 2009; 94:2828-34. [PMID: 19470622 PMCID: PMC2730877 DOI: 10.1210/jc.2009-0638] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT It is unclear whether the pattern of GH delivery to peripheral tissues has important effects. OBJECTIVE The aim of the study was to compare the effects of pulsatile vs. continuous administration of GH upon metabolic and IGF-I parameters in obese subjects. SETTING The study was conducted at the General Clinical Research Center at the University of Michigan Medical Center. PARTICIPANTS Four men and five women with abdominal obesity (body mass index, 33 +/- 3 kg/m(2); body fat, 40 +/- 3%) participated in the study. INTERVENTION GH (0.5 mg/m(2) . d) was given iv for 3 d as: 1) continuous infusion (C); and 2) pulsatile boluses (P) (15% of the dose at 0700, 1300, and 1800 h and 55% at 2400 h). These trials were preceded by a basal period (B) when subjects received normal saline. MAIN OUTCOME MEASURES Rate of lipolysis and hepatic glucose production were evaluated using stable isotope tracer techniques. The composite index of insulin sensitivity (Matsuda index) was assessed using oral glucose tolerance test. RESULTS The increase in plasma IGF-I concentrations was greater (P < 0.05) with continuous GH infusion (211 +/- 31, 423 +/- 38, and 309 +/- 34 microg/liter for B, C, and P, respectively). Muscle IGF-I mRNA was significantly increased (P < 0.05) only after the continuous GH infusion (1.2 +/- 0.4, 4.4 +/- 1.3, and 2.3 +/- 0.6 arbitrary units, for B, C, and P, respectively). Only pulsatile GH augmented the rate of lipolysis (4.1 +/- 0.3, 4.8 +/- 0.7, and 7.1 +/- 1.1 mumol/kg . min for B, C, and P, respectively). GH had no effect on hepatic glucose production, but both modes of GH administration were equally effective in impairing insulin sensitivity. CONCLUSION These findings indicate that, in obese subjects, discrete components of GH secretory pattern may differentially affect IGF-I generation and lipolytic responses.
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Affiliation(s)
- Sowmya Surya
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan, 3920 Taubman Center, Ann Arbor, MI 48109-5354, USA
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Surya S, Horowitz JF, Goldenberg N, Sakharova A, Harber M, Cornford AS, Symons K, Barkan AL. The Pattern of Growth Hormone Delivery to Peripheral Tissues Determines Insulin-Like Growth Factor-1 and Lipolytic Responses in Obese Subjects. Mol Endocrinol 2009. [DOI: 10.1210/mend.23.8.9997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Knuth ND, Shrivastava CR, Horowitz JF. Reducing dietary fat from a meal increases the bioavailability of exogenous carbohydrate without altering plasma glucose concentration. J Appl Physiol (1985) 2008; 106:122-9. [PMID: 19008494 DOI: 10.1152/japplphysiol.90404.2008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The primary goal of this study was to determine the acute glycemic and endocrine responses to the reduction of fat content from a meal. On three separate occasions, nine overweight subjects (body mass index = 30 +/- 1 kg/m(2); 5 men, 4 women) consumed 1) a control meal ( approximately 800 kcal; 100 g of carbohydrate, 31 g of fat, and 30 g of protein), 2) a low-fat meal ( approximately 530 kcal; 100 g of carbohydrate, 1 g of fat, and 30 g of protein), or 3) a low-fat meal plus lipid infusion [same meal as low-fat meal, but the total energy provided was the same as control (800 kcal), with the "missing" fat ( approximately 30 g) provided via an intravenous lipid infusion]. All three meals contained [(13)C]glucose (3 mg/kg body wt) to assess the bioavailability of ingested glucose. During the 5-h period after each meal, we measured the recovery of [(13)C]glucose in plasma, plasma glucose, and insulin concentrations. We also measured plasma concentration of the gastrointestinal peptides: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and peptide YY(3-36) (PYY(3-36)). The recovery of the ingested [(13)C]glucose in the hour after ingestion was greater (P < 0.05) after the low-fat than after the control meal [area under the curve (AUC): 1,206 +/- 252 and 687 +/- 161 microM.h, respectively]. However, removing dietary fat from the meal did not affect the plasma concentration of glucose or insulin. Importantly, [(13)C]glucose recovery was not different during the low-fat and lipid infusion trials (AUC: 1,206 +/- 252 and 1,134 +/- 247 microM.h, respectively), indicating that the accelerated delivery of exogenous glucose found after removing fat from the meal is due exclusively to the reduction of fat in the gastrointestinal tract. In parallel with these findings, the reduction in fat calories from the meal reduced plasma concentration of GIP, GLP-1, and PYY(3-36). In summary, these data suggest that removing fat from the diet expedited exogenous glucose delivery into the systemic circulation and reduced the concentration of key gastrointestinal peptides, yet maintained plasma glucose concentration at control levels.
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Affiliation(s)
- Nicolas D Knuth
- Division of Kinesiology, The Univ. of Michigan, Ann Arbor, MI 48109-2214, USA
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