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Norton L, Shannon C, Gastaldelli A, DeFronzo RA. Insulin: The master regulator of glucose metabolism. Metabolism 2022; 129:155142. [PMID: 35066003 DOI: 10.1016/j.metabol.2022.155142] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 01/13/2022] [Accepted: 01/16/2022] [Indexed: 02/07/2023]
Abstract
Insulin is the master regulator of glucose, lipid, and protein metabolism. Following ingestion of an oral glucose load or mixed meal, the plasma glucose concentration rises, insulin secretion by the beta cells is stimulated and the hyperinsulinemia, working in concert with hyperglycemia, causes: (i) suppression of endogenous (primarily reflects hepatic) glucose production, (ii) stimulation of glucose uptake by muscle, liver, and adipocytes, (iii) inhibition of lipolysis leading to a decline in plasma FFA concentration which contributes to the suppression of hepatic glucose production and augmentation of muscle glucose uptake, and (iv) vasodilation in muscle, which contributes to enhanced muscle glucose disposal. Herein, the integrated physiologic impact of insulin to maintain normal glucose homeostasis is reviewed and the molecular basis of insulin's diverse actions in muscle, liver, adipocytes, and vasculature are discussed.
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Affiliation(s)
- Luke Norton
- Diabetes Division, UT Health, San Antonio, TX, United States of America
| | - Chris Shannon
- Diabetes Division, UT Health, San Antonio, TX, United States of America
| | - Amalia Gastaldelli
- Diabetes Division, UT Health, San Antonio, TX, United States of America; Cardiometabolic Risk Unit Institute of Clinical Physiology, CNR, Pisa, Italy
| | - Ralph A DeFronzo
- Diabetes Division, UT Health, San Antonio, TX, United States of America.
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2
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Tripathi R, Banerjee SK, Nirala JP, Mathur R. Simultaneous exposure to electromagnetic field from mobile phone and unimpeded fructose drinking during pre-, peri-, and post-pubertal stages perturbs the hypothalamic and hepatic regulation of energy homeostasis by early adulthood: experimental evidence. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:7438-7451. [PMID: 34476698 DOI: 10.1007/s11356-021-15841-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 08/02/2021] [Indexed: 06/13/2023]
Abstract
The present-day children-adolescents ubiquitously use the mobile phones and unrestrictedly consume fructose-laden diet. Unfortunately, a rise in the incidence of insulin resistance and fatty liver syndrome in young adults has also been recorded. To delineate a possible correlate, the effect of exposure to electromagnetic field (EMF) from the mobile phone and unrestricted fructose intake during pre-, peri-, and post-pubertal stages of development on orexigenic and anorexigenic signals arising from the hypothalamus and liver of rats is investigated here. The study design included four arms, i.e., "Normal", "Exposure Only (ExpO)", "Fructose Only (FruO)", and "Exposure with Fructose (EF)", wherein weaned rats received either "normal chow and drinking water" or "normal chow and fructose (15%) drinking solution" in presence and absence of EMF exposure (2 h/day) for 8 weeks. The results indicate that the total calories consumed by the EF were higher by early adulthood than normal, possibly under the influence of the raised levels of the orexigenic hormone, i.e., ghrelin, and it reflected as raised rate of weight gain. At early adulthood, the EF recorded mitigated response and sensitivity of insulin. Despite EF being a "fed-state", both centrally and peripherally, the glycolysis was restrained, but the gluconeogenesis was raised. Additionally, the altered lipid profile and the glycogen levels indicate that the EF developed fatty liver. The energy homeostasis of the EF was compromised as evidenced by (a) reduced expression of the glucosensors-GLUT2 and glucokinase in the hypothalamus and liver and (b) reduced expression of the cellular energy regulator-AMPK, orexigenic peptide-NPY, and anorexigenic peptide-POMC in the hypothalamus. Taken together, the present study evidences that the exposure to EMFfrom the mobile phone and unrestricted fructose intake during childhood-adolescence impairs the central and peripheral pathways that mediate the glucosensing, glucoregulation, feeding, and satiety behavior by early adulthood.
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Affiliation(s)
- Ruchi Tripathi
- Department of Pharmacology, Delhi Institute of Pharmaceutical Sciences & Research, New Delhi, India
| | - Sanjay Kumar Banerjee
- Drug Discovery Research Centre, Translational Health Science and Technology Institute, Faridabad, India
- Current Address: Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Guwahati, India
| | - Jay Prakash Nirala
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Rajani Mathur
- Department of Pharmacology, Delhi Institute of Pharmaceutical Sciences & Research, New Delhi, India.
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3
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Zhu S, Li Y, Gao H, Hou G, Cui X, Chen S, Ding C. Identification and assessment of pulmonary Cryptococcus neoformans infection by blood serum surface-enhanced Raman spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 260:119978. [PMID: 34077861 DOI: 10.1016/j.saa.2021.119978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 04/06/2021] [Accepted: 05/17/2021] [Indexed: 06/12/2023]
Abstract
Cryptococcus neoformans (C. neoformans) is a causative agent for acute pulmonary infection, which can further develop to lethal meningoencephalitis if untreated. The meningoencephalitis infection can be prevented, if timely treatment on pulmonary cryptococcal infection can be implemented based on its early diagnosis and accurate assessment. In this study, blood serum surface-enhanced Raman spectroscopy (SERS) method was investigated on identification and assessment of pulmonary C. neoformans infection. The serum SERS measurements were collected from the mice infected with C. neoformans and the healthy mice, in which the infected mice were further divided into four subgroups according to the duration of infection. Based on those SRES measurements, biochemical differences were analyzed among those different groups to investigate the potential biomarkers for identifying and assessing the pulmonary C. neoformans infection. Furthermore, partial least square (PLS) analysis followed by linear discriminant analysis (LDA) model was employed to identify pulmonary cryptococcal infection and to assess the degrees of infection with the accuracies of 96.7% and 85.3%, respectively. Therefore, our study has demonstrated the great clinical potential of using serum SERS technique for an accurate identification and assessment of pulmonary cryptococcal infection.
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Affiliation(s)
- Shanshan Zhu
- Research Institute for Medical and Biological Engineering, Ningbo University, Ningbo 315211, China; College of Medicine and Biological Information Engineering, Northeastern University, Shenyang 110169, China
| | - Yanjian Li
- College of Life and Health Sciences, Northeastern University, Shenyang 110169, China
| | - Han Gao
- College of Medicine and Biological Information Engineering, Northeastern University, Shenyang 110169, China
| | - Gang Hou
- Department of Pulmonary and Critical Care Medicine, China-Japan Friendship Hospital, Beijing 100029, China; National Center of Respiratory Medicine, China
| | - Xiaoyu Cui
- College of Medicine and Biological Information Engineering, Northeastern University, Shenyang 110169, China; Key Laboratory of Intelligent Computing in Medical Image, Ministry of Education, China
| | - Shuo Chen
- College of Medicine and Biological Information Engineering, Northeastern University, Shenyang 110169, China; Key Laboratory of Intelligent Computing in Medical Image, Ministry of Education, China.
| | - Chen Ding
- College of Life and Health Sciences, Northeastern University, Shenyang 110169, China.
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Hjelholt AJ, Charidemou E, Griffin JL, Pedersen SB, Gudiksen A, Pilegaard H, Jessen N, Møller N, Jørgensen JOL. Insulin resistance induced by growth hormone is linked to lipolysis and associated with suppressed pyruvate dehydrogenase activity in skeletal muscle: a 2 × 2 factorial, randomised, crossover study in human individuals. Diabetologia 2020; 63:2641-2653. [PMID: 32945898 DOI: 10.1007/s00125-020-05262-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 07/15/2020] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS Growth hormone (GH) causes insulin resistance that is linked to lipolysis, but the underlying mechanisms are unclear. We investigated if GH-induced insulin resistance in skeletal muscle involves accumulation of diacylglycerol (DAG) and ceramide as well as impaired insulin signalling, or substrate competition between fatty acids and glucose. METHODS Nine GH-deficient male participants were randomised and examined in a 2 × 2 factorial design with and without administration of GH and acipimox (an anti-lipolytic compound). As-treated analyses were performed, wherefore data from three visits from two patients were excluded due to incorrect GH administration. The primary outcome was insulin sensitivity, expressed as the AUC of the glucose infusion rate (GIRAUC), and furthermore, the levels of DAGs and ceramides, insulin signalling and the activity of the active form of pyruvate dehydrogenase (PDHa) were assessed in skeletal muscle biopsies obtained in the basal state and during a hyperinsulinaemic-euglycaemic clamp (HEC). RESULTS Co-administration of acipimox completely suppressed the GH-induced elevation in serum levels of NEFA (GH versus GH+acipimox, p < 0.0001) and abrogated GH-induced insulin resistance (mean GIRAUC [95% CI] [mg min-1 kg-1] during the HEC: control, 595 [493, 718]; GH, 468 [382, 573]; GH+acipimox, 654 [539, 794]; acipimox, 754 [618, 921]; GH vs GH+acipimox: p = 0.004). GH did not significantly change either the accumulation of DAGs and ceramides or insulin signalling in skeletal muscle, but GH antagonised the insulin-stimulated increase in PDHa activity (mean ± SEM [% from the basal state to the HEC]: control, 47 ± 19; GH, -15 ± 21; GH+acipimox, 3 ± 21; acipimox, 57 ± 22; main effect: p = 0.02). CONCLUSIONS/INTERPRETATION GH-induced insulin resistance in skeletal muscle is: (1) causally linked to lipolysis; (2) not associated with either accumulation of DAGs and ceramides or impaired insulin signalling; (3) likely to involve substrate competition between glucose and lipid intermediates. TRIAL REGISTRATION ClinicalTrials.gov NCT02782208 FUNDING: The work was supported by the Grant for Growth Innovation (GGI), which was funded by Merck KGaA, Darmstadt, Germany. Graphical abstract.
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Affiliation(s)
- Astrid J Hjelholt
- Medical Research Laboratory, Department of Clinical Medicine, Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N, Denmark.
- Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus C, Denmark.
| | - Evelina Charidemou
- Department of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, UK
| | - Julian L Griffin
- Department of Biochemistry and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, UK
| | - Steen B Pedersen
- Medical Research Laboratory, Department of Clinical Medicine, Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N, Denmark
| | - Anders Gudiksen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Henriette Pilegaard
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Niels Jessen
- Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus C, Denmark
- Steno Diabetes Centre Aarhus, Aarhus University Hospital, Aarhus N, Denmark
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
| | - Niels Møller
- Medical Research Laboratory, Department of Clinical Medicine, Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N, Denmark
| | - Jens O L Jørgensen
- Medical Research Laboratory, Department of Clinical Medicine, Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N, Denmark
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Shakil MS, Hasan MA, Uddin MF, Islam A, Nahar A, Das H, Khan MNI, Dey BP, Rokeya B, Hoque SM. In Vivo Toxicity Studies of Chitosan-Coated Cobalt Ferrite Nanocomplex for Its Application as MRI Contrast Dye. ACS APPLIED BIO MATERIALS 2020; 3:7952-7964. [DOI: 10.1021/acsabm.0c01069] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Md. Salman Shakil
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar Union 1342, Bangladesh
- Department of Pharmacology & Toxicology, University of Otago, Dunedin 9016, New Zealand
| | - Md. Ashraful Hasan
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar Union 1342, Bangladesh
| | - Md. Forhad Uddin
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar Union 1342, Bangladesh
| | - Aminul Islam
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
- Department of Physics, Dhaka University, Dhaka 1000, Bangladesh
| | - Arijun Nahar
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
| | - Harinarayan Das
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
| | | | - Bishnu Pada Dey
- Department of Pathology, Bangabandhu Sheikh Mujib Medical University, Dhaka 1000, Bangladesh
| | - Begum Rokeya
- Department of Pharmacology, Bangladesh Institute of Health Sciences, Dhaka 1216, Bangladesh
| | - S. Manjura Hoque
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
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Broskey NT, Zou K, Dohm GL, Houmard JA. Plasma Lactate as a Marker for Metabolic Health. Exerc Sport Sci Rev 2020; 48:119-124. [PMID: 32271180 DOI: 10.1249/jes.0000000000000220] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Blood lactate concentrations traditionally have been used as an index of exercise intensity or clinical hyperlactatemia. However, more recent data suggest that fasting plasma lactate can also be indicative of the risk for subsequent metabolic disease. The hypothesis presented is that fasting blood lactate accumulation reflects impaired mitochondrial substrate use, which in turn influences metabolic disease risk.
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Affiliation(s)
| | - Kai Zou
- Department of Exercise and Health Sciences, University of Massachusetts Boston, Boston, MA
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Høgild ML, Gudiksen A, Pilegaard H, Stødkilde-Jørgensen H, Pedersen SB, Møller N, Jørgensen JOL, Jessen N. Redundancy in regulation of lipid accumulation in skeletal muscle during prolonged fasting in obese men. Physiol Rep 2020; 7:e14285. [PMID: 31724339 PMCID: PMC6854099 DOI: 10.14814/phy2.14285] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Fasting in human subjects shifts skeletal muscle metabolism toward lipid utilization and accumulation, including intramyocellular lipid (IMCL) deposition. Growth hormone (GH) secretion amplifies during fasting and promotes lipolysis and lipid oxidation, but it is unknown to which degree lipid deposition and metabolism in skeletal muscle during fasting depends on GH action. To test this, we studied nine obese but otherwise healthy men thrice: (a) in the postabsorptive state (“CTRL”), (b) during 72‐hr fasting (“FAST”), and (c) during 72‐hr fasting and treatment with a GH antagonist (GHA) (“FAST + GHA”). IMCL was assessed by magnetic resonance spectroscopy (MRS) and blood samples were drawn for plasma metabolomics assessment while muscle biopsies were obtained for measurements of regulators of substrate metabolism. Prolonged fasting was associated with elevated GH levels and a pronounced GHA‐independent increase in circulating medium‐ and long‐chain fatty acids, glycerol, and ketone bodies indicating increased supply of lipid intermediates to skeletal muscle. Additionally, fasting was associated with a release of short‐, medium‐, and long‐chain acylcarnitines to the circulation from an increased β‐oxidation. This was consistent with a ≈55%–60% decrease in pyruvate dehydrogenase (PDHa) activity. Opposite, IMCL content increased ≈75% with prolonged fasting without an effect of GHA. We suggest that prolonged fasting increases lipid uptake in skeletal muscle and saturates lipid oxidation, both favoring IMCL deposition. This occurs without a detectable effect of GHA on skeletal muscle lipid metabolism.
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Affiliation(s)
- Morten L Høgild
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Anders Gudiksen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | | | - Hans Stødkilde-Jørgensen
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,The MR Research Center, Aarhus University Hospital, Copenhagen, Denmark
| | - Steen Bønløkke Pedersen
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Niels Møller
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Jens O L Jørgensen
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Niels Jessen
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus, Denmark.,Department of Biomedicine, Aarhus University, Aarhus, Denmark
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8
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Parry SA, Turner MC, Woods RM, James LJ, Ferguson RA, Cocks M, Whytock KL, Strauss JA, Shepherd SO, Wagenmakers AJM, van Hall G, Hulston CJ. High-Fat Overfeeding Impairs Peripheral Glucose Metabolism and Muscle Microvascular eNOS Ser1177 Phosphorylation. J Clin Endocrinol Metab 2020; 105:5568321. [PMID: 31513265 DOI: 10.1210/clinem/dgz018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Accepted: 09/06/2019] [Indexed: 11/19/2022]
Abstract
CONTEXT The mechanisms responsible for dietary fat-induced insulin resistance of skeletal muscle and its microvasculature are only partially understood. OBJECTIVE To determine the impact of high-fat overfeeding on postprandial glucose fluxes, muscle insulin signaling, and muscle microvascular endothelial nitric oxide synthase (eNOS) content and activation. DESIGN Fifteen non-obese volunteers consumed a high-fat (64%) high-energy (+47%) diet for 7 days. Experiments were performed before and after the diet. Stable isotope tracers were used to determine glucose fluxes in response to carbohydrate plus protein ingestion. Muscle insulin signaling was determined as well as the content and activation state of muscle microvascular eNOS. RESULTS High-fat overfeeding impaired postprandial glycemic control as demonstrated by higher concentrations of glucose (+11%; P = 0.004) and insulin (+19%; P = 0.035). Carbohydrate plus protein ingestion suppressed endogenous glucose production to a similar extent before and after the diet. Conversely, high-fat overfeeding reduced whole-body glucose clearance (-16%; P = 0.021) and peripheral insulin sensitivity (-26%; P = 0.006). This occurred despite only minor alterations in skeletal muscle insulin signaling. High-fat overfeeding reduced eNOS content in terminal arterioles (P = 0.017) and abolished the increase in eNOS Ser1177 phosphorylation that was seen after carbohydrate plus protein ingestion. CONCLUSION High-fat overfeeding impaired whole-body glycemic control due to reduced glucose clearance, not elevated endogenous glucose production. The finding that high-fat overfeeding abolished insulin-mediated eNOS Ser1177 phosphorylation in the terminal arterioles suggests that impairments in the vasodilatory capacity of the skeletal muscle microvasculature may contribute to early dietary fat-induced impairments in glycemic control.
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Affiliation(s)
- Siôn A Parry
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
| | - Mark C Turner
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
- University Hospitals of Leicester NHS Trust, Infirmary Square, Leicester, UK
| | - Rachel M Woods
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
| | - Lewis J James
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
| | - Richard A Ferguson
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
| | - Matthew Cocks
- School of Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Katie L Whytock
- School of Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Juliette A Strauss
- School of Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Sam O Shepherd
- School of Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Anton J M Wagenmakers
- School of Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK
| | - Gerrit van Hall
- Clinical Metabolomics Core Facility, Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Carl J Hulston
- School of Sport, Exercise & Health Sciences, Loughborough University, Loughborough, UK
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Zou K, Hinkley JM, Park S, Zheng D, Jones TE, Pories WJ, Hornby PJ, Lenhard J, Dohm GL, Houmard JA. Altered tricarboxylic acid cycle flux in primary myotubes from severely obese humans. Int J Obes (Lond) 2019; 43:895-905. [PMID: 29892037 DOI: 10.1038/s41366-018-0137-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 04/27/2018] [Accepted: 05/10/2018] [Indexed: 11/08/2022]
Abstract
BACKGROUND/OBJECTIVE The partitioning of glucose toward glycolytic end products rather than glucose oxidation and glycogen storage is evident in skeletal muscle with severe obesity and type 2 diabetes. The purpose of the present study was to determine the possible mechanism by which severe obesity alters insulin-mediated glucose partitioning in human skeletal muscle. SUBJECTS/METHODS Primary human skeletal muscle cells (HSkMC) were isolated from lean (BMI = 23.6 ± 2.6 kg/m2, n = 9) and severely obese (BMI = 48.8 ± 1.9 kg/m2, n = 8) female subjects. Glucose oxidation, glycogen synthesis, non-oxidized glycolysis, pyruvate oxidation, and targeted TCA cycle metabolomics were examined in differentiated myotubes under basal and insulin-stimulated conditions. RESULTS Myotubes derived from severely obese subjects exhibited attenuated response of glycogen synthesis (20.3%; 95% CI [4.7, 28.8]; P = 0.017) and glucose oxidation (5.6%; 95% CI [0.3, 8.6]; P = 0.046) with a concomitant greater increase (23.8%; 95% CI [5.7, 47.8]; P = 0.004) in non-oxidized glycolytic end products with insulin stimulation in comparison to the lean group (34.2% [24.9, 45.1]; 13.1% [8.6, 16.4], and 2.9% [-4.1, 12.2], respectively). These obesity-related alterations in glucose partitioning appeared to be linked with reduced TCA cycle flux, as 2-[14C]-pyruvate oxidation (358.4 pmol/mg protein/min [303.7, 432.9] vs. lean 439.2 pmol/mg protein/min [393.6, 463.1]; P = 0.013) along with several TCA cycle intermediates, were suppressed in the skeletal muscle of severely obese individuals. CONCLUSIONS These data suggest that with severe obesity the partitioning of glucose toward anaerobic glycolysis in response to insulin is a resilient characteristic of human skeletal muscle. This altered glucose partitioning appeared to be due, at least in part, to a reduction in TCA cycle flux.
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Affiliation(s)
- Kai Zou
- Department of Exercise and Health Sciences, University of Massachusetts Boston, Boston, MA, USA.
- Department of Kinesiology, East Carolina University, Greenville, NC, USA.
- Human Performance Laboratory, East Carolina University, Greenville, NC, USA.
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA.
| | - J Matthew Hinkley
- Department of Kinesiology, East Carolina University, Greenville, NC, USA
- Human Performance Laboratory, East Carolina University, Greenville, NC, USA
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, FL, USA
| | - Sanghee Park
- Department of Kinesiology, East Carolina University, Greenville, NC, USA
- Human Performance Laboratory, East Carolina University, Greenville, NC, USA
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA
| | - Donghai Zheng
- Department of Kinesiology, East Carolina University, Greenville, NC, USA
- Human Performance Laboratory, East Carolina University, Greenville, NC, USA
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA
| | - Terry E Jones
- Department of Physical Therapy, East Carolina University, Greenville, NC, USA
| | - Walter J Pories
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA
- Department of Surgery, East Carolina University, Greenville, NC, USA
| | | | - James Lenhard
- Janssen Research & Development LLC, Spring House, PA, USA
| | - G Lynis Dohm
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA
- Department of Physiology, East Carolina University, Greenville, NC, USA
| | - Joseph A Houmard
- Department of Kinesiology, East Carolina University, Greenville, NC, USA
- Human Performance Laboratory, East Carolina University, Greenville, NC, USA
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA
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10
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Effects of Centella asiatica on skeletal muscle structure and key enzymes of glucose and glycogen metabolism in type 2 diabetic rats. Biomed Pharmacother 2019; 112:108715. [DOI: 10.1016/j.biopha.2019.108715] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 02/20/2019] [Accepted: 02/20/2019] [Indexed: 12/19/2022] Open
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11
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Tella T, Masola B, Mukaratirwa S. The effect of Psidium guajava aqueous leaf extract on liver glycogen enzymes, hormone sensitive lipase and serum lipid profile in diabetic rats. Biomed Pharmacother 2018; 109:2441-2446. [PMID: 30551504 DOI: 10.1016/j.biopha.2018.11.137] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 11/26/2018] [Accepted: 11/27/2018] [Indexed: 11/19/2022] Open
Abstract
Diabetes mellitus is characterized by hyperglycaemia that results from defects in insulin secretion or insulin action and is accompanied by general disturbances metabolism. Psidium guajava (PG) leaf is known to have antidiabetic effects that include lowering of blood glucose. The aim of the study was to investigate the effect of PG leaf extract on tissue activity of glycogen synthase (GS) and glycogen phosphorylase (GP); tissue activity of hormone sensitive lipase (HSL); serum lipid profile; and serum enzyme biomarkers of tissue damage. Diabetes was induced in male Sprague-Dawley rats with a single dose of 40 mg/kg body weight streptozotocin. The aqueous extract of PG leaves was used to treat both normal and diabetic animals (400 mg/kg body weight) for 2 weeks while control animals were treated with the vehicle. At the end of the treatment period, blood, liver and adipose tissue samples were collected from the euthanized animals. The results show that PG extract significantly decreased (P < 0.05) HSL activity in adipose tissue and liver of diabetic animals which was accompanied by increased glycogen levels, reduced serum triglycerides, total cholesterol, LDL-cholesterol and increased HDL-cholesterol. This study demonstrates that P. guajava has significant anti-diabetic effects that include increased glycogen storage and reduced HSL activity in the liver and adipose tissue with an improved serum lipid profile.
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Affiliation(s)
- Toluwani Tella
- Discipline of Biochemistry, School of Life Sciences, University of KwaZulu-Natal (Westville Campus), Private Bag X54001, Durban 4000, South Africa
| | - Bubuya Masola
- Discipline of Biochemistry, School of Life Sciences, University of KwaZulu-Natal (Westville Campus), Private Bag X54001, Durban 4000, South Africa
| | - Samson Mukaratirwa
- Discipline of Biological Sciences, School of Life Sciences, University of KwaZulu-Natal (Westville Campus), Private Bag X54001, Durban 4000, South Africa.
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Bakshi I, Suryana E, Small L, Quek LE, Brandon AE, Turner N, Cooney GJ. Fructose bisphosphatase 2 overexpression increases glucose uptake in skeletal muscle. J Endocrinol 2018; 237:101-111. [PMID: 29507044 DOI: 10.1530/joe-17-0555] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 03/05/2018] [Indexed: 12/31/2022]
Abstract
Skeletal muscle is a major tissue for glucose metabolism and can store glucose as glycogen, convert glucose to lactate via glycolysis and fully oxidise glucose to CO2 Muscle has a limited capacity for gluconeogenesis but can convert lactate and alanine to glycogen. Gluconeogenesis requires FBP2, a muscle-specific form of fructose bisphosphatase that converts fructose-1,6-bisphosphate (F-1,6-bisP) to fructose-6-phosphate (F-6-P) opposing the activity of the ATP-consuming enzyme phosphofructokinase (PFK). In mammalian muscle, the activity of PFK is normally 100 times higher than FBP2 and therefore energy wasting cycling between PFK and FBP2 is low. In an attempt to increase substrate cycling between F-6-P and F-1,6-bisP and alter glucose metabolism, we overexpressed FBP2 using a muscle-specific adeno-associated virus (AAV-tMCK-FBP2). AAV was injected into the right tibialis muscle of rats, while the control contralateral left tibialis received a saline injection. Rats were fed a chow or 45% fat diet (HFD) for 5 weeks after which, hyperinsulinaemic-euglycaemic clamps were performed. Infection of the right tibialis with AAV-tMCK-FBP2 increased FBP2 activity 10 fold on average in chow and HFD rats (P < 0.0001). Overexpression of FBP2 significantly increased insulin-stimulated glucose uptake in tibialis of chow animals (control 14.3 ± 1.7; FBP2 17.6 ± 1.6 µmol/min/100 g) and HFD animals (control 9.6 ± 1.1; FBP2 11.2 ± 1.1µmol/min/100 g). The results suggest that increasing the capacity for cycling between F-1,6-bisP and F-6-P can increase the metabolism of glucose by introducing a futile cycle in muscle, but this increase is not sufficient to overcome muscle insulin resistance.
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Affiliation(s)
- Ishita Bakshi
- Diabetes and Metabolism DivisionGarvan Institute, Sydney, New South Wales, Australia
| | - Eurwin Suryana
- Diabetes and Metabolism DivisionGarvan Institute, Sydney, New South Wales, Australia
| | - Lewin Small
- Diabetes and Metabolism DivisionGarvan Institute, Sydney, New South Wales, Australia
| | - Lake-Ee Quek
- School of Mathematics and StatisticsUniversity of Sydney, Charles Perkins Centre, Sydney, New South Wales, Australia
| | - Amanda E Brandon
- Diabetes and Metabolism DivisionGarvan Institute, Sydney, New South Wales, Australia
- Sydney Medical SchoolCharles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Nigel Turner
- Department of PharmacologySchool of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Gregory J Cooney
- Diabetes and Metabolism DivisionGarvan Institute, Sydney, New South Wales, Australia
- Sydney Medical SchoolCharles Perkins Centre, University of Sydney, Sydney, New South Wales, Australia
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13
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Henley ZA, Bax BD, Inglesby LM, Champigny A, Gaines S, Faulder P, Le J, Thomas DA, Washio Y, Baldwin IR. From PIM1 to PI3Kδ via GSK3β: Target Hopping through the Kinome. ACS Med Chem Lett 2017; 8:1093-1098. [PMID: 29057057 DOI: 10.1021/acsmedchemlett.7b00296] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 09/05/2017] [Indexed: 02/07/2023] Open
Abstract
Selective inhibitors of phosphoinositide 3-kinase delta are of interest for the treatment of inflammatory diseases. Initial optimization of a 3-substituted indazole hit compound targeting the kinase PIM1 focused on improving selectivity over GSK3β through consideration of differences in the ATP binding pockets. Continued kinase cross-screening showed PI3Kδ activity in a series of 4,6-disubstituted indazole compounds, and subsequent structure-activity relationship exploration led to the discovery of an indole-containing lead compound as a potent PI3Kδ inhibitor with selectivity over the other PI3K isoforms.
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Affiliation(s)
- Zoë A. Henley
- Refractory Respiratory Inflammation DPU, GlaxoSmithKline R&D, Gunnels Wood Road, Stevenage, SG1 2NY, U.K
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14
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Elam MB, Majumdar G, Mozhui K, Gerling IC, Vera SR, Fish-Trotter H, Williams RW, Childress RD, Raghow R. Patients experiencing statin-induced myalgia exhibit a unique program of skeletal muscle gene expression following statin re-challenge. PLoS One 2017; 12:e0181308. [PMID: 28771594 PMCID: PMC5542661 DOI: 10.1371/journal.pone.0181308] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 06/29/2017] [Indexed: 01/21/2023] Open
Abstract
Statins, the 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase inhibitors, are widely prescribed for treatment of hypercholesterolemia. Although statins are generally well tolerated, up to ten percent of statin-treated patients experience myalgia symptoms, defined as muscle pain without elevated creatinine phosphokinase (CPK) levels. Myalgia is the most frequent reason for discontinuation of statin therapy. The mechanisms underlying statin myalgia are not clearly understood. To elucidate changes in gene expression associated with statin myalgia, we compared profiles of gene expression in skeletal muscle biopsies from patients with statin myalgia who were undergoing statin re-challenge (cases) versus those of statin-tolerant controls. A robust separation of case and control cohorts was revealed by Principal Component Analysis of differentially expressed genes (DEGs). To identify putative gene expression and metabolic pathways that may be perturbed in skeletal muscles of patients with statin myalgia, we subjected DEGs to Ingenuity Pathways (IPA) and DAVID (Database for Annotation, Visualization and Integrated Discovery) analyses. The most prominent pathways altered by statins included cellular stress, apoptosis, cell senescence and DNA repair (TP53, BARD1, Mre11 and RAD51); activation of pro-inflammatory immune response (CXCL12, CST5, POU2F1); protein catabolism, cholesterol biosynthesis, protein prenylation and RAS-GTPase activation (FDFT1, LSS, TP53, UBD, ATF2, H-ras). Based on these data we tentatively conclude that persistent myalgia in response to statins may emanate from cellular stress underpinned by mechanisms of post-inflammatory repair and regeneration. We also posit that this subset of individuals is genetically predisposed to eliciting altered statin metabolism and/or increased end-organ susceptibility that lead to a range of statin-induced myopathies. This mechanistic scenario is further bolstered by the discovery that a number of single nucleotide polymorphisms (e.g., SLCO1B1, SLCO2B1 and RYR2) associated with statin myalgia and myositis were observed with increased frequency among patients with statin myalgia.
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Affiliation(s)
- Marshall B. Elam
- Department of Veterans Affairs Medical Center-Memphis, Memphis, Tennessee, United States of America
- Department of Pharmacology, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
- * E-mail: (MBE); (RR)
| | - Gipsy Majumdar
- Department of Veterans Affairs Medical Center-Memphis, Memphis, Tennessee, United States of America
- Department of Pharmacology, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
| | - Khyobeni Mozhui
- Department of Preventive Medicine, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
| | - Ivan C. Gerling
- Department of Veterans Affairs Medical Center-Memphis, Memphis, Tennessee, United States of America
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
| | - Santiago R. Vera
- Department of Veterans Affairs Medical Center-Memphis, Memphis, Tennessee, United States of America
| | - Hannah Fish-Trotter
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
| | - Robert W. Williams
- Department of Genetics, Genomics and Informatics, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Richard D. Childress
- Department of Veterans Affairs Medical Center-Memphis, Memphis, Tennessee, United States of America
- Department of Medicine, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
| | - Rajendra Raghow
- Department of Veterans Affairs Medical Center-Memphis, Memphis, Tennessee, United States of America
- Department of Pharmacology, University of Tennessee Health Sciences Center, Memphis, Tennessee, United States of America
- * E-mail: (MBE); (RR)
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15
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Bosy-Westphal A, Hägele F, Nas A. Impact of dietary glycemic challenge on fuel partitioning. Eur J Clin Nutr 2016; 71:327-330. [PMID: 27901033 DOI: 10.1038/ejcn.2016.230] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 10/11/2016] [Indexed: 01/04/2023]
Abstract
The 'carbohydrate-insulin theory of obesity' is used to justify popular health claims stating that carbohydrates make you fat or a high glycemic load and consumption of sugar-sweetened beverages (SSBs) and breakfast skipping increase fat gain. According to this theory, the elevated postprandial insulin secretion to a high glycemic challenge is blamed as a causal mechanism by directing nutrients away from oxidation in muscle towards storage in adipose tissue. Scientific evidence is however largely disagreeing with an adverse effect of postprandial hyperinsulinemia on fuel partitioning. Possible reasons for this disagreement are differences in insulin sensitivity and energy balance. Diet-induced hyperinsulinemia may lead to a higher fat storage only at a positive energy balance. A shift in fuel partitioning towards fat storage requires improved or maintained insulin sensitivity in adipose tissue when compared with skeletal muscle. This may be the case during refeeding (after weight loss), physical inactivity or in metabolically healthy obese subjects (relative to insulin-resistant subjects). The adverse effect of a high-glycemic diet, SSBs consumption or breakfast skipping on body weight is likely due to increased energy consumption rather than to increased fat storage.
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Affiliation(s)
- A Bosy-Westphal
- Institut für Ernährungsmedizin, Angewandte Ernährungswissenschaft, Universität Hohenheim, Stuttgart, Germany
| | - F Hägele
- Institut für Ernährungsmedizin, Angewandte Ernährungswissenschaft, Universität Hohenheim, Stuttgart, Germany
| | - A Nas
- Institut für Ernährungsmedizin, Angewandte Ernährungswissenschaft, Universität Hohenheim, Stuttgart, Germany
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16
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Consitt LA, Saxena G, Saneda A, Houmard JA. Age-related impairments in skeletal muscle PDH phosphorylation and plasma lactate are indicative of metabolic inflexibility and the effects of exercise training. Am J Physiol Endocrinol Metab 2016; 311:E145-56. [PMID: 27221120 PMCID: PMC4967149 DOI: 10.1152/ajpendo.00452.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 05/19/2016] [Indexed: 01/12/2023]
Abstract
The purpose of this study was to determine whether plasma lactate and skeletal muscle glucose regulatory pathways, specifically PDH dephosphorylation, are impaired during hyperinsulinemic conditions in middle- to older-aged individuals and determine whether exercise training could improve key variables responsible for skeletal muscle PDH regulation. Eighteen young (19-29 yr; n = 9 males and 9 females) and 20 middle- to older-aged (57-82 yr; n = 10 males and 10 females) individuals underwent a 2-h euglycemic hyperinsulinemic clamp. Plasma samples were obtained at baseline and at 30, 50, 90, and 120 min for analysis of lactate, and skeletal muscle biopsies were performed at 60 min for analysis of protein associated with glucose metabolism. In response to insulin, plasma lactate was elevated in aged individuals when normalized to insulin action. Insulin-stimulated phosphorylation of skeletal muscle PDH on serine sites 232, 293, and 300 decreased in young individuals only. Changes in insulin-stimulated PDH phosphorylation were positively related to changes in plasma lactate. No age-related differences were observed in skeletal muscle phosphorylation of LDH, GSK-3α, or GSK-3β in response to insulin or PDP1, PDP2, PDK2, PDK4, or MPC1 total protein. Twelve weeks of endurance- or strength-oriented exercise training improved insulin-stimulated PDH dephosphorylation, which was related to a reduced lactate response. These findings suggest that impairments in insulin-induced PDH regulation in a sedentary aging population contribute to impaired glucose metabolism and that exercise training is an effective intervention for treating metabolic inflexibility.
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Affiliation(s)
- Leslie A Consitt
- Department of Biomedical Sciences, Ohio University, Athens, Ohio; Ohio Musculoskeletal and Neurological Institute, Ohio University, Athens, Ohio; Diabetes Institute, Ohio University, Athens, Ohio;
| | - Gunjan Saxena
- Department of Biomedical Sciences, Ohio University, Athens, Ohio
| | - Alicson Saneda
- Department of Biological Sciences, Ohio University, Athens, Ohio
| | - Joseph A Houmard
- Department of Kinesiology, Human Performance Laboratory, East Carolina University, Greenville, North Carolina; and East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina
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17
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Andersen LW, Berg KM, Montissol S, Sulmonte C, Balkema J, Cocchi MN, Wolfe RE, Balasubramanyam A, Liu X, Donnino MW. Pyruvate Dehydrogenase Activity Is Decreased in Emergency Department Patients With Diabetic Ketoacidosis. Acad Emerg Med 2016; 23:685-9. [PMID: 26733088 DOI: 10.1111/acem.12897] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 11/07/2015] [Accepted: 11/08/2015] [Indexed: 11/26/2022]
Abstract
OBJECTIVES The pyruvate dehydrogenase complex (PDH) is an essential enzyme in aerobic metabolism. Ketones are known to inhibit PDH activity, but the extent of this inhibition is unknown in patients with diabetic ketoacidosis (DKA). METHODS We enrolled adult patients presenting to the emergency department in hyperglycemic crisis. Patients were classified as DKA or hyperglycemia without ketoacidosis based on laboratory criteria. Healthy controls were also enrolled. PDH activity and quantity were measured in isolated peripheral blood mononuclear cells. We compared PDH values between groups and measured the relationship of PDH values to measures of acid-base status. RESULTS Twenty-seven patients (17 with DKA) and 31 controls were enrolled. Patients with DKA had lower PDH activity and quantity compared to the two other groups. PDH activity was significantly correlated with serum bicarbonate and pH and inversely correlated with the anion gap. CONCLUSIONS DKA is associated with greater suppression of PDH activity than hyperglycemia without ketoacidosis, and this is correlated with measures of acid-base status. Future studies may determine whether PDH depression plays a role in the pathophysiology of DKA and whether modification of PDH could decrease time to DKA resolution.
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Affiliation(s)
- Lars W. Andersen
- The Department of Emergency Medicine; Beth Israel Deaconess Medical Center; Boston MA
- The Department of Anesthesiology; Aarhus University Hospital; Aarhus Denmark
| | - Katherine M. Berg
- The Department of Medicine; Division of Pulmonary and Critical Care; Beth Israel Deaconess Medical Center; Boston MA
| | - Sophia Montissol
- The Department of Emergency Medicine; Beth Israel Deaconess Medical Center; Boston MA
| | - Christopher Sulmonte
- The Department of Emergency Medicine; Beth Israel Deaconess Medical Center; Boston MA
| | - Julia Balkema
- The Department of Emergency Medicine; Beth Israel Deaconess Medical Center; Boston MA
- The Department of Anesthesia Critical Care; Division of Critical Care; Beth Israel Deaconess Medical Center; Boston MA
| | - Michael N. Cocchi
- The Department of Emergency Medicine; Beth Israel Deaconess Medical Center; Boston MA
- The Department of Anesthesia Critical Care; Division of Critical Care; Beth Israel Deaconess Medical Center; Boston MA
| | - Richard E. Wolfe
- The Department of Emergency Medicine; Beth Israel Deaconess Medical Center; Boston MA
| | - Ashok Balasubramanyam
- The Translational Metabolism Unit; Diabetes Research Center; Division of Diabetes, Endocrinology and Metabolism; Baylor College of Medicine; Houston TX
- The Endocrine Service; Ben Taub General Hospital; Houston TX
| | - Xiaowen Liu
- The Department of Emergency Medicine; Beth Israel Deaconess Medical Center; Boston MA
| | - Michael W. Donnino
- The Department of Emergency Medicine; Beth Israel Deaconess Medical Center; Boston MA
- The Department of Medicine; Division of Pulmonary and Critical Care; Beth Israel Deaconess Medical Center; Boston MA
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18
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Mukundwa A, Mukaratirwa S, Masola B. Effects of oleanolic acid on the insulin signaling pathway in skeletal muscle of streptozotocin-induced diabetic male Sprague-Dawley rats. J Diabetes 2016; 8:98-108. [PMID: 25564701 DOI: 10.1111/1753-0407.12260] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/08/2014] [Accepted: 12/19/2014] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND The pant-derived triterpene oleanolic acid (OA) has been shown to have antidiabetic effects, but its action on the insulin signaling cascade has not been fully elucidated. The aim of the present study was to investigate the effects of OA on aspects of the phosphatidylinositol 3-kinase/Akt insulin signaling cascade in skeletal muscle of streptozotocin-induced type 1 diabetic male Sprague-Dawley rats. METHODS Diabetic and non-diabetic rats were treated with insulin (4 IU/kg), OA (80 mg/kg), and the combination of OA + insulin in acute 60-min and sub-chronic 14-day studies. Single and daily doses were administered in the acute and sub-chronic studies, respectively. In acute studies, phosphorylated (p-) Akt and p-glycogen synthase (GS) expression was evaluated. In sub-chronic studies, GS and glycogen phosphorylase (GP) expression and activity were evaluated, as were glycogen levels. RESULTS The findings show that OA enhances insulin-stimulated hypoglycemic effects in diabetic rats. In the acute study, OA increased levels of p-Akt and decreased levels of p-GS. In the sub-chronic study, OA increased both GS and GP activity, whereas OA + insulin increased GS and decreased GP activity. Treatment of rats with OA and OA + insulin increased GS expression in the skeletal muscle of diabetic rats and decreased GP expression. Glycogen levels were increased by OA but decreased OA + insulin treatment. CONCLUSION Oleanolic acid in synergy with insulin can enhance activation of the insulin signaling pathway. Furthermore, the present study provides evidence of OA activation of insulin signaling enzymes independent of insulin.
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Affiliation(s)
- Andrew Mukundwa
- Discipline of Biochemistry, School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Durban, South Africa
| | - Samson Mukaratirwa
- Discipline of Biological Sciences, School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Durban, South Africa
| | - Bubuya Masola
- Discipline of Biochemistry, School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Durban, South Africa
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Hauton D, Al-Shammari A, Gaffney EA, Egginton S. Maternal hypoxia decreases capillary supply and increases metabolic inefficiency leading to divergence in myocardial oxygen supply and demand. PLoS One 2015; 10:e0127424. [PMID: 26030353 PMCID: PMC4452690 DOI: 10.1371/journal.pone.0127424] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 04/15/2015] [Indexed: 12/04/2022] Open
Abstract
Maternal hypoxia is associated with a decrease in left ventricular capillary density while cardiac performance is preserved, implying a mismatch between metabolism and diffusive exchange. We hypothesised this requires a switch in substrate metabolism to maximise efficiency of ATP production from limited oxygen availability. Rat pups from pregnant females exposed to hypoxia (FIO2=0.12) at days 10-20 of pregnancy were grown to adulthood and working hearts perfused ex vivo. 14C-labelled glucose and 3H-palmitate were provided as substrates and metabolism quantified from recovery of 14CO2 and 3H2O, respectively. Hearts of male offspring subjected to Maternal Hypoxia showed a 20% decrease in cardiac output (P<0.05), despite recording a 2-fold increase in glucose oxidation (P<0.01) and 2.5-fold increase (P<0.01) in palmitate oxidation. Addition of insulin to Maternal Hypoxic hearts, further increased glucose oxidation (P<0.01) and suppressed palmitate oxidation (P<0.05), suggesting preservation in insulin signalling in the heart. In vitro enzyme activity measurements showed that Maternal Hypoxia increased both total and the active component of cardiac pyruvate dehydrogenase (both P<0.01), although pyruvate dehydrogenase sensitivity to insulin was lost (NS), while citrate synthase activity declined by 30% (P<0.001) and acetyl-CoA carboxylase activity was unchanged by Maternal Hypoxia, indicating realignment of the metabolic machinery to optimise oxygen utilisation. Capillary density was quantified and oxygen diffusion characteristics examined, with calculated capillary domain area increased by 30% (P<0.001). Calculated metabolic efficiency decreased 4-fold (P<0.01) for Maternal Hypoxia hearts. Paradoxically, the decline in citrate synthase activity and increased metabolism suggest that the scope of individual mitochondria had declined, rendering the myocardium potentially more sensitive to metabolic stress. However, decreasing citrate synthase may be essential to preserve local PO2, minimising regions of hypoxia and hence maximising the area of myocardium able to preserve cardiac output following maternal hypoxia.
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Affiliation(s)
- David Hauton
- Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds, United Kingdom
- * E-mail:
| | - Abdullah Al-Shammari
- Department of Mathematics, Faculty of Sciences, Kuwait University, Kuwait City, Kuwait
| | - Eamonn A. Gaffney
- Wolfson Centre for Mathematical Biology, Mathematical Institute, University of Oxford, Oxford, United Kingdom
| | - Stuart Egginton
- School of Biomedical Science, University of Leeds, Leeds, United Kingdom
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20
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Wang B, Ding Z, Wang W, Hwang J, Liao YH, Ivy JL. The effect of an amino acid beverage on glucose response and glycogen replenishment after strenuous exercise. Eur J Appl Physiol 2015; 115:1283-94. [PMID: 25600772 DOI: 10.1007/s00421-015-3098-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 12/31/2014] [Indexed: 11/26/2022]
Abstract
PURPOSE We previously reported that an amino acid mixture (AA) was able to lower the glucose response to an oral glucose challenge in both rats and humans. Increased glucose uptake and glycogen storage in muscle might be associated with the faster blood glucose clearance. We therefore tested the effect of two different doses of AA provided with a carbohydrate supplement on blood glucose homeostasis and muscle glycogen replenishment in human subjects after strenuous aerobic exercise. METHODS Ten subjects received a carbohydrate (1.2 g/kg body weight, CHO), CHO/HAA (CHO + 13 g AA), or CHO/LAA (CHO + 6.5 g AA) supplement immediately and 2 h after an intense cycling bout. Muscle biopsies were performed immediately and 4 h after exercise. RESULTS The glucose responses for CHO/HAA and CHO/LAA during recovery were significantly lower than CHO, as was the glucose area under the curve (CHO/HAA 1259.9 ± 27.7, CHO/LAA 1251.5 ± 47.7, CHO 1376.8 ± 52.9 mmol/L 4 h, p < 0.05). Glycogen storage rate was significantly lower in CHO/HAA compared with CHO, while it did not differ significantly between CHO/LAA or CHO (CHO/HAA 15.4 ± 2.0, CHO/LAA 18.1 ± 2.0, CHO 21.5 ± 1.4 µmol/g wet muscle 4 h). CHO/HAA caused a significantly higher insulin response and a greater effect on mTOR and Akt/PKB phosphorylation compared with CHO. Phosphorylation of AS160 and glycogen synthase did not differ across treatments. Likewise, there were no differences in blood lactate across treatments. CONCLUSIONS The AA lowered the glucose response to a carbohydrate supplement after strenuous exercise. However, it was not effective in facilitating subsequent muscle glycogen storage.
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Affiliation(s)
- Bei Wang
- Department of Kinesiology and Health Education, Exercise Physiology and Metabolism Laboratory, University of Texas at Austin, Austin, TX, USA,
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21
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Carolo dos Santos K, Pereira Braga C, Octavio Barbanera P, Rodrigues Ferreira Seiva F, Fernandes Junior A, Fernandes AAH. Cardiac energy metabolism and oxidative stress biomarkers in diabetic rat treated with resveratrol. PLoS One 2014; 9:e102775. [PMID: 25050809 PMCID: PMC4106839 DOI: 10.1371/journal.pone.0102775] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 06/24/2014] [Indexed: 02/07/2023] Open
Abstract
Resveratrol (RSV), polyphenol from grape, was studied to evaluate its effects on calorimetric parameters, energy metabolism, and antioxidants in the myocardium of diabetic rats. The animals were randomly divided into four groups (n = 8): C (control group): normal rats; C-RSV: normal rats receiving RSV; DM: diabetic rats; and DM-RSV: diabetics rats receiving RSV. Type 1 diabetes mellitus was induced with administration of streptozotocin (STZ; 60 mg−1 body weight, single dose, i.p.). After 48 hours of STZ administration, the animals received RSV (1.0 mg/kg/day) for gavage for 30 days. Food, water, and energy intake were higher in the DM group, while administration of RSV caused decreases (p<0.05) in these parameters. The glycemia decreased and higher final body weight increased in DM-RSV when compared with the DM group. The diabetic rats showed higher serum-free fatty acid, which was normalized with RSV. Oxygen consumption (VO2) and carbon dioxide production (VCO2) decreased (p<0.05) in the DM group. This was accompanied by reductions in RQ. The C-RSV group showed higher VO2 and VCO2 values. Pyruvate dehydrogenase activity was lower in the DM group and normalizes with RSV. The DM group exhibited higher myocardial β-hydroxyacyl coenzyme-A dehydrogenase and citrate synthase activity, and RSV decreased the activity of these enzymes. The DM group had higher cardiac lactate dehydrogenase compared to the DM-RSV group. Myocardial protein carbonyl was increased in the DM group. RSV increased reduced glutathione in the cardiac tissue of diabetic animals. The glutathione reductase activity was higher in the DM-RSV group compared to the DM group. In conclusion, diabetes is accompanied by cardiac energy metabolism dysfunction and change in the biomarkers of oxidative stress. The cardioprotective effect may be mediated through RVS's ability to normalize free fatty acid oxidation, enhance utilization glucose, and control the biomarkers' level of oxidative stress under diabetic conditions.
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Affiliation(s)
- Klinsmann Carolo dos Santos
- Department of Chemistry and Biochemistry, Institute of Bioscience, São Paulo State University (UNESP), Botucatu/São Paulo, Brazil
| | - Camila Pereira Braga
- Department of Chemistry and Biochemistry, Institute of Bioscience, São Paulo State University (UNESP), Botucatu/São Paulo, Brazil
| | - Pedro Octavio Barbanera
- Department of Chemistry and Biochemistry, Institute of Bioscience, São Paulo State University (UNESP), Botucatu/São Paulo, Brazil
| | | | - Ary Fernandes Junior
- Department of Microbiology and Immunology, Institute of Bioscience, São Paulo State University (UNESP), Botucatu/São Paulo, Brazil
| | - Ana Angélica Henrique Fernandes
- Department of Chemistry and Biochemistry, Institute of Bioscience, São Paulo State University (UNESP), Botucatu/São Paulo, Brazil
- * E-mail:
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22
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Zhao X, Bak S, Pedersen AJT, Jensen ON, Højlund K. Insulin Increases Phosphorylation of Mitochondrial Proteins in Human Skeletal Muscle in Vivo. J Proteome Res 2014; 13:2359-69. [DOI: 10.1021/pr401163t] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Xiaolu Zhao
- Department
of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
- College
of Life Science, Wuhan University, Wuhan, P. R. China 430072
| | - Steffen Bak
- Department
of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
- Section of Molecular Diabetes & Metabolism, Institute of Clinical Research and Institute of Molecular Medicine, University of Southern Denmark, DK-5000 Odense C, Denmark
| | | | - Ole Nørregaard Jensen
- Department
of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Kurt Højlund
- Section of Molecular Diabetes & Metabolism, Institute of Clinical Research and Institute of Molecular Medicine, University of Southern Denmark, DK-5000 Odense C, Denmark
- Department
of Endocrinology, Odense University Hospital, DK-5000 Odense
M, Denmark
- Section
of Molecular Physiology, The August Krogh Centre, Department of Nutrition,
Exercise and Sports, University of Copenhagen, 2100 Copenhagen, Denmark
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Nellemann B, Vendelbo MH, Nielsen TS, Bak AM, Høgild M, Pedersen SB, Biensø RS, Pilegaard H, Møller N, Jessen N, Jørgensen JOL. Growth hormone-induced insulin resistance in human subjects involves reduced pyruvate dehydrogenase activity. Acta Physiol (Oxf) 2014; 210:392-402. [PMID: 24148194 DOI: 10.1111/apha.12183] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 09/09/2013] [Accepted: 10/17/2013] [Indexed: 12/15/2022]
Abstract
AIM Insulin resistance induced by growth hormone (GH) is linked to promotion of lipolysis by unknown mechanisms. We hypothesized that suppression of the activity of pyruvate dehydrogenase in the active form (PDHa) underlies GH-induced insulin resistance similar to what is observed during fasting. METHODS Eight healthy male subjects were studied four times in a randomized, single-blinded parallel design: Control, GH, Fasting (36 h) and GH + Fasting. GH (30 ng × kg(-1) × min(-1)) or saline was infused throughout the metabolic study day. Substrate metabolism and insulin sensitivity were assessed by indirect calorimetry and isotopically determined rates of glucose turnover before and after a hyperinsulinemic euglycemic clamp. PDHa activity, PDH-E1α phosphorylation, PDK4 expression and activation of insulin signalling proteins were assessed in skeletal muscle. RESULTS Both fasting and GH promoted lipolysis, which was associated with ≈50% reduction in insulin sensitivity compared with the control day. PDHa activity was significantly reduced by GH as well as fasting. This was associated with increased inhibitory PDH-E1α phosphorylation on site 1 (Ser(293)) and 2 (Ser(300)) and up-regulation of PDK4 mRNA, while canonical insulin signalling to glucose transport was unaffected. CONCLUSION Competition between intermediates of glucose and fatty acids seems to play a causal role in insulin resistance induced by GH in human subjects.
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Affiliation(s)
- B. Nellemann
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - M. H. Vendelbo
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - T. S. Nielsen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - A. M. Bak
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - M. Høgild
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - S. B. Pedersen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - R. S. Biensø
- Centre of Inflammation and Metabolism & August Krogh Centre; Department of Biology; University of Copenhagen; Copenhagen Denmark
| | - H. Pilegaard
- Centre of Inflammation and Metabolism & August Krogh Centre; Department of Biology; University of Copenhagen; Copenhagen Denmark
| | - N. Møller
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - N. Jessen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - J. O. L. Jørgensen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
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Kim JH, Kim JW, Kim SC, Lee YJ. Kiwifruit (Actinidia chinensis) extract annuls chronic insulininduced insulin resistance in l6 skeletal muscle cells. Food Sci Biotechnol 2013. [DOI: 10.1007/s10068-013-0188-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Beck-Nielsen H. The role of glycogen synthase in the development of hyperglycemia in type 2 diabetes: 'To store or not to store glucose, that's the question'. Diabetes Metab Res Rev 2012; 28:635-44. [PMID: 22926827 DOI: 10.1002/dmrr.2337] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This review deals with the role of glycogen storage in skeletal muscle for the development of insulin resistance and type 2 diabetes. Specifically, the role of the enzyme glycogen synthase, which seems to be locked in its hyperphosphorylated and inactivated state, is discussed. This defect seems to be secondary to ectopic lipid disposition in the muscle cells. These molecular defects are discussed in the context of the overall pathophysiology of hyperglycemia in type 2 diabetic subjects.
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Munsters MJM, Saris WHM. Effects of meal frequency on metabolic profiles and substrate partitioning in lean healthy males. PLoS One 2012; 7:e38632. [PMID: 22719910 PMCID: PMC3374835 DOI: 10.1371/journal.pone.0038632] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 05/08/2012] [Indexed: 11/29/2022] Open
Abstract
Introduction The daily number of meals has an effect on postprandial glucose and insulin responses, which may affect substrate partitioning and thus weight control. This study investigated the effects of meal frequency on 24 h profiles of metabolic markers and substrate partitioning. Methods Twelve (BMI:21.6±0.6 kg/m2) healthy male subjects stayed after 3 days of food intake and physical activity standardization 2×36 hours in a respiration chamber to measure substrate partitioning. All subjects randomly received two isoenergetic diets with a Low meal Frequency (3×; LFr) or a High meal Frequency (14×; HFr) consisting of 15 En% protein, 30 En% fat, and 55 En% carbohydrates. Blood was sampled at fixed time points during the day to measure metabolic markers and satiety hormones. Results Glucose and insulin profiles showed greater fluctuations, but a lower AUC of glucose in the LFr diet compared with the HFr diet. No differences between the frequency diets were observed on fat and carbohydrate oxidation. Though, protein oxidation and RMR (in this case SMR + DIT) were significantly increased in the LFr diet compared with the HFr diet. The LFr diet increased satiety and reduced hunger ratings compared with the HFr diet during the day. Conclusion The higher rise and subsequently fall of insulin in the LFr diet did not lead to a higher fat oxidation as hypothesized. The LFr diet decreased glucose levels throughout the day (AUC) indicating glycemic improvements. RMR and appetite control increased in the LFr diet, which can be relevant for body weight control on the long term. Trial Registration ClinicalTrails.gov NCT01034293
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Affiliation(s)
- Marjet J M Munsters
- Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands.
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Saravanan R, Vengatash babu K, Ramachandran V. Effect of Rebaudioside A, a diterpenoid on glucose homeostasis in STZ-induced diabetic rats. J Physiol Biochem 2012; 68:421-31. [PMID: 22374587 DOI: 10.1007/s13105-012-0156-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2011] [Accepted: 02/07/2012] [Indexed: 11/25/2022]
Abstract
Rebaudioside A (Reb A), a major constituent of Stevia rebaudiana, was recently proposed as an insulinotropic agent. The aim of this investigation was to evaluate the antihyperglycemic effect of Reb A on the activities of hepatic enzymes of carbohydrate metabolism in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in adult male Albino Wistar rats, weighing 180-200 g, by a single intraperitoneal injection at a dose of STZ (40 mg/kg body weight). Diabetic rats showed significant (P<0.05) increase in the levels of plasma glucose and glycosylated hemoglobin and significant (P<0.05) decrease in the levels of plasma insulin and hemoglobin. Activities of gluconeogenic enzymes such as glucose-6-phosphatase and fructose-1,6-bisphosphatase were significantly (P<0.05) increased while hexokinase and glucose-6-phosphate dehydrogenase were significantly (P<0.05) decreased in the liver along with glycogen. Oral treatment with Reb A to diabetic rats significantly (P<0.05) decreased blood glucose and reversed these hepatic carbohydrate metabolizing enzymes in a significant manner. Histopathology changes of pancreas confirmed the protective effects of Reb A in diabetic rats. Thus, the results show that Reb A possesses an antihyperglycemic activity and provide evidence for its traditional usage in the control of diabetes.
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Affiliation(s)
- Ramalingam Saravanan
- Department of Biochemistry and Biotechnology, Faculty of Science, Annamalai University, Annamalainagar 608 002 Tamil Nadu, India,
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Ryan AS, Ortmeyer HK, Sorkin JD. Exercise with calorie restriction improves insulin sensitivity and glycogen synthase activity in obese postmenopausal women with impaired glucose tolerance. Am J Physiol Endocrinol Metab 2012; 302:E145-52. [PMID: 22008454 PMCID: PMC3328088 DOI: 10.1152/ajpendo.00618.2010] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Our objective was to compare the effects of in vivo insulin on skeletal muscle glycogen synthase (GS) activity in normal (NGT) vs. impaired glucose-tolerant (IGT) obese postmenopausal women and to determine whether an increase in insulin activation of GS is associated with an improvement in insulin sensitivity (M) following calorie restriction (CR) and/or aerobic exercise plus calorie restriction (AEX + CR) in women with NGT and IGT. We did a longitudinal, clinical intervention study of CR compared with AEX + CR. Overweight and obese women, 49-76 yr old, completed 6 mo of CR (n = 46) or AEX + CR (n = 50) with Vo(2 max), body composition, and glucose tolerance testing. Hyperinsulinemic euglycemic (80 mU·m(-2)·min(-1)) clamps (n = 73) and skeletal muscle biopsies (before and during clamp) (n = 58) were performed before and after the interventions (n = 50). After 120 min of hyperinsulinemia during the clamp, GS fractional activity and insulin's effect to increase GS fractional activity (insulin - basal) were significantly lower in IGT vs. NGT (P < 0.01) at baseline. GS total activity increased during the clamp in NGT (P < 0.05), but not IGT, at baseline. CR and AEX + CR resulted in a significant 8% weight loss with reductions in total fat mass, visceral fat, subcutaneous fat, and intramuscular fat. Overall, M increased (P < 0.01), and the change in M (postintervention - preintervention) was associated with the change in insulin-stimulated GS fractional activity (partial r = 0.44, P < 0.005). In IGT, the change (postintervention - preintervention) in insulin-stimulated GS total activity was greater following AEX + CR than CR alone (P < 0.05). In IGT, insulin-stimulated GS-independent (P < 0.005) and fractional activity (P = 0.06) increased following AEX + CR. We conclude that the greatest benefits at the whole body and cellular level (insulin activation of GS) in older women at highest risk for diabetes are derived from a lifestyle intervention that includes exercise and diet.
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Affiliation(s)
- Alice S Ryan
- Division. of Gerontology, Baltimore Veterans Affairs Medical Center, 10 N. Greene St., Baltimore, MD 21201, USA.
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Kiilerich K, Ringholm S, Biensø RS, Fisher JP, Iversen N, van Hall G, Wojtaszewski JFP, Saltin B, Lundby C, Calbet JAL, Pilegaard H. Exercise-induced pyruvate dehydrogenase activation is not affected by 7 days of bed rest. J Appl Physiol (1985) 2011; 111:751-7. [DOI: 10.1152/japplphysiol.00063.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To test the hypothesis that physical inactivity impairs the exercise-induced modulation of pyruvate dehydrogenase (PDH), six healthy normally physically active male subjects completed 7 days of bed rest. Before and immediately after the bed rest, the subjects completed an oral glucose tolerance test (OGTT) and a one-legged knee extensor exercise bout [45 min at 60% maximal load (Wmax)] with muscle biopsies obtained from vastus lateralis before, immediately after exercise, and at 3 h of recovery. Blood samples were taken from the femoral vein and artery before and after 40 min of exercise. Glucose intake elicited a larger ( P ≤ 0.05) insulin response after bed rest than before, indicating glucose intolerance. There were no differences in lactate release/uptake across the exercising muscle before and after bed rest, but glucose uptake after 40 min of exercise was larger ( P ≤ 0.05) before bed rest than after. Muscle glycogen content tended to be higher (0.05< P ≤ 0.10) after bed rest than before, but muscle glycogen breakdown in response to exercise was similar before and after bed rest. PDH-E1α protein content did not change in response to bed rest or in response to the exercise intervention. Exercise increased ( P ≤ 0.05) the activity of PDH in the active form (PDHa) and induced ( P ≤ 0.05) dephosphorylation of PDH-E1α on Ser293, Ser295 and Ser300, with no difference before and after bed rest. In conclusion, although 7 days of bed rest induced whole body glucose intolerance, exercise-induced PDH regulation in skeletal muscle was not changed. This suggests that exercise-induced PDH regulation in skeletal muscle is maintained in glucose-intolerant (e.g., insulin resistant) individuals.
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Affiliation(s)
- Kristian Kiilerich
- Centre of Inflammation and Metabolism,
- Copenhagen Muscle Research Centre, and
- Department of Biology, August Krogh Building, University of Copenhagen, Copenhagen, Denmark
| | - Stine Ringholm
- Centre of Inflammation and Metabolism,
- Copenhagen Muscle Research Centre, and
- Department of Biology, August Krogh Building, University of Copenhagen, Copenhagen, Denmark
| | - Rasmus S. Biensø
- Centre of Inflammation and Metabolism,
- Copenhagen Muscle Research Centre, and
- Department of Biology, August Krogh Building, University of Copenhagen, Copenhagen, Denmark
| | - James P. Fisher
- School of Sport and Exercise Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Ninna Iversen
- Centre of Inflammation and Metabolism,
- Copenhagen Muscle Research Centre, and
- Department of Biology, August Krogh Building, University of Copenhagen, Copenhagen, Denmark
| | - Gerrit van Hall
- Metabolic Mass-Spectrometry Facility, Rigshospitalet and Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen
| | - Jørgen F. P. Wojtaszewski
- Copenhagen Muscle Research Centre, and
- Section of Human Physiology, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen
| | - Bengt Saltin
- Copenhagen Muscle Research Centre, and
- Rigshospitalet, Section 7652, Copenhagen, Denmark; and
| | - Carsten Lundby
- Copenhagen Muscle Research Centre, and
- Rigshospitalet, Section 7652, Copenhagen, Denmark; and
| | - Jose A. L. Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Islands
| | - Henriette Pilegaard
- Centre of Inflammation and Metabolism,
- Copenhagen Muscle Research Centre, and
- Department of Biology, August Krogh Building, University of Copenhagen, Copenhagen, Denmark
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Acclimation temperature affects the metabolic response of amphibian skeletal muscle to insulin. Comp Biochem Physiol A Mol Integr Physiol 2011; 160:72-80. [PMID: 21605693 DOI: 10.1016/j.cbpa.2011.05.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 05/08/2011] [Accepted: 05/09/2011] [Indexed: 11/22/2022]
Abstract
Frog skeletal muscle mainly utilizes the substrates glucose and lactate for energy metabolism. The goal of this study was to determine the effect of insulin on the uptake and metabolic fate of lactate and glucose at rest in skeletal muscle of the American bullfrog, Lithobates catesbeiana, under varying temperature regimens. We hypothesize that lactate and glucose metabolic pathways will respond differently to the presence of insulin in cold versus warm acclimated frog tissues, suggesting an interaction between temperature and metabolism under varying environmental conditions. We employed radiolabeled tracer techniques to measure in vitro uptake, oxidation, and incorporation of glucose and lactate into glycogen by isolated muscles from bullfrogs acclimated to 5 °C (cold) or 25 °C (warm). Isolated bundles from Sartorius muscles were incubated at 5 °C, 15 °C, or 25 °C, and in the presence and absence of 0.05 IU/mL bovine insulin. Insulin treatment in the warm acclimated and incubated frogs resulted in an increase in glucose incorporation into glycogen, and an increase in intracellular [glucose] of 0.5 μmol/g (P<0.05). Under the same conditions lactate incorporation into glycogen was reduced (P<0.05) in insulin-treated muscle. When compared to the warm treatment group, cold acclimation and incubation resulted in increased rates of glucose oxidation and glycogen synthesis, and a reduction in free intracellular glucose levels (P<0.05). When muscles from either acclimation group were incubated at an intermediate temperature of 15 °C, insulin's effect on substrate metabolism was attenuated or even reversed. Therefore, a significant interaction between insulin and acclimation condition in controlling skeletal muscle metabolism appears to exist. Our findings further suggest that one of insulin's actions in frog muscle is to increase glucose incorporation into glycogen, and to reduce reliance on lactate as the primary metabolic fuel.
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Joya-Galeana J, Fernandez M, Cervera A, Reyna S, Ghosh S, Triplitt C, Musi N, DeFronzo RA, Cersosimo E. Effects of insulin and oral anti-diabetic agents on glucose metabolism, vascular dysfunction and skeletal muscle inflammation in type 2 diabetic subjects. Diabetes Metab Res Rev 2011; 27:373-82. [PMID: 21309063 PMCID: PMC4416699 DOI: 10.1002/dmrr.1185] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND To test potential differences between the actions of anti-diabetic medications, we examined the effects of oral hypoglycaemic agents versus glargine-apidra insulin therapy in T2DM. METHODS T2DM subjects were randomized to either oral hypoglycaemic agents (pioglitazone, metformin and glipizide, n = 9) or insulin therapy (n = 12) for 6 months. Carotid intimal media thickness, vascular reactivity (flow-mediated vasodilatation; percent change in brachial artery basal diameter post-ischaemia) and sublingual nitrate were measured with ultrasonography. Euglycemic hyperinsulinemic (80 mU/m(2) ) clamp with [3]-3H-glucose and muscle biopsies were performed. RESULTS Fasting plasma glucose (~257 to ~124 mg/dL, oral hypoglycaemic agents and ~256 to ~142 mg/dL, IT) and HbA(1c) (~10.3 to ~6.4%, OHA and ~10.7 to ~7.1%, IT) improved comparably. Endogenous glucose production (~2.1 to ~1.7 mg/kg/min, oral hypoglycaemic agents and ~2.3 to ~2.0 mg/kg/min, insulin therapy) and endogenous glucose production suppression by insulin (~0.4 to ~0.3 mg/kg min, oral hypoglycaemic agents and ~0.5 to ~0.7 mg/kg min, insulin therapy) were different. Total glucose disposal × 100 increased in the oral hypoglycaemic agents group (~5.2 to ~8.1; p = 0.03), but not in insulin therapy (~6.0 to ~5.4 mg/kg/min/µU/mL × 100). OHA reduced CIMT (~0.080 to ~0.068 cm; p < 0.05), whereas insulin therapy did not (~0.075 to ~0.072 cm). After sublingual nitrate, brachial artery basal diameter increased in the OHA group (~8.7 to ~18.2%), but not in insulin therapy (~11.2 to ~15.0%; p < 0.02). Except for plasma adiponectin (~7 to ~15, oral hypoglycaemic agents versus ~6 to ~10, IT), changes in inflammatory markers in the circulation and in muscle (IκBα, super-oxidase dismutase 2, monocyte-chemo-attractant protein 1, p-ERK and JNK) were equivalent. CONCLUSIONS Oral hypoglycaemic agents and insulin therapy treated patients achieved adequate glycemic control and the effects on circulating and muscle inflammatory biomarkers were similar, but only oral hypoglycaemic agents improved insulin sensitivity, vascular function and carotid intimal media thickness. These findings in a small sample suggest that the use of oral hypoglycaemic agents provides additional benefits to patients with T2DM.
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Affiliation(s)
- J Joya-Galeana
- Diabetes Division, Texas Diabetes Institute, University of Texas Health Science Center, San Antonio, TX, USA
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Tisdale PB, Seevaratnam N, Macdonald IA, Tsintzas K, Bennett AJ. Skeletal muscle metabolic gene expression is not affected by dichloroacetate-mediated modulation of substrate utilisation. ANNALS OF NUTRITION AND METABOLISM 2011; 58:19-24. [PMID: 21304220 DOI: 10.1159/000322971] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Accepted: 11/22/2010] [Indexed: 12/21/2022]
Abstract
AIM This study investigated whether changing fuel use, by increasing pyruvate dehydrogenase complex (PDC) flux, independently of plasma substrate availability and insulin signalling, would alter metabolic gene expression. METHODS The PDC activator, dichloroacetate (DCA), was administered as an intravenous infusion in healthy male subjects at a rate of 50 mg kg(-1) min(-1), for 90 min. Saline was infused as a control (CON) on a separate occasion in a randomised sequence. Muscle biopsies were taken from the vastus lateralis at 0 and 30 min into the infusion and 90 min after infusion. Gene expression was quantified using RT-qPCR, and immunoblotting was used to confirm that there were no changes in insulin signalling via the PI3K/Akt pathway. RESULTS Blood glucose concentrations fell during both trials but 3 h after the start of the infusion they were lower in DCA (p < 0.05) than CON. Blood lactate concentrations also declined in both trials (p < 0.01), however, this decrease was also more pronounced in DCA than CON (p < 0.001). Carbohydrate oxidation was increased by DCA, 0.037 ± 0.017 g min(-1) (p < 0.05) at 3 h with no change observed in CON. UCP3 and PGC1α mRNA expression were induced in CON (as a response to continued fasting) but this was attenuated by DCA. Akt phosphorylation and the expression of other metabolic genes and transcription factors were unchanged throughout the intervention. CONCLUSION It is concluded that PDC flux can be increased independently of plasma substrate availability, without causing downstream alterations to metabolic gene expression in the short term.
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Affiliation(s)
- Paul B Tisdale
- School of Biomedical Sciences, Queens Medical Centre, University of Nottingham, Nottingham, UK.
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Kruszynska YT, Ciaraldi TP, Henry RR. Regulation of Glucose Metabolism in Skeletal Muscle. Compr Physiol 2011. [DOI: 10.1002/cphy.cp070218] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Eriksen M, Pørneki AD, Skov V, Burns JS, Beck-Nielsen H, Glintborg D, Gaster M. Insulin resistance is not conserved in myotubes established from women with PCOS. PLoS One 2010; 5:e14469. [PMID: 21209881 PMCID: PMC3012693 DOI: 10.1371/journal.pone.0014469] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Accepted: 12/07/2010] [Indexed: 12/25/2022] Open
Abstract
Background Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among premenopausal women, who often develop insulin resistance. We tested the hypothesis that insulin resistance in skeletal muscle of patients with polycystic ovary syndrome (PCOS) is an intrinsic defect, by investigating the metabolic characteristics and gene expression of in vitro differentiated myotubes established from well characterized PCOS subjects. Methods Using radiotracer techniques, RT-PCR and enzyme kinetic analysis we examined myotubes established from PCOS subjects with or without pioglitazone treatment, versus healthy control subjects who had been extensively metabolically characterized in vivo. Results Myotubes established from PCOS and matched control subjects comprehensively expressed all insulin-sensitive biomarkers; glucose uptake and oxidation, glycogen synthesis and lipid uptake. There were no significant differences between groups either at baseline or during acute insulin stimulation, although in vivo skeletal muscle was insulin resistant. In particular, we found no evidence for defects in insulin-stimulated glycogen synthase activity between groups. Myotubes established from PCOS patients with or without pioglitazone treatment also showed no significant differences between groups, neither at baseline nor during acute insulin stimulation, although in vivo pioglitazone treatment significantly improved insulin sensitivity. Consistently, the myotube cultures failed to show differences in mRNA levels of genes previously demonstrated to differ in PCOS patients with or without pioglitazone treatment (PLEK, SLC22A16, and TTBK). Conclusion These results suggest that the mechanisms governing insulin resistance in skeletal muscle of PCOS patients in vivo are not primary, but rather adaptive. Trial Registration ClinicalTrials.gov NCT00145340
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Affiliation(s)
- Mette Eriksen
- Department of Endocrinology, Odense University Hospital, Odense, Denmark
- University of Southern Denmark, Odense, Denmark
| | - Ann Dorte Pørneki
- Clinic for Molecular Endocrinology, Department of Endocrinology, Odense University Hospital and Medical Biotechnology Center, University of Southern Denmark, Odense, Denmark
| | - Vibe Skov
- Department of Clinical Biochemistry and Pharmacology and Department of Clinical Genetics, Human MicroArray Center, Odense University Hospital, Odense, Denmark
| | - Jorge S. Burns
- Clinic for Molecular Endocrinology, Department of Endocrinology, Odense University Hospital and Medical Biotechnology Center, University of Southern Denmark, Odense, Denmark
| | | | - Dorte Glintborg
- Department of Endocrinology, Odense University Hospital, Odense, Denmark
| | - Michael Gaster
- Department of Endocrinology, Odense University Hospital, Odense, Denmark
- University of Southern Denmark, Odense, Denmark
- Clinic for Molecular Endocrinology, Department of Endocrinology, Odense University Hospital and Medical Biotechnology Center, University of Southern Denmark, Odense, Denmark
- * E-mail:
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Li Y, Solomon TPJ, Haus JM, Saidel GM, Cabrera ME, Kirwan JP. Computational model of cellular metabolic dynamics: effect of insulin on glucose disposal in human skeletal muscle. Am J Physiol Endocrinol Metab 2010; 298:E1198-209. [PMID: 20332360 PMCID: PMC2886522 DOI: 10.1152/ajpendo.00713.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Accepted: 03/09/2010] [Indexed: 12/14/2022]
Abstract
Identifying the mechanisms by which insulin regulates glucose metabolism in skeletal muscle is critical to understanding the etiology of insulin resistance and type 2 diabetes. Our knowledge of these mechanisms is limited by the difficulty of obtaining in vivo intracellular data. To quantitatively distinguish significant transport and metabolic mechanisms from limited experimental data, we developed a physiologically based, multiscale mathematical model of cellular metabolic dynamics in skeletal muscle. The model describes mass transport and metabolic processes including distinctive processes of the cytosol and mitochondria. The model simulated skeletal muscle metabolic responses to insulin corresponding to human hyperinsulinemic-euglycemic clamp studies. Insulin-mediated rate of glucose disposal was the primary model input. For model validation, simulations were compared with experimental data: intracellular metabolite concentrations and patterns of glucose disposal. Model variations were simulated to investigate three alternative mechanisms to explain insulin enhancements: Model 1 (M.1), simple mass action; M.2, insulin-mediated activation of key metabolic enzymes (i.e., hexokinase, glycogen synthase, pyruvate dehydrogenase); or M.3, parallel activation by a phenomenological insulin-mediated intracellular signal that modifies reaction rate coefficients. These simulations indicated that models M.1 and M.2 were not sufficient to explain the experimentally measured metabolic responses. However, by application of mechanism M.3, the model predicts metabolite concentration changes and glucose partitioning patterns consistent with experimental data. The reaction rate fluxes quantified by this detailed model of insulin/glucose metabolism provide information that can be used to evaluate the development of type 2 diabetes.
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Affiliation(s)
- Yanjun Li
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
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Pathogenesis of insulin resistance in skeletal muscle. J Biomed Biotechnol 2010; 2010:476279. [PMID: 20445742 PMCID: PMC2860140 DOI: 10.1155/2010/476279] [Citation(s) in RCA: 364] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 01/20/2010] [Indexed: 12/16/2022] Open
Abstract
Insulin resistance in skeletal muscle is manifested by decreased insulin-stimulated glucose uptake and results from impaired insulin signaling and multiple post-receptor intracellular defects including impaired glucose transport, glucose phosphorylation, and reduced glucose oxidation and glycogen synthesis. Insulin resistance is a core defect in type 2 diabetes, it is also associated with obesity and the metabolic syndrome. Dysregulation of fatty acid metabolism plays a pivotal role in the pathogenesis of insulin resistance in skeletal muscle. Recent studies have reported a mitochondrial defect in oxidative phosphorylation in skeletal muscle in variety of insulin resistant states. In this review, we summarize the cellular and molecular defects that contribute to the development of insulin resistance in skeletal muscle.
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Daisy P, Balasubramanian K, Rajalakshmi M, Eliza J, Selvaraj J. Insulin mimetic impact of Catechin isolated from Cassia fistula on the glucose oxidation and molecular mechanisms of glucose uptake on Streptozotocin-induced diabetic Wistar rats. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2010; 17:28-36. [PMID: 19931438 DOI: 10.1016/j.phymed.2009.10.018] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Accepted: 10/15/2009] [Indexed: 05/13/2023]
Abstract
Diabetes mellitus is the most common and serious metabolic disorder among people all over the world. Many plants have successfully been used to overcome this problem. Cassia fistula, an ethnomedicnal plant, is widely used in Indian medicine to treat diabetes. Methanol extract of stem of plant, reduced the blood glucose levels in Streptozotocin-induced diabetic rats. Bioassay guided fractionation was followed to isolate Catechin from methanol extract. Catechin was administered to Streptozotocin (60mg/kg b.w.)-induced diabetic male Wistar rats at different doses (5, 10, 20mg/kg b.w.) for 6 weeks to assess its effect on fasting plasma glucose. The plasma glucose was significantly (p<0.05) reduced when compared to the control. Oral administration of Catechin (20mg/kg b.w.) markedly increased tissue glycogen, and (14)C-glucose oxidation without any change in plasma insulin and C-peptide. Catechin restored the altered Glucokinase, glucose-6 Phosphatase, Glycogen Synthase and Glycogen Phosphorylase levels to near normal. GLUT4 mRNA and protein expression were enhanced after Catechin treatment. The results of this experimental study indicated that Catechin possesses hypo-glycemic, Glucose oxidizing and insulin mimetic activities and hence it could be used as a drug for treating diabetes.
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Affiliation(s)
- P Daisy
- PG & Research Department of Biotechnology & Bioinformatics, Holy Cross College (Autonomous), Trichy 620002, Tamilnadu, India.
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Defronzo RA. Banting Lecture. From the triumvirate to the ominous octet: a new paradigm for the treatment of type 2 diabetes mellitus. Diabetes 2009; 58:773-95. [PMID: 19336687 PMCID: PMC2661582 DOI: 10.2337/db09-9028] [Citation(s) in RCA: 1799] [Impact Index Per Article: 119.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Ralph A Defronzo
- Diabetes Division, University of Texas Health Science Center, San Antonio, Texas, USA.
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Fructose modifies the hormonal response and modulates lipid metabolism during aerobic exercise after glucose supplementation. Clin Sci (Lond) 2009; 116:137-45. [PMID: 18533896 DOI: 10.1042/cs20080120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The metabolic response when aerobic exercise is performed after the ingestion of glucose plus fructose is unclear. In the present study, we administered two beverages containing GluF (glucose+fructose) or Glu (glucose alone) in a randomized cross-over design to 20 healthy aerobically trained volunteers to compare the hormonal and lipid responses provoked during aerobic exercise and the recovery phase. After ingesting the beverages and a 15-min resting period, volunteers performed 30 min of moderate aerobic exercise. Urinary and blood samples were taken at baseline (t(-15)), during the exercise (t(0), t(15) and t(30)) and during the recovery phase (t(45), t(75) and t(105)). Plasma insulin concentrations were higher halfway through the exercise period and during acute recuperation (t(15) and t(75); P<0.05) following ingestion of GluF than after Glu alone, without any differences between the effects of either intervention on plasma glucose concentrations. Towards the end of the exercise period, urinary catecholamine concentrations were lower following GluF (t(45); P<0.05). Plasma triacylglycerol (triglyceride) concentrations were higher after the ingestion of GluF compared with Glu (t(15), t(30), t(45) and t(105); P<0.05). Furthermore, with GluF, we observed higher levels of lipoperoxides (t(15), t(30), t(45) and t(105); P<0.05) and oxidized LDL (low-density lipoprotein; t(30); P<0.05) compared with after the ingestion of Glu alone. In conclusion, hormonal and lipid alterations are provoked during aerobic exercise and recovery by the addition of a dose of fructose to the pre-exercise ingestion of glucose.
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Earnest CP. Exercise interval training: An improved stimulus for improving the physiology of pre-diabetes. Med Hypotheses 2008; 71:752-61. [DOI: 10.1016/j.mehy.2008.06.024] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 04/22/2008] [Accepted: 06/23/2008] [Indexed: 10/21/2022]
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Hulstrøm V, Højlund K, Vinten J, Beck-Nielsen H, Levin K. Adiponectin and its response to thiazolidinediones are associated with insulin-mediated glucose metabolism in type 2 diabetic patients and their first-degree relatives. Diabetes Obes Metab 2008; 10:1019-28. [PMID: 18284435 DOI: 10.1111/j.1463-1326.2008.00854.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Patients with type 2 diabetes (T2D) and their first-degree relatives (FDRs) are characterized by hypoadiponectinaema and insulin resistance. In T2D patients, plasma adiponectin and insulin sensitivity (SI) increase in response to thiazolidinediones (TZDs). These findings suggest a role for adiponectin in the regulation of SI. We studied the relationship between plasma adiponectin and glucose and lipid metabolism and the effect of troglitazone (200 mg/day) for 12 weeks in 19 normoglycaemic, obese FDR and 20 obese T2D patients, using euglycaemic-hyperinsulinaemic clamps, glycolytic flux calculations and indirect calorimetry. Plasma adiponectin was similar in both groups, despite higher glucose disposal (Rd), glucose oxidation and glycolytic flux and lower lipid oxidation during insulin stimulation in FDR compared with T2D patients. Plasma adiponectin correlated with insulin-stimulated Rd, non-oxidative glucose disposal (NOGD), glucose storage and SI in both groups after adjustment for sex and body fat. The troglitazone-mediated upregulation of plasma adiponectin was associated with increased insulin-stimulated Rd, NOGD and glucose storage in both groups. No effect on endogenous glucose production was observed. In FDR, plasma adiponectin correlated with insulin-stimulated glycogen synthase activity and the troglitazone-induced increase in plasma adiponectin correlated with the improvement in insulin-stimulated Rd and SI after adjustment for sex and body fat. In conclusion, plasma adiponectin in weight-matched FDR and T2D patients is comparably low and correlates with insulin-mediated glucose uptake and storage. Moreover, these data provide evidence for an adiponectin-dependent insulin-sensitizing effect of TZDs at an early stage before development of T2D and that this effect is exerted mainly on insulin-mediated glucose metabolism.
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Affiliation(s)
- V Hulstrøm
- Department of Medical Physiology, The Panum Institute, University of Copenhagen, Copenhagen N, Denmark
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Kiilerich K, Birk JB, Damsgaard R, Wojtaszewski JFP, Pilegaard H. Regulation of PDH in human arm and leg muscles at rest and during intense exercise. Am J Physiol Endocrinol Metab 2008; 294:E36-42. [PMID: 17957032 DOI: 10.1152/ajpendo.00352.2007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To test the hypothesis that pyruvate dehydrogenase (PDH) is differentially regulated in specific human muscles, regulation of PDH was examined in triceps, deltoid, and vastus lateralis at rest and during intense exercise. To elicit considerable glycogen use, subjects performed 30 min of exhaustive arm cycling on two occasions and leg cycling exercise on a third day. Muscle biopsies were obtained from deltoid or triceps on the arm exercise days and from vastus lateralis on the leg cycling day. Resting PDH protein content and phosphorylation on PDH-E1 alpha sites 1 and 2 were higher (P < or = 0.05) in vastus lateralis than in triceps and deltoid as was the activity of oxidative enzymes. Net muscle glycogen utilization was similar in vastus lateralis and triceps ( approximately 50%) but less in deltoid (likely reflecting less recruitment of deltoid), while muscle lactate accumulation was approximately 55% higher (P < or = 0.05) in triceps than vastus lateralis. Exercise induced (P < or = 0.05) dephosphorylation of both PDH-E1 alpha site 1 and site 2 in all three muscles, but it was more pronounced at PDH-E1 alpha site 1 in triceps than in vastus lateralis (P < or = 0.05). The increase in activity of the active form of PDH (PDHa) after 10 min of exercise was more marked in vastus lateralis ( approximately 246%) than in triceps ( approximately 160%), but when it was related to total PDH-E1 alpha protein content, no difference was evident. In conclusion, PDH protein content seems to be related to metabolic enzyme profile, rather than myosin heavy chain composition, and less PDH capacity in triceps is a likely contributing factor to higher lactate accumulation in triceps than in vastus lateralis.
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Affiliation(s)
- Kristian Kiilerich
- Copenhagen Muscle Research Center, August Krogh Bldg., University of Copenhagen, 2100 Copenhagen, Denmark.
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Wilson CAM, Preller A, Valenzuela MA, Ureta T. Measurement of glycogen synthase activity in crude extracts by CE. Electrophoresis 2007; 28:2888-92. [PMID: 17702064 DOI: 10.1002/elps.200700040] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Glycogen synthase catalyzes the incorporation of UDP-glucose into glycogen. The activity of the enzyme is usually measured either by a spectrophotometric method or by a radioassay. The first one is not suitable because of the difficulties regarding the use of coupled enzymes in crude extracts, while the second is a time-consuming method involving glycogen isolation and manipulation of radioactivity. We have used a CZE technique as a novel approach to measure glycogen synthase activity. The separations were performed at 22 kV (36 microA) in uncoated capillaries (53 cmx50 microm). Sample injection time was 30 s and nucleotides were monitored at 254 nm. Best resolution was achieved in 20 mM tetraborate buffer, pH 9.2. Curves of absorbance as a function of UDP and UDP-glucose concentration were linear. Enzyme activity in oocyte extracts was linear with respect to time (up to15 min) and enzyme concentration. The K(m app.) for UDP-glucose was 0.87 mM, a value identical to the one reported using the radioassay. CZE enables easy quantitation of compounds, high sensitivity, and automation of the process. Small sample sizes are required, interferences by auxiliary enzymes and manipulation of radioactivity are avoided, and analysis time is significantly diminished.
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Affiliation(s)
- Christian A M Wilson
- Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Casilla, Santiago, Chile
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Tsintzas K, Chokkalingam K, Jewell K, Norton L, Macdonald IA, Constantin-Teodosiu D. Elevated free fatty acids attenuate the insulin-induced suppression of PDK4 gene expression in human skeletal muscle: potential role of intramuscular long-chain acyl-coenzyme A. J Clin Endocrinol Metab 2007; 92:3967-72. [PMID: 17652214 DOI: 10.1210/jc.2007-1104] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
AIM We investigated the effect of elevated plasma free fatty acid and insulin concentrations on PDK4 mRNA transcript and protein content and long-chain acyl-coenzyme A accumulation in human skeletal muscle. METHODS On two occasions, 10 healthy men underwent hyperinsulinemic-euglycemic clamps for 6 h with (LIPID) and without (CON) iv Intralipid (20% at 90 ml/h) plus heparin (200 U prime + 600 U/h) infusion. RESULTS Glucose disposal was approximately 50% lower at the end of the clamp in the LIPID compared with the CON trial (37.8 +/- 4.4 and 79.6 +/- 4.0 micromol/kg lean mass.min, respectively; P < 0.01). In the LIPID trial, muscle long-chain acyl-coenzyme A concentration increased after 6 h, but not 3 h of lipid infusion (P < 0.01). Muscle PDK4 mRNA, but not protein, was down-regulated by 2-fold within 3 h in both clamps and decreased further (6-fold; P < 0.01) at 6 h in the CON but not the LIPID clamp. The lipid-induced attenuation in the suppression of PDK4 gene expression was not dependent on the activation of the Akt/FOXO3 pathway. CONCLUSION Accumulation of im lipids plays a more important role than impaired activation of Akt-mediated pathways in the regulation of muscle PDK4 gene expression in lipid-induced acute insulin-resistant states.
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Affiliation(s)
- Kostas Tsintzas
- Centre for Integrated Systems Biology and Medicine, Institute of Clinical Research, School of Biomedical Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom.
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Muthusamy T, Dhevika S, Murugesan P, Balasubramanian K. Testosterone deficiency impairs glucose oxidation through defective insulin and its receptor gene expression in target tissues of adult male rats. Life Sci 2007; 81:534-42. [PMID: 17673259 DOI: 10.1016/j.lfs.2007.06.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 06/06/2007] [Accepted: 06/15/2007] [Indexed: 11/29/2022]
Abstract
Testosterone and insulin interact in their actions on target tissues. Most of the studies that address this issue have focused on the physiological concentration of testosterone, which maintains normal insulin sensitivity but has deleterious effects on the same when the concentration of testosterone is out of this range. However, molecular basis of the action of testosterone in the early step of insulin action is not known. The present study has been designed to assess the impact of testosterone on insulin receptor gene expression and glucose oxidation in target tissues of adult male rat. Adult male albino rats were orchidectomized and supplemented with testosterone (100 microg/100 g b. wt., twice daily) for 15 days from the 11th day of post orchidectomy. On the day after the last treatment, animals were euthanized and blood was collected for the assay of plasma glucose, serum testosterone and insulin. Skeletal muscles, such as gracilis and quadriceps, liver and adipose tissue were dissected out and used for the assay of various parameters such as insulin receptor concentration, insulin receptor mRNA level and glucose oxidation. Testosterone deprivation due to orchidectomy decreased serum insulin concentration. In addition to this, insulin receptor number and its mRNA level and glucose oxidation in target tissues were significantly decreased (p<0.05) when compared to control. However, testosterone replacement in orchidectomized rats restored all these parameters to control level. It is concluded from this study that testosterone deficiency-induced defective glucose oxidation in skeletal muscles, liver and adipose tissue is mediated through impaired expression of insulin and its receptor gene.
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Affiliation(s)
- Thirupathi Muthusamy
- Department of Endocrinology, Dr ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai-600 113, Tamil Nadu, India
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Clark JA, Burny I, Sarnaik AP, Audhya TK. Acute thiamine deficiency in diabetic ketoacidosis: Diagnosis and management. Pediatr Crit Care Med 2006; 7:595-9. [PMID: 17006386 DOI: 10.1097/01.pcc.0000244463.59230.da] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
OBJECTIVE Persistent encephalopathy in a patient with diabetic ketoacidosis is often feared as a sign of cerebral edema. Although thiamine deficiency is a rare diagnosis in children, marginal nutritional status and osmotic diuresis may be risk factors. The objective was to describe a heretofore unreported cause of encephalopathy in a child with diabetic ketoacidosis and review the mechanisms and pathophysiology of thiamine deficiency in this clinical scenario. DESIGN Case report and review of the literature. SETTING Pediatric intensive care unit of a tertiary care pediatric hospital. PATIENT A 13-yr-old girl. INTERVENTIONS Treatment of dehydration and hyperglycemia, osmotherapy, and intravenous thiamine administration. MEASUREMENTS AND MAIN RESULTS The patient presented with new-onset diabetes mellitus, severe diabetic ketoacidosis, and significant encephalopathy. Despite biochemical improvement with treatment of dehydration and hyperglycemia, her encephalopathy persisted. Computed tomography did not show cerebral edema and she showed no response to osmotherapy. Quantitative and functional assays revealed severe thiamine deficiency. The patient showed an immediate and dramatic response to intravenous thiamine administration. CONCLUSIONS The clinical improvement as well as lab investigations suggests that thiamine deficiency was the cause of this child's encephalopathy. Because potential mechanisms exist for thiamine deficiency in diabetes mellitus and institution of insulin and glucose therapy may stress thiamine body stores, thiamine deficiency should be considered in children with diabetic ketoacidosis whose encephalopathy does not improve with improvement of biochemical status.
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Affiliation(s)
- Jeff A Clark
- Division of Critical Care Medicine, Children's Hospital of Michigan/Wayne State University, Detroit, MI, USA
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Ortmeyer HK, Adall Y, Marciani KR, Katsiaras A, Ryan AS, Bodkin NL, Hansen BC. Skeletal muscle glycogen synthase subcellular localization: effects of insulin and PPAR-α agonist (K-111) administration in rhesus monkeys. Am J Physiol Regul Integr Comp Physiol 2005; 288:R1509-17. [PMID: 15761185 DOI: 10.1152/ajpregu.00692.2004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Insulin covalently and allosterically regulates glycogen synthase (GS) and may also cause the translocation of GS from glycogen-poor to glycogen-rich locations. We examined the possible role of subcellular localization of GS and glycogen in insulin activation of GS in skeletal muscle of six obese monkeys and determined whether 1) insulin stimulation during a hyperinsulinemic euglycemic clamp and/or peroxisome proliferator-activated receptor (PPAR)-α agonist treatment (K-111, 3 mg·kg−1·day−1; Kowa) induced translocation of GS and 2) translocation of GS was associated with insulin activation of GS. GS and glycogen were present in all fractions obtained by differential centrifugation, except for the cytosolic fraction, under both basal and insulin-stimulated conditions. We found no evidence for translocation of GS by insulin. GS total (GST) activity was strongly associated with glycogen content ( r = 0.70, P < 0.001). Six weeks of treatment with K-111 increased GST activity in all fractions, except the cytosolic fraction, and mean GST activity, GS independent activity, and glycogen content were significantly higher in the insulin-stimulated samples compared with basal samples, effects not seen with vehicle. The increase in GST activity was strongly related to the increase in glycogen content during the hyperinsulinemic euglycemic clamp after K-111 administration ( r = 0.74, P < 0.001). Neither GS protein expression nor GS gene expression was affected by insulin or by K-111 treatment. We conclude that 1) in vivo insulin does not cause translocation of GS from a glycogen-poor to a glycogen-rich location in primate skeletal muscle and 2) the mechanism of action of K-111 to improve insulin sensitivity includes an increase in GST activity without an increase in GS gene or protein expression.
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Affiliation(s)
- Heidi K Ortmeyer
- Obesity and Diabetes Research Center, Deparment of Physiology, University of Maryland School of Medicine, 10 N. Greene St., Rm 4B-201, Baltimore, MD 21201, USA.
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Gaster M, Beck-Nielsen H. The reduced insulin-mediated glucose oxidation in skeletal muscle from type 2 diabetic subjects may be of genetic origin—evidence from cultured myotubes. Biochim Biophys Acta Mol Basis Dis 2004; 1690:85-91. [PMID: 15337174 DOI: 10.1016/j.bbadis.2004.05.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2004] [Revised: 05/25/2004] [Accepted: 05/25/2004] [Indexed: 11/24/2022]
Abstract
Several defects in response to insulin have been described in vivo and in vitro in type 2 diabetes: a decreased glucose transport, defective glucose oxidation and altered glycogen synthesis. At present, it is unknown whether glucose oxidation is primarily affected or secondarily affected by, e.g. increased free fatty acids (FFA). The aim of this study was to evaluate whether myotubes established from type 2 diabetic subjects express a primarily or a FFA-induced reduced insulin-mediated glucose oxidation. We have therefore investigated glucose oxidation under basal, physiological conditions and during acute insulin stimulation with/without FFA. We found that myotubes established from type 2 diabetic subjects express a reduced insulin-stimulated increase in glucose oxidation. Moreover, an acute exposure to FFA reduces insulin-mediated glucose oxidation without alterations in glucose uptake and glycogen synthesis. Thus, we conclude that the diminished increase in insulin-stimulated glucose oxidation seen in type 2 diabetic subjects in vivo may be of genetic origin. Moreover, the glucose-fatty acid cycle seems not to be crucial for the pathophysiology of insulin resistance.
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Affiliation(s)
- Michael Gaster
- Department of Endocrinology, Odense University Hospital, DK-5000, Odense, Denmark.
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Pehleman TL, Peters SJ, Heigenhauser GJF, Spriet LL. Enzymatic regulation of glucose disposal in human skeletal muscle after a high-fat, low-carbohydrate diet. J Appl Physiol (1985) 2004; 98:100-7. [PMID: 15310747 DOI: 10.1152/japplphysiol.00686.2004] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whole body glucose disposal and skeletal muscle hexokinase, glycogen synthase (GS), pyruvate dehydrogenase (PDH), and PDH kinase (PDK) activities were measured in aerobically trained men after a standardized control diet (Con; 51% carbohydrate, 29% fat, and 20% protein of total energy intake) and a 56-h eucaloric, high-fat, low-carbohydrate diet (HF/LC; 5% carbohydrate, 73% fat, and 22% protein). An oral glucose tolerance test (OGTT; 1 g/kg) was administered after the Con and HF/LC diets with vastus lateralis muscle biopsies sampled pre-OGTT and 75 min after ingestion of the oral glucose load. The 90-min area under the blood glucose and plasma insulin concentration vs. time curves increased by 2-fold and 1.25-fold, respectively, after the HF/LC diet. The pre-OGTT fraction of GS in its active form and the maximal activity of hexokinase were not affected by the HF/LC diet. However, the HF/LC diet increased PDK activity (0.19 +/- 0.05 vs. 0.08 +/- 0.02 min(-1)) and decreased PDH activation (0.38 +/- 0.08 vs. 0.79 +/- 0.10 mmol acetyl-CoA.kg wet muscle(-1).min(-1)) before the OGTT vs. Con. During the OGTT, GS and PDH activation increased by the same magnitude in both diets, such that PDH activation remained lower during the HF/LC OGTT (0.60 +/- 0.11 vs. 1.04 +/- 0.09 mmol acetyl-CoA.kg(-1).min(-1)). These data demonstrate that the decreased glucose disposal during the OGTT after the 56-h HF/LC diet was in part related to decreased oxidative carbohydrate disposal in skeletal muscle and not to decreased glycogen storage. The rapid increase in PDK activity during the HF/LC diet appeared to account for the reduced potential for oxidative carbohydrate disposal.
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Affiliation(s)
- Tanya L Pehleman
- Dept. of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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