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Nogueira L, Zemljic-Harpf AE, Yusufi R, Ranjbar M, Susanto C, Tang K, Mahata SK, Jennings PA, Breen EC. E-cigarette aerosol impairs male mouse skeletal muscle force development and prevents recovery from injury. Am J Physiol Regul Integr Comp Physiol 2022; 323:R849-R860. [PMID: 36250633 PMCID: PMC9678407 DOI: 10.1152/ajpregu.00314.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 10/05/2022] [Accepted: 10/06/2022] [Indexed: 11/22/2022]
Abstract
To date, there has been a lag between the rise in E-cigarette use and an understanding of the long-term health effects. Inhalation of E-cigarette aerosol delivers high doses of nicotine, raises systemic cytokine levels, and compromises cardiopulmonary function. The consequences for muscle function have not been thoroughly investigated. The present study tests the hypothesis that exposure to nicotine-containing aerosol impairs locomotor muscle function, limits exercise tolerance, and interferes with muscle repair in male mice. Nicotine-containing aerosol reduced the maximal force produced by the extensor digitorum longus (EDL) by 30%-40% and, the speed achieved in treadmill running by 8%. Nicotine aerosol exposure also decreased adrenal and increased plasma epinephrine and norepinephrine levels, and these changes in catecholamines manifested as increased muscle and liver glycogen stores. In nicotine aerosol exposed mice, muscle regenerating from overuse injury only recovered force to 80% of noninjured levels. However, the structure of neuromuscular junctions (NMJs) was not affected by e-cigarette aerosols. Interestingly, the vehicle used to dissolve nicotine in these vaping devices, polyethylene glycol (PG) and vegetable glycerin (VG), decreased running speed by 11% and prevented full recovery from a lengthening contraction protocol (LCP) injury. In both types of aerosol exposures, cardiac left ventricular systolic function was preserved, but left ventricular myocardial relaxation was altered. These data suggest that E-cigarette use may have a negative impact on muscle force and regeneration due to compromised glucose metabolism and contractile function in male mice.NEW & NOTEWORTHY In male mice, nicotine-containing E-cigarette aerosol compromises muscle contractile function, regeneration from injury, and whole body running speeds. The vehicle used to deliver nicotine, propylene glycol, and vegetable glycerin, also reduces running speed and impairs the restoration of muscle function in injured muscle. However, the predominant effects of nicotine in this inhaled aerosol are evident in altered catecholamine levels, increased glycogen content, decreased running capacity, and impaired recovery of force following an overuse injury.
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Affiliation(s)
- Leonardo Nogueira
- Department of Medicine, University of California, San Diego, La Jolla, California
- School of Exercise and Nutritional Sciences, College of Health and Human Services, San Diego State University, San Diego, California
| | - Alice E Zemljic-Harpf
- Department of Anesthesiology, University of California, San Diego, La Jolla, California
- Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Raihana Yusufi
- Department of Medicine, University of California, San Diego, La Jolla, California
| | - Maryam Ranjbar
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California
| | - Christopher Susanto
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California
| | - Kechun Tang
- Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Sushil K Mahata
- Department of Medicine, University of California, San Diego, La Jolla, California
- Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Patricia A Jennings
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California
| | - Ellen C Breen
- Department of Medicine, University of California, San Diego, La Jolla, California
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Zhu Y, Fan Z, Zhao Q, Li J, Cai G, Wang R, Liang Y, Lu N, Kang J, Luo D, Tao H, Li Y, Huang J, Wu S. Brain-Type Glycogen Phosphorylase Is Crucial for Astrocytic Glycogen Accumulation in Chronic Social Defeat Stress-Induced Depression in Mice. Front Mol Neurosci 2022; 14:819440. [PMID: 35140588 PMCID: PMC8820374 DOI: 10.3389/fnmol.2021.819440] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Accepted: 12/30/2021] [Indexed: 01/12/2023] Open
Abstract
Astrocytic glycogen plays an important role in brain energy metabolism. However, the contribution of glycogen metabolism to stress-induced depression remains unclear. Chronic social defeat stress was used to induce depression-like behaviors in mice, assessed with behavioral tests. Glycogen concentration in the medial prefrontal cortex (mPFC) and the expression of key enzymes of the glycogen metabolism were investigated using Western blots, immunofluorescent staining, electron microscopy, and biochemical assays. Stereotaxic surgery and viral-mediated gene transfer were applied to knockdown or overexpress brain-type glycogen phosphorylase (PYGB) in the mPFC. The glycogen content increased in the mPFC after stress. Glycogenolytic dysfunction due to inactivation of PYGB was responsible for glycogen accumulation. Behavioral tests on astrocyte-specific PYGB overexpression mice showed that augmenting astrocytic PYGB reduces susceptibility to depression when compared with stress-susceptible mice. Conversely, PYGB genetic down-regulation in the mPFC was sufficient to induce glycogen accumulation and depression-like behaviors. Furthermore, PYGB overexpression in the mPFC decreases susceptibility to depression, at least partially by rescuing glycogen phosphorylase activity to maintain glycogen metabolism homeostasis during stress. These findings indicate that (1) glycogen accumulation occurs in mice following stress and (2) glycogenolysis reprogramming leads to glycogen accumulation in astrocytes and PYGB contributes to stress-induced depression-like behaviors. Pharmacological tools acting on glycogenolysis might constitute a promising therapy for depression.
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Affiliation(s)
- Yuanyuan Zhu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Ze Fan
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
- State Key Laboratory of Military Stomatology, Department of Anesthesiology, School of Stomatology, Fourth Military Medical University, Xi’an, China
| | - Qiuying Zhao
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Jiaqi Li
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Guohong Cai
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Rui Wang
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Yi Liang
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Naining Lu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Junjun Kang
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
| | - Danlei Luo
- Center for Brain Science, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Huiren Tao
- Department of Spine Surgery, Shenzhen University General Hospital, Shenzhen, China
| | - Yan Li
- Center for Brain Science, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
- *Correspondence: Yan Li,
| | - Jing Huang
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
- Jing Huang,
| | - Shengxi Wu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi’an, China
- Shengxi Wu,
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Al-Yousif N, Rawal S, Jurczak M, Mahmud H, Shah FA. Endogenous Glucose Production in Critical Illness. Nutr Clin Pract 2021; 36:344-359. [PMID: 33682953 DOI: 10.1002/ncp.10646] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Regulation of endogenous glucose production (EGP) by hormonal, neuronal, and metabolic signaling pathways contributes to the maintenance of euglycemia under normal physiologic conditions. EGP is defined by the generation of glucose from substrates through glycogenolysis and gluconeogenesis, usually in fasted states, for local and systemic use. Abnormal increases in EGP are noted in patients with diabetes mellitus type 2, and elevated EGP may also impact the pathogenesis of nonalcoholic fatty liver disease and congestive heart failure. In this narrative review, we performed a literature search in PubMed to identify recently published English language articles characterizing EGP in critical illness. Evidence from preclinical and clinical studies demonstrates that critical illness can disrupt EGP through multiple mechanisms including increased systemic inflammation, counterregulatory hormone and catecholamine release, alterations in the hypothalamic-pituitary axis, insulin resistance, lactic acidosis, and iatrogenic insults such as vasopressors and glucocorticoids administered as part of clinical care. EGP contributes to hyperglycemia in critical illness when abnormally elevated and to hypoglycemia when abnormally depressed, each of which has been independently associated with increased mortality. Increased EGP may also promote protein catabolism that could worsen critical illness myopathy and impede recovery. Better understanding of the mechanisms and factors contributing to dysregulated EGP in critical illness may help in the development of therapeutic strategies that promote euglycemia, reduce intensive care unit-associated catabolism, and improve patient outcomes.
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Affiliation(s)
- Nameer Al-Yousif
- Department of Internal Medicine, UPMC Mercy Hospital, Pittsburgh, Pennsylvania, USA
| | - Sagar Rawal
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Michael Jurczak
- Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Hussain Mahmud
- Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Faraaz Ali Shah
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, USA
- Acute Lung Injury Center of Excellence, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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4
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Steiner JL, Johnson BR, Hickner RC, Ormsbee MJ, Williamson DL, Gordon BS. Adrenal stress hormone action in skeletal muscle during exercise training: An old dog with new tricks? Acta Physiol (Oxf) 2021; 231:e13522. [PMID: 32506657 DOI: 10.1111/apha.13522] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 05/29/2020] [Accepted: 05/29/2020] [Indexed: 12/12/2022]
Abstract
Exercise is a key component of a healthy lifestyle as it helps maintain a healthy body weight and reduces the risk of various morbidities and co-morbidities. Exercise is an acute physiological stress that initiates a multitude of processes that attempt to restore physiological homeostasis and promote adaptation. A component of the stress response to exercise is the rapid release of hormones from the adrenal gland including glucocorticoids, the catecholamines and aldosterone. While each hormone targets several tissues throughout the body, skeletal muscle is of interest as it is central to physical function and various metabolic processes. Indeed, adrenal stress hormones have been shown to elicit specific performance benefits on the muscle. However, how the acute, short-lived release of these stress hormones during exercise influences adaptations of skeletal muscle to long-term training remains largely unknown. Thus, the objective of this review was to briefly highlight the known impact of adrenal stress hormones on skeletal muscle metabolism and function (Old Dog), and critically examine the current evidence supporting a role for these endogenous hormones in mediating long-term training adaptations in skeletal muscle (New Tricks).
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Affiliation(s)
- Jennifer L. Steiner
- Department of Nutrition, Food and Exercise Sciences Florida State University Tallahassee FL USA
- Institute of Sports Sciences and Medicine Florida State University Tallahassee FL USA
| | - Bonde R. Johnson
- Department of Nutrition, Food and Exercise Sciences Florida State University Tallahassee FL USA
| | - Robert C. Hickner
- Department of Nutrition, Food and Exercise Sciences Florida State University Tallahassee FL USA
- Institute of Sports Sciences and Medicine Florida State University Tallahassee FL USA
- Department of Biokinetics, Exercise and Leisure Sciences University of KwaZulu‐Natal Durban South Africa
| | - Michael J. Ormsbee
- Department of Nutrition, Food and Exercise Sciences Florida State University Tallahassee FL USA
- Institute of Sports Sciences and Medicine Florida State University Tallahassee FL USA
- Department of Biokinetics, Exercise and Leisure Sciences University of KwaZulu‐Natal Durban South Africa
| | - David L. Williamson
- Kinesiology Program School of Behavioral Sciences and Education Pennsylvania State University at Harrisburg Middletown PA USA
| | - Bradley S. Gordon
- Department of Nutrition, Food and Exercise Sciences Florida State University Tallahassee FL USA
- Institute of Sports Sciences and Medicine Florida State University Tallahassee FL USA
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5
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Davis MA, Camacho LE, Anderson MJ, Steffens NR, Pendleton AL, Kelly AC, Limesand SW. Chronically elevated norepinephrine concentrations lower glucose uptake in fetal sheep. Am J Physiol Regul Integr Comp Physiol 2020; 319:R255-R263. [PMID: 32667834 PMCID: PMC7509250 DOI: 10.1152/ajpregu.00365.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 07/13/2020] [Accepted: 07/13/2020] [Indexed: 12/13/2022]
Abstract
Fetal conditions associated with placental insufficiency and intrauterine growth restriction (IUGR) chronically elevate plasma norepinephrine (NE) concentrations. Our objective was to evaluate the effects of chronically elevated NE on insulin-stimulated glucose metabolism in normally grown, non-IUGR fetal sheep, which are independent of other IUGR-related reductions in nutrients and oxygen availability. After surgical placement of catheters, near-term fetuses received either a saline (control) or NE intravenous infusion with controlled euglycemia. In NE fetuses, plasma NE concentrations were 5.5-fold greater than controls, and fetal euglycemia was maintained with a maternal insulin infusion. Insulin secretion was blunted in NE fetuses during an intravenous glucose tolerance test. Weight-specific fluxes for glucose were measured during a euinsulinemic-euglycemic clamp (EEC) and a hyperinsulinemic-euglycemic clamp (HEC). Plasma glucose and insulin concentrations were not different between groups within each clamp, but insulin concentrations increased 10-fold between the EEC and the HEC. During the EEC, rates of glucose uptake (umbilical uptake + exogenous infusion) and glucose utilization were 47% and 35% lower (P < 0.05) in NE fetuses compared with controls. During the HEC, rates of glucose uptake were 28% lower (P < 0.05) in NE fetuses than controls. Glucose production was undetectable in either group, and glucose oxidation was unaffected by the NE infusion. These findings indicate that chronic exposure to high plasma NE concentrations lowers rates of net glucose uptake in the fetus without affecting glucose oxidation rates or initiating endogenous glucose production. Lower fetal glucose uptake was independent of insulin, which indicates insulin resistance as a consequence of chronically elevated NE.
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Affiliation(s)
- Melissa A Davis
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Leticia E Camacho
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Miranda J Anderson
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Nathan R Steffens
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Alexander L Pendleton
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Amy C Kelly
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Sean W Limesand
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
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6
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Nishihama K, Maki K, Okano Y, Hashimoto R, Hotta Y, Uemura M, Yasuma T, Suzuki T, Hayashi T, Ishikawa E, Yano Y, Gabazza EC, Ito M, Takei Y. A case of type 2 diabetes mellitus with metformin-associated lactic acidosis initially presenting the appearance of a sulfonylurea-related hypoglycemic attack. Acute Med Surg 2016; 4:123-126. [PMID: 29123848 PMCID: PMC5667282 DOI: 10.1002/ams2.233] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Accepted: 06/28/2016] [Indexed: 01/12/2023] Open
Abstract
Case A 64‐year‐old Japanese woman with diabetes mellitus was admitted for hypoglycemia. Her diabetes had been under good control with glimepiride, voglibose, exenatide, and metformin for a few years. Although overt proteinuria was observed, the serum creatinine values were within normal range during the routine outpatient follow‐up. Hypoglycemic attack caused by glimepiride and loss of appetite by urinary tract infection were diagnosed. Then, metformin‐associated lactic acidosis with acute renal failure caused by dehydration was detected. Outcome Her condition was improved by continuous veno‐venous hemodiafiltration and hemodialysis, known to be useful to remove metformin. Conclusion We reported a case of metformin‐associated lactic acidosis with hypoglycemia during routine treatment of diabetes that was successfully rescued by early renal replacement therapy.
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Affiliation(s)
- Kota Nishihama
- Department of Diabetes, Metabolism and Endocrinology Mie University Graduate School of Medicine Tsu Japan
| | - Kanako Maki
- Department of Diabetes and Endocrinology Mie University Hospital Tsu Japan
| | - Yuko Okano
- Department of Diabetes and Endocrinology Mie University Hospital Tsu Japan
| | - Rei Hashimoto
- Department of Diabetes and Endocrinology Mie University Hospital Tsu Japan
| | - Yasuhiro Hotta
- Department of Diabetes and Endocrinology Mie University Hospital Tsu Japan
| | - Mei Uemura
- Department of Diabetes, Metabolism and Endocrinology Mie University Graduate School of Medicine Tsu Japan
| | - Taro Yasuma
- Department of Immunology Mie University Graduate School of Medicine Tsu Japan
| | - Toshinari Suzuki
- Department of Diabetes and Endocrinology Mie University Hospital Tsu Japan
| | - Toyomi Hayashi
- Department of Diabetes and Endocrinology Mie University Hospital Tsu Japan
| | - Eiji Ishikawa
- Department of Cardiology and Nephrology Mie University Graduate School of Medicine Tsu Japan
| | - Yutaka Yano
- Department of Diabetes, Metabolism and Endocrinology Mie University Graduate School of Medicine Tsu Japan
| | - Esteban C Gabazza
- Department of Immunology Mie University Graduate School of Medicine Tsu Japan
| | - Masaaki Ito
- Department of Cardiology and Nephrology Mie University Graduate School of Medicine Tsu Japan
| | - Yoshiyuki Takei
- Department of Gastroenterology and Hepatology Mie University Graduate School of Medicine Tsu Japan
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7
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Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
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Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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8
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Jensen J, Rustad PI, Kolnes AJ, Lai YC. The role of skeletal muscle glycogen breakdown for regulation of insulin sensitivity by exercise. Front Physiol 2011; 2:112. [PMID: 22232606 PMCID: PMC3248697 DOI: 10.3389/fphys.2011.00112] [Citation(s) in RCA: 219] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 12/09/2011] [Indexed: 12/12/2022] Open
Abstract
Glycogen is the storage form of carbohydrates in mammals. In humans the majority of glycogen is stored in skeletal muscles (∼500 g) and the liver (∼100 g). Food is supplied in larger meals, but the blood glucose concentration has to be kept within narrow limits to survive and stay healthy. Therefore, the body has to cope with periods of excess carbohydrates and periods without supplementation. Healthy persons remove blood glucose rapidly when glucose is in excess, but insulin-stimulated glucose disposal is reduced in insulin resistant and type 2 diabetic subjects. During a hyperinsulinemic euglycemic clamp, 70-90% of glucose disposal will be stored as muscle glycogen in healthy subjects. The glycogen stores in skeletal muscles are limited because an efficient feedback-mediated inhibition of glycogen synthase prevents accumulation. De novo lipid synthesis can contribute to glucose disposal when glycogen stores are filled. Exercise physiologists normally consider glycogen's main function as energy substrate. Glycogen is the main energy substrate during exercise intensity above 70% of maximal oxygen uptake ([Formula: see text]) and fatigue develops when the glycogen stores are depleted in the active muscles. After exercise, the rate of glycogen synthesis is increased to replete glycogen stores, and blood glucose is the substrate. Indeed insulin-stimulated glucose uptake and glycogen synthesis is elevated after exercise, which, from an evolutional point of view, will favor glycogen repletion and preparation for new "fight or flight" events. In the modern society, the reduced glycogen stores in skeletal muscles after exercise allows carbohydrates to be stored as muscle glycogen and prevents that glucose is channeled to de novo lipid synthesis, which over time will causes ectopic fat accumulation and insulin resistance. The reduction of skeletal muscle glycogen after exercise allows a healthy storage of carbohydrates after meals and prevents development of type 2 diabetes.
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Affiliation(s)
- Jørgen Jensen
- Department of Physical Performance, Norwegian School of Sport Sciences Oslo, Norway
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9
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Battram DS, Graham TE, Dela F. Caffeine's impairment of insulin-mediated glucose disposal cannot be solely attributed to adrenaline in humans. J Physiol 2007; 583:1069-77. [PMID: 17656440 PMCID: PMC2277186 DOI: 10.1113/jphysiol.2007.130526] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Caffeine (CAF) impedes insulin-mediated glucose disposal (IMGD) and increases plasma adrenaline concentrations ([ADR]; 0.6 nm). While the antagonism of ADR abolishes the CAF effect, infusion of ADR (0.75 nm) has no effect on IMGD. We have now examined CAF and ADR in concert to determine whether or not they elicit an additive response on IMGD. We hypothesized that CAF + ADR would elicit a greater effect than either CAF or ADR alone (i.e. that CAF effects would not be solely attributed to ADR). Subjects (n = 8) completed four trials in a randomized manner. An isoglycaemic-hyperinsulinaemic clamp was performed 30 min after the following treatments were administered: (1) placebo capsules and saline infusion ([ADR] = 0.29 nm) (PL trial), (2) CAF capsules (dose = 5 mg kg(-1)) and saline infusion ([ADR] = 0.62 nm) (CAF trial), (3) PL capsules and ADR infusion ([ADR] = 1.19 nm) (ADR trial), and (4) CAF capsules (dose = 5 mg kg(-1)) and ADR infusion ([ADR] = 0.93 nm) (CAF + ADR trial). As expected, CAF, ADR and CAF + ADR decreased (P <or= 0.05) IMGD compared to PL. CAF + ADR resulted in a more pronounced decrease in IMGD versus PL (42%) compared to CAF (26%) or ADR (24%) alone; however, the effect was not fully additive (P = 0.08). Furthermore, CAF decreased IMGD to a similar magnitude as ADR despite a 50% lower [ADR]. In summary, while ADR contributes to the CAF-induced impairment in IMGD, it is not solely responsible for caffeine's effects.
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Affiliation(s)
- D S Battram
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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10
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Forbes SC, Kowalchuk JM, Thompson RT, Marsh GD. Effects of hyperventilation on phosphocreatine kinetics and muscle deoxygenation during moderate-intensity plantar flexion exercise. J Appl Physiol (1985) 2007; 102:1565-73. [PMID: 17218429 DOI: 10.1152/japplphysiol.00895.2006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of controlled voluntary hyperventilation (Hyp) on phosphocreatine (PCr) kinetics and muscle deoxygenation were examined during moderate-intensity plantar flexion exercise. Male subjects ( n = 7) performed trials consisting of 20-min rest, 6-min exercise, and 10-min recovery in control [Con; end-tidal Pco2(PetCO2) ∼ 33 mmHg] and Hyp (PetCO2∼17 mmHg) conditions. Phosphorus-31 magnetic resonance and near-infrared spectroscopy were used simultaneously to monitor intramuscular acid-base status, high-energy phosphates, and muscle oxygenation. Resting intracellular hydrogen ion concentration ([H+]i) was lower ( P < 0.05) in Hyp [90 nM (SD 3)] than Con [96 nM (SD 4)]; however, at end exercise, [H+]iwas greater ( P < 0.05) in Hyp [128 nM (SD 19)] than Con [120 nM (SD 17)]. At rest, [PCr] was not different between Con [36 mM (SD 2)] and Hyp [36 mM (SD 1)]. The time constant (τ) of PCr breakdown during transition from rest to exercise was greater ( P < 0.05) in Hyp [39 s (SD 22)] than Con [32 s (SD 22)], and the PCr amplitude was greater ( P < 0.05) in Hyp [26% (SD 4)] than Con [22% (SD 6)]. The deoxyhemoglobin and/or deoxymyoglobin (HHb) τ was similar between Hyp [13 s (SD 8)] and Con [10 s (SD 3)]; however, the amplitude was increased ( P < 0.05) in Hyp [40 arbitrary units (au) (SD 23)] compared with Con [26 au (SD 17)]. In conclusion, our results indicate that Hyp-induced hypocapnia enhanced substrate-level phosphorylation during moderate-intensity exercise. In addition, the increased amplitude of the HHb response suggests a reduced local muscle perfusion in Hyp compared with Con.
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Affiliation(s)
- S C Forbes
- School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
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11
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Battram DS, Bugaresti J, Gusba J, Graham TE. Acute caffeine ingestion does not impair glucose tolerance in persons with tetraplegia. J Appl Physiol (1985) 2006; 102:374-81. [PMID: 17068214 DOI: 10.1152/japplphysiol.00901.2006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Acute caffeine (Caf) ingestion impairs glucose tolerance in able-bodied humans during an oral glucose tolerance test (OGTT). The mechanism responsible for this effect remains unclear, however, it is suggested to be due to the accompanying increase in epinephrine concentration. We examined whether or not Caf would elicit a glucose intolerance in persons with tetraplegia (TP) who do not exhibit an increased epinephrine response following Caf ingestion. All TP [n = 14; 9 incomplete (Inc) lesion, 5 complete (Com) lesion] completed two OGTT 1 h after consuming either gelatin (Pl) or Caf capsules (dose = 4 mg/kg). Blood samples were collected at baseline (time = 0 min), 1 h after capsule ingestion (time = 60 min), and every 30 min during the OGTT (time = 90-180 min). Glucose, insulin, proinsulin, and C-peptide responses were similar (P > 0.05) between treatments, demonstrating no effect of Caf on glucose tolerance. This lack of a Caf effect may be due to the low epinephrine concentration that remained unchanged (P > 0.05) throughout all experiments. Interestingly, the Com exhibited a 50% higher glucose response (P <or= 0.05) and a 46% (P > 0.05) lower insulin response (vs. Inc), suggesting a more pronounced glucose intolerance within this subgroup. Furthermore, nine TP (5 Com, 4 Inc) had glucose levels of >or= 7.8 mM at the end of the OGTT (time = 180 min), classifying them as glucose intolerant. In summary, acute Caf ingestion does not increase epinephrine concentration or impair glucose tolerance in TP.
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Affiliation(s)
- D S Battram
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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de Beaudrap P, Witten G, Biltz G, Perrier E. Mechanistic model of fuel selection in the muscle. J Theor Biol 2006; 242:151-63. [PMID: 16574156 DOI: 10.1016/j.jtbi.2006.02.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Revised: 02/16/2006] [Accepted: 02/16/2006] [Indexed: 11/24/2022]
Abstract
Fuel selection in human muscle is key to explaining insulin resistance. In obesity and type 2 diabetes mellitus, there is an increased content of lipid within and around muscle fibers. Changes in muscle fuel partitioning of lipid, between oxidation and storage of fat, contribute to the accumulation of intramuscular triglycerides and to the pathogenesis of both obesity and type 2 diabetes mellitus. A mathematical model of the aggregated metabolism in skeletal muscle was developed and the effects of fuel selection for lean and obese individuals under fasting conditions, insulin-stimulated conditions, and oscillating insulin conditions were examined. Model results were complementary to prior observations that elevated lipid oxidation during insulin-stimulated conditions is correlated with insulin resistance. The model also adequately simulated metabolic inflexibility between fat and glucose oxidation in the obese individual. A novel sensitivity analysis indicated the strong interaction effects of parameters of glucose and lipid oxidation pathways on the variables of each pathway.
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Affiliation(s)
- P de Beaudrap
- Institut de Recherche et de Développement. 32, avenue Henri Varagnat, 93143 Bondy cedex, France
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13
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Hutchinson DS, Bengtsson T. AMP-activated protein kinase activation by adrenoceptors in L6 skeletal muscle cells: mediation by alpha1-adrenoceptors causing glucose uptake. Diabetes 2006; 55:682-90. [PMID: 16505231 DOI: 10.2337/diabetes.55.03.06.db05-0901] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AMP-activated protein kinase (AMPK), which functions as a sensor of cellular energy homeostasis, was phosphorylated after norepinephrine stimulation in L6 skeletal muscle cells. This effect was mediated by alpha1-adrenoceptors, with no stimulatory effects due to interactions at alpha2- or beta-adrenoceptors. Alpha1-adrenoceptors are Gq-coupled receptors, and calcium but not phorbol esters could mimic the effect of alpha1-adrenergic stimulation; and we show that protein kinase C is not involved as an upstream signal to AMPK by alpha1-adrenergic stimulation and that the AMP-to-ATP ratio is unaltered after alpha1-adrenergic stimulation. We further show that glucose uptake mediated by alpha1- but not by beta-adrenoceptors can be inhibited by AMPK inhibition. Acetyl-CoA carboxylase (ACC) is phosphorylated at Ser218 by AMPK, and alpha1- but not beta-adrenoceptor stimulation results in phosphorylation of ACC at this residue. These results suggest a novel pathway where alpha1-adrenoceptor activation, independent of protein kinase C, leads to activation of AMPK in skeletal muscle, which contributes to alpha1-adrenoceptor-mediated increases in glucose uptake.
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Affiliation(s)
- Dana S Hutchinson
- Department of Physiology, The Wenner-Gren Institute, Stockholm University, SE 10691 Stockholm, Sweden
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14
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Asensio C, Jimenez M, Kühne F, Rohner-Jeanrenaud F, Muzzin P. The lack of beta-adrenoceptors results in enhanced insulin sensitivity in mice exhibiting increased adiposity and glucose intolerance. Diabetes 2005; 54:3490-5. [PMID: 16306366 DOI: 10.2337/diabetes.54.12.3490] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We and others have previously shown that triple knockout mice lacking the beta1/beta2/beta3-adrenoceptors (beta-less mice) developed a progressive obesity at adulthood. Here, we studied the glucose homeostasis in beta-less mice before the onset of obesity. We show that beta-less mice have increased fat mass and are glucose intolerant. In addition, we observed that beta-less mice have impaired glucose-induced insulin secretion and exhibit an increase in liver PEPCK gene expression in the fed state, suggesting that they have increased gluconeogenesis. Although these characteristics are usually associated with insulin resistance, beta-less mice exhibit enhanced insulin sensitivity during insulin tolerance tests. This is keeping with the results obtained during euglycemic-hyperinsulinemic clamps showing that beta-less mice display increased insulin responsiveness with normal suppression of hepatic glucose production. Altogether, our results suggest that an intact beta-adrenergic system is required to regulate overall glucose homeostasis and, in particular, insulin-mediated glucose uptake, most likely at the level of muscles and adipose tissue.
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Affiliation(s)
- Cédric Asensio
- Department of Cell Physiology and Metabolism, Medical University Centre, Geneva, Switzerland.
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15
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Battram DS, Graham TE, Richter EA, Dela F. The effect of caffeine on glucose kinetics in humans--influence of adrenaline. J Physiol 2005; 569:347-55. [PMID: 16150793 PMCID: PMC1464218 DOI: 10.1113/jphysiol.2005.097444] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
While caffeine impedes insulin-mediated glucose disposal in humans, its effect on endo-genous glucose production (EGP) remains unknown. In addition, the mechanism involved in these effects is unclear, but may be due to the accompanying increase in adrenaline concentration. We studied the effect of caffeine on EGP and glucose infusion rates (GIR), and whether or not adrenaline can account for all of caffeine's effects. Subjects completed three isoglycaemic-hyperinsulinaemic clamps (with 3-[(3)H]glucose infusion) 30 min after ingesting: (1) placebo capsules (n= 12); (2) caffeine capsules (5 mg kg(-1)) (n= 12); and either (3) placebo plus a high-dose adrenaline infusion (HAdr; adrenaline concentration, 1.2 nM; n= 8) or (4) placebo plus a low-dose adrenaline infusion (LAdr; adrenaline concentration, 0.75 nM; n= 6). With caffeine, adrenaline increased to 0.6 nM but no effect on EGP was observed. While caffeine and HAdr decreased GIR by 13 (P < 0.05) and 34% (P < 0.05) versus the placebo, respectively, LAdr did not result in a significant reduction (5%) in GIR versus the placebo. Due to the fact that both caffeine and LAdr resulted in similar adrenaline concentrations, but resulted in different decreases in GIR, it is concluded that adrenaline alone does not account for the effects of caffeine and additional mechanisms must be involved.
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Affiliation(s)
- Danielle S Battram
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
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16
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Tremblay F, Krebs M, Dombrowski L, Brehm A, Bernroider E, Roth E, Nowotny P, Waldhäusl W, Marette A, Roden M. Overactivation of S6 kinase 1 as a cause of human insulin resistance during increased amino acid availability. Diabetes 2005; 54:2674-84. [PMID: 16123357 DOI: 10.2337/diabetes.54.9.2674] [Citation(s) in RCA: 276] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
To examine the molecular mechanisms by which plasma amino acid elevation impairs insulin action, we studied seven healthy men twice in random order during infusion of an amino acid mixture or saline (total plasma amino acid approximately 6 vs. approximately 2 mmol/l). Somatostatin-insulin-glucose clamps created conditions of low peripheral hyperinsulinemia ( approximately 100 pmol/l, 0-180 min) and prandial-like peripheral hyperinsulinemia ( approximately 430 pmol/l, 180-360 min). At low peripheral hyperinsulinemia, endogenous glucose production (EGP) did not change during amino acid infusion but decreased by approximately 70% during saline infusion (EGP(150-180 min) 11 +/- 1 vs. 3 +/- 1 mumol . kg(-1) . min(-1), P = 0.001). Prandial-like peripheral hyperinsulinemia completely suppressed EGP during both protocols, whereas whole-body rate of glucose disappearance (R(d)) was approximately 33% lower during amino acid infusion (R(d) (330-360 min) 50 +/- 4 vs. 75 +/- 6 mumol . kg(-1) . min(-1), P = 0.002) indicating insulin resistance. In skeletal muscle biopsies taken before and after prandial-like peripheral hyperinsulinemia, plasma amino acid elevation markedly increased the ability of insulin to activate S6 kinase 1 compared with saline infusion ( approximately 3.7- vs. approximately 1.9-fold over baseline). Furthermore, amino acid infusion increased the inhibitory insulin receptor substrate-1 phosphorylation at Ser312 and Ser636/639 and decreased insulin-induced phosphoinositide 3-kinase activity. However, plasma amino acid elevation failed to reduce insulin-induced Akt/protein kinase B and glycogen synthase kinase 3alpha phosphorylation. In conclusion, amino acids impair 1) insulin-mediated suppression of glucose production and 2) insulin-stimulated glucose disposal in skeletal muscle. Our results suggest that overactivation of the mammalian target of rapamycin/S6 kinase 1 pathway and inhibitory serine phosphorylation of insulin receptor substrate-1 underlie the impairment of insulin action in amino acid-infused humans.
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Affiliation(s)
- Frédéric Tremblay
- Department of Internal Medicine III, Währinger Gürtel 18-20, A-1090 Vienna, Austria
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17
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Aftab Guy D, Sandoval D, Richardson MA, Tate D, Davis SN. Effects of glycemic control on target organ responses to epinephrine in type 1 diabetes. Am J Physiol Endocrinol Metab 2005; 289:E258-65. [PMID: 15784645 DOI: 10.1152/ajpendo.00311.2004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Severe hypoglycemia occurs in intensively treated patients with type 1 diabetes mellitus (T1DM) due in part to deficient epinephrine counterregulatory responses. Previously, we have found that T1DM patients demonstrated a spectrum of altered responses to epinephrine at a variety of target organs compared with nondiabetic healthy subjects. What is not known is whether intensive glycemic control further modifies target organ responses in individuals with T1DM. Therefore, the aim of this study is to assess whether there is tissue specific (liver, muscle, adipose tissue, pancreas and cardiovascular) resistance to epinephrine in intensively controlled (IC) T1DM compared with those with conventional control (CC). Eight IC patients (age 33 +/- 4 yr, BMI 24 +/- 2 kg/m2, Hb A1C 6.7 +/- 0.1%), and 11 CC patients (age 35 +/- 3 yr, BMI 25 +/- 1 kg/m2, Hb A1C 9.6 +/- 0.1%) underwent two separate randomized, single-blind, 2-h hyperinsulinemic euglycemic clamp studies with (EPI) and without (NO EPI) epinephrine infusion. Epinephrine levels during EPI were similar in all groups (5,197 +/- 344 pmol/l). Glucose (5.3 +/- 0.1 mmol/l) and insulin levels (515 +/- 44 pmol/l) were similar in all groups during the glucose clamps. Endogenous glucose production (EGP) and glucose uptake (R(d)) were determined using [3-H3]glucose. Muscle biopsy was performed at the end of each study. IC had a significantly reduced EGP and R(d) responses to EPI compared with CC. Glucagon responses to EPI were similarly blunted in both IC and CC. Free fatty acid and glycerol response to EPI was greater in CC compared with IC. There was a significantly greater systolic blood pressure response to EPI in CC. We conclude that, despite similar epinephrine, insulin, and glucose levels, intensively treated T1DM patients had reduced cardiovascular, skeletal muscle, hepatic, and adipose target organ responses to EPI compared with conventionally treated T1DM patients.
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Affiliation(s)
- Deanna Aftab Guy
- 715 PRB, Div. of Diabetes, Endocrinology & Metabolism, Vanderbilt Univ. School of Medicine, Nashville, TN 37232-6303, USA
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18
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Serlie MJM, de Haan JH, Tack CJ, Verberne HJ, Ackermans MT, Heerschap A, Sauerwein HP. Glycogen synthesis in human gastrocnemius muscle is not representative of whole-body muscle glycogen synthesis. Diabetes 2005; 54:1277-82. [PMID: 15855310 DOI: 10.2337/diabetes.54.5.1277] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The introduction of 13C magnetic resonance spectroscopy (MRS) has enabled noninvasive measurement of muscle glycogen synthesis in humans. Conclusions based on measurements by the MRS technique assume that glucose metabolism in gastrocnemius muscle is representative for all skeletal muscles and thus can be extrapolated to whole-body muscle glucose metabolism. An alternative method to assess whole-body muscle glycogen synthesis is the use of [3-(3)H]glucose. In the present study, we compared this method to the MRS technique, which is a well-validated technique for measuring muscle glycogen synthesis. Muscle glycogen synthesis was measured in the gastrocnemius muscle of six lean healthy subjects by MRS and by the isotope method during a hyperinsulinemic-euglycemic clamp. Mean muscle glycogen synthesis as measured by the isotope method was 115 +/- 26 micromol x kg(-1) muscle x min(-1) vs. 178 +/- 72 micromol x kg(-1) muscle x min(-1) (P = 0.03) measured by MRS. Glycogen synthesis rates measured by MRS exceeded 100% of glucose uptake in three of the six subjects. We conclude that glycogen synthesis rates measured in gastrocnemius muscle cannot be extrapolated to whole-body muscle glycogen synthesis.
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Affiliation(s)
- Mireille J M Serlie
- Academic Medical Centre, Department of Endocrinology and Metabolism (F5-169), Meibergdreef 9, 1105AZ Amsterdam, The Netherlands.
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Guy DA, Sandoval D, Richardson MA, Tate D, Flakoll PJ, Davis SN. Differing physiological effects of epinephrine in type 1 diabetes and nondiabetic humans. Am J Physiol Endocrinol Metab 2005; 288:E178-86. [PMID: 15585598 DOI: 10.1152/ajpendo.00310.2004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Acute increases of the key counterregulatory hormone epinephrine can be modified by a number of physiological and pathological conditions in type 1 diabetic patients (T1DM). However, it is undecided whether the physiological effects of epinephrine are also reduced in T1DM. Therefore, the aim of this study was to determine whether target organ (liver, muscle, adipose tissue, pancreas, cardiovascular) responses to epinephrine differ between healthy subjects and T1DM patients. Thirty-four age- and weight-matched T1DM (n = 17) and healthy subjects (n = 17) underwent two randomized, single-blind, 2-h hyperinsulinemic euglycemic clamp studies with (Epi) and without epinephrine infusion. Muscle biopsy was performed at the end of each study. Epinephrine levels during Epi were similar in all groups (4,039 +/- 384 pmol/l). Glucose (5.3 +/- 0.06 mmol/l) and insulin levels (462 +/- 18 pmol/l) were also similar in all groups during the glucose clamps. Glucagon responses to Epi were absent in T1DM and significantly reduced compared with healthy subjects. Endogenous glucose production during the final 30 min was significantly greater during Epi in healthy subjects compared with T1DM (8.4 +/- 1.3 vs. 4.4 +/- 0.6 micromol.kg(-1).min(-1), P = 0.041). Glucose uptake showed almost a twofold greater decrease with Epi in healthy subjects vs. T1DM (Delta31 +/- 2 vs. Delta17 +/- 2 nmol.kg(-1).min(-1), respectively, P = 0.026). Glycerol, beta-hydroxybutyrate, and nonesterified fatty acid (NEFA) all increased significantly more in T1DM compared with healthy subjects. Increases in systolic blood pressure were greater in healthy subjects, but reductions of diastolic blood pressure were greater in T1DM patients with Epi. Reduction of glycogen synthase was significantly greater during epinephrine infusion in T1DM vs. healthy subjects. In summary, despite equivalent epinephrine, insulin, and glucose levels, changes in glucose flux, glucagon, and cardiovascular responses were greater in healthy subjects compared with T1DM. However, T1DM patients had greater lipolytic responses (glycerol and NEFA) during Epi. Thus we conclude that there is a spectrum of significant in vivo physiological differences of epinephrine action at the liver, muscle, adipose tissue, pancreas, and cardiovascular system between T1DM and healthy subjects.
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Affiliation(s)
- Deanna Aftab Guy
- Division of Pediatric Endocrinology, Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232-6303, USA
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20
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Thong FSL, Derave W, Kiens B, Graham TE, Ursø B, Wojtaszewski JFP, Hansen BF, Richter EA. Caffeine-induced impairment of insulin action but not insulin signaling in human skeletal muscle is reduced by exercise. Diabetes 2002; 51:583-90. [PMID: 11872654 DOI: 10.2337/diabetes.51.3.583] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We investigated the effects of caffeine ingestion on skeletal muscle glucose uptake, glycogen synthase (GS) activity, and insulin signaling intermediates during a 100-min euglycemic-hyperinsulinemic (100 microU/ml) clamp. On two occasions, seven men performed 1-h one-legged knee extensor exercise at 3 h before the clamp. Caffeine (5 mg/kg) or placebo was administered in a randomized, double-blind fashion 1 h before the clamp. During the clamp, whole-body glucose disposal was reduced (P < 0.05) in caffeine (37.5 +/- 3.1 micromol x min(-1) x kg(-1)) vs. placebo (54.1 +/- 2.9 micromol x min(-1) x kg(-1)). In accordance, the total area under the curve over 100 min (AUC(0--100 min)) for insulin-stimulated glucose uptake in caffeine was reduced (P < 0.05) by approximately 50% in rested and exercised muscle. Caffeine also reduced (P < 0.05) GS activity before and during insulin infusion in both legs. Exercise increased insulin sensitivity of leg glucose uptake in both caffeine and placebo. Insulin increased insulin receptor tyrosine kinase (IRTK), insulin receptor substrate 1-associated phosphatidylinositol (PI) 3-kinase activities, and Ser(473) phosphorylation of protein kinase B (PKB)/Akt significantly but similarly in rested and exercised legs. Furthermore, insulin significantly decreased glycogen synthase kinase-3alpha (GSK-3alpha) activity equally in both legs. Caffeine did not alter insulin signaling in either leg. Plasma epinephrine and muscle cAMP concentrations were increased in caffeine. We conclude that 1) caffeine impairs insulin-stimulated glucose uptake and GS activity in rested and exercised human skeletal muscle; 2) caffeine-induced impairment of insulin-stimulated muscle glucose uptake and downregulation of GS activity are not accompanied by alterations in IRTK, PI 3-kinase, PKB/Akt, or GSK-3alpha but may be associated with increases in epinephrine and intramuscular cAMP concentrations; and 3) exercise reduces the detrimental effects of caffeine on insulin action in muscle.
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Affiliation(s)
- Farah S L Thong
- Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Canada.
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21
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Krebs M, Krssak M, Bernroider E, Anderwald C, Brehm A, Meyerspeer M, Nowotny P, Roth E, Waldhäusl W, Roden M. Mechanism of amino acid-induced skeletal muscle insulin resistance in humans. Diabetes 2002; 51:599-605. [PMID: 11872656 DOI: 10.2337/diabetes.51.3.599] [Citation(s) in RCA: 291] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Plasma concentrations of amino acids are frequently elevated in insulin-resistant states, and a protein-enriched diet can impair glucose metabolism. This study examined effects of short-term plasma amino acid (AA) elevation on whole-body glucose disposal and cellular insulin action in skeletal muscle. Seven healthy men were studied for 5.5 h during euglycemic (5.5 mmol/l), hyperinsulinemic (430 pmol/l), fasting glucagon (65 ng/l), and growth hormone (0.4 microg/l) somatostatin clamp tests in the presence of low (approximately 1.6 mmol/l) and increased (approximately 4.6 mmol/l) plasma AA concentrations. Glucose turnover was measured with D-[6,6-(2)H(2)]glucose. Intramuscular concentrations of glycogen and glucose-6-phosphate (G6P) were monitored using (13)C and (31)P nuclear magnetic resonance spectroscopy, respectively. A approximately 2.1-fold elevation of plasma AAs reduced whole-body glucose disposal by 25% (P < 0.01). Rates of muscle glycogen synthesis decreased by 64% (180--315 min, 24 plus minus 3; control, 67 plus minus 10 micromol center dot l(-1) center dot min(-1); P < 0.01), which was accompanied by a reduction in G6P starting at 130 min (DeltaG6P(260--300 min), 18 plus minus 19; control, 103 plus minus 33 micromol/l; P < 0.05). In conclusion, plasma amino acid elevation induces skeletal muscle insulin resistance in humans by inhibition of glucose transport/phosphorylation, resulting in marked reduction of glycogen synthesis.
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Affiliation(s)
- Michael Krebs
- Division of Endocrinology and Metabolism, Department of Internal Medicine III, University of Vienna Medical School, Vienna, Austria
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Ye JM, Lim-Fraser M, Cooney GJ, Cooper GJ, Iglesias MA, Watson DG, Choong B, Kraegen EW. Evidence that amylin stimulates lipolysis in vivo: a possible mediator of induced insulin resistance. Am J Physiol Endocrinol Metab 2001; 280:E562-9. [PMID: 11254462 DOI: 10.1152/ajpendo.2001.280.4.e562] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study investigated the role of amylin in lipid metabolism and its possible implications for insulin resistance. In 5- to 7-h-fasted conscious rats, infusion of rat amylin (5 nmol/h for 4 h) elevated plasma glucose, lactate, and insulin (P <0.05 vs. control, repeated-measures ANOVA) with peak values occurring within 60 min. Despite the insulin rise, plasma nonesterified fatty acids (NEFA) and glycerol were also elevated (P < 0.001 vs. control), and these elevations (80% above basal) were sustained over the 4-h infusion period. Although unaltered in plasma, triglyceride content in liver was increased by 28% (P < 0.001) with a similar tendency in muscle (18%, P = 0.1). Infusion of the rat amylin antagonist amylin-(8-37) (125 nmol/h) induced opposite basal plasma changes to amylin, i.e., lowered plasma NEFA, glycerol, glucose, and insulin levels (all P < 0.05 vs. control); additionally, amylin-(8-37) blocked amylin-induced elevations of these parameters (P < 0.01). Treatment with acipimox (10 mg/kg), an anti-lipolytic agent, before or after amylin infusion blocked amylin's effects on plasma NEFA, glycerol, and insulin but not on glucose and lactate. We conclude that amylin could exert a lipolytic-like action in vivo that is blocked by and is opposite to effects of its antagonist amylin-(8-37). Further studies are warranted to examine the physiological implications of lipid mobilization for amylin-induced insulin resistance.
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Affiliation(s)
- J M Ye
- Garvan Institute of Medical Research, St. Vincent's Hospital, 384 Victoria Street, Darlinghurst, Sydney, New South Wales 2010, Australia.
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