Exercising for Insulin Sensitivity – Is There a Mechanistic Relationship With Quantitative Changes in Skeletal Muscle Mass?

Skeletal muscle (SM) tissue has been repetitively shown to play a major role in whole-body glucose homeostasis and overall metabolic health. Hence, SM hypertrophy through resistance training (RT) has been suggested to be favorable to glucose homeostasis in different populations, from young healthy to type 2 diabetic (T2D) individuals. While RT has been shown to contribute to improved metabolic health, including insulin sensitivity surrogates, in multiple studies, a universal understanding of a mechanistic explanation is currently lacking. Furthermore, exercised-improved glucose homeostasis and quantitative changes of SM mass have been hypothesized to be concurrent but not necessarily causally associated. With a straightforward focus on exercise interventions, this narrative review aims to highlight the current level of evidence of the impact of SM hypertrophy on glucose homeostasis, as well various mechanisms that are likely to explain those effects. These mechanistic insights could provide a strengthened rationale for future research assessing alternative RT strategies to the current classical modalities, such as low-load, high repetition RT or high-volume circuit-style RT, in metabolically impaired populations.

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Myofibrillar distribution of succinate dehydrogenase activity and lipid stores differs in skeletal muscle tissue of paraplegic subjects

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00270.2011 ◽

2012 ◽

Vol 302 (3) ◽

pp. E365-E373 ◽

Cited By ~ 7

Author(s):

Richard A. M. Jonkers ◽

Marlou L. Dirks ◽

Christine I. H. C. Nabuurs ◽

Henk M. De Feyter ◽

Stephan F. E. Praet ◽

...

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Succinate Dehydrogenase ◽

Muscle Tissue ◽

Muscle Fiber ◽

Muscle Fibers ◽

Oxidative Capacity ◽

Skeletal Muscle Tissue ◽

Whole Body ◽

The Impact

Lack of physical activity has been related to an increased risk of developing insulin resistance. This study aimed to assess the impact of chronic muscle deconditioning on whole body insulin sensitivity, muscle oxidative capacity, and intramyocellular lipid (IMCL) content in subjects with paraplegia. Nine subjects with paraplegia and nine able-bodied, lean controls were recruited. An oral glucose tolerance test was performed to assess whole body insulin sensitivity. IMCL content was determined both in vivo and in vitro using1H-magnetic resonance spectroscopy and fluorescence microscopy, respectively. Muscle biopsy samples were stained for succinate dehydrogenase (SDH) activity to measure muscle fiber oxidative capacity. Subcellular distributions of IMCL and SDH activity were determined by defining subsarcolemmal and intermyofibrillar areas on histological samples. SDH activity was 57 ± 14% lower in muscle fibers derived from subjects with paraplegia when compared with controls ( P < 0.05), but IMCL content and whole body insulin sensitivity did not differ between groups. In muscle fibers taken from controls, both SDH activity and IMCL content were higher in the subsarcolemmal region than in the intermyofibrillar area. This typical subcellular SDH and IMCL distribution pattern was lost in muscle fibers collected from subjects with paraplegia and had changed toward a more uniform distribution. In conclusion, the lower metabolic demand in deconditioned muscle of subjects with paraplegia results in a significant decline in muscle fiber oxidative capacity and is accompanied by changes in the subcellular distribution patterns of SDH activity and IMCL. However, loss of muscle activity due to paraplegia is not associated with substantial lipid accumulation in skeletal muscle tissue.

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Impaired Skeletal Muscle β-Adrenergic Activation and Lipolysis Are Associated with Whole-Body Insulin Resistance in Rats Bred for Low Intrinsic Exercise Capacity

Endocrinology ◽

10.1210/en.2009-0158 ◽

2009 ◽

Vol 150 (11) ◽

pp. 4883-4891 ◽

Cited By ~ 38

Author(s):

Sarah J. Lessard ◽

Donato A. Rivas ◽

Zhi-Ping Chen ◽

Bryce J. van Denderen ◽

Matthew J. Watt ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Sensitivity ◽

Protein Content ◽

Exercise Capacity ◽

Metabolic Health ◽

Whole Body ◽

Receptor Protein ◽

Endurance Capacity ◽

Triacylglycerol Lipase

Rats selectively bred for high endurance running capacity (HCR) have higher insulin sensitivity and improved metabolic health compared with those bred for low endurance capacity (LCR). We investigated several skeletal muscle characteristics, in vitro and in vivo, that could contribute to the metabolic phenotypes observed in sedentary LCR and HCR rats. After 16 generations of selective breeding, HCR had approximately 400% higher running capacity (P < 0.001), improved insulin sensitivity (P < 0.001), and lower fasting plasma glucose and triglycerides (P < 0.05) compared with LCR. Skeletal muscle ceramide and diacylglycerol content, basal AMP-activated protein kinase (AMPK) activity, and basal lipolysis were similar between LCR and HCR. However, the stimulation of lipolysis in response to 10 μm isoproterenol was 70% higher in HCR (P = 0.004). Impaired isoproterenol sensitivity in LCR was associated with lower basal triacylglycerol lipase activity, Ser660 phosphorylation of HSL, and β2-adrenergic receptor protein content in skeletal muscle. Expression of the orphan nuclear receptor Nur77, which is induced by β-adrenergic signaling and is associated with insulin sensitivity, was lower in LCR (P < 0.05). Muscle protein content of Nur77 target genes, including uncoupling protein 3, fatty acid translocase/CD36, and the AMPK γ3 subunit were also lower in LCR (P < 0.05). Our investigation associates whole-body insulin resistance with impaired β-adrenergic response and reduced expression of genes that are critical regulators of glucose and lipid metabolism in skeletal muscle. We identify impaired β-adrenergic signal transduction as a potential mechanism for impaired metabolic health after artificial selection for low intrinsic exercise capacity.

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Delivery of adiponectin gene to skeletal muscle using ultrasound targeted microbubbles improves insulin sensitivity and whole body glucose homeostasis

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00493.2012 ◽

2013 ◽

Vol 304 (2) ◽

pp. E168-E175 ◽

Cited By ~ 13

Author(s):

Vivian Vu ◽

Ying Liu ◽

Sanjana Sen ◽

Aimin Xu ◽

Gary Sweeney

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Glucose Homeostasis ◽

Fluorescent Protein ◽

Systemic Circulation ◽

Tolerance Test ◽

Whole Body ◽

Glucose Disposal ◽

Adiponectin Gene ◽

Green Fluorescent

Numerous studies have shown that adiponectin confers antidiabetic effects via both insulin-like and insulin-sensitizing actions. The majority of adiponectin in circulation is derived from adipocytes; however, other tissues such as skeletal muscle can produce adiponectin. This study was designed to investigate the functional significance of adiponectin produced by skeletal muscle. We encapsulated the adiponectin gene in lipid-coated microspheres filled with octafluoropropane gas that were injected into the systemic circulation and destroyed within the microvasculature of skeletal muscle using ultrasound. We first demonstrated safe and successful targeting of luciferase and green fluorescent protein reporter genes to skeletal muscle using this approach and then confirmed efficient overexpression of adiponectin mRNA and oligomeric protein forms. Glucose tolerance test indicated that overexpression of adiponectin in skeletal muscle was able to improve glucose intolerance induced by feeding mice a high-fat diet (HFD), and this correlated with improved skeletal muscle insulin signaling. We then performed hyperinsulinemic-euglycemic clamp studies and demonstrated that adiponectin overexpression attenuated the decreases in glucose infusion rate, glucose disposal, and increase in glucose appearance induced by HFD. Ultrasound-targeted microbubble destruction (UTMD) delivery of adiponectin to skeletal muscle also enhanced serum adiponectin levels and improved hepatic insulin sensitivity. In conclusion, our data show that UTMD efficiently delivers adiponectin to skeletal muscle and that this improves insulin sensitivity and glucose homeostasis.

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Selective activation of PPARγ in skeletal muscle induces endogenous production of adiponectin and protects mice from diet-induced insulin resistance

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00446.2009 ◽

2010 ◽

Vol 298 (1) ◽

pp. E28-E37 ◽

Cited By ~ 69

Author(s):

Rajesh H. Amin ◽

Suresh T. Mathews ◽

Heidi S. Camp ◽

Liyun Ding ◽

Todd Leff

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Sensitivity ◽

Transgenic Mice ◽

Muscle Tissue ◽

Glucose Homeostasis ◽

Muscle Cells ◽

Whole Body ◽

Fiber Types ◽

Dependent Manner

The nuclear receptor peroxisome proliferator-activated receptor (PPAR)γ plays a key role in regulating whole body glucose homeostasis and insulin sensitivity. Although it is expressed most highly in adipose, it is also present at lower levels in many tissues, including skeletal muscle. The role muscle PPARγ plays in metabolic regulation and in mediating the antidiabetic effects of the thiazolidinediones is not understood. The goal of this work was to examine the molecular and physiological effects of PPARγ activation in muscle cells. We found that pharmacological activation of PPARγ in primary cultured myocytes, and genetic activation of muscle PPARγ in muscle tissue of transgenic mice, induced the production of adiponectin directly from muscle cells. This muscle-produced adiponectin was functional and capable of stimulating adiponectin signaling in myocytes. In addition, elevated skeletal muscle PPARγ activity in transgenic mice provided a significant protection from high-fat diet-induced insulin resistance and associated changes in muscle phenotype, including reduced myocyte lipid content and an increase in the proportion of oxidative muscle fiber types. Our findings demonstrate that PPARγ activation in skeletal muscle can have a significant protective effect on whole body glucose homeostasis and insulin resistance and that myocytes can produce and secrete functional adiponectin in a PPARγ-dependent manner. We propose that activation of PPARγ in myocytes induces a local production of adiponectin that acts on muscle tissue to improve insulin sensitivity.

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Effect of training on insulin binding to rat skeletal muscle sarcolemmal vesicles

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1986.250.5.e570 ◽

1986 ◽

Vol 250 (5) ◽

pp. E570-E575

Author(s):

G. K. Grimditch ◽

R. J. Barnard ◽

S. A. Kaplan ◽

E. Sternlicht

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Exercise Training ◽

Insulin Binding ◽

Whole Body ◽

Rat Skeletal Muscle ◽

Binding Studies ◽

Muscle Enzyme ◽

Intravenous Glucose ◽

High Affinity

We examined the hypothesis that the exercise training-induced increase in skeletal muscle insulin sensitivity is mediated by adaptations in insulin binding to sarcolemmal (SL) insulin receptors. Insulin binding studies were performed on rat skeletal muscle SL isolated from control and trained rats. No significant differences were noted between groups in body weight or fat. An intravenous glucose tolerance test showed an increase in whole-body insulin sensitivity with training, and specific D-glucose transport studies on isolated SL vesicles indicated that this was due in part to adaptations in skeletal muscle. Enzyme marker analyses revealed no differences in yield, purity, or contamination of SL membranes between the two groups. Scatchard analyses indicated no significant differences in the number of insulin binding sites per milligram SL protein on the high-affinity (15.0 +/- 4.1 vs. 18.1 +/- 6.4 X 10(9)) or on the low-affinity portions (925 +/- 80 vs. 884 +/- 106 X 10(9)) of the curves. The association constants of the high-affinity (0.764 +/- 0.154 vs. 0.685 +/- 0.264 X 10(9) M-1) and of the low affinity sites (0.0096 +/- 0.0012 vs. 0.0102 +/- 0.0012 X 10(9) M-1) also were similar. These results do not support the hypothesis that the increased sensitivity to insulin after exercise training is due to changes in SL insulin receptor binding.

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Antecubital Vein Cannula Position Impacts Assessment of Forearm Glucose Uptake During an Oral Glucose Challenge in Healthy Volunteers

Experimental and Clinical Endocrinology & Diabetes ◽

10.1055/a-1275-4038 ◽

2020 ◽

Author(s):

Cécile Bétry ◽

Aline V. Nixon ◽

Paul L. Greenhaff ◽

Elizabeth J. Simpson

Keyword(s):

Skeletal Muscle ◽

Blood Glucose ◽

Glucose Uptake ◽

Venous Blood ◽

Whole Body ◽

Oral Glucose ◽

Antecubital Vein ◽

Glucose Challenge ◽

The Impact

Abstract Introduction Skeletal muscle is a major site for whole-body glucose disposal, and determination of skeletal muscle glucose uptake is an important metabolic measurement, particularly in research focussed on interventions that impact muscle insulin sensitivity. Calculating arterial-venous difference in blood glucose can be used as an indirect measure for assessing glucose uptake. However, the possibility of multiple tissues contributing to the composition of venous blood, and the differential in glucose uptake kinetics between tissue types, suggests that sampling from different vein sites could influence the estimation of glucose uptake. This study aimed to determine the impact of venous cannula position on calculated forearm glucose uptake following an oral glucose challenge in resting and post-exercise states. Materials and Methods In 9 young, lean, males, the impact of sampling blood from two antecubital vein positions; the perforating vein (‘perforating’ visit) and, at the bifurcation of superficial and perforating veins (‘bifurcation’ visit), was assessed. Brachial artery blood flow and arterialised-venous and venous blood glucose concentrations were measured in 3 physiological states; resting-fasted, resting-fed, and fed following intermittent forearm muscle contraction (fed-exercise). Results Following glucose ingestion, forearm glucose uptake area under the curve was greater for the ‘perforating’ than for the ‘bifurcation’ visit in the resting-fed (5.92±1.56 vs. 3.69±1.35 mmol/60 min, P<0.01) and fed-exercise (17.38±7.73 vs. 11.40±7.31 mmol/75 min, P<0.05) states. Discussion Antecubital vein cannula position impacts calculated postprandial forearm glucose uptake. These findings have implications for longitudinal intervention studies where serial determination of forearm glucose uptake is required.

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Branched-chain amino acid metabolism is regulated by ERRα in primary human myotubes and is further impaired by glucose loading in type 2 diabetes

Diabetologia ◽

10.1007/s00125-021-05481-9 ◽

2021 ◽

Author(s):

Rasmus J. O. Sjögren ◽

David Rizo-Roca ◽

Alexander V. Chibalin ◽

Elin Chorell ◽

Regula Furrer ◽

...

Keyword(s):

Type 2 Diabetes ◽

Skeletal Muscle ◽

Amino Acid ◽

Glucose Homeostasis ◽

Gene Set ◽

Branched Chain Amino Acid ◽

Human Myotubes ◽

Branched Chain ◽

The Impact

Abstract Aims/hypothesis Increased levels of branched-chain amino acids (BCAAs) are associated with type 2 diabetes pathogenesis. However, most metabolomic studies are limited to an analysis of plasma metabolites under fasting conditions, rather than the dynamic shift in response to a metabolic challenge. Moreover, metabolomic profiles of peripheral tissues involved in glucose homeostasis are scarce and the transcriptomic regulation of genes involved in BCAA catabolism is partially unknown. This study aimed to identify differences in circulating and skeletal muscle BCAA levels in response to an OGTT in individuals with normal glucose tolerance (NGT) or type 2 diabetes. Additionally, transcription factors involved in the regulation of the BCAA gene set were identified. Methods Plasma and vastus lateralis muscle biopsies were obtained from individuals with NGT or type 2 diabetes before and after an OGTT. Plasma and quadriceps muscles were harvested from skeletal muscle-specific Ppargc1a knockout and transgenic mice. BCAA-related metabolites and genes were assessed by LC-MS/MS and quantitative RT-PCR, respectively. Small interfering RNA and adenovirus-mediated overexpression techniques were used in primary human skeletal muscle cells to study the role of PPARGC1A and ESRRA in the expression of the BCAA gene set. Radiolabelled leucine was used to analyse the impact of oestrogen-related receptor α (ERRα) knockdown on leucine oxidation. Results Impairments in BCAA catabolism in people with type 2 diabetes under fasting conditions were exacerbated after a glucose load. Branched-chain keto acids were reduced 37–56% after an OGTT in the NGT group, whereas no changes were detected in individuals with type 2 diabetes. These changes were concomitant with a stronger correlation with glucose homeostasis biomarkers and downregulated expression of branched-chain amino acid transaminase 2, branched-chain keto acid dehydrogenase complex subunits and 69% of downstream BCAA-related genes in skeletal muscle. In primary human myotubes overexpressing peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α, encoded by PPARGC1A), 61% of the analysed BCAA genes were upregulated, while 67% were downregulated in the quadriceps of skeletal muscle-specific Ppargc1a knockout mice. ESRRA (encoding ERRα) silencing completely abrogated the PGC-1α-induced upregulation of BCAA-related genes in primary human myotubes. Conclusions/interpretation Metabolic inflexibility in type 2 diabetes impacts BCAA homeostasis and attenuates the decrease in circulating and skeletal muscle BCAA-related metabolites after a glucose challenge. Transcriptional regulation of BCAA genes in primary human myotubes via PGC-1α is ERRα-dependent. Graphical abstract

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Low intrinsic running capacity is associated with reduced skeletal muscle substrate oxidation and lower mitochondrial content in white skeletal muscle

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00659.2010 ◽

2011 ◽

Vol 300 (4) ◽

pp. R835-R843 ◽

Cited By ~ 38

Author(s):

Donato A. Rivas ◽

Sarah J. Lessard ◽

Misato Saito ◽

Anna M. Friedhuber ◽

Lauren G. Koch ◽

...

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Aerobic Capacity ◽

Artificial Selection ◽

White Muscle ◽

Metabolic Diseases ◽

Metabolic Health ◽

Mitochondrial Content ◽

Red Muscle ◽

Selection For

Chronic metabolic diseases develop from the complex interaction of environmental and genetic factors, although the extent to which each contributes to these disorders is unknown. Here, we test the hypothesis that artificial selection for low intrinsic aerobic running capacity is associated with reduced skeletal muscle metabolism and impaired metabolic health. Rat models for low- (LCR) and high- (HCR) intrinsic running capacity were derived from genetically heterogeneous N:NIH stock for 20 generations. Artificial selection produced a 530% difference in running capacity between LCR/HCR, which was associated with significant functional differences in glucose and lipid handling by skeletal muscle, as assessed by hindlimb perfusion. LCR had reduced rates of skeletal muscle glucose uptake (∼30%; P = 0.04), glucose oxidation (∼50%; P = 0.04), and lipid oxidation (∼40%; P = 0.02). Artificial selection for low aerobic capacity was also linked with reduced molecular signaling, decreased muscle glycogen, and triglyceride storage, and a lower mitochondrial content in skeletal muscle, with the most profound changes to these parameters evident in white rather than red muscle. We show that a low intrinsic aerobic running capacity confers reduced insulin sensitivity in skeletal muscle and is associated with impaired markers of metabolic health compared with high intrinsic running capacity. Furthermore, selection for high running capacity, in the absence of exercise training, endows increased skeletal muscle insulin sensitivity and oxidative capacity in specifically white muscle rather than red muscle. These data provide evidence that differences in white muscle may have a role in the divergent aerobic capacity observed in this generation of LCR/HCR.

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Hepatokine ERAP1 impairs skeletal muscle insulin sensitivity via ADRB2/PKA pathway

10.21203/rs.3.rs-37586/v1 ◽

2020 ◽

Author(s):

Feifan Guo ◽

Yuguo Niu ◽

Haizhou Jiang ◽

Hanrui Yin ◽

Fenfen Wang ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Sensitivity ◽

Neutralizing Antibodies ◽

Leptin Receptor ◽

Whole Body ◽

C2c12 Myotubes ◽

Insulin Resistant ◽

Skeletal Muscle Insulin Sensitivity ◽

Pka Pathway

Abstract The current study aimed to investigate the role of endoplasmic reticulum aminopeptidase 1 (ERAP1), a novel hepatokine, in whole-body glucose metabolism. Here, we found that hepatic ERAP1 levels were increased in insulin-resistant leptin-receptor-mutated (db/db) and high-fat diet (HFD)-fed mice. Consistently, hepatic ERAP1 overexpression attenuated skeletal muscle (SM) insulin sensitivity, whereas knockdown ameliorated SM insulin resistance. Furthermore, serum and hepatic ERAP1 levels were positively correlated, and recombinant mouse ERAP1 or conditioned medium with high ERAP1 content (CM-ERAP1) attenuated insulin signaling in C2C12 myotubes, and CM-ERAP1 or HFD-induced insulin resistance was blocked by ERAP1 neutralizing antibodies. Mechanistically, ERAP1 reduced ADRB2 expression and interrupted ADRB2-dependent signaling in C2C12 myotubes. Finally, ERAP1 inhibition via global knockout or the inhibitor thimerosal improved insulin sensitivity. Together, ERAP1 is a hepatokine that impairs SM and whole-body insulin sensitivity, and its inhibition might provide a therapeutic strategy for diabetes, particularly for those with SM insulin resistance.

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Do Patients with Prostate Cancer Benefit from Exercise Interventions? A Systematic Review and Meta-Analysis

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph19020972 ◽

2022 ◽

Vol 19 (2) ◽

pp. 972

Author(s):

Martin Færch Andersen ◽

Julie Midtgaard ◽

Eik Dybboe Bjerre

Keyword(s):

Prostate Cancer ◽

Aerobic Exercise ◽

Meta Analysis ◽

Healthcare Providers ◽

Cardiovascular Fitness ◽

Metabolic Health ◽

Whole Body ◽

Exercise Interventions ◽

General Mental Health ◽

General Physical

Men diagnosed and treated for prostate cancer experience severe adverse effects on quality of life (QoL) and metabolic health, some of which may be preventable or reversible with exercise, the benefits of which healthcare providers and patients increasingly acknowledge, though existing evidence on its effects varies in significance and magnitude. We aimed to review the effect of exercise on QoL and metabolic health in a broad prostate cancer population. A systematic search was conducted in nine databases and eligible trials were included in the meta-analytic procedure. All outcomes were stratified into aerobic exercise, resistance exercise, and a combination of both. The review identified 33 randomised controlled trials (2567 participants) eligible for inclusion. Exercise had a borderline small positive effect on cancer-specific QoL (standardised mean difference (SMD) = 0.10, 95% confidence interval (CI) −0.01–0.22), and a moderate to large effect on cardiovascular fitness (SMD = 0.46, 95% CI 0.34–0.59) with aerobic exercise being the superior modality (SMD = 0.60, 95% CI 0.29–0.90). A positive significant effect was seen in lower body strength, whole-body fat mass, general mental health, and blood pressure. No significant effect was seen in fatigue, lean body mass, and general physical health. We thereby conclude that exercise is effective in improving metabolic health in men diagnosed with prostate cancer, with aerobic exercise as the superior modality. The effect of exercise on QoL was small and not mediated by choice of exercise modality.

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