RESUMEN
The aim of the present study was to investigate the fiber type-specific abundance of autophagy-related proteins after an overnight fast and following ingestion of a mixed meal in human skeletal muscle. Twelve overweight, healthy young male volunteers underwent a 3-h mixed meal tolerance test following an overnight fast. Blood samples were collected in the overnight-fasted state and throughout the 180-min postmeal period. Skeletal muscle biopsies were collected in the fasted state, and at 30 and 90 min after meal ingestion. Protein content of key autophagy markers and upstream signaling responses were measured in whole muscle and pooled single fibers using immunoblotting. In the fasted state, type I fibers displayed lower LC3B-I but higher LC3B-II abundance and higher LC3B-II/LC3B-I ratio compared with type II fibers (P < 0.05). However, there were no fiber type differences in p62/SQSTM1, unc-51 like autophagy activating kinase (ULK1), ATG5, or ATG12 (P > 0.05). Compared with the fasted state, there was a reduction in LC3B-II abundance, indicative of lower autophagosome content, in whole muscle and in both type I and type II fibers following meal ingestion (P < 0.05). This reduction in autophagosome content occurred alongside similar increases in p-AktS473 and p-mTORS2448 in both type I and type II muscle fibers (P < 0.05). In human skeletal muscle, type I fibers have a greater autophagosome content than type II fibers in the overnight-fasted state despite comparable abundance of other key upstream autophagy proteins. Autophagy is rapidly inhibited in both fiber types following the ingestion of a mixed meal.NEW & NOTEWORTHY This study examined the fiber type-specific content of key autophagy proteins in human muscle. We showed that markers of autophagosome content are higher in type I fibers in the overnight-fasted state, whereas autophagy is rapidly inhibited in both type I and type II fibers after the ingestion of a mixed meal.
Asunto(s)
Autofagia , Músculo Esquelético , Autofagosomas , Ingestión de Alimentos , Humanos , Masculino , Fibras Musculares EsqueléticasRESUMEN
OBJECTIVE: To investigate the effect of high fat diet-induced insulin resistance on autophagy markers in the liver and skeletal muscle of mice in the fasted state and following an oral glucose bolus. METHODS: Forty C57BL/6J male mice were fed either a high fat, high sucrose (HFSD, n = 20) or standard chow control (CON, n = 20) diet for 16 weeks. Upon trial completion, mice were gavaged with water or glucose and skeletal muscle and liver were collected 15 min post gavage. Protein abundance and gene expression of autophagy markers and activation of related signalling pathways were assessed. RESULTS: Compared to CON, the HFSD intervention increased LC3B-II and p62/SQSTM1 protein abundance in the liver which is indicative of elevated autophagosome content via reduced clearance. These changes coincided with inhibitory autophagy signalling through elevated p-mTOR S2448 and p-ULK1S758. HFSD did not alter autophagy markers in skeletal muscle. Administration of an oral glucose bolus had no effect on autophagy markers or upstream signalling responses in either tissue regardless of diet. CONCLUSION: HFSD induces tissue-specific autophagy impairments, with autophagosome accumulation indicating reduced lysosomal clearance in the liver. In contrast, autophagy markers were unchanged in skeletal muscle, indicating that autophagy is not involved in the development of skeletal muscle insulin resistance.
Asunto(s)
Autofagia , Resistencia a la Insulina , Metabolismo de los Lípidos , Músculo Esquelético/metabolismo , Animales , Dieta de Carga de Carbohidratos/efectos adversos , Dieta Alta en Grasa/efectos adversos , Hígado/metabolismo , Masculino , Ratones Endogámicos C57BLRESUMEN
AIMS/HYPOTHESIS: This study aimed to examine the metabolic health of young apparently healthy non-obese adults to better understand mechanisms of hyperinsulinaemia. METHODS: Non-obese (BMI < 30 kg/m2) adults aged 18-35 years (N = 254) underwent a stable isotope-labelled OGTT. Insulin sensitivity, glucose effectiveness and beta cell function were determined using oral minimal models. Individuals were stratified into quartiles based on their insulin response during the OGTT, with quartile 1 having the lowest and quartile 4 the highest responses. RESULTS: Thirteen per cent of individuals had impaired fasting glucose (IFG; n = 14) or impaired glucose tolerance (IGT; n = 19), allowing comparisons across the continuum of insulin responses within the spectrum of normoglycaemia and prediabetes. BMI (~24 kg/m2) was similar across insulin quartiles and in those with IFG and IGT. Despite similar glycaemic excursions, fasting insulin, triacylglycerols and cholesterol were elevated in quartile 4. Insulin sensitivity was lowest in quartile 4, and accompanied by increased insulin secretion and reduced insulin clearance. Individuals with IFG had similar insulin sensitivity and beta cell function to those in quartiles 2 and 3, but were more insulin sensitive than individuals in quartile 4. While individuals with IGT had a similar degree of insulin resistance to quartile 4, they exhibited a more severe defect in beta cell function. Plasma branched-chain amino acids were not elevated in quartile 4, IFG or IGT. CONCLUSIONS/INTERPRETATION: Hyperinsulinaemia within normoglycaemic young, non-obese adults manifests due to increased insulin secretion and reduced insulin clearance. Individual phenotypic characterisation revealed that the most hyperinsulinaemic were more similar to individuals with IGT than IFG, suggesting that hyperinsulinaemic individuals may be on the continuum toward IGT. Furthermore, plasma branched-chain amino acids may not be an effective biomarker in identifying hyperinsulinaemia and insulin resistance in young non-obese adults.
Asunto(s)
Aminoácidos/sangre , Hiperinsulinismo/metabolismo , Secreción de Insulina/fisiología , Insulina/sangre , Adolescente , Adulto , Glucemia/metabolismo , Ayuno/sangre , Femenino , Prueba de Tolerancia a la Glucosa , Humanos , Hiperinsulinismo/sangre , Resistencia a la Insulina/fisiología , Lípidos/sangre , Masculino , Adulto JovenRESUMEN
Reciprocal regulation of hepatic glycolysis and gluconeogenesis contributes to systemic metabolic homeostasis. Recent evidence from lower order organisms has found that reversible post-translational modification of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), particularly acetylation, contributes to the reciprocal regulation of glycolysis/gluconeogenesis. However, whether this occurs in mammalian hepatocytes in vitro or in vivo is unknown. Several proteomics studies have identified 4 lysine residues in critical regions of mammalian GAPDH that are altered by multiple post-translational modifications. In FAO hepatoma cells, mutation of all 4 lysine residues (4K-R GAPDH) to mimic their unmodified state reduced GAPDH glycolytic activity and glycolytic flux and increased gluconeogenic GAPDH activity and glucose production. Hepatic expression of 4K-R GAPDH in mice increased GAPDH gluconeogenic activity and the contribution of gluconeogenesis to endogenous glucose production in the unfed state. Consistent with the increased reliance on the energy-consuming gluconeogenic pathway, plasma free fatty acids and ketones were elevated in mice expressing 4K-R GAPDH, suggesting enhanced lipolysis and hepatic fatty acid oxidation. In normal mice, food withholding and refeeding, as well as hormonal regulators of reciprocal glycolysis/gluconeogenesis, such as insulin, glucagon, and norepinephrine, had no effect on global GAPDH acetylation. However, GAPDH acetylation was reduced in obese and type 2 diabetic db/db mice. These findings show that post-translational modification of GAPDH lysine residues regulates hepatic and systemic metabolism, revealing an unappreciated role for hepatic GAPDH in substrate selection and utilization.-Bond, S. T., Howlett, K. F., Kowalski, G. M., Mason, S., Connor, T., Cooper, A., Streltsov, V., Bruce, C. R., Walder, K. R., McGee, S. L. Lysine post-translational modification of glyceraldehyde-3-phosphate dehydrogenase regulates hepatic and systemic metabolism.
Asunto(s)
Regulación Enzimológica de la Expresión Génica/fisiología , Gliceraldehído-3-Fosfato Deshidrogenasa (Fosforilante)/metabolismo , Hígado/metabolismo , Lisina , Procesamiento Proteico-Postraduccional/fisiología , Secuencia de Aminoácidos , Animales , Clonación Molecular , Gliceraldehído-3-Fosfato Deshidrogenasa (Fosforilante)/genética , Ratones , RatasRESUMEN
Normal skeletal muscle metabolism is essential for whole body metabolic homoeostasis and disruptions in muscle metabolism are associated with a number of chronic diseases. Transcriptional control of metabolic enzyme expression is a major regulatory mechanism for muscle metabolic processes. Substantial evidence is emerging that highlights the importance of epigenetic mechanisms in this process. This review will examine the importance of epigenetics in the regulation of muscle metabolism, with a particular emphasis on DNA methylation and histone acetylation as epigenetic control points. The emerging cross-talk between metabolism and epigenetics in the context of health and disease will also be examined. The concept of inheritance of skeletal muscle metabolic phenotypes will be discussed, in addition to emerging epigenetic therapies that could be used to alter muscle metabolism in chronic disease states.
Asunto(s)
Epigénesis Genética/genética , Regulación de la Expresión Génica/genética , Músculo Esquelético/metabolismo , Procesamiento Proteico-Postraduccional/genética , Acetilación/efectos de los fármacos , Animales , Metilación de ADN/genética , HumanosRESUMEN
Altered metabolism in tissues such as the liver, skeletal muscle and adipose tissue is observed in metabolic diseases characterized by nutrient excess and energy imbalance, such as obesity and type 2 diabetes. These alterations in metabolism can include resistance to the hormone insulin, lipid accumulation, mitochondrial dysfunction and transcriptional remodelling of major metabolic pathways. The underlying assumption has been that these same alterations in metabolism are fundamental to the pathogenesis of metabolic diseases. An alternative view is that these alterations in metabolism occur to protect cell and tissue viability in the face of constant positive energy balance. This speculative review presents evidence that many of the metabolic adaptations that occur in metabolic diseases characterized by nutrient excess can be viewed as protective in nature, rather than pathogenic per se for disease progression. Finally, we also briefly discuss the usefulness and potential pitfalls of therapeutic approaches that attempt to correct these same metabolic defects when energy balance is not altered, and the potential links between metabolic survival responses and other chronic diseases such as cancer.
Asunto(s)
Diabetes Mellitus Tipo 2/metabolismo , Metabolismo Energético/fisiología , Resistencia a la Insulina/fisiología , Obesidad/metabolismo , Hipernutrición/metabolismo , Animales , Diabetes Mellitus Tipo 2/diagnóstico , Humanos , Obesidad/diagnóstico , Hipernutrición/diagnósticoRESUMEN
Obesity causes a range of tissue dysfunctions that increases the risk for morbidity and mortality. Protein kinase D (PKD) represents a family of stress-activated intracellular signalling proteins that regulate essential processes such as cell proliferation and differentiation, cell survival, and exocytosis. Evidence suggests that PKD regulates the cellular adaptations to the obese environment in metabolically important tissues and drives the development of a variety of diseases. This review explores the role that PKD plays in tissue dysfunction in obesity, with special consideration of the development of obesity-mediated cardiomyopathy, a distinct cardiovascular disease that occurs in the absence of common comorbidities and leads to eventual heart failure and death. The downstream mechanisms mediated by PKD that could contribute to dysfunctions observed in the heart and other metabolically important tissues in obesity, and the predicted cell types involved are discussed to suggest potential targets for the development of therapeutics against obesity-related disease.
Asunto(s)
Obesidad , Proteína Quinasa C , Humanos , Proteína Quinasa C/metabolismo , Proteína Quinasa C/genética , Obesidad/metabolismo , Obesidad/patología , Obesidad/genética , Animales , Miocardio/metabolismo , Miocardio/patología , Transducción de Señal , Cardiomiopatías/metabolismo , Cardiomiopatías/genética , Cardiomiopatías/patologíaRESUMEN
There are epidemiological associations between obesity and type 2 diabetes, cardiovascular disease and Alzheimer's disease. The role of amyloid beta 42 (Aß42) in these diverse chronic diseases is obscure. Here we show that adipose tissue releases Aß42, which is increased from adipose tissue of male mice with obesity and is associated with higher plasma Aß42. Increasing circulating Aß42 levels in male mice without obesity has no effect on systemic glucose homeostasis but has obesity-like effects on the heart, including reduced cardiac glucose clearance and impaired cardiac function. The closely related Aß40 isoform does not have these same effects on the heart. Administration of an Aß-neutralising antibody prevents obesity-induced cardiac dysfunction and hypertrophy. Furthermore, Aß-neutralising antibody administration in established obesity prevents further deterioration of cardiac function. Multi-contrast transcriptomic analyses reveal that Aß42 impacts pathways of mitochondrial metabolism and exposure of cardiomyocytes to Aß42 inhibits mitochondrial complex I. These data reveal a role for systemic Aß42 in the development of cardiac disease in obesity and suggest that therapeutics designed for Alzheimer's disease could be effective in combating obesity-induced heart failure.
Asunto(s)
Enfermedad de Alzheimer , Diabetes Mellitus Tipo 2 , Masculino , Ratones , Animales , Péptidos beta-Amiloides , Diabetes Mellitus Tipo 2/complicaciones , Anticuerpos Neutralizantes , Obesidad/complicaciones , Glucosa , Fragmentos de PéptidosRESUMEN
Intramuscular lipid (IMCL) utilization during exercise was controversial as numerous studies did not observe a decline in IMCL content post-exercise when assessed in muscle biopsies using biochemical techniques. Contemporary techniques including immunofluorescence microscopy and 1H-magnetic resonance spectroscopy (1H-MRS) offer advantages over biochemical techniques. The primary aim of this systematic review, meta-analysis, and meta-regression was to examine the net degradation of IMCL in response to an acute bout of cycling exercise in humans, as assessed with different analytical approaches. A secondary aim was to explore the factors influencing IMCL degradation including feeding status, exercise variables, and participant characteristics. A total of 44 studies met the inclusion criteria using biochemical, immunofluorescence, and 1H-MRS techniques. A meta-analysis was completed using a random effects model and percentage change in IMCL content calculated from the standardized mean difference. Cycling exercise resulted in a net degradation of IMCL regardless of technique (total effect -23.7%, 95% CI = -28.7 to -18.7%) and there was no difference when comparing fasted versus fed-state exercise (P > 0.05). IMCL degradation using immunofluorescence techniques detected larger effects in type I fibers compared with whole muscle using biochemical techniques (P = 0.003) and in type I fibers compared with type II fibers (P < 0.001). Although IMCL degradation was associated with exercise duration, VÌo2max, and BMI, none of these factors independently related to the change in IMCL content. These findings provide strong evidence that the analytical approach can influence the assessment of IMCL degradation in human skeletal muscle in response to exercise.
Asunto(s)
Ejercicio Físico , Músculo Esquelético , Humanos , Ciclismo/fisiología , Ejercicio Físico/fisiología , Metabolismo de los Lípidos , Lípidos , Músculo Esquelético/fisiologíaRESUMEN
Obesity is associated with ectopic accumulation of lipids, which is implicated in the development of insulin resistance, type 2 diabetes mellitus and cardiovascular disease. As the global prevalence of obesity continues to rise, it is becoming increasingly important to understand the underlying cellular mechanisms of this disease. Protein kinase D (PKD) is an intracellular signalling kinase with well characterized roles in intracellular vesicle transport and secretion, cancer cell proliferation and cardiac hypertrophy. However, emerging evidence also highlights PKD as a novel nutrient sensor. PKD activation is mediated by the accumulation of the lipid intermediate diacylglycerol, and PKD activity in the liver, heart and adipose tissue increases upon feeding. In obesity, PKD signalling is linked to reduced insulin signalling and dysfunction in adipose tissue, liver and heart, whilst in the pancreas, PKD is essential for the compensatory increase in glucose-stimulated insulin secretion from ß-cells during obesity. Collectively, these studies reveal aspects of PKD signalling that are involved in the tissue-specific responses to obesity. This review summarizes the emerging evidence suggesting that PKD plays an important role in regulating the adaptive response to the obese environment.
Asunto(s)
Nutrientes , Obesidad/enzimología , Proteína Quinasa C/fisiología , Ingestión de Alimentos , HumanosRESUMEN
OBJECTIVE: The glucose tolerance test (GTT) is widely used in human and animal biomedical and pharmaceutical research. Despite its prevalent use, particularly in mouse metabolic phenotyping, to the best of our knowledge we are not aware of any studies that have attempted to qualitatively compare the metabolic events during a GTT in mice with those performed in humans. METHODS: Stable isotope labelled oral glucose tolerance tests (siOGTTs; [6,6-2H2]glucose) were performed in both human and mouse cohorts to provide greater resolution into postprandial glucose kinetics. The siOGTT allows for the partitioning of circulating glucose into that derived from exogenous and endogenous sources. Young adults spanning the spectrum of normal glucose tolerance (n = 221), impaired fasting (n = 14), and impaired glucose tolerance (n = 19) underwent a 75g siOGTT, whereas a 50 mg siOGTT was performed on chow (n = 43) and high-fat high-sucrose fed C57Bl6 male mice (n = 46). RESULTS: During the siOGTT in humans, there is a long period (>3hr) of glucose absorption and, accordingly, a large, sustained insulin response and robust suppression of lipolysis and endogenous glucose production (EGP), even in the presence of glucose intolerance. In contrast, mice appear to be highly reliant on glucose effectiveness to clear exogenous glucose and experience only modest, transient insulin responses with little, if any, suppression of EGP. In addition to the impaired stimulation of glucose uptake, mice with the worst glucose tolerance appear to have a paradoxical and persistent rise in EGP during the OGTT, likely related to handling stress. CONCLUSIONS: The metabolic response to the OGTT in mice and humans is highly divergent. The potential reasons for these differences and their impact on the interpretation of mouse glucose tolerance data and their translation to humans are discussed.
Asunto(s)
Deuterio/química , Marcaje Isotópico , Adolescente , Adulto , Animales , Femenino , Glucosa/metabolismo , Intolerancia a la Glucosa , Prueba de Tolerancia a la Glucosa , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Adulto JovenRESUMEN
AIMS: This study investigated the association between the basal (rest) insulin-signaling proteins, Akt, and the Akt substrate AS160, metabolic risk factors, inflammatory markers and aerobic fitness, in middle-aged women with varying numbers of metabolic risk factors for type 2 diabetes. METHODS: Sixteen women (n=16) aged 51.3 +/- 5.1 (mean +/- SD) years provided muscle biopsies and blood samples at rest. In addition, anthropometric characteristics and aerobic power were assessed and the number of metabolic risk factors for each participant was determined (IDF criteria). RESULTS: The mean number of metabolic risk factors was 1.6 +/- 1.2. Total Akt was negatively correlated with IL-1beta (r = -0.45, p = 0.046), IL-6 (r = -0.44, p = 0.052) and TNF-alpha (r = -0.51, p = 0.025). Phosphorylated AS160 was positively correlated with HDL (r = 0.58, p = 0.024) and aerobic fitness (r = 0.51, p = 0.047). Furthermore, a multiple regression analysis revealed that both HDL (t = 2.5, p = 0.032) and VO2peak (t = 2.4, p = 0.037) were better predictors for phosphorylated AS160 than TNF-alpha or IL-6 (p > 0.05). CONCLUSIONS: Elevated inflammatory markers and increased metabolic risk factors may inhibit insulin-signaling protein phosphorylation in middle-aged women, thereby increasing insulin resistance under basal conditions. Furthermore, higher HDL and fitness levels are associated with an increased AS160 phosphorylation, which may in turn reduce insulin resistance.
Asunto(s)
Proteínas Activadoras de GTPasa/metabolismo , Inflamación/metabolismo , Aptitud Física/fisiología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Glucemia , Presión Sanguínea , Western Blotting , Femenino , Humanos , Inflamación/fisiopatología , Resistencia a la Insulina/fisiología , Lipoproteínas HDL/sangre , Persona de Mediana Edad , Músculo Esquelético/metabolismo , Fosforilación , Factores de Riesgo , Triglicéridos/sangre , Circunferencia de la CinturaRESUMEN
There is a persistent, aberrant accumulation of V0/V1 versican in skeletal muscles from patients with Duchenne muscular dystrophy and in diaphragm muscles from mdx mice. Versican is a provisional matrix protein implicated in fibrosis and inflammation in various disease states, yet its role in the pathogenesis of muscular dystrophy is not known. Here, female mdx and male hdf mice (haploinsufficient for the versican allele) were bred. In the resulting F1 mdx-hdf male pups, V0/V1 versican expression in diaphragm muscles was decreased by 50% compared to mdx littermates at 20-26 weeks of age. In mdx-hdf mice, spontaneous physical activity increased by 17% and there was a concomitant decrease in total energy expenditure and whole-body glucose oxidation. Versican reduction improved the ex vivo strength and endurance of diaphragm muscle strips. These changes in diaphragm contractile properties in mdx-hdf mice were associated with decreased monocyte and macrophage infiltration and a reduction in the proportion of fibres expressing the slow type I myosin heavy chain isoform. Given the high metabolic cost of inflammation in dystrophy, an attenuated inflammatory response may contribute to the effects of versican reduction on whole-body metabolism. Altogether, versican reduction ameliorates the dystrophic pathology of mdx-hdf mice as evidenced by improved diaphragm contractile function and increased physical activity.
Asunto(s)
Matriz Extracelular/metabolismo , Inflamación/prevención & control , Contracción Muscular , Músculo Esquelético/fisiología , Distrofia Muscular Animal/terapia , Distrofia Muscular de Duchenne/terapia , Versicanos/antagonistas & inhibidores , Animales , Femenino , Inflamación/etiología , Inflamación/patología , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos mdx , Distrofia Muscular Animal/complicaciones , Distrofia Muscular Animal/genética , Distrofia Muscular Animal/patología , Distrofia Muscular de Duchenne/complicaciones , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/patología , Versicanos/genéticaRESUMEN
Protein kinase D (PKD) is emerging as an important kinase regulating energy balance and glucose metabolism; however, whether hepatic PKD activity can be targeted to regulate these processes is currently unclear. In this study, hepatic PKD activity was reduced using adeno-associated virus vectors to express a dominant-negative (DN) version of PKD1, which impairs the action of all three PKD isoforms. In chow-fed mice, hepatic DN PKD expression increased whole-body glucose oxidation, but had only mild effects on glucose and insulin tolerance and no effects on glucose homeostasis following fasting and refeeding. However, circulating VLDL cholesterol was reduced under these conditions and was associated with hepatic fatty acid accumulation, but not lipids involved in lipoprotein synthesis. The limited effects on glucose homeostasis in DN PKD mice was despite reduced expression of gluconeogenic genes under both fasted and refed conditions, and enhanced pyruvate tolerance. The requirement for PKD for gluconeogenic capacity was supported by in vitro studies in cultured FAO hepatoma cells expressing DN PKD, which produced less glucose under basal conditions. Although these pathways are increased in obesity, the expression of DN PKD in the liver of mice fed a high-fat diet had no impact on glucose tolerance, insulin action, pyruvate tolerance or plasma VLDL. Together, these data suggest that PKD signalling in the liver regulates metabolic pathways involved in substrate redistribution under conditions of normal nutrient availability, but not under conditions of overnutrition such as in obesity.
Asunto(s)
VLDL-Colesterol/sangre , Hígado/enzimología , Proteína Quinasa C/metabolismo , Animales , Glucemia/metabolismo , Dieta Alta en Grasa , Masculino , Ratones , Obesidad/sangre , Obesidad/enzimología , Transducción de Señal/fisiología , Triglicéridos/sangreRESUMEN
OBJECTIVE: Protein kinase D (PKD) signaling has been implicated in stress-induced cardiac remodeling and function as well as metabolic processes including contraction-mediated cardiac glucose uptake. PKD has recently emerged as a nutrient-sensing kinase that is activated in high-lipid environments, such as in obesity. However, the role of PKD signaling in cardiac glucose metabolism and cardiac function in both normal and obese conditions remains unknown. METHODS: A cardiac-specific and inducible dominant negative (DN) PKD mouse model was developed. Echocardiography was used to assess cardiac function, while metabolic phenotyping was performed, including stable isotope metabolomics on cardiac tissue in mice fed either regular chow or a high-fat diet (43% calories from fat). RESULTS: Cardiac PKD activity declined by â¼90% following DN PKD induction in adult mice. The mice had diminished basal cardiac glucose clearance, suggesting impaired contraction-mediated glucose uptake, but normal cardiac function. In obesity studies, systolic function indices were reduced in control mice, but not in cardiac DN PKD mice. Using targeted stable isotope metabolomic analyses, no differences in glucose flux through glycolysis or the TCA cycle were observed between groups. CONCLUSIONS: The data show that PKD contributes to cardiac dysfunction in obesity and highlight the redundancy in cardiac glucose metabolism that maintains cardiac glucose flux in vivo. The data suggest that impairments in contraction-mediated glucose uptake are unlikely to drive cardiac dysfunction in both normal and metabolic disease states.
Asunto(s)
Glucosa/metabolismo , Miocardio/metabolismo , Proteína Quinasa C/metabolismo , Animales , Dieta Alta en Grasa , Femenino , Técnicas de Sustitución del Gen/métodos , Corazón/fisiología , Insulina/metabolismo , Resistencia a la Insulina/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Miocitos Cardíacos/metabolismo , Obesidad/metabolismo , Obesidad/fisiopatología , Fosforilación , Proteína Quinasa C/genética , Transducción de SeñalRESUMEN
CONTEXT: Insulin resistance (IR) remains a global health challenge. Lipidomics offers an opportunity to identify biomarkers and better understand mechanisms of IR associated with abnormal lipid metabolism. OBJECTIVE: The objective of this article is to determine plasma lipid species associated with indices of IR and evaluate the lipidome response to an oral glucose tolerance test (OGTT). DESIGN AND SETTING: This study was community based and cross-sectional. PARTICIPANTS AND SAMPLE: Plasma samples (collected at 0 and 120 min during an OGTT) from nonobese, young adults age 18 to 34 years (n = 246) were analyzed using liquid chromatography-tandem mass spectrometry. MAIN OUTCOME MEASURES: The associations between indices of IR and lipid classes and species (with a sex interaction term), or changes in lipid levels during an OGTT, were tested using linear models (adjusted for age, sex, body mass index, total cholesterol, high-density lipoprotein cholesterol, and triglycerides). RESULTS: Some (213) and (199) lipid species were associated with the homeostatic model assessment of insulin resistance and insulin area under curve (AUC), respectively. Alkylphosphatidylcholine (10), alkenylphosphatidylcholine (23), and alkylphosphatidylethanolamine (6) species were associated with insulin AUC in men only. Species of phosphatidylcholine (7) and sphingomyelin (5) were associated in women only. In response to an OGTT, a perturbation in the plasma lipidome, particularly in acylcarnitine species, was observed; and the changes in many lipid species were associated with insulin AUC. CONCLUSIONS: The plasma lipidome and changes in lipid levels during an OGTT were associated with indices of IR. These findings underlie the involvement of molecular lipid species in the pathogenesis of IR and possibly crosstalk between IR and sex-specific regulation of lipid metabolism.
Asunto(s)
Biomarcadores/sangre , Intolerancia a la Glucosa/epidemiología , Prueba de Tolerancia a la Glucosa/métodos , Resistencia a la Insulina , Lipidómica/métodos , Lípidos/sangre , Obesidad/fisiopatología , Adolescente , Adulto , Australia/epidemiología , Estudios de Cohortes , Estudios Transversales , Femenino , Estudios de Seguimiento , Intolerancia a la Glucosa/sangre , Humanos , Masculino , Pronóstico , Adulto JovenRESUMEN
From a cell signaling perspective, short-duration intense muscular work is typically associated with resistance training and linked to pathways that stimulate growth. However, brief repeated sessions of sprint or high-intensity interval exercise induce rapid phenotypic changes that resemble traditional endurance training. We tested the hypothesis that an acute session of intense intermittent cycle exercise would activate signaling cascades linked to mitochondrial biogenesis in human skeletal muscle. Biopsies (vastus lateralis) were obtained from six young men who performed four 30-s "all out" exercise bouts interspersed with 4 min of rest (<80 kJ total work). Phosphorylation of AMP-activated protein kinase (AMPK; subunits alpha1 and alpha2) and the p38 mitogen-activated protein kinase (MAPK) was higher (P Asunto(s)
Proteínas Quinasas Activadas por AMP/metabolismo
, Ciclismo/fisiología
, Ejercicio Físico/fisiología
, Proteínas de Choque Térmico/metabolismo
, Sistema de Señalización de MAP Quinasas
, Músculo Esquelético/enzimología
, Factores de Transcripción/metabolismo
, Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo
, Expresión Génica
, Proteínas de Choque Térmico/genética
, Humanos
, Masculino
, Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma
, Fosforilación
, Proteínas Proto-Oncogénicas c-akt/metabolismo
, Factores de Transcripción/genética
, Adulto Joven
RESUMEN
A bout of prolonged aerobic exercise can enhance the sensitivity of muscle glucose uptake to insulin, and this may be mediated by activation of 5'-adenosine monophosphate-activated protein kinase (AMPK). The aim of this study was to examine whether high-intensity short-term exercise resulting in a significantly greater increase in the activation of AMPK is more effective in enhancing muscle insulin sensitivity compared with low-intensity prolonged aerobic exercise. We measured insulin sensitivity after high-intensity intermittent swimming (HIS) or low-intensity continuous swimming (LIS) exercise in rat epitrochlearis muscle. During HIS, the rats underwent eight 20-second bouts of swimming with a weight equal to 18% of body weight. The LIS rats swam with no load for 3 hours. High-intensity intermittent swimming increased (P < .05) 2-deoxyglucose uptake approximately 8-fold, whereas LIS increased it (P < .05) approximately 2-fold immediately after exercise compared with rested muscle. This response was associated with an increase (P < .05) in phosphorylation of AMPK Thr(172) and its downstream target acetyl-coenzyme A carboxylase (ACC) Ser(79) in HIS (13- and 6-fold, respectively) and LIS (2.8- and 2-fold, respectively) immediately after exercise. In contrast, submaximal (30 microU/mL) insulin-stimulated 2-deoxyglucose uptake measured 4 hours after exercise was 73% and 46% higher (P < .05) in LIS and HIS, respectively, compared with rest. The HIS exercise resulted in a greater activation of AMPK compared with LIS, but insulin sensitivity was higher after LIS compared with HIS. The results suggest that HIS is not more effective in enhancing insulin sensitivity than LIS. Thus, AMPK activation immediately after exercise may not be the only factor that determines the magnitude of the exercise-induced increase in insulin sensitivity in rat epitrochlearis muscle.
Asunto(s)
Insulina/farmacología , Músculo Esquelético/metabolismo , Condicionamiento Físico Animal , Natación , Acetil-CoA Carboxilasa/metabolismo , Adenilato Quinasa/metabolismo , Animales , Glucosa/metabolismo , Transportador de Glucosa de Tipo 4/análisis , Glucógeno/análisis , Masculino , Músculo Esquelético/química , Fosforilación , Proteínas Proto-Oncogénicas c-akt/metabolismo , Ratas , Ratas Wistar , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismoRESUMEN
The purpose of the present study was to determine in human skeletal muscle whether a single exercise bout and 7 days of consecutive endurance (cycling) training 1) increased insulin-stimulated Akt pSer(473) and 2) altered the abundance of the protein tyrosine phosphatases (PTPases), PTP1B and SHP2. In healthy, untrained men (n = 8; 24 +/- 1 yr), glucose infusion rate during a hyperinsulinemic euglycemic clamp, when compared with untrained values, was not improved 24 h following a single 60-min bout of endurance cycling but was significantly increased ( approximately 30%; P < 0.05) 24 h following completion of 7 days of exercise training. Insulin-stimulated Akt pSer(473) was approximately 50% higher (P < 0.05) 24 h following the acute bout of exercise, with this effect remaining after 7 days of training (P < 0.05). Insulin-stimulated insulin receptor and insulin receptor substrate-1 tyrosine phosphorylation were not altered 24 h after acute exercise and short-term training. Insulin did not acutely regulate the localization of the PTPases, PTP1B or SHP2, although cytosolic protein abundance of SHP2 was increased (P < 0.05; main effect) 24 h following acute exercise and short-term training. In conclusion, insulin-sensitive Akt pSer(473) and cytosolic SHP2 protein abundance are higher after acute exercise and short-term training, and this effect appears largely due to the residual effects of the last bout of prior exercise. The significance of exercise-induced alterations in cytosolic SHP2 and insulin-stimulated Akt pSer(473) on the improvement in insulin sensitivity requires further elucidation.
Asunto(s)
Ejercicio Físico/fisiología , Insulina/administración & dosificación , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Músculo Esquelético/fisiología , Resistencia Física/fisiología , Proteínas Tirosina Fosfatasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Adaptación Fisiológica/efectos de los fármacos , Adaptación Fisiológica/fisiología , Adulto , Citosol/metabolismo , Humanos , Masculino , Músculo Esquelético/efectos de los fármacos , Fosforilación , Resistencia Física/efectos de los fármacos , Aptitud Física/fisiología , Proteína Tirosina Fosfatasa no Receptora Tipo 1 , Proteína Tirosina Fosfatasa no Receptora Tipo 11RESUMEN
Exercise increases skeletal muscle insulin action but the underlying mechanisms mediating this are equivocal. In mouse skeletal muscle, prior exercise enhances insulin-stimulated insulin receptor substrate-2 (IRS-2) signaling (Diabetes 2002;51:479-83), but it is unknown if this also occurs in humans. Hyperinsulinemic-euglycemic clamps were performed on 7 untrained males at rest and immediately after 60 minutes of cycling exercise at approximately 75% Vo2peak. Muscle biopsies were obtained at basal, immediately after exercise, and at 30 and 120 minutes of hyperinsulinemia. Insulin infusion increased (P < .05) insulin receptor tyrosine phosphorylation similarly in both the rest and exercise trials. Under resting conditions, insulin infusion resulted in a small, but non-statistically significant increase in IRS-2-associated phosphatidylinositol 3 (PI 3)-kinase activity over basal levels. Exercise per se decreased (P < .05) IRS-2-associated PI 3-kinase activity. After exercise, insulin-stimulated IRS-2-associated PI 3-kinase activity tended to increase at 30 minutes and further increased (P < .05) at 120 minutes when compared with the resting trial. Insulin increased (P < .05) Akt Ser473 and GSK-3alpha/beta Ser21/Ser9 phosphorylation in both trials, with the response tending to be higher in the exercise trial. In conclusion, in the immediate period after an acute bout of exercise, insulin-stimulated IRS-2 signaling is enhanced in human skeletal muscle.