RESUMO
In response to skeletal muscle contraction during exercise, paracrine factors coordinate tissue remodeling, which underlies this healthy adaptation. Here we describe a pH-sensing metabolite signal that initiates muscle remodeling upon exercise. In mice and humans, exercising skeletal muscle releases the mitochondrial metabolite succinate into the local interstitium and circulation. Selective secretion of succinate is facilitated by its transient protonation, which occurs upon muscle cell acidification. In the protonated monocarboxylic form, succinate is rendered a transport substrate for monocarboxylate transporter 1, which facilitates pH-gated release. Upon secretion, succinate signals via its cognate receptor SUCNR1 in non-myofibrillar cells in muscle tissue to control muscle-remodeling transcriptional programs. This succinate-SUCNR1 signaling is required for paracrine regulation of muscle innervation, muscle matrix remodeling, and muscle strength in response to exercise training. In sum, we define a bioenergetic sensor in muscle that utilizes intracellular pH and succinate to coordinate tissue adaptation to exercise.
Assuntos
Músculo Esquelético/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Ácido Succínico/metabolismo , Animais , Humanos , Concentração de Íons de Hidrogênio , Inflamação/metabolismo , Camundongos , Mitocôndrias/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Contração Muscular , Receptores Acoplados a Proteínas G/fisiologia , Transdução de Sinais , Succinatos/metabolismo , Simportadores/metabolismoRESUMO
Exercise confers protection against obesity, type 2 diabetes and other cardiometabolic diseases1-5. However, the molecular and cellular mechanisms that mediate the metabolic benefits of physical activity remain unclear6. Here we show that exercise stimulates the production of N-lactoyl-phenylalanine (Lac-Phe), a blood-borne signalling metabolite that suppresses feeding and obesity. The biosynthesis of Lac-Phe from lactate and phenylalanine occurs in CNDP2+ cells, including macrophages, monocytes and other immune and epithelial cells localized to diverse organs. In diet-induced obese mice, pharmacological-mediated increases in Lac-Phe reduces food intake without affecting movement or energy expenditure. Chronic administration of Lac-Phe decreases adiposity and body weight and improves glucose homeostasis. Conversely, genetic ablation of Lac-Phe biosynthesis in mice increases food intake and obesity following exercise training. Last, large activity-inducible increases in circulating Lac-Phe are also observed in humans and racehorses, establishing this metabolite as a molecular effector associated with physical activity across multiple activity modalities and mammalian species. These data define a conserved exercise-inducible metabolite that controls food intake and influences systemic energy balance.
Assuntos
Ingestão de Alimentos , Comportamento Alimentar , Obesidade , Fenilalanina , Condicionamento Físico Animal , Adiposidade/efeitos dos fármacos , Animais , Peso Corporal/efeitos dos fármacos , Diabetes Mellitus Tipo 2 , Modelos Animais de Doenças , Ingestão de Alimentos/fisiologia , Metabolismo Energético , Comportamento Alimentar/fisiologia , Glucose/metabolismo , Ácido Láctico/metabolismo , Camundongos , Obesidade/metabolismo , Obesidade/prevenção & controle , Fenilalanina/administração & dosagem , Fenilalanina/análogos & derivados , Fenilalanina/metabolismo , Fenilalanina/farmacologia , Condicionamento Físico Animal/fisiologiaRESUMO
Glucose is the universal fuel of most mammalian cells, and it is largely replenished through dietary intake. Glucose availability to tissues is paramount for the maintenance of homeostatic energetics and, hence, supply should match demand by the consuming organs. In its journey through the body, glucose encounters cellular barriers for transit at the levels of the absorbing intestinal epithelial wall, the renal epithelium mediating glucose reabsorption, and the tight capillary endothelia (especially in the brain). Glucose transiting through these cellular barriers must escape degradation to ensure optimal glucose delivery to the bloodstream or tissues. The liver, which stores glycogen and generates glucose de novo, must similarly be able to release it intact to the circulation. We present the most up-to-date knowledge on glucose handling by the gut, liver, brain endothelium, and kidney, and discuss underlying molecular mechanisms and open questions. Diseases associated with defects in glucose delivery and homeostasis are also briefly addressed. We propose that the universal problem of sparing glucose from catabolism in favor of translocation across the barriers posed by epithelia and endothelia is resolved through common mechanisms involving glucose transfer to the endoplasmic reticulum, from where glucose exits the cells via unconventional cellular mechanisms.
Assuntos
Encéfalo , Glucose , Animais , Humanos , Glucose/metabolismo , Epitélio/metabolismo , Encéfalo/metabolismo , Transporte Biológico , Intestinos , Mamíferos/metabolismoRESUMO
The molecular events governing skeletal muscle glucose uptake have pharmacological potential for managing insulin resistance in conditions such as obesity, diabetes, and cancer. With no current pharmacological treatments to target skeletal muscle insulin sensitivity, there is an unmet need to identify the molecular mechanisms that control insulin sensitivity in skeletal muscle. Here, the Rho guanine dissociation inhibitor α (RhoGDIα) is identified as a point of control in the regulation of insulin sensitivity. In skeletal muscle cells, RhoGDIα interacted with, and thereby inhibited, the Rho GTPase Rac1. In response to insulin, RhoGDIα was phosphorylated at S101 and Rac1 dissociated from RhoGDIα to facilitate skeletal muscle GLUT4 translocation. Accordingly, siRNA-mediated RhoGDIα depletion increased Rac1 activity and elevated GLUT4 translocation. Consistent with RhoGDIα's inhibitory effect, rAAV-mediated RhoGDIα overexpression in mouse muscle decreased insulin-stimulated glucose uptake and was detrimental to whole-body glucose tolerance. Aligning with RhoGDIα's negative role in insulin sensitivity, RhoGDIα protein content was elevated in skeletal muscle from insulin-resistant patients with type 2 diabetes. These data identify RhoGDIα as a clinically relevant controller of skeletal muscle insulin sensitivity and whole-body glucose homeostasis, mechanistically by modulating Rac1 activity.
Assuntos
Diabetes Mellitus Tipo 2 , Resistência à Insulina , Inibidor alfa de Dissociação do Nucleotídeo Guanina rho , Animais , Camundongos , Diabetes Mellitus Tipo 2/metabolismo , Glucose/metabolismo , Insulina/metabolismo , Músculo Esquelético/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismo , Inibidor alfa de Dissociação do Nucleotídeo Guanina rho/metabolismoRESUMO
Women typically have less muscle mass and more fat mass than men, while at the same time possessing similar or even greater whole-body insulin sensitivity. Our study aimed to investigate the molecular factors in primarily adipose tissue, but also in skeletal muscle, contributing to this sex difference. In healthy, moderately active premenopausal women and men with normal weight (28 ± 5 and 23 ± 3 years old; BMI 22.2 ± 1.9 and 23.7 ± 1.7) and in healthy, recreationally active women and men with overweight (32.2 ± 6 and 31.0 ± 5 years old; BMI 29.8 ± 4.3 & 30.9 ± 3.7) matched at age, BMI, and fitness level, we assessed insulin sensitivity and glucose tolerance with a hyperinsulinemic-euglycemic clamp or oral glucose tolerance test and studied subcutaneous adipose tissue and skeletal muscle samples with western blotting. Additionally, we traced glucose-stimulated glucose disposal in adipose tissues of female and male C57BL/6J littermate mice aged 16 weeks and measured glucose metabolic proteins. Our findings revealed greater protein expression related to glucose disposal in the subcutaneous adipose tissue (AKT2, insulin receptor, glucose transport 4) and skeletal muscle (hexokinase II, pyruvate dehydrogenase) in women compared to matched men with normal weight and with overweight. This increased protein capacity for glucose uptake extended to white adipose tissues of mice accompanied with ~2-fold greater glucose uptake compared to male mice. Furthermore, even in the obese state, women displayed better glucose tolerance than matched men, despite having 46% body fat and 20 kg less lean mass. In conclusion, our findings suggest that the superior potential for glucose disposal in female subcutaneous adipose tissue and skeletal muscle, driven by greater expression of various glucose metabolic proteins, compensates for their lower muscle mass. This likely explains women's superior glucose tolerance and tissue insulin sensitivity compared to men.
Assuntos
Glucose , Músculo Esquelético , Feminino , Humanos , Masculino , Músculo Esquelético/metabolismo , Adulto , Glucose/metabolismo , Animais , Camundongos , Camundongos Endogâmicos C57BL , Tecido Adiposo/metabolismo , Resistência à Insulina/fisiologia , Adulto Jovem , Teste de Tolerância a Glucose , Sobrepeso/metabolismo , Técnica Clamp de GlucoseRESUMO
Arginine methylation is a protein posttranslational modification important for the development of skeletal muscle mass and function. Despite this, our understanding of the regulation of arginine methylation under settings of health and disease remains largely undefined. Here, we investigated the regulation of arginine methylation in skeletal muscles in response to exercise and hypertrophic growth, and in diseases involving metabolic dysfunction and atrophy. We report a limited regulation of arginine methylation under physiological settings that promote muscle health, such as during growth and acute exercise, nor in disease models of insulin resistance. In contrast, we saw a significant remodeling of asymmetric dimethylation in models of atrophy characterized by the loss of innervation, including in muscle biopsies from patients with myotrophic lateral sclerosis (ALS). Mass spectrometry-based quantification of the proteome and asymmetric arginine dimethylome of skeletal muscle from individuals with ALS revealed the largest compendium of protein changes with the identification of 793 regulated proteins, and novel site-specific changes in asymmetric dimethyl arginine (aDMA) of key sarcomeric and cytoskeletal proteins. Finally, we show that in vivo overexpression of PRMT1 and aDMA resulted in increased fatigue resistance and functional recovery in mice. Our study provides evidence for asymmetric dimethylation as a regulator of muscle pathophysiology and presents a valuable proteomics resource and rationale for numerous methylated and nonmethylated proteins, including PRMT1, to be pursued for therapeutic development in ALS.
Assuntos
Esclerose Lateral Amiotrófica , Arginina , Músculo Esquelético , Proteína-Arginina N-Metiltransferases , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Arginina/metabolismo , Arginina/análogos & derivados , Humanos , Esclerose Lateral Amiotrófica/metabolismo , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/patologia , Animais , Camundongos , Proteína-Arginina N-Metiltransferases/metabolismo , Proteína-Arginina N-Metiltransferases/genética , Masculino , Metilação , Feminino , Processamento de Proteína Pós-Traducional , Camundongos Endogâmicos C57BL , Proteoma/metabolismoRESUMO
AIMS/HYPOTHESIS: Exercise has a profound effect on insulin sensitivity in skeletal muscle. The euglycaemic-hyperinsulinaemic clamp (EHC) is the gold standard for assessment of insulin sensitivity but it does not reflect the hyperglycaemia that occurs after eating a meal. In previous EHC investigations, it has been shown that the interstitial glucose concentration in muscle is decreased to a larger extent in previously exercised muscle than in rested muscle. This suggests that previously exercised muscle may increase its glucose uptake more than rested muscle if glucose supply is increased by hyperglycaemia. Therefore, we hypothesised that the exercise-induced increase in muscle insulin sensitivity would appear greater after eating a meal than previously observed with the EHC. METHODS: Ten recreationally active men performed dynamic one-legged knee extensor exercise for 1 h. Following this, both femoral veins and one femoral artery were cannulated. Subsequently, 4 h after exercise, a solid meal followed by two liquid meals were ingested over 1 h and glucose uptake in the two legs was measured for 3 h. Muscle biopsies from both legs were obtained before the meal test and 90 min after the meal test was initiated. Data obtained in previous studies using the EHC (n=106 participants from 13 EHC studies) were used for comparison with the meal-test data obtained in this study. RESULTS: Plasma glucose and insulin peaked 45 min after initiation of the meal test. Following the meal test, leg glucose uptake and glucose clearance increased twice as much in the exercised leg than in the rested leg; this difference is twice as big as that observed in previous investigations using EHCs. Glucose uptake in the rested leg plateaued after 15 min, alongside elevated muscle glucose 6-phosphate levels, suggestive of compromised muscle glucose metabolism. In contrast, glucose uptake in the exercised leg plateaued 45 min after initiation of the meal test and there were no signs of compromised glucose metabolism. Phosphorylation of the TBC1 domain family member 4 (TBC1D4; p-TBC1D4Ser704) and glycogen synthase activity were greater in the exercised leg compared with the rested leg. Muscle interstitial glucose concentration increased with ingestion of meals, although it was 16% lower in the exercised leg than in the rested leg. CONCLUSIONS/INTERPRETATION: Hyperglycaemia after meal ingestion results in larger differences in muscle glucose uptake between rested and exercised muscle than previously observed during EHCs. These findings indicate that the ability of exercise to increase insulin-stimulated muscle glucose uptake is even greater when evaluated with a meal test than has previously been shown with EHCs.
Assuntos
Glicemia , Exercício Físico , Técnica Clamp de Glucose , Resistência à Insulina , Insulina , Refeições , Músculo Esquelético , Humanos , Masculino , Exercício Físico/fisiologia , Músculo Esquelético/metabolismo , Resistência à Insulina/fisiologia , Adulto , Glicemia/metabolismo , Insulina/metabolismo , Insulina/sangue , Adulto Jovem , Refeições/fisiologiaRESUMO
BACKGROUND: Metabolic effects of empagliflozin treatment include lowered glucose and insulin concentrations, elevated free fatty acids and ketone bodies and have been suggested to contribute to the cardiovascular benefits of empagliflozin treatment, possibly through an improved cardiac function. We aimed to evaluate the influence of these metabolic changes on cardiac function in patients with T2D. METHODS: In a randomized cross-over design, the SGLT2 inhibitor empagliflozin (E) was compared with insulin (I) treatment titrated to the same level of glycemic control in 17 patients with type 2 diabetes, BMI of > 28 kg/m2, C-peptide > 500 pM. Treatments lasted 5 weeks and were preceded by 3-week washouts (WO). At the end of treatments and washouts, cardiac diastolic function was determined with magnetic resonance imaging from left ventricle early peak-filling rate and left atrial passive emptying fraction (primary and key secondary endpoints); systolic function from left ventricle ejection fraction (secondary endpoint). Coupling between cardiac function and fatty acid concentrations, was studied on a separate day with a second scan after reduction of plasma fatty acids with acipimox. Data are Mean ± standard error. Between treatment difference (ΔT: E-I) and treatments effects (ΔE: E-WO or ΔI: I -WO) were evaluated using Students' t-test or Wilcoxon signed rank test as appropriate. RESULTS: Glucose concentrations were similar, fatty acids, ketone bodies and lipid oxidation increased while insulin concentrations decreased on empagliflozin compared with insulin treatment. Cardiac diastolic and systolic function were unchanged by either treatment. Acipimox decreased fatty acids with 35% at all visits, and this led to reduced cardiac diastolic (ΔT: -51 ± 22 ml/s (p < 0.05); ΔE: -33 ± 26 ml/s (ns); ΔI: 37 ± 26 (ns, p < 0.05 vs ΔE)) and systolic function (ΔT: -3 ± 1% (p < 0.05); ΔE: -3 ± 1% (p < 0.05): ΔI: 1 ± 2 (ns, ns vs ΔE)) under chronotropic stress during empagliflozin compared to insulin treatment. CONCLUSIONS: Despite significant metabolic differences, cardiac function did not differ on empagliflozin compared with insulin treatment. Impaired cardiac function during acipimox treatment, could suggest greater cardiac reliance on lipid metabolism for proper function during empagliflozin treatment in patients with type 2 diabetes. TRIAL REGISTRATION: EudraCT 2017-002101-35, August 2017.
Assuntos
Apêndice Atrial , Diabetes Mellitus Tipo 2 , Humanos , Insulina , Diabetes Mellitus Tipo 2/diagnóstico , Diabetes Mellitus Tipo 2/tratamento farmacológico , Estudos Cross-Over , Glucose , Ácidos Graxos , Corpos CetônicosRESUMO
Exercise stimulates cellular and physiological adaptations that are associated with widespread health benefits. To uncover conserved protein phosphorylation events underlying this adaptive response, we performed mass spectrometry-based phosphoproteomic analyses of skeletal muscle from two widely used rodent models: treadmill running in mice and in situ muscle contraction in rats. We overlaid these phosphoproteomic signatures with cycling in humans to identify common cross-species phosphosite responses, as well as unique model-specific regulation. We identified > 22,000 phosphosites, revealing orthologous protein phosphorylation and overlapping signaling pathways regulated by exercise. This included two conserved phosphosites on stromal interaction molecule 1 (STIM1), which we validate as AMPK substrates. Furthermore, we demonstrate that AMPK-mediated phosphorylation of STIM1 negatively regulates store-operated calcium entry, and this is beneficial for exercise in Drosophila. This integrated cross-species resource of exercise-regulated signaling in human, mouse, and rat skeletal muscle has uncovered conserved networks and unraveled crosstalk between AMPK and intracellular calcium flux.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Canais de Cálcio/metabolismo , Cálcio/metabolismo , Proteômica/métodos , Molécula 1 de Interação Estromal/metabolismo , Animais , Sinalização do Cálcio/fisiologia , Drosophila , Feminino , Humanos , Masculino , Proteínas de Membrana , Camundongos , Músculo Esquelético/metabolismo , Fosforilação , Conformação Proteica , Ratos , Ratos Wistar , Transdução de Sinais , Molécula 1 de Interação Estromal/química , Molécula 1 de Interação Estromal/genéticaRESUMO
BACKGROUND: Insulin resistance is a critical cause of metabolic dysfunctions. Metabolic dysfunction is common in patients with cancer and is associated with higher cancer recurrence rates and reduced overall survival. Yet, insulin resistance is rarely considered in the clinic and thus it is uncertain how frequently this condition occurs in patients with cancer. METHODS: To address this knowledge gap, we performed a systematic review and a meta-analysis guided by the Preferred Items for Systematic Review and Meta-Analyses (PRISMA) statement. We included studies assessing insulin resistance in patients with various cancer diagnoses, using the gold-standard hyperinsulinemic-euglycemic clamp method. Studies eligible for inclusion were as follows: (1) included cancer patients older than 18 years of age; (2) included an age-matched control group consisting of individuals without cancer or other types of neoplasms; (3) measured insulin sensitivity using the hyperinsulinemic-euglycemic clamp method. We searched the databases MEDLINE, Embase, and Cochrane Central Register of Controlled Trials for articles published from database inception through March 2023 with no language restriction, supplemented by backward and forward citation searching. Bias was assessed using funnel plot. FINDINGS: Fifteen studies satisfied the criteria. The mean insulin-stimulated rate of glucose disposal (Rd) was 7.5 mg/kg/min in control subjects (n = 154), and 4.7 mg/kg/min in patients with a cancer diagnosis (n = 187). Thus, the Rd mean difference was -2.61 mg/kg/min [95% confidence interval, -3.04; -2.19], p<.01). Heterogeneity among the included studies was insignificant (p=.24). INTERPRETATION: These findings suggest that patients with a cancer diagnosis are markedly insulin resistant. As metabolic dysfunction in patients with cancer associates with increased recurrence and reduced overall survival, future studies should address if ameliorating insulin resistance in this population can improve these outcomes thereby improving patient care.Key pointsMetabolic dysfunction increases cancer recurrence rates and reduces survival for patients with cancer.Insulin resistance is a critical cause of metabolic dysfunctions.To date, no comprehensive compilation of research investigating insulin resistance in cancer patients has been produced.In this meta-analysis, we found that patients with various cancers were markedly insulin-resistant.
Assuntos
Resistência à Insulina , Insulinas , Neoplasias , HumanosRESUMO
In mice, exercise is suggested to activate the mechanistic target of rapamycin complex 2 (mTORC2) in skeletal muscle, and mTORC2 is required for normal muscle glucose uptake during exercise. Whether this translates to human skeletal muscle and what signaling pathways facilitate the exercise-induced mTORC2 activation is unknown. We herein tested the hypothesis that exercise increases mTORC2 activity in human skeletal muscle and investigated if ß2-adrenergic receptor (AR) activation mediates exercise-induced mTORC2 activation. We examined several mTORC2 activity readouts (p-NDRG1 Thr346, p-Akt Ser473, p-mTOR S2481, and p-Akt Thr450) in human skeletal muscle biopsies after uphill walking or cycling exercise. In mouse muscles, we assessed mTORC2 activity readouts following acute activation of muscle ß2-adrenergic or GS signaling and during in vivo and ex vivo muscle contractions. Exercise increased phosphorylation of NDRG1 Thr346 in human soleus, gastrocnemius, and vastus lateralis muscle, without changing p-Akt Ser473, p-Akt Thr450, and p-mTOR Ser2481. In mouse muscle, stimulation of ß2-adrenergic or GS signaling and ex vivo contractions failed to increase p-NDRG1 Thr346, whereas in vivo contractions were sufficient to induce p-NDRG1 Thr346. In conclusion, the mTORC2 activity readout p-NDRG1 Thr346 is a novel exercise-responsive signaling protein in human skeletal muscle. Notably, contraction-induced p-NDRG1 Thr346 appears to require a systemic factor. Unlike exercise, and in contrast to published data obtained in cultured muscles cells, stimulation of ß2-adrenergic signaling is not sufficient to trigger NDRG1 phosphorylation in mature mouse skeletal muscle.NEW & NOTEWORTHY The mTORC2 readout p-NDRG Thr346 is a novel exercise-responsive protein in human skeletal muscle. ß2-AR and GS signaling are not sufficient to induce mTORC2 signaling in adult muscle. In vivo, but not ex vivo, contraction induced p-NDRG Thr346, which indicates requirement of a systemic factor for exercise-induced mTORC2 activation.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Alvo Mecanístico do Complexo 2 de Rapamicina/metabolismo , Músculo Esquelético/metabolismo , Transdução de Sinais/fisiologia , Caminhada/fisiologia , Adulto , Animais , Células Cultivadas , Feminino , Fibroblastos/metabolismo , Voluntários Saudáveis , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Contração Muscular/fisiologia , Fosforilação/fisiologia , Receptores Adrenérgicos beta 2/metabolismo , Adulto JovemRESUMO
The interaction between insulin and exercise is an example of balancing and modifying the effects of two opposing metabolic regulatory forces under varying conditions. While insulin is secreted after food intake and is the primary hormone increasing glucose storage as glycogen and fatty acid storage as triglycerides, exercise is a condition where fuel stores need to be mobilized and oxidized. Thus, during physical activity the fuel storage effects of insulin need to be suppressed. This is done primarily by inhibiting insulin secretion during exercise as well as activating local and systemic fuel mobilizing processes. In contrast, following exercise there is a need for refilling the fuel depots mobilized during exercise, particularly the glycogen stores in muscle. This process is facilitated by an increase in insulin sensitivity of the muscles previously engaged in physical activity which directs glucose to glycogen resynthesis. In physically trained individuals, insulin sensitivity is also higher than in untrained individuals due to adaptations in the vasculature, skeletal muscle and adipose tissue. In this paper, we review the interactions between insulin and exercise during and after exercise, as well as the effects of regular exercise training on insulin action.
Assuntos
Exercício Físico , Glucose/metabolismo , Glicogênio/metabolismo , Insulina/metabolismo , Músculos/metabolismo , Animais , HumanosRESUMO
Exercise in humans increases muscle glucose uptake up to 100-fold compared with rest. The magnitude of increase depends on exercise intensity and duration. Although knockout of glucose transporter type 4 (GLUT4) convincingly has shown that GLUT4 is necessary for exercise to increase muscle glucose uptake, studies only show an approximate twofold increase in GLUT4 translocation to the muscle cell membrane when transitioning from rest to exercise. Therefore, there is a big discrepancy between the increase in glucose uptake and GLUT4 translocation. It is suggested that either the methods for measurements of GLUT4 translocation in muscle grossly underestimate the real translocation of GLUT4 or, alternatively, GLUT4 intrinsic activity increases in muscle during exercise, perhaps due to increased muscle temperature and/or mechanical effects during contraction/relaxation cycles.
Assuntos
Exercício Físico/fisiologia , Transportador de Glucose Tipo 4/metabolismo , Glucose/metabolismo , Músculo Esquelético/metabolismo , Animais , Metabolismo dos Carboidratos/fisiologia , Humanos , Insulina/metabolismo , Contração Muscular/fisiologia , Transporte ProteicoRESUMO
BACKGROUND: Roux-en-Y gastric bypass (RYGB) surgery is a therapeutic intervention for morbid obesity and type 2 diabetes (T2D) that improves metabolic regulation. Follistatin (Fst) could be implicated in improved glycemia as it is highly regulated by RYGB. However, it is unknown if metabolic status, such as T2D, alters the Fst response to RYGB. In addition, the effect of RYGB on the Fst target, activin A, is unknown in individuals with obesity and T2D, but is needed to interpret the functional effects of altering Fst. Finally, whether Fst-regulated intracellular signaling contributes to beneficial effects of RYGB is undetermined. METHODS: Circulating Fst and activin A were measured before, 1 week, and 1 year after RYGB surgery in a total of 20 individuals with obesity, 10 with normoglycemia (NGT) and 10 with preoperative T2D. Intracellular signaling downstream of the Activin receptor type IIB (ActRIIB) signaling pathway was analyzed in skeletal muscle and adipose tissue. RESULTS: The doubling in circulating Fst observed in subjects with NGT 1-week and 1-year post surgery was absent in T2D. After 1 week, RYGB reduced activin A by 27% (p < 0.001) and 20% (p < 0.01) in subjects with NGT and T2D, respectively; a reduction that tended to be maintained in the subjects with T2D at 1-year post-RYGB (-15%; p = 0.0592). RYGB had no effects on skeletal muscle ActRIIB signaling. In contrast, adipose tissue phosphorylation of SMAD2Ser465/467, p70S6KThr389, S6RPSer235/236, and 4E-BP1Thr37/49 was highly regulated, particularly 1-year post-RYGB (p < 0.05). CONCLUSIONS: In subjects with preoperative T2D, RYGB did not increase circulating Fst contrasting subjects with NGT, while the reduction in activin A was maintained. ActRIIB signaling was upregulated in adipose tissue, but not skeletal muscle, following RYGB in both individuals with NGT and T2D. Our results suggest a role of adipose tissue ActRIIB signaling for the beneficial effects of RYGB surgery.
Assuntos
Receptores de Activinas Tipo II/análise , Ativinas/sangue , Ativinas/metabolismo , Diabetes Mellitus Tipo 2/complicações , Folistatina/sangue , Folistatina/metabolismo , Obesidade Mórbida , Tecido Adiposo/metabolismo , Adulto , Biópsia , Glicemia , Feminino , Seguimentos , Derivação Gástrica , Glucose/metabolismo , Controle Glicêmico , Humanos , Subunidades beta de Inibinas/metabolismo , Masculino , Pessoa de Meia-Idade , Músculos/metabolismo , Obesidade Mórbida/complicações , Obesidade Mórbida/metabolismo , Obesidade Mórbida/fisiopatologia , Obesidade Mórbida/cirurgia , Transdução de Sinais , Fatores de TempoRESUMO
The maintenance of muscle function is extremely important for whole body health and exercise is essential to this process. The ubiquitin-proteasome system (UPS) is required for muscle adaptation following exercise but little is known about acute posttranslational regulation and proteome remodeling during and after high-intensity exercise. Here, we used quantitative proteomics to study ubiquitin signaling dynamics in human skeletal muscle biopsies from healthy males before, during, and after a single bout of high-intensity exercise. Exercise resulted in a marked depletion of protein ubiquitylation in the vastus lateralis muscle consistent with proteasome activation. This was also associated with acute posttranslational modification of protein abundance. Integration of these data with phosphoproteomics identified co-regulated proximal modifications suggesting a cross talk between phosphorylation and ubiquitylation. We also identified additional protein modification cross talk and showed acute activation of protein NEDDylation. In vitro experiments revealed that cAMP-dependent activation of the proteasome requires NEDD8, an ubiquitin-like protein involved in protein NEDDylation, to maintain cellular protein ubiquitylation levels. Our data reveal the complexity of ubiquitin signaling and proteome remodeling in muscle during and after high-intensity exercise. We propose a model whereby exercise and the resulting cAMP signaling activate both the proteasome and ubiquitylation via NEDDylation to rapidly remove potentially damaged proteins.
Assuntos
Exercício Físico , Músculo Esquelético/metabolismo , Proteína NEDD8/química , Complexo de Endopeptidases do Proteassoma/metabolismo , Processamento de Proteína Pós-Traducional , Proteoma/análise , Ubiquitina/metabolismo , Ubiquitinação , Adulto , Células HEK293 , Humanos , Masculino , Proteína NEDD8/metabolismo , Fosforilação , Transdução de SinaisRESUMO
Thyroid hormones are important for homeostatic control of energy metabolism and body temperature. Although skeletal muscle is considered a key site for thyroid action, the contribution of thyroid hormone receptor signaling in muscle to whole-body energy metabolism and body temperature has not been resolved. Here, we show that T3-induced increase in energy expenditure requires thyroid hormone receptor alpha 1 (TRα1 ) in skeletal muscle, but that T3-mediated elevation in body temperature is achieved in the absence of muscle-TRα1 . In slow-twitch soleus muscle, loss-of-function of TRα1 (TRαHSACre ) alters the fiber-type composition toward a more oxidative phenotype. The change in fiber-type composition, however, does not influence the running capacity or motivation to run. RNA-sequencing of soleus muscle from WT mice and TRαHSACre mice revealed differentiated transcriptional regulation of genes associated with muscle thermogenesis, such as sarcolipin and UCP3, providing molecular clues pertaining to the mechanistic underpinnings of TRα1 -linked control of whole-body metabolic rate. Together, this work establishes a fundamental role for skeletal muscle in T3-stimulated increase in whole-body energy expenditure.
Assuntos
Metabolismo Energético/efeitos dos fármacos , Fibras Musculares de Contração Rápida/fisiologia , Fibras Musculares de Contração Lenta/fisiologia , Músculo Esquelético/fisiologia , Receptores alfa dos Hormônios Tireóideos/fisiologia , Hormônios Tireóideos/farmacologia , Animais , Masculino , Camundongos , Camundongos Knockout , Fibras Musculares de Contração Rápida/citologia , Fibras Musculares de Contração Rápida/efeitos dos fármacos , Fibras Musculares de Contração Lenta/citologia , Fibras Musculares de Contração Lenta/efeitos dos fármacos , Músculo Esquelético/citologia , Músculo Esquelético/efeitos dos fármacos , Condicionamento Físico Animal , TranscriptomaRESUMO
Excessive circulating FAs have been proposed to promote insulin resistance (IR) of glucose metabolism by increasing the oxidation of FAs over glucose. Therefore, inhibition of FA oxidation (FAOX) has been suggested to ameliorate IR. However, prolonged inhibition of FAOX would presumably cause lipid accumulation and thereby promote lipotoxicity. To understand the glycemic consequences of acute and prolonged FAOX inhibition, we treated mice with the carnitine palmitoyltransferase 1 (CPT-1) inhibitor, etomoxir (eto), in combination with short-term 45% high fat diet feeding to increase FA availability. Eto acutely increased glucose oxidation and peripheral glucose disposal, and lowered circulating glucose, but this was associated with increased circulating FAs and triacylglycerol accumulation in the liver and heart within hours. Several days of FAOX inhibition by daily eto administration induced hepatic steatosis and glucose intolerance, specific to CPT-1 inhibition by eto. Lower whole-body insulin sensitivity was accompanied by reduction in brown adipose tissue (BAT) uncoupling protein 1 (UCP1) protein content, diminished BAT glucose clearance, and increased hepatic glucose production. Collectively, these data suggest that pharmacological inhibition of FAOX is not a viable strategy to treat IR, and that sufficient rates of FAOX are required for maintaining liver and BAT metabolic function.
Assuntos
Compostos de Epóxi/farmacologia , Ácidos Graxos/metabolismo , Glucose/metabolismo , Animais , Dieta Hiperlipídica , Compostos de Epóxi/administração & dosagem , Ácidos Graxos/química , Intolerância à Glucose/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Oxirredução/efeitos dos fármacosRESUMO
AIMS/HYPOTHESIS: Treatment with the α3ß4 nicotinic acetylcholine receptor (nAChR) agonist, 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), improves glucose tolerance in diet-induced obese (DIO) mice, but the physiological and molecular mechanisms are unknown. METHODS: DMPP (10 mg/kg body weight, s.c.) was administered either in a single injection (acute) or daily for up to 14 days (chronic) in DIO wild-type (WT) and Chrnb4 knockout (KO) mice and glucose tolerance, tissue-specific tracer-based glucose metabolism, and insulin signalling were assessed. RESULTS: In WT mice, but not in Chrnb4 KO mice, single acute treatment with DMPP induced transient hyperglycaemia, which was accompanied by high plasma adrenaline (epinephrine) levels, upregulated hepatic gluconeogenic genes, and decreased hepatic glycogen content. In contrast to these acute effects, chronic DMPP treatment in WT mice elicited improvements in glucose tolerance already evident after three consecutive days of DMPP treatment. After seven days of DMPP treatment, glucose tolerance was markedly improved, also in comparison with mice that were pair-fed to DMPP-treated mice. The glycaemic benefit of chronic DMPP was absent in Chrnb4 KO mice. Chronic DMPP increased insulin-stimulated glucose clearance into brown adipose tissue (+69%), heart (+93%), gastrocnemius muscle (+74%) and quadriceps muscle (+59%), with no effect in white adipose tissues. After chronic DMPP treatment, plasma adrenaline levels did not increase following an injection with DMPP. In glucose-stimulated skeletal muscle, we detected a decreased phosphorylation of the inhibitory Ser640 phosphorylation site on glycogen synthase and a congruent increase in glycogen accumulation following chronic DMPP treatment. CONCLUSIONS/INTERPRETATION: Our data suggest that DMPP acutely induces adrenaline release and hepatic glycogenolysis, while chronic DMPP-mediated activation of ß4-containing nAChRs improves peripheral insulin sensitivity independently of changes in body weight via mechanisms that could involve increased non-oxidative glucose disposal into skeletal muscle.
Assuntos
Obesidade/tratamento farmacológico , Obesidade/metabolismo , Receptores Nicotínicos/metabolismo , Animais , Glicemia/efeitos dos fármacos , Catecolaminas/metabolismo , Iodeto de Dimetilfenilpiperazina/uso terapêutico , Hiperglicemia/tratamento farmacológico , Hiperglicemia/metabolismo , Resistência à Insulina/fisiologia , Masculino , Camundongos , Camundongos Knockout , Agonistas Nicotínicos/uso terapêuticoRESUMO
KEY POINTS: Rodent studies suggest muscle fibre type-specific insulin response in the recovery from exercise. The current study investigates muscle fibre type-specific insulin action in the recovery from exercise in healthy subjects. In type I and type II muscle fibres, key proteins in glucose metabolism are similarly regulated by insulin during recovery from exercise. Our findings imply that both type I and type II muscle fibres contribute to the phenomenon of increased insulin sensitivity in the recovery from a single bout of exercise in humans. ABSTRACT: Human skeletal muscle consists of slow-twitch (type I) and fast-twitch (type II) muscle fibres. Muscle insulin action, regulating glucose uptake and metabolism, is improved following a single exercise bout. Rodent studies suggest that this phenomenon is confined to specific muscle fibre types. Whether this phenomenon is also confined to specific fibre types in humans has not been described. To investigate this, nine healthy men underwent a euglycaemic hyperinsulinaemic clamp (EHC) in the recovery from a single bout of one-legged knee-extensor exercise. Pools of type I and type II fibres were prepared from muscle biopsies taken in the rested and prior exercised leg before and after the EHC. AMPK γ3 and TBC1D4 - two key proteins regulating muscle insulin action following exercise - were higher expressed in type II than type I fibres. However, phosphor-regulation of TBC1D4 was similar between fibre types when related to the total amount of TBC1D4 protein. The activating dephosphorylation of glycogen synthase was also similar in the two fibre types. Thus, insulin-induced regulation of key proteins important for transport and intracellular flux of glucose towards glycogen storage in the recovery from exercise, does not differ between fibre types. In conclusion, the insulin-sensitizing effect of a single bout of exercise includes both type I and type II fibres in human skeletal muscle. This may be an important observation for future pharmacological strategies targeting muscle insulin sensitivity in humans.
Assuntos
Exercício Físico , Insulina , Glicogênio , Humanos , Fibras Musculares Esqueléticas , Músculo EsqueléticoRESUMO
KEY POINTS: Increased insulin action is an important component of the health benefits of exercise, but its regulation is complex and not fully elucidated. Previous studies of insulin-stimulated GLUT4 translocation to the skeletal muscle membrane found insufficient increases to explain the increases in glucose uptake. By determination of leg glucose uptake and interstitial muscle glucose concentration, insulin-induced muscle membrane permeability to glucose was calculated 4 h after one-legged knee-extensor exercise during a submaximal euglycaemic-hyperinsulinaemic clamp. It was found that during submaximal insulin stimulation, muscle membrane permeability to glucose in humans increases twice as much in previously exercised vs. rested muscle and outstrips the supply of glucose, which then becomes limiting for glucose uptake. This methodology can now be employed to determine muscle membrane permeability to glucose in people with diabetes, who have reduced insulin action, and in principle can also be used to determine membrane permeability to other substrates or metabolites. ABSTRACT: Increased insulin action is an important component of the health benefits of exercise, but the regulation of insulin action in vivo is complex and not fully elucidated. Previously determined increases in skeletal muscle insulin-stimulated GLUT4 translocation are inconsistent and mostly cannot explain the increases in insulin action in humans. Here we used leg glucose uptake (LGU) and interstitial muscle glucose concentration to calculate insulin-induced muscle membrane permeability to glucose, a variable not previously possible to quantify in humans. Muscle membrane permeability to glucose, measured 4 h after one-legged knee-extensor exercise, increased â¼17-fold during a submaximal euglycaemic-hyperinsulinaemic clamp in rested muscle (R) and â¼36-fold in exercised muscle (EX). Femoral arterial infusion of NG -monomethyl l-arginine acetate or ATP decreased and increased, respectively, leg blood flow (LBF) in both legs but did not affect membrane glucose permeability. Decreasing LBF reduced interstitial glucose concentrations to â¼2 mM in the exercised but only to â¼3.5 mM in non-exercised muscle and abrogated the augmented effect of insulin on LGU in the EX leg. Increasing LBF by ATP infusion increased LGU in both legs with uptake higher in the EX leg. We conclude that it is possible to measure functional muscle membrane permeability to glucose in humans and it increases twice as much in exercised vs. rested muscle during submaximal insulin stimulation. We also show that muscle perfusion is an important regulator of muscle glucose uptake when membrane permeability to glucose is high and we show that the capillary wall can be a significant barrier for glucose transport.