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1.
Mediators Inflamm ; 2016: 1536047, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27999451

RESUMO

Free fatty acid receptor-4 (FFAR4), also known as GPR120, has been reported to mediate the beneficial effects of omega-3 polyunsaturated fatty acids (ω3-PUFAs) by inducing an anti-inflammatory immune response. Thus, activation of FFAR4 has been reported to ameliorate chronic low-grade inflammation and insulin resistance accompanying obesity. However, conflicting reports on the role of FFAR4 in mediating the effects of ω3-PUFAs are emerging, suggesting that FFAR4 may not be the sole effector. Hence analyses of the importance of this receptor in relation to other signaling pathways and prominent effects of ω3-PUFAs remain to be elucidated. In the present study, we used Ffar4 knockouts (KO) and heterozygous (HET) mice fed either low fat, low sucrose reference diet; high fat, high sucrose ω3-PUFA; or high fat, high sucrose ω6-PUFA diet for 36 weeks. We demonstrate that both KO and HET mice fed ω3-PUFAs were protected against obesity, hepatic triacylglycerol accumulation, and whole-body insulin resistance. Moreover, ω3-PUFA fed mice had increased circulating protein levels of the anti-inflammatory adipokine, adiponectin, decreased fasting insulin levels, and decreased mRNA expression of several proinflammatory molecules within visceral adipose tissue. In conclusion, we find that FFAR4 signaling is not required for the reported anti-inflammatory and insulin-sensitizing effects mediated by ω3-PUFAs.


Assuntos
Anti-Inflamatórios/farmacologia , Ácidos Graxos Ômega-3/farmacologia , Fígado/efeitos dos fármacos , Músculos/efeitos dos fármacos , Receptores Acoplados a Proteínas G/metabolismo , Animais , Dieta Hiperlipídica , Insulina/farmacologia , Resistência à Insulina , Fígado/metabolismo , Masculino , Camundongos , Camundongos Knockout , Músculos/metabolismo , Receptores Acoplados a Proteínas G/genética
2.
Am J Physiol Regul Integr Comp Physiol ; 309(5): R510-24, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26062634

RESUMO

Roux-en-Y gastric bypass (RYGB) leads to increased peripheral insulin sensitivity. The aim of this study was to investigate the effect of RYGB on expression and regulation of proteins involved in regulation of peripheral glucose metabolism. Skeletal muscle and adipose tissue biopsies from glucose-tolerant and type 2 diabetic subjects at fasting and during a hyperinsulinemic-euglycemic clamp before as well as 1 wk and 3 and 12 mo after RYGB were analyzed for relevant insulin effector proteins/signaling components. Improvement in peripheral insulin sensitivity mainly occurred at 12 mo postsurgery when major weight loss was evident and occurred concomitantly with alterations in plasma adiponectin and in protein expression/signaling in peripheral tissues. In skeletal muscle, protein expression of GLUT4, phosphorylated levels of TBC1D4, as well as insulin-induced changes in phosphorylation of Akt and glycogen synthase activity were enhanced 12 mo postsurgery. In adipose tissue, protein expression of GLUT4, Akt2, TBC1D4, and acetyl-CoA carboxylase (ACC), phosphorylated levels of AMP-activated protein kinase and ACC, as well as insulin-induced changes in phosphorylation of Akt and TBC1D4, were enhanced 12 mo postsurgery. Adipose tissue from glucose-tolerant subjects was the most responsive to RYGB compared with type 2 diabetic patients, whereas changes in skeletal muscle were largely similar in these two groups. In conclusion, an improved molecular insulin-sensitive phenotype of skeletal muscle and adipose tissue appears to contribute to the improved whole body insulin action following a substantial weight loss after RYGB.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Derivação Gástrica , Insulina/metabolismo , Obesidade/cirurgia , Músculo Quadríceps/metabolismo , Transdução de Sinais , Gordura Subcutânea Abdominal/metabolismo , Adulto , Diabetes Mellitus Tipo 2/etiologia , Diabetes Mellitus Tipo 2/fisiopatologia , Metabolismo Energético , Feminino , Humanos , Resistência à Insulina , Masculino , Obesidade/complicações , Obesidade/metabolismo , Obesidade/fisiopatologia , Fenótipo , Músculo Quadríceps/enzimologia , Gordura Subcutânea Abdominal/enzimologia , Fatores de Tempo , Resultado do Tratamento , Redução de Peso
3.
Am J Physiol Regul Integr Comp Physiol ; 307(9): R1136-45, 2014 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-25163924

RESUMO

The aim of the present study was to investigate lipid-induced regulation of lipid binding proteins in human skeletal muscle and the impact hereof on insulin sensitivity. Eleven healthy male subjects underwent a 3-day hypercaloric and high-fat diet regime. Muscle biopsies were taken before and after the diet intervention, and giant sarcolemmal vesicles were prepared. The high-fat diet induced decreased insulin sensitivity, but this was not associated with a relocation of FAT/CD36 or FABPpm protein to the sarcolemma. However, FAT/CD36 and FABPpm mRNA, but not the proteins, were upregulated by increased fatty acid availability. This suggests a time dependency in the upregulation of FAT/CD36 and FABPpm protein during high availability of plasma fatty acids. Furthermore, we did not detect FATP1 and FATP4 protein in giant sarcolemmal vesicles obtained from human skeletal muscle. In conclusion, this study shows that a short-term lipid-load increases mRNA content of key lipid handling proteins in human muscle. However, decreased insulin sensitivity after a high-fat diet is not accompanied with relocation of FAT/CD36 or FABPpm protein to the sarcolemma. Finally, FATP1 and FATP4 protein was located intracellularly but not at the sarcolemma in humans.


Assuntos
Membrana Celular/fisiologia , Gorduras na Dieta/administração & dosagem , Metabolismo dos Lipídeos/fisiologia , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/fisiologia , Transporte Proteico/fisiologia , Beclometasona , Ácidos Graxos/sangue , Ácidos Graxos/metabolismo , Humanos , Insulina/sangue , Insulina/metabolismo , Resistência à Insulina/fisiologia , Masculino , Consumo de Oxigênio , Adulto Jovem
4.
J Physiol ; 591(20): 5141-55, 2013 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-23878361

RESUMO

In skeletal muscle hormone-sensitive lipase (HSL) has long been accepted to be the principal enzyme responsible for lipolysis of intramyocellular triacylglycerol (IMTG) during contractions. However, this notion is based on in vitro lipase activity data, which may not reflect the in vivo lipolytic activity. We investigated lipolysis of IMTG in soleus muscles electrically stimulated to contract ex vivo during acute pharmacological inhibition of HSL in rat muscles and in muscles from HSL knockout (HSL-KO) mice. Measurements of IMTG are complicated by the presence of adipocytes located between the muscle fibres. To circumvent the problem with this contamination we analysed intramyocellular lipid droplet content histochemically. At maximal inhibition of HSL in rat muscles, contraction-induced breakdown of IMTG was identical to that seen in control muscles (P < 0.001). In response to contractions IMTG staining decreased significantly in both HSL-KO and WT muscles (P < 0.05). In vitro TG hydrolase activity data revealed that adipose triglyceride lipase (ATGL) and HSL collectively account for ∼98% of the TG hydrolase activity in mouse skeletal muscle, other TG lipases accordingly being of negligible importance for lipolysis of IMTG. The present study is the first to demonstrate that contraction-induced lipolysis of IMTG occurs in the absence of HSL activity in rat and mouse skeletal muscle. Furthermore, the results suggest that ATGL is activated and plays a major role in lipolysis of IMTG during muscle contractions.


Assuntos
Lipólise , Contração Muscular , Músculo Esquelético/metabolismo , Esterol Esterase/metabolismo , Animais , Lipase/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Músculo Esquelético/enzimologia , Músculo Esquelético/fisiologia , Ratos , Ratos Wistar , Esterol Esterase/antagonistas & inibidores , Esterol Esterase/genética , Triglicerídeos/metabolismo
5.
Mol Metab ; 47: 101174, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33549847

RESUMO

OBJECTIVE: The goal of this study was to investigate the importance of central hormone-sensitive lipase (HSL) expression in the regulation of food intake and body weight in mice to clarify whether intracellular lipolysis in the mammalian hypothalamus plays a role in regulating appetite. METHODS: Using pharmacological and genetic approaches, we investigated the role of HSL in the rodent brain in the regulation of feeding and energy homeostasis under basal conditions during acute stress and high-fat diet feeding. RESULTS: We found that HSL, a key enzyme in the catabolism of cellular lipid stores, is expressed in the appetite-regulating centers in the hypothalamus and is activated by acute stress through a mechanism similar to that observed in adipose tissue and skeletal muscle. Inhibition of HSL in rodent models by a synthetic ligand, global knockout, or brain-specific deletion of HSL prevents a decrease in food intake normally seen in response to acute stress and is associated with the increased expression of orexigenic peptides neuropeptide Y (NPY) and agouti-related peptide (AgRP). Increased food intake can be reversed by adeno-associated virus-mediated reintroduction of HSL in neurons of the mediobasal hypothalamus. Importantly, metabolic stress induced by a high-fat diet also enhances the hyperphagic phenotype of HSL-deficient mice. Specific deletion of HSL in the ventromedial hypothalamic nucleus (VMH) or AgRP neurons reveals that HSL in the VMH plays a role in both acute stress-induced food intake and high-fat diet-induced obesity. CONCLUSIONS: Our results indicate that HSL activity in the mediobasal hypothalamus is involved in the acute reduction in food intake during the acute stress response and sensing of a high-fat diet.


Assuntos
Apetite/fisiologia , Homeostase , Hipotálamo/metabolismo , Esterol Esterase/metabolismo , Proteína Relacionada com Agouti/metabolismo , Animais , Peso Corporal , Dieta Hiperlipídica/efeitos adversos , Ingestão de Alimentos , Metabolismo Energético , Feminino , Hiperfagia/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios/metabolismo , Neuropeptídeo Y/metabolismo , Obesidade/metabolismo , Fatores de Processamento de RNA , Esterol Esterase/genética , Estresse Fisiológico/genética , Transcriptoma
6.
Diabetes ; 69(11): 2267-2280, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32873590

RESUMO

Women with polycystic ovary syndrome (PCOS) have been shown to be less insulin sensitive compared with control (CON) women, independent of BMI. Training is associated with molecular adaptations in skeletal muscle, improving glucose uptake and metabolism in both healthy individuals and patients with type 2 diabetes. In the current study, lean hyperandrogenic women with PCOS (n = 9) and healthy CON women (n = 9) completed 14 weeks of controlled and supervised exercise training. In CON, the training intervention increased whole-body insulin action by 26% and insulin-stimulated leg glucose uptake by 53% together with increased insulin-stimulated leg blood flow and a more oxidative muscle fiber type distribution. In PCOS, no such changes were found, despite similar training intensity and improvements in VO2max In skeletal muscle of CON but not PCOS, training increased GLUT4 and HKII mRNA and protein expressions. These data suggest that the impaired increase in whole-body insulin action in women with PCOS with training is caused by an impaired ability to upregulate key glucose-handling proteins for insulin-stimulated glucose uptake in skeletal muscle and insulin-stimulated leg blood flow. Still, other important benefits of exercise training appeared in women with PCOS, including an improvement of the hyperandrogenic state.


Assuntos
Exercício Físico/fisiologia , Hiperandrogenismo/metabolismo , Insulina , Síndrome do Ovário Policístico/metabolismo , Adaptação Fisiológica , Feminino , Homeostase , Humanos , Fígado/metabolismo , Músculo Esquelético/metabolismo , Oxirredução , Testosterona/sangue
7.
J Appl Physiol (1985) ; 106(4): 1385-93, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18927264

RESUMO

The knowledge about the effect of estradiol on tendon connective tissue is limited. Therefore, we studied the influence of estradiol on tendon synthesis, structure, and biomechanical properties in postmenopausal women. Nonusers (control, n = 10) or habitual users of oral estradiol replacement therapy (ERT, n = 10) were studied at rest and in response to one-legged resistance exercise. Synthesis of tendon collagen was determined by stable isotope incorporation [fractional synthesis rate (FSR)] and microdialysis technique (NH(2)-terminal propeptide of type I collagen synthesis). Tendon area and fibril characteristics were determined by MRI and transmission electron microscopy, whereas tendon biomechanical properties were measured during isometric maximal voluntary contraction by ultrasound recording. Tendon FSR was markedly higher in ERT users (P < 0.001), whereas no group difference was seen in tendon NH(2)-terminal propeptide of type I collagen synthesis (P = 0.32). In ERT users, positive correlations between serum estradiol (s-estradiol) and tendon synthesis were observed, whereas change in tendon synthesis from rest to exercise was negatively correlated to s-estradiol. Tendon area, fibril density, fibril volume fraction, and fibril mean area did not differ between groups. However, the percentage of medium-sized fibrils was higher in ERT users (P < 0.05), whereas the percentage of large fibrils tended to be greater in control (P = 0.10). A lower Young's modulus (GPa/%) was found in ERT users (P < 0.05). In conclusion, estradiol administration was associated with higher tendon FSR and a higher relative number of smaller fibrils. Whereas this indicates stimulated collagen turnover in the resting state, collagen responses to exercise were negatively associated with s-estradiol. These results indicate a pivotal role for estradiol in maintaining homeostasis of female connective tissue.


Assuntos
Colágeno/biossíntese , Terapia de Reposição de Estrogênios , Pós-Menopausa/fisiologia , Tendões/anatomia & histologia , Tendões/metabolismo , Idoso , Fenômenos Biomecânicos , Densidade Óssea , Osso e Ossos/metabolismo , Estudos Transversais , Feminino , Humanos , Proteínas de Ligação a Fator de Crescimento Semelhante a Insulina/biossíntese , Fator de Crescimento Insulin-Like I/biossíntese , Microdiálise , Microscopia Eletrônica de Transmissão , Pessoa de Meia-Idade , Ligamento Patelar/anatomia & histologia , Ligamento Patelar/efeitos dos fármacos , Ligamento Patelar/metabolismo , Prolina/sangue , Tendões/efeitos dos fármacos
8.
Diabetes ; 68(3): 502-514, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30626608

RESUMO

The ADAMTS9 rs4607103 C allele is one of the few gene variants proposed to increase the risk of type 2 diabetes through an impairment of insulin sensitivity. We show that the variant is associated with increased expression of the secreted ADAMTS9 and decreased insulin sensitivity and signaling in human skeletal muscle. In line with this, mice lacking Adamts9 selectively in skeletal muscle have improved insulin sensitivity. The molecular link between ADAMTS9 and insulin signaling was characterized further in a model where ADAMTS9 was overexpressed in skeletal muscle. This selective overexpression resulted in decreased insulin signaling presumably mediated through alterations of the integrin ß1 signaling pathway and disruption of the intracellular cytoskeletal organization. Furthermore, this led to impaired mitochondrial function in mouse muscle-an observation found to be of translational character because humans carrying the ADAMTS9 risk allele have decreased expression of mitochondrial markers. Finally, we found that the link between ADAMTS9 overexpression and impaired insulin signaling could be due to accumulation of harmful lipid intermediates. Our findings contribute to the understanding of the molecular mechanisms underlying insulin resistance and type 2 diabetes and point to inhibition of ADAMTS9 as a potential novel mode of treating insulin resistance.


Assuntos
Proteína ADAMTS9/metabolismo , Matriz Extracelular/metabolismo , Insulina/metabolismo , Músculo Esquelético/metabolismo , Proteína ADAMTS9/genética , Alelos , Animais , Humanos , Imuno-Histoquímica , Resistência à Insulina/genética , Resistência à Insulina/fisiologia , Integrina beta1/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout
9.
Diabetes ; 66(10): 2583-2595, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28768703

RESUMO

To understand the mechanisms in lipid-induced insulin resistance, a more physiological approach is to enhance fatty acid (FA) availability through the diet. Nine healthy men ingested two hypercaloric diets (in 75% excess of habitual caloric intake) for 3 days, enriched in unsaturated FA (78 energy % [E%] fat) (UNSAT) or carbohydrates (80 E% carbohydrate) (CHO) as well as a eucaloric control diet (CON). Compared with CON, the UNSAT diet reduced whole-body and leg glucose disposal during a hyperinsulinemic-euglycemic clamp, while decreasing hepatic glucose production. In muscle, diacylglycerol (DAG) and intramyocellular triacylglycerol were increased. The accumulated DAG was sn-1,3 DAG, which is known not to activate PKC, and insulin signaling was intact. UNSAT decreased PDH-E1α protein content and increased inhibitory PDH-E1α Ser300 phosphorylation and FA oxidation. CHO increased whole-body and leg insulin sensitivity, while increasing hepatic glucose production. After CHO, muscle PDH-E1α Ser300 phosphorylation was decreased, and glucose oxidation increased. After UNSAT, but not CHO, muscle glucose-6-phosphate content was 103% higher compared with CON during the clamp. Thus, PDH-E1α expression and covalent regulation, and hence the tricarboxylic acid cycle influx of pyruvate-derived acetyl-CoA relative to ß-oxidation-derived acetyl-CoA, are suggested to impact on insulin-stimulated glucose uptake. Taken together, the oxidative metabolic fluxes of glucose and FA are powerful and opposite regulators of insulin action in muscle.


Assuntos
Metabolismo dos Carboidratos/fisiologia , Gorduras na Dieta/efeitos adversos , Resistência à Insulina/fisiologia , Adulto , Ciclo do Ácido Cítrico/genética , Ciclo do Ácido Cítrico/fisiologia , Diglicerídeos/metabolismo , Ácidos Graxos/sangue , Ácidos Graxos/metabolismo , Humanos , Fígado/metabolismo , Masculino , Músculo Esquelético/metabolismo , Oxirredução , Fosforilação/genética , Fosforilação/fisiologia , Piruvato Desidrogenase (Lipoamida)/genética , Piruvato Desidrogenase (Lipoamida)/metabolismo , Triglicerídeos/metabolismo , Adulto Jovem
10.
Diabetes ; 65(10): 2932-42, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27489310

RESUMO

Type 2 diabetes and skeletal muscle insulin resistance have been linked to accumulation of the intramyocellular lipid-intermediate diacylglycerol (DAG). However, recent animal and human studies have questioned such an association. Given that DAG appears in different stereoisomers and has different reactivity in vitro, we investigated whether the described function of DAGs as mediators of lipid-induced insulin resistance was dependent on the different DAG isomers. We measured insulin-stimulated glucose uptake in hormone-sensitive lipase (HSL) knockout (KO) mice after treadmill exercise to stimulate the accumulation of DAGs in skeletal muscle. We found that, despite an increased DAG content in muscle after exercise in HSL KO mice, the HSL KO mice showed a higher insulin-stimulated glucose uptake postexercise compared with wild-type mice. Further analysis of the chemical structure and cellular localization of DAG in skeletal muscle revealed that HSL KO mice accumulated sn-1,3 DAG and not sn-1,2 DAG. Accordingly, these results highlight the importance of taking the chemical structure and cellular localization of DAG into account when evaluating the role of DAG in lipid-induced insulin resistance in skeletal muscle and that the accumulation of sn-1,3 DAG originating from lipolysis does not inhibit insulin-stimulated glucose uptake.


Assuntos
Diglicerídeos/metabolismo , Resistência à Insulina/fisiologia , Lipólise/fisiologia , Músculo Esquelético/metabolismo , Condicionamento Físico Animal/fisiologia , Animais , Transporte Biológico/efeitos dos fármacos , Glucose/metabolismo , Insulina/farmacologia , Resistência à Insulina/genética , Lipólise/efeitos dos fármacos , Lipólise/genética , Camundongos , Camundongos Knockout , Esterol Esterase/deficiência , Esterol Esterase/genética , Esterol Esterase/metabolismo
11.
Physiol Behav ; 164(Pt A): 300-5, 2016 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-27306083

RESUMO

It is well known that physical activity has several health benefits, yet many people do not exercise. Dopamine levels in the striatum of the brain are thought to be important for the motivation to exercise. Conversely, we hypothesized that muscle quality can affect the motivation to exercise through alterations of the brain dopamine levels specifically in the striatal region. To test this hypothesis, transgenic mice overexpressing an inactivatable dominant negative α2 AMPK construct (AMPK α2 KD) in muscles and littermate wildtype (WT) mice were tested. AMPK α2 KD mice have impaired running capacity and display reduced voluntary wheel running activity. Striatal content of dopamine and its metabolites were measured under basal physiological conditions and after cocaine-induced dopamine efflux from the ventral striatum by in vivo microdialysis. Moreover, cocaine-induced locomotor activity was tested in an open field test. Furthermore, we investigated maximal running capacity and voluntary running over a period of 19days. AMPK α2 KD mice ran 30% less in daily distance compared to WT. Furthermore, AMPK α2 KD mice showed significantly decreased locomotor activity in the open field test compared to WT when treated with saline or cocaine, respectively, but the increase induced by cocaine was similar in AMPK α2 KD and WT mice. The efflux of dopamine in ventral striatum after cocaine treatment increased similarly by 2.5-fold in the two genotypes, and basal levels of dopamine and its metabolites DOPAC and HVA were also similar between genotypes. These findings show that decreased AMPK activity in muscle leads to decreased voluntary activity which is not due to secondary abnormalities in dopamine levels in the ventral striatum or sensitivity to cocaine. Thus, decreased voluntary activity in AMPK muscle deficient mice is most likely unrelated to regulation of brain dopamine content and metabolism.


Assuntos
Proteínas Quinases Ativadas por AMP/deficiência , Corpo Estriado/metabolismo , Dopamina/metabolismo , Músculo Esquelético/metabolismo , Corrida/fisiologia , Ácido 3,4-Di-Hidroxifenilacético/metabolismo , Proteínas Quinases Ativadas por AMP/genética , Animais , Cocaína/farmacologia , Corpo Estriado/efeitos dos fármacos , Inibidores da Captação de Dopamina/farmacologia , Ácido Homovanílico/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Mutação
12.
Cell Signal ; 28(6): 663-74, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26976209

RESUMO

During induction of the autophagosomal degradation process, LC3-I is lipidated to LC3-II and associates to the cargo isolation membrane allowing for autophagosome formation. Lipidation of LC3 results in an increased LC3-II/LC3-I ratio, and this ratio is an often used marker for autophagy in various tissues, including skeletal muscle. From cell studies AMPK has been proposed to be necessary and sufficient for LC3 lipidation. The aim of the present study was to investigate the role of AMPK in regulation of LC3 lipidation as a marker of autophagy in skeletal muscle. We observed an increase in the LC3-II/LC3-I ratio in skeletal muscle of AMPKα2 kinase-dead (KD) (p<0.001) and wild type (WT) (p<0.05) mice after 12h of fasting, which was greater (p<0.05) in AMPKα2 KD mice than in WT. The fasting-induced increase in the LC3-II/LC3-I ratio in both genotypes coincided with an initial decrease (p<0.01) in plasma insulin concentration, a subsequent decrease in muscle mTORC1 signaling and increased (p<0.05) levels of the autophagy-promoting proteins, FoxO3a and ULK1. Furthermore, a higher (p<0.01) LC3-II/LC3-I ratio was observed in old compared to young mice. We were not able to detect any change in LC3 lipidation with either in vivo treadmill exercise or in situ contractions. Collectively, these findings suggest that AMPKα2 is not necessary for induction of LC3 lipidation with fasting and aging. Furthermore, LC3 lipidation is increased in muscle lacking functional AMPKα2 during fasting and aging. Moreover, LC3 lipidation seems not to be a universal response to muscle contraction in mice.


Assuntos
Proteínas Quinases Ativadas por AMP/fisiologia , Autofagia , Proteínas Associadas aos Microtúbulos/metabolismo , Músculo Esquelético/metabolismo , Proteínas Quinases Ativadas por AMP/genética , Proteínas Quinases Ativadas por AMP/metabolismo , Envelhecimento/fisiologia , Animais , Biomarcadores , Feminino , Técnicas de Introdução de Genes , Metabolismo dos Lipídeos , Camundongos Endogâmicos C57BL , Contração Muscular , Músculo Esquelético/enzimologia , Músculo Esquelético/fisiologia , Fator 2 de Elongação de Peptídeos/genética , Condicionamento Físico Animal , Transdução de Sinais
13.
Metabolism ; 65(12): 1706-1719, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27832859

RESUMO

BACKGROUND: The obesogenic potential of high-fat diets (HFD) in rodents is attenuated when the protein:carbohydrate ratio is increased. However, it is not known if intake of an HFD irrespective of the protein:carbohydrate ratio and in the absence of weight gain, affects glucose homeostasis and the gut microbiota. METHODS: We fed C57BL6/J mice 3 different HFDs with decreasing protein:carbohydrate ratios for 8weeks and compared the results to a LFD reference group. We analyzed the gut microbiota composition by 16S rDNA amplicon sequencing and the intestinal gene expression by real-time PCR. Whole body glucose homeostasis was evaluated by insulin and glucose tolerance tests as well as by a hyperinsulinemic euglycemic clamp experiment. RESULTS: Compared with LFD-fed reference mice, HFD-fed mice, irrespective of protein:carbohydrate ratio, exhibited impaired glucose tolerance, whereas no differences were observed during insulin tolerance tests. The hyperinsulinemic euglycemic clamp revealed tissue-specific effects on glucose homeostasis in all HFD-fed groups. HFD-fed mice exhibited decreased insulin-stimulated glucose uptake in white but not in brown adipose tissue, and sustained endogenous glucose production under insulin-stimulated conditions. We observed no impairment of insulin-stimulated glucose uptake in skeletal muscles of different fiber type composition. HFD-feeding altered the gut microbiota composition paralleled by increased expression of pro-inflammatory cytokines and genes involved in gluconeogenesis in intestinal epithelial cells of the jejunum. CONCLUSIONS: Intake of a HFD profoundly affected glucose homeostasis, gut inflammatory responses, and gut microbiota composition in the absence of fat mass accretion.


Assuntos
Gorduras na Dieta/farmacologia , Inflamação/induzido quimicamente , Resistência à Insulina , Intestinos/patologia , Aumento de Peso , Tecido Adiposo Branco/metabolismo , Animais , Glicemia/metabolismo , Glicemia/fisiologia , Intolerância à Glucose , Homeostase/efeitos dos fármacos , Intestinos/microbiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microbiota/efeitos dos fármacos , Músculo Esquelético/metabolismo
14.
Mol Metab ; 5(8): 646-655, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27656402

RESUMO

OBJECTIVE: We have recently shown that acute inhibition of both mTOR complexes (mTORC1 and mTORC2) increases whole-body lipid utilization, while mTORC1 inhibition had no effect. Therefore, we tested the hypothesis that mTORC2 regulates lipid metabolism in skeletal muscle. METHODS: Body composition, substrate utilization and muscle lipid storage were measured in mice lacking mTORC2 activity in skeletal muscle (specific knockout of RICTOR (Ric mKO)). We further examined the RICTOR/mTORC2-controlled muscle metabolome and proteome; and performed follow-up studies in other genetic mouse models and in cell culture. RESULTS: Ric mKO mice exhibited a greater reliance on fat as an energy substrate, a re-partitioning of lean to fat mass and an increase in intramyocellular triglyceride (IMTG) content, along with increases in several lipid metabolites in muscle. Unbiased proteomics revealed an increase in the expression of the lipid droplet binding protein Perilipin 3 (PLIN3) in muscle from Ric mKO mice. This was associated with increased AMPK activity in Ric mKO muscle. Reducing AMPK kinase activity decreased muscle PLIN3 expression and IMTG content. AMPK agonism, in turn, increased PLIN3 expression in a FoxO1 dependent manner. PLIN3 overexpression was sufficient to increase triglyceride content in muscle cells. CONCLUSIONS: We identified a novel link between mTORC2 and PLIN3, which regulates lipid storage in muscle. While mTORC2 is a negative regulator, we further identified AMPK as a positive regulator of PLIN3, which impacts whole-body substrate utilization and nutrient partitioning.

15.
Diabetes ; 63(5): 1725-37, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24241533

RESUMO

Roux-en-Y gastric bypass (RYGB) improves glycemic control within days after surgery, and changes in insulin sensitivity and ß-cell function are likely to be involved. We studied 10 obese patients with type 2 diabetes (T2D) and 10 obese glucose-tolerant subjects before and 1 week, 3 months, and 1 year after RYGB. Participants were included after a preoperative diet-induced total weight loss of -9.2 ± 1.2%. Hepatic and peripheral insulin sensitivity were assessed using the hyperinsulinemic- euglycemic clamp combined with the glucose tracer technique, and ß-cell function was evaluated in response to an intravenous glucose-glucagon challenge as well as an oral glucose load. Within 1 week, RYGB reduced basal glucose production, improved basal hepatic insulin sensitivity, and increased insulin clearance, highlighting the liver as an important organ responsible for early effects on glucose metabolism after surgery. Insulin-mediated glucose disposal and suppression of fatty acids did not improve immediately after surgery but increased at 3 months and 1 year; this increase likely was related to the reduction in body weight. Insulin secretion increased after RYGB only in patients with T2D and only in response to oral glucose, underscoring the importance of the changed gut anatomy.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Resistência à Insulina/fisiologia , Insulina/metabolismo , Fígado/metabolismo , Obesidade/metabolismo , Adulto , Glicemia/metabolismo , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/cirurgia , Feminino , Derivação Gástrica , Técnica Clamp de Glucose , Humanos , Secreção de Insulina , Células Secretoras de Insulina/metabolismo , Masculino , Pessoa de Meia-Idade , Obesidade/complicações , Obesidade/cirurgia , Período Pós-Prandial
16.
Diabetes ; 62(5): 1490-9, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23349504

RESUMO

Lipid metabolism is important for health and insulin action, yet the fundamental process of regulating lipid metabolism during muscle contraction is incompletely understood. Here, we show that liver kinase B1 (LKB1) muscle-specific knockout (LKB1 MKO) mice display decreased fatty acid (FA) oxidation during treadmill exercise. LKB1 MKO mice also show decreased muscle SIK3 activity, increased histone deacetylase 4 expression, decreased NAD⁺ concentration and SIRT1 activity, and decreased expression of genes involved in FA oxidation. In AMP-activated protein kinase (AMPK)α2 KO mice, substrate use was similar to that in WT mice, which excluded that decreased FA oxidation in LKB1 MKO mice was due to decreased AMPKα2 activity. Additionally, LKB1 MKO muscle demonstrated decreased FA oxidation in vitro. A markedly decreased phosphorylation of TBC1D1, a proposed regulator of FA transport, and a low CoA content could contribute to the low FA oxidation in LKB1 MKO. LKB1 deficiency did not reduce muscle glucose uptake or oxidation during exercise in vivo, excluding a general impairment of substrate use during exercise in LKB1 MKO mice. Our findings demonstrate that LKB1 is a novel molecular regulator of major importance for FA oxidation but not glucose uptake in muscle during exercise.


Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Ácidos Graxos não Esterificados/metabolismo , Atividade Motora , Músculo Esquelético/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Quinases Ativadas por AMP/genética , Animais , Transporte Biológico , Coenzima A/metabolismo , Regulação para Baixo , Proteínas Ativadoras de GTPase , Regulação da Expressão Gênica , Glucose/metabolismo , Camundongos , Camundongos Knockout , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Músculo Esquelético/enzimologia , Músculo Esquelético/ultraestrutura , NAD/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Oxirredução , Fosforilação , Processamento de Proteína Pós-Traducional , Proteínas Serina-Treonina Quinases/genética , Distribuição Aleatória
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