RESUMO
OBJECTIVE: The amino acid Arginine (Arg) is the main biological precursor of nitric oxide (NO) and has been described to improve insulin sensitivity in diabetes and obesity. We investigated the molecular mechanisms involved in the long-term effects of Arg on glucose and lipid metabolism. MATERIALS AND METHODS: L6 myotubes were treated with Arg (7 mmol/L) for 6 days. D-Mannitol (7 mmol/L) was used as control; spermine NONOate (10 µmol/L) and L-NAME (100 µmol/L) were used to evaluate the NO/c-GMP pathway role. Basal and insulin-induced (120 nmol/L) glycogen synthesis, glucose uptake and lipid oxidation, c-GMP and nitrite levels, and the intracellular signaling pathways were evaluated. RESULTS: Arg-treatment increased: 1) basal and insulin-stimulated glycogen synthesis; 2) glucose uptake; 3) palmitate oxidation; 4) p-Akt (Ser(473)), total and plasma membrane GLUT4 content, total and p-AMPK-α and p-ACC (Ser(79)), p-GSK-3α/ß (Ser(21/9)) and 5) nitrite and c-GMP levels. L-NAME treatment suppressed Arg effects on: 1) nitrite and c-GMP content; 2) glycogen synthesis and glucose uptake; 3) basal and insulin-stimulated p-Akt (Ser(473)), total and p-AMPK-α and ACC, and nNOS expression. CONCLUSION: We provide evidence that Arg improves glucose and lipid metabolism in skeletal muscle, in parallel with increased phosphorylation of Akt and AMPK-α. These effects were mediated by the NO/c-GMP pathway. Thus, arginine treatment enhances signal transduction and has a beneficial effect of metabolism in skeletal muscle through direct activation of Akt and AMPK pathways.
Assuntos
Glucose/metabolismo , Metabolismo dos Lipídeos/efeitos dos fármacos , Fibras Musculares Esqueléticas/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Espermina/análogos & derivados , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Arginina/antagonistas & inibidores , Arginina/farmacologia , Western Blotting , Linhagem Celular , Transportador de Glucose Tipo 4/metabolismo , Quinase 3 da Glicogênio Sintase/metabolismo , Fibras Musculares Esqueléticas/citologia , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/citologia , Músculo Esquelético/metabolismo , NG-Nitroarginina Metil Éster/farmacologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Ratos , Transdução de Sinais/efeitos dos fármacos , Espermina/farmacologiaRESUMO
We have shown that rats chronically treated with Arginine (Arg), although normoglycemic, exhibit hyperinsulinemia and decreased blood glucose disappearance rate after an insulin challenge. Attempting to investigate the processes underlying these alterations, male Wistar rats were treated with Arg (35 mg/d), in drinking water, for 4 wk. Rats were then acutely stimulated with insulin, and the soleus and extensorum digitalis longus muscles, white adipose tissue (WAT), and liver were excised for total and/or phosphorylated insulin receptor (IR), IR substrate 1/2, Akt, Janus kinase 2, signal transducer and activator of transcription (STAT) 1/3/5, and p85alpha/55alpha determination. Muscles and WAT were also used for plasma membrane (PM) and microsome evaluation of glucose transporter (GLUT) 4 content. Pituitary GH mRNA, GH, and liver IGF-I mRNA expression were estimated. It was shown that Arg treatment: 1) did not affect phosphotyrosine-IR, whereas it decreased phosphotyrosine-IR substrate 1/2 and phosphoserine-Akt content in all tissues studied, indicating that insulin signaling is impaired at post-receptor level; 2) decreased PM GLUT4 content in both muscles and WAT; 3) increased the pituitary GH mRNA, GH, and liver IGF-I mRNA expression, the levels of phosphotyrosine-STAT5 in both muscles, phosphotyrosine-Janus kinase 2 in extensorum digitalis longus, phosphotyrosine-STAT3 in liver, and WAT as well as total p85alpha in soleus, indicating that GH signaling is enhanced in these tissues; and 4) increased p55alpha total content in muscles, WAT, and liver. The present findings provide the molecular mechanisms by which insulin resistance and, by extension, reduced GLUT4 content in PM of muscles and WAT take place after chronic administration of Arg, and further suggest a putative role for GH in its genesis, considering its diabetogenic effect.
Assuntos
Tecido Adiposo/efeitos dos fármacos , Arginina/farmacologia , Hormônio do Crescimento/fisiologia , Insulina/metabolismo , Fígado/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Tecido Adiposo/metabolismo , Animais , Regulação para Baixo/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Hormônio do Crescimento/genética , Hormônio do Crescimento/metabolismo , Proteínas Substratos do Receptor de Insulina/metabolismo , Fator de Crescimento Insulin-Like I/genética , Fator de Crescimento Insulin-Like I/metabolismo , Fígado/metabolismo , Masculino , Músculo Esquelético/metabolismo , Proteína Oncogênica v-akt/metabolismo , Fosforilação/efeitos dos fármacos , Ratos , Ratos Wistar , Receptor de Insulina/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Fatores de TempoRESUMO
BACKGROUND: The pathogenesis of chronic hepatitis C is still a matter of debate. CD4+ and CD8+ T lymphocytes (TL) are typically observed within the portal and periportal spaces of affected livers, but their functional role in hepatitis C progression has not been fully elucidated. METHODS: CD4+ and CD8+ TL were quantified by immunohistochemistry in portal and periportal spaces of 39 liver biopsies from patients with chronic hepatitis C. They were associated to demographic data, histological parameters, laboratory findings of patients and hepatitis C genotypes. RESULTS: There was high numbers of CD4+ and CD8+ TL from which the density of CD4+ T was higher than CD8+ TL in portal and periportal spaces. CD4+ and CD8+ TL were directly correlated to intensity of interface hepatitis. CD8+ TL correlated to serum enzyme levels. CONCLUSION: The high numbers of CD4+ and CD8+ TL in portal and periportal spaces and their correlation to interface hepatitis suggest that hepatitis C evolution depends on the action of intrahepatic T lymphocytes, lending support to the notion of an immune-mediated mechanism in the pathogenesis of chronic hepatitis C.
Assuntos
Relação CD4-CD8 , Hepacivirus/imunologia , Hepatite C Crônica/imunologia , Fígado/virologia , Adolescente , Adulto , Progressão da Doença , Feminino , Genótipo , Hepacivirus/genética , Hepatite C Crônica/patologia , Humanos , Imuno-Histoquímica , Fígado/irrigação sanguínea , Fígado/patologia , Masculino , Pessoa de Meia-Idade , Índice de Gravidade de DoençaRESUMO
Arginine (Arg) presents a potent growth hormone (GH) releasing activity. In vivo and in vitro studies carried out in our laboratory have demonstrated that acute treatment with Arg also increases GH gene expression. Taking into account the recognizable diabetogenic role of GH and that Arg increases insulin release, this study aimed at evaluating the effects of oral chronic administration of Arg on GH gene expression, by Northern blotting analysis, and on the insulin sensitivity, by means of the Insulin Tolerance Test (ITT), blood glucose decay rate (kitt) and insulin plasma concentration. We demonstrated that rats that consumed Arg ( approximately 35 mg/day) in drinking water, during 4 weeks, presented an increase in GH mRNA content (p < 0.01), a decreased peripheral response to insulin, as shown by the reduced blood glucose decay rate (p < 0.05), and a higher insulin plasma concentration (p < 0.01) than control group. Arg treatment did not modify the animals' food and water intake, while it decreased the heart rate and the arterial blood pressure compared to control group (p < 0.05). According to the results presented herein we conclude that chronic oral administration of arginine increases GH gene expression and induces insulin resistance. The arterial blood pressure decrease has already been pointed out in the literature, and seems to occur in response to the dilating effect of nitric oxide generated from Arg, as well as from NO generation in central and peripheral neuronal populations that express NOS and are involved in the autonomic regulation of the cardiac function.