Statin modulates insulin signaling and insulin resistance in liver and muscle of rats fed a high-fat diet.

Recent studies have shown that statins might have relevant effects on insulin resistance in animal models and in humans. However, the molecular mechanisms that account for this improvement in insulin sensitivity are not well established. The aim of the present study was to investigate the effect of a statin on insulin sensitivity and insulin signaling in liver and muscle of rats fed on a high-fat diet (HFD) for 4 weeks, treated or not with lovastatin during the last week. Our data show that treatment with lovastatin results in a marked improvement in insulin sensitivity characterized by an increase in glucose disappearance rate during the insulin tolerance test. This increase in insulin sensitivity was associated with an increase in insulin-induced insulin receptor (IR) tyrosine phosphorylation and, in parallel, a decrease in IR serine phosphorylation and association with PTP1B. Our data also show that lovastatin treatment was associated with an increase in insulin-stimulated insulin receptor substrate (IRS) 1/phosphatidylinositol 3-kinase/Akt pathway in the liver and muscle of HFD-fed rats in parallel with a decrease in the inflammatory pathway (c-jun N-terminal kinase and I kappa beta kinase (IKKbeta)/inhibitor of kappaB/nuclear factor kappaB) related to insulin resistance. In summary, statin treatment improves insulin sensitivity in HFD-fed rats by reversing the decrease in the insulin-stimulated IRS-1/phosphatidylinositol 3-kinase/Akt pathway in liver and muscle. The effect of statins on insulin action is further supported by our findings that HFD rats treated with statin show a reduction in IRS-1 serine phosphorylation, I kappa kinase (IKK)/inhibitor of kappaB/nuclear factor kappaB pathway, and c-jun N-terminal kinase activity, associated with an improvement in insulin action. Overall, these results provide important new insight into the mechanism of statin action in insulin sensitivity.

[New mechanisms by which physical exercise improves insulin resistance in the skeletal muscle]. / Novos mecanismos pelos quais o exercício físico melhora a resistência à insulina no músculo esquelético.

Insulin resistance of skeletal muscle glucose transport is a key-defect for the development of impaired glucose tolerance and type 2 diabetes. However, it is known that both an acute bout of exercise and chronic endurance exercise training can bring beneficial effects on insulin action in insulin-resistant states. However, little is currently known about the molecular effects of acute exercise on muscle insulin signaling in the post-exercise state in insulin-resistant organisms. This review provides new insight into the mechanism through which acute exercise restores insulin sensitivity, highlighting an important role for inflammatory proteins and S-nitrosation in the regulation of insulin signaling proteins in skeletal muscle.

Novos mecanismos pelos quais o exercício físico melhora a resistência à insulina no músculo esquelético: [revisão] / New mechanisms by which physical exercise improves insulin resistance in the skeletal muscle: [revision]

O prejuízo no transporte de glicose estimulada por insulina no músculo constitui um defeito crucial para o estabelecimento da intolerância à glicose e do diabetes tipo 2. Por outro lado, é notório o conhecimento de que tanto o exercício aeróbio agudo quanto o crônico podem ter efeitos benéficos na ação da insulina em estados de resistência à insulina. No entanto, pouco se sabe sobre os efeitos moleculares pós-exercício sobre a sinalização da insulina no músculo esquelético. Assim, esta revisãoapresenta novos entendimentos sobre os mecanismos por meio dos quais o exercício agudo restaura a sensibilidade à insulina, com destaque ao importante papel que proteínas inflamatórias e a S-nitrosação possuem sobre a regulação de proteínas da via de sinalização da insulina no músculo esquelético.

Insulin resistance of skeletal muscle glucose transport is a key-defect for the development of impaired glucose tolerance and type 2 diabetes. However, it is known that both an acute bout of exercise and chronic endurance exercise training can bring beneficial effects on insulin action in insulin-resistant states. However, little is currently known about the molecular effects of acute exercise on muscle insulin signaling in the post-exercise state in insulin-resistant organisms. This review provides new insight into the mechanism through which acute exercise restores insulin sensitivity, highlighting an important role for inflammatory proteins and S-nitrosation in the regulation of insulin signaling proteins in skeletal muscle.