Site and Mechanism of Leptin Action in a Rodent Form of Congenital Lipodystrophy

J Clin Invest. 2004 Feb;113(3):414-24. doi: 10.1172/JCI19511.

Abstract

Lipodystrophy is characterized by the complete or partial absence of adipose tissue, insulin resistance, hepatic steatosis, and leptin deficiency. Here, we show that low-dose central leptin corrects the insulin resistance and fatty liver of lipodystrophic aP2-nSREBP-1c mice, while the same dose given peripherally does not. Central leptin also repressed stearoyl-CoA desaturase-1 (SCD-1) RNA and enzymatic activity, which were increased in livers of lipodystrophic mice. aP2-nSREBP-1c mice homozygous for an SCD-1 deletion had markedly reduced hepatic steatosis, increased saturated fatty acids, decreased acetyl-CoA carboxylase activity, and decreased malonyl-CoA levels in the liver. Despite the reduction in hepatic steatosis, these mice remained diabetic. A leptin dose-response curve showed that subcutaneous leptin improved hyperglycemia and hyperinsulinemia in aP2-nSREBP-1c mice at doses that did not substantially alter hepatic steatosis or hepatic SCD enzymatic activity. Leptin treatment at this dose improved insulin-stimulated insulin receptor and insulin receptor substrate 2 (IRS-2) phosphorylation, IRS-2-associated PI3K activity, and Akt activity in liver. Together, these data suggest that CNS-mediated repression of SCD-1 contributes to leptin's antisteatotic actions. Intracerebroventricular leptin improves glucose homeostasis by improving insulin signal transduction in liver, but in this case the effect appears to be independent of SCD-1.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Disease Models, Animal
  • Female
  • Gene Expression Profiling
  • Leptin / metabolism*
  • Lipodystrophy / metabolism*
  • Liver / metabolism
  • Liver / pathology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Muscle, Skeletal / metabolism
  • Phylogeny
  • Stearoyl-CoA Desaturase / metabolism

Substances

  • Leptin
  • Stearoyl-CoA Desaturase