The orphan nuclear receptor small heterodimer partner is required for thiazolidinedione effects in leptin-deficient mice

Abstract

Background: Small heterodimer partner (SHP, NR0B2) is involved in diverse metabolic pathways, including hepatic bile acid, lipid and glucose homeostasis, and has been implicated in effects on the peroxisome proliferator-activated receptor γ (PPARγ), a master regulator of adipogenesis and the receptor for antidiabetic drugs thiazolidinediones (TZDs). In this study, we aim to investigate the role of SHP in TZD response by comparing TZD-treated leptin-deficient (ob/ob) and leptin-, SHP-deficient (ob/ob;Shp -/-) double mutant mice. Results: Both ob/ob and double mutant ob/ob;Shp -/- mice developed hyperglycemia, insulin resistance, and hyperlipidemia, but hepatic fat accumulation was decreased in the double mutant ob/ob;Shp -/- mice. PPARγ2 mRNA levels were markedly lower in ob/ob;Shp -/- liver and decreased to a lesser extent in adipose tissue. The TZD troglitazone did not reduce glucose or circulating triglyceride levels in ob/ob;Shp -/- mice. Expression of the adipocytokines, such as adiponectin and resistin, was not stimulated by troglitazone treatment. Expression of hepatic lipogenic genes was also reduced in ob/ob;Shp -/- mice. Moreover, overexpression of SHP by adenovirus infection increased PPARγ2 mRNA levels in mouse primary hepatocytes. Conclusions: Our results suggest that SHP is required for both antidiabetic and hypolipidemic effects of TZDs in ob/ob mice through regulation of PPARγ expression.