Cannabinoid type 1 receptor blockade promotes mitochondrial biogenesis through endothelial nitric oxide synthase expression in white adipocytes

Abstract

OBJECTIVE-Cannabinoid type 1 (CB1) receptor blockade decreases body weight and adiposity in obese subjects; however, the underlying mechanism is not yet fully understood. Nitric oxide (NO) produced by endothelial NO synthase (eNOS) induces mitochondrial biogenesis and function in adipocytes. This study was undertaken to test whether CB1 receptor blockade increases the espression of eNOS and mitochondrial biogenesis in white adipocytes. RESEARCH DESIGN AND METHODS-We examined the effects on eNOS and mitochondrial biogenesis of selective pharmacological blockade of CB1 receptors by SR141716 (rimon- abant) in mouse primary white adipocytes. We also examined eNOS expression and mitochondrial biogenesis in white adipose tissue (WAT) and isolated mature white adipocytes of CB1 receptor-deficient (CB1-/-) and chronically SR141716-treated mice on either a standard or high-fat diet. RESULTS-SR141716 treatment increased eNOS expression in cultured white adipocytes. Moreover, SR141716 increased mito- chondrial DNA amount, mRNA levels of genes involved in mitochondrial biogenesis, and mitochondrial mass and function through eNOS induction, as demonstrated by reversal of SR141716 effects by small interfering RNA-mediated decrease in eNOS. While high-fat diet-fed wild-type mice showed reduced eNOS expression and mitochondrial biogenesis in WAT and isolated mature white adipocytes, genetic CB1 receptor deletion or chronic treatment with SR141716 restored these parameters to the levels observed in wild-type mice on the standard diet, an effect linked to the prevention of adiposity and body weight increase. CONCLUSIONS-CB1 receptor blockade increases mitochon- drial biogenesis in white adipocytes by inducing the expression of eNOS. This is linked to the prevention of high-fat diet-induced fat accumulation, without concomitant changes in food intake. © 2008 by the American Diabetes Association.