In vivo ET-1 release from adipose tissue was increased 2.5-fold in obesity, and ET-1 selectively attenuated the antilipolytic effect of insulin in visceral adipocytes via ET(B)R signaling.
Observational
Does endothelin-1 mediate regional differences in adipocyte lipolysis and insulin resistance in obesity?
Endothelin-1 released from human adipose tissue links fat accumulation to insulin resistance by selectively counteracting insulin inhibition of visceral adipocyte lipolysis.
Effect estimate: 2.5-fold increase
OBJECTIVE: Visceral obesity increases risk of insulin resistance and type 2 diabetes. This may partly be due to a region-specific resistance to insulin's antilipolytic effect in visceral adipocytes. We investigated whether adipose tissue releases the vascular peptide endothelin-1 (ET-1) and whether ET-1 could account for regional differences in lipolysis. RESEARCH DESIGN AND METHODS: One group consisted of eleven obese and eleven nonobese subjects in whom ET-1 levels were compared between abdominal subcutaneous and arterialized blood samples. A second group included subjects undergoing anti-obesity surgery. Abdominal subcutaneous and visceral adipose tissues were obtained to study the effect of ET-1 on differentiated adipocytes regarding lipolysis and gene and protein expression. RESULTS: Adipose tissue had a marked net release of ET-1 in vivo, which was 2.5-fold increased in obesity. In adipocytes treated with ET-1, the antilipolytic effect of insulin was attenuated in visceral but not in subcutaneous adipocytes, which could not be explained by effects of ET-1 on adipocyte differentiation. ET-1 decreased the expression of insulin receptor, insulin receptor substrate-1 and phosphodiesterase-3B and increased the expression of endothelin receptor-B (ET(B)R) in visceral but not in subcutaneous adipocytes. These effects were mediated via ET(B)R with signals through protein kinase C and calmodulin pathways. The effect of ET-1 could be mimicked by knockdown of IRS-1. CONCLUSIONS: ET-1 is released from human adipose tissue and links fat accumulation to insulin resistance. It selectively counteracts insulin inhibition of visceral adipocyte lipolysis via ET(B)R signaling pathways, which affect multiple steps in insulin signaling.
Harmelen et al. (Tue,) conducted a observational in Obesity. Endothelin-1 (ET-1) vs. Nonobese subjects / Subcutaneous adipocytes was evaluated on ET-1 release and effect on adipocyte lipolysis (2.5-fold increase). In vivo ET-1 release from adipose tissue was increased 2.5-fold in obesity, and ET-1 selectively attenuated the antilipolytic effect of insulin in visceral adipocytes via ET(B)R signaling.