Twist1 in Human White Adipose Tissue and Obesity

Abstract

Twist1 is a transcription factor implicated in the regulation of TNFα signaling and was recently shown to be highly expressed in both human and murine adipose tissue, but its role in obesity is unknown. Our objective was to assess the expression of twist1 in human white adipose tissue (WAT), its relationship to obesity and insulin sensitivity, and how it modifies TNFα-mediated inflammation in adipocytes. Twist mRNA levels were measured in WAT from 130 nonobese and obese subjects, and its relation to clinical parameters was assessed. Twist1 expression was measured before and after weight loss as well as in different adipose regions. Human in vitro differentiated adipocytes were treated with TNFα under control conditions or after twist1 gene silencing by RNA interference. Gene expression and secretion of proinflammatory proteins were measured. Twist1 expression was low in obese subjects and increased after weight loss. Twist1 mRNA levels correlated with adiponectin levels and inversely with insulin resistance as well as adipocyte volume (P < 0.001 for all). Low twist1 expression associated with a hypertrophic adipose tissue and high secretion of TNFα and monocyte chemoattractant protein-1 from WAT. Finally, twist1 silencing in human adipocytes enhanced TNFα-induced monocyte chemoattractant protein-1 expression and secretion, which was paralleled by an increase in the mRNA expression of the nuclear factor-κB gene RelA. Low twist1 expression in human WAT correlates with obesity and an insulin-resistant phenotype, which may be mediated by an increased sensitivity to the proinflammatory effect of TNFα.