Effects of inorganic HgCl2 on adipogenesis

Mercury is a common pollutant that alters glucose metabolism in adipocytes; however, the effect of HgCl2 on differentiating adipocytes and their subsequent metabolic function is not well understood. Two adipocyte models, the 3T3-L1 and C3H10T1/2 (10T1/2) cell lines, were differentiated in the presence of HgCl2. To assess the amount of differentiation in a population, markers of differentiation (i.e., PPARgamma and GLUT 4 expression and lipid accumulation) and functions of adipocytes (i.e., glucose transport and insulin-induced glucose transport) were measured. HgCl2 exposure significantly decreased the number of phenotypic adipocytes and PPARgamma expression in both 3T3-L1 and 10T1/2 cells without effects on cell viability. GLUT 4 was significantly reduced by HgCl2 treatment in 10T1/2 but not 3T3-L1 cells. Exposure to HgCl2 during differentiation increased basal glucose uptake in a dose-dependent manner (up to 2.5-fold) and decreased insulin-induced glucose uptake in 3T3-L1 adipocytes. In contrast, HgCl2 had little effect on basal or insulin-induced glucose uptake in 10T1/2 cells, possibly due to their lower insulin responsiveness. We examined the effect of HgCl2 exposure on signaling event involved in differentiation of adipocytes and cellular stress, namely, the phosphorylation of ERK1/2 and JNK, respectively. HgCl2 exposure had no effect on ERK1/2 phosphorylation in either cell line, increased JNK phosphorylation in the 10T1/2, and had no effect on JNK phosphorylation in 3T3-L1 cells. These data indicate HgCl2 exposure can inhibit the differentiation of fibroblasts into adipocytes as well as influence signaling events and the subsequent metabolic activity of differentiated adipocytes.