Humoral regulation of resistin expression in 3T3-L1 and mouse adipose cells

Resistin is a hormone secreted by adipocytes that acts on skeletal muscle myocytes, hepatocytes, and adipocytes themselves, reducing their sensitivity to insulin. In the present study, we investigated how the expression of resistin is affected by glucose and by mediators known to affect insulin sensitivity, including insulin, dexamethasone, tumor necrosis factor-alpha (TNF-alpha), epinephrine, and somatropin. We found that resistin expression in 3T3-L1 adipocytes was significantly upregulated by high glucose concentrations and was suppressed by insulin. Dexamethasone increased expression of both resistin mRNA and protein 2.5- to 3.5-fold in 3T3-L1 adipocytes and by approximately 70% in white adipose tissue from mice. In contrast, treatment with troglitazone, a thiazolidinedione antihyperglycemic agent, or TNF-alpha suppressed resistin expression by approximately 80%. Epinephrine and somatropin were both moderately inhibitory, reducing expression of both the transcript and the protein by 30-50% in 3T3-L1 adipocytes. Taken together, these data make it clear that resistin expression is regulated by a variety of hormones and that cytokines are related to glucose metabolism. Furthermore, they suggest that these factors affect insulin sensitivity and fat tissue mass in part by altering the expression and eventual secretion of resistin from adipose cells.