The
adiponutrin/PNPLA3 gene is highly expressed in adipose tissue and liver. Its expression is down-regulated by fasting and rapidly induced by refeeding a high
carbohydrate diet. We aimed to determine whether the promoter region of
adiponutrin is regulated by
glucose and
insulin. Endogenous
adiponutrin mRNA was increased in mouse 3T3-L1 and human SGBS adipocytes and in human HepG2 cells cultured in 25 mM
glucose compared to absence of
glucose. A 3100 bp 5'-upstream region of the human
adiponutrin gene was cloned into a
luciferase reporter plasmid and used in transient transfection studies. Promoter activity was up-regulated by 25 mM
glucose, 4.7-fold in HepG2 cells and 2-fold in CHO cells. The effect was shown in CHO cells to be concentration dependent and to depend on
glucose metabolism as a non-metabolisable analogue was without effect. In CHO cells constitutively expressing human
insulin receptor (CHO-IR), there was a concentration dependent increase of promoter activity by
insulin in the presence of
glucose. Cotransfection with an expression plasmid for upstream stimulatory factor 2 (USF2), increased promoter activity 1.6-fold in CHO-IR cells. The combined effect of
insulin and USF2 (2.3-fold) was greater than the individual effects. Cotransfection of
carbohydrate-response element
binding protein did not elicit any induction of promoter activity. These results point to potential mechanisms for the observed in vivo nutritional regulation of
adiponutrin expression and its up-regulation in
fatty liver and by
obesity.