Abstract
Krüppel-like factor 14 (KLF14) is a member of the Cys(2)/His(2) zinc-finger DNA-binding proteins. Despite strong evidence showing that a polymorphism in the Klf14 gene is closely linked to the development of type 2 diabetes, the physiological and metabolic functions of KLF14 still remain unclear. In the present study, we investigated the role of KLF14 in the regulation of hepatic gluconeogenesis. Adenoviruses expressing KLF14 (Ad-Klf14) or KLF14-specific shRNAs (Ad-shKlf14) were injected into normal C57BL/6J, db/db diabetic, or high-fat diet-induced obese (DIO) mice. Gene expression, hepatic glucose production, glucose tolerance, and insulin resistance were tested in C57BL/6J, db/db, and DIO mice and primary hepatocytes. Our results demonstrate that KLF14 expression is induced in the livers of normal C57BL/6J mice upon fasting and significantly up-regulated in the livers of db/db mice, suggesting a physiological link between KLF14 and gluconeogenesis. Adenovirus-mediated overexpression of KLF14 in primary hepatocytes increased both the mRNA and protein levels of peroxisome proliferator-activated receptor-γ coactivator 1α (Pgc-1α, also known as Ppargc1a), thereby stimulating cellular glucose production. Conversely, knockdown of KLF14 expression led to a reduction in PGC-1α, subsequently inhibiting glucose output in primary hepatocytes. Finally, forced expression of KLF14 in the livers of normal mice increased the plasma glucose levels and impaired glucose tolerance; in contrast, KLF14 knockdown in diabetic mouse livers improved glucose tolerance. Taken together, our data strongly indicate that KLF14 modulates hepatic gluconeogenesis.