Abstract
Obesity-related hepatic steatosis is commonly associated with central fat accumulation and alterations in adipocytokine secretion; however, the connection between nonobese hepatic steatosis and adipocytokines remains unclear. We aim to investigate this connection using an animal model of conditional hepatitis C virus (HCV) core-transgenic mice. Double transgenic mice (DTM) with doxycycline (dox)-regulated hepatic overexpression of the HCV core protein were fed standard rodent chow ad libitum following 1 month of a dox-rich diet. The mice exhibited nonobese hepatic steatosis at 2 months of age. The levels of leptin and adiponectin were assessed in 2-month-old DTM (i.e., HCV core-tetracycline transactivator (tTA)) and single transgenic mice (STM; i.e., tTA). The total fat mass and the body fat distribution of the mice were evaluated using dual-energy X-ray absorptiometry (DEXA) and magnetic resonance imaging (MRI). Microarray analyses and quantitative real-time PCR were conducted using RNA obtained from the visceral fat of paired DTM and STM. Adiponectin was administered intraperitoneally to the 2-month-old DTM. No significant differences of the various fat components were noted between the DTM and STM. Leptin mRNA was downregulated in the visceral fat of DTM (P = 0.011), and serum adiponectin protein levels were reduced in the DTM compared with those in the STM (P = 0.035). Adiponectin treatment also significantly ameliorated hepatic steatosis in the DTM compared to the controls (P = 0.024). In conclusion, HCV core-induced nonobese hepatic steatosis is associated with downregulation of the leptin gene in visceral fat and concurrent hypoadiponectinemia; however, these effects may be ameliorated by adiponectin treatment.