To determine the in vivo function of IRF9 on hepatic lipid metabolism and insulin sensitivity, we used adenovirus
infection, a well-established method, to overexpress IRF9 in mouse liver. The adenovirus-mediated gene-transfer approach acutely delivers genes to the liver without confounding developmental effects that commonly occur during chronic overexpression.[27, 28] After 20 weeks of HFD feeding, the mice were injected with an IRF9-expressing adenovirus through the jugular vein. Four weeks after adenovirus injection, the protein expression level of IRF9 had a more than four-fold increase in the liver, but remained unchanged in WAT and skeletal muscle (Fig. 4A). IF staining of HNF4 and IRF9 confirmed the elevation of IRF9 expression in hepatocytes, rather than in other types of cells selleck kinase inhibitor (Fig. 4B). Four weeks after adenovirus injection, mice with IRF9 overexpression had lower liver weight than those PD0325901 WT mice injected with an adenovirus-expressing GFP as a control (Fig. 4C). H&E and Oil Red O staining revealed lower hepatic
lipid accumulation in livers with IRF9 overexpressed (Fig. 4D). Hepatic TG, TC, and nonesterified fatty acid (NEFA) contents were also lower in IRF9-overexpressing mice than in control mice (Supporting Fig. 4A). IRF9-injected mice displayed lower ALT, AST, and ALP levels (Supporting Fig. 4B). All these factors indicate that IRF9 promotes hepatic lipid metabolism and protects liver function. IRF9-overexpressing mice displayed lower fasting serum glucose and insulin levels when on an HFD than did control animals (Fig. 4E). Both the IPGTT and IPITT showed improved
glucose regulation in IRF9-overexpressing mice (Fig. 4F and 4G). Consistent with these results, the insulin-signaling pathway was up-regulated in IRF9-overexpressing livers, compared to control livers, as measured by immunoblotting (Fig. 4H). Moreover, liver-specific IRF9 overexpression ameliorated obesity-induced inflammation in the liver. Decreased proinflammatory markers (e.g., F4/80, CD11c, TNF-α, IL-1β, IL-6, and MCP-1) and increased anti-inflammatory markers (e.g., 上海皓元医药股份有限公司 IL-10, arignase 1, mannose receptor, C type 1, MGL1, and MGL2) were detected by real-time PCR and indicate a shift in the balance to M2-like macrophages (Supporting Fig. 4C). To rule out any potential effect of unidentified components of the HFD on our results, we used a genetic obesity model to assess the metabolic role of IRF9. We fed NC to leptin-deficient (ob/ob) mice, which spontaneously develop obesity. As with the dietary model described above, we injected male ob/ob mice with IRF9 adenovirus through the jugular vein for liver-specific IRF9 overexpression (Fig. 5A,B). Four weeks later, hepatic lipid depots were greatly reduced in the IRF9-overexpressing mice, compared to the GFP adenovirus-injected controls (Fig. 5C,D).