The nuclear receptor farnesoid X receptor (FXR), an endogenous sensor for bile acids, plays an important role in cholesterol, lipid and carbohydrate metabolism. The objective of this study is to examine the effect of FXR activation on diet-induced obesity and hepatic steatosis. Activation of FXR by its synthetic agonist, 3-[2-[2-Chloro-4-[[3-(2,6-dichlorophenyl)-5-(1-methylethyl)-4-isoxazolyl]methoxy]phenyl]ethenyl]benzoic acid (GW4064), suppressed weight gain in C57BL/6 mice fed with either a high-fat diet (HFD) or high-fat, high-cholesterol diet. GW4064 treatment of mice on HFD significantly repressed diet-induced hepatic steatosis as evidenced by lower triglyceride and free fatty acid level in the liver. Analysis of genes involved in lipid metabolism showed GW4064 markedly reduced lipid transporter CD36 expression without affecting expression of genes that are directly involved in lipogenesis. GW4064 treatment attenuated hepatic inflammation while having no effect on white adipose tissue. In addition, activation of FXR by GW4064 avoided diet-induced hyperinsulinemia and hyperglycemia through decreasing the transcript levels of phosphoenolpyruvate carboxykinase (Pepck) and glucose-6-phosphatase (G6pase), two key enzymes in gluconeogenesis. These results verify the important function of FXR in diet-induced obesity and suggest that FXR agonists are promising therapeutic agents for obesity-associated metabolic disorders.

High-fat diet (HFD) induced obesity is associated with low-grade inflammation, insulin resistance (IR), and glucose intolerance. The objective of this study is to assess the effect of interleukin 10 (IL10), an anti-inflammatory cytokine, on blocking HFD-induced obesity and obesity-associated metabolic disorders by hydrodynamic delivery of IL10-containing plasmid. Animals fed a regular chow or HFD received two injections (one on day 1 and the other on day 31) of plasmids containing green fluorescence protein (GFP) or mouse IL10 (mIL10) gene. Blood concentration of mIL10 reached ~200 ng/ml on day 7 in animals receiving mIL10 plasmid DNA. The transfection efficiency of liver cells was the same in animals fed a regular chow or HFD. No difference was seen in animals on regular chow when injected with plasmids containing either gfp or mIL10 gene. Overexpression of mIL10 prevented weight gain of animals on HFD. Intraperitoneal glucose tolerance test (IPGTT) and insulin tolerance tests (ITT) showed that mIL10 maintained insulin sensitivity and prevented glucose intolerance. The mechanistic study reveals that mIL10 suppressed macrophage infiltration and reduced the development of crown-like structures in adipose tissue (AT). Collectively, these results suggest that maintaining a higher level of IL10 through gene transfer could be an effective strategy in preventing diet-induced obesity.

Purpose To assess the effect of immune modulators on high fat diet-induced obesity and insulin resistance. Methods C57BL/6 mice were fed a high fat diet and injected intraperitoneally with cyclosporine A, fingolimod, or vehicle twice weekly for 15 weeks. Body weight and food intake were manually measured every other day. Glucose tolerance test, insulin sensitivity, and body composition were examined and compared between the control and the immune modulator treated animals. Tissue samples were collected at the end of the experiment and examined for serum biochemistry, histology, and mRNA levels of marker genes for inflammation, and glucose and lipid metabolism in white and brown adipose tissues and in the liver. Results Cyclosporine A and fingolimod suppressed high fat diet-induced weight gain, reduced hepatic fat accumulation, and improved insulin sensitivity. The beneficial effects are associated with altered expression of F4/80, Cd68, Il-6, Tnf-α, and Mcp-1 genes, which are involved in macrophage-related chronic inflammation in adipose and hepatic tissues. Conclusion Immune modulation represents an important intervention for obesity and obesity-associated insulin resistance.