FAT/CD36 Deficiency Exacerbates Hepatic Iinsulin Resistance In Mice

Objective: To investigate the molecular mechanisms of liver insulin resistance(IR) in FAT/CD36 deficiency mice fed with high-fat diet,and is trying to provide an important theoretical for the prevention and therapy of IR and type 2 diabetes mellitus(T2DM) in FAT/CD36 deficiency.Method: The first part, 8-week-old male WT mice were fed with NCD or HFD for 12 weeks. During feeding, body weight of mice were measured weekly,in the eleventh and twelfth week were processing glucose tolerance test(GTT) and insulin tolerance test(ITT) in mice. After taking serum and liver tissue of mice do the following tests: serum glucose and insulin; liver tissue paraffin section H&E staining, frozen sections Oil Red O(ORO) staining and TG content detection; Western Blotting was used to check liver FAT/CD36 of protein expression; Western-blot was used to detect liver insulin signaling pathways(AKT and p-AKT) related protein expression.The second part, eight weeks old male WT and FAT/CD36 knockout(CD36-/-) mice were fed with HFD for 12 weeks. During feeding, body weight of mice were measured weekly; After taking serum and liver tissue of mice do the following tests:Weigh liver weight; measuring serum insulin,TG, FFA and TC; serum TNF-α, IL-6 level detected; liver tissue H&E staining, ORO staining and TG content detection; RT-PCR was used to detect inflammatory cytokines(TNF-α, IL-6,IL-1β, MCP-1, MIP-1 and MIP-2), liver tissue macrophage marker(F4/80) immunohistochemical staining; Western-blot was used to check liver insulin signaling pathway(PI3K, AKT and p-AKT) associated protein expression.The third part, the human hepatoma cell line(Hep G2) cells to be TNF-α(25ng/ml) and IL-6(20ng/ml) treatment. Experimental HepG2 cells were divided into control group, TNF-α groups and IL-6 groups were treated 24 hours after the following tests: glucose uptake and glucose consumption test in cells, was used to check the glucose metabolism; Western-blot was used to detect the cellular insulin signaling pathway(IRS1,AKT and p-AKT) related protein expression.Results: The first part, the mice were fed high-fat diet can significantly increase the body weight. Serum glucose was significantly increased. GTT and ITT finding glucose tolerance and insulin sensitivity significantly damage. FAT/CD36 protein levels,liver lipid accumulation was significantly increased. High-fat can significant damage the insulin signaling pathways associated protein expression of liver.The second part, high-fat diet in the sixth weeks later, the body weight of FAT/CD36 deficiency mice can significantly reduce, but increased liver /body weight ratio. Serum insulin,IL-6, TG, FFA and TC were increased. Liver steatosis, TG content, the degree of macrophage infiltration and inflammation were increased in liver. FAT/CD36 deficiency can significantly damage the liver insulin signaling pathways associated protein expression.The third part, HepG2 cell glucose uptake and glucose consumption were damage in cell treated inflammatory. Inflammatory state can significantly damage the insulin signaling pathway associated protein expression of cells.Conclusion: In vivo and vitro experiments suggest that high-fat diet induced WT mice liver FAT/CD36 protein abnormally high expression, accompanied by the occurrence of hepatic insulin resistance. FAT/CD36 deficiency can aggravated the high-fat diet induced insulin resistance in the liver, which may be due to FAT/CD36 deficiency can promote liver expression of MCP-1, thereby increasing the macrophage infiltration and inflammation in liver. Inflammatory cytokines damage the insulin signaling pathway in hepatic cell, leading to insulin resistance.