[Effect of ginsenoside Rb1 in ameliorating insulin resistance and ectopic fat deposition in obese mice induced by high fat diet].

Ginsenoside Rb1 is an active component in ginseng. Previous in vitro experiments showed that ginsenoside Rb1, could inhibit lipolysis and promote glucose transporter in adipocytes. This study focused on the effect of ginsenoside Rb1 in insulin resistance and ectopic fat deposit in obese mice induced by high fat diet and its molecular mechanism. Obese male C57/L mice induced by high fat diet were randomly divided into the diet-induced obesity group (DIO group), the ginsenoside Rb1 group (Rb1 group) and the rosiglitazone group (Rog group), and continuously fed with high fat diet. In addition, male C57/L mice fed with normal diet were selected as the normal group (NC group). Mice in Rb1 group and Rog groups were intraperitoneally injected with ginsenoside Rb1 and rosiglitazone with the dosage of 20 mg x kg(-1) and 10 mg x kg(-1), respectively. NC and DIO groups were intraperitoneally injected with the same amount of saline. Two weeks later, the intraperitoneal glucose tolerance test (IPGTT) was performed. Three days later, the mice were killed, and their serum samples were collected to detect insulin and free fatty acid (FFA). Their livers were weighed to examine the triglyceride content, and a pathological detection was performed. Epididymal adipose tissues were weighed, and PDE3B, HSL and perilipin were detected by Western blotting. The results showed that the treatment with ginsenoside Rb1 for two weeks could improve the glucose tolerance of obese mice. Except for 0-120 min, the areas under the glucose tolerance curve (0-30 min, 0-60 min and 0-90 min) in the Rb1 group were less than that in the DIO group (P < 0.05, n = 5), with a much lower HOMA-IR (P < 0.05, n = 5). The fat level of obese mice was significantly reduced by Rbl (P < 0.05, n = 5), and so were liver weight/weight (P < 0.05, n = 8). The increased serum FFA of obese mice declined after the treatment of Rb1 (P < 0.05, n = 8). Rb1 could partially recover the expression of perilipin in adipose tissues, but without obvious change in the expressions of PDE3B and HSL and the phosphorylated activation. The above findings indicated that ginsenoside Rb1 could reduce the release of FFA and alleviate the ectopic deposit of triglyceride by up-regulating the expression of perilipin in adipose tissue, which may be one of its mechanisms for improving the insulin resistance and abnormal glucose metabolism of organisms.