Possible role of ginsenoside Rb1 on regulation of rat liver triglycerides

We have studied the effects of ginsenoside Rb-1 (GRb(1)) on the change in lipid contents in rat liver. When GRb(1) was administered intraperitoneally to rats, liver microsomal cytochrome P-450 content and NADPH-cytochrome P-450 reductase activity were lower than those in control rats. The contents of triglyceride (TG) and cholesterol were decreased, but those of total phospholipid, phosphatidylcholine, and phosphatidylethanolamine were increased in the GRb(1)-treated group compared with controls. These results indicate that GRb(1) might be involved in lipid metabolism by regulating the activity of microsomal cytochrome P-450 monooxygenase. Although liver TG levels were reduced by GRb(1), the levels of TG and beta-lipoprotein in serum from the GRb(1)-treated group did not change as compared with those in controls. Thus we suggest that the decrease in liver TG levels with GRb(1)-treatment is not associated with the secretion of TG-rich very low-density lipoprotein. Furthermore, the level of cAMP was also significantly increased in the GRb(1)-treated group as compared with that in controls. Additionally, the cAMP level was more markedly increased as compared with that in the GRb(1)-treated group or control group when GRb(1) was exogenously added to the reaction system for measuring cAMP production in homogenates from control group liver. Accordingly, these results demonstrate that GRb(1) might lower TG levels via cAMP-production in the liver, and GRb(1) might be an interesting candidate to for a modulator of cAMP-mediated effects, especially within the liver steatosis system.