Previous studies have shown that probiotics have positive effects on hyperlipidemia by lowering the serum lipid concentration and improving the lipid profile. To explore the mechanism by which probiotic-fermented milk improves lipid metabolism, the transcription of genes regulated by liver X receptors (LXRs), 5'-AMP-activated protein kinase, and the farnesoid X receptor (FXR), which play integral roles in lipid metabolism, was investigated in hyperlipidemic rats. Compared with rats fed a high-fat diet, the administration of probiotic-fermented milk significantly lowered the levels of total cholesterol (TC) and total triglycerides (TG) in rat serum and viscera (P < 0.05) and significantly increased the level of total bile acid in the rat liver and small intestine (P < 0.05). The quantitative PCR results showed that the probiotics ameliorated the TC levels in the rats by activating the transcription of genes involved in the LXR axis, which promoted TC reverse transport and increased the conversion of TC to bile acids. The level of TG in the hyperlipidemic rats was ameliorated by the inhibition of the transcription of carbohydrate reaction element binding protein genes and activation of the transcription of PPARα genes. The regulation of lipid metabolism-related gene transcription by the single probiotic (Lactobacillus rhamnosus LV108)-fermented milk was more effective than that by the combined probiotic (L. rhamnosus LV108, Lactobacillus casei grx12, and Lactobacillus fermentum grx08)-fermented milk (P < 0.05).
Keywords: AMPK; FXR; LXRs; fermented milk; hyperlipidemic rats; lipid metabolism; probiotics.