Liuwei Dihuang Formula Ameliorates Aberrant Cholesterol Metabolism in Postmenopausal APOE^-/- Mice by Regulating Intestinal Microbiota and Bile Acid Metabolism

  OBJECTIVE  To investigate the regulation of intestinal microbiota and bile acid metabolism by Liuwei Dihuang formula (LW) to ameliorate postmenopausal cholesterol metabolism abnormalities and its possible mechanism of action.

  METHODS  APOE^-/- mice with bilateral ovariectomy were given a high-fat diet to replicate the postmenopausal cholesterol abnormality model, 0.13 mg·kg^-1 estrogen and 9.0 g·kg^-1 LW were used for treatment. The levels of total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-c) and high-density lipoprotein cholesterol (HDL-c) in serum, TC in liver and feces were measured by biochemical methods. The levels of tumor necrosis factor α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in serum were measured by enzyme-linked immunoassay. The levels of total bile acids (TBA) in the liver, serum, gallbladder and feces were measured by biochemical methods. Hepatic lipid damage was observed by HE and oil red staining. Fecal bile acids were quantified by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). 16S rRNA sequencing was used to analyze the colonic microbiota of mice. The correlation between postmenopausal fecal bile acid fractions and intestinal microbiota was analyzed.

  RESULTS  LW reduced serum TC, TG, LDL-c as well as TNF-α, IL-1β, IL-6 levels (P < 0.01) and increased HDL-c level in models (P < 0.01). LW ameliorated liver injury and reduced liver lipid accumulation. LW also reduced serum, gallbladder and hepatic TBA levels (P < 0.01) and increased fecal TBA excretion (P < 0.01); it also reduced fecal levels of conjugated bile acids such as TαMCA, TβMCA, TCA, TCDCA, TDCA and CA(P < 0.05, P < 0.01) and increased the level of secondary bile acid LCA (P < 0.01). LW restored the balance of colonic microbiota in model mice, upregulated the relative abundance of Allobaculum (P < 0.01), and downregulated the relative abundance of Oscillospira and Prevotella (P < 0.05).

  CONCLUSION  LW ameliorates the cholesterol abnormalities in model mice by reshaping the composition of the colonic microbiota to restore the balance of the microbiota and increasing the excretion of fecal secondary bile acids to reduce cholesterol deposition in the serum and liver.