Protective effect of flavonoids extract of Hippophae rhamnoides L. on alcoholic fatty liver disease through regulating intestinal flora and inhibiting TAK1/p38MAPK/p65NF-κB pathway

The therapeutic properties of Hippophae rhamnoides L. were already known in ancient Greece as well as in Tibetan and Mongolian medicine. Modern studies have indicated that Hippophae rhamnoides L. fermentation liquid protected against alcoholic fatty liver disease (AFLD). However, the underlying mechanism of Hippophae rhamnoides L. flavonoids extract (HLF) treating AFLD remains elusive.This study aimed to investigate the hepatoprotective effect of HLF in mice with AFLD and the interaction between AFLD and gut microbiota.Chemical constituents of HLF were analyzed by Liquid Chromatography-Ion Trap-ESI-Mass Spectrometry. The Hepatoprotective effect of HLF was evaluated in mice with AFLD induced by alcohol (six groups, n = 10) daily at doses of 0.1, 0.2, and 0.4 g/kg for 30 consecutive days. At the end of experiment, mice were sacrificed and the liver, serum and feces were harvested for analysis. The liver histological changes were observed by H&E staining and oil red O staining. Moreover, the alterations of fecal microflora were detected by 16S rRNA gene sequencing. The inflammatory related genes were determined by qRT-PCR and western blotting respectively.The results showed that the oral administration of HLF remarkably alleviated hepatic lipid accumulation by decreasing the levels of ALT, AST, TG and TC. The levels of TNF-α, TGF-β, and IL-6 were also reduced after treatment with HLF. Meanwhile, the protein and mRNA expression of NF-kB p65, MAPK p38 and TAK-1 in the liver of mice with AFLD were all reduced by HLF compared with model group. Furthermore, the 16S rRNA gene sequencing analysis demonstrated that HLF treatment can help restore the imbalance of intestinal microbial ecosystem and reverse the changes in Fimicutes/Bacterodietes, Clostridiales, Lachnospiraceae, S24-7, and Prevotella in mice with AFLD.HLF can effectively ameliorate liver injury in mice with AFLD, and regulate the composition of gut microbiota. Its regulatory mechanism may be related to TAK1/p38MAPK/p65NF-κB pathway. This study may provide novel insights into the mechanism of HLF on AFLD and a basis for promising clinical usage.