Intestinal HIF‐1α Deletion Exacerbates Alcoholic Liver Disease Mediated by Intestinal Dysbiosis and Barrier Dysfunction
Authors: Shao Tuo , Li Fengyuan , McClain Craig , Feng Wenke 
Published: November 2023

Background

Alcoholic liver disease (ALD) is characterized by increased gut permeability and bacterial translocation. Hypoxia Inducible Factor 1α (HIF‐1α) has been implicated in transcriptional regulation of intestinal barrier integrity and inflammation. However, the link between intestinal HIF‐1α regulation and ALD is unclear. We aimed to test our hypothesis that HIF‐1α plays a critical role in gut microbiota homeostasis and the maintenance of intestinal barrier integrity in a mouse model of ALD.

Methods

Wide type (WT) and intestinal epithelial‐specific HIF‐1α knockout mice (IEhif‐1α−/−) were pair‐fed modified Lieber‐DeCarli 5% (w/v) alcohol containing liquid diet or subjected to chronic‐binge alcohol exposure model. Serum was collected for measurement of ALT and AST levels, and LPS concentrations using commercial kits. Liver steatosis was determined by liver tissue triglyceride (TG) measurement and histological analysis of liver sections. mRNA and protein levels of target genes in intestine and liver tissues were determined by real time RT‐PCR analysis and Western blotting, respectively. Fecal microbiota were analyzed by 16S pyrosequencing. In vitro study using T84 epithelial cell lines was conducted to determine the effect of HIF‐1 activation on bacterial growth. Antibiotics, probiotics and dimethyloxalylglycine (DMOG) were used to test their efficacy in the treatment of ALD.

Results

Alcohol feeding significantly increased serum levels of ALT, AST and LPS in the WT mice. These elevations were more pronounced in IEhif‐1α−/− mice. Histology examination revealed that hepatic lipid accumulation is increased by alcohol exposure, and it was exaggerated in IEhif‐1α−/− mice. Liver TG concentration was increased by alcohol exposure in the WT mice and further elevated in the KO mice. Intestinal HIF‐1α deletion resulted in a marked increase in hepatic inflammatory cytokine expression. In the IEhif‐1α−/− mice, alcohol exposure disrupted intestinal structure integrity. Metagenomic analysis of the fecal samples of IEhif‐1α−/− mice exposed to alcohol showed an elevated dysbiosis. Alcohol exposure decreased the expression of Claudin‐1, CRAMP, P‐gp, and β‐Defensins, which are HIF1α transcription target genes and important for intestinal barrier integrity and antimicrobial activity. Non‐absorbable antibiotics treatment attenuated ALD in both WT and IEhif‐1α−/− mice, indicating that alcohol‐induced dysbiosis is a contributing factor in ALD. Moreover, we showed that probiotics (Lactobacillus rhamnosus GG (LGG)) administration significantly reduced hepatic steatosis in WT mice but not in IEhif‐1α−/− mice, implying a requirement for HIF1α in the beneficial effect of LGG in ALD. Furthermore, DMOG‐conditioned T84 culture media markedly decreased fecal bacterial growth.

Conclusions

Our results demonstrated that intestinal HIF1α is required for the adaptation response to alcohol exposure‐induced changes in intestinal microbiota and barrier function associated with elevated endotoxemia and hepatic steatosis and injury. HIF1α is also required for beneficial effects of LGG on ALD.

Support or Funding Information

Supported by grants from the NIH and the Veterans Administration.