Effects of moderate, voluntary ethanol consumption on the rat and human gut microbiome.

Many alcohol-induced health complications are directly attributable to the toxicity of alcohol or its metabolites, but another potential health impact of alcohol may be on the microbial communities of the human gut. Clear distinctions between healthy and diseased-state gut microbiota have been observed in subjects with metabolic diseases, and recent studies suggest that chronic alcoholism is linked to gut microbiome dysbiosis. Here, we investigated the effects of moderate levels of alcohol consumption on the gut microbiome in both rats and humans. The gut microbiota of rats voluntarily consuming a 20 percent ethanol solution, on alternate days, were compared with a non-exposed control group to identify differential taxonomic and functional profiles. Gut microbial diversity profiles were determined using culture-independent amplification, next-generation sequencing and bioinformatic analysis of bacterial 16S ribosomal RNA gene sequence libraries. Our results showed that, compared with controls, ethanol-consuming rats experienced a significant decline in the biodiversity of their gut microbiomes, a state generally associated with dysbiosis. We also observed significant shifts in the overall diversity of the gut microbial communities and a dramatic change in the relative abundance of particular microbes, such as the Lactobacilli. We also compared our results to human fecal microbiome data collected as part of the citizen science American Gut Project. In contrast to the rat data, human drinkers had significantly higher gut microbial biodiversity than non-drinkers. However, we also observed that microbes that differed among the human subjects displayed similar trends in the rat model, including bacteria implicated in metabolic disease.

Effects of Moderate Ethanol Consumption on Lipid Metabolism and Inflammation Through Regulation of Gene Expression in Rats.

AIMS: Epidemiological studies and experimental data from rodent models have reported a non-linear relationship between consumption of alcohol and cardiovascular disease (CVD) risk that suggests that light-to-moderate drinking as opposed to excessive consumption may provide some cardiovascular benefits. The present study examined potential mechanisms by which moderate alcohol consumption may provide a protective effect against CVD. SHORT SUMMARY: Wistar rats exposed for 3 months to a 20% ethanol intermittent-access voluntary drinking paradigm displayed a reduction in epididymal fat, blood glucose and non-HDL and total cholesterol. These effects were accompanied by decreased expression of Hmgcr, Srebp-2, Cox-2 and RelA, indicating downregulation of genes involved in cholesterol synthesis and inflammation. METHODS: Twenty-four male Wistar rats voluntarily consumed a 20% v/v ethanol solution on alternate days for 13 weeks (ethanol-treated) or were given access to water alone (non-ethanol-exposed control). RESULTS: There was no difference in body weight gain between the two groups, however, epididymal fat weight was lower in ethanol-fed rats (P = 0.030). Blood glucose, total cholesterol, non-high-density lipoprotein (HDL) and oxidized low-density lipoprotein (LDL) levels were lower in the ethanol group compared to controls (P < 0.05). There was a significant reduction in the expression of hydroxymethylglutaryl-coenzyme A reductase and sterol regulatory element-binding protein-2 in ethanol-treated rats (P < 0.05), suggesting that ethanol may have lowered cholesterol levels via downregulation of genes involved in cholesterol synthesis. Paraoxonase-1, which is associated with inhibition of LDL cholesterol oxidation, was upregulated in the ethanol group (P = 0.029). Ethanol-treated rats exhibited significantly lower levels of high-mobility box group protein 1 (P ≤ 0.05). Cyclooxygenase-2 and RelA gene expression were significantly lower in ethanol-treated rats (P < 0.05), indicating possible anti-inflammatory effects. CONCLUSIONS: These findings suggest that moderate ethanol consumption may potentially contribute to improved cardiovascular outcomes by reducing body fat, improving blood cholesterol and blood glucose, and modulation of gene expression involved in inflammation and/or cholesterol synthesis.