Characterization of gut microbiota composition and functions in patients with chronic alcohol overconsumption

Abstract

Excessive alcohol intake can alter the gut microbiota, which may underlie the pathophysiology of alcohol-related diseases. We examined gut microbiota composition and functions in patients with alcohol overconsumption for >10 years, compared to a control group of patients with a history of no or low alcohol intake. Faecal microbiota composition was assessed by 16S rRNA sequencing. Gut microbiota functions were evaluated by quantification of short-chain fatty acids (SCFAs) and predictive metagenome profiling (PICRUSt). Twenty-four patients, mean age 64.8 years (19 males), with alcohol overconsumption, and 18 control patients, mean age 58.2 years (14 males) were included. The two groups were comparable regarding basic clinical variables. Nutritional assessment revealed lower total score on the screening tool Mini Nutritional Assessment, lower muscle mass as assessed by handgrip strength, and lower plasma vitamin C levels in the alcohol overconsumption group. Bacteria from phylum Proteobacteria were found in higher relative abundance, while bacteria from genus Faecalibacterium were found in lower relative abundance in the group of alcohol overconsumers. The group also had higher levels of the genera Sutterella, Holdemania and Clostridium, and lower concentration and percentage of butyric acid. When applying PICRUSt to predict the metagenomic composition, we found that genes related to invasion of epithelial cells were more common in the group of alcohol overconsumers. We conclude that gut microbiota composition and functions in patients with alcohol overconsumption differ from patients with low consumption of alcohol, and seem to be skewed into a putative pro-inflammatory direction.

Keywords: Clostridium; Faecalibacterium; Holdemania; Nutritional screening; PICRUSt; Proteobacteria; Sutterella; short-chain fatty acids.

Figure 1.

Flow chart of inclusion process.

Figure 2.

Relative bacterial composition at the phylum level. (a) Pie charts depicting the average relative abundance for major phyla for alcohol overconsumers (n = 24) and controls (n = 18). (b) Relative abundance of Proteobacteria for alcohol overconsumers (n = 24) and controls (n = 18). The lines represent median values.

Figure 3.

Differences in bacterial composition between alcohol overconsumers (n = 24) and controls (n = 18) at genus level. The lines represent median values. (a) Faecalibacterium levels. (b) Clostridium levels. (c) Sutterella levels. (d) Holdemania levels.

Figure 4.

Cross-taxa validation and functional characterization of gut microbiota in alcohol overconsumers (n = 24) and controls (n = 18), where green color indicates taxa enriched (↑) in alcohol overconsumers, and red color indicates taxa depleted (↓) in alcohol overconsumers. (a) Taxa with statistical different relative levels between alcohol overconsumers (n = 24) and controls (n = 18), with effect size, across all taxa. (b) Cladogram showing phylogenetic relationships between taxa that are statistically different. (c) Barchart with KEGG orthology functional terms identified by PICRUSt as different in alcohol overconsumers (n = 24) and controls (n = 18).