Eubacterium rectale is a potential marker of altered gut microbiota in psoriasis and psoriatic arthritis

Abstract

Previous studies have profiled the gut microbiota among psoriatic patients compared to that among healthy individuals. However, a comprehensive understanding of the magnitude, direction, and detailed compositional and functional profiles remains limited. Additionally, research exploring the gut microbiota in the context of both plaque psoriasis (PsO) and psoriatic arthritis (PsA) is lacking. To assess the taxonomic and functional characteristics of the gut microbiota in PsO and PsA patients and investigate potential links between the gut microbiota and disease pathogenesis. We collected fecal samples from 70 psoriatic patients (44 PsO and 26 PsA) and 25 age- and gender-matched healthy controls (HC) and employed deep metagenomic sequencing to characterize their gut microbiota. We noted significant alternations in the gut microbiota compositions of both PsO and PsA patients compared to those of HC. Despite limited effect sizes in alpha diversity (12.3% reduction of microbial richness but unchanged evenness in psoriatic patients) and beta diversity (disease accounts for 3.5% of total variations), we consistently observed substantial reductions of Eubacterium rectale in both PsO and PsA patients, with PsA patients exhibiting even lower levels of E. rectale than PsO patients. Additionally, two Alistipes species were also depleted in psoriatic patients. These microorganisms are known to play crucial roles in carbohydrate metabolism pathways, mainly producing short-chain fatty acids with anti-inflammatory effects. Overall, our observations supplemented the profiling of altered gut microbiota in patients with PsO and PsA at the species level and described a link between the dominant short-chain fatty acid-producing bacterial species and systemic immunity in psoriatic patients.

Importance: In this observational clinical study with sufficient sample size and metagenomic sequencing to profile the gut microbiota, we identified consistent signals of the depleted abundance of Eubacterium rectale and related functional genes among psoriatic patients, including those with psoriatic arthritis. E. rectale may serve as an ecologically important functional unit in the gut microbiota, holding potential as a diagnostic marker and target for therapeutic interventions to achieve lasting effects. Our findings provide comprehensive gut microbiota profiling in psoriasis, resolving previous contradictions and generating new hypotheses for further investigation. These insights may significantly impact psoriasis management and related conditions.

Keywords: Eubacterium rectale; gut microbiota; metagenomics; psoriasis; psoriatic arthritis.

Fig 1

Alternations in gut microbiome among patients compared to age-matched healthy controls. (a, b) Boxplot of the number of metagenomics-inferred bacterial species (MGS species) in each sample by (a) comparing psoriatic patients (plaque psoriasis (PsO) and psoriatic arthritis (PsA) together) to healthy controls, the P-value is provided by the Wilcoxon rank-sum test; and (b) comparing PsO, PsA, and healthy controls, the P-value is provided by a Kruskal–Wallis test with a post hoc Conover test. (c, d) Principle coordinate analysis (PCoA) based on Bray–Curtis distance inferred from the MGS species profile. The main scatter plot represents the coordinates of each sample; boxplots on the side represent the distribution of either PC1 or PC2 coordinates in each group, with (c) comparing psoriatic patients to healthy controls and (d) comparing PsO, PsA, and healthy controls.

Fig 2

Differential abundance metagenomics-inferred bacterial species (MGS species) identified using logistic regression. (a) The volcano plots show the comparison of patients with psoriasis to healthy controls. An estimated odds ratio (OR)>1 indicates psoriatic patients are enriched and vice versa. MGS species with an adjusted P ≤ 0.01 or a revised P ≤ 0.1 and an OR <0.2 are highlighted as red dots and labeled. (b) Heatmap of relative abundance of MGS species with an adjusted P ≤ 0.2. Column and row dendrograms are plotted using pairwise Euclidian distances. PsO indicates plaque psoriasis, and PsA indicates psoriatic arthritis.

Fig 3

Differential abundance KEGG pathways identified using logistic regression. (a) The volcano plots show the comparison of psoriatic patients to healthy controls. An OR >1 indicates psoriatic patients are enriched and vice versa. Pathways with an adjusted P ≤ 0.1 or an adjusted P < 0.2 and an OR <0.2 are highlighted as red dots and labeled. (b) Heatmap of relative abundance of KEGG pathways with an adjusted P < 0.2. Column and row dendrograms are plotted using pairwise Euclidian distances. PsO indicates plaque psoriasis, and PsA indicates psoriatic arthritis.