Gut microbiota compositional and functional fingerprint in patients with alcohol use disorder and alcohol-associated liver disease

Background & aims: Alcohol use disorder (AUD) represents the most common cause of liver disease. The gut microbiota plays a critical role in the progression of alcohol-related liver damage. Aim of this study was to characterize the gut microbial composition and function in AUD patients with alcohol-associated liver disease (AALD). Methods: This study included 36 AUD patients (14 with cirrhosis) who were active drinkers and an equal number of matched controls. Stool microbial composition, serum levels of lipopolysaccharide, cytokines/chemokines and gut microbiota functional profile were assessed. Results: AUD patients had a decreased microbial alpha diversity as compared to controls (0.092 vs 0.130, P =.047) and a specific gut microbial signature. The reduction of Akkermansia and the increase in Bacteroides were able to identify AUD patients with an accuracy of 93.4%. Serum levels of lipopolysaccharide (4.91 vs 2.43, P =.009) and pro-inflammatory mediators (tumour necrosis factor alpha 60.85 vs 15.08, P =.001; interleukin [IL] 1beta 4.43 vs 1.72, P =.0001; monocyte chemoattractant protein 1 225.22 vs 16.43, P =.006; IL6 1.87 vs 1.23, P =.008) were significantly increased in AUD patients compared to controls and in cirrhotic patients compared to non-cirrhotic ones (IL6 3.74 vs 1.39, P =.019; IL8 57.60 vs 6.53, P =.004). The AUD-associated gut microbiota showed an increased expression of gamma-aminobutyric acid (GABA) metabolic pathways and energy metabolism. Conclusions: AUD patients present a specific gut microbial fingerprint, associated with increased endotoxaemia, systemic inflammatory status and functional alterations that may be involved in the progression of the AALD and in the pathogenesis of AUD.