Gut microbiota: its role in hepatic encephalopathy

Area of Science:

• Gastroenterology
• Microbiology
• Hepatology

Background:

• Ammonia is central to hepatic encephalopathy (HE) pathogenesis, originating from gut bacteria and host enzymes.
• Fecal microbiota composition in cirrhosis patients correlates with disease severity (CTP, MELD) and HE development.
• The cirrhosis dysbiosis ratio (CDR) differentiates between healthy, compensated, and decompensated cirrhosis patients.

Purpose of the Study:

• To investigate the role of gut microbiota alterations in the pathogenesis of hepatic encephalopathy (HE) in cirrhosis patients.
• To analyze the impact of HE and its treatments (lactulose, rifaximin) on fecal and colonic mucosal microbiota.
• To explore the relationship between microbial changes, ammonia metabolism, and cognitive function in HE.

Main Methods:

• Utilized non-culture techniques like pyrosequencing of bacterial 16S ribosomal RNA to characterize fecal microbiota.
• Compared sigmoid colonic mucosal microbiota in cirrhosis patients with and without HE.
• Assessed changes in fecal microbiome composition following lactulose treatment and withdrawal, and rifaximin therapy.

Main Results:

• Sigmoid colonic mucosal microbiota differ between cirrhosis patients with and without HE, unlike stool microbiota.
• Pathogenic colonic bacteria are linked to cognitive impairment and inflammation, suggesting mucosal interface involvement in HE.
• Lactulose and rifaximin treatments induced only modest changes in fecal microbiome composition, despite clinical improvements.

Conclusions:

• Gut microbiota dysbiosis and alterations at the mucosal interface play a significant role in HE pathogenesis.
• The therapeutic benefits of lactulose and rifaximin may stem from modified microbial metabolic functions rather than substantial microbiome shifts.
• Targeting microbial metabolic pathways could be a promising strategy for managing HE.