Linkage of gut microbiome with cognition in hepatic encephalopathy

Abstract

Hepatic encephalopathy (HE) has been related to gut bacteria and inflammation in the setting of intestinal barrier dysfunction. We aimed to link the gut microbiome with cognition and inflammation in HE using a systems biology approach. Multitag pyrosequencing (MTPS) was performed on stool of cirrhotics and age-matched controls. Cirrhotics with/without HE underwent cognitive testing, inflammatory cytokines, and endotoxin analysis. Patients with HE were compared with those without HE using a correlation-network analysis. A select group of patients with HE (n = 7) on lactulose underwent stool MTPS before and after lactulose withdrawal over 14 days. Twenty-five patients [17 HE (all on lactulose, 6 also on rifaximin) and 8 without HE, age 56 ± 6 yr, model for end-stage liver disease score 16 ± 6] and ten controls were included. Fecal microbiota in cirrhotics were significantly different (higher Enterobacteriaceae, Alcaligeneceae, and Fusobacteriaceae and lower Ruminococcaceae and Lachnospiraceae) compared with controls. We found altered flora (higher Veillonellaceae), poor cognition, endotoxemia, and inflammation (IL-6, TNF-α, IL-2, and IL-13) in HE compared with cirrhotics without HE. In the cirrhosis group, Alcaligeneceae and Porphyromonadaceae were positively correlated with cognitive impairment. Fusobacteriaceae, Veillonellaceae, and Enterobacteriaceae were positively and Ruminococcaceae negatively related to inflammation. Network-analysis comparison showed robust correlations (all P < 1E-5) only in the HE group between the microbiome, cognition, and IL-23, IL-2, and IL-13. Lactulose withdrawal did not change the microbiome significantly beyond Fecalibacterium reduction. We concluded that cirrhosis, especially when complicated with HE, is associated with significant alterations in the stool microbiome compared with healthy individuals. Specific bacterial families (Alcaligeneceae, Porphyromonadaceae, Enterobacteriaceae) are strongly associated with cognition and inflammation in HE.

Fig. 1.

Principal coordinate analysis of the fecal microbiome of controls and cirrhotic patients. This graph shows the variation in fecal microbiome plotted on a principal coordinate analysis plot. Points that are closer to each other are similar with respect to their stool microbiota. The healthy controls represented by the black dots are clustered together, whereas the cirrhotic patients represented by the gray dots are distant from the controls. This indicates a difference in the stool microbiome of healthy controls compared to cirrhotic patients.

Fig. 2.

Correlation-network analysis of cirrhotic patients with and without hepatic encephalopathy (HE). Only correlations with a coefficient >r = 0.90 are displayed. Gray nodes indicate microbiome families; white nodes indicate cognitive tests; and black nodes are serum inflammatory markers. A black line connecting nodes indicates positive correlation, and a dashed line indicates negative correlation >0.90. The P values for the correlations are displayed on the lines connecting the nodes in A and B. MELD, model for end-stage liver disease score; DST, digit symbol test; LDTe, line drawing test errors. A: patients with HE (n = 17) have a high number of significant correlations. There are significant positive correlations between IL-23 and several bacterial families. Prevotellaceae and Fusobacteriaceae are positively correlated with inflammation. Because a low score on DST and high one on LDTe indicate poor performance, Alcaligenaceae and Porphyromonadaceae were correlated with poor cognition. The P values for all these correlations are less than the 4th decimal place, indicating a very high significance. B: patients without HE have very few significant correlations (n = 8). There was a significant negative correlation between MELD score and Ruminococcaceae and a positive correlation between Veillonellaceae and Porphyromonadaceae.