Figure 5.

Associations of plasma histidine and steatosis degree with the gut microbiota and Hut genes

(A and B) Volcano plots of differential bacterial families associated with (A) the circulating histidine levels and (B) hepatic steatosis in the discovery cohort (n = 73), identified using the analysis of microbiomes with bias correction (ANCOM-BC), controlling for age, BMI, gender, and country. The log₂(FC) associated with a unit change in the plasma histidine levels and the −log₁₀(p value) adjusted for multiple testing are plotted for each family.

(C) Histidine utilization pathways. The first three pathways appear to be universal. There are two different degradation pathways for formiminoglutamate depending on the genera: hydrolyzation to formamide and glutamate or hydrolyzation to formylglutamate and subsequent hydrolyzation to formate and glutamate.

(D‒G) Violin plots of the centered log ratio-transformed microbial genes involved in histidine utilization (hutH, hutU, hutI, and hutG, respectively) in subjects with a steatosis degree lower or higher than 33%.

(H) Volcano plots of differential bacterial families associated with the hepatic steatosis degree (liver biopsy) in the animal supplementation study for the comparison of NAFLD+vehicle vs. NAFLD+HAA, identified using ANCOM-BC. The log₂(FC) and the −log₁₀(p value) adjusted for multiple testing are plotted for each taxon. Significantly different taxa are colored according to phylum.

(I–K) Genus levels of (I) Roseburia and (J) Akkermansia and (K) qPCR of microbial genes expression involved in histidine utilization (hutH and hutG). ∗p < 0.05, ∗∗∗∗p < 0.0001. (K) Data are mean ± SEM.