Figure 2. Quantitative analysis of dietary and circulating nutrient contributions to gut microbiome. See also^{Figure S3,S4}.

(A) Experimental design. Mice were fed chow containing ¹³C-protein, ¹³C-inulin, ¹³C-fatty acids, or ¹⁵N-protein for 24 h. Alternatively, mice were intravenously infused with ¹³C-lactate, ¹³C-3-hydroxybutyrate or ¹⁵N-urea for 24 h. The labeling of cecal content metabolites was analyzed by LC-MS.

(B) Contribution of dietary and circulating nutrients to carbohydrate fermentation pathways in gut microbiome. Mean ± s.e. N = 4.

(C) Contribution of dietary and circulating nutrients to cecal amino acid carbon. The names of essential amino acids (EAA) are written in blue and non-essential amino acids (NEAA) in black. Mean ± s.e. N = 4.

(D) Contribution of dietary and circulating nutrients to cecal amino acid nitrogen. As in (C), for nitrogen.

(E) Positive correlation, across amino acids in the cecal contents, of carbon contribution from dietary inulin and nitrogen contribution from circulating urea. Mean ± s.e. N = 4.