Differential Effects of Sulfur Amino Acid-Restricted and Low-Calorie Diets on Gut Microbiome Profile and Bile Acid Composition in Male C57BL6/J Mice

Abstract

Diet can affect health and longevity by altering the gut microbiome profile. Sulfur amino acid restriction (SAAR), like caloric restriction, extends lifespan. But, its effect on the gut microbiome profile and functional significance of such effects are understudied. We investigated whether SAAR alters the gut microbiome profile and bile acid composition, an index of microbial metabolism. We also compared these changes with those induced by a 12% low-calorie diet (LCD). Male 21-week-old C57BL6/J mice were fed control (CD; 0.86% methionine), SAAR (0.12% methionine), and LCD diets (0.86% methionine). After 10 weeks on the diet, plasma markers and fecal microbial profiles were determined. SAAR mice had lower body weights and IGF-1, and higher food intake and FGF-21 than CD mice. Compared to SAAR mice, LCD mice had higher body weights, and lower FGF-21 and food intake, but similar IGF-1. β-Diversity indices were different between SAAR and LCD, and LCD and CD, but not between CD and SAAR. In groupwise comparisons of individual taxa, differences were more discernable between SAAR and LCD than between other groups. Abundances of Firmicutes, Clostridiaceae, and Turicibacteraceae were higher, but Verrucomicrobia was lower in SAAR than in LCD. Secondary bile acids and the ratio of secondary to primary bile acids were lower in SAAR than in LCD. SAAR favored bile acid conjugation with glycine at the expense of taurine. Overall, SAAR and LCD diets induced distinct changes in the gut microbiome and bile acid profiles. Additional studies on the role of these changes in improving health and lifespan are warranted.

Keywords: Clostridiales; Firmicutes; Lifespan; Methionine restriction; Sulfur metabolism.

Figure 1.

Differential effects of low-calorie diet (LCD) and sulfur amino acid-restricted diet (SAAR) on morphometrics and plasma markers. Male 21-week-old C57BL6/J mice were fed a control diet (CD, 0.86% methionine without cysteine with ad libitum intake); SAAR (0.12% methionine without cysteine with ad libitum intake); and LCD (CD with total caloric intake matched to the SAAR group) for 10 weeks. (A) Body weights during the study period, (B) cumulative weight gain, (C) food intake on a body weight basis, (D) cumulative food intake on a body weight basis, (E) plasma IGF-1, and (F) plasma FGF-21. Notes: n = 7–9 per group; error bars represent standard errors. *p ≤ .05, **p ≤ .01, ***p ≤ .001, ****p ≤ .0001.

Figure 2.

Low-calorie diet (LCD) and sulfur amino acid-restricted diet (SAAR) alter β-diversity of the gut microbiome. (A) Differences in the microbiome profiles (β-diversity) of the 3 dietary interventions were calculated using Bray–Curtis distance matrix. (B–D) To quantify dissimilarity in microbiome composition between groups, plots and p-values were generated by using nonmetric multidimensional scaling and nonparametric analysis of similarity, respectively. β-Diversity indices were not different between (B) control diet (CD) and SAAR, but significantly different between (C) SAAR and LCD, and (D) LCD and CD. Notes: n = 7–9 per group. Circle with dot indicates outlier in the LCD group. *p ≤ .05, **p ≤ .01, *** P ≤ .001.

Figure 3.

Differential effects of low-calorie diet (LCD) and sulfur amino acid-restricted diet (SAAR) on the mean abundances of selected taxa. (A–C) Phylum, (D–F) family, and (G–I) species. Overall, groupwise comparisons of selected taxa show that SAAR and LCD were the 2 diet groups that were most different. Notes: Percentage represents percent of total bacteria; error bars represent standard errors; n = 7–9 per group. *p ≤ .05, **p ≤ .01, ***p ≤ .001, ****p ≤ .0001.

Figure 4.

Sulfur amino acid-restricted diet (SAAR) alters plasma concentration (A–C) and conjugation (D–F) of bile acids. (A) Plasma total bile acids, (B) plasma secondary bile acids, (C) ratio of secondary/primary bile acids, (D) total conjugated bile acids, (E) taurine-conjugated bile acids, and (F) glycine-conjugated bile acids. Notes: n = 7–9 per group; error bars indicate standard errors. *p ≤ .05. **p ≤ .01.