Dietary amino acid source elicits sex-specific metabolic response to diet-induced NAFLD in murine model.

Non-alcoholic fatty liver disease (NAFLD) is a sexually dimorphic disease influenced by dietary factors. Here, we assess the metabolic and hepatic effects of dietary amino acid (AA) source in Western diet (WD)-induced NAFLD in male and female mice. The AA source was either casein or a free AA mixture mimicking the composition of casein. As expected, males fed a casein-based WD displayed glucose intolerance, fasting hyperglycemia, and insulin-resistance and developed NAFLD associated with changes in hepatic gene expression and dysbiosis. In contrast, males fed the AA-based WD showed no steatosis, a similar gene expression profile as males fed a control diet, and a distinct microbiota composition compared to males fed a casein-based WD. Females were protected against WD-induced liver damage, hepatic gene expression, and gut microbiota changes regardless of the AA source. Thus, free dietary AA intake prevents the unhealthy metabolic outcomes of a WD in a sex-specific manner. Six-week-old male and female C57BL/6J mice were purchased from Charles Rivers Laboratories (L’Arbresle, France), kept 1 week for acclimatization, and then randomly allocated to the different experimental groups. Mice (n=12 per group and per sex) were fed a chow diet (CD; 70% carbohydrate, 4% fat, and 14% protein, Figure S1a), a Western diet (WD; 61% carbohydrate, 20% fat, and 14% protein, Figure S1a) or diets identical to the CD or WD except for protein being replaced by a free amino acid mixture mimicking the amino acid composition of casein (SAAJ INRAE, Jouy) for 15 weeks.