Sexually Dimorphic Effects of Dietary Methionine Restriction are Dependent on Age when the Diet is Introduced.

OBJECTIVE: Restricting dietary methionine to 0.17% in male mice increases energy expenditure, reduces fat deposition, and improves metabolic health. The goal of this work was to compare each of these responses in postweaning male and female mice and in physically mature male and female mice.
METHODS: Methionine-restricted (MR) diets were fed to age-matched cohorts of male and female mice for 8 to 10 weeks beginning at 8 weeks of age or beginning at 4 months of age. The physiological and transcriptional responses to MR were compared in the respective cohorts.
RESULTS: Dietary MR produced sexually dimorphic changes in body composition in young growing animals, with males preserving lean at the expense of fat and females preserving fat at the expense of lean. The effects of MR on energy balance were comparable between sexes when the diet was initiated after attainment of physical maturity (4 months), and metabolic and endocrine responses were also comparable between males and females after 8 weeks on the MR diet.
CONCLUSIONS: The sexually dimorphic effects of MR are limited to nutrient partitioning between lean and fat tissue deposition in young, growing mice. Introduction of the diet after physical maturity produced comparable effects on growth and metabolic responses in male and female mice.