Dietary restriction of isoleucine increases healthspan and lifespan of genetically heterogeneous mice

Abstract Low protein (LP) diets promote health and longevity in diverse species. Although the precise components of an LP diet that mediate its beneficial effects have not been defined, reducing dietary levels of the three branched-chain amino acids (BCAAs) leucine, isoleucine and valine promotes metabolic health in both sexes, and increases lifespan while reducing frailty in male, but not female, C57BL/6J mice. Each BCAA has unique metabolic effects, and we recently showed that restriction of isoleucine is both sufficient to promote metabolic health and required for the metabolic benefits of an LP diet in male C57BL/6J mice. Here, we tested the hypothesis that specifically restricting isoleucine could promote healthy aging in genetically heterogenous UM-HET3 mice. We find that a reduced isoleucine diet improves the metabolic health of both young and old HET3 mice, promoting leanness and glycemic control. Restriction of isoleucine starting in adult, 6 month old HET3 mice reprograms hepatic metabolism in a way distinct from an LP diet. Finally, we find that a reduced isoleucine diet reduces frailty and extends the lifespan of both male and female HET3 mice, but to a much greater degree in males. Our results demonstrate that restricting dietary isoleucine can increase health span and longevity in a genetically diverse population of mice, and suggests that reducing dietary levels of isoleucine may have great potential as a geroprotective intervention.