Leucine Catabolism is Associated with Longevity in Female Eastern Lubber Grasshoppers
Abstract
Background & Aims: Dietary isoleucine restriction can improve metabolic health and increase lifespan. It has been hypothesized that shifts in branched-chain amino acid catabolism drives this longevity effect. Impaired branched-chain amino acid catabolism is linked to several age-related diseases. We investigated whether dietary isoleucine restriction increases leucine catabolism and associates with longevity and full reproduction.
Methods: In two experiments, adult female Eastern Lubber grasshoppers (Romalea microptera) were assigned to either a high-quality diet (Balanced ile), or diets with varying isoleucine content (Moderate ile-R and Severe ile-R). In Experiment 1, we used a low-energy (Low Lettuce) group as a positive control for catabolism. In Experiment 2, we used an ad libitum lettuce (Ad Lib Lett) control to show the reproduction versus longevity trade-off.
Results: The Bal ile, Mod ile-R, and Sev ile-R diets all extended lifespan and increased leucine catabolism relative to the Ad Lib Lett group. The Sev ile-R and Low Lett groups showed the highest leucine catabolism but reduced reproduction. The Bal ile and Mod ile-R groups showed intermediate leucine catabolism—higher than Ad Lib Lett; lower than Low Lett—while sustaining reproduction similar to the Ad Lib Lett group. Valine catabolism showed similar patterns without consistent significant differences across groups. We observed no compensatory feeding on low isoleucine diets. However, isoleucine catabolism in the Mod ile-R and Sev ile-R groups did not exceed that of the Low Lett group, suggesting that the increased leucine and valine catabolism was driven by diet composition rather than energy deficit.
Conclusion: Weak leucine catabolism is linked to a short lifespan, while excessive catabolism is linked to impaired reproduction. Intermediate levels of leucine catabolism were associated with longevity and sustained reproduction.