Cysteine protease cathepsin B promotes lysosome integrity to extend the lifespan of alternative day fasting worms.

Alternative day fasting (ADF) has been shown to enhance the lifespan of animals. However, human trials evaluating the efficacy of ADF have only recently emerged, presenting challenges due to the extreme nature of this dietary regimen. To better understand the effects of ADF, we investigated its impact using Caenorhabditis elegans as a model organism. Our findings reveal that ADF extends the lifespan of worms nourished on animal-based protein source, while those fed with plant-based protein as the primary protein source do not experience such benefits. Remarkably, initiating ADF during midlife is sufficient to prolong lifespan, whereas implementation during youth results in developmental damage, and in older age, fails to provide additional extension effects. Furthermore, we discovered that midlife ADF up-regulates the expression of two cysteine protease cathepsin B genes, cpr-2 and cpr-5, which preserve lysosomal integrity and enhance its function in digesting aggregated proteins, as well as enhancing lipid metabolism and ameliorating neurodegenerative disease markers and phenomena during aging. This suggests that midlife ADF has long lasting anti-aging effects and may delay the onset of related diseases, specifically in animals consuming animal-based protein source. These findings offer valuable insights into the effects of ADF and provide guidance for future research and potential applications in individuals.