Aging Reduces Intestinal Stem Cell Activity in Killifish and Intermittent Fasting Reverses Intestinal Gene Expression Patterns

The process of aging is associated with a decline in cell, tissue, and organ function, leading to a range of health problems. Increasing evidence indicates that dietary restriction can counteract age-dependent effects and improve health and longevity in whole organisms, but less is known about the influence of aging and the impact of nutrition on individual organs of an organism. In this study, we examined the intestine of the very short-lived aging model system, the African turquoise killifish (Nothobranchius furzeri), throughout its lifetime. We investigated the effects of age and nutrition on the preservation of gut tissue at stages corresponding to human neonatal, adolescent, adult, and old age, and integrated morphological measurements, histology, and transcriptomics. The intestinal mucosa is characterized by folds and intervening interfold regions, where intestinal stem cells localize. The stem cells occur in clusters, and the cycle time of stem cells increases with age. We also observed a reduction in intestinal length and volume with age. Age-dependent transcriptomic profiling revealed significant changes in the expression of peripheral circadian clock genes and stem cell niche markers. Notably, the majority of these genes maintained their adult gene expression levels in old age following intermittent fasting during adulthood. Therefore, our results demonstrate that the decline in structural intestinal tissue homeostasis is associated with a decline in stem cell activity that can be counteracted by intermittent fasting. Since the intestinal mucosa of killifish is similar to that of mammals, the results of this study can be translated to general gut biology.