Sex-specific longitudinal reversal of aging in old frail mice

Important studies report acute rejuvenation of mammalian cells and tissues by blood heterochronicity, old plasma dilution, defined factors, and partial reprogramming. And extension of rodent lifespan via single-prong methods was tried in recent years. Here, we examined whether simultaneous calibration of pathways that change with aging in opposite directions would be more effective in increasing healthspan and lifespan. Moreover, we started with the challenging age group - frail 25-months-old mice that are equivalent to ~75-year-old people. We used an Alk5 inhibitor (A5i) of the age-elevated, pro-fibrotic transforming growth factor-beta (TGF-β) pathway that regulates inflammatory factors, including IL-11, and oxytocin (OT) that is diminished with age and controls tissue homeostasis via G-protein-coupled receptor and ERK signaling. Treatment of old frail male mice with OT+A5i resulted in a remarkable 73% life extension from that time, and a 14% increase in the overall median lifespan. Further, these animals had significantly increased healthspan, with improved physical performance, endurance, short term memory, and resilience to mortality. Intriguingly, these benefits manifested only in the male and not in the female mice, yet OT+A5i had positive effects on fertility of middle-aged female mice. Mechanistically, the bio-orthogonal metabolic proteomics on the blood serum demonstrated that the acute, 7-day, treatment of the old mice with OT+A5i youthfully restored systemic signaling determinants and reduced protein noise in old mice of both sexes. However, after 4 months of OT+A5i, only old male, but not female, mice remained responsive, showing the youthful normalization of systemic proteome. These findings establish the significant health-span extension capacity of OT+A5i and emphasize the differences in aging and in response to longevity therapeutics between the sexes.