Aging is a major risk factor for type 2 diabetes (T2D) and cellular senescence plays a critical role in β-cell dysfunction leading to T2D. Exercise is a central component in the treatment of T2D and has been shown to attenuate many of the biochemical changes that occur with aging including senescence, but nothing is known about the effects of exercise on β-cells and their aging process. To test the hypothesis that exercise decreases β-cell senescence we used two mouse models of insulin resistance: high-fat diet (HFD, 60% kcal from fat, 6 wks) and insulin receptor antagonist S961 (40nM/wk for 2 wks) . Exercise (treadmill, 1 h/day, 5 times/wk for 2 wks at 17 cm/s and 5% incline) prevented entrance of β-cells into senescence and reversed established senescence in both males and females across the lifespan (started at 1.5-9m or 14m old mice) as seen by a decrease in one or several of the following markers: βGal, p21Cip1 and p16Ink4a. This decrease in senescence was accompanied by improved glucose stimulated insulin secretion characterized by recovery of glucose responsiveness in islets from HFD and S961 exercised animals. Islets cultured with serum from trained animals showed decreased p21Cip1 mRNA, indicating a circulatory factor (s) was responsible for these effects. Exercise increased serum glucagon expression, identified as such factor. Incubation of human and mouse islets with glucagon (1nM) decreased p21Cip1 mRNA, and using AMPK agonist (1uM C99) and antagonist (5uM Compound C) , we found that AMPK mediates the glucagon-stimulated decrease in p21Cip1. Human cadaveric donor islets treated with serum obtained before and after 10-weeks of exercise-training in people with T2D demonstrated that training decreased senescence markers through AMPK activation. In conclusion, exercise has anti-aging effects on mouse and human pancreatic islets by decreasing senescence and improving function. This is a novel mechanism of the effects of exercise on β-cell aging with implications for the treatment of T2D. Disclosure P.Carapeto: None. J.Kahng: None. A.T.Alves wagner: None. R.Middelbeek: Research Support; Novo Nordisk. M.F.Hirshman: Stock/Shareholder; Abbott, AbbVie Inc., Amgen Inc., Colgate-Palmolive, Eli Lilly and Company, Medtronic. L.J.Goodyear: None. C.Aguayo-mazzucato: Consultant; eGenesis. Funding American Diabetes Association (1-17-PMF-009) ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001; Short-Term Research Experience for Underrepresented Persons (1R25DK113652) ; NIDDK grant (K23-DK114550) ; NIH grant (R01DK099511) and the Joslin Diabetes Center DRC (P30 DK36836) .