Reduced circulating insulin enhances insulin sensitivity in old mice and extends lifespan

The causal relationships between insulin levels, insulin resistance, and longevity are not fully elucidated. Genetic down-regulation of insulin/insulin-like growth factor 1 (Igf1) signaling components can extend invertebrate and mammalian lifespan, but insulin resistance, a natural form of decreased insulin signaling, is associated with greater risk of age-related disease in mammals. We compared Ins2+/- mice to Ins2+/+ littermate controls, on a genetically stable Ins1-null background. Proteomic and transcriptomic analyses of livers from 25 week-old mice suggested potential for healthier aging and altered insulin sensitivity in Ins2+/- mice. Halving Ins2 lowered circulating insulin by 25-34% in aged female mice, without altering Igf1 or circulating Igf1. Remarkably, decreased insulin led to lower fasting glucose and improved insulin sensitivity in aged mice. Moreover, lowered insulin caused significant lifespan extension, observed across two diverse diets. Our study indicates that elevated insulin contributes to age-dependent insulin resistance, and that limiting basal insulin levels can extend lifespan. Overall design: RNAsequencing expression profiles of livers and triceps surae hindlimb muscle from 25 week-old Ins1-/-;Ins2+/- and Ins1-/-;Ins2+/+ littermate control mice on one of two different diets (Diet A and B)

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Templeman NM, Flibotte S, Chik JHL, Sinha S, Lim GE, Foster LJ, Nislow C, Johnson JD