Glucose increases the lifespan of post-reproductiveC. elegansindependently of FOXO

ABSTRACT Aging is one of the most critical risk factors for the development of metabolic syndromes 1 . Prominent metabolic diseases, namely type 2 diabetes and insulin resistance, have a strong association with endoplasmic reticulum (ER) stress 2 . Upon ER stress, the unfolded protein response (UPR) is activated to limit cellular damage by adapting to stress conditions and restoring ER homeostasis 3,4 . However, adaptive genes upregulated from the UPR tend to decrease with age 5 . Although stress resistance correlates with increased longevity in a variety of model organisms, the links between the UPR, ER stress resistance, and longevity remain poorly understood. Here, we show that supplementing bacteria diet with 2% glucose (high glucose diet, HGD) in post-reproductive 7-day-old (7DO) C. elegans significantly extend their lifespan in contrast to shortening the lifespan of reproductive 3-day-old (3DO) animals. The insulin-IGF receptor DAF-2 and its immediate downstream target, phosphoinositide 3-kinase (PI3K) AGE-1, were found to be critical factors in extending the lifespan of 7DO worms on HGD. The downstream transcription factor forkhead box O (FOXO) DAF-16 did not extend the lifespan of 7DO worms on HGD in contrast of its previously reported role in modulating lifespan of 3DO worms 6 . Furthermore, we identified that UPR activation through the highly conserved ATF-6 and PEK-1 sensors significantly extended the longevity of 7DO worms on HGD but not through the IRE-1 sensor. Our results demonstrate that HGD extends lifespan of post-reproductive worms in a UPR-dependent manner but independently of FOXO. Based on these observations, we hypothesise that HGD activates the otherwise quiescent UPR in aged worms to overcome age-related stress and to restore ER homeostasis. In contrast, young adult animals subjected to HGD leads to unresolved ER stress, conversely leading to a deleterious stress response.