Abstract
High glucose diets are unhealthy, although the mechanisms by which elevated glucose is harmful to whole animal physiology are not well understood. In Caenorhabditis elegans, high glucose shortens lifespan, while chemically inflicted glucose restriction promotes longevity. We investigated the impact of glucose metabolism on aging quality (maintained locomotory capacity and median lifespan) and found that, in addition to shortening lifespan, excess glucose negatively impacts locomotory healthspan. Conversely, disrupting glucose utilization by knockdown of glycolysis-specific genes results in large mid-age physical improvements via a mechanism that requires the FOXO transcription factor DAF-16. Adult locomotory capacity is extended by glycolysis disruption, but maximum lifespan is not, indicating that limiting glycolysis can increase the proportion of life spent in mobility health. We also considered the largely ignored role of glucose biosynthesis (gluconeogenesis) in adult health. Directed perturbations of gluconeogenic genes that specify single direction enzymatic reactions for glucose synthesis decrease locomotory healthspan, suggesting that gluconeogenesis is needed for healthy aging. Consistent with this idea, overexpression of the central gluconeogenic gene pck-2 (encoding PEPCK) increases health measures via a mechanism that requires DAF-16 to promote pck-2 expression in specific intestinal cells. Dietary restriction also features DAF-16-dependent pck-2 expression in the intestine, and the healthspan benefits conferred by dietary restriction require pck-2. Together, our results describe a new paradigm in which nutritional signals engage gluconeogenesis to influence aging quality via DAF-16. These data underscore the idea that promotion of gluconeogenesis might be an unappreciated goal for healthy aging and could constitute a novel target for pharmacological interventions that counter high glucose consequences, including diabetes.
Highlights
How to live at peak health over adult life is a challenge of our time
We show that the two opposing glucose metabolism pathways–glycolysis and gluconeogenesis–have dramatically opposite effects on health: glycolytic activity responsible for sugar catabolism is detrimental, but driving gluconeogenesis promotes healthy aging
The powerful longevity regulator DAF-16 is required for the healthspan effects of gluconeogenesis
Summary
How to live at peak health over adult life is a challenge of our time. Successful aging, defined by some as the prolonged maintenance of physical and cognitive function coupled with avoidance of debilitating disease, can most certainly be influenced by activity and diet [1]. Epidemiological studies support that high sugar diets impair health, tightly controlled studies of metabolic influences on aging quality are difficult to conduct in the human population, which is heterogeneous in genetics, activity, and food consumption patterns. Animal models have been highly instructive regarding conserved metabolic states that promote or defer age-associated decline. In the facile aging model Caenorhabditis elegans, high glucose in growth medium shortens lifespan independently of associated osmotic change or glucose metabolism by bacterial food, in part via insulin-like signaling [13,14,15,16,17,18,19,20]. The insulin/ IGF-1 receptor ortholog DAF-2 activates the AGE-1 PI3 kinase to signal downstream to inhibit the activity of longevity-promoting transcription factors including DAF-16/FOXO. Low insulin signaling activity activates DAF-16-mediated transcription to promote longevity [21,22,23,24,25,26,27,28]
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