The Molecular Mechanisms of Lifespan Extension by Alpha-Ketoglutarate in Caenorhabditis elegans

As the elderly population is now the fastest growing age group in the United States, there is an imminent need to understand the molecular mechanisms of aging and develop new approaches to counter aging and the maladies that come with it. Modulation of metabolism, either by dietary restriction or pharmacologic or genetic alteration of metabolic pathways, can extend lifespan and delay age-related diseases in evolutionarily diverse organisms. Here we demonstrate, for the first time, a role for alpha-ketoglutarate (alpha-KG) in the regulation of aging. Alpha-KG serves many functions in the cell, including being an intermediate of the tricarboxylic acid cycle, a precursor for several amino acids, and a substrate for alpha-KG-dependent oxygenases. We show that alpha-KG extends the mean lifespan of adult Caenorhabditis elegans by about 50%, and provide evidence to suggest that this is not due to the metabolism of alpha-KG into other metabolites. Other metabolites have been shown to extend lifespan as well, but without a well defined mechanism. Research on small molecules in aging has been hindered by the inability to identify drug targets. We use a label-free, unbiased drug target identification strategy termed DARTS (drug affinity responsive target stability) to uncover a new binding target of alpha-KG, the beta subunit of the ATP synthase. We reveal that alpha-KG inhibits ATP synthase in in vitro and in vivo assays using both worm and mammalian models. Consistently, genetic or pharmacological inhibition of ATP synthase yields the same phenotypes as alpha-KG: increased lifespan, decreased ATP levels, lower oxygen consumption rates, elevated levels of reactive oxygen species, and reduced target of rapamycin signaling. However, unlike genetic inhibition of ATP synthase, alpha-KG does not induce the mitochondrial unfolded protein response, cause larval arrest, or slow pharyngeal pumping rates. Remarkably, alpha-KG does not further increase the lifespan of dietary restricted animals and is elevated during starvation, a testament to it being a key regulator of dietary restriction mediated lifespan extension. Like dietary restriction, alpha-KG also induces autophagy, and we provide evidence to suggest that autophagy may play an essential role for the longevity of alpha-KG treated animals. Our findings posit alpha-KG as a key regulator of metabolic pathways in response to nutrient status, and suggest new strategies for the prevention and treatment of aging and age-related diseases