The metabolite α-ketoglutarate extends lifespan by inhibiting ATP synthase and TOR

Abstract

Metabolism and ageing are intimately linked. Compared to ad libitum feeding, dietary restriction (DR) or calorie restriction (CR) consistently extends lifespan and delays age-related diseases in evolutionarily diverse organisms1,2. Similar conditions of nutrient limitation and genetic or pharmacological perturbations of nutrient or energy metabolism also have longevity benefits3,4. Recently, several metabolites have been identified that modulate ageing5,6 with largely undefined molecular mechanisms. Here we show that the tricarboxylic acid (TCA) cycle intermediate α-ketoglutarate (α-KG) extends the lifespan of adult C. elegans. ATP synthase subunit beta is identified as a novel binding protein of α-KG using a small-molecule target identification strategy called DARTS (drug affinity responsive target stability)7. The ATP synthase, also known as Complex V of the mitochondrial electron transport chain (ETC), is the main cellular energy-generating machinery and is highly conserved throughout evolution8,9. Although complete loss of mitochondrial function is detrimental, partial suppression of the ETC has been shown to extend C. elegans lifespan10–13. We show that α-KG inhibits ATP synthase and, similar to ATP synthase knockdown, inhibition by α-KG leads to reduced ATP content, decreased oxygen consumption, and increased autophagy in both C. elegans and mammalian cells. We provide evidence that the lifespan increase by α-KG requires ATP synthase subunit beta and is dependent on the target of rapamycin (TOR) downstream. Endogenous α-KG levels are increased upon starvation and α-KG does not extend the lifespan of DR animals, indicating that α-KG is a key metabolite that mediates longevity by DR. Our analyses uncover new molecular links between a common metabolite, a universal cellular energy generator, and DR in the regulation of organismal lifespan, thus suggesting new strategies for the prevention and treatment of ageing and age-related diseases.

Chronic mTOR inhibition in mice with rapamycin alters T, B, myeloid, and innate lymphoid cells and gut flora and prolongs life of immune‐deficient mice

“…Instead, long‐term eRapa produced modest global intestinal metagenomic changes and significant changes in few specific operational taxonomic units. Nonetheless, specific effects could be important to understand as we found an association between eRapa‐mediated gut metagenomes and immune effects, and intestinal bacterial products can extend lifespan, including through mTOR (Chin et al ., 2014). …”

Mitochondrial metabolites extend lifespan

“…In all four instances, worms were incubated with 10 m m of the test compound in the presence of 50 μ m 5‐fluorodeoxyuridine (FuDR), to sterilize animals. This test dose is comparable to the concentration of α‐ketoglutarte previously found to extend life in worms (Chin et al ., 2014). Although 1–2 orders of magnitude greater than most intermediary metabolites (Dienel, 2009), the effective delivery dose for each compound was likely much less than 10 m m for the following reasons.…”

“…α‐ketoglutarate was recently shown to bind and inhibit the β‐subunit (ATP‐2) of the mitochondrial F 1 F o ATP synthase (complex V) in both worm and bovine heart mitochondrial samples, and to extend nematode lifespan (Chin et al ., 2014). Using the same drug affinity responsive target stability (DARTS) assay originally used to identify α‐ketoglutarate binding to ATP‐2, we found no evidence that 3M2OB, 3M2OV, 4M2OV, or pyruvate could bind ATP‐2 in whole‐worm lysates (data not shown).…”

“…We also found evidence that 3M2OB weakly inhibited mitochondrial complex V activity. This is of interest because the structurally related compound α‐ketoglutarate was recently shown to inhibit complex V, and to increase autophagy and extend the life of wild‐type worms (Chin et al ., 2014). α‐ketoglutarate was also shown in the same study to inhibit complex V in mouse and human cell lines and to reduce target of rapamycin (TOR) activity.…”

“…Our most recent evidence suggests that these chemicals may arise following functional impairment of three closely related α‐ketoacid dehydrogenase complexes: branched‐chain α‐ketoacid dehydrogenase (BCKADH), α‐ketoglutarate dehydrogenase (α‐KGDH), and pyruvate dehydrogenase (PDH) (Butler et al ., 2013). The ensemble of α‐hydroxyacids and α‐ketoacids in Mit mutants is of particular interest because these compounds share structural similarity with α‐ketoglutarate, a metabolite recently shown to bind the β‐subunit (ATP‐2) of the mitochondrial F 1 F o ATP synthase (complex V) and to extend nematode lifespan (Chin et al ., 2014). Binding by α‐ketoglutarate reduced complex V activity, decreased oxygen consumption, and increased autophagy.…”