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.

It has recently been hypothesized that hepatocyte CHO metabolites (hexose-or triose-phosphates) might not only stimulate ChREBP and activate DNL, but might also serve as a signal to enhance HGP (17,18). This hypothesis derives in part from the counterintuitive observation that while ChREBP is known to stimulate glycolysis through transactivation of glycolytic genes (22), it may also transactivate expression of G6pc encoding the enzyme er, from skeletal muscle and adipose tissue enhances hepatic DNL (20). Additionally, siRNA-mediated knockdown of ChREBP in ob/ob mice decreases hepatic DNL in the setting of persistent hyperinsulinemia (21). Thus, hepatic DNL may be regulated by increased substrate delivery independently of insulin signaling. However, whether increasing intrahepatic CHO metabolites might also signal to increase glucose production has not been fully explored.

Despite containing an α-amino acid, the versatile cofactor S-adenosylmethionine (SAM) is not a known building block for non-ribosomal peptide synthetase (NRPS) assembly lines. Here we report an unusual NRPS module from colibactin biosynthesis that uses SAM for amide bond formation and subsequent cyclopropanation. Our findings showcase a new use for SAM and reveal a novel biosynthetic route to a functional group that likely mediates colibactin’s genotoxicity.

The accumulation of amyloid ␤ (A␤) in Alzheimer's disease is caused by an imbalance of production and clearance, which leads to increased soluble A␤ species and extracellular plaque formation in the brain. Multiple A␤-lowering therapies are currently in development: an important goal is to characterize the molecular mechanisms of action and effects on physiological processing of A␤, as well as other amyloid precursor protein (APP) metabolites, in models which approximate human A␤ physiology. To this end, we report the translation of the human in vivo stable-isotope-labeling kinetics (SILK) method to a rhesus monkey cisterna magna ported (CMP) nonhuman primate model, and use the model to test the mechanisms of action of a ␥-secretase inhibitor (GSI). A major concern of inhibiting the enzymes which produce A␤ (␤-and ␥-secretase) is that precursors of A␤ may accumulate and cause a rapid increase in A␤ production when enzyme inhibition discontinues. In this study, the GSI MK-0752 was administered to conscious CMP rhesus monkeys in conjunction with in vivo stable-isotope-labeling, and dose-dependently reduced newly generated CNS A␤. In contrast to systemic A␤ metabolism, CNS A␤ production was not increased after the GSI was cleared. These results indicate that most of the CNS APP was metabolized to products other than A␤, including C-terminal truncated forms of A␤: 1-14, 1-15 and 1-16; this demonstrates an alternative degradation pathway for CNS amyloid precursor protein during ␥-secretase inhibition.

Apolipoprotein E (ApoE) is the strongest genetic risk factor for Alzheimer’s disease and has been implicated in the risk for other neurological disorders. The three common ApoE isoforms (ApoE2, E3, and E4) each differ by a single amino acid, with ApoE4 increasing and ApoE2 decreasing the risk of Alzheimer’s disease (AD). Both the isoform and amount of ApoE in the brain modulate AD pathology by altering the extent of amyloid beta (Aβ) peptide deposition. Therefore, quantifying ApoE isoform production and clearance rates may advance our understanding of the role of ApoE in health and disease. To measure the kinetics of ApoE in the central nervous system (CNS), we applied in vivo stable isotope labeling to quantify the fractional turnover rates of ApoE isoforms in 18 cognitively-normal adults and in ApoE3 and ApoE4 targeted-replacement mice. No isoform-specific differences in CNS ApoE3 and ApoE4 turnover rates were observed when measured in human CSF or mouse brain. However, CNS and peripheral ApoE isoform turnover rates differed substantially, which is consistent with previous reports and suggests that the pathways responsible for ApoE metabolism are different in the CNS and the periphery. We also demonstrate a slower turnover rate for CSF ApoE than that for amyloid beta, another molecule critically important in AD pathogenesis.