Two human metabolites rescue a C. elegans model of Alzheimer’s disease via a cytosolic unfolded protein response

Age-related changes in cellular metabolism can affect brain homeostasis, creating conditions that are permissive to the onset and progression of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Although the roles of metabolites have been extensively studied with regard to cellular signaling pathways, their effects on protein aggregation remain relatively unexplored. By computationally analysing the Human Metabolome Database, we identified two endogenous metabolites, carnosine and kynurenic acid, that inhibit the aggregation of the amyloid beta peptide (A beta) and rescue a C. elegans model of Alzheimer's disease. We found that these metabolites act by triggering a cytosolic unfolded protein response through the transcription factor HSF-1 and downstream chaperones HSP40/J-proteins DNJ-12 and DNJ-19. These results help rationalise previous observations regarding the possible anti-ageing benefits of these metabolites by providing a mechanism for their action. Taken together, our findings provide a link between metabolite homeostasis and protein homeostasis, which could inspire preventative interventions against neurodegenerative disorders. Joshi et al. identify two human metabolites, carnosine and kynurenic acid, that rescue a C. elegans model of Alzheimer's disease by inhibiting the aggregation of the amyloid beta peptide in vivo. They find that these metabolites trigger a cytosolic unfolded protein response through the transcription factor HSF-1 and molecular chaperones DNJ-12 and DNJ-19, thus providing mechanistic links between metabolite homeostasis and protein homeostasis to further insights into interventions against neurodegenerative diseases.