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Metabolic stress is a primary pathogenic event in transgenic Caenorhabditis elegans expressing pan-neuronal human amyloid beta

Teo E1,2, Ravi S3,4, Barardo D2,5, Kim HS2, Fong S6, Cazenave-Gassiot A, Tan TY, Ching J, Kovalik JP, Wenk MR, Gunawan R, Moore PK, Halliwell B, Tolwinski N, Gruber J (2019) Elife.  2019 Oct;8. pii: e50069. doi: 10.7554/eLife.50069. 

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Alzheimer's disease (AD) is the most common neurodegenerative disease affecting the elderly worldwide. Mitochondrial dysfunction has been proposed as a key event in the etiology of AD. We have previously modeled amyloid-beta (Aβ)-induced mitochondrial dysfunction in a transgenic Caenorhabditis elegans strain by expressing human Aβ peptide specifically in neurons (GRU102).

Here, we focus on the deeper 
metabolic changes associated with this Aβ-induced mitochondrial dysfunction. Integrating metabolomics, transcriptomics and computational modeling, we identify alterations in Tricarboxylic Acid (TCA) cycle metabolism following even low-level Aβ expression. In particular, GRU102 showed reduced activity of a rate-limiting TCA cycle enzyme, alpha-ketoglutarate dehydrogenase. These defects were associated with elevation of protein carbonyl content specifically in mitochondria. Importantly, metabolic failure occurred before any significant increase in global protein aggregate was detectable. Treatment with an anti-diabetes drug, Metformin, reversed Aβ-induced metabolic defects, reduced protein aggregation and normalized lifespan of GRU102.

Our results point to 
metabolic dysfunction as an early and causative event in Aβ-induced pathology and a promising target for intervention.