Peroxisomes orchestrate metabolic flexibility and longevity via an interorganelle cascade.

Aging impairs coordinated organelle dynamics essential for lipid metabolism, causing a decline in intracellular metabolic flexibility. However, the drivers of organelle collapse and their temporal order remain unclear. Here we identify peroxisomal function as a critical regulator of metabolic flexibility during youth and low-energy states. Using Caenorhabditis elegans, we show that fasting robustly induces peroxisomal function in youth, whereas this response is blunted during aging. Loss of peroxisomal import via PRX-5 declines over age, causing pathological lipid droplet expansion, dysfunctional mitochondrial bioenergetics and metabolic inflexibility. Although targeted PRX-5 degradation recapitulates metabolic aging, its overexpression preserves lipid dynamics and mitochondrial integrity. Notably, dietary restriction maintains peroxisomal pathways and organelle coordination into late life and peroxisomal function causally underpins dietary restriction-mediated longevity. Our findings highlight peroxisomes as central upstream regulators of a dynamic interorganelle cascade driving metabolic plasticity and highlight peroxisomal maintenance as a key determinant of metabolic flexibility during aging.