DDHD2 provides a flux of saturated fatty acids for neuronal energy and function

Although fatty acids support mitochondrial ATP production in most tissues, neurons are believed to rely exclusively on glucose for energy. Here we show that genetic ablation of the triglyceride and phospholipid lipase Ddhd2 impairs mitochondrial respiration and ATP synthesis in cultured neurons, despite increased glycolysis. This defect arises from reduced levels of long-chain saturated free fatty acids, particularly myristic, palmitic and stearic acids, normally released in an activity-dependent manner by Ddhd2. Inhibition of mitochondrial fatty acid import in wild-type neurons similarly reduced mitochondrial respiration and ATP production. Saturated fatty acyl-coenzyme A treatment restored mitochondrial energy production in Ddhd2 knockout neurons. When provided in combination, these activated fatty acyl-CoA supplements also rescued defects in membrane trafficking, synaptic function and protein homeostasis. These findings uncover that neurons perform β-oxidation of endogenous long-chain free fatty acids to meet ATP demands and reveal a potential therapeutic strategy for hereditary spastic paraplegia 54 caused by DDHD2 mutations.