Acyl-CoA synthetase 6 is required for brain docosahexaenoic acid retention and neuroprotection during aging

The omega-3 fatty acid docosahexaenoic acid (DHA) inversely relates to neurological impairments with aging; however, limited nondietary models manipulating brain DHA have hindered a direct linkage. We discovered that loss of long-chain acyl-CoA synthetase 6 in mice (Acsl6(–/–)) depletes brain membrane phospholipid DHA levels, independent of diet. Here, Acsl6(–/–) brains contained lower DHA compared with controls across the life span. The loss of DHA- and increased arachidonate-enriched phospholipids were visualized by MALDI imaging predominantly in neuron-rich regions where single-molecule RNA in situ hybridization localized Acsl6 to neurons. ACSL6 is also astrocytic; however, we found that astrocyte-specific ACSL6 depletion did not alter membrane DHA because astrocytes express a non–DHA-preferring ACSL6 variant. Across the life span, Acsl6(–/–) mice exhibited hyperlocomotion, impairments in working spatial memory, and increased cholesterol biosynthesis genes. Aging caused Acsl6(–/–) brains to decrease the expression of membrane, bioenergetic, ribosomal, and synaptic genes and increase the expression of immune response genes. With age, the Acsl6(–/–) cerebellum became inflamed and gliotic. Together, our findings suggest that ACSL6 promotes membrane DHA enrichment in neurons, but not in astrocytes, and is important for neuronal DHA levels across the life span. The loss of ACSL6 impacts motor function, memory, and age-related neuroinflammation, reflecting the importance of neuronal ACSL6-mediated lipid metabolism across the life span.