CYP46A1 activation by low-dose efavirenz uncovers the link between brain cholesterol metabolism, energetics, and vasculature

CYP46A1 converts cholesterol to 24-hydroxycholesterol, the principal mechanism for brain cholesterol removal and turnover. CYP46A1 can be allosterically activated with low-dose anti-HIV drug efavirenz and mitigate the manifestations of various neurologic diseases in mouse models and Niemann-Pick type C disease in humans. Yet the underlying reasons for such a broad range of efavirenz therapeutic effects are currently unknown. Here 5XFAD mice, a model of Alzheimer's disease, were treated with low-dose efavirenz, and assessed for changes in their brain proteome, acetylproteome, and metabolome. Sex-independent increases in brain levels of phosphatidylcholines, sphingomyelins, and certain amino acids were documented, and various functional enrichments were identified. The most notable related to brain energy production, vascularization, and prevention of glutamatergic overactivation. Unexpectedly, these and many other enrichments were mediated by different proteins in female and male 5XFAD mice. Efavirenz treatment of 5XFAD mice was repeated, and energy-related compounds were quantified in the brain after in vivo isotopic labeling. Cerebral vasculature was assessed as well. We found increased glycolysis branching, carbon flux through the tricarboxylic acid cycle, and use of alternative energy sources (fatty acids, ketone bodies, and amino acids). Sex-independent improvements in brain vascularization and integrity of the blood-brain barrier were also documented. Collectively, our data suggested that CYP46A1 activation by efavirenz increases brain metabolic flexibility and thereby brain energetics. This enables the increase in production of the building blocks for cellular and tissue repair and rescue of brain pathology, thus explaining the therapeutic benefits for the broad spectrum of neurologic disorders.