Mechanism of Ketogenic Diet: Impact of Beta – Hydroxybutyrate and Decanoic Acid on Sirtuins, Energy Metabolism and Cellular Lipids in a Murine Hippocampal Neuronal Cell Model

Ketogenic diet (KD), is a high-fat, low-carbohydrate diet used in the treatment of pharmaco refractory epilepsy, inborn errors of metabolism, neurodegenerative disorders, and cancer. Although several mechanisms of action have been proposed for KD, the exact molecular and biochemical pathways have not been completely elucidated. Sirtuins (SIRT), a group of seven NAD+-dependent enzymes regulate vital cellular functions like mitochondrial respiratory chain (MRC)/oxidative phosphorylation, fatty acid oxidation, glucose metabolism and detoxification of reactive oxygen species (ROS). These mechanisms are altered under KD treatment and are amongst the mechanisms proposed to mediate the anti-epileptic and neuroprotective effects of the KD. In this research, we hypothesized that sirtuins mediate the action of KD and that energy metabolism and lipid composition in neurons is altered under KD treatment. Hippocampal murine neurons (HT22 cell line) were cultured under standard or low glucose conditions and further incubated with KD metabolites – either beta-hydroxybutyrate (BHB) or decanoic acid (C10). Sirtuins 1 – 4, MRC complexes and cellular lipids were analyzed in control (untreated) and KD incubated groups. BHB and C10 incubated cells showed an upregulation of SIRT1 and SIRT3, higher MRC and citrate synthase enzyme capacities. Incubation with both the KD metabolites led to reduction in cellular cholesterol, while C10 incubation led to higher quantities of cellular phospholipids and sphingomyelin. Phospholipids to cholesterol ratios in neurons were significantly altered under BHB and C10 incubations. Upregulation of sirtuins, MRC and alteration of cellular lipids may contribute to the mechanism of action of KD.