Chronic Ketosis Modulates HIF1α-Mediated Inflammatory Response in Rat Brain

Hypoxia inducible factor alpha (HIF1α) is associated with neuroprotection conferred by diet-induced ketosis, but the underlying mechanism remains unclear. In this study, we use a ketogenic diet in rodents to induce a metabolic state of chronic ketosis, as measured by elevated blood ketone bodies. Chronic ketosis correlates with neuroprotection in both aged and following focal cerebral ischemia and reperfusion (via middle cerebral artery occlusion, MCAO) in mouse and rat models. Ketone bodies are known to be used efficiently by the brain, and metabolism of ketone bodies is associated with increased cytosolic succinate levels that inhibits prolyl hydroxylases allowing HIF1α to accumulate. Ketosis also regulates inflammatory pathways, and HIF1α is reported to be essential for gene expression of interleukin 10 (IL10). Therefore, we hypothesized that ketosis-stabilized HIF1α modulates the expression of inflammatory cytokines orchestrating neuroprotection. To test changes in cytokine levels in rodent brain, 8-week-rats were fed either the standard chow diet (SD) or the KG diet for 4 weeks before ischemia experiments (MCAO) were performed and the brain tissues were collected. Consistent with our hypothesis, immunoblotting analysis shows IL10 levels were significantly higher in KG diet rat brain compared to SD, whereas the TNFα and IL6 levels were significantly lower in the brains of KG diet-fed group.