β-hydroxybutyrate Protects Against Oxidative Insult and Inflammation via Sirtuin1

Objectives: Chronic inflammation is a leading cause of pathogenesis within the oral cavity. Intriguingly, β-hydroxybutyrate (βHB), a major metabolite from consuming a ketogenic diet, alleviates progression of neuroinflammation. Expanding links between oral and neurological disorders suggest that activation of nicotinamide adenine dinucleotide-dependent deacetylase Situin1 (Sirt1) may attenuate inflammation and neuronal injury. However, whether the Sirt1 is essential for βHB action has yet to be elucidated. The purpose of this study was to investigate whether βHB can affect Sirt1 expression and whether this action underlies βHB-induced disease modifying effects.
Methods: Using in vitro cell culture of HT22 hippocampal neurons, BV2 microglia, and human gingival fibroblasts (HGF), we tested (1) the mRNA expression level of Sirt1 following exposure to βHB for 24 hr; and (2) changes in mRNA cytokine expression and neuronal cell viability after co-applied with either βHB or these compounds: [1µg/ml] lipopolysaccharide (LPS; an endotoxin), [250 µM] hydrogen peroxide (H₂O₂), and [10 µM] EX527 (a Sirt1 blocker). They were monitored using MTT assays and real time-PCR through analysis of genomic DNA using primers for tumor necrosis factor (TNF)-α, Interleukin (IL)-6, IL-1β, and Sirt1.
Results: In both HT22 and HGF cells, βHB elevated cell viability while administering H₂O₂ or LPS. LPS elevated the release of inflammatory cytokines in HGF cells, whereas this effect was strongly suppressed by βHB administration. PCR analysis from BV2 cells yielded a reduction in inflammatory cytokines compatible with a significant increase in the expression of Sirt1. EX527 exhibited partial inhibition in βHB-induced neuroprotective effects.
Conclusions: This study has shown that ketones produce anti-inflammatory and neuroprotective effects via the regulation of inflammatory cytokines and the promotion of Sirt1. Further research is needed to uncover the mechanisms behind this action and effects on a systemic level modeling neurodegenerative disease and periodontal disease.