Abstract
The ketogenic diet (KD) is a high fat, adequate protein, low carbohydrate diet that has been used clinically to treat refractory pediatric epilepsy for nearly a century. Emerging evidence suggests that the KD is broadly neuroprotective and health‐promoting; therefore, it is now being investigated as a preventative strategy and/or treatment for a wide variety of disorders, including many neurological diseases, cancer, obesity, and diabetes, as well as for enhancing athletic performance and human resilience capabilities. Recently, studies have revealed that many of the beneficial effects associated with the KD are mechanistically attributable to the ketone bodies, leading our lab and others to develop and test exogenous ketone supplements (KS) which elevate blood ketones without the need for severe carbohydrate restriction. In order to further our understanding of this new technology, we sought to characterize the metabolic and physiologic effects, safety, and toxicity of KS in healthy rats. The KS tested included the R,S‐1,3‐butanediol acetoacetate diester, 1,3‐butanediol, medium chain triglyceride oil, caprylic acid, and beta‐hydroxybutyrate mineral salts, alone and in various combinations. Healthy rats were administered KS by oral gavage or in their food in an acute (once), sub‐chronic (1 month), or chronic (4 months) fashion, and were analyzed for a variety of metabolic and physiologic biomarkers. Acute and chronic KS rapidly elevated blood ketones to therapeutic levels (2–5mM) and simultaneously decreased blood glucose. Sub‐chronic KS treatment significantly altered the global metabolome. Medium chain fatty acids and dicarboxylic acids were elevated with KS treatment. Carnitine and deoxycarnitine was decreased with KS, while acetyl coA and acetylcarnitine were elevated, suggesting enhanced mitochondrial LCFA oxidation. Kreb's cycle intermediates, including citrate, succinate, and fumarate, were elevated with KS. The neurotransmitter adenosine was elevated with KS, while some purine nucleotide breakdown products were also elevated. Markers of both oxidative stress (oxidized glutathione) and antioxidant capacity (carnosine and anserine) were elevated by KS. Metabolites associated with the gut microbiome or nutrient absorption, such as indoleproprionate, 2‐hydroxyisobutyrate, and coprostanol, were altered. Inflammatory profiling following chronic KS administration revealed decreases in many pro‐inflammatory cytokines, including IL‐1β, IL‐6, IFN‐γ, MCP‐1, and RANTES. KS appears safe as there were no signs of toxicity or adverse changes in total cholesterol, HDL, LDL, triglycerides, or markers of liver/kidney function over the chronic treatment protocol. KS may be a useful alternative or adjuvant to the KD for disorders where nutritional ketosis is therapeutic.
