Impact of Raising B-OHB Directly With MCT Oil on NLPR3 Inflammasome Activation in Healthy, Young Adults

The potential for a ketogenic diet to reduce inflammation has become increasingly popular in recent years, but direct scientific evidence to demonstrate that ketones impact inflammatory mechanisms in humans does not exist. B-hydroxybutyrate (B-OHB) is the most abundant circulating ketone and recent evidence indicates that B-OHB may be able to act as a direct signal to inhibit cellular pathways involved in inflammation.

B-OHB can be raised naturally by induction of nutritional ketosis, which is a normal physiological response to severe reductions in carbohydrate or caloric intake. In this state, free fatty acids are converted to ketone bodies (primarily B-hydroxybutyrate [B-OHB]) by the liver in order to provide essential fuel for metabolically active tissues. However, determining the direct effects of B-OHB in human ketogenic diet studies is difficult due to the numerous metabolic adaptations that occur in nutritional ketosis (e.g., reduced insulin, elevated free fatty acids, stable glucose) and the propensity for participants to lose body and fat mass over longer period.

B-OHB can also be raised independent of diet by supplementation with medium chain triglyceride (MCT) oil, allowing for induction of ketosis without the additional metabolic adaptations. In addition to being an important fuel source, recent interest has focused on a potential signaling role for B-OHB with cell culture and animal studies describing anti-inflammatory, anti-oxidant, and anti-cancer effects. The cellular pathways through which B-OHB is proposed to reduce inflammation, include the NLPR3 inflammasome and histone deacetylases (HDACs), both of which play important roles in regulating cellular inflammation. The NLRP3 inflammasome pathway is an immune complex which, upon activation, initiates downstream pro-inflammatory cascades including the activation of caspase-1 and interleukin (IL)-1B. These pro-inflammatory cascades have been implicated in the propagation of sterile inflammation, which has been identified as a major contributor to certain chronic inflammatory diseases such as type 2 diabetes and atherosclerosis. HDACs are enzymes typically found within the nucleus and have the ability to regulate signaling through innate immune pathways. B-OHB has been shown to have the ability to inhibit HDACs, and consequently has the potential to decrease oxidative stress and inflammation. The NLRP3 inflammasome and HDACs are responsive to the intracellular nutritional milieu and thus their activity may be able to be modulated through increases in B-OHB.

The use of MCT oil supplements will allow the investigators to raise blood B-OHB independent of diet, and thus directly test the immunomodulatory effects of B-OHB in healthy, adult males. This fundamental research is needed to understand whether ketones have direct immunomodulatory effects or if it is the widespread systemic metabolic adaptation to a ketogenic diet that might impact inflammatory processes.

The overall objective of this pilot study is to determine if directly raising B-OHB through supplementation with MCT oil impacts innate immune cell function and/or phenotype. Based on previous cell culture and animal research showing that B-OHB can reduce pro-inflammatory signaling, it is hypothesized that raising B-OHB with MCT oil supplementation will result in a attenuation of caspase-1 activation and mature IL-1B secretion, both markers of NLRP3 inflammasome activation. Additionally, it is hypothesized that raised B-OHB will result in greater histone acetylation, as B-OHB has been shown to be an HDAC inhibitor.