Impact of ketone bodies on age-related inflammation and healthspan extension

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Project Summary Aging is characterized by systemic chronic low-grade inflammation. The basic mechanisms leading to this inflammation are unknown, making it impossible to develop targeted therapies to prevent chronic disease in the elderly. While the precise source of this increased inflammation is not known, a primary candidate is the NLRP3 inflammasome. Activation of inflammasomes is a highly regulated process that requires two signals leading to activation of caspase-1 and secretion of the proinflammatory cytokines IL-1β and IL-18 from innate immune cells. Aberrant activation of the NLRP3 inflammasome contributes to chronic inflammation as old mice with genetic deletion of NLRP3 are protected from age-related diseases that limit healthspan, including cognitive decline, metabolic disease, bone loss, and immune senescence. Lifespan-extending interventions such as calorie restriction reduce NLRP3 activation and are characterized by a metabolic adaptation that leads to increased production of the ketone body β-hydroxybutyrate (BHB). Importantly, BHB is sufficient to inhibit NLRP3 activation in innate immune cells from aged mice and humans. The overall hypothesis of this proposal is that the negative regulatory effects of BHB upon NLRP3 activation can alleviate dysregulated inflammation during aging. This hypothesis will be tested in two aims: (1) Determine the protective role of ketones in dysregulated inflammatory responses against infection (1a) or chronic sterile inflammation in visceral adipose tissue (1b); and (2) Define cellular metabolic changes during aging that regulate innate immune inflammation. Acute inflammatory responses will be evaluated in lung infections or lung injury models. Sterile inflammation will be evaluated in visceral adipose tissue by leukocytosis, pro-inflammatory immune profiles, and ensuing metabolic health will be tested by glucose and insulin tolerance tests. The ketogenic pathway is being targeted by conditional deletion of ketogenic enzyme in innate immune cell subsets including neutrophils and macropages. The proposal also seeks additional scientific training for the candidate in experimental methods, including in vitro assays, CyTOF, and RNAseq analysis. This proposal also incorporates training in professional development including responsible conduct of research, teaching experience, grant writing, and leadership opportunities. Completion of these objectives will make the candidate ideally suited for obtaining a tenure-track faculty position and becoming an independent scientist. These studies will highlight BHB as a regulatory metabolite that coordinates metabolism with the immune system to dampen inflammation. The long- term goal of this application is to prepare the candidate for transition to an independent scientific career studying innate immune origins and regulation of inflammation during aging, ultimately identifying novel therapeutic targets to decrease age-related inflammation and extend healthspan.