Effects of Fructooligosacharides on western diet-induced hypothalamic inflammation - This proposal focuses on dietary fiber supplementation, a promising way to help people lose weight and lower their risk of heart disease. These beneficial effects of fiber are largely attributed to the products of its fermentation by the gut microbiota, the Short-Chain Fatty Acids (SCFAs). The body can detect these SCFAs through mainly two receptors: Free Fatty Acid 2 and 3 (FFA2/FFA3). Interestingly, SCFAs can act directly on the central nervous system (CNS) to regulate energy balance and improve inflammation. On the last decade, high fat diet (HFD)-induced obesity has been associated with an inflammatory response orchestrated by the CNS resident microglia that appears on the hypothalamus on the first days of HFD feeding. Notably, blocking inflammation in microglia prevents diet induced obesity (DIO). These findings suggest that early onset inflammation in hypothalamic microglia plays a major role in the pathogenesis of DIO. Recently, we found that adding the fiber Fructooligosacharides (FOS) to a western diet (High Fat-High Sugar) for 8 weeks in mice, increased SCFAs in the blood, prevented weight gain and reduced hypothalamic inflammation markers. Curiously, we observed similar anti-inflammatory effects on the hypothalamus at the first day of diet. Interestingly, these effects were associated with decreased bodyweight gain and fat accumulation at the first week of treatment. These findings indicate that early blocking of hypothalamic inflammation may mediate the effects of fibers. However, the specific mechanisms remain unknown. Based on these results, we hypothesize that dietary fiber supplementation prevents western diet-induced obesity by reducing the inflammatory activation of hypothalamic microglia through modulating SCFAs-FFA2/3 signaling. We proposed to test if dietary fiber effects are mediated by SCFAs-FFA2/FFA3 signaling by using gut microbiota depleted (no SCFAs production) and FFA2/FFA3 double knock out mice models. Second, we propose to test if FOS supplementation inhibits microglia inflammatory activation to prevent acute hypothalamic inflammation and DIO in a mouse model with chemogenetic activation of microglial inflammatory signaling. Finally, we propose to study the effects of WD and FOS supplementation on the transcriptome of hypothalamic glia using two innovative technologies: PiP-seq scRNA17 for single cell resolution and translating ribosome affinity purification (TRAP) on microglial-specific cre-lines for microglia focused analysis. For the completion of the aims outlined above, the candidate counts with a unique background in transcriptomic and dietary strategies to treat metabolic syndrome. The mentoring team is composed of 5 experts: Pingwen Xu (Mentor), Terry Unterman (Co-mentor), Brian Layden (Co-mentor), Martin Valdearcos (consultant) and Mauricio Dorfman (consultant). Results from this proposal will increase our understanding in the mechanism by which FOS exerts beneficial metabolic effects. This is a crucial step for the design of new therapeutics to prevent/treat obesity based in FOS supplementation or related molecular pathways.
