Abstract Body (Do not enter title and authors here): Background: Inulin is a non-digestible prebiotic dietary fiber that can promote metabolic health including reduced body weight and improved glucose metabolism via effects on gut microbiota. We hypothesize that inulin prevents obesity-associated cardiometabolic alterations by augmenting the production of short-chain fatty acids (SCFA) from gut microbiota, which activate free fatty acid receptor 2 (FFAR2), a major SCFA receptor, in murine adipose tissue.
Methods: 8-week-old male C57BL/6J (wild-type, WT; n=34) and adipocyte FFAR2-knockout (Ad-FFAR2 KO; n=25) mice were fed a high-fat high-sucrose (HFHS) diet for 8 weeks, then randomized into experimental groups to receive either continued HFHS (n=8-13), or HFHS containing inulin (10% w/w chicory root inulin; n=17-21) for a further 5 weeks. Body weight was recorded weekly, food intake, body composition, and indirect calorimetry were assessed before and after the inulin intervention, and intraperitoneal glucose and insulin tolerance tests were performed. Subcutaneous and visceral white adipose tissue (WAT) samples were collected at the study termination.
Results: HFHS-fed Ad-FFAR2 KO mice showed higher body weight (7.4%), fat mass, and WAT weight due to increased food intake, with worse glucose tolerance compared to WT mice. In WT mice, inulin significantly reduced body weight gain and body adiposity. These effects were associated with reduced locomotor activity and respiratory quotient (RQ) without effects on energy expenditure and were accompanied by improvements in glucose tolerance. Strikingly, inulin had no effect on body weight or body adiposity in Ad-FFAR2 KO mice but reduced RQ, locomotor activity, and improved glucose tolerance similar to WT mice.
Conclusions: Our findings suggest that FFAR2 signaling in adipose tissue is crucial for improving cardiometabolic outcomes in obesity and that gut metabolites responsive to dietary interventions, such as inulin, are potential targets for obesity treatment strategies.