Lymphotoxin regulates commensal responses to enable diet-induced obesity

Abstract

Innate immune responses influence the composition of gut microbiota. Fu and colleagues show that weight gain incurred with high-fat diets is dependent on intact lymphotoxin signaling that regulates IL-23 and IL-22 production. Microbiota are essential for weight gain in mouse models of diet-induced obesity (DIO), but the pathways that cause the microbiota to induce weight gain are unknown. We report that mice deficient in lymphotoxin, a key molecule in gut immunity, were resistant to DIO. Ltbr−/− mice had different microbial community composition compared to their heterozygous littermates, including an overgrowth of segmented filamentous bacteria (SFB). Furthermore, cecal transplantation conferred leanness to germ-free recipients. Housing Ltbr−/− mice with their obese siblings rescued weight gain in Ltbr−/− mice, demonstrating the communicability of the obese phenotype. Ltbr−/− mice lacked interleukin 23 (IL-23) and IL-22, which can regulate SFB. Mice deficient in these pathways also resisted DIO, demonstrating that intact mucosal immunity guides diet-induced changes to the microbiota to enable obesity.