Gut mycobiome core species causally modulate metabolic health in mice

The gut microbiome causally contributes to obesity; however, the role of fungi remains understudied. We previously identified three core species of the infant gut mycobiome ( Rhodotorula mucilaginosa , Malassezia restricta and Candida albicans ) that correlated with body mass index, however their causal contributions to obesity development are unknown. In gnotobiotic mice, we evaluated the effects of early-life colonization by these fungal species on metabolic health in mice fed standard (SD) or high-fat-high-sucrose (HFHS) diets. Each species resulted in bacterial microbiome compositional and functional differences. R. mucilaginosa and M. restricta increased adiposity in mice fed SD, while only R. mucilaginosa exacerbated metabolic disease. In contrast, C. albicans resulted in leanness and resistance to diet-induced obesity. This phenotype was accompanied by enhanced white adipose tissue inflammation (type 1 and type 17 responses). This work revealed that three common fungal colonizers have distinct causal influences on obesity and metabolic inflammation and justifies the consideration of fungi in microbiome research on host metabolism.