The gut microbiota as a versatile immunomodulator in obesity and associated metabolic disorders

Obesity has reached epidemic proportions and is associated with chronic-low-grade inflammation and metabolic morbidities. Energy-dense diets and a sedentary lifestyle are determinants of obesity. The gut microbiome is a novel biological factor involved in obesity via interactions with the host and the diet. The gut microbiome act as a synergistic force protecting or aggravating the effects of the diet on the metabolic phenotype. The role of the microbiome in the regulation of intestinal and systemic immunity is one of the mechanisms by which it contributes to the host's response to the diet and to the pathophysiology of diet-induced obesity. Here, we review the mechanisms whereby “obesogenic” diets and the microbiome impact immunity, locally and systemically, focusing on the consequences in the gut–adipose tissue axis. We also review the structural and microbial metabolites that influence immunity and how advances in this field could help design microbiome-informed strategies to tackle obesity-related disorders more effectively.This study has been supported by the European Marie Skłodowska-Curie Action of H2020 MicroILCs (grant agreement: 890545) and the Spanish Ministry of Science and Innovation (MICINN) (grant AGL2017-88801-P). The FPU contract to R L-G from Spanish Ministry of Universities and the contract of Garantía Juvenil to CB-V from MICINN are fully acknowledged.Peer reviewe