The role of immune responses and microbiota in adipose tissue homeostasis

White and brown adipose tissue form a metabolic organ that plays a crucial role in regulating body energy homeostasis. Adipose tissue is richly vascularized and innervated to respond to a variety of environmental signals. Adipose tissue also contains diverse populations of innate and adaptive immune cells. These immune cells contribute to the regulation of adipose tissue function, and adipocytes in turn signal to immune cells in response to metabolic and environmental triggers. The gut microbiota have recently emerged as an additional factor that affects adipose tissue homeostasis. This can occur either directly via metabolites and bacterial products or indirectly via its effects on immune cells. Natural, co-evolved microbiota, if encountered in early postnatal life, have been shown to confer protection against obesity in later periods of life. The complexity of these factors and interactions warrants further investigation and may ultimately provide opportunities for therapeutic interventions that prevent obesity and metabolic disease.