Brown and Beige Fat: Therapeutic Potential in Obesity

BACKGROUND: The epidemic of obesity and type 2 diabetes presents a serious challenge to scientific and biomedical communities worldwide. There has been an upsurge of interest in the adipocyte coincident with the onset of the obesity epidemic and the realization that adipose tissue plays a major role in the regulation of metabolic function. CONTENT: Adipose tissue, best known for its role in fat storage, can also suppress weight gain and metabolic disease through the action of specialized, heat-producing adipocytes. Brown adipocytes are located in dedicated depots and express constitutively high levels of thermogenic genes, whereas inducible ‘brown-like’ adipocytes, also known as beige cells, develop in white fat in response to various activators. The activities of brown and beige fat cells reduce metabolic disease, including obesity, in mice and correlate with leanness in humans. Many genes and pathways that regulate brown and beige adipocyte biology have now been identified, providing a variety of promising therapeutic targets for metabolic disease. SUMMARY: The complexity of adipose tissue presents numerous challenges but also several opportunities for therapeutic intervention. There is persuasive evidence from animal models that enhancement of the function of brown adipocytes, beige adipocytes or both in humans could be very effective for treating type 2 diabetes and obesity. Moreover, there are now an extensive variety of factors and pathways that could potentially be targeted for therapeutic effects. In particular, the discoveries of circulating factors, such as irisin, fibroblast growth factor (FGF)21 and natriuretic peptides, that enhance brown and beige fat function in mice have garnered tremendous interest. Certainly, the next decade will see massive efforts to use beige and brown fat to ameliorate human metabolic disease. KEYWORDS: obesity, white adipose tissue, brown adipose tissue, beige adipose tissue, adipose organ, thermogenesis, energy expenditure