Chemokine receptors on the defensive - the surprising role of CXCR4 in brown adipose tissue

Obesity, which is triggered by over-nutrition and supported by the excessive expansion of adipose tissue due to hyperplasia and hypertrophy, has been linked to an increased incidence of type 2 diabetes, hypertension, cardiovascular disease and cancer. Since obesity-induced co-morbidities impose a significant financial burden on healthcare systems in Western societies, clear understanding of molecules and mechanisms supporting physiologic and pathologic activities of adipose tissue is mandatory. Abundant evidence shows that development of obesity is facilitated by a low-grade inflammation fueled by infiltration of pro-inflammatory leukocytes into white adipose tissue pads, which is in part mediated by chemokines and chemokine receptors.  However, not all members of the chemokine system facilitate development of obesity. In this publication we highlight a surprising role of CXCR4 in fat cells where this chemokine receptor promotes energy expenditure and prevents excessive inflammatory leukocyte recruitment into adipose tissue, and by so doing, limits obesity.