Ccr7 null mice are protected against diet-induced obesity via Ucp1 upregulation and enhanced energy expenditure

The chemokine receptor CCR7, expressed on various immune cells, is associated with cell migration and lympho-node homing. Mice lacking Ccr7 are protected from diet-induced obesity and subsequent insulin resistance. We evaluated the mechanism underlying these protective effects from the standpoint of energy expenditure. Wild-type and Ccr7 null mice were fed a high-fat diet, and the regulation of energy metabolism and energy metabolism-related molecules, e.g., Ucp1, , and , were evaluated. Food intake did not differ between groups. O consumption and CO production were higher in Ccr7 null mice than in wild-type mice, despite a similar respiratory quotient and glucose and lipid utilization, suggesting that energy expenditure increased in Ccr7 null mice via enhanced metabolism. In white adipose tissues of Ccr7 null mice, , , , , and expression increased. Similarly, in brown adipose tissues of Ccr7 null mice, , , , , and expression increased. In both white and brown adipose tissues, Ucp1 gene and protein expression levels were higher in null mice than in wild-type mice. In Ccr7 null mice, browning of white adipocytes as well as the activation of brown adipocytes cause enhanced energy metabolism, resulting in protection against diet-induced obesity.