Oxytocin receptor-deficient mice developed late-onset obesity

The oxytocin receptor has been suggested to be involved in energy metabolism, such as food intake and energy consumption. Here, we demonstrate that oxytocin receptor-deficient (Oxtr(-/-)) male mice exhibited late-onset obesity with increases in abdominal fat pads and fasting plasma triglycerides. Daily food intake and spontaneous motor activity of Oxtr(-/-) mice were not significantly different as compared with wild-type mice. In contrast, brown adipose tissue in Oxtr(-/-) mice contained large lipid droplets and cold-induced thermogenesis was impaired. This study demonstrates that oxytocin receptor plays essential roles in the regulation of energy homeostasis.