CLOCK and obesity due to melanocortin 4 receptor deficiency: Cardiomyocyte-specific circadian Clock mutant (CCM) mice reveal Clock as the direct regulator of triglyceride metabolism in the heart [22] and an adipocyte-specific deletion of Arntl in mice results in obesity [23], which is associated with a reduced number of polyunsaturated fatty acids in adipocyte triglycerides.