BMAL1 and obesity due to melanocortin 4 receptor deficiency: In the liver, circadian mRNA and protein expression of clock genes such as PER1, PER2, BMAL1 and CLOCK and circadian-related metabolic regulators, such as AMPK, lipogenic enzymes, and gluconeogenic proteins are changed in response to HFD feeding, leading to obesity and insulin resistance (29, 31).