PER2 and obesity due to melanocortin 4 receptor deficiency: Interestingly, in whole fat tissue of mice with high fat induced obesity both Clock and Bmal1 genes presented a different tendency with a significant attenuated expression profile during 24 h while Per2 expression diminish only selective during the night period [21], while CLOCK Δ19 and BMAL1(−/−) clock disruption determines low levels of FFA and glycerol with accumulation of triglycerides and increased adiposity [22].