In relation to cellular metabolism, metformin has been reported to foster SIRT1 activity to maintain proper circadian rhythm of CLOCK and BMAL1 during obesity, since the absence of SIRT1 inhibits function of CLOCK and BMAL1 in an obese phenotype (Caton et al., 2011[25]). The gene discussed is SIRT1; the disease is obesity due to melanocortin 4 receptor deficiency.