Importantly, circadian disruption—due to factors such as shift work, sleep deprivation, or irregular eating patterns—has been shown to impair HDAC and SIRT activity, disrupt BHB production, and predispose individuals to metabolic diseases, including non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, and Type 2 Diabetes Mellitus (T2D). The gene discussed is HDAC9; the disease is type 2 diabetes mellitus.