The Qo site is an external quinol oxidation site on the intermembrane space side of the cytochrome bc1 complex (complex III), where ubiquinol is oxidized and can form a semiquinone intermediate, providing a recognized site for ROS generation (as opposed to the internal Qi site, where quinone is reduced).Clinical biopsies reveal that complex I activity in T2DM skeletal muscle is reduced by approximately 40%, showing a significant positive correlation with systemic insulin sensitivity (22). The gene discussed is INS; the disease is type 2 diabetes mellitus.