Cyb5r3 Regulates β-cell Secretory and Mitochondrial Function (A) Glucose-induced insulin secretion in Min6 cells transduced with Ad-shCyb5r3 or Ad-shScramble. (B) Basal respiration in Min6 cells stably expressing GFP, shCyb5r3, or shCyb5r4. (C–F) ETC complex I-IV activity in mitochondrial fractions, (G) ROS levels in the presence or absence of 0.5 mM palmitate, (H) NAD/NADH ratios, (I) NADH levels, and (J) Lactate levels in Min6 cells transduced with Ad-shCyb or Ad-shScr. All data are presented as means ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 by Student t test. All experiments were performed at least three times unless otherwise indicated.