Effect of NADK overexpression on NADK mRNA (A), total (NADPH + NADP+) levels (B), NADPH/(NADPH + NADP+) ratio (C), insulin secretion (D), and NADH/(NADH + NAD+) and ATP/ADP ratio (E) in INS-1 832/13 cells. Nucleotides were determined using NADPH/NADP+, NADH/NAD+, and ATP/ADP kits (Abcam, Cambridge, MA) according to the manufacturer's protocol. Insulin secretion was determined by ELISA (Alpco, Salem, NH). Data are means ± SE from 3–5 independent experiments performed in duplicate or triplicate measurements. 2G, 2 mM glucose; 16G, 16 mM glucose. *P < 0.05 NADK(+) vs. NADK control; #P < 0.05 2G vs. 16G.