Nicotinamide overload may play a role in the development of type 2 diabetes

Figure 4 Effects of N¹-methylnicotinamide on H₂O₂ generation and NAD levels. A, B: Cumulative effects of nicotinamide (NM, 0.5 or 2 g/kg) and N¹-methylnicotinamide (NMN, 0.5 or 2 g/kg) on rat plasma H₂O₂ levels; C: H₂O₂ concentrations in the supernatant of cultured human erythrocytes with or without 3 h exposure to different concentrations of NMN. For each concentration, n = 4; D, E: NAD (NAD⁺ and NADH) contents in muscle (D) and liver (E) of rats treated with saline (control) or a cumulative dose of 2 g/kg NMN; F: NAD and NADH contents and NAD/NADH ratio in the erythrocytes (RBCs) of rats with or without cumulative exposure to NMN; G: NAD and NADH contents, and NAD/NADH ratio in human RBCs with (n = 4) or without (control, n = 4) 4 h exposure to 10 μmol/L NMN in vitro. ^aP < 0.05 vs control, ^bP < 0.01 vs control. Bar graphs indicate mean ± SD.