NMN was given in this Japanese study to mice with type 2 diabetes using a 7 day protocol to increase NAD+ levels and reverse insulin intolerance
We administered NMN at a dose of 500 mg/kg body weight/day intraperitoneally to HFD-fed male and female diabetic mice for 10 and 7 consecutive days, respectively. No overt abnormalities or changes in body weight were detected during this time (data not shown). NMN administration successfully restored NAD+ levels in the liver and WAT of diabetic mice, and even in diabetic skeletal muscle, a moderate but significant increase in NAD+ was detected (Figure 1B). These results demonstrate the efficacy of NMN treatment in ameliorating the underlying defect in NAD+ biosynthesis in HFD-induced diabetes.
Strikingly, NMN administration completely normalized impaired glucose tolerance in diabetic female mice (Figure 2A).