Dear Hager,

From my experiments and observations, the combined administration of streptozotocin (STZ) with and nicotinamide (NA) to adult rats results in the development of a diabetic syndrome, characterizes by moderate and stable hyperglycemia. This syndrome is similar to T2DM in humans and is thus a suitable model for short and long-term studies.

    In our laboratory, for induction of non-insulin dependent diabetes mellitus (NIDDM), the method of Masiello et al [Masiello P, Broca C, Gross R, Roye M, Manteghetti M, Hillaire-Buys D, Novelli M, Ribes G: Experimental NIDDM: development of a new model in adult rats administered STZ and NA. Diabetes 1998; 47, 224-9] was used.

    In the majority of experiments, NA is given to rats 15 min before STZ to induce NIDDM in rats. Administration of the diabetogenic dose of STZ to rats causes a decrease in body weight; however, this is attenuated by pre-treatment of animals with NA. Numerous studies have also demonstrated that the STZ-induced increase in blood glucose is significantly blunted when NA is administered prior to STZ. The advantageous effect of NA on blood glucose is due to the protection of B-cells against demage of STZ and is accompanied by increased blood insulin.

    The severity of diabetes in experimental rats strongly depends on the doses of STZ and NA given to these animals (Check out the following minireview).

Perhaps reading this review will help

https://www.ncbi.nlm.nih.gov/pubmed/18087688

Male Wistar rats were fed with high-fat diet for 8 weeks, then different dosage of STZ (20 mg/kg, 25 mg/kg, 30 mg/kg) was injected intraperitoneally. Observed the body weight, fasting glucose and 2 h postload glucose for 7 weeks.

https://www.ncbi.nlm.nih.gov/pubmed/20459021