Hello 

You can use nicotinamide Human adipose-derived mesenchymal stem cells :

protocol :

Human adipose-derived mesenchymal stem cells

cells were cultured in 2% FBS/DMEM/F12 medium

and supplemented with 100 ng/ml epidermal growth factor

(EGF) and 2% B27 (Sigma) for 3 days. In stage 3, cells were

exposed to a cocktail of 10 ng/ml glucagons-like peptide-1

(GLP-1), 10 ng/ml betacellulin, 10 ng/ml hepatocyte growth

factor (HGF), 10 mmol/l nicotinamide, 2% B27, 0.1 mmol/l

β-mercaptoethanol (Sigma) for 7 days.

Remarks

1-Gene expression profile was analyzed every 24 hours for 3 days.

2-Down-regulation of ABCG-2 and up-regulation of pancreatic developmental transcription factors (Isl-1, Ipf-1 and Ngn3) were observed, together with induction of islet hormones insulin, glucagon, and somatostatin.

also , read articles in attachment

Good Luck 

Thanks so much dear Saleh