title: Effect of C-peptide Alone or in Combination with Nicotinamide on Insulin Levels from Pancreatic Islets in Mouse.
abstract: BACKGROUND
  Both c-peptide and nicotinamide are known to increase blood insulin in diabetes. In the present study, we examined the effect of c-peptide alone or in combination with nicotinamide on insulin levels in pancreatic islets in mice.
  
  
  METHODS
  This study was conducted with 60 adult male Naval Medical Research Institute (NMARI) mice weighing 25 to 30 g. Pancreatic islets from normal mice were isolated by the collagenase digestion method. Mice were divided into ten groups of six (n = 6): control, glyburide (1 and 10 μM), C-peptide (50 and 100 nM), nicotinamide (10, 25, and 100 mM), nicotinamide + C-peptide (100 mM and 100 nM), and buffer in different glucose concentrations (2.8, 5.6, and 16.7 mM). Insulin secretion was measured using insulin radioimmunoassay method.
  
  
  RESULTS
  Insulin secretion significantly increased at 16.7 mM glucose concentration compared with 2.8 and 5.6 mM glucose concentrations. Incubation of islets at 2.8 and 5.6 mM glucose concentrations and nicotinamide + C-peptide, nicotinamide 25 and 100 mM, and C-peptide 100 nM significantly increased insulin secretion compared with the control group. In addition, incubation of islets at 16.7 mM glucose with nicotinamide + C-peptide significantly increased insulin secretion. Glyburide at 10 μM concentration was more effective than nicotinamide at 10 and 100 mM, C-peptide 50 and 100 nM in the presence of 16.7 mM glucose concentration. However, the combination of nicotinamide + C-peptide was more effective than glyburide at a concentration of 10 μM in the presence of a 16.7 mM glucose concentration.
  
  
  CONCLUSIONS
  This paper suggests that c-peptide, nicotinamide, and the combination of c-peptide and nicotinamide in-creases insulin secretion from pancreatic islets.
authors.affiliation: Health Research Institute, Diabetes Research Center, Department of Physiology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz 61335-189, Iran.
authors.forename: Akram
authors.initials: A
authors.lastname: Ahangarpour
authors.affiliation: School of medicine, Department of Physiology and Member of Student Research Committee of Ahvaz Jundishapur University of Medical Science, Ahvaz 61335-189, Iran.
authors.forename: Fatemeh Ramezani
authors.initials: FR
authors.lastname: Ali Akbari
authors.affiliation: Department of Physiology, Physiology Research Center of Ahvaz Jundishapur University of Medical Sciences, Ahvaz 61335-189, Iran.
authors.forename: Hadi Fathi
authors.initials: HF
authors.lastname: Moghadam
keywords: C-peptide; glyburide; insulin; islets; mice; nicotinamide