Effects Of L-carnosine On Nit-1 Islet Cells Function, Proliferation And Apoptosis.

Objective:L-carnosine is a dipeptide degraded predominantly by CN1, which was recently recognised as a protective factor in diabetic patients. we therefore investigate the protective effect of L-carnosine on vitroβ-cell impairment induced by high glucose and the effect of insulin secretion and the additional mechenism.Methods:1. NIT-1 cells on Control glucose(11.1 mmol/L)and High glucose (33.3 mmol/L)condition for 72h were stimulated by various glucose and L-carnosine, the insulin level were detected by radio-immunity technique.2.NIT-1 cells were divided into 4 groups according to different culture condition: group C(11.1mmol/L Glucose),group H(33.3 mmol/L Glucose),group H+A(33.3mmol/L Glucose+1mmol/L L-carnosine),group H+B(33.3mmol/L Gluco -se +20mmol/L L-carnosine). Afer 72h, proliferative cells and apoptotic cells were identified by BRDU and flow cytometry (AnnexinV-FITC /PI) respectively, RT-PCR was used to meassure the bcl-2mRNA and caspase-3mRNA levels.Results:(1) the insulin secretion were decreased in high glucose group (P < 0.01) compare to that of Control group; High level (20mmol/L) L-carnosine increases the insulin secretion both in Control and High glucose group compared to that of cultured without L-carnosine, while no glucose stimulation(P < 0.01).(2) Increased proliferative rate was detected in H group compared to C group, that is, an augment of 63.59%±3.7% (P <0.01), group H+A increased 23.44%±6.08% than group H (P <0.01), group H+B increased not significantly (P >0.05); apoptosis rate: H group increased 75.15%±7.61% than C group (P <0.01), H+A group decreased 58.17%±6.92% than H group (P <0.01), H+B group decreased significantly (P <0.01), yet have a higher apoptic rate than H+A group.(3) caspase-3mRNA levels in H group uppered (P <0.05 vs C group), in H+A goup declined (P <0.05 vs.H group), in H+B group delined (P >0.05 vs.H group); while bcl-2 mRNA expression in H group decreased (P <0.05 vs C group) and in H+A group increased (P <0.01 vs H group), in H+B group increased (P >0.05 vs.H group).Conclusion:(1) Chronic high glucose condition inhibits insulin secretion of NIT-1 cells, higher concentrations of L-carnosine can directly stimulate NIT-1 cells insulin secretion.(2) Chronic high glucose condition increases cells proliferation and apoptosis, yet the overall cell numbers declined; lower near-physiological levels of L-carnosine for a long time promotes cells proliferation and reduce apoptosis, therefore have an increased cell numbers;(3) caspsase-3 and bcl-2 genes may take part in the process of NIT-1 cells proliferation and apoptosis,and of preservation of NIT-1 cells resulted from L-carnosine.