Effect Of Polysaccharide Of Dendrobium Candidum On Insulin Secretion, Nitrogen Monoxidum Production And Expression Of Interleukin-1β In Rat Pancreatic Islet Cell Tumor Line INS-1Cells

OBJECTIVE:To investigate the effect of polysaccharide of dendrobium candidum (PDC) oninsulin secretion, nitrogen monoxidum production and expression of interleukin-1β inrat pancreatic islet cell tumor line INS-1cells and explore the probalble mechanism ofhypoglycemic effect and protection of pancreatic islet beta cell induced by PDC.METHODS:The rat pancreatic islet cell tumor line INS-1cells were treated with high glucose(33.3mmol/L) for48h to induce the injury. Meanwhile, INS-1cells were treated withPDC (100,200and400μg/mL) for48h. The cells were divided into the controlgroup, high glucose group, different concentration PDC (100,200and400μg/mL)group and high glucose+different concentration PDC (100,200and400μg/mL)group. MTT assay was used to detect the cell viability. We measured the rates ofapoptosis of INS-1cells by flow cytometry. The levels of insulin and nitrogenmonoxidum in culture medium were measured by the radio-immunity assay andnitrate reductase assay, respectively. The mRNA expression of interleukin-1β andprotein expressin of inducible nitricoxide synthase in INS-1cells were measured byReal-time PCR and Western blot, respectively.RESULTS:(1) Compared with the control group, the cell viability was decreasedsignificantly (P<0.05), the apoptosis of INS-1cells was significantly increased(P<0.05), the level of insulin in culture medium was significantly decreased (P<0.05),the level of nitrogen monoxidum in culture medium was significantly increased(P<0.05), the mRNA expression of interleukin-1β and protein expressin of induciblenitricoxide synthase in INS-1cells were significantly increased in high glucose group(all P<0.05).(2) Compared with the control group, PDC (100,200and400μg/mL) did not affect the cell viability and apoptosis of INS-1cells (all P＞0.05). The level ofnitrogen monoxidum and protein expressin of inducible nitricoxide synthase in INS-1cells had no significant difference between control group and PDC (100,200and400μg/mL) group (all P＞0.05). PDC (100,200and400μg/mL) increased significantlythe level of insulin in culture medium and the mRNA expression of interleukin-1β inINS-1cells in dose dependent manner.(3) Compared with the high glucose group, the cell viability was increasedsignificantly (P<0.05), the apoptosis of INS-1cells was significantly decreased(P<0.05), the level of insulin in culture medium was significantly increased (P<0.05),the level of nitrogen monoxidum in culture medium was significantly decreased(P<0.05), the mRNA expression of interleukin-1β and protein expressin of induciblenitricoxide synthase in INS-1cells were significantly decreased in high glucose+different concentration PDC (100,200and400μg/mL) group in dose dependentmanner (all P<0.05).CONCLUSIONS:Polysaccharide of dendrobium candidum inhibits the decrease of insulinsecretion and increase of NO production and interleukin-1β expression induced byhigh glucose in rat pancreatic islet cell tumor line INS-1cells.