INTRODUCTION: The mechanism for beta-cell dysfunction induced by glucosamine has not yet fully been investigated previously. AIM: To investigate the effects of glucosamine on insulin release or gene expression related to glucose metabolism in rat islets cultured with glucosamine for 24 hours. METHODOLOGY: After islets were cultured with glucosamine or diazoxide, we measured glucose- or arginine-induced insulin release by using radioimmunoassay (RIA) and gene expressions by semiquantitative polymerase/chain reaction. RESULTS: Coculture with glucosamine inhibited 27 mmol/L glucose-induced insulin release with no effects on 20 mmol/L arginine-induced insulin release. Coculture with diazoxide did not restore the impaired glucose-induced insulin release. In glucosamine-cultured islets, glucose-transporter type 2 or glucokinase mRNA expression decreased, whereas hexokinase mRNA increased. Phosphofructokinase-A, pyruvate dehydrogenase E1alpha, or pyruvate carboxylase mRNA was not affected by the addition of glucosamine. Pancreatic and duodenal homeobox-1, preproinsulin, or p21 (induced by oxidative stress) mRNA expression did not change, whereas uncoupling protein 2 mRNA, which plays an important role in thermogenesis, decreased in glucosamine-cultured islets. CONCLUSION: These data imply that glucosamine impairs glucose-induced insulin release probably through the inhibition of glucose metabolism.
INTRODUCTION: The mechanism for beta-cell dysfunction induced by glucosamine has not yet fully been investigated previously. AIM: To investigate the effects of glucosamine on insulin release or gene expression related to glucose metabolism in rat islets cultured with glucosamine for 24 hours. METHODOLOGY: After islets were cultured with glucosamine or diazoxide, we measured glucose- or arginine-induced insulin release by using radioimmunoassay (RIA) and gene expressions by semiquantitative polymerase/chain reaction. RESULTS: Coculture with glucosamine inhibited 27 mmol/L glucose-induced insulin release with no effects on 20 mmol/L arginine-induced insulin release. Coculture with diazoxide did not restore the impaired glucose-induced insulin release. In glucosamine-cultured islets, glucose-transporter type 2 or glucokinase mRNA expression decreased, whereas hexokinase mRNA increased. Phosphofructokinase-A, pyruvate dehydrogenase E1alpha, or pyruvate carboxylase mRNA was not affected by the addition of glucosamine. Pancreatic and duodenal homeobox-1, preproinsulin, or p21 (induced by oxidative stress) mRNA expression did not change, whereas uncoupling protein 2 mRNA, which plays an important role in thermogenesis, decreased in glucosamine-cultured islets. CONCLUSION: These data imply that glucosamine impairs glucose-induced insulin release probably through the inhibition of glucose metabolism.