糖耐量受损大鼠胰岛α细胞胰高血糖素及神经肽Y的表达

Expressions of glucagon and neuropeptide Y in α cells of pancreatic islets in rats with impaired glucose tolerance

目的 测定并比较胰岛素抵抗 (IR)、糖耐量受损 (IGT)及 2型糖尿病 (DM )大鼠模型胰岛α细胞中胰高血糖素 (GLC)、神经肽Y(NPY)、β细胞中胰岛素 (INS)蛋白表达变化及胰岛中NPYmRNA表达 ,确定IR、IGT、2型DM大鼠模型胰岛α细胞是否存在IR。方法 分别用高脂饮食 /缓冲液 ,高脂饮食 /小剂量链脲佐菌素制备IR、IGT与 2型DM大鼠模型 ;采用荧光单标记及双标记法分别对各组大鼠胰岛α细胞中NPY、GLC及 β细胞中INS进行蛋白的定位、定量分析。采用原位杂交定位、定量分析胰岛中NPYmRNA。结果 实验性IR、IGT及 2型DM大鼠模型的生化代谢指标及发病过程与临床相关疾病的表现一致 ;各组大鼠胰岛α细胞GLC及NPY平均光密度 (MOD)值与正常对照组 ( 687± 12 7,2 75± 14 )相比 ,分别为IR组 175 5± 2 2 6,64 6± 12 2 ;IGT组 172 0± 10 8,5 99± 63及 2型DM组 1986± 88,5 85± 67,均显著增高 (均P <0 .0 1)。与正常对照组 ( 14 2 5± 2 2 0 )比较 ,上述各组胰岛 β细胞INS蛋白表达亦显著增高 ,3组分别为 2 0 73± 3 40 (P <0 .0 1) ;1976± 2 0 0 (P <0 .0 1)和 170 9± 184(P <0 .0 5 ) ,表达NPY及GLC的α细胞分布方式由正常的胰岛外周向全胰岛分布改变。正常对照组未发现NPYmRNA表达 ,但在其余各组是全胰岛表达?

Objective To measure and compare glucagon (GLC) and neuropeptide Y (NPY) expressions of islet α cells, insulin (INS) expression of islet β cells and NPY mRNA expression in pancreatic islets in rat models of insulin resistance (IR), impaired glucose tolerance (IGT) and type 2 diabetes mellitus (DM), and to determine the existence of IR of α cells in rat models. Methods Rat models of IR, IGT and type 2 DM were established with high fat diet/buffer or high fat diet/low dose streptozotocin. With these rat models, the distributions and concentrations of NPY and GLC of α cells and INS of β cells were measured by double-labelled immunofluorescence staining and single-labelled immunofluorescence staining respectively, and the contents of NPY mRNA in islets were determined by in situ hybridization (ISH). Results The biochemical and metabolic characteristics and the pathogenesis processes of rat models were consistent with clinical feature of related diseases. As compared with the mean optical density (MOD) of GLC and NPY expressions of α cells in normal control (NC) group (687±127 and 275±14 respectively), the MOD of GLC and NPY in IR group (1755±226, 646±122), IGT group (1720±108, 599±63) and type 2 DM group (1986±88, 585±67) were significantly increased (all P<0.01). The MOD of INS expression of β cells in IR group (2073±340), IGT group (1976±200) and type 2 DM group (1709±184) were all higher than that in NC group (1425±220) (P<0.01, P<0.01 and P<0.05, respectively). The expessions of NPY and GLC in α cells were increased and the distribution of these α cells changed from peripheral site of islet to the whole islet. The expression of NPY mRNA was not found in islets of NC group, but distributed in the whole islets of IR, IGT and type 2 DM groups. Conclusion The elevated expressions of GLC and NPY were not suppressed by endogenous hyperinsulinism in IR, IGT and type 2 DM groups, strongly supporting the hypothesis that the endogenous insulin resistance of islet α cells exists in these groups.