Department of Endocrinology and Metabolism, University of Pisa, Via Paradisa 2, Pisa, Italy.
Diabetologia. 2012 Dec;55(12):3262-72. doi: 10.1007/s00125-012-2716-9. Epub 2012 Sep 11.
AIMS/HYPOTHESIS: Glucagon-like peptide 1 (GLP-1) is a major incretin, mainly produced by the intestinal L cells, with beneficial actions on pancreatic beta cells. However, while in vivo only very small amounts of GLP-1 reach the pancreas in bioactive form, some observations indicate that GLP-1 may also be produced in the islets. We performed comprehensive morphological, functional and molecular studies to evaluate the presence and various features of a local GLP-1 system in human pancreatic islet cells, including those from type 2 diabetic patients.
The presence of insulin, glucagon, GLP-1, proconvertase (PC) 1/3 and PC2 was determined in human pancreas by immunohistochemistry with confocal microscopy. Islets were isolated from non-diabetic and type 2 diabetic donors. GLP-1 protein abundance was evaluated by immunoblotting and matrix-assisted laser desorption-ionisation-time of flight (MALDI-TOF) mass spectrometry. Single alpha and beta cell suspensions were obtained by enzymatic dissociation and FACS sorting. Glucagon and GLP-1 release were measured in response to nutrients.
Confocal microscopy showed the presence of GLP-1-like and PC1/3 immunoreactivity in subsets of alpha cells, whereas GLP-1 was not observed in beta cells. The presence of GLP-1 in isolated islets was confirmed by immunoblotting, followed by mass spectrometry. Isolated islets and alpha (but not beta) cell fractions released GLP-1, which was regulated by glucose and arginine. PC1/3 (also known as PCSK1) gene expression was shown in alpha cells. GLP-1 release was significantly higher from type 2 diabetic than from non-diabetic isolated islets.
CONCLUSIONS/INTERPRETATION: We have shown the presence of a functionally competent GLP-1 system in human pancreatic islets, which resides in alpha cells and might be modulated by type 2 diabetes.
目的/假设：胰高血糖素样肽 1（GLP-1）是一种主要的肠促胰岛素，主要由肠道 L 细胞产生，对胰腺β细胞有有益作用。然而，尽管体内只有很少量的 GLP-1 以生物活性形式到达胰腺，但一些观察结果表明，GLP-1 也可能在胰岛中产生。我们进行了全面的形态学、功能和分子研究，以评估人胰岛细胞中局部 GLP-1 系统的存在和各种特征，包括来自 2 型糖尿病患者的胰岛细胞。
通过免疫荧光共聚焦显微镜检测人胰腺中胰岛素、胰高血糖素、GLP-1、前转化酶（PC）1/3 和 PC2 的存在。从非糖尿病和 2 型糖尿病供体中分离胰岛。通过免疫印迹和基质辅助激光解吸电离飞行时间（MALDI-TOF）质谱法评估 GLP-1 蛋白丰度。通过酶解和 FACS 分选获得单个α和β细胞悬浮液。测量营养物质刺激下胰高血糖素和 GLP-1 的释放。
共聚焦显微镜显示 GLP-1 样和 PC1/3 免疫反应性存在于部分α细胞中，而β细胞中未观察到 GLP-1。免疫印迹和质谱法证实了分离胰岛中 GLP-1 的存在。分离的胰岛和α（但不是β）细胞部分释放 GLP-1，其受葡萄糖和精氨酸调节。在α细胞中显示了 PC1/3（也称为 PCSK1）基因表达。与非糖尿病分离胰岛相比，来自 2 型糖尿病患者的分离胰岛释放的 GLP-1 明显更高。
结论/解释：我们已经证明了人胰岛中存在功能完整的 GLP-1 系统，该系统存在于α细胞中，可能受 2 型糖尿病的调节。
