GLP-1 metabolite GLP-1(9-36) is a systemic inhibitor of mouse and human pancreatic islet glucagon secretion
GLP-1 metabolite GLP-1(9-36) is a systemic inhibitor of mouse and human pancreatic islet glucagon secretion
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GLP-1 代谢物 GLP-1(9-36) 是小鼠和人胰岛胰高血糖素分泌的全身抑制剂
DOI：
10.1007/s00125-023-06060-w
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发表时间：
2023
期刊：
影响因子：
8.2
通讯作者：
Gandasi N
中科院分区：
文献类型：
--
作者：
Gandasi N
目的/假设糖尿病与胰岛素分泌受损有关，通常因高血糖素分泌过多而加重。理想情况下，治疗性干预应该纠正这两种缺陷。胰高血糖素样肽1(GLP-1)具有这种能力，但它究竟是如何发挥其降血糖作用的仍不清楚。在其释放后，GLP-1从GLP-1(7-36)迅速降解为GLP-1(9-36)。我们假设代谢产物GLP-1(9-36)(以前被认为是非生物活性的)对胰升糖素的分泌有直接的抑制作用，这种机制在糖尿病患者中会受到损害。方法我们结合了小鼠和人的胰岛(包括来自2型糖尿病供者的胰岛)的胰高血糖素分泌测量，分泌颗粒动力学的全内反射荧光显微镜成像，细胞内钙离子的记录和蛋白激酶A活性的测定，免疫细胞化学，通过体内生理和GTP结合蛋白解离实验，探讨GLP-1对胰岛高血糖素分泌的抑制作用及代谢产物GLP-1(9-36)的作用。结果GLP-1(7-36)对胰岛高血糖素分泌有抑制作用，IC50为2.5pmol/L，在低糖浓度下抑制作用尤为明显。降解产物GLP-1(9-36)具有这种能力。GLP-1(9-36)在GLP-1受体遗传/药物失活后仍具有降血糖作用。GLP-1(9-36)也能有效地抑制β-肾上腺素能刺激、氨基酸和膜去极化所引起的胰升糖素分泌。在胰岛α细胞中，GLP-1(9-36)通过对ω-agatoxin敏感的电压门控钙通道抑制Ca~(2+)内流，导致对接的分泌颗粒池对百日咳毒素敏感的枯竭，这种作用可被胰高血糖素受体拮抗剂REMD2.59和L-168049所阻止。在2型糖尿病供者的阿尔法细胞中，GLP-1(9-36)抑制胰高血糖素分泌和减少停靠颗粒数量的能力丧失。在体内，在胰岛素诱导的低血糖期间，外源性高浓度的GLP-1(9-36)(>；100pmol/L)导致循环中的胰高血糖素小幅下降(30%)。这种作用被REMD2.59取消，REMD2.59使循环中的胰升糖素迅速增加225%(根据血糖的变化进行调整)，而不影响胰升糖素的含量。结论GLP-1代谢产物GLP-1(9-36)是一种全身性的胰升糖素分泌抑制物。我们认为，在小鼠和2型糖尿病患者中，在遗传/药物失活胰高血糖素信号后观察到的循环中胰高血糖素的增加反映了GLP-1(9-36)‘S的降糖作用的去除。
Aims/hypothesisDiabetes mellitus is associated with impaired insulin secretion, often aggravated by oversecretion of glucagon. Therapeutic interventions should ideally correct both defects. Glucagon-like peptide 1 (GLP-1) has this capability but exactly how it exerts its glucagonostatic effect remains obscure. Following its release GLP-1 is rapidly degraded from GLP-1(7–36) to GLP-1(9–36). We hypothesised that the metabolite GLP-1(9–36) (previously believed to be biologically inactive) exerts a direct inhibitory effect on glucagon secretion and that this mechanism becomes impaired in diabetes.MethodsWe used a combination of glucagon secretion measurements in mouse and human islets (including islets from donors with type 2 diabetes), total internal reflection fluorescence microscopy imaging of secretory granule dynamics, recordings of cytoplasmic Ca2+and measurements of protein kinase A activity, immunocytochemistry, in vivo physiology and GTP-binding protein dissociation studies to explore how GLP-1 exerts its inhibitory effect on glucagon secretion and the role of the metabolite GLP-1(9–36).ResultsGLP-1(7–36) inhibited glucagon secretion in isolated islets with an IC50of 2.5 pmol/l. The effect was particularly strong at low glucose concentrations. The degradation product GLP-1(9–36) shared this capacity. GLP-1(9–36) retained its glucagonostatic effects after genetic/pharmacological inactivation of the GLP-1 receptor. GLP-1(9–36) also potently inhibited glucagon secretion evoked by β-adrenergic stimulation, amino acids and membrane depolarisation. In islet alpha cells, GLP-1(9–36) led to inhibition of Ca2+entry via voltage-gated Ca2+channels sensitive to ω-agatoxin, with consequential pertussis-toxin-sensitive depletion of the docked pool of secretory granules, effects that were prevented by the glucagon receptor antagonists REMD2.59 and L-168049. The capacity of GLP-1(9–36) to inhibit glucagon secretion and reduce the number of docked granules was lost in alpha cells from human donors with type 2 diabetes. In vivo, high exogenous concentrations of GLP-1(9–36) (>100 pmol/l) resulted in a small (30%) lowering of circulating glucagon during insulin-induced hypoglycaemia. This effect was abolished by REMD2.59, which promptly increased circulating glucagon by >225% (adjusted for the change in plasma glucose) without affecting pancreatic glucagon content.Conclusions/interpretationWe conclude that the GLP-1 metabolite GLP-1(9–36) is a systemic inhibitor of glucagon secretion. We propose that the increase in circulating glucagon observed following genetic/pharmacological inactivation of glucagon signalling in mice and in people with type 2 diabetes reflects the removal of GLP-1(9–36)’s glucagonostatic action.Graphical Abstract