Loss-of-function mutation of the GPR40 gene associates with abnormal stimulated insulin secretion by acting on intracellular calcium mobilization
Loss-of-function mutation of the GPR40 gene associates with abnormal stimulated insulin secretion by acting on intracellular calcium mobilization
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DOI：
10.1210/jc.2007-2680
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发表时间：
2008-09-01
影响因子：
5.8
通讯作者：
Frittitta, Lucia
中科院分区：
文献类型：
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作者：
Vettor, Roberto;Granzotto, Marnie;Frittitta, Lucia
背景：游离脂肪酸（FFAs）急性刺激但慢性损害葡萄糖刺激的β细胞胰岛素分泌。G蛋白偶联跨膜受体40 （GPR40）介导FFAs对胰岛素分泌的急性和慢性影响，并在葡萄糖稳态中发挥作用。关于GPR40基因异常对人类胰岛素分泌和代谢调节的影响的信息有限。研究设计和结果：在体内研究中，我们筛选了734名受试者GPR40编码区，并鉴定出一个新的单核苷酸突变（Gly180Ser）。平均等位基因频率为0.75%，从非肥胖者（0.42%）到中度肥胖者（体重指数30 ~ 39.9 kg/m(2), 1.07%）和重度肥胖者（体重指数>= 40 kg/m(2), 2.60%），等位基因频率逐渐增加（P < 0.05）。研究了11例Gly/Ser突变携带者GPR40突变与胰岛素分泌和代谢改变之间的关系。这些受试者的胰岛素分泌（通过口服糖耐量试验得出的胰岛素原指数）显著低于692名Gly/Gly携带者（86.0 +/- 48.2 vs. 183.7 +/- 134.4, P < 0.005）。此外，一项病例对照研究表明，6名Gly/Ser患者的血浆胰岛素和c肽对脂质负荷的反应显著（P < 0.05）低于12名Gly/Gly携带者。体外实验表明，与转染aequorin和突变Gly/Ser GPR40的HeLa细胞相比，油酸处理后细胞内Ca2+浓度显著降低。用呋喃-2乙酰氧基甲酯证实了这一事实。结论：这种新发现的GPR40变异导致功能丧失，由于细胞内Ca2+浓度增加受损，阻止β细胞充分感知脂质作为胰岛素分泌刺激的能力。
Background: Free fatty acids (FFAs) acutely stimulate but chronically impair glucose-stimulated insulin secretion from beta-cells. The G protein-coupled transmembrane receptor 40 (GPR40) mediates both acute and chronic effects of FFAs on insulin secretion and plays a role in glucose homeostasis. Limited information is available on the effect of GPR40 genetic abnormalities on insulin secretion and metabolic regulation in human subjects.Study Design and Results: For in vivo studies, we screened 734 subjects for the coding region of GPR40 and identified a new single-nucleotide mutation (Gly180Ser). The mean allele frequency was 0.75%, which progressively increased (P < 0.05) from nonobese subjects (0.42%) to moderately obese (body mass index = 30-39.9 kg/m(2), 1.07%) and severely obese patients (body mass index >= 40 kg/m(2), 2.60%). The relationship between the GPR40 mutation, insulin secretion, and metabolic alterations was studied in 11 Gly/Ser mutation carriers. In these subjects, insulin secretion (insulinogenic index derived from oral glucose tolerance test) was significantly lower than in 692 Gly/Gly carriers (86.0 +/- 48.2 vs. 183.7 +/- 134.4, P < 0.005). Moreover, a case-control study indicated that plasma insulin and C-peptide responses to a lipid load were significantly (P < 0.05) lower in six Gly/Ser than in 12 Gly/Gly carriers. In vitro experiments in HeLa cells cotransfected with aequorin and the mutated Gly/Ser GPR40 indicated that intracellular Ca2+ concentration increase after oleic acid was significantly lower than in Gly/Gly GPR40-transfected cells. This fact was confirmed using fura-2 acetoxymethyl ester.Conclusions: This newly identified GPR40 variant results in a loss of function that prevents the beta-cell ability to adequately sense lipids as an insulin secretory stimulus because of impaired intracellular Ca2+ concentration increase.