Lauffer Lina M, Iakoubov Roman, Brubaker Patricia L
Department of Physiology, University of Toronto, Toronto, Ontario, Canada.
Diabetes. 2009 May;58(5):1058-66. doi: 10.2337/db08-1237. Epub 2009 Feb 10.
Intestinal L-cells secrete the incretin glucagon-like peptide-1 (GLP-1) in response to ingestion of nutrients, especially long-chain fatty acids. The Galphas-coupled receptor GPR119 binds the long-chain fatty acid derivate oleoylethanolamide (OEA), and GPR119 agonists enhance GLP-1 secretion. We therefore hypothesized that OEA stimulates GLP-1 release through a GPR119-dependent mechanism.
Murine (m) GLUTag, human (h) NCI-H716, and primary fetal rat intestinal L-cell models were used for RT-PCR and for cAMP and GLP-1 radioimmunoassay. Anesthetized rats received intravenous or intraileal OEA, and plasma bioactive GLP-1, insulin, and glucose levels were determined by enzyme-linked immunosorbent assay or glucose analyzer.
GPR119 messenger RNA was detected in all L-cell models. OEA treatment (10 micromol/l) of mGLUTag cells increased cAMP levels (P < 0.05) and GLP-1 secretion (P < 0.001) in all models, with desensitization of the secretory response at higher concentrations. GLP-1 secretion was further enhanced by prevention of OEA degradation using the fatty acid amide hydrolase inhibitor, URB597 (P < 0.05-0.001 vs. OEA alone), and was abolished by H89-induced inhibition of protein kinase A. OEA-induced cAMP levels and GLP-1 secretion were significantly reduced in mGLUTag cells transfected with GPR119-specific small interfering RNA (P < 0.05). Application of OEA (10 micromol/l) directly into the rat ileum, but not intravenously, increased plasma bioactive GLP-1 levels in euglycemic animals by 1.5-fold (P < 0.05) and insulin levels by 3.9-fold (P < 0.01) but only in the presence of hyperglycemia.
The results of these studies demonstrate, for the first time, that OEA increases GLP-1 secretion from intestinal L-cells through activation of the novel GPR119 fatty acid derivate receptor in vitro and in vivo.
肠道L细胞会在摄入营养物质，尤其是长链脂肪酸后分泌肠促胰岛素胰高血糖素样肽-1（GLP-1）。与Gαs偶联的受体GPR119可结合长链脂肪酸衍生物油酰乙醇胺（OEA），且GPR119激动剂可增强GLP-1分泌。因此，我们推测OEA通过GPR119依赖性机制刺激GLP-1释放。
使用小鼠（m）GLUTag、人（h）NCI-H716和原代胎鼠肠道L细胞模型进行逆转录聚合酶链反应（RT-PCR）以及环磷酸腺苷（cAMP）和GLP-1放射免疫测定。对麻醉大鼠静脉注射或回肠内注射OEA，通过酶联免疫吸附测定或葡萄糖分析仪测定血浆生物活性GLP-1、胰岛素和葡萄糖水平。
在所有L细胞模型中均检测到GPR119信使核糖核酸（mRNA）。在所有模型中，用10微摩尔/升的OEA处理mGLUTag细胞可提高cAMP水平（P<0.05）和GLP-1分泌（P<0.001），在较高浓度下分泌反应会脱敏。使用脂肪酸酰胺水解酶抑制剂URB597防止OEA降解可进一步增强GLP-1分泌（与单独使用OEA相比，P<0.05至0.001），而H89诱导的蛋白激酶A抑制可消除这种增强作用。在转染了GPR119特异性小干扰RNA的mGLUTag细胞中，OEA诱导的cAMP水平和GLP-1分泌显著降低（P<0.05）。将10微摩尔/升的OEA直接注入大鼠回肠而非静脉注射，可使血糖正常动物的血浆生物活性GLP-1水平升高1.5倍（P<0.05），胰岛素水平升高3.9倍（P<0.01），但仅在存在高血糖的情况下。
这些研究结果首次证明，OEA在体外和体内通过激活新型GPR119脂肪酸衍生物受体增加肠道L细胞的GLP-1分泌。
