Search for nutrients or drugs to improve metabolism by use of regulatory mechanism of ghrelin receptor gene transcription

虽然糖尿病或肥胖症患者需要严格限制热量摄入，但通常很难继续下去。Ghrelin是生长激素促分泌素受体（GHS-R）的配体，从胃中分离得到，具有刺激食欲和生长激素分泌的作用。此外，我们还报道了ghrelin在培养肝细胞中对抗胰岛素作用的作用。本研究通过荧光素酶检测系统，寻找哪些营养素或药物可能影响GHS-R基因的转录。GHS-R/Luc的转录活性位于GHS-R基因5 ′侧翼区的-608 ~-534p之间，可能与AP_2或bHLH结合。凝胶迁移实验表明，该区域的荧光标记DNA可与HepG_2细胞核蛋白特异性结合。二十碳五烯酸（EPA）或曲格列酮轻微抑制GHS-R/Luc活性。这些结果表明，EPA或曲格列酮增强胰岛素敏感性，至少部分，通过下调GHS-R。另一方面，胆固醇脂质，油基乙醇酰胺，引起GHS-R/Luc活性略有增加。我们有经验的病人谁采取了某种减肥茶，随后成为糖尿病。这种减肥茶抑制葡萄糖诱导的胰腺细胞RIN-5 F的胰岛素分泌。然而，这种茶没有改变GHS-R/Luc活性。维生素C、E、胰岛素、ghrelin和瘦素不改变GHS-R/Luc活性。由于EPA导致GHS-R下调，我们在年轻志愿者中挑战富含多不饱和脂肪酸（PUFA）的饮食。富含PUFA的饮食导致HOMA-IR增加，血浆脂联素水平升高。总之，测量参与代谢的基因的转录活性是寻找预防糖尿病或肥胖的营养素或药物的有用方法。

A though patients with diabetes or obesity require severe restriction of calorie intake, it is usually hard to continue. Ghrelin, a ligand for growth hormone secretagogue receptor (GHS-R), was isolated from stomach and reported to play roles in stimulation of appetite as well as GH secretion. In addition, we have reported the role of ghrelin against insulin action in cultured hepatocytes In this study, we searched which nutrients or drugs might affect GHS-R gene transcription by luciferase assay system. The transcriptional activity (GHS-R/Luc) was located between -608 and -534p of 5'-flanking region of GHS-R gene, where AP_2 or bHLH was expected to bind. Gel shift assay demonstrated that fluorecent labeled DNA of this region specifically bound to nuclear proteins extracted from HepG_2 cells. Eicosa-pentaenoic acid (EPA) or troglitazone slightly inhibited GHS-R/Luc activity. These results suggest that EPA or troglitazone enhance insulin sensitivity, at least in part, by down-regulation of GHS-R. On the other hand, anorexic lipid, oleylethanolamide, caused a slight increase in GHS-R/Luc activity. We have experienced patients who had taken a certain diet tea and subsequently became diabetic. This diet tea inhibited glucose-induced insulin secretion from cultured pancreatic cells RIN-5F. However, this tea did not change GHS-R/Luc activity. Vitamin C,E, insulin, ghrelin, and leptin did not change GHS-R/Luc activity. As EPA caused down-regulation of GHS-R, we challenged polyunsaturated fatty acid (PUFA)-rich diet in young volunteer. The PUFA-rich diet caused an increase in HOMA-IR with a precedent elevation of plasma adiponectin levels. In conclusion, measurement of transcriptional activity of genes involved in metabolism is a useful way to search nutrients or drugs for prevention of diabetes or obesity.