Search and functional analysis for novel bioactive peptides associated with regulation of energy balance and feeding behavior

肥胖是世界范围内最严重的问题之一，因为它与生活方式相关的疾病有关，如高血压，心血管疾病和2型糖尿病。本研究的目的是确定与能量平衡和摄食行为调节相关的孤儿GPCR的内源性配体，并阐明配体的生化和病理生理学意义，我们建立了稳定表达人BRS-3或其他孤儿GPCR的哺乳动物细胞系，以监测大鼠组织提取物诱导的细胞内第二信使的变化。分别使用FLIPR System（Molecular Device）和AlphaScreen（Packard）测量细胞内钙浓度和环AMP的变化。在大鼠脑和肠提取物中发现了BRS-3的几种[Ca^<2+>] i增加活性。通过连续色谱法进一步纯化这些肽，以证明已知肽与BRS-3具有交叉反应性。在大鼠脑提取物中发现了另一种孤儿受体的最高[Ca^<2+>] i增加活性。最后将其纯化为单一肽，部分氨基酸序列表明这是一种新的肽。Ghrelin是本实验室从胃中分离纯化的一种新的生长激素促分泌素受体的内源性配体，它是一种酰化肽，具有刺激摄食和生长激素分泌的作用。一个单一的静脉注射生长抑素降低了大鼠的全身血浆中生长激素释放肽的浓度，并持续输注生长抑素到胃动脉的血管灌注大鼠胃抑制生长激素释放肽分泌。这些发现表明，胃生长激素释放肽从胃分泌的调节胃生长抑素。

Obesity is one of the most serious problems worldwide, because it is associated with lifestyle-related disease such as hypertension, cardiovascular disease and type 2 diabetes. The aims of this study are to identify endogenous ligands for orphan GPCRs associated with regulation of energy balance and feeding behavior, and to clarify the biochemical and pathophysiological significance of the ligands.We established stable mammalian cell lines expressing human BRS-3 or other orphan GPCRs to monitor changes in the intracellular second messenger that were induced by rat tissue extracts. Changes in the intracellular calcium concentration and cyclic AMP were measured using the FLIPR System (Molecular Device) and AlphaScreen (Packard), respectively. Several [Ca^<2+>]I-increasing activities for BRS-3 were found in rat brain and intestinal extracts. These were further purified by successive chromatography to prove known peptides, having cross-reactivity to BRS-3. The highest [Ca^<2+>]I-increasing activity for one other orphan receptor was found in rat brain extract. This was finally purified as a single peptide, and partial amino acid sequence indicated that this was a novel peptide. This peptide inhibited food intake in rats when injected intracerebroventricularly.Ghrelin, a novel peptide purified from stomach as an endogenous ligand for the growth hormone secretagogue receptor in our laboratory, is an acylated peptide that stimulates food intake and the secretion of growth hormone. A single intravenous injection of somatostatin reduced the systemic plasma concentration of ghrelin in rats, and continuous infusion of somatostatin into the gastric artery of the vascularly perfused rat stomach suppressed ghrelin secretion. These findings indicate that ghrelin secretion from the stomach is regulated by gastric somatostatin.