阻断(前)肾素受体改善MSG大鼠胰岛素抵抗及其机制研究

Recent studies demostrated that prorenin-renin-(pro)renin receptor system may participate in the occurrence of insulin resistance, but the mechanisms are still unclear. We have testified that the quantity of (P)RR expression in pancreas including the exocrine area and islet and adipose tissue increased obviously in the MSG rat, and were down expression with sitagliptin treatment. The results suggested that (P)RR may play important role in the occurrence and development of insulin resistance. In this study, the rats with insulin resistance and β cell deficit were created by neonatally treated with MSG and given high-energy diet and then treated with handle region peptide (HRP), losartan and antisterone and combination. The system insulin resistance, insulin sensitivity of skeletal muscle and adipose tissue and functions of β cells of the animals were evaluated after 4 weeks treatment according to euglycemic byperinsulinemic clamp test, deoxyglucose uptake in vitro, and OGTT respectively. The possible mecannisms of improvement of glucose metabolism by blocking (P)RR including abnormal expression of tissue RAS, ativations of oxidative stress and imflamation, abnormal insulin signal transduction in the tissue of pancreat, adipose and skeletal muscle were investigated. This study will testify functions of β cells and insulin sensitivity are improved by blocking (P)RR and supply new direction of treatment for insulin resistance.

近期研究显示前肾素-肾素-(前)肾素受体((P)RR）在胰岛素抵抗中有一定作用。我们证明MSG大鼠胰腺外分泌部及胰岛和白色脂肪的(P)RR表达量均明显增加。应用西格列汀干预MSG大鼠，改善胰岛素抵抗和β细胞功能的同时胰腺和脂肪的(P)RR表达均下调，提示(P)RR可能参与胰岛素抵抗的发生发展。本研究通过给予新生大鼠MSG皮下注射，断奶后给予高脂饮食，建立胰岛素抵抗合并β细胞缺陷的动物模型。通过给予该模型(P)RR抑制剂HRP，氯沙坦，安体舒通及联合用药，通过钳夹试验、脂肪及骨骼肌葡萄糖摄取率检测和OGTT分别评估系统、组织的胰岛素敏感性和β细胞功能，探讨胰腺、脂肪和骨骼肌局部RAS、氧化应激与炎症、胰岛素信号转导通路异常等在(P)RR阻断后改善糖代谢中的作用。从而证明阻断(P)RR能改善胰岛功能和胰岛素敏感性，且与氯沙坦和安体舒通存在一定协同作用。阻断(P)RR为胰岛素抵抗防治提供新靶点。

肾素-血管紧张素-醛固酮系统（RAAS）在机体调节水电解质平衡中起重要作用。研究表明，组织局部RAAS在糖代谢平衡中发挥重要作用。（前）肾素受体（P）RR处于RAAS上游部位，可与（前）肾素特异性结合而使前肾素具备肾素活性，并启动细胞信号转导通路发挥效应。MSG大鼠通过给予新生SD大鼠左旋谷氨酸单钠，可特异性破坏下丘脑弓状核，成年后大鼠出现胰岛素抵抗和β细胞功能缺陷。本项目以MSG大鼠作为载体，应用手把区域多肽（HRP）阻断（P）RR效应后评估其对MSG大鼠糖代谢状态的影响及进行机制探讨。研究表明，HRP可以显著改善MSG大鼠胰岛素抵抗状态，但不能改善b细胞功能状态，总体上不能改善雄性MSG大鼠的糖代谢状态。在MSG大鼠白色脂肪的研究中，HRP可以显著抑制NADPH氧化酶亚单位P22phox和P47phox的表达。在胰岛中，HRP虽轻度增加胰岛β-mass的水平，但是对α-mass无显著影响，且不能改善胰岛纤维化。MSG大鼠胰岛中增殖细胞（PCNA阳性细胞）与α细胞分布区域一致，且明显较正常SD大鼠增多。HRP不能改变PCNA阳性细胞数量。HRP可以改善胰岛局部的NADPH亚单位P22phox的表达。在棕色脂肪中，可以检测到包括（前）肾素，（P）RR，血管紧张素原这些局部RAAS组分的表达。氯沙坦和HRP 干预后棕色脂肪心脏型脂肪酸结合蛋白（hFABP）表达均明显升高。联合应用HRP 和氯沙坦可以显著提高棕色脂肪β3受体的表达。应用HRP、氯沙坦及联合HRP 和氯沙坦均可显著增加棕色脂肪UCP-1的表达。HRP对雌性MSG大鼠效应与雄性大鼠有显著差异。HRP可显著改善雌性MSG大鼠胰岛素敏感性和β细胞功能，HRP干预后其血糖水平较对照组显著改善。HRP可增加雌性MSG大鼠胰岛β-mass和抑制局部氧化应激，该效应与雄性MSG大鼠一致。HRP减少雌性MSG大鼠胰岛PCNA阳性细胞数量，抑制胰岛纤维化水平。综上所述，HRP可以改善MSG大鼠胰岛素抵抗，但仅在雌性动物能改善胰岛b细胞功能，HRP改善糖代谢状态在雄性动物中表现不显著。HRP的雌雄差异主要体现在HRP对胰岛病理学形态的作用上。本项目进一步证实了（P）RR参与糖代谢调节。HRP在一定程度上阻断（P）RR效应，且该效应的发挥与性激素相关。（P）RR的阻断可能是糖代谢异常防治的潜在靶点。