GOAT/ghrelin轴自分泌/旁分泌机制在新型代谢手术袖状胃切除术缓解糖尿病中的作用

Sleeve gastrectomy is a simple and safe procedure. It has not the anatomic changes in accord with foregut hypothesis and hindergut hypothesis of bypass surgery but has an equivalent efficacy for resolution of type 2 diabetes melitus. Orexigenic hormone ghrelin has been signifciantly reduced following sleeve gastrectomy in patients with type 2 diabetes melitus whose ghrelin level has been lowered compared with health counterpart, indicating the significance of GOAT on modulation of AG/UAG ratio in glucose metabolism via autocrine/paracrine way. We found that the characteristic secretion curve induced by hunger-ingestion disapeared following SG. According to the override inhibition principle and the phenomena of reduced appetite even under negative energy balance in patients underwent SG, we hypothesized that local sythesis of ghrelin decreased in hypothalamus and pancreas, the mTOR pathway was activated with the reduction of negative modulation from ghrelin. The GOAT was inhibited, AG/UAG ration lowered and the ingestion pulse was inhibited and insulin secretion was enhanced. We use the rat with diabetes as the material. Following SG, AG was injected to rebuild the ghrelin secretion curve. Following antangonist the GHSR, blocking NPY/AgRP protein and inhibition of mTOR pathway, modulation of GOAT/ghrelin axis and change in ingestion impulse and secretion of insulin were evaluated. We intended to elucidate the mechanism by which SG resolute type 2 diabetes melitus with low ghrelin level and the function of autocrine/paracrine pathway in hypothalamus and pancreas.

袖状胃切除术（SG）安全简单，不具备旁路手术前肠假说/后肠假说的解剖基础却具有相似的缓解糖尿病疗效。SG使糖尿病患者本已低于正常的促食欲激素ghrelin进一步降低却可以缓解糖尿病,提示GOAT调控ghrelin比例并以自分泌/旁分泌作用影响糖代谢。前期工作发现SG后ghrelin特殊波形分泌消失，我们推断下丘脑和胰腺局部的ghrelin因"超负抑制"合成减少，mTOR通路由于ghrelin负相调节丧失而激活，进而降低GOAT活性，下调AG/UAG比例而抑制摄食冲动和促进胰岛素分泌。本研究以糖尿病大鼠SG为参照，观察对比术后腹腔注射AG恢复循环ghrelin分泌曲线、阻断GHSR、拮抗NPY/AgRP蛋白、抑制mTOR通路对GOAT/ghrelin轴调控下丘脑摄食冲动和胰腺胰岛素分泌的影响，阐明SG形成的低ghrelin水平影响GOAT/ghrelin轴自分泌/旁分泌作用缓解糖尿病的机制。

袖状胃切除术（SG）是目前治疗病态性肥胖及II型糖尿病的有效手段，其最主要的激素改变是显著降低血清ghrelin水平，明确其对GOAT/ghrelin轴的影响以及对下丘脑摄食冲动以及胰岛素分泌的影响是本研究的主要内容。本研究1、通过饲料+STZ成功构建糖尿病大鼠模型，2、实施袖状胃手术干预，结果发现与糖尿病大鼠和空白手术组对比，袖状胃切除术后空腹血糖由15.88±2.32 mmol/L降至9±1.17 mmol/L，OGTT各时间点血糖及血糖的曲线下面积（AUC）均较其余两组低（p<0.05）。说明袖状胃切除术有效缓解糖尿病；3、TG、AG水平及AG/TG比例均较对照组提示显著的下降趋势，具有统计学差异，提示SG术后对GOAT/ghrelin轴的调控具有重要作用。同时研究发现，行SG后大鼠ghrelin分泌曲线呈明显的缓和低平趋势，失去原有的与饮食相关的多相波峰模式，这与课题的最初设想一致。以上结果提示SG具有缓解糖尿病的效果，与降低血清ghrelin水平，特别是分泌波形有关。进一步研究发现：4、SG后，下丘脑preproghrelin 以及GOAT mRNA表达均降低、局部ghrelin以及GOAT蛋白表达降低、GHSR蛋白表达增高，明确了SG对下丘脑GOAT/ghrelin轴的影响模式；SG术后下丘脑mTOR处于激活状态，其上游p-AKt和p-mTOR以及下游p-P70S6K在术后明显增高，阻断GHSR后下游p-AKt和p-mTOR表达进一步增加，但NPY、AgRP及c-fos mRNA表达差异不显著，根据本部分结果推断，虽然袖状胃切除可以降低下丘脑局部的ghrelin以及GOAT表达，但在手术造成的负能量平衡下激活了mTOR通路，而后者的效应与ghrelin下降的效应相反，最终导致袖状胃切除后摄食冲动并无变化。5、SG对胰腺分泌胰岛素具有刺激作用，OGTT 0分钟、30分钟、90分钟和120分钟胰岛素均较其余两组低（p<0.05），60分钟及120分钟胰岛素较其余两组高（p<0.05）。术后HOMA-IR较术前明显降低（p<0.05）。高葡萄糖钳夹技术提示SG可改善胰岛素储备受损的状况。由于受建模手术引起粘连的影响，胰腺标本取材收到显著影响，胰腺GOAT/ghrelin轴的表达及调控的影响，实验结果不满意。本研究的研究内容均已完成，实验目标基本达成。