麩醯胺對於糖尿病下肢缺血小鼠內皮前驅細胞之影響

糖尿病為常見之慢性代謝異常疾病，有高心血管疾病發生風險，可能與糖尿病患體內較低的內皮前驅細胞 (endothelial progenitor cells, EPCs)有關。EPCs由骨髓細胞生成，會分化為具有功能之內皮細胞，能夠修復內皮細胞並參與血管新生作用。麩醯胺 (glutamine, GLN) 為人體中含量最豐富的游離胺基酸，先前研究指出GLN具有抗氧化、抗發炎及免疫調節之作用。本實驗以糖尿病下肢缺血動物模式探討給予GLN對EPCs調動及血管內皮修復之影響。實驗共分八組分別為糖尿病、糖尿病缺血1、7、21天犧牲組、糖尿病麩醯胺及糖尿病缺血麩醯胺1、7、21天犧牲組。以AIN-93G為基本飲食，麩醯胺組以含量占總氮量25%之GLN取代部分酪蛋白。實驗結果發現添加GLN的組別會顯著增加糖尿病缺血小鼠血液EPCs比率、血漿stromal-derived factor (SDF)-1濃度、肌肉vascular endothelial growth factor (VEGF)蛋白表現量、肌肉matrix metalloproteinase-9、SDF-1、hypoxia-inducible factors-1、VEGF mRNA表現量，組織免疫染色也顯示缺血組織有較高的CD31表現量。本研究結果顯示飲食中添加GLN能促進EPCs之調動、增加血液EPCs比率，並有助於改善缺血組織之血管修復作用。

關鍵字

糖尿病；下肢缺血；麩胺酸；內皮前驅細胞

並列摘要

Diabetes is a metabolic disorder with increased risk of vascular diseases, any may due to the lower percentage of endothelial progenitor cells (EPCs). EPCs are cells derived from bone marrow that are able to differentiate to mature endothelial cells (ECs), and are involved in neovascularization, wound healing, tissue regeneration, and tissue remodeling. Glutamine (GLN) is the most abundant free amino acid in the plasma and body, previous studies showed that GLN exerts immunomodulatory and antioxidant properties. This study investigated the effects of oral glutamine (GLN) supplementation on circulating EPC mobilization and expressions of tissue EPC-releasing markers in diabetic mice subjected to hindlimb ischemia. Diabetic mice were divided into 2 non-ischemic groups and 4 ischemic groups. One of the non-ischemic and 2 ischemic groups were fed the control diet, while the remaining 3 groups received diets with identical components except that part of the casein was replaced by GLN. The respective diets were fed to the mice for 3 weeks, and then the non-ischemic mice were sacrificed. Unilateral hindlimb ischemia was created in the ischemic groups, and mice were sacrificed at 1 or 7 days after ischemia. Their blood and ischemic muscle tissues were collected for further analyses. Results showed that plasma matrix metallopeptidase (MMP)-9 and the circulating EPC percentage increased after limb ischemia in a diabetic condition. Compared to groups without GLN, GLN supplementation upregulated plasma stromal cell-derived factor (SDF)-1 and muscle MMP-9, SDF-1, hypoxia-inducible factor-1, and vascular endothelial growth factor gene expressions. The CD31-immunoreactive intensities were also higher in the ischemic limb. These findings suggest that GLN supplementation enhanced circulating EPC mobilization that may promote endothelium repair at ischemic tissue in diabetic mice subjected to limb ischemia.