一种新型铬(Ⅲ)配合物的降血糖活性、作用机制及安全性研究

Chromium(Ⅲ), as one of the important trace elements in the body, has shown significantly anti-diabetic activity. Due to the low absorption rate of chromium salts, it has become necessary for designing and development of new organic chromium compounds. The organic chromium compounds, as the functional component of secondary anti-diabetic functional foods or nutrient supplement, have been used over the world. As so far, chromium picolinate is the most commonly applied dietary supplement. However, it was reported that chromium picolinate has shown the genotoxicity and cytotoxicity which may caused by the ligand (picolinate), and its safety has been concerned by the people. Currently, the study on the novel and non-toxic organic chromium complex with hypoglycemic activity is an important project. Chromium(III) malate complex was synthesized in a single step reaction by chelating chromium(III) with L-malic acid which was selected as the natural ligand. Chromium(III) malate complex had beneficial influences on the improvement of controlling blood glucose in alloxan-induced diabetic mice. Chromium(III) malate complex did not cause oxidative DNA damage, and was non-toxic in the acute and subacute toxicity studies. Chromium(III) malate complex has potential application for being as the functional component of secondary anti-diabetic functional foods or nutrient supplement. In the further investigation, the project is therefore to evaluate anti-hyperglycemic activity of the chromium(III) malate complex in type 2 diabetes an study its action mechanism, study the regular pattern of absorption, distribution, metabolism and elimination, and the bioavailability of chromium(III) malate complex in rats, and elucidate the transport and conversion of the chromium(III) malate complex in biological media. It is also to evaluate the toxicity of the chromium(III) malate complex. The project will provide a scientific basis for research and development of a non-toxic organic chromium complex for being as secondary anti-diabetic functienonal foods and nutritional supplement.

铬(Ⅲ)是人体重要的微量元素之一，并具有降血糖功能。相对无机铬，有机铬的吸收率高且安全,作为辅助降血糖功能食品的功效成分和营养素补充剂已得到广泛应用。目前市场上应用最广的是吡啶甲酸铬，但有研究报道它会产生DNA毒性、细胞毒性等，且其毒性与配体吡啶甲酸有关，其安全性已备受关注。因此，降血糖活性好、安全性高的新型有机铬配合物的研究是当前重要课题之一。申请人以天然活性物质苹果酸为配体，合成了苹果酸铬，发现它能明显降低四氧嘧啶所致糖尿病小鼠的血糖值，急性和亚急性毒性试验期内均无明显毒性，且不氧化损伤DNA，具有很好的应用前景。本项目将进一步考察苹果酸铬对2型糖尿病的降血糖活性，并探明作用机制；研究其在体内的吸收、分布、代谢和排泄规律及生物利用度，揭示体内吸收和转运机制；同时对其进行安全性毒理学研究，为安全性高的新型有机铬辅助降血糖功能食品和营养素补充剂的研究开发提供科学依据。

本项目研究了一种新型铬(Ⅲ)配合物-苹果酸铬的降血糖活性、作用机制及安全性。采用2型糖尿病大鼠模型，胰岛素抵抗大鼠BRL肝表皮细胞、3T3-L1脂肪细胞和L6肌细胞模型，研究了苹果酸铬对2型糖尿病大鼠的降血糖活性、量效关系及其作用机制。结果表明，苹果酸铬可显著降低2型糖尿病大鼠的空腹血糖值，呈剂量依赖关系，并显著降低2型糖尿病大鼠血清胰岛素水平、胰岛素抵抗指数和C-肽水平，增加肝脏中肝糖原、葡萄糖-6-磷酸酶和葡萄糖激酶含量，对2型糖尿病大鼠血清总胆固醇、高密度脂蛋白、低密度脂蛋白和甘油三酯水平也有较好的改善作用；苹果酸铬可通过改善胰岛素抵抗细胞胰岛素敏感性通路相关蛋白和基因(Irs-1、p-Irs-1、PPARγ、PI3K和p38-MAPK蛋白，Irs-1、PPARγ、PI3K和p38-MAPK mRNA)表达、上调葡萄糖摄取通路相关蛋白和基因(Glut4、p-AMPKβ1和Akt蛋白，Glut4、AMPKα2和Akt2 mRNA) 表达，从而达到改善胰岛素抵抗和降血糖作用。采用健康SD大鼠、Caco-2单层细胞模型、等温滴定量热（ITC）法和光谱实验等，研究了苹果酸铬在体内的吸收、分布、代谢和排泄规律及生物利用度。结果表明，苹果酸铬体内动力学参数符合二室模型，雄性大鼠的相对生物利用度显著高于雌性大鼠，绝对生物利用度无显著差异；苹果酸铬在Caco-2细胞中的转运和摄取主要是经被动扩散的途径吸收；苹果酸铬可与人血清白蛋白和脱铁-转铁蛋白形成复合物，影响其荧光强度，该结合过程是自发进行的放热过程（ΔH<0，ΔG<0），两者间的作用力主要为氢键和范德华力。选用组氨酸缺陷型鼠伤寒沙门氏菌组、健康ICR小鼠和SD大鼠，研究了苹果酸铬的遗传毒性、亚慢性毒性和慢性毒性，在实验剂量范围内，试验结果皆为阴性。可见，苹果酸铬对2型糖尿病大鼠具有较好的降血糖活性，在新型有机铬辅助降血糖功能食品和营养素补充剂方面有较好的应用前景。