【作者】 乔伟；

【导师】 周安国； 王之盛；

【作者基本信息】 四川农业大学 ， 动物营养与饲料科学， 2009， 博士

【摘要】 本文分别以SD大鼠和L6骨骼肌细胞为研究对象,通过体内和体外两部分试验,研究了自备小肽铬对大鼠生长性能和糖代谢的影响与作用机理。体内试验,以吡啶羧酸铬为试验对照,研究了不同水平小肽铬对大鼠生长性能和糖代谢的影响。选用72只健康的清洁级SD大鼠(雌雄各半),按体重一致的原则分6个处理,每个处理6个重复,每个重复2只大鼠;分别在6组大鼠的基础日粮中添加0、100、200、500、1000μg/kg铬(小肽铬源)和200μg/kg铬(吡啶羧酸铬源)。饲养期间,大鼠自由采食,饮用双重蒸馏水,试验期35 d。试验结果表明:饲粮小肽铬显著提高大鼠日增重(ADG)和饲料转化效率(FE)。500μg/kg的小肽铬源铬,提高ADG可达17.5%(P＜0.05),比吡啶羧酸铬高6.8个百分点。提高FE可达23.2%(P＜0.05),比吡啶羧酸铬高14个百分点。达最大ADG和最高FE的饲粮小肽铬添加量分别为524和528μg/kg。饲粮添加小肽铬,显著影响生理生化参数。200μg/kg和500μg/kg的小肽铬分别显著降低胰岛素水平39.2%和24.5%(P＜0.05),500μg/kg的小肽铬显著提高乳酸脱氢酶(LDH)和肌酸激酶(CK)活性(P＜0.05)。饲粮添加267μg/kg小肽铬,可最大限度提高胰岛素效率。饲粮小肽铬也显著促进骨骼肌糖代谢。500μg/kg的小肽铬显著提高琥珀酸脱氢酶(SDH)活性(P＜0.05),提高总ATP酶活性20.8%(P=0.053),显著增加乳酸(LD)、丙酮酸(PD)和肌糖原含量(P＜0.05)。体外试验,以L6骨骼肌细胞为研究对象,在模拟生理胰岛素水平和不含胰岛素的培养条件下,考察了小肽铬对葡萄糖代谢的影响与作用机理,各分4个处理,每个处理4个重复;以不添加任何铬源为空白对照,以三氯化铬和吡啶羧酸铬处理为试验对照,测定糖分解代谢和合成代谢过程的中间产物、起关键调控作用的酶活性,及糖代谢调控相关蛋白mRNA表达的量。试验结果表明:在生理胰岛素水平和不含胰岛素条件下添加小肽铬,均可促进骨骼肌细胞对葡萄糖的吸收和代谢,显著提高已糖激酶(HK)、LDH、苹果酸脱氢酶(MDH)、SDH和CK活性(P＜0.05),显著增加LD和PD浓度(P＜0.05)。基因表达测定表明,骨骼肌细胞在生理胰岛素水平或不含胰岛素的条件下培养,小肽铬均能显著上调胰岛素受体(IR)、葡萄糖转运载体蛋白4(GLUT4)、糖原合成酶(GS)和解偶联蛋白3(UCP3)mRNA的表达(P＜0.05)。添加小肽铬对上述指标的提高幅度均大于三氯化铬和吡啶羧酸铬。综合两部分试验结果发现:①小肽铬增强胰岛素效率、促进糖代谢、提高能量利用效率,提高饲料利用效率,作用效果优于三氯化铬和吡啶羧酸铬;②小肽铬对糖代谢的促进作用可不依赖于胰岛素,并能显著增强胰岛素的作用;③小肽铬通过上调IR、GLUT4和UCP3 mRNA的表达量,提高细胞对葡萄糖的摄取和转运,促进糖酵解和三羧酸循环,增强糖分解代谢供能;并通过上调GS mRNA的表达水平,促进肌糖原合成,增加能量的贮备,从而提高能量利用效率,提高大鼠生长性能和饲料转化效率。更多还原

【Abstract】 Chromium (Cr) is an essential trace mineral of humans and animals. Despite over five decades of endeavour, the role of Cr at cell and molecular level has been a poorly understood field of study. Two experiments were conducted to invertigate the influence of CrSP (Chromium chelated small peptides) on glucose metabolism and the possible mechanisms on cell and molecular level.Trial 1 Effects of CrSP on the growth performance and glucose metabolism in Spargue-Dawley (SD) ratsIn this experiment, 72 SD rats with initial body weight of 65±5 g were randomly assigned to six dietary treatment groups (n=12). The first group was offered a basal diet as a control. The second, third, fourth and fifth groups received basal diet supplemented with 100, 200, 500 and 1000μg/kg Cr (CrSP), and the sixth group was offered basal diet supplemented with 200μg/kg Cr in the form of chromium picolinate (CrPic), respectively. At the end of the 5-week trial, average daily gain (ADG), food efficiency (FE), and sera concentrations of insulin, glucose, and glucose metabolism-related enzymes were determined. The results indicated that rats that received 500μg/kg CrSP exhibited great improvement in ADG and FE compared to the control group and CrPic group (P<0.05). There was not significant difference between the gtoups of 100, 200μg/kg CrSP. 200μg/kg CrPic and the control group (P>0.05). The results of blood biochemical parmeters in SD rat showed that the concentration of blood glucose and insulin were both significantly decreased (P<0.05), enzyme activity of LDH and SDH were significantly increased (P<0.05), and the LD, PD and muscle glycogen in the skeletal muscle were significantly increased (P<0.05), with the supplementation of 500μg/kg CrSP.Trial 2 Effects of CrSP on the glucose metabolism in L6 skeletal muscle cells and Approach to the MechanismThe aim of the second part of this study was to evaluate the impact of three different chromium forms as chromic chloride (CrCl), chromium picolinate (CrPic), and CrSP on glucose uptake and metabolism in vitro. The result showed that in cultured L6 skeletal muscle cells, chromium augmented insulin-stimulated glucose uptake and metabolism as assessed by a reduced glucose concentration of culture medium (P<0.05). And the glucose metabolism relative enzymy activity,such as HK、LDH、MDH、SDH were significantly increased (P<0.05). At the molecular level, insulin signifieantly increased the mRNA levels of insulin receptor (ER), glucose transporter 4 (GLUT4), glycogen synthase (GS) and uncoupling protein- 3 (UCP3), and these impacts can be enhanced by the addition of chromium (P<0.05), especially in the form of CrSP.Collectively, results of this study demonstrate that chromium improves glucose catabolism and anabolism through enhances the function of insulin, improves the glucose metabolism relative enzymy activity of HK、LDH、MDH and SDH, upregulates the mRNA levels of IR, GLUT4, GS, and UCP3 in skeletal muscle cells. CrSP has independent insulin like function, and has higher efficacy on glucose uptake and metabolism compared to the forms of CrCl and CrPic.更多还原