Effects Of Chromium Chelated Small Peptides On Growth Performance And Glucose Metabolism In Spargue-Dawley Rats And Approach To The Mechanism

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.