| Objective To compare the change of glucose transporter4(GLUT4), homeostasis model assessment of insulin resistance(HOMA-IR) and glucogen in impaired glucose tolerance (IGT) rats after intervention with exendin-4, and to analyse the correlation between GLUT4mRNA and HOMA-IR, to investigate the mechanisms of exendin-4improvement insulin resistance of skeletal muscle in rats with IGT.Methods To purchase54male Wistar rats in4-5weeks from animal breeding center of Shanxi Medical University. one week adaptive feeding later(five/cage), the rats were distributed into the Conventional feed group (The first group, n=18) and High fat and sugar diet feed group(The second group, n=36) randomly. All rats free access to water, free action. All rats morning and evening twice a day feeding, daily food intaked for each rat to vote for3%of body weight. At the twelfth week, do oral glucose tolerance test (OGTT):after fasting8h, cut the tail blood and measure fasting blood glucose (FBG), intragastric administration with50%glucose injection2g/kg body weight, after2hours measure2h postprandial blood glucose (2hBG). Building a successful model was7.8mmol/L≤2hPG<11.1mmol/L and continued for more than a week.The first group rats, blood glucose to normal, and being set to the normal glucose tolerance group(NGT/NaCl group, n=16) and continue to give regular feed and freedom drinking water and free action. Thirty-two rats of the second group were into models, model success rate is88%, and randomly divided the second group into two groups, Exendin-4intervention group (IGT/Ex group, n=16) and the impaired glucose tolerane (IGT/NaCl group, n=16). To continue give high-fat high-sugar feeding and freedom drinking water and free action. Select randomly half of the rats from NGT/NaCl group, IGT/NaCl group and IGT/Ex group respectively, do OGTT test, measure FBG and2hBG. After fasting12-14h, anesthetized rats, taken abdominal primary venous blood, measure TG and TC and FIN, calculation HOMA-IR. Then quickly remove skeletal muscle measure the expression of GLUT4mRNA by real time quantitative polymerase chain reaction(RT-PCR); Obverse the change of GLUT4in skeletal muscle cells using immunohistochemical staining methods; Obverse the change of glycogen in skeletal muscle cells using PAS staining methods. The remaining rats in IGT/Ex group received Exendin-45ug/kg subcutaneously, twice daily, the NGT/NaCl and IGT/NaCl group were given equal volume of saline injection.4weeks later, put to death the other half of rats, measure the points above.All results were measured by (x±s), using SPSS13.0software package, multiple groups means were compared with single factor analysis of variance. P<0.05was considered statistically significant.Results1. The changes of biochemical indices in each group Before intervention, compared with the NGT/NaCl group, the2hBG of rats in the IGT/NaCl group and the IGT/EX group were higher (5.96±0.77vs.9.69±0.33)(5.96±0.77vs.9.28±0.38), the differences were also significant (both P<0.05); The FBG of rats were higher(4.76±0.50vs.5.04±0.47)(4.76±0.50vs.5.14±0.48), but the differences were not significant (both P>0.05); The TG of rats were higher (0.87±0.22vs.2.08± 0.21)(0.87±0.22vs.2.12±0.21) and the differences were also significant (both P<0.05); The TC of rats were higher (0.84±0.19vs.1.91±0.16)(0.84±0.19vs.2.00±0.17), the differences were also significant (both P<0.05); Compared with the IGT/NaCl group, the FBQTG and TC in IGT/EX group were higher(5.04±0.47vs.5.14±0.48)(2.08±0.21vs.2.12±0.21)(1.91±0.16vs.2.00±0.17), but the differences were not significant (P>0.05). After intervented with Exendin-44weeks, compared with the IGT/NaCl group, the2hBG, the TG and TC of rats in the IGT/Ex group were decreased(10.28±0.38vs.7.19±0.34)(2.22±0.14vs.1.06±0.13)、(2.09±0.18vs.1.02±0.09), the differences were significant (both P<0.05); The FBG in the IGT/Ex group were decreased (5.06±0.45vs.5.02±0.47), but the difference was not significant (P>0.05). Compared with the IGT/Ex group before intervented, the2hBG, the TG and TC levels were decreased (10.28±0.38vs.7.19±0.34)(2.12±0.21vs.1.06±0.13)(2.00±0.17vs.1.02±0.09), the differences were significant (both P<0.05); The FBG was also decreased (5.14±0.48vs.5.02±0.47), but the difference was not significant (P>0.05). Compared with the NGT/NaCl group, the FBG,2hBG, TG and TC were higher (4.72±0.42vs.5.02±0.47)(6.26±0.53vs.7.19±0.3)(0.89±0.23vs.1.06±0.13)(0.89±0.20vs.1.02±0.09), but the differences were not significant (P>0.05).2. The change of fasting plasma insulin and HOMA-IR in each group Before intervention, compared with the NGT/NaCl group, the FIN of rats in the IGT/NaCl group and the IGT/Ex group were higher(7.83±0.70vs.16.98±1.51)(7.83±0.70vs.17.08±1.73) and the differences were also significant (both P<0.05); The HOMA-IR of rats were higher (1.02±0.23vs.1.89±0.34)(1.02±0.23vs.1.98±0.24) and the differences were also significant (both P<0.05); Compared with the IGT/NaCl group, the FIN of rats in the IGT/Ex group was higher (16.98±1.51vs.17.08±1.73), the HOMA-IR was higher(1.89±0.34vs.1.98±0.24), but the differences were not significant (both P>0.05). After intervented with Exendin-44weeks, compared with the IGT/NaCl group, the FIN of rats in the IGT/Ex group was lower(17.02±1.57vs.13.65±2.17) the difference was significant (P<0.05), the HOMA-IR of rats was lower (1.90±0.14vs.1.53±0.19) the difference was significant (P<0.05); Compared with the IGT/Ex group before intervented, the level of FIN was lower(17.08±1.73vs.13.65±2.17) the difference was significant (both P<0.05), the HOMA-IR was lower (1.98±0.24vs.1.53±0.19), the difference was significant (both P<0.05). Compared with the NGT/NaCl group, the FIN was higher (7.76±0.60vs.13.65±2.17), the HOMA-IR was higher(1.02±0.23vs.1.53±0.19), the differences were significant (both P<0.05).3. Expression of GLUT4mRNA in skeletal muscle in each group Before intervention, compared with the NGT/NaCl group, the expression of GLUT4mRNA with rats in the IGT/NaCl group and the IGT/Ex group were decreased (2.84±0.37vs.0.12±0.06)(2.84±0.37vs.0.11±0.07) and the differences were significant (both P<0.05); Compared with the IGT/NaCl group, the expression of GLUT4mRNA with rats in the IGT/Ex group was lower (0.12±0.06vs.0.11±0.07) but the difference was not significant (P>0.05). After intervented with Exendin-44weeks, compared with the IGT/NaCl at the same period and IGT/Ex group before intervention, the expression of GLUT4mRNA in the IGT/Ex group was increased (0.11±0.04vs.1.47±0.27)(0.11±0.06vs.1.47±0.27) the differences were significant (both P<0.05). Compared with the NGT/NaCl group, the level of GLUT4mRNA was lower (2.76±0.49vs.1.47±0.27), the difference was significant (P<0.05).4. Expression of GLUT4in skeletal muscle cells in each group Before intervention, compared with the NGT/NaCl group, the skeletal muscle cells in IGT/NaCl group and IGT/Ex group were less colored while the skeletal muscle cells in NGT/NaCl group were colored extensively, and more colored granules. After intervented with Exendin-44weeks, the color in skeletal muscle cells in the IGT/Ex group was more than the IGT/NaCl group at the same period and the IGT/Ex group before intervention, mainly expressed in cytoplasm.5. Correlation analysis From the scatter diagram between GLUT4mRNA and HOMA-IR, HOMA-IR is decreased with the rise of GLUT4mRNA in skeletal muscle. The GLUT4mRNA of skeletal muscle is negative correlation with HOMA-IR(r=-0.75, P<0.05).6. The change of glycogen in skeletal muscle cells in each group Before intervention, compared with the NGT/NaCl, the skeletal muscle cells in IGT/NaCl control group and IGT/Ex group were less colored while the skeletal muscle cells in NGT/NaCl group were colored extensively. After intervented with Exendin-4twenty-eight days, the color in skeletal muscle cells in the IGT/Ex group was more than the IGT/NaCl group at the same period and the IGT/Ex group before intervention.Conclusions1.The decline of GLUT4and glycogen in skeletal muscle is a reason of insulin resistance of skeletal muscle.3. GLP-1receptor agonist (Exendin-4) could up-regulate expression of GLUT4and increase glycogen synthesis of skeletal muscle, ameliorate insulin resistance of skeletal muscle, which provides a theoretical basis for GLP-1to improve insulin resistance. |
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