| Objective To compare the changes of hepatic glucagon, glucagon receptor and glycogen expression in normoal glucose tolerance (NGT) rats, impaired glueose tolerance (IGT) and IGT rats with GLP-1agonists intervention, and to explore protective effect and possible mechanism of GLP-1agonists on the hepatic glucagons pathway.Methods Fifty-four male Wistar rats in4-5weeks (150g-180g) of clean grade were purchased in Institute of Chinese Medicine of Shanxi. After one week adaptive feeding (five/cage), they were divided into A group (n=18) and B group (n=36) randomly. The A group rats were fed by normal diet (13.4kJ/g, which accounted for10.2%of calories, fat and protein accounted for23.3%respectively, carbohydrate accounted for66.5%); The B group rats were given high-sugar and high-fat feed (21.8kJ/g, which accounted for56.0%of calories, fat and protein accounted for7.0%respectively, carbohydrates accounted for37.0%) and free access to water, at room temperature controlled at18-22℃, relative humidity30%-70%. Two groups of rats twice a day morning and evening feeding, daily food in take for each rat to vote for3%of body weight. When12weeks, do oral glucose tolerance test (OGTT):after fasting8h, cut the tail blood and rapid blood glucose meters measure fasting blood glucose (FBG), intragastric administration with50%glucose injection2g/kg body weight, after2h cut the tail blood again and measure2h postprandial blood glucose (2hPG). Building a suceessful model was7.8mmol/L≤2hPG<11.1mmol/L and continued for more than a week. The A group, blood glucose to normal, and being setted to normoal glucose tolerance control group (NGT group, n=18). Thirty-two rats in B group were into models, it has the making model success rate of over88%, and randomly divided the B group into two groups, the impaired glucose tolerance group (IGT group, n=16), Exendin-4interventionin group (Ex group, n=16). Select randomly nine rats in NGT group, eight rats in IGT group and Ex group respectively, weighing, and then do oral glucose tolerance test measure2hPG. The next day, anesthetized rats with5%chloral hydrate by intraperitoneal injection0.6ml/100g body weight, taken abdominal primary venous blood, rapid centrifugation of blood samples of serum specimens, the way of Radioimmunoassay under test glucagon, measure blood fat figures such as TG and TC. Quickly remove the liver, for western blot detection the glucagon receptor expression and PAS detection glycogen. The remaining rats in NGT group continue to give normal diet, the IGT group and Ex group were to continue to give high-sugar high-fat feeding and freedom drinking water. Ex group received Exendin-4(Eli Lilly and Company to provide) lOug/kg subcutaneously, twice daily, in the NGT group and the IGT group were given equal volume of saline injection. When interventing4weeks, weighing, and then measure2hPG. The next day, anesthetized rats, taken abdominal primary venous blood, to detect fast plasma glucagons and quickly remove the liver, to detect glucagon receptor and glycogen. All results were measured by (x±s), using SPSS17.0software package, multiple groups means were compared with single factor analysis of variance, LSD test.P≤0.05was considered statistically significant.Results1The changes of general signs in each groups Before intervention, the rats in NGT group have moderate size and good spirit. They are agile and responsive to outside stimulation. The fur of the rats is shiny and the elasticity is good. Compared with NGT group, rats in the IGT group and Ex Group are obesity, especially abdominal obesity, apathetic, unresponsive to the outside, slow and hair less shiny, poor flexibility. After intervented with Exendin-44weeks, compared with the IGT group at the same period and the Ex group before intervented, Ex group shape is uniform, spirit improved clearly, sensitive to the outside, obviously agile, hair gloss and elasticity are improved markedly.2.The changes of clinical characteristics and biochemical indices between rats in each groups Before intervention, compared with the NGT group, the body weigh of rats and2hPG in the IGT group and Ex group were higher (448.67±12.90vs.514.13±13.41)(448.67±12.90vs.513.12±11.86) and the differences were also significant (both P<0.05). The2hPG of rats were higher (5.96±0.77vs.9.69±0.33)(5.96±0.77vs.9.26±0.38), the differences were also significant (both P<0.05). The FBG of rats were higher(4.79±0.55vs.5.05±0.72)(4.79±0.55vs.5.23±0.39), 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 roup, the body weigh and the2hPG of rats in the Ex group was lower (514.13±13.41vs.513.12±11.86)(9.69±0.33vs.9.28±0.38); the FBG, TG and TC were higher(5.05±0.72vs.5.23±0.39)(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 group, the body weigh, the2hPG, the TG and TC of rats in the Ex group were decreased (520.75±18.42vs.445.88±20.29)(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 Ex group were decreased (4.98±.36vs.4.89±0.31), but the difference was not significant (P>0.05). Compared with the Ex group before intervented, the levels were decreased (520.75±18.42vs.445.88±20.29)(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 (5.05±0.72vs.4.89±0.313), but the difference was not significant (P>0.05). Compared with the NGT group, the levels all above were higher (459±11.20vs.445.88±20.29)(4.93±0.39vs.4.89±0.31)(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 difference was not significant (P>0.05).3.The levels of blood glucagon in each groups Before intervention, compared with the NGT group, the blood glucagon in the IGT group and Ex group were higher (88.18±6.94vs.118.89±3.53)(88.18±6.94vs.116.12±3.37) and the differences were significant (both P<0.05). Compared with the IGT group, the blood glucagon in the Ex group was higher (118.89±3.53vs.116.12±3.37) but the difference was not significant (P>0.05). After intervented with Exendin-44weeks, compared with the IGT group at the same period, the blood glucagon in the Ex group was decreased (118.39±4.36vs.86.89±6.23), the differences was significant (P<0.05). Compared with the Ex group before intervented, the levels was also lower (116.12±3.37vs.86.89±6.23), the difference wes significant (P<0.05). Compared with the NGT group, the level was decreased (88.07±7.34vs.86.89±6.23), but the difference was not significant (P>0.05).4.The expression of glucagon receptor in liver with eath groups Before intervention, compared with the NGT group, the expression of glucagon receptor with rats in the IGT group ind the Ex group were increased (0.79±0.03vs.1.18±0.07vs.1.15±0.04) and the differences were significant (both P<0.05). Compared with the IGT group, the expression of glucagon receptor with rats in the Ex group was higher (1.18±0.07vs.1.15±0.04) but the difference was not significant (P>0.05). After intervented with Exendin-44weeks, compared with the IGT and Ex group, the expression of glucagon receptor in the Ex group was decreased (1.17+0.10vs.0.88±0.05) the differences was significant (both P<0.05).5. The content of glycogen in liver with eath groups Before intervention, compared with the NGT group, the content of glycogen with rats in the IGT group and the Ex group were reduced. Compared with the IGT group, the different content of glycogen with rats in the Ex group was not significant. After intervented with Exendin-44weeks, compared with the IGT and Ex group, the content of glycogen in the Ex group was increased, the differences was significant.Conclusions1. The rats with impaired glucose tolerance, the expression of glucagon and glucagon receptor with rats was increased, the content of glycogen in liver was reduced. 2. The rats with impaired glucose tolerance, GLP-1receptor agonist, Exendin-4, could reduce glucagon, inhibit glucagon receptor and increase the content of glycogen. |
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