اثر تمرينات هوازي بر بيان ناقل 4 گلوكز (GLUT4) در عضله دوقلو و گلوكز خون در رت هاي ديابتي (نوع 2) شده با نيكوتين آميد و STZ

The effect of aerobic training on Glucose transporter type 4 expression in Gastrocnemius muscle and blood glucose of type 2 diabetes rats induced by Nicotinamide and STZ

زمينه و هدف انتقال غشايي گلوكز از مهمترين تعيين كننده هاي هايپرگليسيمي در ديابتي هاي نوع 2 است. مطالعه حاضر با هدف تعيين اثر تمرينات هوازي بر بيان ناقل 4 گلوكز (GLUT4) در عضله دوقلوي رت هاي ديابتي نوع 2 است. روش كار 16 سر رت نر ويستار 10 هفته اي (20 ± 220 گرم) از طريق تزريق درون صفاقي نيكوتين آميد و استرپتوزوتوسين (STZ) ديابتي نوع 2 شدند و به شيوه تصادفي به گروه هاي ورزش هوازي (8 = n) و كنترل (8 = n) تقسيم شدند. گروه ورزش در يك دوره تمرينات هوازي 12 هفته اي به تعداد 5 جلسه در هفته در قالب دويدن روي تريدميل شركت نمودند. 48 ساعت پس از آخرين جلسه تمريني، سطوح ناشتايي گلوكز و بيان GLUT4 در عضله دوقلو در دو گروه اندازه گيري شد. از آزمون آماري تي مستقل در سطح معني داري كمتر از 5 درصد جهت مقايسه متغيرها بين گروه ها استفاده شد. يافته ها: در مقايسه با رت هاي گروه كنترل، سطوح گلوكز ناشتا در پاسخ به تمرينات هوازي به ميزان معني كاهش يافت (0/001 = p). تمرينات هوازي همچنين به افزايش معني دار بيان GLUT4 در عضله دوقلو نسبت به گروه كنترل منجر شد (0/029 = p). نتيجه گيري: بر پايه شواهد موجود، كاهش سطوح گلوكز در پاسخ به تمرينات هوازي در رت هاي ديابتي نوع 2 را مي توان به افزايش بيان GLUT4 در عضله دوقلو نسبت داد. با اين وجود، اجراي مطالعات بيشتر با هدف شناخت ديگر مكانيسم هاي موثر بر سطوح گلوكز در پاسخ به تمرينات ورزشي در رت هاي ديابتي مورد نياز است.

In recent decades, the role of genetic factors in both secretion of insulin from the pancreas and insulin resistance in target tissues has got particular importance. Some genetic factors such as TCF7L2 and its polymorphisms or GLP-1 severely affect the synthesis and secretion of insulin from beta cells (2, 3). On the other hand, some other genetic components, such as FOXO1, PPARy, and FTO, also affect the energy homeostasis and metabolism of glucose and fat in target tissues such as skeletal muscles and fatty tissue. Membrane glucose transport is one of the most important determinants of hyperglycemia in type 2 diabetics. The purpose of this study was to determine the effect of aerobic training on the expression of 4-glucose transporter (GLUT4) in expression in gastrocnemius muscle in type 2 diabetic rats (T2D). Methods In this experimental-applied study, eighteen 10-weeks-old male Wistar rats (220 ± 20 g), procured from the institutional animal house facility were used for all the experiments and after induction of T2D were randomly divided into exercise (aerobic training / 12 weeks, n = 8) and control (no training, n = 8) groups aimed to determine the effect of aerobic training on GLUT4 expression in gastrocnemius muscle. Sample size and the number of rats in each groups designed according to the same previous studies that assessed gene expression in diabetes rats in response to exercise training. Animals were maintained under standardized conditions (12-h light/dark cycle, 25 ± 2 °C & humidity 45-55 %). The rats were left for 1 week for acclimatization prior to the commencement of the experiment. The study was approved by department of Exercise physiology of Amirkabir University of Technology, Iran and carried out in accordance with CPCSEA (Committee for the Purpose of Control and Supervision of Experiment on Animal) guidelines. T2D induced by STZ and Nicotinamide injection (dissolved in citrate buffer, pH 4.5). Hyperglycemia was confirmed by elevated blood glucose levels on day 7 after diabetes induction and only animals with fasting blood glucose level between 150-400 mg/dl were selected for were served as T2D rats and used in the study. The exercise group participated in a 12-week aerobic exercise (5 days/weekly) in the form of running on the treadmill.Finally, 48 hours after the lasted exercise session, the fasting rats in both groups (with 10-12 hours overnight fast) were anesthetized through intraperitoneal injection of 10% ketamine at a dose of 50 mg/kg along with 2% xylosine at a dose of 10 mg/kg, after which they were underwent dissection. After the rats were anesthetized, blood samples were collected through cardiac puncture. Then, subcutaneous fatty tissue was removed and immersed in RNA later until biochemical analysis was performed for determine GLUT4 expression. The blood samples were used to analyze the blood glucose and serum insulin. The serum was separated by centrifugation (5 min, 3,000 rpm) and was analyzed for glucose by glucose using a Cobas 6000 Analyzer (Roche, Germany). Glucose was determined by the oxidase method (Pars Azmoon kit, Tehran). The remaining serum samples were then stored at −20 ◦C until the insulin determination was made by ELISA method (Demeditec, Germany) and the intra- assay and inter-assay coefficient of variation of the method were 2.6% and 2.88 respectively.The RNA was extracted by Rneasy protect mini kit (QIAGEN) from subcutaneous fatty tissue according to manufactures instructions (19). RT-Real time PCR quantification of FTO mRNA was performed with Rotor gene 6000 system using One Step SYBR PrimeScript RT PCR kit (Takara co.) according to manufactures instructions. Melting curve analysis was performed at the end of PCR cycles in order to validate the specificity of the expected PCR product. We used RNA Polymrasell as a normalizer.Data were analyzed by computer using the Statistical Package for Social Sciences (SPSS) for Windows, version 16.0. Normal distribution of data was analyzed by the Kolmogorov-Smirnov normality test. Independent student t test was used for comparison of variables between two groups. A p-value of less than 0.05 was considered to be statistically significant Results Compare to control rats, Fasting glucose level decreased significant in response to aerobic training (p = 0.001). Aerobic training also resulted in significant increase in GLUT4 expression in Gastrocnemius muscle (p = 0.029). Conclusion Based on the available evidence, a decrease in glucose levels in response to aerobic training in T2D rats can be attributed to an increase in GLUT4 expression in twin muscle. However, further studies are needed to identify other effective mechanisms on glucose levels in response to exercise training in diabetes rats.