The Influence Of Different Concentration Of High Glucose On The Expression Of Visfatin In Neonatal Rat Cardiomyocyte

Objective: For a long time, the adipose tissue has been considered as a terminally differentiated organ for storage of energy. With the discovery of many adipocytokines, the endocrine function of adipose tissue is also gradually being recognized, and adipose tissue as an endocrine organ has become a consensus of the academia. Adipocytokines play an important role in regulation of the balance of energy metabolism throughout the body, the dyssecretosis of which will lead to a variety of metabolic disorders, they are closely related to insulin resistance (IR), obesity, diabetes, coronary heart disease, hyperlipidemia and regarded as being the intermediate links of IR and cardiovascular diseases.Visfatin, as a new discovered adipocytokine, mainly derives from visceral adipose tissue. Insulin-mimetic actions of visfatin can reduce blood glucose and promote the synthesis and accumulation of adipose. With the exception of relation with obesity, insulin resistance and other metabolic disorders, visfatin also has a variety of other biological functions, may be related to vulnerable plaque, vascular proliferation, endothelial dysfunction, inflammation, involves in the pathophysiology of coronary heart disease and has become a research hotspot in recent years.Visfatin plays a role in lowering the blood glucose, because it can be combined with non-insulin binding sites on the insulin receptor, the activation of insulin signaling pathway promote muscle cells and adipocytes to uptake glucose and inhibit glucose output in hepatic. Insulin resistance is one of important pathogenesises in the Type 2 diabetes. The clinical studies about visfatin and Type 2 diabetes become more in-depth. Foreign scholars have found that the visfatin levels of patients with type 2 diabetes increase than non- diabetic patients[15]. Studies have found that in cultured 3T3-L1 adipocytes, dexamethasone could up-regulated the expression of visfatin-mRNA, whereas growth hormone,TNF-α,soproterenol inhibited the expression of visfatin-mRNA in different degree, and showed a time and dose dependent manner. Insulin resistance caused the changes of hormone levels which can regulate the expression of visfatin-mRNA, suggesting that visfatin may be the connection bond of obesity and insulin resistance. Some scholars through the glucose clamp test in the normal person confirmed that increasing the concentration of glucose in a short time (4 h) would increase the expression levels of visfatin in circulation vicariously, but the outer infusion of insulin or somatostatin could block the induction of high glucose to visfatin[18]. Currently, researches about visfatin are more concentrated in the adipocytes. The studies have found that visfatin is expressed in skeletal muscle, bone marrow stromal cells and liver. Then, whether the cardiac myocytes could express visfatin? There are not any relative reports about the role of hyperglycemia in the visfatin expression of cardiomyocytes.In this study,we observe that the influence of different concentration of glucose on the expression of visfatin in neonatal rat cardiomyocyte. In order to research the role of visfatin in the pathogenesis of diabetes,and provide new ideas for the clinical diagnosis and treatment of cardiovascular disease associated with diabetes mellitus.Methods: Primary cultures the cardiomyocytes from the hearts of 2-3 days'neonatal Sprague-Dawley (SD) rats aseptically , regardless of sex.After 48 hours'culture with serum and 24 hours'culture without serum,cells in good conditions are selected and put into 11 groups randomly.They are 6 groups in glucose part.①lower concentration of glucose control group(5.5mmol/L),②25mmol/L glucose group,③30mmol/L glucose group,④50mmol/L glucose group,⑤80mmol/L glucose group,⑥hypertonic control group.They are 5 groups in different stimulation time part.①6 hours group,②12 hours group,③24 hours group,④48 hours group,⑤control group. Culture these cardiomyocytes with different concentration of glucose for 48 hours and high glucose (50mmol/L) for different time, use GAPDH as the internal control ,then detect the expression of visfatin-mRNA and visfatin-protein with RT-PCR and western- blot.Results: (1)With the elevation of glucose concentration, the expression of visfatin-mRNA and protein increased in neonatal rat cardiomyocyte. The influence of high glucose on the visfatin expression in cardiomyocytes is due to the concentration of glucose, not the osmotic pressure. (2)When treating with the high glucose within 24 hours, the expression of visfatin-mRNA and protein in myocardial cells significantly increased with time; but after 24 hours the expression of visfatin didn't change significantly comparable with 24 hours group.Conclusion: The cardiomyocytes can express visfatin. The higher concentration of glucose can increase the expression of visfatin in cardiomyocytes in vitro. As the elevation of glucose concentration, in cardiomyocyte the expression of visfatin also increases.The influence of high glucose on the visfatin expression in cardiomyocytes is due to the concentration of glucose, not the osmotic pressure caused. Within 24 hours, the expression of visfatin in cardiomyocytes significantly increased with time.