Study On The Effect Of Adiponectin On Atherosclerosis In Diabetes Mellitus

Objective: To investigate the influence and primary mechanisms of adiponectin on the inflammatory responses in vascular endothelial cell.Methods: Human umbilical vein endothelial cells (HUVECs) were cultured in vitro and divided into 4 groups: (1) control group; (2) TNF-αstimulation group: HUVECs were incubated with human recombinant TNF-α(0,10,20,50ng/ml) for 6h; (3) TNF-α+ PDTC group: HUVECs were pre-incubated with PDTC for 1h, and then exposed to 20ng/ml TNF-αfor 6h; (4) TNF-α+ adiponectin group: HUVECs were pre-incubated with adiponectin for 18h, and then exposed to 10ng/ml TNF-αfor 6h. the concentrations of MCP-1 released from HUVECs were measured using ABC-ELISA.Results: Expression of MCP-1 was increased in HUVECs stimulated by TNF-αfor 6h, compared with that of control group (P<0.01). If HUVECs were incubated with 10, 50 and 100μmol/L PDTC for 1 hour, and then exposed to 10μg/L human recombinant TNF-αfor 6 hours, the expression of MCP-1 was decreased a dose dependent manner, compared with simple TNF-αstimulation(P<0.01). Adiponectin (25, 50 mg/L) also inhibited the MCP-1 release induced by TNF-α(P<0.01), but 12.5mg/L adiponectin has no effect on the MCP-1 release induced by TNF-α(P>0.05).Conclusions: Adiponectin can modulate endothelial inflammatory response through effecting the expressions of some inflammatory factors, and adiponectin has protective actions in the initiation and progression of atherosclerosis.PartⅡStudy on the serum adiponectin levels in type 2 diabetic ratsObjective: To explore the association between serum adiponectin levels and type 2 diabetes.Methods: Male Wistar rats, 2-month-old, weighing 206.35±12.48g were housed under controlled temperature conditions and a 12h light/12h dark circle. Hyperglycemia was induced by the intraperitoneal injection of streptozotocin (30mg/kg). After 72h following streptozotocin administration, blood was collected from tail vein and was analyzed for blood glucose. Animals showing fasting blood glucose higher than 300mg/dL (16.7mmol/L) were considered as type 2 diabetic rats and used for this study. Animals were divided into two groups: (1) control group: Rats treated with normal diet for 16 weeks, n=8; (2) diabetic group: Diabetic rats treated with fat-rich-diet containing 3% cholesterol for 16 weeks, n=10. ELISA was used to identify the levels of serum adiponectin and sICAM-1. CRP was measured with immunoturbidimetry. TC, TG, HDL-C and LDL-C were measured with chemical methods.Results: The levels of plasma glucose, TC, TG, LDL-C, CRP and sICAM-1 were highly increased (P<0.05), but the levels of HDL-C were decreased (P<0.05) in type 2 diabetic rats, compared with those of control group. The results of correlation analysis show that the levels of serum adiponectin were negatively correlated with TC, TG, LDL-C and CRP (P<0.05) and were positively correlated with HDL-C (P<0.05), but no significant correlation with sICAM-1 was observed.Conclusions: Serum adiponectin concentrations were decreased in type 2 diabetic rats, and hypoadiponectinemia is closely related with type 2 diabetes. PartⅢIntervention study on the influence of adiponectin on the early phase of atherosclerosis in diabetic ratsObjective: To investigate whether the increased plasma concentration of adiponectin could actually reduce the expression of inflammatory cytokines in diabetic rats.Methods: Replication-defective recombinant adenovirus expressing the full-length apM1 cDNA gene (Ad-APN) was constructed with AdEasyTM Adenoviral Vector System. Animals were divided into two groups: (1) DM group: Diabetic rats were treated with"atherogenic"diet containing 20% fat, 3% cholesterol and 0.5% sodium cholate; (2) DM+Ad-APN group: Diabetic rats were treated with"atherogenic"diet, and at the age of 14 weeks, Ad-APN was injected via tail vein (2×108 pfu each). All animals were treated for 16 weeks. ELISA was used to identify the levels of plasma adiponectin and sICAM-1. CRP was measured with immunoturbidimetry. The expression of MCP-1, ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1) mRNA in the aortic tissue was detected by RT-PCR and real-time PCR. TC, TG, HDL-C and LDL-C were measured with chemical methods.Results: The levels of plasma glucose, TC and TG in diabetic rats were 7.46±1.73mmol/L, 206.88±28.62mg/dL and 65.52±18.59mg/dL. After 14 days of adenovirus injection, the plasma adiponectin levels in Ad-APN-treated diabetic rats increased to 68.4±19.2μg/mL. However, no significant difference of plasma glucose,TG, TC, HDL-C and LDL-C was observed between the two groups(P>0.05). In Ad-APN-treated diabetic rats, the levels of plasma sICAM-1 and CRP were reduced by 22% (P<0.01) and 21% (P<0.01) respectively, compared with that of diabetic rats. The RT-PCR and real-time PCR revealed that Ad-APN treatment suppressed the mRNA levels of MCP-1, VCAM-1 and ICAM-1 in the aortic tissue (P<0.05).Conclusions: The elevated plasma adiponectin inhibits the expression of inflammatory cytokines in diabetic rats at both the protein and mRNA levels, suggesting that adiponectin has an anti-inflammatory property and suppresses the initiation and progression of atherosclerosis in diabetic rats.