Although oxidization of LDL is known to be a crucial step for atherosclerotic progression, the significance of oxidized HDL remains to be clarified. The purpose of this study was to determine the relationships of oxidized HDL with blood coagulation and fibrinolysis in patients with diabetes. The subjects were outpatients with type 2 diabetes (n = 163; median hemoglobin A1c, 6.9%). Activities of blood coagulation and fibrinolysis were evaluated by levels of thrombin-anti-thrombin complex (TAT) and plasmin-α2 plasmin inhibitor complex (PIC), respectively. Relationships of oxidized HDL with TAT and PIC were investigated by using linear regression analysis and logistic regression analysis. Oxidized HDL showed a significant inverse correlation with TAT and a marginally significant correlation with PIC (Spearman's rank correlation coefficient: TAT, - 0.205 [p < 0.01]; PIC, - 0.135 [p = 0.087]). Prevalence of high TAT was significantly lower in the 3rd tertile group for oxidized HDL than in its 1st tertile (20.4 vs. 5.6%, p < 0.05), and prevalence of high PIC was marginally significantly lower in the 3rd tertile group for oxidized HDL than in its 1st tertile (40.7 vs. 24.1%, p = 0.099). In multivariate logistic regression analysis using age, gender, smoking, alcohol drinking, BMI, hemoglobin A1c, therapy for dyslipidemia, therapy for diabetes and anti-coagulation therapy as explanatory variables, odds ratios for high TAT and high PIC in the 3rd tertile group for oxidized HDL versus its 1st tertile group were significantly lower than the reference level of 1.00 (high TAT: 0.19 [0.04-0.99], p < 0.05; high PIC: 0.33 [0.12-0.95], p < 0.05). The frequency of high TAT or high PIC was lower in the higher tertile group for oxidized HDL than in its lower tertile group. Thus, oxidized HDL is thought to be inversely associated with both blood coagulation and fibrinolysis in patients with type 2 diabetes.
Background
Resveratrol has been shown to inhibit platelet aggregation. However, the mechanism for this action of resveratrol remains to be clarified. The purpose of this study was to elucidate the Ca2+-related mechanism for the inhibitory action of resveratrol on platelet aggregation.
Methods
Ca2+ entry and subsequent aggregation of human platelets induced by different stimulants including thrombin, thapsigargin, and 1-oleoyl-2-acetylglycerol (OAG) were measured by the fluorescence method and light transmittance method, respectively. Each stimulant was added to a nominally Ca2+-free medium containing platelets, and then CaCl2 was added to the medium to induce Ca2+ influx into platelets.
Results
Thapsigargin-induced Ca2+ entry into platelets and subsequent platelet aggregation were significantly inhibited in the presence of resveratrol at 6.25 μM or higher concentrations, while OAG-induced Ca2+ entry and subsequent platelet aggregation were not affected by resveratrol at concentrations up to 50 μM. In the nominally Ca2+-free medium, thrombin induced a small transient increase in intracellular Ca2+ concentrations, which was attenuated in the presence of resveratrol at 12.5 μM or higher concentrations. Thrombin-induced Ca2+ entry into platelets and subsequent platelet aggregation were significantly inhibited in the presence of resveratrol at 12.5 μM or higher concentrations.
Conclusions
The results suggest that resveratrol inhibits thrombin-induced platelet aggregation through decreasing Ca2+ release from its stores and inhibiting store-operated Ca2+ influx into platelets.
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