Insulin Directly Reduces Platelet Sensitivity to Aggregating Agents: Studies In Vitro and In Vivo
Insulin Directly Reduces Platelet Sensitivity to Aggregating Agents: Studies In Vitro and In Vivo
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DOI：
10.2337/diab.37.6.780
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发表时间：
1988-06
期刊：
影响因子：
7.7
通讯作者：
M. Trovati;G. Anfossi;F. Cavalot;P. Massucco;E. Mularoni;G. Emanuelli
中科院分区：
文献类型：
--
作者：
M. Trovati;G. Anfossi;F. Cavalot;P. Massucco;E. Mularoni;G. Emanuelli
本研究的目的是在体外和体内研究胰岛素对血小板功能的影响。在体外研究中，我们通过将禁食受试者的富血小板血浆（PRP）与终浓度为40 μU/ml的人常规胰岛素一起孵育30分钟，评估胰岛素在生理激素浓度下是否影响血小板功能。我们观察到血小板对所有使用的聚集剂（即 ADP、血小板活化因子 (PAF)、肾上腺素、胶原蛋白和花生四烯酸钠）的敏感性显着降低。为了研究胰岛素对血小板的作用是否具有剂量依赖性，我们将禁食受试者的PRP与不同浓度的人常规胰岛素（40、80、120和160μU/ml）孵育5分钟，我们观察到胰岛素诱导的血小板对聚集剂敏感性的降低是一种剂量依赖性现象。此外，与胰岛素孵育 5 分钟和 30 分钟后血小板反应的比较表明，胰岛素对血小板聚集的影响是时间依赖性的。其抑制活性缺乏特异性表明胰岛素不会干扰每种聚集剂在特定位点的初始结合，但会影响血小板聚集的常见步骤。我们的研究排除了胰岛素降低血小板功能的血小板内 cAMP 水平或血栓素 A2 产生的可能性，因为这种激素降低了血小板 cAMP 浓度（这种现象本身促进血小板聚集），并且不会改变胶原蛋白或花生四烯酸钠诱导的血小板产生血栓素 A2（通过其稳定代谢物血栓素 B2 的放射免疫测定来测量）。胰岛素似乎有助于改变血小板膜的特性，正如红细胞已经被证明的那样。体内研究包括三项胰岛素对男性志愿者血小板功能影响的研究：1）正常血糖-高胰岛素（40μU/ml）钳夹90分钟，然后进行60分钟正常血糖； 2) 正常血糖-高胰岛素 (160-μU/ml) 钳夹 30 分钟，然后进行 60 分钟正常血糖； 3) 静脉推注人常规胰岛素 (3.84 U/m2)。在这三项研究中，我们连续测量了血小板对 ADP、PAF、肾上腺素、胶原蛋白和花生四烯酸钠的敏感性。我们观察到体内胰岛素在 40 μU/ml 的生理浓度下可减少血小板聚集。对于一些聚集剂，我们证明了胰岛素作用的剂量和时间依赖性。后者在胰岛素输注后逆转。当胰岛素以静脉推注形式给药并在低血糖出现之前研究血小板聚集时，我们观察到仅 10 分钟后即可检测到胰岛素对血小板的影响。总之，这项研究表明胰岛素可能在血小板功能的生理调节中发挥作用，并且长期胰岛素缺乏可能是糖尿病患者中经常观察到的血小板聚集性增强的原因。
The aim of this study was to investigate the influence of insulin on platelet function, both in vitro and in vivo. For the in vitro investigation, we evaluated whether insulin affects platelet function at a physiological hormone concentration by incubating the platelet-rich plasma (PRP) of fasting subjects with human regular insulin at the final concentration of 40 μU/ml for 30 min; we observed a significant reduction of platelet sensitivity to all the aggregating agents employed, i.e., ADP, platelet-activating factor (PAF), epinephrine, collagen, and Na+ arachidonate. To investigate whether the insulin effect on platelets is dose dependent, we incubated the PRP of fasting subjects with different concentrations of human regular insulin (40, 80, 120, and 160 μU/ml) for 5 min, and we observed that the insulin-induced reduction of platelet sensitivity to aggregating agents is a dose-dependent phenomenon. Furthermore, the comparison between the platelet responses after 5 and 30 min of incubation with insulin showed that the insulin effect on platelet aggregation is time dependent. The lack of specificity of its inhibiting activity suggests that insulin does not interfere with the initial binding of each aggregating agent at specific sites but does influence a common step of platelet aggregation. Our study rules out the possibility that insulin reduces platelet-function–modifying intraplatelet cAMP levels or thromboxane A2 production, because this hormone decreases the platelet concentrations of cAMP–a phenomenon that, per se, promotes platelet aggregation–and does not modify collagen or Na+ arachidonate–induced platelet production of thromboxane A2, measured by radioimmunoassay of its stable-metabolite thromboxane B2. Insulin seems to help in modifying platelet membrane properties, as has already been shown for erythrocytes. The in vivo investigation comprised three studies of the influence of insulin on platelet function in male volunteers: 1) a euglycemic-hyperinsulinemic (40-μU/ml) clamp for 90 min followed by 60 min of euglycemia; 2) a euglycemic-hyperinsulinemic (160-μU/ml) clamp for 30 min followed by 60 min of euglycemia; and 3) an intravenous bolus of human regular insulin (3.84 U/m2). Throughout the three studies, we serially measured platelet sensitivity to ADP, PAF, epinephrine, collagen, and Na+ arachidonate. We observed that insulin in vivo and at the physiologic concentration of 40 μU/ml reduced platelet aggregation. For some aggregating agents, we demonstrated a dose and time dependence of the insulin effect. The latter was reversed after the insulin infusion. When insulin was administered as an intravenous bolus and platelet aggregation was studied before the appearance of hypoglycemia, we observed that insulin influence on platelets can be detected after only 10 min. In conclusion, this study suggests that insulin may have a role in the physiological modulation of platelet function and that the long-term insulin deficiency might account for the enhanced platelet aggregability frequently observed in diabetic patients.