Summary. Arachidonic acid uptake activity was measured in platelets obtained from 27 Type 2 diabetic patients and 18 agematched control subjects. In both groups after 1 h incubation almost all the incorporated 14C-arachidonic acid was located in the phospholipids of the platelets. Arachidonic acid was predominantly incorporated into phosphatidylcholine. The radioactivity incorporated into platelets increased linearly with incubation time, up to 90 min. The linear increase was observed at arachidonic acid concentrations of 0.1-1.0 ~tg/ml in both groups. The rate of incorporation of radioactivity in diabetic platelets was about 1.4 times higher than that in control platelets at all arachidonic acid concentrations studied. The arachidonic acid uptake activity of diabetic platelets (577 + 26 ng/60 min per 109platelets) was significantly higher than that in control platelets (410_ 26 ng/60 rain per 109plate -lets).No significant correlations were found between the arachidonic acid uptake activity and fasting plasma glucose, total cholesterol or triglyceride levels. The arachidonic acid uptake activity of platelets was significantly higher in diabetic patients with proliferative retinopathy than in those with little or no background retinopathy. In addition, there were no significant differences between control and diabetic subjects in the uptake activity of platelets for linoleic acid and oleic acid. These data may explain the elevated arachidonic acid content in diabetic platelet phospholipids and enhancement of thromboxane synthesis in diabetes.Key words: Arachidonic acid uptake, platelet phospholipids, Type 2 diabetes, retinopathy, platelet-rich plasma, non-esterifled fatty acid.Thromboxane A2 (TXA2), biosynthesized from arachidonic acid in platelet phospholipids, plays an important rrle in the process of platelet aggregation [1,2]. It is postulated that the balance between platelet TXA2 and vascular prostacyclin production might be a crucial step in the development of atherosclerosis and arterial thrombosis in diabetes mellitus. Recently, Kalofoutis and Lekakis [3] and we [4] have demonstrated that the arachidonic acid content of platelet phospholipids was increased in diabetes. It is generally accepted that the TXA2 synthesis rate is regulated at the step of liberation of arachidonic acid from membrane phospholipids [5]. Therefore, increased esterified arachidonic acid content in phospholipids might modulate TXA2 production in diabetes.In this study, we examined the t4C-arachidonic acid uptake activity of platelets obtained from Type 2 (noninsulin-dependent) diabetic patients and age-matched control subjects, to clarify the mechanisms of increased arachidonic acid levels in platelet phospholipids in diabetes.
Subjects and methods
SubjectsThe Type 2 diabetic subjects included in the study were t0 men and 17 women ranging in age between 48 and 86 years (mean 67 + 2 years). Eleven patients were treated with insulin and 16 were treated with sulphonylureas. The control subjects (five men and 13 women, age range 46-79...