Circulating platelet–leukocyte aggregates: A marker of microvascular injury in diabetic patients

Abstract Diabetes is associated with multiple disorders including metabolic, cellular and blood disturbances leading to vascular complications. Increased circulating levels of platelet–leukocyte aggregates (PLA) have been described in several thrombotic diseases. In this study, we have evaluated circulating PLA in diabetic patients and we have investigated whether they may be a marker of vascular complications. Using flow cytometry assay, we have quantified PLA percentages in 65 diabetics including 20 patients with type I and 45 with type II diabetes, and 25 healthy subjects. Specific labelling identified platelet–polymorphonuclear aggregates (PPA) and platelet–monocyte aggregates (PMA). We have observed a significant increase of PPA and PMA levels in diabetics (22 ± 12% and 45 ± 18%, respectively) compared to controls (7 ± 4% and 19 ± 10%, respectively) ( p < 0.01). However, both PPA and PMA values were similar in the two diabetes types. Circulating PPA and PMA were significantly enhanced in diabetics with vascular lesions (PPA: 24 ± 13%; PMA: 50 ± 18%) than in diabetics without vascular lesions (PPA: 18 ± 8%; PMA: 38 ± 15%) ( p < 0.05 and p < 0.01). Patients with PPA > 18% and/or PMA > 38% showed a more important vascular injury (OR: 6; 95% CI: 1.6–23). Increased PMA circulating rate is particularly correlated to retinopathic injury (OR: 19; 95% CI: 2.3–154). Our findings established a relationship between increased circulating PLA levels, particularly PMA, and the incidence of microvascular complications in diabetes. They reinforce the concept of pro-inflammatory cells involvement in diabetic retinopathy pathogenesis and their link with thrombotic process.