Circulating Platelet-Leukocyte Aggregates as a Marker of Microvascular Lesions in Diabetic Patients.

Introduction: Evolution of diabetes is associated with multiple disorders including metabolic, cellular and blood disturbances leading to various vascular complications (micro-and macro-angiopathies). Increased circulating levels of platelet-leukocyte aggregates (PLA) have been described in several thrombotic diseases.

Material and Methods: In this study, we have evaluated the circulating PLA in diabetic patients and we have investigated whether they may be linked to the vascular complications currently occurring during diabetes evolution. Using flow cytometry assay, we have quantified PLA percentages in 65 diabetics (37 males/28 females, 57 ± 11 years old) including 20 patients with type I and 45 with type II diabetes, and 25 healthy subjects (15 males/10 females, 44 ± 9 years old). Labelling approach using specific monoclonal antibodies permitted us to identify platelet-polymorphonuclear aggregates (PPA) and platelet-monocyte aggregates (PMA).

Results: We have observed a significant increase of PPA and PMA levels in diabetics (22 ± 12% and 45 ± 18%, respectively) compared to control subjects (7 ± 4% and 19 ± 10%, respectively). However, both PPA and PMA values were similar in the two types of diabetes and they were not correlated to the disease duration. Circulating PPA and PMA percentages were significantly enhanced in diabetics with vascular lesions (n=37; PPA: 24 ± 13%; PMA: 50 ± 18%) than in diabetics without vascular lesions (n=28; PPA: 18 ± 8%; PMA: 38 ± 15%). Patients with PPA > 18% and /or PMA > 38% had a more important vascular thrombotic damage (OR: 6; 95%; IC: 1.6; 23). The increased PMA circulating percentage seems to be more specific for micro-retinopathy occurrence (OR: 19, 95% IC: 2.3; 154). The rare patients with elevated PMA percentage and without vascular lesions have a shorter duration of diabetes (7 ± 5 years) than patients presenting retinopathy lesions (16 ± 11 years).

Conclusion: Together our findings established a relationship between increased circulating PLA rate, particularly that of PMA, and the incidence of microvascular complications in diabetic patients. In addition, they reinforce the concept that pro-inflammatory cells are involved in diabetic retinopathy pathogenesis.