Platelet function and activation in mixed ancestry subjects with hyperglycemia, from the Western Cape, South Africa

Abstract

Type 2 diabetes mellitus (T2DM) is a metabolic disorder which is characterised by insulin resistance, defective insulin secretion or both. The chronic state of hyperglycemia in diabetes is associated with microvascular complications and macrovascular complications which account for an estimated 80% of deaths as a result of cardiovascular complications. Type 2 diabetes mellitus is an inflammatory disease and pro- inflammatory stimuli in the form of activated endothelial cells, render the vascular endothelial surface attractive for both platelets and leukocytes. Activated platelets bind to the exposed extracellular matrix (ECM) and also to each other in both physiological haemostasis and pathological thrombosis. They can also adhere to leukocytes. Platelet leukocyte interactions are divided into 3 stages; these include the initiation of the interaction, stabilization of the aggregates and amplification of leukocyte activation. This study attempts to contribute to the current knowledge of T2DM by investigating the percentage of monocytes and neutrophils forming aggregates with platelets in pre-diabetes and diabetes and comparing this to non- diabetes individuals as well as the up regulation of pro-thrombotic and activation antigens on the surface of monocytes and neutrophils (Tissue Factor and CD69). Levels of platelet activation and function will be determined by both plate monocyte aggregates (PMA) and platelet neutrophil aggregates (PNA). A total of 124 individuals were recruited from Bellville South, Cape Town, South Africa. This comprised of diabetes (DM) (n=15), pre-diabetes (pre-T2DM) (n=25) and controls (n=84). All individuals were screened for diabetes using the oral glucose tolerance test (OGTT). Platelet leukocyte measurements were performed using the Navios 8-colour flow cytometer. The median percentage of circulating platelets bound to monocytes (%PMAs) was significantly increased in the T2DM 49.04[36.78-62] and the Pre-T2DM 48.96[36.72-61.2],groups, compared to the control group 7.2[5.4-9], p<0.0001. The median %PNAs, which show interactions between neutrophils and platelets, were significantly increased in the T2DM group 13.56[10.17-16.95] compared to the control group 6.01[4.51-7.51] p<0.0001. Platelet monocyte aggregates (PMAs) were higher in both the pre-T2DM and T2DM groups when compared to the control group indicating increased interactions between platelets and monocytes. In addition to forming aggregates with leukocytes, the platelets were able to initiate activation and phenotypic change to the leukocytes by increasing the expression of CD69 and TF (CD142). This finding provides further evidence that there is a link between the inflammatory process and the prothrombotic activity evident in diabetes and pre-diabetes individuals. Furthermore, we describe elevated levels of circulating activated neutrophils which directly correlate with increased PNA formation in both the pre-T2DM and T2DM group.