Collagen-induced p38 MAP kinase activation is a biomarker of platelet hyper-aggregation in patients with diabetes mellitus

Aims: We developed a novel method for diagnosing platelet hyper-aggregation in patients with type 2 diabetes mellitus (DM). Main methods: By measuring the dose response of platelet aggregation to collagen, an individual ED₅₀ was determined. Based on the normal range identified in non-DM controls (mean ± two SEM = 0.460 ± 0.082 μg/ml, n = 47), type 2 DM patients were divided into high ED₅₀ (ED₅₀ > 0.542 μg/ml; n = 32: group I) or low ED₅₀ groups (ED₅₀ < 0.378 μg/ml; n = 32; group II). In these patients, collagen-induced levels of phospho-p38 MAPK and phospho-p44/p42 MAPK were measured using Western blots and enzyme-linked immunosorbent assays (ELISA). Key findings: In group II, the collagen (0.3 and 1 μg/ml)-induced levels of both phospho-p38 MAPK and phospho-p44/p42 MAPK measured by western blot analysis were found to be significantly higher than those in group I. The individual ED₅₀ was found to be significantly correlated with the collagen-induced levels of phospho-p38 MAPK and phospho-p44/p42 MAPK. This correlation was also observed when ELISA was used to measure phospho-p38 MAPK levels in a different population of DM patients (n = 90). Significance: These results strongly suggest that the phosphorylation levels of collagen-induced p38 MAPK and p44/p42 MAPK represent the hyperaggregability of platelets and that the quantification of phospho-p38 MAPK can be a new and useful diagnostic biomarker of platelet hyper-aggregation in DM patients.