Platelet-derived growth factor and growth-promoting activity in the serum samples and platelets of patients with non-insulin-dependent diabetes mellitus

Although platelet-derived growth factor (PDGF) is thought to be a major mediator of atherosclerotic disease, the pathophysiology of diabetic vasculopathy, including atheroscierosis, is unclear. By means of an enzyme immunoassay that used a monoclonal antibody against human PDGF-B chain, PDGF-like immunoreactivity was determined in serum, platelet-poor plasma, and platelet lysate of 28 patients with non-insulin-dependent diabetes mellitus and 11 control subjects. Growth-promoting activity was also measured by tritiated thymidine incorporation into DNA of cultured human fibroblasts. The PDGF-like immunoreactivity in serum was correlated (r = 0.42; p < 0.01) with that in platelet lysate prepared from a fixed volume of blood. Furthermore, a correlation (r = 0.70; p < 0.001) was found between the PDGF-like immunore-activity and the growth-promoting activity in platelet lysate but not in serum. There was no significant difference between patients with diabetes and control subjects with respect to the PDGF-like immunoreactivity in serum or in platelet lysate (36.2 ± 2.2 vs 42.8 ± 3.1 ng/ml or 49.1 ± 2.4 vs 56.2 ± 3.4 ng/mg protein; mean ± SEM). In contrast, the serum growth-promoting activity was lower (p < 0.05) in patients with diabetes than In control subjects (88.1% ± 7.1% vs 117.4% ± 6.9%) and there was a negative correlation (r = -0.39; p < 0.05) between the serum growth-promoting activity and the fasting plasma glucose level. The growth-promoting activity in platelet lysate of patients with diabetes did not differ from that of the control subjects (59.9% ± 11.6% vs 65.9% ± 11.2%). In platelet-poor plasma, the PDGF-like immunoreactivity was at the limit of detection (2 ng/ml) and the growth-promoting activity was consistently low. These results suggest that the PDGF quantities In serum samples and platelet lysate were not different in the diabetic state and that the low concentration of growth-promoting activity in diabetic serum was caused by an alteration in circulating factors other than PDGF.