Insulin-induced release of plasminogen activator from human blood platelets

Insulin resistance in prostate cancer patients and predisposing them to acute ischemic heart disease

Lack of insulin or insulin resistance (IR) plays a central role in diabetes mellitus and makes diabetics prone to acute ischemic heart disease (AIHD). It has likewise been found that many cancer patients, including prostate cancer patients die of AIHD. Previously it has been delineated from our laboratory that dermcidin could induce anomalous platelet aggregation in AIHD and also impaired nitric oxide and insulin activity and furthermore dermcidin was also found in a few types of cancer patients. To determine the role of this protein in prostatic malignancy, a retrospective case-control study was conducted and blood was collected from prostate cancer patients and healthy normal volunteers. So, we measured the level of dermcidin protein and analyzed the IR by Homeostasis Model Assessment (HOMA) score calculation. Nitric oxide was measured by methemoglobin method. HDL, glycated hemoglobin (HbA1c), BMI, hs-cTroponin-T were measured for the validation of the patients' status in the presence of Dermcidin isoform-2 (DCN-2). Multiple logistic regression model adjusted for age and BMI identified that the HOMA score was significantly elevated in prostate cancer patients (OR = 7.19, P<0.001). Prostate cancer patients are associated with lower level of NO and higher level of both proteins dermcidin (OR = 1.12, P<0.001) and hs-TroponinT (OR = 1.76, P<0.001). From the results, it can be interpreted that IR plays a key role in the pathophysiology of prostate cancer where dermcidin was the cause of IR through NO inhibition leading to AIHD was also explained by high-sensitive fifth generation cTroponin-T (hs-cTroponinT) and HbA1c level which are associated with endothelial dysfunction.

Isolation and study of insulin activated nitric oxide synthase inhibitory protein in acute myocardial infarction subjects

Insulin inhibits platelet aggregation through nitric oxide synthesis by stimulating platelet insulin activated nitric oxide synthase. Impaired platelet insulin activated nitric oxide synthase in acute myocardial infarction (AMI) patients had been reported and thus our aim was to identify and isolate the factors impairing insulin activated nitric oxide in acute myocardial infarction patients' plasma and study its effect on platelets aggregation in vitro. The insulin activated nitric oxide synthase inhibitor was identified as a protein and was purified from the plasma of AMI subjects using DEAE cellulose and Sephadex G-50 column, molecular weight determined by SDS-PAGE, nitric oxide quantified by methaemoglobin method, inhibitor protein quantified in plasma by immunoblot and ELISA, platelet aggregation studies done using an aggregometer, thromboxane-A2 in the platelets determined by radioimmunoassay, (125)I-insulin radioligand binding studies done using normal subject platelets. The purified nitric oxide synthase inhibitor protein was ~66 kDa, concentration in AMI subjects' plasma varied from 114 to 9,090 μM and was undetected in normal subjects' plasma. The inhibitor protein competes with insulin for insulin receptor binding sites. The Incubation of the normal subject PRP with 5.0 μM inhibitor for 30 min followed by 0.4 μM ADP addition caused platelet aggregation in vitro, 130 μM aspirin or 400 μU insulin/ml addition was able to abrogate 0.4 μM ADP induced platelet aggregation even in the presence of 5.0 μM inhibitor. A potent inhibitory protein against insulin activated nitric oxide synthase in platelets appears in circulation of AMI subjects impairing nitric oxide production, potentiating ADP induced platelet aggregation and increasing the thromboxane-A2 level in platelets.

Demonstration of a novel circulating anti-prostacyclin receptor antibody

Although coronary artery disease (CAD) is appreciated to be accelerated in patients with chronic spinal cord injury (SCI), the underlying mechanism of CAD in SCI remains obscure. We have recently shown that platelets from subjects with SCI develop resistance to the inhibitory effect of prostacyclin (PGI2) on the platelet stimulation of thrombin generation. The loss of the inhibitory effect was due to the loss of high-affinity prostanoid receptors, which may contribute to atherogenesis in SCI. Incubation of normal, non-SCI platelets in SCI plasma (n = 12) also resulted in the loss of high-affinity binding of PGI2 (Kd1 = 9.1 +/- 2.0 nM; n1 = 170 +/- 32 sites per cell vs. Kd1 = 7.2 +/- 1.1 nM; n1 = 23 +/- 8 sites per cell), with no significant change in the low-affinity receptors (Kd2 = 1.9 +/- 0.1 microM; n2 = 1,832 +/- 232 sites per cell vs. Kd2 = 1. 6 +/- 0.1 microM; n2 = 1,740 +/- 161 sites per cell) as determined by Scatchard analysis of the binding of [3H]PGE1. The loss of high-affinity PGI2 binding led to the failure of PGI2 to inhibit the platelet-stimulated thrombin generation. The increase of cellular cyclic AMP level, mediated through the binding of PGI2 to low-affinity receptors in platelets, was unaffected in SCI platelets. PAGE and immunoblot of SCI plasma showed the presence of an IgG band, which specifically blocked the binding of [3H]PGE1 to the high-affinity PGI2 receptors of normal platelets. PAGE of the reduced IgG band, the amino acid sequence of the novel band as a heavy chain of IgG that inhibits the binding of [3H]PGE1 to the high-affinity platelet PGI2 receptor, demonstrates that the specific recognition and inhibition of high-affinity PGI2 binding to platelets was due to an anti-prostacyclin receptor antibody present in SCI plasma.