Plasminogen activator inhibitor-1 antigen concentrations during insulin and oral glucose tolerance tests in obese man

Effect of insulin versus sulfonylurea therapy on cardiovascular risk factors and fibrinolysis in type II diabetes

In non-insulin-dependent diabetes mellitus (NIDDM), cardiovascular risk factors improve during treatment, but whether insulin (I) differs from sulfonylurea (SU) therapy is unclear. To separate the contributions of improved diabetic control versus treatment regimen to risk factors, we examined the effects of SU and I on insulin sensitivity, basal and post-glucose load levels of insulin-like molecules, fibrinolysis, and lipid concentrations. Twenty poorly controlled, diet-treated NIDDM subjects were given I or SU each for a period of 16 weeks in a randomized crossover study, with a 4-week washout period between each treatment. Subjects were studied at the baselines (B1 and B2) and after each treatment. Treatment with I or SU produced similar improvements in glycemia (hemoglobin A1 [HbA1] B1, 11.7% +/- 2.1%; SU, 8.5% +/- 0.9%; I, 8.6% +/- 1.2%) and the metabolic clearance rate of glucose ([MCR-G] B1, 1.86 x/divided by 1.4; SU, 2.36 x/divided by 1.4 (P = .005 vB1); I, 2.27 x/divided by 1.4 (P = .07 vB1) ml x kg(-1) x min(-1)). On SU therapy, subjects had higher fasting and post-glucose load levels of intact proinsulin compared with B1 and I (fasting, 13.9 x/divided by 2.6 v 9.5 x/divided by 2.2 (P = .004) and 9.1 x/divided by 2.4 pmol x L(-1) (P = .01), respectively). Plasminogen activator inhibitor-1 (PAI-1) activity and antigen were higher than at B1 on SU therapy (23.7 v 19.9 AU x mL(-1) (P = .02) and 47.6 v 32.2 ng x mL(-1) (P = .006), respectively), but not on I. There were no changes compared with B1 and no differences between the two therapies in total, very-low-density lipoprotein (VLDL), and intermediate-density lipoprotein (IDL) cholesterol and triglyceride, low-density lipoprotein (LDL), high-density lipoprotein 2 (HDL2) and HDL3 cholesterol, apolipoprotein (apo) A1, A2, and B1, or lipoprotein (a) [Lp(a)] levels. In conclusion, (1) treatment with SU or I resulted in equal improvement in glycemia and insulin sensitivity, (2) intact proinsulin and PAI-1 antigen and activity were higher on SU, and (3) there were no differences in lipid concentrations with improved glycemia or between therapies.

Relationship of hepatic and peripheral insulin resistance with plasminogen activator inhibitor-1 in Pima Indians

Plasminogen activator inhibitor-1 (PAI-1) is related to insulin resistance and several components of the insulin resistance syndrome, and PAI-1 levels are elevated in subjects with non-insulin-dependent diabetes mellitus. Many Pima Indians are obese, insulin-resistant, and hyperinsulinemic, and they have high rates of diabetes but a low risk of ischemic heart disease. In contrast to whites and Asians, PAI-1 activity is similar between nondiabetic and diabetic Pima Indians. We therefore examined the association of PAI-1 with hepatic and peripheral insulin action measured using the hyperinsulinemic-euglycemic clamp. To investigate if insulin per se has any effect on PAI-1 in vivo, we also assessed the effects of endogenous (during a 75-g oral glucose load) and exogenous (during hyperinsulinemic clamp) insulin on PAI-1 antigen. Twenty-one (14 men and seven women; mean age, 26.3 +/- 4.8 years) Pima Indians underwent a 75-g oral glucose tolerance test (OGTT) and a sequential hyperinsulinemic-euglycemic clamp. Peripheral insulin action was measured as absolute glucose uptake (M value) and normalized to estimated metabolic body size (EMBS). Hepatic insulin action was measured as percent suppression of basal hepatic glucose output during hyperinsulinemia. PAI-1 antigen was determined using a two-site enzyme-linked immunosorbent assay that detects only free PAI-1. PAI-1 antigen concentrations were significantly related to body mass index ([BMI] rs = .54, P = .012), waist (rs=.52, P=.016) and thigh (rs=.63, P=.002) circumference, and fasting plasma insulin concentration (rs=.59, P=.004). PAI-1 antigen concentrations were not significantly associated with peripheral glucose uptake (M value) during either low-dose (rs= -.01, P=NS) or high-dose (rs= -.11, P=NS) insulin infusion. PAI-1 antigen was negatively correlated with basal hepatic glucose output (rs= -.57, P=.013) and percent suppression of hepatic glucose output during hyperinsulinemia (rs= -.69, P=.005). However, this relationship was largely due to the confounding effects of BMI, waist and thigh girth, fasting insulin, and 2-hour postload glucose concentrations, and was not significant when controlled for these variables (partial rs= -.30, P=NS). There was no significant relationship of PAI-1 antigen concentration with glucose storage or glucose oxidation. Despite a threefold increase in plasma insulin concentrations during the OGTT, there were no significant changes in PAI-1 antigen concentrations (median, 57, 61, 55, and 44 ng/mL at 0, 60, 120, and 180 minutes, respectively; P=NS by ANOVA). During the hyperinsulinemic clamp, mean plasma insulin concentrations at the end of low-dose (240 pmol/m2/min) and high-dose (2,400 pmol/m2/min) infusions were 1,005 and 14,230 pmol/L, respectively. However, PAI-1 antigen concentrations at the end of low-dose and high-dose insulin infusions were similar to those at baseline (median, 63, 43, and 58 ng/mL, respectively; P=NS by ANOVA). PAI-1 antigen in Pima Indians is related to several components of the insulin resistance syndrome. However, direct measurement of insulin resistance indicates that hepatic but not peripheral insulin resistance is related to PAI-1 antigen. Neither endogenous nor exogenous hyperinsulinemia for short periods had any significant effect on PAI-1 antigen concentrations. Short-term hyperinsulinemia is unlikely to be an important regulator of PAI-1 in Pima Indians. The relationship of PAI-1 antigen to hepatic insulin resistance is largely dependent on the relationship of PAI-1 to indices of obesity and fasting insulin concentrations.

The ACE-inhibitor lisinopril affects plasma insulin levels but not fibrinolytic parameters

There is evidence that ACE-inhibitors exert beneficial effects on endogenous fibrinolysis in patients with previous myocardial infarction. It is still unknown if this effect is restricted to this patient group only and by which mechanisms ACE-inhibitors exhibit the profibrinolytic effects. One possible explanation might be the positive influence of ACE-inhibitors on insulin metabolism by decreasing plasma insulin which in turn could decrease PAI-1, a major regulator of the fibrinolytic system. Therefore the present study examines the relationship between insulin and PAI-1 plasma levels during intravenous glucose tolerance tests before and after administration with the ACE-inhibitor lisinopril in 12 male obese patients with angiographically proven coronary artery disease and borderline hypertension. After a 4-weeks wash-out period glucose tolerance tests were performed before and after lisinopril-treatment (10mgs/d) for 12 weeks. After the treatment period, fasting plasma insulin level decreased from 15.6 +/- 2.1 to 11 +/- 1.8 uU/ml, p < or = 0.01. Stimulated levels of insulin during glucose tolerance test also significantly decreased by lisinopril (peak insulin from 57 +/- 10 to 41.2 +/- 7.3 uU/ml, p < or = 0.02). Basal plasma tissue plasminogen activator antigen, PAI-1 total antigen and PAI-1 "active" antigen were unaffected by therapy (8.4 +/- 0.5 vs 8.6 +/- 0.5 ng/ml, 118 +/- 20 vs 124 +/- 16 ng/ml and 21 +/- 7 vs 30 +/- 7 ng/ml, respectively). Our data confirm a beneficial effect of lisinopril on plasma levels of insulin but failed to demonstrate any profibrinolytic effect in this study population, thus questioning the postulated mechanism of influencing endogenous fibrinolysis by changes of plasma insulin.

No influence of proinsulin and insulin on plasma levels of plasminogen activator inhibitor type 1 and tissue plasminogen activator in young women before and during intake of contraceptive steroids

Clinical observations in patients predisposed to cardiovascular disorders and recent experimental observations suggest that proinsulin and insulin participate in the regulation of fibrinolysis in vivo. In the present study, we examined if proinsulin and insulin affect the constitutive (fasting) secretion of plasminogen activator inhibitor type 1 (PAI-1) and tissue plasminogen activator (t-PA) in young healthy women (N = 17). We also measured the antigen concentrations of PAI-1 and t-PA during slow and fast changes in proinsulin and insulin levels induced by oral (OGTT) and intravenous (IVGTT) glucose tolerance tests. The assessments were performed before and after 6 months of treatment with contraceptive steroids, which have a well-defined influence on the fibrinolytic variables. We observed no consistent correlations between fasting values of proinsulin, insulin, PAI-1, and t-PA either before or during hormonal treatment. Before hormonal treatment, PAI-1 and t-PA antigen levels decreased (P < .05) during the hyperproinsulinemia and hyperinsulinemia induced by the OGTT and IVGTT. After hormonal intake for 6 months, a decrease only in t-PA concentrations during the OGTT was observed despite similar proinsulin and insulin responses to the glucose loads. Our findings suggest that proinsulin and insulin have no influence on the regulation of plasma levels of PAI-1 and t-PA in young healthy women, irrespective of intake of contraceptive steroids.