Elevated fibrinogen and plasminogen activator inhibitor (PAI-1) in hypertension are related to metabolic risk factors for cardiovascular disease

Insulin sensitivity is not an independent determinant of plasma plasminogen activator inhibitor-1 activity

It recently has been hypothesized that increased plasma plasminogen activator inhibitor-1 (PAI-1) activity could be a possible link between insulin resistance and coronary heart disease. However, it is not known whether insulin sensitivity per se is a determinant of plasma PAI-1 activity or whether other intermediates could explain this association. We investigated the relationship between plasma PAI-1 activity and insulin sensitivity, obesity, distribution of body fat, blood pressure, plasma insulin concentration, and serum lipid levels in normoglycemic men (n = 61) and women (n = 77) 53 to 61 years old who participated in a previous population-based study. Insulin sensitivity was estimated by the minimal model from a frequently sampled intravenous glucose tolerance test. In univariate analyses, PAI-1 correlated positively with body mass index, waist-to-hip ratio (WHR), fasting and 2-hour insulin levels, and triglyceride level in both men and women. Furthermore, in women PAI-1 correlated inversely with high-density lipoprotein (HDL) cholesterol level. There was an inverse relationship between PAI-1 and insulin sensitivity (r = -.39, P < .01 in men; r = -.38, P < .001 in women). In multivariate analyses in men, insulin sensitivity failed to show any significant association with PAI-1. In contrast, triglyceride level and body mass index were independently associated with PAI-1. Also in women, insulin sensitivity was not independently associated with PAI-1. In women, WHR and HDL cholesterol concentration or WHR and 2-hour insulin concentration were independently related to PAI-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Holding smokers accountable for heart disease costs

This article discusses escalating health care costs in terms of their principal component, cardiovascular diseases. The role of cigarette smoking is highlighted throughout. A Smoker's Accountability Trust is proposed for the prevention of nonfatal myocardial infarction. It is demonstrated that this approach can contain costs by controlling the root causes of their acceleration.

The effect of obesity on fibrinolytic activity and plasma lipoprotein (a) levels in patients with type 2 diabetes mellitus in Korea

To determine whether previously reported abnormalities in fibrinolytic activity and plasma lipoprotein (a) levels could reflect obesity rather than diabetes per se, plasma concentrations of tissue-type plasminogen activator (t-PA), type 1 plasminogen activator inhibitor (PAI-1), and lipoprotein (a) (Lp (a)) were investigated in sixty-four type 2 diabetic patients (56.1 +/- 9.5 years; body mass index, 24.6 +/- 3.3 kg/m2) and thirty-two control subjects (57.9 +/- 8.9 years; body mass index, 24.6 +/- 3.4 kg/m2). Both the plasma t-PA and PAI-1 antigen levels were similar between the diabetic group (10.6 +/- 3.8 ng/ml; 27.7 +/- 11.6 ng/ml) and the control group (12.2 +/- 3.5 ng/ml; 27.7 +/- 9.6 ng/ml). The PAI-1 levels were evenly distributed from 5.93 to 52.7 ng/ml in diabetic patients. The difference of Lp (a) levels between the two groups was negligible (the diabetic group, median 11 mg/dl (range 0-72 mg/dl); the control group, median 13 mg/dl (range 0-55 mg/dl)). Significant correlations between PAI-1 levels and body mass index (BMI) were observed in both groups. In the diabetic group, PAI-1 levels also correlated with fasting C-peptide levels (r = 0.54, P < 0.01) and serum triglyceride levels (r = 0.28, P < 0.05). However, we could not find a significant association between either t-PA or PAI-1 levels and Lp (a) levels in the diabetic and control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibrinogen and fibrinolytic variables in relation to anthropometry, lipids and blood pressure. The Northern Sweden MONICA Study

Fibrinolysis is dependent upon plasminogen activator (tPA) activity while high fibrinogen levels increase the risk of thromboembolic events. From a cross-sectional population sample of 1558 men and women aged 25 to 64 years, plasma fibrinogen, tPA activity and plasminogen activator inhibitor-1 (PAI) activity were determined using specific assays. Associations with body mass index (BMI), waist-hip ratio (WHR), serum lipids and blood pressure were calculated with uni- and multivariate models where age and smoking were also introduced. In men age, truncal obesity, short height and low HDL cholesterol independently predicted fibrinogen (R2 0.20) while in women obesity per se, total cholesterol, systolic blood pressure, smoking and age were predictors (R2 0.29). tPA activity was negatively associated with BMI and serum triglyceride levels and positively with age in both sexes. In men diastolic blood pressure (R2 0.22) and in women WHR further independently predicted low fibrinolytic activity. HDL was associated with greater fibrinolysis in women (R2 0.15). Relationships with PAI-1 activity were essentially the reverse of tPA but stronger. Prospective interventional studies are needed to answer the question of causality.

Insulin and PAI-1 levels during oral glucose tolerance test in patients with coronary heart disease

The present study was performed to investigate the acute effects of physiologically induced hyperinsulinemia on plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator (t-PA) and triglycerides (TG). Forty-one male patients with chronic coronary heart disease (CHD) and moderate hypertriglyceridemia were studied for 3 h; 33 of them during an oral glucose tolerance test (OGTT), whereas eight patients served as controls, receiving water only. All subjects in the OGTT group were adequate responders to glucose administration, giving peak values of glucose (median 6.90 mmol l-1) and insulin (median 123 mU l-1) after 1 h. TG were unchanged throughout the test period in both groups. After 1 h PAI-1 activity and antigen decreased significantly more in the OGTT group than in the controls (median values: PAI-1 act 23-12 vs. 12-12 U ml-1; (p < 0.001). PAI-ag 45-35 vs. 18-16 ng ml-1 (p < 0.05)). t-PA increased more in the OGTT group (0.70-1.20 vs. 0.50-0.63 IU ml-1 (p = 0.08)). These differences tailored off after 3 h. We conclude that acute hyperinsulinemia, when generated during an OGTT, stimulates fibrinolysis with a consequent decrease in PAI-1 activity, but give no change in TG. The postulated regulating role of insulin for the steady state levels of PAI-1 could probably not be elucidated in the present dynamic model.

Increased plasma activity of plasminogen activator inhibitor 1 (PAI-1) in two patients with Klinefelter's syndrome complicated by leg ulcers

Klinefelter's syndrome is the most frequent major abnormality of sexual differentiation in men with two or more X-chromosomes, and affects one in 500 males. The syndrome is characterized by eunuchoid body proportions, scanty facial and body hair, gynaecomastia, and small firm testes. Leg ulcers, especially in combination with hyperpigmentation, have been reported in association with Klinefelter's syndrome. Thromboembolic processes are also frequently observed. The leg ulcers in patients with Klinefelter's syndrome are usually attributed to venous insufficiency. We describe two patients with Klinefelter's syndrome associated with recurrent ulcers and hyperpigmentation on both legs, in whom no venous or other underlying cause could be found. The patients were not taking any drugs, in particular no supplemental androgen therapy. Both had normal plasma testosterone values. We detected increased activity of plasminogen activator inhibitor 1 (PAI-1), with only a partial decrease upon venous occlusion. A possible role for this inhibitor of fibrinolysis in the pathogenesis of ulceration is discussed.

Relationship between hemorrheologic factors and insulin sensitivity in healthy young men

The present study aimed at testing a possible relationship between hemorrheologic factors, such as hematocrit, fibrinogen, and whole-blood viscosity, and insulin sensitivity in healthy humans. Twenty-one 21-year-old men were studied with the hyperinsulinemic euglycemic glucose clamp technique. We found statistically significant negative correlations between the glucose disposal rate (GDR) and calculated whole-blood viscosity at both high (r = -.55, P = .01) and low (r = -.51, P = .01) shear rates. We observed negative associations between GDR and fibrinogen (r = -.66, P = .002), GDR and hematocrit (r = -.63, P = .002), GDR and body mass index (r = -.51, P = .007), and GDR and resting heart rate (r = -.46, P = .04). Using stepwise multiple regression considering whole-blood viscosity, body mass index, mean arterial blood pressure, and heart rate as independent variables, we found that only whole-blood viscosity and body mass index were independent explanatory variables of the GDR. Together they accounted for 63% of the variability in the GDR in our subjects. These results suggest hemorrheologic, and therefore indirectly hemodynamic, factors as correlates to insulin sensitivity.

Metformin and metoprolol CR treatment in non-obese men

OBJECTIVE

To study the effect of metformin and metoprolol CR on insulin sensitivity, blood lipids, fibrinolytic activity and blood pressure.

DESIGN

A double-blind, placebo controlled, triple cross-over study with randomization to either metformin, 850 mg b.i.d., or metoprolol CR 100 mg o.d., or placebo for a period of 18 weeks. The glucose uptake was measured with the euglycaemic clamp technique after every 6 weeks' treatment period. Blood pressure and blood samples were taken every 3rd week.

SUBJECTS

Eighteen non-obese men (53 +/- 6 years of age).

RESULTS

Metformin decreased C-peptide (P < 0.02), FFA (P < 0.003), total and low-density lipoprotein cholesterol, tissue plasminogen activator antigen and the urinary potassium excretion (P < 0.05 for all), but not blood pressure compared to placebo. Metoprolol CR reduced diastolic blood pressure and pulse rate; fasting free fatty acids and the urinary potassium increased (P < 0.05 for all). No effect of metformin or metoprolol CR was seen on the glucose disposal rate, blood glucose, plasma insulin, triglycerides, high-density lipoprotein cholesterol, lipoprotein(a), uric acid or plasminogen activator inhibitor 1 activity or antigen. The glucose uptake was not particularly decreased in these subjects.

CONCLUSION

The study shows that metformin has some favourable effects on metabolism and that metoprolol CR is fairly neutral in this regard. The lack of effect of metformin on glucose disposal rate and blood pressure can be explained by the fact that the individuals studied were neither insulin resistant nor hypertensive. The data does not preclude an antihypertensive effect by treating a concomitant insulin resistance.

High fibrinogen and plasminogen activator inhibitor activity in growth hormone-deficient adults

Hypopituitary patients on routine replacement therapy except growth hormone (GH) have an increased risk of death from cardiovascular diseases compared with healthy subjects. Untreated GH deficiency might explain the premature death from vascular disease. Plasminogen activator inhibitor (PAI-1) activity, fibrinogen, insulin, blood lipid, and blood pressure levels were studied in 20 GH-deficient adults (10 men, 10 women) 50 +/- 11 years old with routine hormone replacement therapy (except GH) and compared with 20 healthy control subjects matched for sex, age, and body mass index. GH-deficient subjects had a higher waist-to-hip circumference ratio (P < .001), serum triglycerides (P < .02), PAI-1 activity (13.2 +/- 10.6 versus 6.8 +/- 4.8 U/mL [P < .05]), and fibrinogen (3.2 +/- 0.7 versus 2.4 +/- 0.6 g/L [P < .001]) and lower blood glucose (P < .05) compared with control subjects. Blood pressure, insulin, and cholesterol levels were similar. The aberrations found in this study might contribute to an increased atherothrombotic propensity and play a role in the pathogenesis of cardiovascular disease.

Circadian variation in fibrinolytic activity in patients with variant angina

BACKGROUND

Coronary artery spasm induces activation of the coagulation system. Turnover and maintenance of thrombus depend not only on formation but also on lysis. The relation between coronary spasm and fibrinolytic system has not been elucidated.

OBJECTIVE

To examine whether there is impairment of or a circadian variation in fibrinolytic activity in patients with variant angina.

METHODS

Plasminogen activator inhibitor (PAI) activity and concentrations of tissue plasminogen activator (t-PA) antigen were measured in venous plasma samples taken at 2200, 0600, and 1400 and 24 h Holter tapes were recorded in 15 patients with variant angina, 12 patients with stable exertional angina, and 12 controls.

RESULTS

There were significant circadian variations in PAI activity and t-PA antigen with peak values at 0600 in all three groups. Mean (SEM) PAI activity (IU/ml) at 2200, 0600, and 1400 was 6.1 (1.1), 11.0 (1.3), and 4.4 (0.6) in the variant angina group; 1.8 (0.7), 5.6 (1.1), and 1.2 (0.3) in the stable exertional angina group; and 1.1 (0.5), 4.5 (0.8), and 0.7 (0.3) in the control group. Furthermore, both plasma PAI activity and t-PA antigen concentrations were significantly higher in the variant angina group than in the stable exertional angina group and the control group at each sampling time.

CONCLUSIONS

In patients with variant angina there was a circadian variation in fibrinolytic activity, which was lowest in the early morning, and impaired fibrinolytic activity particularly in the early morning, when attacks of angina occur most frequently.

Fibrinogen: an important risk factor for atherothrombotic diseases

Epidemiological follow-up studies have suggested that fibrinogen is a major, primary cardiovascular risk factor. Cross-sectional results also show associations between fibrinogen and cardiovascular risk factors or diseases. Clinical cohort studies demonstrate that fibrinogen might also be a secondary risk factor. The determinants of the plasma level of fibrinogen in health and disease are known only incompletely. Our understanding of the mechanisms involved in the atherogenic actions of fibrinogen is similarly fragmentary. These might include blood coagulation, blood rheology, platelet aggregation, direct effects on the vascular wall, and the acute phase response. Thus, many questions are yet to be answered. Nevertheless, the data available at present strongly suggest that fibrinogen represents a major, independent cardiovascular risk factor. Fibrinogen should be considered for screening programmes aimed at identifying individuals at risk.

Minimal genetic influences on plasma fibrinogen level in adult males in the NHLBI twin study

Plasma fibrinogen was determined in 189 twins participating at the Indiana center during the third examination of the NHLBI twin study with a mean age of 63 years. Moderate heritability estimates were obtained from 44 complete MZ pairs and 39 complete DZ pairs. After adjustment of fibrinogen levels for age and other confounding variables related to cardiovascular disease risk, the maximum likelihood heritability estimate was only 30% (p = 0.03). Plasma fibrinogen was most strongly associated with smoking and the presence of diabetes. Omitting all subjects with diabetes or cardiovascular disease further reduced the heritability estimates slightly, and most path models including genetic parameters provided no significant improvement in fit over a model determined solely by random environmental effects. Our results are consistent with the environment rather than genetic influences having a greater influence on the level of plasma fibrinogen.

Involvement of the hemostatic system in the insulin resistance syndrome. A study of 1500 patients with angina pectoris. The ECAT Angina Pectoris Study Group

Hyperinsulinemia, a major indicator of insulin resistance, may exert its influence on the risk of coronary artery disease partially through disturbances of the hemostatic system. The relations of fasting insulin concentrations with the degree of coronary atherosclerosis, other coronary risk factors (including some markers of the insulin resistance syndrome such as body mass index and triglyceride), markers of inflammation, and hemostatic factors were investigated in 1484 patients with angina pectoris. Mean insulin levels were higher in patients with one or more coronary vessel stenoses than in those without (9.9 microU/mL compared with 9.0 microU/mL, P < .0001). However, the association the presence of vessel stenoses was stronger in patients with a previous myocardial infarction than in those without. Insulin increased markedly (P < .0001) and independently of other risk factors with age body mass index, triglyceride concentration, and markers of inflammation, such as white blood cell count and C-reactive protein. The strongest relations between insulin and hemostatic factors were observed with fibrinolytic variables, particularly plasminogen activator inhibitor-1 (PAI-1) levels (r = .44, P < .0001). This relation decreased somewhat (r = .29) after simultaneous adjustment for markers of the insulin resistance syndrome, mainly body mass index and triglycerides, but not after adjustment for markers of inflammation. Therefore, we propose that increased PAI-1 levels, which are essentially related to the classic metabolic aspect of the insulin resistance syndrome, have to be included in this syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin resistance in hypertension: a focused review

The associations between insulin resistance, hyperinsulinemia, and hypertension are well recognized. The insulin resistance and hyperinsulinemia associated with hypertension is the result of increased renal tubular sodium reabsorption, increased sympathetic nervous system activity, and increased arterial wall smooth muscle reactivity. In insulin resistant states, intracellular calcium and sodium accumulation is thought to be the fundamental underlying abnormality. These is evidence that hyperinsulinemia is an independent risk factor for coronary artery disease. Therefore, therapeutic considerations in patients with insulin resistance should include nonpharmacologic methods for increasing insulin sensitivity as well as avoiding the deleterious effects on insulin action and lipid metabolism of various antihypertensive medications. Of the currently available antihypertensives therapies, the angiotensin-converting enzyme inhibitors, the alpha antagonists, and the calcium channel blockers are the most rational choices for treating patients with hypertension with evidence of coexisting insulin resistance.

Insulin resistance and risk factors for coronary heart disease

In this presentation an effort has been made to review the impact of resistance to insulin-mediated glucose uptake and/or hyperinsulinaemia on various metabolic end-points and clinical syndromes. Insulin resistance is present in the great majority of patients with states of glucose intolerance, but frank decompensation of glucose homoeostasis does not occur if individuals can maintain a state of compensatory hyperinsulinaemia. Although compensatory hyperinsulinaemia may prevent the development of NIDDM in insulin-resistant individuals, there is substantial evidence that insulin resistance and/or hyperinsulinaemia is associated with higher plasma concentrations of triglyceride, uric acid and plasminogen activator inhibitor 1 and with lower HDL cholesterol concentrations. Obesity, decreased physical activity and possibly cigarette smoking accentuate the degree of insulin resistance and its manifestations, and a genetic basis is also involved. Resistance to insulin-mediated glucose uptake and/or hyperinsulinaemia have been shown to be associated with high blood pressure, microvascular angina and CHD. Thus, resistance to insulin-mediated glucose uptake is a common phenomenon, which makes a major contribution to the aetiology and clinical course of common and serious diseases. Based on the above considerations, it is difficult to over-emphasize the health-related implication of a defect in insulin-mediated glucose uptake.

Relationship between plasma plasminogen activator inhibitor-1 activity and VLDL triglyceride concentration, insulin levels and insulin sensitivity: studies in randomly selected normo- and hypertriglyceridaemic men

Impaired fibrinolytic function secondary to elevated plasma plasminogen activator inhibitor-1 activity, hypertriglyceridaemia and hyperinsulinaemia are frequent findings in patients with coronary heart disease. It has been debated whether VLDL or insulin is the major regulator of plasma plasminogen activator inhibitor-1 activity. This study examines the relationships between plasma plasminogen activator inhibitor-1 activity and VLDL triglyceride concentration, fasting and post-oral glucose load insulin levels and insulin sensitivity, as estimated by the minimal model method. Subjects studied were randomly selected hypertriglyceridaemic (n = 65) and age-matched normotriglyceridaemic (n = 61) men, aged 40-50 years, recruited in a population survey. Plasma plasminogen activator inhibitor-1 activity was higher in the hypertriglyceridaemic than in the normotriglyceridaemic group (21 +/- 14 vs 10 +/- 8 mU/l; p < 0.01). The hypertriglyceridaemic group had higher serum insulin, basal as well as 2 h after intake of the oral glucose load, and a lower insulin sensitivity index. In univariate analysis, plasma plasminogen activator inhibitor-1 activity correlated positively with VLDL triglycerides in both the hyper- and normotriglyceridaemic groups (r = 0.43 r = 0.60, respectively) and negatively with the insulin sensitivity index (r = -0.35 r = -0.44, respectively). In multivariate analysis, VLDL triglyceride levels were found to be independently related to plasma plasminogen activator inhibitor-1 activity in both groups, whereas insulin sensitivity/serum insulin levels were not. An unexpected finding was that the serum activity of the enzyme gamma glutamyl transpeptidase appeared to influence the relationships for plasma plasminogen activator inhibitor-1 in the hypertriglyceridaemic group.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between plasminogen activator inhibitor-1 and insulin resistance in newly diagnosed type 2 diabetes mellitus

It is not clear whether elevated levels of the fibrinolytic inhibitor, plasminogen activator inhibitor-1 (PAl-1) in Type 2 diabetes mellitus are the result of obesity or coexistent atherosclerosis. Therefore the relationship between PAl-1 and insulin resistance, determined by the homeostasis model assessment (HOMA) was investigated in a group of 26 insulin-resistant, normotensive newly diagnosed Type 2 diabetic patients with a low probability of atherosclerosis. Compared with a normal control group, closely matched for body mass index (BMI), fibrinolytic activity was depressed in the diabetic patients due to elevated levels of the inhibitor PAl-1, 17.6 (11.1-28) vs 8.4 (4.9-14.1) IU ml-1, p < 0.001. PAl-1 was related to BMI, r = 0.59, p < 0.001 plasma insulin, r = 0.66, p < 0.001; insulin resistance, r = 0.54, p < 0.005 and urinary albumin excretion, r = 0.48, p < 0.01, but not HbA1c or fasting glucose. PAl-1 was not related to blood pressure or plasma triglyceride levels. This study suggests that at the time of diagnosis of Type 2 diabetes mellitus, elevated PAl-1 levels are already linked to other risk factors for vascular disease including hyperinsulinaemia, insulin resistance, and urinary albumin excretion, and this is not the result of obesity or coexistent atherosclerosis.

The cardiovascular risk factor plasminogen activator inhibitor type 1 is related to insulin resistance

The cardiovascular risk factor plasminogen activator inhibitor type 1 (PAI-1) has been associated with abdominal obesity, hypertension, hypertriglyceridemia, hyperinsulinemia, glucose intolerance, and type II diabetes, conditions known to be linked with insulin resistance. To determine whether PAI-1 is related to insulin resistance, we studied nine obese nondiabetics and 10 obese type II diabetics by means of a sequential hyperinsulinemic euglycemic clamp study. Plasma PAI-1 antigen (Ag) correlated significantly with peripheral insulin resistance, represented by the insulin level at which peripheral glucose uptake (PGU) is half-maximal ([ED50PGU] r = .87, P < .001). Multiple regression analysis including indices of hepatic and peripheral insulin action, fasting plasma insulin levels, triglyceride levels, blood pressure (BP), waist to hip ratio (WHR), and body mass index (BMI) disclosed ED50PGU to account for 76% of the variance of PAI-1 Ag. We suggest that PAI-1 contributes to the increased cardiovascular risk encountered with insulin resistance.

Changes in insulin and lipid metabolism in males with asymptomatic hyperuricaemia

OBJECTIVES

To define the effect of asymptomatic hyperuricaemia on various facets of glucose, insulin, and lipoprotein metabolism.

DESIGN

Case control study in health volunteers.

SETTING

The volunteers for this study were selected on the basis of their laboratory results from a larger population participating in a general survey in one large factory.

SUBJECTS

The study population consisted of 40 healthy males: 20 with asymptomatic hyperuricaemia (serum uric acid concentration equal to or greater than 420 mmol l-1) and 20 with normal serum uric acid concentrations (180-320 mmol l-1). The two groups were similar in terms of age, general obesity (estimated by body mass index), smoking and alcohol intake, and estimate of work and leisure time activity.

INTERVENTIONS

All subjects received a 75 g oral glucose challenge, with blood taken before and at frequent intervals thereafter.

MAIN OUTCOME MEASURES

Fasting plasma glucose, insulin, and lipid concentrations and plasma glucose and insulin responses to the oral glucose challenge.

RESULTS

By selection, mean (+/- SEM) serum uric acid concentration was higher in the hyperuricaemic individuals (454 +/- 7 vs. 274 +/- 12 mmol l-1). In addition, the plasma insulin response to oral glucose was increased in individuals with asymptomatic hyperuricaemia (P < 0.005) as were both systolic (136 +/- 3 vs. 126 +/- 3 mmHg, P < 0.05) and diastolic (91 +/- 1 vs. 82 +/- 1, P < 0.01) blood pressure. Furthermore, subjects with asymptomatic hyperuricaemia were dyslipidaemic (higher plasma TG and cholesterol and lower HDL-cholesterol concentrations) as compared to the normouricaemic control group (P < 0.07-0.005).

CONCLUSIONS

These results provide a possible explanation for the well-known association of hyperuricaemia with coronary heart disease, as well as suggesting that hyperuricaemia be added to the cluster of metabolic and haemodynamic abnormalities associated with insulin resistance and/or hyperinsulinaemia and designated as Syndrome X.

Insulin resistance and hyperinsulinemia in individuals with small, dense low density lipoprotein particles

Subjects characterized by a predominance of small LDL particles (pattern B) have changes in plasma triglyceride (TG) and HDL-cholesterol concentrations consistent with the presence of resistance to insulin-mediated glucose uptake. To pursue this issue, plasma glucose and insulin responses to oral glucose, insulin-mediated glucose disposal, and lipoprotein concentrations were measured in subjects categorized on the basis of LDL peak diameter measured by gradient gel electrophoresis. Subjects with pattern B had higher (P < 0.05-0.001) total integrated plasma glucose (20.7 +/- 1.0 mmol/liter.h) and insulin (1,743 +/- 293 pmol/liter.h) responses to oral glucose compared with glucose (16.3 +/- 0.4 and 19.2 +/- 0.8 mmol/liter.h) and insulin (856 +/- 60 and 1,222 +/- 168 pmol/liter.h) responses in those with either pattern A or an intermediate pattern. Pattern B individuals were shown to be more insulin resistant on the basis of higher steady state plasma glucose concentrations (SSPG, 10.4 +/- 1.0, P < 0.002, vs. 7.5 +/- 0.7 and 6.0 +/- 0.4 mmol/liter) after a constant infusion of somatostatin, glucose, and insulin than those with either the intermediate or pattern A subclass. Pattern B subjects also had higher concentrations of (P < 0.001) TG (1.98 +/- 0.15 vs. 1.33 +/- 0.17 and 0.77 +/- 0.05 mmol/liter) and lower (P < 0.01-0.001) HDL cholesterol (1.12 +/- 0.06 vs. 1.34 +/- 0.05 vs. 1.45 +/- 0.05 mmol/liter) than those with either the intermediate or pattern A. Finally, significant (P < 0.001) correlation coefficients existed between LDL diameter and SSPG (r = -0.44); glucose (r = -0.41) and insulin (r = -0.38) responses; TG (r = -0.65) and HDL-cholesterol (r = 0.42) concentrations; and systolic (r = -0.34) and diastolic (r = -0.34) blood pressure. Thus, pattern B subjects are insulin resistant, have higher glucose, insulin, and TG, lower HDL-cholesterol levels, and higher blood pressure than those with pattern A or intermediate.

Vascular insulin abnormalities, hypertension, and accelerated atherosclerosis

There is accumulating evidence that insulin resistance, glucose intolerance, and hyperinsulinemia exist in people with high blood pressure, and it has been suggested that insulin resistance and hyperinsulinemia may be of great importance in the origin of hypertension and its ultimate clinical course. Of importance are the recent observations that persons with normal glucose tolerance, selected on the basis of hyperinsulinemia, had higher blood pressure than matched individuals with normoinsulinemia. Hypertension in in insulin-resistant states generally has been attributed to hyperinsulinemia, with resulting increases in sympathetic nervous system activity. However, recent data from our laboratory suggest that cellular insulin resistance rather than hyperinsulinemia per se may lead to hypertension. The basic tenet proposed in this article is that a deficiency of insulin at the cellular level represents a common mechanism that is involved in the development of hypertension in both type I and type II diabetes mellitus. Insulin has an important role in the modulation of cellular calcium metabolism. Decreased insulin action on vascular smooth muscle cells may contribute both to hypertension and to accelerated atherosclerosis. Recent observations suggest that an impaired cellular response to insulin predisposes to increased vascular smooth muscle tone (the hallmark of hypertension in the diabetic state). For example, recently reported studies from our laboratory demonstrate that insulin attenuates the vascular contractile response to phenylephrine, serotonin, and potassium chloride. Thus, it appears that insulin normally modulates (attenuates) vascular smooth muscle contractile responses to vasoactive factors, and insulin resistance should accordingly be associated with enhanced vascular reactivity.

Effects of a high-fat, sucrose diet on serum insulin and related atherosclerotic risk factors in rats

Hyperinsulinemia, hypertension, hypertriglyceridemia and obesity are all risk factors for atherosclerosis. The clustering of these risk factors in the same individual greatly increases the risk for atherosclerosis and has been termed 'Syndrome X' or 'The Deadly Quartet' The purpose of the present study was to investigate the effects of diet on these risk factors in inbred, female Fischer 344 rats. Animals were raised on ad lib diets consisting of high-fat, sucrose (HFS) or low-fat, complex-carbohydrate (LFCC). After 2 years, the HFS rats were obese (38% +/- 1% vs. 15% +/- 1% body fat), hypertensive (140 +/- 3 vs. 123 +/- 3 mmHg), hyperinsulinemic (439 +/- 118 vs. 98 +/- 10 pmol/l), and hypertriglyceridemic (1.1 +/- 0.2 vs. 0.4 +/- 0.07 mmol/l). The HFS rats also exhibited enhanced clotting and impaired fibrinolytic response to streptokinase. All these differences between the two groups were statistically significant (P < 0.05). Insulin was significantly correlated with body weight (r = 0.71), triglycerides (r = 0.48), and systolic blood pressure (r = 0.70). Total cholesterol was slightly, but not significantly higher, in the HFS group (2.8 +/- 0.3 vs 2.2 +/- 0.1 mmol/l) while HDL-cholesterol was unchanged. These results show that many risk factors for atherosclerosis can be induced in inbred rats by feeding a HFS diet. Aggregation of risk factors was found in the HFS group but not in the LFCC group. In fact, most of the rats on the LFCC diet developed no risk factors after 2 years, indicating that the development of risk factors is not an aging phenomenon.

Relation of hemostatic risk factors to other risk factors for coronary heart disease and to sex hormones in men

The present study was carried out to explore the possible relation of plasma plasminogen activator inhibitor-1 (PAI-1), fibrinogen, and factor VII levels to other risk factors for coronary heart disease (CHD) and to serum sex hormone levels. The study group comprised 48 apparently healthy men. To avoid the confounding factor of obesity, correlations were determined in the 30 men in this group with a body mass index (BMI) < 26.4, after controlling for age. PAI-1 correlated with testosterone, estradiol/testosterone, and free testosterone/testosterone (FT/T), and fibrinogen correlated with FT/T. All three hemostatic factors correlated with glucose and with the ratio of cholesterol/high density lipoprotein cholesterol, while PAI-1 correlated with diastolic blood pressure. To test the effect of obesity, correlations were determined in the entire group of 48 men, which included 18 subjects with a BMI > 26.4. All three hemostatic factors correlated with BMI in this group after controlling for age; however, on controlling for testosterone, only PAI-1 correlated with BMI. Fibrinogen correlated with age in both groups after controlling for testosterone or BMI. These correlations support the hypothesis that PAI-1, fibrinogen, and factor VII are related to other risk factors for CHD and that an alteration in the sex hormone milieu may be the underlying factor linking them.

The role of fibrinogen as a cardiovascular risk factor

Several epidemiological studies have produced longitudinal data identifying fibrinogen as a major cardiovascular risk factor. Cross-sectional results show strong associations between fibrinogen and a variety of demographic variables, cardiovascular risk factors, or diseases. Clinical cohort studies demonstrate that fibrinogen might also be a risk factor for the sequelae of cardiovascular disease. Knowledge about the determinants of the plasma level of fibrinogen in health and disease is as yet incomplete. Understanding of the mechanisms leading to the atherothrombogenic action of fibrinogen is also fragmentary. Fibrinogen strongly affects blood coagulation, blood rheology and platelet aggregation; in addition fibrinogen and its metabolites have direct effects on the vascular wall. Finally, fibrinogen is a prominent acute phase protein. All of these phenomena might provide some insight into the pathophysiological mechanisms involved. It is concluded that fibrinogen represents a major, independent risk factor that should now be included into the cardiovascular risk profile.

Low blood pressure and blood glucose levels in Alzheimer's disease. Evidence for a hypometabolic disorder?

OBJECTIVE

To test possible differences between patients with Alzheimer's disease (AD) and patients with other forms of dementia and the healthy population concerning body composition, blood pressure, metabolic data and leukoaraiosis (LA).

DESIGN

Retrospective study on data collected according to a predefined protocol.

SETTING

A geriatric, neuropsychiatric diagnostic unit.

SUBJECTS

Seventy-one consecutive patients with dementia.

MAIN OUTCOME MEASURES

Body mass index, blood pressure, metabolism and LA in AD compared to other dementia forms.

RESULTS

Mean blood pressure and fasting blood glucose levels were lower in patients with AD, 94 +/- 12 mmHg and 4.3 +/- 0.5 mmol l-1, compared to patients with unspecified dementia (NUD), 100 +/- 10 mmHg and 5.5 +/- 2.5 mmol l-1 (P < 0.05) and vascular dementia (VAD), 114 +/- 12 mmHg and 5.6 +/- 1.6 mmol l-1 (P < 0.001) and the age-matched healthy population. Body mass index, serum cholesterol and cortisol were similar in all groups of dementia patients whereas triglycerides were highest in the VAD group. No cases of diabetes or treatment for hypertension were found in the AD group while the prevalence was 21% and 36% for diabetes in the NUD and VAD groups and 8% in the population from the same region. There were 16% with antihypertensive treatment in dementia NUD, 50% in VAD, and 30% in the general population. Treated or newly detected hypothyreosis was present in 11% of the AD patients, none in the other dementia groups and 2% in the general population. Smoking was least common in AD. Degree of LA correlated with blood pressure and blood glucose levels.

CONCLUSIONS

AD was clearly different to other dementia patients. They had lower blood pressure, blood glucose and higher prevalence of hypothyreosis than the healthy, age-matched population. These findings may indicate that AD could be a hypometabolic disorder.

Plasminogen activator inhibitor activity in diabetic and nondiabetic survivors of myocardial infarction

Recent studies suggest that plasminogen activator inhibitor (PAI-1) may be a risk factor for recurrent myocardial infarction. We measured PAI-1 activity and antigen and tissue-type plasminogen activator (t-PA) antigen in 35 (20 nondiabetic and 15 diabetic) subjects with no clinical or electrocardiographic evidence of ischemic heart disease and in 74 (50 nondiabetic and 24 diabetic subjects) who had survived a myocardial infarction in the preceding 6-24 months. Levels of PAI-1 activity (18.7 +/- 5.6 versus 12.0 +/- 3.8 arbitrary units [AU] per milliliter, p = 0.001) and t-PA antigen (7.0 +/- 1.9 versus 4.6 +/- 2.0 ng/mL, p = 0.001) were significantly higher in diabetic compared with nondiabetic control subjects. Survivors of myocardial infarction had higher levels of PAI-1 activity and antigen and t-PA antigen than control subjects, and the diabetic survivors had higher levels of PAI-1 activity (25.3 +/- 6.7 versus 20.1 +/- 7.1 AU/mL, p = 0.004) and t-PA antigen (10.6 +/- 4.3 versus 8.4 +/- 3.3 ng/mL, p = 0.03) than the nondiabetic survivors. No difference in PAI-1 antigen levels was found between the diabetic subjects and either the nondiabetic control subjects or survivors of myocardial infarction. After venous occlusion in control subjects, there was a significant increase in PAI-1 antigen (mean 26.7%, range 14.1-58.1% in nondiabetics and mean 25.2%, range 6.2-39.7% in diabetics) and t-PA antigen (mean 78.3%, range 13.6-186.2% for nondiabetic and mean 40.7%, range 17.5-76.2% for diabetic subjects), but in the survivors of myocardial infarction, no significant effect of venous occlusion was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Coagulation and fibrinolytic system impairment in insulin dependent diabetes mellitus

Selected coagulation and fibrinolytic parameters were assessed in 40 insulin dependent diabetes mellitus patients with varying degrees of metabolic control; 30 healthy subjects matched for age and sex formed the control group. Activated Partial Thromboplastin Time, Prothrombin Time, Fibrinogen, Factor VII, Antithrombin III, Protein C, Plasminogen, alpha 2-Plasmin Inhibitor, Plasminogen Activator Inhibitor-1, tissue-Plasminogen Activator were functionally evaluated. Antigenic levels of tissue-Plasminogen Activator, Thrombin-Antithrombin complexes and fibrinolytic specific product B beta 15-42 were also determined. Compared to the control group diabetic patients displayed significantly higher levels of Fibrinogen (p < 0.01), Factor VII (p < 0.01), Thrombin-Antithrombin complexes (p < 0.01) and Plasminogen Activator Inhibitor-1 activity (p < 0.01). Regardless of the normal level of the tissue-Plasminogen Activator-related antigen, diabetic patients had tissue-Plasminogen Activator activity lower than the control group (p < 0.05). Coagulation Factor VII and Thrombin-Antithrombin complexes were increased only in the patients with poor metabolic control (p < 0.01). Activated Partial Thromboplastin Time, Prothrombin Time, Antithrombin III, Protein C, Plasminogen, alpha 2-Plasmin Inhibitor, B beta 15-42 fibrin peptide were found to be in the normal range. Fibrinogen correlated positively with fasting blood glucose (p < 0.05) and Thrombin-Antithrombin complexes with glycosylated haemoglobin (p < 0.05), whereas Factor VII was positively correlated with glycemia (p < 0.01) and glycosylated haemoglobin (p < 0.05). Higher levels of Fibrinogen were found in patients affected by nephropathy (p < 0.005) or neuropathy (p < 0.05). These results demonstrate an impairment of the haemostatic balance in diabetic patients, that is a possible hypercoagulable state, which represents an important factor in the pathogenesis of atherosclerotic complications.

Plasma plasminogen activator inhibitor activity and tissue plasminogen activator levels in patients with unstable angina and those with coronary spastic angina

Plasminogen activator inhibitor (PAI) activity and tissue plasminogen activator (TPA) antigen were measured in venous samples in 14 patients with unstable angina consisting of eight patients with organic stenosed coronary arteries and six patients with coronary spastic angina (unstable angina group); in 14 patients with stable exertional angina (stable exertional angina group); and in 14 patients with chest pain syndrome (chest pain syndrome group). The plasma levels of PAI activity were higher (p less than 0.01) in the unstable angina group than in the stable exertional angina group and the chest pain syndrome group (12.3 +/- 1.0 versus 5.1 +/- 0.7 and 4.8 +/- 0.6 IU/ml). The plasma levels of TPA antigen were also higher (p less than 0.05) in the unstable angina group than in the stable exertional angina group and the chest pain syndrome group (10.2 +/- 1.3 versus 6.5 +/- 0.8 and 6.0 +/- 0.7 ng/ml). There were no significant differences in PAI activity and TPA antigen levels between the stable exertional angina group and the chest pain syndrome group. Furthermore, both PAI activity and TPA antigen levels in the unstable angina group decreased to the levels in the stable exertional angina group and the chest pain syndrome group after treatment (p less than 0.01). In conclusion, the increased plasma PAI activity in patients with unstable angina and in those with coronary spastic angina indicates that the fibrinolytic system is impaired in these patients.

On the role of coagulation and fibrinolysis in atherosclerosis

Atherosclerosis is probably caused by multiple interacting factors such as disturbed lipid metabolism; endothelial cell damage, leading to platelet aggregation and monocyte invasion with the release of mitogenic factors; and disorders of fibrin balance, leading to persisting fibrin deposits. Deficient fibrinolysis may (1) predispose to fibrin deposition and contribute to the pathogenesis of atherosclerosis and (2) contribute to occlusive thrombus formation on fissured plaque, provoking atherothrombosis. Prospective epidemiologic studies have so far not provided definitive evidence that deficient fibrinolysis constitutes a significant risk factor for the development of atherosclerosis. Two recent findings, however, strongly suggest a contribution: (1) Increased lipoprotein(a) levels that reduce tissue-type plasminogen activator (t-PA)-mediated clot lysis are a clear risk factor for atherosclerosis; and (2) increased plasminogen activator inhibitor-1 (PAI-1) levels in patients with disturbed glucose tolerance predispose to an accelerated development of atherosclerotic disease. However, deficient fibrinolysis constitutes a risk factor for the development of thrombotic complications (acute myocardial infarction) in patients with coronary artery disease. The potential role of deficient fibrinolysis in the pathogenesis of atherosclerosis and of atherothrombosis suggests that drugs normalizing deficient endogenous fibrinolysis by either reducing PAI-1 synthesis or by stimulating endogenous t-PA synthesis may be of clinical value. Although regulation of the gene expression of PAI-1 and t-PA is presently under active investigation, no potent specific and safe agents to downregulate PAI-1 or to upregulate t-PA have as yet been identified. Retinoic acid appears to be a specific inducer of t-PA synthesis in human endothelial cells in culture and may constitute a model for the development of drugs that stimulate endogenous t-PA synthesis.

Evidence of decreased fibrinolytic activity in hypertensive premenopausal women

In 29 lean, premenopausal, never-treated hypertensive women (142 +/- 2/93 +/- 1 mmHg, mean +/- SEM) plasminogen activator inhibitor (PAI-1) was elevated (11.0 +/- 1.5 U/ml vs 6.3 +/- 1.0 U/ml, p less than 0.05) compared to healthy, normotensive women (113 +/- 2/71 +/- 2 mmHg). Euglobulin clot lysis time tended to be longer in the hypertensive than in the normotensive women (p = 0.06). PAI-1 was positively correlated to triglycerides (r = 0.60, p less than 0.001), haematocrit (r = 0.45, p less than 0.05), insulin (r = 0.38, p less than 0.05) and body mass index (r = 0.38, p less than 0.05), and inversely correlated to HDL cholesterol (r = -0.43, p less than 0.05) in the hypertensive women. Fibrinogen was not significantly different in the hypertensive and normotensive women, while the hypertensive smokers had higher fibrinogen than the hypertensive non-smokers (3.01 +/- 0.17 g/l vs 2.54 +/- 0.10 g/l, p less than 0.05). All participants were investigated in the same phase of the menstrual cycle. Despite that, oestradiol was significantly lower in the hypertensive than in the normotensive women (0.57 +/- 0.06 vs 0.81 +/- 0.09 nmol l-1, p less than 0.05), while progesterone was similar in the two groups. These results suggest that premenopausal, never-treated hypertensive women are characterized by low oestradiol levels as well as decreased fibrinolytic activity. PAI-1 seems to be associated with other risk factors for cardiovascular disease in hypertensive women.

Diabetes mellitus and hypertension

Diabetes mellitus and hypertension are common diseases that coexist at a greater frequency than chance alone would predict. Hypertension in the diabetic individual markedly increases the risk and accelerates the course of cardiac disease, peripheral vascular disease, stroke, retinopathy, and nephropathy. Our understanding of the factors that markedly increase the frequency of hypertension in the diabetic individual remains incomplete. Diabetic nephropathy is an important factor involved in the development of hypertension in diabetics, particularly type I patients. However, the etiology of hypertension in the majority of diabetic patients cannot be explained by underlying renal disease and remains "essential" in nature. The hallmark of hypertension in type I and type II diabetics appears to be increased peripheral vascular resistance. Increased exchangeable sodium may also play a role in the pathogenesis of blood pressure in diabetics. There is increasing evidence that insulin resistance/hyperinsulinemia may play a key role in the pathogenesis of hypertension in both subtle and overt abnormalities of carbohydrate metabolism. Population studies suggest that elevated insulin levels, which often occurs in type II diabetes mellitus, is an independent risk factor for cardiovascular disease. Other cardiovascular risk factors in diabetic individuals include abnormalities of lipid metabolism, platelet function, and clotting factors. The goal of antihypertensive therapy in the patient with coexistent diabetes is to reduce the inordinate cardiovascular risk as well as lowering blood pressure.

Metformin and blood pressure

Hypertension appears to predispose to both atheroma and thrombus formation and is a risk factor for stroke and coronary artery disease. Insulin resistance and hyperinsulinaemia are also associated with hypertension, whether treated or untreated and irrespective of obesity. In an attempt to treat the possible insulin resistance in hypertension, an antidiabetic agent, metformin, which enhances glucose uptake, was given to non-obese, non-diabetic, untreated hypertensives in a pilot study. Metformin improved insulin sensitivity, decreased plasma insulin, serum cholesterol and triglycerides, increased fibrinolytic activity and markedly decreased blood pressure. These findings support the concept that insulin resistance may be important in cases of primary hypertension, i.e. those with concomitant metabolic and possibly also fibrinolytic abnormalities. Furthermore, the results indicate that insulin resistance may precede hypertension in these cases.

Insulin resistance, hyperinsulinemia, and cardiovascular disease. The need for novel dietary prevention strategies

Insulin resistance associated with hyperinsulinemia (metabolic syndrome) emerged in recent years as an important health risk which is present in approximately 25% of the normal population in western industrialized societies. Insulin resistance as assessed for the whole body arises from a reduced glucose utilization of skeletal muscle. If the metabolic syndrome persists over a prolonged period of time, detrimental influences on the cardiovascular system become apparent involving diabetes mellitus, hypertension, and arteriosclerosis. Of particular pathogenic relevance is an unbalanced influence of insulin arising either from a diminished or enhanced insulin action depending on whether the various tissues of the body exhibit a reduced or unchanged insulin sensitivity. Since insulin resistance and hyperinsulinemia appear to be affected by various lifestyle factors, the unique opportunity exists of reducing cardiovascular mortality by correcting this syndrome at a time when degenerative changes have not occurred in the cardiovascular system. Of great importance is the finding that dietary factors can have a modulatory action on insulin sensitivity. In animal experiments, an increased intake of (saturated) fat and refined carbohydrates increased insulin resistance. Since psychosocial distress is expected to be associated with a sustained activation of the sympathoadrenal axis, it is likely also to aggravate the metabolic syndrome. A factor with a beneficial action appears to be physical exercise. In view of the high incidence of cardiovascular diseases, further research on lifestyle factors with an insulin-sensitizing or insulin-desensitizing action is required. Of prime importance is the reevaluation of established dietary recommendations and diets should be designed which take into account the individual cardiovascular risk factor profile.

Role of diet and exercise in the management of hyperinsulinemia and associated atherosclerotic risk factors

Hyperinsulinemia, hypertension, hypertriglyceridemia and obesity are independent risk factors for coronary artery disease and are often found in the same person. This study investigated the effects of an intensive, 3-week, dietary and exercise program on these risk factors. The group was divided into diabetic patients (non-insulin-dependent diabetes mellitus [NIDDM], n = 13), insulin-resistant persons (n = 29) and those with normal insulin, less than or equal to 10 microU/ml (n = 30). The normal groups had very small but statistically significant decreases in all of the risk factors. The patients with NIDDM had the greatest decreases. Insulin was reduced from 40 +/- 15 to 27 +/- 11 microU/ml, blood pressure from 142 +/- 9/83 +/- 3 to 132 +/- 6/71 +/- 3 mm Hg, triglycerides from 353 +/- 76 to 196 +/- 31 mg/dl and body mass index from 31.1 +/- 4.0 to 29.7 +/- 3.7 kg/m2. Although there was a significant weight loss for the group with NIDDM, resulting in the decrease in body mass index, 8 of 9 patients who were initially overweight were still overweight at the end of the program, and 5 of the 8 were still obese (body mass index greater than 30 kg/m2), indicating that normalization of body weight is not a requisite for a reduction or normalization of other risk factors. Insulin was reduced from 18.2 +/- 1.8 to 11.6 +/- 1.2 microU/ml in the insulin-resistant group, with 17 of the 29 subjects achieving normal fasting insulin (less than 10 microU/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of free testosterone on antigen levels of plasminogen activator inhibitor-1 in premenopausal women with central obesity

Women with upper body obesity are at increased risk for cardiovascular disease (CVD). Several studies have demonstrated a reduced fibrinolytic activity in these patients, mainly due to an enhanced activity of plasminogen activator inhibitor-1 (PAI-1). Since an increase of androgenic activity is a feature of central obesity in women, the present study was aimed at evaluating the possibility of a relationship between androgens and PAI-1 (antigen and activity) in 20 premenopausal women, 10 with upper body obesity and 10 controls. In obese women, PAI-1 antigen showed a positive Pearson correlation with free testosterone (FT), insulin, c-peptide, triglycerides (TG), and waist to hip ratio (WHR) (P less than .01), whereas PAI-1 activity correlated positively only with insulin and WHR (P less than .01). In control women, PAI-1 antigen and activity were positively related only to TG (P less than .01). When we applied the multiple regression model with stepwise backward method to our data, both PAI-1 antigen and activity did not maintain any significant association. However, when the data from both the groups were pooled (n = 20), and PAI-1 antigen was considered as the dependent variable, body weight (Sig T = 0.0001), TG (Sig T = 0.0053), FT (Sig T = 0.013), and luteinizing hormone (LH) (Sig T = 0.0474) met the stepwise criteria, suggesting an independent effect of each of these parameters on PAI-1 antigen. On the other hand, when PAI-1 activity was tested as the dependent variable, only body weight maintained a significant relationship with this parameter (Sig T = 0.0006).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin resistance and cardiovascular drugs

Under certain circumstances the effect of insulin to promote glucose uptake in peripheral tissues is reduced because of a resistance to insulin action. This insulin resistance and the resulting hyperinsulinaemia are now recognised as common background factors that may be responsible for hypertension, hyperlipidaemia, decreased thrombolysis and also impaired glucose tolerance and diabetes. Hyperinsulinaemia has also been identified as an independent risk factor for coronary heart disease and promotes smooth muscle cell growth and plaque formation. A series of studies have now demonstrated that treatment with selective beta-blockers as well as thiazide diuretics impair insulin sensitivity by 15-30% and causes a compensatory increase in insulin concentrations. Furthermore, lipoprotein concentrations are affected in an unfavourable way. This is in contrast to the drugs belonging to ACE-inhibitors, calcium-channel blockers and alpha 1-blocker classes that are either neutral or may have the opposite effects in these respects.

Epidemiologic and clinical aspects of insulin resistance and hyperinsulinemia

Epidemiologic studies have shown that insulin is a risk factor for coronary heart disease (CHD). Clinical studies have also demonstrated positive correlations between insulin and blood pressure, triglycerides, total cholesterol, fibrinogen, and plasminogen activator inhibitor. Moreover, there is an inverse correlation between insulin and high-density lipoprotein (HDL). These studies have provided evidence in support of the biologic plausibility of epidemiologic observations, but they have not clearly established insulin's role in the pathogenesis of human cardiovascular diseases (CVD) such as hypertension. In fact, there is considerable evidence that insulin resistance (abnormal nonoxidative glucose disposal), not hyperinsulinemia, is the primary insulin-related abnormality in human hypertension, and that hyperinsulinemia occurs as a response to insulin resistance. Skeletal muscle appears to be the primary site of insulin resistance in essential hypertension, although other organs, such as the kidneys and liver--key sites for cell and water homeostasis and lipoprotein regulation, respectively--may respond normally to insulin. Adipocytes also appear to be a site of insulin resistance. Thus, the putative interrelationship between hyperinsulinemia and insulin resistance, on the one hand, and with blood pressure and lipoproteins, on the other, is a complex one and may involve organ-specific insulin resistance. Altered cation transport is one of several mechanisms by which insulin resistance might raise blood pressure. The Na+, K(+)-ATPase and Ca(2+)-ATPase pumps are insulin sensitive. Thus, when insulin resistance is present, the activity of these pumps in the smooth muscle of the arterial wall might be reduced. This would lead to an intracellular accumulation of sodium and calcium, thereby sensitizing the vascular wall to pressor substances. Moreover, secondary hyperinsulinemia will occur, and insulin has been shown to stimulate sympathetic nervous system activity and to increase renal tubular absorption of sodium. Insulin is also a growth factor and therefore might have a trophic effect on the vessel wall, one that could initiate and/or sustain hypertension as well as atherosclerosis. Abnormal lipoprotein metabolism is yet another possible explanation for the accelerated atherosclerosis that has been observed in persons with abnormal carbohydrate tolerance and insulin resistance. Hyperinsulinemia and insulin resistance both play a role in the expression of elevated very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) levels as well as in the depression of HDL levels. Coronary risk reduction has been disappointing when blood pressure has been lowered with treatment regimens based on thiazide diuretics and/or beta blockers. Thiazides and some beta blockers may further impair tissue insulin sensitivity and often cause blood lipoprotein abnormalities.(ABSTRACT TRUNCATED AT 400 WORDS)