Insulin resistance, compensatory hyperinsulinaemia, and coronary heart disease

Lean, nondiabetic Asian Indians have decreased insulin sensitivity and insulin clearance, and raised leptin compared to Caucasians and Chinese subjects

OBJECTIVE

To study and compare the insulin sensitivity of healthy, nondiabetic Asian Indians with that of two other ethnic groups (Caucasian and Chinese) living in Singapore.

DESIGN

Study of insulin sensitivity using euglycaemic hyperinsulinaemic glucose clamp.

SUBJECTS

A total of 10 healthy, lean, young male subjects of each ethnic group, matched for age, body mass index (BMI) and physical activity. They all had normal glucose tolerance and had no family history of diabetes.

MEASUREMENTS

Anthropometric parameters (BMI, waist-hip ratio (WHR) and percentage body fat (PBF)), fasting lipid profile and leptin concentration, insulin sensitivity index, and insulin clearance.

RESULTS

Healthy lean (BMI 22.1+/-1.5 kg/m(2) (mean+/-s.d.)) Indians had significantly higher fasting serum leptin (5.1+/-2.5 vs Chinese 1.0+/-0.9 vs Caucasian 2.3+/-1.2 ng/ml; P<0.001), lower insulin sensitivity index (9.9+/-3.3 vs Chinese 14.1+/-3.5 vs Caucasian 18.8+/-9.2 mg/min kg fat-free mass/microU/ml; P<0.002), and lower insulin clearance (461.4+/-54.8 vs Chinese 621.0+/-99.3 vs Caucasian 646.9+/-49.2 ml/min m(2); P<0.001). Indians also had a higher PBF (26.5+/-5.2 vs Chinese 19.5+/-2.2 vs Caucasians 22.9+/-1.4%; P<0.001), diastolic blood pressure (P=0.036), fasting insulin (P<0.006) and fasting triglyceride (P=0.022). Stepwise regression analysis showed that ethnicity was the only significant independent determinant variable for the differences in insulin sensitivity index (P=0.008).

CONCLUSION

Healthy lean nondiabetic Indians were more insulin resistant compared to other ethnic groups despite the similarity in living environment. These findings may warrant preventive health-care strategies for type II diabetes and coronary artery disease to target Indians at an earlier stage compared to other ethnic groups.

Plasma leptin, fatty acids, and tumor necrosis factor-receptor and insulin resistance in children

OBJECTIVE

To evaluate the effect of plasma leptin, nonsterified fatty acids (NEFAs), and tumor necrosis factor-receptor 1 (TNFR1) on plasma insulin and insulin-resistance status in children.

RESEARCH METHODS AND PROCEDURES

One thousand thirty-two children (521 boys and 511 girls) were included in this study. We measured plasma insulin and leptin levels by radioimmunoassay, plasma NEFA levels by enzymatic acyl-coenzyme A synthase-acyl-coenzyme A oxidase spectrophotometric methods, and TNFR1 levels by enzyme-linked immunosorbent assay. We calculated insulin resistance index (IRI) using homeostasis model assessment and calculated insulin-resistance syndrome summary score (IRS) by adding the quartile ranks from the distribution of systolic blood pressure (BP), serum triglyceride, high-density lipoprotein-cholesterol (inverse), and insulin levels.

RESULTS

Overweight children had higher BP, plasma leptin, and insulin levels and higher IRI and IRS than normal-weight children. Plasma leptin and TNFR1 were positively correlated with insulin levels, IRI, and IRS. The correlation coefficients of leptin and TNFR1 in IRI were 0.53 and 0.12, respectively, for boys and 0.25 and 0.18, respectively, for girls. In multivariate regression analyses, TNFR1 was positively associated with insulin level and IRI in girls; NEFA was positively associated only with IRS. Plasma leptin levels were significantly positively associated with insulin levels, IRI, and IRS, even after adjusting for BMI and other potential confounders.

DISCUSSION

Overweight children had higher BP, plasma insulin, and leptin levels and adverse insulin-resistance status than normal-weight children. Plasma leptin levels, rather than NEFA and TNFR1, may play a significant role in the development of hyperinsulinemia and insulin resistance in children.

Recurrence of insulin resistant metabolic syndrome following liver transplantation

Insulin resistant metabolic syndrome is a major clinical disorder including hyperlipidaemia, hypertension, impaired glucose tolerance and/or type 2 diabetes and central obesity, which are well established cardiovascular risk factors. We report the case of a 61-year-old woman who developed severe hypercholesterolaemia and hypertriglyceridaemia after liver transplantation. In her forties she had hypertension, mixed hyperlipidaemia, mild hyperglycaemia and moderate abdominal obesity, suggesting the presence of the metabolic syndrome. She had liver enzyme elevation and severe steatosis and hepatomegaly at ultrasonography. At age 52, cryptogenic liver cirrhosis was diagnosed and rapidly progressing liver failure developed. In 1992 she underwent liver transplantation. Seven years after transplant the patient had abdominal obesity, high blood pressure, marked hypercholesterolaemia, hypertriglyceridaemia and moderate elevation of alanine aminotransferase. She also had impaired glucose tolerance and markedly increased basal and post-glucose load plasma insulin levels. Steatohepatitis was demonstrated by serial liver biopsies. This is the first case that reports the recurrence of the metabolic syndrome following liver transplantation. We postulate that metabolic syndrome may have promoted fatty liver and subsequent progression to end stage liver disease. We also stress the need for careful management of the metabolic syndrome in order to decrease the long-term risk for cardiovascular disease.

Pharmacotherapy of diabetes mellitus: implications for the prevention and treatment of cardiovascular disease

Diabetes mellitus in adults is associated with an increased risk of premature vascular disease and a higher mortality rate. The presence of other risk factors, often seen in diabetic patients, such as systemic hypertension, augments the rate of vascular diseases. Evidence is growing that tight control of hyperglycemia using insulin and/or oral hypoglycemic agents will modify this risk. More aggressive control of concomitant hypertension and/or hyperlipidemia is also required. Diabetic patients who have myocardial infarctions do worse than nondiabetic patients. Various strategies to improve outcomes include the use of tight blood glucose control, and various coronary interventions are currently under clinical study.

Increased atherosclerosis in diabetic dyslipidemic swine: protection by atorvastatin involves decreased VLDL triglycerides but minimal effects on the lipoprotein profile

Male Yucatan swine were allocated to four groups (n = 5-6 pigs per group): low fat (3%) fed control, high fat/2% cholesterol (CH) fed (HF), high fat/CH fed with alloxan-induced diabetes (DF) and DF pigs that were treated with atorvastatin (80 mg/day; DF+A). Pigs were fed two meals per day and daily insulin injections were used in diabetic pigs to maintain plasma glucose between 250 and 350 mg/dl. Diabetic dyslipidemic (DF) pigs exhibited greater coronary atherosclerosis and increased collagen deposition in internal mammary artery compared with normoglycemic hyperlipidemic pigs. Although total and LDL CH concentrations did not differ, triglyceride (TG) were increased in DF pigs and FPLC analysis indicated that the LDL/HDL CH ratio was significantly increased in DF compared with HF pigs. The LDL fraction of DF pigs contained larger, lipid enriched particles resembling IDL. Consumption of the high fat/CH diet caused a moderate increase in the percentage of 14:0 fatty acids in plasma lipids and this was compensated by small-moderate declines in several unsaturated fatty acids. There was a significant increase in phospholipid arachidonic acid in DF compared with HF pigs. Atorvastatin protected diabetic pigs from atherosclerosis and decreased total and VLDL TG, but exerted minimal effects on the FPLC lipoprotein and plasma fatty acid profiles and plasma concentrations of total and LDL CH, vitamin A, vitamin E, and lysophosphatidylcholine. Across all groups the plasma CH concentration was positively correlated with hepatic CH concentration. These findings suggest that atorvastatin's protection against coronary artery atherosclerosis in diabetes may involve effects on plasma VLDL TG concentration. Lack of major effects on other lipid parameters, including the LDL/HDL ratio, suggests that atorvastatin may have yet other anti-atherogenic effects, possibly directly in the vessel wall.

Insulin improves fasting and postprandial lipemia in type 2 diabetes

BACKGROUND: The purpose of the investigation presented here was to study the effects of insulin therapy in type 2 diabetes mellitus (type 2 DM) not only on glycemic control but also on other components of the metabolic syndrome, including lipid metabolism, blood pressure, and body weight. METHODS: Twelve patients with type 2 DM were studied before and after replacement of sulphonylurea treatment with insulin for 4 months. RESULTS: Insulin therapy resulted in a significant decrease in fasting glucose levels by 26%; glycated hemoglobin decreased by 17% and fructosamine values by 19%. With insulin treatment, fasting plasma triglyceride levels decreased by 28% and total HDL cholesterol and HDL(3) cholesterol increased by 17 and 11%, respectively. Low-density lipoprotein (LDL) cholesterol showed no significant change. The magnitude of postprandial lipemia after ingestion of a standard fatty meal decreased by 38%. Insulin treatment was also accompanied by a 21% increase in lipoprotein lipase (LPL) activity in postheparin plasma and by a 20% increase in cholesteryl ester transfer protein (CETP) activity. Hepatic lipase activity was not changed significantly with insulin. Mean BMI decreased from 28.5+/-4.2 to 28.0+/-3.1 kg/m(2) (P=0.02), which is in keeping with the finding that peripheral insulin levels did not increase and which can be explained by the fact that the insulin regimen was combined with dietary counseling. Accordingly, blood pressure showed no significant change. CONCLUSION: Our study demonstrates that judicious replacement of sulfonylurea treatment with insulin therapy, together with dietary counseling, can result in a simultaneous improvement in the major stigmata of the metabolic syndrome, i.e. a significant improvement in glycemic control and lipid metabolism without unfavorable effects on body weight and blood pressure.

Proinsulin is an independent predictor of coronary heart disease: Report from a 27-year follow-up study

BACKGROUND

Some, but not all, studies have reported a relationship between plasma insulin and coronary heart disease (CHD). Conventional nonspecific insulin assays are also measuring various fractions of proinsulin-like molecules due to cross-reactivity. The long-term relationship between proinsulin-like molecules and CHD is largely unknown. For this reason, the longitudinal relationships between intact proinsulin, split proinsulin, specific insulin, immunoreactive insulin, and CHD, were studied in a population-based cohort of 50-year-old men (n=874), with a follow-up of 27 years.

METHODS AND RESULTS

Fasting proinsulin-like molecule and specific-insulin concentrations were measured in plasma (stored frozen since baseline 1970 to 1973) by specific 2-site immunometric assays. Immunoreactive insulin concentrations were determined at baseline. The associations between proinsulin-like molecules, specific insulin, immunoreactive insulin, and CHD mortality (International Classification of Diseases [9th revision] codes 410 to 414) were analyzed using Cox's proportional hazards regression and presented as hazard ratios (HRs) with their 95% confidence intervals (CIs) for a 1-SD increase in a predictor variable. In the univariate analysis, intact proinsulin (HR, 1.69; 95% CI, 1.41 to 2.01) was the strongest predictor of death from CHD. In the multivariate analysis, smoking (HR, 1.57; 95% CI, 1.03 to 2.38), intact proinsulin (HR, 1.47; 95% CI, 1.18 to 1.82), systolic blood pressure (HR, 1.38; 95% CI, 1.14 to 1.66), and LDL/HDL cholesterol ratio (HR, 1.31; 95% CI, 1.12 to 1.53) were independent predictors of CHD mortality (adjusted for body mass index, triglycerides, and fasting glucose), whereas specific insulin and immunoreactive insulin were not (HR, 1.12; 95% CI, 0.90 to 1.40). The increased risk was restricted to the upper third of the proinsulin distribution.

CONCLUSION

Increased proinsulin concentrations predict death and morbidity caused by CHD over a period of 27 years, independent of other major cardiovascular risk factors.

A link between polymorphonuclear leukocyte intracellular calcium, plasma insulin, and essential hypertension

BACKGROUND

Intracellular ionized calcium ([Ca2+]i) is a key mediator in the activation and oxidant production by peripheral polymorphonuclear leukocytes (PMN). Primed PMN contribute to oxidative stress (OS) and inflammation in essential hypertension (EH). Elevated [Ca2+]i has been described in insulin-resistant states and in various cell types in EH but not in EH PMN. The aim of this study was to evaluate the levels of [Ca2+]i in peripheral EH PMN in relation to plasma insulin levels and blood pressure (BP).

METHODS

The PMN were separated from blood of 20 nonsmoking, nonobese untreated EH patients, age range 20 to 60 years and from 20 age- and gender-matched healthy individuals (NC). Plasma glucose and insulin levels 2 h after a 75-g oral glucose load, reflected insulin resistance. PMN [Ca2+]i was measured by flow cytometry in isolated cells stained with Fluo-3.

RESULTS

The EH PMNs showed significantly increased [Ca2+]i compared to NC PMN. Eighty percent of EH patients showed significantly higher plasma insulin levels after glucose load. Linear regression analysis showed significant correlation between 1) PMN [Ca2+]i and mean arterial pressure (MAP) (r = 0.5, P < .006); 2) PMN [Ca2+]i and fasting plasma insulin (r = 0.7, P < .005); and 3) fasting plasma insulin and MAP (r = 0.4, P < .04).

CONCLUSIONS

This study adds PMN to previously described cells exhibiting elevated [Ca2+]i, contributing to OS and inflammation. The correlation of individual BP with both PMN [Ca2+]i and plasma insulin levels, together with the fact that elevated [Ca2+]i mediates PMN priming, suggest that elevated [Ca2+]i and insulin are involved in the pathogenesis of hypertension-induced vascular injury in EH.

An evolutionary analysis of the aetiology and pathogenesis of juvenile-onset myopia

The available evidence suggests that both genes and environment play a crucial role in the development of juvenile-onset myopia. When the human visual system is examined from an evolutionary perspective, it becomes apparent that humans, living in the original environmental niche for which our species is genetically adapted (as hunter-gatherers), are either slightly hypermetropic or emmetropic and rarely develop myopia. Myopia occurs when novel environmental conditions associated with modern civilization are introduced into the hunter-gatherer lifestyle. The excessive near work of reading is most frequently cited as the main environmental stressor underlying the development of myopia. In this review we point out how a previously unrecognized diet-related malady (chronic hyperinsulinaemia) may play a key role in the pathogenesis of juvenile-onset myopia because of its interaction with hormonal regulation of vitreal chamber growth.

Factors of insulin resistance syndrome--related phenotypes are linked to genetic locations on chromosomes 6 and 7 in nondiabetic mexican-americans

Insulin resistance syndrome (IRS)-related phenotypes, such as hyperinsulinemia, obesity-related traits, impaired glucose tolerance, dyslipidemia, and hypertension, tend to cluster into factors. We attempted to identify loci influencing the factors of IRS-related phenotypes using phenotypic data from 261 nondiabetic subjects distributed across 27 low-income Mexican-American extended families. Principal component factor analyses were performed using eight IRS-related phenotypes: fasting glucose (FG), fasting specific insulin (FSI), BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), HDL cholesterol, ln triglycerides (ln TGs), and leptin (LEP). The factor analysis yielded three factors: factor 1 (BMI, LEP, and FSI), factor 2 (DBP and SBP), and factor 3 (HDL and ln TG). We conducted multipoint variance components linkage analyses on these factors with the program SOLAR using a 10--15 cM map. We found significant evidence for linkage of factor 1 to two regions on chromosome 6 near markers D6S403 (logarithm of odds [LOD] = 4.2) and D6S264 (LOD = 4.9). We also found strong evidence for linkage of factor 3 to a genetic location on chromosome 7 between markers D7S479 and D7S471 (LOD = 3.2). In conclusion, we found substantial evidence for susceptibility loci on chromosomes 6 and 7 that appear to influence the factors representing the IRS-related phenotypes in Mexican-Americans.

Hypertension and obesity

Obesity, as defined by bodily weight (body weight) and by bodily conformation-derived variables, accompanies hypertension in many patients. Both conditions are independent cardiovascular risk factors. In a formal survey carried out in the adult general population of Uruguay (LATIR Study, 575 adult and elderly subjects of whom 41.6% were males), we found the prevalence of hypertension to be 28.5% (95% CI: 24.9-32.4%) and that 74.4% of hypertensive individuals had a body mass index (BMI) higher than 25 kg/m(2) (95% CI: 67.0-80.8%). This association between obesity and hypertension forms part of a broader relationship between body weight and blood pressure (BP). In the general population, BP bears a positive linear correlation with BMI and waist-to-hip ratio over the continuous ranges of normal and unfavourable values of these three variables (r = 0.42, P < 0.001 for the correlation between BMI and mean BP, LATIR Study). Patients who present hypertension and obesity usually present other unfavourable conditions for cardiovascular prognosis, including changes in carbohydrate and lipid metabolism, hyperuricaemia, left ventricular hypertrophy, and/or the obstructive sleep apnoea syndrome. On average, hypertension is salt-sensitive in obese patients, and plasma volume and cardiac index are increased. Adequate control of body weight results in substantial reductions in total blood volume, cardiac output, BP and left ventricular mass, and in an amelioration or the disappearance of sleep apnoea. Adequate sodium intake restriction must form part of any diet prescribed to obese hypertensive patients. Various drug classes may be used to treat hypertension efficaciously in patients who also present obesity.

Insulin causes endothelial dysfunction in humans: sites and mechanisms

BACKGROUND

Insulin resistance is often accompanied by hyperinsulinemia and may predispose to atherosclerosis. Endothelium plays a central role in atherogenesis. The in vivo effects of hyperinsulinemia on endothelial function of large conduit arteries are unknown.

METHODS AND RESULTS

Twenty-five healthy subjects were enrolled for study. In study A (n=9), subjects underwent both a time-control saline study and a euglycemic low-dose insulin (insulin approximately 110 pmol/L) clamp for 6 hours. Study B (n=5) was identical to study A except that the euglycemic clamp was performed at high physiological insulin concentrations (approximately 440 pmol/L). In study C (n=7), subjects underwent two 4-hour euglycemic insulin (approximately 110 pmol/L) clamps with and without the concomitant infusion of an antioxidant (vitamin C). In study D (n=4), two saline time-control studies were performed with and without the concomitant infusion of vitamin C. In all studies, both at baseline and throughout the experimental period, endothelium-dependent (flow-mediated) and endothelium-independent (nitroglycerin-induced) vasodilation was assessed in femoral and brachial arteries by echo Doppler. Both low (study A) and high physiological (study B) hyperinsulinemia abolished endothelium-dependent vasodilation, whereas endothelium-independent vasodilation was unaffected. Vitamin C fully restored insulin-impaired endothelial function without affecting endothelium-independent vasodilation (study C). Vitamin C had no effects on endothelium-dependent or endothelium-independent vasodilation during saline control studies (study D).

CONCLUSIONS

Modest hyperinsulinemia, mimicking fasting hyperinsulinemia of insulin-resistant states, abrogates endothelium-dependent vasodilation in large conduit arteries, probably by increasing oxidant stress. These data may provide a novel pathophysiological basis to the epidemiological link between hyperinsulinemia/insulin-resistance and atherosclerosis in humans.

Effect of TNF-alpha--converting enzyme inhibitor on insulin resistance in fructose-fed rats

Insulin resistance is associated with hypertension, obesity, dyslipidemia, and type 2 diabetes. It is well known that tumor necrosis factor (TNF)-alpha is one of the factors linked to obesity-induced insulin resistance; however, there have been no reports on the role of TNF-alpha in insulin resistance in nonobese insulin-resistant hypertensives. We tested the hypothesis that TNF-alpha affects insulin resistance in nonobese insulin-resistant hypertensive fructose-fed rats (FFR) and that a TNF-alpha--converting enzyme (TACE) inhibitor that blocks TNF-alpha secretion improves insulin resistance in FFR. Six-week-old male Sprague-Dawley rats were fed either standard chow (control) or fructose-rich chow (FFR) for 6 weeks. For the last two weeks of a six-week period of either diet, the rats were treated with a vehicle (control or FFR) or a TACE inhibitor (100 mg/kg/d of KB-R7785; FFR+TACE-I) in peritoneal injection. At the age of 12 weeks, insulin sensitivity was assessed in all conscious rats by the euglycemic hyperinsulinemic glucose clamp technique. While FFR had higher blood pressure than the control rats (P<0.01), the TACE inhibitor did not change blood pressure. Insulin sensitivity (M-value) was reduced in FFR compared with that in the control rats (16.7 +/- 1.1 mg/kg per min and 10.3 +/- 0.6 mg/kg per min in the control rats and FFR, respectively, P<0.001), and the TACE inhibitor improved insulin sensitivity to the level of the control rats (14.3 +/- 1.2 mg/kg per min in FFR+TACE-I, P<0.01). These data indicate that TNF-alpha plays a major role in insulin resistance in nonobese insulin-resistant models and also suggest that TACE would be a good target for controlling insulin resistance not only in obese models but also in nonobese insulin-resistant models.

Lack of association of insulin resistance and carotid intimal medial thickness in non-diabetic Asian Indian subjects

OBJECTIVE

Atherosclerosis is associated with insulin resistance (IR) and dyslipidaemia. Impaired glucose tolerance (IGT) is characterised by IR and is associated with a higher risk of atherosclerosis. The objective of the present study was to test whether early atherosclerosis indicated by intimal medial thickness (IMT) of common carotid artery (CCA) and internal carotid artery (ICA) is higher in IGT than in normoglycaemic subjects (NGT) and to look for an association of IMT with IR and dyslipidaemia.

STUDY DESIGN AND METHODS

Ninety-nine randomly selected non-diabetic subjects aged >or=35 years (48 NGT and 51 IGT) were studied. Measurements of body mass index (BMI), waist/hip ratio (WHR), blood pressure, cholesterol-total, HDL, LDL, VLDL, triglycerides (TG), lipoprotein (a), apolipoprotein-A1 (Apo A1) and apolipoprotein-B (Apo B) and ratio of Apo A1/Apo B were estimated. Insulin resistance (HOMA-IR) was calculated using the fasting plasma insulin and glucose values. IMT of CCA and ICA were measured using high-resolution beta-mode ultrasonography.

RESULTS

Subjects with IGT and NGT were matched for BMI and WHR; HOMA-IR was higher in IGT vs NGT (7.92+/-4.2 vs 6.07+/-3.76, p = 0.028). Age-adjusted IMT values were similar in NGT and IGT (CCA 0.59+/-0.17 and 0.63+/-0.22 mm and ICA 0.44+/-0.10 and 0.45+/-0.10 mm, respectively). Further analyses were done in the total group. Multiple linear regression analyses showed that CCA-IMT was significantly associated with age and negatively associated with Apo A1/Apo B ratio. ICA-IMT was associated with age only. IMT was significantly correlated with cholesterol-total and LDL-cholesterol and apolipoproteins. It was not associated with IR.

CONCLUSION

In southern Indians, IGT did not influence the IMT. Although insulin resistance was higher in IGT, it was not associated with higher IMT. Conventional risk factors such as cholesterol, LDL-cholesterol and apolipoproteins showed association with IMT in the insulin-resistant population.

Association of serum apolipoprotein A-I (but not high-density lipoprotein cholesterol) with healed myocardial infarction in men independent of serum insulin and C-peptide

Low serum levels of high-density lipoprotein (HDL) cholesterol or apolipoprotein A-I and high serum levels of insulin increase the risk of coronary heart disease (CHD) and can indicate insulin resistance. We tested the strength, independence, and interactions of associations between HDL cholesterol (or apolipoprotein A-I), insulin (or C-peptide), glucose, and CHD in 95 male nondiabetic patients with CHD who were <60 years old, in 92 probands from the PROCAM study, and in 61 non-cardiologic patients; all subjects were matched by age, body mass index, and smoking habits. Systemic hypertension (odds radio [OR] 2.8, 95% confidence intervals [CI] 1.6 to 4.8), high serum levels of glucose (OR 2.3, 95% CI 1.6 to 4.8), insulin (OR 2.1, 95% CI 1.3 to 3.6), and C-peptide (OR 4.1, 95% CI 2.2 to 7.5) as well as low serum levels of HDL cholesterol (OR 2.0, 95% CI 1.1 to 3.5) or apolipoprotein A-I (OR 3.9, 95% CI 2.1 to 7.1) had significant associations with CHD. At multivariate analysis, systolic blood pressure, glucose, apolipoprotein A-I, and C-peptide, but not HDL cholesterol and insulin, had consistent independent associations with CHD. Thus, the combined measurement of apolipoprotein A-I and C-peptide may improve the identification of nondiabetic patients at increased risk for CHD.

Congestive heart failure in type 2 diabetes: prevalence, incidence, and risk factors

OBJECTIVE

To estimate the prevalence and incidence of congestive heart failure (CHF) in populations with and without type 2 diabetes and to identify risk factors for diabetes-associated CHF.

RESEARCH DESIGN AND METHODS

We searched the inpatient and outpatient electronic medical records of 9,591 individuals diagnosed with type 2 diabetes before 1 January 1997 and those of an age- and sex-matched control group without diabetes for a diagnosis of CHF. Among those without a baseline diagnosis of CHF, we searched forward for 30 months for incident cases of CHF. We constructed multiple logistic regression models to identify risk factors for both prevalent and incident CHF.

RESULTS

CHF was prevalent in 11.8% (n = 1,131) of diabetic subjects and 4.5% (n = 435) of control subjects at baseline. We observed incident cases of CHF in 7.7% of diabetic subjects free of CHF at baseline (650 of 8,460) and in 3.4% of control subjects (314 of 9,156). In diabetic subjects, age, diabetes duration, insulin use, ischemic heart disease, and elevated serum creatinine were independent risk factors for both prevalent and incident CHF. Better glycemic control at baseline, and improved glycemic and blood pressure control at follow-up predicted the development of CHF.

CONCLUSIONS

Despite controlling for age, duration of diabetes, presence of ischemic heart disease, and presence of hypertension, insulin use was associated with both prevalent and incident CHF. Why insulin use and better glycemic control both at baseline and follow-up independently predicted CHF deserves further study.

Plasma insulin, leptin, and soluble TNF receptors levels in relation to obesity-related atherogenic and thrombogenic cardiovascular disease risk factors among men

Obesity is related to cardiovascular disease (CVD) morbidity and mortality, however, the mechanisms for the development of obesity-induced CVD risk remain unclear. Hyperinsulinemia and insulin resistance are considered key components in the metabolic cardiovascular syndrome and as independent risk factors for CVD. Plasma leptin and tumor necrosis factor-alpha (TNF-alpha), two adipocyte products, are also proposed to be associated with the development of CVD risk. The purpose of this study is to evaluate the association of plasma leptin, soluble TNF receptors (sTNF-R), and insulin levels as possible mediators of the effect of obesity on atherogenic and thrombogenic CVD risk factors among men. From the Health Professionals Follow-up Study (HPFS), we selected 268 men, aged 47--83 years, who were free of CVD, diabetes, and cancer (except non-melanoma skin cancer), and who had provided a fasting blood sample in 1994. We measured plasma insulin and leptin levels by radioimmunoassay and sTNF-R levels by ELISA. Men in the highest quintile of body mass index (BMI, mean=30.5 kg/m(2)) were less physically active and had a more adverse cardiovascular lipid and homeostatic profile, as indicated by levels of insulin, triglyceride (TG), tissue plasminogen activator (t-PA) antigen levels, and apolipoprotein A1 (Apo-A1). In a multivariate regression model controlling for age, smoking, alcohol intake, physical activity and diet, BMI was inversely associated with HDL-cholesterol (HDL-C) and Apo-A1 and positively associated with TG, Apo-B and t-PA antigen levels. The associations between BMI and these CVD risk factors were only slightly changed after adjusting for leptin and/or sTNF-R; but were substantially attenuated after controlling for insulin levels. These data suggest that the association between obesity and biological predictors of CVD may be mediated through changes in plasma insulin, rather than leptin or sTNF-R levels. However, plasma leptin may still play a role in CVD through independent effects on lipid metabolism.

Effects of balloon injury on neointimal hyperplasia in streptozotocin-induced diabetes and in hyperinsulinemic nondiabetic pancreatic islet-transplanted rats

BACKGROUND

The mechanisms of increased neointimal hyperplasia after coronary interventions in diabetic patients are still unknown.

METHODS AND RESULTS

Glucose and insulin effects on in vitro vascular smooth muscle cell (VSMC) proliferation and migration were assessed. The effect of balloon injury on neointimal hyperplasia was studied in streptozotocin-induced diabetic rats with or without adjunct insulin therapy. To study the effect of balloon injury in nondiabetic rats with hyperinsulinemia, pancreatic islets were transplanted under the kidney capsule in normal rats. Glucose did not increase VSMC proliferation and migration in vitro. In contrast, insulin induced a significant increase in VSMC proliferation and migration in cell cultures. Furthermore, in VSMC culture, insulin increased MAPK activation. A reduction in neointimal hyperplasia was consistently documented after vascular injury in hyperglycemic streptozotocin-induced diabetic rats. Insulin therapy significantly increased neointimal hyperplasia in these rats. This effect of hyperinsulinemia was totally abolished by transfection on the arterial wall of the N17H-ras-negative mutant gene. Finally, after experimental balloon angioplasty in hyperinsulinemic nondiabetic islet-transplanted rats, a significant increase in neointimal hyperplasia was observed.

CONCLUSIONS

In rats with streptozotocin-induced diabetes, balloon injury was not associated with an increase in neointimal formation. Exogenous insulin administration in diabetic rats and islet transplantation in nondiabetic rats increased both blood insulin levels and neointimal hyperplasia after balloon injury. Hyperinsulinemia through activation of the ras/MAPK pathway, rather than hyperglycemia per se, seems to be of crucial importance in determining the exaggerated neointimal hyperplasia after balloon angioplasty in diabetic animals.

Protein kinase C activation and its pharmacological inhibition in vascular disease

Vascular complications in diabetes mellitus are known to be associated with the activation of the protein kinase C (PKC) pathway through the de novo synthesis of diacylglycerol (DAG) from glycolytic intermediates. Specific PKC isoforms, mainly the beta- and delta-isoforms, have been shown to be persistently activated in diabetic mellitus. Multiple studies have reported that the activation of PKC leads to increased production of extracellular matrix and cytokines, enhances contractility, permeability and vascular cell proliferation, induces the activation of cytosolic phospholipase A2 and inhibits the activity of Na+-K+-ATPase. These events are not only frequently observed in diabetes mellitus but are also involved in the actions of vasoactive agents or oxidative stress. Inhibition of PKC by two different kinds of PKC inhibitors - LY333531, a selective PKC-beta-isoform inhibitor, and vitamin E, d-alpha-tocopheron - were able to prevent or reverse the various vascular dysfunctions in vitro and in vivo. Clinical studies using these compounds are now ongoing to evaluate the significance of DAG-PKC pathway activation in the development of vascular complications in diabetic patients.

The contribution of positron emission tomography to the study of ischemic heart failure

Cardiac imaging with positron emission tomography offers unrivaled sensitivity and specificity to probe cardiovascular physiology in health and disease. The use of positron emission tomography to noninvasively measure regional myocardial blood flow and assess myocardial viability in patients with ventricular dysfunction and coronary artery disease has contributed greatly to our understanding of the pathophysiology of ischemic heart failure. The advances and the need for further studies to establish both the natural history of such ventricular dysfunction and the role of coronary revascularization are discussed.

Premature adrenarche--normal variant or forerunner of adult disease?

Adrenarche is the puberty of the adrenal gland. The descriptive term pubarche indicates the appearance of pubic hair, which may be accompanied by axillary hair. This process is considered premature if it occurs before age 8 yr in girls and 9 yr in boys. The chief hormonal product of adrenarche is dehydroepiandrosterone (DHEA) and its sulfated product DHEA-S. The well documented evolution of adrenarche in primates and man is incompatible with either a neutral or harmful role for DHEA and implies most likely a positive role for some aspect of young adult pubertal maturation and developmental maturation. Premature adrenarche has no adverse effects on the onset and progression of gonadarche in final height. Both extra- and intraadrenal factors regulate adrenal androgen secretion. Recent studies have shown that premature adrenarche in childhood may have consequences such as functional ovarian hyperandrogenism, polycystic ovarian syndrome, and insulin resistance in later life, sometimes already recognizable in childhood or adolescence. Premature adrenarche may thus be a forerunner of syndrome X in some children. The association of these endocrine-metabolic abnormalities with reduced fetal growth and their genetic basis remain to be elucidated.

Insulin resistance, cardiovascular risk factors and ultrasonically measured early arterial disease in normotensive Type 2 diabetic subjects

BACKGROUND

The objective of the study was to examine the relationship between serum fasting insulin, insulin sensitivity S(i), cardiovascular risk factors, and asymptomatic early atherosclerosis in normotensive Type 2 diabetic subjects.

METHODS

Specific insulin was measured using an enzyme-linked immunosorbent assay (ELISA) and insulin sensitivity was assessed with an insulin-modified frequently sampled intravenous glucose tolerance test (FSIVGTT). Early atherosclerotic change was assessed using carotid intima media thickness (IMT) and an arterial ultrasound score (AUS) measured by high-resolution B-mode ultrasound.

RESULTS

On bivariate analysis, there was a positive correlation between S(i) and high density lipoprotein (HDL) cholesterol (r(s)=0.27, p<0.05), and a negative correlation between S(i) and body mass index (BMI) (r(s)=-0.42, p<0.001), HbA(1c) (r(s)=-0.29, p<0.05) and serum triglyceride (r(s)=-0.30, p<0.05). There was a positive correlation between carotid IMT and age (r(s)=0.41, p<0.0005), and a positive association with male sex (p<0.0001) as well as with smoking (p<0.0001). However, we found no correlation between carotid IMT and fasting specific insulin (r(s)=-0.04) or S(i) (r(s)=-0.08). On multiple regression analyses, only age and serum triglycerides appeared to be significant independent variables with respect to carotid IMT whereas age, male sex and smoking emerged jointly significant with respect to AUS. There were no independent associations between carotid IMT or AUS with other variables including using either fasting specific insulin or S(i) as markers on insulin resistance separately.

CONCLUSION

Carotid IMT and AUS in Type 2 diabetes are closely associated with age, male sex and smoking. The relationships between serum insulin and insulin resistance with ultrasonically measured early arterial disease in Type 2 diabetes remain unclear.

Occlusive vascular diseases in oral contraceptive users. Epidemiology, pathology and mechanisms

Despite being an unprecedented departure from normal physiology, the combined oral contraceptive is not only highly effective, but it also has a remarkably good safety record. Concerns over safety persist, though, particularly with regard to venous thromboembolism (VTE), stroke and myocardial infarction (MI). Epidemiological studies consistently show an increase in risk of VTE, but the results are more contentious with regard to arterial diseases. Despite 40 years of research, the mechanisms behind these adverse effects are not understood. In this review, we integrate information from published studies of the epidemiology and pathology of the occlusive vascular diseases and their risk factors to identify likely explanations for pathogenesis in oral contraceptive users. Oral contraceptives induce both prothrombotic and fibrinolytic changes in haemostatic factors and an imbalance in haemostasis is likely to be important in oral contraceptive-induced VTE. The complexity of the changes involved and the difficulty of ascribing clinical significance has meant that uncertainty persists. A seriously under-researched area concerns vascular changes in oral contraceptive users. Histologically, endothelial and intimal proliferation have been identified in women exposed to high plasma estrogen concentrations and these lesions are associated with thrombotic occlusion. Other structural changes may result in increased vascular permeability, loss of vascular tone and venous stasis. With regard to arterial disease risk, epidemiological information relating to dose effects and joint effects with other risk factors, and studies of pathology and changes in risk factors, suggests that oral contraceptive use per se does not cause arterial disease. It can, nevertheless, synergise very powerfully with subclinical endothelial damage to promote arterial occlusion. Accordingly, the prothrombotic effects of the oral contraceptive estrogen intervene in a cycle of endothelial damage and repair which would otherwise remain clinically silent or would ultimately progress - in, for example, the presence of cigarette smoking or hypertension - to atherosclerosis. Future work in this area should focus on modification of the effects of established risk factors by oral contraceptive use rather than modification of the supposed risk of oral contraceptive use by established risk factors. Attempts to understand vascular occlusion in oral contraceptive users in terms of the general features of VTE or with reference to atherosclerosis may be limiting, and future work needs to acknowledge that such occlusions may have unique features. Unequivocal identification of the mechanisms involved would contribute considerably to the alleviation of fears over vascular disease and to the development of even safer formulations.

Plasma leptin concentrations and obesity in relation to insulin resistance syndrome components among school children in Taiwan--The Taipei Children Heart Study

OBJECTIVE

Leptin, an adipose tissue-derived product of the obesity (OB) gene, is an important regulator of energy metabolism and may be associated with the occurrence of insulin resistance and diabetes in humans. The purpose of this study was to evaluate the association of plasma leptin concentration with obesity and the components of insulin resistance syndrome (IRS) among school children in Taiwan.

METHODS

After multistage sampling of 85 junior high schools in Taipei, we randomly selected 1,264 children (617 boys and 647 girls) aged 12-16y. Obesity measurements included body mass index (BMI) and waist-to-hip circumference ratio (WHR). We calculated an IRS summary score for each individual by adding the quartile ranks from the distribution of systolic blood pressure (BP), serum triglyceride (TG), HDL-cholesterol (inverse), and insulin levels.

RESULTS

Boys had a higher BMI and WHR, BP and IRS score and lower leptin, insulin, TG and HDL-C levels than girls. BMI, WHR and plasma leptin levels were significantly associated with the IRS summary score and each of its components in both genders. Children with higher plasma leptin levels (> 75th percentiles) have significantly higher BP, TG, insulin levels and IRS score than children with low leptin levels. The associations between plasma leptin level and the IRS components and score were still significant after adjusting for BMI in boys, but less so in girls. In both genders, after adjusting for WHR, plasma leptin levels were still significantly associated with the IRS components and summary score (P< 0.001). The final model that included the standard covariates, BMI and leptin, but not WHR, was the most predictive of the IRS summary score among school children.

CONCLUSIONS

Insulin resistance syndrome in childhood, characterized by high blood pressure, dyslipidemia, and hyperinsulinemia, may be an early marker of cardiovascular risk. From the present BMI and leptin in combination are the most predictive markers of insulin resistance syndrome among school children in Taiwan.

Pharmacotherapy of type 2 diabetes mellitus

OBJECTIVE

To review the drug treatments and some of the popular, nontraditional remedies now available for type 2 diabetes mellitus, as well as selected investigational agents; to describe each medication's place in the overall approach to treatment.

DATA SOURCES

English-language journals, abstracts, review articles, and newspaper accounts.

DATA SYNTHESIS

In the past five years, there has been tremendous progress in the pharmacotherapy of diabetes, particularly type 2 diabetes. Several new agents have entered the clinical arena, and many more are in the late stages of investigation leading to approval. Sulfonylureas stimulate the production and release of insulin; these drugs must be used in patients with an intact pancreas. The meglitinides are nonsulfonylurea agents that are also insulin secretagogues. Unlike the sulfonylureas, repaglinide appears to require the presence of glucose to close the adenosine triphosphate-sensitive potassium channels and induce calcium influx. Metformin reduces hepatic glucose production in some patients and increases peripheral glucose utilization, but its use is hampered by a high percentage of adverse reactions. Disaccharidase inhibitors effectively compensate for the defective early-phase insulin release by slowing the production of sugars from carbohydrates. Thiazolidinediones appear to activate peroxisome proliferator-activated receptor gamma, which is involved in the metabolism of lipids. Short-acting insulin and the role of weight-loss agents are also discussed.

CONCLUSIONS

The availability of new options for diabetes therapy provides a chance for successful therapy in a larger number of patients. However, it is important to consider how much true benefit these new forms of treatment will have on the diabetic community. The best choice for a patient remains controversial.

Effects of oral and transdermal 17beta-estradiol with cyclical oral norethindrone acetate on insulin sensitivity, secretion, and elimination in postmenopausal women

Few studies have examined the effects of 17beta-estradiol on parameters of insulin and glucose metabolism. We studied 42 healthy, untreated postmenopausal women seeking relief from menopausal symptoms. They were randomized to receive either oral 17beta-estradiol 2 mg daily combined with sequential oral norethindrone acetate (NETA) 1 mg daily from days 12 to 22, or transdermal 17beta-estradiol 0.05 mg daily combined with sequential oral NETA 1 mg daily from days 17 to 28. Intravenous glucose tolerance tests (IVGTTs) were performed at baseline and after 46 weeks (estrogen-alone phase) and 48 weeks (combined phase) of completed therapy. Mathematical modeling analysis of plasma glucose, insulin, and C-peptide concentration profiles provided measures of insulin resistance, secretion, and elimination. Both types of therapy were associated with a decrease in fasting insulin and glucose levels. Insulin sensitivity was increased by oral estradiol during the estrogen-alone phase but was reversed by the addition of NETA. Transdermal estradiol did not affect insulin sensitivity. Hepatic insulin uptake and insulin secretion were increased with both types of treatment. The oral regimen of estradiol therapy was favorable to both insulin elimination and sensitivity. Transdermal estradiol therapy had relatively few effects on insulin metabolism.

A switch in the direction of the effect of insulin on the partitioning of hepatic fatty acids for the formation of secreted triacylglycerol occurs in vivo, as predicted from studies with perfused livers

The direct effects of insulin on hepatic triacylglycerol secretion are important because they may determine the degree of postprandial hyperlipidaemia, a known risk factor for the development of atherosclerotic lesions. Previous work from this laboratory, conducted on isolated perfused rat livers [Zammit, V.A., Lankester, D.J., Brown, A.M. & Park, B.S. (1999) Eur. J. Biochem. 263, 859-864], has indicated that the effect of insulin on hepatic triacylglycerol secretion is dependent on the prior physiological state of the donor animals. In this paper, we demonstrate that a switch in the direction of insulin action on hepatic partitioning of fatty acyl moieties towards triacylglycerol secretion also occurs in vivo between the fed, normoinsulinaemic state and the fasted or severely insulin-deficient states. The partitioning of fatty acids in the liver of awake, unstressed rats was studied using selective labelling of hepatic fatty acids during hyperinsulinaemic-euglycaemic clamps achieved through the use of hepatocyte-targeted liposome-encapsulated insulin preparations. The data show that, whereas in the fed, normoinsulinaemic state, insulinization of the liver raises the proportion of fatty acids directed towards secreted triacylglycerol, in the fasted or insulin-deficient states, insulin inhibits the partitioning of acyl moieties into secreted triacylglycerol. These data show that observations on the direction of insulin action on hepatic triacylglycerol secretion obtained using isolated perfused rat livers are reflected in the effects of the hormone on hepatic fatty acid partitioning in vivo. They offer an explanation for the positive relationship between chronic hyperinsulinaemia, hepatic VLDL-triacylglycerol secretion and hypertriglyceridaemia observed previously in insulin-resistant states.

The adipoinsular axis: effects of leptin on pancreatic beta-cells

The prevalence of obesity and related diabetes mellitus is increasing worldwide. Here we review evidence for the existence of an adipoinsular axis, a dual hormonal feedback loop involving the hormones insulin and leptin produced by pancreatic beta-cells and adipose tissue, respectively. Insulin is adipogenic, increases body fat mass, and stimulates the production and secretion of leptin, the satiety hormone that acts centrally to reduce food intake and increase energy expenditure. Leptin in turn suppresses insulin secretion by both central actions and direct actions on beta-cells. Because plasma levels of leptin are directly proportional to body fat mass, an increase of adiposity increases plasma leptin, thereby curtailing insulin production and further increasing fat mass. We propose that the adipoinsular axis is designed to maintain nutrient balance and that dysregulation of this axis may contribute to obesity and the development of hyperinsulinemia associated with diabetes.

Dyslipidemia and vascular dysfunction in diabetic pigs fed an atherogenic diet

Diabetic patients typically have not only hyperglycemia but also dyslipidemia. Study of the pathogenic components of the diabetic milieu and mechanisms of accelerated atherosclerosis is hindered by inadequate animal models. A potentially suitable animal model for human diabetic dyslipidemia is the pig, because it carries a large fraction of total cholesterol in low-density lipoprotein (LDL), similar to humans. In this study, male Sinclair miniature pigs were made diabetic by destroying the insulin-producing cells of the pancreas with alloxan and then were fed a high fat and high cholesterol diet for comparison with pigs fed a nondiabetic high fat and high cholesterol diet and control pigs. Diabetic pigs exhibited hyperglycemia, but plasma urea nitrogen, creatinine, and transaminase levels were in the normal range, indicating no adverse effects on kidney and liver function. The lipoprotein profile in diabetic pigs was similar to that found in human diabetic patients and was characterized by hypertriglyceridemia (2.8-fold increase versus control and high fat-fed pigs) and a profound shift of cholesterol distribution into the LDL fraction (81%) versus the distribution in high fat-fed (64%) and control (57%) pigs. LDL particles were lipid-enriched and more heterogeneous in diabetic pigs. Apolipoprotein B was distributed among a much broader spectrum of LDL particles, and apolipoprotein E was partially redistributed from high-density lipoprotein to apolipoprotein B-containing lipoproteins in diabetic pigs. There was little change in apolipoprotein A-I distribution. Diabetic pigs showed several early signs of excess vascular disease. In diabetic pigs, 75% of the coronary artery segments showed contractile oscillations in response to prostaglandin F(2alpha) compared with 25% in high fat-fed pigs and 10% in control pigs. Endothelium-dependent relaxation of brachial arteries was nearly abolished in diabetic pigs but unchanged in high fat-fed versus control pigs. Carotid artery Sudan IV staining for fatty streaks was significantly increased only in diabetic pigs. This porcine model should provide insights into the etiology of human diabetic dyslipidemia and facilitate study of peripheral vascular and coronary artery disease in diabetic patients.

Assessment of the function and effect of diabetes education programs in Taiwan

A multi-center prospective study was conducted to assess the function and impact of diabetic education programs on diabetic control. A total of 208 subjects with type 2 diabetes were recruited. Diabetes self-care, assessed by questionnaire, was evaluated before, and 4 months after attending a diabetes education course. A total of 121 subjects who received advanced diabetes education courses were designated as the experimental group. A second group of 87 cases receiving a basic course served as controls. In addition to basic knowledge, the advanced education programs included dietary control, blood glucose monitoring, management of hypoglycemia, medication compliance, foot care and exercise. Diabetes self-care techniques were significantly improved in the experimental group. The overall score for diabetes self-care techniques improved in both groups at the 4th month over baseline values. The change was significant with the controls' (P < 0.001). Multiple regression analysis confirmed the intensity of diabetic education was the only significant variable correlated with the decrease of fasting blood glucose and systolic blood pressure. In conclusion, integrated and intensive diabetes education program in diabetes education centers provides an effective method for improving diabetes self-care techniques and metabolic outcome.

Screening for cardiovascular disease. Concepts, conflicts, and consensus

CVD in the United States is prevalent, costly, and disabling. Wherever in the arterial tree atherosclerosis occurs, the process appears to begin in youth, to develop under the influence of the same risk factors, and to be amenable to the same interventions. The relationship between CVD and its associated risk factors is continuous, is graded, and extends below thresholds previously defined as normal. This observation, in turn, is based on an appreciation that in our society, the gap between normal and optimal can be considerable. CVD is a multifactorial process, often related to modifiable lifestyle choices; we focus on any single risk factor to the exclusion of others puts patients in danger. Because risk factors rarely occur in isolation, risk assessment must be as multifactorial as the underlying disease process. By understanding differences between risk factors in terms of the impact of their modification on the underlying disease, targeted interventions become possible that are tailored to the likelihood of an individual patient acquiring CVD. To change the overall prevalence of an epidemic disease such as CVD, however, such a high-risk approach must be applied in concert with a population strategy that seeks to effect smaller degrees of change in the large segment of society that may be at only moderate risk but--because of their great numbers--bears most of the morbidity and mortality of CVD. Finally, despite the remarkable progress that has been made in our understanding of the pathophysiology of CVD and the effectiveness of risk factor modification, significant gaps remain between knowledge and behavior. Fewer than 50% of diabetics are even aware that they have the disease. Only a third of those whose lipid levels qualify them for treatment receive intervention of any kind, including dietary advice. Only 27% of hypertensives have their blood pressure adequately controlled. The potential impact of more vigorous screening practices in the primary care setting on the health of individuals and communities cannot be overstated.

Pharmacologic therapy for type 2 diabetes mellitus

Type 2 diabetes mellitus is a chronic metabolic disorder that results from defects in both insulin secretion and insulin action. An elevated rate of basal hepatic glucose production in the presence of hyperinsulinemia is the primary cause of fasting hyperglycemia; after a meal, impaired suppression of hepatic glucose production by insulin and decreased insulin-mediated glucose uptake by muscle contribute almost equally to postprandial hyperglycemia. In the United States, five classes of oral agents, each of which works through a different mechanism of action, are currently available to improve glycemic control in patients with type 2 diabetes. The recently completed United Kingdom Prospective Diabetes Study (UKPDS) has shown that type 2 diabetes mellitus is a progressive disorder that can be treated initially with oral agent monotherapy but will eventually require the addition of other oral agents, and that in many patients, insulin therapy will be needed to achieve targeted glycemic levels. In the UKPDS, improved glycemic control, irrespective of the agent used (sulfonylureas, metformin, or insulin), decreased the incidence of microvascular complications (retinopathy, neuropathy, and nephropathy). This review examines the goals of antihyperglycemic therapy and reviews the mechanism of action, efficacy, nonglycemic benefits, cost, and safety profile of each of the five approved classes of oral agents. A rationale for the use of these oral agents as monotherapy, in combination with each other, and in combination with insulin is provided.

Insulin resistance and systemic hypertension

There is a complex relation among insulin sensitivity, hypertension, and endothelial function. Although there are few prospective data on the relation between insulin levels and the development of hypertension, there is some evidence that insulin resistance precedes the onset of established hypertension in high-risk patients. Because insulin is a vasodilator, it would need to activate a variety of other potential physiologic mechanisms to play a causal role in the pathogenesis of hypertension. There are changes in the arterial wall in patients with hyperinsulinemia, and characteristic decreases in elasticity of the arterial wall have been noted in hypertensive patients with insulin resistance. Hyperglycemia, hyperinsulinemia, and hypertriglyceridemia appear to jointly contribute to increased arterial stiffness. There are, however, ethnic and racial disparities in the association of insulin, insulin sensitivity, and blood pressure, as this relation is not strongly observed in the black population in the United States and elsewhere. This may reflect complex relations among obesity, diabetes, and hypertension, which are more common in patients with African ancestry, although recent evidence supports the probability that the differences are genetically determined. Whatever the precise mechanisms, clinical investigations demonstrate the benefit of early interventions to improve insulin sensitivity and control hypertension, as well as to reduce hypercholesterolemia. In particular, enhanced insulin sensitivity may improve hypertension and its subsequent damage to vessel walls.

Insulin sensitivity, insulin action, and fibrinolysis activity in nondiabetic and diabetic obese subjects

Because inconsistencies occur with regard to the relative contribution of insulin to the hypofibrinolysis characteristic of obesity and diabetes, we explored the relationship between insulin and fibrinolysis, assessing both insulin sensitivity and insulin action. Seventeen markedly obese subjects (body mass index [BMI], 34.0+/-1.6 kg/m2; 12 nondiabetic and five diabetic) were studied using the three-step euglycemic-hyperinsulinemic clamp technique. Since the circadian rhythm of the fibrinolytic system may obscure a true effect of insulin, variations in fibrinolysis parameters observed during the glucose clamp were compared with those occurring spontaneously because of the circadian rhythm. Compared with six normal-weight subjects (BMI, 21.0+/-0.9 kg/m2), all obese subjects exhibited basal hyperinsulinism (fasting plasma insulin, 16.0+/-1.4 v 9.8+/-1.3 microU/microL, P < .001; fasting plasma C-peptide, 1.4+/-0.2 v 0.5+/-0.2 ng/mL, P < .001), hypofibrinolysis (euglobulin lysis time [ELT], 378+/-29 v 222+/-31 minutes, P=.01; tissue plasminogen activator [tPA] antigen, 7.8+/-0.9 v 4.2+/-0.5 ng/mL, P=.04; plasminogen activator inhibitor type 1 [PAI-1] activity, 22.2+/-2.5 v3.9+/-0.6 AU/mL, P=.004), and marked insulin resistance (M value, ie, the maximal glucose disposal rate, 9.1+/-0.6 v 18.6+/-0.8 mg/(kg x min), P < .001). The M value correlated inversely with tPA antigen (r=-.46, P=.05). During insulin infusion, values for fibrinolysis parameters decreased, but were not different compared with variations due to the circadian rhythm. In conclusion, our findings together with previously reported data reinforce the idea that chronic hyperinsulinism is linked to hypofibrinolysis, but insulin does not seem to acutely regulate the fibrinolysis system.

ACE inhibition but not angiotensin II antagonism reduces plasma fibrinogen and insulin resistance in overweight hypertensive patients

The aim of this study was to compare the effects of the angiotensin-converting enzyme (ACE) inhibitor perindopril and the angiotensin II antagonist losartan on insulin sensitivity and plasma fibrinogen in overweight hypertensive patients. Twenty-eight overweight mild to moderate [diastolic blood pressure (DBP) >90 and <110 mm Hg] hypertensives aged 43-64 years, after a 4-week placebo period, were randomized to perindopril, 4 mg o.d., or losartan, 50 mg o.d., for 6 weeks. Then, after a new placebo period, patients were crossed to the alternative regimen for further 6 weeks. At the end of the placebo and of the treatment periods, blood pressure was measured, plasma fibrinogen was evaluated, and insulin sensitivity was assessed by the euglycemic, hyperinsulinemic clamp technique. Glucose infusion rate (GIR) during the last 30 min of clamp and total glucose requirement (TGR) were evaluated. Both perindopril and losartan reduced SBP (by a mean of 20.2 mm Hg, p < 0.001 vs. placebo; and 15.8 mm Hg, p = 0.002 vs. placebo, respectively) and DBP (by a mean of 15.2 mm Hg, p = 0.001 vs. placebo, and 11.8 mm Hg, p = 0.01 vs. placebo respectively), with no difference between the two treatments. GIR was significantly increased by perindopril (+2.91 mg/min/kg, p = 0.042 vs. placebo), but not by losartan (+0.28 mg/min/kg, NS). TGR was not modified by losartan but was increased by perindopril (+9.3 g, p = 0.042 vs. placebo). Plasma fibrinogen levels were reduced by perindopril (-53.4 mg/dl, p = 0.022 vs. placebo) but not by losartan (-16.8 mg/dl, NS). The perindopril-induced decrease in fibrinogen was correlated with the increase in GIR (r = 0.39; p < 0.01). These findings suggest that fibrinogen decrease produced by the ACE inhibitor is related to its action on insulin sensitivity, which seems to be dependent not on angiotensin II blockade but rather on other mechanisms.

Issues surrounding tight glycemic control in people with type 2 diabetes mellitus

OBJECTIVE

To review the prospective evidence surrounding the issue of tight glycemic control in people with type 2 diabetes mellitus and resultant long-term complications.

DATA SOURCE

Conference proceedings and a MEDLINE search (1966-February 1998) identified pertinent English-language publications on type 2 diabetes in humans. Key search terms included insulin resistance, diabetes mellitus, non-insulin-dependent, macrovascular complications, microvascular complications, and intensive glycemic control.

STUDY SELECTION

Selection of prospective epidemiologic and clinical studies were limited to those focusing on the management of type 2 diabetes. All articles with pertinent information relevant to the scope of this article were reviewed.

DATA SYNTHESIS

The pathophysiology of type 1 and type 2 diabetes differ; however, both share chronic complications that significantly affect morbidity and mortality. People with type 1 diabetes have an absolute deficiency of insulin, whereas people with type 2 diabetes have varying degrees of insulin resistance and an inadequate compensatory insulin secretory response. The Diabetes Control and Complications Trial (DCCT) has clearly indicated that intense control of blood glucose in type 1 diabetes prevents and slows the progression of microvascular (i.e., retinopathy, nephropathy) and neuropathic complications. The Kumamoto study showed similar results in nonobese patients with type 2 diabetes. Intense insulin therapy in both populations has proven advantageous, thus supporting a common pathophysiologic process for the microvascular and neuropathic complications. Trends were seen toward fewer macrovascular (atherosclerotic disease) complications in the intensive insulin arm of the DCCT. Conversely, trends were seen toward an increase in macrovascular complications in the VA Cooperative study in people with type 2 diabetes using intensive insulin therapy. This may suggest a discordance in the pathophysiology of macrovascular disease between type 1 and type 2 diabetes. Additionally, it remains uncertain whether tight glycemic control prevents the onset or slows the progression of macrovascular disease. Two studies (the University Group Diabetes Program and the Veterans Affairs Cooperative Study on Glycemic Control and Complications in Type 2 Diabetes) to date have examined pharmacotherapy options for patients with type 2 diabetes and resultant macrovascular complications. It has yet to be determined whether any therapeutic intervention will decrease the morbidity and mortality of macrovascular disease in this population.

CONCLUSIONS

In type 2 diabetes, limited prospective evidence does support tight glycemic control to help prevent or slow the progression of microvascular and neuropathic complications. It is uncertain whether tight glycemic control decreases macrovascular complications and which pharmacotherapeutic agent(s) is/are the best options. However, therapy that improves glucose control in combination with aggressive risk factor management should be initiated and enforced in patients with type 2 diabetes in an effort to reduce long-term complications.

Insulin resistance versus insulin deficiency in non-insulin-dependent diabetes mellitus: problems and prospects

A definitive assessment of the relative roles of insulin resistance and insulin deficiency in the etiology of NIDDM is hampered by several problems. 1) Due to better methodology, data on insulin resistance are generally more accurate and consistent than data on insulin deficiency. 2) In source data, case-control studies are prone to selection bias, while epidemiological associations, whether cross-sectional or longitudinal, are liable to misinterpretation. 3) Insulin secretion and action are physiologically interconnected at multiple levels, so that an initial defect in either is likely to lead with time to a deficit in the companion function. The fact that both insulin resistance and impaired insulin release have been found to precede and predict NIDDM in prospective studies may be in part a reflection of just such relatedness. 4) Direct genetic analysis is effective in rarer forms of glucose intolerance (MODY, mitochondrial mutations, etc.) but encounters serious difficulties with typical late-onset NIDDM. Despite these uncertainties, the weight of current evidence supports the view that insulin resistance is very important in the etiology of typical NIDDM for the following reasons: 1) it is found in the majority of patients with the manifest disease; 2) it is only partially reversible by any form of treatment (117); 3) it can be traced back through earlier stages of IGT and high-risk conditions; and 4) it predicts subsequent development of the disease with remarkable consistency in both prediabetic and normoglycemic states. Of conceptual importance is also the fact that the key cellular mechanisms of skeletal muscle insulin resistance (defective stimulation of glucose transport, phosphorylation, and storage into glycogen) have been confirmed in NIDDM subjects by a variety of in vivo techniques [ranging from catheter balance (118) to multiple tracer kinetics (119) to 13C nuclear magnetic resonance spectroscopy (120)], and have been detected also in normoglycemic NIDDM offspring (121). If insulin resistance is a characteristic finding in many cases of NIDDM, insulin-sensitive NIDDM does exist. On the other hand, given the tight homeostatic control of plasma glucose levels in humans, beta-cell dysfunction, relative or absolute, is a sine qua non for the development of diabetes. If insulin deficiency must be present whereas insulin resistance may be present, is this proof that the former is etiologically primary to the latter? If so, do we have convincing evidence that the primacy of insulin deficiency is genetic in nature? The answer to both questions is negative on several accounts. The defect in insulin secretion in overt NIDDM is functionally severe but anatomically modest: beta-cell mass is reduced by 20-40% in patients with long-standing NIDDM (122). Moreover, the insulin secretory deficit is progressively worse with more severe hyperglycemia (123) and recovers considerably upon improving glycemic control (124). These observations indicate that part of the insulin deficiency is acquired (through glucose toxicity, lipotoxicity, or both). In addition, although insulin deficiency is necessary for diabetes, it may not always be sufficient to cause NIDDM. In fact, subtle defects in the beta-cell response to glucose may be widespread in the population (108, 125) and only cause frank hyperglycemia when obesity/insulin resistance stress the secretory machinery. Conceivably, there could be beta-cell dysfunction without NIDDM just as there is insulin resistance without diabetes. Incidentally, any defect in insulin secretion, whether in normoglycemic or hyperglycemic persons, could be due to other factors than primary beta-cell dysfunction: amyloid deposits in the pancreas (126), changes in insulin secretagogues (amylin, GLP-1, GIP, galanin) (127-130), early intrauterine malnutrition (131). Finally, the predictive power of early changes in insulin secretion for the development of typical NIDDM is generally lower than that of insulin

Abdominal obesity, impaired nonesterified fatty acid suppression, and insulin-mediated glucose disposal are early metabolic abnormalities in families with premature myocardial infarction

British Indian Asian men aged <40 years have a twofold to threefold increased risk of death from coronary heart disease (CHD) compared with British whites. Epidemiological studies have suggested an association between glucose intolerance and hyperinsulinemia with premature CHD in Indian Asians. We tested the association of insulin action with myocardial infarction (MI) by using the hyperinsulinemic-euglycemic clamp in 17 MI patients: 8 Punjabi Sikhs (PSMIs), 9 British whites (BWMIs), and 17 control subjects (9 PSCs and 8 BWCs). Metabolic factors associated with insulin resistance were investigated in 51 MI patients (24 PSMIs and 27 BWMIs) and 53 control subjects (28 PSCs and 25 BWCs). Familial aggregation of defective insulin action was examined by studying five pedigrees of Sikh survivors of MI. Sikh survivors of premature MI demonstrated impaired insulin-mediated glucose uptake (P<.001) by use of the clamp technique and nonesterified fatty acid (NEFA) suppression (P<.05) by using both clamp techniques and the oral glucose tolerance test, as compared with Sikh control subjects. White patients had impaired insulin-mediated glucose uptake but normal NEFA suppression. Metabolic factors usually associated with insulin resistance, including increased 2-hour post-oral glucose tolerance test triglycerides, smaller low density lipoprotein particle size, and increased plasminogen activator inhibitor-1, were present in white (all P<.05) but surprisingly absent in Sikh (all P>.05) MI patients compared with respective ethnic control subjects. Fasting glucose and total cholesterol levels did not differ between patients and control subjects. Abdominal obesity, impaired NEFA suppression after oral glucose, and fasting hyperinsulinemia were present in Sikh MI patients and their nondiabetic first-degree relatives compared with Sikh control subjects. PS survivors of premature MI demonstrated impaired insulin-mediated glucose disposal and NEFA suppression compared with ethnic control subjects. BWMI patients showed abnormalities of carbohydrate, but not of NEFA, metabolism compared with white control subjects. Defects of insulin action manifested as abdominal obesity, impaired NEFA suppression, and fasting hyperinsulinemia are present in Sikh MI patients and their asymptomatic, nondiabetic, first-degree relatives. We suggest that these defects may be early metabolic markers that predict risk of premature MI among PSs.

Adverse lipid and coronary heart disease risk profiles in young women with polycystic ovary syndrome: results of a case-control study

Polycystic ovary syndrome (PCOS), a disorder of hyperandrogenism and chronic anovulation affects 5%-10% of all women. Women with PCOS often have elevated cardiovascular risk factors. A total of 244 PCOS cases were identified through the Division of Reproductive Endocrinology at Magee-Womens Hospital and were age-matched to 244 neighborhood controls. The average age of cases and controls was 35.3 +/- 7.4 and 36.7 +/- 7.7. Women with PCOS compared to controls had substantially higher LDL-C and total cholesterol levels at each age group under 45 years after adjustment for body mass index, hormone use, and insulin levels. In the over 40-year age group, little difference was noted between cases and controls. Among cases and controls (<40), PCOS predicted LDL-C, total cholesterol and triglycerides, but did not have a significant effect on lipid levels in older cases and controls after controlling for the other variables. The primarily pre- to perimenopausal PCOS cases > or =40 years of age have similar LDL-C and total cholesterol levels as their age-matched controls, probably reflecting the LDL-C increase with age among controls.

Mitogenic factors accelerate later-age diseases: insulin as a paradigm

Some genes are expressed differently in earlier and later generations of most cell lines. Many diseases become clinically expressed only later in life, and show clustering of the age at onset in the affected siblings, which may be related to the changing expression with age of the genes involved. Because insulin and its receptor are extremely ancient and well preserved structures with almost universal mitogenic effects, insulin may serve a paradigm of this process. It is suggested that by stimulating cell proliferation, hyperinsulinemia speeds up the appearance of later generations of cells with different expression of the genes. Insulin resistance, accompanying any hyperinsulinemia and considered to be a pathogenetic factor of some common later-age diseases, involves only some biochemical, but not mitogenic effects of the hormone. In humans, high levels of insulin in blood are encountered both physiologically after meals and in many pathological conditions: insulin therapy inevitably causes peripheral hyperinsulinemia; in type 2 diabetes hyperinsulinemia precedes hyperglycemia by many years; hyperinsulinemia is an independent risk factor of atherosclerosis, of type 2 diabetes itself, of some forms of dementia and other diseases; obesity is an obligatory hyperinsulinemic condition. The opposite of hyperalimentation, i.e. calorie restriction (at least, in rodents) may exert its life-prolonging effects through decreasing insulinemia and therefore the rate of cell proliferation. Insulin is only one example, and different mitogens regulate proliferation of different cells. It is likely that growth factors in general accelerating the replication of cells, play a role in speeding up the appearance of later-age diseases involving these cells.

Insulin and risk of cardiovascular disease: a meta-analysis

BACKGROUND

Our purposes were to estimate the strength of the longitudinal relationship between hyperinsulinemia and cardiovascular diseases (CVD) from the available literature and to identify study characteristics that modify this relationship.

METHODS AND RESULTS

Articles were identified by means of a MEDLINE and Embase search and citation tracking. Eligible studies were prospective population-based cohort studies and nested case-control studies on the relationship between, on the one hand, fasting or nonfasting insulin levels and, on the other hand, myocardial infarction, death from coronary heart disease, and/or ECG abnormalities. Data were extracted pertaining to insulin measurements, type of outcome studied, adjustment for confounding, sex, mean age of the study population, follow-up period, insulin assay, and ethnic background (white or nonwhite). Associations of insulin and CVD were reexpressed in a uniform manner, an estimate of relative risk (RR) and 95% CI, to be used in meta-regression analyses. Twelve of 17 potentially eligible articles provided sufficient information. Overall, a weak positive association was found. The meta-analysis resulted in an estimated summary RR (95% CI) of 1.18 (1.08 to 1.29) for differences in insulin level, equivalent to the difference between the 75th and the 25th percentiles of the general population in The Netherlands. Ethnic background and type of insulin assay modified the relationship between insulin and CVD with borderline significance.

CONCLUSIONS

Hyperinsulinemia is a weak risk indicator for the occurrence of CVD. The relationship between hyperinsulinemia and CVD was modified by ethnic background and by the type of insulin assay involved.

Hyperinsulinemia and cardiovascular disease in elderly men: the Honolulu Heart Program

Hyperinsulinemia has been associated with cardiovascular disease (CVD), but whether this relation is independent of other CVD risk factors is uncertain. Most studies have focused on coronary heart disease (CHD), but few have included peripheral vascular disease (PVD) and stroke. Moreover, evidence in elderly and minority populations is limited. Between 1991 and 1993, 3562 elderly (71 to 93 years) Japanese-American men from the Honolulu Heart Program were examined and had fasting insulin levels measured. Hyperinsulinemia, defined as a fasting insulin > or =95th percentile among nonobese men with normal glucose tolerance and no diabetic history or medication use, was observed in 22% of the population. Subjects with hyperinsulinemia had a more adverse CVD risk factor profile and had higher age-adjusted prevalences of CHD, angina, PVD, thromboembolic stroke, and hemorrhagic stroke compared with those without hyperinsulinemia. Age-adjusted fasting insulin levels but not 2-hour levels were also significantly elevated (P<.01) in those with prevalent CVD compared with those without. In logistic regression analyses, adjustment for multiple CVD risk factors attenuated the relations of hyperinsulinemia with CHD, angina, and PVD to nonsignificant levels, whereas those involving thromboembolic and hemorrhagic stroke were strengthened and remained significant (odds ratios=2.27 and 7.53, 95% confidence intervals=1.25 to 4.13 and 1.65 to 34.25, respectively). When multivariate analyses were restricted to nondiabetic subjects, associations were slightly weaker and in general nonsignificant. Nondiabetic men with thromboembolic stroke were twice as likely to have hyperinsulinemia as those who were stroke-free, although this association was of borderline significance (odds ratio= 1.99, 95% confidence interval=0.95 to 4.17, P=.069). In subjects with elevated total cholesterol levels, somewhat stronger associations were observed for PVD and stroke but not for CHD. Although further prospective studies are indicated, particularly for PVD and stroke, these cross-sectional results are consistent with an indirect role for insulin in CVD, wherein hyperinsulinemia or an underlying insulin-resistant state may adversely affect other CVD risk factors or serve as a marker for an atherogenic or thrombogenic state.

Acanthosis nigricans as a risk factor for non-insulin dependent diabetes mellitus

The prevalences of obesity and of non-insulin dependent diabetes mellitus (NIDDM) have increased in the United States population over the past two decades, and thus diabetes prevention has become a major concern of public health agencies such as the National Institutes of Health. Identification of individuals at risk for diabetes is an essential first step in designing and implementing intervention programs. Insulin resistance is the hallmark of the pathophysiology of NIDDM. Subjects with hyperinsulinemia, impaired glucose tolerance, or gestational diabetes are well accepted as being at high risk for diabetes. We propose that the easily identifiable skin lesion, acanthosis nigricans, is common in the major minority groups in the United States and that its presence is a surrogate for laboratory-determined hyperinsulinemia.

Post-transplant hyperlipidaemia

The correction of post-transplant hyperlipidaemia warrants the judicious and timely use of pharmacological agents with dietary modification and exercise. Reduction in hyperlipidaemia may have some role in decreasing the incidence of chronic rejection of allografts. The awareness that the morbidity and mortality of atherosclerotic disease may be lowered by active intervention will result in a better quality of life for transplant recipients.

Does insulin resistance unite the separate components of the insulin resistance syndrome? Evidence from the Miami Community Health Study

A number of coronary heart disease risk factors have been identified that often cluster together to increase the risk of macrovascular disease. This cluster is referred to as the insulin resistance syndrome, and the risk factors commonly include dyslipidemia, elevated blood pressure, an android pattern of body fat distribution, and glucose intolerance. Whether hyperinsulinemia or insulin resistance per se provides a common pathway for these metabolic abnormalities is unclear. The authors studied 50 nondiabetic persons who had completed a euglycemic hyperinsulinemic clamp protocol in addition to a 75-g oral glucose tolerance test and other measures of the coronary risk profile. Using principal-component analysis, we reduced nine coronary risk factors to two uncorrelated factors that explained 54.5% of the variance. Factor 1 consisted of positive loadings for uric acid, systolic and diastolic blood pressure, triglyceride concentration, and waist girth and negative loadings for HDL cholesterol and the rate of insulin-mediated glucose disposal (M, in milligrams per kilogram of body weight per minute). M also loaded on factor 2, along with fasting insulin and glucose concentrations, diastolic blood pressure, and waist girth. The observation that M loaded on both factors suggests that a resistance to insulin action may provide the mechanism uniting the features of the insulin resistance syndrome. Hyperinsulinemia with concomitant insulin resistance may be necessary to produce this metabolic derangement, as well as the increased risk of macrovascular complications.

Insulin resistance implications for type II diabetes mellitus and coronary heart disease

PURPOSE

To review information on the implications of insulin resistance for type II diabetes mellitus (non-insulin-dependent diabetes mellitus) and coronary heart disease, and to derive guidance from this information for the management of these conditions.

DATA SOURCES

A MEDLINE search of English-language articles published between 1985 and July 1996, and review of the bibliographies of articles obtained through the MEDLINE search and textbooks.

STUDY SELECTION

Primary research articles, reviews and perspectives on the epidemiology of diabetes and cardiovascular diseases and on intervention outcomes in these diseases.

DATA EXTRACTION

Study design and quality were assessed, with particular attention to methods, study population size and other characteristics. Conclusions of review articles and perspectives were analyzed critically.

DATA SYNTHESIS

Type II diabetes is associated with a two- to fourfold excess of coronary heart disease, compared to nondiabetic populations. In most studies, glycemia and duration of clinical diabetes were found to be only weak risk factors for coronary heart disease. Conventional coronary heart disease risk factors such as dyslipidemia and hypertension have been associated with coronary heart disease in type II diabetes subjects. Hyperinsulinemia and insulin resistance have been predictive of the development of type II diabetes and, in some studies, of coronary heart disease.

CONCLUSION

Strategies to prevent the development of coronary heart disease in diabetic and possibly prediabetic subjects should emphasize a multifactorial approach, including: a) improved glycemic control; b) aggressive treatment of risk factors for coronary heart disease, including insulin resistance; c) primary prevention of NIDDM; and d) use of glucose lowering agents that improve insulin sensitivity and cardiovascular risk factors.

Decreased glucose tolerance, not decreased insulin sensitivity, is a maturational abnormality in the male offspring of a parent with early coronary artery disease

We investigated whether the male offspring of a parent with early coronary artery disease (before the age of 60; n = 61) exhibit decreased insulin sensitivity compared with controls matched for age and body mass index (BMI) (n = 39). The insulin sensitivity index (S[I]) was determined by the minimal modeling method of Bergman from a frequently sampled intravenous glucose tolerance test with intravenous tolbutamide. Offspring and controls had a similar S[I], insulin-independent glucose utilization (S[G]), first-phase insulin response (AIR[G]), and area under the glucose curve. When subjects were separated into two age groups, younger subjects aged 15 to 30 years and older subjects aged 31 to 45 years, important differences were seen. S[G] was significantly increased in younger offspring compared with controls (22.8 +/- 2.3 v 16.8 +/- 2.3 x 10(-3) x min(-1), P < .05). Older offspring had a significantly increased area under the glucose curve compared with controls (18,250 +/- 322 v 17,225 +/- 347 mg/dL x min(-1), P < .05). Older offspring also had decreased S[I] compared with younger offspring (5.0 +/- 0.4 v 6.6 +/- 0.9 x 10(-4) x min(-1) x micro U/mL, P < .05), but this difference was eliminated after adjusting for BMI and waist to hip ratio (5.5 +/- 0.4 v5.8 +/- 0.9 x 10(-3) x min(-1), nonsignificant). This study does not support the concept that insulin resistance is an early atherogenic risk factor in offspring at risk for coronary disease because of their family history. However, it does point to the importance of maturational changes in glucose homeostasis in these offspring.

Lowering of plasma phospholipid transfer protein activity by acute hyperglycaemia-induced hyperinsulinaemia in healthy men

Human plasma contains two lipid transfer proteins involved in the remodelling of plasma lipoproteins; cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP). CETP mediates the transfer/exchange of cholesterylesters, triglycerides and phospholipids between high-density lipoproteins (HDL) and chylomicron (remnants), very low-density lipoproteins (VLDL) and low density lipoproteins (LDL). The physiological function of PLTP is unknown. It is able to transfer phospholipids (but not neutral lipids) between lipoproteins and to modulate HDL particle size in vitro. The effects of acute endogenous hyperinsulinaemia on plasma CETP and PLTP activity, as well as on lipid and lipoprotein levels, were assessed in eight healthy men during a 3-h hyperglycaemic clamp. Another group of seven men received an infusion of an equal volume of saline in order to detect possible dilution effects or effects on lipoprotein changes over time (control group). Plasma cholesterol and triglyceride concentrations fell during the clamp and the decreases were significantly different from the minor changes during saline infusion in the control group (p < 0.05 and p < 0.01, respectively). Plasma CETP activity levels did not change, but plasma PLTP activity levels decreased by 7.7 and 5.1% after 2 and 3 h of hyperglycaemia (p < 0.01 for each time-point). The hyperglycaemia-induced mean percentage change in PLTP activity levels during the 3 h of the clamp was greater than the essentially absent change during the NaCl infusion (p < 0.05). Plasma PLTP activity during the clamp was related negatively to the insulin sensitivity index (p < 0.01 by analysis of covariance). It is concluded that acute hyperglycaemia-induced hyperinsulinaemia lowers plasma PLTP, but not CETP activity levels, either directly or in conjunction with an effect on plasma lipoproteins.