Insulin, body mass index, and cardiovascular risk factors in premenopausal women

Glucocorticoids and type 2 diabetes: from physiology to pathology

Type 2 diabetes mellitus is the result of interaction between genetic and environmental factors, leading to heterogeneous and progressive pancreatic β-cell dysfunction. Overweight and obesity are major contributors to the development of insulin resistance and impaired glucose tolerance. The inability of β cells to secrete enough insulin produces type 2 diabetes. Abnormalities in other hormones such as reduced secretion of the incretin glucagon-like peptide 1 (GLP-1), hyperglucagonemia, and raised concentrations of other counterregulatory hormones also contribute to insulin resistance, reduced insulin secretion, and hyperglycaemia in type 2 diabetes. Clinical-overt and experimental cortisol excess is associated with profound metabolic disturbances of intermediate metabolism resulting in abdominal obesity, insulin resistance, and low HDL-cholesterol levels, which can lead to diabetes. It was therefore suggested that subtle abnormalities in cortisol secretion and action are one of the missing links between insulin resistance and other features of the metabolic syndrome. The aim of this paper is to address the role of glucocorticoids on glucose homeostasis and to explain the relationship between hypercortisolism and type 2 diabetes.

Obesity, Diabetes, the Cardiorenal Syndrome, and Risk for Cancer

Numerous epidemiological studies confirm that the prevalence of obesity and the cardiorenal metabolic syndrome (CRS) is extraordinarily high and that the rates have increased dramatically in the last three decades. In addition, epidemiological data demonstrate that obesity, the CRS, and diabetes are inextricably linked and are all associated with an increased incidence of a number of solid tissue cancers. The mechanisms for this association have been examined, including, but not limited to, higher levels of insulin and free levels of insulin-like growth factor and insulin resistance in obesity and the CRS. Mortality, morbidity, and the associated health care costs which are the link between obesity, the CRS, and diabetes are just beginning to be examined. In addition, we review the advantages of implementing lifestyle and surgical changes to modify obesity, lessening the development of the CRS, diabetes, and associated cancers. Epidemiological data regarding the general mechanisms of the pathogenesis of cancers associated with obesity, the CRS, and diabetes (specifically colon, pancreas, esophageal, liver, breast, prostate, thyroid, and renal carcinomas) are reviewed. The mechanisms by which obesity and other components of the CRS contribute to the pathogenesis of these cancers, such as hormone alterations and insulin- and insulin-like growth factor-dependent pathways of tumor pathogenesis, include the attending roles of inflammation and oxidative stress. Emphasis has been placed on obesity as a modifiable risk factor which, when addressed, provides a reduction in the rate of cancer deaths. In a second part to be published in the next issue of this journal, the relationship between diabetes and cancer will be reviewed in detail.

Insulin resistance, hyperinsulinemia, and hypertension: an epidemiologic approach

During the past 2 decades, numerous experimental studies have provided solid evidence for the existence of several mechanisms connecting insulin resistance and hyperinsulinemia with blood pressure elevation, within the context of the cardiometabolic syndrome. In parallel, several groups have attempted to examine these associations from an epidemiologic perspective, but relevant findings were less consistent and not extensively discussed. Hyperinsulinemia has been associated with high blood pressure levels and hypertension development in cross-sectional, case-control, and prospective cohort studies. An association between insulin resistance and hypertension is also evident in existing studies, but prospective data on this relation are limited. Moreover, most of the evidence supporting close associations between these factors derives from Caucasian and Japanese populations, whereas data in other populations are not in agreement. This review summarizes and evaluates the relevant epidemiologic evidence to elucidate an important aspect of the relationship between hypertension and the cardiometabolic syndrome.

Sex differences in the relation of depressive symptoms, hostility, and anger expression to indices of glucose metabolism in nondiabetic adults

This study examined the relation of depressive symptomatology, hostility, and anger expression to indices of glucose metabolism and tested whether gender moderates these associations in a sample of 135 healthy, nondiabetic adults (75 men, 60 women). The severity of depressive symptoms, hostility, and anger expression was positively associated with estimated insulin resistance (IR) and insulin in women but not in men. Anger expression was positively associated with glucose in women only. A summary score of depressive symptoms, hostility, and anger expression was positively associated with estimated IR, insulin, and glucose in women but not in men. Hence, in women, IR and elevated levels of fasting insulin and glucose may be one pathophysiological mechanism mediating the increased risk of cardiovascular disease and Type 2 diabetes associated with these psychological attributes.

The metabolic syndrome in Chinese, Malays and Asian Indians. Factor analysis of data from the 1998 Singapore National Health Survey

We used factor analysis to define and compare the manner in which the various features of the metabolic syndrome are linked or clustered in Chinese, Malays and Asian Indians. One thousand nine hundred and fifty seven men (1324 Chinese, 391 Malays and 261 Asian Indians) and 2308 women (1622 Chinese, 391 Malays and 296 Asian Indians) were examined. Anthropometry, blood pressure, serum glucose, lipid concentrations, and serum insulin were measured for all subjects. These data were then subjected to factor analysis which reduced the variables examined to three factors in all ethnic groups and both genders. The first (dyslipidemia) factor was positively loaded for obesity, insulin resistance (IR), fasting triglyceride and negatively loaded for HDL-cholesterol. The second (hyperglycemia) factor was positively loaded for IR and blood glucose. The third (hypertension) factor was positively loaded for obesity and blood pressure. IR was positively loaded in the hypertension factor in Malay women but not in others. Rather than a single entity causally associated with insulin resistance (IR), our findings support a concept in which the metabolic syndrome represents several distinct entities (dyslipidemia, hypertension and hyperglycemia). It appears that Malay females may be more prone to develop hypertension in association with IR.

Insulin sensitivity and cardiovascular risk factors in hypertensive and normotensive native Ghanaians

AIMS/HYPOTHESIS

The objective of this study was to examine the relationships among insulin and insulin sensitivity and risk factors for cardiovascular diseases in native Ghanaians with and without hypertension.

METHODS

We measured the anthropometric parameters, systolic and diastolic blood pressure, fasting serum triglycerides, cholesterol and high-density lipoprotein cholesterol and fasting and stimulated glucose, insulin and C-peptide of 200 Ghanaian subjects, who were between 25 to 74 years of age, and residing in the Accra Metropolitan area. Serum glucose, C-peptide and insulin concentrations were measured at baseline (fasting) and also 2 h after 75 gm oral glucose drink. Homeostasis model assessment was used to measure insulin resistance. Hypertension was defined as a blood pressure higher than 140/90 mmHg.

RESULTS

There were 53 subjects with hypertension (HBP) and 147 subjects with normal blood pressure (NBP). The mean BMI, waist circumference and waist-to-hip circumference ratio for HBP and NBP subjects were 27.4+/-0.8, 24.8+/-0.4 kg/m(2); 89.8+/-11.7, 81.1+/-0.9 cm; and 0.87+/-0.08, 0.82+/-0.08 respectively, (p<0.05). The fasting and 2-h plasma glucose concentrations in HBP and NBP subjects were 5.5+/-0.2, 7.2+/-0.3 mmol/l and 5.2+/-01, 6.8+/-0.2 mmol/l respectively (p>0.05). The corresponding fasting and 2-h insulin concentrations were 10.0+/-0.7, 8.0+/-0.4 uU/ml and 47.3+/-3.7, 37.3+/-2.5 uU/ml respectively (p<0.05). The insulin resistance index (HOMA-IR) in the HBP and the NBP groups were 2.49+/-0.2 and 1.95+/-0.13 (p<0.05). The two groups had similar fasting and stimulated C-peptide, lipids and HDL concentrations. Correlations were found between blood pressure and the concentrations of lipids, HDL, fasting and stimulated insulin and C-peptide, and between fasting insulin and HOMA-IR with lipids and HDL concentrations. On multiple regression analysis, fasting insulin and HOMA-IR did not influence blood pressure variations significantly.

CONCLUSIONS/INTERPRETATION

We found clustering of hyperinsulinaemia, insulin resistance and truncal obesity in hypertensive Ghanaian subjects but dissociation between insulin resistance, hypertension and atherogenic lipid and lipoprotein profile.

Fat-specific satiety in humans for fat high in linoleic acid vs fat high in oleic acid

OBJECTIVE

To investigate the effect of 2 week use of oils high in linoleic (LA), gamma-linolenic (GLA) and oleic acid (OA) on energy intake (EI), macronutrient composition, parameters of appetite and taste perception.

DESIGN

A randomized placebo-controlled 2-week treatment, followed by a test day.

SETTING

Two-week treatments, daily life; test day, laboratory restaurant.

SUBJECTS

Eight overweight men and eight overweight women (body mass index 27.4+/-1.5 kg/m(2)).

INTERVENTIONS

Three 2 week treatments, in which subjects replaced their habitual fat products by three different oils (relatively) high in LA (66.8%), GLA (20.2%) or OA (79.6%, placebo). The wash-out periods were 2 weeks. Before each intervention period, taste perception and sensory specific satiety was tested.

RESULTS

Even though energy intake was higher during dinner, subjects ate relatively less fat with LA (45.0+/-9.4 E%, P<0.05) than with OA (48.3+/-8.3 E%). Subjects did not distinguish the oils with the different fatty acids from each other. There was no relation between satiety or fat-specific satiety and taste characterization without as well as with sucrose. Although no differences were seen for the AUC of the appetite profile, aet 15:00 h subjects were less satiated with LA (46.1+/-6.2 mm, P<0.05) or GLA (45.1+/-5.8 mm, P<0.01) than after treatment OA (62.5+/-4.8 mm). 24 h EI on the test day was 7.6--8.0 MJ and did not differ between treatments.

CONCLUSIONS

Fat-specific satiety during dinner with LA vs OA was shown after a 2-week treatment of each oil, but no change in general satiety. Fat specific satiety was not related to taste perception or characterization of the oils.

Is physical activity as effective in reducing risk of cardiovascular disease as estrogen replacement therapy in postmenopausal women?

Coronary heart disease (CHD) is known as a disease of postmenopausal women. While hormone replacement therapy is recommended increasingly to postmenopausal women for the prevention of CHD, the potential impact of non-pharmacologic interventions on cardiovascular disease reduction has been largely unexplored. The purpose of this article is to develop the understanding of the research literature on three risk factors by which estrogen and physical activity, a non-pharmacologic intervention, may confer cardiovascular protection in postmenopausal women. Three risk factors are lipoproteins, systolic pressure, and changes in the vascular endothelial functions. Effects of estrogen and physical activity on these biological factors are compared.

Regulation of Plasma fatty acid metabolism

Although adipose tissue serves a crucial function in energy storage, excess adipose tissue--that is, obesity--is often associated with diabetes and cardiovascular disease. A common thread in the weave of complications is increased plasma concentrations of fatty acids. In the present review, we have focused on two specific points that relate to obesity: (i) What are the metabolic consequences of increased free fatty acid concentrations? and (ii) What are the physiological factors that are involved in the regulation of fatty acid uptake or release from adipose tissue? We have tried to emphasize new factors that act as hormones on adipose tissue and in so doing regulate the net concentration of circulating free fatty acids.

Clustering of cardiovascular risk factors in hyperinsulinemia in Japanese without diabetes

Clustering of cardiovascular risk factors in hyperinsulinemia was investigated in 247 Japanese subjects without diabetes. After adjustment for age and sex, the highest quartile of the summed values of insulin concentrations after oral glucose loading showed high odds ratios (OR; 95% confidence intervals) for the prevalence of cardiovascular risk factors: OR = 2.02 (1.07-3.83) for hypertension, 3.91 (1.82-8.40) for hypertriglyceridemia, 2.41 (1.30-4.46) for low high-density lipoprotein cholesterol, 2.41 (1.28-4.51) for impaired glucose tolerance, and 3.58 (1.44-8.88) for high uric acid. Two or more of these factors were clinically elevated in 50% of those in the highest quartile of the summed values of insulin, compared to 16-28% of those in the lower three quartiles. These findings were slightly attenuated after further adjustment for body mass index and sum of skinfolds. In conclusion, multiple risk factors for cardiovascular disease existed in the subjects with hyperinsulinemia in Japanese without diabetes.

Genetic relationship between measures of HDL phenotypes and insulin concentrations

We used data from the San Antonio Family Heart Study to determine the HDL correlates of the insulin resistance syndrome (IRS), as reflected by insulin concentrations in nondiabetic subjects. We measured insulin concentrations both in the fasting state and 2 hours after a glucose challenge (2-hour insulin) and we assessed seven aspects of HDL phenotype, including size and concentration of both lipid and protein components. Measurements were obtained from 1202 nondiabetic members of 42 families. Initial quantitative genetic analyses revealed that a substantial portion of phenotypic variation in the nine variables was due to genes (heritabilities, h2, ranged from 0.32 to 0.47). We then conducted a series of bivariate genetic analyses, which indicated that there were significant additive genetic correlations (ie, pleiotropy) between the two measures of insulin and five of seven HDL measures tested, including concentrations of HDL cholesterol (fasting insulin only) and triglyceride, and HDL size distributions of apoAI, apoAII, and cholesterol; concentrations of apoAI and apoAII were not genetically related to either insulin measure. Increased insulin levels were associated with relatively smaller HDL phenotypes, and considering a similar association with small, dense LDLs, this finding suggests a common effect of insulin resistance on particle size distributions for these lipoproteins. Thus, these results suggest the existence of genes that pleiotropically influence variation in both HDLs and insulin levels and therefore contribute to the clustering of proatherogenic traits in the IRS.

Progress in population analyses of the insulin resistance syndrome

Insulin resistance is associated with a variety of cardiovascular risk factors including hypertension, dyslipidemia, and non-insulin-dependent diabetes. In blacks, the relation between insulin resistance, hypertension, and atherosclerosis has been questioned. Most data collected on the Insulin Resistance Syndrome have been collected in nondiabetic subjects; therefore, no inference can be drawn to exogenous insulin use in diabetic subjects where improved glycemic control is usually associated with improved cardiovascular risk factors (especially dyslipidemia) in the absence of weight gain.

The acylation stimulating protein pathway: clinical implications

OBJECTIVES

The present review will focus particularly on acylation stimulating protein (ASP) and its role in adipose tissue. Two issues will be addressed (1) in vitro biochemical characterization of ASP in cell culture studies, and (2) in vivo clinical relevance for normal physiology and in pathological conditions.

CONCLUSIONS

Fat is In! There can be no question that in recent years fat tissue has become recognized as more than just a passive storage site. It is a metabolically active tissue that, under normal conditions, allows the efficient clearance of triglyceride and glucose for storage as energy. Under abnormal conditions, adipose tissue dysfunction is associated with obesity, diabetes and coronary heart disease. Adipose tissue function may be controlled by many factors.

Epidemiology of hypertension and insulin resistance syndrome

INSULIN RESISTANCE SYNDROME: Insulin resistance syndrome (syndrome X) indicates that insulin resistance is associated with and may be the cause of several metabolic conditions including hypertension, dyslipidemia, non-insulin dependent diabetes mellitus (NIDDM).

HYPERTENSION

Although the association between insulin resistance and hypertension remains somewhat controversial, hypertensive subjects are clearly at increased risk of developing NIDDM. Insulin concentrations are a relatively weak predictor of the development of hypertension. It is possible that the relation between insulin, blood pressure and atherosclerosis may be weaker in blacks. However, antihypertensive agents that worsen insulin resistance may further increase the risk of NIDDM already present in subjects with hypertension.

Insulin sensitivity and blood pressure in a biethnic sample: the Miami Community Health Study

An association between blood pressure and insulin sensitivity among normotensive African-Americans has not been demonstrated consistently in epidemiologic studies. Part of the discrepancy may be due to studying persons with profound obesity-an insulin-resistant state itself. The association between insulin-mediated glucose uptake (i.e., insulin sensitivity) and blood pressure was examined among 25 nondiabetic African-American and 28 white non-Hispanic persons aged 25-44 years who ranged from normal weight to obese, using the hyperinsulinemic euglycemic clamp technique. In bivariate analyses, insulin sensitivity was inversely related to systolic (p < 0.01) and diastolic blood pressure (p = 0.08) among African-American persons and to diastolic blood pressure among white non-Hispanic subjects (p < 0.05). Covariate adjustment for age and sex had only a marginal effect on these results. When the data were pooled and further adjusted for ethnicity, insulin sensitivity remained significantly associated with both systolic and diastolic blood pressure (p < 0.01 for each). To consider the effect of obesity, body mass index (BMI) was divided at the sample median (26.5 kg/m2) and the analyses were repeated within each stratum. Among those whose BMI was below the median value, each increment in insulin sensitivity was associated with a 2-mmHg decrease in systolic blood pressure (p = 0.02). These results suggest that ethnicity was not a strong effect modifier in this sample and indicated that insulin sensitivity was inversely related to blood pressure level in these normotensive African-American and white, non-Hispanic participants.

Cardiovascular risk factors and the prediabetic syndrome

Cardiovascular disease is increased 2- to 4-fold in non-insulin-dependent diabetes mellitus (NIDDM); yet in most studies, there is a relatively weak relationship between the frequency of coronary heart disease (CHD) and the duration of diabetes and severity of hyperglycaemia. A number of authors have suggested that the prediabetic stage may contribute to the risk of CHD in NIDDM. Hyperinsulinaemia and insulin resistance have been strongly associated with the development of NIDDM. Data are less conclusive about the relationship of hyperinsulinaemia to the development of CHD in nondiabetic subjects. Relatively little data are available on hyperinsulinaemia and/or insulin resistance to CHD in NIDDM subjects. Tight control of glycaemia with exogenous insulin improves cardiovascular risk factors in NIDDM subjects and therefore is unlikely to increase the risk of CHD. Although the relation of insulin to CHD in the general population is somewhat controversial, insulin is clearly related to multiple cardiovascular risk factors (especially elevated triglyceride, decreased high-density lipoprotein, small dense low-density lipoprotein, impaired glucose tolerance and increased plasminogen activator inhibitor 1 (PAI-1)). However, the relation of insulin resistance to hypertension remains controversial.

Hypertension and overweight associated with hyperinsulinaemia and glucose tolerance: a longitudinal study of the Finnish and Dutch cohorts of the Seven Countries Study

To elucidate the role of hypertension as part of the insulin resistance syndrome, the longitudinal relationships of hypertension and overweight with hyperinsulinaemia and glucose tolerance were examined in the Dutch and Finnish cohorts of the Seven Countries Study (Zutphen, and east and west Finland). Three cohorts of men, born between 1900 and 1919, were first examined in 1959/1960. At the 30-year follow-up survey a 2-h glucose tolerance test was carried out on 619 of the surviving men, and fasting insulin was also measured. Blood pressure and body mass index (BMI) were measured several times during the entire 30-year follow-up period. In cross-sectional analyses, men with diabetes and impaired glucose tolerance at the 30-year follow-up examination had a significantly higher systolic blood pressure and a higher prevalence of hypertension than men with normal glucose tolerance, independent of age, cohort and BMI (p < 0.01). These differences had already been seen 5, 20 and 30 years earlier. Subjects with hyperinsulinaemia (fasting insulin > or = 9.2 mU/l) had a higher BMI and a higher prevalence of hypertension. This cross-sectional association with hypertension was independent of age, cohort and BMI. BMI levels of men with hyperinsulinaemia had been shown to be higher 5, 20 and 30 years earlier, but blood pressure levels had not. These results indicate that hypertension is independently associated with glucose tolerance and insulin resistance in three Caucasian cohorts. Changes in blood pressure precede abnormal glucose tolerance but not hyperinsulinaemia; therefore, glucose tolerance appears to be a stronger correlate of hypertension than hyperinsulinaemia.

Hyperinsulinaemia and decreased plasma levels of dehydroepiandrosterone sulfate in premenopausal women with coronary heart disease

OBJECTIVES

The purpose of the study was to establish plasma levels of insulin, ovarian sex hormones and dehydroepiandrosterone sulfate (DHEA-S) and to evaluate their correlations with lipids in premenopausal women with angiographically demonstrated coronary stenosis.

DESIGN

Differences in plasma levels of insulin, ovarian sex hormones, DHEA-S and lipids between groups were compared by analysis of variance.

SETTING

From January 1993 until December 1993 patients were diagnosed in the Outpatient Clinic of the Department of Endocrinology Medical Centre for Postgraduate Education, Warsaw.

SUBJECTS

Premenopausal women with normal oral glucose tolerance test (OGTT) results, with and without coronary stenosis were studied: 21 women after acute myocardial infarction with angiographically demonstrated coronary stenosis (women with CHD), and 14 women with chest pain, a positive exercise test without significant changes of coronary arteries on coronarography (women with normal coronarography, NC). The control group consisted of nine, healthy women with no risk factors for CHD.

MAIN OUTCOME MEASURES

In premenopausal women with CHD, the decreased plasma level of DHEA-S and hyperinsulinaemia were anticipated.

RESULTS

In women with CHD, the plasma levels of DHEA-S (926.5 +/- 83 ng mL-1) were significantly lower than those in women with NC (1375.7 +/- 181 ng mL-1) and in healthy controls (1984 +/- 127 ng mL-1), P < 0.02 and P < 0.001, respectively. The fasting insulin and insulin response to an OGTT in women with CHD and with NC was higher than in healthy subjects. A significant decrease of high-density lipoprotein (HDL) cholesterol, HDL-2 cholesterol and apolipoprotein A-I, and an increase of total cholesterol, low-density lipoprotein cholesterol C and apolipoprotein B levels in women with CHD compared to healthy controls were observed. A negative correlation between fasting insulin and the plasma levels of DHEA-S was established.

CONCLUSION

In premenopausal women, hyperinsulinaemia and decreased DHEA-S levels may contribute to the development of coronary atherosclerosis.

Effect of large-volume liposuction on sex hormones and glucose- and lipid metabolism in females

Nine consecutive patients who underwent syringe-assisted liposuction with a mean aspirate volume of 3633 mL (range: 1800-5500) had their lipids, lipoproteins, and sex hormones measured pre- and postoperatively. Seven of the patients also underwent an oral glucose tolerance test with measurements of insulin and C-peptide. The major finding was a significant increase in HDL cholesterol and apolipoprotein A1, while there was no significant change in sex hormones or glucose levels 9-12 months after the liposuction procedure. The results indicate that large-volume liposuction might decrease the risk of cardiovascular disease in these patients.

Corticosteroids: do they damage the cardiovascular system?

Since their introduction for the treatment of rheumatoid arthritis, corticosteroids have become widely used as effective agents in the control of inflammatory diseases. Although there have been undoubted benefits upon mortality in diseases such as systemic lupus erythematosus, many patients survive only to suffer a high incidence of premature atherosclerosis. There is also evidence of increased rates of vascular mortality in other corticosteroid-treated diseases, such as rheumatoid arthritis, reversible airways obstruction and transplant recipients. Possible mechanisms of damage include elevated blood pressure, impaired glucose tolerance, dyslipidaemia, and imbalances in thrombosis and fibrinolysis. This paper reviews the clinical evidence supporting the contention that there is an excess cardiovascular mortality in steroid-treated patients and the underlying mechanisms, and points to further areas of research.

Hyperinsulinemia, risk factors, and coronary heart disease. The Zutphen Elderly Study

We investigated the association between fasting insulin concentration--an indicator of insulin resistance in nondiabetic individuals--cardiovascular risk factors, and coronary heart disease in a study of 390 men in the town of Zutphen. In 1990, an extensive examination was carried out on the participating men (aged 70 to 89 years). Fasting insulin levels were determined and a number of other risk factors measured. Known and newly diagnosed diabetics were excluded from the data analyses. Fasting insulin concentration was significantly associated with levels of glucose, triglycerides, uric acid, serum albumin, creatinine, and fibrinogen as well as resting heart rate. Inverse associations with high-density lipoprotein cholesterol and factor VII activity were observed. These results were independent of confounding factors such as age, body mass index, ratio of subscapular to triceps skinfold thicknesses, cigarette smoking, physical activity, and alcohol consumption. Men with a fasting insulin level higher than 80 pmol/L (highest quartile of the distribution) had a significantly higher prevalence of coronary heart disease and especially of myocardial infarction. This result was independent of potential confounding variables as well as of possible intermediates (total and high-density lipoprotein cholesterol, hypertension, serum triglycerides, fasting glucose, and other risk factors related to fasting insulin) (odds ratio, 2.2; 95% confidence interval, 1.2-4.0). No association between fasting insulin level and hypertension or blood pressure was observed. These results show that fasting insulin is an important indicator of coronary heart disease in elderly men. Clotting factors, resting heart rate, uric acid, serum albumin, and creatinine may also play a role in this metabolic syndrome.

Is hyperinsulinaemia a central characteristic of a chronic cardiovascular risk factor clustering syndrome? Mixed findings in Asian Indian, Creole and Chinese Mauritians. Mauritius Noncommunicable Disease Study Group

The aim of the study was to investigate whether the constellation of cardiovascular disease risk factors, described as Insulin Resistance Syndrome, exists in the multi-ethnic population of Mauritius, and to assess whether hyperinsulinaemia is the key feature of this syndrome. A sample of 5080 Mauritian subjects (aged 25-74 years) was examined in a noncommunicable diseases survey in 1987. Survey procedure included an oral glucose tolerance test, and anthropometric, blood pressure, plasma lipids and serum insulin measurements. Abnormal glucose tolerance (diabetes and impaired glucose tolerance), general obesity, upper-body obesity, hypertension, low HDL-cholesterol, and hypertriglyceridaemia were defined as risk factor conditions. Mean values for a series of risk factor variables were compared between reference subjects (no risk factors) and those with a risk factor condition (either one condition only, or in combination with one or more others). Prevalence estimates for each risk factor condition in combination with three or more other conditions were three to four times greater than expected by chance, and levels of risk factors for subjects with more than one risk factor condition were further away from the reference levels than for those with just one condition. Fasting and 2-h serum insulin levels were elevated for each condition when in combination with others, or to a lesser extent when isolated. However, this was not the case for isolated hypertension where insulin levels were not elevated. When adjusted for age, sex, and body mass index, insulin levels were only significantly elevated in subjects with upper-body obesity if in association with general obesity.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperinsulinemia predicts multiple atherogenic changes in lipoproteins in elderly subjects

Several studies have shown that hyperinsulinemia and insulin resistance are associated with high triglyceride and low high-density lipoprotein (HDL) cholesterol levels. However, previous studies have been cross-sectional, and thus the presence of hyperinsulinemia or insulin resistance could be a consequence of the underlying lipid disorder instead of its cause. Therefore, we examined the relation of fasting insulin level measured in a cross-sectional study in nondiabetic subjects 65 to 74 years old (n = 881) to the risk of developing lipid disorders 3.5 years later. The incidence of the following lipid abnormalities was calculated: hypertriglyceridemia (n = 49/732, incident cases/subjects free of the particular disorder at baseline), high low-density lipoprotein (LDL) cholesterol level (n = 43/696), low HDL cholesterol level (n = 33/708), high apolipoprotein (apo) B level (n = 72/699), low apoAI level (n = 47/711), low serum LDL cholesterol/serum apoB ratio (n = 55/685), and low serum HDL cholesterol/serum apoAI ratio (n = 48/707). Baseline insulin level was not significantly associated with the development of high LDL cholesterol or low HDL cholesterol levels. Baseline insulin was associated with the development of hypertriglyceridemia (odds ratio [OR], 1.64; 95% confidence interval [CI], 1.12 to 2.40; P = .011), high apoB (OR, 1.54; 95% CI, 1.13 to 2.10; P = .006), low apoAI (OR, 1.72; 95% CI, 1.22 to 2.42; P = .002), low LDL cholesterol/apoB ratio (OR, 1.99; 95% CI, 1.36 to 2.90; P < .001), and low HDL cholesterol/apoAI ratio (OR, 1.93; 95% CI, 1.34 to 2.79; P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Is there a sex difference in the association of plasma insulin level and insulin sensitivity with serum lipids and lipoproteins?

Previous studies on the relationship between the plasma insulin level, insulin sensitivity (SI), serum lipids, and lipoproteins have been performed predominantly in men. Therefore, we investigated whether there is a sex difference in the association of insulin level during an oral glucose tolerance test and SI with lipids and lipoproteins among normoglycemic men and women aged 53 to 61 years. SI was determined by the minimal model from the frequently sampled intravenous glucose tolerance test (IVGTT). There were no correlations between total cholesterol or low-density lipoprotein (LDL) cholesterol and insulin level or SI. High-density lipoprotein (HDL) cholesterol correlated inversely with fasting insulin (r = -.26, P < .05 in men; r = -.29, P < .01 in women) and 2-hour insulin (r = -.31, P < .01 in men; r = -.39, P < .001 in women) and positively with SI (r = .28, P = .05 in men; r = .43, P < .001 in women). Total and very-low-density lipoprotein (VLDL) triglycerides correlated positively with fasting insulin (r = .43, P < .001 in men; r = .42, P < .001 in women) and 2-hour insulin (r = .50, P < .001 in men; r = .31, P < .01 in women) and inversely with (r = -.49, P < .001 in men; r = -.40, P < .001 in women). In multiple regression analyses including age, body mass index (BMI), waist to hip ratio, 2-hour glucose, fasting or 2-hour insulin, and SI, only BMI was associated with HDL cholesterol level in men.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin resistance, lipoproteins, body fat and hemostasis in nonobese men with angina and a normal or abnormal coronary angiogram

OBJECTIVES

The aim of this study was to compare metabolic risk factors in men with anginal chest pain and a normal or abnormal coronary angiogram with those in healthy men.

BACKGROUND

Risk factors for coronary heart disease, including lipoprotein abnormalities, hypertension and adiposity, may be metabolically interlinked, with insulin resistance and hyperinsulinemia being pivotal to these disturbances.

METHODS

Glucose and insulin metabolism, lipids and lipoproteins, hemostasis, blood pressure and body fat distribution were measured in 77 nonobese middle-aged men who had anginal chest pain (39 with an abnormal coronary angiogram and 38 with no detectable angiographic abnormality) and were compared with those of 40 healthy men of similar age and body mass index.

RESULTS

Patients with chest pain had higher insulin responses to an intravenous glucose challenge, lower insulin sensitivity, lower high density lipoprotein (HDL) and subfraction 2 cholesterol, lower apolipoprotein AI, higher triglycerides, greater android fat and higher systolic blood pressure at rest compared with levels in healthy control subjects (p < 0.05). Those with an abnormal coronary angiogram had lower tissue plasminogen activator levels, higher plasminogen activator inhibitor 1 levels and more android fat than did those with a normal angiogram (p < 0.05). Insulin sensitivity correlated positively with HDL (p < 0.05) and subfraction 2 (p < 0.001) cholesterol and negatively with triglycerides (p < 0.01), android fat proportion (p < 0.01) and systolic blood pressure (p < 0.05), whereas insulin response showed converse correlations.

CONCLUSIONS

These findings provide new evidence of the central role of insulin resistance and hyperinsulinemia in the development of risk factors associated with coronary heart disease.

Serum insulin and ECG abnormalities suggesting coronary heart disease in the populations of Mauritius and Nauru: cross-sectional and longitudinal associations

Cross-sectional associations between insulin and ECG abnormalities suggestive of 'possible' and 'probable' coronary heart disease (CHD) in the populations of Nauru (n = 568) and Mauritius (n = 3280) have been examined in both non-diabetic and diabetic subjects. Additionally, the longitudinal relationship between baseline insulin and incident ECG abnormalities has been explored in non-diabetic Nauruans (n = 177) over 5 years. Age-adjusted mean 2-hour serum insulin was generally higher in subjects with ECG abnormalities than those with a normal ECG, but the difference was significant only for non-diabetic Mauritian men (p < 0.01). There was no clear association between prevalence of ECG abnormalities and quintiles of fasting or 2-hr insulin in Mauritians, and in non-diabetic Nauruans there was a non-significant positive association between prevalence of ECG abnormalities and tertiles of 2-hr insulin. Logistic regression analyses showed a slight positive association between 2-hr insulin and ECG abnormalities in non-diabetic Mauritians (p = 0.06 in males, p = 0.09 in females), and non-diabetic male Nauruans (p = 0.054) independent of possible confounders. Fasting insulin was not associated in any group. In longitudinal analyses in Nauruans there were no significant differences in mean baseline fasting or 2-hr serum insulin between subjects who maintained a normal ECG and those who developed abnormalities consistent with 'possible CHD' (there were no changes suggestive of 'probable CHD'). The incidence of ECG changes suggesting 'possible CHD' was slightly higher in the upper tertile of baseline fasting insulin in both sexes and 2-hr insulin in females, but when other factors were accounted for, multiple logistic regression analyses did not support this finding. Data from the populations of Mauritius and Nauru do not support a major role for serum insulin in ECG abnormalities suggestive of CHD.

Metabolic and behavioral covariates of high-density lipoprotein cholesterol and triglyceride concentrations in postmenopausal women

OBJECTIVE

To determine predictors of high-density lipoprotein cholesterol (HDL) and triglyceride (TG) concentrations in postmenopausal women.

DESIGN

Cross-sectional study.

SETTING

Clinical research facility.

PARTICIPANTS

One hundred twenty-seven healthy, relatively sedentary, postmenopausal women not on estrogen replacement, mean age 57 years.

MEASUREMENTS

Alcohol intake, cigarette smoking, aerobic fitness (VO2max), body mass index (BMI), percent body fat, waist-hip ratio, lipids and lipoproteins, fasting plasma glucose (FPG), and insulin (FPI) concentrations.

RESULTS

In univariate analyses, HDL was significantly (P < 0.05) inversely related to BMI, waist-hip ratio, smoking, FPG, and FPI, and directly related to VO2max and alcohol intake. Triglycerides were related directly to BMI, waist-hip ratio, percent body fat, FPG, and FPI, and inversely to VO2max. In stepwise multiple regressions, BMI, waist-hip ratio, alcohol, smoking, and FPG were significantly associated with HDL (R2 for the model = 0.43). Addition of TG to these models reduced relations of BMI and waist-hip ratio, but not the other variables, to insignificance. For triglycerides, waist-hip ratio, alcohol, smoking, FPG, and FPI were significant predictors (R2 = 0.33). VO2max and percent body fat did not contribute to any model.

CONCLUSIONS

Obesity, abdominal obesity, smoking, alcohol intake, and measures of carbohydrate metabolism predict HDL and triglyceride concentrations in postmenopausal women.

Insulin and hypertension: are they related?

It has been postulated that insulin resistance and the concomitant compensatory hyperinsulinemia contribute to the pathogenesis of hypertension, possibly by stimulating the sympathetic nervous system, promoting renal sodium reabsorption, modulating cation transport, and/or stimulating vascular smooth muscle hypertrophy. The purpose of this article is to present a comprehensive up-to-date review of the literature and critically examine the insulin resistance-hyperinsulinemia-hypertension hypothesis.

Differential effects of body fatness and body fat distribution on risk factor for cardiovascular disease in women. Impact of weight loss

This study examines the role of obesity and body fat distribution (ie, waist-to-hip ratio [WHR]) on cardiovascular disease (CVD) risk factors in 50 nondiabetic, obese (body mass index [BMI], 31 +/- 2 kg/m2, mean +/- SD), 45 +/- 10-year-old women. The data obtained at baseline and after weight loss were analyzed after dividing subjects by WHR into upper-body (WHR > 0.80) and lower-body (WHR < or = 0.80) groups and by median-split BMI into more obese (BMI > or = 31) and less obese (BMI < 31) groups. At baseline, the upper-body obese women, when compared with lower-body obese women, had higher plasma triglycerides (TGs) (175 +/- 85 versus 111 +/- 47 mg/dL, respectively; P < .001) and lower high-density lipoprotein cholesterol (HDL-C) (44 +/- 10 versus 54 +/- 11, respectively; P < .01) but similar total and low-density lipoprotein cholesterol levels and blood pressure. There were no significant differences in these CVD risk factors at baseline by BMI split. Although weight loss (-9 +/- 5 kg) lowered blood pressure and TGs irrespective of WHR or BMI, only upper-body obese women raised HDL-C. Moreover, the magnitude of the changes was greatest in women with an upper-body fat distribution. In women with WHR > 0.80, HDL-C increased by 11%, to 49 mg/dL (P < .001), and TGs decreased by 24%, to 134 mg/dL (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of nutrition in the prevention and treatment of coronary heart disease in women

Coronary heart disease (CHD) is the major cause of death in women. Because the manifestation of CHD differs in women and men (men are more likely to have acute CHD and women are more likely to have chronic CHD), it is imperative to explore the unique aspects of CHD in women. In addition, there is a critical need to increase our understanding of the effect of CHD risk factor modification on coronary morbidity and mortality in women. Several major CHD risk factors in women, such as elevated blood lipids and lipoproteins, body weight, and, frequently, hypertension, are beneficially responsive to nutrition intervention. Approximately 27% of all women and 50% of women aged 55 to 74 years are candidates for dietary intervention. The fact that women respond positively to dietary intervention has been well established by researchers. Studies are needed to determine the efficacy of risk factor modification achieved by dietary and other hygienic approaches as well as by other more rigorous therapies (eg, drugs and surgery) on the primary and secondary prevention of CHD in women. Finally, it will be important to understand the effects of gender, menopausal status, and age on dietary responsiveness. We must gain a better understanding of these issues so that we may significantly reduce the incidence of CHD in women.

Sodium-lithium countertransport activity is decreased after weight loss in healthy obese men

Maximal red blood cell (RBC) sodium-lithium countertransport activity has been consistently related to essential hypertension and may be a marker for risk of developing hypertension. Although there is strong evidence for genetic control of sodium-lithium countertransport, increasing evidence suggests that obesity and insulin-glucose metabolism are related to countertransport activity. This study was performed to determine whether countertransport activity decreases with weight loss in healthy obese adults. Forty-five healthy, white, obese adults were studied at baseline and after 6 months of behavioral dietary intervention. Weight loss was 11.5 kg (25.4 lb) in 24 men and 8.1 kg (17.8 lb) in 21 women. Sodium-lithium countertransport activity decreased 55.0 mumol Li/L RBC/h in men (P < .001, paired t test) and 14.6 mumol Li/L RBC/h in women (NS). Change in countertransport activity was correlated with change in body mass index (BMI) in men (r = .52, P < .01) and women (r = .27, NS) and was also strongly correlated with change in fasting glucose levels in both men and women (r = .50 and r = .56, respectively; P < .01) and with change in fasting insulin levels in men (r = .42, P = .04). Change in countertransport activity was not significantly related to change in physical exercise or serum lipid levels. There was a large decrease in systolic blood pressure in men (10.0 mm Hg, P < .001) and a smaller decrease in women (4.1 mm Hg, P < .05). These changes were significantly correlated with change in weight, but not with change in countertransport or baseline countertransport activity.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Influence of insulin resistance, secretion, and clearance on serum cholesterol, triglycerides, lipoprotein cholesterol, and blood pressure in healthy men

Relations between serum lipids, lipoproteins, blood pressure, and insulin metabolism were investigated in 158 healthy men aged 19-77 years and with body mass indexes (BMIs) of 19-41 kg.m-2. Mathematical modeling analysis of glucose, insulin, and C-peptide concentrations during an intravenous glucose tolerance test was used to measure parameters of insulin metabolism. In univariate analysis, both fasting and postglucose insulin concentrations showed significant positive associations with fasting serum triglyceride levels (r = 0.33 and 0.38, respectively) and systolic (r = 0.22 and 0.26) and diastolic (r = 0.21 and 0.24) blood pressure and negative associations with high density lipoprotein subfraction 2 cholesterol (HDL2; r = -0.21 and -0.25). In multivariate analysis, the associations between insulin and HDL2 cholesterol concentrations were found to depend on triglyceride levels. Insulin resistance and basal pancreatic insulin secretion showed significant positive associations with serum triglycerides, which were independent of the effects of age, BMI, and fat distribution. Hepatic insulin throughout was independently associated with HDL2 cholesterol. Associations of insulin-related variables with blood pressure were generally dependent on age and BMI. These results underline the importance of insulin sensitivity and insulin concentrations as determinants of triglyceride metabolism. They also indicate a close relation between hepatic insulin handling and HDL2 concentration that is independent of triglyceride metabolism.

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.

Clinical and metabolic considerations of long-term oral contraceptive use

Newer lower dose formulations are associated with an improved cardiovascular disease risk marker profile, which supports their use for longer periods and among older women. Epidemiologic studies of the newer formulations are limited. Without clinical information, an evaluation of the effects of more recent formulations on metabolic risk markers for cardiovascular disease is useful. In a large cross-sectional study, a reduction in the progestin dose and use of alternative progestins substantially reduced the proportion of oral contraceptive users with values associated with an increased risk of cardiovascular disease. No progression in metabolic changes was found by analyzing the effect of the duration of oral contraceptive use. The user's age interacted positively with the oral contraceptive--induced increase in serum triglyceride levels, but there was no interaction of age with the oral contraceptive's effect on oral glucose tolerance, glucose and insulin responses, low-density lipoprotein cholesterol, or high-density lipoprotein subfraction 2 cholesterol levels.

Insulin resistance--modelling studies

Elevated insulin concentrations are independent predictors of coronary heart disease (CHD) and are related to high blood pressure, low serum HDL-cholesterol and elevated serum triglyceride. Insulin resistance is a major determinant of the plasma insulin concentration. Computer modelling of plasma glucose, insulin and C-peptide concentrations during an intravenous glucose tolerance test enables quantification of the determinants of plasma insulin concentration. The association between risk markers of CHD and model-derived measures of determinants of plasma insulin concentration in a group of healthy males has been investigated. In univariate linear regression analysis of the glucose, insulin and C-peptide data, the incremental insulin area during the second phase (10-180 min.) was found to be the strongest predictor of lipid, lipoprotein and blood pressure variables. Variations in insulin sensitivity and hepatic insulin throughput contribute to variation in the insulin response and may be secondary correlates of lipids, lipoproteins and blood pressure.

Relation between insulinemia, body mass index, and lipoprotein composition in healthy, nondiabetic men and women

Altered lipoprotein composition may be a better predictor of cardiovascular disease than modestly increased serum lipid concentrations, although possible interactions between lipoprotein composition, obesity, and insulinemia have not been fully elucidated. Therefore, we investigated the association between different measures of insulinemia and lipoproteins in 297 healthy Caucasian men (body mass index [BMI] less than 27 in 233, greater than 27 [obese] in 64) and 295 healthy Caucasian women (BMI less than 25 in 198, greater than 25 [obese] in 97). Associations observed in both obese and nonobese men and women were between increasing tertiles of most insulin measures and serum triglyceride concentrations (p = 0.079-0.004) and the ratio of low density lipoprotein to high density lipoprotein cholesterol (p = 0.094-0.008). Graded reductions in the high density lipoprotein cholesterol to apolipoprotein A-I ratio were also recorded in obese women, with increasing tertiles of fasting (p = 0.014-0.007) and postglucose load (p = 0.001) serum insulin levels, after correcting for BMI and triglyceride concentrations. Less marked graded increases in the triglyceride to apolipoprotein B ratios were recorded in obese women with increasing tertiles of fasting (p = 0.001-0.006) and postglucose challenge (p = 0.081) insulinemic measures. In men with normal or slightly elevated cholesterol levels (fasting serum cholesterol less than 6.5 mmol/l), hyperapobetalipoproteinemia was recorded with increasing tertiles of insulinemia (p = 0.006, correcting for BMI and triglyceride concentrations), as well as in subjects with hypertriglyceridemia (fasting serum triglycerides greater than 1.70 mmol/l) (p = 0.004, correcting for BMI and age). Hyperinsulinemia and insulin resistance are associated with altered lipoprotein composition in obese women, presumably reflecting a complex interplay between sex hormones, body mass, and insulin action. Insulin resistance appears to be more associated with apolipoprotein B concentrations in men. The hyperinsulinemic nondiabetic subject may be at increased risk of cardiovascular disease because of altered concentrations of apolipoprotein concentrations and lipoprotein composition.

A longitudinal study on glucose tolerance and other cardiovascular risk factors: associations within an elderly population

From 1971 until 1975, 204 patients from a general practice, aged 64-87 at entry, were examined annually. At every examination body weight, serum lipids, and systolic blood pressure were measured, and a complete glucose tolerance test was carried out. Clinically diagnosed diabetics were excluded. Adjusted for age and sex, the annual change in the area under the glucose curve (AUC) was significantly associated with body weight change. Changes in serum total cholesterol, serum triglycerides, and systolic blood pressure were also associated with body weight change. The results were independent of potential confounders such as alcohol use, smoking habits, presence of cardiovascular disease, and baseline levels of the different risk factors. The change in AUC was also associated with changes in serum total cholesterol, independent of confounders such as body weight. Changes in AUC were not related to changes in systolic blood pressure and serum triglycerides. The results of this study suggest that changes in glucose tolerance are not only related to changes in body weight, but also to changes in serum cholesterol.

Fasting serum insulin in relation to fat distribution, serum lipid profile, and blood pressure in European women: the European Fat Distribution Study

Samples of 38-year-old women were randomly selected from five European centers: Ede (The Netherlands), Warsaw (Poland), Gothenburg (Sweden), Verona (northern Italy), and Afragola (Naples-southern Italy). In total, 452 healthy women were studied. Anthropometric measurements were taken by one operator in each country after common training of all operators and blood parameters of all women were determined in one laboratory. Body mass index (BMI) was different among centers, mainly due to the higher values in southern Italy. Women from southern Europe had more central fat distribution than women from north European centers. Fasting serum insulin was higher in women from Poland and The Netherlands than in the other three centers. After adjustment for BMI, fasting insulin was significantly related to subscapular skinfold, subscapular to triceps skinfold ratio, waist circumference, and waist to thigh circumference ratio, although the partial correlations varied somewhat between the centers. In the pooled data, waist circumference showed the highest correlations with fasting serum insulin when adjusted for BMI. Fasting serum insulin showed significant partial correlations, adjusted for BMI, with lipid profile and blood pressure only in women from the two Italian centers. In the pooled data, fasting serum insulin was significantly positively correlated with serum triglycerides and total cholesterol and negatively to high-density lipoprotein (HDL) cholesterol and HDL/total cholesterol, independently of BMI and waist circumference. While blood pressure was not related to insulin in the pooled women, when adjusted for BMI and waist circumference; here as well, there were some differences in relationships between the centers.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum insulin and other cardiovascular risk indicators in children, adolescents and young adults

We wanted to determine the levels of fasting serum insulin during growth, the tracking of serum insulin, and the correlation of serum insulin with other coronary heart disease risk indicators in children and young adults. In 1986 2433 subjects, aged nine to 24 were studied, and insulin data were available from the same population in 1980 and 1983. Serum insulin levels showed a peak during puberty in both sexes and the decline in insulin continued after the age of 21. Tracking of serum insulin was only moderate, especially in females and young boys. Serum insulin correlated positively with body mass index, concentrations of serum triglycerides, and blood pressure, and inversely with the concentration of high density lipoprotein cholesterol. High triglycerides, high systolic blood pressure, and low level of high density lipoprotein cholesterol clustered among subjects within the highest insulin quartile. Our results suggest that the insulin resistance phenomenon, caused mainly by obesity and leading to unfavourable levels of other coronary heart disease risk indicators, is already developing in children and young adults. This suggests that preventing obesity in early life is important.

Are insulin and hypertension independently related?

Hyperinsulinemia has been proposed as the common pathogenetic mechanism of obesity, non-insulin-dependent diabetes mellitus, and hypertension. We examined the cross-sectional relationship between fasting and postchallenge insulin levels and hypertensive status in a population-based study of 653 men and 784 women, aged 50 to 93 years, in Rancho Bernardo, California. Hypertensive subjects had slightly but not significantly higher fasting plasma insulin levels than did normotensive subjects, but significantly higher postchallenge insulin levels. After stratification for obesity and glucose intolerance, there was no significant difference between the mean age-adjusted fasting or postchallenge insulin levels of those with and those without hypertension in 12 possible subgroups. Analysis of variance of both fasting and postchallenge insulin levels also failed to reveal a significant relationship between insulin and hypertensive status after adjusting for age, sex, body mass index, and diabetes. The current study does not support the hypothesis that insulin is independently associated with hypertension.

Relationship of endogenous sex steroid hormones to lipids and apoproteins in postmenopausal women

The relationships between blood levels of estrogen and lipoprotein lipids and apoproteins were evaluated in 120 women early in the climacteric. Among women who were 1-year amenorrheic, not taking hormone replacement therapy, and with follicle-stimulating hormone levels greater than 720 ng/ml, serum estradiol levels were positively related to concentrations of the high density lipoprotein 2 cholesterol (HDL2c) subfraction. There was a substantial decrease in HDL2c and apoprotein (apo) A-I in women whose estradiol levels decreased to less than or equal to 2.5 pg/ml from the first to the second postmenopausal examination. In a sample of women evaluated during the perimenopause (3-months' amenorrheic), those with the highest concentrations of estradiol or estrone showed a (nonsignificantly) higher level of HDL2c and a lower level of low density lipoprotein cholesterol (LDLc) than did those with the lowest concentration of estradiol or estrone. Estradiol levels declined dramatically between the perimenopausal and the postmenopausal examinations, and this was accompanied by a decrease in HDL2c and a nonsignificant increase in LDLc. HDL2c levels fell substantially in those women whose estradiol decreased below the sensitivity of the assay. The change, however, was not statistically significant. Estrone is the primary postmenopausal estrogen, and levels are directly related to obesity, as are levels of insulin. The interrelationship among obesity, conversion of estrone to estradiol at the tissue level, and insulin (or insulin sensitivity) is probably the primary determinant of HDLc concentration among postmenopausal women.

An assault on old friends: thiazide diuretics under siege

The adverse biochemical effects of thiazide use are of uncertain clinical significance. Thiazides raise LDL cholesterol only slightly in long-term studies and do not decrease HDL cholesterol. The evidence linking thiazide-induced hypokalemia with arrhythmias and sudden death is tenuous at best. Thiazide diuretics cause glucose intolerance, but no strong evidence has been advanced to suggest that this is dangerous. Because these effects are probably related to hypokalemia, a randomized trial comparing the effects of thiazides with thiazides plus a potassium-sparing diuretic on LDL cholesterol, ectopy on 48 hour ambulatory cardiac monitoring, fasting glucose and insulin, and post-glucose tolerance glucose and insulin would be of interest. The most compelling reason for continuing to use thiazides is that they have been shown in long-term randomized studies to reduce cardiovascular risk. Beta-blockers are the only other class of anti-hypertensive agent for which this claim can be made. The importance of long-term clinical trials in assessing the efficacy and toxicity of therapeutic agents is illustrated by the study that found clofibrate reduced cholesterol levels and coronary disease but increased total mortality. This finding remained undetected until a large randomized long-term trial was completed. Thiazide diuretics have not reduced the rate of coronary disease to the degree expected from epidemiologic studies, but the short length of the randomized trials may be responsible. It is not clear that other anti-hypertensive agents will be superior. Thiazides are less expensive than other anti-hypertensive agents being touted as metabolically safer; the cost issue is not a trivial matter.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of fasting insulin with blood pressure and lipids in young adults. The CARDIA study

The association of insulin with cardiovascular disease (CVD) may be mediated in part by the associations of insulin with CVD risk factors, particularly blood pressure and serum lipids. These associations were examined in 4576 black and white young adults in the CARDIA Study. Fasting insulin level was correlated in univariate analysis with systolic blood pressure (r = 0.16), diastolic blood pressure (r = 0.13), triglycerides (r = 0.27), total cholesterol (r = 0.10), high density lipoprotein (HDL) cholesterol (r = -0.25), and low density lipoprotein (LDL) cholesterol (r = 0.14), and with age, sex, race, glucose, body mass index, alcohol intake, cigarette use, physical activity, and treadmill duration (all p less than 0.0001). After adjustment for these covariates, insulin remained positively associated with blood pressure, triglycerides, total and LDL cholesterol, and apolipoprotein B and was negatively associated with HDL, HDL2 and HDL3 cholesterol, and apolipoprotein A-I in all four race-sex groups. Higher levels of fasting insulin are associated with unfavorable levels of CVD risk factors in young adults; these associations, though relatively small, can be expected to increase the risk of atherosclerosis. Demonstration of these relationships in a large, racially diverse, healthy population suggests that insulin may be an important intermediate risk factor for CVD in a broad segment of the U.S. population.