Hyperdynamic circulation and the insulin resistance syndrome ("syndrome X")

Resting heart rate and the risk of type 2 diabetes: A systematic review and dose--response meta-analysis of cohort studies

BACKGROUND

High resting heart rate has been associated with increased risk of type 2 diabetes in several studies, but the available data are not consistent and it is unclear if there is a dose-response relationship between resting heart rate and type 2 diabetes risk. We aimed to clarify this association by conducting a systematic review and meta-analysis of published studies.

METHODS AND RESULTS

PubMed, Embase and Ovid Medline databases were searched for prospective studies published up until October 11th, 2013. Summary relative risks were estimated using a random effects model. Ten cohort studies with >5628 cases and 119,915 participants were included. The summary RR for high vs. low resting heart rate was 1.83 (95% CI: 1.28-2.60, I(2) = 88%, n = 7), and in the dose-response analysis the summary RR was 1.20 (95% CI: 1.07-1.34, I(2) = 93%, n = 9) for an increase of 10 beats per minute. The heterogeneity was to a large degree explained by two studies. There was evidence of nonlinear associations between resting heart rate (pnonlinearity < 0.0001) and risk of type 2 diabetes.

CONCLUSION

The current meta-analysis indicates a strong positive association between high resting heart rate and the risk of type 2 diabetes. As a non-invasive marker of type 2 diabetes risk, resting heart rate may have potential in the clinical setting, especially for interventions aimed at lowering the risk of type 2 diabetes. Additional studies are needed to clarify the mechanisms that may be responsible for the assoiation between resting heart rate and type 2 diabetes.

Differential impact of heart rate on arterial wall stiffness and thickness in young adults: The Bogalusa Heart Study

Heart rate, a hemodynamic parameter, is an important determinant of arterial wall stiffness. However, information on the relationship of heart rate to arterial wall thickness is inconsistent. This study examined the influence of heart rate on arterial stiffness and thickness in Black and White young adults. The study cohort consisted of 255 Black and 659 White adults age 25 to 43 years enrolled in the Bogalusa Heart Study. Carotid artery intima-media thickness (IMT) was measured by B-mode ultrasound and aorta-femoral pulse wave velocity (af-PWV) by echo-Doppler. There was no difference in heart rate between Blacks and Whites. Males vs. females displayed lower heart rate and higher segmental and composite carotid IMT; Blacks vs. Whites had higher composite carotid IMT (0.83 mm vs. 0.80 mm, P < .01) and af-PWV (5.4 m/s vs. 5.2 m/s, P < .01). In a multivariate regression model adjusting for traditional cardiovascular risk variables, heart rate was independently associated with af-PWV (standardized regression coefficient: beta = .14, P = .01 for Blacks; beta = .06, P = .07 for Whites; beta = .09, P = .003 for total sample), but not with carotid IMT. These results indicate that heart rate plays differential roles in the development of arterial stiffness and subclinical atherosclerosis during young adulthood.

Platycodon grandiflorum modifies adipokines and the glucose uptake in high-fat diet in mice and L6 muscle cells

OBJECTIVES

Obesity and diabetes have become the most common human health problems worldwide. Obesity's contribution to type 2 diabetes might be due to dysregulation of adipokines and glucose uptake.

METHODS

In this study, we performed in-vivo and in-vitro studies to evaluate the effects of Platycodon grandiflorum extract (PGE) on adipokines and glucose uptake. Before study, platycodin D concentrations were analysed by HPLC in PGE prepared in water, in 50% ethanol and in 80% ethanol, and we selected the 80% ethanol extract as the PGE for this study based on the HPLC results.

KEY FINDINGS

We found that inclusion of PGE in the high-fat diet (HFD) markedly attenuated food intake, body weight, epididymal fat weight, adipocyte size and blood glucose levels by the oral glucose tolerance test in mice, and maintained serum levels of adiponectin, resistin, leptin, fructosamine and triglycerides. Gene expression analysis revealed that PGE up-regulated adiponectin, and down-regulated TNF-α and leptin in fat tissue. In L6 muscle cells in vitro, PGE increased insulin-stimulated glucose uptake.

CONCLUSIONS

  We conclude that PGE may improve obesity in mice fed an HFD and glucose uptake in L6 muscle cells by modifying adipokines, and could offer clinical benefits as a supplement to treat obesity and diabetes.

The prognostic significance of heart rate for cardiovascular disease and hypertension

Five decades ago, hypertension was a debated risk factor for the development of cardiovascular disease. After further studies and the introduction of antihypertensive medications, few, if any, have doubted the important role hypertension plays as a cardiovascular risk factor. Today, a growing body of evidence emphasizes the relationship between heart rate and hypertension, and heart rate and cardiovascular disease, which makes the measurement of heart rate an important component of the cardiovascular risk assessment. Current European guidelines for managing arterial hypertension recommend the measurement of heart rate for risk stratification, but there still are no recommendations for treatment. This review discusses the evidence for a relationship between heart rate and cardiovascular mortality and morbidity and hypertension.

Independent and combined associations of abdominal obesity and seated resting heart rate with type 2 diabetes among older Chinese: the Guangzhou Biobank Cohort Study

BACKGROUND

Central obesity and poor physical fitness predict the development of type 2 diabetes and cardiovascular mortality among Caucasian populations. We studied the independent and combined effect of abdominal obesity and seated resting heart rate used as an indicator of physical fitness, on the presence of type 2 diabetes among 30 519 older residents of Guangzhou, Southern China.

METHODS

Participants were stratified into four groups, based on the Asian criteria for abdominal obesity (≥90/≥ 80 cm in men/women) and the 75% cut-off point for seated resting heart rate (≥83 beats per min). The association with type 2 diabetes was assessed using multivariable logistic regression.

RESULTS

A total of 3777 (12.7%) volunteers were diagnosed with type 2 diabetes, which was independently associated with seated resting heart rate and, in particular, increasing levels of abdominal obesity (p < 0.001). An odds ratio of 3.93 (95% confidence interval = 3.48-4.43) was identified for type 2 diabetes in participants who were obese with a seated resting heart rate ≥ 83 beats per min after adjusting for potential confounders.

CONCLUSIONS

Higher seated resting heart rate, a marker of poor physical fitness, independently doubles the risk of type 2 diabetes. The strength of this association is further increased when abdominal obesity is considered.

Prospective Study of Placental Angiogenic Factors and Maternal Vascular Function Before and After Preeclampsia and Gestational Hypertension

Background— Preeclampsia is a life-threatening pregnancy syndrome of uncertain origin. To elucidate the pathogenesis, we evaluated the temporal relationships between changes in vascular function and circulating biomarkers of angiogenic activity before and after the onset of preeclampsia and gestational hypertension.

Methods and Results— Maternal mean arterial pressure, uterine artery pulsatility index, brachial artery flow-mediated dilatation, and serum concentrations of placental growth factor (PlGF), soluble fms-like tyrosine kinase 1 (sFlt-1), and soluble endoglin were prospectively measured in 159 women from 10 weeks gestation until 12 weeks postpartum. At 10 to 17 weeks, women who developed preterm preeclampsia had lower serum PlGF ( P =0.003), higher soluble endoglin ( P =0.006), and higher sFlt-1:PlGF ratio ( P =0.005) compared with women who later developed term preeclampsia, gestational hypertension, or normotensive pregnancy. At 10 to 17 weeks, mean arterial pressure inversely correlated with serum PlGF ( r =−0.19, P =0.02); at 18 to 25 weeks, with soluble endoglin ( r =0.18, P =0.02); and at 26 to 33 weeks, with sFlt-1 ( r =0.28, P <0.001). At 23 to 25 weeks, uterine artery pulsatility index correlated with serum soluble endoglin ( r =0.19, P =0.02) and sFlt-1 levels ( r =0.17, P =0.03). Flow-mediated dilatation was higher during a pregnancy with gestational hypertension compared with preeclampsia ( P =0.001). Twelve weeks postpartum, serum PlGF was higher in women who had a hypertensive pregnancy compared with a normotensive pregnancy ( P <0.001).

Conclusions— These observations support a role for placenta-derived angiogenic biomarkers in the control of maternal vascular resistance of preeclampsia. Gestational hypertension develops differently, with a hyperdynamic circulation and angiogenic biomarker profile similar to normotensive pregnancy. Larger studies of unselected women are needed to ascertain whether measures of these angiogenic biomarkers assist with the prediction and prognosis of preeclampsia and whether postpartum measures of serum PlGF have a role in predicting future cardiovascular disease.

Reduced arterial compliance associated with metabolic syndrome in Chinese children and adolescents

OBJECTIVE

To explore the metabolic syndrome and its association with arterial compliance in Chinese children and adolescents.

METHODS

337 participants aged 6 to 18 years with males accounted for 55.8% were grouped according to their traits of metablic syndrome. Anthropometry, blood pressure, fasting plasma glucose, insulin and serum lipid profile were measured. Homeostasis model was assessed and insulin resistance (HOMA-IR) index was measured and calculated for estimating individual insulin resistance. Arterial compliance was also measured using digital pulse wave analyzing method (Micro medical, London), and stiffness index was calculated.

RESULTS

The stiffness index in participants with metablic syndrome was significant higher than that in participants with no riskof metablic syndrome [(7.69 +/- 1.63) vs (6.25 +/- 0.86) m/s, P < 0.01] and stiffness index and HOMA-IR were progressively increased with the increase of traits of metablic syndrom (P for linear trend < 0.001). After gender, age, and pubertal development were adjusted, both traits of metablic syndrome and HOMA-IR were correlated positively with stiffness index (both P < 0.05).

CONCLUSION

The clustering of metablic syndrome was closely associated with risk at increased arterial stiffness in Chinese children and adolescents. It was suggested that arterial compliance assessment of children and adolescents might be an important measure for prevention of cardiovascular diseases.

Pulse pressure, prehypertension, and mortality: the San Antonio heart study

BACKGROUND

Prehypertension increases mortality risk. Pulse pressure is also associated with increased mortality. Nevertheless, the impact of pulse pressure on the relationship between prehypertension and mortality is not known in individuals who are free of diabetes and cardiovascular disease.

METHODS

Cox regression analysis was used to examine mortality risk among 3,632 (97.0%) participants in the San Antonio Heart Study (age range, 25-64 years; mean follow-up, 15.2 years). Results were adjusted for age, sex, ethnicity, education, body mass index (BMI), smoking, and total cholesterol concentration. The Seventh Report of the Joint Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) categories were used for blood pressure staging: normal, <120/80 mm Hg; prehypertension, 120-139/80-89 mm Hg.

RESULTS

Prehypertension prevalence was 31.6% at baseline. There were 218 deaths during the follow-up period. Prehypertension-predicted mortality (all-cause, hazard ratio (HR) 1.49 (1.12-1.99); cardiovascular, HR 1.79 (1.07-3.02)). Relative to normal blood pressure plus pulse pressure in the lower tertile, prehypertension plus pulse pressure in the upper tertile was associated with increased mortality (all-cause, HR 2.14 (1.38-3.32); cardiovascular, HR 2.47 (1.13-5.39)); however, prehypertension plus pulse pressure in the lower tertile was not significantly associated with mortality (all-cause, HR 1.19 (0.52-2.67); cardiovascular, HR 0.43 (0.05-3.40)).

CONCLUSIONS

Prehypertension increases mortality risk (all-cause and cardiovascular) in individuals who are free of diabetes and cardiovascular disease. Nevertheless, this relationship is not evident in individuals with narrow pulse pressure. Therefore, pulse pressure may be a relevant measure of blood pressure for the definition of normal blood pressure.

Cardiovascular Risks Associated With Obesity in Children and Adolescents

Introduction: The aim of this paper is to review the cardiovascular (CVS) risks associated with obesity in children and adolescents. Both short-term and long-term CVS consequences, the mechanisms of how these develop and the measures that can alter or reverse these CVS events are reviewed. Materials and Methods:Selected publications include original articles and review papers that report on studies of CVS risks and consequences related to childhood obesity. Some papers that contain data from adults studies are also included if the contents help to explain some underlying mechanisms or illustrate the continuation of related CVS changes into adulthood. Results: Obese children and adolescents have an increased risk for CVS complications that include elevation of blood pressure, clustering of CVS risk factors (Metabolic Syndrome), changes to arterial wall thickness, elasticity and endothelium, as well as changes in left ventricular structure and function. Some of these cardiovascular problems may be initiated or potentiated by obstructive sleep apnoea that can accompany obesity in children. Many of such changes have been noted to reverse or improve with weight reduction. Conclusions:Early development of CVS risks in obese children and the possible continuation of CVS complications into adulthood have been observed. Obstructive sleep apnoea in obese children can further contribute to such CVS risks. These findings underscore the importance of prevention of childhood obesity as a priority over management of obesity in children. The prevalence of obesity has risen by three-folds or more in many countries since 1980. In 2005, it was estimated that globally there are about 1.6 billion overweight adults and at least 400 million of them are obese. This increase in the prevalence of adults being overweight and obese comes with a heavy price. The cost of healthcare has significantly increased and is expected to increase even more because of the close association between obesity and various chronic diseases. Key words: Endothelial function, Hypertension, Metabolic syndrome, Obstructive sleep apnoea

Increased sympathetic reactivity may predict insulin resistance: an 18-year follow-up study

Insulin resistance and sympathetic activity are related by a positive feedback system. However, which precedes the other still remains unclear. The present study aimed to investigate the predictive role of sympathoadrenal activity in the development of insulin resistance in an 18-year follow-up study. We also examined whether reactivity to 2 different stress tests, a cold pressor test and a mental stress test, would differ in their predictive power. The 2 tests are supposed to represent different reactivity mechanisms: alpha- and beta-adrenergic responses, respectively. At entry, arterial plasma epinephrine and norepinephrine concentrations were measured in 99 healthy men (age, 19.3 +/- 0.4 years, mean +/- SD) during rest, a mental stress test, and a cold pressor test. Fasting plasma glucose concentration was measured at entry and at follow-up. Insulin resistance at follow-up was calculated using the homeostasis model assessment of insulin resistance (HOMA-IR). Eighty subjects (81%) were eligible for follow-up after 18.0 +/- 0.9 years (mean +/- SD). The norepinephrine responses to cold pressor test at entry predicted plasma glucose concentration (r = 0.301, P = .010) and HOMA-IR (r = 0.383, P = .004) at follow-up in univariate analyses. In multiple regression analyses, corrected for fasting glucose at entry, family history of diabetes, blood pressure-lowering medication, body mass index at entry, and level of exercise, norepinephrine response to cold pressor test was found to be a positive predictor of future HOMA-IR (P = .010). This is the first long-term follow-up study in white subjects showing that sympathetic reactivity predicts future insulin resistance 18 years later. These findings may provide further insights into the pathophysiologic mechanisms of insulin resistance.

Association between heart rate and multiple risk factor syndrome: cross-sectional analysis of a screened cohort in Okinawa, Japan

BACKGROUND

Increased heart rate (HR) and metabolic syndrome are risk factors for cardiovascular morbidity and mortality, but their relationship has not been studied in a large, screened cohort.

METHODS AND RESULTS

The association between HR and multiple risk factor syndrome, resembling metabolic syndrome, was examined in participants of a health evaluation program in 1997. Of the 8,432 subjects (5,223 males, 3,209 females, 18-89 years of age), 1,502 (1,185 males, 317 females) were diagnosed with multiple risk factor syndrome and these subjects had higher HR than those without the syndrome (p<0.0001); subjects with a higher number of risk factors had higher HR than those with fewer risk factors (males, p<0.0001; females, p<0.0001). After adjusting for age, sex, and lifestyle factors, subjects within the highest HR quartile had a 2.5-fold higher risk for multiple risk factor syndrome than those in the lowest quartile (p<0.0001). An increase of 10 beats/min was associated with an approximately 30% increase in the risk for multiple risk factor syndrome.

CONCLUSIONS

A higher HR is closely associated with multiple risk factor syndrome.

Microcirculation in obesity: an unexplored domain

Obesity is traditionally linked to diabetes and cardiovascular diseases. Very recent experimental, clinical and epidemiological, sometimes provocative, data challenge this automaticity by showing that not the amount but the distribution of fat is the important determinant. Moderate abdominal fat accumulation may thus be more harmful than even consequent overweight. In view of the worldwide burden of obesity, factors leading to it in children and young adults must urgently be identified. Since obesity is a very complex cardiometabolic situation, this will require to focus investigations on uncomplicated obese subjects and adequate animal models. The recent discovery of intergenerational transmissions of obesity risk factors and also the key role played by gestational and perinatal events (epigenetic factors) give rise to completely new concepts and research avenues. Considering the potential close relationship between microcirculation and tissue metabolism, demonstrations of structural and/or functional abnormalities in microvascular physiology very early in life of subjects at risk for obesity might provide a solid basis for further investigations of such links. Microcirculation(arterioles, capillaries and venules) is conceivably a key compartment determining over one or several decades the translation of genetic and epigenetic factors into fat accumulation. Available animal models should serve to answer this cardinal question.

Acute elevation of plasma non-esterified fatty acids increases pulse wave velocity and induces peripheral vasodilation in humans in vivo

Plasma NEFA (non-esterified fatty acid) concentrations are elevated in patients with obesity. In the present study we first aimed to provide an integral haemodynamic profile of elevated plasma NEFAs by the simultaneous assessment of blood pressure, pulse wave velocity, FBF (forearm blood flow) and sympathetic nervous system activity during acute elevation of NEFAs. Secondly, we hypothesized that NEFA-induced vasodilation is mediated by adenosine receptor stimulation. In a randomized cross-over trial in healthy subjects, Intralipid® was infused for 2 h to elevate plasma NEFAs. Glycerol was administered as the Control infusion. We assessed blood pressure, pulse wave velocity, FBF (using venous occlusion plethysmography) and sympathetic nervous system activity by measurement of noradrenaline and adrenaline. During the last 15 min of Intralipid®/Control infusion, the adenosine receptor antagonist caffeine (90 μg·min−1·dl−1) was administered into the brachial artery of the non-dominant arm. Compared with Control infusion, Intralipid® increased pulse wave velocity, SBP (systolic blood pressure) and pulse pressure, as well as FBF (from 1.8±0.2 to 2.7±0.6 and from 2.3±0.2 to 2.7±0.6 ml·min−1·dl−1 for Intralipid® compared with Control infusion; P<0.05, n=9). Although in a positive control study caffeine attenuated adenosine-induced forearm vasodilation (P<0.01, n=6), caffeine had no effect on Intralipid®-induced vasodilation (P=0.5). In conclusion, elevation of plasma NEFA levels increased pulse wave velocity, SBP and pulse pressure. FBF was also increased, either by baroreflex-mediated inhibition of the sympathetic nervous system or by a direct vasodilating effect of NEFAs. As the adenosine receptor antagonist caffeine could not antagonize the vasodilator response, this response is not mediated by adenosine receptor stimulation.

Association of metabolic syndrome with arterial compliance in children and adolescents

The association of metabolic syndrome (MS) with arterial compliance in children and adolescents was explored. 337 subjects (188 men and 149 women) aged 6-18 (10.95 ± 3.01) years, out of "Beijing Child Metabolic Syndrome Study", were divided into three case groups (one component, two components, three & more components of MS) and one control group based on the Cook's MS definition in children and adolescents. Measurements including anthropometry, blood pressure, fasting plasma glucose and insulin, serum lipid profile were done. Homeostasis model assessment for insulin resistance (HOMA-IR) index was calculated for estimating individual insulin resistance. Arterial compliance was measured using digital pulse wave analyzing method from the pulse trace machine (Micro medical, London), and then the stiffness index (SI) was determined. The mean value of SI in MS group was significant higher than that in control group [(7.69 ± 1.63) vs (6.25 ± 0.86) m/s, P<0.01]. With the increase of the clustering of MS components, SI and HOMA-IR were gradually increased. After taking account of gender, age and pubertal development, the partial correlation analysis showed that the amount of components of MS and HOMA-IR were positively correlated with SI (both P values were less than 0.05). The arterial compliance of MS group was significantly lowered in children and adolescents, and with the increase of the clustering of MS components, arterial compliance was gradually decreased. It was suggested that arterial compliance assessment in children and adolescents was important for early prevention of cardiovascular diseases.

Heart rate as a predictor of development of sustained hypertension in subjects screened for stage 1 hypertension: the HARVEST Study

OBJECTIVE

Whether heart rate predicts the development of sustained hypertension in individuals with hypertension is not well known. We carried out a prospective study to investigate whether clinic and ambulatory heart rates assessed at baseline and changes in clinic heart rate during 6 months of follow-up were independent predictors of subsequent blood pressure (BP).

METHODS

The study was conducted in a cohort of 1103 white, stage 1 hypertensive individuals from the HARVEST study, never treated for hypertension and followed-up for an average of 6.4 years. Data were adjusted for baseline BP, age, sex, body fatness, physical activity habits, parental hypertension, duration of hypertension, cigarette smoking, alcohol consumption, and change of body weight from baseline.

RESULTS

Clinic heart rate and heart rate changes during the first 6 months of follow-up were independent predictors of subsequent systolic blood pressure (SBP) and diastolic blood pressure (DBP) regardless of initial BP and other confounders (all P < 0.01). A significant interaction was found between sex (male) and baseline resting heart rate on final SBP (P = 0.017) and DBP (P < 0.001). The ambulatory heart rate and the heart rate white-coat effect did not add prognostic information to that provided by the clinic heart rate. Patients whose heart rate was persistently elevated during the study had a doubled fully adjusted risk (95% confidence interval 1.4-2.9) of developing sustained hypertension in comparison with subjects with a normal heart rate.

CONCLUSIONS

Baseline clinic heart rate and heart rate changes during the first few months of follow-up are independent predictors of the development of sustained hypertension in young persons screened for stage 1 hypertension.

Obstructive sleep apnea and insulin resistance: a role for microcirculation?

Obstructive sleep apnea is an increasingly recognized medical problem. The recent attention to its frequency in the general population and its important role in metabolic, vascular, and behavioral aspects have sharply increased the number and nature of investigations, thereby revealing new aspects that open new approaches in research. Whereas obstructive sleep apnea is a well-known phenomenon accompanying obesity and diabetes, new findings strongly suggest that this close relationship may also operate in the opposite direction. Indeed obstructive sleep apnea may be a primary feature inducing or aggravating a series of vascular and metabolic disturbances closely resembling the metabolic syndrome. This review will discuss established and potential mechanisms responsible for these changes. Obstructive sleep apnea indeed appears to gather all the elements necessary to induce insulin resistance, hypertension, and possibly heart failure. After careful analysis of these modifications and considering how they are intertwined, we propose that microcirculation could represent the common denominator mediating the progression of this pathology, as it is eventually the case in the metabolic syndrome and diabetes domain. This plausible hypothesis is discussed in detail and should be verified by appropriate preclinical and clinical protocols, which are now achievable by using noninvasive techniques in humans.

Pathogenesis and etiology of essential hypertension: role of dietary carbohydrate

The development of essential hypertension (EH) is proposed to be the result of a cascade of metabolic alterations, with high insulin levels/hyperinsulinemia and an abnormal reaction to the vasodilatory effect of insulin as the initiating factors. It is well established that insulin causes vasodilatation of peripheral resistance vessels. In normal subjects, this insulin-induced vasodilatation and decrease of the peripheral vascular resistance (PVR) is compensated by an SNS-mediated re-vasoconstriction in order to avoid hypotension, with the net effect of a slight decrease in blood pressure and no significant effect on peripheral vascular resistance. In contrast, in genetically predisposed subjects, prone to the development of essential hypertension, the insulin-induced vasodilatation is compensated by an increased heart rate and cardiac output (to avoid hypotension), mediated by an abnormal sympathetic overactivity, (characterised by high norepinephrine spillover rates and (frequently) a hyperdynamic circulation), while the PVR remains low during the early phase of developing EH. During the course of chronic hypertension, the SNS-overactivity leads to progressive trophic alterations of vessel walls, and structural and functional vascular remodeling, with narrowing of arterial resistance vessels and an increasing PVR. Vascular remodeling and lumen narrowing not only affect peripheral resistance vessels, but also kidney vessels. Narrowing and decreased distensibility of preglomerular kidney vessels lead to chronic activation of the Renin-Angiotensin-Aldosterone-System, with reinforcement and fixation of hypertension. High-glycemic index nutrition is suggested to play a key role in the etiology of hypertension: The chronic stimulus of pancreatic beta-cells due to high-glycemic index nutrition may cause cell hypertrophy and dysfunction, resulting in postprandial hyperinsulinemia, and -- in susceptible subjects -- the development of EH. Since significant evidence suggests that hyperinsulinemia also represents a key factor for the development of obesity, insulin resistance and the metabolic syndrome, the well-known common association of EH and these metabolic alterations becomes quite understandable.

Effects of morin on blood pressure and metabolic changes in fructose-induced hypertensive rats

High fructose (HF) feeding induces a moderate increase in blood pressure in rats, which is associated with insulin resistance, hyperinsulinemia, and hypertriglyceridemia. In the present study, we examined the chronic effect of morin, a flavonoid isolated from medicinal plants, on blood pressure, lipid profiles, and serum insulin and glucose in HF-induced hypertensive rats. Rats were divided into control group and HF-fed group during the first three weeks of experiments. Then, rats were further divided into four groups and treated for 4 more weeks as follows: 1) control group; 2) morin-treated (intraperitoneal 5 mg/kg/d) control group; 3) HF-fed group; 4) morin-treated, HF-fed group (n=8, each group). Morin-treated HF-fed group showed lower systolic blood pressure (SBP) (132.0+/-2.5 mmHg vs. 142.8+/-2.2 mmHg, p<0.05), lower serum insulin level (1.21+/-0.27 vs. 2.73+/-0.30 microIU/dl, p<0.05), and lower plasma triglycerides (47.8+/-5.0 vs. 65.5+/-5.0 mg/dl, p<0.05) than those of HF-fed group. Morin treatment also suppressed mRNA expression of endothelin-1 (ET-1) in the thoracic aorta from HF-induced hypertensive rats. Moreover, decreased renal sodium excretion in HF-induced hypertensive rats was ameliorated by morin treatment. In conclusion, the results of this study demonstrate that morin has an anti-hypertensive effect in HF-induced hypertensive rats. This effect of morin may be associated with the suppression of serum insulin and plasma triglyceride level, with the down-regulation of ET-1 in the thoracic aorta, and with the partial amelioration of renal dysfunctions in HF-induced hypertensive rats.

Long-term prognostic value of resting heart rate in patients with suspected or proven coronary artery disease

AIMS

Heart rate reduction is the cornerstone of the treatment of angina. The purpose of this study was to explore the prognostic value of heart rate in patients with stable coronary artery disease (CAD).

METHODS AND RESULTS

We assessed the relationship between resting heart rate at baseline and cardiovascular mortality/morbidity, while adjusting for risk factors. A total of 24 913 patients with suspected or proven CAD from the Coronary Artery Surgery Study registry were studied for a median follow-up of 14.7 years. All-cause and cardiovascular mortality and cardiovascular rehospitalizations were increased with increasing heart rate (P<0.0001). Patients with resting heart rate > or =83 bpm at baseline had a significantly higher risk for total mortality [hazard ratio (HR)=1.32, CI 1.19-1.47, P<0.0001] and cardiovascular mortality (HR=1.31, CI 1.15-1.48, P<0.0001) after adjustment for multiple clinical variables when compared with the reference group. When comparing patients with heart rates between 77-82 and > or =83 bpm with patients with a heart rate < or =62 bpm, the HR values for time to first cardiovascular rehospitalization were 1.11 and 1.14, respectively (P<0.001 for both).

CONCLUSION

Resting heart rate is a simple measurement with prognostic implications. High resting heart rate is a predictor for total and cardiovascular mortality independent of other risk factors in patients with CAD.

Influence of metabolic syndrome on arterial stiffness and its age-related change in young adults: the Bogalusa Heart Study

Increased arterial stiffness is associated with risk variables of metabolic syndrome in middle-aged and older adults. However, information regarding the influence of the metabolic syndrome on arterial stiffness and its rate of change with age in young adults is limited. These aspects were examined in a sample of 806 asymptomatic, healthy young adults aged 24-44 years from a black-white community. Brachial to ankle pulse wave velocity (baPWV) measured by an oscillometric method was used as an index of arterial stiffness. baPWV increased with the increasing number of metabolic syndrome components, defined by National Cholesterol Education Program Adult Treatment Panel III (1256, 1314, and 1422 cm/s for those with 0, 1-2, and 3-5 components, respectively, P for trend <0.001). Furthermore, the rate of change (slope) of baPWV with age increased as the number of metabolic syndrome components increased (4.1, 10.7, and 18.7 cm/s per year for those with 0, 1-2, and 3-5 components, respectively; P for comparison of slopes <0.001). These findings by showing the deleterious effects of metabolic syndrome on arterial stiffness and its age-related increase in young adults underscore the importance of this syndrome in cardiovascular risk assessment even in a younger population. Further longitudinal studies are needed to confirm the current cross-sectional findings.

Correlates of carotid artery stiffness in young adults: The Bogalusa Heart Study

Decreased arterial elasticity, an independent risk factor for cardiovascular (C-V) disease, is associated with C-V risk factors in middle-aged and older individuals. However, information is limited in this regard in young adults. This aspect was examined in a community-based sample of 516 black and white subjects aged 25-38 years (71% white, 39% male). The common carotid artery elasticity was measured from M-mode ultrasonography as Peterson's elastic modulus (Ep) and relative wall thickness-adjusted Young's elastic modulus (YEM). Blacks and males had higher Ep (P < 0.05); males had higher YEM (P < 0.0001); and blacks had higher wall thickness (P < 0.01). For the entire sample adjusted for race and gender both Ep and YEM correlated significantly (P < 0.05-0.0001) with age, BMI, waist, systolic and diastolic blood pressures, heart rate, product of heart rate and pulse pressure, triglycerides, total cholesterol to HDL cholesterol ratio, insulin and glucose. In a multivariate regression model that included hemodynamic variables, systolic blood pressure, product of heart rate and pulse pressure, age, triglycerides, BMI, and male gender (for YEM only) were independent correlates of Ep (R2 = 0.38) and YEM (R2 = 0.25). When the hemodynamic variables were excluded from the model, age, triglycerides, BMI, black race (Ep only), male gender, parental history of hypertension, HDL cholesterol (inverse association), and insulin (marginal significance) remained independent correlates of Ep (R2 = 0.20) and YEM (R2 = 16). Both Ep and YEM increased (P for trend P < 0.0001) with increasing number of independent continuous risk factors (defined as values above or below the age, race, and gender-specific extreme quintiles) that were retained in the regression models. The observed increasing arterial stiffness (or decreased elasticity) with increasing number of risk factors related to insulin resistance syndrome in free-living, asymptomatic young adults has important implications for prevention.

Microcirculation in insulin resistance and diabetes: more than just a complication

The microvascular bed is an anatomical entity which is governed by specific, highly regulated mechanisms which are closely adapted to the specific function of each vascular segment. Among those, small arteriolar vasomotion and capacity of small vessels to constrict in response to physical and humoral stimuli play a major role. Other processes of importance for the adequacy of nutritive perfusion are haemorheological properties of whole blood and red cells, adhesiveness of leukocytes and capillary permeability. This review provides some description of these phenomena, how they impact on organ function and how they appear in diabetes. Metformin, as a unique example among the drug arsenal, exerts various effects preferentially at the level of smallest vessels (arterioles, capillaries, venules). This review summarises our actual knowledge and includes several new data showing its high potential for reducing microvascular dysfunction. Most of these unique properties have also been demonstrated in non-diabetic animals or humans, suggesting they are intrinsic to the drug and not secondary to diabetic metabolic improvement. A particular focus is put on the relevance of metformin's capacity to stimulate slow wave arteriolar vasomotion and improve functional capillary density, whereby nutritive flow can be re-established. Finally, the implication of microcirculation in other aspects of insulin resistance and diabetes, such as macroangiopathy and metabolic control, is discussed and strengthens the concept of a broad involvement of microvascular dysfunction in these diseases as well as the potential interest of introducing adapted treatment early in the history of a patient's diabetes.

The burden of uncontrolled hypertension: morbidity and mortality associated with disease progression

Even small elevations above optimal blood pressure values (<120/80 mm Hg) increase the likelihood of developing hypertension (blood pressure >or=140/90 mm Hg) and incurring target organ damage. Until recently, the main emphasis in hypertension treatment had been lowering diastolic blood pressure; however, in the past decade, the important contributions of systolic hypertension, increased pulse pressure, and a blunted reduction in nocturnal blood pressure have been described. Primary hypertension arises from complex, interrelated pathologies. Among the contributors are genetic, environmental, metabolic, vascular, and endothelial factors. Signs of target organ damage herald a poorer prognosis and may present in the heart, blood vessels, kidneys, brain, or eyes. Later consequences include cardiac, cerebrovascular, vascular, and renal morbidities and death. The goal in treating hypertension is to prevent cardiovascular and renal complications. Thus, hypertensive patients with high-normal blood pressure values may benefit from intensive lifestyle interventions to further reduce blood pressure. This is particularly true in patients with additional cardiovascular risk factors. Because of the complex nature of hypertension, it is not surprising that single antihypertensive agents normalize blood pressure for less than a majority of hypertensive patients. Using combination antihypertensive therapy consisting of agents from two or more different antihypertensive drug classes not only increases the likelihood of achieving the target blood pressure goal, but also offers the potential for greater protection against target organ damage by targeting separate pathologic mechanisms.

The potential role of adenosine in the pathophysiology of the insulin resistance syndrome

An increased intracellular availability of the co-enzyme A esters of long-chain fatty acids is thought to underlie many aspects of the insulin resistance syndrome. However, the cause of clustering of a hyperdynamic circulation, sympathetic activation, hypertension, hyperuricaemia, and a raised haematocrit in the insulin resistance syndrome remains to be elucidated. We propose a mechanism that expands the etiological role of long-chain fatty acids. By inhibiting adenine nucleotide translocators, elevated intracellular concentrations of the co-enzyme A esters of long-chain fatty acids impair mitochondrial oxidative phosphorylation. This is expected to result in a chronic systemic increase in extracellular adenosine concentrations. As adenosine stimulates the sympathetic nervous system, induces systemic vasodilatation, stimulates erythropoiesis, and induces renal vasoconstriction with renal sodium retention, increased extracellular ADO concentrations may be the common denominator explaining the above-mentioned and still unexplained phenomena associated with the insulin resistance syndrome. Along the same lines, hyperuricaemia can be explained by the fact that adenosine is broken down to urate and because of increased renal urate retention.

Birth weight and the metabolic syndrome: thrifty phenotype or thrifty genotype?

BACKGROUND

Inverse correlations have been reported between birth weight and the Metabolic Syndrome (abdominal obesity, insulin resistance, hyperinsulinemia, glucose intolerance, dyslipidemia, and hypertension). These correlations are thought to reflect primarily nutritional inadequacies during fetal and early life. We explored familial influences on these correlations.

METHODS

Using birth weight data on 602 subjects from 65 pedigrees, we partitioned phenotypic correlations into familial and non-familial. The former are usually regarded as reflecting primarily genetic influences, although they may also reflect environmental influences that are shared by family members, and the latter reflect random environmental influences.

RESULTS

A consistent pattern of positive familial and inverse non-familial correlations were observed. The strongest familial correlations were between birth weight and fasting insulin (r = 0.58, p = 0.002), leptin (r = 0.48, p = 0.021), split proinsulin (r=0.51, p = 0.090), and heart rate (r = 0.39, p = 0.037). An inverse familial correlation was observed with HDL cholesterol (r = -0.28, p = 0.018). Non-familial correlations were weaker and only two-- subscapular-to-triceps skinfold ratio and fasting insulin--were statistically significant.

CONCLUSION

Since the familial and non-familial correlations were in opposite directions, we attribute the former to the pleiotropic effects of genes. Specifically, we conclude that genes that increase birth weight also worsen the Metabolic Syndrome in adult life. Since the inverse correlations reported in the literature reflect mainly cohorts born in the early part of the 20th century, improved maternal nutrition since then may have allowed the expression of genetic influences in our participants, all of whom were born after 1950.

Consequences of the increased autonomic nervous drive in hypertension, heart failure and diabetes

It is estimated that 40 million people in the USA have hypertension, 14 million are diabetic and 4 million suffer congestive heart failure. Since all three conditions are age-related, as the longevity in industrialized societies continues to improve, the overall burden of congestive heart failure, hypertension and diabetes will increase. These major diseases of civilization are characteristically associated with an increased autonomic cardiovascular drive. In our terminology the output that emanates from the central nervous system via sympathetic and parasympathetic efferents is referred to as "tone". The overall "drive" depends on the balance between inhibitory (parasympathetic) and excitatory (sympathetic) tone and the organ's responsiveness to that tone. The responsiveness, in turn, depends on the receptors' properties as well as on the intrinsic functional or anatomic properties of the responding organs. These components can change independently. For example, in the course of hypertension the alpha-adrenergic responsiveness increases whereas the beta-adrenergic responses are down-regulated. Another example is: plasma noradrenaline and sympathetic tone are increased in elderly subjects but their circulation does not show any tell-tale response of increased sympathetic tone, presumably because the responses to sympathetic tone decrease with aging. These complex interactions between the autonomic tone and organ responsiveness determine to a great extent the overall clinical impact of the autonomic abnormality in hypertension, non-insulin-dependent diabetes mellitus and in congestive heart failure. The major thesis of this review is that, whether primary or secondary, whether easily discerned or hidden, an enhanced autonomic drive, independent of the underlying condition, greatly increases the risk of poor cardiovascular outcomes. It follows that targeting the underlying autonomic imbalance in congestive heart failure, hypertension and diabetes may not only be pathophysiologically sound but such an approach may also lead to better outcomes.

Heart rate as a risk factor for atherosclerosis and cardiovascular mortality: the effect of antihypertensive drugs

The aim of this review is to highlight the importance of heart rate (HR) as a risk factor for cardiovascular disease, and to discuss the classes of drugs which can be potentially useful in clinical conditions in which an elevated HR may be present. Numerous studies have shown that high resting HR is prospectively related to the development of atherosclerosis and of cardiovascular events. This relationship was independent of other major risk factors for atherosclerosis and was observed in the general population, in elderly people, in hypertensive cohorts and in patients with myocardial infarction or heart failure. The clustering of several risk factors in individuals with fast heart rate may explain why cardiovascular morbidity is higher in individuals with tachycardia. Sympathetic overactivity seems to be responsible for both the increase in HR, blood pressure and the metabolic abnormalities. Experimental studies in monkeys have shown that HR can also exert a direct atherogenetic action on the arteries through increased wall stress. Moreover, tachycardia can favour the occurrence of ventricular arrhythmias and sudden death. Reduction of HR appears as an additional goal of antihypertensive therapy. If fast HR in hypertension is a marker of increased sympathetic tone, agents which decrease HR through a decline of sympathetic outflow should be particularly efficacious. Beta-blockers retard the development of coronary atherosclerosis in cholesterol-fed monkeys and have proven to be beneficial in patients with myocardial infarction or with heart failure, but their efficacy appear limited in hypertension, probably on account of their unfavourable metabolic profile. Phenylalkylamines are devoid of this untoward effect, and seem to act also through inhibition of sympathetic discharge from the CNS. Mibefradil, a more recent calcium antagonist that selectively blocks voltage-dependent T-type calcium channels decreases HR without affecting left ventricular contractility. New drugs with agonistic properties at the I1-imidazoline receptors of the rostral ventrolateral medulla are effective in reducing blood pressure and HR by inhibiting the sympathetic outflow and improved metabolic parameters in obese or fructose-fed rats. The goal of antihypertensive therapy in the future will be to prevent or reverse those functional abnormalities which accompany the hypertensive condition. In patients with tachycardia the reduction of HR appears a desirable additional goal of therapy.

Parental hyperdynamic circulation predicts insulin resistance in offspring: The Tecumseh Offspring Study

Controversy surrounds the pathogenetic mechanisms of the relationship between hyperdynamic circulation and insulin resistance. Two hundred eight children and young adults (mean age, 17.2+/-3.0 years; range, 11 to 26 years) from the Tecumseh Offspring Study whose parents had been assessed with Doppler echocardiography at the age of 34 years during the previous Tecumseh Blood Pressure Study were considered for this analysis. Offspring data were stratified according to tertiles of parental cardiac index. Parents in the top cardiac index tertile had increased heart rate (P=0.001), stroke volume (P=0.0001), left ventricular fractional shortening (P=0.02), and plasma epinephrine (P=0.02) compared with parents in the other tertiles. Body mass index (BMI) and blood pressure were similar in all groups. Offspring of parents with a high cardiac index had greater BMI (P=0.001), skinfold thickness (P=0.008), and waist/hip ratio (P=0.02), higher diastolic blood pressure (P=0.02) and plasma insulin level (P=0.001), and higher heart rate during Stroop's color test (P=0.02) than offspring of parents with a lower cardiac index. In a multivariate regression analysis, offspring BMI was predicted by parental BMI and cardiac index (P=0.0001 and 0.003, respectively). The mother-child relationship explained most of the cardiac index-BMI association. In summary, parental hyperdynamic circulation was an important predictor of overweight, abnormal fat distribution, increased blood pressure, and hyperinsulinemia in offspring. Our results illustrate the complexity of interaction between a genetic tendency and its phenotypic expression. We speculate that the degree of beta-adrenergic responsiveness may be a major determinant of the phenotypic differences between the parents and offspring found in this study.

Heart rate and subsequent blood pressure in young adults: the CARDIA study

The objective of the present study was to examine the hypothesis that baseline heart rate (HR) predicts subsequent blood pressure (BP) independently of baseline BP. In the multicenter longitudinal Coronary Artery Risk Development in Young Adults study of black and white men and women initially aged 18 to 30 years, we studied 4762 participants who were not current users of antihypertensive drugs and had no history of heart problems at the baseline examination (1985-1986). In each race-sex subgroup, we estimated the effect of baseline HR on BP 2, 5, 7, and 10 years later by use of repeated measures regression analysis, adjusting for baseline BP, age, education, body fatness, physical fitness, fasting insulin, parental hypertension, cigarette smoking, alcohol consumption, oral contraceptive use, and change of body mass index from baseline. The association between baseline HR and subsequent systolic BP (SBP) was explained by multivariable adjustment. However, HR was an independent predictor of subsequent diastolic BP (DBP) regardless of initial BP and other confounders in white men, white women, and black men (0.7 mm Hg increase per 10 bpm). We incorporated the part of the association that was already present at baseline by not adjusting for baseline DBP: the mean increase in subsequent DBP was 1.3 mm Hg per 10 bpm in white men, white women, and black men. A high HR may be considered a risk factor for subsequent high DBP in young persons.

Energy expenditure of young Polynesian and European women in New Zealand and relations to body composition

BACKGROUND

Reduced energy expenditure and excessive energy intake have been hypothesized to cause obesity. New Zealanders of Polynesian origin have a higher prevalence of obesity than do those of European origin.

OBJECTIVE

We investigated relations between components of energy expenditure and body composition.

DESIGN

We measured total energy expenditure (TEE) and resting metabolic rate (RMR) in 80 young women [40 New Zealand (NZ) Polynesian and 40 NZ European] aged 18-27 y by the doubly labeled water method and indirect calorimetry, respectively. Each group was partitioned into nonobese and obese on the basis of percentage body fat.

RESULTS

TEE and body weight were highly correlated in nonobese NZ Europeans (n = 23, r = 0.76, P < 0.001), obese NZ Europeans (r = 0.58, P = 0.016), and nonobese NZ Polynesians (n = 25, r = 0.59, P = 0.002) but not in obese NZ Polynesians (r = 0.11, P = 0.70). Activity energy expenditure (AEE = TEE - RMR) was similar in obese Polynesians and Europeans (mean+/-SD: 5.5+/-2.2 and 5.2+/-1.9 MJ/d, respectively), but significantly higher in nonobese Polynesians (5.7+/-2.5 MJ/d) than in their European counterparts (3.8+/-1.9 MJ/d, P = 0.005). Similar trends were seen when AEE adjusted for body weight and TEE/RMR were compared among the subgroups. Body weight and RMR together accounted for 66% of the variation in TEE for the European group but only 17% for the Polynesian group.

CONCLUSION

Care should be taken in applying "Caucasian norms" relating to energy expenditure to NZ Polynesian people.

Insulin stimulates epinephrine release under euglycemic conditions in humans

In healthy subjects, acute physiological hyperinsulinemia induces activation of the sympathetic nervous system, but in the absence of hypoglycemia, plasma epinephrine levels have not been found to increase during insulin administration. However, the venous level of epinephrine reflects the net result of release, clearance, and uptake and therefore is not a good measure of adrenomedullary epinephrine secretion. The influence of 90 minutes of euglycemic physiological hyperinsulinemia (60 mU x m(-2) x min(-1); plasma insulin concentration, approximately 700 pmol x L[-1]) on epinephrine kinetics using the 3H-epinephrine tracer method was studied in 12 healthy normotensive, non-obese subjects. After bolus injection, [3H]-epinephrine was continuously infused with arterial and venous blood sampling at regular intervals, enabling calculation of total body (systemic) and forearm epinephrine release and clearance. Studies were performed in the basal state and during sympathetic stimulation by lower-body negative pressure (LBNP) of -15 mm Hg for 15 minutes. Control experiments ("sham" clamps, but with LBNP) were performed in four of the 12 individuals. Euglycemic hyperinsulinemia (all arterial glucose samples > or = 4.2 mmol x L[-1]) induced an increase of the arterial epinephrine concentration (P = .03), and tended to increase total body epinephrine release (P = .08). Total body epinephrine clearance did not change during hyperinsulinemia. The insulin-induced increase in forearm blood flow ([FBF] by plethysmography, from 3.0 +/- 0.4 to 3.8 +/- 0.6 mL x dL(-1) x min(-1), P = .01) was strongly correlated with the increase in arterial epinephrine (r = .78, P < .01). Plasma epinephrine concentrations did not change during control experiments (sham clamp). Sympathetic stimulation alone as induced by LBNP did not stimulate epinephrine release. However, the combination of insulin and LBNP significantly increased epinephrine release (from 0.37 +/- 0.06 to 0.56 +/- 0.12 nmol x m(-2) x min(-1), P = .03). We conclude that acute physiological hyperinsulinemia under euglycemic conditions induces epinephrine release. This effect is enhanced when hyperinsulinemia is combined with sympathetic stimulation by LBNP. Due to increased forearm removal, venous epinephrine concentrations hardly change. Epinephrine release was strongly correlated with the hemodynamic effects of insulin.

Haemodynamic actions of insulin

Several lines of evidence indicate a significant association between insulin and cardiovascular disease. This association might be explained by direct (cardio) vascular effects of insulin. Two hemodynamic actions of insulin are discussed in this review; it induces direct vasodilation in skeletal muscle and stimulation of the sympathetic nervous system. These closely linked effects normally offset each other. Although more insight has been obtained into responses in insulin-resistant individuals and possible mechanisms, direct evidence to support a causative role for insulin is not yet available.

Blood pressure, insulin resistance and left ventricular function in alcoholics

OBJECTIVE

To estimate the arterial blood pressure, left ventricular function and insulin secretion in alcoholics.

DESIGN

We examined hospitalized patients between the second and seventh day of acute alcohol withdrawal and after a month of abstinence by 24 h ambulatory blood pressure monitoring, a standard oral glucose-tolerance test with determination of insulinaemia, two-dimensional and M-mode echocardiography and pulsed-wave Doppler statistical analysis was performed using Student's t test P < 0.05 was considered statistically significant

PATIENTS

Fifty alcoholics aged 36.3 +/- 5.4 years with a history of alcohol abuse for a mean of 12 years.

MAIN OUTCOME

We expected the cessation of drinking to exert an influence by lowering the blood pressure and left ventricular function with a concomitant lowering of the insulin resistance.

RESULTS

During acute alcohol withdrawal the systolic (121.6 +/- 7.7 versus +115.8 +/- 8.7 mmHg) and diastolic blood pressures (74.5 +/- 6.3 versus 72.0 +/- 7.9 mmHg) were significantly higher. The nocturnal fall in blood pressure was smaller and the variability of the blood pressure was blunted. This period was characterized by hyperinsulinaemia detected by the glucose-tolerance test [In (SUMins) 8957 +/- 0.47 versus 8558 +/- 0.651] correlated to hyperdynamic circulation (cardiac index 3.38 +/- 0.86 versus 3.09 +/- 0.69 I/min per m2). The early: late atrial filling ratio had increased significantly after 1 month of abstinence (1.98 +/- 0.43 versus 2.08 +/- 0.50).

CONCLUSIONS

One month of abstinence from drinking decreases the blood pressure and improves the diurnal profile of the blood pressure and the left ventricular diastolic function. Hyperinsulinaemia, which is observed during acute restriction of alcohol consumption, could be one of the causes responsible for hyperdynamic circulation.

Psychosocial stress and the insulin resistance syndrome

We examined the association between psychosocial stress-related variables and insulin resistance syndrome (IRS) risk-factor clustering. In 90 middle-aged male volunteers, psychosocial stress-related variables, defined as feelings of excessive tiredness and as personality and behavioral factors reflecting a stress-inducing life-style (type A behavior, hostility, and anger), were significantly correlated with the hyperinsulinemia, hyperglycemia, dyslipidemia, hypertension, increased abdominal obesity, and increased plasminogen activator inhibitor-1 (PAI-1) antigen comprising the IRS. The correlations remained significant after adjusting for body mass index (BMI), age, educational level, smoking status, alcohol consumption, and physical activity. However, the different stress-related factors reflected different risk-factor clustering profiles. Type A behavior was associated with normotension and a normal metabolic profile (canonical r = .50, chi2(36) = 59.1, P = .008). Hostility was related to elevated systolic blood pressure (SBP) and elevated triglycerides (TGs) (canonical r = .38, chi2(14) = 23.2, P = .052), whereas feelings of excessive tiredness were related to abdominal obesity, augmented glycemic responses to glucose ingestion, dyslipidemia, and increased PAI-1 antigen (canonical r = .39, chi2(24) = 36.8, P = .046). Although hostility and feelings of excessive tiredness have partly overlapping but clearly different clinical and metabolic correlates, their combination represents a full-blown IRS. Thus, even though insulin resistance is presumably to some extent genetically determined, these results suggest that considering psychosocial stress may be beneficial in understanding IRS risk-factor clustering.

Insulin resistance syndrome and autonomically mediated physiological responses to experimentally induced mental stress in adolescent boys

We investigated the relationship between hemodynamic and other autonomically mediated responses to experimentally induced mental stress and the parameters of the insulin resistance syndrome (IRS) in 48 healthy adolescent boys. Mental stress was induced with mental arithmetic and the Stroop Color-Word Test. Heart rate (HR), finger blood volume (FBV), and skin conductance level (SCL) were recorded continuously during task performance. IRS parameters measured were serum insulin, high-density lipoprotein (HDL) cholesterol, serum triglyceride (TG), systolic blood pressure (SBP), subscapular skinfold (SSF), and subscapular to triceps skinfold ratio (STR). The results indicated that a high level and an increasing linear trend of HR and FBV during task performance were related, independently of each other and of body mass index (BMI), to a high insulin concentration. An increasing linear trend of HR during mental stress was also related to high SSFs independently of MI. In addition, a high SCL during task performance was associated with high TG levels, SSFs, and STRs. It is discussed whether stress-induced sympathetic overactivity might contribute to the development of the IRS.

Distribution and correlates of insulin in elderly men. The Honolulu Heart Program

The role of insulin in cardiovascular disease is uncertain, and studies in elderly or minority populations are infrequent. Fasting and 2-hour insulin concentrations and their cross-sectional associations with cardiovascular risk factors were examined in 3562 elderly (aged 71 to 93 years) Japanese American men from the Honolulu Heart Program who were reexamined between 1991 and 1993. Insulin distributions were skewed (mean and median: 16.8 and 12 microU/mL for fasting; 117.2 and 93 microU/mL for 2-hour); fasting but not 2-hour insulin levels declined significantly with age (P < .0001 and P = .54, respectively). Factors most strongly correlated with insulin included measures of obesity, fat distribution, and levels of triglyceride, glucose (r = .38 to r = .50 fasting, r = .21 to r = .27 2-hour), and HDL cholesterol (r = -.41 and r = -.22, respectively). Other correlates included fibrinogen, hematocrit, heart rate, blood pressure, cigarettes per day (all positive), alcohol, physical activity, and forced vital capacity (negative). Associations were also evident across risk factor quintiles. Insulin levels were significantly elevated in men with hypertension and diabetes. In multiple linear regression analyses, log10 fasting insulin was positively and independently associated with body mass index, triglycerides, glucose, fibrinogen, hematocrit, heart rate, diabetes, and hypertension and negatively associated with HDL cholesterol, physical activity, and forced vital capacity. In general, results were similar for log10 2-hour insulin and when subjects who fasted < 12 hours or had diabetes were excluded. Substitution of medication use and blood pressure for hypertension indicated independent associations of medication use but not blood pressure with insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperdynamic circulation and cardiovascular risk in children and adolescents. The Bogalusa Heart Study

BACKGROUND

Hyperdynamic circulation has been reported to be associated with adverse levels of insulin, blood pressure, adiposity, and lipoproteins in the adult population. Whether this putatively insulin-mediated association also occurs in early life is not known. This aspect was examined in 2229 children and adolescents 8 to 17 years old living in Bogalusa, La.

METHODS AND RESULTS

Individuals were categorized as hyperdynamic (pulse pressure and heart rate in the upper quartile of the race-sex-age distribution), intermediate, and hypodynamic (pulse pressure and heart rate in the bottom quartile). Systolic blood pressure was significantly greater with a hyperdynamic circulation in both sexes (P < .0001), and several measures of obesity were greater with a hyperdynamic circulation. Hyperdynamic circulation was associated with statistically significant increases in triglyceride (P < .05) and fasting insulin (P < .01) in boys independently of age, race, and obesity. A decreasing trend with HDL cholesterol (P = .06) was also observed in boys. A significant association with total cholesterol (P < .05) was observed only in girls. In the analysis stratified by percent body fat, many of these features still occurred in obese individuals (top quartile) but not in lean individuals (bottom quartile). Further, when a subset of this cohort (n = 1074) was followed over a 3-year period, the above trend persisted significantly in boys.

CONCLUSIONS

The present study demonstrates that a hyperdynamic state as defined is associated with increased insulin levels and an adverse cardiovascular risk in early life.

New targets for lipid lowering and atherosclerosis prevention

The effectiveness of plasma lipid lowering in the clinic is well supported by a growing number of contributions, indicating the significant improvement in cardiovascular risk in primary and particularly in secondary prevention. While these studies have clearly indicated that the more potent agents for cholesterol reduction can provide a very effective help, other pathways of lipid metabolism have gained interest. These should be evaluated, in the hope of providing a more complete answer to the question of regulating lipid absorption, distribution, and tissue deposition. In addition to newer more potent systemic lipid-lowering drugs (in particular hydroxymethylglutaryl coenzyme A reductase inhibitors), nonsystemic agents, including cholesterol sequestrants, are receiving attention. Some of these are effective at low concentrations, thus providing a potentially powerful tool for plasma cholesterol regulation. Another area of development is that of acyl coenzyme A cholesterol acyltransferase inhibitors, i.e., drugs interfering with cholesterol esterification in tissues, particularly in the arterial wall; the major problem with these seems to be that of poor tolerability and of lack of definitive proof of plasma cholesterol reduction in humans. At present, drugs for the treatment of elevated lipoprotein(a) levels are not available, with few exceptions; in this case, a better understanding of the regulation of lipoprotein(a) metabolism and of the potential benefit of treatment seems necessary. Elevation of congenitally low high density lipoprotein cholesterol levels may also be an important target: microsomal enzyme inducers have been tested, but have not provided a clinically significant response; drugs with a mixed endocrine-hypolipidemic activity possibly may prove effective. Other targets, e.g., the correction of the lipoprotein pattern characterized by "small low density lipoprotein," and the development of drugs specifically acting on the cholesteryl ester transfer protein and lipoprotein lipase systems, are being explored. Finally, new areas of development are in recombinant apolipoproteins (apo's) and in gene therapy. One case, i.e., that of apo A-I/HDL, is entering the clinical field; the mutant apo A-IMilano might provide help because of a combined cholesterol removing/fibrinolytic activity. In the case of gene therapy, at present, data on low density lipoprotein receptor replacement are encouraging. Further options, such as gene transfer in the arterial wall to induce vascular protection/disobliteration of occlusions, are also being tested.

Left ventricular contractility and insulin resistance in essential hypertension

The relationship between fasting insulin as well as the insulin response to an oral glucose tolerance test and echocardiographic cardiac geometry and function was assessed in 55 never-treated lean patients with essential hypertension and normal glucose tolerance and 31 age- and gender-matched normal subjects. The ratio of the area under the curve of the response of insulin and glucose to the oral glucose load was positively correlated with supine heart rate (r values of 0.37) or left ventricular contractility estimated by the end-systolic wall stress to end-systolic volume index ratio and the afterload-corrected fractional shortening (r = 0.59 and 0.36, respectively). No correlation between insulin and left ventricular mass index was observed. When hypertensive patients were divided into those without (n = 39) and with insulin resistance (n = 16), as defined by an elevated value of the ratio of the area under the curve of the response of insulin and glucose, it appeared that both heart rate, end-systolic wall stress to end-systolic volume index ratio and afterload-corrected fractional shortening were higher in patients with insulin resistance, whereas age, arterial pressure, left ventricular mass index, urinary electrolytes, and plasma renin activity were similar in the two groups. These results suggest that increased cardiac systolic performance and heart rate may be associated with insulin resistance in a subset of lean patients with never-treated essential hypertension.

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.