Several factors associated with the insulin resistance syndrome are predictors of left ventricular systolic dysfunction in a male population after 20 years of follow-up

Thiazolidinedione insulin sensitizers and the heart: a tale of two organs?

Thiazolidinediones (TZDs) are relatively new agents for the treatment of type 2 diabetes. They act as agonists at the PPAR-gamma nuclear receptor and their therapeutic effects include decreased insulin resistance and hyperglycaemia, an improved plasma lipid, inflammation and pro-coagulant profile, and amelioration of hypertension, microalbuminuria and hepatic steatosis. The most common side effects of TZDs include weight gain and oedema, with occasional reports of congestive heart failure (CHF). This review discusses the benefit-risk profile of TZDs in treating patients with type 2 diabetes, with particular reference to the heart. To provide context, we explore briefly the epidemiology and pathophysiology of heart failure in patients with type 2 diabetes, touch on the association of heart disease and cardiovascular mortality with antihyperglycaemic treatment modalities other than TZDs, and then focus on the effects of TZDs on the heart, cardiovascular risk factors and outcomes. We describe the cluster of host factors, which seems to predispose patients with type 2 diabetes to TZD-induced or TZD-exacerbated oedema and CHF and then provide an overview of the putative mechanisms of these TZD-related side effects. We also propose that certain diuretics (amiloride and spironolactone), by targeting the distal nephron that expresses PPARgamma in collecting duct cells, might be of benefit in ameliorating the fluid retention and oedema associated with TZDs.

Insulin-resistant cardiomyopathy clinical evidence, mechanisms, and treatment options

Increasing evidence points to insulin resistance as a primary etiologic factor in the development of nonischemic heart failure (HF). The myocardium normally responds to injury by altering substrate metabolism to increase energy efficiency. Insulin resistance prevents this adaptive response and can lead to further injury by contributing to lipotoxicity, sympathetic up-regulation, inflammation, oxidative stress, and fibrosis. Animal models have repeatedly demonstrated the existence of an insulin-resistant cardiomyopathy, one that is characterized by inefficient energy metabolism and is reversible by improving energy use. Clinical studies in humans strongly support the link between insulin resistance and nonischemic HF. Insulin resistance is highly prevalent in the nonischemic HF population, predates the development of HF, independently defines a worse prognosis, and predicts response to antiadrenergic therapy. Potential options for treatment include metabolic-modulating agents and antidiabetic drugs. This article reviews the basic science evidence, animal experiments, and human clinical data supporting the existence of an "insulin-resistant cardiomyopathy" and proposes specific potential therapeutic approaches.

Heart failure in the diabetic patient

This review examines the extent of the increased rate of heart failure (HF) in the diabetic patient, along with the possible causes for this increase and the poor prognosis associated with HF. Also reviewed are the therapies that are available for the treatment of diabetic HF and whether intensifying the use of these therapies might improve the worsened clinical outcomes for the patient who has diabetes.

Cardiovascular morbidity and mortality of the metabolic syndrome

Cardiovascular disease remains the single leading cause of morbidity and mortality in the United States. The metabolic syndrome has received increased attention in recent years, partly because of the growing prevalence of obesity and its association with cardiovascular disease. This article reviews current evidence from longitudinal observational studies that evaluated the impact of metabolic syndrome on cardiovascular morbidity and mortality in various population subsets. The approach to cardiovascular risk assessment in individuals who have multiple risk factors and the clinical implications of diagnosing the metabolic syndrome are also discussed.

Increasing number of components of the metabolic syndrome and cardiac structural and functional abnormalities--cross-sectional study of the general population

Background

We aimed to assess whether we could identify a graded association between increasing number of components of the metabolic syndrome and cardiac structural and functional abnormalities independently of predicted risk of coronary heart disease by the Framingham risk score.

Methods

We conducted a cross-sectional study on a random sample of the urban population of Porto aged 45 years or over. Six hundred and eighty-four participants were included. Data were collected by a structured clinical interview with a physician, ECG and a transthoracic M-mode and 2D echocardiogram. The metabolic syndrome was defined according to ATPIII-NCEP. The association between the number of features of the metabolic syndrome and the cardiac structural and functional abnormalities was assessed by 3 multivariate regression models: adjusting for age and gender, adjusting for the 10-year predicted risk of coronary heart disease by Framingham risk score and adjusting for age, gender and systolic blood pressure.

Results

There was a positive association between the number of features of metabolic syndrome and parameters of cardiac structure and function, with a consistent and statistically significant trend for all cardiac variables considered when adjusting for age and gender. Parameters of left ventricular geometry patterns, left atrial diameter and diastolic dysfunction maintained this trend when taking into account the 10-year predicted risk of coronary heart disease by the Framingham score as an independent variable, while left ventricular systolic dysfunction did not. The prevalence of left ventricular diastolic dysfunction, and the mean left ventricular mass, left ventricular diameter and left atrial diameter increased significantly with the number of features of the metabolic syndrome when additionally adjusting for systolic blood pressure as a continuous variable.

Conclusion

Increasing severity of metabolic syndrome was associated with increasingly compromised structure and function of the heart. This association was independent of Framingham risk score for indirect indices of diastolic dysfunction but not systolic dysfunction, and was not explained by blood pressure level.

Patients with dilated cardiomyopathy possess insulin resistance independently of cardiac dysfunction or serum tumor necrosis factor-alpha

It has recently been reported that insulin resistance is prevalent in patients with dilated cardiomyopathy (DCM); however, it remains unclear whether insulin resistance is directly induced by DCM or if it is caused by congestive heart failure associated with DCM. We evaluated homeostasis model assessment insulin resistance (HOMA-R) in 14 patients with DCM in comparison with 9 patients with valvular heart diseases (VHD). We also measured the level of serum tumor necrosis factor (TNF)-alpha as a possible causative factor for inducing insulin resistance. Even after the adjustment for age, body mass index, and cardiac function, HOMA-R was significantly higher in patients with DCM than in those with VHD (P = 0.012) (mean +/- SEM: 3.51 +/- 0.59, and 0.80 +/- 0.64, respectively). The serum TNF-alpha level tended to be higher in patients with DCM than in those with VHD; however, the difference was not significant. In conclusion, patients with DCM possess insulin resistance independently of the severity of cardiac dysfunction or serum TNF-alpha, suggesting that insulin resistance in patients with DCM may be closely associated with the pathogenic condition of DCM itself.

Serum calcium is independently associated with insulin sensitivity measured with euglycaemic-hyperinsulinaemic clamp in a community-based cohort

AIMS/HYPOTHESIS

Diabetes mellitus type 2 is associated with altered calcium metabolism. Moreover, in diseases with supranormal serum calcium levels, such as primary hyperparathyroidism, the prevalence of diabetes is increased. Relatively little is known about the relationship between serum calcium concentration and the underlying causes of diabetes-insulin resistance and defective insulin secretion-in the normocalcaemic general population.

MATERIALS AND METHODS

We investigated associations between serum calcium concentration and insulin sensitivity and secretion in a population-based cohort of elderly men (Uppsala Longitudinal Study of Adult Men, n = 961). Insulin sensitivity index (M/I; glucose disposal rate [M] divided by mean insulin concentration [I]) was assessed using euglycaemic-hyperinsulinaemic clamp, and insulin secretion was estimated from the early insulin response (EIR) during an OGTT.

RESULTS

In a multivariable linear regression model adjusting for BMI, physical activity, smoking, consumption of tea, alcohol, coffee and dietary calcium, serum phosphate and serum creatinine, 1 SD increase in serum calcium was associated with 0.17 mg kg(-1) min(-1) (mU/l)(-1) x 100 (0.024 mg kg(-1) min(-1) [pmol/l](-1) x 100) decrease in M/I (p = 0.01). The results remained robust in individuals with normal fasting glucose, normal glucose tolerance and serum calcium within the normal range (n = 413, regression coefficient for 1 SD increase -0.45, p = 0.001). Serum calcium was not associated with EIR. Dietary intake of calcium was not independently associated with insulin sensitivity or EIR.

CONCLUSION/INTERPRETATION

Our data support the notion that endogenous calcium may be involved early in the development of diabetes and that this effect is mediated mainly through effects on insulin sensitivity rather than defective insulin secretion. Dietary intake of calcium does not seem to influence insulin sensitivity.

Thiazolidinediones and their Fluid-Related Adverse Effects

Thiazolidinediones (TZDs) or glitazones are agents that are widely used for the treatment of type 2 diabetes mellitus. These drugs have a multitude of therapeutic effects including reduction in insulin resistance and hyperglycaemia, anti-inflammatory effects and amelioration of hypertension, microalbuminuria and hepatic steatosis. The TZD molecular target, peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear transcription factor, is expressed diffusely in humans, including many tissues comprising the cardiovascular and renal systems. This suggests a potential for TZDs to elicit perturbing effects on these systems, which are independent of their effects on glucose and lipid metabolism. One of the most common adverse effects of TZDs is fluid retention, which can result in, or exacerbate, oedema and congestive heart failure (CHF). The frequency of peripheral oedema is approximately 5% when TZDs are used in mono- or combination oral therapy, and about 15% when used with insulin. Patients with type 2 diabetes are at high risk of myriad morbid complications, including CHF. The development of CHF, particularly in the elderly, is a harbinger of premature mortality. TZD-induced oedema is largely peripheral, may have its origins in changes in haemodynamics, with some contribution from molecules, which regulate cell and tissue permeability (e.g. vascular endothelial growth factor and protein kinase Cbeta), and remains the preponderant manifestation of TZD-induced fluid retention even in those with existing heart failure. Preclinical and pilot clinical data attest to the fact that at least part of the fluid retention derives from a direct effect of TZDs on sodium reabsorption via the renal medullary collecting duct, a mechanism that is sensitive to diuretic agents that have this nephron segment as their site of action, in whole or in part (spironolactone, amiloride and hydrochlorothiazide). Our review suggests various potential clinical strategies by which TZD-induced fluid retention might be effectively monitored and addressed.

Diabetic cardiomyopathy

This article focuses on advances in the understanding of the pathogenesis and treatment of diabetic cardiomyopathy. Patients with diabetes are at an elevated risk for heart failure, and comorbid heart failure confers an increased risk of morbidity and mortality. Diabetic cardiomyopathy and to apply proven lifesaving therapies in all heart failure patients, including those with diabetes, in the absence of contraindications or intolerance.

Metabolic syndrome and risk for heart failure in middle-aged men

OBJECTIVE

To explore metabolic syndrome as a possible risk factor for development of heart failure (HF).

DESIGN

Community-based cohort study.

SETTING

Uppsala, Sweden.

PARTICIPANTS

2314 50-year-old men free from HF, myocardial infarction and valvular disease at baseline were enrolled between 1970 and 1974 and were followed up until the age of 70. A modified National Cholesterol Education Program definition of metabolic syndrome was used with body mass index in the place of waist circumference.

MAIN OUTCOME MEASURE

First hospitalisation for HF.

RESULTS

In multivariable Cox proportional hazards models adjusted for established risk factors for HF (hypertension, diabetes, ECG left ventricular hypertrophy, smoking and body mass index), the presence at baseline of metabolic syndrome (hazard ratio 1.66, 95% confidence interval (CI) 1.02 to 2.70) was a predictor of subsequent HF. This relation was even stronger after adjustment for the presence of an acute myocardial infarction during follow up in addition to the other established risk factors for HF (hazard ratio 1.80, 95% CI 1.11 to 2.91).

CONCLUSION

Metabolic syndrome was a significant predictor of HF, independent of established risk factors for HF including an interim myocardial infarction, during two decades of follow up in a community-based sample of middle-aged men. This implies that metabolic syndrome provides important risk information beyond that of established risk factors for HF.

Metabolic syndrome and the risk of cardiovascular disease in older adults

OBJECTIVES

The purpose of this study was to assess whether metabolic syndrome (MetSyn) predicts a higher risk for cardiovascular events in older adults.

BACKGROUND

The importance of MetSyn as a risk factor has not previously focused on older adults and deserves further study.

METHODS

We studied the impact of MetSyn (38% prevalence) on outcomes in 3,035 participants in the Health, Aging, and Body Composition (Health ABC) study (51% women, 42% black, ages 70 to 79 years).

RESULTS

During a 6-year follow-up, there were 434 deaths overall, 472 coronary events (CE), 213 myocardial infarctions (MI), and 231 heart failure (HF) hospital stays; 59% of the subjects had at least one hospital stay. Coronary events, MI, HF, and overall hospital stays occurred significantly more in subjects with MetSyn (19.9% vs. 12.9% for CE, 9.1% vs. 5.7% for MI, 10.0% vs. 6.1% for HF, and 63.1% vs. 56.1% for overall hospital stay; all p < 0.001). No significant differences in overall mortality was seen; however, there was a trend toward higher cardiovascular mortality (5.1% vs. 3.8%, p = 0.067) and coronary mortality (4.5% vs. 3.2%, p = 0.051) in patients with MetSyn. After adjusting for baseline characteristics, patients with MetSyn were at a significantly higher risk for CE (hazard ratio [HR] 1.56, 95% confidence interval [CI] 1.28 to 1.91), MI (HR 1.51, 95% CI 1.12 to 2.05), and HF hospital stay (HR 1.49, 95% CI 1.10 to 2.00). Women and whites with MetSyn had a higher coronary mortality rate. The CE rate was higher among subjects with diabetes and with MetSyn; those with both had the highest risk.

CONCLUSIONS

Overall, subjects over 70 years are at high risk for cardiovascular events; MetSyn in this group is associated with a significantly greater risk.

Myocardial and vascular dysfunction and exercise capacity in the metabolic syndrome

The metabolic syndrome (MS) is associated with cardiovascular risk exceeding that expected from atherosclerotic risk factors, but the mechanism of this association is unclear. We sought to determine the effects of the MS on myocardial and vascular function and cardiorespiratory fitness in 393 subjects with significant risk factors but no cardiovascular disease and negative stress echocardiographic findings. Myocardial function was assessed by global strain rate, strain, and regional systolic velocity (s(m)) and diastolic velocity (e(m)) using tissue Doppler imaging. Arterial compliance was assessed using the pulse pressure method, involving simultaneous radial applanation tonometry and echocardiographic measurement of stroke volume. Exercise capacity was measured by expired gas analysis. Significant and incremental variations in left ventricular systolic (s(m), global strain, and strain rate) and diastolic (e(m)) function were found according to the number of components of MS (p <0.001). MS contributed to reduced systolic and diastolic function even in those without left ventricular hypertrophy (p <0.01). A similar dose-response association was present between the number of components of the MS and exercise capacity (p <0.001) and arterial compliance. The global strain rate and e(m) were independent predictors of exercise capacity. In conclusion, subclinical left ventricular dysfunction corresponded to the degree of metabolic burden, and these myocardial changes were associated with reduced cardiorespiratory fitness. Subjects with MS who also have subclinical myocardial abnormalities and reduced cardiorespiratory fitness may have a higher risk of cardiovascular disease events and heart failure.

Novel metabolic risk factors for heart failure

OBJECTIVES

Our objectives were to explore novel metabolic risk factors for development of heart failure (HF).

BACKGROUND

In the past decade, considerable knowledge has been gained from limited samples regarding novel risk factors for HF, but the importance of these in the general population is largely unexplored.

METHODS

In a community-based prospective study of 2,321 middle-aged men free from HF and valvular disease at baseline, variables reflecting glucose and lipid metabolism and variables involved in oxidative processes were compared with established risk factors for HF (prior myocardial infarction, hypertension, diabetes, electrocardiographic left ventricular hypertrophy, smoking, obesity, and serum cholesterol) using Cox proportional hazards analyses.

RESULTS

During a median follow-up time of 29 years, 259 subjects developed HF. In a multivariable Cox proportional hazards backward stepwise model, a 1-SD increase of fasting proinsulin (hazard ratio [HR] 1.38, 95% confidence interval [CI] 1.15 to 1.66) and apolipoprotein B/A-I-ratio (HR 1.27, 95% CI 1.09 to 1.48) increased the risk, whereas a 1-SD increase in serum beta-carotene (HR 0.79, 95% CI 0.66 to 0.94) decreased the risk of HF. These variables also remained significant when adjusting for acute myocardial infarction during follow-up.

CONCLUSIONS

Novel variables reflecting insulin resistance and dyslipidemia, together with a low beta-carotene level, were found to predict HF independently of established risk factors. If confirmed, our observations could have large clinical implications, as they may offer new approaches in the prevention of HF.

Myocardial dysfunction in rheumatoid arthritis: epidemiology and pathogenesis

Data from population- and clinic-based epidemiologic studies of rheumatoid arthritis patients suggest that individuals with rheumatoid arthritis are at risk for developing clinically evident congestive heart failure. Many established risk factors for congestive heart failure are over-represented in rheumatoid arthritis and likely account for some of the increased risk observed. In particular, data from animal models of cytokine-induced congestive heart failure have implicated the same inflammatory cytokines produced in abundance by rheumatoid synovium as the driving force behind maladaptive processes in the myocardium leading to congestive heart failure. At present, however, the direct effects of inflammatory cytokines (and rheumatoid arthritis therapies) on the myocardia of rheumatoid arthritis patients are incompletely understood.

Insulin resistance, dietary fat intake and blood pressure predict left ventricular diastolic function 20 years later

BACKGROUND AND AIMS

Our knowledge on the development of left ventricular diastolic dysfunction is scarce. Thus, we aimed to investigate the relationship between left ventricular diastolic function and a wide variety of cardiovascular risk factors, including dietary factors using both cross-sectional and longitudinal data with 20 years follow-up.

METHOD AND RESULTS

A population-based cohort of 505 50-year-old men was examined with determinations of blood pressure, insulin, glucose and fatty acid composition of serum cholesterol esters. A reinvestigation 20 years later also included hyperinsulinaemic euglycaemic clamp, 7-day diet record and Doppler echocardiography with determination of left ventricular diastolic function (early (E) and late (A) peak mitral velocities and left atrial diameter). Blood pressure both at age 50 and 70 was negatively correlated to the E/A ratio (r=-0.15, p<0.001 and r=-0.23, p<0.001) at age 70. Insulin resistance at age 50 and 70 were negatively correlated to the A-wave and left atrial diameter at follow-up. A fatty acid profile indicating a diet high in saturated fats at age 50 was correlated to an increased left atrial diameter 20 years later and the dietary intake of fat was negatively correlated to the E/A ratio (r=-0.09, p<0.05) at age 70. All findings were independent of myocardial infarction and cardiovascular medication.

CONCLUSION

Apart from blood pressure, insulin resistance and dietary fat intake predicted left ventricular diastolic function after 20 years. These findings suggest that both hemodynamic and metabolic factors may play a role for left ventricular diastolic function and disclose new possibilities for prevention of left ventricular diastolic dysfunction.

A Doppler-derived index of combined left ventricular systolic and diastolic function is an independent predictor of cardiovascular mortality in elderly men

BACKGROUND

Few studies on echocardiographic and Doppler indices of cardiac function as predictors for cardiovascular mortality have been performed in the general population. The novel myocardial performance index (MPI, also denoted as Tei-Doppler index) has been suggested to reflect both left ventricular (LV) systolic and diastolic function.

METHODS

We investigated whether 10 different echocardiographic and Doppler indices of cardiac function predicted cardiovascular mortality by using a population-based cohort of 583 seventy-year-old men with a mean follow-up time of 6.8 years.

RESULTS

In a multivariate Cox proportional hazard analysis for a 1-SD increase including LV ejection fraction, E/A ratio, MPI, and traditional cardiovascular risk factors (previous myocardial infarction, hyperlipidemia, hypertension, diabetes, smoking status, and LV hypertrophy), both ejection fraction (hazard ratio [HR] = 0.59, 95% CI 0.38-0.90, P < .05) and MPI (HR = 2.92, 95% CI 1.71-4.97, P < .0001) were found to be independent predictors for cardiovascular mortality. After excluding subjects with coronary heart disease, only MPI remained a significant predictor (HR = 2.18, 95% CI 1.11-4.27, P < .03, for 1-SD increase), and neither ejection fraction, E/A ratio, nor any of the cardiovascular risk factors remained significant predictors.

CONCLUSION

Myocardial performance index is a predictor for cardiovascular mortality, independent of other measurements of cardiac function and of traditional cardiovascular risk factors in elderly men free from coronary heart disease.

The Doppler-Derived Myocardial Performance Index Is Determined by Both Left Ventricular Systolic and Diastolic Function as Well as by Afterload and Left Ventricular Mass

OBJECTIVES

To investigate if the newly developed Doppler-derived myocardial performance index (MPI, also denoted TEI-index) is associated with variables reflecting both left ventricular (LV) systolic and diastolic function, as well as variables reflecting preload, afterload, and LV geometry.

MATERIAL

An echocardiographic examination including Doppler was carried out in 446 men aged 70 in a population-based survey (the ULSAM-study, Uppsala Longitudinal Study of Adult Men).

RESULTS

In multiple regression analysis, MPI was independently associated with ejection fraction (P < 0.001), E/A ratio (P < 0.001), total peripheral resistance index (P < 0.001), stroke volume to pulse pressure ratio (P < 0.02), stroke index (P < 0.01), and LV mass (P < 0.04), but not with heart rate or blood pressure.

CONCLUSION

The echocardiographically determined myocardial performance index is determined by both LV systolic and diastolic function as well as by afterload and left ventricular mass.

Insulin resistance in idiopathic dilated cardiomyopathy

OBJECTIVES

This study was designed to quantify the prevalence of abnormal glucose tolerance and insulin resistance in patients with idiopathic dilated cardiomyopathy (IDCM).

BACKGROUND

Insulin resistance is an independent risk factor for mortality in patients with heart failure (HF) and is a known risk factor for ischemic cardiomyopathy. Though potential physiologic links between insulin resistance and HF have been hypothesized, the relationship between insulin resistance and IDCM remains unclear.

METHODS

A total of 230 consecutive patients from a university HF clinic were screened for IDCM, the absence of diabetes mellitus, and the lack of significant co-morbid conditions. Oral glucose tolerance tests were performed in the 43 patients with IDCM who met these criteria, and their plasma glucose and insulin responses were compared with those of 40 healthy volunteers, matched for age, gender, and body mass index.

RESULTS

Plasma glucose responses were higher during the oral glucose tolerance tests in patients with IDCM (p < 0.01), associated with significantly higher plasma insulin concentrations following the oral glucose challenge (p < 0.01). In addition, abnormalities of glucose tolerance were significantly (p < 0.05) more common in patients with IDCM (49% vs. 23%).

CONCLUSIONS

Insulin resistance and abnormal glucose tolerance are more prevalent in patients with IDCM and represent potentially reversible metabolic derangements in these individuals.

Metabolic syndrome amplifies the age-associated increases in vascular thickness and stiffness

OBJECTIVES

We sought to evaluate whether the clustering of multiple components of the metabolic syndrome (MS) has a greater impact on these vascular parameters than individual components of MS.

BACKGROUND

Intima-media thickness (IMT) and vascular stiffness have been shown to be independent predictors of adverse cardiovascular events. The MS is defined as the clustering of three or more of the cardiovascular risk factors of dysglycemia, hypertension, dyslipidemia, and obesity.

METHODS

Carotid IMT and stiffness were derived via B-mode ultrasonography in 471 participants from the Baltimore Longitudinal Study on Aging, who were without clinical cardiovascular disease and not receiving antihypertensive therapy.

RESULTS

The MS conferred a disproportionate increase in carotid IMT (+16%, p < 0.0001) and stiffness (+32%, p < 0.0001), compared with control subjects. Multiple regression models, which included age, gender, smoking, low-density lipoprotein, as well as each individual component of MS as continuous variables, showed that MS was an independent determinant of both IMT (p = 0.002) and stiffness (p = 0.012). The MS was associated with a greater prevalence of subjects whose values were in the highest quartiles of IMT, stiffness, or both.

CONCLUSIONS

Even after taking into account each individual component of MS, the clustering of at least three of these components is independently associated with increased IMT and stiffness. This suggests that the components of MS interact to synergistically impact vascular thickness and stiffness. Future studies should examine whether the excess cardiovascular risk associated with MS is partly mediated through the amplified alterations in these vascular properties.

Endothelial vasodilatory function is related to the proportions of saturated fatty acids and alpha-linolenic acid in young men, but not in women

BACKGROUND

Fatty acid composition of serum lipids is associated with cardiovascular disease. As attenuated endothelium-dependent vasodilation (EDV) is an early event in atherosclerosis, we investigated the relationships between endothelial vasodilatory function and the proportion of serum fatty acids, reflecting dietary fat quality, in 74 healthy men and women, aged 20-30 years.

DESIGN

Endothelium-dependent vasodilation and endothelium-independent vasodilation (EIDV) was studied in the forearm during local administration of methacholine (2 and 4 micro g min-1) and nitroprusside (5 and 10 micro g min-1). Forearm blood flow was determined with venous occlusion plethysmography. An endothelial function index was calculated as the EDV/EIDV ratio.

RESULTS

The endothelial function index was inversely related to the total proportion of saturated fatty acids (r = -0.41, P < 0.05), in particular lauric and myristic acid (r = -0.37 and r = -0.36, respectively, P < 0.05 for both), and was positively related to the proportion of alpha-linolenic acid (r = 0.45, P < 0.01) in men only. Total serum nonesterified fatty acid (NEFA) concentration was not significantly related to endothelial vasodilatory function. By multiple stepwise regression analysis, including age, blood pressure, body mass index, and serum cholesterol, triglyceride and NEFA as confounders, myristic acid and alpha-linolenic acid were independent predictors of the endothelial function index in men only (r = -0.39 and r = 0.47, respectively, P < 0.01 for both).

CONCLUSIONS

We conclude that serum fatty acid composition predicts endothelial vasodilatory dysfunction independently of serum NEFA and cholesterol levels in young, healthy men in their third decade of life, whereas fatty acid composition seems to be less important in women at this age. As a result of the large number of analyses performed, these findings need to be verified by other studies.

Dietary fat, fatty acid composition in plasma and the metabolic syndrome

PURPOSE OF REVIEW

The metabolic syndrome, a cluster of disorders often including abdominal obesity, is associated with a high risk of cardiovascular disease and premature death. Insulin resistance is a key feature of the metabolic syndrome. Observational studies have indicated that the type of fat in the diet may be related to the development of insulin resistance and the metabolic syndrome, also independent of possible effects on body weight. Dietary surveys are often imprecise. One way to monitor the type of fat in the diet is to record the fatty acid composition in plasma. This review summarizes recent data on the relationships between fatty acid composition in plasma and insulin resistance, diabetes and other disorders related to the metabolic syndrome.

RECENT FINDINGS

Insulin resistance and insulin resistant states are often associated with the fatty acid pattern in plasma, characterized by an increased proportion of palmitic (16 : 0) and a low proportion of linoleic (18 : 2 n-6) acids, with a distribution of other fatty acids indicating an increased activity of delta-9 and delta-6 desaturase. This shows that there may be a causal relationship between the type of fat in the diet and insulin action, an assumption supported by recent dietary intervention studies.

SUMMARY

In a public health perspective these results, from both observational and intervention studies, underline the importance of fat quality in the diet for the development of a number of prevalent diseases. Taken together with several earlier studies and recent epidemiological findings, they give strong support to present dietary guidelines.

Heart rate recovery after exercise is related to the insulin resistance syndrome and heart rate variability in elderly men

OBJECTIVE

We investigated the associations between heart rate recovery after exercise (as a suggested measure of vagal activity), heart rate variability, and measurements of the insulin resistance syndrome.

MATERIAL AND METHODS

Seventy men aged 70 years were examined with a symptom-limited bicycle exercise test, a 24-hour heart rate variability test, and different measurements of different components of the insulin resistance syndrome.

RESULTS

Heart rate recovery after exercise (mean +/- SD 20 +/- 9 beats during the first minute) was related to both the SD of the R-R interval and the low frequency power at the heart rate variability analyses (r = 0.39, P <.002 for both). Furthermore, heart rate recovery after exercise was related to insulin sensitivity at the hyperinsulinemic eugleucemic clamp (r = 0.28, P <.03), and to high-density lipoprotein cholesterol and exercise capacity, and inversely to obesity and insulin and glucose levels 2 hours after an oral glucose load (P <.05 for all). Heart rate recovery after exercise was not related to left ventricular mass measured by means of echocardiography or to the number of ventricular premature complexes at a 24-hour Holter recording.

CONCLUSION

Heart rate recovery 1 minute after exercise was related to measurements of 24-hour heart rate variability. Furthermore, heart rate recovery after exercise was related to several of the major components of the insulin resistance syndrome, thereby establishing a link between this syndrome and cardiac autonomic nervous activity.