Left ventricular contractility and insulin resistance in essential hypertension

Compliance with behavioral guidelines for diet, physical activity and sedentary behaviors is related to insulin resistance among overweight and obese youth

Background

Overweight and obesity are established risk factors for insulin resistance in youth. A number of behavioral recommendations have been publicized with the goal of improving glycemic control. However, there is limited information about whether meeting these behavioral recommendations actually reduces insulin resistance.

Findings

92 youths 11 - 16 years with BMI ≥ 85% underwent oral glucose tolerance testing. HOMA-IR and AUC_Insulin/AUC_Glucose were calculated as measures of insulin resistance. Dietary and physical activity (PA) measures were performed. Assessments included whether or not participants met recommended levels of diet, PA and sedentary behaviors.

62% youths met criteria for insulin resistance. 82% (75/92) met at least one behavioral recommendation. Participants who met ≥ 1 dietary, sedentary, or PA recommendations had significantly reduced insulin resistance as compared with youth who did not. This relationship remained significant in multivariate modeling of insulin resistance adjusting for age, sex, and BMI.

Conclusions

Even relatively minor behavior change may reduce insulin resistance in youth at risk for diabetes. Our findings support the relevance of current behavioral interventions for glycemic control.

Trials Registration

Clinical Trials #NCT00412165.

Metabolic syndrome and cardiometabolic risk: an update

Several lines of evidence show that metabolic syndrome represents an important therapeutic challenge for the forthcoming years. This is because of the epidemic burden of this multifaceted disease, the adverse impact on cardiovascular risk, as well as the problems posed in its management. This paper will provide an up-to-date report on metabolic syndrome and cardiometabolic risk, focusing in particular on the epidemiological profile of the disease, the impact on risk profile and target organ damage as well as some of the main pathophysiological features of the condition. The general therapeutic recommendations, provided by the 2007 European Society of Hypertension/European Society of Cardiology Guidelines, will be briefly discussed.

Ventricular ectopic activity, left ventricular mass, hyperinsulinemia, and intracellular magnesium in normotensive patients with obesity

Insulin resistance, a well-known feature of obesity, is associated with several pathological changes, which are potentially arrhythmogenic. Ventricular ectopic activity in normotensive obese patients has not been studied in detail. Therefore the authors designed a study to investigate potential relationships among ventricular ectopic activity, left ventricular mass, hyperinsulinemia, and intracellular magnesium concentration in obese patients. Thirty-two obese patients and 32 nonobese control subjects, who were referred to outpatient department because of ventricular ectopy, participated in the study. The groups were matched for age and gender. All had normal glucose tolerance. All subjects underwent a 75-g glucose tolerance test, and blood samples were obtained at 30, 60, and 120 minutes thereafter for determination of glucose and insulin concentrations. Echocardiography was performed and left ventricular mass index was calculated. The number of ventricular ectopic beats per hour (VEB/hour) was recorded by 24-hour ECG Holter monitoring. Plasma and erythrocyte magnesium concentrations were determined by atomic absorption spectrophotometer. Obese patients had higher body weight, body mass index, heart rate, and left ventricular mass index. Obese subjects had higher fasting insulin as well as insulin/glucose ratio and broader area under the curve of insulin (AUC-I) compared to nonobese subjects. Insulin sensitivity appeared to be lower in the obese group. Holter monitoring showed more VEB/hour in the obese group. Magnesium concentration in serum and in erythrocytes was lower in obese persons. In the obese group a positive correlation was found between left ventricular mass index and fasting insulin (r=0.345, p=0.027), insulin/glucose index (r=0.351, p=0.049), and AUC-I (r=0.405, p=0.011). The number of VEB/hour in obese patients was in positive correlation with age (r=0.681, p<0.001), left ventricular mass index (r=0.542, p=0.001), fasting insulin (r=0.380, p=0.016), and AUC-I (r=0.493, p=0.002) and in negative correlation with magnesium concentration in erythrocytes (r=-0.457, p=0.004). Multiple regression analysis showed that age and AUC-I are the only determinants of VEB/hour and together explained 56% of the variability in the obese subjects. It appears that in obese normotensive subjects, ventricular ectopic beats are related to age, insulin resistance, left ventricular mass index, and decreased intracellular magnesium content.

Diastolic function and insulin resistance in essential hypertension

We studied the relationship of insulin metabolism to diastolic function in 41 hypertensive patients and 24 healthy subjects. They underwent a 75-g oral glucose tolerance test. Integrated response of insulin to the glucose load was calculated as the area under the curve of insulin (AUC-I) and glucose (AUC-G). The ratio AUC-I/AUC-G was taken as an index of insulin resistance. Echocardiographic examination was performed to measure left ventricular mass. We used pulsed Doppler technique to assess the ratio of early to late transmitral peak velocity (E/A). The hypertensives had higher fasting insulin concentrations, insulin levels at 60 min and at 120 min after oral glucose load. They had higher AUC-I and higher index of insulin resistance compared to normotensives. Patients with hypertension had a lower E/A ratio in comparison to normotensive volunteers. In all subjects, the E/A ratio was negatively correlated with fasting insulin and insulin concentrations at 30, at 60 and at 120 min, AUC-I and insulin resistance index. Multiple regression analysis was performed to evaluate the above relationships, when the effects of confounding factors such as age, heart rate and systolic blood pressure were taken into account. We found that E/A ratio is negatively correlated to insulin concentrations at 120 min and to AUC-I in hyperinsulinemic subgroup of subjects (fasting insulin> 10). We conclude, that insulin metabolism and E/A ratio, which reflects diastolic function of the left ventricle, are related in hypertension.

Early impairment of coronary flow reserve in young men with borderline hypertension

OBJECTIVES

The purpose of this study was to investigate whether functional abnormalities in coronary vasomotion are present in young healthy asymptomatic men fulfilling the World Health Organization (WHO) criteria for borderline hypertension.

BACKGROUND

Previous studies have reported reduced coronary flow reserve in middle-aged subjects with sustained hypertension and hypertension-induced microvascular heart disease or left ventricular hypertrophy.

METHODS

Myocardial blood flow was measured at baseline and during dipyridamole-induced hyperemia by means of positron emission tomography and oxygen-15-labeled water in asymptomatic young men with borderline hypertension (group 1: n = 16, mean +/- SD age 37 +/- 4 years, 24-h ambulatory blood pressure 135 +/- 10/81 +/- 9 mm Hg) and matched healthy control subjects (group 2: n = 19, age 35 +/- 3 years, 24-h ambulatory blood pressure 119 +/- 8/69 +/- 8 mm Hg, p < 0.001). Left ventricular (LV) mass, dimensions and function were measured by echocardiography.

RESULTS

LV mass, dimensions and diastolic function were similar in the study groups. Baseline myocardial blood flow was similar (0.83 +/- 0.21 vs. 0.80 +/- 0.22 ml/g per min, group 1 vs. group 2, respectively, p = NS), and a significant increase in flow was detected after dipyridamole infusion (0.56 mg/kg body weight in 4 min intravenously) in both groups. However, the flow response to dipyridamole was significantly lower in group 1, leading to lower hyperemic flow in group 1 than in group 2 (2.85 +/- 1.20 vs. 3.80 +/- 1.44 ml/g per min, respectively). Consequently, the coronary flow response was lower in hypertensive than in normotensive men (3.46 +/- 1.23 vs. 4.99 +/- 2.5 ml/g per min, group 1 vs. group 2, respectively, p < 0.05).

CONCLUSIONS

These results demonstrate reduced coronary reactivity present in young asymptomatic men with borderline hypertension and no signs of hypertension-induced angina or left ventricular hypertrophy. Because baseline basal myocardial blood flow was unchanged, the reduction in coronary flow reserve depends on an impaired maximal vasodilator capacity.

Are insulin metabolism and night-time blood pressure related to left ventricular hypertrophy?

Essential hypertensives in whom blood pressure does not fall during sleep (non-dippers) are thought to be at greater risk of cardiovascular morbidity. Insulin resistance is also suggested to be a risk factor for cardiovascular morbidity. The purpose of the present study was to evaluate the relationship of insulin metabolism to left ventricular hypertrophy in dippers and non-dippers. Thirty male, non-diabetic out-patients with newly diagnosed arterial hypertension were included in the study: 21 dippers (mean age 45+/-13 years; body mass index 28.2+/-4.0 kg/m2) and nine non-dippers (mean age 48+/-10 years, body mass index 28.6+/-3.9 kg/m2). Patients were subdivided into dippers and non-dippers on the basis of 24-h ambulatory blood pressure monitoring. Insulin and glucose responses to an oral glucose load have been evaluated. C-peptide levels were determined. Left ventricular mass was assessed by echocardiography. Non-dippers had significantly higher mean night-time systolic (non-dippers: 148+/-9; dippers: 123+/-16 mmHg; P<0.001), diastolic blood pressure (non-dippers: 90+/-8; dippers: 77+/-8 mmHg; P<0.001) and non-significantly higher left ventricular mass (279+/-92 g) and left ventricular mass index (135+/-46 g/m2). No significant difference was found between C-peptide, insulin, glucose levels and incremental areas between the two groups. Night-time blood pressure, insulin, C-peptide and glucose did not correlate with left ventricular mass in non-dippers. Dippers showed a positive correlation between fasting C-peptide and left ventricular mass (r=0.48, P=0.02) and between glucose and left ventricular mass (r=0.42, P=0.05). Our data indicate that night-time blood pressure and insulin are not related to left ventricular hypertrophy in patients with essential hypertension.