Aarno Hautanen

Associations Between Human Aldosterone Synthase (CYP11B2) Gene Polymorphisms and Left Ventricular Size, Mass, and Function

BACKGROUND Aldosterone has direct and indirect effects on the heart, and genetic variations in aldosterone synthesis could therefore influence cardiac structure and function. Such variations might be associated with polymorphisms in the gene encoding aldosterone synthase (CYP11B2), the enzyme catalyzing the last steps of aldosterone biosynthesis. METHODS AND RESULTS A Finnish population sample of 84 persons (44 women) aged 36 to 37 years was studied by M-mode and Doppler echocardiography to assess left ventricular size, mass, and function. Subjects were genotyped through the use of the polymerase chain reaction for two diallelic polymorphisms in CYP11B2: one in the transcriptional regulatory region (promoter) and the other in the second intron. In multiple regression analyses, the CYP11B2 promoter genotype predicted statistically significant variations in left ventricular end-diastolic diameter (beta=.40, P<.0001), end-systolic diameter (beta=.33, P=.0009), and mass (beta=.17, P=.023). These effects were independent of potentially confounding factors, including sex, body size, blood pressure, physical activity, smoking, and ethanol consumption. Genotype groups also differed in a measure of left ventricular diastolic function, the heart rate-adjusted atrial filling fraction (P=.018). Increased dietary salt, which is known to predict increased left ventricular mass, had this effect only in association with certain CYP11B2 genotypes (P<.001). CONCLUSIONS Genetic variations in or near the aldosterone synthase (CYP11B2) gene strongly affect left ventricular size and mass in young adults free of clinical heart disease. These polymorphisms may also influence the response of the left ventricle to increases in dietary salt.

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.

Adrenal androgens and testosterone as coronary risk factors in the Helsinki Heart Study

We investigated the role of adrenal androgens, cortisol, testosterone and sex-hormone binding globulin (SHBG) as coronary risk factors using a nested case-control design. The study population consisted of 62 cases with cardiac end-points and 97 controls on placebo during the last 4 years in the Helsinki Heart Study. Serum concentrations of dehydroepiandrosterone, dehydroepiandrosterone sulfate (DHEAS), androstenedione, androstanediol glucuronide, cortisol, testosterone, and SHBG at the first annual visit of the 5-year study period were determined by radioimmunoassays. The only significant difference was found in DHEAS, with cases having higher levels than controls (P < 0.04). DHEAS levels were positively associated with smoking (P < 0.001), alcohol consumption (P < 0.04) and triglyceride levels (P < 0.002) and with systolic (P < 0.04) and diastolic (P < 0.006) blood pressures, and negatively associated with age (P < 0.01) and HDL-cholesterol (P < 0.03). The association between DHEAS and the CHD risk was studied using logistic regression analyses with the classical risk factors--age, smoking, blood pressure, and lipid levels--as covariates in the models. Studies of the joint effects of age and DHEAS disclosed that the risk associated with elevated DHEAS was confirmed to older men (odds ratio (OR) 7.3, 95%, CI 2.3-23.3). A similar analysis with smoking revealed that the DHEAS-related risk was mainly found in smokers (OR 3.4, 95% CI 1.5-8.2). One possible explanation for these results is that some form of mild steroid biosynthetic defect of the adrenals or functional adrenal hyperplasia associated with high DHEAS levels increases the CHD risk in this population.

Association of Chronic Stress With Plasminogen Activator Inhibitor–1 in Healthy Middle-aged Men

The effect of chronic stress on tissue-type plasminogen activator (TPA) and plasminogen activator inhibitor-1 (PAI-1) antigens was studied in 69 healthy middle-aged men. Chronic stress, defined as feelings of fatigue, lack of energy, increased irritability, and demoralization, was positively associated with plasma concentrations of PAI-1 antigen but was unrelated to TPA. The association remained unaltered after controlling for age, smoking, alcohol consumption, and physical activity but became nonsignificant after further controlling for abdominal obesity, BMI, and serum insulin and triglyceride levels. This attenuated association implies that the relationship between vital exhaustion and PAI-1 may be secondary to the effects of the metabolic variables. Thus, the present study shows that long-term stress affects the fibrinolytic system and suggests that obesity and insulin and triglyceride concentrations, which are closely correlated with the fibrinolytic parameters, may mediate the association. These findings are consistent with the hypothesis that chronic stress causes increased synthesis of PAI-1, thus promoting the risk for atherothrombotic disease by decreasing the likelihood of spontaneous fibrinolysis and increasing the likelihood of fibrin deposition.

Testosterone, Sex Hormone-Binding Globulin and the Metabolic Syndrome in Men : An Individual Participant Data Meta-Analysis of Observational Studies

Background Low total testosterone (TT) and sex hormone-binding globulin (SHBG) concentrations have been associated with the metabolic syndrome (MetS) in men, but the reported strength of association varies considerably. Objectives We aimed to investigate whether associations differ across specific subgroups (according to age and body mass index (BMI)) and individual MetS components. Data sources Two previously published meta-analyses including an updated systematic search in PubMed and EMBASE. Study Eligibility Criteria Cross-sectional or prospective observational studies with data on TT and/or SHBG concentrations in combination with MetS in men. Methods We conducted an individual participant data meta-analysis of 20 observational studies. Mixed effects models were used to assess cross-sectional and prospective associations of TT, SHBG and free testosterone (FT) with MetS and its individual components. Multivariable adjusted odds ratios (ORs) and hazard ratios (HRs) were calculated and effect modification by age and BMI was studied. Results Men with low concentrations of TT, SHBG or FT were more likely to have prevalent MetS (ORs per quartile decrease were 1.69 (95% CI 1.60-1.77), 1.73 (95% CI 1.62-1.85) and 1.46 (95% CI 1.36-1.57) for TT, SHBG and FT, respectively) and incident MetS (HRs per quartile decrease were 1.25 (95% CI 1.16-1.36), 1.44 (95% 1.30-1.60) and 1.14 (95% 1.01-1.28) for TT, SHBG and FT, respectively). Overall, the magnitude of associations was largest in non-overweight men and varied across individual components: stronger associations were observed with hypertriglyceridemia, abdominal obesity and hyperglycaemia and associations were weakest for hypertension. Conclusions Associations of testosterone and SHBG with MetS vary according to BMI and individual MetS components. These findings provide further insights into the pathophysiological mechanisms linking low testosterone and SHBG concentrations to cardiometabolic risk.

Vital Exhaustion, Anger Expression, and Pituitary and Adrenocortical Hormones: Implications for the Insulin Resistance Syndrome

This study was undertaken to examine whether there are psychological factors that can incline an individual toward coronary heart disease and that can in turn identify a pattern of pituitary and adrenocortical responses that is associated with the Insulin Resistance Syndrome (IRS). The study was performed with 69 normotensive and 21 unmedicated borderline hypertensive men (age range, 30 to 55 years). Type A behavior, hostility (defined as cynicism, pessimism, and paranoia), vital exhaustion, and anger expressions were the behavioral variables studied. Among these, only the vital exhaustion-anger-out factor identified the neuroendocrine pattern that predicted the IRS. This neuroendocrine pattern consisted primarily of an adrenal responsiveness to ACTH and secondarily of a high mean basal cortisol-to-mean basal ACTH ratio. The contribution of this last variable was, however, slightly questionable. Instead of the traditional coronary-prone factors, ie, type A behavior and hostility, the findings emphasize the significance of vital exhaustion and emotional distress. The findings have been discussed in terms of defeat reaction, hypocortisolemia, and visceral obesity.

Baroreflex sensitivity and variants of the renin angiotensin system genes

OBJECTIVES Because the renin-angiotensin-aldosterone system (RAS) modifies cardiovascular autonomic regulation, we studied the possible associations between baroreflex sensitivity (BRS) and polymorphism in the RAS genes. BACKGROUND Wide intersubject variability in BRS is not well explained by cardiovascular risk factors or life style, suggesting a genetic component responsible for the variation of BRS. METHODS Baroreflex sensitivity as measured from the overshoot phase of the Valsalva maneuver and genetic polymorphisms were examined in a random sample of 161 women and 154 men aged 41 to 61 years and then in an independent random cohort of 29 men and 37 women aged 36 to 37 years. An insertion/deletion (I/D) polymorphism of angiotensin-converting enzyme (ACE), M235T variants of angiotensinogen (AGT) and two diallelic polymorphisms in the gene encoding aldosterone synthase (CYP11B2), one in the promoter (-344C/T) and the other in the second intron, were identified by polymerase chain reaction. RESULTS In the older population, BRS differed significantly across CYP11B2 genotype groups in women (10.1 +/- 4.5, 8.7 +/- 3.8 and 7.1 +/- 3.2 ms x mm Hg(-1) in genotypes -344TT, CT and CC, respectively, p = 0.003 and 11.1 +/- 4.4, 8.9 +/- 4.1 and 7.5 +/- 3.4 ms x mm Hg(-1) in intron 2 genotypes 1/1, 1/2 and 2/2, respectively, p = 0.002), but not in men. No comparable associations were found for BRS with the I/D polymorphism of ACE or the M235T variant of AGT. In the younger population, BRS was even more strongly related to the CYP11B2 promoter genotype (p = 0.0003). The association was statistically significant both in men (p = 0.015) and in women (p = 0.03). CONCLUSIONS Common genetic polymorphisms in the aldosterone synthase (CYP11B2) gene is associated with interindividual variation in BRS.

Joint Effects of an Aldosterone Synthase (CYP11B2) Gene Polymorphism and Classic Risk Factors on Risk of Myocardial Infarction

BACKGROUND The -344C allele of a 2-allele (C or T) polymorphism in the promoter of the gene encoding aldosterone synthase (CYP11B2) is associated with increased left ventricular size and mass and with decreased baroreflex sensitivity, known risk factors for morbidity and mortality associated with myocardial infarction (MI). We hypothesized that this polymorphism was a risk factor for MI. METHODS AND RESULTS We used a nested case-control design to investigate the relationships between this polymorphism and the risk of nonfatal MI in 141 cases and 270 matched controls from the Helsinki Heart Study, a coronary primary prevention trial in dyslipidemic, middle-aged men. There was a nonsignificant trend of increasing risk of MI with number of copies of the -344C allele. However, this allele was associated in a gene dosage-dependent manner with markedly increased MI risk conferred by classic risk factors. Whereas smoking conferred a relative risk of MI of 2.50 (P=0.0001) compared with nonsmokers in the entire study population, the relative risk increased to 4.67 in -344CC homozygous smokers (relative to nonsmokers with the same genotype, P=0.003) and decreased to 1.09 in -344TT homozygotes relative to nonsmokers with this genotype. Similar joint effects were noted with genotype and decreased HDL cholesterol level as combined risk factors. CONCLUSIONS Smoking and dyslipidemia are more potent risk factors for nonfatal MI in males who have the -344C allele of CYP11B2.

Cigarette smoking is associated with elevated adrenal androgen response to adrenocorticotropin

Cigarette smoking alters the pattern of endogenous steroid levels. We examined this phenomenon in two separate male groups. Group A consisted of 189 dyslipidemic men participating in the Helsinki Heart Study and group B of 100 men including patients with heart disease and healthy controls. The subjects in the latter group underwent ACTH-testing. In group A, smokers had significantly higher basal androstenedione and dehydroepiandrosterone sulfate (DHEAS) levels and androstenedione/cortisol ratios than nonsmokers. Mean concentrations of cortisol, dehydroepiandrosterone (DHEA), androstanediol glucuronide, testosterone, and sex-hormone binding globulin (SHBG) did not differ between smokers and nonsmokers. In group B, smokers had lower high density lipoprotein (HDL)-cholesterol and apolipoprotein AI and higher triglyceride levels than nonsmokers. Basal androstenedione and ACTH stimulated androstenedione and DHEA concentrations were higher in smokers. No significant differences were found in basal insulin, SHBG, estrone, estradiol, testosterone, free testosterone, and dihydrotestosterone concentrations between smokers and nonsmokers. These results suggest that smoking decreases the activity of either 21- or 11 beta-hydroxylase in the adrenal cortex, which results in increased secretion of adrenal androgens.

Association of stress and depression with regional fat distribution in healthy middle-aged men.

We examined whether the association of regional fat distribution with stress, defined in terms of vital exhaustion, and depression varies according to the total amount of body fat accumulation in healthy middle-aged men (n=64). Regional fat distribution was measured using the waist-to-hip circumference ratio (WHR), and the total amount of body fat accumulation was measured using the body mass index (BMI). The results indicate that WHR in lean men was associated with characteristics contrary to those in moderately obese men. In lean men WHR tended to be associated with a high level of stress, while in moderately obese men an association was found with a low level of stress and a low level of depressive symptomatology. The present results support the suggestion that there is a difference between abdominal obesity at different degrees of generalized obesity, and they are likely to further our understanding about the differing risk for cardiovascular disorders posed by abdominal obesity in lean men compared to abdominal obesity in moderately obese men.