ACE genotype and endothelium-dependent vasodilation of conduit arteries and forearm microcirculation in humans

IgE-Mediated Anaphylaxis to Foods, Venom, and Drugs: Influence of Serum Angiotensin Converting Enzyme Levels and Genotype

Circulating angiotensin-II protects the circulation against sudden falls in blood pressure and is generated by the enzymatic action of angiotensin converting enzyme (ACE) on angiotensin-I. The ACE genes have 2 allelic forms, “I” and “D.” The “D” genotype has both highest angiotensin-II generation and serum ACE levels compared to “I”. 120 patients with IgE-anaphylaxis, 119 healthy controls, and 49 atopics had serum ACE levels, ACE genotype, and renin levels determined. Plasma renin levels were identical for all groups. Serum ACE levels and genotypes were similar for healthy controls (HC) and atopics, but lower in anaphylaxis (P = 0.012), with ACE genotypes also showing increased “I” genes (P = 0.009). This effect was more pronounced in subjects manifesting airway angioedema and cardiovascular collapse (AACVS) than mild cutaneous and respiratory (CRA) symptoms. AACVS was significantly associated with the presence of “I” genes. For “ID” genotype OR is 5.6, 95% CI 1.8 to 17.4, and for “II” genotype OR is 44, 95% CI 5 to 1891 within the anaphylaxis group = 0.001. The results show a difference in the genotype frequency between control and anaphylaxis, suggesting a role for the renin angiotensin system in anaphylaxis manifesting with airway angioedema and cardiovascular collapse.

A multilocus candidate approach identifies ACE and HIF1A as susceptibility genes for cellulite

BACKGROUND

Cellulite is a common complex cosmetic problem for many post-adolescent women characterised by relief alterations of the skin surface, which give the skin an orange-peel appearance. Although genetic factors have been suggested to play a role in the development of cellulite, the genetic background of this condition remains unclear. We therefore conducted a multi-locus genetic study examining the potential associations of candidate gene variants in oestrogen receptors, endothelial function/adipose tissue hypoxia, lipid metabolism, extracellular matrix homeostasis, inflammation and adipose tissue biology, with the risk of cellulite.

METHODS

Using a case-control study of 200 lean women with cellulite and 200 age- and BMI-matched controls (grade 0 according to Nurnberger-Muller scale), we examined the association of cellulite with 25 polymorphisms in 15 candidate genes.

RESULTS

Two of the 25 polymorphisms were significantly associated with cellulite at the P < 0.01 level. After allowance for age, body mass index, the prevalence of contraceptive use and smoking in logistic regression analysis, the multivariable-adjusted odds ratios for cellulite were 1.19 (95% CI: 1.10-1.51; P < 0.01) for ACE rs1799752 and 0.61 (95% CI: 0.45-0.88, P < 0.01) for HIF1A rs11549465.

CONCLUSIONS

This study, which demonstrates an independent role of ACE and HIF1A in predisposing to cellulite, may provide novel information on the pathophysiology of this common cosmetic problem, and offer a topic for research for novel beautification interventions.

Heritability of flow-mediated dilation: a twin study

BACKGROUND

Endothelial dysfunction assessed by brachial artery flow-mediated dilation (FMD) is a marker for early atherosclerotic vascular disease and future cardiovascular events.

OBJECTIVE

To estimate the heritability of brachial artery FMD using a twin design.

METHODS

We estimated the heritability of FMD using 94 middle-aged male twin pairs. FMD was measured by ultrasound, and traditional coronary heart disease risk factors were measured. Genetic modeling techniques were used to determine the relative contributions of genes and environment to the variation in FMD.

RESULTS

The mean age of the twin participants was 54.9 +/- 2.8 years. The mean FMD was 0.047 +/- 0.030. The intraclass correlation coefficient was higher in MZ twins [0.38, 95% confidence interval (CI) 0.32-0.43] than in DZ twins (0.19, 95% CI 0.11-0.26), suggesting a role of genetic influence in FMD variation. Structural equation modeling showed that both genetic and unique environmental factors contributed significantly to the variation in FMD. The crude FMD heritability was 0.37 (95% CI 0.15-0.54). After adjustment for traditional cardiovascular risk factors, including age, total cholesterol, blood pressure, and body mass index, the heritability of FMD was 39% (95% CI 0.18-0.56). The remaining variation in FMD could be explained by individual-specific environment.

CONCLUSION

This is the first study using twins to estimate the relative contributions of genetics and environment to the variation in FMD in a US population. Our results demonstrate a moderate genetic effect on brachial artery FMD, independent of traditional coronary risk factors. Our data also highlight the importance of unique environment on the variability in FMD.

Angiotensin-converting enzyme gene polymorphism and coronary reactivity in young men

The purpose of the study was to examine whether the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene affects the vasodilatory properties of coronary arteries in healthy men. The ACE genotypes of 128 men (mean age 35 +/- 4 years) were determined and related to myocardial blood flow. The blood flow was measured by positron emission tomography at rest and during vasodilation caused by adenosine or dipyridamole infusion. The coronary flows and resistances at rest and during stimulation with adenosine or dipyridamole did not differ between the ACE genotypes. Furthermore, this polymorphism had no effect on coronary flow reserve corrected by a rate-pressure product. In conclusion, the ACE I/D polymorphism does not seem to affect myocardial reactivity--an early indicator of atherosclerosis--in healthy subjects.

Comparison of the effect of enalapril and losartan in conjunction with surgical coronary revascularisation versus revascularisation alone on systemic endothelial function

OBJECTIVES

To investigate the effect of enalapril, losartan, and surgical coronary revascularisation on endothelial function, and the role of the angiotensin converting enzyme (ACE) insertion (I)/deletion (D) polymorphism.

DESIGN

Randomised, controlled, blinded end point study.

SETTING

University tertiary referral cardiac centre.

PATIENTS AND INTERVENTIONS

49 men awaiting coronary artery bypass grafting (CABG) were randomly assigned to treatment with losartan, enalapril, or control for two months before and three months after surgery.

MAIN OUTCOME MEASURES

Endothelial function was blindly analysed by brachial artery flow mediated dilatation (FMD) and ACE I/D genotype was determined.

RESULTS

FMD was impaired at baseline (1.0-1.7%) and after five months had improved to 5.2% with enalapril (p = 0.015), 5.0% with losartan (p = 0.0004), and 3.0% with CABG alone (p = 0.05). Patients with the II genotype had lower baseline FMD than those with DI or DD (0.1% v 1.7%, p = 0.038) and after enalapril or losartan treatment had greater improvement in FMD (mean (SEM) 7.1 (1.1)%) than patients with DI (3.1 (1.3)%, p = 0.024) or DD genotype (3.1 (1.1)%, p = 0.02).

CONCLUSIONS

Enalapril and losartan, with surgical coronary revascularisation, significantly improve systemic endothelial function. Revascularisation alone produces a quantitatively smaller, but still significant, improvement. The ACE genotype significantly modulates this response. Patients with the II genotype have a more pronounced impairment in endothelial function at baseline and a greater improvement in response to treatment with these agents.

Acute hyperglycemia does not affect the reactivity of coronary microcirculation in humans

OBJECTIVE

There is some evidence that acute hyperglycemia (H) may cause vascular dysfunction in normal subjects. This study investigates whether acute, short-term H affects coronary vasodilatory function in healthy subjects.

DESIGN

Diastolic peak flow velocity in the left anterior descending coronary artery was measured at rest and after dipyridamole (0.56 mg/kg over 4 min) using transthoracic color Doppler echocardiography in 13 healthy men. Coronary flow reserve (CFR) was defined as the ratio of dipyridamole-induced coronary peak diastolic to resting peak diastolic flow velocity. CFR was measured both in euglycemia (E) and after 3 h H ( approximately 14 mmol/liter) by a variable infusion of glucose and octreotide (0.4 mg/h) to prevent increase in insulin concentration.

RESULTS

Fasting plasma glucose increased to 14.3 +/- 0.33 mmol/liter during the study and maintained variability within less than 10%. Plasma insulin remained nearly stable during H. Resting diastolic flow velocity was 18.5 +/- 0.6 cm/sec in E and increased to 20.0 +/- 0.7 cm/sec during H (P < 0.005). Dipyridamole infusion produced a marked increase in coronary flow velocity, which reached values of 50.8 +/- 2.9 cm/sec in E and 51.8 +/- 2.1 cm/sec in H (P = not significant). CFR was 2.78 +/- 0.16 in E and 2.59 +/- 0.12 in H (P = not significant).

CONCLUSION

Our study indicates that short-term hyperglycemia does not affect the vasodilatory response of coronary microcirculation in healthy subjects.

Arterial and renal consequences of partial genetic deficiency in tissue kallikrein activity in humans

Tissue kallikrein (TK), the major kinin-forming enzyme, is synthesized in several organs, including the kidney and arteries. A loss-of-function polymorphism of the human TK gene (R53H) induces a substantial decrease in enzyme activity. As inactivation of the TK gene in the mouse induces endothelial dysfunction, we investigated the vascular, hormonal, and renal phenotypes of carriers of the 53H allele. In a crossover study, 30 R53R-homozygous and 10 R53H-heterozygous young normotensive white males were randomly assigned to receive both a low sodium-high potassium diet to stimulate TK synthesis and a high sodium-low potassium diet to suppress TK synthesis, each for 1 week. Urinary kallikrein activity was 50-60% lower in R53H subjects than in R53R subjects. Acute flow-dependent vasodilatation and endothelium-independent vasodilatation of the brachial artery were both unaffected in R53H subjects. In contrast, R53H subjects consistently exhibited an increase in wall shear stress and a paradoxical reduction in artery diameter and lumen compared with R53R subjects. Renal and hormonal adaptation to diets was unaffected in R53H subjects. The partial genetic deficiency in TK activity is associated with an inward remodeling of the brachial artery, which is not adapted to a chronic increase in wall shear stress, indicating a new form of arterial dysfunction affecting 5-7% of white people.

Insulin treatment and cardiovascular disease; friend or foe? A point of view

BACKGROUND

Several observational studies have shown that higher insulin levels are associated with an increased risk of cardiovascular disease. If higher endogenous insulin levels are causally related to cardiovascular disease, one might expect an increased risk of cardiovascular disease in patients treated with insulin, as this results in high circulating insulin levels. Such risk elevation might counteract the benefits of tight glucose control. Our objective was to explore the relationship between insulin therapy and cardiovascular disease in Type 1 and Type 2 diabetes mellitus using information from available literature.

SUMMARY OF COMMENT

Several experimental studies in animals and humans support the presence of a harmful effect of insulin on the vascular endothelium. In prospective follow-up studies increased insulin dosage was associated with increased risks of cardiovascular disease, although confounding by indication could not be excluded. Randomized controlled trials in diabetic patients, comparing conventional with intensive glucose-lowering treatment, although showing a reduction in microvascular disease, showed no significant difference in the incidence of cardiovascular disease. The results with respect to exposure to insulin are, however, difficult to interpret due to insufficient information on exposure to insulin levels as well as confounding by glycaemic control and body mass index. In addition, these studies were not designed to address the question whether higher insulin use relates to increased cardiovascular risk.

CONCLUSION

Published research provides conflicting evidence as to whether exposure to high levels of exogenous insulin in diabetes mellitus affects the risk of cardiovascular disease. The currently available studies have a number of serious methodological restraints that limit accurate interpretation and conclusions in this area.

Endothelial dysfunction in patients with asthma: the role of polymorphisms of ACE and endothelial NOS genes

OBJECTIVES

Polymorphisms of the angiotensin converting enzyme (ACE) and endothelial nitric oxide (eNOS) genes have been implicated in asthma pathogenesis. Angiotensin II and NO have important roles in maintaining vascular tone. In this study, the relationship between endothelial dysfunction and ACE and eNOS gene polymorphisms was investigated in patients with asthma.

METHODS

This cross-sectional, controlled study was conducted at the Yedikule Chest Disease Hospital and Cardiology Center in a University Hospital. Forty-nine patients with asthma (18 male, 31 female; mean age: 33+/-12 years) and 49 age- and sex-matched healthy controls (20 male, 29 female; mean age: 30+/-8 years) were included. Pulmonary function tests and flow-mediated dilatation of the brachial artery [endothelium dependent dilatation (EDD)] were examined by high-resolution ultrasonography. The ACE and eNOS genotypes were determined by PCR.

RESULTS

Asthma patients showed lower EDD (12+/-6% vs. 22+/-6%, p<0.001) as compared to controls. The EDD was correlated with both predicted value of FEV1 (r=0.31, p=0.04) and predicted value of FVC (r=0.37, p=0.013). Conversely, EDD values in patients with moderate asthma were significantly lower than those in patients with mild asthma (10.1+/-5.2% vs. 14.1+/-5.7%, p=0.017). However, the ACE and eNOS genotype distribution was not significantly different between controls and asthma groups. Furthermore, EDD was not associated with both gene polymorphism of ACE and eNOS.

CONCLUSION

Patients with asthma have decreased vasodilatatory response to shear stress (EDD). Decreased EDD is correlated with the severity of asthma, but not with the distribution of ACE and eNOS genotypes.

Interactive effects of the ACE DD polymorphism with the NOS III homozygous G849T (Glu298-->Asp) variant in determining endothelial function in coronary artery disease

The products of nitric oxide synthase (NOS) and angiotensin-converting enzyme (ACE) play a critical role in determining vessel wall structure and function. Polymorphisms in both genes have been independently demonstrated to influence propensity to cardiovascular events. The purpose of this study was to determine the influence of the homozygous G849T (Glu298-->Asp) polymorphism in NOS III on peripheral conduit artery endothelial function and to elucidate the modifier role, if any, of a common ACE polymorphism. Three hundred and ninety-seven consecutive subjects presenting to the cardiac catheterization laboratory of the University of Michigan over a period of 18 months were recruited. DNA was extracted and polymerase chain reaction (PCR) analysis for ACE and NOS polymorphisms performed. Patients with homozygosity for G849T at both loci (TT) who belong to DD and II ACE genotype (groups 1 and 2) and those who are negative for this polymorphism (GG) and belong to either DD or II genotype (groups 3 and 4) were identified. The four groups then underwent determination of conduit endothelial function. Heterozygosity of Glu298-Asp or the ID variant of the ACE were not studied. Median FMD value in the TT-DD group was 0.20 (-3.17, 2.01) compared with 2.23% (-0.29, 4.17) in the GG-II group. Median values in the TT-II and the GG-DD groups were 3.04 (-1.16, 6.61) and 2.46% (-1.83, 6.52) respectively. These values were not statistically significant (p > 0.05 by one-way ANOVA). Median nitroglycerin-mediated dilation in the four groups did not differ between the four groups (p = NS by ANOVA). Atherosclerosis burdens as assessed by angiography were not different across the groups. In conclusion, the homozygous NOS III variant (GG) status does not seem to interact additively with the ACE homozygous DD genotype in determining flow-mediated vasodilation in individuals with established atherosclerosis and pre-existent endothelial dysfunction.

Angiotensin-Converting Enzyme Insertion/Deletion Polymorphism Modulates Coronary Release of Tissue Plasminogen Activator in Response to Bradykinin

The aim of this study was to assess the relationship between the angiotensin converting enzyme gene (ACE) genotype and endothelium-dependent coronary vasomotor and fibrinolytic activity. The ACE DD genotype has been reported to be a risk factor for myocardial infarction. However, the mechanism is unknown. The fibrinolytic and renin-angiotensin systems are linked via ACE at the vascular beds. We studied 73 patients (II: n=24; ID: n=37; DD: n=12) who underwent diagnostic cardiac catheterization. Graded doses of bradykinin (BK) (0.2, 0.6, 2.0 microg/min) and acetylcholine (30,100 microg/min) were administered into the left coronary artery. Coronary blood flow (CBF) was evaluated by measuring Doppler flow velocity. Blood samples were taken from the aorta (Ao) and the coronary sinus (CS). Coronary release of tPA antigen was determined as a CS-Ao gradientXCBFX[(100-hematocrit) / 100]. ACE genotypes were determined using polymerase chain reaction. The ACE genotype did not appear to affect coronary macro- and microvascular responses induced by BK or acetylcholine. Coronary tissue plasminogen activator (tPA) release induced by BK was depressed in subjects with the ACE DD genotype. ACE levels in the DD genotype were significantly higher than those in the ID or II genotype. In all of the subjects, there was a significant negative correlation between the serum level of ACE activity and net coronary tPA release in response to BK at 0.6 microg/min. In conclusions, the DD genotype of the ACE gene impairs the coronary release of tPA induced by BK.

Insulin resistance and endothelial dysfunction

Insulin has multiple metabolic actions, including effects on blood vessels. Insulin normally increases blood flow by a mechanism which involves generation of nitric oxide (NO) via the arginine-NO pathway. Although insulin itself is a weak and physiologically unimportant vasodilatator, it appears to markedly potentiate endothelium-dependent vasodilatation. Therefore, anything that impairs insulin action in endothelial cells can be expected to be associated with endothelial dysfunction, i.e. loss of NO bioactivity in the vessel wall. Consistent with the idea that insulin resistance and endothelial dysfunction frequently coexist, all insulin-resistant conditions examined to date have been associated with endothelial dysfunction. However, the latter can also be caused by factors other than insulin resistance-such as a high concentration of low-density lipoprotein (LDL) cholesterol. Therapies which reverse insulin resistance-such as exercise, insulin and inhibitors of the renin-angiotensin-aldosterone (RAA) axis-also reverse endothelial dysfunction, which may thus be an inherent feature of insulin resistance.