Polymorphism Gln27Glu of ß2 Adrenergic Receptors in Patients with Ischaemic Cardiomyopathy.

BACKGROUND: Polymorphisms of the Adrenergic Receptors (ARs) might affect the development and progression of Heart Failure (HF) and the response to treatment with ß-blockade therapy. OBJECTIVE: To examine the role of the Gln27Glu polymorphism of ß2-AR in HF development and to assess the hypothesis that Gln27Glu is associated with coronary artery disease in patients with ischaemic HF. METHODS: In this case control study we enrolled 155 consecutive patients with symptomatic HF of ischaemic aetiology with impaired Left Ventricular Ejection Fraction (LVEF) ≤35%. The control group consisted of 133 patients with no obstructive coronary artery disease and or evidence of HF. RESULTS: Concerning HF and control subjects there was no significant differences in the prevalence of Gln27Gln homozygotes (46 vs. 44%, p=0.82). In HF patients concerning the differences in patient characteristics between allele categories (Gln27Gln vs. Gln27Glu/Glu27Glu) there was no difference in risk factors, LVEF, treatment, the clinical status and NYHA categorization of patients, and in the prevalence of multi-vessel coronary artery disease. Interestingly, participants homozygous for Gln had significant higher prevalence of previous myocardial infarction (Gln27Gln vs. Gln27Glu/Glu27Glu: 77 vs. 23%, p=0.02). CONCLUSION: The present study shows that the Gln27Gln genotype of ß2-AR is the most predominant while the Glu27Glu is the least prevalent in our HF population. There was no difference in the prevalence of polymorphism Gln27Glu between HF patients and control subjects. However, the presence of Glu allele was associated with lower myocardial infarction rate.

From rest to stressed: endothelin-1 levels in young healthy smokers and non-smokers.

INTRODUCTION: Endothelin-1 (ET-1) is a potent vasoconstrictor produced by vascular endothelial cells, and a known marker of endothelial dysfunction. However, the acute and chronic effects of smoking and nicotine gum on the ET-1 response to acute physical stress in young healthy smokers have not been investigated. METHODS: Healthy smokers (n=35) and non-smokers (n=35) underwent an exercise test to exhaustion (maximal oxygen consumption) on a treadmill. Smokers were assessed a) after 12h smoking abstinence (termed chronic smoking), b) immediately after smoking one cigarette (termed acute smoking), and c) immediately after chewing nicotine gum. Blood was drawn immediately pre-exercise, and 3 minutes post-exercise. During exercise, cardiorespiratory parameters were obtained breath-by-breath using an automated metabolic cart. Plasma ET-1 levels were quantified using enzyme-linked immunosorbent-assay. The above protocol was designed to incorporate exercise as a vascular stressor to reveal changes that would not be detected at rest. RESULTS: Mean age was 28.6±7.2 years and body mass index (BMI) was 23.6±3.2 kg/m(2). Post-exercise ET-1 levels were significantly lower than pre-exercise levels in non-smokers (P<0.001) and smokers under all three conditions (P=0.005, P<0.001, P=0.001, respectively). There were no differences in post-exercise ET-1 levels between non-smokers and smokers under all three conditions, however the absolute and relative decrease in ET-1 levels was significantly smaller in chronic smokers compared with non-smokers (P=0.007 and P=0.004). Chronic smokers had a significantly lower exercise-induced change in tidal volume (P=0.050), fraction of expired CO2 (P=0.021), oxygen consumption (P=0.005), carbon dioxide elimination (P=0.004) and peak expiratory flow (P=0.003) compared with non-smokers. Furthermore, the decrease in ET-1 observed in non-smokers in response to exercise was significantly associated with exercise induced-changes in inspiratory time, time for a tidal volume cycle, respiratory frequency, inspired minute ventilation and peak inspiratory flow. CONCLUSIONS: An acute decrease of circulating ET-1 in response to acute maximal exercise in young healthy individuals was noted. Chronic smokers had a significantly diminished decrease in ET-1 compared with non-smokers, however there were no significant differences in the ET-1 response between smokers under the three smoking conditions. Smokers were not able to achieve the same exercise-induced changes in cardiorespiratory parameters as non-smokers. By incorporating exercise as a vascular stressor in our study, we have taken a novel approach to provide evidence of an altered ET-1 and cardiorespiratory response that would not otherwise be observed at rest in young active healthy smokers.