Genetic determinants of the development of chronic heart failure and the degree of endothelial dysfunction in patients with coronary artery disease and arterial hypertension

The dissertation is devoted to the study of genetic determinants associated with the development of chronic heart failure (CHF) and the degree of endothelial dysfunction in patients with coronary artery disease and arterial hypertension. The work analyzes the alleles and genotype frequencies of polymorphic loci of the interleukin-1β gene, the type 1 angiotensin II receptor gene, the angiotensinogen gene, and the endothelial NO synthase gene, as well as their associations with the severity and course of CHF and with the state of vasomotor endothelial function. The data obtained indicate the existence of sex-related differences in the patterns of association and suggest that the investigated polymorphisms may be regarded as potential markers of risk and prognosis of CHF in this category of patients.

Relevance of the topic. Despite significant advances in the treatment of cardiovascular diseases, the prevalence of chronic heart failure (CHF) is not only not declining but is continuously rising. Among all patients seeking care at medical institutions of the Russian Federation, 38.6% present signs of CHF. In 2002, the Russian Federation had 8.1 million people with clear signs of chronic heart failure, of whom 3.4 million had terminal functional class III–IV disease [Ageev F. T. et al., 2004]. In 2003, decompensation of CHF was the cause of hospitalization in cardiology departments for almost every second patient (49%), and CHF appeared in the diagnosis of 92% of hospitalized patients [Cleland J. G. et al., 2003]. In addition to its wide prevalence, heart failure is characterized by high rates of disability and mortality. One-year mortality among patients with clinically manifest CHF reaches 26–29% [Danielyan M. O., 2001]. A conclusion common to all epidemiological studies is that the incidence of heart failure rises sharply with increasing age of patients.

Studies of the human genome have made early, presymptomatic diagnosis of not only monogenic but also many multifactorial diseases a reality [Baranov V. S., 2000]. In practice, this goal can be achieved by molecular testing of candidate genes [Baranov V. S. et al., 2000; Le Corvoisier P. et al., 2003]. The latter can be defined as genes whose heritable variants (polymorphisms) are compatible with life but, in combination with adverse environmental factors (medications, dietary products, harmful habits, infections, environmental pollution), may cause various pathological conditions and diseases, including such common ones as atherosclerosis, coronary artery disease, diabetes mellitus, and others.

Among the causes of CHF, the leading multifactorial diseases are arterial hypertension (AH) and coronary artery disease (CAD). According to the Russian EPOKHA-O-CHF study, in 4/5 of all Russian patients with HF the disease is associated with AH and in 2/3 of patients with CAD [Ageev F. T. et al., 2004].

It has long been established that in the development of cardiovascular diseases in general and of CHF in particular, endothelial dysfunction (ED) occupies a special place as a typical pathological process underlying disturbances of microcirculation in organs and tissues [Mayansky D. N., 2007]. Endothelial dysfunction participates in the development of CHF through increased activity of the tissue and circulating renin–angiotensin–aldosterone system (RAAS), suppression of endothelial NO synthase expression, which leads to chronic reduction of blood flow and an abnormal vascular response to shear stress, elevation of pro-inflammatory cytokines, increased concentration of free radicals, and elevation of low-density and very low-density lipoproteins, etc. [Naseem K. M., 2005; Denisov E. N. et al., 2007].

A considerable number of genes involved in the development of CHF are currently being studied. These include the genes of aldosterone synthase, TNF-α, transforming growth factor β-1, brain natriuretic peptide, endothelial NO synthase, and others [Moiseev V. S., 2000; Bleumink G. S. et al., 2004; Gubaev K. I. et al., 2006; Kitsios G. et al., 2007; Pilbrow A. P. et al., 2007; Kuznetsova T. Yu. et al., 2007].

Thus, molecular genetic studies may play an important role in the early detection of cardiovascular diseases before the manifest clinical symptomatology, and may be of value in the substantiated prediction of complications and outcomes, and in increasing the effectiveness of treatment.

Initial hypothesis: genetic determinants of the risk of development, severity, and course of CHF, as well as of the degree of endothelial dysfunction, may be identified in patients with CAD and AH and may be used to single out groups at increased risk of CHF and to predict the course of the disease.

Aim of the study: To evaluate the significance of determining genetic determinants of the risk of development, severity, and course of chronic heart failure, as well as of the degree of endothelial dysfunction, in patients with coronary artery disease and arterial hypertension.

Objectives of the study:

1. To identify genetic markers of the risk of CHF development in patients with CAD and AH.

2. To determine the frequencies of alleles and genotypes of the C+3953T polymorphism of the IL-1β gene, VNTR (intron 2) of the IL-1Ra gene, A1166C of the AT2R1 gene, M235T of the AGT gene, and Glu298Asp and 4a/4b of the endothelial NO synthase gene in CHF patients with CAD and AH, depending on the severity and course of CHF.

3. To analyze the associations of polymorphic variants of the studied genes with the severity and course of CHF in patients with CAD and AH.

4. To investigate the vasomotor endothelial function in CAD and AH patients with varying severity and course of CHF against the background of basic therapy.

5. To analyze the associations of polymorphic variants of the studied genes with echocardiographic indices of the structural and functional state of the left ventricle and with the state of vasomotor endothelial function.

Scientific novelty. In a study of the C+3953T polymorphism of the IL-1β gene, VNTR of the IL-1Ra gene, and Glu298Asp and 4a/4b of the eNOS gene in patients with CAD and AH, it was found that the C allele and the C/C genotype of the C+3953T polymorphic locus of the IL-1β gene, as well as the Glu/Glu genotype of the Glu298Asp polymorphic locus of the eNOS gene, are associated with an increased risk of CHF development independently of age, hypercholesterolemia, smoking, family history of CAD and AH, and prior myocardial infarction. In studying the relationships of polymorphic variants of these genes and of the AT2R1 gene (A1166C), gender differences were identified for the first time: in the male population, the C allele and CC genotype of the IL-1β gene (C+3953T) and the Glu/Glu genotype of the eNOS gene (Gln298Asp) were associated with an increased risk of CHF, whereas in women only carriage of the C allele of the AT2R1 gene (A1166C) was a factor of increased risk of this pathology.

Data on new genetic determinants of the course of CHF against the background of CAD and AH were obtained: genotypes containing the C allele of the AT2R1 gene (A1166C), the C/C genotype of the IL-1β gene (C+3953T), and the Glu/Glu genotype (Glu298Asp) of the eNOS gene are associated with an unfavorable course of CHF, while predictors of a favorable course of CHF are carriage of the T allele of the IL-1β gene (C+3953T), carriage of the Asp allele of the eNOS gene (Glu298Asp), and the A/A genotype of the AT2R1 gene (A1166C).

This study demonstrated the influence of the M235T polymorphism of the AGT gene, the C+3953T polymorphism of the IL-1β gene, and the Glu298Asp polymorphism of the eNOS gene on the severity of clinical manifestations of CHF in patients with CAD and AH. An association was established between the T/T genotype of the AGT gene (M235T), the C/C genotype of the IL-1β gene (C+3953T), the Glu/Glu genotype of the eNOS gene (Glu298Asp), and more severe clinical manifestations of CHF, whereas carriage of the M allele of the AGT gene (M235T), the T allele of the IL-1β gene (C+3953T), and the Asp allele of the eNOS gene (Glu298Asp) played a protective role.

The study revealed an association between the state of vasomotor endothelial function and the C+3953T polymorphism of the IL-1β gene, whereas with respect to the M235T polymorphism of the AGT gene and the VNTR (intron 2) polymorphism of the IL-1Ra gene the differences were not statistically significant.

For the first time, an interrelation was shown between the polymorphisms of the studied genes, the degree of endothelial dysfunction, and the development and progression of CHF in patients with CAD and AH.

Practical significance. The results of this work make it possible to use genetic markers in CAD and AH patients as criteria for individual prognosis, for the formation of groups at increased risk of CHF (taking into account the sex-related differences identified), and for the assessment of the severity and course of CHF in order to enhance motivation and responsiveness to prevention and treatment. For this purpose, the results of genetic investigation of polymorphic variants of the interleukin-1β gene (C+3953T), endothelial NO synthase gene (Glu298Asp), angiotensinogen gene (M235T), and type 1 AT2 receptor gene (A1166C) can be used.

Statements for defense:

1. Polymorphisms of the IL-1β (C+3953T), AGT (M235T), AT2R1 (A1166C), and endothelial NO synthase (Glu298Asp) genes are associated with the risk of development, severity, and course of chronic heart failure in patients with coronary artery disease and arterial hypertension.

2. Associations between the risk of developing chronic heart failure against the background of coronary artery disease and arterial hypertension and polymorphisms of the IL-1β (C+3953T), AGT (M235T), and endothelial NO synthase (Glu298Asp) genes are detected only in the male population, while the A1166C polymorphism of the AT2R1 gene is associated with the risk of chronic heart failure only in women.

3. Endothelial dysfunction increases with the progression of chronic heart failure in patients with coronary artery disease and arterial hypertension, and its degree is associated with polymorphisms of the IL-1β (C+3953T), endothelial NO synthase (Glu298Asp), and type 1 AT2 receptor (A1166C) genes, indicating an interrelation between the polymorphic variants of the studied genes, the degree of vascular endothelial dysfunction, and the risk of development, severity, and course of chronic heart failure.