The angiotensin converting enzyme genetic polymorphism in acute coronary syndrome--ACE polymorphism as a risk factor of acute coronary syndrome

Interplay of Angiotensin Peptides, Vasopressin, and Insulin in the Heart: Experimental and Clinical Evidence of Altered Interactions in Obesity and Diabetes Mellitus

The present review draws attention to the specific role of angiotensin peptides [angiotensin II (Ang II), angiotensin-(1-7) (Ang-(1-7)], vasopressin (AVP), and insulin in the regulation of the coronary blood flow and cardiac contractions. The interactions of angiotensin peptides, AVP, and insulin in the heart and in the brain are also discussed. The intracardiac production and the supply of angiotensin peptides and AVP from the systemic circulation enable their easy access to the coronary vessels and the cardiomyocytes. Coronary vessels and cardiomyocytes are furnished with AT1 receptors, AT2 receptors, Ang (1-7) receptors, vasopressin V1 receptors, and insulin receptor substrates. The presence of some of these molecules in the same cells creates good conditions for their interaction at the signaling level. The broad spectrum of actions allows for the engagement of angiotensin peptides, AVP, and insulin in the regulation of the most vital cardiac processes, including (1) cardiac tissue oxygenation, energy production, and metabolism; (2) the generation of the other cardiovascular compounds, such as nitric oxide, bradykinin (Bk), and endothelin; and (3) the regulation of cardiac work by the autonomic nervous system and the cardiovascular neurons of the brain. Multiple experimental studies and clinical observations show that the interactions of Ang II, Ang(1-7), AVP, and insulin in the heart and in the brain are markedly altered during heart failure, hypertension, obesity, and diabetes mellitus, especially when these diseases coexist. A survey of the literature presented in the review provides evidence for the belief that very individualized treatment, including interactions of angiotensins and vasopressin with insulin, should be applied in patients suffering from both the cardiovascular and metabolic diseases.

Genetic background of acute coronary syndromes

Acute coronary syndromes (ACS) are one of the major causes of mortality nowadays. Although much is known about factors involved in atherogenesis and acute coronary events, there are still many cases in which a lack of classical risk factors, together with family history, suggests the presence of an unrevealed genetic predisposition and molecular mechanisms. This paper reviews genetic predisposition to ACS. It also indicates which genes are linked to the processes of destabilization and rupture of atherosclerotic plaque and thus may be potential targets for more effective prophylaxis and treatment.

Polymorphisms in the RAS and cardiac function

Since the discovery of the polymorphism in the angiotensin converting enzyme (ACE) and the consequences of this polymorphism on the activity levels of the enzyme, numerous association studies have been performed. However, these investigations do not often adhere to the most stringent criteria for such studies. The initial study reporting a positive association of the ACE polymorphism and myocardial infarction showed an increased risk of the DD genotype. This initial association was eventually refuted by a large, well conducted association study, which found a risk ratio of 1.02 after combining their own data with all published data. Although such large, well conducted association studies have not been performed in left ventricular (LV) hypertrophy, the association between DD genotype and hypertrophy is more convincing with a 192% excess risk of LV hypertrophy in untreated hypertensives. The role of ACE genotype in LV growth is well established, especially in athletes. In heart failure, large studies or meta-analyses have not been performed, because most studies have selected different end-points. This hampers a proper meta-analysis of the results obtained in associations with heart failure. As most association studies do not fulfill the criteria for good association studies and use too small sample sizes, it remains important to perform a meta-analysis to add meaning to the results of such studies. Above all, it is important to obey the rules set for association studies, large sample size, small P values, report associations that make biological sense and alleles that affect the gene product in a physiologically meaningful way.

Large-scale test of hypothesised associations between the angiotensin-converting-enzyme insertion/deletion polymorphism and myocardial infarction in about 5000 cases and 6000 controls. International Studies of Infarct Survival (ISIS) Collaborators

BACKGROUND

The original report of a possible association between myocardial infarction and the insertion/deletion (I/D) polymorphism of the gene for the angiotensin-1-converting enzyme (ACE) indicated a risk ratio for myocardial infarction with the DD genotype of 1.34 (95% CI 1.05-1.70), and the association was claimed to be particularly strong in a retrospectively defined low-risk subgroup (3.2 [95% CI 1.7-5.9). Subsequent investigations reached varying conclusions, but all were small, and much larger studies were needed.

METHODS

4629 myocardial infarction cases and 5934 controls were compared. Cases were UK men aged 30-54 years and women aged 30-64 years recruited on presentation to hospital with confirmed myocardial infarction. Controls were aged 30-64 years with no history of cardiovascular disease, but were siblings or children of myocardial infarction survivors, or spouses of such relatives. All risk-ratio calculations allow for this relatedness of some of the controls. An updated meta-analysis of previous studies was also conducted.

FINDINGS

The ACE DD genotype was found in 1359 (29.4%) of the myocardial infarction cases and in 1637 (27.6%) of the controls (risk ratio 1.10 [95% CI 1.00-1.21]). The association between myocardial infarction and the DD genotype did not seem to be stronger in the subgroup defined as low risk by previously used criteria (234 [28%] of 836 cases and 911 [28%] of 3253 controls: risk ratio 1.04 [95% CI 0.87-1.24]), or in any other subgroup. Nor was the ACE I/D genotype predictive of subsequent survival.

INTERPRETATION

This study involved many more cases than any previously reported study of this question, but did not confirm the existence of any substantial association. In an updated meta-analysis of these results with those of previously published studies, the risk ratio for myocardial infarction with the DD genotype seems to lie in the range 1.0 to about 1.1. Although an increase in risk of up to about 10-15% cannot be ruled out, substantially more extreme risks can be. Moreover, there are not especially strong associations in the subgroups previously selected for emphasis. These findings illustrate the need for some studies of candidate genes to involve much larger populations than is customary, without undue emphasis on retrospectively defined subgroups.