DD angiotensin-converting enzyme gene polymorphism is associated with endothelial dysfunction in normal humans

Angiotensin converting enzyme insertion/deletion genotype is associated with leukoaraiosis in lacunar syndromes

OBJECTIVES

Pathological and clinical data suggest that patients presenting with ischaemic lacunar syndromes may be a heterogenous group. Those with isolated lacunar infarction are thought to have localised atherosclerosis whereas in those with coexisting leukoaraiois a distinct diffuse small vessel vasculopathy may be the predominant underlying pathology. The ACE insertion/deletion (I/D) polymorphism is an important candidate gene in ischaemic cerebrovascular disease but, where lacunar stroke specifically has been examined, there have been discrepant reports concerning a possible association. It was hypothesised that the influence of the ACE gene may be different among the two subgroups of ischaemic lacunar stroke reflecting the heterogeneity of the small vessel disease phenotype.

METHODS

Eighty four consecutive patients presenting with classic lacunar syndromes were studied. All had acute cranial CT to exclude primary intracerebral haemorrhage and these were subsequently assessed for the presence and extent of leukoaraiosis. All patients were genotyped for the ACE insertion/deletion polymorphism.

RESULTS

There was a significant difference in the distribution of ACE genotype with the DD genotype occurring more often in patients with leukoaraiosis and the II and ID genotypes occurring more often among those in whom this was absent (chi(2)=9.06, p=0.01). In a logistic regression model the ACE DD genotype remained as an independent predictor for the presence of leukoaraiosis (p=0.02) in patients presenting with classic lacunar syndromes.

CONCLUSION

This study supports the hypothesis that there may be different types of small vessel disease in patients with classic lacunar syndromes and that the influence of the ACE DD genotype may be relevant in mediating the diffuse form of vessel injury.

Genetic determinants of vascular reactivity

Blood pressure is controlled by a complex combination of processes that influence cardiac output and peripheral vascular resistance. Multiple genes potentially influence each parameter involved in the control of blood pressure, and individuals with the same blood pressor level do not necessarily have the same genotype at relevant loci, nor do individuals with the same genotype at particular loci necessarily have the same blood pressure. Nevertheless, pharmacogenetic studies of vascular reactivity will certainly allow the analysis of the mechanisms affected by genes, and lead to a better understanding of the epidemiologic observations seen in large groups of patients. Polymorphisms in the genes of the renin-angiotensin system allow definition of the "genetic profile" associated with a higher risk of cardiovascular disease, and can also be linked to significant changes in vascular reactivity in arteries isolated from patients carrying the polymorphisms.

Contribution of gene polymorphisms in the renin-angiotensin system to macroangiopathy in patients with diabetic nephropathy

The renin-angiotensin system is important in the control of hemodynamic status and pathogenesis of macrovascular disease, which is a major cause of morbidity and mortality in patients with type 2 diabetes with nephropathy. Serum angiotensin-converting enzyme (ACE) and angiotensinogen (Atg) levels are related to their respective gene polymorphisms. Seventy patients with type 2 diabetes with overt nephropathy (serum creatinine >/= 1.5 mg/dL) were studied. Serum ACE activity was measured by the spectrophotometric method. ACE deletion/insertion (D/I) and Atg M235T genotypes were determined by polymerase chain reaction. Patients with and without macroangiopathy were compared. Those with macroangiopathy had increased ACE activity (median, 60.9 U/L; range, 37.9 to 100 U/L versus without macroangiopathy, 47.9 U/L; range, 11.2 to 84.5 U/L; P = 0.01) and prevalence of ACE DD/DI genotypes (DD/DI:II: with macroangiopathy, 61%:39% versus without macroangiopathy, 34%:66%; P = 0.03). Multivariate analysis using age; sex; duration of diabetes; glycemic, blood pressure, and lipid level control; serum creatinine level; and presence of the ACE D allele showed that presence of the D allele (P = 0.03; odds ratio, 1.8; confidence interval, 1.1 to 3.1) and serum creatinine level (P = 0.0007) were independent risk factors for macroangiopathy. Association of the D allele became insignificant after serum ACE activity was included in the analysis in which only serum ACE activity (P = 0.004) and serum creatinine level (P = 0.01) were independent risk factors. Neither Atg M235T nor its synergistic effect with the ACE D allele showed an association with macroangiopathy. In conclusion, the ACE D allele is associated with macroangiopathy in Chinese patients with type 2 diabetes with nephropathy. The association is dependent on its effect on serum ACE activity, which is an independent risk factor for the development of macroangiopathy.

Polymorphisms in the renin-angiotensin system and endothelium-dependent vasodilation in normotensive subjects

BACKGROUND

Our aim was to test the hypothesis that genes encoding components in the renin-angiotensin system influence endothelial vasodilatory function.

METHODS

In 59 apparently healthy, normotensive individuals, endothelium-dependent vasodilation (EDV) and endothelial-independent vasodilation (EIDV) was evaluated by infusing metacholine and sodium nitroprusside into the brachial artery. Forearm blood flow was measured by venous occlusion plethysmography. The ACE insertion (I)/deletion (D) polymorphism, the T174M and M235T angiotensinogen restriction fragments length polymorphisms, the angiotensin II receptor type 1 (AT1R) A1166C, and the aldosterone synthase gene (CYP11B2) C-344T polymorphisms were analysed.

RESULTS

When analysing the ACE, the two angiotensinogen and the aldosterone synthase CYP11B2 genotypes independently, no significant association with endothelial vasodilatory function was found. However, a significant reduction in endothelium-dependent vasodilation was observed in the subjects (n=9) with the ACE D allele and the angiotensinogen T174M genotype (P<0.05). Subjects with the AT1R genotype AC showed a reduction in both EDV (P=0.05) and EIDV (P=0.04) when compared with those with the AA genotype.

CONCLUSIONS

The subjects with the ACE D allele in combination with the angiotensinogen T174M genotype are associated with a reduced EDV. This together with the observation that the AC AT1R genotype is associated with a reduction in both EDV and EIDV, supports the hypothesis that endothelial vasodilatory function is influenced by genes in the renin-angiotensinogen system.

The kallikrein-kininogen-kinin system: lessons from the quantification of endogenous kinins

The purpose of the present review is to describe the place of endogenous kinins, mainly bradykinin (BK) and des-Arg(9)-BK in the kallikrein-kininogen-kinin system, to review and compare the different analytical methods reported for the assessment of endogenous kinins, to explain the difficulties and the pitfalls for their quantifications in biologic samples and finally to see how the results obtained by these methods could complement and extend the pharmacological evidence of their pathophysiological role.

Stroke: development, prevention and treatment with peptidase inhibitors

Stroke is the leading cause of long-term disability in the United States and affects more people than any other neurologic disorder. Hypertension is a major risk factor associated with stroke. Several anti-hypertensive agents have been used to treat chronic hypertension to reduce the morbidity and mortality of stroke. Previous experimental studies have shown reduced stroke mortality with angiotensin-converting enzyme (ACE) inhibitors. This review discusses the development of stroke and potential use of ACE inhibitors in prevention and treatment of this disease. Furthermore, this review focuses on current investigations aimed at cellular mechanisms involved in stroke-induced microvascular alterations.

The ACE I/D polymorphism and human physical performance

The D allele of the angiotensin-converting enzyme (ACE) I/D polymorphism is associated with elevated levels of serum and tissue ACE, increased production of the vasopressor angiotensin II and a reduction in the half-life of the vasodilator bradykinin. Several cardiac and renal conditions appear to have a worse prognosis in subjects homozygous for the D allele, whereas the I allele has been associated with enhanced endurance performance in elite distance runners, rowers and mountaineers. The nature of the gene-environment interaction between ACE I/D polymorphisms and physical training, an overview of recent findings and a discussion of possible underlying mechanisms is the subject of this review.

The DD-ACE genotype and cardiovascular disease

The renin-angiotensin-aldosterone system (RAS) plays a pivotal role in the cardiovascular system, and the therapeutic agents which interact with this pathway have a significant impact in both heart failure and following myocardial infarction (MI). Polymorphisms within the genes controlling this enzyme system may also contribute to the pathogenesis of cardiovascular disease. Over the last decade an association between a polymorphism of the angiotensin converting enzyme (ACE) gene (called the DD-ACE polymorphism) and phenotypic expression of cardiovascular disease, namely MI, has been reported. Since then, several small case-controlled studies have confirmed an association with manifestations of ischaemic heart disease or various other cardiac end points. However, in a large prospective study the ACE gene was found to confer no appreciable risk. This review article considers the evidence that links polymorphisms of the ACE gene with cardiovascular disease. The Medline database (1990 - 2000) was searched using the keywords myocardial infarction, ischaemic heart disease, angiotensin converting enzyme, polymorphisms (a search of the reference citations of relevant articles was also performed), and clinical studies on cardiovascular disease related to the ACE genotype were selected. Taken together, the available evidence supports the notion that the DD-ACE genotype adversely influences specific cardiovascular diseases, but appears to do so in specific geographical areas and in particular patient subgroups. It is not yet known whether it does this through an interaction with other genes or by as yet unexplained biochemical mechanisms. However, the impact of the DD-ACE genotype appears to be small and its clinical manifestations rather heterogeneous. This finding is not in contrast to the overall impact of the renin-angiotensin system in cardiovascular disease, given the fact that the ACE enzyme is only one component in the renin-angiotensin cascade and that one genetic variant cannot be expected to contribute more than a minor individual impact in genetically complex multifactorial cardiovascular disease.

Context-dependent genetic effects in hypertension

There is a growing frustration with the limitations and inconsistencies of single locus candidate gene association and linkage studies. This frustration is exacerbated by the knowledge that a large influx of genotypic and gene expression data is expected to emerge over the next 5 years, and we are not prepared for the type of multigenic conceptual framework that will be necessary to analyze that data. A review of the hypertension genetic literature reveals substantial evidence for the importance of both genetic and environmental contexts on the mapping between single locus polymorphisms and risk of disease. These trends indicate that the current reliance on simple single gene studies to elucidate the complex etiology of hypertension needs to undergo some kind of transformation. It is suggested that even a minor shift to a more systematic investigation of context-dependent effects will increase our understanding of the multidimensional genetic and environmental realities underneath current studies. This shift is also necessary if we are to gain a deeper understanding of the specific ways in which an individual's risk of hypertension is a consequence of the inter- actions among genes and environments.