From pharmacogenomics to improved patient outcomes: angiotensin I-converting enzyme as an example

ACE gene polymorphism is associated with COPD and COPD with pulmonary hypertension: a meta-analysis

Purpose

Angiotensin-converting enzyme (ACE) gene I/D polymorphism has been studied in relation to the susceptibility to COPD and COPD with pulmonary hypertension (PH) with inconclusive results. We performed the first comprehensive meta-analysis to evaluate accurately the association between the ACE gene polymorphism and the risk of COPD.

Methods

Data were analyzed using odds ratios (ORs) and the corresponding 95% CIs to measure the strength of the models. Subgroup analyses were conducted by ethnicity and complication which referred to PH.

Results

In total, 15 studies (2,635 participants) were included in our study, of which four studies (288 participants) were for PH subgroup. The overall analysis results indicated that the ACE gene polymorphism was not associated with COPD susceptibility in all gene models. However, the ethnic subgroup analysis results indicated that ACE gene polymorphism was associated with Asians’ susceptibility to COPD (DD+DI vs II, OR=1.47, P=0.019, 95% CI: 1.07–2.02). Further, the overall results of the present study detected no statistical significance between ACE gene polymorphism and the risk of COPD with PH, but the homozygote variant (DD) increased the risk of PH in Asian COPD patients (DD vs ID+II, OR=2.05, P=0.05, 95% CI: 1.00–4.19).

Conclusion

The current study suggests that ACE polymorphism, particularly the homozygote variant (DD), might contribute to the risk of COPD and COPD with PH among Asians. Further studies with larger sample size and more ethnicities are expected to be conducted in the future to validate the results.

The role and regulation of cardiac angiotensin-converting enzyme for noninvasive molecular imaging in heart failure

Congestive heart failure is a pathologic condition characterized by progressive decrease in left ventricular contractility and consequent decline of cardiac output. There is convincing clinical and experimental evidence that the renin-angiotensin system (RAS) and its primary effector peptide, angiotensin II, are linked to the pathophysiology of interstitial fibrosis, cardiac remodeling, and heart failure. In addition to the traditional endocrine or circulating RAS, an active tissue RAS has been characterized. Tissue angiotensin-converting enzyme and locally synthesized angiotensin II, for example, by chymase, exert local trophic effects that modulate gene expression, which regulates growth and proliferation in both myocytes and nonmyocytes. The existence of the tissue RAS offers an opportunity for targeted imaging, which may be of considerable value for guiding medical therapy.

Imaging the renin-angiotensin-aldosterone system in the heart

The influence of the renin-angiotensin system (RAS) is recognized in cardiac and vascular injury. An extrinsic RAS has been known for decades, and an equally important intrinsic RAS has been discovered recently. The latter leads to pathologic tissue alterations in the absence of systemic stimuli and may be the main source of local tissue effects of RAS. A new radiotracer fluorobenzoyl-lisinopril was synthesized by radiolabeling benzoic acid active ester with 18F and reacting that with the epsilon-amino group of lisinopril. The presence of angiotensin-converting enzyme (ACE) activity and angiotensin II receptors was examined in relation to myocardial fibrosis. This tissue-specific radioligand represents the first study of ACE in the human heart. This article presents preliminary data on imaging the RAS in the human cardiac tissue and discusses the potential for clinical application of these imaging techniques to human patients.

Association of GNB3 gene with pulse pressure and clustering of risk factors for cardiovascular disease in Japanese

Heterotrimeric guanine nucleotide-binding proteins (G proteins) mediate many pathways including the beta-adrenergic signaling pathway. The C825T polymorphism in the gene coding for the beta3 subunit of G proteins (GNB3) has been shown to be associated with several phenotypes such as hypertension, obesity, and diabetes mellitus comprising the metabolic syndrome. The GNB3 C825T polymorphism may therefore be associated with many atherosclerosis-related phenotypes. On these grounds, we studied the C825T polymorphism in relation to atherosclerosis-related phenotypes in a large Japanese population. Analyses in general linear models showed that T carriers had a significantly wider pulse pressure (P=0.0089) as well as a significantly higher systolic blood pressure (P=0.026). In contrast, analyses in logistic regression models showed that the C825T polymorphism was not significantly associated with each of the four major classical risk factors for cardiovascular and cerebrovascular disease (obesity, hypertension, hypertriglyceridemia, and diabetes mellitus). However, a significantly higher percentage of subjects had none of the four disorders in CC homozygotes than in T carriers (P=0.026). Thus, the C825T polymorphism was significantly associated with clustering of these four risk factors. Although the effect of the gene on each phenotype appears to be weak, considering the combined impact of the effects of the C825T polymorphism on risk factors, the GNB3 gene may be an important gene for human health.

The role of cost-effectiveness analysis in the era of pharmacogenomics

The broad availability of genetic information and technologies heralds an era when practitioners will utilise genomic testing to individualise patients' care. Pharmacogenomics uses a spectrum of approaches to explore the association of genetic variation with drug efficacy or toxicity. Investigators have described a broad array of genetic polymorphisms that confer inter-individual differences in drug response. Pharmacogenomics offers the potential to improve drug effectiveness, reduce adverse drug reactions and provide cost-effective care. However, it has had little impact on current clinical practice and the economic implications of pharmacogenomics remain unclear. Assessing the incremental cost effectiveness of a pharmacogenomic strategy involves examination of factors associated with the genotype of interest, the genomic test, the disease state and the treatment. A pharmacogenomic strategy is likely to be cost effective when: (i) the polymorphism under consideration is prevalent in the population and has a high degree of penetrance; (ii) genetic testing is highly sensitive and specific, and less costly alternative tests that could be used to individualise therapy are not readily available; (iii) the disease state involves outcomes with significant morbidity or mortality if left untreated; and (iv) the treatment involves significant outcomes and/or costs that can be impacted by genotype-individualised therapy. We foresee pharmacogenomic applications being particularly relevant for drugs: with a narrow therapeutic index or a high degree of variability in inter-individual response; where there are limitations in current methods for monitoring their adverse effects and treatment responses; and where there are few alternative treatment options. Because of the characteristics of chemotherapeutic agents and the severity of clinical outcomes in cancer, oncology appears to be one of the most appropriate disease areas for the application of pharmacogenomics. We have developed a framework which can assist researchers, pharmacists, physicians, and policy makers in evaluating the implications of specific strategies, and identifying when formal cost-effectiveness analyses should be conducted to quantitatively evaluate the benefits of pharmacogenomics.

Pathophysiologic implications of angiotensin I-converting enzyme as a mechanosensor: diabetes

If somatic angiotensin I-converting enzyme (ACE) were a mechanosensor, as recently claimed, it would provide insight into the molecular origin of most adult diseases, such as diabetes, cancer, autoimmune diseases, and psychiatric disease, as well as aging itself. The "ACE as mechanosensor" hypothesis holds that tissue ACE is activated by turbulent flow with each heart beat, so that age-dependent diseases begin with a signal from the vasculature. Activation of ACE would thus represent the first of many amplification steps ("cascades"), placing it at the origin of most age-dependent diseases. As a corollary, effective inhibition of tissue ACE might significantly delay the progression of most diseases of aging. In this paper we will explore how useful this hypothesis is in explaining the molecular pathogenesis of diabetes and its complications, in which aging is accelerated.

Is "somatic" angiotensin I-converting enzyme a mechanosensor?

"Somatic" angiotensin I-converting enzyme (ACE) appears to be one of the evolutionary advances that made a closed circulation possible, and may have contributed to the Cambrian "explosion" of species approximately 540 million years ago. It also appears to be at the origin of a large number of common human diseases. A model is proposed in which the duplicated form of ACE ("somatic" ACE) functions as a mechanotransducer, defending downstream vessels and tissues from an increase in pressure. In the model, ACE senses shear stress (blood velocity) in regions of turbulent blood flow. An increase in shear stress strips an autoinhibitor tripeptide, FQP, from the N-terminal active site, thereby activating it. The C-terminal domain is constitutively activated by chloride. This model explains the clinical superiority of hydrophobic ACE inhibitors relative to hydrophilic ones.