Personalized vascular medicine: individualizing drug therapy

The Association between Gly460Trp-Polymorphism of Alpha-Adducin 1 Gene (ADD1) and Arterial Hypertension Development in Ukrainian Population

Arterial hypertension (AH) belongs to the diseases with genetic predisposition that determines the necessity of research on the genetic component's influence on this disease development. It is suggested that one of the salt-sensitive arterial hypertension potential markers may be the alpha-adducin gene because its protein product is involved in the ion transport regulation in the renal epithelium. Thus, the aim of the study was to investigate the association between ADD1 Gly460Trp-polymorphism and the AH development risk among patients with different risk factors in the Ukrainian population. The study included 232 Ukrainians: 120 patients with diagnosed arterial hypertension and 112 practically healthy individuals. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was used for ADD1 Gly460Trp-polymorphism genotyping. The ADD1 Gly460Trp-polymorphic locus is an important predictor of arterial hypertension development in the Ukrainian population, but other nongenetic factors should be considered in further studies.

Quantile-dependent expressivity of postprandial lipemia

Purpose

“Quantile-dependent expressivity” describes an effect of the genotype that depends upon the level of the phenotype (e.g., whether a subject’s triglycerides are high or low relative to its population distribution). Prior analyses suggest that the effect of a genetic risk score (GRS) on fasting plasma triglyceride levels increases with the percentile of the triglyceride distribution. Postprandial lipemia is well suited for testing quantile-dependent expressivity because it exposes each individual’s genotype to substantial increases in their plasma triglyceride concentrations. Ninety-seven published papers were identified that plotted mean triglyceride response vs. time and genotype, which were converted into quantitative data. Separately, for each published graph, standard least-squares regression analysis was used to compare the genotype differences at time t (dependent variable) to average triglyceride concentrations at time t (independent variable) to assess whether the genetic effect size increased in association with higher triglyceride concentrations and whether the phenomenon could explain purported genetic interactions with sex, diet, disease, BMI, and drugs.

Results

Consistent with the phenomenon, genetic effect sizes increased (P≤0.05) with increasing triglyceride concentrations for polymorphisms associated with ABCA1, ANGPTL4, APOA1, APOA2, APOA4, APOA5, APOB, APOC3, APOE, CETP, FABP2, FATP6, GALNT2, GCKR, HL, IL1b, LEPR, LOX-1, LPL, MC4R, MTTP, NPY, SORT1, SULF2, TNFA, TCF7L2, and TM6SF2. The effect size for these polymorphisms showed a progressively increasing dose-response, with intermediate effect sizes at intermediate triglyceride concentrations. Quantile-dependent expressivity provided an alternative interpretation to their interactions with sex, drugs, disease, diet, and age, which have been traditionally ascribed to gene-environment interactions and genetic predictors of drug efficacy (i.e., personalized medicine).

Conclusion

Quantile-dependent expressivity applies to the majority of genetic variants affecting postprandial triglycerides, which may arise because the impaired functionalities of these variants increase at higher triglyceride concentrations. Purported gene-drug interactions may be the manifestations of quantile-dependent expressivity, rather than genetic predictors of drug efficacy.

Personalized Medicine in the Treatment of Atrial Fibrillation: Myth or Reality?

Due to the spectacular progress made in human genomic studies, molecular biology and genetics have become an essential part of modern medicine making it possible to early detect the risk factors and select the personalized treatment. The genetic studies have been widely used in the diagnosis and treatment of arrhythmias. Significant advances in the study of electrophysiological and genetic mechanisms of life-threatening arrhythmias have been achieved through studies of familial conditions with high risk of sudden cardiac death. However, the area of special interest for a practitioner is the identification of mutations associated with atrial fibrillation (AF). The novel methods enable us to study histological, structural, cellular and molecular causes of this arrhythmia. The two main directions of molecular genetic studies of AF are the identification of genetic mutations causing familial atrial fibrillation and the study of different genes polymorphism predisposing to arrhythmia in general population. Gene polymorphism screening helps both identify AF risk factors and predict its evolution from paroxysmal to chronic type. Emerging genetic studies provided explanation for the variable efficacy of antiarrhythmic drugs. It can be assumed that the clinical use of genetic methods will allow accurate and personalized selection of antiarrhythmics. Currently, therapeutic drug monitoring is widely recommended for a number of medications including cytostatics, aminoglycosides, anticonvulsants, and, by some researchers, antiarrhythmic and anticoagulant drugs. Medicine from the very beginning was intended to be personalized, but until recently it was a little more than a myth. The discovery of the human genome makes it possible to choose the most effective treatment with minimal adverse drug reactions for a particular patient.

Prediction of Ischemic Events after Percutaneous Coronary Intervention: Thrombelastography Profiles and Factor XIIIa Activity

Background  High plasma fibrin clot strength (MA) measured by thrombelastography (TEG) is associated with increased risk of cardiac events after percutaneous coronary interventions (PCIs). Factor XIIIa (FXIIIa) cross-links soluble fibrin, shortens clot formation time (TEG-K), and increases final clot strength (MA).

Methods  We analyzed platelet-poor plasma from patients with previous PCI. Kaolin-activated TEG (R, K, MA) in citrate platelet-poor plasma and FXIIIa were measured ( n  = 257). Combined primary endpoint was defined as recurrent myocardial infarction (MI) or cardiovascular death (CVD). Relationship of FXIIIa and TEG measurements on cardiac risk was explored.

Results  FXIIIa correlated with TEG-MA ( p  = 0.002) and inversely with TEG-K ( p  < 0.001). High MA (≥35.35 mm; p  = 0.001), low K (<1.15 min; p  = 0.038), and elevated FXIIIa (≥83.51%; p  = 0.011) were associated with increased risk of CVD or MI. Inclusion of FXIIIa activity and low TEG-K in risk scores did not improve risk prediction as compared with high TEG-MA alone.

Conclusion  FXIIIa is associated with higher plasma TEG-MA and low TEG-K. High FXIIIa activity is associated with a modest increase in cardiovascular risk after PCI, but is less sensitive and specific than TEG-MA. Addition of FXIIIa does not provide additional risk stratification beyond risk associated with high fibrin clot strength phenotype measured by TEG.

Pharmacogenomics of oral antiplatelet drugs

Pharmacogenomics has been implicated in the response variability of antiplatelet drugs in coronary artery disease (CAD), particularly for aspirin and clopidogrel. A large number of studies and several meta-analyses have been published on this topic, but until recently, there have been no clear conclusions and no definite guidelines on the clinical use of pharmacogenetic testing before prescribing antiplatelet drugs for CAD. In this review, the available evidence is summarized. The most consistent results are on clopidogrel, where CYP2C19 loss-of-function alleles are associated with stent thrombosis events. We recommend to genotype for CYP2C19 loss-of-function alleles in patients with CAD who are to undergo percutaneous coronary intervention and stenting, and to adjust the antiplatelet treatment based on the genotyping results.

Progressive renal decline as the major feature of diabetic nephropathy in type 1 diabetes

Despite almost universal implementation of renoprotective therapies over the past 25 years, the risk of end-stage renal disease (ESRD) in type 1 diabetes (T1D) is not decreasing, and ESRD remains the major cause of excess morbidity and premature mortality [1]. Such a state of affairs prompts a call to action. In this review we re-evaluated the proteinuria-centric model of diabetic nephropathy and showed its deficiencies. On the basis of extensive studies that we have been conducting on the patients attending the Joslin Clinic, we propose that progressive renal decline, not abnormalities in urinary albumin excretion, should be considered as the major feature of disease processes leading to ESRD in T1D. The etiology of diabetic nephropathy should be reconsidered in light of our new findings so our perspective can be broadened regarding new therapeutic targets available for interrupting the progressive renal decline in T1D. Reduction in the loss of glomerular filtration rate, not reduction of albumin excretion rate, should become the measure for evaluating the effectiveness of new therapeutic interventions. We need new accurate methods for early diagnosis of patients at risk of progressive renal decline or, better still, for detecting in advance which patients will have rapid, moderate or minimal rate of progression to ESRD.

High risk of ESRD in type 1 diabetes: new strategies are needed to retard progressive renal function decline

Care of patients with type 1 diabetes (T1D) has changed during the past 30 years. Tools to control hyperglycemia have improved and it was shown that improvement in glycemic control diminished the risk of late diabetic complications, including nephropathy. Moreover, in patients with impaired renal function, aggressive treatment of hypertension and renoprotective blockade of the renin-angiotensin system were shown to postpone end-stage renal disease (ESRD), albeit for a short while. Despite these achievements, the incidence of ESRD caused by T1D in the US population has not decreased but rather has increased over the past 20 years, although it now occurs at slightly older ages. This state of affairs is a call to action. This should begin with adopting a new model of diabetic nephropathy in human beings. In that model, instead of microalbuminuria or proteinuria, the focus should be on diagnosis and treatment of progressive renal function decline that leads to ESRD. Such a model has received significant support in clinical and epidemiologic studies. Investigation of mechanisms of such progressive renal function decline should help in the identification of new therapeutic targets and the development of new interventions. To evaluate these interventions, accurate diagnostic algorithms are needed so T1D patients will be stratified according to time to onset to ESRD. Consistent with concepts of personalized medicine, the new interventions should be tailored to and evaluated in patients predicted to have rapid, moderate, or even slow progression to ESRD.

Pharmacogenetics of P450 oxidoreductase: implications in drug metabolism and therapy

The redox reaction of cytochrome P450 enzymes (CYP) is an important physiological and biochemical reaction in the human body, as it is involved in the oxidative metabolism of both endogenous and exogenous substrates. Cytochrome P450 oxidoreductase (POR) is the only obligate electron donor for all of the hepatic microsomal CYP enzymes. It plays a crucial role in drug metabolism and treatment by not only acting as an electron donor involved in drug metabolism mediated by CYP enzymes but also by directly inducing the transformation of some antitumor precursors. Studies have found that the gene encoding human POR is highly polymorphic, which is of considerable clinical significance as it affects the metabolism and curative effects of clinically used drugs. This review aims to discuss the effect of POR and its genetic polymorphisms on drug metabolism and therapy, as well as the potential mechanisms of POR pharmacogenetics.

Prospects of personalized medicine in cardiovascular diseases

Cardiovascular diseases remain the dominant cause of death worldwide. In the last decades, the remarkable advances in human genetic and genomic research, plus the now common use of genome-wide association studies, have led to the identification of numerous genetic variants associated with specific cardiovascular traits and diseases. Although the clinical applications are limited because the genetic risk of common cardiovascular disease is still unexplained, and the mechanisms of action of the genetic factor(s) are not known, these research advances have, in turn, widely opened the concept of personalized medicine. In this paper, the status and prospects of personalized medicine for cardiovascular disease will be presented. This will be followed by a discussion of issues regarding the implementation of personalized medicine.

Personalized medicine in cardiovascular diseases

Personalized medicine is a novel medical model with all decisions and practices being tailored to individual patients in whatever ways possible. In the era of genomics, personalized medicine combines the genetic information for additional benefit in preventive and therapeutic strategies. Personalized medicine may allow the physician to provide a better therapy for patients in terms of efficiency, safety and treatment length to reduce the associated costs. There was a remarkable growth in scientific publication on personalized medicine within the past few years in the cardiovascular field. However, so far, only very few cardiologists in the USA are incorporating personalized medicine into clinical treatment. We review the concepts, strengths, limitations and challenges of personalized medicine with a particular focus on cardiovascular diseases (CVDs). There are many challenges from both scientific and policy perspectives to personalized medicine, which can overcome them by comprehensive concept and understanding, clinical application, and evidence based practices. Individualized medicine serves a pivotal role in the evolution of national and global healthcare reform, especially, in the CVDs fields. Ultimately, personalized medicine will affect the entire landscape of health care system in the near future.