State of Play of Pharmacogenetics and Personalized Medicine in Heart Failure

The Role of Personalized Medicine in Companion Animal Cardiology

Cardiomyopathies remain one of the most common inherited cardiac diseases in both human and veterinary patients. To date, well over 100 mutated genes are known to cause cardiomyopathies in humans with only a handful known in cats and dogs. This review highlights the need and use of personalized one-health approaches to cardiovascular case management and advancement in pharmacogenetic-based therapy in veterinary medicine. Personalized medicine holds promise in understanding the molecular basis of disease and ultimately will unlock the next generation of targeted novel pharmaceuticals and aid in the reversal of detrimental effects at a molecular level.

Personalized medicine: going to the dogs?

Interindividual variation in drug response occurs in canine patients just as it does in human patients. Although canine pharmacogenetics still lags behind human pharmacogenetics, significant life-saving discoveries in the field have been made over the last 20 years, but much remains to be done. This article summarizes the available published data about the presence and impact of genetic polymorphisms on canine drug transporters, drug-metabolizing enzymes, drug receptors/targets, and plasma protein binding while comparing them to their human counterparts when applicable. In addition, precision medicine in cancer treatment as an application of canine pharmacogenetics and pertinent considerations for canine pharmacogenetics testing is reviewed. The field is poised to transition from single pharmacogene-based studies, pharmacogenetics, to pharmacogenomic-based studies to enhance our understanding of interindividual variation of drug response in dogs. Advances made in the field of canine pharmacogenetics will not only improve the health and well-being of dogs and dog breeds, but may provide insight into individual drug efficacy and toxicity in human patients as well.

Cardiac molecular imaging to track left ventricular remodeling in heart failure

Cardiac left ventricular (LV) remodeling is the final common pathway of most primary cardiovascular diseases that manifest clinically as heart failure (HF). The more advanced the systolic HF and LV dysfunction, the worse the prognosis. The knowledge of the molecular, cellular, and neurohormonal mechanisms that lead to myocardial dysfunction and symptomatic HF has expanded rapidly and has allowed sophisticated approaches to understanding and management of the disease. New therapeutic targets for pharmacologic intervention in HF have also been identified through discovery of novel cellular and molecular components of membrane-bound receptor-mediated intracellular signal transduction cascades. Despite all advances, however, the prognosis of systolic HF has remained poor in general. This is, at least in part, related to the (1) relatively late institution of treatment due to reliance on gross functional and structural abnormalities that define the "heart failure phenotype" clinically; (2) remarkable genetic-based interindividual variations in the contribution of each of the many molecular components of cardiac remodeling; and (3) inability to monitor the activity of individual pathways to cardiac remodeling in order to estimate the potential benefits of pharmacologic agents, monitor the need for dose titration, and minimize side effects. Imaging of the recognized ultrastructural components of cardiac remodeling can allow redefinition of heart failure based on its "molecular phenotype," and provide a guide to implementation of "personalized" and "evidence-based" evaluation, treatment, and longitudinal monitoring of the disease beyond what is currently available through randomized controlled clinical trials.

The future of pharmacogenetics in the treatment of heart failure

Heart failure is a common disease with high levels of morbidity and mortality. Current treatment comprises β-blockers, ACE inhibitors, aldosterone antagonists and diuretics. Variation in clinical response seen in patients begs the question of whether there is a pharmacogenetic component yet to be identified. To date, the genes most studied involve the β-1, β-2, α-2 adrenergic receptors and the renin-angiotensin-aldosterone pathway, mainly focusing on SNPs. However results have been inconsistent. Genome-wide association studies and next-generation sequencing are seen as alternative approaches to discovering genetic variations influencing drug response. Hopefully future research will lay the foundations for genotype-led drug management in these patients with the ultimate aim of improving their clinical outcome.

Effect of low-dose diuretics on the level of serum cystatin C and prognosis in patients with asymptomatic chronic heart failure

The aim of the present study was to investigate the effect of low-dose diuretics on the serum cystatin C (CysC) and serum creatinine (Scr) levels, and on the prognosis in patients with asymptomatic chronic heart failure (HF). A total of 66 asymptomatic chronic HF patients were divided into the observation and control groups (n=33 in each group). Patients in the control group were treated with a routine treatment, while the patients in the observation group were treated with the diuretic hydrochlorothiazide along with the same routine treatment as the control group. The left ventricular ejection fraction (LVEF), serum CysC levels, Scr levels, heart function, prognosis, adverse reactions and complications of the patients in the two groups were compared prior to and following treatment. The LVEF increased in the two groups following treatment, while the levels of serum CysC and Scr decreased. The LVEF in the observation group increased following treatment for 1, 3 and 6 months compared with the LVEF values in the control group. In addition, the levels of serum CysC and Scr in the observation group were found to be lower compared with those in the control group (P<0.05). The incidence of adverse prognosis following treatment for 6 months in the observation group was lower compared with that in the control group (P<0.05). The proportion of HF patients with New York Heart Association (NYHA) class I and II increased following treatment for 6 months in the two groups (P<0.05). However, in the observation group, a higher number of patients exhibited class I and II disease after treatment for 6 months compared with the number in the control group (P<0.05). Furthermore, no statistically significant difference was observed between adverse reactions and complications in the two groups (P>0.05). In conclusion, low-dose diuretics may effectively improve the cardiac and renal functions and prognosis in asymptomatic chronic HF patients, without increasing the incidence of side effects.

Pro-arrhythmic action of autoantibodies against the second extracellular loop of β1-adrenoceptor and its underlying molecular mechanisms

OBJECTIVES

The incidence of arrhythmia is associated with autoantibodies against the second extracellular loop of β1-adrenergic receptor (β1-AAbs). The current study was designed to determine the mechanisms by which arrhythmia experimentally might be induced by β1-AAbs.

METHODS

Blood samples were collected from patients with varied arrhythmias or coronary heart disease (CHD) and healthy subjects. The titer of β1-AAbs was assessed. Passive immunization rat models with β1-AAbs were established to determine whether β1-AAbs induced arrhythmia. Conventional intracellular microelectrode technique and whole cell patch clamp were employed to record action potential duration (APD), resting potential (RP), L-type calcium current (ICa-L), sodium-calcium exchange current (INCX), transient outward potassium current (Ito), inward rectifier potassium current (Ik1) and delayed rectifier potassium current (Ik).

RESULTS

High levels of β1-AAbs were found in the sera of heart disease patients, especially in ventricular arrhythmia (VA). Transfusion with β1-AAbs could induce arrhythmias in normal rats in vivo. β1-AAbs purified from the sera of active immunized rats induced triggered activity (TA), delayed after depolarization (DAD), and prolonged APD in the papillary muscles of rats. β1-AAbs prolonged QT interval, increased ICa-L and decreased IK1, Ito and INa-Ca in rat ventricular myocytes in vitro. All these effects can be inhibited by β1-AR blocker metoprolol.

CONCLUSIONS

These results demonstrate for the first time that β1-AAbs could directly induce ventricular arrhythmia by prolonging QT interval.