Leptin, leptin gene and leptin receptor gene polymorphism in heart failure with preserved ejection fraction

Myocardial Metabolic Reprogramming in HFpEF

Heart failure (HF) caused by structural or functional cardiac abnormalities is a significant cause of morbidity and mortality worldwide. While HF with reduced ejection fraction (HErEF) is well understood, more than half of patients have HF with preserved ejection fraction (HFpEF). Currently, the treatment for HFpEF primarily focuses on symptom alleviation, lacking specific drugs. The stressed heart undergoes metabolic switches in substrate preference, which is a compensatory process involved in cardiac pathological remodeling. Although metabolic reprogramming in HF has gained attention in recent years, its role in HFpEF still requires further elucidation. In this review, we present a summary of cardiac mitochondrial dysfunction and cardiac metabolic reprogramming in HFpEF. Additionally, we emphasize potential therapeutic approaches that target metabolic reprogramming for the treatment of HFpEF.

The emerging role of leptin in obesity-associated cardiac fibrosis: evidence and mechanism

Cardiac fibrosis is a hallmark of various cardiovascular diseases, which is quite commonly found in obesity, and may contribute to the increased incidence of heart failure arrhythmias, and sudden cardiac death in obese populations. As an endogenous regulator of adiposity metabolism, body mass, and energy balance, obesity, characterized by increased circulating levels of the adipocyte-derived hormone leptin, is a critical contributor to the pathogenesis of cardiac fibrosis. Although there are some gaps in our knowledge linking leptin and cardiac fibrosis, this review will focus on the interplay between leptin and major effectors involved in the pathogenesis underlying cardiac fibrosis at both cellular and molecular levels based on the current reports. The profibrotic effect of leptin is predominantly mediated by activated cardiac fibroblasts but may also involve cardiomyocytes, endothelial cells, and immune cells. Moreover, a series of molecular signals with a known profibrotic property is closely involved in leptin-induced fibrotic events. A more comprehensive understanding of the underlying mechanisms through which leptin contributes to the pathogenesis of cardiac fibrosis may open up a new avenue for the rapid emergence of a novel therapy for preventing or even reversing obesity-associated cardiac fibrosis.

New Biomarkers and Their Potential Role in Heart Failure Treatment Optimisation-An African Perspective

Heart failure is a clinical syndrome resulting from various cardiovascular diseases of different aetiologies and pathophysiology. These varying pathologies involve several complex mechanisms that lead to the activation of the neurohumoral system, inflammation, angiogenesis, apoptosis, fibrosis, and eventually adverse cardiac remodelling associated with a progressive decline in cardiac function. Once a diagnosis is made, the cardiac function has a gradual decline characterised by multiple hospital admissions. It is therefore imperative to identify patients at different stages of the heart failure continuum to better risk stratify and initiate optimal management strategies. Biomarkers may play a role in the diagnosis, prognostication, and monitoring response to treatment. This review discusses the epidemiology of heart failure and biomarkers commonly used in clinical practice such as natriuretic peptides and cardiac troponins. In addition, we provide a brief overview of novel biomarkers and genetic coding and non-coding biomarkers used in the management of patients with heart failure. We also discuss barriers that hinder the clinical application of novel biomarkers. Finally, we appraise the value of polygenic risk scoring, focusing on sub-Saharan Africa.

Gene polymorphism of leptin and risk for heart disease, obesity, and high BMI: a systematic review and pooled analysis in adult obese subjects

Objectives

Leptin polymorphism (LEP) has been associated with coronary heart disease (CAD), obesity, and high body mass index (BMI). However, we performed a systematic review and meta-analysis to discover the association because previous studies reached different conclusions.

Methods

Review Manager, version 5.3.5, and Stata, version 15.0, were used for statistical analysis. We calculated the effect size of the studies using the OR with the corresponding 95% CI, and two-sided (bilateral) p-values of 0.05 were considered significant. To determine heterogeneity among the selected studies, the Q test and I2 statistics were used. Meta-regression was used to examine the disease (heart disease, obesity, and high BMI) and heterogeneity between these subgroups.

Results

Eleven studies with 18,984 subjects were included in this study. The G-2548A (rs12112075), rs7799039, and A19G (rs2167270) polymorphisms of the leptin gene (but not the Lys656Asn (rs1805094) polymorphism) are associated with an increased risk of cardiovascular disease. Our pooled analysis revealed an association between the G-2548A (rs12112075) polymorphism and heart disease, high BMI, and obesity. This indicates that individuals carrying the AA allele are at an increased risk for heart disease, high BMI, and obesity. People with heart failure and coronary artery disease did not have the rs7799039 polymorphism or its alleles linked to them.

Conclusions

Combined analysis of data from current and published research suggests that the leptin gene polymorphisms G-2548A (rs12112075), rs7799039, and A19G (rs2167270) (but not the Lys656Asn (rs1805094) polymorphism) are associated with an increased risk of cardiovascular disease. Further research is needed to understand this association.

Dysregulated Epicardial Adipose Tissue as a Risk Factor and Potential Therapeutic Target of Heart Failure with Preserved Ejection Fraction in Diabetes

Cardiovascular (CV) disease and heart failure (HF) are the leading cause of mortality in type 2 diabetes (T2DM), a metabolic disease which represents a fast-growing health challenge worldwide. Specifically, T2DM induces a cluster of systemic metabolic and non-metabolic signaling which may promote myocardium derangements such as inflammation, fibrosis, and myocyte stiffness, which represent the hallmarks of heart failure with preserved ejection fraction (HFpEF). On the other hand, several observational studies have reported that patients with T2DM have an abnormally enlarged and biologically transformed epicardial adipose tissue (EAT) compared with non-diabetic controls. This expanded EAT not only causes a mechanical constriction of the diastolic filling but is also a source of pro-inflammatory mediators capable of causing inflammation, microcirculatory dysfunction and fibrosis of the underlying myocardium, thus impairing the relaxability of the left ventricle and increasing its filling pressure. In addition to representing a potential CV risk factor, emerging evidence shows that EAT may guide the therapeutic decision in diabetic patients as drugs such as metformin, glucagon-like peptide‑1 (GLP-1) receptor agonists and sodium-glucose cotransporter 2 inhibitors (SGLT2-Is), have been associated with attenuation of EAT enlargement.

Differential Pathophysiological Mechanisms in Heart Failure With a Reduced or Preserved Ejection Fraction in Diabetes

Diabetes promotes the development of both heart failure with a reduced ejection fraction and heart failure with a preserved ejection fraction through diverse mechanisms, which are likely mediated through hyperinsulinemia rather than hyperglycemia. Diabetes promotes nutrient surplus signaling (through Akt and mammalian target of rapamycin complex 1) and inhibits nutrient deprivation signaling (through sirtuin-1 and its downstream effectors); this suppresses autophagy and promotes endoplasmic reticulum and oxidative stress and mitochondrial dysfunction, thereby undermining the health of diabetic cardiomyocytes. The hyperinsulinemia of diabetes may also activate sodium-hydrogen exchangers in cardiomyocytes (leading to injury and loss) and in the proximal renal tubules (leading to sodium retention). Diabetes may cause epicardial adipose tissue expansion, and the resulting secretion of proinflammatory adipocytokines onto the adjoining myocardium can lead to coronary microcirculatory dysfunction and myocardial inflammation and fibrosis. Interestingly, sodium-glucose cotransporter 2 (SGLT2) inhibitors-the only class of antidiabetic medication that reduces serious heart failure events-may act to mitigate each of these mechanisms. SGLT2 inhibitors up-regulate sirtuin-1 and its downstream effectors and autophagic flux, thus explaining the actions of these drugs to reduce oxidative stress, normalize mitochondrial structure and function, and mute proinflammatory pathways in the stressed myocardium. Inhibition of SGLT2 may also lead to a reduction in the activity of sodium-hydrogen exchangers in the kidney (leading to diuresis) and in the heart (attenuating the development of cardiac hypertrophy and systolic dysfunction). Finally, SGLT2 inhibitors reduce the mass and mute the adverse biology of epicardial adipose tissue (and reduce the secretion of leptin), thus explaining the capacity of these drugs to mitigate myocardial inflammation, microcirculatory dysfunction, and fibrosis, and improve ventricular filling dynamics. The pathophysiological mechanisms by which SGLT2 inhibitors may benefit heart failure likely differ depending on ejection fraction, but each represents interference with distinct pathways by which hyperinsulinemia may adversely affect cardiac structure and function.

Characterization of the inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction: a hypothesis to explain influence of sex on the evolution and potential treatment of the disease

Accumulating evidence points to the existence of an inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction (HFpEF), which is characterized by biomarkers of inflammation, an expanded epicardial adipose tissue mass, microvascular endothelial dysfunction, normal-to-mildly increased left ventricular volumes and systolic blood pressures, and possibly, altered activity of adipocyte-associated inflammatory mediators. A broad range of adipogenic metabolic and systemic inflammatory disorders - e.g. obesity, diabetes and metabolic syndrome as well as rheumatoid arthritis and psoriasis - can cause this phenotype, independent of the presence of large vessel coronary artery disease. Interestingly, when compared with men, women are both at greater risk of and may suffer greater cardiac consequences from these systemic inflammatory and metabolic disorders. Women show disproportionate increases in left ventricular filling pressures following increases in central blood volume and have greater arterial stiffness than men. Additionally, they are particularly predisposed to epicardial and intramyocardial fat expansion and imbalances in adipocyte-associated proinflammatory mediators. The hormonal interrelationships seen in inflammatory-metabolic phenotype may explain why mineralocorticoid receptor antagonists and neprilysin inhibitors may be more effective in women than in men with HFpEF. Recognition of the inflammatory-metabolic phenotype may improve an understanding of the pathogenesis of HFpEF and enhance the ability to design clinical trials of interventions in this heterogeneous syndrome.

Adiposity and Incident Heart Failure and its Subtypes: MESA (Multi-Ethnic Study of Atherosclerosis)

OBJECTIVES

This study sought to compare various measures of adiposity with risk for incident hospitalized heart failure (HF) with preserved ejection fraction (HFpEF) and reduced ejection fraction (HFrEF).

BACKGROUND

Obesity is a risk factor for HF, particularly HFpEF. It is unknown which measures of adiposity, including anthropometrics and computed tomography (CT)-measured fat area, are most predictive of HF subtypes.

METHODS

The authors studied 1,806 participants of the MESA (Multi-Ethnic Study of Atherosclerosis) study without baseline cardiovascular disease who underwent anthropometrics (body mass index [BMI] and waist circumference) and an abdominal CT. Subcutaneous and visceral adipose tissue (VAT) were measured from a single CT slice at L2-L3. Cox hazard models were used to examine associations of adiposity with incident hospitalized HFpEF and HFrEF events. Fully adjusted models included demographics, HF risk factors, and N-terminal pro-B-type natriuretic peptide.

RESULTS

Over a mean follow-up of 11 years, there were 34 HFpEF and 36 HFrEF events. The fully adjusted hazard ratio (95% confidence interval [CI]) per 1-SD higher of each anthropometric and CT-measured adiposity measures for incident HFpEF were as follows: BMI HR: 1.66; 95% CI: 1.12 to 2.45; waist circumference HR: 1.59; 95% CI: 1.05 to 2.40; and VAT HR: 2.24; 95% CI: 1.44 to 3.49. None of these adiposity measures were associated with HFrEF. Even among overweight/obese adults (BMI ≥25 kg/m2), assessment of VAT (per 1-SD) was strongly associated with HFpEF (HR: 2.78; 95% CI: 1.62 to 4.76). Subcutaneous adipose tissue was neither associated with HFpEF nor HFrEF.

CONCLUSIONS

In a multiethnic cohort free of cardiovascular disease, CT-measured VAT was independently associated with incident hospitalized HFpEF but not HFrEF. Measuring visceral fat at the time of CT imaging for other indications may offer additional prognostication of HF risk. (Multi-Ethnic Study of Atherosclerosis [MESA]; NCT00005487).

Leptin, cardiovascular diseases and type 2 diabetes mellitus

Leptin, an adipokine that is implicated in the control of food intake via appetite suppression, may also stimulate oxidative stress, inflammation, thrombosis, arterial stiffness, angiogenesis and atherogenesis. These leptin-induced effects may predispose to the development of cardiovascular diseases. In the present review we discuss the evidence linking leptin levels with the presence, severity and/or prognosis of both coronary artery disease and non-cardiac vascular diseases such as stroke, carotid artery disease, peripheral artery disease (PAD) and abdominal aortic aneurysms (AAA) as well as with chronic kidney disease (CKD) and type 2 diabetes mellitus (T2DM). Leptin levels have been positively associated with the presence, severity, extent and lesion complexity of coronary atherosclerosis as well as with the presence, severity and poor clinical outcomes of both ischemic and hemorrhagic strokes. But conflicting results also exist. Furthermore, leptin was reported to independently predict common carotid intima-media thickness and carotid plaque instability. A link between hyperleptinemia and PAD has been reported, whereas limited data were available on the potential association between leptin and AAA. Elevated leptin concentrations have also been related to CKD incidence and progression as well as with insulin resistance, T2DM, micro- and macrovascular diabetic complications. Statins and antidiabetic drugs (including sitagliptin, metformin, pioglitazone, liraglutide and empagliflozin) may affect leptin levels. Further research is needed to establish the potential use (if any) of leptin as a therapeutic target in these diseases.

Leptin Receptor Gene Polymorphism and the Risk of Cardiovascular Disease: A Systemic Review and Meta-Analysis

OBJECTIVE

Few studies have assessed the association between leptin receptor (LEPR) gene polymorphism and the risk of cardiovascular disease (CVD). Of the few epidemiological studies on this topic, the results are still controversial.

METHODS

PubMed and Embase were screened for studies from their inception to 9 October 2016. The pooled odds ratio (OR) with the corresponding confidence intervals (CI) were used to measure the effect size for studies that reported the association under allelic, homozygous, and dominant models. Pre-specified characteristics were conducted in the subgroup analysis. Heterogeneity between subgroups was evaluated by meta-regression analysis.

RESULTS

Seven eligible studies involving 44,133 participants were included in our meta-analysis. Borderline significant association was observed between the LEPR gene polymorphism (rs1137101, rs1137100, rs6700896, and rs8179183) and the increased risk of CVD with considerable heterogeneity under the allelic model, and the overall pooled OR (95% CI) was 1.10 (0.99, 1.22). The LEPR gene variant rs6700896, 109G allele, and 109GG genotype were significantly associated with the increased risk of CVD. Furthermore, stratified group analysis revealed that the association was more pronounced for stroke. Race-differences might also cause the considerable heterogeneity and non-significant association.

CONCLUSIONS

This is the first systematic review and meta-analysis to investigate the association between LEPR gene variants and CVD risk. Some LEPR gene variants were significantly associated with the increased risk of CVD. However, the present study is limited in its small number of included studies, considerable heterogeneity, and observational study design. Further research is still warranted to confirm the magnitude of the association.

High plasma leptin levels are associated with impaired diastolic function in patients with coronary artery disease

BACKGROUND AND AIMS

Obese subjects have elevated leptin levels, which have been associated with increased risk of cardiovascular events. Because leptin has direct cellular effects on various tissues, we tested the hypothesis that leptin levels are associated with cardiac structure or function in patients with coronary artery disease (CAD).

METHODS AND RESULTS

The study population consisted of 1 601 CAD patients, of whom 42% had type 2 diabetes mellitus. Plasma leptin was measured in fasted state and an echocardiography performed. Leptin levels were not related to LV dimensions or LV ejection fraction (NS for all), but higher leptin levels were associated with elevated E/E' (9.43 vs. 11.94 in the lowest and the highest leptin quartile, respectively; p=0.018 for trend). Correspondingly, a decreasing trend was observed in E/A (1.15 vs. 1.06; p=0.037). These associations were independent of obesity and other relevant confounding variables.

CONCLUSION

We conclude that elevated plasma leptin levels are associated with impaired left ventricular diastolic function in patients with CAD independently of obesity and other confounding variables. Leptin may be one of the mechanistic links explaining the development of congestive heart failure in obese subjects.

The potential contribution of circulating and locally produced leptin to cardiac hypertrophy and failure

Leptin is a 16 kDa peptide that was first identified in 1994 through positional cloning of the mouse obesity gene. Although the primary function of leptin is to act a satiety factor through its actions on the hypothalamus, it is now widely recognized that leptin can exert effects on many other organs through activation of its receptors, which are ubiquitously expressed. Leptin is secreted primarily by white adipocytes, but it is also produced by other tissues including the heart where it can exert effects in an autocrine or paracrine manner. One of these effects involves the induction of cardiomyocyte hypertrophy, which appears to occur via multiple cell signalling mechanisms. As adipocytes are the primary site of leptin production, plasma leptin concentrations are generally positively related with body mass index and the degree of adiposity. However, hyperleptinemia is also associated with cardiovascular disease, including heart failure, in the absence of obesity. Here we review the potential role of leptin in heart disease, particularly pertaining to its potential contribution to myocardial remodelling and heart failure, as well as the underlying mechanisms. We further discuss potential interactions between leptin and another adipokine, adiponectin, and the potential implications of this interaction in terms of fully understanding leptin’s effects.

Leptin in heart failure

INTRODUCTION

In the study of heart failure (HF), biomarkers have served as an important tool for diagnostic, therapeutic and prognostic assessment. Their main categories in the area of HF are markers of ventricular dysfunction, inflammation, metabolism, neurohormones, oxidative stress, myocardial injury and extracellular matrix remodeling.

AREAS COVERED

Leptin contributes to the modulation of metabolism, respiratory control and inflammation, which are factors associated with cardiovascular disease. Serum levels of leptin in patients with HF have shown conflicting results in previous studies. Most studies have suggested that serum leptin levels may be increased in patients without cachexia. On the other hand, leptin levels are decreased in patients with advanced HF and cardiac cachexia or specific HF etiologies such as Chagas' disease. Other studies have showed that leptin levels were related to exercise intolerance. The only exception of the direct correlation of serum leptin levels with severity of CHF is present in CHF with cardiac cachexia, because patients with cardiac cachexia have plasma leptin concentrations lower than those without cardiac cachexia.

EXPERT OPINION

These findings can make leptin an important diagnostic and prognostic marker for HF and be included in routine investigation of patients with HF.