Multi-variable biomarker approach in identifying incident heart failure in chronic kidney disease: results from the Chronic Renal Insufficiency Cohort study

FGF23 and klotho at the intersection of kidney and cardiovascular disease

Cardiovascular disease is the leading cause of death in patients with chronic kidney disease (CKD). As CKD progresses, CKD-specific risk factors, such as disordered mineral homeostasis, amplify traditional cardiovascular risk factors. Fibroblast growth factor 23 (FGF23) regulates mineral homeostasis by activating complexes of FGF receptors and transmembrane klotho co-receptors. A soluble form of klotho also acts as a 'portable' FGF23 co-receptor in tissues that do not express klotho. In progressive CKD, rising circulating FGF23 levels in combination with decreasing kidney expression of klotho results in klotho-independent effects of FGF23 on the heart that promote left ventricular hypertrophy, heart failure, atrial fibrillation and death. Emerging data suggest that soluble klotho might mitigate some of these effects via several candidate mechanisms. More research is needed to investigate FGF23 excess and klotho deficiency in specific cardiovascular complications of CKD, but the pathophysiological primacy of FGF23 excess versus klotho deficiency might never be precisely resolved, given the entangled feedback loops that they share. Therefore, randomized trials should prioritize clinical practicality over scientific certainty by targeting disordered mineral homeostasis holistically in an effort to improve cardiovascular outcomes in patients with CKD.

Proteomic Pathways across Ejection Fraction Spectrum in Heart Failure: an EXSCEL Substudy

Background

Ejection fraction (EF) is a key component of heart failure (HF) classification, including the increasingly codified HF with mildly reduced EF (HFmrEF) category. However, the biologic basis of HFmrEF as an entity distinct from HF with preserved EF (HFpEF) and reduced EF (HFrEF) has not been well characterized.

Methods

The EXSCEL trial randomized participants with type 2 diabetes (T2DM) to once-weekly exenatide (EQW) vs. placebo. For this study, profiling of ∼5000 proteins using the SomaLogic SomaScan platform was performed in baseline and 12-month serum samples from N=1199 participants with prevalent HF at baseline. Principal component analysis (PCA) and ANOVA (FDR p<0.1) were used to determine differences in proteins between three EF groups, as previously curated in EXSCEL (EF>55% [HFpEF], EF 40-55% [HFmrEF], EF<40% [HFrEF]). Cox proportional hazards was used to assess association between baseline levels of significant proteins, and changes in protein level between baseline and 12-month, with time-to-HF hospitalization. Mixed models were used to assess whether significant proteins changed differentially with exenatide vs. placebo therapy.

Results

Of N=1199 EXSCEL participants with prevalent HF, 284 (24%), 704 (59%) and 211 (18%) had HFpEF, HFmrEF and HFrEF, respectively. Eight PCA protein factors and 221 individual proteins within these factors differed significantly across the three EF groups. Levels of the majority of proteins (83%) demonstrated concordance between HFmrEF and HFpEF, but higher levels in HFrEF, predominated by the domain of extracellular matrix regulation, e.g. COL28A1 and tenascin C [TNC]; p<0.0001. Concordance between HFmrEF and HFrEF was observed in a minority of proteins (1%) including MMP-9 (p<0.0001). Biologic pathways of epithelial mesenchymal transition, ECM receptor interaction, complement and coagulation cascades, and cytokine receptor interaction demonstrated enrichment among proteins with the dominant pattern, i.e. HFmrEF-HFpEF concordance. Baseline levels of 208 (94%) of the 221 proteins were associated with time-to-incident HF hospitalization including domains of extracellular matrix (COL28A1, TNC), angiogenesis (ANG2, VEGFa, VEGFd), myocyte stretch (NT-proBNP), and renal function (cystatin-C). Change in levels of 10 of the 221 proteins from baseline to 12 months (including increase in TNC) predicted incident HF hospitalization (p<0.05). Levels of 30 of the 221 significant proteins (including TNC, NT-proBNP, ANG2) were reduced differentially by EQW compared with placebo (interaction p<0.0001).

Conclusions

In this HF substudy of a large clinical trial of people with T2DM, we found that serum levels of most proteins across multiple biologic domains were similar between HFmrEF and HFpEF. HFmrEF may be more biologically similar to HFpEF than HFrEF, and specific related biomarkers may offer unique data on prognosis and pharmacotherapy modification with variability by EF.

Renal Insufficiency Increases the Combined Risk of Left Ventricular Hypertrophy and Dysfunction in Patients at High Risk of Cardiovascular Diseases

BACKGROUND

The identification of asymptomatic structural and functional cardiac abnormalities can help us to recognize early and intervene in patients at pre-heart failure (HF). However, few studies have adequately evaluated the associations of renal function and left ventricular (LV) structure and function in patients at high risk of cardiovascular diseases (CVD).

METHODS

Patients undergoing coronary angiography and/or percutaneous coronary interventions were enrolled from the Cardiorenal ImprovemeNt II (CIN-II) cohort study, and their echocardiography and renal function were assessed at admission. Patients were divided into five groups according to their estimated glomerular filtration rate (eGFR). Our outcomes were LV hypertrophy and LV systolic and diastolic dysfunction. Multivariable logistic regression analyses were conducted to investigate the associations of eGFR with LV hypertrophy and LV systolic and diastolic dysfunction.

RESULTS

A total of 5610 patients (mean age: 61.6 ± 10.6 years; 27.3% female) were included in the final analysis. The prevalence of LV hypertrophy assessed by echocardiography was 29.0%, 34.8%, 51.9%, 66.7%, and 74.3% for the eGFR categories >90, 61-90, 31-60, 16-30, and ≤15 mL/min per 1.73 m² or for patients needing dialysis, respectively. Multivariate logistic regression analysis showed that subjects with eGFR levels of ≤15 mL/min per 1.73 m2 or needing dialysis (OR: 4.66, 95% CI: 2.96-7.54), as well as those with eGFR levels of 16-30 (OR: 3.87, 95% CI: 2.43-6.24), 31-60 (OR: 2.00, 95% CI: 1.64-2.45), and 61-90 (OR: 1.23, 95% CI: 1.07-1.42), were significantly associated with LV hypertrophy. This reduction in renal function was also significantly associated with LV systolic and diastolic dysfunction (all P for trend <0.001). In addition, a per one unit decrease in eGFR was associated with a 2% heightened combined risk of LV hypertrophy and systolic and diastolic dysfunction.

CONCLUSIONS

Among patients at high risk of CVD, poor renal function was strongly associated with cardiac structural and functional abnormalities. In addition, the presence or absence of CAD did not change the associations. The results may have implications for the pathophysiology behind cardiorenal syndrome.

Direct and indirect effects of fibroblast growth factor 23 on the heart

Fibroblast growth factor (FGF)23 is a bone-derived phosphotropic hormone that regulates phosphate and mineral homeostasis. Recent studies have provided evidence that a high plasma concentration of FGF23 is associated with cardiac disease, including left ventricular hypertrophy (LVH), heart failure, atrial fibrillation, and cardiac death. Experimental studies have shown that FGF23 activates fibroblast growth factor receptor 4 (FGFR4)/phospholipase Cγ/calcineurin/nuclear factor of activated T-cells signaling in cardiomyocytes and induces cardiac hypertrophy in rodents. Activation of FGFR4 by FGF23 normally requires the co-receptor α-klotho, and klotho-independent signaling occurs only under conditions characterized by extremely high FGF23 concentrations. Recent studies have demonstrated that FGF23 activates the renin-angiotensin-aldosterone system (RAAS) and induces LVH, at least in part as a result of lower vitamin D activation. Moreover, crosstalk between FGF23 and RAAS results in the induction of cardiac hypertrophy and fibrosis. In this review, we summarize the results of studies regarding the relationships between FGF23 and cardiac events, and describe the potential direct and indirect mechanisms whereby FGF23 induces LVH.

A Bibliometric and Visualized Analysis of Uremic Cardiomyopathy From 1990 to 2021

Background

Uremic cardiomyopathy is commonly presented in chronic kidney disease (CKD), and it severely affects the prognosis of patients with CKD. In the past few decades, the investigation of uremic cardiomyopathy has developed rapidly. However, no report has summarized the situation of uremic cardiomyopathy research to date. This study aimed to evaluate the state of uremic cardiomyopathy research in the last 30 years and identify important topics and achievements, as well as emerging trends through bibliometric analysis.

Materials and Methods

Publications related to uremic cardiomyopathy were collected from Science Citation Index Expanded. HistCite, VOSviewer, CiteSpace, and the Bibliometrix Package were used for bibliometric analysis and visualization, including the analysis of the overall distribution of the annual publication, leading countries, and active institutions and authors, core journals, co-cited references, and keywords.

Results

A total of 2,403 studies related to uremic cardiomyopathy were obtained, and progress related to uremic cardiomyopathy was slower in past 3 years. A total of 10,077 authors from 2,697 institutions in 89 countries or regions reported investigations on uremic cardiomyopathy. The United States of America was the most productive and the most cited country. Myles Wolf, Joseph I Shapiro, and Carmine Zoccali published most articles in uremic cardiomyopathy, and journals in nephrology possessed core status in the field. Phosphate metabolism was the hotspot in uremic cardiomyopathy research in recent years, and future progress may concentrate on phosphate metabolism, endogenous natriuretic factors, and novel biomarkers.

Conclusion

The United States of America and European countries played central roles in uremic cardiomyopathy research, while Chinese scholars should be more involved in this field. Global publications on uremic cardiomyopathy have entered platform stage, and the fibroblast growth factor-23-klotho axis remained a hotspot in this field. Endogenous natriuretic factors and novel biomarkers may be potential directions in future investigations.