A bidirectional Mendelian randomization study supports causal effects of kidney function on blood pressure

Educational attainment, body mass index, and smoking as mediators in kidney disease risk: a two-step Mendelian randomization study

BACKGROUND

Educational attainment (EA) has been linked to various health outcomes, including kidney disease (KD). However, the underlying mechanisms remain unclear. This study aims to assess the causal relationship between EA and KD and quantify the mediation effects of modifiable risk factors using a Mendelian randomization (MR) approach.

METHODS

We performed a two-sample MR analysis utilizing summary statistics from large-scale European genome-wide association studies (GWAS). EA (NGWAS = 766,345) was used as the exposure, and KD (Ncase/Ncontrol= 5,951/212,871) was the outcome. A two-step MR method was applied to identify and quantify the mediation effects of 24 candidate risk factors.

RESULTS

Each additional 4.2 years of genetically predicted EA was associated with a 32% reduced risk of KD (odds ratio [OR] 0.68; 95% confidence interval [CI] 0.56, 0.83). Among the 24 candidate risk factors, body mass index (BMI) mediated 21.8% of this protective effect, while smoking heaviness mediated 18.7%.

CONCLUSIONS

This study provides robust evidence that EA exerts a protective effect against KD, partially mediated by BMI and smoking. These findings highlight the potential for targeted public health interventions aimed at mitigating obesity and smoking-related risks to reduce KD incidence, particularly among individuals with lower educational attainment.

Renal-Cardiac Crosstalk in the Pathogenesis and Progression of Heart Failure

Chronic kidney disease (CKD) represents a global health issue with a high socioeconomic impact. Beyond a progressive decline of kidney function, patients with CKD are at increased risk of cardiovascular diseases, including heart failure (HF) and sudden cardiac death. HF in CKD can manifest both as HF with reduced ejection fraction and HF with preserved ejection fraction, with the latter further increasing in relative importance in the more advanced stages of CKD. Typical cardiac remodeling characteristics in uremic cardiomyopathy include left ventricular hypertrophy, myocardial fibrosis, cardiac electrical dysregulation, capillary rarefaction, and microvascular dysfunction, which are triggered by increased cardiac preload, cardiac afterload, and preload and afterload-independent factors. The pathophysiological mechanisms underlying cardiac remodeling in CKD are multifactorial and include neurohormonal activation (with increased activation of the renin-angiotensin-aldosterone system, the sympathetic nervous system, and mineralocorticoid receptor signaling), cardiac steroid activation, mitochondrial dysfunction, inflammation, innate immune activation, and oxidative stress. Furthermore, disturbances in cardiac metabolism and calcium homeostasis, macrovascular and microvascular dysfunction, increased cellular profibrotic responses, the accumulation of uremic retention solutes, and mineral and bone disorders also contribute to cardiovascular disease and HF in CKD. Here, we review the current knowledge of HF in CKD, including the clinical characteristics and pathophysiological mechanisms revealed in animal studies. We also elaborate on the detrimental impact of comorbidities of CKD on HF using hypertension as an example and discuss the clinical characteristics of hypertensive heart disease and the genetic predisposition. Overall, this review aims to increase the understanding of HF in CKD to support future research and clinical translational approaches for improved diagnosis and therapy of this vulnerable patient population.

Distinct pathway-based effects of blood pressure and body mass index on cardiovascular traits: comparison of novel Mendelian randomization approaches

BACKGROUND

Mendelian randomization (MR) leverages trait associated genetic variants as instrumental variables (IVs) to determine causal relationships in epidemiology. However, genetic IVs for complex traits are typically highly heterogeneous and, at a molecular level, exert effects on different biological processes. Exploration of the biological underpinnings of such heterogeneity can enhance our understanding of disease mechanisms and inform therapeutic strategies. Here, we introduce a new approach to instrument partitioning based on enrichment of Mendelian disease categories (pathway-partitioned) and compare it to an existing method based on genetic colocalization in contrasting tissues (tissue-partitioned).

METHODS

We employed individual- and summary-level MR methodologies using SNPs grouped by pathway informed by proximity to Mendelian disease genes affecting the renal system or vasculature (for blood pressure (BP)), or mental health and metabolic disorders (for body mass index (BMI)). We compared the causal effects of pathway-partitioned SNPs on cardiometabolic outcomes with those derived using tissue-partitioned SNPs informed by colocalization with gene expression in kidney, artery (BP), or adipose and brain tissues (BMI). Additionally, we assessed the likelihood that estimates observed for partitioned exposures could emerge by chance using random SNP sampling.

RESULTS

Our pathway-partitioned findings suggest the causal relationship between systolic BP and heart disease is predominantly driven by vessel over renal pathways. The stronger effect attributed to kidney over artery tissue in our tissue-partitioned MR hints at a multifaceted interplay between pathways in the disease aetiology. We consistently identified a dominant role for vessel (pathway) and artery (tissue) driving the negative directional effect of diastolic BP on left ventricular stroke volume and positive directional effect of systolic BP on type 2 diabetes. We also found when dissecting the BMI pathway contribution to atrial fibrillation that metabolic-pathway and brain-tissue IVs predominantly drove the causal effects relative to mental health and adipose in pathway- and tissue-partitioned MR analyses, respectively.

CONCLUSIONS

This study presents a novel approach to dissecting heterogeneity in MR by integrating clinical phenotypes associated with Mendelian disease. Our findings emphasize the importance of understanding pathway-/tissue-specific contributions to complex exposures when interpreting causal relationships in MR. Importantly, we advocate caution and robust validation when interpreting pathway-partitioned effect size differences.

Causality of genetically determined serum metabolites on thoracic and abdominal aortic aneurysm: Mendelian randomization study

BackgroundAortic aneurysms (AA), including thoracic (TAA) and abdominal (AAA) types, are life-threatening conditions with complex and poorly understood mechanisms. Metabolic alterations, particularly in amino acid and energy metabolism, have been linked to AA, but their roles remain unclear due to limited and confounded observational evidence.ObjectiveThis research aimed to comprehensively investigate the potential causal links between serum metabolites and the development of thoracic (TAA) and abdominal (AAA) aortic aneurysms.MethodsWe analyzed serum metabolites from the Metabolomics data, using datasets of 353,049 individuals for TAA (3510 cases) and 353,087 individuals for AAA (3548 cases). Mendelian randomization (MR) techniques, including MR-Egger regression and inverse-variance weighting (IVW), assessed causality, with heterogeneity tested using Cochran's Q and I2 statistics, and pleiotropy via the MR-Egger intercept. Sensitivity was further checked through leave-one-out analysis. SNP annotations identified genes linked to TAA and AAA, and metabolic pathways were also analyzed.ResultsNine metabolites were causally linked to TAA, with three as risk factors, while 18 metabolites were associated with AAA, including eight risk factors. 3-dehydrocarnitine showed contrasting effects, acting as a risk factor for TAA (OR = 2.704; P = 0.031) and a protective factor for AAA (OR = 0.303; P = 0.025). Pathway analysis revealed TAA-related pathways such as "Pyruvaldehyde degradation" and "Arginine biosynthesis," while AAA was linked to "Phenylalanine metabolism" and "Valine, leucine, and isoleucine biosynthesis." No horizontal pleiotropy was detected, and results were robust.ConclusionsIdentified metabolites and pathways may serve as potential biomarkers and therapeutic targets for the clinical assessment and prevention of TAA and AAA.

The prevention and management of chronic kidney disease among patients with metabolic syndrome

Treatment of patients with chronic kidney disease (CKD) requires implementation of prevention and management strategies that reduce the risk of kidney failure and CKD-associated cardiovascular risk. Metabolic syndrome is characterized by obesity, high blood pressure, dyslipidemia, and hyperglycemia, and it is common among patients with CKD. Large-scale randomized trials have led to significant advances in the management of CKD, with 5 pharmacotherapies now proven to be nephroprotective and/or cardioprotective in certain types of patients. Renin-angiotensin system inhibitors and sodium-glucose cotransporter 2 inhibitors slow kidney disease progression and reduce heart failure complications for most patients with CKD. In addition, statin-based regimens reduce low-density lipoprotein cholesterol and lower the risk of atherosclerotic disease (with no clinically meaningful effect on kidney outcomes). For patients with type 2 diabetes and albuminuric CKD, the nonsteroidal mineralocorticoid receptor antagonist finerenone and the glucagon-like peptide-1 receptor agonist semaglutide also confer cardiorenal benefits, with semaglutide additionally effective at reducing weight. Together, these randomized data strongly suggest that metabolic syndrome mediates some of the cardiorenal risk observed in CKD. Considered separately, the trials help elucidate which components of metabolic syndrome influence the pathophysiology of kidney disease progression and which separately modify risk of atherosclerotic and nonatherosclerotic cardiovascular outcomes. As we predict complementary and different mechanisms of nephroprotection and cardioprotection for these different interventions, it seems logical that they should be deployed together to maximize benefits. Even when combined, however, these therapies are not a cure, so further trials remain important to reduce the residual cardiorenal risks associated with CKD.

Allergic diseases and T2DM: a bidirectional multivariable Mendelian randomization study and mediation analysis

BACKGROUND

Clinical studies involving observation have uncovered a mutual relationship between allergic disorders and diabetes, yet the precise causal link remains undetermined.

METHODS

We conducted two-sample bidirectional Mendelian randomization analyses using single nucleotide polymorphisms (SNPs) associated with allergic conditions (asthma, allergic rhinitis, atopic dermatitis) from genome-wide studies and SNPs related to type 2 diabetes from FinnGen. Initially, we evaluated the causal link between allergic disorders and type 2 diabetes through a univariate Mendelian randomization study, incorporating inverse variance weighting, MR-Egger, and the weighted median estimator. To address potential confounding, we employed multivariate Mendelian randomization. Finally, we validated mediators influencing the correlation between asthma and type 2 diabetes.

RESULTS

The Inverse variance weighted method showed that asthma genetically increased the risk of type 2 diabetes [Asthma-type 2 diabetes: β(95%CI)＝0.892 (0.152-1.632), p = 0.018]. Allergic rhinitis and type 2 diabetes exhibit a mutual protective effect: β(95% CI)＝-1.333 (-2.617 to -0.049), p = 0.042; type 2 diabetes-Allergic rhinitis: β(95%CI)＝-0.002 (-0.004 to -0.000), p = 0.018. The Multivariable Mendelian randomization study results showed that after excluding confounding factors, asthma still demonstrates statistical significance in relation to type 2 diabetes. Through mediation analysis, it was discovered that lung function and the percentage of monocytes in leukocytes exert an inhibitory effect on the mediation between asthma and type 2 diabetes.

CONCLUSION

The Multivariable Mendelian randomization study indicates asthma as a risk factor for type 2 diabetes. Lung function, and the percentage of monocytes in leukocytes, play an inhibitory role in asthma and type 2 diabetes mediating effects.

Analysis of shared pathogenic mechanisms and drug targets in myocardial infarction and gastric cancer based on transcriptomics and machine learning

Background

Recent studies have suggested a potential association between gastric cancer (GC) and myocardial infarction (MI), with shared pathogenic factors. This study aimed to identify these common factors and potential pharmacologic targets.

Methods

Data from the IEU Open GWAS project were used. Two-sample Mendelian randomization (MR) analysis was used to explore the causal link between MI and GC. Transcriptome analysis identified common differentially expressed genes, followed by enrichment analysis. Drug target MR analysis and eQTLs validated these associations with GC, and the Steiger direction test confirmed their direction. The random forest and Lasso algorithms were used to identify genes with diagnostic value, leading to nomogram construction. The performance of the model was evaluated via ROC, calibration, and decision curves. Correlations between diagnostic genes and immune cell infiltration were analyzed.

Results

MI was linked to increased GC risk (OR=1.112, P=0.04). Seventy-four genes, which are related mainly to ubiquitin-dependent proteasome pathways, were commonly differentially expressed between MI and GC. Nine genes were consistently associated with GC, and eight had diagnostic value. The nomogram built on these eight genes had strong predictive performance (AUC=0.950, validation set AUC=0.957). Immune cell infiltration analysis revealed significant correlations between several genes and immune cells, such as T cells, macrophages, neutrophils, B cells, and dendritic cells.

Conclusion

MI is associated with an increased risk of developing GC, and both share common pathogenic factors. The nomogram constructed based on 8 genes with diagnostic value had good predictive performance.

Combined and mediating effects of remnant cholesterol and renal function on hypertension risk in Chinese middle-aged and elderly people

Background

Emerging evidence indicates a potential correlation between remnant cholesterol (RC) and the development of vascular damage and hypertension. Nevertheless, the precise relationship between RC and hypertension in relation to renal function remains uncertain. The objective of this investigation was to employ a cohort design to evaluate the intricate correlation between RC and renal function in relation to hypertension.

Methods

The present investigation utilized data from the China Health and Retirement Longitudinal Study (CHARLS), encompassing a total of 5,109 participants, for comprehensive data analysis and examination. Cox regression analysis was employed to examine the interplay among RC, renal function, and hypertension within the context of this research study. This study utilized restricted cubic spline (RCS) analysis to elucidate the interaction between RC, renal function, and hypertension, specifically examining the mediating role of renal function in the RC-hypertension nexus. Furthermore, we employed mediation analysis to investigate the potential mediating role of renal function in the association between RC and hypertension.

Results

After a 9-year follow-up period, the incidence of hypertension in the population under investigation was observed to be 19.01%. The Kaplan-Meier curves demonstrated a notable and statistically significant elevation in the prevalence of hypertension within the subgroup characterized by higher RC and impaired renal function (P <0.001). However, in Cox regression analyses, the risk of developing hypertension was significantly higher (P <0.05) in those with high RC and high estimated glomerular filtration rate (eGFR), and those with high RC and low eGFR, compared with those with low RC and high eGFR, after adjusting for confounders. The analysis of RCS demonstrated a significant positive linear correlation between baseline RC and the prevalence of hypertension. Additionally, there was a notable negative linear correlation observed between eGFR levels and the prevalence of hypertension. RC and eGFR did not interact with any of the subgroup variables. eGFR lowering mediated 6% of the associations between RC and hypertension.

Conclusion

The findings of this study unveiled a substantial correlation between elevated RC, diminished eGFR levels, and the risk of developing hypertension. In addition, renal function may mediate the correlation between RC and hypertension risk.

Causal relations between immune cells and cerebral hemorrhage: a bidirectional Mendelian randomization study

BACKGROUND

Previous studies have shown that an increased number of immune cells is closely associated with the onset and course changes of intracerebral hemorrhage, but the exact causal relationship has not been clarified. The aim of this study was to investigate the causal relationship between immune cells and intracerebral hemorrhage by a two-way Mendelian randomization method.

METHODS

Two sets of SNPs were used as instrumental variables and two-way Mendelian randomization analyses were performed and leave-one-out method were used to assess the validity and heterogeneity of the included genetic variation instruments. The level of multiplicity and heterogeneity of the included genetic variance instruments was assessed.

RESULTS

The results showed a clear causal relationship between three immune cells and intracerebral hemorrhage, and no heterogeneity between SNPs related to intracerebral hemorrhage, while scatterplot and funnel plot confirmed that the causality was less likely to be biased; MR-Egger results suggested that no genetic pleiotropy was found. Leave-one-out analysis was applied to suggest that the MR analysis results for a single SNP were robust; meanwhile, Meta-analysis was applied to combine the two intracerebral hemorrhage datasets, and the analysis results suggested that in the fixed-effects model and random-effects model, the immunocyte CD66b on Granulocytic Myeloid-Derived Suppressor Cells and other three immune cells were significantly causally associated with intracerebral hemorrhage, while the heterogeneity test suggested that there was no significant difference between the different datasets.

CONCLUSIONS

The present study found a significant causal relationship between specific immune cell phenotypes and intracerebral hemorrhage by Mendelian randomization analysis.

Preoperative predictive indicators for resolution of hypertension in patients with unilateral primary aldosteronism: development of a nomogram model

BACKGROUND

Primary aldosteronism (PA) is the leading surgically treatable cause of hypertension, with adrenalectomy as the definitive treatment for unilateral PA (UPA). However, some patients have persistent hypertension after surgery. This study aims to identify preoperative factors affecting surgical outcomes and develop a predictive model for postoperative hypertension resolution.

METHODS

We reviewed and analyzed the medical records of 206 patients who underwent unilateral adrenalectomy for UPA at Qilu Hospital of Shandong University (2011-2022). As a training cohort, the data of the 166 patients from 2013 to 2022 was analyzed using univariate and multivariate logistic regression to explore the relationship between preoperative clinical and biochemical data and postoperative BP normalization. The remaining 40 patients from 2011 to 2012 were used as a validation cohort. A predictive model of the nomogram was constructed utilizing significant variables through multivariate logistic regression analysis. The model's effectiveness was evaluated using receiver operating characteristic (ROC) curves, decision curve analysis (DCA), and calibration curves and compared with previous prediction models using the Delong test.

RESULTS

In the training cohort of 166 patients, 78 (46.9%) achieved postoperative normotension without medication, while 88 (53.1%) required ongoing antihypertensive treatment. Multifactorial analysis identified age, number of antihypertensive medications, preoperative maximum systolic blood pressure (SBP), left ventricular ejection fraction (LVEF), serum creatinine (Cr) levels, and a history of hypokalemia as independent predictors of postoperative BP normalization. Calibration curves showed excellent agreement between predicted and actual outcomes, and DCA indicated that clinical interventions based on this model are beneficial at various risk thresholds. Comparison with previous models showed our model outperformed the Aldosteronoma Resolution Score (ARS) in the Asian population and was comparable to the Morisaki score.

CONCLUSION

A predictive model developed with variables including age, number of anti-hypertensive medications, preoperative maximum SBP, LVEF, serum Cr levels, and history of hypokalemia effectively predicts therapeutic outcomes following unilateral adrenalectomy for UPA patients.

Investigating the dual causative pathways linking immune cells and venous thromboembolism via Mendelian randomization analysis

BACKGROUND

Venous thromboembolism (VTE) is a common vascular disease with a significant global burden, influenced by multiple factors, such as genetic, environmental, and immune components. Immune responses and shifts in immune cell profiles are closely linked to the development and progression of VTE, yet current studies are limited by confounding factors and reverse causation. To address these limitations, this study uses Mendelian randomization to explore the causal relationship between immune cell traits and VTE, aiming to provide insights into underlying mechanisms.

METHODS

We utilized GWAS data on 731 immunological traits (n = 3757) from the IEU OpenGWAS project and VTE (21021 cases, 391160 controls) from Finngen public data. Five commonly used Mendelian randomization (MR) methods were employed, including inverse-variance weighted (IVW), MR-Egger regression, weighted median estimator (WME), and both weighted and simple models to analyze their associations. Sensitivity checks for the results included pleiotropy tests, heterogeneity tests, and leave-one-out analyses.

RESULTS

From a strictly statistical perspective, no significant associations were observed after FDR correction. However, our exploratory analysis suggested potential trends between immune cell traits and VTE. When immune cells were considered as the exposure and VTE as the outcome, 44 immune cell traits were suggestively associated with VTE based on uncorrected p-values. Conversely, when VTE was considered as the exposure, it appeared to influence immune cell traits. Specifically, secreting CD4 regulatory T cells (OR = 0.9084; 95% CI: 0.8418-0.9804; P = 0.0135; FDR = 0.7339) and activated and resting CD4 regulatory T cells (OR = 0.9275; 95% CI: 0.8622-0.9977; P = 0.0433; FDR = 0.8048) suggested a potential protective trend against VTE. On the other hand, B cells expressing CD20 (OR = 1.0697; 95% CI: 1.0227-1.1188; P = 0.0033; FDR = 0.5767) and myeloid cells expressing CD33 (OR = 1.0199; 95% CI: 1.0021-1.0382; P = 0.0296; FDR = 0.7339) may be linked to an increased risk of VTE.

CONCLUSIONS

From a strict statistical perspective, no significant associations were identified after FDR correction. However, our analysis using MR method suggests a potential link between VTE and immune cell traits, suggesting the complex interplay between the immune system and thrombotic events. While this study is exploratory and needs validation, the findings of this study are hypothesis-generating with resect to the mechanisms underlying VTE and encourage further investigation into the role of immune activity in VTE pathology.

Mendelian Randomization Studies: Opening a New Window in the Study of Metabolic Diseases and Chronic Kidney Disease

It is widely recognized that a strong correlation exists between metabolic diseases and chronic kidney disease (CKD). Based on bibliometric statistics, the overall number of Mendelian randomization (MR) analysis in relation to metabolic diseases and CKD has increased since 2005. In recent years, this topic has emerged as a significant area of research interest. In clinical studies, RCTs are often limited due to the intricate causal interplay between metabolic diseases and CKD, which makes it difficult to ascertain the precise etiology of these conditions definitively. In MR studies, genetic variation is incorporated as an instrumental variable (IV). They elucidate the possible causal relationships between associated risk factors and disease risks by including individual innate genetic markers. It is widely believed that MR avoids confounding and can reverse effects to the greatest extent possible. As an increasingly popular technology in the medical field, MR studies have become a popular technology in causal relationships investigation, particularly in epidemiological etiology studies. At present, MR has been widely used for the investigation of medical etiologies, drug development, and decision-making in public health. The article aims to offer insights into the causal relationship between metabolic diseases and CKD, as well as strategies for prevention and treatment, through a summary of MR-related research on these conditions.

Unraveling the causal relationship and potential mechanisms between osteoarthritis and breast cancer: insights from mendelian randomization and bioinformatics analysis

OBJECTIVE

To investigate the effect of osteoarthritis (OA) on the development of breast cancer (BC), and reveal the potential mechanisms underlying the association between them.

METHODS

A two-step, multivariable Mendelian Randomization (MR) analysis was performed, using statistics from genome-wide association studies (GWAS), to determine the effect of OA on BC and explore the role of major depressive disorder (MDD) in mediating it. Furthermore, transcriptomic analysis based on the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were utilized to establish a prognostic model and explore the underlying mechanisms. Additionally, BC cells and nude mice were used to verify the role of RTN4 in BC.

RESULTS

The two-sample MR analysis implied a causal relationship between OA and BC at the genetic level, and the mediating MR analysis identified that MDD may play a potential role in mediating it, accounting for approximately 12.20%. Then, we constructed a prognostic model (OA-score) with six genes screened out from datasets and selected RTN4 as the representative gene for validation study. It was demonstrated that high OA-score was an independent risk factor for breast cancer, and patients with low OA-score were more likely to have better OS, higher infiltration level of DC and CD 4 + T cells, and higher expression of some immune checkpoints. Moreover, the knockdown of RTN4 inhibited breast cancer cell proliferation, migration and invasion.

CONCLUSION

Our study identified the causal influence of OA on BC mediated by MDD at the genetic level. OA-Score may potentially serve as a new prognostic biomarker for OA related BC patients.

Identification of potential drug targets for diabetic polyneuropathy through Mendelian randomization analysis

BACKGROUND

Diabetic polyneuropathy (DPN) is a common diabetes complication with limited treatment options. We aimed to identify circulating plasma proteins as potential therapeutic targets for DPN using Mendelian Randomization (MR).

METHODS

The protein quantitative trait loci (pQTLs) utilized in this study were derived from seven previously published genome-wide association studies (GWASs) on plasma proteomics. The DPN data were obtained from the IEU OpenGWAS project. This study employed two-sample MR using MR-Egger and inverse-variance weighted methods to evaluate the causal relationship between plasma proteins and DPN risk, with Cochran's Q test, and I2 statistics, among other methods, used to validate the robustness of the results.

RESULTS

Using cis-pQTLs as genetic instruments, we identified 62 proteins associated with DPN, with 33 increasing the risk and 29 decreasing the risk of DPN. Using cis-pQTLs + trans-pQTLs, we identified 116 proteins associated with DPN, with 44 increasing the risk and 72 decreasing the risk of DPN. Steiger directionality tests indicated that the causal relationships between circulating plasma proteins and DPN were consistent with expected directions.

CONCLUSION

This study identified 96 circulating plasma proteins with genetically determined levels that affect the risk of DPN, providing new potential targets for DPN drug development, particularly ITM2B, CREG1, CD14, and PLXNA4.

Engineering of Kidney-Targeting Fluorophores with Tunable Emission from NIR-I to NIR-II for Early Diagnosis of Kidney Disease

The development of rapidly distributed and retained probes within the kidneys is important for accurately diagnosing kidney diseases. Although molecular imaging shows the potential for non-intrusively interrogating kidney disease-related biomarkers, the limited kidney contrast of many fluorophores, owing to their relatively low distribution in the kidney, hinders their effectiveness for kidney disease detection. Herein, for the first time, an amino-functionalization strategy is proposed to construct a library of kidney-targeting fluorophores NHcy with tunable emissions from NIR-I to NIR-II. Among these, NHcy-8 is the first small-molecule NIR-II dye without a renal clearance moiety, designed specifically for kidney-targeting imaging. Building on this class of NIR-II fluorophore, the first NIR-II small-molecule kidney-targeting pH probe NIR-II-pH is developed, which exhibits a desirable kidney distribution after intravenous injection and is fluorescent only after activation by acidosis. NIR-II in vivo fluorescence/photoacoustic imaging of kidney disease models induced by cisplatin and renal I/R injury using NIR-II-pH reveals increasingly severe metabolic acidosis as the disease progressed, enabling sensitive detection of the onset of acidosis 36 h (cisplatin group) earlier than clinical methods. Thus, this study introduces a practical NIR-II kidney-targeting probe and provides a useful molecular blueprint for guiding kidney-targeting NIR-II fluorophores as diagnostic aids for kidney diseases.

Global Trends and Hotspots in the Association between Chronic Kidney Disease and Cardiovascular Diseases: A Bibliometric Analysis from 2010 to 2023

INTRODUCTION

This study endeavors to evaluate the distribution patterns and research frontiers within the international literature on the association between chronic kidney disease and cardiovascular diseases in the medical field, through bibliometric analysis and visualized information.

METHODS

The Web of Science Core Collection database was selected as the data source from 2010 to 2023, and articles related to the association between chronic kidney disease and cardiovascular diseases were retrieved. The article data were analyzed through CiteSpace for bibliometric mapping, involving the examination of keywords, references, country/region distributions, and institutional contributions to identify and understand the evolving research dynamics and frontiers in this interdisciplinary field.

RESULTS

A total of 2,936 publications on the association between chronic kidney disease and cardiovascular diseases were included. The country with the most publications was USA (n = 904), and the institution with the most publications was University of Pennsylvania (n = 116). The most frequent keywords were chronic kidney disease (n = 2,194), cardiovascular disease (n = 1,188), and mortality (n = 604). The top 20 keywords and top 10 references that burst during 2010 to 2023 were listed.

CONCLUSION

The association between chronic kidney disease and cardiovascular diseases has sparked extensive research, particularly in high-prevalence areas. From 2010 to 2023, publications on the association between chronic kidney disease and cardiovascular diseases show a linear increase. Current research hotspots and frontiers are mainly in cardiovascular-kidney-metabolic syndrome; innovative therapies and drug impact; gut microbiome; Mendelian randomization analysis. Overall, our study offers a comprehensive scientometric analysis of the association between chronic kidney disease and cardiovascular diseases, providing valuable insights for both researchers and healthcare professionals in the field.

Investigating the metabolomic pathways in female reproductive endocrine disorders: a Mendelian randomization study

Introduction

Reproductive endocrine disorders (RED), including polycystic ovary syndrome (PCOS), endometriosis (EMs), and female infertility (FI), significantly affect women's health globally, with varying prevalence across different regions. These conditions can be addressed through medication, surgical interventions, and lifestyle modifications. However, the limited understanding of RED's etiology and the substantial economic burden of its treatment highlight the importance of investigating its pathogenesis. Metabolites play a critical role in metabolic processes and are potentially linked to the development of RED. Despite existing studies suggesting correlations between metabolites and RED, conclusive evidence remains scarce, primarily due to the observational nature of these studies, which are prone to confounding factors.

Methods

This study utilized Mendelian Randomization (MR) to explore the causal relationship between metabolites and RED, leveraging genetic variants associated with metabolite levels as instrumental variables to minimize confounding and reverse causality. Data were obtained from the Metabolomics GWAS Server and the IEU OpenGWAS project. Instrumental variables were selected based on their association with the human gut microbiota composition, and the GWAS summary statistics for metabolites, PCOS, EMs, and FI were analyzed. The MR-Egger regression and random-effects inverse-variance weighted (IVW) methods were employed to validate the causal relationship. Cochran's Q test was employed to evaluate heterogeneity, sensitivity analysis was performed using leave-one-out analysis, and for pleiotropy analysis, the intercept term of MR-Egger's method was investigated.

Results

The MR analysis revealed significant associations between various metabolites and RED conditions. For instance, a positive association was found between 1-palmitoylglycerophosphocholine and PCOS, while a negative association was noted between phenylacetate and FI. The study identified several metabolites associated with an increased risk and others with protective effects against PCOS, EMs, and FI. These findings highlight the complex interplay between metabolites and RED, suggesting potential pathways through which these conditions could be influenced or treated.

Conclusion

This MR study provides valuable insights into the causal relationship between metabolites and female reproductive endocrine disorders, suggesting that metabolic alterations play a significant role in the pathogenesis of PCOS, EMs, and FI, and offering a foundation for future research and therapeutic development.

Relationship between immune cells and diabetic nephropathy: a Mendelian randomization study

OBJECTIVE

Although previous studies have suggested potential correlations between immunocytes and diabetic nephropathy (DN), the causal correlations between them remain unclarified. In this study, we employed Mendelian randomization (MR) to analyze the potential causative correlations between immune 731 cells and DN.

METHODS

We used the Genome-Wide Association Studies (GWAS) database to aggregate signatures of immune cells and DN from European and East Asian populations. Single-nucleotide polymorphisms (SNPs) were used as instrumental variables. MR analysis was conducted using Mendelian randomization-Egger (MR-Egger) regression and the random-effects inverse-variance weighted (IVW) method.

RESULTS

A total of 3,571 SNPs were included as instrumental variables. The MR-Egger regression model indicated no genetic pleiotropy (P = 0.6284). The results of the IVW method indicated a statistically significant causal relationship between immune cell HLA-DR on CD14-CD16- (P = 0.029), CD45RA-CD28-CD8 + T cell% T cells (P = 0.0278), CD11c on myeloid dendritic cells (P = 0.0352), HLA-DR on CD14+ monocytes (P < 0.001), CD27 on CD24 + CD27 + B cells (P = 0.0334), CD27 on IgD + CD24 + B cells (P = 0.0137), CD4 on CD39 + CD4 + T cells (P = 0.0347), CD28 on CD39 + CD4 + T cells (P = 0.0414), CD39 on CD39 + CD4 + T cells (P = 0.0426), and DN. Additionally, there was no heterogeneity in SNPs related HLA-DR on CD14-CD16-cells and DN(I2 = 32%, Cochran's Q = 2.9476, P = 0.2291). Moreover, leave-one-out analysis showed a causal correlation between HLA-DR on CD14-CD16- cells and DN.

CONCLUSION

Higher expression of immune cell HLA-DR on CD14-CD16- cells may indicate a lower risk of DN.

Mendelian randomization analysis using multiple biomarkers of an underlying common exposure

Mendelian randomization (MR) analysis is increasingly popular for testing the causal effect of exposures on disease outcomes using data from genome-wide association studies. In some settings, the underlying exposure, such as systematic inflammation, may not be directly observable, but measurements can be available on multiple biomarkers or other types of traits that are co-regulated by the exposure. We propose a method for MR analysis on latent exposures (MRLE), which tests the significance for, and the direction of, the effect of a latent exposure by leveraging information from multiple related traits. The method is developed by constructing a set of estimating functions based on the second-order moments of GWAS summary association statistics for the observable traits, under a structural equation model where genetic variants are assumed to have indirect effects through the latent exposure and potentially direct effects on the traits. Simulation studies show that MRLE has well-controlled type I error rates and enhanced power compared to single-trait MR tests under various types of pleiotropy. Applications of MRLE using genetic association statistics across five inflammatory biomarkers (CRP, IL-6, IL-8, TNF-α, and MCP-1) provide evidence for potential causal effects of inflammation on increasing the risk of coronary artery disease, colorectal cancer, and rheumatoid arthritis, while standard MR analysis for individual biomarkers fails to detect consistent evidence for such effects.

MR-SPLIT: A novel method to address selection and weak instrument bias in one-sample Mendelian randomization studies

Mendelian Randomization (MR) is a widely embraced approach to assess causality in epidemiological studies. Two-stage least squares (2SLS) method is a predominant technique in MR analysis. However, it can lead to biased estimates when instrumental variables (IVs) are weak. Moreover, the issue of the winner's curse could emerge when utilizing the same dataset for both IV selection and causal effect estimation, leading to biased estimates of causal effects and high false positives. Focusing on one-sample MR analysis, this paper introduces a novel method termed Mendelian Randomization with adaptive Sample-sPLitting with cross-fitting InstrumenTs (MR-SPLIT), designed to address bias issues due to IV selection and weak IVs, under the 2SLS IV regression framework. We show that the MR-SPLIT estimator is more efficient than its counterpart cross-fitting MR (CFMR) estimator. Additionally, we introduce a multiple sample-splitting technique to enhance the robustness of the method. We conduct extensive simulation studies to compare the performance of our method with its counterparts. The results underscored its superiority in bias reduction, effective type I error control, and increased power. We further demonstrate its utility through the application of a real-world dataset. Our study underscores the importance of addressing bias issues due to IV selection and weak IVs in one-sample MR analyses and provides a robust solution to the challenge.

Causal relationship analysis between 35 blood/urine metabolites and gastroesophageal reflux disease: A Mendelian randomization combined meta-analysis study

Gastroesophageal reflux disease (GERD) is a common condition worldwide. Despite numerous studies on GERD, the causal relationships between blood/urine metabolites and GERD remain unclear. This study aims to explore the causal relationships between GERD and 35 blood/urine metabolites. In this study, we conducted Mendelian randomization (MR) analyses for 35 blood/urine metabolites with GERD phenotypes from the FinnGen R10 and UKB databases separately. We then performed a meta-analysis of the inverse variance weighted results from the 2 MR analyses and applied multiple corrections to the significant P values from the meta-analysis. Finally, we conducted reverse causality validation for the corrected positive blood/urine metabolite phenotypes with GERD. After conducting MR analysis combined with meta-analysis and performing multiple corrections, we found significant positive causal associations between only 3 blood/urine metabolites and GERD, with no significant reverse associations. Among them, 2 are risk factors for the occurrence of GERD: alanine aminotransferase levels (odds ratio (OR) = 1.120, 95% confidence interval (CI) = 1.064-1.180, P = .0005) and urate levels (OR = 1.095, 95% CI = 1.044-1.147, P = .005). Additionally, sex hormone-binding globulin levels are protective against GERD (OR = 0.928, 95% CI = 0.896-0.961, P = .0009). Elevated levels of the metabolites alanine aminotransferase and urate are associated with an increased risk of GERD, identifying them as risk factors for the condition. In contrast, higher levels of SHBG are linked to a decreased risk of GERD, indicating that SHBG is a protective factor against the disease.

Intrarenal pH-Responsive Self-Assembly of Luminescent Gold Nanoparticles for Diagnosis of Early Kidney Injury

Metabolic acidosis-induced kidney injury (MAKI) is asymptomatic and lack of clinical biomarkers in early stage, but rapidly progresses to severe renal fibrosis and ultimately results in end-stage kidney failure. Therefore, developing rapid and noninvasive strategies direct responsive to renal tubular acidic microenvironment rather than delayed biomarkers are essential for timely renoprotective interventions. Herein, we develop pH-responsive luminescent gold nanoparticles (p-AuNPs) in the second near-infrared emission co-coated with 2,3-dimethylaleic anhydride conjugated β-mercaptoethylamine and cationic 2-diethylaminoethanethiol hydrochloride, which showed sensitive pH-induced charge reversal and intrarenal self-assembly for highly sensitive and long-time (~24 h) imaging of different stages of MAKI. By integrating advantages of pH-induced intrarenal self-assembly and enhanced interactions between pH-triggered positively charged p-AuNPs and renal tubular cells, the early- and late-stage MAKI could be differentiated rapidly within 10 min post-injection (p.i.) with contrast index (CI) of 3.5 and 4.3, respectively. The corresponding maximum CI could reach 5.1 and 9.2 at 12 h p.i., respectively. Furthermore, p-AuNPs were demonstrated to effectively real-time monitor progressive recovery of kidney injury in MAKI mice after therapy, and also exhibit outstanding capabilities for drug screening. This pH-responsive strategy showed great promise for feedback on kidney dysfunction progression, opening new possibilities for early-stage diagnosis of pH-related diseases.

Inflammatory factors and the risk of urolithiasis: a bidirectional Mendelian randomization study

Background

Urolithiasis is a prevalent condition encountered in urology. Over the past decade, its global incidence has been on an upward trajectory; paired with a high recurrence rate, this presents considerable health and economic burdens. Although inflammatory factors are pivotal in the onset and progression of urolithiasis, their causal linkages remain elusive.

Method

Mendelian randomization (MR) is predicated upon genome-wide association studies (GWASs). It integrates bioinformatics analyses to reveal causal relationships between exposures and outcomes, rendering it an effective method with minimized bias. Drawing from a publicly accessible GWAS meta-analysis comprising 8,293 samples, we identified 41 genetic variations associated with inflammatory cytokines as instrumental variables. Outcome data on upper urinary tract stones, which included renal and ureteral stones (9,713 cases and 366,693 controls), and lower urinary tract stones, including bladder and urethral stones (1,398 cases and 366,693 controls), were derived from the FinnGen Consortium R9 dataset. By leveraging the bidirectional MR methodology, we aimed to decipher the causal interplay between inflammatory markers and urolithiasis.

Results

Our study comprehensively elucidated the association between genetic inflammatory markers and urolithiasis via bidirectional Mendelian randomization. Post-MR analysis of the 41 genetic inflammation markers revealed that elevated levels of circulating interleukin-2 (IL-2) (OR = 0.921, 95% CI = 0.848-0.999) suggest a reduced risk for renal stone disease, while heightened stem cell growth factor beta (SCGF-β) (OR = 1.150, 95% CI = 1.009-1.310) and diminished macrophage inflammatory protein 1 beta (MIP-1β) (OR = 0.863, 95% CI = 0.779-0.956) levels suggest an augmented risk for lower urinary tract stones. Furthermore, renal stone disease appeared to elevate IL-2 (β = 0.145, 95% CI = 0.013-0.276) and cutaneous T cell-attracting chemokine (CTACK) (β = 0.145, 95% CI = 0.013-0.276) levels in the bloodstream, whereas lower urinary tract stones were linked to a surge in interleukin-5 (IL-5) (β = 0.142, 95% CI = 0.057-0.226), interleukin-7 (IL-7) (β = 0.108, 95% CI = 0.024-0.192), interleukin-8 (IL-8) (β = 0.127, 95% CI = 0.044-0.210), growth regulated oncogene alpha (GRO-α) (β = 0.086, 95% CI = 0.004-0.169), monokine induced by interferon-gamma (MIG) (β = 0.099, 95% CI = 0.008-0.191) and macrophage inflammatory protein 1 alpha (MIP-1α) (β = 0.126, 95% CI = 0.044-0.208) levels.

Conclusion

These discoveries intimate the instrumental role of IL-2 in the onset and progression of upper urinary tract stones. SCGF-β and MIP-1β influence the development of lower urinary tract stones. Urolithiasis also impacts the expression of cytokines such as IL-2, CTACK, IL-5, IL-7, IL-8, GRO-α, MIG, and MIP-1α. There is a pressing need for further investigation to ascertain whether these biomarkers can be harnessed to prevent or treat urolithiasis.

Kidney Volume and Risk of Incident Kidney Outcomes

BACKGROUND

Low total kidney volume (TKV) is a risk factor for chronic kidney disease (CKD). However, evaluations of nonlinear relationships, incident events, causal inference, and prognostic utility beyond traditional biomarkers are lacking.

METHODS

TKV, height-adjusted TKV, and body surface area-adjusted TKV (BSA-TKV) of 34,595 White British ancestry participants were derived from the UK Biobank. Association with incident CKD, acute kidney injury (AKI), and cardiovascular events were assessed with Cox proportional hazard models. Prognostic thresholds for CKD risk stratification were identified using a modified Mazumdar method with bootstrap resampling. Two-sample Mendelian randomization was performed to assess the bidirectional association of genetically predicted TKV with kidney and cardiovascular traits.

RESULTS

Adjusted for eGFR and albuminuria, a lower TKV of 10 mL was associated with a 6% higher risk of incident CKD (hazard ratio [HR] 1.06, 95% confidence interval [CI] 1.03 to 1.08, P = 5.8 x 10-6) in contrast to no association with incident AKI (HR 1.00, 95% CI 0.98 to 1.02, P = 0.66). Comparison of nested models demonstrated improved accuracy over the CKD Prognosis Consortium Incident CKD Risk Score with the addition of BSA-TKV or prognostic thresholds at 119 (10th percentile) and 145 mL/m2 (50th percentile). In Mendelian randomization, a lower genetically predicted TKV by 10 mL was associated with 10% higher CKD risk (odds ratio [OR] 1.10, 95% CI 1.06 to 1.14, P = 1.3 x 10-7). Reciprocally, an elevated risk of genetically predicted CKD by 2-fold was associated with a lower TKV by 7.88 mL (95% CI -9.81 to -5.95, P = 1.2 x 10-15). There were no significant observational or Mendelian randomization associations of TKV with cardiovascular complications.

CONCLUSIONS

Kidney volume was associated with incident CKD independent of traditional risk factors including baseline eGFR and albuminuria. Mendelian randomization demonstrated a bidirectional relationship between kidney volume and CKD.

Kidney Function Measures and Mortality: A Mendelian Randomization Study

RATIONALE & OBJECTIVE

Individuals with a low estimated glomerular filtration rate (eGFR) are at a high risk of death. However, the causes underpinning this association are largely uncertain. This study aimed to assess the causal relationship of low eGFR with all-cause and cause-specific mortality.

STUDY DESIGN

Retrospective cohort study incorporating Mendelian randomization (MR).

SETTING & PARTICIPANTS

Individual-level data from 436,214 White participants (54.3% female; aged 56.8±8.0 years) included in the UK Biobank.

EXPOSURES

eGFR estimated using cystatin C (eGFRcyst).

OUTCOMES

The outcomes of interest included all-cause mortality, cardiovascular mortality, cancer mortality, infection mortality, and other-cause mortality.

ANALYTICAL APPROACH

Cox proportional hazards analysis for the conventional observational analyses; linear and nonlinear MR analyses implemented using genetic allele scores as instrumental variables representing kidney function to estimate the effect of kidney function on the survival outcomes.

RESULTS

During a median follow-up of 12.1 years, there were 30,489 deaths, 6,098 of which were attributed to cardiovascular events, 15,538 to cancer, 1,516 to infection, and 7,227 to other events. In the conventional observational analysis, eGFRcyst exhibited a nonlinear association with all the outcomes. MR analysis suggested that a genetically predicted lower eGFRcyst was linearly associated with a higher rate of cardiovascular mortality (HR, 1.43; 95% CI, 1.18-1.75) across the entire measurement range (every 10-mL/min/1.73m2 decrement). Nonetheless, no causal associations between eGFRcyst and all-cause mortality (HR, 1.07; 95% CI, 0.98-1.17) or any types of noncardiovascular mortality were detected.

LIMITATIONS

Potential misclassification of the actual cause of death, a nonrepresentative sample, and potential error in the interpretation of the magnitude of associations generated in MR analyses.

CONCLUSIONS

These findings suggest a potential causal association between low eGFR and cardiovascular mortality in the general population, but no causal relationship with all-cause mortality or noncardiovascular mortality was observed. Further studies in other populations are warranted to confirm these findings.

PLAIN-LANGUAGE SUMMARY

This study investigated the existence of a causal relationship between lower kidney function and death of different causes. Using data from 436,214 people in the United Kingdom, we applied conventional statistical analyses and those incorporating genetic data to implement Mendelian randomization, an approach that estimates causal associations. The observational analysis showed a nonlinear association between kidney function and various types of mortality outcomes. However, Mendelian randomization analysis suggested a linear increase in the risk of cardiovascular mortality with lower kidney function, but no causal link between the level of kidney function and all-cause or noncardiovascular mortality was identified. Managing kidney health may help reduce cardiovascular mortality, but caution is needed in interpreting the magnitudes of these results. Further validation in other populations and in those with advanced kidney failure is needed.

Inflammatory bowel disease and allergic diseases: A Mendelian randomization study

BACKGROUND

Inflammatory bowel disease (IBD) and allergic diseases possess similar genetic backgrounds and pathogenesis. Observational studies have shown a correlation, but the exact direction of cause and effect remains unclear. The aim of this Mendelian randomization (MR) study is to assess bidirectional causality between inflammatory bowel disease and allergic diseases.

METHOD

We comprehensively analyzed the causal relationship between inflammatory bowel disease (IBD), Crohn's disease (CD), ulcerative colitis (UC) and allergic disease (asthma, Hay fever, and eczema) as a whole, allergic conjunctivitis (AC), atopic dermatitis (AD), allergic asthma (AAS), and allergic rhinitis (AR) by performing a bidirectional Mendelian randomization study using summary-level data from genome-wide association studies. The analysis results mainly came from the random-effects model of inverse variance weighted (IVW-RE). In addition, multivariate Mendelian randomization (MVMR) analysis was conducted to adjust the effect of body mass index (BMI) on the instrumental variables.

RESULTS

The IVW-RE method revealed that IBD genetically increased the risk of allergic disease as a whole (OR = 1.03, 95% CI = 1.01-1.04, fdr.p = .015), AC (OR = 1.04, 95% CI = 1.01-1.06, fdr.p = .011), and AD (OR = 1.06, 95% CI = 1.02-1.09, fdr.p = .004). Subgroup analysis further confirmed that CD increased the risk of allergic disease as a whole (OR = 1.02, 95% CI = 1.00-1.03, fdr.p = .031), AC (OR = 1.03, 95% CI = 1.01-1.05, fdr.p = .012), AD (OR = 1.06, 95% CI = 1.02-1.09, fdr.p = 2E-05), AAS (OR = 1.05, 95% CI = 1.02-1.08, fdr.p = .002) and AR (OR = 1.03, 95% CI = 1.00-1.07, fdr.p = .025), UC increased the risk of AAS (OR = 1.02, 95% CI = 0.98-1.07, fdr.p = .038). MVMR results showed that after taking BMI as secondary exposure, the causal effects of IBD on AC, IBD on AD, CD on allergic disease as a whole, CD on AC, CD on AD, CD on AAS, and CD on AR were still statistically significant. No significant association was observed in the reverse MR analysis.

CONCLUSION

This Mendelian randomized study demonstrated that IBD is a risk factor for allergic diseases, which is largely attributed to its subtype CD increasing the risk of AC, AD, ASS, and AR. Further investigations are needed to explore the causal relationship between allergic diseases and IBD.

Osteoarthritis and hypertension: observational and Mendelian randomization analyses

BACKGROUND

The association between osteoarthritis (OA) and hypertension is a subject of ongoing debate in observational research, and the underlying causal relationship between them remains elusive.

METHODS

This study retrospectively included 24,871 participants in the National Health and Nutrition Examination Survey (NHANES) from 2013 to 2020. Weighted logistic regression was performed to investigate the connection between OA and hypertension. Additionally, Mendelian randomization (MR) analysis was conducted to explore the potential causal relationship between OA and hypertension.

RESULTS

In the NHANES data, after adjusting for multiple confounding factors, there was no significant relationship between OA and hypertension (OR 1.30, 95% CI, 0.97-1.73, P = 0.089). However, among males, OA appeared to be associated with a higher risk of hypertension (OR 2.25, 95% CI, 1.17-4.32, P = 0.019). Furthermore, MR results indicate no relationship between multiple OA phenotypes and hypertension: knee OA (IVW, OR 1.024, 95% CI: 0.931-1.126, P = 0.626), hip OA (IVW, OR 0.990, 95% CI: 0.941-1.042, P = 0.704), knee or hip OA (IVW, OR 1.005, 95% CI: 0.915-1.105, P = 0.911), and OA from UK Biobank (IVW, OR 0.796, 95% CI: 0.233-2.714, P = 0.715). Importantly, these findings remained consistent across different genders and in reverse MR.

CONCLUSIONS

Our study found that OA patients had a higher risk of hypertension only among males in the observational study. However, MR analysis did not uncover any causal relationship between OA and hypertension.

Effects of Metabolic Syndrome and Its Components on Chronic Kidney Disease and Renal Function: A Two-Sample Mendelian Randomization Study

Objective: The association of metabolic syndrome (MetS) and its components with chronic kidney disease (CKD) and renal function remains controversial in observational studies. To comprehensively investigate the association between MetS and its components with CKD and renal function, a Mendelian randomization (MR) study was performed. Methods: The inverse variance weighting (IVW) of random effects was used as the main estimation method, while MR-Egger and weighted median analysis results were used for auxiliary judgments. Cochran's Q test, MR-Egger intercept test, leave-one-out analysis, and funnel plots were used to assess heterogeneity and pleiotropy. Results: The MR analyses of genetically predicted MetS and its components' association with CKD risk and renal function showed the following causal associations: hypertension with CKD risk; MetS and obesity with increased blood urea nitrogen and decreased estimated glomerular filtration rate based on cystatin C; hypertension and diabetes with increased urine albumin-creatinine ratio and increased risk of microalbuminuria; and CKD with increased triglyceride. Conclusion: Based on genetic data, this study demonstrated an association between hypertension and CKD risk and a causal association between other MetS components and renal function. The early diagnosis and prevention of MetS and its components might be essential for CKD management.

Plasma metabolites and risk of myocardial infarction: a bidirectional Mendelian randomization study

BACKGROUND

Myocardial infarction (MI) is a critical cardiovascular event with multifaceted etiology, involving several genetic and environmental factors. It is essential to understand the function of plasma metabolites in the development of MI and unravel its complex pathogenesis.

METHODS

This study employed a bidirectional Mendelian randomization (MR) approach to investigate the causal relationships between plasma metabolites and MI risk. We used genetic instruments as proxies for plasma metabolites and MI and conducted MR analyses in both directions to assess the impact of metabolites on MI risk and vice versa. In addition, the large-scale genome-wide association studies datasets was used to identify genetic variants associated with plasma metabolite (1400 metabolites) and MI (20,917 individuals with MI and 440,906 individuals without MI) susceptibility. Inverse variance weighted was the primary method for estimating causal effects. MR estimates are expressed as beta coefficients or odds ratio (OR) with 95% CI.

RESULTS

We identified 14 plasma metabolites associated with the occurrence of MI (P < 0.05), among which 8 plasma metabolites [propionylglycine levels (OR = 0.922, 95% CI: 0.881-0.965, P < 0.001), gamma-glutamylglycine levels (OR = 0.903, 95% CI: 0.861-0.948, P < 0.001), hexadecanedioate (C16-DC) levels (OR = 0.941, 95% CI: 0.911-0.973, P < 0.001), pentose acid levels (OR = 0.923, 95% CI: 0.877-0.972, P = 0.002), X-24546 levels (OR = 0.936, 95% CI: 0.902-0.971, P < 0.001), glycine levels (OR = 0.936, 95% CI: 0.909-0.964, P < 0.001), glycine to serine ratio (OR = 0.930, 95% CI: 0.888-0.974, P = 0.002), and mannose to trans-4-hydroxyproline ratio (OR = 0.912, 95% CI: 0.869-0.958, P < 0.001)] were correlated with a decreased risk of MI, whereas the remaining 6 plasma metabolites [1-palmitoyl-2-arachidonoyl-GPE (16:0/20:4) levels (OR = 1.051, 95% CI: 1.018-1.084, P = 0.002), behenoyl dihydrosphingomyelin (d18:0/22:0) levels (OR = 1.076, 95% CI: 1.027-1.128, P = 0.002), 1-stearoyl-2-docosahexaenoyl-GPE (18:0/22:6) levels (OR = 1.067, 95% CI: 1.027-1.109, P = 0.001), alpha-ketobutyrate levels (OR = 1.108, 95% CI: 1.041-1.180, P = 0.001), 5-acetylamino-6-formylamino-3-methyluracil levels (OR = 1.047, 95% CI: 1.019-1.076, P < 0.001), and N-acetylputrescine to (N (1) + N (8))-acetylspermidine ratio (OR = 1.045, 95% CI: 1.018-1.073, P < 0.001)] were associated with an increased risk of MI. Furthermore, we also observed that the mentioned relationships were unaffected by horizontal pleiotropy (P > 0.05). On the contrary, MI did not lead to significant alterations in the levels of the aforementioned 14 plasma metabolites (P > 0.05 for each comparison).

CONCLUSIONS

Our bidirectional MR study identified 14 plasma metabolites associated with the occurrence of MI, among which 13 plasma metabolites have not been reported previously. These findings provide valuable insights for the early diagnosis of MI and potential therapeutic targets.

Eicosanoids and Related Metabolites Associated with ESKD in a Community-Based Cohort

Key Points

High-throughput eicosanoid profiling can identify metabolites that may play a protective role in the development of kidney disease. In contrast to many other nonlipid metabolites, eicosanoid levels are minimally related with kidney filtration cross-sectionally.

Background

Eicosanoids are derivatives of polyunsaturated fatty acids and participate in the inflammatory response and the maintenance of endothelial function. Specific eicosanoids have been linked to various diseases, including hypertension and asthma, and may also reduce renal blood flow. A systematic investigation of eicosanoid-related metabolites and adverse kidney outcomes could identify key mediators of kidney disease and inform ongoing work in drug development.

Methods

Profiling of eicosanoid-related metabolites was performed in 9650 participants in the Atherosclerosis Risk in Communities Study (visit 2; mean age, 57 years). The associations between metabolite levels and the development of ESKD was investigated using Cox proportional hazards regression (n =256 events; median follow-up, 25.5 years). Metabolites with statistically significant associations with ESKD were evaluated for a potential causal role using bidirectional Mendelian randomization techniques, linking genetic instruments for eicosanoid levels to genomewide association study summary statistics of eGFR.

Results

The 223 eicosanoid-related metabolites that were profiled and passed quality control (QC) were generally uncorrelated with eGFR in cross-sectional analyses (median Spearman correlation, −0.03; IQR, −0.05 to 0.002). In models adjusted for multiple covariates, including baseline eGFR, three metabolites had statistically significant associations with ESKD (P value < 0.05/223). These included a hydroxyoctadecenoic acid, a dihydroxydocosapentaenoic acid, and arachidonic acid, with higher levels of the former two protective against ESKD and higher levels of arachidonic acid having a positive association with risk of ESKD. Mendelian randomization analyses suggested a causal role for the hydroxyoctadecenoic and arachidonic acid in determining eGFR. Spectral analysis identified the former metabolite as either 11-hydroxy-9-octadecenoic acid or 10-hydroxy-11-octadecenoic acid.

Conclusions

High-throughput eicosanoid profiling can identify metabolites that may play a protective role in the development of kidney disease.

Identification of Novel Risk Variants of Inflammatory Factors Related to Myeloproliferative Neoplasm: A Bidirectional Mendelian Randomization Study

Epidemiological and experimental evidence has linked chronic inflammation to the etiology of myeloproliferative neoplasm (MPN). However, it remains unclear whether genetic associations with specific inflammatory biomarkers are causal or due to bias. This study aimed to assess the effect of C-reactive protein (CRP) and systemic inflammatory regulators on MPN within a bidirectional Mendelian randomization design. Genetic associations with MPN were derived from a publicly available genome-wide association study (GWAS) comprising 1,086 cases and 407,155 controls of European ancestry. Additionally, data on inflammation were extracted from two GWASs focusing on CRP and cytokines. The causal relationships between exposure and outcome were explored using the inverse variance weighted (IVW) method. To confirm the final results, multiple sensitivity analyses, including MR-Egger, weighted median, and MR-pleiotropy residual sum and outlier (MR-PRESSO), were simultaneously employed. Our results suggest that lower levels of macrophage-migration inhibitory factor (IVW estimate odds ratio [OR IVW] per SD genetic cytokines change: 0.641; 95% confidence interval [CI]: 0.427-0.964; p  = 0.032) and higher levels of interleukin-2 receptor α (lL2Rα, 1.377, 95% CI: 1.006-1.883; p  = 0.046) are associated with an increased risk of MPN. Genetically predicted MPN is related to increased levels of RANTES (IVW estimate β: 0.043, 95% CI: 0.002-0.084; p  = 0.039) and interleukin-10 (IVW estimate β: 0.030, 95% CI: 0.001-0.060; p  = 0.041). This study provides evidence for a causal relationship between CRP, systemic inflammatory regulators, and MPN, and new insights into the etiology, prevention, and prognosis of MPN.

Exploring the gut mycobiome: differential composition and clinical associations in hypertension, chronic kidney disease, and their comorbidity

Background

Hypertension (HTN) and chronic kidney disease (CKD) pose significant global health challenges and often coexist, amplifying cardiovascular risks. Recent attention has turned to the gut mycobiome as a potential factor in their pathophysiology. Our study sought to examine the gut fungal profile in individuals with HTN, CKD, and the concurrent HTN+CKD condition, investigating its connections with serum cytokines, renal function, and blood pressure.

Methods and materials

We investigated three distinct participant groups: a cohort of 50 healthy controls (HC), 50 individuals diagnosed with HTN-only, and 50 participants suffering from both HTN and CKD (HTN+CKD). To facilitate our research, we gathered fecal and blood samples and conducted a comprehensive analysis of serum cytokines. Moreover, fungal DNA extraction was conducted with meticulous care, followed by sequencing of the Internal Transcribed Spacer (ITS) region.

Results

HTN+CKD patients displayed distinctive fungal composition with increased richness and diversity compared to controls. In contrast, HTN-only patients exhibited minimal fungal differences. Specific fungal genera were notably altered in HTN+CKD patients, characterized by increased Apiotrichum and Saccharomyces levels and reduced Candida abundance. Our correlation analyses revealed significant associations between fungal genera and serum cytokines. Moreover, certain fungal taxa, such as Apiotrichum and Saccharomyces, exhibited positive correlations with renal function, while others, including Septoria, Nakaseomyces, and Saccharomyces, were linked to blood pressure, particularly diastolic pressure.

Conclusion

Gut mycobiome dysbiosis in individuals with comorbid HTN and CKD differs significantly from that observed in HTN-only and healthy controls. The interactions between serum cytokines, renal function, and blood pressure emphasize the potential impact of the fungal microbiome on these conditions. Additional research is required to clarify the underlying mechanisms and identify therapeutic opportunities associated with mycobiome dysbiosis in HTN and CKD.

Mendelian randomization for nephrologists

Confounding is a major limitation of observational studies. Mendelian randomization (MR) is a powerful study design that uses genetic variants as instrumental variables to enable examination of the causal effect of an exposure on an outcome in observational data. With the emergence of large-scale genome-wide association studies in nephrology over the past decade, MR has become a popular method to establish causal inferences. However, MR is a complex and challenging methodology that requires careful consideration to ensure robust results. This review article aims to summarize the basic concepts of MR, its application and relevance in nephrology, and the methodological challenges and limitations as well as discuss the current guidelines for design and reporting. With reference to a clinically relevant example of examining the causal relationship between the estimated glomerular filtration rate and cancer, this review outlines the key steps to conducting an MR study, including the key considerations and potential pitfalls at each step. These include defining the clinical question, selecting the data sources, identifying and refining appropriate genetic variants by considering linkage disequilibrium and associations with potential confounders, harmonization of variants across data sets, validation of the genetic instrument by assessing its strength, estimation of the causal effects, confirming the validity of the findings, and interpreting and reporting results.

Identification of circulating proteins associated with general cognitive function among middle-aged and older adults

Identifying circulating proteins associated with cognitive function may point to biomarkers and molecular process of cognitive impairment. Few studies have investigated the association between circulating proteins and cognitive function. We identify 246 protein measures quantified by the SomaScan assay as associated with cognitive function (p < 4.9E-5, n up to 7289). Of these, 45 were replicated using SomaScan data, and three were replicated using Olink data at Bonferroni-corrected significance. Enrichment analysis linked the proteins associated with general cognitive function to cell signaling pathways and synapse architecture. Mendelian randomization analysis implicated higher levels of NECTIN2, a protein mediating viral entry into neuronal cells, with higher Alzheimer's disease (AD) risk (p = 2.5E-26). Levels of 14 other protein measures were implicated as consequences of AD susceptibility (p < 2.0E-4). Proteins implicated as causes or consequences of AD susceptibility may provide new insight into the potential relationship between immunity and AD susceptibility as well as potential therapeutic targets.

Management of Hypertension in Diabetic Kidney Disease

Hypertension is a critical component of cardiovascular disease progression in patients with chronic kidney disease, and specifically diabetic kidney disease (DKD). Causation versus correlation remains up for debate, but what has been confirmed is the delay of DKD progression when hypertension is controlled or moved to guideline drive ranges. Many medications have been studied and used in real world experience for best outcomes, and we discuss below the proven winners thus far making up the renin angiotensin aldosterone system. As well, we discuss guideline changing medications including sodium-glucose cotransporter 2 inhibitors and newer generation mineralocorticoid receptor antagonists. With the growing prevalence of diabetes and DKD in the population, newer agents are emerging in multiple drug class and will be highlighted below. Clinicians continue to search for the optimal care plans for this challenging patient population.

Beyond Tissue replacement: The Emerging role of smart implants in healthcare

Smart implants are increasingly used to treat various diseases, track patient status, and restore tissue and organ function. These devices support internal organs, actively stimulate nerves, and monitor essential functions. With continuous monitoring or stimulation, patient observation quality and subsequent treatment can be improved. Additionally, using biodegradable and entirely excreted implant materials eliminates the need for surgical removal, providing a patient-friendly solution. In this review, we classify smart implants and discuss the latest prototypes, materials, and technologies employed in their creation. Our focus lies in exploring medical devices beyond replacing an organ or tissue and incorporating new functionality through sensors and electronic circuits. We also examine the advantages, opportunities, and challenges of creating implantable devices that preserve all critical functions. By presenting an in-depth overview of the current state-of-the-art smart implants, we shed light on persistent issues and limitations while discussing potential avenues for future advancements in materials used for these devices.

Association between depression and COPD: results from the NHANES 2013-2018 and a bidirectional Mendelian randomization analysis

BACKGROUND

Observational studies showed a bidirectional association between depression and chronic obstructive pulmonary disease (COPD). However, it is unclear whether the observed association is causal. Thus we estimated the relationship using observational studies combined with bidirectional Mendelian randomization [MR].

MATERIALS AND METHODS

The study included 9977 participants from the 2013-2018 National Health and Nutrition Examination Survey and used weighted logistic regression analysis to assess the association between depression and COPD, followed by a bidirectional Mendelian randomization analysis to verify their causality.

RESULTS

Adjusted-weighted logistic regression in observational studies showed a significant association between COPD and mild depression (OR (95% CI): 1.81 (1.30, 2.52), P = 0.002) and COPD and depression (OR (95% CI): 1.93 (1.49, 2.50), P < 0.001). MR suggested depression may play a causal role in COPD risk (OR (95% CI): 1.45 (1.32, 1.60), P < 0.001), but more evidence for reverse causation is lacking (reverse MR OR (95% CI): 1.03 (0.99, 1.07), P = 0.151).

CONCLUSION

In conclusion, our study found depression may play a potential causal role in the morbidity of COPD suggesting depression might be the etiology of COPD. This finding needs to be validated in further prospective cohort studies with large sample sizes and adequate follow-up time.

Effects of epigenetic age acceleration on kidney function: a Mendelian randomization study

BACKGROUND

Previous studies have reported cross-sectional associations between measures of epigenetic age acceleration (EAA) and kidney function phenotypes. However, the temporal and potentially causal relationships between these variables remain unclear. We conducted a bidirectional two-sample Mendelian randomization study of EAA and kidney function. Genetic instruments for EAA and estimate glomerular filtration rate (eGFR) were identified from previous genome-wide association study (GWAS) meta-analyses of European-ancestry participants. Causal effects of EAA on kidney function and kidney function on EAA were assessed through summary-based Mendelian randomization utilizing data from the CKDGen GWAS meta-analysis of log-transformed estimated glomerular filtration rate (log-eGFR; n = 5,67,460) and GWAS meta-analyses of EAA (n = 34,710). An allele score-based Mendelian randomization leveraging individual-level data from UK Biobank participants (n = 4,33,462) further examined the effects of EAA on kidney function.

RESULTS

Using summary-based Mendelian randomization, we found that each 5 year increase in intrinsic EAA (IEAA) and GrimAge acceleration (GrimAA) was associated with - 0.01 and - 0.02 unit decreases in log-eGFR, respectively (P = 0.02 and P = 0.09, respectively), findings which were strongly supported by allele-based Mendelian randomization study (both P < 0.001). Summary-based Mendelian randomization identified 24% increased odds of CKD with each 5-unit increase in IEAA (P = 0.05), with consistent findings observed in allele score-based analysis (P = 0.07). Reverse-direction Mendelian randomization identified potentially causal effects of decreased kidney function on HannumAge acceleration (HannumAA), GrimAA, and PhenoAge acceleration (PhenoAA), conferring 3.14, 1.99, and 2.88 year decreases in HanumAA, GrimAA, and PhenoAA, respectively (P = 0.003, 0.05, and 0.002, respectively) with each 1-unit increase in log-eGFR.

CONCLUSION

This study supports bidirectional causal relationships between EAA and kidney function, pointing to potential prevention and therapeutic strategies.

Kidney function may partially mediated the protective effect of urinary uromodulin on kidney stone

The causal links between urinary uromodulin (uUMOD) and kidney stone disease (KSD) are still not clarified in general population. We assessed their relationships combining 2-sample Mendelian randomization (MR) and multivariable (MVMR) designs among general population of European ancestry. The summary information for uUMOD indexed to creatinine levels (29,315 individuals) and KSD (395,044 individuals) were from 2 independent genome-wide association studies (GWAS). The primary causal effects of exposures on outcomes were evaluated using inverse variance-weighted (IVW) regression model. Multiple sensitivity analyses were also performed. In 2-sample MR, we found that 1-unit higher genetically predicted uUMOD levels were associated with a lower risk of KSD (OR = 0.62; 95% CI 0.55-0.71; P = 2.83E-13). In reverse, we did not find the effect of KSD on uUOMD using IVW (beta = 0.00; 95% CI - 0.06-0.05; P = 0.872) and other sensitivity analyses. In MVMR, uUMOD indexed to creatinine levels were directly associated with the risk of KSD after introducing eGFR, SBP, urinary sodium or all three factors (OR = 0.71; 95% CI 0.64-0.79; P = 1.57E-09). Furthermore, our study supported that the protective effect of uUMOD on KSD may be partially mediated by eGFR (beta = - 0.09; 95% CI - 0.13 to - 0.06; mediation proportion = 20%). Our study supported that the protective effect of genetically predicted higher uUMOD levels on KSD may be partially mediated by eGFR decline, but not via SBP or urinary sodium. uUMOD might be a treatment target in preventing KSD in general population.

Effects of Intensive Systolic Blood Pressure Lowering on End-Stage Kidney Disease and Kidney Function Decline in Adults With Type 2 Diabetes Mellitus and Cardiovascular Risk Factors: A Post Hoc Analysis of ACCORD-BP and SPRINT

OBJECTIVE

To determine the effects of intensive systolic blood pressure (SBP) lowering on the risk of major adverse kidney outcomes in people with type 2 diabetes mellitus (T2DM) and/or prediabetes and cardiovascular risk factors.

RESEARCH DESIGN AND METHODS

This post hoc ACCORD-BP subgroup analysis included participants in the standard glucose-lowering arm with cardiovascular risk factors required for SPRINT eligibility. Cox proportional hazards regression models compared the hazard for the composite of dialysis, kidney transplant, sustained estimated glomerular filtration rate (eGFR) <15 mL/min/1.73 m2, serum creatinine >3.3 mg/dL, or a sustained eGFR decline ≥57% between the intensive (<120 mmHg) and standard (<140 mmHg) SBP-lowering arms.

RESULTS

The study cohort included 1,966 SPRINT-eligible ACCORD-BP participants (40% women) with a mean age of 63 years. The mean SBP achieved after randomization was 120 ± 14 and 134 ± 15 mmHg in the intensive and standard arms, respectively. The kidney composite outcome occurred at a rate of 9.5 and 7.2 events per 1,000 person-years in the intensive and standard BP arms (hazard ratio [HR] 1.35 [95% CI 0.85-2.14]; P = 0.20). Intensive SBP lowering did not affect the risk of moderately (HR 0.96 [95% CI 0.76-1.20]) or severely (HR 0.92 [95% CI 0.66-1.28]) increased albuminuria. Including SPRINT participants with prediabetes in the cohort did not change the overall results.

CONCLUSIONS

This post hoc subgroup analysis suggests that intensive SBP lowering does not increase the risk of major adverse kidney events in individuals with T2DM and cardiovascular risk factors.

Association of Pre- and Post-Donation Renal Function with Midterm Estimated Glomerular Filtration Rate in Living Kidney Donors: A Retrospective Study

PURPOSE

The estimated glomerular filtration rate (eGFR) at 6 months after donation (eGFR_6m) is strongly associated with the risk of end-stage renal disease in living kidney donors. This study aimed to investigate the incidence of eGFR_6m <60 mL/min/1.73 m² (eGFR_6m <60) and identify the risk factors that can predict the occurrence of eGFR_6m <60 in living kidney donors.

MATERIALS AND METHODS

Living kidney donors who underwent nephrectomy at Severance Hospital between January 2009 and December 2019 were identified. We excluded 94 of 1233 donors whose creatinine values at 6 months after donation were missing. The risk factors for eGFR_6m <60 were assessed using multivariate regression analysis. The optimal cutoff points for candidate risk factors for predicting eGFR_6m <60 occurrence were determined using the Youden index.

RESULTS

The eGFR_6m <60 occurred in 17.3% of the participants. Older age (≥44 years), history of hypertension, lower preoperative eGFR (<101 mL/min/1.73 m²), and degree of increase in creatinine levels on postoperative day 2 compared to those before surgery (ΔCr2_pre) (≥0.39 mg/dL) increased the risk of eGFR_6m <60. The addition of ΔCr2_pre to preoperative eGFR yielded a higher predictive accuracy for predicting eGFR_6m <60 than that with preoperative eGFR alone {area under the receiver operating characteristic curve=0.886 [95% confidence interval (CI), 0.863-0.908] vs. 0.862 (95% CI, 0.838-0.887), p<0.001}.

CONCLUSION

The incidence of eGFR_6m <60 was 17.3%. Older age, lower preoperative eGFR, history of hypertension, and greater ΔCr2_pre were associated with the occurrence of eGFR_6m <60 after living donor nephrectomy. The combination of preoperative eGFR and ΔCr2_pre showed the highest predictive power for eGFR_6m <60.

Impairment of kidney function and kidney cancer: A bidirectional Mendelian randomization study

BACKGROUND

Many observational epidemiology studies discovered that kidney cancer and impaired kidney function have a bidirectional relationship. However, it remains unclear whether these two kinds of traits are causally linked. In this study, we aimed to investigate the bidirectional causal relation between kidney cancer and kidney function biomarkers (creatinine-based estimated glomerular filtration rate (eGFRcrea), cystatin C-based estimated glomerular filtration rate (eGFRcys), blood urea nitrogen (BUN), serum urate, and urinary albumin-to-creatinine ratio (UACR)).

METHODS

For both directions, single-nucleotide polymorphisms (SNPs), as genetic instruments, for the five kidney function traits were selected from up to 1,004,040 individuals, and SNPs for kidney cancer were from 408,786 participants(1338 cases). In the main analysis, we applied two state-of-the-art MR methods, namely, contamination mixture and Robust Adjusted Profile Score to downweight the effect of weak instrument bias, pleiotropy, and extreme outliers. We additionally conducted traditional MR analyses as sensitivity analyses. Summary-level data of European ancestry were extracted from UK Biobank, Chronic Kidney Disease Genetics Consortium, and Kaiser Permanente.

RESULTS

Based on 99 SNPs, we found that the eGFRcrea had a significant negative causal effect on the risk of kidney cancer (OR = 0.007, 95% CI:2.6 × 10-4 -0.569, p = 0.041). After adjusting for body composition or diabetes, urate had a significant negative causal effect on kidney cancer (OR <1, p < 0.05). For UACR, it showed a strong causal effect on kidney cancer, after adjusting for body composition (OR = 14.503, 95% CI: 2.546-96.001, p = 0.032). Due to lacking significant signals and effect power for the reverse MR, further investigations are warranted.

CONCLUSIONS

Our study suggested a potential causal effect of damaged kidney function on kidney cancer. EGFRcrea and UACR might be causally associated with kidney cancer, especially when patients were comorbid with obesity or diabetes. We called for larger sample-size studies to further unravel the underlying causal relationship and the exact mechanism.

A genomic deep field view of hypertension

Blood pressure is regulated by a complex neurohumoral system including the renin-angiotensin-aldosterone system, natriuretic peptides, endothelial pathways, the sympathetic nervous system, and the immune system. This review charts the evolution of our understanding of the genomic basis of hypertension at increasing resolution over the last 5 decades from monogenic causes to polygenic associations, spanning ∼30 monogenic rare variants and >1500 single nucleotide variants. Unexpected early wins from blood pressure genomics include deepening of our understanding of the complex causation of hypertension; refinement of causal estimates bidirectionally between blood pressure, risk factors, and outcomes through Mendelian randomization; risk stratification using polygenic risk scores; and opportunities for precision medicine and drug repurposing.

Contributions of obesity to kidney health and disease: insights from Mendelian randomization and the human kidney transcriptomics

AIMS

Obesity and kidney diseases are common complex disorders with an increasing clinical and economic impact on healthcare around the globe. Our objective was to examine if modifiable anthropometric obesity indices show putatively causal association with kidney health and disease and highlight biological mechanisms of potential relevance to the association between obesity and the kidney.

METHODS AND RESULTS

We performed observational, one-sample, two-sample Mendelian randomization (MR) and multivariable MR studies in ∼300 000 participants of white-British ancestry from UK Biobank and participants of predominantly European ancestry from genome-wide association studies. The MR analyses revealed that increasing values of genetically predicted body mass index and waist circumference were causally associated with biochemical indices of renal function, kidney health index (a composite renal outcome derived from blood biochemistry, urine analysis, and International Classification of Disease-based kidney disease diagnoses), and both acute and chronic kidney diseases of different aetiologies including hypertensive renal disease and diabetic nephropathy. Approximately 13-16% and 21-26% of the potentially causal effect of obesity indices on kidney health were mediated by blood pressure and type 2 diabetes, respectively. A total of 61 pathways mapping primarily onto transcriptional/translational regulation, innate and adaptive immunity, and extracellular matrix and metabolism were associated with obesity measures in gene set enrichment analysis in up to 467 kidney transcriptomes.

CONCLUSIONS

Our data show that a putatively causal association of obesity with renal health is largely independent of blood pressure and type 2 diabetes and uncover the signatures of obesity on the transcriptome of human kidney.

Determining the Relationship Between Blood Pressure, Kidney Function, and Chronic Kidney Disease: Insights From Genetic Epidemiology

BACKGROUND

It is well established that decreased kidney function can increase blood pressure (BP), but it is unproven whether moderately elevated BP causes chronic kidney disease (CKD) or glomerular hyperfiltration.

METHODS

311 119 White British UK Biobank participants were included in logistic regression analyses to estimate the odds of CKD (defined as long-term kidney replacement therapy, estimated glomerular filtration rate [eGFR]< 60mL/min/1.73m², or urinary albumin:creatinine ratio ≥3 mg/mmol) associated with higher genetically predicted BP using genetic risk scores comprising 219 systolic and 223 diastolic BP loci. Analyses estimating associations with clinical categories of eGFR and urinary albumin:creatinine ratio were also conducted, with an eGFR ≥120 mL (min·1.73m²) considered evidence of glomerular hyperfiltration.

RESULTS

21 623 participants had CKD: 7781 with reduced eGFR and 15 500 with albuminuria. 1828 participants had an eGFR ≥120 mL/min/1.73m². Each genetically predicted 10 mmHg higher systolic BP and 5 mmHg higher diastolic BP were associated with a 37% (95% CI, 1.29-1.45) and 19% (1.14-1.25) higher odds of CKD, respectively. Associations were evident for both the reduced eGFR and albuminuria components of the CKD outcome. The odds of hyperfiltration (versus an eGFR ≥60 and <90 mL/min/1.73m² were 49% higher (95% CI, 1.21-1.84) for each genetically predicted 10 mmHg higher systolic BP. Associations with CKD and hyperfiltration were similar irrespective of preexisting diabetes, vascular disease, or different levels of adiposity.

CONCLUSIONS

In this general population, genetic epidemiological evidence supports a causal role of life-long differences in BP for decreased kidney function, glomerular hyperfiltration, and albuminuria. Physiological autoregulation may not afford complete renal protection against the moderate BP elevations.

Mild-to-Moderate Kidney Dysfunction and Cardiovascular Disease: Observational and Mendelian Randomization Analyses

BACKGROUND

End-stage renal disease is associated with a high risk of cardiovascular events. It is unknown, however, whether mild-to-moderate kidney dysfunction is causally related to coronary heart disease (CHD) and stroke.

METHODS

Observational analyses were conducted using individual-level data from 4 population data sources (Emerging Risk Factors Collaboration, EPIC-CVD [European Prospective Investigation into Cancer and Nutrition-Cardiovascular Disease Study], Million Veteran Program, and UK Biobank), comprising 648 135 participants with no history of cardiovascular disease or diabetes at baseline, yielding 42 858 and 15 693 incident CHD and stroke events, respectively, during 6.8 million person-years of follow-up. Using a genetic risk score of 218 variants for estimated glomerular filtration rate (eGFR), we conducted Mendelian randomization analyses involving 413 718 participants (25 917 CHD and 8622 strokes) in EPIC-CVD, Million Veteran Program, and UK Biobank.

RESULTS

There were U-shaped observational associations of creatinine-based eGFR with CHD and stroke, with higher risk in participants with eGFR values <60 or >105 mL·min-1·1.73 m-2, compared with those with eGFR between 60 and 105 mL·min-1·1.73 m-2. Mendelian randomization analyses for CHD showed an association among participants with eGFR <60 mL·min-1·1.73 m-2, with a 14% (95% CI, 3%-27%) higher CHD risk per 5 mL·min-1·1.73 m-2 lower genetically predicted eGFR, but not for those with eGFR >105 mL·min-1·1.73 m-2. Results were not materially different after adjustment for factors associated with the eGFR genetic risk score, such as lipoprotein(a), triglycerides, hemoglobin A1c, and blood pressure. Mendelian randomization results for stroke were nonsignificant but broadly similar to those for CHD.

CONCLUSIONS

In people without manifest cardiovascular disease or diabetes, mild-to-moderate kidney dysfunction is causally related to risk of CHD, highlighting the potential value of preventive approaches that preserve and modulate kidney function.

Blood Pressure Mediated the Effects of Urinary Uromodulin Levels on Myocardial Infarction: a Mendelian Randomization Study

Background:

The causal links between urinary uromodulin (uUMOD) and cardiovascular disease (CVD) are still not clarified.

Methods:

We first assessed the relationship between uUMOD and CVD using bidirectional 2-sample Mendelian randomization. Then, multivariable Mendelian randomization and product of the coefficients methods were used to investigate the role of blood pressure in mediating the effect of uUMOD on CVD.

Results:

1-unit higher uUMOD level was associated with a higher risk of myocardial infarction (MI), with an odds ratio of 1.08 ([95% CI, 1.02–1.14]; P =0.009), while MI was not associated with uUMOD levels in reverse. Our study did not support the causal effects of uUMOD on other CVD outcomes, including coronary artery disease, atrial fibrillation, heart failure, and ischemic stroke. In multivariable Mendelian Randomization, the direct effects of uUMOD on MI were attenuated to null after introducing systolic blood pressure or diastolic blood pressure. Mediation analysis showed that the indirect effect of uUMOD on MI mediated by systolic blood pressure or diastolic blood pressure was 1.05 ([95% CI, 1.04–1.06]; mediation proportion=69%) and 1.07 ([95% CI, 1.05–1.08]; mediation proportion=87%), respectively. Similar results were found in sensitivity analysis based on different sets of genetic instruments.

Conclusions:

Our findings provide evidence for the effect of higher uUMOD on increasing blood pressure, which mediates a consequent effect on MI risk in the general population. Further studies are necessary to verify the associations between uUMOD and other CVD outcomes.

Kidney omics in hypertension: from statistical associations to biological mechanisms and clinical applications

Hypertension is a major cardiovascular disease risk factor and contributor to premature death globally. Family-based investigations confirmed a significant heritable component of blood pressure (BP), whereas genome-wide association studies revealed >1000 common and rare genetic variants associated with BP and/or hypertension. The kidney is not only an organ of key relevance to BP regulation and the development of hypertension, but it also acts as the tissue mediator of genetic predisposition to hypertension. The identity of kidney genes, pathways, and related mechanisms underlying the genetic associations with BP has started to emerge through integration of genomics with kidney transcriptomics, epigenomics, and other omics as well as through applications of causal inference, such as Mendelian randomization. Single-cell methods further enabled mapping of BP-associated kidney genes to cell types, and in conjunction with other omics, started to illuminate the biological mechanisms underpinning associations of BP-associated genetic variants and kidney genes. Polygenic risk scores derived from genome-wide association studies and refined on kidney omics hold the promise of enhanced diagnostic prediction, whereas kidney omics-informed drug discovery is likely to contribute new therapeutic opportunities for hypertension and hypertension-mediated kidney damage.

Serum bilirubin and kidney function: a Mendelian randomization study

Background

Further investigation is needed to determine the causal effects of serum bilirubin on the risk of chronic kidney disease (CKD).

Methods

This study is a Mendelian randomization (MR) analysis. Among the well-known single-nucleotide polymorphisms (SNPs) related to serum bilirubin levels, rs4149056 in the SLCO1B1 gene was selected as the genetic instrument for single-variant MR analysis, as it was found to be less related to possible confounders than other SNPs. The association between genetic predisposition for bilirubin levels and estimated glomerular filtration rate (eGFR) or CKD was assessed in 337 129 individuals of white British ancestry from the UK Biobank cohort. Two-sample MR based on summary-level data was also performed. SNPs related to total or direct bilirubin levels were collected from a previous genome-wide association study and confounder-associated SNPs were discarded. The independent CKDGen meta-analysis data for CKD were employed as the outcome summary statistics.

Results

The alleles of rs4149056 associated with higher bilirubin levels were associated with better kidney function in the UK Biobank data. In the summary-level MR, both of the genetically predicted total bilirubin {per 5 µmol/L increase; odds ratio [OR] 0.931 [95% confidence interval (CI) 0.871-0.995]} and direct bilirubin [per 1 µmol/L increase; OR 0.910 (95% CI 0.834-0.993)] levels were significantly associated with a lower risk of CKD, supported by the causal estimates from various MR sensitivity analyses.

Conclusion

Genetic predisposition for higher serum bilirubin levels is associated with better kidney function. This result suggests that higher serum bilirubin levels may have causal protective effects against kidney function impairment.