Genetic overlap and causal inferences between kidney function and cerebrovascular disease

Genetic Architecture of Neurological Disorders and Their Endophenotypes: Insights from Genetic Association Studies

Population-scale genetic association studies of complex neurologic diseases have identified the underlying genetic architecture as multifactorial. Despite the study sample sizes reaching the millions, the identified disease-related genes explain only a small fraction of the phenotypic variance. Notable advancements in statistical methods now enable researchers to gain insights even from genomic regions where genotype-phenotype associations do not reach statistical significance. Such studies confirm a highly interconnected molecular network comprising a core group of genes directly involved in the disease process, alongside an expanded peripheral network, each contributing a small but potentially important (modulatory) effect. Additionally, causal inference methods, utilizing genetic instruments, have shed light on putative causal links between risk factors and clinical endpoints. In light of the pervasive genetic overlap or pleiotropy, however, caution is warranted in interpreting causal relationships inferred from these analyses. In this chapter, I will introduce the genetic association model, provide insights into the current state of genetic association studies, and discuss potential future directions.

Genetic biomarkers of cognitive impairment and dementia of potential interest in CKD patients

This review discusses genetic variants associated with cognitive dysfunction in chronic kidney disease (CKD) patients, emphasising the limited research in this area. Four studies have explored genetic markers of cognitive dysfunction in CKD, with findings suggesting shared genetic biomarkers between Alzheimer's Disease and CKD.Because of the limited specific research on genetic markers of cognitive dysfunction and dementia in CKD, we extracted data from the current literature studies on genetic markers in the general population that may be relevant to the CKD population. These markers include Apolipoprotein E (APOE), Complement Receptor 1 (CR1), Clusterin (CLU), Sortilin-related receptor 1 (SORL1), Catechol-O-methyltransferase (COMT), and Brain-derived neurotrophic factor (BDNF), all of which are known to be associated with cognitive dysfunction and dementia in other populations. These genes play various roles in lipid metabolism, inflammation, Aβ clearance, and neuronal function, making them potential candidates for studying cognitive decline in CKD patients.CKD-specific research is needed to understand the role of these genetic markers in CKD-related cognitive dysfunction. Investigating how these genes influence cognitive decline in CKD patients could provide valuable insights into early detection, targeted interventions, and personalised treatment strategies. Overall, genetic studies to enhance our understanding and management of cognitive dysfunction in CKD represent a clinical research priority in this population.

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.

Development and validation of a nomogram predictive model for cerebral small vessel disease: a comprehensive retrospective analysis

Background

Cerebral small vessel disease (CSVD) is a significant contributor to stroke, intracerebral hemorrhages, and vascular dementia, particularly in the elderly. Early diagnosis remains challenging. This study aimed to develop and validate a novel nomogram for the early diagnosis of cerebral small vessel disease (CSVD). We focused on integrating cerebrovascular risk factors and blood biochemical markers to identify individuals at high risk of CSVD, thus enabling early intervention.

Methods

In a retrospective study conducted at the neurology department of the Affiliated Hospital of Hebei University from January 2020 to June 2022, 587 patients were enrolled. The patients were randomly divided into a training set (70%, n = 412) and a validation set (30%, n = 175). The nomogram was developed using multivariable logistic regression analysis, with variables selected through the Least Absolute Shrinkage and Selection Operator (LASSO) technique. The performance of the nomogram was evaluated based on the area under the receiver operating characteristic curve (AUC-ROC), calibration plots, and decision curve analysis (DCA).

Results

Out of 88 analyzed biomarkers, 32 showed significant differences between the CSVD and non-CSVD groups. The LASSO regression identified 12 significant indicators, with nine being independent clinical predictors of CSVD. The AUC-ROC values of the nomogram were 0.849 (95% CI: 0.821-0.894) in the training set and 0.863 (95% CI: 0.810-0.917) in the validation set, indicating excellent discriminative ability. Calibration plots demonstrated good agreement between predicted and observed probabilities in both sets. DCA showed that the nomogram had significant clinical utility.

Conclusions

The study successfully developed a nomogram predictive model for CSVD, incorporating nine clinical predictive factors. This model offers a valuable tool for early identification and risk assessment of CSVD, potentially enhancing clinical decision-making and patient outcomes.

Interplay Between Chronic Kidney Disease, Hypertension, and Stroke: Insights From a Multivariable Mendelian Randomization Analysis

BACKGROUND AND OBJECTIVES

Chronic kidney disease (CKD) increases the risk of stroke, but the extent through which this association is mediated by hypertension is unknown. We leveraged large-scale genetic data to explore causal relationships between CKD, hypertension, and cerebrovascular disease phenotypes.

METHODS

We used data from genome-wide association studies of European ancestry to identify genetic proxies for kidney function (CKD diagnosis, estimated glomerular filtration rate [eGFR], and urinary albumin-to-creatinine ratio [UACR]), systolic blood pressure (SBP), and cerebrovascular disease (ischemic stroke and its subtypes and intracerebral hemorrhage). We then conducted univariable, multivariable, and mediation Mendelian randomization (MR) analyses to investigate the effect of kidney function on stroke risk and the proportion of this effect mediated through hypertension.

RESULTS

Univariable MR revealed associations between genetically determined lower eGFR and risk of all stroke (odds ratio [OR] per 1-log decrement in eGFR, 1.77; 95% CI 1.31-2.40; p < 0.001), ischemic stroke (OR 1.81; 95% CI 1.31-2.51; p < 0.001), and most strongly with large artery stroke (LAS) (OR 3.00; 95% CI 1.33-6.75; p = 0.008). These associations remained significant in the multivariable MR analysis, controlling for SBP (OR 1.98; 95% CI 1.39-2.82; p < 0.001 for all stroke; OR 2.16; 95% CI 1.48-3.17; p < 0.001 for ischemic stroke; OR 4.35; 95% CI 1.84-10.27; p = 0.001 for LAS), with only a small proportion of the total effects mediated by SBP (6.5% [0.7%-16.8%], 6.6% [0.8%-18.3%], and 7.2% [0.5%-24.8%], respectively). Total, direct and indirect effect estimates were similar across a number of sensitivity analyses (weighted median, MR-Egger regression).

DISCUSSION

Our results demonstrate an independent causal effect of impaired kidney function, as assessed by decreased eGFR, on stroke risk, particularly LAS, even when controlled for SBP. Targeted prevention of kidney disease could lower atherosclerotic stroke risk independent of hypertension.

Genetic evidence supporting the causal role of gut microbiota in chronic kidney disease and chronic systemic inflammation in CKD: a bilateral two-sample Mendelian randomization study

Background

The association of gut microbiota (GM) and chronic kidney disease (CKD), and the relevancy of GM and chronic systemic inflammation in CKD, were revealed on the basis of researches on gut-kidney axis in previous studies. However, their causal relationships are still unclear.

Objective

To uncover the causal relationships between GM and CKD, as well as all known GM from eligible statistics and chronic systemic inflammation in CKD, we performed two-sample Mendelian randomization (MR) analysis.

Materials and methods

We acquired the latest and most comprehensive summary statistics of genome-wide association study (GWAS) from the published materials of GWAS involving GM, CKD, estimated glomerular filtration rate (eGFR), c-reactive protein (CRP) and urine albumin creatine ratio (UACR). Subsequently, two-sample MR analysis using the inverse-variance weighted (IVW) method was used to determine the causality of exposure and outcome. Based on it, additional analysis and sensitivity analysis verified the significant results, and the possibility of reverse causality was also assessed by reverse MR analysis during this study.

Results

At the locus-wide significance threshold, IVW method and additional analysis suggested that the protective factors for CKD included family Lachnospiraceae (P=0.049), genus Eubacterium eligens group (P=0.002), genus Intestinimonas (P=0.009), genus Streptococcu (P=0.003) and order Desulfovibrionales (P=0.001). Simultaneously, results showed that genus LachnospiraceaeUCG010 (P=0.029) was a risk factor for CKD. Higher abundance of genus Desulfovibrio (P=0.048) was correlated with higher eGFR; higher abundance of genus Parasutterella (P=0.018) was correlated with higher UACR; higher abundance of class Negativicutes (P=0.003), genus Eisenbergiella (P=0.021), order Selenomonadales (P=0.003) were correlated with higher CRP levels; higher abundance of class Mollicutes (0.024), family Prevotellaceae (P=0.030), phylum Tenericutes (P=0.024) were correlated with lower levels of CRP. No significant pleiotropy or heterogeneity was found in the results of sensitivity analysis, and no significant causality was found in reverse MR analysis.

Conclusion

This study highlighted associations within gut-kidney axis, and the causal relationships between GM and CKD, as well as GM and chronic systemic inflammation in CKD were also revealed. Meanwhile, we expanded specific causal gut microbiota through comprehensive searches. With further studies for causal gut microbiota, they may have the potential to be new biomarkers for targeted prevention of CKD and chronic systemic inflammation in CKD.

Relationship between chronic kidney disease and cerebral white matter hyperintensities: a systematic review

Background

This systematic review summarizes available evidence on the relationship between white matter hyperintensities (WMH) volumetric quantification on brain MRI scans and chronic kidney disease (CKD).

Methods

The literature search was performed in March 2022 using MEDLINE PubMed Central, Scopus and Web of Science - Publons as search engines. Relevant articles investigating, with a quantitative volumetric approach, the link between WMH and CKD patients were selected.

Results

The database search strategy found 987 articles, after excluding duplicates, the titles and abstracts of the remaining 320 articles were examined. Subsequently 276 articles were excluded as they were not relevant to the topic. Of the 44 articles evaluated for eligibility, 36 were excluded because the quantitative analysis of WMH was not volumetric. Finally, 8 articles were included in this systematic review.

Conclusions

Literature on this topic is extremely heterogeneous in terms of methodology and samples. However, evidence shows that there is a relationship between CKD and WMH volume of the brain. We recommend that quantifiable biomarkers such as estimated glomerular filtration rate (eGFR) and urine albumin to creatinine ratio (UACR) should be included in studies dealing with cerebrovascular disease. The biological and molecular mechanisms underlying cerebrovascular damage in patients with chronic renal failure deserve to be further explored.

Appraising the Causal Role of Risk Factors in Coronary Artery Disease and Stroke: A Systematic Review of Mendelian Randomization Studies

BACKGROUND Mendelian randomization (MR) offers a powerful approach to study potential causal associations between exposures and health outcomes by using genetic variants associated with an exposure as instrumental variables. In this systematic review, we aimed to summarize previous MR studies and to evaluate the evidence for causality for a broad range of exposures in relation to coronary artery disease and stroke. METHODS AND RESULTS MR studies investigating the association of any genetically predicted exposure with coronary artery disease or stroke were identified. Studies were classified into 4 categories built on the significance of the main MR analysis results and its concordance with sensitivity analyses, namely, robust, probable, suggestive, and insufficient. Studies reporting associations that did not perform any sensitivity analysis were classified as nonevaluable. We identified 2725 associations eligible for evaluation, examining 535 distinct exposures. Of them, 141 were classified as robust, 353 as probable, 110 as suggestive, and 926 had insufficient evidence. The most robust associations were observed for anthropometric traits, lipids, and lipoproteins and type 2 diabetes with coronary artery; disease and clinical measurements with coronary artery disease and stroke; and thrombotic factors with stroke. CONCLUSIONS Despite the large number of studies that have been conducted, only a limited number of associations were supported by robust evidence. Approximately half of the studies reporting associations presented an MR sensitivity analysis along with the main analysis that further supported the causality of associations. Future research should focus on more thorough assessments of sensitivity MR analyses and further assessments of mediation effects or nonlinearity of associations.

Association of polygenic scores with chronic kidney disease phenotypes in a longitudinal study of older adults

Risk of chronic kidney disease (CKD) is influenced by environmental and genetic factors and increases sharply in individuals 70 years and older. Polygenic scores (PGS) for kidney disease-related traits have shown promise but require validation in well-characterized cohorts. Here, we assessed the performance of recently developed PGSs for CKD-related traits in a longitudinal cohort of healthy older individuals enrolled in the Australian ASPREE randomized controlled trial of daily low-dose aspirin with CKD risk at baseline and longitudinally. Among 11,813 genotyped participants aged 70 years or more with baseline eGFR measures, we tested associations between PGSs and measured eGFR at baseline, clinical phenotype of CKD, and longitudinal rate of eGFR decline spanning up to six years of follow-up per participant. A PGS for eGFR was associated with baseline eGFR, with a significant decrease of 3.9 mL/min/1.73m2 (95% confidence interval -4.17 to -3.68) per standard deviation (SD) increase of the PGS. This PGS, as well as a PGS for CKD stage 3 were both associated with higher risk of baseline CKD stage 3 in cross-sectional analysis (Odds Ratio 1.75 per SD, 95% confidence interval 1.66-1.85, and Odds Ratio 1.51 per SD, 95% confidence interval 1.43-1.59, respectively). Longitudinally, two separate PGSs for eGFR slope were associated with significant kidney function decline during follow-up. Thus, our study demonstrates that kidney function has a considerable genetic component in older adults, and that new PGSs for kidney disease-related phenotypes may have potential utility for CKD risk prediction in advanced age.

A Genomic Risk Score Identifies Individuals at High Risk for Intracerebral Hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) has an estimated heritability of 29%. We developed a genomic risk score for ICH and determined its predictive power in comparison to standard clinical risk factors.

METHODS

We combined genome-wide association data from individuals of European ancestry for ICH and related traits in a meta-genomic risk score ([metaGRS]; 2.6 million variants). We tested associations with ICH and its predictive performance in addition to clinical risk factors in a held-out validation dataset (842 cases and 796 controls). We tested associations with risk of incident ICH in the population-based UK Biobank cohort (486 784 individuals, 1526 events, median follow-up 11.3 years).

RESULTS

One SD increment in the metaGRS was significantly associated with 31% higher odds for ICH (95% CI, 1.16-1.48) in age-, sex- and clinical risk factor-adjusted models. The metaGRS identified individuals with almost 5-fold higher odds for ICH in the top score percentile (odds ratio, 4.83 [95% CI, 1.56-21.2]). Predictive models for ICH incorporating the metaGRS in addition to clinical predictors showed superior performance compared to the clinical risk factors alone (c-index, 0.695 versus 0.686). The metaGRS showed similar associations for lobar and nonlobar ICH, independent of the known APOE risk locus for lobar ICH. In the UK Biobank, the metaGRS was associated with higher risk of incident ICH (hazard ratio, 1.15 [95% CI, 1.09-1.21]). The associations were significant within both a relatively high-risk population of antithrombotic medications users, as well as among a relatively low-risk population with a good control of vascular risk factors and no use of anticoagulants.

CONCLUSIONS

We developed and validated a genomic risk score that predicts lifetime risk of ICH beyond established clinical risk factors among individuals of European ancestry. Whether implementation of the score in risk prognostication models for high-risk populations, such as patients under antithrombotic treatment, could improve clinical decision making should be explored in future studies.

A Primer in Precision Nephrology: Optimizing Outcomes in Kidney Health and Disease through Data-Driven Medicine

This year marks the 63rd anniversary of the International Society of Nephrology, which signaled nephrology's emergence as a modern medical discipline. In this article, we briefly trace the course of nephrology's history to show a clear arc in its evolution-of increasing resolution in nephrological data-an arc that is converging with computational capabilities to enable precision nephrology. In general, precision medicine refers to tailoring treatment to the individual characteristics of patients. For an operational definition, this tailoring takes the form of an optimization, in which treatments are selected to maximize a patient's expected health with respect to all available data. Because modern health data are large and high resolution, this optimization process requires computational intervention, and it must be tuned to the contours of specific medical disciplines. An advantage of this operational definition for precision medicine is that it allows us to better understand what precision medicine means in the context of a specific medical discipline. The goal of this article was to demonstrate how to instantiate this definition of precision medicine for the field of nephrology. Correspondingly, the goal of precision nephrology was to answer two related questions: ( 1 ) How do we optimize kidney health with respect to all available data? and ( 2 ) How do we optimize general health with respect to kidney data?

Low estimated glomerular filtration rate explains the association between hyperhomocysteinemia and in-hospital mortality among patients with ischemic stroke/transient ischemic attack or intracerebral hemorrhage: Results from the Chinese Stroke Center Alliance

OBJECTIVES

To investigate the association between hyperhomocysteinemia (HHcy) and in-hospital mortality following ischemic stroke (IS), transient ischemic attack (TIA), or intracerebral hemorrhage (ICH).

METHODS

Data on patients with ischemic cerebrovascular disease (IS/TIA) or ICH enrolled in the Chinese Stroke Center Alliance (CSCA) from 2015 to 2019 were extracted. Patient characteristics and in-hospital mortality were analyzed and multiple adjusted logistic regression analyses performed to investigate the association between blood tHcy (total homocysteine) and in-hospital mortality in patients with HHcy (tHcy ⩾ 15 µmol) and patients with normohomocysteinemia (nHcy) (tHcy < 15 µmol).

RESULTS

A total of 823,622 participants were included. Mean (SD) age was 65.9 (12.1), and 62.5% (n = 514,888) were male. A total of 379,807 (46.0%) patients were identified as having HHcy, and 70,364 (8.5%) patients had an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m². An eGFR < 60 mL/min/1.73 m² was the strongest independent risk factor for HHcy in both patients with IS/TIA (adjusted odds ratio (aOR) 2.67, 95% confidence interval (CI): 2.49-2.86), and those with ICH (2.94, 2.46-3.50). On multivariable logistic regression, after adjusting for potential confounding factors, HHcy was associated with in-hospital mortality (aOR: 1.25, 95% CI: 1.13-1.37 for patients with IS/TIA; aOR: 1.40, 95% CI: 1.12-1.76 for patients with ICH). However, after additionally adjusting for eGFR, this association disappeared among patients with both IS/TIA (aOR: 1.09, 95% CI: 0.99-1.20) and those with ICH (aOR: 1.17, 9% CI: 0.96-1.43).

CONCLUSION

HHcy was associated with in-hospital mortality among the patients with IS/TIA or ICH but this association disappeared after controlling for eGFR, suggesting HHcy was acting as a marker of poor renal function which itself was the predictor of poor outcome. Our results suggest the prevention and management of renal impairment may be an important measure in the reduction of mortality in patients with HHcy after IS/TIA or ICH.

Association of Chronic Kidney Disease With Risk of Intracerebral Hemorrhage

Importance

The evidence linking chronic kidney disease (CKD) to spontaneous intracerebral hemorrhage (ICH) is inconclusive owing to possible confounding by comorbidities that frequently coexist in patients with these 2 diseases.

Objective

To determine whether there is an association between CKD and ICH risk.

Design, Setting, and Participants

A 3-stage study that combined observational and genetic analyses was conducted. First, the association between CKD and ICH risk was tested in the Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) study, a multicenter case-control study in the US. All participants with available data on CKD from ERICH were included. Second, this analysis was replicated in the UK Biobank (UKB), an ongoing population study in the UK. All participants in the UKB were included in this study. Third, mendelian randomization analyses were implemented in the UKB using 27 CKD-related genetic variants to test for genetic associations. ERICH was conducted from August 1, 2010, to August 1, 2017, and observed participants for 1 year. The UKB enrolled participants between 2006 and 2010 and will continue to observe them for 30 years. Data analysis was performed from November 11, 2019, to May 10, 2022.

Exposures

CKD stages 1 to 5.

Main Outcomes and Measures

The outcome of interest was ICH, ascertained in ERICH via expert review of neuroimages and in the UKB via a combination of self-reported data and International Statistical Classification of Diseases, Tenth Revision, codes.

Results

In the ERICH study, a total of 2914 participants with ICH and 2954 controls who had available data on CKD were evaluated (mean [SD] age, 61.6 [14.0] years; 2433 female participants [41.5%]; 3435 male participants [58.5%]); CKD was found to be independently associated with higher risk of ICH (odds ratio [OR], 1.95; 95% CI, 1.35-2.89; P < .001). This association was not modified by race and ethnicity. Replication in the UKB with 1341 participants with ICH and 501 195 controls (mean [SD] age, 56.5 [8.1] years; 273 402 female participants [54.4%]; 229 134 male participants [45.6%]) confirmed this association (OR, 1.28; 95% CI, 1.01-1.62; P = .04). Mendelian randomization analyses indicated that genetically determined CKD was associated with ICH risk (OR, 1.56; 95% CI, 1.13-2.16; P = .007).

Conclusions and Relevance

In this 3-stage study that combined observational and genetic analyses among study participants enrolled in 2 large observational studies with different characteristics and study designs, CKD was consistently associated with higher risk of ICH. Mendelian randomization analyses suggest that this association was causal. Further studies are needed to identify the specific biological pathways that mediate this association.

Development and validation of a nomogram to predict the 30-day mortality risk of patients with intracerebral hemorrhage

Background

Intracerebral hemorrhage (ICH) is a stroke syndrome with an unfavorable prognosis. Currently, there is no comprehensive clinical indicator for mortality prediction of ICH patients. The purpose of our study was to construct and evaluate a nomogram for predicting the 30-day mortality risk of ICH patients.

Methods

ICH patients were extracted from the MIMIC-III database according to the ICD-9 code and randomly divided into training and verification cohorts. The least absolute shrinkage and selection operator (LASSO) method and multivariate logistic regression were applied to determine independent risk factors. These risk factors were used to construct a nomogram model for predicting the 30-day mortality risk of ICH patients. The nomogram was verified by the area under the receiver operating characteristic curve (AUC), integrated discrimination improvement (IDI), net reclassification improvement (NRI), and decision curve analysis (DCA).

Results

A total of 890 ICH patients were included in the study. Logistic regression analysis revealed that age (OR = 1.05, P < 0.001), Glasgow Coma Scale score (OR = 0.91, P < 0.001), creatinine (OR = 1.30, P < 0.001), white blood cell count (OR = 1.10, P < 0.001), temperature (OR = 1.73, P < 0.001), glucose (OR = 1.01, P < 0.001), urine output (OR = 1.00, P = 0.020), and bleeding volume (OR = 1.02, P < 0.001) were independent risk factors for 30-day mortality of ICH patients. The calibration curve indicated that the nomogram was well calibrated. When predicting the 30-day mortality risk, the nomogram exhibited good discrimination in the training and validation cohorts (C-index: 0.782 and 0.778, respectively). The AUCs were 0.778, 0.733, and 0.728 for the nomogram, Simplified Acute Physiology Score II (SAPSII), and Oxford Acute Severity of Illness Score (OASIS), respectively, in the validation cohort. The IDI and NRI calculations and DCA analysis revealed that the nomogram model had a greater net benefit than the SAPSII and OASIS scoring systems.

Conclusion

This study identified independent risk factors for 30-day mortality of ICH patients and constructed a predictive nomogram model, which may help to improve the prognosis of ICH patients.

Covert vascular brain injury in chronic kidney disease

Chronic kidney disease (CKD) contributes to the increased risk of stroke and dementia. Accumulating evidence indicates that structural brain abnormalities, such as cerebral small vessel disease, including white matter hyperintensities, lacunes, perivascular spaces, and cerebral microbleeds, as well as brain atrophy, are common in patients with CKD. All of these imaging findings have been implicated in the development of stroke and dementia. The brain and kidney exhibit similar impairments and promote structural brain abnormalities due to shared vascular risk factors and similar anatomical and physiological susceptibility to vascular injury in patients with CKD. This indicates that kidney function has a significant effect on brain aging. However, as most results are derived from cross-sectional observational studies, the exact pathophysiology of structural brain abnormalities in CKD remains unclear. The early detection of structural brain abnormalities in CKD in the asymptomatic or subclinical phase (covert) should enable stroke risk prediction and guide clinicians on more targeted interventions to prevent stroke in patients with CKD. This article summarizes the currently available clinical evidence linking covert vascular brain injuries with CKD.

Genome-Wide Studies in Ischaemic Stroke: Are Genetics Only Useful for Finding Genes?

Ischaemic stroke is a complex disease with some degree of heritability. This means that heritability factors, such as genetics, could be risk factors for ischaemic stroke. The era of genome-wide studies has revealed some of these heritable risk factors, although the data generated by these studies may also be useful in other disciplines. Analysis of these data can be used to understand the biological mechanisms associated with stroke risk and stroke outcome, to determine the causality between stroke and other diseases without the need for expensive clinical trials, or to find potential drug targets with higher success rates than other strategies. In this review we will discuss several of the most relevant studies regarding the genetics of ischaemic stroke and the potential use of the data generated.

Etiology and Outcome of Ischemic Stroke in Patients With Renal Impairment Including Chronic Kidney Disease: Japan Stroke Data Bank

Background and Objectives

Chronic kidney disease is a worldwide public health problem that is recognized as an established risk factor for stroke. It remains unclear whether its distribution and clinical impact are consistent across ischemic stroke subtypes in patients with renal impairment. We examined whether renal impairment was associated with the proportion of each stroke subtype vs ischemic stroke overall and with functional outcomes after each stroke subtype.

Methods

Study participants were 10,392 adult patients with an acute stroke from the register of the Japan Stroke Data Bank, a hospital-based multicenter stroke registration database, between October 2016 and December 2019, whose baseline serum creatinine levels or a dipstick proteinuria result were available. All ischemic strokes were classified according to the Trial of Org 10172 in Acute Stroke Treatment criteria. Unfavorable functional outcome was defined as modified Rankin Scale (mRS) score 3–6 at discharge. Mixed effect logistic regression was used to determine the relationship between the outcomes and the estimated glomerular filtration rate (eGFR), eGFR strata (<45, 45–59, ≥60 mL/min/1.73 m²), or dipstick proteinuria ≥1 adjusted for covariates.

Results

Overall, 2,419 (23%) patients had eGFR 45–59 mL/min/1.73 m² and 1,976 (19%) had eGFR <45 mL/min/1.73 m², including 185 patients (1.8%) receiving hemodialysis. Both eGFR 45–59 and eGFR <45 mL/min/1.73 m² were associated with a higher proportion of cardioembolic stroke (odds ratio [OR], 1.21 [95% CI, 1.05–1.39] and 1.55 [1.34–1.79], respectively) and a lower proportion of small vessel occlusion (0.79 [0.69–0.90] and 0.68 [0.59–0.79], respectively). A similar association with the proportion of these 2 subtypes was proven in the analyses using decreased eGFR as continuous values. Both eGFR <45 mL/min/1.73 m² and proteinuria were associated with unfavorable functional outcomes in patients with cardioembolic stroke (OR, 1.30 [95% CI, 1.01–1.69] and 3.18 [2.03–4.98], respectively) and small vessel occlusion (OR, 1.44 [1.01–2.07] and 2.08 [1.08–3.98], respectively).

Discussion

Renal impairment contributes to the different distributions and clinical effects across specific stroke subtypes, particularly evident in cardioembolic stroke and small vessel occlusion. This possibly indicates shared mechanisms of susceptibility and potentially enhancing pathways.

Disentangling the Relationship Between Chronic Kidney Disease and Cognitive Disorders

Chronic kidney disease (CKD) is a rapidly rising global health burden that affects nearly 40% of older adults. Epidemiologic data suggest that individuals at all stages of chronic kidney disease (CKD) have a higher risk of developing cognitive disorders and dementia, and thus represent a vulnerable population. It is currently unknown to what extent this risk may be attributable to a clustering of traditional risk factors such as hypertension and diabetes mellitus leading to a high prevalence of both symptomatic and subclinical ischaemic cerebrovascular lesions, or whether other potential mechanisms, including direct neuronal injury by uraemic toxins or dialysis-specific factors could also be involved. These knowledge gaps may lead to suboptimal prevention and treatment strategies being implemented in this group. In this review, we explore the mechanisms of susceptibility and risk in the relationship between CKD and cognitive disorders.

Regional cerebral gray matter atrophy is associated with cognitive impairment in hemodialysis patients: a cross-sectional and longitudinal voxel-based morphological MRI study

This study aimed to explore gray matter volume (GMV) changes in patients undergoing hemodialysis and assess the clinical risk factors associated with GMV changes and the relationship between GMV changes and neuropsychologic test results. Eighty-eight hemodialysis patients and 76 healthy controls (HCs) were recruited in this study. Fifty patients underwent follow-up examinations (follow-up duration: 1.75 ± 0.55 years), including magnetic resonance imaging, blood biochemical, and neuropsychologic testing. Changes in GMV between the patients and HCs were assessed. Longitudinal GMV changes were also explored in the patients. The clinical risk factors associated with longitudinal GMV changes and the correlations between longitudinal GMV changes and neuropsychologic test results were analyzed in the patients. Patients undergoing hemodialysis had diffusely decreased GMV compared with HCs (with age, sex, and total intracranial volume [TIV] as covariates, P<0.001, voxel-wise threshold false discovery rate [FDR] corrected). Compared with patients at baseline, regional decreased GMV were found in patients at follow-up (with age and TIV as covariates, P<0.05, voxel-wise threshold FDR corrected). Increased serum urea concentrations, parathyroid hormone levels, and hemodialysis duration were independent risk factors for decreased GMV in patients undergoing hemodialysis (all P<0.05, FDR corrected). Patients undergoing hemodialysis had lower mini-mental state examination (MMSE) (27[26, 29]) and Montreal cognitive assessment (MoCA) (22[19.5, 24.0]) scores than those of the HCs (30[29, 30] and 28[26.9, 29]) (all P<0.05). The MMSE scores of the patients at follow-up (26[25, 28.5]) were lower than those of patients at baseline (28[25, 29.5]) (P=0.02). The decreased left caudate volumes were positively correlated with reduced MMSE scores in hemodialysis patients (r_s=0.437, P=0.033). Patients undergoing hemodialysis had noticeable GM atrophy over time, related to cognitive impairments.

Interactions Between Kidney Function and Cerebrovascular Disease: Vessel Pathology That Fires Together Wires Together

The kidney and the brain, as high-flow end organs relying on autoregulatory mechanisms, have unique anatomic and physiological hemodynamic properties. Similarly, the two organs share a common pattern of microvascular dysfunction as a result of aging and exposure to vascular risk factors (e.g., hypertension, diabetes and smoking) and therefore progress in parallel into a systemic condition known as small vessel disease (SVD). Many epidemiological studies have shown that even mild renal dysfunction is robustly associated with acute and chronic forms of cerebrovascular disease. Beyond ischemic SVD, kidney impairment increases the risk of acute cerebrovascular events related to different underlying pathologies, notably large artery stroke and intracerebral hemorrhage. Other chronic cerebral manifestations of SVD are variably associated with kidney disease. Observational data have suggested the hypothesis that kidney function influences cerebrovascular disease independently and adjunctively to the effect of known vascular risk factors, which affect both renal and cerebral microvasculature. In addition to confirming this independent association, recent large-scale human genetic studies have contributed to disentangling potentially causal associations from shared genetic predisposition and resolving the uncertainty around the direction of causality between kidney and cerebrovascular disease. Accelerated atherosclerosis, impaired cerebral autoregulation, remodeling of the cerebral vasculature, chronic inflammation and endothelial dysfunction can be proposed to explain the additive mechanisms through which renal dysfunction leads to cerebral SVD and other cerebrovascular events. Genetic epidemiology also can help identify new pathological pathways which wire kidney dysfunction and cerebral vascular pathology together. The need for identifying additional pathological mechanisms underlying kidney and cerebrovascular disease is attested to by the limited effect of current therapeutic options in preventing cerebrovascular disease in patients with kidney impairment.

Kidney damage causally affects the brain cortical structure: A Mendelian randomization study

BACKGROUND

Alterations in the brain cortical structures of patients with chronic kidney disease (CKD) have been reported; however, the cause has not been determined yet. Herein, we used Mendelian randomization (MR) to reveal the causal effect of kidney damage on brain cortical structure.

METHODS

Genome-wide association studies summary data of estimated glomerular filtration rate (eGFR) in 480,698 participants from the CKDGen Consortium were used to identify genetically predicted eGFR. Data from 567,460 individuals from the CKDGen Consortium were used to assess genetically determined CKD; 302,687 participants from the UK Biobank were used to evaluate genetically predicted albuminuria. Further, data from 51,665 patients from the ENIGMA Consortium were used to assess the relationship between genetic predisposition and reduced eGFR, CKD, and progressive albuminuria with alterations in cortical thickness (TH) or surficial area (SA) of the brain. Magnetic resonance imaging was used to measure the SA and TH globally and in 34 functional regions. Inverse-variance weighted was used as the primary estimate whereas MR Pleiotropy RESidual Sum and Outlier, MR-Egger and weighted median were used to detect heterogeneity and pleiotropy.

FINDINGS

At the global level, albuminuria decreased TH (β = -0.07 mm, 95% CI: -0.12 mm to -0.02 mm, P = 0.004); at the functional level, albuminuria reduced TH of pars opercularis gyrus without global weighted (β = -0.11 mm, 95% CI: -0.16 mm to -0.07 mm, P = 3.74×10^-6). No pleiotropy was detected.

INTERPRETATION

Kidney damage causally influences the cortex structure which suggests the existence of a kidney-brain axis.

FUNDING

This study was supported by the Science and Technology Planning Project of Guangdong Province (Grant No. 2020A1515111119 and 2017B020227007), the National Key Research and Development Program of China (Grant No. 2018YFA0902803), the National Natural Science Foundation of China (Grant No. 81825016, 81961128027, 81772719, 81772728), the Key Areas Research and Development Program of Guangdong (Grant No. 2018B010109006), Guangdong Special Support Program (2017TX04R246), Grant KLB09001 from the Key Laboratory of Malignant Tumor Gene Regulation and Target Therapy of Guangdong Higher Education Institutes, and Grants from the Guangdong Science and Technology Department (2020B1212060018).

Effects of chemerin and homocysteine levels and their associations with occurrence and development of ischemic cerebrovascular disease

Background

The current study was conducted to explore the effects of chemerin and homocysteine (Hcy) levels and their associations with the occurrence and development of ischemic cerebrovascular disease (ICVD).

Methods

There involved a total of 187 patients with ICVD and 190 healthy people for physical examination in Cangzhou Central hospital from January 2020 to April 2021. The participants enrolled were divided into four groups based on the digital subtraction angiography: mild stenosis group (64 cases, stenosis rate 30-49 %), moderate stenosis group (72 cases, stenosis rate 50-69 %), severe stenosis group (51 cases, stenosis rate 70-99 %) and control group (190 cases, in healthy condition). The laboratory indexes of ICVD group and control group were observed and the four groups were further compared. Pearson linear correlation was applied to analyze the link between chemerin and Hcy levels and the degree of cerebral vascular stenosis in ICVD patients, and multivariate logistic regression was used to analyze the influencing factors of ICVD.

Results

No significant difference was found in general information including age, gender, body mass index (BMI), heart rate, systolic blood pressure, diastolic blood pressure, smoking and drinking between the two groups (P > 0.05). Moreover, there was no significant difference in fasting blood glucose (FBG), total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) levels between the two groups (P > 0.05). However, the levels of triglyceride (TG), low density lipoprotein cholesterol (LDL-C), chemerin and Hcy in ICVD group were significantly higher than those in control group (P < 0.05). When comparing the four groups, there was no significant difference in FBG and TC levels (P > 0.05). The levels of TG, LDL-C, chemerin and Hcy in mild, moderate and severe stenosis groups were higher than those in control group, the above levels in moderate and severe stenosis group were higher than those in mild stenosis group, and severe stenosis group higher than moderate stenosis group (P < 0.05). Chemerin and Hcy levels were positively correlated with the degree of cerebral vascular stenosis in ICVD patients (r = 0.612, 0.519, P < 0.001). ICVD was regarded as the dependent variable, and the abovementioned general data as well as significant laboratory indicators, including TG, LDL-C, chemerin and Hcy, as independent variables. The results of multivariate logistic regression analysis revealed that TG, LDL-C, chemerin and Hcy were independent influencing factors of ICVD.

Conclusions

Chemerin and Hcy levels exerted a close link to the occurrence and development of ICVD as independent influencing factors.

Mendelian Randomization Studies in Stroke: Exploration of Risk Factors and Drug Targets With Human Genetic Data

Elucidating the causes of stroke is key to developing effective preventive strategies. The Mendelian randomization approach leverages genetic variants related to an exposure of interest to investigate the effects of varying that exposure on disease risk. The random allocation of genetic variants at conception reduces confounding from environmental factors and thus strengthens causal inference, analogous to treatment allocation in a randomized controlled trial. With the recent explosion in the availability of human genetic data, Mendelian randomization has proven a valuable tool for studying risk factors for stroke. In this review, we provide an overview of recent developments in the application of Mendelian randomization to unravel the pathophysiology of stroke subtypes and identify therapeutic targets for clinical translation. The approach has offered novel insight into the differential effects of risk factors and antihypertensive, lipid-lowering, and anticoagulant drug classes on risk of stroke subtypes. Analyses have further facilitated the prioritization of novel drug targets, such as for inflammatory pathways underlying large artery atherosclerotic stroke and for the coagulation cascade that contributes to cardioembolic stroke. With continued methodological advances coupled with the rapidly increasing availability of genetic data related to a broad range of stroke phenotypes, the potential for Mendelian randomization in this context is expanding exponentially.

Vascular Calcification as a Novel Risk Factor for Kidney Function Deterioration in the Nonelderly

Background

The relationship between vascular calcification and chronic kidney disease is well known. However, whether vascular calcification affects renal function deterioration remains unclear. We investigated whether kidney function deteriorated more rapidly in individuals with higher vascular calcification indicated by the coronary artery calcium score (CACS).

Methods and Results

Individuals with a normal estimated glomerular filtration rate (>60 mL/min per 1.73 m²) who underwent cardiac computed tomography in our institution (a tertiary teaching hospital in Cheonan, Korea) from January 2010 to July 2012 were retrospectively reviewed. All participants were aged 20 to 65 years. Among 739 patients, 447, 175, and 117 had CACSs of 0, 1 to 99, and ≥100 units, respectively. The participants were followed for 7.8 (interquartile range, 5.5–8.8) years. The adjusted annual estimated glomerular filtration rates declined more rapidly in patients in the CACS ≥100 group compared with those in the CACS 0 group (adjusted‐β, −0.40; 95% CI, −0.80 to −0.03) when estimated using a linear mixed model. The adjusted hazard ratio in the CACS ≥100 group for Kidney Disease: Improving Global Outcomes criteria (a drop in estimated glomerular filtration rate category accompanied by a 25% or greater drop in estimated glomerular filtration rate) was 2.52 (1.13–5.61). After propensity score matching, more prevalent renal outcomes (13.2%) were observed in patients with a CACS of ≥100 compared with those with a CACS of 0 (1.9%), with statistical significance (P=0.004).

Conclusions

Our results showed that renal function declined more rapidly in patients with higher CACSs, suggesting that vascular calcification might be associated with chronic kidney disease progression.

Diabetes, Albuminuria and the Kidney-Brain Axis

Cognitive decline and kidney disease are significant public health problems that share similar characteristics and risk factors. The pathophysiology of the kidney-brain axis is not completely understood, and studies analysing the relationship between the biomarkers of kidney damage and cognitive impairment show different results. This article focuses on the epidemiological and clinical aspects concerning the association of albuminuria, a marker for endothelial dysfunction and microvascular disease, and cognitive impairment in patients with chronic kidney disease, diabetic kidney disease and end-stage kidney disease. Most studies show a positive relationship between albuminuria and cognitive impairment in all groups, but evidence in type 2 diabetes (T2D) patients is limited. We briefly discuss the mechanisms underlying these associations, such as damage to the microvascular circulation, leading to hypoperfusion and blood pressure fluctuations, as well as increased inflammation and oxidative stress, both in the brain and in the kidneys. Further clinical and epidemiological studies developed to understand the interplay between the kidneys and brain diseases will hopefully lead to a reduction in cognitive impairment in these patients.

Using Mendelian randomization study to assess the renal effects of antihypertensive drugs

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors and/or in combination with calcium channel blockers (CCBs) are generally recommended as the first-line antihypertensive therapy for people with hypertension and kidney dysfunction. Evidence from large randomized controlled trials comprehensively comparing renal effects of different classes of antihypertensive drugs is lacking.

METHODS

We used a Mendelian randomization study to obtain unconfounded associations of genetic proxies for antihypertensives with kidney function. Specifically, we used published genetic variants in genes regulating target proteins of these drugs and then applied to a meta-analysis of the largest available genome-wide association studies of kidney function (estimated glomerular filtration rate (eGFR), urine albumin-to-creatinine ratio (UACR), and albuminuria). Inverse variance weighting was used as the main analysis and to combine estimates from different sources.

RESULTS

Genetically predicted ACE inhibition was associated with higher eGFR (effect size 0.06, 95% confidence interval (CI) 0.008, 0.11), while genetic proxies for beta-blockers were associated with lower eGFR (- 0.02, 95% CI - 0.04, - 0.004) when meta-analyzing the UK Biobank and CKDGen. Genetic proxies for CCBs were associated with lower UACR (- 0.15, 95% CI - 0.28, - 0.02) and lower risk of albuminuria (odds ratio 0.58, 95% CI 0.37, 0.90) in CKDGen. The associations were robust to using different analysis methods and different genetic instruments.

CONCLUSIONS

Our findings suggest the reno-protective associations of genetically proxied ACE inhibitors and CCBs, while genetic proxies for beta-blockers may be related to lower eGFR. Understanding the underlying mechanisms would be valuable, with implications for drug development and repositioning of treatments for kidney disease.

Brain arteriolosclerosis

Brain arteriolosclerosis (B-ASC), characterized by pathologic arteriolar wall thickening, is a common finding at autopsy in aged persons and is associated with cognitive impairment. Hypertension and diabetes are widely recognized as risk factors for B-ASC. Recent research indicates other and more complex risk factors and pathogenetic mechanisms. Here, we describe aspects of the unique architecture of brain arterioles, histomorphologic features of B-ASC, relevant neuroimaging findings, epidemiology and association with aging, established genetic risk factors, and the co-occurrence of B-ASC with other neuropathologic conditions such as Alzheimer's disease and limbic-predominant age-related TDP-43 encephalopathy (LATE). There may also be complex physiologic interactions between metabolic syndrome (e.g., hypertension and inflammation) and brain arteriolar pathology. Although there is no universally applied diagnostic methodology, several classification schemes and neuroimaging techniques are used to diagnose and categorize cerebral small vessel disease pathologies that include B-ASC, microinfarcts, microbleeds, lacunar infarcts, and cerebral amyloid angiopathy (CAA). In clinical-pathologic studies that factored in comorbid diseases, B-ASC was independently associated with impairments of global cognition, episodic memory, working memory, and perceptual speed, and has been linked to autonomic dysfunction and motor symptoms including parkinsonism. We conclude by discussing critical knowledge gaps related to B-ASC and suggest that there are probably subcategories of B-ASC that differ in pathogenesis. Observed in over 80% of autopsied individuals beyond 80 years of age, B-ASC is a complex and under-studied contributor to neurologic disability.

Impact of multimorbidity on risk and outcome of stroke: Lessons from chronic kidney disease

With both an aging population and greater post-stroke survival, multimorbidity is a growing healthcare challenge, affecting over 40% of stroke patients, and rising rapidly and predictably with increasing age. Commonly defined as the co-occurrence of two or more chronic conditions, multimorbidity burden is a strong adverse prognostic factor, associated with greater short- and long-term stroke mortality, worse rehabilitation outcomes, and reduced use of secondary prevention. Chronic kidney disease can be considered as the archetypal comorbidity, being age-dependent and also affecting about 40% of stroke patients. Chronic kidney disease and stroke share very similar traditional cardiovascular risk factor profiles such as hypertension and diabetes, though novel chronic kidney disease-specific risk factors such as inflammation and oxidative stress have also been proposed. Using chronic kidney disease as an exemplar condition, we explore the mechanisms of risk in multimorbidity, implications for management, impact on stroke severity, and downstream consequences such as post-stroke cognitive impairment and dementia.