Εndothelial and microvascular function in CKD: Evaluation methods and associations with outcomes

Understanding endothelial dysfunction in kidney transplantation: assessment techniques, existing evidence and research needs

INTRODUCTION

KTRs have substantially lower risk for cardiovascular events compared to dialysis, but it remains significantly higher than that in general population, due to the synergistic action of traditional and nontraditional factors. Among them, endothelial dysfunction is suggested to be involved pathogenetically in cardiovascular and renal disease progression, with its improvement being another potential benefit of transplantation.

AREAS COVERED

VOP was the first technique to be used, followed by several functional methods, most commonly FMD. Over the years, several biomarkers of endothelial dysfunction have been used to assess microvascular function. The totality of evidence in KTRs suggests the improvement of endothelial dysfunction after transplantation, but with several gaps in knowledge, including rarity of studies using novel, more accurate techniques. This review presents the current functional methods and biomarkers used to evaluate microvascular and endothelial function in KTRs, discussing the existing evidence on their changes after transplantation and their associations with comorbidities and outcomes in this population. A comprehensive literature search was conducted in PubMed and Scopus for articles published until December 2024.

EXPERT OPINION

Novel methods assessing endothelial function offer a comprehensive, real-time evaluation of microvascular function and should be more widely used to enhance our understanding in this area.

Vascular endothelial dysfunction in pediatric rheumatic diseases: a systematic review and meta-analysis

OBJECTIVES

Endothelial dysfunction is associated with increased cardiovascular risk in individuals with autoimmune diseases. This systematic review and meta-analysis included studies assessing endothelial function with functional methods in children with rheumatic diseases versus controls.

METHODS

Literature search involved PubMed and Scopus databases (from inception to February 2024) and manual reference screening. Studies assessing endothelial function by all available functional methods were eligible. Study quality was evaluated via Newcastle-Ottawa scale.

RESULTS

Twenty-four studies (880 children with rheumatic diseases, 784 controls) were included in meta-analysis. Pooled analysis showed significantly impaired endothelial function in patients versus controls (SMD: -0.74, 95%CI -1.10 to -0.39) but with high heterogeneity (I2 = 91%, p < 0.001); sensitivity analysis including only high-quality studies confirmed this finding (SMD: -0.83, 95%CI -1.20 to -0.46). In subgroup analyses according to type of rheumatic disease, significantly impaired endothelial function was showed for patients with juvenile idiopathic arthritis (SMD: -1.05, 95%CI -1.84 to -0.25), vasculitis (SMD: -0.74, 95%CI -1.11 to -0.37) and juvenile systemic sclerosis (SMD -2.48, 95%CI -4.34 to -0.61).

CONCLUSIONS

Children with rheumatic diseases show impaired endothelial function. Future studies are needed to elucidate whether endothelial dysfunction is involved in high cardiovascular risk of these patients.

PROSPERO REGISTRATION NUMBER

CRD42023413799.

Effect of heart failure and atrial fibrillation on cardiorespiratory fitness in hemodialysis patients

PURPOSE

Heart failure (HF) and atrial fibrillation (AF) are highly prevalent in hemodialysis. They are well-known significant modifiers of the disease associations with cardiovascular outcomes, but there is a lack of evidence regarding the effects of HF and AF on cardiorespiratory fitness. This study is the first to examine the possible association of the presence of HF and AF with exercise intolerance in patients undergoing hemodialysis.

METHODS

This analysis included 40 sex- and age-matched participants [10 hemodialysis patients with HF or AF, 10 hemodialysis patients without HF or AF, 10 patients with HF or AF without chronic kidney disease (CKD) and 10 healthy controls] that underwent CPET and spirometry examinations. The total of patients with HF had preserved ejection fraction.

RESULTS

VO2peak(ml/kg/min) showed a graded increase between hemodialysis patients with HF or AF, hemodialysis patients without HF or AF, non-CKD patients with HF or AF and controls (13.17 ± 2.45 vs 15.26 ± 3.29 vs 19.64 ± 5.84 vs 25.11 ± 6.94 ml/kg/min, p < 0.001); VO2peak(ml/min) followed the same pattern (1172 ± 197 vs 1269 ± 314 vs 1817 ± 583 vs 1952 ± 592 ml/min respectively, p = 0.001). VO2peak(%predicted), VO2AT(ml/kg/min), VO2AT(ml/min) and maximal work load significantly differed between the study groups, with a tendency for higher values from hemodialysis patients to non-CKD patients with HF or AF and to healthy controls. FEV1 and FVC levels were similar between the study groups. In the whole population, VO2peak(ml/kg/min) showed a positive correlation with hemoglobin (r = 0.663, p < 0.001) and negative correlations with high-sensitivity cardiac troponin I (r = - 0.493, p = 0.001) and BNP (r = - 0.479, p = 0.002).

CONCLUSION

Hemodialysis patients have low exercise tolerance, and the presence of HF or AF is associated with further decreased values of VO2peak, the most important determinant of cardiorespiratory fitness.

Effect of Avenciguat on Albuminuria in Patients with CKD: Two Randomized Placebo-Controlled Trials

Key Points

Background

Avenciguat is a novel, potent soluble guanylate cyclase activator in development for CKD. Two trials investigated avenciguat in diabetic (NCT04750577) and non-diabetic (NCT04736628) CKD.

Methods

A prespecified pooled analysis of two randomized, double-blind, placebo-controlled trials of identical design. Adults with CKD (eGFR ≥20 and <90 ml/min per 1.73 m2, urine albumin–creatinine ratio [UACR] ≥200 and <3500 mg/g) were randomized to 20 weeks of placebo or avenciguat 1, 2, or 3 mg three times daily (TID), adjunctive to angiotensin-converting enzyme inhibitor or angiotensin receptor blocker. The primary end point was change from baseline in UACR in 10-hour urine at week 20, analyzed per protocol. The secondary end point was UACR change from baseline in first morning void urine at week 20. Safety was monitored throughout.

Results

Overall, 500 patients (mean age 62 years [SD 13]; mean eGFR 44 ml/min per 1.73 m2 [SD 18] and median 10-hour UACR 719 [interquartile range, 379–1285] mg/g) received placebo (n=122) or avenciguat 1 mg (n=125), 2 mg (n=126), or 3 mg (n=127) TID. All 243 patients in study one and 27 of 261 patients in study two had diabetes mellitus. Avenciguat 1, 2, and 3 mg TID reduced UACR in 10-hour and first morning void urine versus placebo throughout the treatment period. At week 20, placebo-corrected geometric mean changes (95% confidence interval) from baseline in UACR in 10-hour urine with avenciguat 1, 2, and 3 mg TID were −15.5% (−26.4 to −3.0), −13.2% (−24.6 to −0.1), and −21.5% (−31.7 to −9.8), respectively, analyzed per protocol. Corresponding changes in first morning void urine were −19.4% (−30.0 to −7.3), −15.5% (−26.9 to −2.5), and −23.4% (−33.5 to −11.8), respectively. Avenciguat was well tolerated; the overall frequency of adverse events was low and similar to placebo. The number of patients who discontinued the study drug because of adverse events with avenciguat 1, 2, and 3 mg TID were five (4%), 11 (9%), and 11 (9%), respectively, compared with four (3%) in the placebo group.

Conclusions

Avenciguat lowered albuminuria and was well tolerated in patients with CKD.

Clinical Trial registry name and registration number:

A Study to Test the Effect of Different Doses of BI 685509 on Kidney Function in People With Diabetic Kidney Disease, NCT04750577, and A Study to Test the Effect of Different Doses of Avenciguat (BI 685509) on Kidney Function in People With Chronic Kidney Disease, NCT04736628.

Podcast

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Frail hypertensive older adults with prediabetes and chronic kidney disease: insights on organ damage and cognitive performance - preliminary results from the CARYATID study

BACKGROUND

Hypertension and chronic kidney disease (CKD) pose significant public health challenges, sharing intertwined pathophysiological mechanisms. Prediabetes is recognized as a precursor to diabetes and is often accompanied by cardiovascular comorbidities such as hypertension, elevating the risk of pre-frailty and frailty. Albuminuria is a hallmark of organ damage in hypertension amplifying the risk of pre-frailty, frailty, and cognitive decline in older adults. We explored the association between albuminuria and cognitive impairment in frail older adults with prediabetes and CKD, assessing cognitive levels based on estimated glomerular filtration rate (eGFR).

METHODS

We conducted a study involving consecutive frail older patients with hypertension recruited from March 2021 to March 2023 at the ASL (local health unit of the Italian Ministry of Health) of Avellino, Italy, followed up after three months. Inclusion criteria comprised age over 65 years, prior diagnosis of hypertension without secondary causes, prediabetes, frailty status, Montreal Cognitive Assessment (MoCA) score < 26, and CKD with eGFR > 15 ml/min.

RESULTS

237 patients completed the study. We examined the association between albuminuria and MoCA Score, revealing a significant inverse correlation (r: 0.8846; p < 0.0001). Subsequently, we compared MoCA Score based on eGFR, observing a significant difference (p < 0.0001). These findings were further supported by a multivariable regression analysis, with albuminuria as the dependent variable.

CONCLUSIONS

Our study represents the pioneering effort to establish a significant correlation between albuminuria and eGFR with cognitive function in frail hypertensive older adults afflicted with prediabetes and CKD.

Cerebral oxygenation during exercise deteriorates with advancing chronic kidney disease

BACKGROUND

Cognitive impairment and exercise intolerance are common in chronic kidney disease (CKD). Cerebral perfusion and oxygenation play a major role in both cognitive function and exercise execution. This study aimed to examine cerebral oxygenation during a mild physical stress in patients at different CKD stages and controls without CKD.

METHODS

Ninety participants (18 per CKD stage 2, 3a, 3b and 4 and 18 controls) underwent a 3-min intermittent handgrip exercise at 35% of their maximal voluntary contraction. During exercise, cerebral oxygenation [oxyhaemoglobin (O2Hb), deoxyhaemoglobin (HHb) and total haemoglobin (tHb)] was assessed by near-infrared spectroscopy. Indices of microvascular (muscle hyperaemic response) and macrovascular function (carotid intima-media thickness and pulse wave velocity (PWV)) and cognitive and physical activity status were also evaluated.

RESULTS

No differences in age, sex and body mass index were detected among groups. The mini-mental state examination score was significantly reduced with advancing CKD stages (controls: 29.2 ± 1.2, stage 2: 28.7 ± 1.0, stage 3a: 27.8 ± 1.9, stage 3b: 28.0 ± 1.8, stage 4: 27.6 ± 1.5; P = .019). Similar trends were observed for physical activity levels and handgrip strength. The average response in cerebral oxygenation (O2Hb) during exercise was lower with advancing CKD stages (controls: 2.50 ± 1.54, stage 2: 1.30 ± 1.05, stage 3a: 1.24 ± 0.93, stage 3b: 1.11 ± 0.89, stage 4: 0.97 ± 0.80 μmol/l; P < .001). The average tHb response (index of regional blood volume) showed a similar decreasing trend (P = .003); no differences in HHb among groups were detected. In univariate linear analysis, older age, lower estimated glomerular filtration rate (eGFR), Hb, microvascular hyperaemic response and increased PWV were associated with poor O2Hb response during exercise. In the multiple model, eGFR was the only parameter independently associated with the O2Hb response.

CONCLUSIONS

Brain activation during a mild physical task appears to decrease with advancing CKD as suggested by the smaller increase in cerebral oxygenation. This may contribute to impaired cognitive function and reduced exercise tolerance with advancing CKD.

Association of omega 3 polyunsaturated fatty acids with incident chronic kidney disease: pooled analysis of 19 cohorts

OBJECTIVE

To assess the prospective associations of circulating levels of omega 3 polyunsaturated fatty acid (n-3 PUFA) biomarkers (including plant derived α linolenic acid and seafood derived eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid) with incident chronic kidney disease (CKD).

DESIGN

Pooled analysis.

DATA SOURCES

A consortium of 19 studies from 12 countries identified up to May 2020.

STUDY SELECTION

Prospective studies with measured n-3 PUFA biomarker data and incident CKD based on estimated glomerular filtration rate.

DATA EXTRACTION AND SYNTHESIS

Each participating cohort conducted de novo analysis with prespecified and consistent exposures, outcomes, covariates, and models. The results were pooled across cohorts using inverse variance weighted meta-analysis.

MAIN OUTCOME MEASURES

Primary outcome of incident CKD was defined as new onset estimated glomerular filtration rate <60 mL/min/1.73 m2. In a sensitivity analysis, incident CKD was defined as new onset estimated glomerular filtration rate <60 mL/min/1.73 m2 and <75% of baseline rate.

RESULTS

25 570 participants were included in the primary outcome analysis and 4944 (19.3%) developed incident CKD during follow-up (weighted median 11.3 years). In multivariable adjusted models, higher levels of total seafood n-3 PUFAs were associated with a lower incident CKD risk (relative risk per interquintile range 0.92, 95% confidence interval 0.86 to 0.98; P=0.009, I2=9.9%). In categorical analyses, participants with total seafood n-3 PUFA level in the highest fifth had 13% lower risk of incident CKD compared with those in the lowest fifth (0.87, 0.80 to 0.96; P=0.005, I2=0.0%). Plant derived α linolenic acid levels were not associated with incident CKD (1.00, 0.94 to 1.06; P=0.94, I2=5.8%). Similar results were obtained in the sensitivity analysis. The association appeared consistent across subgroups by age (≥60 v <60 years), estimated glomerular filtration rate (60-89 v ≥90 mL/min/1.73 m2), hypertension, diabetes, and coronary heart disease at baseline.

CONCLUSIONS

Higher seafood derived n-3 PUFA levels were associated with lower risk of incident CKD, although this association was not found for plant derived n-3 PUFAs. These results support a favourable role for seafood derived n-3 PUFAs in preventing CKD.

Muscle Oxygenation and Microvascular Reactivity Across Different Stages of CKD: A Near-Infrared Spectroscopy Study

RATIONALE & OBJECTIVE

Previous studies in chronic kidney disease (CKD) showed that vascular dysfunction in different circulatory beds progressively deteriorates with worsening CKD severity. This study evaluated muscle oxygenation and microvascular reactivity at rest, during an occlusion-reperfusion maneuver, and during exercise in patients with different stages of CKD versus controls.

STUDY DESIGN

Observational controlled study.

SETTING & PARTICIPANTS

90 participants (18 per CKD stage 2, 3a, 3b, and 4, as well as 18 controls).

PREDICTOR

CKD stage.

OUTCOME

The primary outcome was muscle oxygenation at rest. Secondary outcomes were muscle oxygenation during occlusion-reperfusion and exercise, and muscle microvascular reactivity (hyperemic response).

ANALYTICAL APPROACH

Continuous measurement of muscle oxygenation [tissue saturation index (TSI)] using near-infrared spectroscopy at rest, during occlusion-reperfusion, and during a 3-minute handgrip exercise (at 35% of maximal voluntary contraction). Aortic pulse wave velocity and carotid intima-media thickness were also recorded.

RESULTS

Resting muscle oxygenation did not differ across the study groups (controls: 64.3% ± 2.9%; CKD stage 2: 63.8% ± 4.2%; CKD stage 3a: 64.1% ± 4.1%; CKD stage 3b: 62.3% ± 3.3%; CKD stage 4: 62.7% ± 4.3%; P=0.6). During occlusion, no significant differences among groups were detected in the TSI occlusion magnitude and TSI occlusion slope. However, during reperfusion the maximum TSI value was significantly lower in groups of patients with more advanced CKD stages compared with controls, as was the hyperemic response (controls: 11.2%±3.7%; CKD stage 2: 8.3%±4.6%; CKD stage 3: 7.8%±5.5%; CKD stage 3b: 7.3%±4.4%; CKD stage 4: 7.2%±3.3%; P=0.04). During the handgrip exercise, the average decline in TSI was marginally lower in patients with CKD than controls, but no significant differences were detected across CKD stages.

LIMITATIONS

Moderate sample size, cross-sectional evaluation.

CONCLUSIONS

Although no differences were observed in muscle oxygenation at rest or during occlusion, the microvascular hyperemic response during reperfusion was significantly impaired in CKD and was most prominent in more advanced CKD stages. This impaired ability of microvasculature to respond to stimuli may be a crucial component of the adverse vascular profile of patients with CKD and may contribute to exercise intolerance.

Prediction of acute kidney injury using a combined model of inflammatory vascular endothelium biomarkers and ultrasound indices

BACKGROUND

Acute kidney injury (AKI) is a common complication of sepsis, with the burden of long hospital admission. Early prediction of AKI is the most effective strategy for intervention and improvement of the outcomes.

OBJECTIVE

In our study, we aimed to investigate the predictive performance of the combined model using ultrasound indices (grayscale and Doppler indieces), endothelium injury (E-selectin, VCAM-1, ICAM1, Angiopoietin 2, syndecan-1, and eNOS) as well as inflammatory biomarkers (TNF-a, and IL-1β) to identify AKI.

METHODS

Sixty albino rats were divided into control and lipopolysaccharide (LPS) groups. Renal ultrasound, biochemical and immunohistological variables were recorded 6 hrs, 24 hrs, and 48 hrs after AKI.

RESULTS

Endothelium injury and inflammatory markers were found to be significantly increased early after AKI, and correlated significantly with kidney size reduction and renal resistance indices elevation.

CONCLUSIONS

Using area under the curve (AUC), the combined model was analyzed based on ultrasound and biochemical variables and provided the highest predictive value for renal injury.

Endothelial Function Assessment by Flow-Mediated Dilation Method: A Valuable Tool in the Evaluation of the Cardiovascular System

Cardiovascular diseases (CVDs) in the course of atherosclerosis are one of the most critical public health problems in the world. Endothelial cells synthesize numerous biologically active substances involved in regulating the functions of the cardiovascular system. Endothelial dysfunction is an essential element in the pathogenesis of atherosclerosis. Thus, the assessment of endothelial function in people without overt CVD allows for a more accurate estimate of the risk of developing CVD and cardiovascular events. The assessment of endothelial function is primarily used in scientific research, and to a lesser extent in clinical practice. Among the tools for assessing endothelial function, we can distinguish biochemical and physical methods, while physical methods can be divided into invasive and non-invasive methods. Flow-mediated dilation (FMD) is based on the ultrasound assessment of changes in the diameter of the brachial artery as a result of increased blood flow. FMD is a non-invasive, safe, and repeatable test, but it must be performed by qualified and experienced medical staff. The purpose of this paper is to present the literature review results on the assessment of endothelial function using the FMD method, including its methodology, applications in clinical practice and research, limitations, and future perspectives.

Endothelial Dysfunction in Heart Failure With Preserved Ejection Fraction: What are the Experimental Proofs?

Heart failure with preserved ejection fraction (HFpEF) has been recognized as the greatest single unmet need in cardiovascular medicine. Indeed, the morbi-mortality of HFpEF is high and as the population ages and the comorbidities increase, so considerably does the prevalence of HFpEF. However, HFpEF pathophysiology is still poorly understood and therapeutic targets are missing. An unifying, but untested, theory of the pathophysiology of HFpEF, proposed in 2013, suggests that cardiovascular risk factors lead to a systemic inflammation, which triggers endothelial cells (EC) and coronary microvascular dysfunction. This cardiac small vessel disease is proposed to be responsible for cardiac wall stiffening and diastolic dysfunction. This paradigm is based on the fact that microvascular dysfunction is highly prevalent in HFpEF patients. More specifically, HFpEF patients have been shown to have decreased cardiac microvascular density, systemic endothelial dysfunction and a lower mean coronary flow reserve. Importantly, impaired coronary microvascular function has been associated with the severity of HF. This review discusses evidence supporting the causal role of endothelial dysfunction in the pathophysiology of HFpEF in human and experimental models.