Reduction of Arterial Stiffness After Kidney Transplantation: A Systematic Review and Meta-Analysis

Interplay between periodontitis and chronic kidney disease

Periodontitis is a ubiquitous chronic inflammatory disease affecting the supporting tissues of the teeth and is a major cause of multiple tooth loss. Despite being preventable, periodontitis and dental caries are responsible for more years lost to disability than any other human condition. The most severe form of periodontitis affects 1 billion individuals, and its prevalence is increasing globally. Periodontitis arises from a dysregulated and hyperactive inflammatory response to dysbiosis in the periodontal microbiome. This response has systemic effects associated with premature mortality and elevated risk of several systemic non-communicable diseases (NCDs), including atheromatous cardiovascular disease, type 2 diabetes and chronic kidney disease (CKD). This risk association between periodontitis and NCDs is independent of their shared common risk factors, suggesting that periodontitis is a non-traditional risk factor for NCDs such as CKD. As periodontitis progresses, the immune cells and mediators underpinning its pathophysiology leak into the systemic circulation through the ulcerated oral mucosal lining, inducing in a systemic inflammatory profile that closely mirrors that observed in patients with CKD. The relationship between periodontitis and CKD seems to be bi-directional, but large-scale intervention studies are required to clarify causality and could lead to new care pathways for managing each condition as an exposure for the other.

Inflammation and Arterial Stiffness as Drivers of Cardiovascular Risk in Kidney Disease

BACKGROUND

Patients with chronic kidney disease (CKD) have an increased cardiovascular (CV) risk. The lower the glomerular filtration rate, the higher the CV risk.

SUMMARY

Current data suggest that several uremic toxins lead to vascular inflammation and oxidative stress that, in turn, lead to endothelial dysfunction, changes in smooth muscle cells' phenotype, and increased degradation of elastin and collagen fibers. These processes lead to both functional and structural arterial stiffening and explain part of the increased risk of acute myocardial infarction and stroke reported in patients with CKD. Considering that, at least in patients with end-stage kidney disease, the reduction of arterial stiffness is associated with a parallel decrease of the CV risk; vascular function is a potential target for therapy to reduce the CV risk.

KEY MESSAGES

In this review, we explore mechanisms of vascular dysfunction in CKD, paying particular attention to inflammation, reporting current data in other models of mild and severe inflammation, and discussing the vascular effect of several drugs currently used in nephrology.

Exercise for chronic kidney disease: effects on vascular and cardiopulmonary function

Patients with chronic kidney disease (CKD) have an exacerbated prevalence of cardiovascular disease (CVD). Vascular dysfunction, characterized by impaired endothelial function and arterial stiffness, and markedly low cardiorespiratory fitness levels are hallmark manifestations of the disease that contribute to the CVD burden. Despite advancements in blood pressure and lipid lowering pharmacological therapies, CVD remains markedly prevalent across the spectrum of CKD. This highlights a stagnation in effective clinical strategies to improve cardiovascular health and reinforces the critical need for adjuvant lifestyle strategies such as physical activity and exercise training to be incorporated into routine clinical care. This narrative review provides an overview of the known effects of exercise on vascular and cardiopulmonary function across the spectrum of CKD. The physiological mechanisms of vascular dysfunction that serve as exercise-specific therapeutic targets are highlighted and future perspectives are discussed.

Improved Arterial Stiffness Indices 3 and 6 Months after Living-donor Renal Transplantation

Arterial stiffness is a non-traditional risk factor of cardiovascular disease and may explain part of the excess cardiovascular risk in chronic kidney disease patients. Successful renal transplantation (RT) may restore renal function and improve several metabolic abnormalities involved in arterial stiffness. This prospective study conducted non-invasive assessments of arterial stiffness indices [the augmentation index (AI) and pulse wave velocity (PWV)] in end-stage kidney disease (ESKD) patients before RT and 3 and 6 months after living-donor RT, alongside the effects of age and calcineurin inhibitors on arterial stiffness. The study included 26 ESKD patients (22 males and 4 females; mean age, 34.07 years; median duration of dialysis, 10 months) scheduled for RT and followed up for three visits (within 1 week before transplantation, and 3 and 6 months after transplantation). Six months after successful RT, the patients had nearly normal serum creatinine and significantly improved serum phosphate and intact parathyroid hormone levels. The pretransplant AI was 21.53% ± 13.61% which reduced significantly 6 months after RT to 16.19% ± 10.74% (P <0.05). Although there was a reduction in PWV 6 months after RT from the pre-transplant PWV, it was not significant. A significant correlation between age and the augmentation index was noted 3 and 6 months after RT. Patients on tacrolimus-based immunosuppression after RT showed significant improvements in the AI compared with patients on a cyclosporine-based regimen. RT helped to improve arterial stiffness indices, resulting in reduced cardiovascular risk.

Wnt/β-catenin pathway inhibitors, bone metabolism and vascular health in kidney transplant patients

BACKGROUND AND OBJECTIVES

Sclerostin, dickkopf-related protein 1 (DKK1), fibroblast growth factor-23 (FGF23) and α-klotho have been shown to play an important role in bone and vascular disease of chronic kidney disease. We aimed to evaluate the evolution of these bone markers in newly kidney transplanted patients, and whether they are associated with bone metabolism and vascular stiffness.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

This is a longitudinal single-center observational cohort study. Circulating levels of Wnt/β-catenin pathway inhibitors (sclerostin, DKK1, FGF23 and α-klotho), arterial stiffness (carotid-femoral pulse-wave velocity (PWV), carotid-radial PWV, PWV ratio, augmented index) and bone parameters were assessed before (M0), and at 3 (M3) and 6 months (M6) after transplantation. Generalized estimating equations were conducted for comparative analyses between the three time points. We used a marginal structural model for repeated measures for the impact of changes in bone markers on the evolution of arterial stiffness. Multivariate linear regression analyses were performed for the associations between Wnt/β-catenin pathway inhibitors and mineral metabolism parameters.

RESULTS

We included 79 patients (70% male; median age of 53 (44-60) years old). The levels of sclerostin (2.06 ± 1.18 ng/mL at M0 to 0.88 ± 0.29 ng/mL at M6, p ≤ 0.001), DKK1 (364.0 ± 266.7 pg/mL at M0 to 246.7 ± 149.1 pg/mL at M6, p ≤ 0.001), FGF23 (5595 ± 9603 RU/mL at M0 to 137 ± 215 RU/mL at M6, p ≤ 0.001) and α-klotho (457.6 ± 148.6 pg/mL at M0 to 109.8 ± 120.7 pg/mL at M6, p < 0.05) decreased significantly after kidney transplant. Sclerostin and FGF23 were positively associated with carotid-femoral (standardized β = 0.432, p = 0.037 and standardized β = 0.592, p = 0.005) and carotid-radial PWV (standardized β = 0.259, p = 0.029 and standardized β = 0.242, p = 0.006) throughout the 6 months of follow-up. The nature of the associations between bone markers and bone metabolism parameters varies after kidney transplant.

CONCLUSIONS

The circulating levels of Wnt/β-catenin pathway inhibitors and α-klotho significantly decrease after kidney transplantation, while sclerostin and FGF23 levels might be associated with improvement of vascular stiffness and blood pressure.

Association between Long-Term Change in Arterial Stiffness and Cardiovascular Outcomes in Kidney Transplant Recipients: Insights from the TRANSARTE Study

(1) Background: Increased arterial stiffness is associated with cardiovascular (CV) diseases in end-stage renal disease (ESRD) patients, and CV mortality remains higher in kidney transplantation (KT) recipients compared to in the general population. KT is associated with an improvement in arterial stiffness in the early post-transplant period, followed by a potential re-worsening in the late period. In a cohort of KT patients, we evaluated the associations of pulse-wave velocity (PWV) measured at different time-points (pre-transplant, and early and late post-transplant periods) with CV morbi-mortality, as well as the evolution between these measurements with CV morbi-mortality. (2) Methods: Forty KT recipients with a 10-year follow-up were included. The association of PWV with CV events was assessed with multivariable cox analysis. Backward linear regressions were conducted to identify the determinants of PWV at 1 year and those of the long-term evolution of PWV after KT (delta PWV at 1 year—latest PWV). (3) Results: The absence of arterial stiffening during the long-term follow-up after KT is associated with a lower CV outcome rate (HR for the delta PWV = 0.76 (0.58−0.98), p = 0.036). Age at KT is associated with the worsening of arterial stiffness in the late post-transplantation period (β for the delta PWV = −0.104, p = 0.031). A high PWV at 1 year was associated with a potential for recovery during follow-up (β = 0.744, p < 0.0001). (4) Conclusions: The absence of PWV worsening in the late post-transplantation period was significantly associated with a lower risk of CV events, whereas early changes in PWV were not. Finding an intervention capable of reducing long-term PWV could improve the prognosis of KT recipients.

Insights from the 4C-T Study suggest increased cardiovascular burden in girls with end stage kidney disease before and after kidney transplantation

Mortality in children with kidney failure is higher in girls than boys with cardiovascular complications representing the most common causes of death. Pulse wave velocity (PWV), a measure of vascular stiffness, predicts cardiovascular mortality in adults. Here, PWV in children with kidney failure undergoing kidney replacement therapy was investigated to determine sex differences and potential contributing factors. Two-hundred-thirty-five children (80 girls; 34%) undergoing transplantation (150 pre-emptive, 85 with prior dialysis) having at least one PWV measurement pre- and/or post-transplantation from a prospective cohort were analyzed. Longitudinal analyses (median/maximum follow-up time of 6/9 years) were performed for PWV z-scores (PWVz) using linear mixed regression models and further stratified by the categories of time: pre-kidney replacement therapy and post-transplantation. PWVz significantly increased by 0.094 per year and was significantly higher in girls (PWVz +0.295) compared to boys, independent of the underlying kidney disease. During pre-kidney replacement therapy, an average estimated GFR decline of 4ml/min/1.73m² per year was associated with a PWVz increase of 0.16 in girls only. Higher diastolic blood pressure and low density lipoprotein were independently associated with higher PWVz during pre-kidney replacement therapy in both sexes. In girls post-transplantation, an estimated GFR decline of 4ml/min/1.73m² per year pre-kidney replacement therapy and a longer time (over 12 months) to transplantation were significantly associated with higher PWVz of 0.22 and of 0.57, respectively. PWVz increased further after transplantation and was positively associated with time on dialysis and diastolic blood pressure in both sexes. Thus, our findings demonstrate that girls with advanced chronic kidney disease are more susceptible to develop vascular stiffening compared to boys, this difference persist after transplantation and might contribute to higher mortality rates seen in girls with kidney failure.

The ViKTORIES trial: A randomized, double-blind, placebo-controlled trial of vitamin K supplementation to improve vascular health in kidney transplant recipients

Premature cardiovascular disease and death with a functioning graft are leading causes of death and graft loss, respectively, in kidney transplant recipients (KTRs). Vascular stiffness and calcification are markers of cardiovascular disease that are prevalent in KTR and associated with subclinical vitamin K deficiency. We performed a single-center, phase II, parallel-group, randomized, double-blind, placebo-controlled trial (ISRCTN22012044) to test whether vitamin K supplementation reduced vascular stiffness (MRI-based aortic distensibility) or calcification (coronary artery calcium score on computed tomography) in KTR over 1 year of treatment. The primary outcome was between-group difference in vascular stiffness (ascending aortic distensibility). KTRs were recruited between September 2017 and June 2018, and randomized 1:1 to vitamin K (menadiol diphosphate 5 mg; n = 45) or placebo (n = 45) thrice weekly. Baseline demographics, clinical history, and immunosuppression regimens were similar between groups. There was no impact of vitamin K on vascular stiffness (treatment effect -0.23 [95% CI -0.75 to 0.29] × 10^-3  mmHg^-1 ; p = .377), vascular calcification (treatment effect -141 [95% CI - 320 to 38] units; p = .124), nor any other outcome measure. In this heterogeneous cohort of prevalent KTR, vitamin K supplementation did not reduce vascular stiffness or calcification over 1 year. Improving vascular health in KTR is likely to require a multifaceted approach.

Peripheral Vascular Disease and Kidney Transplant Outcomes: Rethinking an Important Ongoing Complication

Peripheral vascular disease (PVD) is highly prevalent in patients on the waiting list for kidney transplantation (KT) and after transplantation and is associated with impaired transplant outcomes. Multiple traditional and nontraditional risk factors, as well as uremia- and transplant-related factors, affect 2 processes that can coexist, atherosclerosis and arteriosclerosis, leading to PVD. Some pathogenic mechanisms, such as inflammation-related endothelial dysfunction, mineral metabolism disorders, lipid alterations, or diabetic status, may contribute to the development and progression of PVD. Early detection of PVD before and after KT, better understanding of the mechanisms of vascular damage, and application of suitable therapeutic approaches could all minimize the impact of PVD on transplant outcomes. This review focuses on the following issues: (1) definition, epidemiological data, diagnosis, risk factors, and pathogenic mechanisms in KT candidates and recipients; (2) adverse clinical consequences and outcomes; and (3) classical and new therapeutic approaches.

Effects of living kidney donation on arterial stiffness: a systematic review protocol

INTRODUCTION

Kidney donors have been reported to have accelerated progression of aortic stiffness and decreased glomerular filtration compared with healthy non-donors. This is a concern because increased aortic stiffness is an independent predictor of overall cardiovascular disease and all-cause mortality in the general population. To confirm if arterial stiffness increases after donation, we will systematically review all studies that evaluated indices of arterial stiffness in healthy individuals who underwent unilateral nephrectomy for kidney donation compared with age-matched healthy non-nephrectomised controls.

METHODS/ANALYSIS

We will comprehensively search for studies published between 1 January 1960 and 15 March 2021 in MEDLINE, EMBASE, Cochrane Central, OVID and EBM reviews. All prospective (cohort, case-control, case series and before-and-after studies) and retrospective non-randomised studies reporting indices of arterial stiffness in nephrectomised and non-nephrectomised healthy participants will be included. Primary outcome will be the difference in the functional metrics of arterial stiffness between donors and non-donors. Secondary outcomes will be the differences in systolic/diastolic blood pressures, serum creatinine, glomerular filtration, carotid artery intima-media thickness and vascular calcification. Study screening, selection and data extraction will be performed by two independent reviewers. Risk of bias will be independently assessed with the ROBINS-I tool and confidence in evidence by the Grading of Recommendations Assessment, Development and Evaluation recommendations. Qualitative and quantitative data syntheses as well as clinical and statistical heterogeneity (Forest plots, I2 and Cochran's Q statistics) will be evaluated. If clinical and statistical heterogeneity are acceptable, inverse variance-weighted effects will be analysed by random effect models.

ETHICS AND DISSEMINATION

No ethical approval is necessary. Our results will be disseminated through peer-review publication and presentations to guide stakeholders on the evaluation and follow-up care of kidney donors.

PROSPERO REGISTRATION NUMBER

CRD42020185551.

Variations in Circulating Active MMP-9 Levels During Renal Replacement Therapy

Renal replacement therapy (RRT) is complicated by a chronic state of inflammation and a high mortality risk. However, different RRT modalities can have a selective impact on markers of inflammation and oxidative stress. We evaluated the levels of active matrix metalloproteinase (MMP)-9 in patients undergoing two types of dialysis (high-flux dialysis (HFD) and on-line hemodiafiltration (OL-HDF)) and in kidney transplantation (KT) recipients. Active MMP-9 was measured by zymography and ELISA before (pre-) and after (post-) one dialysis session, and at baseline and follow-up (7 and 14 days, and 1, 3, 6, and 12 months) after KT. Active MMP-9 decreased post-dialysis only in HFD patients, while the levels in OL-HDF patients were already lower before dialysis. Active MMP-9 increased at 7 and 14 days post-KT and was restored to baseline levels three months post-KT, coinciding with an improvement in renal function and plasma creatinine. Active MMP-9 correlated with pulse pressure as an indicator of arterial stiffness both in dialysis patients and KT recipients. In conclusion, active MMP-9 is better controlled in OL-HDF than in HFD and is restored to baseline levels along with stabilization of renal parameters after KT. Active MMP-9 might act as a biomarker of arterial stiffness in RRT.

Positive correlation of serum fibroblast growth factor 23 with peripheral arterial stiffness in kidney transplantation patients

BACKGROUND

Fibroblast growth factor 23 (FGF-23) has a role in arterial stiffness (AS) apart from regulating mineral metabolism. We investigated the association between FGF-23 concentration and peripheral AS in renal transplantation (RT) recipients.

METHODS

The fasting blood samples of RT recipients (n = 66) were collected and analyzed.

RESULTS

A total of 29 (43.9%) RT recipients were classified under the peripheral AS group. The RT recipients in this group had a higher prevalence of diabetes (P < 0.001), hypertension (P = 0.001), and metabolic syndrome (P = 0.023); longer post-RT duration (P = 0.006); higher systolic blood pressure (P < 0.001) and diastolic blood pressure (P = 0.024); and higher fasting glucose (P = 0.002), total cholesterol (P = 0.049), blood urea nitrogen (P = 0.027), phosphorus (P = 0.047), and FGF-23 concentrations (P = 0.003) and FGF-23/α-klotho ratio (P < 0.001) but lower klotho concentrations (P = 0.025) than those in the control group. Moreover, FGF-23 concentration (adjusted odds ratio: 1.057, 95% confidence interval: 1.011-1.105, P = 0.015) was found to be an independent predictor of peripheral AS in RT recipients.

CONCLUSIONS

Serum FGF-23 concentration was a significant predictor of peripheral AS in RT recipients.

A Systematic Review and Meta-analysis of Nonpharmacologic-based Interventions for Aortic Stiffness in End-Stage Renal Disease

Introduction

Increased carotid-femoral pulse wave velocity (cf-PWV) in end-stage renal disease (ESRD) indicates enhanced aortic stiffness and mortality risk. We conducted a systematic review and meta-analysis of nonpharmacologic interventions in adults with ESRD to determine their effects on cf-PWV, systolic blood pressure (SBP), and intervention-associated adverse events.

Methods

MEDLINE, EMBASE, and EBM databases were searched. Study screening, selection, data collection, and methodological quality assessments were performed by 2 independent reviewers. Pooled-effect estimates from mean differences and 95% confidence intervals (CIs) were calculated using random effect models.

Results

A total of 2166 subjects with ESRD from 33 studies (17 randomized; 16 nonrandomized) were included. Four intervention-comparator pairs were meta-analyzed. Quality of evidence ranged from very low to moderate. Kidney transplantation decreased cf-PWV (−0.70 m/s; CI: –1.3 to −0.11; P = 0.02) and SBP (−8.3 mm Hg; CI: −13.2 to −3.3; P < 0.001) over pretransplantation. In randomized trials, control of fluid overload by bio-impedance reduced cf-PWV (−1.90 m/s; CI: −3.3 to −0.5); P = 0.02) and SBP (−4.3 mm Hg; CI: −7.7 to −0.93); P = 0.01) compared with clinical assessment alone. Cross-sectional studies also demonstrated significantly lower cf-PWV and SBP in normovolemia compared with hypervolemia (P ≤ 0.01). Low calcium dialysate decreased cf-PWV (−1.70 m/s; CI: −2.4 to −1.0; P < 0.00001) without affecting SBP (−1.6 mm Hg; CI: −8.9 to 5.8; P = 0.61). Intradialytic exercise compared with no exercise reduced cf-PWV (−1.13 m/s; CI: −2.2 to −0.03; P = 0.04), but not SBP (+0.5 mm Hg; CI: −9.5 to 10.4); P = 0.93).

Conclusions

Several nonpharmacologic interventions effectively decrease aortic stiffness in ESRD. The impact of these interventions on cardiovascular outcomes and mortality risk reduction in ESRD requires further study.

Arterial Stiffness in the Heart Disease of CKD

CKD frequently leads to chronic cardiac dysfunction. This complex relationship has been termed as cardiorenal syndrome type 4 or cardio-renal link. Despite numerous studies and reviews focused on the pathophysiology and therapy of this syndrome, the role of arterial stiffness has been frequently overlooked. In this regard, several pathogenic factors, including uremic toxins (i.e., uric acid, phosphates, endothelin-1, advanced glycation end-products, and asymmetric dimethylarginine), can be involved. Their effect on the arterial wall, direct or mediated by chronic inflammation and oxidative stress, results in arterial stiffening and decreased vascular compliance. The increase in aortic stiffness results in increased cardiac workload and reduced coronary artery perfusion pressure that, in turn, may lead to microvascular cardiac ischemia. Conversely, reduced arterial stiffness has been associated with increased survival. Several approaches can be considered to reduce vascular stiffness and improve vascular function in patients with CKD. This review primarily discusses current understanding of the mechanisms concerning uremic toxins, arterial stiffening, and impaired cardiac function, and the therapeutic options to reduce arterial stiffness in patients with CKD.

Cardiovascular Risk Assessment in Pediatric Liver Transplant Patients

OBJECTIVES

Cardiovascular (CV) diseases play a leading role in the mortality of adult liver transplant (LT) recipients. However, data regarding CV risk factors in children after LT remain sparse. The present study assessed the presence of CV risk factors and signs of CV impairment in LT children.

METHODS

A total of 42 LT recipients (21 men, age 9.93 ± 3.57 years) were studied. Body composition [body mass index standard deviation score, percentage of body fat (by bioimpedance analysis)], lipid profiles, glycemic control, blood pressure, and arterial stiffness [assessed by aortic pulse wave velocity (PWV)] were evaluated. The effect of different treatment modalities [tacrolimus (TAC) (n = 30) or cyclosporine (CyA) (n = 11)] was also analyzed.

RESULTS

Almost 18% of children were overweight or obese. Patients on TAC had a significantly higher body fat mass and percentage of body fat compared with the CyA group (P < 0.02). Borderline to high lipid values were present in 40% of patients. Children on CyA had higher serum cholesterol levels compared to TAC (P < 0.004). Nineteen percent of patients had hypertension. Half of the patients had glomerular filtration rate values <90 mL/min/1.73 m, whereas PWV values were above the 95th percentile in 12%.

CONCLUSIONS

Increased body fat, chronic kidney disease, high lipid content, hypertension, and increased arterial stiffness are already present and are in part related to the type of immunosuppression regimen in LT children >5 years following transplantation. Long-term follow-up is needed to evaluate their impact on CV health and survival.

The Impact of Uremic Toxins on Vascular Smooth Muscle Cell Function

Chronic kidney disease (CKD) is associated with profound vascular remodeling, which accelerates the progression of cardiovascular disease. This remodeling is characterized by intimal hyperplasia, accelerated atherosclerosis, excessive vascular calcification, and vascular stiffness. Vascular smooth muscle cell (VSMC) dysfunction has a key role in the remodeling process. Under uremic conditions, VSMCs can switch from a contractile phenotype to a synthetic phenotype, and undergo abnormal proliferation, migration, senescence, apoptosis, and calcification. A growing body of data from experiments in vitro and animal models suggests that uremic toxins (such as inorganic phosphate, indoxyl sulfate and advanced-glycation end products) may directly impact the VSMCs’ physiological functions. Chronic, low-grade inflammation and oxidative stress—hallmarks of CKD—are also strong inducers of VSMC dysfunction. Here, we review current knowledge about the impact of uremic toxins on VSMC function in CKD, and the consequences for pathological vascular remodeling.