Are advanced glycation end products cardiovascular risk factors in patients with CRF?

Urinary excretion of amino acids and their advanced glycation end-products (AGEs) in adult kidney transplant recipients with emphasis on lysine: furosine excretion is associated with cardiovascular and all-cause mortality

Arginine (Arg) and lysine (Lys) moieties of proteins undergo various post-translational modifications (PTM) including enzymatic N^G- and N^ε-methylation and non-enzymatic N^G- and N^ε-glycation. In a large cohort of stable kidney transplant recipients (KTR, n = 686), high plasma and low urinary concentrations of asymmetric dimethylarginine (ADMA), an abundant PTM metabolite of Arg, were associated with cardiovascular and all-cause mortality. Thus, the prediction of the same biomarker regarding mortality may depend on the biological sample. In another large cohort of stable KTR (n = 555), higher plasma concentrations of N^ε-carboxymethyl-lysine (CML) and N^ε-carboxyethyl-lysine (CEL), two advanced glycation end-products (AGEs) of Lys, were associated with higher cardiovascular mortality. Yet, the associations of urinary AGEs with mortality are unknown. In the present study, we measured 24 h urinary excretion of Lys, CML, and furosine in 630 KTR and 41 healthy kidney donors before and after donation. Our result indicate that lower urinary CML and lower furosine excretion rates are associated with higher mortality in KTR, thus resembling the associations of ADMA. Lower furosine excretion rates were also associated with higher cardiovascular mortality. The 24 h urinary excretion rate of amino acids and their metabolites decreased post-donation (varying as little as − 24% for CEL, and as much as − 62% for ADMA). For most amino acids, the excretion rate was lower in KTR than in donors pre-donation [except for S-(1-carboxyethyl)-l-cysteine (CEC) and N^G-carboxyethylarginine (CEA)]. Simultaneous GC–MS measurement of free amino acids, their PTM metabolites and AGEs in urine is a non-invasive approach in kidney transplantation.

Circulating Advanced Glycation End Products and Their Soluble Receptors in Relation to All-Cause and Cardiovascular Mortality: A Systematic Review and Meta-analysis of Prospective Observational Studies

Advanced glycation end products (AGEs) are involved in the development of several age-related complications. The protective role of soluble receptors for AGEs (sRAGE) against deleterious effects of AGEs has been indicated in several studies. However, findings on the association of AGEs or sRAGE with mortality are equivocal. In this meta-analysis we aimed to present a quantitative estimation of the association between circulating AGEs or sRAGE and all-cause or cardiovascular disease (CVD) mortality. A comprehensive literature search was performed to determine relevant publications through the online databases including PubMed, Scopus, and Web of Science up to 29 November 2020. Prospective observational studies assessing the association between circulating AGEs or sRAGE and all-cause or CVD mortality were included. Seven studies with a total of 3718 participants and 733 mortality cases (345 CVD deaths) were included in the meta-analysis for assessing the association between circulating AGEs and mortality. Our results showed that higher circulating AGEs were associated with increased risk of all-cause (pooled effect measure: 1.05; 95% CI: 1.01, 1.09; P = 0.018, I2 = 77.7%) and CVD mortality (pooled effect measure: 1.08; 95% CI: 1.01, 1.14; P = 0.015, I2 = 80.2%), respectively. The association between sRAGE and mortality was assessed in 14 studies with a total of 16,335 participants and 2844 mortality cases (419 CVD deaths). Serum concentrations of sRAGE were not associated with the risk of all-cause mortality (pooled effect measure: 1.01; 95% CI: 1.00, 1.01; P = 0.205, I2 = 75.5%), whereas there was a significant link between sRAGE and the risk of CVD mortality (pooled effect measure: 1.02; 95% CI: 1.00, 1.04; P = 0.02, I2 = 78.9%). Our findings showed that a higher serum AGE concentration was associated with increased risk of all-cause and CVD mortality. In addition, higher circulating sRAGE was related to increased risk of CVD mortality. This review was registered at PROSPERO as CRD42021236559.

Association of kidney transplantation with mortality on hemodialysis after graft failure

BACKGROUND

Although a substantial number of patients return to dialysis after kidney transplant failure, it remains controversial whether transplant-failure patients have a higher mortality risk than transplant-naïve patients on dialysis who have never undergone kidney transplantation. We compared outcomes of transplant-failure and transplant-naïve patients on hemodialysis.

METHODS

Data from the Japanese National Dialysis Registry (2012-2013) were analyzed, including 220,438 prevalent hemodialysis patients. Multivariable Cox models were used to compare all-cause, cardiovascular, and infection-related mortality during 1-year follow-up between transplant-failure and transplant-naïve patients. Multiple imputation and propensity score matching were utilized as sensitivity analyses.

RESULTS

During 209,377 patient-years of follow-up, 18,648 all-cause deaths (8.5% of all patients), 7700 cardiovascular deaths (41% of all-cause deaths), and 3806 infection-related deaths (20% of all-cause deaths) were observed. Adjusted hazard ratios [95% confidence intervals] for all-cause, cardiovascular, and infection-related deaths among transplant-failure patients were 0.81 [0.59-1.11], 0.54 [0.30-0.98], and 1.54 [0.92-2.59], respectively. Sensitivity analyses using multiple imputation and propensity score matching yielded similar results.

CONCLUSIONS

This Japanese cohort study suggested that a cardiovascular mortality risk of transplant-failure patients could be significantly lower than that of transplant-naïve patients, while there might be a trend toward a higher infection-related mortality risk in transplant-failure patients. However, this retrospective, single-country study can introduce an immortal time bias in transplant-failure patients, and limit the external validity. Further prospective studies are warranted to improve the comparability of outcomes between transplant-failure and transplant-naïve patients, and to examine worldwide the generalizability of the potential cardiovascular benefit of kidney transplantation even after returning to dialysis.

Establishment of Renal Failure Models by Laparoscopy in Bama Pigs Which Underwent Partial Nephrectomy and Radical Contralateral Nephrectomy

Introduction

The miniature pig possesses unmatched advantages as an animal model because of its high homology with humans. Our experiment aimed to build a chronic renal failure (CRF) model in pigs via laparoscopy.

Material and Methods

Laparoscopic surgery was performed twice to build a CRF model. The first surgery was a left partial nephrectomy and the second was a right radical nephrectomy. Pigs were grouped by the total renal tissue to be resected: ⅔, ¾ or ⅚. Physiological parameters (rectal temperature and heart rate), haematological parameters (WBC and RBC) and renal function (serum creatinine - CR and blood urea nitrogen - BUN) were measured preoperatively and every week postoperatively.

Results

After renal resection the pigs manifested chronic renal failure. Heart rate and body temperature declined to varying degrees over 12 postoperative weeks. No significant difference was observed between the different groups. The result of renal function tests found that postoperative serum CR and BUN in all groups were continuously elevated, and the level of serum CR at two weeks post procedure differed very significantly from its preoperative value (P < 0.05). BUN was significantly elevated at one week (P < 0.05). The renal function decreased significantly faster in the ⅚ group than in the other two groups. The trend of renal function change was similar among groups, but progress was slower in the ⅔ and ¾ groups.

Conclusion

⅚ kidney resection was the optimal miniature pig model of CRF.

Stirring the Pot: Can Dietary Modification Alleviate the Burden of CKD?

Diet is one of the largest modifiable risk factors for chronic kidney disease (CKD)-related death and disability. CKD is largely a progressive disease; however, it is increasingly appreciated that hallmarks of chronic kidney disease such as albuminuria can regress over time. The factors driving albuminuria resolution remain elusive. Since albuminuria is a strong risk factor for GFR loss, modifiable lifestyle factors that lead to an improvement in albuminuria would likely reduce the burden of CKD in high-risk individuals, such as patients with diabetes. Dietary therapy such as protein and sodium restriction has historically been used in the management of CKD. Evidence is emerging to indicate that other nutrients may influence kidney health, either through metabolic or haemodynamic pathways or via the modification of gut homeostasis. This review focuses on the role of diet in the pathogenesis and progression of CKD and discusses the latest findings related to the mechanisms of diet-induced kidney disease. It is possible that optimizing diet quality or restricting dietary intake could be harnessed as an adjunct therapy for CKD prevention or progression in susceptible individuals, thereby reducing the burden of CKD.

Plasma Pentosidine and Its Association with Mortality in Patients with Chronic Kidney Disease

Background

Circulating advanced glycated end-products (AGEs) including pentosidine accumulating in chronic kidney disease (CKD) patients due to retention and increased formation are thought to contribute to cardiovascular disease (CVD). Here we evaluated factors linked to increased plasma pentosidine and its association with mortality in patients with different stages of CKD and undergoing different treatments.

Methods

Plasma pentosidine, biomarkers of inflammation, oxidative stress and nutritional status were investigated in CKD 1–2 (n = 37), CKD 3–4 (n = 54), CKD 5 non-dialyzed (CKD5-ND; n = 386), peritoneal dialysis (PD; n = 74) and hemodialysis (HD; n = 195) patients. Factors predicting plasma pentosidine were analysed by multivariate regression analysis and mortality risk was assessed by GENMOD procedure.

Results

Plasma pentosidine levels, which were higher in CKD5-ND, PD and HD groups than in CKD 1–2 group, were significantly lower in PD than in HD patients, and not different between PD patients and CKD5-ND patients. Pentosidine associated inversely with glomerular filtration rate (GFR), and additionally in PD with 8-hydroxy-2‘-deoxyguanosine (8-OHdG), and interleukin 6 (IL-6); in HD with age, IL-6 and body mass index (BMI); in CKD5-ND with age, 8-OHdG, IL-6, high-sensitive C-reactive protein (hsCRP), and soluble vascular cell adhesion protein-1 (sVCAM-1); in CKD 3–4 with 8-OHdG and sVCAM-1; and in CKD 1–2 with age and sVCAM-1. In multivariate analysis, age (one standard deviation, 1-SD higher), malnutrition (subjective global assessment, SGA), oxidative stress (8-OHdG, 1-SD higher), and belonging to CKD5-ND, HD and PD cohorts associated with 1-SD higher pentosidine. In GENMOD, 1-SD higher pentosidine independently predicted all-cause mortality (relative risk, RR = 1.04; 95% confidence interval, CI, 1.01–1.08, p = 0.01) and CVD mortality (RR = 1.03; 95% CI, 1.01–1.06, p = 0.03) after adjusting for all confounders.

Conclusions

Plasma pentosidine is markedly elevated in CKD and associates with low GFR, oxidative stress and inflammation, and is an independent predictor of mortality in CKD patients.

Advanced glycation end product accumulation: a new enemy to target in chronic kidney disease?

PURPOSE OF REVIEW

The critical role of advanced glycation end products (AGEs) in the progression of chronic diseases and their complications has recently become more apparent. This review summarizes the recent contributions to the field of AGEs in chronic kidney disease (CKD).

RECENT FINDINGS

Over the past 3 decades, AGEs have been implicated in the progression of CKD, and specifically diabetic nephropathy. Although numerous in-vitro and in-vivo studies highlight the detrimental role of AGEs accumulation in tissue injury, few prospective human studies or clinical trials show that inhibiting this process ameliorates disease. Nonetheless, recent studies have focused on the novel mechanisms that contribute to end-organ injury as a result of AGEs accumulation, as well as novel targets of therapy in kidney disease.

SUMMARY

As the prevalence and the incidence of CKD rises in the United States, it is essential to identify therapeutic strategies that either delay the progression of CKD or improve mortality in this population. The focus of this review is on highlighting the recent studies that advance our current understanding of the mechanisms mediating AGEs-induced CKD progression, as well as novel treatment strategies that have the potential to abrogate this disease process.

VIDEO ABSTRACT

http://links.lww.com/CONH/A12.

Circulating soluble receptor for advanced glycation end product (sRAGE) and left ventricular hypertrophy in patients with chronic kidney disease (CKD)

BACKGROUND AND AIM

A decoy receptor for advanced glycation end product (soluble RAGE or sRAGE) is involved in left ventricular hypertrophy (LVH), and cardiomyopathy myocardial damage in experimental models and observational studies in patients with heart failure support the hypothesis that sRAGE attenuates the progression of heart disease and prevents death. Since sRAGE accumulates in patients with chronic kidney disease (CKD) we studied the relationship between plasma sRAGE with LVH in CKD patients.

METHODS AND RESULTS

We enrolled 142 patients with an average estimated glomerular filtration rate (eGFR) of 32 ml/min/1.73 m(2) and 49 healthy control individuals matched for age and gender. Plasma sRAGE was significantly higher in CKD patients than in healthy controls. Significant inverse relationships were found between sRAGE with left ventricular mass index (LVMI) and mean wall thickness (MWT) but no such associations were found in controls. A bootstrap re-sampling validation study confirmed the estimates of the link between sRAGE and these variables. On covariance analysis, the slopes of LVMI and MWT to sRAGE were significantly steeper in CKD patients than in the controls. On logistic regression analysis 1 log unit increase in sRAGE was associated with a 82% decrease in the odds for LVH in CKD patients.

CONCLUSIONS

sRAGE is an inverse marker of LVH in CKD patients. This association generates the hypothesis that the RAGE pathway could be a causal risk factor for LVH in this population and that blockade of this pathway by the endogenous decoy receptor sRAGE could attenuate LVH in the same population.

Role of advanced glycation endproducts and potential therapeutic interventions in dialysis patients

It has been nearly 100 years since the first published report of advanced glycation end products (AGEs) by the French chemist Maillard. Since then, our understanding of AGEs in diseased states has dramatically changed. Especially in the last 25 years, AGEs have been implicated in complications related to aging, neurodegenerative diseases, diabetes, and chronic kidney disease. Although AGE formation has been well characterized by both in vitro and in vivo studies, few prospective human studies exist demonstrating the role of AGEs in patients on chronic renal replacement therapy. As the prevalence of end-stage renal disease (ESRD) in the United States rises, it is essential to identify therapeutic strategies that either delay progression to ESRD or improve morbidity and mortality in this population. This article reviews the role of AGEs, especially those of dietary origin, in ESRD patients as well as potential therapeutic anti-AGE strategies in this population.

Advanced glycation end-products and the kidney

BACKGROUND

Advanced glycation end-products (AGEs) are increased in situations with hyperglycemia and oxidative stress such as diabetes mellitus. They are products of nonenzymatic glycation and oxidation of proteins and lipids. The kidney plays an important role in clearance and metabolism of AGEs.

METHODS

Medline and other relevant databases were searched. In addition, key review articles were scanned for relevant original publication. Finally, original data from our research group were also included.

RESULTS

Kidney podocytes and endothelial cells express specific receptors for AGEs. Their activation leads to multiple pathophysiological effects including hypertrophy with cell cycle arrest and apoptosis, altered migration, and generation of proinflammatory cytokines. AGEs have been primarily implicated in the pathophysiology of diabetic nephropathy and diabetic microvascular complications. AGEs are also involved in other primary renal diseases as well as in the development and progression of atherosclerosis. However, serum or plasma concentrations of AGEs do not correlate well with cardiovascular events in patients with chronic kidney disease (CKD). This is likely due to the fact that serum concentrations failed to correlate with AGEs deposited in target tissues. Several inhibitors of the AGE-RAGE axis are currently tested for various indications.

CONCLUSION

AGEs and their receptors are involved in the pathogenesis of vascular and kidney disease. The role of circulating AGEs as biomarkers for cardiovascular risk estimation is questionable. Whether putative inhibitors of AGEs will get the maturity for its therapeutic use in the future remains open.

Circulating soluble receptor of advanced glycation end product inversely correlates with atherosclerosis in patients with chronic kidney disease

The soluble receptor of advanced glycation end product (sRAGE) prevents vascular damage in experimental animal models, and observational studies in the general population support the hypothesis that sRAGE may exert a protective role on the vasculature. To test this in patients with chronic kidney disease, we determined the relationship between plasma sRAGE and carotid atherosclerosis in 142 patients with an average estimated glomerular filtration rate (eGFR) of 32 ml/min per 1.73 m(2) and 49 healthy control individuals matched for age and gender. Plasma sRAGE was significantly higher in patients with chronic kidney disease than in the control cohort. In an aggregate analysis of the patients and controls, there was a significant inverse relationship between eGFR and sRAGE, with a breakpoint in the regression line at 64 ml/min per 1.73 m(2). Significant inverse relationships were found for sRAGE to intima-media thickness and plaque number in the patients with chronic kidney disease, but no such associations were found in the controls. On covariance analysis, the slopes of intima-media thickness and plaque number to sRAGE were significantly steeper in patients with chronic kidney disease than in the controls. Furthermore, a significant interaction was found between sRAGE and smoking for predicting atherosclerotic plaques in patients with chronic kidney disease. The pathophysiological significance of this correlation will have to await more mechanistic studies.

Effects of exogenous crosslinking on in vitro tensile and compressive moduli of lumbar intervertebral discs

BACKGROUND

Collagen crosslinks may play a vital role in preventing ongoing disc degeneration. Age-accumulating crosslinks have been thought to increase brittleness and reduce fatigue resistance. However recent studies have demonstrated increases in fatigue resistance, joint stability and nutritional flow properties resulting from crosslink augmentation. In this study, multi-directional moduli of bovine lumbar intervertebral discs were measured in vitro, including circumferential tension, radial compression, axial tension, and axial compression in control and crosslinked specimens.

METHODS

Four types of annulus fibrosus specimens were dissected from control and crosslinked discs. Cross-sectional areas were measured using a non-contact laser measurement system and then four separate mechanical tests were conducted using a materials testing machine with custom-made loading fixtures.

FINDINGS

The circumferential specimens demonstrated the highest moduli in both low stiffness and linear elastic regions. After a crosslink treatment, the modulus increased more in circumferential tension compared to axial tension and more in axial compression compared to radial compression. Other tensile properties had higher increases in circumferential tension compared to axial tension after crosslinking.

INTERPRETATION

Assuming form follows function, circumferential tension is the predominant type of stress experienced by non-degenerated annulus fibrosus. The anisotropic mechanical properties of the annulus fibrosus is non-uniformly affected by crosslink augmentation. Dominant effects were in the directions with greater inherent stiffnesses. These results suggest some beneficial effects of crosslink augmentation on the mechanical properties of the annulus fibrosus: increase in ultimate strength, yield strength, toughness, and modulus in the principal stress directions.

Skin autofluorescence, a novel marker for glycemic and oxidative stress-derived advanced glycation endproducts: an overview of current clinical studies, evidence, and limitations

BACKGROUND

Advanced glycation endproducts (AGEs) predict long-term complications in agerelated diseases. However, there are no clinically applicable markers for measuring AGEs in vivo.

METHODS

We have recently introduced the AGE-Reader (DiagnOptics B.V., Groningen, The Netherlands) to noninvasively measure AGE accumulation in the human skin of the forearm, making use of the characteristic autofluorescence (AF) pattern that AGEs encompass. Skin AF is calculated as a ratio of mean intensities detected from the skin between 420-600 nm and 300-420 nm. It correlates with collagen-linked fluorescence and specific skin AGE levels from skin biopsies in diabetes, renal failure, and control subjects. Skin AF levels are increased in patients with diabetes and renal failure and are associated with the presence of vascular complications. Additionally, skin AF is strongly related to the progression of coronary heart disease and mortality, independently of traditional risk factors. Since skin pigmentation might influence skin AF, we have investigated the relation of relative skin reflectance (R%) to skin AF in subjects with varying skin phototypes (SPT).

RESULTS

The data presented in this article suggest that only in subjects with an SPT of V and VI or R% <12%, no reliable measurement can be performed. Therefore, the current prototype of the AGE-Reader is suitable for subjects with SPT I-IV or R% >12%, and more research is needed for a broader application.

CONCLUSION

The AGE-Reader is useful as a noninvasive clinical tool for assessment of risk for long-term vascular complications in diabetes and in other conditions associated with AGE accumulation.

The Advanced Glycation End Product Nε-Carboxymethyllysine Is Not a Predictor of Cardiovascular Events and Renal Outcomes in Patients With Type 2 Diabetic Kidney Disease and Hypertension

BACKGROUND

Advanced glycation end products (AGEs) are implicated in the pathogenesis of vascular damage, especially in patients with diabetes and renal insufficiency. The oxidatively formed AGE N(epsilon)-carboxymethyllysine (CML) is thought to be a marker of oxidative stress.

METHODS

Four hundred fifty patients with type 2 diabetes and nephropathy from the Irbesartan in Diabetic Nephropathy Trial cohort (mean age, 58 +/- 8.2 years; 137 women, 313 men) with a mean glomerular filtration rate of 48.2 mL/min (0.80 mL/s; Modification of Diet in Renal Disease formula) were followed up for 2.6 years. Serum CML was measured by using an enzyme-linked immunosorbent assay. Relationships between CML levels, traditional risk factors, and cardiovascular and renal events were tested in Cox proportional hazards models.

RESULTS

Mean serum CML level was 599.9 +/- 276.0 ng/mL, and mean hemoglobin A1c level was 7.5% +/- 1.6%. One hundred forty-three first cardiovascular events occurred during follow-up; 74 patients died, 44 of cardiovascular causes. Final multivariate analysis showed age (relative risk [RR], 1.87; confidence interval [CI], 1.13 to 3.11; P = 0.016 for the highest compared with lowest quartile), history of prior cardiovascular events (RR, 1.96; CI, 1.35 to 2.85; P < 0.0005), and 24-hour urinary albumin-creatinine ratio (RR, 1.29; CI, 1.11 to 1.50 per doubling; P < 0.0005) to be independent risk factors for a first cardiovascular event, but not CML level. CML level also did not correlate significantly with renal outcome.

CONCLUSION

Serum CML level could not be identified as an independent risk factor for cardiovascular or renal outcomes in the examined population. This suggests that traditional risk factors might have a more important role for these end points or that other AGE compounds, as well as tissue AGE levels, might be of greater relevance compared with serum levels, which remains open to further study.

Genomic damage in chronic renal failure--potential therapeutic interventions

In end-stage renal failure, genomic damage is enhanced. This has been shown both in the predialysis and dialysis phase by various biomarkers, such as micronuclei frequency and single cell gel electrophoresis in lymphocytes as well as with 8-hydroxy-2'-deoxyguanosine in leukocytes. There are also data about mitochondrial DNA deletions and chromosomal abnormalities. Genomic damage may be induced by a multitude of toxic factors and mutagens, in particular via enhanced generation of reactive oxygen species. In in vitro studies, incubation of tubular cells with various AGEs (carboxymethyllysine-BSA, AGE-BSA, and methylglyoxal-BSA) and angiotensin II resulted in a marked DNA damage. Coincubation with various antioxidants as well as the angiotensin II receptor blocker, candesartan, suppressed the toxic action. Moreover, an improved uremic state by daily hemodialysis ameliorated the genomic damage in lymphocytes, as compared to patients on conventional hemodialysis.

Resolving controversies regarding hemodiafiltration versus hemodialysis: the Dutch Convective Transport Study

Hemodialysis patients suffer from a high incidence of cardiovascular disease. Among the many predisposing factors, such as high blood pressure, dyslipidemia, and fluid overload, the accumulation of high molecular weight uremic toxins, the so-called middle molecules, may play an important role. Since convective therapies such as online hemodiafiltration have a better clearance profile for these compounds than standard hemodialysis, it has been suggested that these dialysis strategies may reduce cardiovascular morbidity and mortality. As reliable data on these issues are not available, the Dutch Convective Transport Study (CONTRAST) was recently initiated. This prospective randomized trial was designed to compare online hemodiafiltration with low-flux hemodialysis with respect to cardiovascular morbidity and mortality.

Serum Carboxymethyllysine Predicts Mortality in Hemodialysis Patients

BACKGROUND

Hemodialysis patients show markedly elevated serum levels of advanced glycation end products (AGEs). AGEs have been implicated in the pathogenesis of vascular damage and are regarded as a class of uremic toxins. However, to date, serum AGE level could not be identified as an independent predictor of mortality. The aim of the present study is to test whether serum level of the AGE carboxymethyllysine (CML) predicts all-cause or cardiovascular mortality in hemodialysis patients.

METHODS

Serum total CML concentration was measured by means of enzyme-linked immunosorbent assay in 154 patients receiving long-term hemodialysis. Patients were divided into groups with serum CML levels less and greater than the median (23.8 ng/mg protein). All-cause and cardiovascular mortality were registered during a follow-up of 51 months. The relationship between serum CML level and mortality was tested by using Kaplan-Meier and Cox regression analyses.

RESULTS

In the group with low serum CML levels, 38% of patients died during the follow-up period; 23% had a cardiovascular cause of death. However, in the group with high CML levels, 58% died (P < 0.01) and 36% had a cardiovascular cause of death (P < 0.05). The following parameters proved to be independent risk factors of all-cause mortality: age (hazard ratio, 1.056; P < 0.001), preexisting vascular disease (hazard ratio, 2.53; P < 0.05), smoking (hazard ratio, 3.03; P < 0.005), high serum CML level (hazard ratio, 1.776; P < 0.05), and C-reactive protein level (hazard ratio, 1.017; P < 0.001).

CONCLUSION

The AGE CML may contribute to increased mortality in patients with uremia.

Advanced glycation end products and the kidney

Advanced glycation end products (AGEs) are a heterogeneous group of protein and lipids to which sugar residues are covalently bound. AGE formation is increased in situations with hyperglycemia (e.g., diabetes mellitus) and is also stimulated by oxidative stress, for example in uremia. It appears that activation of the renin-angiotensin system may contribute to AGE formation through various mechanisms. Although AGEs could nonspecifically bind to basement membranes and modify their properties, they also induce specific cellular responses including the release of profibrogenic and proinflammatory cytokines by interacting with the receptor for AGE (RAGE). However, additional receptors could bind AGEs, adding to the complexity of this system. The kidney is both: culprit and target of AGEs. A decrease in renal function increases circulating AGE concentrations by reduced clearance as well as increased formation. On the other hand, AGEs are involved in the structural changes of progressive nephropathies such as glomerulosclerosis, interstitial fibrosis, and tubular atrophy. These effects are most prominent in diabetic nephropathy, but they also contribute to renal pathophysiology in other nondiabetic renal diseases. Interference with AGE formation has therapeutic potential for preventing the progression of chronic renal diseases, as shown from data of animal experiments and, more recently, the first clinical trials.

Kidney transplantation halts cardiovascular disease progression in patients with end-stage renal disease

Morbidity and mortality from cardiovascular disease have a devastating impact on patients with chronic kidney disease (CKD) and end-stage renal disease. Renal function decline in itself is thought to be a strong risk factor for cardiovascular disease (CVD). In this study, we investigated the hypothesis that the elevated CV mortality in kidney transplant patients is due to the preexisting CVD burden and that restoring renal function by a kidney transplant might over time lower the risk for CVD. We analyzed 60,141 first-kidney-transplant patients registered in the USRDS from 1995 to 2000 for the primary endpoint of cardiac death by transplant vintage and compared these rates to all 66813 adult kidney wait listed patients by wait listing vintage, covering the same time period. The CVD rates peaked during the first 3 months following transplantation and decreased subsequently by transplant vintage when censoring for transplant loss. This trend could be shown in living and deceased donor transplants and even in patients with end-stage renal disease secondary to diabetes. In contrast, the CVD rates on the transplant waiting list increased sharply and progressively by wait listing vintage. Despite the many mechanisms that may be in play, the enduring theme underlying rapid progression of atherosclerosis and cardiovascular disease in renal failure is the loss of renal function. The data presented in this paper thus suggest that the development or progression of these lesions could be ameliorated by restoring renal function with a transplant.

Potential cardiovascular risk factors in chronic kidney disease: AGEs, total homocysteine and metabolites, and the C-reactive protein

BACKGROUND

Total homocysteine (tHcy) and advanced glycation end-products (AGEs) are implicated in the pathogenesis of vascular damage. This study aimed to investigate whether elevated serum levels of the AGEs pentosidine, N(epsilon)-carboxymethyllysine (CML) and imidazolone; tHcy, cystathionine, methylmalonic acid (MMA), and 2-methylcitric acid (2-MCA), as well as C-reactive protein (CRP), are related to a higher risk for cardiovascular events.

METHODS

A total of 232 patients with chronic kidney diseases (mean age 57.6 +/- 13.1 years, 82 female and 150 male); 99 with chronic renal failure (CRF), 84 maintenance hemodialysis patients and 49 renal transplant recipients were followed for 2 years. The relationship between the parameters of interest, conventional risk factors and elevated levels of CRP with cardiovascular events was tested in all subjects by the Cox proportional hazards model.

RESULTS

Mean serum levels of AGEs, tHcy, and of the metabolites were found to be significantly increased in all three groups compared to the healthy subjects (P < 0.01, respectively). Fifty-three cardiovascular events occurred during follow-up; a total of 40 patients died. Final multivariate analysis showed diabetes (RR 2.06, 95% CI 1.17-3.60, P= 0.013), end-stage renal disease (ESRD) (RR 4.88, 95% CI 2.40-9.89, P < 0.001) and elevated CRP levels (RR 2.00, 95% CI 1.11-3.60, P= 0.021) as independent risk factors for cardiovascular events.

CONCLUSION

Data from a group consisting of patients with CRF, patients undergoing maintenance hemodialysis treatment, and renal transplant recipients provide evidence that conventional risk factors such as the presence of diabetes, ESRD, as well as elevated levels of the considered risk factor CRP, seem to play a more important role for cardiovascular outcome in patients with chronic kidney disease than elevated levels of AGEs, tHcy, and related metabolites. The evidence suggests that routine CRP measurement can be recommended in cases of chronic renal insufficiency.