End-stage renal disease--not an equal opportunity disease: the role of genetic polymorphisms

Polymorphism related to cardiovascular risk in hemodialysis subjects: a systematic review

Cardiovascular disease (CVD) is one of the leading causes of mortality in hemodialysis (HD) subjects. In addition to the traditional risk factors that are common in these individuals, genetic factors are also involved, with emphasis on single nucleotide polymorphs (SNPs). In this context, the present study aims to systematically review the studies that investigated the polymorphisms associated with cardiovascular risk in this population. In general, the SNPs present in HD individuals are those of genes related to inflammation, oxidative stress and vascular calcification, also able of interfering in the cardiovascular risk of this population. In addition, polymorphisms in genes related to recognized risk factors for CVD, such as dyslipidemia, arterial hypertension and left ventricular hypertrophy, also influence cardiovascular morbidity and mortality.

Current epigenetic aspects the clinical kidney researcher should embrace

Chronic kidney disease (CKD), affecting 10–12% of the world’s adult population, is associated with a considerably elevated risk of serious comorbidities, in particular, premature vascular disease and death. Although a wide spectrum of causative factors has been identified and/or suggested, there is still a large gap of knowledge regarding the underlying mechanisms and the complexity of the CKD phenotype. Epigenetic factors, which calibrate the genetic code, are emerging as important players in the CKD-associated pathophysiology. In this article, we review some of the current knowledge on epigenetic modifications and aspects on their role in the perturbed uraemic milieu, as well as the prospect of applying epigenotype-based diagnostics and preventive and therapeutic tools of clinical relevance to CKD patients. The practical realization of such a paradigm will require that researchers apply a holistic approach, including the full spectrum of the epigenetic landscape as well as the variability between and within tissues in the uraemic milieu.

Relative risk for cardiovascular morbidity in hemodialysis patients regarding gene polymorphism for IL-10, IL-6, and TNF

Uremia-related inflammation is prone to be a key factor to explain high cardiovascular morbidity in hemodialysis patients. Genetic susceptibility may be of importance, including IL-10, IL-6, and TNF. The aim was to analyze IL-10, IL-6, and TNF gene polymorphisms in a group of hemodialysis patients and to correlate the findings with cardiovascular morbidity. This study included 169 patients on regular hemodialysis at Zvezdara University Medical Center. Gene polymorphisms for IL-10, IL-6 and TNF were determined using PCR. These findings were correlated with the cardiovascular morbidity data from patient histories. Heterozygots for IL-10 gene showed significantly lower incidence of cardiovascular events (p = 0.05) and twice lower risk for development of myocardial infarction, but experienced twice higher risk for left ventricular hypertrophy. Regarding TNF gene polymorphism, patients with A allele had 1.5-fold higher risk for cerebrovascular accident and cardiovascular events and 2-fold higher risk for hypertension and peripheral vascular disease. Patients with G allele of IL-6 gene experienced 1.5-fold higher risks for cerebrovascular accident. We need studies with larger number of patients for definitive conclusion about the influence of gene polymorphisms on cardiovascular morbidity in hemodialysis patients and its importance in everyday clinical practice.

Developments in renal pharmacogenomics and applications in chronic kidney disease

Chronic kidney disease (CKD) has shown an increasing prevalence in the last century. CKD encompasses a poor prognosis related to a remarkable number of comorbidities, and many patients suffer from this disease progression. Once the factors linked with CKD evolution are distinguished, it will be possible to provide and enhance a more intensive treatment to high-risk patients. In this review, we focus on the emerging markers that might be predictive or related to CKD progression physiopathology as well as those related to a different pattern of response to treatment, such as inhibitors of the renin–angiotensin system (including angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers; the vitamin D receptor agonist; salt sensitivity hypertension; and progressive kidney-disease markers with identified genetic polymorphisms). Candidate-gene association studies and genome-wide association studies have analyzed the genetic basis for common renal diseases, including CKD and related factors such as diabetes and hypertension. This review will, in brief, consider genotype-based pharmacotherapy, risk prediction, drug target recognition, and personalized treatments, and will mainly focus on findings in CKD patients. An improved understanding will smooth the progress of switching from classical clinical medicine to gene-based medicine.

A genetic predisposition to produce low levels of IL-10 is related to depressive symptoms: a pilot study of patients with end stage renal disease

OBJECTIVE

Heightened levels of inflammation may be associated with an increased risk of depression, particularly among those with inflammatory medical conditions. Although elevated rates of both systemic inflammation and depression have been documented among patients with end stage renal disease (ESRD), the link between these factors has received little empirical evaluation. The goal of this pilot study was to investigate the association between cytokine gene polymorphisms (that are known to influence pro- and anti-inflammatory cytokine production) and depressive symptoms among patients with ESRD.

METHODS

Ninety-three patients with ESRD completed the Beck Depression Inventory-II and the disease-related symptom subscale of the Kidney Disease Quality of Life short form. Patients were genotyped for eight single nucleotide polymorphisms in genes coding for pro-inflammatory (TNF-α, IL-6, IFN-γ) and anti-inflammatory (IL-10, TGF-β1) cytokines.

RESULTS

Regression analyses indicated that patients with the A/A genotype for the IL-10 -1082 polymorphism (lower IL-10 producers) reported significantly greater depressive symptoms than G allele carriers (higher IL-10 producers; b = 0.22, P = 0.011), even after controlling for relevant covariates.

CONCLUSION

These findings provide some support for cytokine theories of depression in the medically ill, and specifically for the protective role of anti-inflammatory processes. Further research is needed to confirm these preliminary results and to explore the possibility of identifying subtypes of depressed patients based on inflammatory profiles, and those who may benefit from anti-inflammatory therapies.

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) and mortality in end-stage renal disease

BACKGROUND

Elevated macrophage inhibitory cytokine-1 (MIC-1/GDF15) levels in serum mediate anorexia and weight loss in some cancer patients and similarly elevated levels occur in chronic kidney disease (CKD). Serum MIC-1/GDF15 is also elevated in chronic inflammatory diseases and predicts atherosclerotic events independently of traditional risk factors. The relationship between chronic inflammation, decreasing body mass index (BMI) and increased mortality in CKD is not well understood and is being actively investigated. MIC-1/GDF15 may link these features of CKD.

METHODS

Cohorts of incident dialysis patients from Sweden (n = 98) and prevalent hemodialysis patients from the USA (n = 381) had serum MIC-1/GDF15, C-reactive protein (CRP) levels and BMI measured at study entry. Additional surrogate markers of nutritional adequacy, body composition and inflammation were assessed in Swedish patients. Patients were followed for all-cause mortality.

RESULTS

In the Swedish cohort, serum MIC-1/GDF15 was associated with decreasing BMI, measures of nutrition and markers of oxidative stress and inflammation. Additionally, high serum MIC-1/GDF15 levels identified patients with evidence of protein-energy wasting who died in the first 3 years of dialysis. The ability of serum MIC-1/GDF15 to predict mortality in the first 3 years of dialysis was confirmed in the USA cohort. In both cohorts, serum MIC-1/GDF15 level was an independent marker of mortality when adjusted for age, CRP, BMI, history of diabetes mellitus and/or cardiovascular disease and glomerular filtration rate or length of time on dialysis at study entry.

CONCLUSIONS

MIC-1/GDF15 is a novel independent serum marker of mortality in CKD capable of significantly improving the mortality prediction of other established markers. MIC-1/GDF15 may mediate protein-energy wasting in CKD and represent a novel therapeutic target for this fatal complication.

Genetic causation of neointimal hyperplasia in hemodialysis vascular access dysfunction

The major cause of hemodialysis vascular access failure is venous stenosis resulting from neointimal hyperplasia. Genetic factors have been shown to be associated with cardiovascular disease and peripheral vascular disease (PVD) in the general population. Genetic factors may also play an important role in vascular access stenosis and development of neointimal hyperplasia by affecting pathways that lead to inflammation, endothelial function, oxidative stress, and vascular smooth muscle proliferation. This review will discuss the role of genetics in understanding neointimal hyperplasia development in hemodialysis vascular access dysfunction and other disease processes with similar neointimal hyperplasia development such as coronary artery disease and PVD.

Assessment of matrix Gla protein, Klotho gene polymorphisms, and oxidative stress in chronic kidney disease

Increased vascular calcification and oxidative stress are considered as extra renal risk factors at the pathogenesis cardiovascular events in chronic kidney disease (CKD). We investigated matrix Gla protein (MGP) (T-138C, Glu60X, Thr83Ala) and Klotho (Cys370Ser) gene polymorphisms, serum MGP levels, and oxidative stress status of 84 CKD patients and 37 healthy controls. The MGP gene Glu60X and Thr83Ala polymorphisms were significantly associated with CKD. The correlation between T-138C genotype of MGP gene, Cys370Ser genotype of Klotho gene, and CKD was not significant (p > 0.05). At the haplotype analysis, the combination of the X allele of Glu60X and the Thr allele of Thr83Ala showed a significantly increased risk of CKD (p < 0.05). X allele, Thr allele, and C allele of T-138C were associated with diabetes mellitus and CKD phenotypes occurring concurrently (p < 0.01). Serum zinc levels were significantly low in end-stage renal disease (ESRD) patients (p = 0.0001). The total comet score frequency of ESRD patients was higher than that of control group (p < 0.05). The urinary 8-hydroxy-2'-deoxyguanosine levels were significantly high in CKD patients (p < 0.05). According to this study, analyzing the distribution of MGP gene and oxidative stress status would be very informative in order to detect their role at CKD.

The FTO gene polymorphism is associated with end-stage renal disease: two large independent case-control studies in a general population

BACKGROUND

Genome-wide association studies identified the FTO (fat mass and obesity gene) gene as an important determinant of body weight. More recently, the FTO gene was reported to be associated with other outcomes, including major risk factors for chronic kidney disease (CKD). We investigated the role of this gene in the risk of end-stage renal disease (ESRD) caused by CKD.

METHODS

We conducted two large population-based case-control studies of ESRD. Study 1 compared 984 haemodialysed patients with ESRD with 2501 participants in the Czech post-MONICA study; Study 2 compared 1188 patients included in a kidney transplantation programme for ESRD with 6681 participants in the Czech HAPIEE study. The frequencies of the FTO rs17817449 single nucleotide polymorphism genotype were compared between cases and controls.

RESULTS

The FTO rs17817449 genotype was significantly associated with CKD in both studies (P-values 0.00004 and 0.006, respectively). In the pooled data, the odds ratios of CKD for GG and GT, versus TT genotype, were 1.37 (95% confidence interval 1.20-1.56) and 1.17 (1.05-1.31), respectively (P for trend <0.0001). Among haemodialysed and kidney transplant patients, the onset of ESRD in GG homozygotes was 3.3 (P = 0.012) and 2.5 (P = 0.032) years, respectively, earlier than in TT homozygotes.

CONCLUSIONS

These two large independent case-control studies in the general population found robust associations between the FTO rs17817449 polymorphism and the ESRD. The results suggest that the morbidities associated with the FTO gene include CKD.

Inflammation gene variants and susceptibility to albuminuria in the U.S. population: analysis in the Third National Health and Nutrition Examination Survey (NHANES III), 1991-1994

BACKGROUND

Albuminuria, a common marker of kidney damage, serves as an important predictive factor for the progression of kidney disease and for the development of cardiovascular disease. While the underlying etiology is unclear, chronic, low-grade inflammation is a suspected key factor. Genetic variants within genes involved in inflammatory processes may, therefore, contribute to the development of albuminuria.

METHODS

We evaluated 60 polymorphisms within 27 inflammatory response genes in participants from the second phase (1991-1994) of the Third National Health and Nutrition Examination Survey (NHANES III), a population-based and nationally representative survey of the United States. Albuminuria was evaluated as logarithm-transformed albumin-to-creatinine ratio (ACR), as ACR ≥ 30 mg/g, and as ACR above sex-specific thresholds. Multivariable linear regression and haplotype trend analyses were conducted to test for genetic associations in 5321 participants aged 20 years or older. Differences in allele and genotype distributions among non-Hispanic whites, non-Hispanic blacks, and Mexican Americans were tested in additive and codominant genetic models.

RESULTS

Variants in several genes were found to be marginally associated (uncorrected P value < 0.05) with log(ACR) in at least one race/ethnic group, but none remained significant in crude or fully-adjusted models when correcting for the false-discovery rate (FDR). In analyses of sex-specific albuminuria, IL1B (rs1143623) among Mexican Americans remained significantly associated with increased odds, while IL1B (rs1143623), CRP (rs1800947) and NOS3 (rs2070744) were significantly associated with ACR ≥ 30 mg/g in this population (additive models, FDR-P < 0.05). In contrast, no variants were found to be associated with albuminuria among non-Hispanic blacks after adjustment for multiple testing. The only variant among non-Hispanic whites significantly associated with any outcome was TNF rs1800750, which failed the test for Hardy-Weinberg proportions in this population. Haplotypes within MBL2, CRP, ADRB2, IL4R, NOS3, and VDR were significantly associated (FDR-P < 0.05) with log(ACR) or albuminuria in at least one race/ethnic group.

CONCLUSIONS

Our findings suggest a small role for genetic variation within inflammation-related genes to the susceptibility to albuminuria. Additional studies are needed to further assess whether genetic variation in these, and untested, inflammation genes alter the susceptibility to kidney damage.

CRP polymorphisms and progression of chronic kidney disease in African Americans

BACKGROUND AND OBJECTIVES

Chronic inflammation may play a role in chronic kidney disease (CKD) progression. CRP gene polymorphisms are associated with serum C-reactive protein (CRP) concentrations. It is unknown if CRP polymorphisms are associated with CKD progression or modify the effectiveness of anti-hypertensive therapy in delaying CKD progression.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We genotyped 642 participants with CKD from the African American Study of Kidney Disease and Hypertension (AASK), selecting five tag polymorphisms: rs2808630, rs1205, rs3093066, rs1417938, and rs3093058. We compared the minor allele frequencies (MAF) of single nucleotide polymorphisms (SNPs) in AASK to MAFs of African Americans from NHANES III. Among AASK participants, we evaluated the association of SNPs with CRP levels and prospectively with a composite: halving the GFR, ESRD, or death.

RESULTS

The MAF was higher for the rs2808630_G allele (P = 0.03) and lower for the rs1205_A allele (P = 0.03) in the AASK compared with NHANES III. Among AASK participants, the rs3093058_T allele predicted higher CRP concentrations (P < 0.0001) but not CKD progression. The rs2808630_GG genotype was associated with higher risk of the composite endpoint compared with the AA genotype (P = 0.002). Participants with the rs2808630_GG genotype on angiotensin converting enzyme inhibitors (ACEIs) versus beta blockers had increased risk of progression (P = 0.03).

CONCLUSION

CRP SNPs that were associated with higher levels of CRP did not predict CKD progression. The rs2808630_GG genotype was associated with higher risk of CKD progression, and in patients with this genotype, ACEIs did not slow progression.

Apolipoprotein E polymorphism in hemodialyzed patients and healthy controls

A possible association between end-stage renal disease (ESRD) and apolipoprotein E (APOE) polymorphism was found in some but not all studies. We have analyzed the APOE genotypes in 995 hemodialyzed patients (cases) and a sample of 6242 healthy individuals (controls) in the Czech Republic. There was a statistically significant difference in the frequency of APOE alleles between cases and controls, with more carriers of the APOE2 allele in ESRD patients (15.9%) than in controls (12.2%) (P = 0.005). The odds ratio of ESRD for the APOE2 allele, compared with APOE3E3 homozygotes, was 1.37 (95% confidence interval 1.13-1.67). The strength of the association increased with the time spent on hemodialysis: the odds ratio of all-cause ESRD in patients dialyzed for eight or more years was 1.27 (0.94-1.71), for 1-8 years 1.41 (1.09-1.81), and less than 1 year (nonsurvivors) 1.94 (0.88-4.18). This study suggests that the APOE2 allele is a possible genetic risk factor for all-cause ESRD in Caucasians.

Prevalence of methylenetetrahydrofolate gene (MTHFR) C677T polymorphism among chronic hemodialysis patients and its association with cardiovascular disease: a cross-sectional analysis

INTRODUCTION

Cardiovascular disease (CVD) remains the main cause of morbidity and mortality in end stage renal disease (ESDR) patients. A common C-T mutation at nucleotide position 677 (C677T) has been identified in the gene coding for methylenetetrahydrofolate reductase (MTHFR), which is involved in the remethylation of homocysteine (Hcy). The C677T mutation decreases MTHFR activity, tends to increase Hcy concentrations in individuals who are homozygous for the T/T genotype, and may predispose to CVD. Recent reports suggested that the T/T genotype may predispose type 2 diabetic and hypertensive patients to the development of progressive renal insufficiency. The aim of this cross-sectional study is to analyze the prevalence of the MTHFR C677T gene polymorphism among a group of chronic dialysis patients in comparison to age- and gender-matched controls. We also examined the possible association between CVD and MTHFR gene mutation in this group of patients.

PATIENTS AND METHODS

Fifty chronic hemodialysis patients were included in the study. They were 29 males and 21 females with a mean age of 41.57 +/- 11.76 years. Three patients (6%) were diabetic (type 2). Mean duration of dialysis was 6.4 +/- 3.2 years (range 1-15 years). CVD was defined as being present if there was a medical history of coronary artery disease, cerebrovascular stroke or transient ischemic attacks. MTHFR C677T gene polymorphism was analyzed by PCR in order to discriminate between homozygous (C/C and T/T) and heterozygous (C/T) genotypes. We also measured serum vitamin B(12), folate, total plasma Hcy (tHcy), lipid profile and serum albumin concentrations in the study group. Thirty healthy subjects (16 males and 14 females with mean age of 37.42 +/- 7.63 years) served as healthy controls.

RESULTS

Thirteen patients (26%) experienced at least one cardiovascular event: two (4%) had a history of ischemic cerebrovascular disease, 13 (26%) had coronary artery disease, and one patient (2%) had myocardial infarction. The C677T mutation of MTHFR was not found to be different in hemodialysis patients and healthy controls. Thirty dialysis patients (60%) and 19 healthy subjects (63.33%) had only the wild-type allele (C/C), 16 dialysis patients (32%) and nine healthy controls (30%) had one T allele (C/T), and four dialysis patients (8%) and two healthy controls (6.67%) had two copies (T/T) of the T allele. There were no differences between patients with the three different MTHFR genotypes (C/C, C/T, T/T) regarding cardiovascular events or cardiovascular risk factors. Age, gender, percentages of diabetic and hypertensive patients, serum folate, vitamin B(12), lipid profile, and tHcy levels were not significantly different between the three groups (P > 0.05). Hemodialysis patients with CVD were significantly older compared to those without CVD (P = 0.02). Diabetes status was significantly associated with cardiovascular events (P = 0.01).

CONCLUSIONS

In the dialysis population that we studied, MTHFR C677T gene polymorphism occurred in a pattern similar to that seen for age- and gender-matched healthy controls. No significant association was detected between the T/T genotype and CVD in dialysis patients. Plasma total homocysteine levels were not affected by mutation of the gene coding for MTHFR, and this may be explained by the normal serum folate and vitamin B(12) levels found in the study group.

Influence of cytokine and intercellular adhesion molecule-1 gene polymorphisms on acute rejection in pediatric renal transplantation

Immune response regulation by cytokines is a key to understanding AGR. The influence of the functional polymorphisms in genes coding for TNF-alpha (-308G > A), IL-10 (-819C > T, and -1082A > G), IFN-gamma [(CA)n], TGF-beta1 (+869T > C), and iCAM-1 (R241G and E469K), in addition to HLA and gender matching on the presentation of AGR in 51 pediatric renal recipients during a 36-month post-transplantation follow-up were analyzed. Also, donors and a control group were genotyped. All groups were within Hardy-Weinberg equilibrium for all polymorphisms except IL-10-819C > T and TNF-alpha (p < 0.005 and p < 0.01, respectively) in recipients. Transplants with gender mismatch showed a higher risk for AGR than those between individuals with gender match (OR, 4.227; p = 0.010). Recipients with a high-production compared with low-production TNF-alpha allele experienced earlier AGR (p = 0.030), and those with high-production alleles of both TNF-alpha and IFN-gamma showed a further increased risk (OR = 11.129, p = 0.024). These findings support the notion that a single genotype cannot by itself explain an event as complex as AGR. The sum or combination of different specific alleles of these genes could better account for the immune response to an allograft.

Ghrelin variants influence development of body mass index and plasma levels of total cholesterol in dialyzed patients

BACKGROUND

Ghrelin is an endogenous hormone expressed predominantly in the stomach. Ghrelin controls growth hormone secretion and also affects the body's energy balance. We analyzed the association of ghrelin variants with body mass index (BMI), albumin as a marker of malnutrition and plasma lipids as risk factors for atherosclerosis in hemodialyzed patients, in whom malnutrition and accelerated atherosclerosis are common complications.

METHODS

Ghrelin variants Arg51>Gln and Leu72> Met were analyzed by PCR-RFLP in 210 hemodialyzed patients, prospectively followed up for 15 months. Changes in body mass index, triglycerides, total cholesterol and albumin over time (after 3, 6, 9, 12 and 15 months of dialysis) were analyzed in subgroups divided according to ghrelin genotypes.

RESULTS

Carriers of at least one of the Gln51 and Met72 alleles lost body weight more quickly than Arg51Arg/Leu72Leu homozygotes (p<0.01). Carriers of the Gln51 allele were at higher risk of developing high cholesterol levels (p<0.01).

CONCLUSIONS

Common ghrelin variants may have an effect on changes in biochemical and anthropometric parameters in hemodialyzed patients over time and could be used in the future to plan individualized therapy.

Is low-frequency distribution of TGF-beta genotype associated with increased risk for end-stage renal disease?

End-stage renal disease has been associated with an inflammatory state. TGF-beta plays a critical role in antiinflammation counteracting inflammatory cytokines, wound healing, and tissue repair. We, therefore, speculated the protective role of TGF-beta in renal inflammation rather than inducing fibrosis. Three polymorphisms of TGF-beta (713-8delC), i.e., C deletion in intron sequence 8 base prior to exon-5 by PCR-RFLP and codon-10, Leu/Pro, and codon-25, Arg/Pro by Amplification Refractory Mutation System (ARMS-PCR) techniques were genotyped in 228 end-stage renal disease (ESRD) patients and 180 controls. Linkage disequilibrium (LD) and haplotype analysis was performed by Arlequin software. Our data showed positive association between codon-10 polymorphism and ESRD risk (P < 0.001; OR 4.845, 95% CI 2.57-9.11 for Pro/Pro). However, genotype frequencies were comparable in patients and controls for 713-8delC, while in the case of codon-25, a trend of higher frequency of Pro/Pro genotype (16.2% versus 10.0%) was observed but the P-value did not reach significant (P = 0.187). Significant association of codon-10 Pro/Pro was observed in patients with glomerulonephritis (P = 0.001; OR 4.138, 95%CI 2.1-8.13). LD was found significant between codon-10 and 25 (P = 0.021). Haplotype "Pro-Pro" showed 1.8-fold higher risk for ESRD (p = 0.003; OR = 1.867, 95%CI = 1.229-2.838). A combined analysis of the effect of TGF-beta (codon-10) with C-deletion and codon-25 showed significant difference for TGF-beta(10)-TGF-beta(C-del) (P = 0.010). In conclusion, the present study suggests that low-producing genotype (Pro/Pro) of TGF-beta (codon-10) polymorphism is associated with ESRD. Haplotype analysis further suggested that "Pro-Pro" (low producer) is associated with higher risk for ESRD. Thus, high-producing genotype of TGF-beta may be beneficial and may play a potential role in the resolution of renal inflammation.

Use of Single-Nucleotide Polymorphisms in the Search for Genetic Modifiers of the Uremic Phenotype

As the modern nephrology community continues to be burdened with growing numbers of patients with end-stage renal disease (ESRD) and exceptionally high mortality rates, it is obvious that progress in the development of preventive and therapeutic strategies has not been sufficient. This urges nephrologists to focus on the underlying mechanisms for ESRD morbidity and mortality, and in particular on cardiovascular disease (CVD), which is the major contributor to premature death in this patient group. The high prevalence of inflammation, vascular ossification, and oxidative stress in ESRD predisposes these patients to CVD. Because genetic risk factors may modulate the pathophysiologic response, genotype-phenotype association studies may provide ways of predicting individual disease progression and may shed some light on key regulatory pathways. Indeed, recent genetic association studies show that polymorphisms in candidate genes related to inflammatory signaling, vascular ossification, and oxidative stress response influence the uremic phenotype. DNA polymorphisms may also be used as nonconfounded tools in observational studies conducted to test causality, as stated by the mendelian randomization approach. To date, the collection of genetic data is no longer a limitation because genetic information is easily accessible in public databases and high-throughput genotyping technologies are available. Advanced bioinformatic tools are now warranted to facilitate the integration of accumulating genetic information with clinical and biochemical end points and, finally, to implement genotype-phenotype data in the care of patients with renal failure to better identify patients at high risk and to design novel personalized therapeutic and preventive strategies.

Inflammation in end-stage renal disease: the hidden enemy

Cardiovascular disease (CVD) remains the major cause of morbidity and mortality in end-stage renal disease (ESRD) patients. As traditional risk factors cannot alone explain the unacceptable high prevalence and incidence of CVD in this high-risk population, inflammation (interrelated to insulin resistance, oxidative stress, wasting and endothelial dysfunction) has been suggested to be a significant contributor. Indeed, several different inflammatory biomarkers, such as high sensitivity C-reactive protein (hs-CRP), have been shown to independently predict mortality in ESRD patients. As CRP is so strongly associated with vascular disease it has been suggested that this hepatic-derived protein is not only a marker, but also a mediator, of vascular disease. Although in vitro data from studies on endothelial cells, monocytes-macrophages and smooth muscle cells support a direct role for CRP in atherogenesis, data from studies performed in vivo have been controversial. The causes of the highly prevalent state of inflammation in ESRD are multiple, including inflammatory signals associated with the dialysis procedure, decreased renal function, volume overload, comorbidity and intercurrent clinical events. As the prevalence of inflammation varies considerably between continents and races, dietary and/or genetic factors may have an impact on inflammation in ESRD. Elevated CRP in dialysis patients could be evaluated at three different levels: (i) national/regional level; (ii) dialysis unit level; and (iii) individual patient level.

Interleukin-1beta and receptor antagonist (IL-1Ra) gene polymorphisms and the prediction of the risk of end-stage renal disease

Cytokines play an important role in the pathogenesis of kidney disease and its progression to end-stage renal disease (ESRD). Inflammation is regulated by the genes of the interleukin 1 (IL-1) gene cluster. Therefore, it was hypothesized that a polymorphism in this gene cluster may be associated with the risk of ESRD. Polymorphisms in the IL-1 gene cluster were examined in a cohort of 222 ESRD patients and 206 controls of similar ethnicity. These individuals were genotyped for IL-1 beta (promoter -511 and exon-5 +3953) genes and a variable number of tandem repeats (VNTR) in the IL-1 receptor antagonist gene (IL-1Ra). There was significant difference in genotype frequencies between ESRD patients and control group for IL-1beta (promoter region and exon-5) and IL-1Ra gene polymorphism (p < 0.001, 0.006 and < 0.001, respectively). A significant difference was observed in IL-1Ra for 1/1 (410/410) and 1/2 (410/240) genotypes, and the risk for ESRD was higher in those carrying the 1/1 genotype (p = 0.014, OR = 1.692, and p < 0.001, OR = 0.163). Also identified was a novel, rare allele of a single copy of 86 bp in ESRD patients as compared with the controls. The haplotype 'T-E2-1' frequency distribution between patients and controls revealed greater than threefold risk (p = 0.001, OR = 3.572, 95% CI = 1.589-8.032). Genetic linkage between the IL-1beta promoter region and exon-5 and between the IL-1beta promoter and IL-1Ra of IL-1 gene demonstrated a strong association among the variants in controls (D' = 0.42, p < 0.001, and D' = 0.39, p=0.001). Thus, the three polymorphisms within the IL-1 cluster are associated with ESRD. This finding is perhaps one of the strongest associations between genotype and ESRD reported, and it suggests that the IL-1 gene cluster affects the risk of development of ESRD.