Kentaro Omori

Gender specific association of aldosterone synthase gene polymorphism with renal survival in patients with IgA nephropathy.

Immunoglobulin A nephropathy (IgAN), which is the most prevalent form of primary glomerulonephritis and one of the major causes of end stage renal disease (ESRD), has a variable clinical course.1–3 Poor prognostic factors for the progression of renal dysfunction in IgAN have been identified as high blood pressure, heavy proteinuria, and a severe histopathological appearance of the renal biopsy.4,5 In addition to these prognostic factors, it has been proposed that several genetic backgrounds are associated with a susceptibility to ESRD in patients with IgAN.6,7 The renin-angiotensin-aldosterone system is an important regulator of blood pressure and plays a central role in the development and progression of end organ damage. Polymorphisms in genes that encode components of this system have been reported to be associated with physiological risk factors for progressive renal dysfunction in IgAN. The most consistent of these is the angiotensinogen ( AGT ) gene, which is associated with essential hypertension and with an increased risk of cardiovascular diseases and renal failure.8–10 A deletion polymorphism in the angiotensin converting enzyme ( ACE ) gene influences the circulating ACE levels, and although it has little effect on blood pressure, it has been associated with an increased risk of cardiovascular diseases in some but not all studies.11–13 Aldosterone is one of the main effectors of the renin-angiotensin system14 and has classically been thought to act as a regulator for the absorption of Na and water, as well as the excretion of K in normal physiology, and as a mediator of oedema in numerous disease states. However, it is now well recognised that the actions of aldosterone are not limited to effects on ion transport in epithelial tissue, and its important role in cardiovascular disease involves non-epithelial tissues.15,16 Recently, it has been shown that …

Continuous Reduction of Protein-Bound Uraemic Toxins with Improved Oxidative Stress by Using the Oral Charcoal Adsorbent AST-120 in Haemodialysis Patients

Accumulation of protein-bound uraemic toxins (PBUTs) is one of the reasons for the development of uraemia-related complications including cardiovascular disease; however, conventional haemodialysis is limited in its ability to remove PBUTs. We aimed to examine whether the oral charcoal adsorbent AST-120 has an additive effect on PBUT removal in haemodialysis patients. During the 4-week study, anuric patients undergoing haemodialysis received AST-120 (6 g/day) in the last 2 weeks (n = 10) or the first 2 weeks (n = 10). Serum levels of total and free PBUTs such as indoxyl sulfate, p-cresyl sulfate, and phenyl sulfate at the pre- and postdialysis sessions were measured before and after AST-120 use and after discontinuation. Levels of the oxidative stress markers oxidized albumin and 8-isoprostane were also measured. AST-120 use induced dramatic reduction of indoxyl sulfate (total, 45.7% [33.2–50.5%]; free, 70.4% [44.8–79.8%]), p-cresyl sulfate (total, 31.1% [25.0–48.0%]; free, 63.5% [49.3–70.9%]), and phenyl sulfate (free, 50.6% [32.3–71.2%]) levels; however, this effect disappeared after the discontinuation of AST-120. AST-120 use also induced substantial reduction of the oxidized albumin and 8-isoprostane levels. In conclusion, oral administration of AST-120 had additive effects on the continuous reduction of some PBUTs in anuric patients undergoing haemodialysis.

Genetic Polymorphism of NPHS1 Modifies the Clinical Manifestations of Ig A Nephropathy

Nephrin, the molecule responsible for congenital nephrotic syndrome of Finnish type, is crucial in maintaining the glomerular filtration barrier. Recently, its complete gene structure and common gene polymorphisms in its exons have been reported, although the functional and clinical significance of these polymorphisms has not yet been elucidated. We investigated a possible association of the NPHS1 polymorphisms with the development of Ig A nephropathy (IgAN), as well as the clinical and histologic manifestations in IgAN. A total of 464 Japanese subjects, including 267 patients with histologically proven IgAN and 197 healthy controls with normal urinalysis, were genotyped for the NPHS1 G349A, G2289A, and T3315C polymorphisms. The frequencies of the genotypes, alleles, and estimated haplotypes of NPHS1 polymorphisms were no different between patients with IgAN and the controls. Within the IgAN group, patients carrying at least one G allele of G349A tended to present with more proteinuria, lower renal function, and more severe histopathologic injury than those with the AA genotype, although the time from the first urinary abnormality to the renal biopsy was no different between both groups. The logistic regression analysis indicated that even after adjusting for the effect of proteinuria and hypertension the GG genotype of NPHS1 G349A was an independent risk factor for the deteriorated renal function at the time of diagnosis. This study suggests that the NPHS1 G349A polymorphism may be associated with heavy proteinuria and a decline in renal function in patients with IgAN.

Genetic polymorphisms in the promoter and 5′ UTR region of the Fc α receptor (CD89) are not associated with a risk of IgA nephropathy

AbstractThe molecular mechanisms of immunoglobulin A glomerulonephritis (IgAN), the most prevalent form of primary glomerulonephritis, remain poorly understood. Recently, the essential role of soluble Fc α receptor (FcαR) in the formation of the pathogenic immune complex has been revealed. We screened genomic DNA samples from patients with IgAN and those with other glomerular diseases for polymorphisms in the promoter and the 5′-untranslated region region of the FcαR gene by direct nucleotide sequencing. We found three common polymorphisms in this region, T-114C, T-27C, and T+56C from the putative transcription initiation site. Each genotype was determined in 151 patients with IgAN and 163 patients with other glomerular diseases shown to have no mesangial IgA deposition by renal biopsy. The haplotype analysis revealed tight linkage disequilibrium among them. An association study for the genotype, allele, and haplotype frequencies of the polymorphisms between the patients with histologically proven IgAN and those with other glomerular diseases showed no significant difference in the genotype, allele, and haplotype distributions between the two groups. The present study indicates that the analyzed polymorphisms of the FcαR gene do not appear to be primarily involved in the susceptibility to IgAN.

Peroxisome proliferator-activated receptor γ C161T polymorphisms and survival of Japanese patients with immunoglobulin A nephropathy

Peroxisome proliferator‐activated receptor γ (PPARγ) plays an important role in lipid metabolism, insulin sensitivity, atherogenesis, and immune regulation. A genetic polymorphism (C161T) at exon 6 of PPARγ gene (PPARG) was reported to be associated with the onset of coronary artery disease. However, there has been no report of an association with renal disease. Genomic DNAs were isolated from 225 Japanese patients with histologically confirmed immunoglobulin A nephropathy (IgAN). The PPARG C161T genotype was determined by polymerase chain reaction‐restriction fragment length polymorphism. The association of the polymorphism with renal prognosis in IgAN patients was analyzed using the Kaplan–Meier method and Cox proportional hazard regression model. The PPARG polymorphism was not associated with the renal survival rate. However, when patients were stratified into those either with or without hypertension at the time of diagnosis, the renal survival of the CT/TT genotypes was significantly better in those without hypertension than those with the CC genotype. We report that the PPARG C161T polymorphism is associated with the survival of IgAN patients without hypertension. The T allele of the polymorphism might have a protective effect on the progression of IgAN.

Renoprotective efficacy of renin–angiotensin inhibitors in IgA nephropathy is influenced by ACE A2350G polymorphism

Immunoglobulin A nephropathy (IgAN) is the most prevalent form of primary glomerulonephritis and one of the principal causes of end stage renal disease (ESRD) throughout the world.1,2 It is a complex disease, in which familial clustering suggests an inherited genetic predisposition. The disease has a variable clinical course, and one third of patients with IgAN progress to ESRD within 10–20 years of its onset.3,4 The mechanisms of interindividual differences in the rate of disease progression are unclear.5 That increased production or activity of angiotensin II plays a detrimental role in the glomerular response to injury has been well documented. Recently, angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blocker (ARB) treatments have been shown to decrease proteinuria by improving glomerular permselectivity in IgAN,6,7 although the therapeutic effect was not recognised in about half of the patients.6 An insertion/deletion (I/D) polymorphism of the angiotensin I converting enzyme gene has been shown to influence the concentration of ACE in the circulation and local tissues.8–10 Many studies have explored the association between the ACE I/D polymorphism and the development and progression of various cardiovascular diseases and renal diseases, including IgAN.11–13 Moreover, several studies have investigated associations between the ACE I/D polymorphism and the therapeutic efficacy of ACE inhibitors. The DD homozygote of the ACE I/D polymorphism has been reported as a risk factor for progression to ESRD in patients with IgAN, as well as a predictive marker for responsiveness to the antiproteinuric effects of ACE inhibitors.14 Other studies, however, reported that patients with the DD genotype were resistant to the renoprotective effects of ACE inhibitors, whether they had non-diabetic or diabetic nephropathy.15–17 Recently, an informative set of 13 single nucleotide polymorphisms (SNPs) across the entire ACE gene has …

Association of the MCP-1 gene polymorphism A-2518G with carpal-tunnel syndrome in hemodialysis patients.

Abstract Carpal-tunnel syndrome (CTS) in long-term hemodialysis patients is caused by the deposition of amyloid as well as by the local inflammatory process. The recruitment of monocytes/macrophages in the tenosynovium, promoted by chemokines such as monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1a (M1P-I α), is thought to play an important role in CTS development. The genetic polymorphism of these chemokines has been identified and their clinical function has been partly revealed. We attempted to analyze the relationship between these polymorphisms and their susceptibility to CTS. The subjects of this study were 366 patients who underwent hemodialysis. Ninety-five patients received surgery for CTS. No significant difference was observed in the genotype distributions of MCP-1 or MIP-lα between patients who received CTS surgery and those that did not. However, with the use of a logistic regression model, the MCP-1 GG genotype was identified as a risk factor for the development of CTS, in addition to the duration and the age of initiation of dialysis, as confirmed by a Cox proportional hazards model. In conclusion, homozygosity for G at -2518 in the MCP-1 gene might be a candidate for the genetic marker of CTS development in Japanese hemodialysis patients.

Mortality Predictors after 10 Years of Dialysis: A Prospective Study of Japanese Hemodialysis Patients

BACKGROUND This work aimed to examine the predictive value for death of various clinical variables after long-term hemodialysis (HD). DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS A total of 947 patients (597 men and 350 women, aged 21 to 93 yr) who were undergoing maintenance HD in Niigata, Japan, were stratified into two cohorts: Those with >10 yr of prior HD at study enrollment (n = 391) and those with < or =10 yr of previous therapy (n = 556). The survival of patients was examined for up to 40 mo (1999 to 2003) with the Cox proportional hazards model. Baseline clinical and dialysis data and serum biochemistries were used as independent variables. For adjustment for bias in patient selection, patient survival in either cohort was analyzed separately. RESULTS In patients with >10 yr of HD, high pulse pressure, cerebrovascular disease, low serum creatinine, and low Kt/V values were the mortality risk predictors, whereas for those with < or =10 yr of HD, age and cerebrovascular disease were independent risk predictors for death. Diabetes, coronary artery disease, serum albumin, and C-reactive protein were NS predictors in those with long-term HD. CONCLUSIONS Providing adequate dosage of dialysis and achieving a better control of pulse pressure may further improve survival in selected patients who had undergone HD for >10 yr.

Circulating Osteoprotegerin Affects Bone Metabolism in Dialysis Patients With Mild Secondary Hyperparathyroidism

Abstract:  Osteoprotegerin (OPG) is a soluble glycoprotein which inhibits osteoclastic formation and activity. Circulating OPG levels are elevated in uremia. The role of elevated circulating OPG levels in uremia remains unknown. Blood samples were obtained from 22 non‐diabetic dialysis patients who underwent iliac bone biopsy examination. The serum OPG concentration was assayed by ELISA. The circulating OPG levels showed a negative correlation with the ratio of eroded surface/bone surface (ES/BS) in biopsied iliac bone samples among 15 of those with plasma intact PTH levels less than 300 pg/mL (P < 0.05, r2 = 0.270). Patients with serum OPG levels less than 2.0 ng/mL showed significantly greater ES/BS values than those with levels ≥3.0 ng/mL, while the intact PTH levels were comparable among those groups. These tendencies disappeared when seven patients with plasma intact PTH levels more than 300 pg/mL were included into the analysis. In conclusion, circulating OPG levels showed a significant negative correlation with a bone resorption parameters in dialysis patients with mild secondary hyperparathyroidism. Circulating OPG might have a suppressive effect on osteoclastic bone resorption in dialysis patients.

Maxacalcitol therapy decreases circulating osteoprotegerin levels in dialysis patients with secondary hyperparathyroidism.

BACKGROUND Osteoprotegerin is a natural glycoprotein which plays a critical role in osteoclast physiology. Elevated levels of circulating osteoprotegerin may account for the development of bone and mineral metabolic abnormalities in uremia. Little is known about the effects of vitamin D therapy on the circulating osteoprotegerin levels in dialysis patients. PATIENTS AND METHODS Fifty chronic dialysis patients whose plasma intact PTH levels were greater than 300 pg/ml were analyzed for the study. Following a four-week washout time during which all vitamin D administration was halted, 10 microg of maxacalcitol was intravenously injected thrice a week. RESULTS The circulating intact PTH, bone-specific alkaline phosphatase and intact osteocalcin levels were significantly lowered, while the serum calcium levels were elevated after the therapy. The osteoprotegerin levels significantly decreased after the therapy (p < 0.0001). CONCLUSION Maxacalcitol therapy reduced the circulating osteoprotegerin levels and improved secondary hyperparathyroidism. The observed effects were the opposite of those expected from previous in vitro studies. Osteoprotegerin may mediate and/or modify the effect of active vitamin D therapy in dialysis patients.