Estimating the Prevalence of Muscle Wasting, Weakness, and Sarcopenia in Hemodialysis Patients.

OBJECTIVES: Haemodialysis (HD) patients suffer from nutritional problems, which include muscle wasting, weakness, and cachexia, and are associated with poor clinical outcomes. The European Working Group for Sarcopenia in Older People (EWGSOP) and Foundations for the National Institute of Health (FNIH) have developed criteria for the assessment of sarcopenia, including the use of non-invasive techniques such as bioelectrical impedance assessment (BIA), anthropometry, and hand grip strength (HGS) dynamometry. This study investigated the prevalence of muscle wasting, weakness, and sarcopenia using the EWGSOP and FNIH criteria. METHODS: BIA was performed in 24 females (f) and 63 males (m) in the post-dialysis period. Total skeletal muscle mass and appendicular skeletal muscle mass were estimated and index values (i.e., muscle mass divided by height2 [kg/m2]) were calculated (Total Skeletal Muscle Index (TSMI) and Appendicular Skeletal Muscle Index (ASMI)). Mid-arm circumference and triceps skin-fold thickness were measured and mid-upper arm muscle circumference (MUAMC) calculated. HGS was measured using a standard protocol and Jamar dynamometer. Suggested cut-points for low muscle mass and grip strength were utilized using the EWGSOP and FNIH criteria with prevalence estimated, including sarcopenia. RESULTS: The prevalence varied depending on methodology: low TSMI (moderate and severe sarcopenia combined) was 55% for whole group: 21% (f) and 68% (m). Low ASMI was 32% for whole group: 25% (f) and 35% (m). Low MUAMC was 25% for whole group: 0% (f) and 30% (m). ASMI highly correlated with Body Mass Index (r = 0.78, P < .001) and MUAMC (r = 0.68, P < .001). Muscle weakness was high regardless of cut-points used (50-71% (f); 60-79% (m)). CONCLUSIONS: Internationally, this is the first study comparing measures of muscle mass (TSMM and ASMM by BIA and MUAMC) and muscle strength (HGS) using this specific methodology in a hemodialysis population. Future work is required to confirm findings.

Age-dependent DNA methylation of genes that are suppressed in stem cells is a hallmark of cancer.

Polycomb group proteins (PCGs) are involved in repression of genes that are required for stem cell differentiation. Recently, it was shown that promoters of PCG target genes (PCGTs) are 12-fold more likely to be methylated in cancer than non-PCGTs. Age is the most important demographic risk factor for cancer, and we hypothesized that its carcinogenic potential may be referred by irreversibly stabilizing stem cell features. To test this, we analyzed the methylation status of over 27,000 CpGs mapping to promoters of approximately 14,000 genes in whole blood samples from 261 postmenopausal women. We demonstrate that stem cell PCGTs are far more likely to become methylated with age than non-targets (odds ratio = 5.3 [3.8-7.4], P < 10(-10)), independently of sex, tissue type, disease state, and methylation platform. We identified a specific subset of 69 PCGT CpGs that undergo hypermethylation with age and validated this methylation signature in seven independent data sets encompassing over 900 samples, including normal and cancer solid tissues and a population of bone marrow mesenchymal stem/stromal cells (P < 10(-5)). We find that the age-PCGT methylation signature is present in preneoplastic conditions and may drive gene expression changes associated with carcinogenesis. These findings shed substantial novel insights into the epigenetic effects of aging and support the view that age may predispose to malignant transformation by irreversibly stabilizing stem cell features.

Association of genetic variants at 3q22 with nephropathy in patients with type 1 diabetes mellitus.

Diabetic nephropathy (DN) is the primary cause of morbidity and mortality in patients with type 1 diabetes mellitus (T1DM) and affects about 30% of these patients. We have previously localized a DN locus on chromosome 3q with suggestive linkage in Finnish individuals. Linkage to this region has also been reported earlier by several other groups. To fine map this locus, we conducted a multistage case-control association study in T1DM patients, comprising 1822 cases with nephropathy and 1874 T1DM patients free of nephropathy, from Finland, Iceland, and the British Isles. At the screening stage, we genotyped 3072 tag SNPs, spanning a 28 Mb region, in 234 patients and 215 controls from Finland. SNPs that met the significance threshold of p < 0.01 at this stage were followed up by a series of sample sets. A genetic variant, rs1866813, in the noncoding region at 3q22 was associated with increased risk of DN (overall p = 7.07 x 10(-6), combined odds ratio [OR] of the allele = 1.33). The estimated genotypic ORs of this variant in all Finnish samples suggested a codominant effect, resulting in significant association, with a p value of 4.7 x 10(-5) (OR = 1.38; 95% confidence interval = 1.18-1.62). Additionally, an 11 kb segment flanked by rs62408925 and rs1866813, two strongly correlated variants (r(2) = 0.95), contains three elements highly conserved across multiple species. Independent replication will clarify the role of the associated variants at 3q22 in influencing the risk of DN.

Heme oxygenase 1: does it have a role in renal cytoprotection?

Heme oxygenase (HO) was first identified as the rate-limiting enzyme in the degradative pathway of heme, but is now recognized to be involved in diverse biological processes. Different isoforms of HO exist; HO-1 (HMOX1) is ubiquitously present in mammalian tissue with low constitutive expression under physiological conditions, but is upregulated in response to a variety of potentially noxious stimuli. HO-1, an integral component of an important cytoprotective mechanism, mediates its action through removal of heme, the generation of heme breakdown reaction products (biliverdin, free iron, and carbon monoxide), and modulation of key cellular molecules. Data from experimental models in which HO-1 was induced or inhibited, together with observations in genetically modified animals, showed a beneficial effect of HO-1 in several pathways leading to kidney injury. The discovery of a functional guanosine thymine tandem repeat polymorphism in the promoter region of the human HO-1 gene has stimulated clinical investigations in a variety of diseases. However, despite theoretical and experimental support for an important pathophysiological role for HO-1, the relevance of this polymorphism in native kidney or renal transplant function is equivocal. This article reviews the molecular genetics of HO-1, its myriad cytoprotective effects allied to how these are mediated, and relates these findings to experimental and clinical evidence of HO-1 involvement in renal disease.

Association of functional haem oxygenase-1 gene promoter polymorphism with polycystic kidney disease and IgA nephropathy.

BACKGROUND: Haem oxygenase-1 (HO-1) is a cytoprotective molecule that is reported to have a protective role in a variety of experimental models of renal injury. A functional dinucleotide repeat (GT)(n) polymorphism, within the HO-1 promoter, regulates HO-1 gene expression; a short number of repeats (S-allele <25) increases transcription. We report the first assessment of the role of this HO-1 gene promoter polymorphism in chronic kidney disease due to autosomal dominant polycystic kidney disease (ADPKD) and IgA nephropathy (IgAN). METHODS: The DNA from 160 patients (99% Caucasian) on renal replacement therapy (RRT) was genotyped. The primary renal disease was ADPKD in 100 patients and biopsy-proven IgAN in 60 patients. RESULTS: Overall, the mean age at commencement of RRT was not significantly different between patients with and without an S-allele (44.1 years versus 45.0 years, P = 0.64). In patients with ADPKD, the age at commencement of RRT was comparable regardless of the HO-1 genotype (47.7 years versus 46.7 years, P = 0.59). The same was true in patients with IgAN (38.3 years versus 42.2 years, P = 0.28). CONCLUSION: This suggests that the functional HO-1 promoter polymorphism does not influence renal survival in CKD due to ADPKD or IgAN.

Pathophysiology of anemia and erythrocytosis.

An increasing understanding of the process of erythropoiesis raises some interesting questions about the pathophysiology, diagnosis and treatment of anemia and erythrocytosis. The mechanisms underlying the development of many of the erythrocytoses, previously characterised as idiopathic, have been elucidated leading to an increased understanding of oxygen homeostasis. Characterisation of anemia and erythrocytosis in relation to serum erythropoietin levels can be a useful addition to clinical diagnostic criteria and provide a rationale for treatment with erythropoiesis stimulating agents (ESAs). Recombinant human erythropoietin as well as other ESAs are now widely used to treat anemias associated with a range of conditions, including chronic kidney disease, chronic inflammatory disorders and cancer. There is also heightened awareness of the potential abuse of ESAs to boost athletic performance in competitive sport. The discovery of erythropoietin receptors outside of the erythropoietic compartment may herald future applications for ESAs in the management of neurological and cardiac diseases. The current controversy concerning optimal hemoglobin levels in chronic kidney disease patients treated with ESAs and the potential negative clinical outcomes of ESA treatment in cancer reinforces the need for cautious evaluation of the pleiotropic effects of ESAs in non-erythroid tissues.

Resequencing of genes for transforming growth factor beta1 (TGFB1) type 1 and 2 receptors (TGFBR1, TGFBR2), and association analysis of variants with diabetic nephropathy.

BACKGROUND: Diabetic nephropathy is the leading cause of end stage renal failure in the western world. There is substantial epidemiological evidence supporting a genetic predisposition to diabetic nephropathy, however the exact molecular mechanisms remain unknown. Transforming growth factor (TGFbeta1) is a crucial mediator in the pathogenesis of diabetic nephropathy. METHODS: We investigated the role of five known single nucleotide polymorphisms (SNPs) in the TGFB1 gene for their association with diabetic nephropathy in an Irish, type 1 diabetic case (n = 272) control (n = 367) collection. The activity of TGFbeta1 is facilitated by the action of type 1 and type 2 receptors, with both receptor genes (TGFBR1 and TGFBR2) shown to be upregulated in diabetic kidney disease. We therefore screened TGFBR1 and TGFBR2 genes for genomic variants using WAVEtrade mark (dHPLC) technology and confirmed variants by direct capillary sequencing. Allele frequencies were determined in forty-eight healthy individuals. Data for all SNPs was assessed for Hardy Weinberg equilibrium, with genotypes and allele frequencies compared using the chi2 test for contingency tables. Patterns of linkage disequilibrium were established and common haplotypes estimated. RESULTS: Fifteen variants were identified in these genes, seven of which are novel, and putatively functional SNPs were subsequently genotyped using TaqMantrade mark, Invadertrade mark or Pyrosequencing(R) technology. No significant differences (p > 0.1) were found in genotype or allele distributions between cases and controls for any of the SNPs assessed. CONCLUSION: Our results suggest common variants in TGFB1, TGFBR1 and TGFBR2 genes do not strongly influence genetic susceptibility to diabetic nephropathy in an Irish Caucasian population.

Association of VEGF-1499C-->T polymorphism with diabetic nephropathy in type 1 diabetes mellitus.

Vascular endothelial growth factor (VEGF) is reported to be implicated in the development of diabetic nephropathy. We performed a case-control study to determine if VEGF-2578C-->A, VEGF-1499C-->T, and VEGF-635G-->C single-nucleotide polymorphisms (SNPs) in the VEGF gene are associated with predisposition to diabetic nephropathy in type 1 diabetes. Genomic DNA was obtained from Irish type 1 diabetic individuals with nephropathy (cases, n=242) and those without nephropathy (controls, n=301), in addition to 400 healthy control samples. These samples were genotyped for the three SNPs using TaqMan or Pyrosequencing technology. Chi-squared analyses revealed no significant differences in genotype or allele frequencies in cases versus controls for VEGF-2578C-->A (genotype, P=.58; allele, P=.52) and VEGF-635G-->C (genotype, P=.58; allele, P=.33). However, a positive association with diabetic nephropathy was observed for the VEGF-1499T allele in the Northern Ireland population (P <.001) and subsequently replicated in a separate population from the Republic of Ireland (P <.001; combined, P <.001). Carriage of the VEGF-1499T allele was associated with a twofold excess risk of developing diabetic nephropathy (OR=2.24, 95% CI=1.50-3.36, P <.0001). No significant differences were found between the healthy control population and the type 1 diabetic population. Our results suggest that the VEGF-1499T allele, or an allele in linkage disequilibrium with this allele, is associated with susceptibility to diabetic nephropathy in the Irish population.

Cost should be the principal determinant of choice of erythropoiesis-stimulating agent in chronic haemodialysis patients.

BACKGROUND/AIMS: Erythropoiesis-stimulating agents (ESAs) are effective in the management of the anaemia of chronic kidney disease but add substantially to the treatment costs. We performed a comparison cross-sectional analysis of ESA prescribing in 4 dialysis centres in Northern Ireland. METHODS: The ESA prescription and current haemoglobin (Hb) concentration for all patients on haemodialysis (HD) treatment for at least 3 months was extracted from the renal data system. RESULTS: A total of 403 patients were analysed, 184 (46%) were prescribed epoetin beta and 219 (54%) darbepoetin alpha. The mean Hb concentrations for both agents were comparable overall (Hb = 11.4 and 11.7 g/dl, p = 0.13), and for subcutaneous (SC) and intravenous (IV) administration: epoetin beta 11.5 g/dl (n = 119) and 11.4 g/dl (n = 65) (p = 0.70), and darbepoetin alpha 11.8 g/dl (n = 39) and 11.6 g/dl (n = 180) (p = 0.49). The mean weekly dose was 7,941 units of epoetin beta with SC and 9,200 units with IV administration (p = 0.10), and 45 mug SC and 46 mug IV of darbepoetin alpha (p = 0.94). The weekly cost of achieving equivalent Hb levels was GBP 61.86 (EUR 90.57/USD 115.68) with SC and GBP 71.67 (EUR 104.93/USD 134.02) with IV epoetin beta, and GBP 70.78 (EUR 103.63/USD 132.36) with SC and GBP 72.18 (EUR 105.68/USD 134.98) with IV darbepoetin alpha. CONCLUSIONS: Epoetin beta and darbepoetin alpha are equally effective ESAs and the choice of ESA prescribed in stable HD patients should be determined by cost.

Association between variation in the actin-binding gene caldesmon and diabetic nephropathy in type 1 diabetes.

Dysfunction of the actin cytoskeleton is a key event in the pathogenesis of diabetic nephropathy. We previously reported that certain cytoskeletal genes are upregulated in mesangial cells exposed to a high extracellular glucose concentration. One such gene, caldesmon, lies on chromosome 7q35, a region linked to nephropathy in family studies, making it a candidate susceptibility gene for diabetic nephropathy. We screened all exons, untranslated regions, and a 5-kb region upstream of the gene for variation using denaturing high-performance liquid chromatography technology. An A>G single nucleotide polymorphism (SNP) at position -579 in the promoter region was associated with nephropathy in a case-control study using 393 type 1 diabetic patients from Northern Ireland (odds ratio [OR] 1.38, 95% CI 1.02-1.86, P = 0.03). A similar trend was found in an independent sample from a second center. When the sample groups were combined (n = 606), the association between the -579G allele and nephropathy remained significant (OR 1.35, 1.07-1.70, P = 0.01). The haplotype structure in the surrounding 7-kb region was determined. No single haplotype was more strongly associated with nephropathy than the -579A>G SNP. These results suggest a role for the caldesmon gene in susceptibility to diabetic nephropathy in type 1 diabetes.

Association of intercellular adhesion molecule-1 gene with type 1 diabetes.

Intercellular adhesion molecule-1 (ICAM-1) functions via its ligands, the leucocyte integrins, in adhesion of immune cells to endothelial cells and in T cell activation. The third immunoglobulin-like extracellular domain binds integrin Mac-1 and contains a common non-conservative aminoacid polymorphism, G241R. Phenotypically, ICAM-1 has been associated with type 1 diabetes, a T-cell-mediated autoimmune disease. We assessed two independent datasets, and noted that R241 was associated with lower risk of type 1 diabetes than is G241 (3695 families, relative risk 0.91, p=0.03; 446 families, 0.60, p=0.006). Our data indicate an aetiological role for ICAM-1 in type 1 diabetes, which needs to be confirmed in future genetic and functional experiments.

Late referral for assessment of renal failure.

It has been recommended that adult patients with a serum creatinine above 150 mumol/l should be referred to a nephrologist for specialist assessment. This study ascertained all patients in Northern Ireland with creatinine above this concentration in 2001 (n = 19 286 ) to see if this triggered referral within the subsequent year. After exclusion of those who were already known to a nephrologist and those who had acute renal failure, it was found that younger patients and diabetic patients were more likely to be referred. There was no difference in referral rates between male and female patients. However, only 6.5% of all non-diabetic subjects and 19% of diabetic patients were referred within 12 months after a first increased serum creatinine test.

Cytokine gene polymorphisms in ischaemic heart disease: investigation using family-based tests of association.

Atherosclerosis has an inflammatory basis, with cytokines, cellular adhesion molecules and pro-inflammatory cells having important roles in the initiation and progression of this process. Interleukin (IL) 6, IL-10 and transforming growth factor (TGF) beta1 have been proposed as important modulators of the atherosclerotic process, with IL-6 having a pro-inflammatory, atherogenic effect and IL-10 and TGF-beta1 having anti-inflammatory, protective roles. The possible role of functional polymorphisms in the promoter regions of the IL-6, IL-10 and TGF-beta1 genes in the susceptibility to ischaemic heart disease (IHD) was investigated in a well-defined Irish population using two recently described family-based tests of association. We genotyped 1,012 individuals from 386 families with at least one member prematurely affected with IHD. Using the combined transmission disequilibrium test (TDT)/sib-TDT and the pedigree disequilibrium test, no association between any of the IL-6 -174G/C, IL-10 -1082G/A and TGF-beta1 -509C/T polymorphisms and IHD was found. Our data demonstrate that, in an Irish population, these polymorphisms are not associated with IHD.

Is screening for factor V Leiden and prothrombin G20210A mutations in renal transplantation worthwhile? Results of a large single-center U.K. study.

This single center study is the largest series of renal transplant recipients and donors screened for the commonest prothrombotic genotypes. A total of 562 transplant recipients and 457 kidney donors were genotyped for the factor V Leiden and prothrombin G20210A mutations. The prevalence of heterozygous factor V Leiden was 3.4% and 2.6% and prothrombin G20210A was 2.0% and 1.1% in recipients and donors, respectively, similar frequencies to that of the general U.K. population. The 30-day and 1-year graft survival rates in recipients with thrombophilic mutations were 93% and 93%, compared with 88% and 82% in patients without these mutations (log-rank P=0.34). Thrombophilia in recipients (odds ratio 0.55; confidence interval 0.06-2.29; P=0.56) or in donors (odds ratio 1.53; confidence interval 0.27-5.74; P=0.46) did not correlate with graft loss at 30 days after transplantation. In contrast to recent reports, this study did not demonstrate an association between thrombophilia and renal allograft loss, and routine screening is not recommended.

Influence of progressive renal dysfunction in chronic heart failure.

Chronic heart failure (CHF) is often associated with impaired renal function due to hypoperfusion. Such patients are very sensitive to changes in renal perfusion pressure, and may develop acute tubular necrosis if the pressure falls too far. The situation is complicated by the use of diuretics, ACE inhibitors and spironolactone, all of which may affect renal function and potassium balance. Chronic renal failure (CRF) may also be associated with fluid overload. Anaemia and hypertension in CRF contribute to the development of left ventricular hypertrophy (LVH), which carries a poor prognosis, so correction of these factors is important.

AINT/ERIC/TACC: an expanding family of proteins with C-terminal coiled coil domains.

The AINT/ERIC/TACC genes encode novel proteins with a coiled coil domain at their C-terminus. The founding member of this expanding family of genes, transforming acidic coiled coil 1 (TACC1), was isolated from a BAC contig spanning the breast cancer amplicon-1 on 8p11. Transfection of cells in vitro with TACC1 resulted in anchorage-independent growth consistent with a more "neoplastic" phenotype. Database searches employing the human TACC1 sequence revealed other novel genes, TACC2 and TACC3, with substantial sequence homology particularly in the C-terminal regions encoding the coiled coil domains. TACC2, located at 10q26, is similar to anti-zuai-1 (AZU-1), a candidate breast tumour suppressor gene, and ECTACC, an endothelial cell TACC which is upregulated by erythropoietin (Epo). The murine homologue of TACC3, murine erythropoietin-induced cDNA (mERIC-1) was also found to be upregulated by Epo in the Friend virus anaemia (FVA) model by differential display-PCR. Human ERIC-1, located at 4p16.3, has been cloned and encodes an 838-amino acid protein whose N- and C-terminal regions are highly homologous to the shorter 558-amino acid murine protein, mERIC-1. In contrast, the central portions of these proteins differ markedly. The murine protein contains four 24 amino acid imperfect repeats. ARNT interacting protein (AINT), a protein expressed during embryonic development in the mouse, binds through its coiled coil region to the aryl hydrocarbon nuclear translocator protein (ARNT) and has a central portion that contains seven of the 24 amino acid repeats found in mERIC-1. Thus mERIC-1 and AINT appear to be developmentally regulated alternative transcripts of the gene. Most members of the TACC family discovered so far contain a novel nine amino acid putative phosphorylation site with the pattern [R/K]-X(3)-[E]-X(3)-Y. Genes with sequence homology to the AINT/ERIC/TACC family in other species include maskin in Xenopus, D-TACC in Drosophila and TACC4 in the rabbit. Maskin contains a peptide sequence conserved among eIF-4E binding proteins that is involved in oocyte development. D-TACC cooperates with another conserved microtubule-associated protein Msps to stabilise spindle poles during cell division. The diversity of function already attributed to this protein family, including both transforming and tumour suppressor properties, should ensure that a new and interesting narrative is about to unfold.

Multiple superoxide dismutase 1/splicing factor serine alanine 15 variants are associated with the development and progression of diabetic nephropathy: the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Genetics study.

BACKGROUND: Despite familial clustering of nephropathy and retinopathy severity in type 1 diabetes, few gene variants have been consistently associated with these outcomes. RESEARCH DESIGN AND METHODS: We performed an individual-based genetic association study with time to renal and retinal outcomes in 1,362 white probands with type 1 diabetes from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study. Specifically, we genotyped 1,411 SNPs that capture common variations in 212 candidate genes for long-term complications and analyzed them for association with the time from DCCT baseline to event for renal and retinal outcomes using multivariate Cox proportion hazards models. To address multiple testing and assist interpretation of the results, false discovery rate q values were calculated separately for each outcome. RESULTS: We observed association between rs17880135 in the 3' region of superoxide dismutase 1 (SOD1) and the incidence of both severe nephropathy (hazard ratio [HR] 2.62 [95% CI 1.64-4.18], P = 5.6 x 10(-5), q = 0.06) and persistent microalbuminuria (1.82 [1.29-2.57], P = 6.4 x 10(-4), q = 0.46). Sequencing and fine-mapping identified additional SOD1 variants, including rs202446, rs9974610, and rs204732, which were also associated (P < 10(-3)) with persistent microalbuminuria, whereas rs17880135 and rs17881180 were similarly associated with the development of severe nephropathy. Attempts to replicate the findings in three cross-sectional case-control studies produced equivocal results. We observed no striking differences between risk genotypes in serum SOD activity, serum SOD1 mass, or SOD1 mRNA expression in lymphoblastoid cell lines. CONCLUSIONS: Multiple variations in SOD1 are significantly associated with persistent microalbuminuria and severe nephropathy in the DCCT/EDIC study.