Obesity and hypertension have differing oxidant handling molecular pathways in age-related chronic kidney disease

Chronic kidney disease (CKD) in ageing is a burden on health systems worldwide. Rat models of age-related CKD linked with obesity and hypertension were used to investigate alterations in oxidant handling and energy metabolism to identify gene targets or markers for age-related CKD. Young adult (3 months) and old (21–24 months) spontaneously-hypertensive (SHR), normotensive Wistar-Kyoto (WKY) and Wistar rats (normotensive, obese in ageing) were compared for renal functional and physiological parameters, renal fibrosis and inflammation, oxidative stress (hemeoxygenase-1/HO-1), apoptosis and cell injury (including Bax:Bcl-2), phosphorylated and non-phosphorylated forms of oxidant and energy sensing proteins (p66Shc, AMPK), signal transduction proteins (ERK1/2, PKB), and transcription factors (NF-κB, FoxO1). All old rats were normoglycemic. Renal fibrosis, tubular epithelial apoptosis, interstitial macrophages and myofibroblasts (all p < 0.05), p66Shc/phospho-p66 (p < 0.05), Bax/Bcl-2 ratio (p < 0.05) and NF-κB expression (p < 0.01) were highest in old obese Wistars. Expression of phospho-FoxO/FoxO was elevated in old Wistars (p < 0.001) and WKYs (p < 0.01). SHRs had high levels in young and old rats. Expression of PKB, phospho-PKB, ERK1/2 and phospho-ERK1/2 were significantly elevated in all aged animals. These results suggest that obesity and hypertension have differing oxidant handling and signalling pathways that act in the pathogenesis of age-related CKD

Laser capture microdissection and multiplex-tandem PCR analysis of proximal tubular epithelial cell signaling in human kidney disease

Interstitial fibrosis, a histological process common to many kidney diseases, is the precursor state to end stage kidney disease, a devastating and costly outcome for the patient and the health system. Fibrosis is historically associated with chronic kidney disease (CKD) but emerging evidence is now linking many forms of acute kidney disease (AKD) with the development of CKD. Indeed, we and others have observed at least some degree of fibrosis in up to 50% of clinically defined cases of AKD. Epithelial cells of the proximal tubule (PTEC) are central in the development of kidney interstitial fibrosis. We combine the novel techniques of laser capture microdissection and multiplex-tandem PCR to identify and quantitate “real time” gene transcription profiles of purified PTEC isolated from human kidney biopsies that describe signaling pathways associated with this pathological fibrotic process. Our results: (i) confirm previous in-vitro and animal model studies; kidney injury molecule-1 is up-regulated in patients with acute tubular injury, inflammation, neutrophil infiltration and a range of chronic disease diagnoses, (ii) provide data to inform treatment; complement component 3 expression correlates with inflammation and acute tubular injury, (iii) identify potential new biomarkers; proline 4-hydroxylase transcription is down-regulated and vimentin is up-regulated across kidney diseases, (iv) describe previously unrecognized feedback mechanisms within PTEC; Smad-3 is down-regulated in many kidney diseases suggesting a possible negative feedback loop for TGF-β in the disease state, whilst tight junction protein-1 is up-regulated in many kidney diseases, suggesting feedback interactions with vimentin expression. These data demonstrate that the combined techniques of laser capture microdissection and multiplex-tandem PCR have the power to study molecular signaling within single cell populations derived from clinically sourced tissue.

Allelic depletion of grem1 attenuates diabetic kidney disease.

OBJECTIVE: Gremlin (grem1) is an antagonist of the bone morphogenetic protein family that plays a key role in limb bud development and kidney formation. There is a growing appreciation that altered grem1 expression may regulate the homeostatic constraints on damage responses in diseases such as diabetic nephropathy. RESEARCH DESIGN AND METHODS: Here we explored whether knockout mice heterozygous for grem1 gene deletion (grem1(+/-)) exhibit protection from the progression of diabetic kidney disease in a streptozotocin-induced model of type 1 diabetes. RESULTS: A marked elevation in grem1 expression was detected in the kidneys and particularly in kidney tubules of diabetic wild-type mice compared with those of littermate controls. In contrast, diabetic grem1(+/-) mice displayed a significant attenuation in grem1 expression at 6 months of diabetes compared with that in age- and sex-matched wild-type controls. Whereas the onset and induction of diabetes were similar between grem1(+/-) and wild-type mice, several indicators of diabetes-associated kidney damage such as increased glomerular basement membrane thickening and microalbuminuria were attenuated in grem1(+/-) mice compared with those in wild-type controls. Markers of renal damage such as fibronectin and connective tissue growth factor were elevated in diabetic wild-type but not in grem1(+/-) kidneys. Levels of pSmad1/5/8 decreased in wild-type but not in grem1(+/-) diabetic kidneys, suggesting that bone morphogenetic protein signaling may be maintained in the absence of grem1. CONCLUSIONS: These data identify grem1 as a potential modifier of renal injury in the context of diabetic kidney disease.

Association of MYH9/APOL1 with chronic kidney disease in a UK population

Following the first report on the association between MYH9 gene variants and glomerular disorders [1], many studies have evaluated MYH9 loci for association with a range of kidney diseases [2]. In 2010, functional mutations in the adjacent APOL1 gene were identified as the primary variants responsible for associations with kidney disease that had previously been attributed to the MHY9 gene [3]. Nevertheless, several loci within MHY9 continue to be independently reported as risk factors for chronic kidney disease (CKD) [2, 4].

Obesity and kidney disease in type 1 and 2 diabetes: an analysis of the National Diabetes Audit

Background: Obesity is increasingly prevalent in many countries. Obesity is a major risk factor for the development of type 2 diabetes but its relationship with diabetic kidney disease (DKD) remains unclear. Some studies have suggested that the metabolic syndrome (including obesity) may be associated with DKD in type 1 diabetes. Aim: To investigate the association between obesity and DKD. Design: Retrospective cross-sectional study. Methods: National Diabetes Audit data were available for the 2007–08 cycle. Type 1 and 2 diabetes patients with both a valid serum creatinine and urinary albumin:creatinine ratio were included. DKD was defined as an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2, albuminuria or both. Logistic regression was used to analyse associations of obesity (body mass index ≥30 kg/m2) and other variables including year of birth, year of diagnosis, ethnicity and stage of kidney disease. Results: A total of 58 791 type 1 and 733 769 type 2 diabetes patients were included in the analysis. After adjustment, when compared with type 1 diabetes patients with normal renal function those with DKD were up to twice as likely to be obese. Type 2 DKD patients were also more likely to be obese. For example, type 2 diabetes patients with an eGFR <15 ml/min/1.73 m2 and normoalbuminuria, microalbuminuria or macroalbuminuria were all more likely to be obese; odds ratios (95% CI) 1.65 (1.3–2.1), 1.56 (1.28–1.92) and 1.27 (1.05–1.54), respectively. Conclusions: This study has highlighted a strong association between obesity and kidney disease in type 1 diabetes and confirmed their association in type 2 diabetes.

Genetic risk factors affecting mitochondrial function are associated with kidney disease in people with Type 1 diabetes

AIM: To evaluate the association with diabetic kidney disease of single nucleotide polymorphisms (SNPs) that may contribute to mitochondrial dysfunction.

METHODS: The mitochondrial genome and 1039 nuclear genes that are integral to mitochondrial function were investigated using a case (n=823 individuals with diabetic kidney disease) vs. control (n=903 individuals with diabetes and no renal disease) approach. All people included in the analysis were of white European origin and were diagnosed with Type 1 diabetes before the age of 31 years. Replication was conducted in 5093 people with similar phenotypes to those of the discovery collection. Association analyses were performed using the plink genetic analysis toolset, with adjustment for relevant covariates.

RESULTS: A total of 25 SNPs were evaluated in the mitochondrial genome, but none were significantly associated with diabetic kidney disease or end-stage renal disease. A total of 38 SNPs in nuclear genes influencing mitochondrial function were nominally associated with diabetic kidney disease and 16 SNPS were associated with end-stage renal disease, secondary to diabetic kidney disease, with meta-analyses confirming the same direction of effect. Three independent signals (seven SNPs) were common to the replication data for both phenotypes with Type 1 diabetes and persistent proteinuria or end-stage renal disease.

CONCLUSIONS: Our results suggest that SNPs in nuclear genes that influence mitochondrial function are significantly associated with diabetic kidney disease in a white European population

Wilms' tumor gene 1 (WT1) expression in childhood acute lymphoblastic leukemia:a wide range of WT1 expression levels, its impact on prognosis and minimal residual disease monitoring

Wilms' tumor gene 1 (WT1) is overexpressed in the majority (70-90%) of acute leukemias and has been identified as an independent adverse prognostic factor, a convenient minimal residual disease (MRD) marker and potential therapeutic target in acute leukemia. We examined WT1 expression patterns in childhood acute lymphoblastic leukemia (ALL), where its clinical implication remains unclear. Using a real-time quantitative PCR designed according to Europe Against Cancer Program recommendations, we evaluated WT1 expression in 125 consecutively enrolled patients with childhood ALL (106 BCP-ALL, 19 T-ALL) and compared it with physiologic WT1 expression in normal and regenerating bone marrow (BM). In childhood B-cell precursor (BCP)-ALL, we detected a wide range of WT1 levels (5 logs) with a median WT1 expression close to that of normal BM. WT1 expression in childhood T-ALL was significantly higher than in BCP-ALL (P<0.001). Patients with MLL-AF4 translocation showed high WT1 overexpression (P<0.01) compared to patients with other or no chromosomal aberrations. Older children (> or =10 years) expressed higher WT1 levels than children under 10 years of age (P<0.001), while there was no difference in WT1 expression in patients with peripheral blood leukocyte count (WBC) > or =50 x 10(9)/l and lower. Analysis of relapsed cases (14/125) indicated that an abnormal increase or decrease in WT1 expression was associated with a significantly increased risk of relapse (P=0.0006), and this prognostic impact of WT1 was independent of other main risk factors (P=0.0012). In summary, our study suggests that WT1 expression in childhood ALL is very variable and much lower than in AML or adult ALL. WT1, thus, will not be a useful marker for MRD detection in childhood ALL, however, it does represent a potential independent risk factor in childhood ALL. Interestingly, a proportion of childhood ALL patients express WT1 at levels below the normal physiological BM WT1 expression, and this reduced WT1 expression appears to be associated with a higher risk of relapse.

Characterization of polycystin-1 in ADPKD pathogenetic mechanism : biogenesis and functional implications by genetic approaches in mouse

La polykystose rénale autosomique dominante (ADPKD) est une des maladies génétiques les plus communes. ADPKD se manifeste le plus souvent au stade adulte par la présence de kystes rénaux, et bien souvent de kystes hépatiques, avec une progression très variable. ADPKD mène à une insuffisance rénale: les seuls recours sont la dialyse puis la transplantation rénale. Les mutations dispersées sur les gènes PKD1 (majoritairement; la protéine polycystine-1, PC1) et PKD2 (la protéine polycystine-2, PC2) sont responsables de l’ADPKD. Le mécanisme pathogénétique de perte de fonction (LOF) et donc d’un effet récessif cellulaire est évoqué comme causatif de l’ADPKD. LOF est en effet supporté par les modèles murins d’inactivation de gènes PKD1/PKD2, qui développent de kystes, quoique in utéro et avec une rapidité impressionnante dans les reins mais pas dans le foie. Malgré de nombreuses études in vitro, le rôle de PC1/PC2 membranaire/ciliaire reste plutôt hypothétique et contexte-dépendant. Ces études ont associé PC1/PC2 à une panoplie de voies de signalisation et ont souligné une complexité structurelle et fonctionnelle exceptionnelle, dont l’implication a été testée notamment chez les modèles de LOF. Toutefois, les observations patho-cellulaires chez l’humain dont une expression soutenue, voire augmentée, de PKD1/PC1 et l’absence de phénotypes extrarénaux particuliers remet en question l’exclusivité du mécanisme de LOF. Il était donc primordial 1) d’éclaircir le mécanisme pathogénétique, 2) de générer des outils in vivo authentiques d’ADPKD en terme d’initiation et de progression de la maladie et 3) de mieux connaitre les fonctions des PC1/PC2 indispensables pour une translation clinique adéquate. Cette thèse aborde tous ces points. Tout d’abord, nous avons démontré qu’une augmentation de PKD1 endogène sauvage, tout comme chez l’humain, est pathogénétique en générant et caractérisant en détail un modèle murin transgénique de Pkd1 (Pkd1TAG). Ce modèle reproduit non seulement les caractéristiques humaines rénales, associées aux défauts du cil primaire, mais aussi extrarénales comme les kystes hépatiques. La sévérité du phénotype corrèle avec le niveau d’expression de Pkd1 ce qui supporte fortement un modèle de dosage. Dans un deuxième temps, nous avons démontré par les études de complémentations génétiques que ces deux organes reposent sur une balance du clivage GPS de Pc1, une modification post-traductionelle typique des aGPCR, et dont l’activité et l’abondance semblent strictement contrôlées. De plus, nous avons caractérisé extensivement la biogénèse de Pc1 et de ses dérivés in vivo générés suite au clivage GPS. Nous avons identifié une toute nouvelle forme et prédominante à la membrane, la forme Pc1deN, en plus de confirmer deux fragments N- et C-terminal de Pc1 (NTF et CTF, respectivement) qui eux s’associent de manière non-covalente. Nous avons démontré de façon importante que le trafic de Pc1deN i.e., une forme NTF détachée du CTF, est toutefois dépendant de l’intégrité du fragment CTF in vivo. Par la suite, nous avons généré un premier modèle humanisant une mutation PKD1 non-sens tronquée au niveau du domaine NTF(E3043X) en la reproduisant chez une souris transgénique (Pkd1extra). Structurellement, cette mutation, qui mimique la forme Pc1deN, s’est également avérée causative de PKD. Le modèle Pkd1extra a permis entre autre de postuler l’existence d’une cross-interaction entre différentes formes de Pc1. De plus, nos deux modèles murins sont tous les deux associés à des niveaux altérés de c-Myc et Pc2, et soutiennent une implication réelle de ces derniers dans l’ADPKD tou comme une interaction fonctionnelle entre les polycystines. Finalement, nous avons démontré un chevauchement significatif entre l’ADPKD et le dommage rénal aigüe (ischémie/AKI) dont une expression augmentée de Pc1 et Pc2 mais aussi une stimulation de plusieurs facteurs cystogéniques tel que la tubérine, la β-caténine et l’oncogène c-Myc. Nos études ont donc apporté des évidences cruciales sur la contribution du gène dosage dans l’ADPKD. Nous avons développé deux modèles murins qui serviront d’outil pour l’analyse de la pathologie humaine ainsi que pour la validation préclinique ADPKD. L’identification d’une nouvelle forme de Pc1 ajoute un niveau de complexité supplémentaire expliquant en partie une capacité de régulation de plusieurs voies de signalisation par Pc1. Nos résultats nous amènent à proposer de nouvelles approches thérapeutiques: d’une part, le ciblage de CTF i.e., de style chaperonne, et d’autre part le ciblage de modulateurs intracellulaires (c-Myc, Pc2, Hif1α). Ensemble, nos travaux sont d’une importance primordiale du point de vue informatif et pratique pour un avancement vers une thérapie contre l’ADPKD. Le partage de voies communes entre AKI et ADPKD ouvre la voie aux approches thérapeutiques parallèles pour un traitement assurément beaucoup plus rapide.

Analysis of the association of polymorphism in the osteoprotegerin gene with susceptibility to chronic kidney disease and periodontitis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Identification of the presence of the mutation of the gene of PKD not associated of HCM in Persian cats - case report

Polycystic kidney disease (PKD) is a hereditary autosomal dominant disorder that mainly affects Persian cats; it is an important cause of chronic kidney disease in this species. Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats, and there is evidence of a genetic origin in some breeds. Although neither of these disorders is rare in cats, according to our literature review, this is the first report of the concomitant occurrence of PKD and HCM in Persian cats in Brazil.

Matrix Metalloproteinase (MMP)-2 Genetic Variants Modify the Circulating MMP-2 Levels in End-Stage Kidney Disease

Background: Matrix metalloproteinases (MMPs) play important roles in the pathophysiology of renal diseases, and imbalanced MMP-2 and its endogenous inhibitor (the tissue inhibitor of metalloproteinases-2; TIMP-2) are implicated in the vascular alterations of end-stage kidney disease (ESKD) patients. We have examined whether MMP-2 gene polymorphisms and haplotypes modify MMP-2 and TIMP-2 levels in ESKD patients as well as the effects of hemodialysis on the concentrations of these biomarkers. Methods: We determined MMP-2 and TIMP-2 plasma levels by gelatin zymography and ELISA, respectively, in 98 ESKD patients and in 38 healthy controls. Genotypes for two relevant MMP-2 polymorphisms (C-T-1306 and C-T-735 in the promoter region) were determined by TaqMan (R) allele discrimination assay and real-time polymerase chain reaction. The software program PHASE 2.1 was used to estimate the haplotype frequencies. Results: We found increased plasma MMP-2 and TIMP-2 levels in ESKD patients compared to controls (p<0.05), and hemodialysis decreased MMP-2 (but not TIMP-2) levels (p<0.05). The T allele for the C-T-735 polymorphism and the C-T haplotype were associated with higher MMP-2 (but not TIMP-2) levels (p<0.05), whereas the C-T-1306 had no effects. Hemodialysis decreased MMP-2 (but not TIMP-2) levels independently of MMP-2 genotypes or haplotypes (p<0.05). Conclusions: MMP-2 genotypes or haplotypes modify MMP-2 levels in ESKD patients, and may help to identify patients with increased MMP-2 activity in plasma. Hemodialysis reduces MMP-2 levels independently of MMP-2 genetic variants. Copyright (C) 2012 S. Karger AG, Basel

Circulating Fibrocytes, their role in renal fibrosis and molecular pathways involved. Possible biomarkers of fibrogenesis in chronic kidney disease

Circulating Fibrocytes (CFs) are bone marrow-derived mesenchymal progenitor cells that express a similar pattern of surface markers related to leukocytes, hematopoietic progenitor cells and fibroblasts. CFs precursor display an ability to differentiate into fibroblasts and Myofibroblasts, as well as adipocytes. Fibrocytes have been shown to contribute to tissue fibrosis in the end-stage renal disease (ESRD), as well as in other fibrotic diseases, leading to fibrogenic process in other organs including lung, cardiac, gut and liver. This evidence has been confirmed by several experimental proofs in mice models of kidney injury. In the present study, we developed a protocol for the study of CFs, by using peripheral blood monocytes cells (PBMCs) samples collected from healthy human volunteers. Thanks to a flow cytometry method, in vitro culture assays and the gene expression assays, we are able to study and characterize this CFs population. Moreover, results confirmed that these approaches are reliable and reproducible for the investigation of the circulating fibrocytes population in whole blood samples. Our final aim is to confirm the presence of a correlation between the renal fibrosis progression, and the different circulating fibrocyte levels in Chronic Kidney Disease (CKD) patients. Thanks to a protocol study presented and accepted by the Ethic Committee we are continuing the study of CFs induction in a cohort of sixty patients affected by CKD, divided in three distinct groups for different glomerular filtration rate (GFR) levels, plus a control group of thirty healthy subjects. Ongoing experiments will determine whether circulating fibrocytes represent novel biomarkers for the study of CKD progression, in the early and late phases of this disease.

Polycystin 1 is required for the structural integrity of blood vessels

Autosomal dominant polycystic kidney disease (ADPKD), often caused by mutations in the PKD1 gene, is associated with life-threatening vascular abnormalities that are commonly attributed to the frequent occurrence of hypertension. A previously reported targeted mutation of the mouse homologue of PKD1 was not associated with vascular fragility, leading to the suggestion that the vascular lesion may be of a secondary nature. Here we demonstrate a primary role of PKD1 mutations in vascular fragility. Mouse embryos homozygous for the mutant allele (Pkd1L) exhibit s.c. edema, vascular leaks, and rupture of blood vessels, culminating in embryonic lethality at embryonic day 15.5. Kidney and pancreatic ductal cysts are present. The Pkd1-encoded protein, mouse polycystin 1, was detected in normal endothelium and the surrounding vascular smooth muscle cells. These data reveal a requisite role for polycystin 1 in maintaining the structural integrity of the vasculature as well as epithelium and suggest that the nature of the PKD1 mutation contributes to the phenotypic variance in ADPKD.