Nephrectomy Model Of Chronic Kidney Disease Research Articles

Dysbiosis of Gut Microbiota Contributes to Uremic Cardiomyopathy via Induction of IFNγ-Producing CD4+ T Cells Expansion.

Uremic cardiomyopathy (UCM) correlates with chronic kidney disease (CKD)-induced morbidity and mortality. Gut microbiota has been involved in the pathogenesis of certain cardiovascular disease, but the role of gut microbiota in the pathogenesis of UCM remains unknown. Here, we performed a case-control study to compare the gut microbiota of patients with CKD and healthy controls by 16S rRNA (rRNA) gene sequencing. To test the causative relationship between gut microbiota and UCM, we performed fecal microbiota transplantation (FMT) in 5/6th nephrectomy model of CKD. We found that opportunistic pathogens, particularly Klebsiella pneumoniae (K. pneumoniae), are markedly enriched in patients with CKD. FMT from CKD patients aggravated diastolic dysfunction in the mouse model. The diastolic dysfunction was associated with microbiome-dependent increases in heart-infiltrating IFNγ+ CD4+ T cells. Monocolonization with K. pneumoniae increased cardiac IFNγ+ CD4+ T cells infiltration and promoted UCM development of the mouse model. A probiotic Bifidobacterium animalis decreased the relative abundance of K. pneumoniae, reduced levels of cardiac IFNγ+ CD4+ T cells and ameliorated the severity of diastolic dysfunction in the mice. Thus, the aberrant gut microbiota in CKD patients, especially K. pneumoniae, contributed to UCM pathogenesis through the induction of heart-infiltrating IFNγ+ CD4+ T cells expansion, proposing that a Gut Microbiota-Gut-Kidney-Heart axis could play a critical role in elucidating the etiology of UCM, and suggesting that modulation of the gut bacteria may serve as a promising target for the amelioration of UCM. IMPORTANCE Uremic cardiomyopathy (UCM) correlates tightly with increased mortality in patients with chronic kidney disease (CKD), yet the pathogenesis of UCM remains incompletely understood, limiting therapeutic approaches. Our study proposed that a Gut Microbiota-Gut-Kidney-Heart axis could play a critical role in understanding etiology of UCM. There is a major need in future clinical trials of patients with CKD to explore if modulation of gut microbiota by fecal microbiota transplantation (FMT), probiotics or antibiotics can alleviate cardiac dysfunction, reduce mortality, and improve life quality.

Preclinical Characterization of Vadadustat (AKB-6548), an Oral Small Molecule Hypoxia-Inducible Factor Prolyl-4-Hydroxylase Inhibitor, for the Potential Treatment of Renal Anemia.

Pharmacological inhibition of prolyl-4-hydroxylase domain (PHD) enzymes stabilizes hypoxia-inducible factors (HIFs), transcription factors that activate target genes that, among others, increase erythropoietin (EPO) synthesis, resulting in the production of new red blood cells (RBCs). Herein, we summarize the preclinical characteristics of the small molecule HIF prolyl-4-hydroxylase inhibitor vadadustat (AKB-6548), which is in development for the treatment of anemia in patients with chronic kidney disease (CKD). Vadadustat inhibits the enzyme activity of all three human PHD isozymes, PHD1, PHD2, and PHD3, with similar low nanomolar inhibitory constant values. PHD enzyme inhibition by vadadustat is competitive with endogenous cofactor 2-oxoglutarate and is insensitive to free iron concentration. In the human hepatocellular carcinoma cell line (Hep 3B) and human umbilical vein endothelial cells, PHD inhibition by vadadustat leads to the time- and concentration-dependent stabilization of HIF-1α and HIF-2α In Hep 3B cells, this in turn results in the synthesis and secretion of EPO; vascular endothelial growth factor is not measured at detectable levels. A single oral dose of vadadustat in rats potently increases circulating levels of EPO, and daily oral dosing for 14 days increases RBC indices in healthy rats and in the 5/6 nephrectomy model of CKD. In mice and dogs, once-daily repeat oral dosing increases hemoglobin and hematocrit. Vadadustat has a relatively short half-life in all nonclinical species evaluated and does not accumulate when administered as a single bolus dose (oral or intravenous) or upon repeat oral dosing. The pharmacological profile of vadadustat supports continued development for treatment of renal anemia. SIGNIFICANCE STATEMENT: Vadadustat (AKB-6548) is an orally bioavailable small molecule prolyl-4-hydroxylase inhibitor in development for anemia of chronic kidney disease. It is an equipotent inhibitor of the three human prolyl-4-hydroxylase domain isoforms, which activates erythropoiesis through stabilization of hypoxia-inducible factor (HIF)-1α and HIF-2α, increasing production of erythropoietin, without detectable stimulation of vascular endothelial growth factor.

Abstract 169: miR-21-5p Regulation of Lipid Content and Peroxidation in H9C2 Cells

Cardiovascular pathologies are the leading single cause of death in chronic kidney disease (CKD) patients. We have found that the 5/6 nephrectomy model of CKD leads to an upregulation of miR-21-5p in the left ventricle 7 weeks after surgery, targeting peroxisome proliferator-activated receptor alpha (PPARα). PPARα is a regulator of fatty acid uptake and metabolism. In our model we find that suppression of miR-21-5p alters the expression of numerous genes involved with fatty acid oxidation and glycolysis, presumably through its regulatory action on PPARα and/or additional targets. We also find that 5/6Nx rats exhibit dyslipidemia and increased left ventricular lipid content at this time. In this study we evaluated the potential for knockdown or overexpression of miR-21-5p to regulate lipid content and peroxidation in H9C2 cells. Cells were transfected with anti-miR-21-5p (40nM), pre-miR-21-5p (20nM) or appropriate scrambled oligonucleotide controls. After 24 hours medium was changed and half of the cells from each transfection group were treated with lipid (0.66 mM oleic acid and 0.33 mM palmitic acid) for 48 hours (n=6/treatment group for each set of experiments). Lipid content, measured by AdipoRed assay (Lonza) was significantly increased with lipid treatment (nearly two-fold). Overexpression of miR-21-5p significantly attenuated this increase (228.0 ± 9.7 vs. 198.2 ± 8.9% of untreated control), while suppression of miR-21-5p augmented lipid content (235.8 ± 11.2 vs. 328.1 ± 12.3% of untreated control). These results were supported by imaging of Oil Red O stained cells. We found that the abundance of malondialdehyde (MDA), a product of lipid peroxidation, was significantly increased in response to lipid treatment. Overexpression of miR-21-5p reduced MDA content in untreated and lipid treated cells, suggesting that miR-21-5p reduces oxidative stress. Suppression of miR-21-5p had no effect on MDA levels. These results indicate that overexpression of miR-21-5p attenuates both lipid content and lipid peroxidation in H9C2 cells. Ongoing studies aimed at evaluation of alterations in fatty acid oxidation and oxidative stress will further aid in determining the functional impact of miR-21-5p on associated pathways in cardiac tissue.

Total renal denervation reduces sympathoexcitation to different target organs in a model of chronic kidney disease.

It is known that increased sympathetic nerve activity in chronic kidney disease (CKD) progressively worsens kidney function and hypertension. We tested the hypothesis that total renal denervation contributes to reduce sympathetic activation to different beds and improves renal function in 5/6 nephrectomy model of CKD in male Wistar rats. After eight weeks of 5/6 nephrectomy surgery there was an increase in mean arterial pressure (CKD 179±22mmHg, n=6 vs. control animals 108±9; p<0.05, n=6) with no changes in heart rate (HR). Sympathetic nerve activity was increased at different levels to the remaining kidney, splanchnic and lumbar beds compared to control (CTL) group (CKD rSNA: 150±50, n=9 vs. CTL 96±15, n=9; CKD sSNA: 129±51, n=5 vs. CTL 34±14, n=6; CKD lSNA: 203±35, n=8 vs. CTL 146±21, spikes/s, n=7, p<0.05). Three weeks after total renal denervation (DNX) MAP was normalized in the CKD rats (124±19mmHg, n=5, p<0.05), with no change in HR. The lSNA was normalized (151±40, n=5, vs. CKD 203±35 spikes/s, n=8) and sSNA was decreased in 49% (64±34, n=5 vs. CKD 129±51 spikes/s, n=5, p<0.05). Renal function, assessed by creatinine plasma levels was improved after renal denervation (CKD 1.50±0.64, n=8; vs. CKD+DNX 0.82±0.22mg/mL, n=8, p<0.05). These findings demonstrate that renal nerves contribute to the maintenance of hypertension in CKD by increasing sympathoexcitation to other beds.

The Effects of Losartan on Expressions of Klotho and Wnt in the 5/6 Nephrectomy Model of Progressive Chronic Kidney Disease

Klotho is a transmembrane protein expressed in different tissues but in particularly high levels in the kidney. Soluble klotho acts an endocrine factor with diverse functions including endothelium protection and reducing inflammation and fibrosis through mechanisms involving Wnt and TGFbeta1 signaling. Renal fibrosis is the end stage of the progressive chronic kidney disease (CKD) and renal klotho is markedly decreased in CKD patients. Renin angiotensin system (RAS) blockade is a relevant therapy to reduce CKD progression since it has a pivotal role in renal fibrogenesis. We investigated the effects of losartan on Klotho/Wnt signaling in 5/6 nephrectomy model of CKD in rats. Adult male Wistar rats underwent 5/6 nephrectomy (NX) were separated into 2 groups, NX control and NX treated with losartan (LOS, 25 mg/kg) in the drinking water from day 1 after nephrectomy. Blood pressure (MAP) was measured weekly. Urine was colected to determine proteinuria. After 8 weeks, rats were sacrificed and the remmnant kidney was removed and prepared to estimate the renal expression of collagen, epithelial‐to‐mesenchymal transition (EMT) marker (FSP1) and Klotho signaling (Klotho, Wnt and GSK3β) by real time PCR. NX rats presented hypertension and proteinuria that were blunted by LOS treatment. LOS also induced a reduction in the expression of the fibrosis markers collagen and FSP1. Klotho was reduced in NX animals and LOS significantly increased the expression. The LOS treatment increased Wnt3 expression and did not change the Wnt7b and GSK3β. These data suggest that besides the reduction in the MAP, the benefical renal effect of losartan may be at least in part due to upregulation of klotho expression.

Mechanisms of dyslipidemia in chronic kidney disease

LETTERS TO THE EDITORMechanisms of dyslipidemia in chronic kidney diseaseMichal Chmielewski and Boleslaw RutkowskiMichal Chmielewski and Boleslaw RutkowskiPublished Online:01 Sep 2009https://doi.org/10.1152/ajprenal.00269.2009MoreSectionsPDF (27 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat to the editor: We have read with interest the article by Kim et al. (3) published in the American Journal of Physiology-Renal Physiology. It extends our understanding of the mechanisms involved in the development of lipid disorders in the course of chronic kidney disease (CKD), an area that is still far from being fully elucidated. In their study on a nephrectomy model of CKD, the authors demonstrated decreased gene expression and protein abundance of the nuclear, i.e., active, fraction of sterol regulatory element-binding protein-2 (SREBP-2) in the remnant kidneys. This nuclear transcription factor is regarded as the major regulator of cholesterol synthesis. Moreover, both gene expression and protein abundance of renal SREBP-1, the transcription factor involved in lipogenesis, was also found to be reduced. We regard this as an important and a very intriguing finding. Previous studies have demonstrated increased SREBP expression in kidneys of animals with diabetic (5) and age-related nephropathy (2). Both in the course of diabetes and in an aging kidney, this increase leads to enhanced lipid synthesis and to renal lipid accumulation, phenomena that contribute to kidney injury and to CKD progression. In contrast, according to the study by Kim et al. (3), CKD caused by nephrectomy results in decreased SREBP expression and lipid synthesis, pointing to a hypothesis that patomechanisms of renal lipid accumulation differ depending on the origin of CKD.Another intriguing conclusion that could be derived from this study is that SREBP expression and lipid synthesis during experimental CKD are different in particular organs. Our studies on a similar model of CKD achieved by a nephrectomy showed enhanced gene expression and protein abundance of SREBP-1 in white adipose tissue (4) and of SREBP-2 in livers (1) of CKD rats. These alterations were followed by increased lipogenesis and cholesterol synthesis in these tissues, contributing to overt hypertriglyceridemia and hypercholesterolemia found in experimental CKD. Increased plasma lipid concentrations, in turn, could enable enhanced lipid influx to the kidneys, a finding demonstrated by Kim et al. (3) in their study. All of these studies complement each other, and still many more are needed to fully clarify the mechanisms that lead to lipid disorders in CKD, their significance in the progression of kidney injury and in patient outcome.REFERENCES1 Chmielewski M, Sucajtys-Szulc E, Kossowska E, Swierczynski J, Rutkowski B, Boguslawski W. Increased gene expression of liver SREBP-2 in experimental chronic renal failure. Atherosclerosis 191: 326–332, 2007.Crossref | PubMed | ISI | Google Scholar2 Jiang T, Liebman SE, Lucia MS, Li J, Levi M. Role of altered renal lipid metabolism and the sterol regulatory element binding proteins in the pathogenesis of age-related renal disease. Kidney Int 68: 2608–2620, 2005.Crossref | PubMed | ISI | Google Scholar3 Kim HJ, Moradi H, Yuan J, Norris K, Vaziri ND. Renal mass reduction results in accumulation of lipids and dysregulation of lipid regulatory proteins in the remnant kidney. Am J Physiol Renal Physiol 296: F1297–F1306, 2009.Link | ISI | Google Scholar4 Korczynska J, Stelmanska E, Nogalska A, Szolkiewicz M, Goyke E, Swierczynski J, Rutkowski B. Upregulation of lipogenic enzymes genes expression in white adipose tissue of rats with chronic renal failure is associated with higher level of sterol regulatory element binding protein-1. Metabolism 53: 1060–1065, 2004.Crossref | PubMed | ISI | Google Scholar5 Sun L, Halaihel N, Zhang W, Rogers T, Levi M. Role of sterol regulatory element-binding protein 1 in regulation of renal lipid metabolism and glomerulosclerosis in diabetes mellitus. J Biol Chem 277: 18919–18927, 2002.Crossref | PubMed | ISI | Google Scholar Download PDF Previous Back to Top FiguresReferencesRelatedInformationCited ByCardiovascular Risk Factors, Inflammation, and Corneal Arcus: The Singapore Malay Eye StudyAmerican Journal of Ophthalmology, Vol. 150, No. 4Reno-protective effects of atorvastatin independent of blood cholesterol loweringAcademic Journal of Second Military Medical University, Vol. 30, No. 7 More from this issue > Volume 297Issue 3September 2009Pages F835-F835 Copyright & PermissionsCopyright © 2009 the American Physiological Societyhttps://doi.org/10.1152/ajprenal.00269.2009PubMed19692497History Published online 1 September 2009 Published in print 1 September 2009 Metrics