Publications by authors named "John C He"

74 Publications

Molecular Analysis of the Kidney From a Patient With COVID-19-Associated Collapsing Glomerulopathy.

Kidney Med 2021 Apr 28. Epub 2021 Apr 28.

Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York.

Recent Case reports suggest COVID-19 is associated with collapsing glomerulopathy in African Americans with risk alleles, however, it is unclear if disease pathogenesis is similar to HIVAN. Here RNA sequencing analysis of a kidney biopsy specimen from a patient with COVID-19-associated collapsing glomerulopathy and risk alleles (G1/G1) revealed similar levels of and mRNA transcripts as compared to 12 control kidney samples downloaded from the GTEx Portal. Whole genome sequencing of the COVID-19-associated collapsing glomerulopathy kidney sample identified four indel gene variants, three of which are of unknown significance with respect to chronic kidney disease and/or FSGS. Molecular profiling of the kidney demonstrated activation of COVID-19-associated cell injury pathways such as inflammation and coagulation. Evidence for direct SARS-CoV-2 infection of kidney cells was lacking, which is consistent with the findings of several recent studies. Interestingly, immunostaining of kidney biopsy sections revealed increased expression of phospho-STAT3 in both COVID-19-associated collapsing glomerulopathy and HIVAN as compared to control kidney tissue. Importantly, IL-6-induced activation of STAT3 may be a targetable mechanism driving COVID-19-associated acute kidney injury.
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http://dx.doi.org/10.1016/j.xkme.2021.02.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8080498PMC
April 2021

Inhibition of apoptosis signal-regulating kinase 1 mitigates the pathogenesis of human immunodeficiency virus-associated nephropathy.

Nephrol Dial Transplant 2021 02;36(3):430-441

Department of Medicine, Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.

Background: Chronic kidney disease (CKD) is a common cause of morbidity and mortality in human immunodeficiency virus (HIV)-positive individuals. Among the HIV-related kidney diseases, HIV-associated nephropathy (HIVAN) is a rapidly progressive renal disease characterized by collapsing focal glomerulosclerosis (GS), microcystic tubular dilation, interstitial inflammation and fibrosis. Although the incidence of end-stage renal disease due to HIVAN has dramatically decreased with the widespread use of antiretroviral therapy, the prevalence of CKD continues to increase in HIV-positive individuals. Recent studies have highlighted the role of apoptosis signal-regulating kinase 1 (ASK1) in driving kidney disease progression through the activation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase and selective ASK-1 inhibitor GS-444217 was recently shown to reduce kidney injury and disease progression in various experimental models. Therefore we examined the efficacy of ASK1 antagonism by GS-444217 in the attenuation of HIVAN in Tg26 mice.

Methods: GS-444217-supplemented rodent chow was administered in Tg26 mice at 4 weeks of age when mild GS and proteinuria were already established. After 6 weeks of treatment, the kidney function assessment and histological analyses were performed and compared between age- and gender-matched control Tg26 and GS-444217-treated Tg26 mice.

Results: GS-444217 attenuated the development of GS, podocyte loss, tubular injury, interstitial inflammation and renal fibrosis in Tg26 mice. These improvements were accompanied by a marked reduction in albuminuria and improved renal function. Taken together, GS-4442217 attenuated the full spectrum of HIVAN pathology in Tg26 mice.

Conclusions: ASK1 signaling cascade is central to the development of HIVAN in Tg26 mice. Our results suggest that the select inhibition of ASK1 could be a potential adjunctive therapy for the treatment of HIVAN.
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http://dx.doi.org/10.1093/ndt/gfaa198DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7898019PMC
February 2021

Nuclear receptors in podocyte biology and glomerular disease.

Nat Rev Nephrol 2021 03 17;17(3):185-204. Epub 2020 Sep 17.

Paris Cardiovascular Center (PARCC), Institut National de la Santé et de la Recherche Médicale (Inserm), Université de Paris, Paris, France.

Nuclear receptors have a broad spectrum of biological functions in normal physiology and in the pathology of various diseases, including glomerular disease. The primary therapies for many glomerular diseases are glucocorticoids, which exert their immunosuppressive and direct podocyte protective effects via the glucocorticoid receptor (GR). As glucocorticoids are associated with important adverse effects and a substantial proportion of patients show resistance to these therapies, the beneficial effects of selective GR modulators are now being explored. Peroxisome proliferator-activated receptor-γ (PPARγ) agonism using thiazolidinediones has potent podocyte cytoprotective and nephroprotective effects. Repurposing of thiazolidinediones or identification of novel PPARγ modulators are potential strategies to treat non-diabetic glomerular disease. Retinoic acid receptor-α is the key mediator of the renal protective effects of retinoic acid, and repair of the endogenous retinoic acid pathway offers another potential therapeutic strategy for glomerular disease. Vitamin D receptor, oestrogen receptor and mineralocorticoid receptor modulators regulate podocyte injury in experimental models. Further studies are needed to better understand the mechanisms of these nuclear receptors, evaluate their synergistic pathways and identify their novel modulators. Here, we focus on the role of nuclear receptors in podocyte biology and non-diabetic glomerular disease.
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http://dx.doi.org/10.1038/s41581-020-00339-6DOI Listing
March 2021

AKI in Hospitalized Patients with COVID-19.

J Am Soc Nephrol 2021 01 3;32(1):151-160. Epub 2020 Sep 3.

Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York.

Background: Early reports indicate that AKI is common among patients with coronavirus disease 2019 (COVID-19) and associated with worse outcomes. However, AKI among hospitalized patients with COVID-19 in the United States is not well described.

Methods: This retrospective, observational study involved a review of data from electronic health records of patients aged ≥18 years with laboratory-confirmed COVID-19 admitted to the Mount Sinai Health System from February 27 to May 30, 2020. We describe the frequency of AKI and dialysis requirement, AKI recovery, and adjusted odds ratios (aORs) with mortality.

Results: Of 3993 hospitalized patients with COVID-19, AKI occurred in 1835 (46%) patients; 347 (19%) of the patients with AKI required dialysis. The proportions with stages 1, 2, or 3 AKI were 39%, 19%, and 42%, respectively. A total of 976 (24%) patients were admitted to intensive care, and 745 (76%) experienced AKI. Of the 435 patients with AKI and urine studies, 84% had proteinuria, 81% had hematuria, and 60% had leukocyturia. Independent predictors of severe AKI were CKD, men, and higher serum potassium at admission. In-hospital mortality was 50% among patients with AKI versus 8% among those without AKI (aOR, 9.2; 95% confidence interval, 7.5 to 11.3). Of survivors with AKI who were discharged, 35% had not recovered to baseline kidney function by the time of discharge. An additional 28 of 77 (36%) patients who had not recovered kidney function at discharge did so on posthospital follow-up.

Conclusions: AKI is common among patients hospitalized with COVID-19 and is associated with high mortality. Of all patients with AKI, only 30% survived with recovery of kidney function by the time of discharge.
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http://dx.doi.org/10.1681/ASN.2020050615DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894657PMC
January 2021

Podocyte and endothelial-specific elimination of BAMBI identifies differential transforming growth factor-β pathways contributing to diabetic glomerulopathy.

Kidney Int 2020 09 26;98(3):601-614. Epub 2020 Apr 26.

Department of Medicine, Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA. Electronic address:

Transforming growth factor-β (TGF-β) is a central mediator of diabetic nephropathy. The effect of TGF-β, mediated by the type I TGF-β receptor, ALK5, and subsequent Smad2/3 activation results in podocyte apoptosis and loss. Previously, we demonstrated that the genetic deletion of the BMP and Activin Membrane-Bound Inhibitor (BAMBI), a negative modulator TGF-β signaling, accelerates diabetic nephropathy in mice. This was associated with heightened ALK1-mediated activation of Smad1/5 in the glomerular endothelial cells (ECs). Therefore, to evaluate the glomerular cell-specific effects of TGF-β in diabetic nephropathy we examined the effects of the podocyte- or EC-specific loss of Bambi (Pod-Bambi-/- or EC-Bambi-/-) in streptozotocin-induced diabetic mice with endothelial nitric oxide synthase deficiency. Interestingly, although hyperglycemia and body weight loss were similar in all groups of diabetic mice, significant hypertension was present only in the diabetic EC-Bambi-/- mice. While the podocyte or EC-specific loss of BAMBI both accelerated the progression of diabetic nephropathy, the worsened podocyte injury and loss observed in the diabetic Pod-Bambi-/- mice were associated with enhanced Smad3 activation. Increased Smad1/5 activation and EC proliferation were apparent only in the glomeruli of diabetic EC-Bambi-/- mice. The enhanced Smad1/5 activation in diabetic EC-Bambi-/- mice was associated with increased glomerular expression of plasmalemma vesicle-associated protein, pointing to the involvement of immature or dedifferentiated glomerular ECs in diabetic nephropathy. Notably, diabetic EC-Bambi-/- mice displayed podocyte injury and loss that were comparable to diabetic Pod-Bambi-/- mice. Thus, our results highlight the glomerular cell-specific contribution of TGF-β signaling and the intricate cross-talk between injured glomerular cells in the progression of diabetic nephropathy.
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http://dx.doi.org/10.1016/j.kint.2020.03.036DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7484013PMC
September 2020

LIM-Nebulette Reinforces Podocyte Structural Integrity by Linking Actin and Vimentin Filaments.

J Am Soc Nephrol 2020 10 31;31(10):2372-2391. Epub 2020 Jul 31.

Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York

Background: Maintenance of the intricate interdigitating morphology of podocytes is crucial for glomerular filtration. One of the key aspects of specialized podocyte morphology is the segregation and organization of distinct cytoskeletal filaments into different subcellular components, for which the exact mechanisms remain poorly understood.

Methods: Cells from rats, mice, and humans were used to describe the cytoskeletal configuration underlying podocyte structure. Screening the time-dependent proteomic changes in the rat puromycin aminonucleoside-induced nephropathy model correlated the actin-binding protein LIM-nebulette strongly with glomerular function. Single-cell RNA sequencing and immunogold labeling were used to determine expression specificity in podocytes. Automated high-content imaging, super-resolution microscopy, atomic force microscopy (AFM), live-cell imaging of calcium, and measurement of motility and adhesion dynamics characterized the physiologic role of LIM-nebulette in podocytes.

Results: knockout mice have increased susceptibility to adriamycin-induced nephropathy and display morphologic, cytoskeletal, and focal adhesion abnormalities with altered calcium dynamics, motility, and Rho GTPase activity. LIM-nebulette expression is decreased in diabetic nephropathy and FSGS patients at both the transcript and protein level. In mice, rats, and humans, LIM-nebulette expression is localized to primary, secondary, and tertiary processes of podocytes, where it colocalizes with focal adhesions as well as with vimentin fibers. LIM-nebulette shRNA knockdown in immortalized human podocytes leads to dysregulation of vimentin filament organization and reduced cellular elasticity as measured by AFM indentation.

Conclusions: LIM-nebulette is a multifunctional cytoskeletal protein that is critical in the maintenance of podocyte structural integrity through active reorganization of focal adhesions, the actin cytoskeleton, and intermediate filaments.
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http://dx.doi.org/10.1681/ASN.2019121261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7609000PMC
October 2020

Endothelin receptor-A mediates degradation of the glomerular endothelial surface layer via pathologic crosstalk between activated podocytes and glomerular endothelial cells.

Kidney Int 2019 10 22;96(4):957-970. Epub 2019 May 22.

Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York. Electronic address:

Emerging evidence of crosstalk between glomerular cells in pathological settings provides opportunities for novel therapeutic discovery. Here we investigated underlying mechanisms of early events leading to filtration barrier defects of podocyte and glomerular endothelial cell crosstalk in the mouse models of primary podocytopathy (podocyte specific transforming growth factor-β receptor 1 signaling activation) or Adriamycin nephropathy. We found that glomerular endothelial surface layer degradation and albuminuria preceded podocyte foot process effacement. These abnormalities were prevented by endothelin receptor-A antagonism and mitochondrial reactive oxygen species scavenging. Additional studies confirmed increased heparanase and hyaluronoglucosaminidase gene expression in glomerular endothelial cells in response to podocyte-released factors and to endothelin-1. Atomic force microscopy measurements showed a significant reduction in the endothelial surface layer by endothelin-1 and podocyte-released factors, which could be prevented by endothelin receptor-A but not endothelin receptor-B antagonism. Thus, our studies provide evidence of early crosstalk between activated podocytes and glomerular endothelial cells resulting in loss of endothelial surface layer, glomerular endothelial cell injury and albuminuria. Hence, activation of endothelin-1-endothelin receptor-A and mitochondrial reactive oxygen species contribute to the pathogenesis of primary podocytopathies in experimental focal segmental glomerulosclerosis.
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http://dx.doi.org/10.1016/j.kint.2019.05.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7200072PMC
October 2019

Disruption of MAGI2-RapGEF2-Rap1 signaling contributes to podocyte dysfunction in congenital nephrotic syndrome caused by mutations in MAGI2.

Kidney Int 2019 09 28;96(3):642-655. Epub 2019 Mar 28.

Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA. Electronic address:

The essential role of membrane associated guanylate kinase 2 (MAGI2) in podocytes is indicated by the phenotypes of severe glomerulosclerosis of both MAGI2 knockout mice and in patients with congenital nephrotic syndrome (CNS) caused by mutations in MAGI2. Here, we show that MAGI2 forms a complex with the Rap1 guanine nucleotide exchange factor, RapGEF2, and that this complex is lost when expressing MAGI2 CNS variants. Co-expression of RapGEF2 with wild-type MAGI2, but not MAGI2 CNS variants, enhanced activation of the small GTPase Rap1, a central signaling node in podocytes. In mice, podocyte-specific RapGEF2 deletion resulted in spontaneous glomerulosclerosis, with qualitative glomerular features comparable to MAGI2 knockout mice. Knockdown of RapGEF2 or MAGI2 in human podocytes caused similar reductions in levels of Rap1 activation and Rap1-mediated downstream signaling. Furthermore, human podocytes expressing MAGI2 CNS variants show severe abnormalities of cellular morphology and dramatic loss of actin cytoskeletal organization, features completely rescued by pharmacological activation of Rap1 via a non-MAGI2 dependent upstream pathway. Finally, immunostaining of kidney sections from patients with congenital nephrotic syndrome and MAGI2 mutations showed reduced podocyte Rap1-mediated signaling. Thus, MAGI2-RapGEF2-Rap1 signaling is essential for normal podocyte function. Hence, disruption of this pathway is an important cause of the renal phenotype induced by MAGI2 CNS mutations.
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http://dx.doi.org/10.1016/j.kint.2019.03.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7259463PMC
September 2019

Targeting STAT3 signaling in kidney disease.

Am J Physiol Renal Physiol 2019 06 3;316(6):F1151-F1161. Epub 2019 Apr 3.

Division of Nephrology, Department of Medicine, Stony Brook University , Stony Brook, New York.

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway is a multifaceted transduction system that regulates cellular responses to incoming signaling ligands. STAT3 is a central member of the JAK/STAT signaling cascade and has long been recognized for its increased transcriptional activity in cancers and autoimmune disorders but has only recently been in the spotlight for its role in the progression of kidney disease. Although genetic knockout and manipulation studies have demonstrated the salutary benefits of inhibiting STAT3 activity in several kidney disease models, pharmacological inhibition has yet to make it to the clinical forefront. In recent years, significant effort has been aimed at suppressing STAT3 activation for treatment of cancers, which has led to the development of a wide variety of STAT3 inhibitors, but only a handful have been tested in kidney disease models. Here, we review the detrimental role of dysregulated STAT3 activation in a variety of kidney diseases and the current progress in the treatment of kidney diseases with pharmacological inhibition of STAT3 activity.
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http://dx.doi.org/10.1152/ajprenal.00034.2019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6620596PMC
June 2019

LRG1 Promotes Diabetic Kidney Disease Progression by Enhancing TGF--Induced Angiogenesis.

J Am Soc Nephrol 2019 04 11;30(4):546-562. Epub 2019 Mar 11.

Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York;

Background: Glomerular endothelial dysfunction and neoangiogenesis have long been implicated in the pathogenesis of diabetic kidney disease (DKD). However, the specific molecular pathways contributing to these processes in the early stages of DKD are not well understood. Our recent transcriptomic profiling of glomerular endothelial cells identified a number of proangiogenic genes that were upregulated in diabetic mice, including leucine-rich -2-glycoprotein 1 (LRG1). LRG1 was previously shown to promote neovascularization in mouse models of ocular disease by potentiating endothelial TGF-/activin receptor-like kinase 1 (ALK1) signaling. However, LRG1's role in the kidney, particularly in the setting of DKD, has been unclear.

Methods: We analyzed expression of LRG1 mRNA in glomeruli of diabetic kidneys and assessed its localization by RNA hybridization. We examined the effects of genetic ablation of on DKD progression in unilaterally nephrectomized, streptozotocin-induced diabetic mice at 12 and 20 weeks after diabetes induction. We also assessed whether plasma LRG1 was associated with renal outcome in patients with type 2 diabetes.

Results: LRG1 localized predominantly to glomerular endothelial cells, and its expression was elevated in the diabetic kidneys. LRG1 ablation markedly attenuated diabetes-induced glomerular angiogenesis, podocyte loss, and the development of diabetic glomerulopathy. These improvements were associated with reduced ALK1-Smad1/5/8 activation in glomeruli of diabetic mice. Moreover, increased plasma LRG1 was associated with worse renal outcome in patients with type 2 diabetes.

Conclusions: These findings identify LRG1 as a potential novel pathogenic mediator of diabetic glomerular neoangiogenesis and a risk factor in DKD progression.
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http://dx.doi.org/10.1681/ASN.2018060599DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6442349PMC
April 2019

Fecal microbiota analysis of polycystic kidney disease patients according to renal function: A pilot study.

Exp Biol Med (Maywood) 2019 04 12;244(6):505-513. Epub 2018 Dec 12.

2 Department of Internal Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.

Impact Statement: The heterogeneity of the renal disease, therapeutic interventions, and the original cause of the renal failure, all directly affect the microbiota. We delineate in this report the direct effect of decreased renal function on the bacterial composition following stringent criteria to eliminate the possibilities of other confounding factors and dissect the direct effects of the uremic milieu. We analyzed the microbiome following three different approaches to further evaluate the effects of mild, moderate and advanced renal insufficiency on the microbiome. We also present here a detailed functional analysis of the projected altered pathways secondary to changes in the microbiome composition.
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http://dx.doi.org/10.1177/1535370218818175DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6547006PMC
April 2019

Role of Krüppel-like factor-2 in kidney disease.

Nephrology (Carlton) 2018 Oct;23 Suppl 4:53-56

Department of Medicine, Nephrology Division, Icahn School of Medicine at Mount Sinai, New York, New York, USA.

Krüppel-like factor-2 (KLF2) is a transcription factor that plays a major role in the regulation of endothelial cell function. KLF2 protects against endothelial cell injury through its anti-inflammatory, anti-thrombotic and anti-angiogenic effects to maintain the normal vascular integrity. Our recent data indicate that KLF2 is down-regulated in glomerular endothelial cells of patients with diabetic kidney disease and that endothelial cell-specific reduction in KLF2 expression in experimental model of diabetic kidney disease exacerbates glomerular endothelial cell injury and accelerates the disease progression. KLF2 is a key transcriptional regulator of endothelial nitric oxide synthase, and its renoprotective function may be mediated through the increased endothelial nitric oxide synthase expression. As KLF2 expression is stimulated by shear stress, we also investigated the role of KLF2 in the nephrectomy mouse model, in which the endothelial KLF2 expression would be increased through glomerular hyperfiltration in the remnant kidney. Reduction of endothelial KLF2 led to increased glomerular endothelial cell injury and progressive kidney disease in uninephrectomized mice. Interestingly, KLF2 expression is also reduced in nephrectomy patients with progressive kidney disease as compared to those with the non-progressive disease. Together, these studies indicate a critical role of KLF2 in maintaining normal glomerular endothelial cell function and that deficiency of KLF2 leads to more progressive kidney disease.
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http://dx.doi.org/10.1111/nep.13456DOI Listing
October 2018

Podocyte-Specific Induction of Krüppel-Like Factor 15 Restores Differentiation Markers and Attenuates Kidney Injury in Proteinuric Kidney Disease.

J Am Soc Nephrol 2018 10 24;29(10):2529-2545. Epub 2018 Aug 24.

Divisions of Nephrology and

Background: Podocyte injury is the hallmark of proteinuric kidney diseases, such as FSGS and minimal change disease, and destabilization of the podocyte's actin cytoskeleton contributes to podocyte dysfunction in many of these conditions. Although agents, such as glucocorticoids and cyclosporin, stabilize the actin cytoskeleton, systemic toxicity hinders chronic use. We previously showed that loss of the kidney-enriched zinc finger transcription factor Krüppel-like factor 15 (KLF15) increases susceptibility to proteinuric kidney disease and attenuates the salutary effects of retinoic acid and glucocorticoids in the podocyte.

Methods: We induced podocyte-specific in two proteinuric murine models, HIV-1 transgenic () mice and adriamycin (ADR)-induced nephropathy, and used RNA sequencing of isolated glomeruli and subsequent enrichment analysis to investigate pathways mediated by podocyte-specific in mice. We also explored in cultured human podocytes the potential mediating role of Wilms Tumor 1 (WT1), a transcription factor critical for podocyte differentiation.

Results: In mice, inducing podocyte-specific attenuated podocyte injury, glomerulosclerosis, tubulointerstitial fibrosis, and inflammation, while improving renal function and overall survival; it also attenuated podocyte injury in ADR-treated mice. Enrichment analysis of RNA sequencing from the mouse model shows that induction activates pathways involved in stabilization of actin cytoskeleton, focal adhesion, and podocyte differentiation. Transcription factor enrichment analysis, with further experimental validation, suggests that KLF15 activity is in part mediated by WT1.

Conclusions: Inducing podocyte-specific attenuates kidney injury by directly and indirectly upregulating genes critical for podocyte differentiation, suggesting that induction might be a potential strategy for treating proteinuric kidney disease.
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http://dx.doi.org/10.1681/ASN.2018030324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6171275PMC
October 2018

Podocyte-Specific Loss of Krüppel-Like Factor 6 Increases Mitochondrial Injury in Diabetic Kidney Disease.

Diabetes 2018 11 16;67(11):2420-2433. Epub 2018 Aug 16.

Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, NY

Mitochondrial injury is uniformly observed in several murine models as well as in individuals with diabetic kidney disease (DKD). Although emerging evidence has highlighted the role of key transcriptional regulators in mitochondrial biogenesis, little is known about the regulation of mitochondrial cytochrome c oxidase assembly in the podocyte under diabetic conditions. We recently reported a critical role of the zinc finger Krüppel-like factor 6 (KLF6) in maintaining mitochondrial function and preventing apoptosis in a proteinuric murine model. In this study, we report that podocyte-specific knockdown of increased the susceptibility to streptozotocin-induced DKD in the resistant C57BL/6 mouse strain. We observed that the loss of in podocytes reduced the expression of with resultant increased mitochondrial injury, leading to activation of the intrinsic apoptotic pathway under diabetic conditions. Conversely, mitochondrial injury and apoptosis were significantly attenuated with overexpression of in cultured human podocytes under hyperglycemic conditions. Finally, we observed a significant reduction in glomerular and podocyte-specific expression of KLF6 in human kidney biopsies with progression of DKD. Collectively, these data suggest that podocyte-specific KLF6 is critical to preventing mitochondrial injury and apoptosis under diabetic conditions.
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http://dx.doi.org/10.2337/db17-0958DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6198342PMC
November 2018

Krüppel-like factor 4 is a negative regulator of STAT3-induced glomerular epithelial cell proliferation.

JCI Insight 2018 06 21;3(12). Epub 2018 Jun 21.

Division of Nephrology, Department of Medicine, Stony Brook University, Stony Brook, New York, USA.

Pathologic glomerular epithelial cell (GEC) hyperplasia is characteristic of both rapidly progressive glomerulonephritis (RPGN) and subtypes of focal segmental glomerulosclerosis (FSGS). Although initial podocyte injury resulting in activation of STAT3 signals GEC proliferation in both diseases, mechanisms regulating this are unknown. Here, we show that the loss of Krüppel-like factor 4 (KLF4), a zinc-finger transcription factor, enhances GEC proliferation in both RPGN and FSGS due to dysregulated STAT3 signaling. We observed that podocyte-specific knockdown of Klf4 (C57BL/6J) increased STAT3 signaling and exacerbated crescent formation after nephrotoxic serum treatment. Interestingly, podocyte-specific knockdown of Klf4 in the FVB/N background alone was sufficient to activate STAT3 signaling, resulting in FSGS with extracapillary proliferation, as well as renal failure and reduced survival. In cultured podocytes, loss of KLF4 resulted in STAT3 activation and cell-cycle reentry, leading to mitotic catastrophe. This triggered IL-6 release into the supernatant, which activated STAT3 signaling in parietal epithelial cells. Conversely, either restoration of KLF4 expression or inhibition of STAT3 signaling improved survival in KLF4-knockdown podocytes. Finally, human kidney biopsy specimens with RPGN exhibited reduced KLF4 expression with a concomitant increase in phospho-STAT3 expression as compared with controls. Collectively, these results suggest the essential role of KLF4/STAT3 signaling in podocyte injury and its regulation of aberrant GEC proliferation.
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http://dx.doi.org/10.1172/jci.insight.98214DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6124441PMC
June 2018

Protein S Protects against Podocyte Injury in Diabetic Nephropathy.

J Am Soc Nephrol 2018 05 6;29(5):1397-1410. Epub 2018 Mar 6.

Renal Section, James J. Peters Veterans Affairs Medical Center, Bronx, New York;

Diabetic nephropathy (DN) is a leading cause of ESRD in the United States, but the molecular mechanisms mediating the early stages of DN are unclear. To assess global changes that occur in early diabetic kidneys and to identify proteins potentially involved in pathogenic pathways in DN progression, we performed proteomic analysis of diabetic and nondiabetic rat glomeruli. Protein S (PS) among the highly upregulated proteins in the diabetic glomeruli. PS exerts multiple biologic effects through the Tyro3, Axl, and Mer (TAM) receptors. Because increased activation of Axl by the PS homolog Gas6 has been implicated in DN progression, we further examined the role of PS in DN. In human kidneys, glomerular PS expression was elevated in early DN but suppressed in advanced DN. However, plasma PS concentrations did not differ between patients with DN and healthy controls. A prominent increase of PS expression also colocalized with the expression of podocyte markers in early diabetic kidneys. In cultured podocytes, high-glucose treatment elevated PS expression, and PS knockdown further enhanced the high-glucose-induced apoptosis. Conversely, PS overexpression in cultured podocytes dampened the high-glucose- and TNF--induced expression of proinflammatory mediators. Tyro3 receptor was upregulated in response to high glucose and mediated the anti-inflammatory response of PS. Podocyte-specific PS loss resulted in accelerated DN in streptozotocin-induced diabetic mice, whereas the transient induction of PS expression in glomerular cells attenuated albuminuria and podocyte loss in diabetic OVE26 mice. Our results support a protective role of PS against glomerular injury in DN progression.
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http://dx.doi.org/10.1681/ASN.2017030234DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5967770PMC
May 2018

Cell shape information is transduced through tension-independent mechanisms.

Nat Commun 2017 12 15;8(1):2145. Epub 2017 Dec 15.

Department of Pharmacological Sciences and Systems Biology Center New York, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.

The shape of a cell within tissues can represent the history of chemical and physical signals that it encounters, but can information from cell shape regulate cellular phenotype independently? Using optimal control theory to constrain reaction-diffusion schemes that are dependent on different surface-to-volume relationships, we find that information from cell shape can be resolved from mechanical signals. We used microfabricated 3-D biomimetic chips to validate predictions that shape-sensing occurs in a tension-independent manner through integrin β signaling pathway in human kidney podocytes and smooth muscle cells. Differential proteomics and functional ablation assays indicate that integrin β is critical in transduction of shape signals through ezrin-radixin-moesin (ERM) family. We used experimentally determined diffusion coefficients and experimentally validated simulations to show that shape sensing is an emergent cellular property enabled by multiple molecular characteristics of integrin β. We conclude that 3-D cell shape information, transduced through tension-independent mechanisms, can regulate phenotype.
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http://dx.doi.org/10.1038/s41467-017-02218-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5732205PMC
December 2017

The Hippo pathway regulator KIBRA promotes podocyte injury by inhibiting YAP signaling and disrupting actin cytoskeletal dynamics.

J Biol Chem 2017 12 5;292(51):21137-21148. Epub 2017 Oct 5.

From the Division of Nephrology,

Kidney podocytes represent a key constituent of the glomerular filtration barrier. Identifying the molecular mechanisms of podocyte injury and survival is important for better understanding and management of kidney diseases. KIBRA (dney in protein), an upstream regulator of the Hippo signaling pathway encoded by the gene, shares the pro-injury properties of its putative binding partner dendrin and antagonizes the pro-survival signaling of the downstream Hippo pathway effector YAP (Yes-associated protein) in and MCF10A cells. We recently identified YAP as an essential component of the glomerular filtration barrier that promotes podocyte survival by inhibiting dendrin pro-apoptotic function. Despite these recent advances, the signaling pathways that mediate podocyte injury remain poorly understood. Here we tested the hypothesis that, similar to its role in other model systems, KIBRA promotes podocyte injury. We found increased expression of KIBRA and phosphorylated YAP protein in glomeruli of patients with biopsy-proven focal segmental glomerulosclerosis (FSGS). KIBRA/ overexpression in murine podocytes promoted LATS kinase phosphorylation, leading to subsequent YAP Ser-127 phosphorylation, YAP cytoplasmic sequestration, and reduction in YAP target gene expression. Functionally, KIBRA overexpression induced significant morphological changes in podocytes, including disruption of the actin cytoskeletal architecture and reduction of focal adhesion size and number, all of which were rescued by subsequent YAP overexpression. Conversely, constitutive KIBRA knockout mice displayed reduced phosphorylated YAP and increased YAP expression at baseline. These mice were protected from acute podocyte foot process effacement following protamine sulfate perfusion. KIBRA knockdown podocytes were also protected against protamine-induced injury. These findings suggest an important role for KIBRA in the pathogenesis of podocyte injury and the progression of proteinuric kidney disease.
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http://dx.doi.org/10.1074/jbc.M117.819029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5743086PMC
December 2017

Identification of a protective proteomic signature and a potential therapeutic target in diabetic nephropathy.

Kidney Int 2017 10;92(4):780-781

Department of Medicine, Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.

In a recent paper in Nature Medicine, Qi et al. set out to identify protective pathways in patients with longstanding diabetes who do not develop diabetic nephropathy. Unbiased proteomic analysis of kidney tissue identified a unique protein signature in unaffected individuals. Studies in vitro and in murine models identified the highly upregulated glycolytic enzyme pyruvate kinase M2 as a potential therapeutic target to prevent or treat diabetic nephropathy.
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http://dx.doi.org/10.1016/j.kint.2017.08.002DOI Listing
October 2017

Advanced glycation end products dietary restriction effects on bacterial gut microbiota in peritoneal dialysis patients; a randomized open label controlled trial.

PLoS One 2017 20;12(9):e0184789. Epub 2017 Sep 20.

Department of Internal Medicine, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.

The modern Western diet is rich in advanced glycation end products (AGEs). We have previously shown an association between dietary AGEs and markers of inflammation and oxidative stress in a population of end stage renal disease (ESRD) patients undergoing peritoneal dialysis (PD). In the current pilot study we explored the effects of dietary AGEs on the gut bacterial microbiota composition in similar patients. AGEs play an important role in the development and progression of cardiovascular (CVD) disease. Plasma concentrations of different bacterial products have been shown to predict the risk of incident major adverse CVD events independently of traditional CVD risk factors, and experimental animal models indicates a possible role AGEs might have on the gut microbiota population. In this pilot randomized open label controlled trial, twenty PD patients habitually consuming a high AGE diet were recruited and randomized into either continuing the same diet (HAGE, n = 10) or a one-month dietary AGE restriction (LAGE, n = 10). Blood and stool samples were collected at baseline and after intervention. Variable regions V3-V4 of 16s rDNA were sequenced and taxa was identified on the phyla, genus, and species levels. Dietary AGE restriction resulted in a significant decrease in serum Nε-(carboxymethyl) lysine (CML) and methylglyoxal-derivatives (MG). At baseline, our total cohort exhibited a lower relative abundance of Bacteroides and Alistipes genus and a higher abundance of Prevotella genus when compared to the published data of healthy population. Dietary AGE restriction altered the bacterial gut microbiota with a significant reduction in Prevotella copri and Bifidobacterium animalis relative abundance and increased Alistipes indistinctus, Clostridium citroniae, Clostridium hathewayi, and Ruminococcus gauvreauii relative abundance. We show in this pilot study significant microbiota differences in peritoneal dialysis patients' population, as well as the effects of dietary AGEs on gut microbiota, which might play a role in the increased cardiovascular events in this population and warrants further studies.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0184789PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5607175PMC
October 2017

The loss of Krüppel-like factor 15 in Foxd1 stromal cells exacerbates kidney fibrosis.

Kidney Int 2017 11 24;92(5):1178-1193. Epub 2017 Jun 24.

Kidney Institute of PLA, Department of Medicine, Changzheng Hospital, Second Military Medical University, Shanghai 200003, People's Republic of China. Electronic address:

Large epidemiological studies clearly demonstrate that multiple episodes of acute kidney injury contribute to the development and progression of kidney fibrosis. Although our understanding of kidney fibrosis has improved in the past two decades, we have limited therapeutic strategies to halt its progression. Myofibroblast differentiation and proliferation remain critical to the progression of kidney fibrosis. Although canonical Wnt signaling can trigger the activation of myofibroblasts in the kidney, mediators of Wnt inhibition in the resident progenitor cells are unclear. Recent studies demonstrate that the loss of a Krüppel-like factor 15 (KLF15), a kidney-enriched zinc-finger transcription factor, exacerbates kidney fibrosis in murine models. Here, we tested whether Klf15 mRNA and protein expression are reduced in late stages of fibrosis in mice that underwent unilateral ureteric obstruction, a model of progressive renal fibrosis. Knockdown of Klf15 in Foxd1-expressing cells (Foxd1-Cre Klf15fl/fl) increased extracellular matrix deposition and myofibroblast proliferation as compared to wildtype (Foxd1-Cre Klf15+/+) mice after three and seven days of ureteral obstruction. This was validated in mice receiving angiotensin II treatment for six weeks. In both these murine models, the increase in renal fibrosis was found in Foxd1-Cre Klf15 mice and accompanied by the activation of Wnt/β-catenin signaling. Furthermore, knockdown of Klf15 in cultured mouse embryonic fibroblasts activated canonical Wnt/β-catenin signaling, increased profibrotic transcripts, and increased proliferation after treatment with a Wnt1 ligand. Conversely, the overexpression of KLF15 inhibited phospho-β-catenin (Ser552) expression in Wnt1-treated cells. Thus, KLF15 has a critical role in attenuating kidney fibrosis by inhibiting the canonical Wnt/β-catenin pathway.
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http://dx.doi.org/10.1016/j.kint.2017.03.037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5651204PMC
November 2017

Fragility of foot process morphology in kidney podocytes arises from chaotic spatial propagation of cytoskeletal instability.

PLoS Comput Biol 2017 03 16;13(3):e1005433. Epub 2017 Mar 16.

R. D. Berlin Center for Cell Analysis & Modeling, U. Connecticut School of Medicine, Farmington, CT, United States of America.

Kidney podocytes' function depends on fingerlike projections (foot processes) that interdigitate with those from neighboring cells to form the glomerular filtration barrier. The integrity of the barrier depends on spatial control of dynamics of actin cytoskeleton in the foot processes. We determined how imbalances in regulation of actin cytoskeletal dynamics could result in pathological morphology. We obtained 3-D electron microscopy images of podocytes and used quantitative features to build dynamical models to investigate how regulation of actin dynamics within foot processes controls local morphology. We find that imbalances in regulation of actin bundling lead to chaotic spatial patterns that could impair the foot process morphology. Simulation results are consistent with experimental observations for cytoskeletal reconfiguration through dysregulated RhoA or Rac1, and they predict compensatory mechanisms for biochemical stability. We conclude that podocyte morphology, optimized for filtration, is intrinsically fragile, whereby local transient biochemical imbalances may lead to permanent morphological changes associated with pathophysiology.
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http://dx.doi.org/10.1371/journal.pcbi.1005433DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5373631PMC
March 2017

A biomimetic gelatin-based platform elicits a pro-differentiation effect on podocytes through mechanotransduction.

Sci Rep 2017 03 6;7:43934. Epub 2017 Mar 6.

Department of Chemistry Columbia University, New York, NY 10027, USA.

Using a gelatin microbial transglutaminase (gelatin-mTG) cell culture platform tuned to exhibit stiffness spanning that of healthy and diseased glomeruli, we demonstrate that kidney podocytes show marked stiffness sensitivity. Podocyte-specific markers that are critical in the formation of the renal filtration barrier are found to be regulated in association with stiffness-mediated cellular behaviors. While podocytes typically de-differentiate in culture and show diminished physiological function in nephropathies characterized by altered tissue stiffness, we show that gelatin-mTG substrates with Young's modulus near that of healthy glomeruli elicit a pro-differentiation and maturation response in podocytes better than substrates either softer or stiffer. The pro-differentiation phenotype is characterized by upregulation of gene and protein expression associated with podocyte function, which is observed for podocytes cultured on gelatin-mTG gels of physiological stiffness independent of extracellular matrix coating type and density. Signaling pathways involved in stiffness-mediated podocyte behaviors are identified, revealing the interdependence of podocyte mechanotransduction and maintenance of their physiological function. This study also highlights the utility of the gelatin-mTG platform as an in vitro system with tunable stiffness over a range relevant for recapitulating mechanical properties of soft tissues, suggesting its potential impact on a wide range of research in cellular biophysics.
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http://dx.doi.org/10.1038/srep43934DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5338254PMC
March 2017

The critical role of Krüppel-like factors in kidney disease.

Am J Physiol Renal Physiol 2017 Feb 16;312(2):F259-F265. Epub 2016 Nov 16.

Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York; and.

Krüppel-like factors (KLFs) are a family of zinc-finger transcription factors critical to mammalian embryonic development, regeneration, and human disease. There is emerging evidence that KLFs play a vital role in key physiological processes in the kidney, ranging from maintenance of glomerular filtration barrier to tubulointerstitial inflammation to progression of kidney fibrosis. Seventeen members of the KLF family have been identified, and several have been well characterized in the kidney. Although they may share some overlap in their downstream targets, their structure and function remain distinct. This review highlights our current knowledge of KLFs in the kidney, which includes their pattern of expression and their function in regulating key biological processes. We will also critically examine the currently available literature on KLFs in the kidney and offer some key areas in need of further investigation.
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http://dx.doi.org/10.1152/ajprenal.00550.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5336586PMC
February 2017

Nanomedicines for renal disease: current status and future applications.

Nat Rev Nephrol 2016 Dec 31;12(12):738-753. Epub 2016 Oct 31.

Center for Nanomedicine and Department of Anaesthesiology, Brigham and Women's Hospital and Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115, USA.

Treatment and management of kidney disease currently presents an enormous global burden, and the application of nanotechnology principles to renal disease therapy, although still at an early stage, has profound transformative potential. The increasing translation of nanomedicines to the clinic, alongside research efforts in tissue regeneration and organ-on-a-chip investigations, are likely to provide novel solutions to treat kidney diseases. Our understanding of renal anatomy and of how the biological and physico-chemical properties of nanomedicines (the combination of a nanocarrier and a drug) influence their interactions with renal tissues has improved dramatically. Tailoring of nanomedicines in terms of kidney retention and binding to key membranes and cell populations associated with renal diseases is now possible and greatly enhances their localization, tolerability, and efficacy. This Review outlines nanomedicine characteristics central to improved targeting of renal cells and highlights the prospects, challenges, and opportunities of nanotechnology-mediated therapies for renal diseases.
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http://dx.doi.org/10.1038/nrneph.2016.156DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5593312PMC
December 2016

MAGI-1 Interacts with Nephrin to Maintain Slit Diaphragm Structure through Enhanced Rap1 Activation in Podocytes.

J Biol Chem 2016 Nov 5;291(47):24406-24417. Epub 2016 Oct 5.

From the Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York 10029,. Electronic address:

MAGI-1 is a multidomain cytosolic scaffolding protein that in the kidney is specifically located at the podocyte slit diaphragm, a specialized junction that is universally injured in proteinuric diseases. There it interacts with several essential molecules, including nephrin and neph1, which are required for slit diaphragm formation and as an intracellular signaling hub. Here, we show that diminished MAGI-1 expression in cultured podocytes reduced nephrin and neph1 membrane localization and weakened tight junction integrity. Global magi1 knock-out mice, however, demonstrated normal glomerular histology and function into adulthood. We hypothesized that a second mild but complementary genetic insult might induce glomerular disease susceptibility in these mice. To identify such a gene, we utilized the developing fly eye to test for functional complementation between MAGI and its binding partners. In this way, we identified diminished expression of fly Hibris (nephrin) or Roughest (neph1) as dramatically exacerbating the effects of MAGI depletion. Indeed, when these combinations were studied in mice, the addition of nephrin, but not neph1, heterozygosity to homozygous deletion of MAGI-1 resulted in spontaneous glomerulosclerosis. In cultured podocytes, MAGI-1 depletion reduced intercellular contact-induced Rap1 activation, a pathway critical for proper podocyte function. Similarly, magi1 knock-out mice showed diminished glomerular Rap1 activation, an effect dramatically enhanced by concomitant nephrin haploinsufficiency. Finally, combined overexpression of MAGI-1 and nephrin increased Rap1 activation, but not when substituting a mutant MAGI-1 that cannot bind nephrin. We conclude that the interaction between nephrin and MAGI-1 regulates Rap1 activation in podocytes to maintain long term slit diaphragm structure.
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http://dx.doi.org/10.1074/jbc.M116.745026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5114397PMC
November 2016

Oral AGE restriction ameliorates insulin resistance in obese individuals with the metabolic syndrome: a randomised controlled trial.

Diabetologia 2016 10 29;59(10):2181-92. Epub 2016 Jul 29.

Department of Medicine, Division of Nephrology, The Icahn School of Medicine at Mount Sinai, New York, NY, USA.

Aims/hypothesis: We previously reported that obese individuals with the metabolic syndrome (at risk), compared with obese individuals without the metabolic syndrome (healthy obese), have elevated serum AGEs that strongly correlate with insulin resistance, oxidative stress and inflammation. We hypothesised that a diet low in AGEs (L-AGE) would improve components of the metabolic syndrome in obese individuals, confirming high AGEs as a new risk factor for the metabolic syndrome.

Methods: A randomised 1 year trial was conducted in obese individuals with the metabolic syndrome in two parallel groups: L-AGE diet vs a regular diet, habitually high in AGEs (Reg-AGE). Participants were allocated to each group by randomisation using random permuted blocks. At baseline and at the end of the trial, we obtained anthropometric variables, blood and urine samples, and performed OGTTs and MRI measurements of visceral and subcutaneous abdominal tissue and carotid artery. Only investigators involved in laboratory determinations were blinded to dietary assignment. Effects on insulin resistance (HOMA-IR) were the primary outcome.

Results: Sixty-one individuals were randomised to a Reg-AGE diet and 77 to an L-AGE diet; the data of 49 and 51, respectively, were analysed at the study end in 2014. The L-AGE diet markedly improved insulin resistance; modestly decreased body weight; lowered AGEs, oxidative stress and inflammation; and enhanced the protective factors sirtuin 1, AGE receptor 1 and glyoxalase I. The Reg-AGE diet raised AGEs and markers of insulin resistance, oxidative stress and inflammation. There were no effects on MRI-assessed measurements. No side effects from the intervention were identified. HOMA-IR came down from 3.1 ± 1.8 to 1.9 ± 1.3 (p < 0.001) in the L-AGE group, while it increased from 2.9 ± 1.2 to 3.6 ± 1.7 (p < 0.002) in the Reg-AGE group.

Conclusions/interpretation: L-AGE ameliorates insulin resistance in obese people with the metabolic syndrome, and may reduce the risk of type 2 diabetes, without necessitating a major reduction in adiposity. Elevated serum AGEs may be used to diagnose and treat 'at-risk' obesity.

Trial Registration: ClinicalTrials.gov NCT01363141 FUNDING: The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases (DK091231).
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http://dx.doi.org/10.1007/s00125-016-4053-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5129175PMC
October 2016

Podocyte injury: the role of proteinuria, urinary plasminogen, and oxidative stress.

Am J Physiol Renal Physiol 2016 12 22;311(6):F1308-F1317. Epub 2016 Jun 22.

Division of Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York.

Podocytes are the key target for injury in proteinuric glomerular diseases that result in podocyte loss, progressive focal segmental glomerular sclerosis (FSGS), and renal failure. Current evidence suggests that the initiation of podocyte injury and associated proteinuria can be separated from factors that drive and maintain these pathogenic processes leading to FSGS. In nephrotic urine aberrant glomerular filtration of plasminogen (Plg) is activated to the biologically active serine protease plasmin by urokinase-type plasminogen activator (uPA). In vivo inhibition of uPA mitigates Plg activation and development of FSGS in several proteinuric models of renal disease including 5/6 nephrectomy. Here, we show that Plg is markedly increased in the urine in two murine models of proteinuric kidney disease associated with podocyte injury: Tg26 HIV-associated nephropathy and the Cd2ap model of FSGS. We show that human podocytes express uPA and three Plg receptors: uPAR, tPA, and Plg-RKT. We demonstrate that Plg treatment of podocytes specifically upregulates NADPH oxidase isoforms NOX2/NOX4 and increases production of mitochondrial-dependent superoxide anion (O) that promotes endothelin-1 synthesis. Plg via O also promotes expression of the B scavenger receptor CD36 and subsequent increased intracellular cholesterol uptake resulting in podocyte apoptosis. Taken together, our findings suggest that following disruption of the glomerular filtration barrier at the onset of proteinuric disease, podocytes are exposed to Plg resulting in further injury mediated by oxidative stress. We suggest that chronic exposure to Plg could serve as a "second hit" in glomerular disease and that Plg is potentially an attractive target for therapeutic intervention.
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http://dx.doi.org/10.1152/ajprenal.00162.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5210206PMC
December 2016

Reduced Krüppel-Like Factor 2 Aggravates Glomerular Endothelial Cell Injury and Kidney Disease in Mice with Unilateral Nephrectomy.

Am J Pathol 2016 08 15;186(8):2021-2031. Epub 2016 Jun 15.

Department of Medicine/Nephrology, Icahn School of Medicine at Mount Sinai, New York, New York; Renal Section, James J. Peters Veterans Affairs Medical Center, Bronx, New York. Electronic address:

Loss of functional nephrons induces compensatory glomerular hyperfiltration and hypertrophy, leading to the progression of chronic kidney disease. Krüppel-like factor 2 (KLF2), a shear-stress-inducible transcription factor, confers protection against endothelial injury. Because glomerular hyperfiltration is associated with shear stress, we hypothesized that KLF2 may be an important factor in the compensatory response to unilateral nephrectomy (UNX). To test this hypothesis, endothelial cell-specific Klf2 heterozygous knockout mice (KO) and their wild-type littermate control (WT) underwent either UNX or sham-operation. WT-UNX mice developed compensatory renal hypertrophy as expected, whereas KO-UNX mice did not. KO-UNX mice exhibited higher blood pressure, reduced glomerular filtration rate, and significant increase in proteinuria and glomerulosclerosis compared to WT-UNX. Expression of endothelial nitric oxide synthase (official name Nos3), a known transcriptional target gene of KLF2, was significantly reduced and dysregulation of other endothelial genes was also observed in the glomeruli of KO-UNX when compared to WT-UNX and sham-operated mice. Furthermore, both podocyte number and expression of podocyte markers were also significantly reduced in KO-UNX glomeruli, indicating a potential cross talk between glomerular endothelial cells and podocytes. Finally, decreased renal expression of KLF2 in nephrectomy patients was associated with the progression of kidney disease. Taken together, our data demonstrate a protective role of KLF2 against glomerular endothelial cell injury and progression of chronic kidney disease in the model of compensatory renal hypertrophy.
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http://dx.doi.org/10.1016/j.ajpath.2016.03.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4973653PMC
August 2016

Krüppel-Like Factor 15 Mediates Glucocorticoid-Induced Restoration of Podocyte Differentiation Markers.

J Am Soc Nephrol 2017 Jan 10;28(1):166-184. Epub 2016 Jun 10.

Department of Pharmacology and Systems Therapeutics and.

Podocyte injury is the inciting event in primary glomerulopathies, such as minimal change disease and primary FSGS, and glucocorticoids remain the initial and often, the primary treatment of choice for these glomerulopathies. Because inflammation is not readily apparent in these diseases, understanding the direct effects of glucocorticoids on the podocyte, independent of the immunomodulatory effects, may lead to the identification of targets downstream of glucocorticoids that minimize toxicity without compromising efficacy. Several studies showed that treatment with glucocorticoids restores podocyte differentiation markers and normal ultrastructure and improves cell survival in murine podocytes. We previously determined that Krüppel-like factor 15 (KLF15), a kidney-enriched zinc finger transcription factor, is required for restoring podocyte differentiation markers in mice and human podocytes under cell stress. Here, we show that in vitro treatment with dexamethasone induced a rapid increase of KLF15 expression in human and murine podocytes and enhanced the affinity of glucocorticoid receptor binding to the promoter region of KLF15 In three independent proteinuric murine models, podocyte-specific loss of Klf15 abrogated dexamethasone-induced podocyte recovery. Furthermore, knockdown of KLF15 reduced cell survival and destabilized the actin cytoskeleton in differentiated human podocytes. Conversely, overexpression of KLF15 stabilized the actin cytoskeleton under cell stress in human podocytes. Finally, the level of KLF15 expression in the podocytes and glomeruli from human biopsy specimens correlated with glucocorticoid responsiveness in 35 patients with minimal change disease or primary FSGS. Thus, these studies identify the critical role of KLF15 in mediating the salutary effects of glucocorticoids in the podocyte.
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http://dx.doi.org/10.1681/ASN.2015060672DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5198263PMC
January 2017