Glucocorticoid- and pioglitazone-induced proteinuria reduction in experimental NS both correlate with glomerular ECM modulation.

Idiopathic nephrotic syndrome (NS) is a common glomerular disease. Although glucocorticoids (GC) are the primary treatment, the PPARγ agonist pioglitazone (Pio) also reduces proteinuria in patients with NS and directly protects podocytes from injury. Because both drugs reduce proteinuria, we hypothesized these effects result from overlapping transcriptional patterns. Systems biology approaches compared glomerular transcriptomes from rats with PAN-induced NS treated with GC vs. Pio and identified 29 commonly regulated genes-of-interest, primarily involved in extracellular matrix (ECM) remodeling. Correlation with clinical idiopathic NS patient datasets confirmed glomerular ECM dysregulation as a potential mechanism of injury. Cellular deconvolution in silico revealed GC- and Pio-induced amelioration of altered genes primarily within podocytes and mesangial cells. While validation studies are indicated, these analyses identified molecular pathways involved in the early stages of NS (prior to scarring), suggesting that targeting glomerular ECM dysregulation may enable a future non-immunosuppressive approach for proteinuria reduction in idiopathic NS.

Inhibition of the glucocorticoid receptor attenuates proteinuric kidney diseases in multiple species.

BACKGROUND AND HYPOTHESIS: Glucocorticoids are the treatment of choice for proteinuric patients with minimal-change disease (MCD) and primary focal and segmental glomerulosclerosis (FSGS). Immunosuppressive as well as direct effects on podocytes are believed to mediate their actions. In this study, we analyzed the anti-proteinuric effects of inhibition of the glucocorticoid receptor (GR) in glomerular epithelial cells, including podocytes. METHODS: We employed genetic and pharmacological approaches to inhibit the GR. Genetically, we used Pax8-Cre/GRfl/fl mice to specifically inactivate the GR in kidney epithelial cells. Pharmacologically, we utilized a glucocorticoid antagonist called mifepristone. RESULTS: Genetic inactivation of GR, specifically in kidney epithelial cells, using Pax8-Cre/GRfl/fl mice, ameliorated proteinuria following protein overload. We further tested the effects of pharmacological GR inhibition in three models and species: the puromycin-aminonucleoside-induced nephrosis model in rats, the protein overload model in mice and the inducible transgenic NTR/MTZ zebrafish larvae with specific and reversible podocyte injury. In all three models, both pharmacological GR activation and inhibition consistently and significantly ameliorated proteinuria. Additionally, we translated our findings to humans, where three nephrotic adult patients with MCD or primary FSGS with contraindications or insufficient responses to corticosteroids, were treated with mifepristone. This treatment resulted in a clinically relevant reduction of proteinuria. CONCLUSIONS: Thus, across multiple species and proteinuria models, both genetic and pharmacological GR inhibition was at least as effective as pronounced GR activation. While, the mechanism remains perplexing, GR inhibition may be a novel and targeted therapeutic approach to treat glomerular proteinuria potentially bypassing adverse actions of steroids.

Increased renal elimination of endogenous and synthetic pyrimidine nucleosides in concentrative nucleoside transporter 1 deficient mice.

Concentrative nucleoside transporters (CNTs) are active nucleoside influx systems, but their in vivo roles are poorly defined. By generating CNT1 knockout (KO) mice, here we identify a role of CNT1 in the renal reabsorption of nucleosides. Deletion of CNT1 in mice increases the urinary excretion of endogenous pyrimidine nucleosides with compensatory alterations in purine nucleoside metabolism. In addition, CNT1 KO mice exhibits high urinary excretion of the nucleoside analog gemcitabine (dFdC), which results in poor tumor growth control in CNT1 KO mice harboring syngeneic pancreatic tumors. Interestingly, increasing the dFdC dose to attain an area under the concentration-time curve level equivalent to that achieved by wild-type (WT) mice rescues antitumor efficacy. The findings provide new insights into how CNT1 regulates reabsorption of endogenous and synthetic nucleosides in murine kidneys and suggest that the functional status of CNTs may account for the optimal action of pyrimidine nucleoside analog therapeutics in humans.

Alternatively Spliced Landscape of PPARγ mRNA in Podocytes Is Distinct from Adipose Tissue.

Podocytes are highly differentiated epithelial cells, and their structural and functional integrity is compromised in a majority of glomerular and renal diseases, leading to proteinuria, chronic kidney disease, and kidney failure. Traditional agonists (e.g., pioglitazone) and selective modulators (e.g., GQ-16) of peroxisome-proliferator-activated-receptor-γ (PPARγ) reduce proteinuria in animal models of glomerular disease and protect podocytes from injury via PPARγ activation. This indicates a pivotal role for PPARγ in maintaining glomerular function through preservation of podocytes distinct from its well-understood role in driving insulin sensitivity and adipogenesis. While its transcriptional role in activating adipokines and adipogenic genes is well-established in adipose tissue, liver and muscle, understanding of podocyte PPARγ signaling remains limited. We performed a comprehensive analysis of PPARγ mRNA variants due to alternative splicing, in human podocytes and compared with adipose tissue. We found that podocytes express the ubiquitous PPARγ Var 1 (encoding γ1) and not Var2 (encoding γ2), which is mostly restricted to adipose tissue and liver. Additionally, we detected expression at very low level of Var4, and barely detectable levels of other variants, Var3, Var11, VartORF4 and Var9, in podocytes. Furthermore, a distinct podocyte vs. adipocyte PPAR-promoter-response-element containing gene expression, enrichment and pathway signature was observed, suggesting differential regulation by podocyte specific PPARγ1 variant, distinct from the adipocyte-specific γ2 variant. In summary, podocytes and glomeruli express several PPARγ variants, including Var1 (γ1) and excluding adipocyte-specific Var2 (γ2), which may have implications in podocyte specific signaling and pathophysiology. This suggests that that new selective PPARγ modulators can be potentially developed that will be able to distinguish between the two forms, γ1 and γ2, thus forming a basis of novel targeted therapeutic avenues.

Adriamycin-Induced Nephropathy is Robust in N and Modest in J Substrain of C57BL/6.

Adriamycin (ADR)-induced nephropathy remains the leading model to study human primary focal segmental glomerulosclerosis (FSGS), a common pathway for podocyte damage and glomerular loss of function that leads to chronic kidney disease. However, the use of this model for reverse genetics is limited by historical categorization of C57BL/6 mice as an ADR-resistant strain, which is also the most common genetically modified strain. Additionally, conflicting reports exist utilizing C57BL/6 for ADR-nephrosis due to lack of understanding of substrain differences (J/N) and variability in ADR dosage, timing, and frequency to induce damage. We have undertaken a systematic approach to elucidate the specifics of ADR-nephrosis in C57BL/6 N and J substrains. We induced nephropathy with 2 doses of ADR, and measured albuminuria for 6 weeks and performed histological evaluations. Our findings revealed induction of robust and modest proteinuria in N and J substrains, respectively. The serum creatinine levels were elevated in N, but not J substrain. Both the substrains showed reduction in body weight with N greater than J, although mortality remained at 0% in both substrains. Histological analysis showed worse renal lesions in the N than the J substrain. Podocyte markers synaptopodin, nephrin, podocin, and WT1 were reduced to a greater extent in the N than the J substrain. In summary, we provide the nephrology community with a reproducible mouse model for FSGS, in a strain otherwise assumed to be ADR-resistant and highlight the differences between J and N substrains. This enables future studies, especially concerning genetically manipulated animal models in C57BL/6.

Daily v. weekly oral vitamin D3 therapy for nutritional rickets in Indian children: a randomised controlled open-label trial.

The aim of the study was to compare the efficacy of daily v. weekly oral vitamin D3 therapy in radiological healing of nutritional rickets. Children 6 months to 12 years (n 132) diagnosed with nutritional rickets were randomised into three groups (n 44): group A - 2000 IU daily vitamin D3 for 12 weeks, B - 60 000 IU weekly for 3 weeks, C - 60 000 IU weekly for 6 weeks. Serum calcium, phosphorus, 25-hydroxyvitamin D (25(OH)D), parathyroid hormone and X-ray score were estimated at baseline and 12 weeks (endline). The proportion of children who achieved complete radiological healing at endline was compared between three groups by χ2 and delta change in laboratory parameters by ANOVA (parametric data) or Kruskal Wallis test (non-parametric data), respectively. Baseline 25(OH)D ≤ 20 ng/ml was seen in 119 (90·2 %), hyperparathyroidism in 90 (68·8 %) and hypocalcaemia in 96 (72·7 %). A total of 120/132 children completed the study. Complete radiological healing seen in 30 (75 %) in group A, 23 (60·5 %) in group B and 26 (61·9 %) in group C; P = 0·15, with comparable endline X-ray scores; P = 0·31. The median (interquartile range (IQR)) delta X-ray score (baseline-endline) was 7 (4,9), 5 (2·25, 6) and 6 (4,7) in groups A, B and C, respectively; P = 0·019. Median (IQR) 25(OH)D endline levels in groups A, B and C were 50·0 (26·5, 66·5), 42·1 (28·4, 54·4) and 53·5 (33·7, 71·2) ng/ml, respectively; P = 0·045. Radiological scores were comparable at endline among daily and weekly vitamin D groups with greater change from baseline in daily supplemented group.

Selective modulator of nuclear receptor PPARγ with reduced adipogenic potential ameliorates experimental nephrotic syndrome.

Glomerular disease manifests as nephrotic syndrome (NS) with high proteinuria and comorbidities, and is frequently refractory to standard treatments. We hypothesized that a selective modulator of PPARγ, GQ-16, will provide therapeutic advantage over traditional PPARγ agonists for NS treatment. We demonstrate in a pre-clinical NS model that proteinuria is reduced with pioglitazone to 64%, and robustly with GQ-16 to 81% of nephrosis, comparable to controls. Although both GQ-16 and pioglitazone restore glomerular-Nphs1, hepatic-Pcsk9 and serum-cholesterol, only GQ-16 restores glomerular-Nrf2, and reduces hypoalbuminemia and hypercoagulopathy. GQ-16 and pioglitazone restore common and distinct glomerular gene expression analyzed by RNA-seq and induce insulin sensitizing adipokines to various degrees. Pioglitazone but not GQ-16 induces more lipid accumulation and aP2 in adipocytes and white adipose tissue. We conclude that selective modulation of PPARγ by a partial agonist, GQ-16, is more advantageous than pioglitazone in reducing proteinuria, NS associated comorbidities, and adipogenic side effects of full PPARγ agonists.

Ionized Blood Magnesium in Sick Children: An Overlooked Electrolyte.

INTRODUCTION: Magnesium is a less frequently monitored electrolyte in critically ill patients. Hypomagnesemia is associated with increased need for mechanical ventilation, mortality and prolonged ICU stay. The present study was undertaken to identify the proportion of children with abnormal magnesium levels and correlate it with disease outcome. METHODS: This observational study included children aged 1 month to 12 years hospitalized at the emergency room. Heparinized blood was collected for determination of ionized magnesium, ionized calcium, sodium, potassium and lactate using Stat Profile Prime Plus (Nova Biomedical, Waltham, MA, USA). Clinical outcomes for duration of hospitalization, and death or discharge were recorded. RESULTS: A total of 154 (102 males) children with median (IQR) age of 11 (4, 49.75) months were enrolled. Sixty one (39.6%) had ionized magnesium levels below 0.42 mmol/l, 63 (40.9%) had normal levels and 30 (19.4%) had hypermagnesemia (>0.59 mmol/l). Hypomagnesemia was associated with hypocalcemia (p < 0.001), hyponatremia (p < 0.001) and hypokalemia (p < 0.02). A higher proportion of children with hypermagnesemia required ventilation than hypomagnesemia (26% vs. 9%) and succumbed (35% vs. 20%), respectively; p > 0.05. Ninety-three (60.3%) had hypocalcemia and 10 (6.5%) children had hypercalcemia. There was good correlation between ionized calcium and magnesium values (r = 0.72, p < 0.001). CONCLUSION: Both hypomagnesemia and hypermagnesemia were seen in critically ill children. Patients with hypomagnesemia had significantly higher proportion of other electrolyte abnormalities.

Point of Care Testing of Serum Electrolytes and Lactate in Sick Children.

OBJECTIVE: To evaluate the electrolyte and lactate abnormalities in hospitalized children using a point of care testing (POCT) device and assess the agreement on the electrolyte abnormalities between POCT and central laboratory analyzer with venous blood. METHODS: This observational study recruited hospitalized children aged 1 month to 12 years within two hours of admission. A paired venous sample and heparinized blood sample were drawn and analyzed by the central laboratory and POCT device (Stat Profile Prime Plus-Nova Biomedical, Waltham, MA, USA) for sodium and potassium. Lactate was measured on the POCT device only. The clinical and outcome parameters of children with electrolyte abnormalities or elevated lactate (>2mmol/L), and the agreement between POCT values and central laboratory values were assessed. RESULTS: A total of 158 children with median (IQR) age 11 (6-10) months and PRISM score 5 (2-9) were enrolled. The proportion of children with abnormal sodium and potassium levels, and acidosis on POCT were 87 (55.1%), 47 (29.7%) and 73 (46.2%), respectively. The interclass coefficient between POCT and laboratory values of sodium and potassium values was 0.74 and 0.71 respectively; P<0.001. Children with hyperlactatemia (81, 51.3%) had higher odds of shock (OR 4.58, 95% CI: 1.6-12.9), mechanical ventilation (OR 2.7, 95% CI 1.1-6.6, P=0.02) and death (OR 3.1, 95% CI 1.3-7.5 P=0.01) compared to those with normal lactate. CONCLUSION: POCT can be used as an adjunct for rapid assessment of biochemical parameters in sick children. Lactate measured by POCT was a good prognostic indicator.

Plasma Cytokine Profiling to Predict Steroid Resistance in Pediatric Nephrotic Syndrome.

INTRODUCTION: Glucocorticoids (GCs) are the primary treatment for nephrotic syndrome (NS), although ∼10% to 20% of children develop steroid-resistant NS (SRNS). Unfortunately, there are no validated biomarkers able to predict SRNS at initial disease presentation. We hypothesized that a plasma cytokine panel could predict SRNS at disease presentation, and identify potential pathways regulating SRNS pathogenesis. METHODS: Paired plasma samples were collected from 26 children with steroid-sensitive NS (SSNS) and 14 with SRNS at NS presentation and after ∼7 weeks of GC therapy, when SSNS versus SRNS was clinically determined. Plasma cytokine profiling was performed with a panel of 27 cytokines. RESULTS: We identified 13 cytokines significantly different in Pretreatment SSNS versus SRNS samples. Statistical modeling identified a cytokine panel (interleukin [IL]-7, IL-9, monocyte chemoattractant protein-1 [MCP-1]) able to discriminate between SSNS and SRNS at disease presentation (receiver operating characteristic [ROC] value = 0.846; sensitivity = 0.643; specificity = 0.846). Furthermore, GC treatment resulted in significant decreases in plasma interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), IL-7, IL-13, and IL-5 in both SSNS and SRNS patients. CONCLUSIONS: These studies suggest that initial GC treatment of NS reduces the plasma cytokines secreted by both CD4+ TH1 cells and TH2 cells, as well as CD8+ T cells. Importantly, a panel of 3 cytokines (IL-7, IL-9, and MCP-1) was able to predict SRNS prior to GC treatment at disease presentation. Although these findings will benefit from validation in a larger cohort, the ability to identify SRNS at disease presentation could greatly benefit patients by enabling both avoidance of unnecessary GC-induced toxicity and earlier transition to more effective alternative treatments.

Comparison of 4DMRI and 4DCT for the preoperative evaluation of patients with primary hyperparathyroidism.

BACKGROUND: Minimally invasive parathyroid surgery is the standard of care in patients with Primary Hyperparathyroidism (PHPT) which requires accurate preoperative localization. Of all the available imaging modalities, 4DCT is considered the best modality for localization, however it entails the risk of ionizing radiation. To circumvent this 4DMRI was evaluated for parathyroid lesion localization. PURPOSE: To evaluate and compare the accuracy of 4DCT and 4DMRI in the localization of parathyroid Lesions. MATERIALS AND METHODS: In this ethically approved observational diagnostic study, 135 patients (age range: 10-75 years, male: female ratio - 1:2.1) with clinically and biochemically suspected PHPT were recruited. Of these, 56 patients underwent both 4DCT and 4DMRI. Six patients with positive imaging who didn't undergo surgery were excluded. A total of 50 patients with 61 proven parathyroid lesions were included for analysis. 48 patients had surgical and histopathological findings for the confirmation of imaging findings. RESULTS: Both 4DCT and 4DMRI correctly detected 59/61 lesions in 48 patients. There was one false positive and two true negatives. In addition, 2 (3.22 %) lesions which were not detected by 4DCT and 4DMRI were found on surgery. The sensitivity of both 4DCT and 4DMRI was 96.7 %; specificity was 66.6 % and accuracy was 95.2 %. CONCLUSION: 4DMRI and 4DCT had similar accuracy for the detection of parathyroid lesions. However, 4DMRI has the advantage of lack of exposure to ionizing radiation, which can be beneficial in younger patients.

Sulfatase 2 Is Associated with Steroid Resistance in Childhood Nephrotic Syndrome.

Glucocorticoid (GC) resistance complicates the treatment of ~10-20% of children with nephrotic syndrome (NS), yet the molecular basis for resistance remains unclear. We used RNAseq analysis and in silico algorithm-based approaches on peripheral blood leukocytes from 12 children both at initial NS presentation and after ~7 weeks of GC therapy to identify a 12-gene panel able to differentiate steroid resistant NS (SRNS) from steroid-sensitive NS (SSNS). Among this panel, subsequent validation and analyses of one biologically relevant candidate, sulfatase 2 (SULF2), in up to a total of 66 children, revealed that both SULF2 leukocyte expression and plasma arylsulfatase activity Post/Pre therapy ratios were greater in SSNS vs. SRNS. However, neither plasma SULF2 endosulfatase activity (measured by VEGF binding activity) nor plasma VEGF levels, distinguished SSNS from SRNS, despite VEGF's reported role as a downstream mediator of SULF2's effects in glomeruli. Experimental studies of NS-related injury in both rat glomeruli and cultured podocytes also revealed decreased SULF2 expression, which were partially reversible by GC treatment of podocytes. These findings together suggest that SULF2 levels and activity are associated with GC resistance in NS, and that SULF2 may play a protective role in NS via the modulation of downstream mediators distinct from VEGF.

Nuclear receptors in podocyte biology and glomerular disease.

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.

Nephrotic syndrome-associated hypercoagulopathy is alleviated by both pioglitazone and glucocorticoid which target two different nuclear receptors.

BACKGROUND: Thrombosis is a potentially life-threatening nephrotic syndrome (NS) complication. We have previously demonstrated that hypercoagulopathy is proportional to NS severity in rat models and that pioglitazone (Pio) reduces proteinuria both independently and in combination with methylprednisolone (MP), a glucocorticoid (GC). However, the effect of these treatments on NS-associated hypercoagulopathy remains unknown. We thus sought to determine the ability of Pio and GC to alleviate NS-associated hypercoagulopathy. METHODS: Puromycin aminonucleoside-induced rat NS was treated with sham, Low- or High-dose MP, Pio, or combination (Pio + Low-MP) and plasma was collected at day 11. Plasma samples were collected from children with steroid-sensitive NS (SSNS) and steroid-resistant NS (SRNS) upon presentation and after 7 weeks of GC therapy. Plasma endogenous thrombin potential (ETP), antithrombin (AT) activity, and albumin (Alb) were measured using thrombin generation, amidolytic, and colorimetric assays, respectively. RESULTS: In a rat model of NS, both High-MP and Pio improved proteinuria and corrected hypoalbuminemia, ETP and AT activity (p < .05). Proteinuria (p = .005) and hypoalbuminemia (p < .001) were correlated with ETP. In childhood NS, while ETP was not different at presentation, GC therapy improved proteinuria, hypoalbuminemia, and ETP in children with SSNS (p < .001) but not SRNS (p = .330). CONCLUSIONS: Both Pio and GC diminish proteinuria and significantly alleviate hypercoagulopathy. Both Pio and MP improved hypercoagulopathy in rats, and successful GC therapy (SSNS) also improved hypercoagulopathy in childhood NS. These data suggest that even a partial reduction in proteinuria may reduce NS-associated thrombotic risk.

Predicting and Defining Steroid Resistance in Pediatric Nephrotic Syndrome Using Plasma Proteomics.

INTRODUCTION: Nephrotic syndrome (NS) is a characterized by massive proteinuria, edema, hypoalbuminemia, and dyslipidemia. Glucocorticoids (GCs), the primary therapy for >60 years, are ineffective in approximately 50% of adults and approximately 20% of children. Unfortunately, there are no validated biomarkers able to predict steroid-resistant NS (SRNS) or to define the pathways regulating SRNS. METHODS: We performed proteomic analyses on paired pediatric NS patient plasma samples obtained both at disease presentation before glucocorticoid initiation and after approximately 7 weeks of GC therapy to identify candidate biomarkers able to either predict steroid resistance before treatment or define critical molecular pathways/targets regulating steroid resistance. RESULTS: Proteomic analyses of 15 paired NS patient samples identified 215 prevalent proteins, including 13 candidate biomarkers that predicted SRNS before GC treatment, and 66 candidate biomarkers that mechanistically differentiated steroid-sensitive NS (SSNS) from SRNS. Ingenuity Pathway Analyses and protein networking pathways approaches further identified proteins and pathways associated with SRNS. Validation using 37 NS patient samples (24 SSNS/13 SRNS) confirmed vitamin D binding protein (VDB) and APOL1 as strong predictive candidate biomarkers for SRNS, and VDB, hemopexin (HPX), adiponectin (ADIPOQ), sex hormone-binding globulin (SHBG), and APOL1 as strong candidate biomarkers to mechanistically distinguish SRNS from SSNS. Logistic regression analysis identified a candidate biomarker panel (VDB, ADIPOQ, and matrix metalloproteinase 2 [MMP-2]) with significant ability to predict SRNS at disease presentation (P = 0.003; area under the receiver operating characteristic curve = 0.78). CONCLUSION: Plasma proteomic analyses and immunoblotting of serial samples in childhood NS identified a candidate biomarker panel able to predict SRNS at disease presentation, as well as candidate molecular targets/pathways associated with clinical steroid resistance.

Predicting and Defining Steroid Resistance in Pediatric Nephrotic Syndrome Using Plasma Metabolomics.

INTRODUCTION: Nephrotic syndrome (NS) is a kidney disease that affects both children and adults. Glucocorticoids have been the primary therapy for >60 years but are ineffective in approximately 20% of children and approximately 50% of adult patients. Unfortunately, patients with steroid-resistant NS (SRNS; vs. steroid-sensitive NS [SSNS]) are at high risk for both glucocorticoid-induced side effects and disease progression. METHODS: We performed proton nuclear magnetic resonance (1H NMR) metabolomic analyses on plasma samples (n = 86) from 45 patients with NS (30 SSNS and 15 SRNS) obtained at initial disease presentation before glucocorticoid initiation and after approximately 7 weeks of glucocorticoid therapy to identify candidate biomarkers able to either predict SRNS before treatment or define critical molecular pathways/targets regulating steroid resistance. RESULTS: Stepwise logistic regression models identified creatinine concentration and glutamine concentration (odds ratio [OR]: 1.01; 95% confidence interval [CI]: 0.99-1.02) as 2 candidate biomarkers predictive of SRNS, and malonate concentration (OR: 0.94; 95% CI: 0.89-1.00) as a third candidate predictive biomarker using a similar model (only in children >3 years). In addition, paired-sample analyses identified several candidate biomarkers with the potential to identify mechanistic molecular pathways/targets that regulate clinical steroid resistance, including lipoproteins, adipate, pyruvate, creatine, glucose, tyrosine, valine, glutamine, and sn-glycero-3-phosphcholine. CONCLUSION: Metabolomic analyses of serial plasma samples from children with SSNS and SRNS identified elevated creatinine and glutamine concentrations, and reduced malonate concentrations, as auspicious candidate biomarkers to predict SRNS at disease onset in pediatric NS, as well as additional candidate biomarkers with the potential to identify mechanistic molecular pathways that may regulate clinical steroid resistance.

Pharmacological and genetic inhibition of downstream targets of p38 MAPK in experimental nephrotic syndrome.

Nie X, Chanley MA, Pengal R, Thomas DB, Agrawal S, Smoyer WE. Pharmacological and genetic inhibition of downstream targets of p38 MAPK in experimental nephrotic syndrome. Am J Physiol Renal Physiol 314: F602-F613, 2018. First published November 29, 2017; doi: 10.1152/ajprenal.00207.2017 .-The p38 MAPK pathway plays a crucial role in various glomerulopathies, with activation being associated with disease and inhibition being associated with disease amelioration. We hypothesized that the downstream targets of p38 MAPK, MAPK-activated protein kinase 2 and/or 3 (MK2 and/or MK3), play an important role in mediating injury in experimental nephrotic syndrome via their actions on their downstream substrates heat shock protein B1 (HSPB1) and cyclooxygenase-2 (COX-2). To test this hypothesis, the effects of both pharmacological and genetic inhibition of MK2 and MK3 were examined in mouse adriamycin (ADR) and rat puromycin aminonucleoside (PAN) nephropathy models. MK2-/-, MK3-/-, and MK2-/-MK3-/- mice were generated in the Sv129 background and subjected to ADR-induced nephropathy. MK2 and MK3 protein expression was completely abrogated in the respective knockout genotypes, and massive proteinuria and renal histopathological changes developed after ADR treatment. Furthermore, renal cortical HSPB1 was induced in all four genotypes by day 21, but HSPB1 was activated only in the wild-type and MK3-/- mice. Expression of the stress proteins HSPB8 and glucose-regulated protein 78 (GRP78) remained unaltered across all genotypes. Finally, while MK2 and/or MK3-knockout downregulated the proinflammatory enzyme COX-2, ADR significantly induced renal cortical COX-2 only in MK2-/- mice. Additionally, pharmacological MK2 inhibition with PF-318 during PAN-induced nephropathy did not result in significant proteinuria reduction in rats. Together, these data suggest that while the inhibition of MK2 and/or MK3 regulates the renal stress response, our currently available approaches are not yet able to safely and effectively reduce proteinuria in experimental nephrotic syndrome and that other p38MAPK downstream targets should also be considered to improve the future treatment of glomerular disease.

Dyslipidaemia in nephrotic syndrome: mechanisms and treatment.

Nephrotic syndrome is a highly prevalent disease that is associated with high morbidity despite notable advances in its treatment. Many of the complications of nephrotic syndrome, including the increased risk of atherosclerosis and thromboembolism, can be linked to dysregulated lipid metabolism and dyslipidaemia. These abnormalities include elevated plasma levels of cholesterol, triglycerides and the apolipoprotein B-containing lipoproteins VLDL and IDL; decreased lipoprotein lipase activity in the endothelium, muscle and adipose tissues; decreased hepatic lipase activity; and increased levels of the enzyme PCSK9. In addition, there is an increase in the plasma levels of immature HDL particles and reduced cholesterol efflux. Studies from the past few years have markedly improved our understanding of the molecular pathogenesis of nephrotic syndrome-associated dyslipidaemia, and also heightened our awareness of the associated exacerbated risks of cardiovascular complications, progressive kidney disease and thromboembolism. Despite the absence of clear guidelines regarding treatment, various strategies are being increasingly utilized, including statins, bile acid sequestrants, fibrates, nicotinic acid and ezetimibe, as well as lipid apheresis, which seem to also induce partial or complete clinical remission of nephrotic syndrome in a substantial percentage of patients. Future potential treatments will likely also include inhibition of PCSK9 using recently-developed anti-PCSK9 monoclonal antibodies and small inhibitory RNAs, as well as targeting newly identified molecular regulators of lipid metabolism that are dysregulated in nephrotic syndrome.

Dyslipidaemia in nephrotic syndrome: mechanisms and treatment.

This corrects the article DOI: 10.1038/nrneph.2017.155.