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Aims/hypothesisThe sodium–glucose cotransporter 2 (SGLT2) inhibitor canagliflozin slows progression of kidney function decline in type 2 diabetes. The aim of this study was to assess the effect of the SGLT2 inhibitor canagliflozin on biomarkers for progression of diabetic kidney disease (DKD).MethodsA canagliflozin mechanism of action (MoA) network model was constructed based on an in vitro transcriptomics experiment in human proximal tubular cells and molecular features linked to SGLT2 inhibitors from scientific literature. This model was mapped onto an established DKD network model that describes molecular processes associated with DKD. Overlapping areas in both networks were subsequently used to select candidate biomarkers that change with canagliflozin therapy. These biomarkers were measured in 296 stored plasma samples from a previously reported 2 year clinical trial comparing canagliflozin with glimepiride.ResultsForty-four proteins present in the canagliflozin MoA molecular model overlapped with proteins in the DKD network model. These proteins were considered candidates for monitoring impact of canagliflozin on DKD pathophysiology. For ten of these proteins, scientific evidence was available suggesting that they are involved in DKD progression. Of these, compared with glimepiride, canagliflozin 300 mg/day decreased plasma levels of TNF receptor 1 (TNFR1; 9.2%; p < 0.001), IL-6 (26.6%; p = 0.010), matrix metalloproteinase 7 (MMP7; 24.9%; p = 0.011) and fibronectin 1 (FN1; 14.9%; p = 0.055) during 2 years of follow-up.Conclusions/interpretationThe observed reduction in TNFR1, IL-6, MMP7 and FN1 suggests that canagliflozin contributes to reversing molecular processes related to inflammation, extracellular matrix turnover and fibrosis.Trial registration ClinicalTrials.gov NCT00968812

ATP and its ultimate degradation product adenosine are potent extracellular signalling molecules that elicit a variety of pathophysiological functions in the kidney through the activation of P2 and P1 purinergic receptors, respectively. Extracellular purines can modulate immune responses, balancing inflammatory processes and immunosuppression; indeed, alterations in extracellular nucleotide and adenosine signalling determine outcomes of inflammation and healing processes. The functional activities of ectonucleotidases such as CD39 and CD73, which hydrolyse pro-inflammatory ATP to generate immunosuppressive adenosine, are therefore pivotal in acute inflammation. Protracted inflammation may result in aberrant adenosinergic signalling, which serves to sustain inflammasome activation and worsen fibrotic reactions. Alterations in the expression of ectonucleotidases on various immune cells, such as regulatory T cells and macrophages, as well as components of the renal vasculature, control purinergic receptor-mediated effects on target tissues within the kidney. The role of CD39 as a rheostat that can have an impact on purinergic signalling in both acute and chronic inflammation is increasingly supported by the literature, as detailed in this Review. Better understanding of these purinergic processes and development of novel drugs targeting these pathways could lead to effective therapies for the management of acute and chronic kidney disease.Purinergic signalling in the kidney maintains homeostasis and mediates injury-induced inflammation. The extracellular conversion of ATP into adenosine is critical for modulating these processes. Here, the authors discuss the pathological conditions associated with extracellular ATP metabolism and novel strategies for their treatment.

MicroRNAs (miRNAs) are endogenous short (20–22 nucleotides) non-coding RNA molecules that mediate gene expression. This is an important regulatory mechanism to modulate fundamental cellular processes such as differentiation, proliferation, death, metabolism, and pathophysiology of many diseases. The miRNA expression profile of the kidney differs greatly from that of other organs, as well as between the different regions in the kidney. In kidneys, miRNAs are indispensable for development and homeostasis. In this review, we explore the involvement of miRNAs in the regulation of blood pressure, hormone, water, and ion balance pertaining to kidney homeostasis. We also highlight their importance in renal pathophysiology, such as in polycystic disease, diabetic nephropathy, nephrogenic diabetes insipidus, hypertension, renal cancer, and kidney fibrosis (epithelial–mesenchymal transition). In addition, we highlight the need for further investigations on miRNA-based studies in the development of diagnostic, prognostic, and therapeutic tools for renal diseases.

Neutrophil gelatinase-associated lipocalin (Ngal, 24p3, SIP24, lipocalin 2, or siderocalin) was originally purified from neutrophils, but with unknown function. Recently, it was identified that Ngal activates nephron formation in the embryonic kidney, is rapidly and massively induced in renal failure and possesses kidney-protective activity. We would like to propose that blood, urine, and kidney Ngal levels are the real-time indicators of active kidney damage, rather than one of many markers of functional nephron number (as Forest Fire Theory). Ngal is a novel iron-carrier protein exerting pleiotropic actions including the upregulation of epithelial marker E-cadherin expression, opening an exciting field in cell biology.

We performed a double-blind placebo-controlled trial to study whether early treatment with erythropoietin could prevent the development of acute kidney injury in patients in two general intensive care units. As a guide for choosing the patients for treatment we measured urinary levels of two biomarkers, the proximal tubular brush border enzymes γ-glutamyl transpeptidase and alkaline phosphatase. Randomization to either placebo or two doses of erythropoietin was triggered by an increase in the biomarker concentration product to levels above 46.3, with a primary outcome of relative average plasma creatinine increase from baseline over 4 to 7 days. Of 529 patients, 162 were randomized within an average of 3.5 h of a positive sample. There was no difference in the incidence of erythropoietin-specific adverse events or in the primary outcome between the placebo and treatment groups. The triggering biomarker concentration product selected patients with more severe illness and at greater risk of acute kidney injury, dialysis, or death; however, the marker elevations were transient. Early intervention with high-dose erythropoietin was safe but did not alter the outcome. Although these two urine biomarkers facilitated our early intervention, their transient increase compromised effective triaging. Further, our study showed that a composite of these two biomarkers was insufficient for risk stratification in a patient population with a heterogeneous onset of injury.

Background Febuxostat immediate release (IR), a xanthine oxidase inhibitor, is indicated for the management of hyperuricemia in patients with gout by lowering urate levels. An extended release (XR) formulation of febuxostat was developed to provide equal or superior efficacy on urate lowering compared with the IR formulation and potentially lower the risk of treatment-initiated gout flares due to an altered pattern of drug exposure. The present study evaluated the efficacy and safety of febuxostat XR and IR formulations in patients with gout and moderate renal impairment (estimated glomerular filtrate rate ≥ 30 and < 60 ml/min). Methods This was an exploratory, 3-month, phase II, multicenter, placebo-controlled, double-blind proof-of-concept study. Patients ( n  = 189) were randomized 1:1:1:1:1 to receive placebo or febuxostat IR 40 mg, XR 40 mg, IR 80 mg, or XR 80 mg once daily. Endpoints included: proportion of patients with serum uric acid (sUA) < 5.0 mg/dl at month 3 (primary endpoint), proportion of patients with sUA < 6.0 mg/dl at month 3, and proportion of patients with ≥ 1 gout flare requiring treatment over 3 months. Results At month 3, all febuxostat treatment groups were associated with greater proportions of patients achieving sUA < 5.0 mg/dl ( p  < 0.05 vs placebo). A greater proportion of patients receiving XR 40 mg achieved sUA < 5.0 mg/dl versus those receiving IR 40 mg ( p  = 0.034); proportions were similar in the IR 80 mg and XR 80 mg groups. Higher proportions of febuxostat-treated patients achieved sUA < 6.0 mg/dl at month 3 ( p  < 0.05 vs placebo) and experienced ≥ 1 gout flare (significant for all comparisons, except XR 40 mg). Incidences of treatment-related adverse events were low across all treatment groups; the majority were mild or moderate with no apparent trends correlating with IR or XR doses. The most common treatment-emergent adverse event was hypertension. One death (unrelated to the study drug) was reported. Conclusions These exploratory data demonstrate that febuxostat (XR and IR) formulations were effective and well tolerated in patients with gout and moderate renal impairment. Trial registration ClinicalTrials.gov, NCT02128490 Registered on 29 April 2014.

Ciliopathies are a group of human disorders caused by dysfunction of primary cilia, ubiquitous microtubule-based organelles involved in transduction of extra-cellular signals to the cell. This function requires the concentration of receptors and channels in the ciliary membrane, which is achieved by complex trafficking mechanisms, in part controlled by the small GTPase RAB8, and by sorting at the transition zone located at the entrance of the ciliary compartment. Mutations in the transition zone gene CC2D2A cause the related Joubert and Meckel syndromes, two typical ciliopathies characterized by central nervous system malformations, and result in loss of ciliary localization of multiple proteins in various models. The precise mechanisms by which CC2D2A and other transition zone proteins control protein entrance into the cilium and how they are linked to vesicular trafficking of incoming cargo remain largely unknown. In this work, we identify the centrosomal protein NINL as a physical interaction partner of CC2D2A. NINL partially co-localizes with CC2D2A at the base of cilia and ninl knockdown in zebrafish leads to photoreceptor outer segment loss, mislocalization of opsins and vesicle accumulation, similar to cc2d2a-/- phenotypes. Moreover, partial ninl knockdown in cc2d2a-/- embryos enhances the retinal phenotype of the mutants, indicating a genetic interaction in vivo, for which an illustration is found in patients from a Joubert Syndrome cohort. Similar to zebrafish cc2d2a mutants, ninl morphants display altered Rab8a localization. Further exploration of the NINL-associated interactome identifies MICAL3, a protein known to interact with Rab8 and to play an important role in vesicle docking and fusion. Together, these data support a model where CC2D2A associates with NINL to provide a docking point for cilia-directed cargo vesicles, suggesting a mechanism by which transition zone proteins can control the protein content of the ciliary compartment.

Iodinated contrast media (CM) are the leading cause of acute renal failure of toxic origin. Between 21% and 50% of patients that receive them develop contrast-induced nephropathy (CIN). All prophylactic measures used so far have failed to provide effective prevention. Since oxidative stress is involved in the damage, a possible preventive strategy could be the administration of antioxidant substances, such as quercetin. This compound has shown renoprotective effects in experimental studies. The aim of this study was to evaluate whether quercetin may be helpful in preventing CIN in patients undergoing coronary catheterization. A clinical phase II study was conducted. Patients were distributed in two groups, namely, CM (patients who only received contrast media) and CM+Q (patients who were pretreated with quercetin orally for 3–5 days). Results showed less incidence of CIN in the CM+Q group, possibly due to glomerular protection, evidenced by a lower increase in serum creatinine and albuminuria; and a lower decrease in the glomerular filtration rate (GFR). Furthermore, in this group, the relative risk of developing CIN observed in patients that received a high dose of contrast media was inferior. In conclusion, this is the first study that demonstrates that quercetin is a promising safe candidate in preventing CIN.

Nephronophthisis (NPHP) is a ciliopathy characterized by renal fibrosis and cyst formation, and accounts for a significant portion of end stage renal disease in children and young adults. Currently, no targeted therapy is available for this disease. INVS/NPHP2 is one of the over 25 NPHP genes identified to date. In mouse, global knockout of Invs leads to renal fibrosis and cysts. However, the precise contribution of different cell types and the relationship between epithelial cysts and interstitial fibrosis remains undefined. Here, we generated and characterized cell-type-specific knockout mouse models of Invs , investigated the impact of removing cilia genetically on phenotype severity in Invs mutants and evaluated the impact of the histone deacetylase inhibitor valproic acid (VPA) on Invs mutants. Epithelial-specific knockout of Invs in Invs flox/flox ;Cdh16-Cre mutant mice resulted in renal cyst formation and severe stromal fibrosis, while Invs flox/flox ;Foxd1-Cre mice, where Invs is deleted in stromal cells, displayed no observable phenotypes up to the young adult stage, highlighting a significant role of epithelial-stromal crosstalk. Further, increased cell proliferation and myofibroblast activation occurred early during disease progression and preceded detectable cyst formation in the Invs flox/flox ;Cdh16-Cre kidney. Moreover, concomitant removal of cilia partially suppressed the phenotypes of the Invs flox/flox ;Cdh16-Cre mutant kidney, supporting a significant interaction of cilia and Invs function in vivo. Finally, VPA reduced cyst burden, decreased cell proliferation and ameliorated kidney function decline in Invs mutant mice. Our results reveal the critical role of renal epithelial cilia in NPHP and suggest the possibility of repurposing VPA for NPHP treatment. One of the most common causes of kidney failure in children and young adults is nephronophthisis. This genetic disease causes cysts and tissue scarring in the kidneys, leading to excessive urine production and extreme tiredness. Unfortunately, there is no targeted therapy available for this condition. Scientists do not fully understand how genetic mutations lead to these symptoms. Previous research in mice showed that blocking the gene for a protein called INVS recreated signs similar to nephronophthisis. However, it is not clear how the different cell types in the kidneys are involved. Previous results suggest that cilia, the hair-like projections on the surface of cells, could be involved in developing cysts in nephronophthisis. To understand how the disease is driven, Li, Xu et al. created a range of genetically modified mice with INVS missing in different cell types. When INVS was removed from cells that line the kidney tubules, the mice developed scarring and cysts. By contrast, there were no symptoms when connective tissue cells were lacking INVS. When Li, Xu et al. removed the cilia from the cells, it helped to reduce the negative impact of the loss of INVS. In addition, a drug called valproic acid reduced the cysts and tissue scarring, and slowed kidney decline in the mutant mice, suggesting the possibility of repurposing this drug for nephronophthisis treatment. These results could help researchers to study other conditions that are influenced by the health of cilia. Future work on nephronophthisis will be needed to understand how INVS causes the disease and the mechanism for the benefits of valproic acid.

Previous studies report conflicting results on the benefit of peritoneal dialysis (PD) patients treated with low glucose degradation product (GDP) solution. The effects of low GDP solution on body fluid status and arterial pulse wave velocity (PWV) have not been studied. We randomly assigned 68 incident PD patients to low GDP (Intervention Group) or conventional solutions (Control Group); 4 dropped off before they received the assigned treatment. Patients were followed for 52 weeks for changes in ultrafiltration, residual renal function, body fluid status and arterial PWV. After 52 weeks, Intervention Group had higher overhydration (3.1 ± 2.6 vs 1.9 ± 2.2 L, p = 0.045) and extracellular water volume (17.7 ± 3.9 vs 15.8 ± 3.1 L, p = 0.034) than Control Group. There was no significant difference in PWV between groups. There was no significant difference in residual renal function between the Groups. Intervention Group had lower ultrafiltration volume than Control Group at 4 weeks (0.45 ± .0.61 vs 0.90 ± 0.79 L/day, p = 0.013), but the difference became insignificant at later time points. Intervention Group had lower serum CRP levels than Control Group (4.17 ± 0.77 vs 4.91 ± 0.95 mg/dL, p < 0.0001). Incident PD patients treated with low GDP solution have less severe systemic inflammation but trends of less ultrafiltration, and more fluid accumulation. However, the effects on ultrafiltration and fluid accumulation disappear with time. The long term effect of low GDP solution requires further study. ClinicalTrials.gov NCT00966615.