Oral alkalinizing supplementation suppressed intrarenal reactive oxidative stress in mild-stage chronic kidney disease: a randomized cohort study.

BACKGROUND: The beneficial effects of oral supplements with alkalinizing agents in patients with chronic kidney disease (CKD) have been limited to the severe stages. We investigated whether two types of supplements, sodium bicarbonate (SB) and potassium citrate/sodium citrate (PCSC), could maintain renal function in patients with mild-stage CKD. METHODS: This was a single-center, open-labeled, randomized cohort trial. Study participants with CKD stages G2, G3a, and G3b were enrolled between March 2013 and January 2019 and randomly assigned by stratification according to age, sex, estimated glomerular filtration rate (eGFR), and diabetes. They were followed up for 6 months (short-term study) for the primary endpoints and extended to 2 years (long-term study) for the secondary endpoints. Supplementary doses were adjusted to achieve an early morning urinary pH of 6.8-7.2. We observed renal dysfunction or new-onset cerebrovascular disease and evaluated urinary surrogate markers for renal injury. RESULTS: Overall, 101 participants were registered and allocated to three groups: standard (n = 32), SB (n = 34), and PCSC (n = 35). Two patients in the standard group attained the primary endpoints (renal stones and overt proteinuria) but were not statistically significant. There was one patient in the standard reduced eGFR during the long-term study (p = 0.042 by ANOVA). SB increased proteinuria (p = 0.0139, baseline vs. 6 months), whereas PCSC significantly reduced proteinuria (p = 0.0061, baseline vs. 1 year, or p = 0.0186, vs. 2 years) and urinary excretion of 8-hydroxy-2'-deoxyguanosine (p = 0.0481, baseline vs. 6 months). CONCLUSION: This study is the first to report supplementation of PCSC reduced intrarenal oxidative stress in patients with mild-stage CKD.

Crosstalk between oxygen signaling and iron metabolism in renal interstitial fibroblasts.

To maintain the oxygen supply, the production of red blood cells (erythrocytes) is promoted under low-oxygen conditions (hypoxia). Oxygen is carried by hemoglobin in erythrocytes, in which the majority of the essential element iron in the body is contained. Because iron metabolism is strictly controlled in a semi-closed recycling system to protect cells from oxidative stress caused by iron, hypoxia-inducible erythropoiesis is closely coordinated by regulatory systems that mobilize stored iron for hemoglobin synthesis. The erythroid growth factor erythropoietin (EPO) is mainly secreted by interstitial fibroblasts in the renal cortex, which are known as renal EPO-producing (REP) cells, and promotes erythropoiesis and iron mobilization. Intriguingly, EPO production is strongly induced by hypoxia through iron-dependent pathways in REP cells. Here, we summarize recent studies on the network mechanisms linking hypoxia-inducible EPO production, erythropoiesis and iron metabolism. Additionally, we introduce disease mechanisms related to disorders in the network mediated by REP cell functions. Furthermore, we propose future studies regarding the application of renal cells derived from the urine of kidney disease patients to investigate the molecular pathology of chronic kidney disease and develop precise and personalized medicine for kidney disease.

Usefulness of gallium-67 scintigraphy for evaluating the histopathological activity in interstitial nephritis.

BACKGROUND: Interstitial nephritis is a common cause of renal failure. Gallium-67 scintigraphy is reportedly useful for diagnosing interstitial nephritis; however, its ability to assess disease activity remains unknown. We aimed to analyze the relationship between the renal uptake of gallium-67 and the disease activity in interstitial nephritis. METHODS: We retrospectively analyzed the data of patients who underwent gallium-67 scintigraphy at a hospital in Tokyo. The renal uptake adjusted for the soft tissues beneath the kidneys was semi-quantitatively evaluated. We compared the renal uptake levels between patients clinically diagnosed with and without interstitial nephritis. Among those undergoing renal biopsy, we evaluated the predictive ability of gallium-67 scintigraphy and analyzed the renal uptake levels regarding the disease activity through a histopathological analysis. RESULTS: We included 143 patients; among them, 30, 17, and 96 patients were clinically diagnosed with interstitial nephritis, other kidney diseases, and non-kidney diseases, respectively. The renal uptake of gallium-67 was the highest among patients with interstitial nephritis. Among the 25 patients who underwent renal biopsy, 15 were pathologically diagnosed with interstitial nephritis. The renal uptake levels showed a high discriminative ability (C-statistic: 0.83). Furthermore, net reclassification improvement with the addition of gallium-67 scintigraphy to N-acetyl-ß-D-glucosaminidase for the prediction of interstitial nephritis was 1.14. Histopathological analysis revealed a positive correlation between renal uptake and inflammation in the cortex and peritubular capillaries. CONCLUSIONS: This study confirmed the diagnostic value and potential usefulness of gallium-67 scintigraphy for evaluating interstitial nephritis.

Activation of α7 nicotinic acetylcholine receptors attenuates monocyte-endothelial adhesion through FUT7 inhibition.

Cholinergic anti-inflammatory pathway (CAP) describes a neuronal-inflammatory reflex centered on systemic cytokine regulation by α7 nicotinic acetylcholine receptor (α7nAChR) activation of spleen-residue macrophage. However, the CAP mechanism attenuating distal tissue inflammation, inducing a low level of systemic inflammation, is lesser known. In this study, we hypothesized that CAP regulates monocyte accessibility by influencing their adhesion to endothelial cells. Using RNA-seq analysis, we identified that α1,3-Fucosyltransferase 7 (FucT-VII), the enzyme required for processing selectin ligands, was significantly downregulated by α7nAChR agonist among other cell-cell adhesion genes. The α7nAChR agonist inhibited monocytic cell line U-937 binding to P-selectin and adhesion to endothelial cells. Furthermore, α7nAChR agonist selectivity was confirmed by α7nAChR knockdown assays, showing that FUT7 inhibition and adhesion attenuation by the agonist was abolished by siRNA targeting α7nAChR encoding gene. Consistently, FUT7 knockdown inhibited the adhesive properties of U-937 and prevented them to adhere to endothelial cells. Overexpression of FUT7 also abrogated the adhesion attenuation induced by GTS-21 indicating that FUT7 inhibition was sufficient for inhibiting adhesion by α7nAChR activation. Our work demonstrated that α7nAChR activation regulates monocyte adhesion to endothelial cells through FUT7 inhibition, providing a novel insight into the CAP mechanism.

What's New in the Molecular Mechanisms of Diabetic Kidney Disease: Recent Advances.

Diabetic kidney disease (DKD) is the leading cause of chronic kidney disease, including end-stage kidney disease, and increases the risk of cardiovascular mortality. Although the treatment options for DKD, including angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, sodium-glucose cotransporter 2 inhibitors, and mineralocorticoid receptor antagonists, have advanced, their efficacy is still limited. Thus, a deeper understanding of the molecular mechanisms of DKD onset and progression is necessary for the development of new and innovative treatments for DKD. The complex pathogenesis of DKD includes various different pathways, and the mechanisms of DKD can be broadly classified into inflammatory, fibrotic, metabolic, and hemodynamic factors. Here, we summarize the recent findings in basic research, focusing on each factor and recent advances in the treatment of DKD. Collective evidence from basic and clinical research studies is helpful for understanding the definitive mechanisms of DKD and their regulatory systems. Further comprehensive exploration is warranted to advance our knowledge of the pathogenesis of DKD and establish novel treatments and preventive strategies.

A novel method for successful induction of interdigitating process formation in conditionally immortalized podocytes from mice, rats, and humans.

Formation of processes in podocytes is regarded as the hallmark of maturity and normal physical condition for the cell. There are many accumulated findings about molecular mechanisms that cause retraction of podocyte processes; however, there is little knowledge of the positive mechanisms that promote process formation in vitro, and most previous reports about this topic have been limited to low-density cultures. Here, we found that process formation can be induced in 100% confluent cultures of conditionally immortalized podocytes in mouse, rat, and human species by combining serum depletion and Y-27632 ROCK inhibitor supplementation on the scaffold of laminin-521(L521). We noted the cytoskeletal reorganization of the radial extension pattern of vimentin filaments and downregulation of actin stress fiber formation under that condition. We also found that additional standard amount of serum, depletion of ROCK inhibitor, or slight mismatch of the scaffold as laminin-511(L511) hinder process formation. These findings suggest that the combination of reduced serum, podocyte-specific scaffold, and intracellular signaling to reduce the overexpression of ROCK are required factors for process formation.

Update on diagnosis, pathophysiology, and management of diabetic kidney disease.

Diabetic kidney disease (DKD) is a chronic complication of diabetes mellitus which may eventually lead to end-stage kidney disease (ESKD). Despite improvements in glycaemic control and blood pressure management with renin-angiotensin-aldosterone system (RAAS) blockade, the current therapy cannot completely halt DKD progression to ESKD in some patients. DKD is a heterogeneous disease entity in terms of its clinical manifestations, histopathology and the rate of progression, which makes it difficult to develop effective therapeutics. It was formerly considered that albuminuria preceded kidney function decline in DKD, but recent epidemiological studies revealed that a distinct group of patients presented kidney dysfunction without developing albuminuria. Other comorbidities, such as hypertension, obesity and gout, also affect the clinical course of DKD. The pathophysiology of DKD is complex and multifactorial, involving both metabolic and haemodynamic factors. These induce activation of intracellular signalling pathways, oxidative stress, hypoxia, dysregulated autophagy and epigenetic changes, which result in kidney inflammation and fibrosis. Recently, two groups of antidiabetic drugs, sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide-1 (GLP-1) receptor agonists, were demonstrated to provide renoprotection on top of their glucose-lowering effects. Several other therapeutic agents are also being developed and evaluated in clinical trials.

Prolyl Hydroxylase Domain Inhibitor Protects against Metabolic Disorders and Associated Kidney Disease in Obese Type 2 Diabetic Mice.

BACKGROUND: Prolyl hydroxylase domain (PHD) inhibitors, which stimulate erythropoietin production through the activation of hypoxia-inducible factor (HIF), are novel therapeutic agents used for treating renal anemia. Several PHD inhibitors, including enarodustat, are currently undergoing phase 2 or phase 3 clinical trials. Because HIF regulates a broad spectrum of genes, PHD inhibitors are expected to have other effects in addition to erythropoiesis, such as protection against metabolic disorders. However, whether such beneficial effects would extend to metabolic disorder-related kidney disease is largely unknown. METHODS: We administered enarodustat or vehicle without enarodustat in feed to diabetic black and tan brachyury (BTBR) ob/ob mice from 4 to 22 weeks of age. To elucidate molecular changes induced by enarodustat, we performed transcriptome analysis of isolated glomeruli and in vitro experiments using murine mesangial cells. RESULTS: Compared with BTBR ob/ob mice that received only vehicle, BTBR ob/ob mice treated with enarodustat displayed lower body weight, reduced blood glucose levels with improved insulin sensitivity, lower total cholesterol levels, higher adiponectin levels, and less adipose tissue, as well as a tendency for lower macrophage infiltration. Enarodustat-treated mice also exhibited reduced albuminuria and amelioration of glomerular epithelial and endothelial damage. Transcriptome analysis of isolated glomeruli revealed reduced expression of C-C motif chemokine ligand 2/monocyte chemoattractant protein-1 (CCL2/MCP-1) in enarodustat-treated mice compared with the vehicle-only group, accompanied by reduced glomerular macrophage infiltration. In vitro experiments demonstrated that both local HIF-1 activation and restoration of adiponectin by enarodustat contributed to CCL2/MCP-1 reduction in mesangial cells. CONCLUSIONS: These results indicate that the PHD inhibitor enarodustat has potential renoprotective effects in addition to its potential to protect against metabolic disorders.

[Renal anemia and hypoxia-inducible factor prolyl hydroxylase inhibitor].

Anemia is a significant complication of chronic kidney disease (CKD), caused by erythropoietin deficiency and reduced iron availability. Erythropoiesis-stimulating agents have been used with iron supplementation to treat anemia; however, they are associated with some problems. Hypoxia-inducible factor prolyl hydroxylase inhibitor (HIF-PHI) is a promising new class of oral therapy for the treatment of anemia associated with CKD. HIF-PHI inhibits HIF-prolyl hydroxylase enzymes and results in the HIF-α accumulation, which leads to increased expression of HIF-responsive genes, including erythropoietin and vascular endothelial growth factor (VEGF). HIF stimulates endogenous erythropoietin production and also reduces circulating hepcidin concentrations, resulting in improved anemia. Many clinical trials demonstrate that HIF-PHI improves anemia in patients with CKD and on dialysis. In addition to treating anemia, HIF-PHI may have multiple potential effects. Several animal experiments show that HIF-PHI protects against ischemic kidney damage that progresses to CKD and also improves metabolic disorders and ameliorates cardiovascular complications. In contrast, malignant tumor and retinopathy should be carefully evaluated due to theoretical concerns that HIF stabilization may result in increased VEGF protein expression. Some adverse events such as shunt occlusion reported in large clinical trials also need attention and warrant further investigations.

JTZ-951, an HIF prolyl hydroxylase inhibitor, suppresses renal interstitial fibroblast transformation and expression of fibrosis-related factors.

Some preceding studies have provided evidence that hypoxia-inducible factor (HIF)-prolyl hydroxylase (PH) inhibitors have therapeutic potential against tubular interstitial fibrosis (TIF). Recently, transformation of renal interstitial fibroblasts (RIFs) into α-smooth muscle actin-positive myofibroblasts with loss of their hypoxia-inducible erythropoietin (EPO) expression has been hypothesized as the central mechanism responsible for TIF with renal anemia (the RIF hypothesis). These reports have suggested that HIF-PH inhibitors may suppress TIF via suppressing transformation of RIFs. However, the direct effect of HIF-PH inhibitors on transformation of RIFs has not been demonstrated because there has been no appropriate assay system. Here, we established a novel in vitro model of the transformation of RIFs. This model expresses key phenotypic changes such as transformation of RIFs accompanied by loss of their hypoxia-inducible EPO expression, as proposed by the RIF hypothesis. Using this model, we demonstrated that JTZ-951, a newly developed HIF-PH inhibitor, stabilized HIF protein in RIFs, suppressed transformation of RIFs, and maintained their hypoxia-inducible EPO expression. JTZ-951 also suppressed the expression of FGF2, FGF7, and FGF18, which are upregulated during transformation of RIFs. Furthermore, expression of Fgf2, Fgf7, and Fgf18 was correlated with TIF in an animal model of TIF. We also demonstrated that not only FGF2, which is a well-known growth-promoting factor, but also FGF18 promoted proliferation of RIFs. These data suggest that JTZ-951 has therapeutic potential against TIF with renal anemia. Furthermore, FGF2, FGF7, and FGF18, which faithfully reflect the anti-TIF effects of JTZ-951, have potential as TIF biomarkers.

Effects of a prolyl hydroxylase inhibitor on kidney and cardiovascular complications in a rat model of chronic kidney disease.

Cardiovascular disease (CVD) is the main cause of death in patients with kidney disease. Hypoxia plays a crucial role in the progression of chronic kidney disease (CKD) and cardiovascular disease, which is associated with fibrosis, inflammation, and oxidative injury. Previous studies have indicated that prolyl hydroxylase (PHD) inhibitors, stabilizers of hypoxia-inducible factors (HIFs), can be used to treat acute organ injuries such as renal ischemia-reperfusion, myocardial infarction, and, in some contexts, CKD. However, the effects of PHD inhibitors on cardiovascular complications in CKD remain unknown. In the present study, we investigated whether HIF activation has a beneficial effect on kidney and cardiovascular outcomes in the remnant kidney model. We used the 5/6 nephrectomy model with the nitric oxide synthase inhibitor Nω-nitro-l-arginine (20 mg/L in the drinking water). Rats received diet with 0.005% enarodustat (PHD inhibitor) or vehicle for 8 wk starting 2 wk before 5/6 nephrectomy. Activation of HIF by the PHD inhibitor reduced cardiac hypertrophy and ameliorated myocardial fibrosis in association with restored capillary density and improvement in mitochondrial morphology. With regard to kidneys, enarodustat ameliorated fibrosis in association with reduced proinflammatory cytokine expression, reduced apoptosis, and restored capillary density, even though renal endpoints such as proteinuria and serum creatinine levels were not significantly affected by enarodustat, except for blood urea nitrogen levels at 4 wk. In addition, cardiac hypertrophy marker genes, including atrial natriuretic peptide, were suppressed in P19CL6 cells treated with enarodustat. These findings suggest that PHD inhibitors might show beneficial effects in cardiovascular complications caused by CKD.

Prolyl hydroxylase inhibition protects the kidneys from ischemia via upregulation of glycogen storage.

Hypoxia-inducible factor (HIF) mediates protection via hypoxic preconditioning in both, in vitro and in vivo ischemia models. However, the underlying mechanism remains largely unknown. Prolyl hydroxylase domain proteins serve as the main HIF regulator via hydroxylation of HIFα leading to its degradation. At present, prolyl hydroxylase inhibitors including enarodustat are under clinical trials for the treatment of renal anemia. In an in vitro model of ischemia produced by oxygen-glucose deprivation of renal proximal tubule cells in culture, enarodustat treatment and siRNA knockdown of prolyl hydroxylase 2, but not of prolyl hydroxylase 1 or prolyl hydroxylase 3, significantly increased the cell viability and reduced the levels of reactive oxygen species. These effects were offset by the simultaneous knockdown of HIF1α. In another in vitro ischemia model induced by the blockade of oxidative phosphorylation with rotenone/antimycin A, enarodustat-enhanced glycogen storage prolonged glycolysis and delayed ATP depletion. Although autophagy is another possible mechanism of prolyl hydroxylase inhibition-induced cytoprotection, gene knockout of a key autophagy associated protein, Atg5, did not affect the protection. Enarodustat increased the expression of several enzymes involved in glycogen synthesis, including phosphoglucomutase 1, glycogen synthase 1, and 1,4-α glucan branching enzyme. Increased glycogen served as substrate for ATP and NADP production and augmented reduction of glutathione. Inhibition of glycogen synthase 1 and glutathione reductase nullified enarodustat's protective effect. Enarodustat also protected the kidneys in a rat ischemia reperfusion injury model and the protection was partially abrogated by inhibiting glycogenolysis. Thus, prolyl hydroxylase inhibition protects the kidney from ischemia via upregulation of glycogen synthesis.

The oral hypoxia-inducible factor prolyl hydroxylase inhibitor enarodustat counteracts alterations in renal energy metabolism in the early stages of diabetic kidney disease.

Hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitors, also known as HIF stabilizers, increase endogenous erythropoietin production and serve as novel therapeutic agents against anemia in chronic kidney disease. HIF induces the expression of various genes related to energy metabolism as an adaptive response to hypoxia. However, it remains obscure how the metabolic reprogramming in renal tissue by HIF stabilization affects the pathophysiology of kidney diseases. Previous studies suggest that systemic metabolic disorders such as hyperglycemia and dyslipidemia cause alterations of renal metabolism, leading to renal dysfunction including diabetic kidney disease. Here, we analyze the effects of enarodustat (JTZ-951), an oral HIF stabilizer, on renal energy metabolism in the early stages of diabetic kidney disease, using streptozotocin-induced diabetic rats and alloxan-induced diabetic mice. Transcriptome analysis revealed that enarodustat counteracts the alterations in diabetic renal metabolism. Transcriptome analysis showed that fatty acid and amino acid metabolisms were upregulated in diabetic renal tissue and downregulated by enarodustat, whereas glucose metabolism was upregulated. These symmetric changes were confirmed by metabolome analysis. Whereas glycolysis and tricarboxylic acid cycle metabolites were accumulated and amino acids reduced in renal tissue of diabetic animals, these metabolic disturbances were mitigated by enarodustat. Furthermore, enarodustat increased the glutathione to glutathione disulfide ratio and relieved oxidative stress in renal tissue of diabetic animals. Thus, HIF stabilization counteracts alterations in renal energy metabolism occurring in incipient diabetic kidney disease.

Hypoxia-inducible factor prolyl hydroxylase inhibitor in the treatment of anemia in chronic kidney disease.

PURPOSE OF REVIEW: Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are orally active small molecules and are launched as novel therapeutic agents for anemia in chronic kidney disease (CKD). In contrast to conventional exogenous erythropoietin (EPO) administration, HIF-PHIs stimulate endogenous EPO production and improve iron metabolism via stabilization of hypoxia-inducible factor (HIF). This review summarizes the mechanism of action, the results of clinical trials, and future perspectives of HIF-PHIs. RECENT FINDINGS: Six HIF-PHIs are currently under phase III studies, some of which have been already completed. According to the results of clinical trials, HIF-PHIs increased and maintained hemoglobin levels in both nondialysis-dependent and dialysis-dependent CKD patients with physiological EPO concentrations. HIF-PHIs also improved iron utilization and were comparably effective regardless of underlying inflammation and iron status. SUMMARY: HIF-PHIs have several advantages including oral administration, physiological EPO secretion, and improved iron utilization. Undoubtedly, HIF-PHIs will pave the new way in the field of treatment of anemia in CKD, but it should be noted that HIFs have pleiotropic effects on a plethora of cellular functions, which might lead to either beneficial or undesirable off-target effects. Intensive postmarketing surveillance is crucially important to identify unexpected consequences.

Nuclear factor erythroid 2-related factor 2 as a treatment target of kidney diseases.

PURPOSE OF REVIEW: Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor which regulates a wider range of downstream pathways than previously thought. This review focuses on the novel findings about the internal regulatory mechanisms of Nrf2, the expanding understanding of its role in maintaining cellular homeostasis and the attempts to broaden the clinical application of its activators. RECENT FINDINGS: Nrf2 is in charge of the maintenance of cellular homeostasis under stress and there exist the internal regulatory mechanisms for Nrf2 which have recently been elucidated. New downstream pathways of Nrf2 have been discovered, including the defense against ferroptosis, the latest concept of cell death. Several Nrf2 activators are at various stages of clinical development and are being tested in clinical trials for chronic kidney disease (CKD) including diabetic kidney disease, Alport syndrome, autosomal dominant polycystic kidney disease and focal segmental glomerulosclerosis. SUMMARY: Nrf2 has been gathering attention as an emerging treatment target of chronic diseases which have oxidative stress and inflammation as their pathogenesis including CKD. Basic and clinical studies are under way to establish its role as a target for treatment of those diseases.

Inhibition of prolyl hydroxylase domain (PHD) by JTZ-951 reduces obesity-related diseases in the liver, white adipose tissue, and kidney in mice with a high-fat diet.

The epidemic of obesity and its complications is rapidly increasing worldwide. Recent drug discoveries established the utility of prolyl hydroxylase domain (PHD) inhibitors as stabilizers of hypoxia-inducible factors (HIFs) in vivo, which are currently in human clinical studies for the treatment of anemia in chronic kidney disease (CKD). These studies suggest a role for PHD inhibitors in ameliorating obesity and hyperlipidemia. We hypothesized that HIF activation using a PHD inhibitor, JTZ-951, protects from obesity-related diseases in the white adipose tissue (WAT), liver, and kidney in mice fed with high-fat diet (HFD). Eight-week-old, C57BL/6J mice were fed with HFD for 20 weeks with or without JTZ-951(0.005%; mixed in chow). Body weight and plasma non-high-density lipoprotein (HDL) cholesterol levels were significantly lower in the JTZ-951 group as compared with the vehicle group. PHD inhibition improved liver steatosis, macrophage infiltration into WAT and adipocyte fibrosis. In the kidney, PHD inhibition reduced albuminuria. Histologically, the number of F4/80- positive infiltrating macrophages and mesangial expansion were milder in the JTZ-951 group. Relative mRNA expression of adiponectin in WAT was higher in the JTZ-951-treated group and inversely correlated with hepatic steatosis score, adipocyte macrophage aggregation, and albuminuria. Activation of HIF ameliorates multiple obesity-related consequences in mice with HFD. The results of the present study offer the promising view that pharmacological PHD inhibition may be beneficial for the treatment of obesity-related diseases that can be ameliorated by weight loss.

Comprehensive three-dimensional analysis (CUBIC-kidney) visualizes abnormal renal sympathetic nerves after ischemia/reperfusion injury.

The sympathetic nervous system is critical in maintaining the homeostasis of renal functions. However, its three-dimensional (3D) structures in the kidney have not been elucidated due to limitation of conventional imaging methods. CUBIC (Clear, Unobstructed Brain/Body Imaging Cocktails and Computational analysis) is a newly developed tissue-clearing technique, which enables whole-organ 3D imaging without thin-sectioning. Comprehensive 3D imaging by CUBIC found that sympathetic nerves are primarily distributed around arteries in the mouse kidney. Notably, the sympathetic innervation density was significantly decreased 10 days after ischemia-reperfusion injury (voluminal ratio of innervation area to kidney) by about 70%. Moreover, norepinephrine levels in kidney tissue (output of sympathetic nerves) were significantly reduced in injured kidneys by 77%, confirming sympathetic denervation after ischemia-reperfusion injury. Time-course imaging indicated that innervation partially recovered although overall denervation persisted 28 days after injury, indicating a continuous sympathetic nervous abnormality during the progression of chronic kidney disease. Thus, CUBIC-kidney, the 3D imaging analysis, can be a strong imaging tool, providing comprehensive, macroscopic perspectives for kidney research.

ATF6α downregulation of PPARα promotes lipotoxicity-induced tubulointerstitial fibrosis.

Tubulointerstitial fibrosis is a strong predictor of progression in patients with chronic kidney disease, and is often accompanied by lipid accumulation in renal tubules. However, the molecular mechanisms modulating the relationship between lipotoxicity and tubulointerstitial fibrosis remain obscure. ATF6α, a transcription factor of the unfolded protein response, is reported to be an upstream regulator of fatty acid metabolism. Owing to their high energy demand, proximal tubular cells (PTCs) use fatty acids as their main energy source. We therefore hypothesized that ATF6α regulates PTC fatty acid metabolism, contributing to lipotoxicity-induced tubulointerstitial fibrosis. Overexpression of activated ATF6α transcriptionally downregulated peroxisome proliferator-activated receptor-α (PPARα), the master regulator of lipid metabolism, leading to reduced activity of fatty acid ß-oxidation and cytosolic accumulation of lipid droplets in a human PTC line (HK-2). ATF6α-induced lipid accumulation caused mitochondrial dysfunction, enhanced apoptosis, and increased expression of connective tissue growth factor (CTGF), as well as reduced cell viability. Atf6α-/- mice had sustained expression of PPARα and less tubular lipid accumulation following unilateral ischemia-reperfusion injury (uIRI), resulting in the amelioration of apoptosis; reduced expression of CTGF, α-smooth muscle actin, and collagen I; and less tubulointerstitial fibrosis. Administration of fenofibrate, a PPARα agonist, reduced lipid accumulation and tubulointerstitial fibrosis in the uIRI model. Taken together, these findings suggest that ATF6α deranges fatty acid metabolism in PTCs, which leads to lipotoxicity-mediated apoptosis and CTGF upregulation, both of which promote tubulointerstitial fibrosis.

Regional variance in patterns of prescriptions for chronic kidney disease in Japan.

BACKGROUND: This study aims to describe the regional variance in prescriptions for chronic kidney disease (CKD) medications and to analyze regional characteristics to identify the sources of these differences by utilizing the National Database of Health Insurance Claims, which provides more than 95% of nationwide claim information for Japan. METHODS: Data regarding the total claimed amount for phosphate binders (PBs), erythropoiesis-stimulating agents (ESAs), carbonaceous adsorbents, and potassium-lowering agents in fiscal year 2015 were obtained. Correlation coefficients were calculated for the claimed amount of these drugs per CKD patient and social and medical variables, including the percentage of the population aged ≥ 65 years and the numbers of hospital beds and certified nephrologists. Subsequent multiple regression analysis was performed using explanatory factors affecting the amount of PB or ESA prescriptions per CKD patient. RESULTS: The total claimed amounts were 585,485,115 for PBs and 2,373,777 for ESAs. Variations in the claimed amount per CKD patient among 47 prefectures were 4.9-, 6.1-, 6.6-, and 6.0-fold for PBs, ESAs, carbonaceous adsorbents and potassium-lowering agents, respectively. The number of nephrologists per CKD patient was positively correlated with the prescribed amount for PBs and ESAs per CKD patient, and independently associated with the prescribed amount also in regression analysis. CONCLUSION: Substantial regional variation in CKD-related drug prescriptions exists even within a uniform health care system. The number of certified nephrologists was associated with the prescribed amount for PBs and ESAs. Further studies are needed to clarify whether geographic distribution of certified nephrologist may affect clinical practice pattern.

Safety and effectiveness of long-term use of darbepoetin alfa in non-dialysis patients with chronic kidney disease: a post-marketing surveillance study in Japan.

BACKGROUND: This post-marketing surveillance (PMS) study evaluated the safety and effectiveness of long-term darbepoetin alfa (darbepoetin) for the treatment of renal anemia in Japanese non-dialysis chronic kidney disease patients. METHODS: Patients were treated with darbepoetin and followed up for 3 years. Adverse events (AEs), adverse drug reactions (ADRs), hemoglobin (Hb) levels, and renal function were assessed. Patients were stratified by Hb level at the time of occurrence of cardiovascular-related AEs. Statistical analyses were performed to explore factors affecting the occurrence of AEs, cardiovascular-related AEs, and composite renal endpoints. RESULTS: In the safety analysis set (5547 patients), AEs and ADRs occurred in 44.4 and 7.1% of patients, respectively. Cardiovascular-related AEs were observed in 12.6% of the overall population. The proportion of patients who presented cardiovascular-related AEs was lower among those with a higher Hb level at the time of occurrence. In the effectiveness analysis set (5024 patients), mean Hb levels remained between 10.0 and 10.6 g/dL (Weeks 4-156). Three months after darbepoetin administration, patients with Hb ≥ 11 g/dL presented fewer composite renal endpoints than those with Hb < 11 g/dL (p = 0.0013), and the cumulative proportion of renal survival was higher in those with Hb ≥ 11 g/dL vs. Hb < 11 g/dL (p < 0.0001). CONCLUSIONS: This PMS study showed the safety and effectiveness of long-term use of darbepoetin in a large number of patients. Patients with Hb ≥ 11 g/dL presented fewer composite renal endpoints than those with Hb < 11 g/dL, without an increase in the incidence of cardiovascular-related AEs.