Hypoxia-inducible factor stabilizers for treating anemia of chronic kidney disease:

Evaluating the safety and efficacy of vadadustat for the treatment of anemia associated with chronic kidney disease

INTRODUCTION

The breakthrough in erythropoietin-stimulating agents in the 1990s improved the prognosis and treatment of complications in chronic kidney disease patients and renal anemia. Discovery of the novel molecular mechanisms for hypoxia-inducible factor (HIF) transcription factor under hypoxic conditions has led to the development of oral drugs, HIF-Prolyl Hydroxylase inhibitors (HIF-PHIs), that constantly activate erythropoietin by inhibiting prolyl hydroxylase. HIF-PHIs have gained rapid approval in Asian countries, including Japan, with six distinct types entering clinical application.

AREAS COVERED

This article provides a comprehensive review of the latest literature, with a particular focus on the effectiveness and safety of vadadustat.

EXPERT OPINION

A phase 3, randomized, open-label, clinical trial (PRO2TECT) demonstrated that vadadustat had the prespecified non-inferiority for hematologic efficacy as compared with darbepoetin alfa in non-dialysis-dependent patients not previously treated with ESA. However, vadadustat did not show non-inferiority in major adverse cardiovascular events in the non-US/non-Europe patients. It may partly because of imbalances of the baseline eGFR level in those countries. In dialysis-dependent patients, a phase 3 clinical trial (INNO2VATE) showed vadadustat was non-inferior to darbepoetin alfa in cardiovascular safety and maintenance of hemoglobin levels. Adverse events including cancer, retinopathy, thrombosis, and vascular calcification should be evaluated in future clinical studies.

Potency-Enhanced Peptidomimetic VHL Ligands with Improved Oral Bioavailability

The von Hippel-Lindau (VHL) protein plays a pivotal role in regulating the hypoxic stress response and has been extensively studied and utilized in the targeted protein degradation field, particularly in the context of bivalent degraders. In this study, we present a comprehensive peptidomimetic structure-activity relationship (SAR) approach, combined with cellular NanoBRET target engagement assays to enhance the existing VHL ligands. Through systematic modifications of the molecule, we identified the 1,2,3-triazole group as an optimal substitute of the left-hand side amide bond that yields 10-fold higher binding activity. Moreover, incorporating conformationally constrained alterations on the methylthiazole benzylamine moiety led to the development of highly potent VHL ligands with picomolar binding affinity and significantly improved oral bioavailability. We anticipate that our optimized VHL ligand, GNE7599, will serve as a valuable tool compound for investigating the VHL pathway and advancing the field of targeted protein degradation.

Pathogenesis of Reinke's Edema of the Vocal Fold

OBJECTIVES

The most frequent etiologic factor of Reinke's edema (RE) is considered to be smoking. However, the mechanism for the onset and development of the disease remains unclear. Hypoxia-inducible factor-1α (HIF-1α) is an oxygen-dependent transcriptional activator which plays crucial roles in angiogenesis in hypoxic microenvironments. HIF-1α induces the expression of vascular endothelial growth factor (VEGF) which involves angiogenesis and enhances vascular permeability. This study investigated the roles of HIF-1α in the pathogenesis of RE.

METHODS

Surgical specimens of RE from patients who underwent endolaryngeal microsurgery were used. Normal vocal folds were used as a control group. Expression of HIF-1α and VEGF was analyzed by immunohistochemistry. Three-dimensional fine structures of the vessels in RE were investigated using correlative light and electron microscopy (CLEM) technique.

RESULTS

HIF-1α and VEGF were broadly expressed in the stromal, inflammatory, and endothelial cells in the lamina propria of the vocal fold of RE. The expression of HIF-1α and VEGF of RE were significantly higher than in the lamina propria of the normal vocal fold mucosa. CLEM showed vascularization and telangiectasia and there were many dilated capillaries with thin endothelium not covered with pericytes indicating the vessels were fragile.

CONCLUSION

Transcription factor HIF-1α and induced VEGF likely play roles in the pathogenesis of RE. And increased vascular permeability with fragile vessels in angiogenesis is likely to be an etiology of RE. Transcription factor HIF-1α and induced VEGF are potential therapeutic targets for RE.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1785-1791, 2024.

Unraveling the role of HIF-1α in sepsis: from pathophysiology to potential therapeutics-a narrative review

Sepsis is characterized by organ dysfunction resulting from a dysregulated inflammatory response triggered by infection, involving multifactorial and intricate molecular mechanisms. Hypoxia-inducible factor-1α (HIF-1α), a notable transcription factor, assumes a pivotal role in the onset and progression of sepsis. This review aims to furnish a comprehensive overview of HIF-1α's mechanism of action in sepsis, scrutinizing its involvement in inflammatory regulation, hypoxia adaptation, immune response, and organ dysfunction. The review encompasses an analysis of the structural features, regulatory activation, and downstream signaling pathways of HIF-1α, alongside its mechanism of action in the pathophysiological processes of sepsis. Furthermore, it will delve into the roles of HIF-1α in modulating the inflammatory response, including its association with inflammatory mediators, immune cell activation, and vasodilation. Additionally, attention will be directed toward the regulatory function of HIF-1α in hypoxic environments and its linkage with intracellular signaling, oxidative stress, and mitochondrial damage. Finally, the potential therapeutic value of HIF-1α as a targeted therapy and its significance in the clinical management of sepsis will be discussed, aiming to serve as a significant reference for an in-depth understanding of sepsis pathogenesis and potential therapeutic targets, as well as to establish a theoretical foundation for clinical applications.

Identification of erythropoietin mimetic peptide 1 linear form in a sealed vial and its administration study in horses for doping control purpose

The erythropoietin mimetic peptide 1 linear form (EMP1-linear), GGTYSCHFGPLTWVCKPQGG-NH2 , was identified in an unknown preparation consisting of white crystalline powder contained in sealed glass vials using ultrahigh performance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS). The white crystalline powder, allegedly used for doping racehorses, was found to contain around 2% (w/w) of EMP1-linear. EMP1-linear can be cyclised in equine plasma at physiological temperature of 37°C by forming an intramolecular disulfide bond to give EMP1, which is a well-known erythropoiesis stimulating agent that can bind to and activate the receptor for cytokine erythropoietin (EPO). Thus, EMP1-linear is a prodrug of EMP1, which is a performance-enhancing doping agent that can be misused in equine sports. In order to identify potential target(s) for detecting the misuse of EMP1-linear in horses, an in vitro metabolic study using horse liver S9 fraction was performed. After incubation, EMP1-linear mainly existed in its cyclic form as EMP1, and four N-terminus truncated in vitro metabolites TYSCHFGPLTWVCKPQGG-NH2 (M1), SCHFGPLTWVCKPQGG-NH2 (M2), WVCKPQGG-NH2 (M3) and VCKPQGG-NH2 (M4) were identified. An intravenous administration study with the preparation of white crystalline powder containing EMP1-linear was also conducted using three retired thoroughbred geldings. EMP1 was detectable only in the postadministration plasma samples, whereas the four identified in vitro metabolites were detected in both postadministration plasma and urine samples. For controlling the misuse of EMP1-linear in horse, its metabolite M3 gave the longest detection time in both plasma and urine and could be detected for up to 4 and 27 h postadministration, respectively.

Evaluation of the Carcinogenic Potential of Enarodustat (JTZ-951), a Hypoxia-Inducible Factor-Prolyl Hydroxylase Inhibitor, in 26-Week Tg.rasH2 Mouse Study and 2-Year Sprague-Dawley Rat Study

Enarodustat (JTZ-951) is an oral hypoxia-inducible factor-prolyl hydroxylase (HIF-PH) inhibitor for the treatment of anemia with chronic kidney disease. Carcinogenicity of enarodustat was evaluated in a 26-week repeated oral dose study in Transgenic rasH2 (Tg.rasH2) mice and a 2-year repeated oral dose study in Sprague-Dawley (SD) rats. The highest dose levels were set at 6 mg/kg in the Tg.rasH2 mouse study and at 1 mg/kg in the SD rat study based on the maximum tolerated doses in the 3-month and 6-month dose-range finding studies, respectively. Enarodustat did not increase the incidence of any tumors or affect survival in these carcinogenicity studies. Pharmacology-related findings including increases in blood RBC parameters were observed at the highest dose levels for each study. The AUC-based exposure margins as protein-unbound drug base are 16.3-/26.0-fold multiple (males/females) for Tg.rasH2 mice and 1.6-/1.1-fold multiple for SD rats when compared with the estimated exposure in human with chronic kidney disease at 8 mg/day (maximum recommended human dose). In conclusion, enarodustat was considered to have no carcinogenic potential at the clinical dose.

Metabolic reprogramming of myeloid-derived suppressor cells in the context of organ transplantation

Myeloid-derived suppressor cells (MDSCs) are naturally occurring leukocytes that develop from immature myeloid cells under inflammatory conditions that were discovered initially in the context of tumor immunity. Because of their robust immune inhibitory activities, there has been growing interest in MDSC-based cellular therapies for transplant tolerance induction. Indeed, various pre-clinical studies have introduced in vivo expansion or adoptive transfer of MDSC as a promising therapeutic strategy leading to a profound extension of allograft survival due to suppression of alloreactive T cells. However, several limitations of cellular therapies using MDSCs remain to be addressed, including their heterogeneous nature and limited expansion capacity. Metabolic reprogramming plays a crucial role for differentiation, proliferation and effector function of immune cells. Notably, recent reports have focused on a distinct metabolic phenotype underlying the differentiation of MDSCs in an inflammatory microenvironment representing a regulatory target. A better understanding of the metabolic reprogramming of MDSCs may thus provide novel insights for MDSC-based treatment approaches in transplantation. In this review, we will summarize recent, interdisciplinary findings on MDSCs metabolic reprogramming, dissect the underlying molecular mechanisms and discuss the relevance for potential treatment approaches in solid-organ transplantation.

No benefit of HIF prolyl hydroxylase inhibition for hypertensive renal damage in renovascular hypertensive rats

Introduction: We previously reported that malignant hypertension is associated with impaired capillary density of target organs. Here, we tested the hypothesis that stabilization of hypoxia-inducible factor (HIF) in a modified "preconditioning" approach prevents the development of malignant hypertension. To stabilize HIF, we employed pharmacological inhibition of HIF prolyl hydroxylases (PHD), that profoundly affect HIF metabolism. Methods: Two-kidney, one-clip renovascular hypertension (2K1C) was induced in rats; controls were sham operated. 2K1C rats received either intermittent injections of the PHD inhibitor ICA (2-(1-chloro-4-hydroxyisoquinoline-3-carboxamido) acetate) or placebo. Thirty-five days after clipping, the frequency of malignant hypertension was assessed (based on weight loss and the occurrence of characteristic vascular lesions). In addition, kidney injury was compared between all ICA treated versus all placebo treated 2K1C, regardless of the occurrence of malignant hypertension. HIF stabilization was evaluated by immunohistochemistry, and HIF target gene expression by RT-PCR. Results: Blood pressure was elevated to the same degree in ICA- and placebo-treated 2K1C compared to control rats. ICA treatment did not affect the frequency of malignant hypertension or the extent of kidney tissue fibrosis, inflammation, or capillary density. There was a trend towards higher mortality and worse kidney function in ICA-treated 2K1C rats. ICA increased the number of HIF-1α-positive renal tubular cell nuclei and induced several HIF-1 target genes. In contrast, expression of HIF-2α protein as well as HIF-2 target genes were markedly enhanced by 2K1C hypertension, irrespective of ICA treatment. Discussion: We conclude that intermittent PHD inhibition did not ameliorate severe renovascular hypertension in rats. We speculate that the unexpected strong renal accumulation of HIF-2α in renovascular hypertension, which could not be further augmented by ICA, may contribute to the lack of a benefit from PHD inhibition.

VBP1 negatively regulates CHIP and selectively inhibits the activity of hypoxia-inducible factor (HIF)-1α but not HIF-2α

Hypoxia-inducible factor-1 (HIF-1) is a critical transcription factor that regulates expression of genes involved in cellular adaptation to low oxygen levels. Aberrant regulation of the HIF-1 signaling pathway is linked to various human diseases. Previous studies have established that HIF-1α is rapidly degraded in a von Hippel-Lindau protien (pVHL)-dependent manner under normoxic conditions. In this study, we find that pVHL binding protein 1 (VBP1) is a negative regulator of HIF-1α but not HIF-2α using zebrafish as an in vivo model and in vitro cell culture models. Deletion of vbp1 in zebrafish caused Hif-1α accumulation and upregulation of Hif target genes. Moreover, vbp1 was involved in induction of hematopoietic stem cells (HSCs) under hypoxic conditions. However, VBP1 interacted with and promoted the degradation of HIF-1α in a pVHL-independent manner. Mechanistically, we identify the ubiquitin ligase CHIP and HSP70 as new VBP1 binding partners, and demonstrate that VBP1 negatively regulated CHIP and facilitated CHIP-mediated degradation of HIF-1α. In patients with clear cell renal cell carcinoma (ccRCC), lower VBP1 expression was associated with worse survival outcomes. In conclusion, our results link VBP1 with CHIP stability and provide insights into underlying molecular mechanisms of HIF-1α-driven pathological processes.

CIRP attenuates acute kidney injury after hypothermic cardiovascular surgery by inhibiting PHD3/HIF-1α-mediated ROS-TGF-β1/p38 MAPK activation and mitochondrial apoptotic pathways

BACKGROUND

The ischemia-reperfusion (IR) environment during deep hypothermic circulatory arrest (DHCA) cardiovascular surgery is a major cause of acute kidney injury (AKI), which lacks preventive measure and treatment. It was reported that cold inducible RNA-binding protein (CIRP) can be induced under hypoxic and hypothermic stress and may have a protective effect on multiple organs. The purpose of this study was to investigate whether CIRP could exert renoprotective effect during hypothermic IR and the potential mechanisms.

METHODS

Utilizing RNA-sequencing, we compared the differences in gene expression between Cirp knockout rats and wild-type rats after DHCA and screened the possible mechanisms. Then, we established the hypothermic oxygen-glucose deprivation (OGD) model using HK-2 cells transfected with siRNA to verify the downstream pathways and explore potential pharmacological approach. The effects of CIRP and enarodustat (JTZ-951) on renal IR injury (IRI) were investigated in vivo and in vitro using multiple levels of pathological and molecular biological experiments.

RESULTS

We discovered that Cirp knockout significantly upregulated rat Phd3 expression, which is the key regulator of HIF-1α, thereby inhibiting HIF-1α after DHCA. In addition, deletion of Cirp in rat model promoted apoptosis and aggravated renal injury by reactive oxygen species (ROS) accumulation and significant activation of the TGF-β1/p38 MAPK inflammatory pathway. Then, based on the HK-2 cell model of hypothermic OGD, we found that CIRP silencing significantly stimulated the expression of the TGF-β1/p38 MAPK inflammatory pathway by activating the PHD3/HIF-1α axis, and induced more severe apoptosis through the mitochondrial cytochrome c-Apaf-1-caspase 9 and FADD-caspase 8 death receptor pathways compared with untransfected cells. However, silencing PHD3 remarkably activated the expression of HIF-1α and alleviated the apoptosis of HK-2 cells in hypothermic OGD. On this basis, by pretreating HK-2 and rats with enarodustat, a novel HIF-1α stabilizer, we found that enarodustat significantly mitigated renal cellular apoptosis under hypothermic IR and reversed the aggravated IRI induced by CIRP defect, both in vitro and in vivo.

CONCLUSION

Our findings indicated that CIRP may confer renoprotection against hypothermic IRI by suppressing PHD3/HIF-1α-mediated apoptosis. PHD3 inhibitors and HIF-1α stabilizers may have clinical value in renal IRI.

Doping and sports endocrinology: growth hormone, IGF-1, insulin, and erythropoietin

Among the substances prohibited by the World Anti-Doping Agency, "peptide hormones, growth factors, related substances, and mimetics" are classified as prohibited both in- and out-of-competition in section S2. This work reviews growth hormone and its releasing peptides, insulin-like growth factor 1 as the main growth factor, insulin, and erythropoietin and other agents that affect erythropoiesis. This review analyzes the prevalence of use among professional athletes and gym clients, the forms of use, dosing, ergogenic effects and effects on physical performance, as well as side effects and anti-doping detection methods.

Responses to Hypoxia: How Fructose Metabolism and Hypoxia-Inducible Factor-1a Pathways Converge in Health and Disease

PURPOSE OF REVIEW

Oxygen is critical for the high output of energy (adenosine triphosphate) generated by oxidative phosphorylation in the mitochondria, and when oxygen delivery is impaired due to systemic hypoxia, impaired or reduced delivery of red blood cells, or from local ischemia, survival processes are activated.

RECENT FINDINGS

One major mechanism is the activation of hypoxia-inducible factors (HIFs) that act to reduce oxygen needs by blocking mitochondrial function and stimulating glucose uptake and glycolysis while also stimulating red blood cell production and local angiogenesis. Recently, endogenous fructose production with uric acid generation has also been shown to occur in hypoxic and ischemic tissues where it also appears to drive the same functions, and indeed, there is evidence that many of hypoxia-inducible factors effects may be mediated by the stimulation of fructose production and metabolism. Unfortunately, while being acutely protective, these same systems in overdrive lead to chronic inflammation and disease and may also be involved in the development of metabolic syndrome and related disease. The benefit of SGLT2 inhibitors may act in part by reducing the delivery of glucose with the stimulation of fructose formation, thereby allowing a conversion from the glycolytic metabolism to one involving mitochondrial metabolism. The use of hypoxia-inducible factor stabilizers is expected to aid the treatment of anemia but, in the long-term, could potentially lead to worsening cardiovascular and metabolic outcomes. We suggest more studies are needed on the use of these agents.

Roxadustat regulates iron metabolism in dialysis-dependent and non-dialysis-dependent chronic kidney disease patients: A meta-analysis

BACKGROUND/PURPOSE

The effect of roxadustat on iron homeostasis in patients with chronic kidney disease (CKD) is unclear. This study aimed to evaluate the efficacy of roxadustat for the treatment of iron metabolism disorders in dialysis-dependent (DD) and non-dialysis-dependent (NDD) CKD patients.

METHODS

We searched the PubMed, Embase, China National Knowledge Internet and Web of Science databases for randomized controlled trials (RCTs). The primary outcomes were changes in serum iron, total iron binding capacity (TIBC), transferrin saturation (TSAT), ferritin, transferrin, and hepcidin. The secondary outcomes included the changes in hemoglobin (Hb) and the incidences of adverse events (AEs) and severe adverse events (SAEs).

RESULTS

Twelve RCTs comprising 4976 participants were included. Compared to the control group, increases in the serum iron (SMD = 0.21, 95% CI: 0.15 to 0.27, P < 0.00001), TIBC (SMD = 1.02, 95% CI: 0.82 to 1.22, P < 0.00001) and transferrin levels (WMD = 0.55, 95% CI: 0.41 to 0.69, P < 0.00001) were found in the roxadustat group. Compared to the control group, decreases in the ferritin levels (WMD = -37.82, 95% CI: -59.89 to -15.74, P = 0.0008) and hepcidin levels (WMD = -24.04, 95% CI: -36.28 to -11.79, P = 0.0001) were observed in the roxadustat group. The meta-analysis showed that roxadustat significantly increases Hb levels (WMD = 0.77, 95% CI: 0.42 to 1.12, P < 0.0001). The incidences of AEs and SAEs in the roxadustat group was significantly higher than that in the control group (RR = 1.03, 95% CI: 1.00 to 1.07, P = 0.04; RR = 1.08, 95% CI: 1.00 to 1.15, P = 0.04).

CONCLUSION

Our findings suggest that roxadustat could effectively improve iron metabolism in patients with CKD.

Dapagliflozin for the treatment of chronic kidney disease

INTRODUCTION

Sodium-dependent glucose cotransporter 2 (SGLT2) is a glucose transporter expressed on the proximal tubular cells, where it reabsorbs glucose from the glomerular filtrate. SGLT2 inhibitors (SGLT2is), initially developed as an antidiabetic drug, have recently attracted considerable attention because they have cardiorenal protective effects. Among SGLT2is, dapagliflozin was the first to demonstrate the renoprotective effect in patients with and without diabetes and has been approved for chronic kidney disease (CKD) treatment.

AREAS COVERED

This review covers the pharmacological characteristics and the clinical efficacy and safety profiles of dapagliflozin, including comparison with other SGLT2is and risk modification strategies.

EXPERT OPINION

In DAPA-CKD, dapagliflozin reduced the primary outcome (≥50% estimated glomerular filtration rate [eGFR] decline, end-stage kidney disease [ESKD], or renal or cardiovascular [CV] death) by 39% in CKD patients. This beneficial effect was consistent across prespecified subgroups, including those based on the presence of diabetes. Dapagliflozin also decreased the CV composite outcome and all-cause death by 29% and 31%, respectively. Although an increased risk of adverse events such as ketoacidosis and volume depletion has been reported, the robust renal and CV benefits of dapagliflozin are expected to outweigh potential risks. SGLT2is, including dapagliflozin, will constitute the mainstay of CKD treatment.

Efficacy and Safety of Daprodustat Vs rhEPO for Anemia in Patients With Chronic Kidney Disease: A Meta-Analysis and Trial Sequential Analysis

Introduction: Daprodustat, a novel hypoxia-inducible factor prolyl-hydroxylase inhibitor (HIF-PHI), its efficacy and safety remain unclear. Thus, we conducted this meta-analysis aiming at investigating its efficacy and safety on the treatment of patients with chronic kidney disease (CKD)-related anemia.

Methods: We systematically searched for relevant studies in PubMed, Embase, Cochrane Library and Clinical Trial Registries databases from inception until December 2021. We selected randomized controlled trials comparing daprodustat with recombinant human erythropoietin (rhEPO) in anemia patients with CKD with or without dialysis.

Results: Seven studies including 7933 patients met the inclusion criteria. For both nondialysis-dependent (NDD-) CKD and dialysis-dependent (DD-) CKD patients, the pooled results showed that there was no significant difference in the changes in hemoglobin levels between the daprodustat and rhEPO groups (mean difference (MD) = −0.01, 95% confidence interval (CI) = −0.38, 0.35, p = 0.95; MD = 0.15, 95% CI = −0.29, 0.60, p = 0.50; respectively). In addition, a significant increase in transferrin saturation (TSAT), total iron binding capacity (TIBC) and total iron was observed in daprodustat groups compared with rhEPO groups in DD-CKD patients (p < 0.05). As for safety, the overall frequency of adverse events was similar between the daprodustat and rhEPO groups in DD-CKD patients (relative risk (RR) = 0.99, 95%CI = 0.92, 1.06, p = 0.76), and the trial sequential analysis (TSA) confirmed this result. But for NDD-CKD patients, the incidence of adverse events in the daprodustat groups was significantly higher than that of rhEPO groups (RR = 1.04, 95%CI = 1.01,1.07, p = 0.02), while the TSA corrected this result. No trend of increasing incidence of serious adverse events was found in all daprodustat treated patients, but the TSA could not confirm this result.

Conclusion: Although daprodustat was noninferior to rhEPO in correcting anemia in both NDD-CKD and DD-CKD patients, it seemed to have a better effect on optimizing iron metabolism in DD-CKD patients. Daprodustat may be a promising alternative for the treatment of anemia in patients with CKD. However, due to the lack of included studies, future researches are needed to further evaluate the therapeutic effect of daprodustat.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/, identifier CRD42021229636.

An evaluation of roxadustat for the treatment of anemia associated with chronic kidney disease

INTRODUCTION

Anemia is one of the major complications of chronic kidney disease (CKD). Erythropoiesis-stimulating agents (ESAs) have been the mainstay of renal anemia treatment. However, there are several safety drawbacks, and a safer and more effective alternative treatment has been sought.

AREAS COVERED

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) have been developed as a novel orally active therapeutic agent for renal anemia. HIF-PHIs stimulate endogenous EPO and optimize iron utilization. Roxadustat is a first-in-class HIF-PHI for the treatment of anemia in CKD patients approved in China, Japan, South Korea, and Chile. The authors herein evaluate the pharmacology of roxadustat and give their expert perspectives on its use.

EXPERT OPINION

Phase 3 clinical trials have demonstrated that roxadustat effectively increases and maintains hemoglobin (Hb) levels in both nondialysis-dependent and dialysis-dependent CKD patients. Roxadustat also improved iron metabolism and reduced intravenous (IV) iron requirements. However, pooled analyses of phase 3 studies have revealed frequent thromboembolic events in the roxadustat group, which might be attributed to rapid changes in Hb and inadequate iron supplementation. Roxadustat is an attractive alternative treatment especially for patients with ESA hyporesponsive due to impaired iron utilization, and so appropriate selection of target patients and its proper use are crucially important.

Ogfod1 deletion increases cardiac beta-alanine levels and protects mice against ischemia-reperfusion injury

AIMS

Prolyl hydroxylation is a post-translational modification that regulates protein stability, turnover, and activity. The proteins that catalyze prolyl hydroxylation belong to the 2-oxoglutarate- and iron-dependent oxygenase family of proteins. 2-oxoglutarate- and iron-dependent oxygenase domain-containing protein 1 (Ogfod1), which hydroxylates a proline in ribosomal protein s23 is a newly-described member of this family. The aims of this study were to investigate roles for Ogfod1 in the heart, and in the heart's response to stress.

METHODS AND RESULTS

We isolated hearts from wild type (WT) and Ogfod1 knockout (KO) mice and performed quantitative proteomics using Tandem Mass Tag labelling coupled to Liquid Chromatography and tandem Mass Spectrometry (LC-MS/MS) to identify protein changes. Ingenuity Pathway Analysis identified "Urate Biosynthesis/Inosine 5'-phosphate Degradation" and "Purine Nucleotides Degradation II (Aerobic)" as the most significantly-enriched pathways. We performed metabolomics analysis and found that both purine and pyrimidine pathways were altered with the purine nucleotide inosine 5'-monophosphate (IMP) showing a 3.5-fold enrichment in KO hearts (P = 0.011) and the pyrimidine catabolism product beta-alanine showing a 1.7-fold enrichment in KO hearts (P = 0.014). As changes in these pathways have been shown to contribute to cardioprotection, we subjected isolated perfused hearts to ischemia and reperfusion (I/R). KO hearts showed a 41.4% decrease in infarct size and a 34% improvement in cardiac function compared to WT hearts. This protection was also evident in an in vivo I/R model. Additionally, our data show that treating isolated perfused WT hearts with carnosine, a metabolite of beta-alanine, improved protection in the context of I/R injury, whereas treating KO hearts with carnosine had no impact on recovery of function or infarct size.

CONCLUSIONS

Taken together, these data show that Ogfod1 deletion alters the myocardial proteome and metabolome to confer protection against I/R injury.

TRANSLATIONAL PERSPECTIVE

Heart disease is the leading cause of death in the US. In characterizing the cardiovascular effects of deleting the prolyl hydroxylase Ogfod1 and investigating its role in disease pathology, we found that deleting Ogfod1 protected hearts against ex vivo and in vivo I/R injury. Ogfod1-KO hearts showed significant metabolomic and proteomic changes that supported altered purine and pyrimidine nucleotide synthesis and turnover. Beta-alanine, a precursor of the anti-oxidant carnosine and a product of pyrimidine degradation, accumulated in KO hearts to help confer cardioprotection. Altogether, these data suggest a role for Ogfod1 downregulation as a therapeutic strategy for heart disease.

Safety and Efficacy of Roxadustat for Anemia in Patients With Chronic Kidney Disease: A Meta-Analysis and Trial Sequential Analysis

Background: Roxadustat, a hypoxia-inducible factor prolyl-hydroxylase inhibitor (HIF-PHI), has been used to treat anemia in patients with chronic kidney disease (CKD). However, its safety and efficacy remain controversial.

Methods: The PubMed, EMBASE, Science Citation Index, Cochrane Central Register of Controlled Trials, and Clinical Trial Registries databases were searched for relevant studies published up to April 2021. We identified randomized controlled trials (RCTs) comparing roxadustat with placebo or erythropoiesis-stimulating agents (ESAs) in anemia patients with CKD with or without dialysis.

Results: Eleven studies including 6,631 patients met the inclusion criteria. In non-dialysis-dependent (NDD-) and dialysis-dependent (DD-) CKD patients, the total adverse events were not significantly different between the roxadustat and control (placebo for NDD-CKD patients and ESA for DD-CKD patients) groups [relative risk (RR) = 1.02, 95% confidence interval (CI) = 1.00, 1.04, P = 0.08, and RR = 1.22, 95% CI = 0.91, 1.64, P = 0.18, respectively], and the trial sequential analysis (TSA) confirmed the result in the NDD-CKD groups. No significant differences in hyperkalemia and infection incidences were found between roxadustat and placebo in the DD-CKD groups. The pooled results showed that roxadustat significantly increased the hemoglobin response rate compared with placebo in the NDD-CKD group and had an effect similar to that of ESA in the DD-CKD group. However, iron metabolism parameters did not seem to be obviously optimized by roxadustat.

Conclusion: Roxadustat can be safely used in CKD patients. Oral roxadustat was more effective than placebo as a therapy for anemia in NDD-CKD patients and non-inferior to ESA in correcting anemia in DD-CKD patients. However, additional clinical trials are still needed to further prove whether roxadustat can optimize iron metabolism.

Von Hippel-Lindau (VHL) small-molecule inhibitor binding increases stability and intracellular levels of VHL protein

Von Hippel-Lindau (VHL) disease is characterized by frequent mutation of VHL protein, a tumor suppressor that functions as the substrate recognition subunit of a Cullin2 RING E3 ligase complex (CRL2VHL). CRL2VHL plays important roles in oxygen sensing by targeting hypoxia-inducible factor-alpha (HIF-α) subunits for ubiquitination and degradation. VHL is also commonly hijacked by bifunctional molecules such as proteolysis-targeting chimeras to induce degradation of target molecules. We previously reported the design and characterization of VHL inhibitors VH032 and VH298 that block the VHL:HIF-α interaction, activate the HIF transcription factor, and induce a hypoxic response, which can be beneficial to treat anemia and mitochondrial diseases. How these compounds affect the global cellular proteome remains unknown. Here, we use unbiased quantitative MS to identify the proteomic changes elicited by the VHL inhibitor compared with hypoxia or the broad-spectrum prolyl-hydroxylase domain enzyme inhibitor IOX2. Our results demonstrate that VHL inhibitors selectively activate the HIF response similar to the changes induced in hypoxia and IOX2 treatment. Interestingly, VHL inhibitors were found to specifically upregulate VHL itself. Our analysis revealed that this occurs via protein stabilization of VHL isoforms and not via changes in transcript levels. Increased VHL levels upon VH298 treatment resulted in turn in reduced levels of HIF-1α protein. This work demonstrates the specificity of VHL inhibitors and reveals different antagonistic effects upon their acute versus prolonged treatment in cells. These findings suggest that therapeutic use of VHL inhibitors may not produce overt side effects from HIF stabilization as previously thought.

Roxadustat treatment for anemia in peritoneal dialysis patients: A randomized controlled trial

BACKGROUND/PURPOSE

Roxadustat, a first-in-class hypoxia-inducible factor prolyl hydroxylase inhibitor, promotes erythropoiesis and regulates iron metabolism. This study investigated the efficacy and safety of roxadustat in Chinese patients with anemia on peritoneal dialysis (PD).

METHODS

One hundred and twenty-nine patients were randomized and treated with roxadustat (n = 86) or erythropoiesis-stimulating agents (ESAs) (n = 43) for 24 weeks. The primary end points were the mean hemoglobin (Hb) level at week 24, the change in average Hb levels from baseline to week 24, and the cumulative response rate throughout the treatment period. The secondary end points included changes in hepcidin and iron indices and serum lipid levels. Subgroup analysis examined the effect of inflammatory status on the efficacy of Hb. Safety was assessed as the occurrence of emergent adverse events after treatment.

RESULTS

The mean average Hb levels at week 24 and average change in Hb levels from baseline to week 24 were 11.5 g/dL and 2.5 g/dL in the roxadustat group and 11.2 g/dL and 2.2 g/dL in the ESAs group, respectively. The cumulative response rate was 96% in the roxadustat group and 92% in the ESAs group at week 24. Roxadustat decreased hepcidin levels and increased total iron-binding capacity. The decreases in total cholesterol and low-density lipoprotein cholesterol were greater with roxadustat than with ESAs. Roxadustat-induced Hb increases were independent of baseline C-reactive protein levels. Common adverse events included hyperkalemia, hypertension, and insomnia.

CONCLUSION

Roxadustat effectively corrected and maintained target Hb levels in Chinese PD patients. This trial was registered in the Chinese Clinical Trial Register (ChiCTR2000035054).

Harnessing Metabolomics to Describe the Pathophysiology Underlying Progression in Diabetic Kidney Disease

PURPOSE OF REVIEW

Diabetic kidney disease (DKD), a leading cause of end-stage kidney disease, is the result of metabolic network alterations in the kidney. Therefore, metabolomics is an effective tool for understanding its pathophysiology, finding key biomarkers, and developing a new treatment strategy. In this review, we summarize the application of metabolomics to DKD research.

RECENT FINDINGS

Alterations in renal energy metabolism including the accumulation of tricarboxylic acid cycle and glucose metabolites are observed in the early stage of DKD, and they finally lead to mitochondrial dysfunction in advanced DKD. Mitochondrial fission-fusion imbalance and dysregulated organelle crosstalk might contribute to this process. Moreover, metabolomics has identified several uremic toxins including phenyl sulfate and tryptophan derivatives as promising biomarkers that mediate DKD progression. Recent advances in metabolomics have clarified the role of dysregulated energy metabolism and uremic toxins in DKD pathophysiology. Integration of multi-omics data will provide additional information for identifying critical drivers of DKD.

Anemia Management in Peritoneal Dialysis: Perspectives From the Asia Pacific Region

Anemia is an important complication in patients with chronic kidney disease. Peritoneal dialysis (PD) is one of the most common modalities of kidney replacement therapy for patients with end-stage kidney disease. PD is particularly prevalent in the Asian Pacific region. Among the different countries and regions, including mainland China, Hong Kong, Japan, Malaysia, Singapore, South Korea, and Thailand, PD accounts for 2.8% to 74.6% of the dialysis population. In addition, 82% to 96% of the PD populations from these countries and regions are receiving erythropoiesis-stimulating agents (ESAs). Asian Pacific countries and regions follow the latest KDIGO (Kidney Disease: Improving Global Outcomes) guidelines for the initiation of treatment of anemia in PD patients. The types of ESAs commonly used include shorter-acting (epoetin alfa and beta) and longer-acting agents, including darbepoetin alfa or methoxy polyethylene glycol-epoetin beta. The most commonly used ESAs in Mainland China, Malaysia, Singapore, and Thailand are the shorter-acting agents, whereas in Hong Kong, Japan, and South Korea, longer-acting ESAs are most common. Oral iron therapy is still the most commonly used iron supplement. The route and dosage of iron administration in PD patients requires more research studies. With the introduction of oral hypoxia-inducible factor prolyl hydroxylase inhibitors into clinical use, the landscape of treatment of anemia in the PD population in the Asia Pacific region may change in the coming years.

Efficacy and safety of vadadustat compared with darbepoetin alfa in Japanese anemic patients on hemodialysis: a Phase 3, multicenter, randomized, double-blind study

Background

Vadadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor that stimulates erythropoiesis.

Methods

The efficacy and safety of vadadustat, compared with darbepoetin alfa, was determined in a Phase 3 double-blind study in Japanese anemic patients on hemodialysis. Patients receiving erythropoiesis-stimulating agents (ESAs) were randomized and switched to either vadadustat or darbepoetin alfa for 52 weeks. Doses were adjusted to maintain a hemoglobin (Hb) level of 10.0–12.0 g/dL. The primary endpoint was average Hb level at Weeks 20 and 24.

Results

Of the 323 randomized patients, 120 and 135 completed the 52-week treatment period in the vadadustat and darbepoetin alfa groups, respectively. The average Hb levels at Weeks 20 and 24 [least square mean (LSM) and 95% confidence interval (CI)] were 10.61 (10.45–10.76) and 10.65 (10.50–10.80) g/dL in the vadadustat and darbepoetin alfa groups, respectively, demonstrating vadadustat’s noninferiority to darbepoetin alfa (difference: −0.05 g/dL; 95% CI −0.26 to 0.17). In both groups, the mean Hb levels were maintained within the target range for 52 weeks. Furthermore, irrespective of patient backgrounds, the LSMs of Hb at Week 52 were within the target range. The most common adverse events were nasopharyngitis, diarrhea and shunt stenosis, which occurred at similar frequencies in both groups. No new safety concerns were identified.

Conclusions

Vadadustat was as well-tolerated and effective as darbepoetin alfa in maintaining Hb levels within the target range. The findings suggest that vadadustat can be an alternative to ESA in the management of anemia in Japanese hemodialysis patients receiving ESA (ClinicalTrials.gov, NCT03439137).

Daprodustat Compared with Epoetin Beta Pegol for Anemia in Japanese Patients Not on Dialysis: A 52-Week Randomized Open-Label Phase 3 Trial

BACKGROUND

Daprodustat is an oral agent that stimulates erythropoiesis by inhibiting the prolyl hydroxylases which mark hypoxia-inducible factor for degradation through hydroxylation. Its safety and efficacy (noninferiority) were assessed in this 52-week, open-label study.

METHODS

Japanese patients not on dialysis (ND) (N = 299) with anemia of CKD (stages G3, G4, and G5) with iron parameters of ferritin >100 ng/mL or transferrin saturation >20% at screening were randomized to daprodustat or epoetin beta pegol (continuous erythropoietin receptor activator [CERA], also known as methoxy polyethylene glycol-epoetin beta). After initiation of the study, the daprodustat starting dose for erythropoiesis-stimulating agent (ESA)-naïve participants was revised, and daprodustat was started at 2 or 4 mg once daily depending on baseline hemoglobin. ESA users switched to daprodustat 4 mg once daily. CERA was started at 25 μg every 2 weeks for ESA-naïve patients and 25-250 μg every 4 weeks for ESA users based on previous ESA dose. In both treatment groups, dose was adjusted every 4 weeks based on hemoglobin level and changed according to a prespecified algorithm. The primary endpoint was mean hemoglobin level during weeks 40-52 in the intention-to-treat (ITT) population. ESA-naïve patients who entered before the protocol amendment revising the daprodustat starting dose were excluded from the ITT population.

RESULTS

Mean hemoglobin levels during weeks 40-52 were 12.0 g/dL in the daprodustat group (n = 108; 95% confidence interval [CI], 11.8-12.1) and 11.9 g/dL for CERA (n = 109; 95% CI 11.7-12.0); the difference between the groups was 0.1 g/dL (95% CI -0.1 to 0.3 g/dL). The lower limit of the 95% CI of the difference was greater than the prespecified margin of -1.0 g/dL. The mean hemoglobin level was within the target range (11.0-13.0 g/dL) during weeks 40-52 for 92% of participants in both groups. There was no meaningful difference in the frequencies of adverse events.

CONCLUSIONS

Oral daprodustat was noninferior to CERA in achieving and maintaining target hemoglobin levels in Japanese ND patients. Daprodustat was well tolerated, with no new safety concerns identified.

Recommendations by the Asian Pacific society of nephrology (APSN) on the appropriate use of HIF-PH inhibitors

Renal anaemia is a common and important complication in patients with chronic kidney disease (CKD). The current standard‐of‐care treatment for renal anaemia in CKD patients involves ensuring adequate iron stores and administration of erythropoietin stimulating agents (ESA). Hypoxia inducible factor (HIF) is a key transcription factor primarily involved in the cellular regulation and efficiency of oxygen delivery. Manipulation of the HIF pathway by the use of HIF‐prolyl hydroxylase inhibitors (HIF‐PHI) has emerged as a novel approach for renal anaemia management. Despite it being approved for clinical use in various Asia‐Pacific countries, its novelty mandates the need for nephrologists and clinicians generally in the region to well understand potential benefits and harms when prescribing this class of drug. The Asian Pacific society of nephrology HIF‐PHI Recommendation Committee, formed by a panel of 11 nephrologists from the Asia‐Pacific region who have clinical experience or have been investigators in HIF‐PHI studies, reviewed and deliberated on the clinical and preclinical data concerning HIF‐PHI. This recommendation summarizes the consensus views of the committee regarding the use of HIF‐PHI, taking into account both available data and expert opinion in areas where evidence remains scarce.

The Asian Pacific society of nephrology HIF‐PHI Recommendation Committee summarizes the consensus views of the committee regarding the use of HIF‐PHI, taking into account both available data and expert opinion in areas where evidence remains scarce.

Improving the safety of intravenous iron treatments for patients with chronic kidney disease

Introduction: Iron-deficiency anemia in chronic kidney disease (CKD) is common and has prognostic, financial, and quality of life implications. Intravenous (IV) iron is a key intervention for optimal management, however, ongoing safety concerns exist. Area covered: The potential side effects associated with IV iron use are addressed as we review the most recent studies. Hypersensitivity reactions and true anaphylaxis are indeed rare with a greater understanding of the nature of labile iron and 'Fishbane' reactions. Hypophosphatemia appears commoner with certain IV iron preparations, however its significance in CKD requires exploration. The long-standing questions regarding oxidative stress and the potential susceptibility to infections and worsening cardiovascular morbidity are discussed. Iron overload secondary to repeat IV iron infusions is plausible, however, a number of guidelines limit and strictly guide prescription. Expert opinion: The past decade has improved our understanding of IV iron administration safety in patients with CKD. Third generation IV iron compounds have minimized hypersensitivity reactions while allowing high doses to be administered safely and rapidly in non-dialysis-dependent CKD patients. However, differences in safety profiles such as hypophosphatemia require further study and therapy should be tailored to the individual. Clinicians should feel confident in using IV iron therapy.

Hypoxia Pathway Proteins are Master Regulators of Erythropoiesis

Erythropoiesis is a complex process driving the production of red blood cells. During homeostasis, adult erythropoiesis takes place in the bone marrow and is tightly controlled by erythropoietin (EPO), a central hormone mainly produced in renal EPO-producing cells. The expression of EPO is strictly regulated by local changes in oxygen partial pressure (pO₂) as under-deprived oxygen (hypoxia); the transcription factor hypoxia-inducible factor-2 induces EPO. However, erythropoiesis regulation extends beyond the well-established hypoxia-inducible factor (HIF)-EPO axis and involves processes modulated by other hypoxia pathway proteins (HPPs), including proteins involved in iron metabolism. The importance of a number of these factors is evident as their altered expression has been associated with various anemia-related disorders, including chronic kidney disease. Eventually, our emerging understanding of HPPs and their regulatory feedback will be instrumental in developing specific therapies for anemic patients and beyond.

Metabolic Optimisation of Regulatory T Cells in Transplantation

Regulatory T (Treg) cells expressing the FOXP3 transcription factor are presently under investigation by many teams globally as a cellular therapy to induce tolerance in transplantation. This is primarily due to their immunosuppressive and homeostatic functions. Depending on the type of allograft, Treg cells will need to infiltrate and function in metabolically diverse microenvironments. This means that any resident and circulating Treg cells need to differentially adapt to counter acute or chronic allograft rejection. However, the links between Treg cell metabolism and function are still not entirely delineated. Current data suggest that Treg cells and their effector counterparts have different metabolite dependencies and metabolic programs. These properties could be exploited to optimize intragraft Treg cell function. In this review, we discuss the current paradigms regarding Treg cell metabolism and outline critical intracellular axes that link metabolism and function. Finally, we discuss how this knowledge could be clinically translated for the benefit of transplant patients.

Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitors in Patients with Renal Anemia: A Meta-Analysis of Randomized Trials

BACKGROUND

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are a new class of treatment for renal anemia in patients with chronic kidney disease (CKD). This meta-analysis was designed to evaluate their efficacy and safety.

METHOD

Eight databases were searched for randomized controlled trials (RCTs). Information about efficacy and safety was extracted and combined using random-effects or fixed-effects models, depending on heterogeneity. Risk of bias was assessed using the method recommended by the Cochrane Centre.

RESULTS

Nineteen articles on RCTs were selected, involving 3,289 participants. We found that HIF-PHIs improved the level of hemoglobin (Hb) (weighted mean difference [WMD] 1.40; 95% CI: 0.96-1.84; p < 0.001), response rate of Hb (risk ratio [RR] 5.95; 95% CI: 3.95-8.96; p < 0.001), and total iron-binding capacity (WMD 42.94; 95% CI: 31.39-54.49; p < 0.001), while reducing the level of hepcidin (WMD -40.42; 95% CI: -50.44 to -30.39; p < 0.001), ferritin (WMD -64.60; 95% CI: -78.56 to -50.64; p < 0.001), and transferrin saturation (WMD -5.57; 95% CI: -8.53 to -2.61; p < 0.001). Meanwhile, there was no evidence of effect on serum iron (WMD 1.60; 95% CI: -3.72 to 6.93; p = 0.55), nor on the incidence of adverse events (AEs) (RR 1.06; 95% CI: 0.99-1.15; p = 0.51) or of serious adverse events (SAEs) (RR 1.14; 95% CI: 0.88-1.46; p = 0.32).

CONCLUSION

HIF-PHIs ameliorate renal anemia and rectify iron metabolism in the short term without increasing the incidence of AEs and SAEs.

Organelle Stress and Crosstalk in Kidney Disease

Organelles play important roles in maintaining cellular homeostasis. Organelle stress responses, especially in mitochondria, endoplasmic reticula (ER), and primary cilia, are deeply involved in kidney disease pathophysiology. Mitochondria are the center of energy production in most eukaryotic cells. Renal proximal tubular cells are highly energy demanding and abundant in mitochondria. Mitochondrial dysfunctions in association with energy metabolism alterations produce reactive oxygen species and promote inflammation in proximal tubular cells, resulting in progression of kidney disease. The ER play critical roles in controlling protein quality. Unfolded protein response (UPR) pathways are the adaptive response to ER stress for maintaining protein homeostasis. UPR pathway dysregulation under pathogenic ER stress often occurs in glomerular and tubulointerstitial cells and promotes progression of kidney disease. The primary cilia sense extracellular signals and maintain calcium homeostasis in cells. Dysfunction of the primary cilia in autosomal dominant polycystic kidney disease reduces the calcium concentration in proximal tubular cells, leading to increased cell proliferation and retention of cyst fluid. In recent years, the direct interaction at membrane contact sites has received increased attention in association with the development of imaging technologies. The part of the ER that is directly connected to mitochondria is termed the mitochondria-associated ER membrane (MAM), which regulates calcium homeostasis and phospholipid metabolism in cells. Disruption of MAM integrity collapses cellular homeostasis and leads to diseases such as diabetes and Alzheimer disease. This review summarizes recent research on organelle stress and crosstalk, and their involvement in kidney disease pathophysiology. In addition, potential treatment options that target organelle stress responses are discussed.

Targeting immunometabolism as an anti-inflammatory strategy

The growing field of immunometabolism has taught us how metabolic cellular reactions and processes not only provide a means to generate ATP and biosynthetic precursors, but are also a way of controlling immunity and inflammation. Metabolic reprogramming of immune cells is essential for both inflammatory as well as anti-inflammatory responses. Four anti-inflammatory therapies, DMF, Metformin, Methotrexate and Rapamycin all work by affecting metabolism and/or regulating or mimicking endogenous metabolites with anti-inflammatory effects. Evidence is emerging for the targeting of specific metabolic events as a strategy to limit inflammation in different contexts. Here we discuss these recent developments and speculate on the prospect of targeting immunometabolism in the effort to develop novel anti-inflammatory therapeutics. As accumulating evidence for roles of an intricate and elaborate network of metabolic processes, including lipid, amino acid and nucleotide metabolism provides key focal points for developing new therapies, we here turn our attention to glycolysis and the TCA cycle to provide examples of how metabolic intermediates and enzymes can provide potential novel therapeutic targets.

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.

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.

Effectiveness of hypoxia-inducible factor prolyl hydroxylase inhibitor roxadustat on renal anemia in non-dialysis-dependent chronic kidney disease: a systematic review and meta-analysis

Background

Renal anemia is a severe complication of chronic kidney disease (CKD) and may worsen its prognosis. Roxadustat is the only oral hypoxia-inducible factor prolyl hydroxylase inhibitor (HIF-PHI) that has been proved effective to treat renal anemia. However, effects of roxadustat on non-dialysis-dependent CKD (NDD-CKD) have yet to be supported by evidence-based medicine.

Methods

Based on the databases of PubMed, EMBASE and Web of Science by 12 April 2019 (CRD42019133225), a meta-analysis of randomized controlled trials (RCTs) on roxadustat for treatment of NDD-CKD was conducted. Primary outcomes were parameters of hemoglobin (Hb) and Hb response. Secondary outcomes were hepcidin, ferritin, total iron binding capacity (TIBC), transferrin saturation (TAST), incidences of diarrhea, adverse events (AEs) and severe adverse events (SAEs). The risk of bias and the quality of evidence were assessed, respectively. Both continuous and binary variables were analyzed by the random effects models. Sensitivity analyses were performed when a significant heterogeneity was observed (P<0.1 and I²>50%).

Results

Finally, three studies with a total of 214 subjects in the roxadustat group and 80 subjects in the placebo group were enrolled. An increase of Hb [weighted mean difference (WMD) =1.22, 95% CI: 0.95 to 1.49, P<0.01], Hb response [odds ratio (OR) =27.74, 95% CI: 10.18 to 75.62, P<0.00001], and TIBC [standard mean difference (SMD) =1.59, 95% CI: 1.17 to 2.01, P<0.00001] was found. A decrease of hepcidin (SMD =-4.46, 95% CI: -5.02 to -3.89, P<0.00001), ferritin (WMD =-61.05, 95% CI: -85.70 to -36.40, P<0.00001) and TAST (WMD =-6.55, 95% CI: -8.82 to -4.29, P<0.00001) were noted as well. Analyses of incidence in diarrhea (OR =1.54, 95% CI: 0.49 to 4.79, P=0.46), AEs (OR =1.31, 95% CI: 0.76 to 2.27, P=0.34) and SAEs (OR =1.25, 95% CI: 0.29 to 5.35, P=0.76) yielded no difference between the roxadustat and the placebo groups.

Conclusions

Roxadustat improved renal anemia of NDD-CKD patients by improving Hb and iron metabolism. Oral administration of roxadustat was relatively safe in that roxadustat did not increase the incidence of AEs and SAEs.

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.

Update on mutations in the HIF: EPO pathway and their role in erythrocytosis

Identification of the underlying defects in congenital erythrocytosis has provided mechanistic insights into the regulation of erythropoiesis and oxygen homeostasis. The Hypoxia Inducible Factor (HIF) pathway plays a key role in this regard. In this pathway, an enzyme, Prolyl Hydroxylase Domain protein 2 (PHD2), constitutively prolyl hydroxylates HIF-2α, thereby targeting HIF-2α for degradation by the von Hippel Lindau (VHL) tumor suppressor protein. Under hypoxia, this modification is attenuated, resulting in the stabilization of HIF-2α and transcriptional activation of the erythropoietin (EPO) gene. Circulating EPO then binds to the EPO receptor (EPOR) on red cell progenitors in the bone marrow, leading to expansion of red cell mass. Loss of function mutations in PHD2 and VHL, as well as gain of function mutations in HIF-2α and EPOR, are well established causes of erythrocytosis. Here, we highlight recent developments that show that the study of this condition is still evolving. Specifically, novel mutations have been identified that either change amino acids in the zinc finger domain of PHD2 or alter splicing of the VHL gene. In addition, continued study of HIF-2α mutations has revealed a distinctive genotype-phenotype correlation. Finally, novel mutations have recently been identified in the EPO gene itself. Thus, the cascade of genes that at a molecular level leads to EPO action, namely PHD2 - > HIF2A - > VHL - > EPO - > EPOR, are all mutational targets in congenital erythrocytosis.

JTZ-951 (enarodustat), a hypoxia-inducibe factor prolyl hydroxylase inhibitor, stabilizes HIF-α protein and induces erythropoiesis without effects on the function of vascular endothelial growth factor

JTZ-951 (enarodustat) is an oral hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor. JTZ-951 has inhibitory activities on human HIF-prolyl hydroxylase 1-3, but not on various receptors or enzymes. In Hep3B cells, JTZ-951 increased HIF-1α and HIF-2α protein levels, erythropoietin (EPO) mRNA levels, and EPO production. In normal rats, after a single oral dose of JTZ-951, the hepatic and renal EPO mRNA levels and plasma EPO concentrations were also increased. In 5/6-nephrectomized rats, repeated oral doses of JTZ-951 once daily or intermittent dosing showed the erythropoiesis stimulating effect. The administration of JTZ-951 at a high dose increased plasma vascular endothelial growth factor (VEGF) levels; however, retinal VEGF mRNA levels and the retinal vascular permeability were not changed. Finally, we evaluated the effect of JTZ-951 in a colorectal cancer cell-inoculated mouse model. Although JTZ-951 at a high dose increased the plasma VEGF, it had no effect on tumor growth. In summary, JTZ-951 induces erythropoiesis without affecting VEGF function. Therefore, it is expected that JTZ-951 will be a new oral candidate that increases and maintains hemoglobin concentrations in renal anemia patients.