Primary and secondary hyperoxaluria: Understanding the enigma

Gut microbiota modulation via fecal microbiota transplantation mitigates hyperoxaluria and calcium oxalate crystal depositions induced by high oxalate diet

Hyperoxaluria, including primary and secondary hyperoxaluria, is a disorder characterized by increased urinary oxalate excretion and could lead to recurrent calcium oxalate kidney stones, nephrocalcinosis and eventually end stage renal disease. For secondary hyperoxaluria, high dietary oxalate (HDOx) or its precursors intake is a key reason. Recently, accumulated studies highlight the important role of gut microbiota in the regulation of oxalate homeostasis. However, the underlying mechanisms involving gut microbiota and metabolite disruptions in secondary hyperoxaluria remain poorly understood. Here, we investigated the therapeutic efficacy of fecal microbiota transplantation (FMT) sourced from healthy rats fed with standard pellet diet against urinary oxalate excretion, renal damage and calcium oxalate (CaOx) crystal depositions via using hyperoxaluria rat models. We observed dose-dependent increases in urinary oxalate excretion and CaOx crystal depositions due to hyperoxaluria, accompanied by significant reductions in gut microbiota diversity characterized by shifts in Ruminococcaceae_UCG-014 and Parasutterella composition. Metabolomic analysis validated these findings, revealing substantial decreases in key metabolites associated with these microbial groups. Transplanting microbes from healthy rats effectively reduced HDOx-induced urinary oxalate excretion and CaOx crystal depositions meanwhile restoring Ruminococcaceae_UCG-014 and Parasutterella populations and their associated metabolites. Furthermore, FMT treatment could significantly decrease the urinary oxalate excretion and CaOx crystal depositions in rat kidneys via, at least in part, upregulating the expressions of intestinal barrier proteins and oxalate transporters in the intestine. In conclusion, our study emphasizes the effectiveness of FMT in countering HDOx-induced hyperoxaluria by restoring gut microbiota and related metabolites. These findings provide insights on the complex connection between secondary hyperoxaluria caused by high dietary oxalate and disruptions in gut microbiota, offering promising avenues for targeted therapeutic strategies.

Liver Transplantation in Primary Hyperoxaluria: A Single-Center 10-Year Experience

BACKGROUND

Primary hyperoxalurias (PHs) are rare inborn errors of metabolism caused by a deficiency of hepatic enzymes, leading to excessive urinary oxalate excretion and the overproduction of oxalate, which accumulates in various organs. If left untreated, PHs can cause serious morbidity, end-stage kidney disease (ESKD), and mortality. Liver transplantation (LT) is a recognized treatment option for children with these diseases. This study aimed to analyze the outcome of PHs disease post-LT from a single center in Iran.

METHODS

This retrospective, single-center study was conducted at the Shiraz Transplant Center from 2012 to 2023, focusing on liver transplant recipients with PH. We evaluated long-term outcomes and post-transplantation results for both deceased donor liver transplantation (DDLT) and living donor liver transplantation (LDLT). Biochemical lab results (pre- and post-transplantation), perioperative data, surgical procedures, transplantation outcomes, and recipient and donor characteristics were reported. Kaplan-Meier survival analysis was used to assess graft and patient survival.

RESULTS

33 recipients with LT (LDLT, n = 6; DDLT, n = 27) were included. The median age at the time of transplantation was 8 years (range: 3-18 years). Following liver transplantation, all of the patients had normalization of liver enzymes. Urine oxalate levels gradually decreased from 198 to 51 (< 45 mg/1.73 m2/day). Among the 33 patients, eight experienced episodes of acute rejection, and five developed chronic rejection. Eight patients underwent kidney transplantation before liver transplantation, while 21 patients initially received liver transplantation. 26 patients survived and remained in good health during a median follow-up period of 7 years (range: 1.5-11 years). For patients with PHs, the survival rates at 6 months, 1 year, 3 years, and 5 years were 100%, 97%, 94%, and 85%, respectively. The graft survival for patients was 100%, 100%, 97%, and 97% at 6 months, 1 year, 3 years, and 5 years, respectively.

CONCLUSIONS

PHs is a rare metabolic disorder, and LT significantly improves both survival and quality of life for affected patients. In our cohort, the majority of patients exhibited favorable long-term outcomes, along with a notable reduction in urine oxalate levels post-transplantation. However, challenges persist, including graft shortages and the risk of renal graft loss due to oxalosis, which continue to affect overall treatment outcomes. These findings highlight the importance of close monitoring and multidisciplinary care in managing PH patients' post-transplant.

Engineered Oxalate Decarboxylase Boosts Activity and Stability for Biological Applications

Oxalate decarboxylase (OxDC) from Bacillus subtilis is a Mn-dependent hexameric enzyme that converts oxalate to carbon dioxide and formate. Recently, OxDC has attracted the interest of the scientific community due to its biotechnological and medical applications for the treatment of hyperoxaluria, a group of pathologic conditions associated with excessive oxalate urinary excretion caused by either increased endogenous production or increased exogenous absorption. The fact that OxDC displays optimum pH in the acidic range represents a big limitation for most biotechnological applications involving processes occurring at neutral pH, where the activity and stability of the enzyme are remarkably reduced. Here, through bioinformatics-guided protein engineering followed by combinatorial mutagenesis and analyses of activity and thermal stability, we identified a double mutant of OxDC endowed with enhanced catalytic efficiency and stability under physiological conditions. The obtained engineered form of OxDC offers a potential tool for improved intestinal oxalate degradation in hyperoxaluria patients.

[Gender Disparities in Urolithiasis with a Special Focus on Oxalate Metabolism in the Liver]

The incidence and prevalence of urolithiasis are increasing in industrialized countries. In particular, an increase has been observed among young adults and women. The gender gap is closing, and gender equality (1:1) with regard to urolithiasis has already been documented for the USA. Studies have demonstrated that women have higher urine pH values than men, which promotes calcium phosphate crystallization. The tendency for men to develop calcium oxalate and uric acid stones is caused by the comparatively lower urine pH values. Malnutrition combined with a lack of exercise and the occurrence of metabolic syndrome with its underlying diseases (insulin resistance, type 2 diabetes mellitus, obesity, dyslipidaemia) are discussed as the causes of the increase in upper tract stone disease in industrialized countries. Non-alcoholic fatty liver disease (NAFLD), as the most common liver disease, is considered one of the complications of metabolic syndrome, with a prevalence of approximately 23% in Germany. Animal experiments and clinical studies have demonstrated a connection between NAFLD and increased oxalate excretion in urine. Based on the literature, NAFLD represents a possible cross-gender risk factor for kidney stone formation and is therefore considered to be a generally modifiable risk factor for recurrent urolithiasis. Simple recommendations concerning NAFLD should complement the general and metabolic workup in everyday clinical practice.

A case report of renal oxalosis and secondary hyperoxaluria due to chronic high vitamin C consumption

Renal oxalosis occurs from supersaturation of the urine with oxalate in the presence of calcium, resulting in deposition of calcium oxalate crystals within renal tissue and, consequently, progressive renal disease. One of the causes of secondary hyperoxaluria is a high intake of vitamin C, which exceeds the renal excretion capacity, and can induce renal oxalosis. We present a case involving a 67-year-old patient with chronic kidney disease and proteinuria, associated with secondary hyperoxaluria and renal oxalosis, who reported prolonged, excessive intake of vitamin C supplements. The patient presented with a gradual worsening of his renal function and proteinuria during the last 6-month period, after an episode of SARS-CoV-2 infection. The kidney biopsy revealed calcium oxalate crystals within the renal tissue. Thorough investigation and history-taking revealed a substantial increase in vitamin C supplementation during the SARS-CoV-2 infection (up to 3 g daily), indicating secondary hyperoxaluria as the causative factor. Overall during the pandemic, supplement consumption dramatically increased and patients were not adequately informed about the risks of various over-the-counter products. Excessive intake of vitamin C, popularized for its supposed health benefits, can lead, among others, to secondary hyperoxaluria and renal oxalosis. Prompt recognition is pivotal to initiate management and to prevent irreversible kidney damage.

OxDc-A0: an oral gastro-tolerant oxalate decarboxylase for treating secondary hyperoxaluria

Secondary hyperoxaluria is an acquired oxalate metabolic disorder characterized by increased urinary oxalate excretion. Reducing exogenous oxalate absorption through enzyme therapy represents a promising therapeutic strategy. However, the extremely acidic pH and protease-rich environment of the upper gastrointestinal tract pose major obstacles for the oral administration of protein therapeutics. OxDc-A0, a novel gastro-tolerant recombinant oxalate decarboxylase, can degrade oxalate in the stomach, thereby limiting the oxalate pool in the gastrointestinal tract and reducing oxalate absorption and urinary excretion. This study aimed to investigate the pharmacodynamics, pharmacokinetics, and safety profile of OxDc-A0 to assess its drug likeliness. The pharmacodynamics were evaluated in vitro and in hyperoxaluria beagle dog model induced by a high-oxalate diet. OxDc-A0 exhibited excellent gastric tolerance and significant efficacy in reducing urinary oxalate excretion in the dog model with hyperoxaluria. The safety of OxDc-A0 was evaluated in Sprague-Dawley rats, beagle dogs, and golden hamsters according to the guidelines for preclinical safety studies. No adverse effects were observed on the central nervous, cardiovascular, or respiratory system in rats or dogs treated orally with OxDc-A0 up to 37,500 U/kg. Pharmacokinetic studies showed that OxDc-A0 is non-systemically absorbed and is mainly distributed in the gastrointestinal tract. Toxicological studies showed that OxDc-A0 has excellent tolerance, with a NOAEL of 37,500 U/kg/day in both rats and dogs. The maximum tolerated dose was ≥ 105,000 U/kg in rats and ≥ 87,000 U/kg in dogs. Overall, OxDc-A0 shows great potential as a new drug candidate for treating secondary hyperoxaluria.

Molecular insights into cell signaling pathways in kidney stone formation

Urolithiasis, or kidney stones, has emerged as a significant public health concern. Despite this, effective treatments targeting stone formation and recurrence are limited. This review delves into the molecular mechanisms underlying the condition. Investigating these molecular aspects can address existing gaps in treatment options. Future research can uncover new therapeutic strategies by targeting downstream pathways, and effector molecules. Cell signaling pathways offer potential targets, as they involve complex interactions that can be modulated to address multiple clinical symptoms. An imbalance in calcium and oxalate levels can lead to kidney stone formation which is characterized by oxidative stress, inflammation, and cell death. The interplay between key organelles like the endoplasmic reticulum and mitochondria triggers stress pathways, including oxidative stress and apoptosis. This review consolidates recent advances in understanding the pathophysiology and signaling events associated with kidney stones.

Identification of a novel GRHPR mutation in primary hyperoxaluria type 2 and establishment of patient-derived iPSC line

This research delves into Primary Hyperoxaluria Type 2 (PH2), an autosomal recessive disorder precipitated by a unique case of compound heterozygous deleterious mutations in the GRHPR gene, specifically the intron2/3 c.214-2 T > G and the exon8 c.864-865delTG, leading to a premature stop codon at p.Val289fsTer22. The intron 2/3 variant (c.214-2 T > G) is a novel finding and is reported for the first time. These mutations are associated with profound alterations in protein structure and function. Employing patient-derived induced pluripotent stem cells (iPSCs), we have successfully generated a patient-specific model that exhibits the hallmarks of pluripotency, including typical stem cell morphology, expression of pluripotency markers, and a normal karyotype. The iPSCs are capable of differentiating into all three germ layers, underscoring their potential for regenerative medicine. The established iPSC line offers a promising platform for drug screening and regenerative medicine approaches for PH2.

Secondary hyperoxaluria: Cause and consequence of chronic kidney disease

Secondary hyperoxaluria is a metabolic disorder characterized by an increase in urinary oxalate excretion. The etiology may arise from an increase in the intake of oxalate or its precursors, decreased elimination at the digestive level, or heightened renal excretion. Recently, the role of the SLC26A6 transporter in the etiopathogenesis of this disease has been identified. This transporter is active at both the intestinal and renal levels, and its mechanism of action is disrupted during systemic inflammation and metabolic syndrome, which could explain the rising incidence of secondary hyperoxaluria in recent decades. Treatment includes hygienic dietary measures, and medications aimed at reducing intestinal absorption by increasing fecal excretion. Different immunomodulatory drugs, microbiome modifiers and SGLT2 inhibitors could constitute new therapeutic targets. Currently, specific treatments for secondary hyperoxaluria are lacking, making early diagnosis and preventive measures against kidney failure the main therapeutic strategies.

A mouse model for the study of diet-induced changes in intestinal microbiome composition on renal calcium oxalate crystal formation

Currently available animal models for calcium oxalate kidney stones are limited in their translational potential. Particularly with increasing interest in gut microbiota involvement in kidney stone disease, there are limited animal models which can be used. As such, we have developed a novel diet-induced hyperoxaluria murine model which addresses some of the shortcomings of other currently available models. Mice C57BL/6 mice were fed a 1.5% sodium oxalate supplemented chow for two weeks and showed no morbidity or mortality. Mice fed the sodium oxalate diet consistently had renal calcium oxalate crystal deposits as confirmed by polarized light microscopy, and energy-dispersive X-ray spectroscopy. We developed a isotope dilution high-performance liquid chromatography/mass spectrometry protocol which confirmed that our model produced both urinary and enteric hyperoxaluria. 16 S ribosomal RNA sequencing of stool samples and cecal contents showed that sodium oxalate is a disruptor of the gut microbiome, and may interfere with commensal microbes in the gut microbiome. With consistent results this mouse model is superior to other models of kidney stone disease, as this model can be applied to investigate topics of oxalate absorption, transport, metabolism, excretion, crystal formation, the gut microbiome and testing of various therapeutic agents for translation to early stages of renal crystal formation in kidney stone disease.

Opportunities in Primary and Enteric Hyperoxaluria at the Cross-Roads Between the Clinic and Laboratory

Hyperoxaluria is a condition in which there is a pathologic abundance of oxalate in the urine through either hepatic overproduction (primary hyperoxaluria [PH]) or excessive enteric absorption of dietary oxalate (enteric hyperoxaluria [EH]). Severity can vary with the most severe forms causing kidney failure and extrarenal manifestations. To address the current challenges and innovations in hyperoxaluria, the 14th International Hyperoxaluria Workshop convened in Perugia, Italy, bringing together international experts for focused presentation and discussion. The objective of the following report was to disseminate an overview of the proceedings and provide substrate for further thought. The format of this paper follows the format of the meeting, addressing, "PH type 1" (PH1) first, followed by "surgery, genetics, and ethics in PH", then "PH types 2 and 3," (PH2 and PH3) and, finally, "EH." Each session began with presentations of the current clinical challenges, followed by discussion of the latest advances in basic and translational research, and concluded with interactive discussions about prioritizing the future of research in the field to best serve the need of the patients.

Impact of diet on renal stone formation

Background and Objectives

The incidence of kidney stones is increasing globally, with a preponderance in adults compared with that in adolescents and children. Dietary habits have been identified as significant contributing factors to kidney stone formation. This literature review aimed to explore the existing evidence on the impact of diet on renal stone formation.

Methods and Study Design

We conducted a comprehensive literature review and included 81 studies published between 1999 and 2023, limiting the search to articles published in English. The extracted data were analyzed to identify common themes, trends, and patterns related to the impact of diet on renal stone formation. We investigated the influence of dietary habits on the risk of nephrolithiasis.

Results

Although the role of fluid intake in relation to stone formation is clear, existing evidence on how different types of beverages (coffee, tea, fruit juices, and soft drinks) affect kidney stone formation is conflicting. Other factors such as protein, sodium chloride, calcium, oxalate, fat, and carbohydrate intake have also been discussed as contributors to nephrolithiasis. Thus, diet should be appropriately modified to reduce the risk of stone formation in susceptible individuals. A history of nephrolithiasis has been found to increase the risk of both chronic kidney disease and end-stage renal disease. The review acknowledges the limitations inherent in conducting a literature review, including the potential for publication bias and the reliance on available published studies.

Conclusions

These findings highlight the importance of understanding and preventing nephrolithiasis.

The Altered Proteomic Landscape in Renal Tubular Epithelial Cells under High Oxalate Stimulation

Our study aimed to apply a proteomic approach to investigate the molecular mechanisms underlying the effects of oxalate on rat renal tubular epithelial cells. NRK-52E cells were treated with or without oxalate and subjected to quantitative proteomics to identify key proteins and key pathological changes under high oxalate stimulation. A total of 268 differentially expressed proteins (DEPs) between oxalate-treated and control groups were identified, with 132 up-regulated and 136 down-regulated proteins. Functional enrichment analysis revealed that DEPs are associated with oxidative stress, apoptosis, ferroptosis, pro-inflammatory cytokines, vitamin D, and biomineralization. SPP1, MFGE8, ANKS1A, and NAP1L1 were up-regulated in the oxalate-treated cells and the hyperoxaluric stone-forming rats, while SUB1, RNPS1, and DGLUCY were down-regulated in both cases. This altered proteomic landscape sheds light on the pathological processes involved in oxalate-induced renal damage and identifies potential biomarkers and therapeutic targets to mitigate the effects of hyperoxaluria and reduce the risk of CaOx stone formation.

Diet-induced hyperoxaluria: A case based mini-review

INTRODUCTION

Oxalate nephropathy (ON) is a rare condition involving the precipitation of calcium oxalate crystals within the nephrons. Primary hyperoxaluria involves enzymatic defects in the metabolism of glyoxylate, while secondary hyperoxaluria includes dietary and malabsorption-related etiologies.

CASE PRESENTATION

We discuss the case of a White male in his 80s who presented to the hospital with acute kidney injury on chronic kidney disease stage 4 in the setting of a new antibiotic prescription. Creatinine had increased to 4.2 mg/dL from a baseline of 2.2 mg/dL, with no etiology identified on urinalysis or renal ultrasound. Renal biopsy then revealed an acute tubular injury with intraluminal calcium oxalate crystals deposits, confirming a diagnosis of ON.

DISCUSSION

A detailed history revealed an excessive dietary intake of oxalate-rich foods, including nuts, and daily ingestion of 2 g of vitamin C. The patient was counselled on adjusting his diet and stopping vitamin C supplementation, which led his creatinine to return close to baseline 2 months post-discharge.

CONCLUSION

Thorough history-taking enables early recognition and timely interventions to possibly avoid hyperoxaluria from progressing to end-stage kidney disease (ESRD).

A CASE OF RETINAL ATHEROSCLEROTIC OXALOSIS DUE TO HYPEROXALURIA IN A PATIENT WITH SHORT GUT SYNDROME

PURPOSE

To describe a severe case of crystalline retinopathy secondary to hyperoxaluria from short gut syndrome.

METHODS

Case report.

RESULTS

A 62-year-old Caucasian woman with short gut syndrome and end-stage renal disease from renal oxalosis presented with chronic bilateral vision loss. She had previously been treated for presumed occlusive vasculitis. Visual acuity on initial examination was 20/400 right eye and 20/100 left eye with an afferent pupillary defect of the right eye. Examination revealed attenuated retinal vasculature and diffuse crystalline infiltration of retinal arterial lumina and throughout the retinas bilaterally. Optical coherence tomography revealed inner retinal atrophy with crystalline deposition in the inner retinal layers. Fluorescein angiography demonstrated delayed vascular filling and dropout consistent with severe ischemic vasculopathy. It was concluded that the short-gut syndrome led to overabsorption of oxalate with subsequent hyperoxaluria leading to retinal atherosclerotic oxalosis.

CONCLUSION

Retinal calcium oxalate deposits due to hyperoxaluria have been previously noted; however, this degree of severe retinal vascular infiltration has not been described. Our patient was receiving hemodialysis, which is associated with high rebound increases in systemic oxalate concentrations. It is important to keep hyperoxaluria in mind as a potential cause of retinopathy in patients with end-stage renal disease presenting with vision loss.

Primary hyperoxaluria: Description of a new oral finding and review of literature

OBJECTIVES

Oro-dental manifestations of hyperoxaluria and dental management of affected patients are rarely reported in the literature. We describe a new oral presentation of primary hyperoxaluria (PH) and review relevant literature about oro-dental manifestations and management of dental complications of hyperoxaluria.

METHODS

A case report of a 44-year-old female who presented with symptoms of temporomandibular joint dysfunction due to hyperoxaluria was described according to the CARE guidelines. In addition, an extensive search of biomedical databases (PubMed, Medline, Google Scholar, and Embase) for articles describing oro-dental manifestations and/or dental management in patients with hyperoxaluria was performed using the key words ("oral" and/or "hyperoxaluria" and/or "dental" and/or "oxalosis"). Included articles were reviewed and data about patient demographics, disease type and stage, oral and dental manifestations, and dental treatment outcome were retrieved and analyzed.

RESULTS

A total of 14 articles describing the oral and dental manifestations in 15 patients with hyperoxaluria were included. Tooth mobility, root resorption, and radiographic alterations were consistently described in all cases. Oral manifestations were described mainly in PH at late stages, and only after the onset of chronic renal disease. Dental management in all reported cases was palliative and aimed to relive pain and treat periodontal infection. Tooth loss due to extraction or uncontrolled mobility was the ultimate outcome in almost all reported cases.

CONCLUSION

Oral and dental manifestations in hyperoxaluria are rarely reported in the literature. Management of tooth mobility and root resorption in hyperoxaluria is challenging and clinical guidelines and evidence-based recommendations are lacking. Early diagnosis and treatment of hyperoxaluria might be the only effective approach to prevent dental and periodontal complications of the disease.

Impact of low-oxalate diet on hyperoxaluria among patients suffering from nephrolithiasis

Low-oxalate diets are useful for treating hyperoxaluria in nephrolithiasis patients. This study was unique in examining how a low-oxalate diet in addition to a standard diet affected hyperoxaluria and renal function tests in nephrolithiasis patients. The effects of a low-oxalate diet were analyzed by different biochemical tests, that is, anthropometric measurements, blood oxalate test, renal function test, electrolyte profile test, and 24 h urine analysis. For this purpose, 112 patients were divided into 2 groups: Group T1 (Conventional diet) and Group T2 (Low-Oxalate diet) for 8 weeks. Each group was tested at the initiation and end of the study. Using SPSS, the obtained data from each parameter were statistically analyzed. The results showed that a low-oxalate diet had a positive effect on patients suffering from nephrolithiasis. Furthermore, after treatment, anthropometric measurement weight (kg) among the control group (T1) was 100.45 ± 5.65 and the treatment group (T2) was 79.71 ± 9.48 kg. The effect of low-oxalate diet on renal function test: creatinine (g/d) among T1 was 2.08 ± 0.86 and T2 was 1.17 ± 0.13, uric acid(mg/d) among T1 was 437.04 ± 24.20 and T2 was 364.61 ± 35.99, urinary oxalate (mg/d) among T1 was 76.84 ± 10.33 and T2 was 39.24 ± 1.51, respectively. Sodium (mEq/d) among T1 was 156.72 ± 6.37 and T2 was 159.84 ± 6.31, potassium (mEq/d) among T1 was 69.91 ± 15.37 and T2 was 89.21 ± 6.31, phosphorus (g/d) among T1 was 0.96 ± 0.07 and T2 was 0.34 ± 0.27, respectively. This study demonstrated that nephrolithiasis patients with hyperoxaluria benefit from low-oxalate diets. Hyperoxaluria patients should eat a low-oxalate diet to use oxalate without affecting metabolism and eliminate it from the kidney without stones.

Multiomics Assessment of the Gut Microbiome in Rare Hyperoxaluric Conditions

Introduction

Hyperoxaluria is a risk factor for kidney stone formation and chronic kidney disease progression. The microbiome is an important protective factor against oxalate accumulation through the activity of its oxalate-degrading enzymes (ODEs). In this cross-sectional study, we leverage multiomics to characterize the microbial community of participants with primary and enteric hyperoxaluria, as well as idiopathic calcium oxalate kidney stone (CKS) formers, focusing on the relationship between oxalate degrading functions of the microbiome.

Methods

Patients diagnosed with type 1 primary hyperoxaluria (PH), enteric hyperoxaluria (EH), and CKS were screened for inclusion in the study. Participants completed a food frequency questionnaire recording their dietary oxalate content while fecal oxalate levels were ascertained. DNA and RNA were extracted from stool samples and sequenced. Metagenomic (MTG) and metatranscriptomic (MTT) data were processed through our bioinformatics pipelines, and microbiome diversity, differential abundance, and networks were subject to statistical analysis in relationship with oxalate levels.

Results

A total of 38 subjects were recruited, including 13 healthy participants, 12 patients with recurrent CKS, 8 with PH, and 5 with EH. Urinary and fecal oxalate were significantly higher in the PH and the EH population compared to healthy controls. At the community level, alpha-diversity and beta-diversity indices were similar across all populations. The respective contributions of single bacterial species to the total oxalate degradative potential were similar in healthy and PH subjects. MTT-based network analysis identified the most interactive bacterial network in patients with PH. Patients with EH had a decreased abundance of multiple major oxalate degraders.

Conclusion

The composition and inferred activity of oxalate-degrading microbiota were differentially associated with host clinical conditions. Identifying these changes improves our understanding of the relationships between dietary constituents, microbiota, and oxalate homeostasis, and suggests new therapeutic approaches protecting against hyperoxaluria.

Expanding the Genetic Spectrum of AGXT Gene Variants in Egyptian Patients with Primary Hyperoxaluria Type I

Introduction: Approximately 80% of primary hyperoxaluria cases are caused by primary hyperoxaluria type 1 (PH1, OMIM# 259900), which is characterized by pathogenic variants in the AGXT gene, resulting in deficiency of the liver-specific enzyme alanine-glyoxylate aminotransferase (AGT). This leads to increased production of oxalate, which cannot be effectively eliminated from the body, resulting in its accumulation primarily in the kidneys and other organs. Subjects and Methods: This study included 17 PH1 Egyptian patients from 12 unrelated families, recruited from the Inherited Kidney Disease Outpatient Clinic and the Dialysis Units, Cairo University Hospitals, during the period from January 2018 to December 2019, aiming to identify the pathogenic variants in the AGXT gene. Results: Six different variants were detected. These included three frameshift and three missense variants, all found in homozygosity within the respective families. The most common variant was c.121G>A;p.(Gly41Arg) detected in four families, followed by c.725dup;p.(Asp243GlyfsTer12) in three families, c.33dup;p.(Lys12Glnfs156) in two families, and c.731T >C;p.(Ile244Thr), c.33delC;p.(Lys12Argfs34), and c.568G>A;p.(Gly190Arg) detected in one family each. Conclusion: Consanguineous Egyptian families with history of renal stones or renal disease suspicious of primary hyperoxaluria should undergo AGXT genetic sequencing, specifically targeting exons 1 and 7, as variants in these two exons account for >75% of disease-causing variants in Egyptian patients with confirmed PH1.

Multimodal Imaging Findings Associated With Cardiac Oxalosis Cardiomyopathy

We report the case of a 50-year-old woman with secondary oxalosis following bowel resection resulting in restrictive cardiomyopathy and a diagnosis of cardiac amyloidosis based on the initial workup. The case documented findings by cardiac magnetic resonance imaging and technetium Tc 99m-labeled pyrophosphate scan in patients with cardiac oxalosis, which can mimic findings in cardiac amyloidosis, expanding the differential diagnosis.

Glycolate oxidase-1 gene variants influence the risk of hyperoxaluria and renal stone development

PURPOSE

Oxalate is an excellent calcium ion attractor with great abundance in the human body, and the liver is the major source of oxalate. The Glycolate oxidase-1 (GOX1) gene is solely responsible for the glycolate and glyoxylate metabolism and produces oxalate. This study has been designed to comprehend the association of genetic variants of the GOX1 gene with the risk of hyperoxaluria and renal stone disease in the Indian population.

METHOD

The present study is a candidate gene approach prospective case-control study carried out on 300 participants (150 cases and 150 controls) at Muljibhai Patel Urological Hospital, Gujarat, India. Biochemical parameters, including serum levels of calcium, creatinine, parathyroid hormone, and 24-h urine metabolites, were performed. The genotyping of GOX1 gene variants rs6086287, rs2235250, rs2255183, and rs2294303 was performed using a customized TaqMan assay probe by RT-PCR.

RESULT

Parathyroid hormone, serum creatinine, and urine metabolites were significantly elevated in nephrolithiasis compared to healthy individuals. All mutated homozygous genotypes GG (rs6086287), TT (rs2235250), GG (rs2255183), and CC (rs2294303) were significantly associated with a high risk of renal stone disease. Individuals diagnosed with hyperoxaluria and carrying TG (rs6086287), AG (rs2255183), and TT (rs2294303) genotypes have a significantly high risk of renal stone disease. Moreover, haplotype analysis and correlation analysis also confirmed the strong association between genetic variants and nephrolithiasis.

CONCLUSION

Genetic variants of the GOX1 genes were associated with renal stone disease. In the presence of risk genotype and hyperoxaluria, the susceptibility to develop renal stone disease risk gets modulated.

Oxalate nephropathy and chronic turmeric supplementation: a case report

We present a case of a 69-year-old man who presented for routine check-up and was incidentally found to have kidney failure with an initially unrevealing history and bland urinary sediment. He was diagnosed with oxalate nephropathy in the setting of chronic turmeric supplementation and chronic antibiotic therapy with associated diarrhea. Our case provides several key insights into oxalate nephropathy. First, the diagnosis requires a high index of clinical suspicion. It is uncommonly suspected clinically unless there is an obvious clue in the history such as Roux-en-Y gastric bypass or ethylene glycol poisoning. Diagnosis can be confirmed by histopathologic findings and corroborated by serum levels of oxalate and 24-hour urinary excretion. Second, the diagnosis can often be missed by the pathologist because of the characteristics of the crystals unless the renal pathologist has made it a rule to examine routinely all H&E sections under polarized light. This must be done on H&E, as the other stains dissolve the crystals. Third, one oxalate crystal in a routine needle biopsy is considered pathologic and potentially contributing to the AKI or to the CKD in an important way. Fourth, secondary oxalosis can be largely mitigated or prevented in many cases, especially iatrogenic cases. This can come through the surgeon or the gastroenterologist providing proper instructions to patients on an oxalate-restricted diet or other specific dietary measures. Lastly, this case highlights the success that results from cooperation and communication between the pathologist and the treating physician.

Targeting the Liver with Nucleic Acid Therapeutics for the Treatment of Systemic Diseases of Liver Origin

Systemic diseases of liver origin (SDLO) are complex diseases in multiple organ systems, such as cardiovascular, musculoskeletal, endocrine, renal, respiratory, and sensory organ systems, caused by irregular liver metabolism and production of functional factors. Examples of such diseases discussed in this article include primary hyperoxaluria, familial hypercholesterolemia, acute hepatic porphyria, hereditary transthyretin amyloidosis, hemophilia, atherosclerotic cardiovascular diseases, α-1 antitrypsin deficiency-associated liver disease, and complement-mediated diseases. Nucleic acid therapeutics use nucleic acids and related compounds as therapeutic agents to alter gene expression for therapeutic purposes. The two most promising, fastest-growing classes of nucleic acid therapeutics are antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs). For each listed SDLO disease, this article discusses epidemiology, symptoms, genetic causes, current treatment options, and advantages and disadvantages of nucleic acid therapeutics by either ASO or siRNA drugs approved or under development. Furthermore, challenges and future perspectives on adverse drug reactions and toxicity of ASO and siRNA drugs for the treatment of SDLO diseases are also discussed. In summary, this review article will highlight the clinical advantages of nucleic acid therapeutics in targeting the liver for the treatment of SDLO diseases. SIGNIFICANCE STATEMENT: Systemic diseases of liver origin (SDLO) contain rare and common complex diseases caused by irregular functions of the liver. Nucleic acid therapeutics have shown promising clinical advantages to treat SDLO. This article aims to provide the most updated information on targeting the liver with antisense oligonucleotides and small interfering RNA drugs. The generated knowledge may stimulate further investigations in this growing field of new therapeutic entities for the treatment of SDLO, which currently have no or limited options for treatment.

Management of Pediatric Urolithiasis in an Italian Tertiary Referral Center: A Retrospective Analysis

Background and Objectives: In recent years, the prevalence of pediatric urolithiasis has increased in North America and Western countries, though it is endemic in developing countries. The aim of this study is to describe the experience of a tertiary pediatric referral center in the surgical management of pediatric urolithiasis. Materials and Methods: We retrospectively reviewed the experience of patients ≤ 16 years old affected by urinary stones who underwent surgery. Results: From April 2021 to September 2023, 31 pediatric patients underwent surgical procedures for stone diseases at our department: 13 preschool-aged (1-5 years) and 18 school-aged (6-16 years) children. During this period, 12 URSs, 17 RIRSs, and 2 PCNLs were recorded. Five patients had residual fragments at first, so three of them underwent a second endourological lithotripsy (2 RIRSs and 1 URS). Complete clearance was finally achieved in 27 patients. The stone composition was evaluated in 25 cases. Conclusions: Numerous innovations in the surgical treatment of pediatric urolithiasis have resulted from the development of smaller devices and new technology. Our results show how, in experienced centers, retrograde and percutaneous lithotripsy are safe and effective procedures for use in pediatric populations.

A Rare Sparkle: A Case of Calcified Kidneys in a Young Infant With Renal Failure

Primary hyperoxaluria-1 (PH1) is an autosomal recessively inherited rare genetic condition due to the deficiency of the hepatic enzyme alanine:glyoxylate aminotransferase which leads to high systemic levels of oxalate and subsequently, early end-stage renal disease and death. Here, we present a case of a three-month-old male infant who presented with loose stools, reduced oral intake, and decreased activity for 12-13 days along with edema and a peeling rash on cheeks, lips, and genitalia. During the entire duration of the inpatient stay, the child was oligoanuric. Kidney ultrasound (USG) was suggestive of bilateral hyperechoic kidneys with increased cortical echogenicity and a computed tomography scan showed bilateral diffusely calcified renal cortices with well-preserved renal architecture. A diagnosis of "oxalate nephropathy" was made from renal biopsy and genetic testing confirmed it to be "primary hyperoxaluria-1". The child was initially managed conservatively, and then peritoneal dialysis was done, following which the child was shifted to intermittent hemodialysis.

Pediatric combined living donor liver and kidney transplantation for primary hyperoxaluria type 2

We report the case of a 12-year-old boy with primary hyperoxaluria type 2 (PH2) presenting with end-stage renal disease and systemic oxalosis who underwent a combined living donor liver and kidney transplant from 3 donors, 1 of whom was a heterozygous carrier of the mutation. Plasma oxalate and creatinine levels normalized immediately following the transplant and remain normal after 18 months. We recommend combined liver and kidney transplantation as the preferred therapeutic option for children with primary hyperoxaluria type 2 with early-onset end-stage renal disease.

Estrogen's Tissue-Specific Regulation of the SLC26A6 Anion Transporter Reveal a Phenotype of Kidney Stone Disease in Estrogen-Deficient Females: A Systematic Review

Kidney stone formation is an intricate process that involves a disruption in the interplay of the multiple organs and systems involved in regulating the concentration of specific ions in the body. Women who have gone through menopause are susceptible to kidney stone disease. This systematic review aims to investigate the potential influence of estrogen on kidney function and oxalate homeostasis, notably through the anion transporter SLC26A6 (also known as putative anion transporter 1 or PAT1) in females. In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 checklist, a systematic search of online databases included Pubmed, ScienceDirect Journals, and Ingenta Connect Journals. Predetermined criteria to include and exclude papers, gathering articles published between 2012 and 2022, were determined. After a thorough analysis, eight articles (three cohorts, one case-control, one in vivo, one in vitro, and two cross-sectional studies) were identified for the final quality assessment review.  The eight selected and quality-assessed articles provided evidence of a directly proportional connection between estrogen and kidney function. A correlation between serum estrogen levels and the development of kidney stone disease was confirmed. Administration of β-estradiol was shown to effectively inhibit the function of the anion transporter PAT1 in a tissue-specific manner. In the case of the kidney, estrogen was observed to down-regulate PAT1, which led to a reduction in oxalate transporting activity and, consequently, a decrease in kidney stone formation. Consensus suggests that serum estrogen levels and optimal kidney functioning are interrelated. Furthermore, analysis of the quality-assessed articles and a comprehensive literature review revealed estrogen's tissue-specific regulation of the PAT1 anion transporter aids in maintaining kidney function and anion homeostasis. Additional research is needed to solidify estrogen's role in kidney stone disease to determine its therapeutic value in clinical practice.

Oxalate (dys)Metabolism: Person-to-Person Variability, Kidney and Cardiometabolic Toxicity

Oxalate is a metabolic end-product whose systemic concentrations are highly variable among individuals. Genetic (primary hyperoxaluria) and non-genetic (e.g., diet, microbiota, renal and metabolic disease) reasons underlie elevated plasma concentrations and tissue accumulation of oxalate, which is toxic to the body. A classic example is the triad of primary hyperoxaluria, nephrolithiasis, and kidney injury. Lessons learned from this example suggest further investigation of other putative factors associated with oxalate dysmetabolism, namely the identification of precursors (glyoxylate, aromatic amino acids, glyoxal and vitamin C), the regulation of the endogenous pathways that produce oxalate, or the microbiota's contribution to oxalate systemic availability. The association between secondary nephrolithiasis and cardiovascular and metabolic diseases (hypertension, type 2 diabetes, and obesity) inspired the authors to perform this comprehensive review about oxalate dysmetabolism and its relation to cardiometabolic toxicity. This perspective may offer something substantial that helps advance understanding of effective management and draws attention to the novel class of treatments available in clinical practice.

Oxalate in Foods: Extraction Conditions, Analytical Methods, Occurrence, and Health Implications

Oxalate is an antinutrient present in a wide range of foods, with plant products, especially green leafy vegetables, being the main sources of dietary oxalates. This compound has been largely associated with hyperoxaluria, kidney stone formation, and, in more severe cases, systematic oxalosis. Due to its impact on human health, it is extremely important to control the amount of oxalate present in foods, particularly for patients with kidney stone issues. In this review, a summary and discussion of the current knowledge on oxalate analysis, its extraction conditions, specific features of analytical methods, reported occurrence in foods, and its health implications are presented. In addition, a brief conclusion and further perspectives on whether high-oxalate foods are truly problematic and can be seen as health threats are shown.

Urinary Lithiasis Risk Assessment after Bariatric Surgery

Malabsorption is a consequence of gastric bypass (GB). GB increases the risk of kidney stone formation. This study aimed to evaluate the accuracy of a screening questionnaire for assessing the risk of lithiasis in this population. We performed a monocentric retrospective study to evaluate a screening questionnaire administered to patients who underwent gastric bypass surgery between 2014 and 2015. Patients were asked to answer a questionnaire that included 22 questions divided into four parts: medical history, episodes of renal colic before and after bypass surgery, and eating habits. A total of 143 patients were included in the study, and the mean age of the patients was 49.1 ± 10.8 years. The time between gastric bypass surgery and the completion of the questionnaire was 50.75 ± 4.95 months. The prevalence of kidney stones in the study population was 19.6%. We found that with a score of ≥6, the sensitivity and specificity were 92.9% and 76.5%, respectively. Positive and negative predictive values were 49.1% and 97.8%, respectively. The ROC curve showed an Area Under the Curve (AUC) of 0.932 ± 0.029 (p < 0.001). We developed a reliable and short questionnaire to identify patients at a high risk of kidney stones after gastric bypass. When the results of the questionnaire were equal to or greater than six, the patient was at a high risk of kidney stone formation. With a good predictive negative value, it could be used in daily practice to screen patients who have undergone gastric bypass and are at a high risk of renal lithiasis.

Oxalate Homeostasis in Non-Stone-Forming Chronic Kidney Disease: A Review of Key Findings and Perspectives

Chronic kidney disease (CKD) is a significant global public health concern associated with high morbidity and mortality rates. The maintenance of oxalate homeostasis plays a critical role in preserving kidney health, particularly in the context of CKD. Although the relationship between oxalate and kidney stone formation has been extensively investigated, our understanding of oxalate homeostasis in non-stone-forming CKD remains limited. This review aims to present an updated analysis of the existing literature, focusing on the intricate mechanisms involved in oxalate homeostasis in patients with CKD. Furthermore, it explores the key factors that influence oxalate accumulation and discusses the potential role of oxalate in CKD progression and prognosis. The review also emphasizes the significance of the gut-kidney axis in CKD oxalate homeostasis and provides an overview of current therapeutic strategies, as well as potential future approaches. By consolidating important findings and perspectives, this review offers a comprehensive understanding of the present knowledge in this field and identifies promising avenues for further research.

Effects of dietary irritants on intestinal homeostasis and the intervention strategies

Abundant diet components are unexplored as vital factors in intestinal homeostasis. Dietary irritants stimulate the nervous system and provoke somatosensory responses, further inducing diarrhea, gut microbiota disorder, intestinal barrier damage or even severe gastrointestinal disease. We depicted the effects of food with piquancy, high fat, low pH, high-refined carbohydrates, and indigestible texture. The mechanism of dietary irritants on intestinal homeostasis were comprehensively summarized. Somatosensory responses to dietary irritants are palpable and have specific chemical and neural mechanisms. In contrast, even low-dose exposure to dietary irritants can involve multiple intestinal barriers. Their mechanisms in intestinal homeostasis are often overlapping and dose-dependent. Therefore, treating symptoms caused by dietary irritants requires personalized nutritional advice. The reprocessing of stimulant foods, additional supplementation with probiotics or prebiotics, and enhancement of the intestinal barrier are effective intervention strategies. This review provides promising preliminary guidelines for the treatment of symptoms and gastrointestinal injury caused by dietary irritants.

Prospective Assessment of the Prevalence of Enter Hyperoxalosis in Kidney Transplant Candidates

Enteric hyperoxalosis (EH) is an emerging cause of kidney transplantation (KT) dysfunction. We sought to determine the prevalence of EH and factors that affect plasma oxalate (POx) among at-risk KT candidates.

Methods

We prospectively measured POx among KT candidates evaluated at our center from 2017 to 2020 with risk factors for EH namely bariatric surgery, inflammatory bowel disease, or cystic fibrosis. EH was defined by a POx ≥10 μmol/L. Period-prevalence of EH was calculated. We compared mean POx across 5 factors: underlying condition, chronic kidney disease (CKD) stage, dialysis modality, phosphate binder type, and body mass index.

Results

Of 40 KT candidates screened, 23 had EH for a 4-y period prevalence of 58%. Mean POx was 21.6 ± 23.5 μmol/L ranging from 0 to 109.6 μmol/L. 40% of screened had POx >20 μmol/L. Sleeve gastrectomy was the most common underlying condition associated with EH. Mean POx did not differ by underlying condition (P = 0.27), CKD stage (P = 0.17), dialysis modality (P = 0.68), phosphate binder (P = 0.58), and body mass index (P = 0.56).

Conclusions

Bariatric surgery and inflammatory bowel disease were associated with a high prevalence of EH among KT candidates. Contrary to prior studies, sleeve gastrectomy was also associated with hyperoxalosis in advanced CKD. POx concentrations observed in EH reached levels associated with tissue and potentially allograft deposition. Concentrations can be as high as that seen in primary hyperoxaluria. More studies are needed to assess if POx is indeed a modifiable factor affecting allograft function in patients with EH.

Analysis of the urinary metabolic profiles in irradiated rats treated with Activated Protein C (APC), a potential mitigator of radiation toxicity

PURPOSE

The goal of the current study was to identify longitudinal changes in urinary metabolites following IR exposure and to determine potential alleviation of radiation toxicities by administration of recombinant APC formulations.

MATERIALS AND METHODS

Female adult WAG/RijCmcr rats were irradiated with 13.0 Gy leg-out partial body X-rays; longitudinally collected urine samples were subject to LC-MS based metabolomic profiling. Sub-cohorts of rats were treated with three variants of recombinant APC namely, rat wildtype (WT) APC, rat 3K3A mutant form of APC, and human WT APC as two bolus injections at 24 and 48 hours post IR.

RESULTS

Radiation induced robust changes in the urinary profiles leading to oxidative stress, severe dyslipidemia, and altered biosynthesis of PUFAs, glycerophospholipids, sphingolipids, and steroids. Alterations were observed in multiple metabolic pathways related to energy metabolism, nucleotide biosynthesis and metabolism that were indicative of disrupted mitochondrial function and DNA damage. On the other hand, sub-cohorts of rats that were treated with rat wildtype-APC showed alleviation of radiation toxicities, in part, at the 90-day time point, while rat 3K3A-APC showed partial alleviation of radiation induced metabolic alterations 14 days after irradiation.

CONCLUSIONS

Taken together, these results show that augmenting the Protein C pathway and activity via administration of recombinant APC may be an effective approach for mitigation of radiation induced normal tissue toxicity.

A case-based review of dietary management of calcium oxalate stones

PURPOSE

The purpose of this paper is to help patients with calcium oxalate stones to access prevention and treatment options with dietary management.

METHODS

Typical cases in our hospital and other hospitals were selected for case review; combined with literature review through PubMed search, comprehensive analysis and suggestions were put forward.

RESULTS

By retrieving the literature with sufficient evidence, selecting, and summarizing, analysis of dietary liquid, oxalate and oxalate precursors, calcium, protein, fruits and vegetables, salt, high dietary fiber, and other content with high evidence index was carried out, respectively.

CONCLUSION

Through the retrospective analysis of typical cases and literature review, the importance of diet management in the prevention and treatment of calcium oxalate stones was emphasized again, and suggestions were put forward to promote the prevention and treatment of calcium oxalate stones.

Pediatric Nephrolithiasis

The prevalence of pediatric nephrolithiasis has increased dramatically in the past two decades for reasons that have yet to be fully elucidated. Workup of pediatric kidney stones should include metabolic assessment to identify and address any risk factors predisposing patients to recurrent stone formation, and treatment should aim to facilitate stone clearance while minimizing complications, radiation and anesthetic exposure, and other risks. Treatment methods include observation and supportive therapy, medical expulsive therapy, and surgical intervention, with choice of treatment method determined by clinicians' assessments of stone size, location, anatomic factors, comorbidities, other risk factors, and preferences and goals of patients and their families. Much of the current research into nephrolithiasis is restricted to adult populations, and more data are needed to better understand many aspects of the epidemiology and treatment of pediatric kidney stones.

Secondary oxalate nephropathy and kidney transplantation

PURPOSE OF REVIEW

Secondary hyperoxaluria is associated with poor kidney allograft outcomes after the kidney transplant. Calcium oxalate (CaOx) deposition is common in early allograft biopsies leading to acute tubular necrosis and poor kidney allograft function. Though treatment options for secondary hyperoxaluria are limited, it is crucial to identify patients at increased risk of oxalate nephropathy after the transplant.

RECENT FINDINGS

Recent data suggest that significant changes in renal replacement therapies and dietary modifications in high-risk patients can prevent kidney allograft damage from the calcium oxalate deposition leading to improve allograft outcomes.

SUMMARY

The accurate and timely diagnosis of secondary oxalate nephropathy in kidney transplant recipients is paramount to preserving graft function in the long-term. This review will discuss the incidence, risk factors, prevention, and management of oxalate nephropathy in the kidney allograft.

Bone marrow oxalosis with pancytopenia in a patient with short bowel syndrome: Report of a case and review of the literature

Systemic oxalosis is a condition in which calcium oxalate crystals deposit into various bodily tissues. Although this may occur as the result of a rare primary syndrome in which an error of glyoxylate metabolism causes an overproduction of oxalate, it is more often seen as a secondary process characterized by increased enteric oxalate absorption. Here, we describe a patient with short bowel syndrome on long-term parenteral nutrition support who developed a unique manifestation of systemic oxalosis, leading to deposition of oxalate crystals within the bone marrow contributing to pancytopenia. In this report, in addition to reviewing the literature on this presumably rare manifestation of oxalosis, we also discuss its pathogenesis in the setting of short bowel syndrome and its management, including prevention.

Randomized Placebo-Controlled Trial of Reloxaliase in Enteric Hyperoxaluria

BACKGROUND: Enteric hyperoxaluria is caused by increased intestinal oxalate absorption and can lead to kidney stones, chronic kidney disease, and kidney failure. Reloxaliase is an orally administered recombinant enzyme that degrades oxalate along the gastrointestinal tract, thereby preventing its absorption. METHODS: We randomly assigned participants with enteric hyperoxaluria to reloxaliase or placebo, three to five times per day with food for 4 weeks. The primary end point was percent change from baseline in 24-hour urinary oxalate (UOx) excretion during weeks 1 to 4. Secondary end points included the proportion of participants with more than a 20% reduction in 24-hour UOx and an efficacy assessment in the bariatric surgery subgroup. RESULTS: A total of 115 patients underwent randomization. The 24-hour UOx decreased from a baseline geometric mean of 83.2 to 67.4 mg/24 hr during weeks 1 to 4 in reloxaliase-treated participants. Corresponding data for placebo-treated participants were 84.2 to 78.1 mg/24 hr. Estimates from the mixed-effect model repeated-measures (MMRM) analysis showed a 22.6% reduction in geometric mean UOx during weeks 1 to 4 for reloxaliase and 9.7% for placebo, a difference of 14.3 percentage points (95% confidence interval [CI], 4.9 to 22.8; P=0.004). A 20% or greater reduction in 24-hour UOx was observed in 48.3% of reloxaliase-treated participants and 31.6% of placebo-treated participants (P=0.06). In the bariatric surgery subgroup, MMRM analysis showed a 21.2% reduction in geometric mean UOx for reloxaliase and a 6.0% reduction for placebo, for a difference of 16.2 percentage points (95% CI, 4.2% to 26.7%). Adverse events occurred in 69% of reloxaliase-treated participants versus 53% of individuals taking placebo and were most commonly gastrointestinal. All but one of the adverse events were grade 1 or 2 in severity; no reloxaliase-treated participants discontinued the study. CONCLUSIONS: Reloxaliase treatment for 4 weeks reduced UOx excretion in patients with enteric hyperoxaluria; adverse events were relatively common, but not dose-limiting. These data establish the foundation for a clinical trial to determine the impact of reloxaliase on nephrolithiasis in patients with enteric hyperoxaluria. (Funded by Allena Pharmaceuticals; ClinicalTrials.gov number, NCT03456830.)

Lumasiran in the Management of Patients with Primary Hyperoxaluria Type 1: From Bench to Bedside

Primary hyperoxaluria (PH) is a rare genetic disease caused by excessive hepatic production and elevated urinary excretion of oxalate that leads to recurrent nephrolithiasis, nephrocalcinosis and, eventually, kidney failure. As glomerular filtration rate declines, oxalate accumulates leading to systemic oxalosis, a debilitating condition with high morbidity and mortality. Although PH is usually diagnosed during infancy, it can present at any age with different phenotypes, ranging from mild symptoms to extremely debilitating manifestations. PH is an autosomal recessive disorder and, to date, three types have been identified: PH1, PH2 and PH3. PH1 is the most common and most aggressive type, accounting for almost 80% of primary hyperoxaluria diagnoses. Until 2020, general treatment for PH1 consisted mainly in high fluid intake, urine alkalization, surgical management of recurrent nephrolithiasis and eventually, if and when kidney failure occurred, intensive dialysis regimens and transplantation strategies (simultaneous or sequential liver-kidney transplant or isolated liver/kidney transplant in carefully selected patients). Specific treatment did and still consists in administration of pyridoxine hydrochloride, although it is only effective in a subset of PH1 patients. Lumasiran, a novel biological drug based on mRNA interference that has been recently approved in the US and European Union, showed promising results and is set to be a turning point in the management of PH1. This literature review aims to summarize the available evidence on PH1 treatment with lumasiran, in order to provide both pediatric and adult nephrologists and clinicians with the knowledge for the identification and management of PH1 patients suitable for treatment.

Oxalobacter formigenes: A new hope as a live biotherapeutic agent in the management of calcium oxalate renal stones

Recent advances in understanding the association of gut microbiota with the host have shown evidence of certain bacterial therapeutic potentiality in preventing and treating metabolic diseases. Hyperoxaluria is a severe challenge in nephrology and has led to the novel gut eubiosis as current therapy. The human gut commensal, obligate anaerobic, and intestinal oxalate-degrading strains of Oxalobacter formigenes have drawn a promising significant interest for the next-generation probiotics (NGPs). This nonpathogenic, potential probiotic, and specialist oxalotrophic properties of O. formigenes give a new hope as a live biotherapeutic agent for calcium oxalate renal therapy. Numerous satisfactory outcomes of in vitro and in vivo studies were achieved on evaluating O. formigenes functionality, but the commercial production of this bacterium is yet to be achieved. This bacterium finds diverse application in dietary and endogenous oxalate degradation and the improvement of gut health, on which we concentrated our attention in this review. The relationship between good anaerobic gut bacterial dysbiosis and renal complications is comprehensively discussed to address the need for the development probiotic formulation. However, the commercial production of this bacteria on a broad scale is complex, with numerous obstacles, mainly because they are oxygen-sensitive and difficult to culture. This review will coherently present the current and available methodologies in producing, stabilizing, and delivering these NGPs to treat calcium stones. Moreover, the study presents the extensive work and key milestones achieved in the research on O. formigenes from tale to the truth.

Protective effect of bee pollen in acute kidney injury, proteinuria, and crystalluria induced by ethylene glycol ingestion in rats

Oxidative stress plays a role in hyperoxaluria-induced kidney injury and crystallization. Bee pollen is a hive product with a high content of antioxidants. The antioxidant content and protective effect of bee pollen extract (BPE) against ethylene glycol (EG) induced crystalluria, and acute kidney injury (AKI) were investigated. The effect of BPE on the EG-induced liver injury and proteinuria was also examined. Ten groups of male Wister rats were treated daily with vehicle, cystone, BPE (100, 250, and 500 mg/kg b.wt.), and group 6-9 treated with EG, EG + BPE (100, 250, and 500 mg/kg b.wt.) and group 10 EG + cystone. The dose of EG was 0.75% v/v, and the dose of cystone was 500 mg/kg b.wt. On day 30, blood and urine samples were collected for analysis. Kidneys were removed for histopathological study. The antioxidant activity of BPE was assessed, and its total phenols and flavonoids were determined. EG significantly increased urine parameters (pH, volume, calcium, phosphorus, uric acid, and protein), blood urea, creatinine, and liver enzymes (P < 0.05). EG decreased creatinine clearance and urine magnesium and caused crystalluria. Treatment with BPE or cystone mitigates EG's effect; BPE was more potent than cystone (P < 0.05). BPE increases urine volume, sodium, and magnesium compared to the control and EG treated groups. BPE reduces proteinuria and prevents AKI, crystalluria, liver injury, and histopathological changes in the kidney tissue caused by EG. BPE might have a protective effect against EG-induced AKI, crystalluria, proteinuria, and stone deposition, most likely by its antioxidant content and activity.

Pathophysiology and Management of Hyperoxaluria and Oxalate Nephropathy: A Review

Hyperoxaluria results from either inherited disorders of glyoxylate metabolism leading to hepatic oxalate overproduction (primary hyperoxaluria), or increased intestinal oxalate absorption (secondary hyperoxaluria). Hyperoxaluria may lead to urinary supersaturation of calcium oxalate and crystal formation, causing urolithiasis and deposition of calcium oxalate crystals in the kidney parenchyma, a condition termed oxalate nephropathy. Considerable progress has been made in the understanding of pathophysiological mechanisms leading to hyperoxaluria and oxalate nephropathy, whose diagnosis is frequently delayed and prognosis too often poor. Fortunately, novel promising targeted therapeutic approaches are on the horizon in patients with primary hyperoxaluria. Patients with secondary hyperoxaluria frequently have long-standing hyperoxaluria-enabling conditions, a fact suggesting the role of triggers of acute kidney injury such as dehydration. Current standard of care in these patients includes management of the underlying cause, high fluid intake, and use of calcium supplements. Overall, prompt recognition of hyperoxaluria and associated oxalate nephropathy is crucial because optimal management may improve outcomes.

Molecular Diagnosis of Primary Hyperoxaluria Type 1 and Distal Renal Tubular Acidosis in Moroccan Patients With Nephrolithiasis and/or Nephrocalcinosis

Nephrolithiasis (NL) and urolithiasis (UL) are usual reasons for hospitalization and presentation in pediatric outpatient departments and their incidence continues to rise worldwide. In Morocco, a previous epidemiological study done in the Fez region between January 2003 and November 2013 reported a prevalence of 0.83% of childhood UL. In two studies, heritability accounted for almost half of all NL or nephrocalcinosis (NC) prevalence. Genetic factors must be considered in the etiological diagnosis of urinary lithiasis in Morocco since the frequency of consanguineous marriages is high. Hereditary tubular disorders, especially distal renal tubular acidosis (dRTA) and Dent disease, and metabolic disorders like idiopathic hypercalciuria and hyperoxaluria are the most common causes of medullary NC. Primary hyperoxaluria type 1 (PH1), which can generate an early onset of NC, and often chronic kidney disease (CKD) should always be considered and thoroughly diagnosed. The aim of this work was to establish a molecular diagnosis of PH1 and dRTA and, thus, to predict and explain the disease phenotype in a cohort of 44 Moroccan patients with NL and/or NC by analyzing the AGXT and ATP6V1B1 genes that cause NL and/or NC when mutated. Disease phenotype was molecularly explained and solved in six of 44 individuals with NL and/or NC (13.6%). In the pediatric subgroup of individuals, a causative mutation in 16.2% was identified, whereas in the adult cohort no pathogenic mutation was detected. In our patients, PH1 was objectified in 67% of cases followed by dRTA in 33% of cases. We suggest that prompt detection and prophylactic treatment of UL are necessary to limit the risk of everlasting renal damage and thus prevent or delay the progression to CKD.

Extended genetic analysis of exome sequencing for primary hyperoxaluria in pediatric urolithiasis patients with hyperoxaluria

PURPOSE

Next generation sequencing-based exome sequencing can be used to identify genetic abnormalities in patients believed to be suffering from primary hyperoxaluria. We outline our efforts to improve the diagnostic capacity of exome sequencing for these patients.

METHODS

We conducted a retrospective analysis of exome sequencing data from 77 pediatric urolithiasis patients with hyperoxaluria of unknown origin. Canonical exome sequencing analysis was performed to identify pathogenic variants in three known primary hyperoxaluria-related genes (AGXT, GRHPR, HOGA1) as per the guidelines of the American College of Medical Genetics. Then, extended exome sequencing analyses of 5'-untranslated region, non-canonical splicing site and copy number variant were performed on patients with negative diagnostic results in these three genes.

RESULTS

Canonical exome sequencing analyses led to the diagnosis of primary hyperoxaluria in 20/77 (26%) patients, including eight, four, and eight patients diagnosed with type 1, 2 and 3 primary hyperoxaluria, respectively. Non-canonical splicing site analyses discovered a pathogenic variant in the HOGA1 gene, which led to the diagnosis of six additional patients with type 3 primary hyperoxaluria, while copy number variant analyses from exome sequencing data identified a 1.8 kb copy number loss that impacted the AGXT gene, resulting in the diagnosis of an additional type 1 primary hyperoxaluria case.

CONCLUSIONS

Extended non-canonical splicing site and copy number variant analyses improve the diagnostic yield of canonical exome sequencing analysis for primary hyperoxaluria from 26% (20/77) to 35% (27/77) in 77 pediatric urolithiasis patients with hyperoxaluria.

Clinical and economic impact of primary hyperoxaluria: a retrospective claims analysis

BACKGROUND: Primary hyperoxaluria (PH) is a family of rare, life-threatening genetic liver disorders characterized by elevated production and excretion of oxalate. To date, the clinical and economic burden associated with PH has not been well characterized due to the rarity of the disease and previous challenges with diagnostic coding that prevented proper identification of patients with PH in claims data. OBJECTIVE: To characterize the clinical and economic costs, as well as health care resource utilization (HCRU), associated with PH relative to a matched cohort of patients without PH. METHODS: Data from the IQVIA PharMetrics Plus Database were used to conduct a retrospective matched-cohort study to compare differences in clinical characteristics, HCRU, and pharmacy and medical costs in patients with PH compared with a matched cohort of patients without PH from January 2014 to December 2019. RESULTS: Overall, 324 patients were included in the PH cohort and 1,620 patients were in the non-PH cohort. The mean age of PH patients was 48.1 years, and approximately 58% of the sample were male. Significantly more patients in the PH cohort than the non-PH cohort were diagnosed with stage 2 chronic kidney disease (CKD; 3.1% vs 0.4%, respectively; P < 0.001), stage 3 CKD (4.6% vs 0.5%; P < 0.001), stage 4 CKD (2.5% vs 0.1%; P < 0.001), and stage 5 CKD or end-stage renal disease (ESRD; 2.2% vs 0.1%; P < 0.001). PH patients had a significantly higher mean Charlson Comorbidity Index composite score than patients in the non-PH cohort (0.79 vs 0.37; P < 0.001). HCRU was significantly higher in patients with PH. The PH cohort had a significantly higher proportion of patients with at least 1 visit to clinicians specializing in nephrology (19% vs 0.4%, respectively; P < 0.001), cardiology (22% vs 12%; P < 0.001), ophthalmology (16% vs 7%; P < 0.001), general surgery (9% vs 6%; P = 0.011), and urology (65% vs 6%; P < 0.001) compared with patients without PH. Mean total annual health care costs in the PH cohort were 65% higher than in the non-PH cohort ($22,549 vs $7,852, respectively; P < 0.001). Similar results were found for total prescription drug costs ($4,125 vs $2,464; P = 0.012). CONCLUSIONS: Despite the rarity of PH, patients with this disease incur substantial clinical and economic burden and may cause financial strain on the health care system. Additional research is warranted to understand the economic and clinical burden of PH stratified by the 3 subtypes of the disease. DISCLOSURES: Funding for this research was provided by Dicerna Pharmaceuticals. Mucha and Hoppe are employed by Dicerna Pharmaceuticals. Silber Miyasoto, Skaar, and Wang are employed by Trinity Life Sciences, which was contracted by Dicerna Pharmaceuticals to conduct the study analysis. Langman is consultant to Dicerna Pharmaceuticals. This study was presented as a poster at the AMCP Nexus 2020 (virtual), October 19-23, 2020, and American Society of Nephrology 2020 (virtual), October 19-25, 2020.

A comparison of the clinical characteristics of pediatric urolithiasis patients with positive and negative molecular diagnoses

PURPOSE

To compare the clinical characteristics of pediatric urolithiasis patients with positive and negative molecular diagnoses.

METHODS

The clinical characteristics corresponding to pediatric urolithiasis patients that had undergone exome sequencing at our hospital between January 2016 and May 2021 were collected. Genetic analysis results were used to separate patients into positive and negative molecular diagnosis groups. Multivariate logistic regression analyses adjusted for visiting age, sex, ethnicity, province, and body mass index were used to compare differences in medical history, diagnostic imaging findings, and renal function between individuals with and without molecular diagnoses.

RESULTS

In total, 194 patients with pediatric urolithiasis of unknown etiology underwent exome sequencing and were included in the present study, of whom 63 obtained urolithiasis-related molecular diagnoses. Relative to cases without a molecular diagnosis, those with a positive molecular diagnosis were more likely to be associated with a positive family history (OR 2.84, 95% CI 1.29-6.29, p = 0.008), consanguineous parents (OR 24.7, 95% CI 1.34-454, p = 0.002), early onset (OR 1.26, 95% CI 1.09-1.45, p < 0.001), nephrocalcinosis (OR 10.6, 95% CI 3.06-36.6, p < 0.001), cast stone (OR 18.9, 95% CI 4.40-81.1, p < 0.001), multiple stones (OR 13.9, 95% CI 6.39-30.2, p < 0.001), bilateral stones (OR 7.04, 95% CI 3.47-14.2, p < 0.001), a lower estimated glomerular filtration rate (OR 1.17, 95% CI 1.07-1.28, p < 0.001), and chronic kidney disease (OR 26.9, 95% CI 1.42-526, p < 0.001).

CONCLUSION

A positive family history, consanguineous parents, early onset, nephrocalcinosis, severe stone burden, and impaired renal function are signals of concern that are suggestive of inherited urolithiasis.