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Abstract A 75-year-old male developed acute kidney injury KDIGO stage 3 a few weeks after Whipple surgery was performed for a distal cholangiocarcinoma. Kidney biopsy revealed oxalate nephropathy. This was attributed to post-Whipple malabsorption, poor compliance with pancreatic enzyme replacement therapy, and daily intake of vitamin C supplements. Pancreatic enzyme replacement therapy was resumed and calcium carbonate initiated, with an improvement in glomerular filtration rate. Unfortunately, due to oncological progression, best supportive care was initiated. We review the pathophysiology and conditions predisposing to secondary hyperoxaluria and oxalate nephropathy. This diagnosis should be considered among the main causes of acute kidney injury following pancreatectomy, with important therapeutic implications.

A 75-year-old male developed acute kidney injury KDIGO stage 3 a few weeks after Whipple surgery was performed for a distal cholangiocarcinoma. Kidney biopsy revealed oxalate nephropathy. This was attributed to post-Whipple malabsorption, poor compliance with pancreatic enzyme replacement therapy, and daily intake of vitamin C supplements. Pancreatic enzyme replacement therapy was resumed and calcium carbonate initiated, with an improvement in glomerular fltration rate. Unfortunately, due to oncological progression, best supportive care was initiated. We review the pathophysiology and conditions predisposing to secondary hyperoxaluria and oxalate nephropathy. This diagnosis should be considered among the main causes of acute kidney injury following pancreatectomy, with important therapeutic implications. [ABSTRACT FROM AUTHOR]

Genome-editing strategies, especially CRISPR-Cas9 systems, have substantially increased the efficiency of innovative therapeutic approaches for monogenic diseases such as primary hyperoxalurias (PHs). We have previously demonstrated that inhibition of glycolate oxidase using CRISPR-Cas9 systems represents a promising therapeutic option for PH type I (PH1). Here, we extended our work evaluating the efficacy of liver-specific inhibition of lactate dehydrogenase (LDH), a key enzyme responsible for converting glyoxylate to oxalate; this strategy would not be limited to PH1, being applicable to other PH subtypes. In this work, we demonstrate a liver-specific inhibition of LDH that resulted in a drastic reduction of LDH levels in the liver of PH1 and PH3 mice after a single-dose delivery of AAV8 vectors expressing the CRISPR-Cas9 system, resulting in reduced urine oxalate levels and kidney damage without signs of toxicity. Deep sequencing analysis revealed that this approach was safe and specific, with no off-targets detected in the liver of treated animals and no on-target/off-tissue events. Altogether, our data provide evidence that in vivo genome editing using CRISPR-Cas9 systems would represent a valuable tool for improved therapeutic approaches for PH.

Contexto. La modificación de los hábitos alimentarios puede reducir la incidencia y la recurrencia de la urolitiasis (UL). Objetivo. Evaluar la influencia de la ingesta de carnes, frutas, hortalizas, huevos y lácteos en el riesgo de sobresaturación urinaria (RSU) en estudiantes sin antecedentes de UL. Metodología. Estudio correlacional de corte transversal con una muestra compuesta por estudiantes voluntarios sin antecedentes de UL en el periodo 2018-2019. Para este estudio se registraron datos personales, clínicos, ingesta diaria y semanal de los alimentos en estudio y se analizó la orina de 24h recogida el día que se completó el registro diario, además, el RSU se determinó con el programa EQUIL AT. Resultados. Participaron 61 estudiantes, 90?% mujeres, con un índice masa corporal y edad promedios de 22,8 Kg/m2 y 25 años. Presentaron RSU 33 mujeres y 4 hombres, por lo que se calculó un 92?% de RSU para ácido úrico. La ingesta diaria de carnes, huevos y quesos fue superior a lo requerido para una alimentación saludable y la de hortalizas, frutas, leche y yogur inferior. No hubo diferencias entre las ingestas del registro diario y semanal, donde los individuos con RSU tuvieron una mayor ingesta de carnes y una menor de frutas, hortalizas y huevos que aquellos sin RSU, siendo significativa la diferencia (p < 0,05). Conclusiones. Se hallaron diferencias significativas en la ingesta de carnes, frutas, hortalizas y huevos en los individuos con RSU respecto a aquellos sin RSU. La ingesta diaria fue la habitual, por lo que la sobresaturación sería continua en los individuos con riesgo. Se podría actuar preventivamente en la modificación de los hábitos alimentarios antes de que se forme el primer cálculo.

Under the action of exogenous, androgenic, genetically determined factors, the metabolism of stone-forming salts of calcium, phosphorus, magnesium, oxalates, uric acid in the blood serum and their active excretion by the kidneys to the state of hypersaturation (oversaturation) is disturbed) urine is formed. When the level of crystallization inhibitors is disturbed, a saturated salt solution crystallizes with the formation of microliths. The formation of stones in the kidneys is possible only in the presence of «building material» - supersaturated saturated urine, therefore, hyperoxaluria is a pre-stone condition. Treatment measures should be aimed at correcting mineral metabolism in the body after establishing the type of hyperoxaluria using laboratory tests: salt transport, calcium load, dietary test - low-calcium diet, thiazide test and determination of the mineral composition of the removed (removed) stone. Genetically consequential conditions (10–15%) count about 30 varieties in which the main sign or symptom in the manifestation of the disease is urolithiasis. Unfortunately, congenital tubulopathies are not sufficiently studied, so the treatment is symptomatic, in some cases simultaneous kidney and liver transplantation options are possible. Clinically, 4 main forms of hypercrystalluria are distinguished: hypercalciuria, hyperoxaluria, hyperuricuria, phosphaturia and mixed forms of crystalluria. Acquired forms of hypercrystalluria, of which they are absorptive (type II intestinal hyperabsorption - absorptive hypercalciuria and absorptive hyperoxaluria), are of main clinical interest, which is characteristic of the course of calcium-oxalate urolithiasis. Metaphylaxis of calcium-oxalate urolithiasis is formed on the basis of these data. [ABSTRACT FROM AUTHOR]

Oxalate, a compound produced by many edible plants and as a terminal metabolite in the liver of mammals, is a toxin that has a detrimental role to human health. Humans and other mammals do possess enzymatic systems to degrade oxalate. Moreover, numerous oxalate-degrading bacteria reside in the mammalian gut and, thus, provide an important function for hosts. The current review focuses on the environmental factors that influence the efficacy of probiotic oxalate-degrading bacteria, relative to oxalate metabolism. We describe the mechanism of oxalate catabolism and its consumption by obligate and facultative anaerobic oxalate-degrading bacteria, in both in vitro and in vivo environments. We also explore the environmental variables that impact oxalate degradation. Studies on single species degrade oxalate have not shown a strong impact on oxalate metabolism, especially in high oxalate conditions such as consumption of foods high in oxalate (such as coffee and chocolate for humans or halogeton in animal feed). Considering effective variables which enhance oxalate degradation could be used in application of effective probiotic as a therapeutic tool in individuals with hyperoxaluria. This study indicates probiotics can be considered a good source of naturally occurring oxalate degrading agent in human colon. [ABSTRACT FROM AUTHOR]

Introduction: Primary hyperoxalurias (PH) are rare and serious genetic diseases. Their prognosis is improved with early medical management. However, diagnosis often occurs at the end-stage of renal failure. To understand this delay, collecting real-world data on the clinical practices of nephrologists may be helpful., Materials and Methods: Between October 2021 and October 2022, a retrospective survey was conducted in France among 76 nephrologists to assess management practices for patients with chronic kidney disease (CKD) of unknown aetiology, associated with urinary lithiasis and/or nephrocalcinosis. Data on patient profiles, tests conducted, diagnoses considered, and management of suspected PH cases were collected., Results: 97% of patients (n = 386/400) underwent a renal examination, 92% (n = 370/400) a thorough urinary check-up, and 65% (n = 260/400) had an interpretable oxaluria value from a 24-hour urine sample (Uox24h). Of these 260 patients, 50% (n = 130/260) had Uox24h > 500 µmol/24 h: 23% (n = 30/130) were suspected of PH by the nephrologists, and 15% (n = 19/130) were referred for genotyping. Considering all criteria, 52 patients were suspected of PH (42% of whom did not have Uox24h > 500 µmol/24 h), and 33% (n = 17/52) were not referred for genotyping., Discussion: The survey highlights nephrologists' adherence to recommendations for prescribing biological tests. However, in cases of hyperoxaluria or suspected PH, genotyping was not always prescribed. The barriers to this prescription need further exploration.

Background. The purpose was to investigate gender features of oxalate excretion in metabolic nephropathy, the state of oxidative stress and antioxidant system, depending on oxalate excretion. Material and methods. One hundred seventy-six children with oxalate nephropathy and 84 healthy children were included in the study. Clinical, instrumental and laboratory methods were used. The level of lipid peroxidation (diene conjugates, malondialdehyde) and antioxidant protection enzyme (redox glutathione, glutathione peroxidase and serum catalase), and peroxidation of proteins (neutral and basic aldehyde and ketone derivatives of dinitrophenylhydrazone) were evaluated. Results. The level of oxalate excretion and oxalate/creatinine ratio in the first void urine of patients with metabolic nephropathy was significantly higher vs. control group (p

Background: Primary hyperoxaluria type 1 (PH1) is a rare genetic disease that can result in irreversible damage to the kidneys and, eventually, extrarenal organs. While kidney failure is a known consequence of PH1, few studies to date have characterized clinical consequences of PH1 prior to kidney failure, and data on healthcare resource use outcomes across different stages of disease severity in PH1 are also limited. To help fill this knowledge gap, this study characterized the clinical and healthcare resource use (HRU) burden in patients with PH1 with varying stages of kidney disease.Methods: Nephrologists in the United States, Canada, United Kingdom, France, Germany, and Italy abstracted chart data from patients with PH1 under their care via an online questionnaire. Eligible patients had confirmed PH1 and ≥2 office visits from 2016 to 2019.Results: A total of 120 patients were analyzed (median age at diagnosis, 17.4 years old, median age at index 19.5 years old, median eGFR at index 45 ml/min/1.73 m2; median follow-up 1.7 years). During follow-up, the most common PH1 manifestations were kidney stones and urinary tract infections (UTIs, both 56.8%), and the most common symptoms were fatigue/weakness (71.7%) and pain (64.6%). With regard to HRU during follow-up, 37.4% required lithotripsy, 31.3% required ureteroscopy, and 9.6% required nephrolithotomy. PH1-related hospitalizations and emergency/urgent care visits were noted for 84.0 and 81.6% of patients, respectively.Conclusions: The current study demonstrated that patients with PH1 across various stages of kidney disease exhibited a substantial clinical burden, including kidney stones, UTIs, fatigue/weakness, and pain, and required frequent HRU, including kidney stone procedures, hospitalizations, and emergency visits. These findings highlight the significant morbidity and HRU burden in patients with PH1.

Oxalate, a compound produced by many edible plants and as a terminal metabolite in the liver of mammals, is a toxin that has a detrimental role to human health. Humans and other mammals do possess enzymatic systems to degrade oxalate. Moreover, numerous oxalate-degrading bacteria reside in the mammalian gut and, thus, provide an important function for hosts. The current review focuses on the environmental factors that influence the efficacy of probiotic oxalate-degrading bacteria, relative to oxalate metabolism. We describe the mechanism of oxalate catabolism and its consumption by obligate and facultative anaerobic oxalate-degrading bacteria, in both in vitro and in vivo environments. We also explore the environmental variables that impact oxalate degradation. Studies on single species degrade oxalate have not shown a strong impact on oxalate metabolism, especially in high oxalate conditions such as consumption of foods high in oxalate (such as coffee and chocolate for humans or halogeton in animal feed). Considering effective variables which enhance oxalate degradation could be used in application of effective probiotic as a therapeutic tool in individuals with hyperoxaluria. This study indicates probiotics can be considered a good source of naturally occurring oxalate degrading agent in human colon.

Objectives: The potential harm associated with the use of IV vitamin C has not been systematically assessed. We aimed to review the available evidence on harm related to such treatment.Data Sources: We searched MEDLINE, EMBASE, Cochrane Library, National Institute of Health Clinical Trials Register, and World Health Organization International Clinical Trials Registry Platform.Study Selection: We included studies in adult population that reported harm related to IV high-dose vitamin C which we defined as greater than or equal to 6 g/d, greater than or equal to 75 mg/kg/d, or greater than or equal to 3 g/m/d.Data Extraction: Two independent investigators screened records and extracted data.Data Synthesis: We identified 8,149 reports, of which 650 full text were assessed for eligibility, leaving 74 eligible studies. In these studies, 2,801 participants received high-dose vitamin C at a median (interquartile range) dose of 22.5 g/d (8.25-63.75 g/d), 455 mg/kg/d (260-925 mg/kg/d), or 70 g/m/d (50-90 g/m/d); and 932 or more adverse events were reported. Among nine double-blind randomized controlled trials (2,310 patients), adverse events were reported in three studies with an event rate per patient for high-dose vitamin C identical to placebo group in one study (0.1 [1/10] vs 0.1 [1/10]), numerically lower in one study (0.80 [672/839] vs 0.82 [709/869]), and numerically higher in one study (0.33 [24/73] vs 0.23 [17/74]). Six double-blind randomized controlled trials reported no adverse event in either group. Five cases of oxalate nephropathy, five cases of hypernatremia, three cases of hemolysis in glucose-6-phosphate dehydrogenase deficiency patients, two cases of glucometer error, and one case of kidney stones were also reported overall.Conclusions: There is no consistent evidence that IV high-dose vitamin C therapy is more harmful than placebo in double-blind randomized controlled trials. However, reports of oxalate nephropathy, hypernatremia, glucometer error, and hemolysis in glucose-6-phosphate dehydrogenase deficiency patients warrant specific monitoring. [ABSTRACT FROM AUTHOR]

Primary oxaluria is a rare hereditary disease of the metabolism, characterized by damage of the kidneys (kidney stones) and the eyes (retinal oxalosis). Its recognition required first the discovery of oxalic acid in the 17th century. The presence of this substance in normal urine and food led to a long dispute between supporters of the "diathesis hypothesis" and the "diet hypothesis", that is between the congenital and acquired metabolic disorder. Both were right, according to the present view: we recognize a very rare hereditary, genetic condition (primary hyperoxaluria) and an acquired one (secondary hyperoxaluria). Notably, the main findings in this paradigm were timed by the discovery of new scientific tools (chemistry, microscopy, organic chemistry and others), except for the eye disease, recognized only 100 years after the invention of the ophthalmoscope. This "organ blindness" phenomenon is further discussed along with the main historical steps of this condition. [ABSTRACT FROM AUTHOR]

Aim. To study clinical peculiarities of chronic obstructive pulmonary disease in patients with comorbid chronic pyelonephritis on the background of urolithiasis with oxaluria. Materials and methods. 60 patients were included into the study and divided into 3 groups. Study groups: I-st group - 18 patients with isolated course of chronic pyelonephritis (CP) and urolithiasis (U) of oxalic and mixed genesis, II-nd group - 19 patients with chronic obstructive pulmonary disease (COPD), study group III - 23 patients with COPD, CP and U of oxalic genesis. Additional control group consisted of 20 practically healthy individuals (PHI) of corresponding age and gender. Laboratory and clinical examination of the patients was conducted. Spectrophotometry with polarization of biologic material was performed. Statistical analysis was done in Primer of Biostatistics, Origin 8.0. Results. Systemic inflammation in patients with COPD and comorbid CP with oxaluria form the syndrome of mutual burdening. This fact was proved by inverse correlation between oxalate salts in sputum (15,5±1,0) mg/24h) and reduction of forced expiratory volume in 1 second (FEV1) in group III. This result was in 2,1 lower than in PHI (r = -0,53,р

The formation of metabolite fibrillar assemblies represents a paradigm shift in the study of human metabolic disorders. Yet, direct clinical relevance has been attributed only to metabolite crystals. A notable example for metabolite crystallization is calcium oxalate crystals observed in various diseases, including primary hyperoxaluria. We unexpectedly observed retinal damage among young hyperoxaluria patients in the absence of crystals. Exploring the possible formation of alternative supramolecular organizations and their biological role, here we show that oxalate can form ordered fibrils with no associated calcium. These fibrils inflict intense retinal cytotoxicity in cultured cells. A rat model injected with oxalate fibrils recaptures patterns of retinal dysfunction observed in patients. Antibodies purified from hyperoxaluria patient sera recognize oxalate fibrils regardless of the presence of calcium. These findings highlight a new molecular basis for oxalate-associated disease, and to our knowledge provide the first direct clinical indication for the pathogenic role of metabolite fibrillar assemblies. Primary hyperoxaluria is a rare genetic condition which involves elevated levels of oxalate in the body, but its role in causing symptoms is not well understood. Here self-assembled oxalate fibrils are implicated in the mechanism of retinopathy in primary hyperoxaluria in humans. [ABSTRACT FROM AUTHOR]

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We present the case of a 29-year-old male from the southern part of India presenting with renal stones, pancytopenia with leukoerythroblastic blood picture, diagnosed on bone marrow (BM) aspiration smears as BM oxalosis. Although it is a rare disorder, BM oxalosis should be considered and BM aspiration and biopsy should be performed in patients presenting with renal stones, pancytopenia with leukoerythroblastic blood picture. Early diagnosis of patients affected by hyperoxaluria is associated with improved long-term survival. [ABSTRACT FROM AUTHOR]

• SbCO Index: paves kidney stone recurrence risk tool. • Key bacteria & gut microbiome's role in stone risk. • Enables microbiome-based therapy for kidney stones. Kidney stone disease, particularly those formed from calcium oxalate crystals, is a significant health challenge, especially in geographic regions with high recurrence rates, known as stone belt regions. Early and precise prediction of stone events is crucial for effective therapeutic intervention. We propose the 'Stool bacterial dysbiosis, Crystalluria, and Oxaluria (SbCO) Value Index,' a composite of three factors: the prevalence of Oxalate Metabolising Bacterial Species (OMBS) in stool, urine crystal examination, and oxalate content in urine, as a tool to quantify the risk of recurrent oxalate nephrolithiasis. Empirical data underscored a notable correlation between gut dysbiosis, crystalluria, and oxaluria. The absence of Oxalobacter formigenes was associated with an elevated recurrence risk. Known OMBS were detected in approximately 3–18% of the general population, with species such as Oxalobacter and Prevotella being identified as key contributors. A lower recurrence risk was observed in patients with high levels of O. formigenes , Lactobacillus , and Bifidobacterium. Conversely, low bacterial levels, combined with high crystalluria and oxaluria were linked to an increased recurrence risk. Our findings suggest the potential of the SbCO index for predicting recurrent kidney stones, highlighting the utility of interventional therapies, informed by targeted analyses of the gut microbiome, as well as urine crystals and metabolites, in managing oxalate nephrolithiasis. This approach could help to pave the way for personalized, microbiome-centered therapeutic strategies. [ABSTRACT FROM AUTHOR]

Primary hyperoxaluria type 1 (PH1) is a rare metabolic disorder characterized by a defect in the liver-specific peroxisomal enzyme alanine-glyoxylate and serine-pyruvate aminotransferase (AGT). This disorder results in hyperoxaluria, recurrent urolithiasis, and nephrocalcinosis. Three forms of PH1 have been reported. Data on the infantile form of PH1 are currently limited in literature. Despite the fact that China is the most populated country in the world, only a few AGXT mutations have been reported in several Chinese PH1 patients. In the present study, we investigated a Chinese family in which two siblings are affected by the infantile form of PH1. Sanger sequencing was carried out on the proband, but the results were misleading. Two novel missense mutations (c.517T > C/p.Cys173Arg and c.667A > C/p.Ser223Arg) of the AGXT gene were successfully detected through whole-exome sequencing. These two mutations occurred in the highly conserved residues of the AGT. Four software programs predicted both mutations as the cause of the disease. A postmortem examination was performed and revealed the occurrence of global nephrocalcinosis on both kidneys. The crystals were collected and analyzed as calcium oxalate monohydrate. This study extends the knowledge on the clinical phenotype–genotype correlation of the AGXT mutation. That is, (i) two novel missense mutations were identified for the infantile form of PH1 and (ii) the same AGXT genotype caused the same infantile form of PH1 within the family. [ABSTRACT FROM AUTHOR]

Chloride/formate exchanger (CFEX; SLC26A6) mediates oxalate transport in various mammalian organs. Studies in Cfex knockout mice indicated its possible role in development of male-dominant hyperoxaluria and oxalate urolithiasis. Rats provide an important model for studying this pathophysiological condition, but data on Cfex (rCfex) localisation and regulation in their organs are limited. Here we applied the RT-PCR and immunochemical methods to investigate rCfex mRNA and protein expression and regulation by sex hormones in the pancreas, small intestine, liver, and kidneys from intact prepubertal and adult as well as gonadectomised adult rats treated with sex hormones. rCfex cDNA-transfected HEK293 cells were used to confirm the specificity of the commercial anti-CFEX antibody. Various biochemical parameters were measured in 24-h urine collected in metabolic cages. rCfex mRNA and related protein expression varied in all tested organs. Sex-independent expression of the rCfex protein was detected in pancreatic intercalated ducts (apical domain), small intestinal enterocytes (brush-border membrane; duodenum > jejunum > ileum), and hepatocytes (canalicular membrane). In kidneys, the rCfex protein was immunolocalised to the proximal tubule brush-border with segment-specific pattern (S1=S2

The point finger of intersection of the XII rib and the outer edge of the long back muscle (m. Sacrospinalis), was determined by the index finger of the left arm and that place was pre-treated with alcohol or iodine. The use of complex treatment: regional lymphotropic antibacterial therapy + vitamin A in chronic pyelonephritis is an effective method of therapy, which leads to the restoration of daily diuresis, has a positive effect on the level of oxaluria, the functional state of the kidneys and cytokine urine profile: IL-10, IL -1, IL-6, IL-8. [ABSTRACT FROM AUTHOR]

Background: Primary hyperoxaluria type 3 (PH3) is a recently described cause of childhood renal calculi. It results from mutations in the HOGA1 gene and most cases have been diagnosed after clinical ascertainment, exclusion of other genetic hyperoxalurias and mutation testing. Metabolite testing has not been widely applied but holds promise for the rapid screening and diagnosis of patients who are not specifically suspected to have PH3.Case-Diagnosis/Treatment: Two cases presented with renal calculi. Urine metabolite testing by tandem mass spectrometry was performed as part of the routine diagnostic work-up for this condition. Both had significantly increased levels of the PH3 urine marker 4-hydroxyglutamate and related metabolites. The diagnosis of PH3 was confirmed by the finding of bi-allelic damaging HOGA1 mutations.Conclusions: Urine screening by tandem mass spectrometry is a rapid, high-throughput test that can detect PH3 cases that may otherwise not be diagnosed. [ABSTRACT FROM AUTHOR]

Background Since plasma oxalate (POx) concentrations increase at lower glomerular filtration rate (GFR) levels, even among those without enteric (EH) or primary hyperoxaluria (PH), the appropriate thresholds for considering a disorder of oxalate metabolism are poorly defined. The current study was completed to establish relationships between POx, GFR, and urine oxalate excretion (UOx) among patients with PH, EH, and routine urinary stone disease (USD). Methods The most recent POx measurement on all Mayo Clinic patients between 2005 and 2015 were electronically pulled from the Lab Information System together with the closest serum creatinine within 14 days and 24 h urine study within 60 days. After exclusion of patients not in steady state at the time of blood draw, 270 patients were available for study. Records were reviewed for clinical diagnoses to categorize patients as PH, EH, or USD. Waste plasma for Pox was also obtained from controls without USD undergoing clinical GFR testing. Results In all 3 groups POx increased as eGFR fell. For any given eGFR, POx was highest in the PH group and lowest in the USD and control groups (p < 0.0001). POx was also influenced by UOx excretion (reflecting total body oxalate burden, absorption from diet and endogenous production). Generalized estimating equations of POx vs eGFR revealed higher average POx levels in PH compared to EH,USD or control, and for EH compared to USD or control. GEE prediction models were created that use POx, UOx, age, and serum creatinine to estimate the probability of a PH diagnosis. Conclusions New models were developed to help interpret POx when considering PH in clinical practice even when it was not previously suspected and/or eGFR is reduced. [ABSTRACT FROM AUTHOR]

Introduction: Prevalence of urinary calculi in children has been increasing in the past years. We performed an analysis of the chemical composition of stones formers of the pediatric population in our geographical area over the years 2005 to 2013.Materials and Methods: Fourier transform infrared spectroscopy was employed for the determination of the calculus composition of a group of Sicilian children, and metabolic studies were performed to formulate the correct diagnosis and establish therapy.Results: The prevalence of stone formation was much higher for boys than for girls, with a sex ratio of 1.9:1. The single most frequent component was found to be calcium oxalate monohydrate, and calcium oxalates (pure or mixed calculi) were the overall most frequent components. Calcium phosphates ranked 2nd for frequency, most often in mixed calculi, while urates ranked 3rd. The metabolic disorder most often associated with pure calcium oxalate monohydrate calculi was hypocitraturia, while hyperoxaluria was predominantly associated with calcium oxalate dihydrate calculi.Conclusions: Mixed calculi had the highest prevalence in our pediatric population. Our data showed that Fourier transform infrared spectroscopy was a useful tool for the determination of the calculi composition. [ABSTRACT FROM AUTHOR]

Primary hyperoxaluria (PH) is a rare genetic condition that disrupts the normal process of glyoxylate metabolism, resulting in an overproduction of oxalate. This excessive oxalate production leads to the accumulation of calcium oxalate (known as oxalosis) throughout various organs in the body. The urinary tract, specifically the renal parenchyma, is the first location where the deposition of calcium oxalate begins in PH. These deposits are responsible for nephrocalcinosis and tubule‑interstitial nephritis which leads to end‑stage renal failure. This is then followed by the accumulation of oxalate in other organs including the bone marrow. Herein, we report the case of a 22-year-old male patient who presented with bicytopenia; he had a history of end-stage renal disease preceded by recurrent urolithiasis and nephrolithiasis episodes since the age of 3 years. A bone marrow biopsy was performed for evaluation of the bicytopenia which led to the diagnosis of PH., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Miry et al.)

Background:Star fruit (SF) is a popular fruit, commonly cultivated in many tropical countries, that contains large amount of oxalate. Acute oxalate nephropathy and direct renal tubular damage through release of free radicals are the main mechanisms involved in SF-induced acute kidney injury (AKI). The aim of this study was to evaluate the protective effect of N-acetylcysteine (NAC) on SF-induced nephrotoxicity due to its potent antioxidant effect. Materials and methods:Male Wistar rats received SF juice (4 mL/100 g body weight) by gavage after a 12 h fasting and water deprivation. Fasting and water deprivation continued for 6 h thereafter to warrant juice absorption. Thereafter, animals were allocated to three experimental groups: SF (n = 6): received tap water; SF + NAC (n = 6): received NAC (4.8 g/L) in drinking water for 48 h after gavage; and Sham (n = 6): no interventions. After 48 h, inulin clearance studies were performed to determine glomerular filtration rate. In a second series of experiment, rats were housed in metabolic cages for additional assessments. Results:SF rats showed markedly reduced inulin clearance associated with hyperoxaluria, renal tubular damage, increased oxidative stress and inflammation. NAC treatment ameliorated all these alterations. Under polarized light microscopy, SF rats exhibited intense calcium oxalate birefringence crystals deposition, dilation of renal tubules and tubular epithelial degeneration, which were attenuate by NAC therapy. Conclusions:Our data show that therapeutic NAC attenuates renal dysfunction in a model of acute oxalate nephropathy following SF ingestion by reducing oxidative stress, oxaluria, and inflammation. This might represent a novel indication of NAC for the treatment of SF-induced AKI. [ABSTRACT FROM PUBLISHER]

Aim:we aimed to establish reference values for urinary oxalate to creatinine ratios in healthy children aged 6–15 years and to investigate the relationship between their nutritional habits and oxalate excretion. Materials and methods: Random urine specimens from 953 healthy children aged 6–15 years were obtained and analyzed for oxalate and creatinine. Additionally, a 24-h dietary recall form was prepared and given to them. The ingredient composition of the diet was calculated. The children were divided into three groups according to age: Group I (69 years,n = 353), Group II (10–12 years,n = 335), and Group III (13–15 years,n = 265). Results:The 95th percentile of the oxalate to creatinine ratio for subjects aged 6–9, 10–12, and 13–15 years were 0.048, 0.042, and 0.042 mg/mg, respectively. The oxalate to creatinine ratio was significantly higher in Group 1 than in Group 2 and Group 3. Urinary oxalate excretion was positively correlated with increased protein intake and negatively correlated with age. A significant positive correlation was determined between urinary oxalate excretion and the proline, serine, protein, and glycine content of diet. Dietary proline intake showed a positive correlation with the urine oxalate to creatinine ratio and was found to be an independent predictor for urinary oxalate. Conclusions:These data lend support to the idea that every country should have its own normal reference values to determine the underlying metabolic risk factor for kidney stone disease since regional variation in the dietary intake of proteins and other nutrients can affect normal urinary excretion of oxalate. [ABSTRACT FROM PUBLISHER]

Bergenin, isolated from Bergenia ligulata is a potent antioxidant and antilithiatic agent. Present work was designed to establish the biochemical role of bergenin on mitochondrial dysfunction in the ethylene glycol induced hyperoxaluric rat model. Bergenin was administrated at a dose of 10 mg/kg body wt i.p. from 14th day of establishing the 28 days hyperoxaluria rat model. α-Tocopherol was given as positive control at a dose of 100 mg/kg body wt i.p. Mitochondrial dysfunction was studied by evaluating the activities of respiratory chain complexes, mitochondrial membrane potential and reactive oxygen species. Histopathological analysis of the kidney tissue was done after Pizzolato staining. Also, expression of monocyte chemoattractant protein −1(MCP-1) and kidney injury marker protein (KIM-1) were studied and the levels of IL-1β were evaluated in kidney tissue homogenate. Mitochondrial dysfunction during stone crystallization was evident by decreased activities of electron transport chain complexes I, II and IV and augmented mitochondrial oxidative stress in hyperoxaluric rats. Bergenin treatment significantly (P<0.05) restored the activities of these complexes. Moreover, it curtailed the lipid peroxidation and up regulated antioxidant levels, ameliorating the state of mitochondrial dysfunction. The protective role of bergenin was also reinforced by reducing IL-1β production and expression of KIM-1 and MCP-1 in the renal tissue. The findings of the present study provide evidence that bergenin exerted protective effects in hyperoxaluria through mitochondrial protection that involves attenuation of oxidative stress. Hence, it presented itself as an effective remedy in combating urolithiasis. [ABSTRACT FROM AUTHOR]

Primary hyperoxaluria is a genetic disorder in glyoxylate metabolism that leads to systemic overproduction of oxalate. Functional deficiency of alanine-glyoxylate aminotransferase in this disease leads to recurrent nephrolithiasis, nephrocalcinosis, systemic oxalosis, and kidney failure. The aim of this study was to determine the molecular etiology of kidney transplant loss in a young Tunisian individual. We present a young man with end-stage renal disease who received a kidney allograft and experienced early graft failure. There were no improvement in kidney function; he required hemodialysis and graft biopsy revealed calcium oxalate crystals, which raised suspicion of primary hyperoxaluria. Genetic study in the AGXT gene by PCR direct sequencing identified three missense changes in heterozygote state: the p. Gly190Arg mutation next to two other novels not previously described. The classification of the deleterious effect of the missense changes was developed using the summered results of four different mutation assessment algorithms, SIFT, PolyPhen, Mutation Taster, and Align-GVGD. This system classified the changes as polymorphism in one and as mutation in other. The patient was compound heterozygous mutations. Structural analysis showed that the novel mutation, p.Pro28Ser mutation, affects near the dimerization interface of AGT and positioned on binding site instead of the inhibitor, amino-oxyacetic acid (AOA). With the novel AGXT mutation, the mutational spectrum of this gene continues to broaden in our population. The diagnosis of PH1 was not recognized until after renal transplant with fatal consequences, which led us to confirm the importance of screening before planning for kidney transplantation in population with a relatively high frequency of AGXT mutation carriers. [ABSTRACT FROM AUTHOR]

Hyperoxaluria corresponds to an excessive urinary excretion of oxalate anions. Hyperoxaluria may be associated with the presence of calcium oxalate monohydrate crystals in kidney tissue and in some cases may lead to renal failure. In this contribution, a set of ten kidney biopsies corresponding to patients affected by hyperoxaluria from various origins such as primary hyperoxaluria or gastrointestinal disease has been investigated through μFourier transform infrared (FTIR) spectroscopy and Field Emission scanning Electron Microscopy (FE-SEM). The complete set of results indicates that if the deposits are mainly constituted of calcium oxalate monohydrate, some of them are made of calcium phosphate apatite, an observation which underlines the use of physicochemical techniques instead of the classical staining procedures. Moreover, FE-SEM observations clearly show a diversity of the crystallite morphology. Such diversity suggests changes in the composition of the milieu along the nephron and different interactions between calcium oxalate crystals and ions or macromolecules such as osteopontin and/or Tamm–Horsfall protein for example. This approach may help the clinician to understand more deeply the biochemical parameters which determine the formation of calcium oxalate monohydrate crystallites in kidney tissue and define the corresponding etiology. [ABSTRACT FROM AUTHOR]

Hyperoxaluria after Roux-en-Y gastric bypass (RYGB) increases the risk for kidney injury. Medical therapies for hyperoxaluria have limited efficacy. A 65-year-old female was evaluated for acute kidney injury [AKI, serum creatinine (Cr) 2.1 mg/dl, baseline Cr 1.0 mg/dl]. She did not have any urinary or gastrointestinal symptoms or exposure to nephrotoxic agents. Sixteen months prior to this evaluation, she underwent RYGB for morbid obesity. Her examination was unremarkable for hypertension or edema and there was no protein or blood on urine dipstick. Kidney biopsy revealed acute tubulointerstitial nephritis with oxalate crystals in tubules. The concurrent finding of severe hyperoxaluria (urine oxalate 150 mg/day) confirmed the diagnosis of oxalate nephropathy. Despite medical management of hyperoxaluria, her AKI worsened. Laparoscopic reversal of RYGB was performed and within 1 month, her hyperoxaluria resolved (urine oxalate 20 mg/day) and AKI improved (Cr 1.7 mg/dl). Surgical reversal of RYGB may be considered in patients with oxalate nephropathy at high risk of pro-gression who fail medical therapy. Physicians need to be aware of the possibility of oxalate nephropathy after RYGB and promptly treat the hyperoxaluria to halt further kidney damage. [ABSTRACT FROM AUTHOR]

Hyperoxaluria is a well-recognised risk factor for urolithiasis and patients with primary hyperoxaluria (PH) gradually build up calcium oxalate deposits leading to chronic kidney disease. Efforts to improve treatment for PH have focused on reducing urine oxalate excretion and thus decreasing lithogenesis. To determine the efficacy of treatments designed to alter a biochemical parameter it is necessary to know the biological and analytical variation of that parameter. In this study, we estimated the intra-individual biological variation of urine oxalate excretion in patients with PH, and from this determined what would constitute a significant change in the form of a reference change value (RCV). Each patient collected four 24-h urines on consecutive weeks. The intra-individual biological variation of oxalate excretion calculated from these samples ranged from 0 to 36 % with a mean of 14 %. The corresponding RCVs were 4-84 % with a mean of 32 %. This result implies that, on average, a reduction of almost one-third in urine oxalate excretion is required to prove an effect from treatment. The wide range of biological variation between individuals may reflect other, as yet unknown, determinants of oxaluria in PH, as well as inaccuracies in urine collection. The data suggest that it is more appropriate to use individual RCVs established prior to treatment to determine its efficacy: a relatively small fall in urine oxalate excretion may be outside the biological variation of some patients but not of others. [ABSTRACT FROM AUTHOR]

Background: The primary hyperoxalurias are inherited disorders of glyoxylate metabolism, which cause over-production of oxalate leading to urolithiasis and subsequent renal failure. Other metabolites may be produced in excess in the different forms of PH: glycolate in PH1, glycerate in PH2 and 4-hydroxy-2-oxoglutarate and 2,4-dihydroxyglutarate in PH3. The aim of this study was to set up and validate a method for the simultaneous analysis of these metabolites in urine and to evaluate its use for preliminary identification of primary hyperoxaluria prior to definitive diagnosis by genetic testing.Methods: Urine samples were derivitized by methoximation and silylation and extracted into organic solvent prior to analysis by gas chromatography mass spectrometry.Results: Recovery of the analytes spiked into urine ranged from 91 to 103% and total analytical imprecision ranged from 3.0 to 13.6%. 4-Hydroxy-2-oxoglutarate was unstable in urine at room temperature, and preservation by acidification was required. Mean urinary glycolate, glycerate and 4-hydroxy-2-oxoglutarate or 2,4-dihydroxyglutarate (expressed as a ratio to creatinine) were significantly higher in patients with PH1, PH2 and PH3, respectively. Low 4-hydroxy-2-oxoglutarate was observed in some patients with PH3, probably due to the instability of this analyte, but all PH3 patients had elevated 2,4-dihydroxyglutarate. During five months of routine service, seven cases of PH were identified by this method and subsequently confirmed by gene sequencing including two with novel mutations in HOGA1.Conclusions: This study confirms that the method is useful in aiding the diagnosis of primary hyperoxaluria and can direct genetic testing. [ABSTRACT FROM AUTHOR]

Roux-en-Y gastric bypass (RYGB) surgery is a popular and extremely effective procedure for sustained weight loss in the morbidly obese. However, hyperoxaluria and oxalate kidney stones frequently develop after RYGB and steatorrhea has been speculated to play a role. We examined the effects of RYGB and the role of dietary fat in an obese rat model by measuring fecal fat content and transmural oxalate fluxes across the distal colon compared to sham-operated controls (SHAM). Direct measurements of fecal fat content confirmed that RYGB on a 10 % fat diet excreted 40-fold more fecal fat than SHAM and, on a 40 % fat diet, RYGB excreted sevenfold more fecal fat than SHAM fed similarly. Results from the transport studies revealed a clear effect of high dietary fat (40 %) on colonic oxalate permeability and tissue conductance ( G) with comparable oxalate fluxes in RYGB and in SHAM. Administering a diet containing 10 % fat to both groups distinguished differences between RYGB and SHAM, revealing a 40 % increase in G in RYGB and a reversal in the direction of net oxalate flux from absorption in SHAM to secretion in RYGB. These changes in colonic oxalate permeability were associated with a fourfold increase in urinary oxalate excretion in RYGB compared to SHAM. Therefore, oxalate solubility and permeability in the RYGB model are promoted by steatorrhea and result in enhanced passive oxalate absorption and hyperoxaluria. To our knowledge, these are the first measurements of intestinal oxalate transport in rats with RYGB. [ABSTRACT FROM AUTHOR]

Primary hyperoxaluria type 1 (PH1) is an inherited metabolic disease that culminates in ESRF. Pre-emptive liver transplantation (pLTx) treats the metabolic defect and avoids the need for kidney transplantation (KTx). An institutional experience of pediatric PH1 LTx is reported and compared to the literature. Between 2004 and 2015, eight children underwent p LTx for PH1. Three underwent pLTx with a median GFR of 40 (30-46) mL/min/1.73 m2 and five underwent sequential combined liver-kidney transplantation (cLKTx); all were on RRT at the time of cLKTx. In one case of pLTx, KTx was required eight and a half yr later. pLTx was performed in older (median 8 vs. 2 yr) and larger children (median 27 vs. 7.75 kg) that had a milder PH1 phenotype. In pediatric PH1, pLTx, ideally, should be performed before renal and extrarenal systemic oxalosis complications have occurred, and pLTx can be used 'early' or 'late.' Early is when renal function is preserved with the aim to avoid renal replacement. However, in late ( GFR < 30 mL/min/1.73 m2), the aim is to stabilize renal function and delay the need for KTx. Ultimately, transplant strategy depends on PH1 phenotype, disease stage, child size, and organ availability. [ABSTRACT FROM AUTHOR]

The hereditary kidney stone disease primary hyperoxaluria type 1 (PH1) is caused by a functional deficiency of the liver-specific, peroxisomal, pyridoxal-phosphate-dependent enzyme, alanine:glyoxylate aminotransferase (AGT). One third of PH1 patients, particularly those expressing the p.[(Pro11Leu; Gly170Arg; Ile340Met)] mutant allele, respond clinically to pharmacological doses of pyridoxine. To gain further insight into the metabolic effects of AGT dysfunction in PH1 and the effect of pyridoxine, we established an “indirect” glycolate cytotoxicity assay using CHO cells expressing glycolate oxidase (GO) and various normal and mutant forms of AGT. In cells expressing GO the great majority of glycolate was converted to oxalate and glyoxylate, with the latter causing the greater decrease in cell survival. Co-expression of normal AGTs and some, but not all, mutant AGT variants partially counteracted this cytotoxicity and led to decreased synthesis of oxalate and glyoxylate. Increasing the extracellular pyridoxine up to 0.3 μM led to an increased metabolic effectiveness of normal AGTs and the AGT-Gly170Arg variant. The increased survival seen with AGT-Gly170Arg was paralleled by a 40% decrease in oxalate and glyoxylate levels. These data support the suggestion that the effectiveness of pharmacological doses of pyridoxine results from an improved metabolic effectiveness of AGT; that is the increased rate of transamination of glyoxylate to glycine. The indirect glycolate toxicity assay used in the present study has potential to be used in cell-based drug screening protocols to identify chemotherapeutics that might enhance or decrease the activity and metabolic effectiveness of AGT and GO, respectively, and be useful in the treatment of PH1. [ABSTRACT FROM AUTHOR]

Primary hyperoxaluria type-3 is characterized by increased oxalate production caused by mutations in the HOGA1 gene encoding 4-hydroxy-2-oxoglutarate aldolase (HOGA1). How the most commonly occurring mutations affect the cellular fates of the expressed HOGA1 mutants is still unknown. We show that two prevalent recombinant HOGA1 mutants are thermally unstable with evidence for chaperone-mediated degradation when expressed in E. coli. In stably transformed HEK-293 cells, protein expression of the Glu315 deletion mutant only becomes detectable during incubation with a 26S proteasome inhibitor. These findings suggest that failure of chaperone-assisted folding leads to targeted cellular degradation and an absolute absence of HOGA1 function. [ABSTRACT FROM AUTHOR]

The interactions between the main cellular sources of ROS, such as mitochondria and NADPH oxidase, are known to play an imperative role in the pathogenesis of hyperoxaluria-induced nephrolithiasis. The present study was designed to investigate the protective effect of a combinatorial therapy based on the attenuation of oxidative stress with antioxidant (N-acetyl cysteine), and NADPH oxidase inhibitor (apocynin), that might be required to effectively eliminate hyperoxaluric manifestations. Hyperoxaluria was induced in male Wistar rats by administering 0.4% ethylene glycol with 1% ammonium chloride in drinking water for 9 days. Hyperoxaluria accentuated renal oxidative stress in terms of increased ROS production and lipid peroxidation. Mitochondrial dysfunction, a central deleterious event in renal stone crystallization, was evident by decreased activities of electron transport chain complex I, II and IV, augmented mitochondrial ROS, reduced GSH/GSSG ratio, which resulted in the mitochondrial permeability transition pore (mPTP) opening as indicated by increased mitochondrial swelling in hyperoxaluric rats. Furthermore, NADPH oxidase activity was significantly increased, with raised expression of NOX1, NOX2, NOX4, p38MAPK and MnSOD, in the renal tissue of hyperoxaluric rats compared to control. However, combinatorial therapy with N-acetyl cysteine (50 mg/kg/day) and apocynin (200 mg/kg/day), intraperitoneally, significantly improved renal functions in hyperoxaluric rats and considerably ameliorated mitochondrial dysfunction. NAC with apocynin was also found to be effective in reducing the redundant activity of NADPH oxidase in renal tissue of hyperoxaluric rats. Hence, our investigation provides novel mechanistic insights that combinatorial approaches using targeted modulators of ROS offer therapeutic benefits in hyperoxaluria-induced nephrolithiasis. [ABSTRACT FROM AUTHOR]

Aim: To investigate whether the sex-dependent expression of hepatic and renal oxalate transporter sat-1 (Slc26a1) changes in a rat model of ethylene glycol (EG)-induced hyperoxaluria. Methods: Rats were given tap water (12 males and 12 females; controls) or EG (12 males and 12 females; 0.75% v/v in tap water) for one month. Oxaluric state was confirmed by biochemical parameters in blood plasma, urine, and tissues. Expression of sat-1 and rate-limiting enzymes of oxalate synthesis, alcohol dehydrogenase 1 (Adh1) and hydroxy-acid oxidase 1 (Hao1), was determined by immunocytochemistry (protein) and/or real time reverse transcription polymerase chain reaction (mRNA). Results: EG-treated males had significantly higher (in µmol/L; mean ± standard deviation) plasma (59.7 ± 27.2 vs 12.9 ± 4.1, P < 0.001) and urine (3716 ± 1726 vs 241 ± 204, P < 0.001) oxalate levels, and more abundant oxalate crystaluria than controls, while the liver and kidney sat-1 protein and mRNA expression did not differ significantly between these groups. EG-treated females, in comparison with controls had significantly higher (in µmol/L) serum oxalate levels (18.8 ± 2.9 vs 11.6 ± 4.9, P < 0.001), unchanged urine oxalate levels, low oxalate crystaluria, and significantly higher expression (in relative fluorescence units) of the liver (1.59 ± 0.61 vs 0.56 ± 0.39, P = 0.006) and kidney (1.77 ± 0.42 vs 0.69 ± 0.27, P < 0.001) sat-1 protein, but not mRNA. The mRNA expression of Adh1 was femaledominant and that of Hao1 male-dominant, but both were unaffected by EG treatment. Conclusions: An increased expression of hepatic and renal oxalate transporting protein sat-1 in EG-treated female rats could protect from hyperoxaluria and oxalate urolithiasis. [ABSTRACT FROM AUTHOR]

This study aimed at evaluating the protective effects of a herbal medication (Tutukon) on the hyperoxaluria induced apoptotic changes and crystal deposition in renal tubular epithelium in rat model. 60 male wistar rats were divided into three different groups (each group n: 20). In Group I severe hyperoxaluria was induced by ethylene glycol (EG) (0.75 %) administration for 28 days. In Group II, in addition to hyperoxaluria induction, animals were treated with Tutukon for 28 days. Group III animals constituted the controls without any specific medication and/or intervention. While the presence and degree of crystal deposition in the tubular lumen were examined histopathologically under light microscopy, tubular apoptotic changes were evaluated using immunohistochemical staining for cysteine-aspartic acid protease-3 (Caspase-3) and tumor necrosis factor alpha (TNF-α) positivity on days 14 and 28, respectively. Evaluation of apoptotic changes by Caspase-3 positivity showed that while the majority of animals undergoing EG only showed evident apoptotic changes ( n: 9), Tutukon application demonstrated a significant limitation with limited or no apoptosis ( n: 7) in these animals. Similar data were noted for TNF alpha expression; while apoptotic changes were evident in 8 (80 %) in Group I animals, limited changes were noted in Tutukon Group ( n: 2). Regarding crystal deposition despite evident changes in Group I (9 animals), like apoptotic alterations, it was again significantly limited in animals receiving Tutukon (4 animals). Renal tubular crystal deposition and apoptotic changes induced by hyperoxaluria play a role in the pathogenesis of urolithiasis and the limitation of these changes might be instituted by Tutukon as a result of its antioxidant and antiinflammatory effects. [ABSTRACT FROM AUTHOR]

Hyperoxaluria significantly increases the risk of calcium oxalate kidney stone formation. Since several bacteria have been shown to metabolize oxalate in vitro, including probiotic bifidobacteria, we focused on the efficiency and possible mechanisms by which bifidobacteria can influence oxalate handling in vivo, especially in the intestines, and compared these results with the reported effects of Oxalobacter formigenes. Bifidobacterium animalis subsp. lactis DSM 10140 and B. adolescentis ATCC 15703 were administered to wild-type (WT) mice and to mice deficient in the hepatic enzyme alanine-glyoxylate aminotransferase ( Agxt, a mouse model of Primary Hyperoxaluria) that were fed an oxalate-supplemented diet. The administration of B. animalis subsp. lactis led to a significant decrease in urinary oxalate excretion in WT and Agxt mice when compared to treatment with B. adolescentis. Detection of B. animalis subsp. lactis in feces revealed that 3 weeks after oral gavage with the bacteria 64 % of WT mice, but only 37 % of Agxt mice were colonized. Examining intestinal oxalate fluxes showed there were no significant changes to net oxalate secretion in colonized animals and were therefore not associated with the changes in urinary oxalate excretion. These results indicate that colonization with B. animalis subsp. lactis decreased urinary oxalate excretion by degrading dietary oxalate thus limiting its absorption across the intestine but it did not promote enteric oxalate excretion as reported for O. formigenes. Preventive or therapeutic administration of B. animalis subsp. lactis appears to have some potential to beneficially influence dietary hyperoxaluria in mice. [ABSTRACT FROM AUTHOR]

Background: Hyperoxaluria causes crystal deposition in the kidney, which leads to oxidative stress and to injury and damage of the renal epithelium. Sodium thiosulfate (STS, Na2S2O3) is an anti-oxidant, which has been used in human medicine for decades. The effect of STS on hyperoxaluria-induced renal damage is not known. Methods: Hyperoxaluria and renal injury were induced in healthy male Wistar rats by chronic exposure to ethylene glycol (EG, 0.75%) in the drinking water for 4 weeks. The treatment effects of STS, NaCl or Na2SO4 were compared. Furthermore, the effects of STS on oxalate-induced oxidative stress were investigated in vitro in renal LLC-PK1 cells. Results: Chronic EG exposure led to hyperoxaluria, oxidative stress, calcium oxalate crystalluria and crystal deposition in the kidneys. Whereas all tested compounds significantly reduced crystal load, only STS-treatment maintained tissue superoxide dismutase activity and urine 8-isoprostaglandin levels in vivo and preserved renal function. In in vitro studies, STS showed the ability to scavenge oxalate-induced ROS accumulation dose dependently, reduced cell-released hydrogen peroxide and preserved superoxide dismutase activity. As a mechanism explaining this finding, STS was able to directly inactivate hydrogen peroxide in cell-free experiments. Conclusions: STS is an antioxidant, which preserves renal function in a chronic EG rat model. Its therapeutic use in oxidative-stress induced renal-failure should be considered. [ABSTRACT FROM AUTHOR]