Acute renal failure with severe loin pain and patchy renal ischaemia after anaerobic exercise (ALPE) (exercise-induced acute renal failure) in a father and child with URAT1 mutations beyond the W258X mutation

Acute renal failure with severe loin pain and patchy renal ischemia after anaerobic exercise

BACKGROUND

There are two known types of exercise-induced acute renal failure. One is the long-known myoglobinuria-induced acute renal failure due to severe rhabdomyolysis, and the other is the recently recognized non-myoglobinuria-induced acute renal failure with mild rhabdomyolysis. Exercise-induced acute renal failure was first reported in 1982. Non-myoglobinuria-induced acute renal failure is associated with severe low back pain and patchy renal vasoconstriction, and it is termed post-exercise acute renal failure because it usually occurs hours after exercise. It is also called acute renal failure with severe loin pain and patchy renal ischemia after anaerobic exercise (ALPE).

AIM

To makes a significant contribution to medical literature as it presents a study that investigated a not-widely-known type of exercise-induced acute renal failure known as ALPE.

METHODS

We performed a database search selecting papers published in the English or Japanese language. A database search was lastly accessed on September 1, 2022. The results of this study were compared with those reported in other case series.

RESULTS

The study evaluated renal hypouricemia as a key risk factor of ALPE. The development of ALPE is due to the sum of risk factors such as exercise, hypouricemia, nonsteroidal anti-inflammatory drugs, vasopressors, and dehydration.

CONCLUSION

In conclusion, hypouricemia plays a key role in the development of ALPE and is often associated with anaerobic exercise. The development of ALPE is a result of the cumulative effects of risk factors such as exercise, hypouricemia, NSAIDs, vasopressors, and dehydration.

Xanthine Oxidoreductase Inhibitors Suppress the Onset of Exercise-Induced AKI in High HPRT Activity Urat1-Uox Double Knockout Mice

BACKGROUND

Hereditary renal hypouricemia type 1 (RHUC1) is caused by URAT1/SLC22A12 dysfunction, resulting in urolithiasis and exercise-induced AKI (EIAKI). However, because there is no useful experimental RHUC1 animal model, the precise pathophysiologic mechanisms underlying EIAKI have yet to be elucidated. We established a high HPRT activity Urat1-Uox double knockout (DKO) mouse as a novel RHUC1 animal model for investigating the cause of EIAKI and the potential therapeutic effect of xanthine oxidoreductase inhibitors (XOIs).

METHODS

The novel Urat1-Uox DKO mice were used in a forced swimming test as loading exercise to explore the onset mechanism of EIAKI and evaluate related purine metabolism and renal injury parameters.

RESULTS

Urat1-Uox DKO mice had uricosuric effects and elevated levels of plasma creatinine and BUN as renal injury markers, and decreased creatinine clearance observed in a forced swimming test. In addition, Urat1-Uox DKO mice had increased NLRP3 inflammasome activity and downregulated levels of Na⁺-K⁺-ATPase protein in the kidney, as Western blot analysis showed. Finally, we demonstrated that topiroxostat and allopurinol, XOIs, improved renal injury and functional parameters of EIAKI.

CONCLUSIONS

Urat1-Uox DKO mice are a useful experimental animal model for human RHUC1. The pathogenic mechanism of EIAKI was found to be due to increased levels of IL-1β via NLRP3 inflammasome signaling and Na⁺-K⁺-ATPase dysfunction associated with excessive urinary urate excretion. In addition, XOIs appear to be a promising therapeutic agent for the treatment of EIAKI.

Prevalence of inherited changes of uric acid levels in kidney dysfunction including stage 5 D and T: a systematic review

Background/aims

Familial juvenile hereditary nephropathy (FJHN) is characterized by hyperuricemia due to severely impaired urinary excretion of urate. Hereditary renal hypouricemia is an inborn error of membrane transport. Because studies of inherited tubulopathy is rare, prevalence and diagnosis of these inherited tubulopathy increase with genetic testing.The aim of this study is to investigate prevalence of clinical features, biochemical profiles, and genetic analysis of patients with changes in serum uric acid levels in inherited tubulopathy.

Main body

The paper has written based on searching PubMed and Google Scholar to identify potentially relevant articles or abstracts. In this retrospective study, a total 65 patients with changes of serum uric acid levels and kidney dysfunction were investigated. Clinical features, laboratory data at initial presentation, management, and outcomes were collected. Forty studies (65 participants) included in this review. The mean ± SD of age of study patients in inherited tubulointerstitial kidney disease was 25.29 ± 14.69 years. Mean ± SD age of patients at time of diagnosis in inherited renal hypouricemia was 18.83 ± 10.59 years. Correlation between exon region in mutated UMOD, SLC22A12, and SLC2A9 genes and serum uric acid levels were assessed and revealed significant statistical correlation between exon region of SLC2A9 mutation and serum uric acid levels. Prevalence of progression to end-stage kidney disease in patients with inherited tubulointerstitial kidney disease and inherited renal hypouricemia were assessed 20% and 2.5%, respectively. There was nephrolithiasis in two patients (2/25, 8%) with inherited renal hypouricemia.

Conclusions

This study shows that UMOD and SLC22A12 gene mutations were responsible for majority of autosomal-dominant tubulointerstitial kidney disease and inherited renal hypouricemia, respectively.

Urat1-Uox double knockout mice are experimental animal models of renal hypouricemia and exercise-induced acute kidney injury

Renal hypouricemia (RHUC) is a hereditary disease characterized by a low level of plasma urate but with normal urinary urate excretion. RHUC type 1 is caused by mutations of the urate transporter URAT1 gene (SLC22A12). However, the plasma urate levels of URAT1 knockout mice are no different from those of wild-type mice. In the present study, a double knockout mouse, in which the URAT1 and uricase (Uox) genes were deleted (Urat1-Uox-DKO), were used as an experimental animal model of RHUC type 1 to investigate RHUC and excise-induced acute kidney injury (EIAKI). Mice were given a variable content of allopurinol for one week followed by HPLC measurement of urate and creatinine concentrations in spot urine and blood from the tail. The urinary excretion of urate in Urat1-Uox-DKO mice was approximately 25 times higher than those of humans. With allopurinol, the plasma urate levels of Urat1-Uox-DKO mice were lower than those of Uox-KO mice. There were no differences in the urinary urate excretions between Urat1-Uox-DKO and Uox-KO mice administered with 9 mg allopurinol /100 g feed. In the absence of allopurinol, plasma creatinine levels of some Urat1-Uox-DKO mice were higher than those of Uox-KO mice. Consequently, hypouricemia and normouricosuria may indicate that the Urat1-Uox-DKO mouse administered with allopurinol may represent a suitable animal model of RHUC type 1. Urat1-Uox-DKO mice without allopurinol exhibited acute kidney injury, thus providing additional benefit as a potential animal model for EIAKI. Finally, our data indicate that allopurinol appears to provide prophylactic effects for EIAKI.

U-shaped relationship between serum uric acid levels and intrarenal hemodynamic parameters in healthy subjects

Hyperuricemia has been reported to affect renal hemodynamics. In a recent study, both low and high levels of serum uric acid (SUA) were found to be associated with loss of kidney function. The goal of this study was to evaluate the relationship between SUA levels and intrarenal hemodynamic parameters in healthy subjects, using plasma clearance of para-aminohippurate (C_PAH) and inulin (C_in). Renal and glomerular hemodynamics were evaluated by simultaneous measurements of C_PAH and C_in in 48 healthy subjects (54.6 ± 13.4 yr). Intrarenal hemodynamic parameters, including efferent and afferent (R_a) arteriolar resistance, were calculated using Gómez's formulas. Relationships of SUA levels with these intrarenal hemodynamic parameters were examined. In quadratic regression analysis, SUA levels had a significant inverse U-shaped relationship with C_in (P < 0.0001, R² = 0.350) and C_PAH (P = 0.0093, R² = 0.188) and a U-shaped relationship with R_a (P = 0.0011, R² = 0.262). In multiple regression analysis with normal (3.5-6.0 mg/dl) and mildly low or high (<3.5 or >6.0 mg/dl) SUA levels entered as dummy variables of zero and one, respectively, mildly low or high SUA levels were significantly and independently associated with R_a (β = 0.230, P = 0.0403) after adjustment for several factors (R² = 0.597, P < 0.0001). Both mild hyperuricemia and mild hypouricemia are significantly associated with increased R_a, although weakly. The increase in R_a in subjects with mild hyperuricemia or hypouricemia may be related to renal hemodynamic abnormalities, possibly leading to a decline in renal function.

Heat Stress Nephropathy From Exercise-Induced Uric Acid Crystalluria: A Perspective on Mesoamerican Nephropathy

Mesoamerican nephropathy (MeN), an epidemic in Central America, is a chronic kidney disease of unknown cause. In this article, we argue that MeN may be a uric acid disorder. Individuals at risk for developing the disease are primarily male workers exposed to heat stress and physical exertion that predisposes to recurrent water and volume depletion, often accompanied by urinary concentration and acidification. Uric acid is generated during heat stress, in part consequent to nucleotide release from muscles. We hypothesize that working in the sugarcane fields may result in cyclic uricosuria in which uric acid concentrations exceed solubility, leading to the formation of dihydrate urate crystals and local injury. Consistent with this hypothesis, we present pilot data documenting the common presence of urate crystals in the urine of sugarcane workers from El Salvador. High end-of-workday urinary uric acid concentrations were common in a pilot study, particularly if urine pH was corrected to 7. Hyperuricemia may induce glomerular hypertension, whereas the increased urinary uric acid may directly injure renal tubules. Thus, MeN may result from exercise and heat stress associated with dehydration-induced hyperuricemia and uricosuria. Increased hydration with water and salt, urinary alkalinization, reduction in sugary beverage intake, and inhibitors of uric acid synthesis should be tested for disease prevention.

A novel homozygous GLUT9 mutation cause recurrent exercise-induced acute renal failure and posterior reversible encephalopathy syndrome

Renal hypouricemia (RHU) is an autosomal recessive hereditary disease characterized by impaired renal urate reabsorption and subsequent profound hypouricemia. There are two types of RHU, type 1 and type 2, caused by the loss-of-function mutation of SLC22A12 and SLC2A9 genes, respectively. RHU predisposes affected people to exercise-induced acute renal failure (EIARF), posterior reversible encephalopathy syndrome (PRES) and nephrolithiasis. A Chinese patient had experienced three episodes of EIARF and one episode of PRES. The investigations showed profound hypouricemia and significantly increased renal excretion of UA. Cranial magnetic resonance imaging showed communicating hydrocephalus. Renal biopsy displayed interlobular artery intimal thickening with reduction of lumen and acute tubulointerstitial injury. The mutational analysis revealed a homozygous splice-site mutation in the SLC2A9 gene encoding glucose transporter 9. The patient was diagnosed as RHU type 2 caused by a loss-of-function mutation of the SLC2A9 gene. Consequently, he was strictly prohibited from strenuous exercise. During the 5-year follow-up, EIARF and PRES never recurred. Strenuous exercise may induce systemic (including renal and cerebrovascular) vasoconstriction eventually resulting in EIARF and PRES in patients with RHU. To our knowledge, this is the first report of a homozygous splice-site mutation in the SLC2A9 gene, renal arteriolar chronic lesion, concurrence of RHU and communicating hydrocephalus.

Recurrent exercise-induced acute renal failure in a young Pakistani man with severe renal hypouricemia and SLC2A9 compound heterozygosity

Background

Familial renal hypouricemia (RHUC) is a hereditary disease characterized by hypouricemia, high renal fractional excretion of uric acid (FE-UA) and can be complicated by acute kidney failure and nephrolithiasis. Loss-of-function mutations in the SLC22A12 gene cause renal hypouricemia type 1 (RHUC1), whereas renal hypouricemia type 2 (RHUC2) is caused by mutations in the SLC2A9 gene.

Case presentation

We describe a 24-year-old Pakistani man who was admitted twice to our hospital for severe exercise-induced acute renal failure (EIARF), abdominal pain and fever; he had very low serum UA levels (0.2 mg/dl the first time and 0.09 mg/dl the second time) and high FE-UA (200% and 732% respectively), suggestive of RHUC. Mutational analyses of both urate transporters revealed a new compound heterozygosity for two distinct missense mutations in the SLC2A9 gene: p.Arg380Trp, already identified in heterozygosity, and p.Gly216Arg, previously found in homozygosity or compound heterozygosity in some RHUC2 patients. Compared with previously reported patients harbouring these mutations, our proband showed the highest FE-UA levels, suggesting that the combination of p.Arg380Trp and p.Gly216Arg mutations most severely affects the renal handling of UA.

Conclusions

The clinical and molecular findings from this patient and a review of the literature provide new insights into the genotype-phenotype correlation of this disorder, supporting the evidence of an autosomal recessive inheritance pattern for RHUC2. Further investigations into the functional properties of GLUT9, URAT1 and other urate transporters are required to assess their potential research and clinical implications.

Clinical characteristics of acute renal failure with severe loin pain and patchy renal vasoconstriction

BACKGROUND

Acute renal failure (ARF) with severe loin pain and patchy renal vasoconstriction (PRV) is a syndrome presenting with sudden loin pain after anaerobic exercise. We aimed to investigate the clinical characteristics and the efficacy of diagnostic imaging studies of patients with this syndrome.

METHODS

We retrospectively selected 17 patients with ARF accompanied by loin or abdominal pain who showed multiple patchy wedge-shaped delayed contrast enhancements on a computerized tomography scan. Information about the clinical characteristics, including the nature of pain and combined symptoms, suspected causes, such as exercise, drug or alcohol intake, and renal hypouricemia, and the results of laboratory and imaging tests were gathered.

RESULTS

The mean age of patients with episodes of ARF accompanied by loin pain was 23.0±6.5 (range 16-35) years old. Pain was mainly located in the loin (70.6%) or abdominal area (76.5%) and continued for approximately 3.5±4.0 days. Exercise was suspected as a primary cause of disease in 12 (70.6%) patients. Maximal serum creatinine was 5.42±3.16 (1.4-12.1) mg/dL 3.1±1.8 (1-7) days after the onset of pain. The peak level of serum uric acid was 9.41±2.91 (6.0-15.8) mg/dL. All of the patients recovered to near-normal renal function, and one patient showed hypouricemia after recovery.

CONCLUSION

ARF with severe loin pain and PRV can present with loin or abdominal pain, even without a history of anaerobic exercise. Careful history taking and appropriate imaging studies are critical in the diagnosis and management of this syndrome.

Oxidative imbalance in idiopathic renal hypouricemia

An important complication of idiopathic renal hypouricemia is exercise-induced acute renal failure (ARF). The most plausible explanation for this complication is that decreased antioxidant potential leads to kidney injury by reactive oxygen species (ROS). We demonstrated this oxidative imbalance by a concomitant assessment of ROS production and antioxidant system capability in a 15- year-old girl with idiopathic renal hypouricemia caused by a mutation in the urate transporter (URAT1) gene. Her serum level of ROS increased with decreasing antioxidant potential capacity soon after the initiation of anaerobic stress due to treadmill exercise. Thereafter, serum levels of ROS and antioxidant potential showed a parallel course, returning to the baseline values at 240 min after exercise. Some patients with idiopathic renal hypouricemia demonstrate oxidative imbalance soon after exercise with a predisposition to exercise-induced acute renal failure. Antioxidant properties may alter this imbalance by augmenting the antioxidant activity.

Organic anion transporters of the SLC22 family: biopharmaceutical, physiological, and pathological roles

The human organic anion transporters OAT1, OAT2, OAT3, OAT4 and URAT1 belong to a family of poly-specific transporters mainly located in kidneys. Selected OATs occur also in liver, placenta, and brain. OATs interact with endogenous metabolic end products such as urate and acidic neutrotransmitter metabolites, as well as with a multitude of widely used drugs, including antibiotics, antihypertensives, antivirals, anti-inflammatory drugs, diuretics and uricosurics. Thereby, OATs play an important role in renal drug elimination and have an impact on pharmacokinetics. In this review we focus on the interaction of human OATs with drugs. We report the affinities of human OATs for drug classes and compare the putative importance of individual OATs for renal drug excretion. The role of OATs as sites of drug-drug interaction and mediators cell toxicity, their gender-dependent regulation in health and diseased states, and the possible impact of single nucleotide polymorphisms are also dealt with.

New insights into renal transport of urate

PURPOSE OF REVIEW

This review focuses on recent progress in the understanding of various aspects of renal transport of urate.

RECENT FINDINGS

Since the molecular cloning of the renal apical urate/anion exchanger URAT1 (SLC22A12), several membrane proteins relevant to the transport of urate have been identified. The molecular identification of two sodium-coupled monocarboxylate transporters, SMCT1(SLC5A8) and SMCT2(SLC5A12), and the emerging role of PDZ (PSD-95, DglA, and ZO-1) scaffold for renal apical transporters have led to a new concept of renal urate transport: urate-transporting multimolecular complex, or 'urate transportsome', that may form an ultimate functional unit including the sodium-coupled urate transport system by linking URAT1 and sodium-coupled monocarboxylate transporters or the coordinated apical urate uptake system by balancing reabsorptive (URAT1) and efflux (NPT1/OATv1 and MRP4) transporters. In addition, genetic variations of the URAT1 gene are associated not only with idiopathic renal hypouricemia but also with reduced renal urate excretion.

SUMMARY

Although our knowledge of renal urate handling has been increased by the molecular identification of urate transport proteins and by results of genetic studies on patients with serum urate disorders, current evidence is insufficient to fully understand the precise mechanism governing the bi-directional transport of urate. Further studies are still necessary.

Analysis of mutations in the urate transporter 1 (URAT1) gene of Japanese patients with hypouricemia in northern Japan and review of the literature

BACKGROUND

Renal hypouricemia is an autosomal recessive disorder resulting from inactivating mutations in the urate transporter 1 (URAT1) encoded by SLC22A12. To date, 10 mutations have been identified and W258X in the URAT1 gene is the predominant cause in middle to southwestern Japan. However, it is still unclear whether there is a regional specific distribution of mutations in northern Japan. In this study, we analyzed mutations in the URAT1 gene of five Japanese patients with renal hypouricemia in northern Japan.

METHODS

Peripheral blood mononuclear cells were isolated from patients with hypouricemia and healthy control subjects. A mutation analysis of the URAT1 gene was performed completely by direct automated sequencing of polymerase chain reaction-amplified DNA products.

RESULTS

We identified two mutations. These mutations [c.269G>A (R90H) and c.774G>A (W258X)] have been reported in Japanese patients. Two of five patients were homozygotes (W258X), two carried single heterozygous mutations (W258X), and the remaining one was a compound heterozygote (R90H and W258X).

CONCLUSIONS

Our study suggests that there is no regional different distribution of the URAT1 genetic mutations in Japanese with renal hypouricemia.

[What is new in pediatric nephrology?]

Recent advances in the knowledge of physiology, genetics, imaging, and therapeutics have lead to novel practical approaches in paediatric nephrology. Many inherited syndromes have been revisited in order to identify precise renal diseases at the molecular level. In addition, a large number of epidemiological studies and clinical trials have allowed guidelines and recommendations to be provided for chronic and end-stage renal failure, urinary tract infection, glomerular diseases, etc.