Accumulation Of 5-oxoproline Research Articles

Acetaminopheninduced high anion gap metabolic acidosis: a potentially under-recognized consequence from a common medication.

While metabolic acidosis is one of the most common complications in patients with chronic kidney disease (CKD), there are several uncommon etiologies that are challenging to diagnose. Here, we describe a patient on peritoneal dialysis who developed high anion gap metabolic acidosis secondary to acquired 5-oxoprolinemia from acetaminophen use. While CKD is a known risk factor for developing this potentially serious complication, this case further highlights how 5-oxoproline accumulation can occur, even with therapeutic dosing of acetaminophen.

High-Anion-Gap Metabolic Acidosis During a Prolonged Hospitalization Following Perforated Diverticulitis: An Educational Case Report.

The metabolic acidoses are generally separated into 2 categories on the basis of an anion gap calculation: high-anion-gap and normal anion-gap metabolic acidosis. When a high-anion-gap metabolic acidosis (HAGMA) is not clearly explained by common etiologies and routine confirmatory testing, specialized testing can definitively establish rare diagnoses such as 5-oxoproline, d-lactate accumulation, or diethylene glycol toxicity. A 56-year-old woman had a prolonged hospital admission following perforated diverticulitis requiring sigmoid resection. Her hospitalization was complicated by feculent peritonitis and surgical wound dehiscence needing prolonged broad-spectrum antibiotics and wound debridements. She developed acute kidney injury and HAGMA in the hospital. Chart review showed that she received a large cumulative dose of acetaminophen during her hospital stay. Laboratory studies showed markedly increased serum 5-oxoproline causing HAGMA. Patient was admitted to the intensive care unit and treated with N-acetylcysteine and renal replacement therapy. After admission to the intensive care unit, the patient continued to require vasopressor and ventilatory support for septic shock and a ventilator-associated pneumonia. After an initial recovery and resolution of her HAGMA, she subsequently suffered recurrent aspirations which were fatal. 1. The acronym GOLD MARK is useful when assessing patients with HAGMA and most causes of HAGMA can be established with routine testing.2. When the etiology of HAGMA remains unclear, additional testing can be required to diagnose rare causes of HAGMA.3. Rare causes of HAGMA are diethylene glycol, 5-oxoproline, and d-lactate accumulation.4. Acidosis secondary to 5-oxoproline accumulation can occur even with "therapeutic" doses of acetaminophen in patients receiving it regularly for a prolonged period and who have depleted glutathione stores.5. Risk factors for glutathione depletion include malnutrition, older age, sepsis, pregnancy, multiple chronic illnesses, and chronic kidney disease.

Metabole acidose met verhoogde anion gap ten gevolge van 5-oxoprolinurie bij gelijktijdig gebruik van acetaminofen en flucloxacilline

Metabolic acidosis with increased anion gap due to 5-oxoprolinuria with concomitant use of acetaminophen and flucloxacillin 5-oxoprolinuria is a relatively rare metabolic disorder in which there is accumulation of 5-oxoproline leading to a high anion gap metabolic acidosis. The acquired form is usually caused by simultaneous use of acetaminophen (also known as paracetamol) and flucloxacillin, which is not uncommon. The exact incidence and prevalence of the acquired form are not known. This disorder is most likely under-reported as the test used for diagnosis is not always performed nor easy accessible. Diagnosing 5-oxoprolinuria requires testing urine or serum of a patient for the presence of organic acids, which are highly elevated in 5-oxoprolinuria. Due to the relative rareness of the disorder, cases are easily missed. 5-oxoprolinuria should always be suspected in a patient with unexplained high anion gap metabolic acidosis and/or therapy with flucloxacillin with or without the concomitant use of acetaminophen. Treating 5-oxoprolinuria is straightforward and consists of stopping the offending drug(s) which mostly leads to a spontaneous recovery. Treatment with sodium bicarbonate and/or N-acetylcysteine are also described in the literature, but at present there is not sufficient evidence supporting their use.

Acetaminophen Use Concomitant with Long-Lasting Flucloxacillin Therapy: A Dangerous Combination.

Acetaminophen and flucloxacillin both interfere with the γ-glutamyl cycle. Long-lasting concomitant use of flucloxacillin and acetaminophen can lead to 5-oxoproline accumulation and severe high anion gap metabolic acidosis. Females and patients with sepsis, impaired kidney and/or liver function, malnutrition, advanced age, congenital 5-oxoprolinase deficiency and supratherapeutic acetaminophen and flucloxacillin dosage are associated with increased risk. Therefore, a critical attitude towards the prescription of acetaminophen concomitant with flucloxacillin in these patients is needed.We present the case of a 79-year-old woman with severe 5-oxoprolinaemia after long-lasting treatment with flucloxacillin and acetaminophen, explaining the toxicological mechanism and risk factors, and we make recommendations for acetaminophen use in patients with long-lasting flucloxacillin treatment.LEARNING POINTSAlthough rare, long-lasting treatment with flucloxacillin concomitant with acetaminophen can lead to severe high anion gap metabolic acidosis.When prescribing long-lasting flucloxacillin therapy in combination with acetaminophen, regular blood gas analysis is needed to evaluate pH and the anion gap.In cases of 5-oxoproline-induced high anion gap metabolic acidosis in patients with long-lasting acetaminophen and flucloxacillin therapy, acetaminophen prescription should be stopped immediately. Replacing flucloxacillin with another antibiotic agent should be considered.

A TYLENOL A DAY BRINGS THE PATIENT TO THE BAY: A CASE OF USUAL DOSING ACETAMINOPHEN TOXICITY

SESSION TITLE: Wednesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM INTRODUCTION: Acetaminophen (APAP) toxicity is responsible for nearly 50% of acute liver failure (ALF) in the United States (1). Most cases are not deliberate overdoses (2). Chronic administration of APAP is associated with additional toxic pathways, leading to organ dysfunction. Presented is a case of ALF due to therapeutic doses of APAP with toxicity from the metabolite 5-oxoproline (pyroglutamic acid). CASE PRESENTATION: An 80 year old man with hypertension, diabetes, and chronic lower back pain presented with nausea and vomiting found to have fulminant liver failure with AST 15,000 and ALT 4,037 along with an anion gap metabolic acidosis. APAP levels ranged between 29 and 34 (10-30 ug/ml). The patient took only two to three APAP tablets daily for chronic lower back pain for the past 2 years as confirmed by family. He denied taking any other medications or herbal supplements. Ethanol, salicylate and CPK levels were normal. IR-guided liver biopsy confirmed APAP toxicity as culprit for ALF. His liver failure progressed with encephalopathy requiring intubation and rapidly worsening renal failure. The diagnosis of 5-oxoproline intoxication was made and after a week of continuous N-acetylcysteine infusion, his ALF resolved. DISCUSSION: Over 10,000 hospitalizations in the United States are due to APAP toxicity, and what is most concerning is that more than 50% of these cases are unintentional and only in the setting of therapeutic use (2, 5). Typically, in acute APAP toxicity the hepatic injury is due to the accumulation of hepatoxic N-acetyl-para-benzoquinoeimine (NAPQI) via depletion of hepatic glutathione stores. In these cases N-acetylcysteine (NAC) increases and repletes glutathione storage by being a glutathione synthesis precursor. However, in chronic APAP use even when taken in recommended doses a different toxic metabolite can accumulate. This metabolite is known as 5-oxoproline is overproduced due to the activation of an ATP depleting cycle (Figure 1). The condition generally resolves with discontinuation of acetaminophen and general supportive measures. Although many reports suggest that administration of N-acetylcysteine may accelerate recovery, this has not been proven. Here NAC increases the negative feedback of γ-glutamylcysteine synthetase, resulting in reduced generation of pyroglutamic acid from γ-glutamylcysteine (7). Other factors lower the dose threshold for APAP toxicity, including alcohol use, malnutrition, use of CYP 450-inducers, and delayed gastric emptying (3). In our patient, malnutrition and ileus may have increased his risk for APAP toxicity, which were both diagnosed during the hospitalization. We present a case of APAP toxicity with likely contribution from the rarely described 5-oxoproline. CONCLUSIONS: ALF from APAP toxicity is not only associated with acute overdose, but also with usual administration. One of these processes is due to the accumulation of 5-oxoproline. Reference #1: Ostapowicz G, et al. “Results of a prospective study of acute liver failure at 17 tertiary care centers in the United States.” Annals of Internal Medicine 2002; 137:947-954. Reference #2: Ghanem CI. “Acetaminophen from liver to brain: new insights into drug pharmacological action and toxicity.” Pharmacological Research. 2016; 109:119–131. Reference #3: Bunchorntavakul C, Reddy KR. “Acetaminophen (APAP or N-Acetyl-p-Aminophenol) and acute liver failure.” Clinical Liver Disease. 2018; 22:325-246. DISCLOSURES: no disclosure on file for Alfredo Astua; No relevant relationships by Dawn Maldonado, source=Web Response No relevant relationships by Michael Megally, source=Web Response

OPLAH ablation leads to accumulation of 5-oxoproline, oxidative stress, fibrosis, and elevated fillings pressures: a murine model for heart failure with a preserved ejection fraction.

The prevalence of heart failure with a preserved ejection fraction (HFpEF) is increasing, but therapeutic options are limited. Oxidative stress is suggested to play an important role in the pathophysiology of HFpEF. However, whether oxidative stress is a bystander due to comorbidities or causative in itself remains unknown. Recent results have shown that depletion of 5-oxoprolinase (OPLAH) leads to 5-oxoproline accumulation, which is an important mediator of oxidative stress in the heart. We hypothesize that oxidative stress induced by elevated levels of 5-oxoproline leads to the onset of a murine HFpEF-like phenotype. Oplah full body knock-out (KO) mice had higher 5-oxoproline levels coupled to increased oxidative stress. Compared with wild-type (WT) littermates, KO mice had increased cardiac and renal fibrosis with concurrent elevated left ventricular (LV) filling pressures, impaired LV relaxation, yet a normal LV ejection fraction. Following the induction of cardiac ischaemia/reperfusion (IR) injury, 52.4% of the KO mice died compared with only 15.4% of the WT mice (P < 0.03). Furthermore, KO mice showed a significantly increased atrial, ventricular, kidney, and liver weights compared with WT mice (P < 0.05 for all). Cardiac and renal fibrosis were more pronounced following cardiac IR injury in the KO mice and these mice developed proteinuria post-IR injury. To further address the link between 5-oxoproline and HFpEF, 5-oxoproline was measured in the plasma of HFpEF patients. Compared with healthy controls (3.8 ± 0.6 µM), 5-oxoproline levels were significantly elevated in HFpEF patients (6.8 ± 1.9 µM, P < 0.0001). Furthermore, levels of 5-oxoproline were independently associated with more concentric remodelling on echocardiography. Oxidative stress induced by 5-oxoproline results in a murine phenotype reminiscent of the clinical manifestation of HFpEF without the need for surgical or pharmacological interference. Better understanding of the role of oxidative stress in HFpEF may potentially lead to novel therapeutic options.

From rodent heart to inborn errors of human metabolism

Recently, van der Pol et al. have linked accumulation of 5-oxoproline to myocardial dysfunction and -in rodent studies- have presented depletion of 5-oxoprolinase (OPLAH) as a result of cardiac injury, while OPLAH overexpression improved cardiac function after ischemic injury [1]. The same publication did also report elevated plasma 5-oxoproline in patients with heart failure and has suggested circulating 5-oxoproline as a potential diagnostic and prognostic biomarker.

Accumulation of 5-oxoproline in myocardial dysfunction and the protective effects of OPLAH.

In response to heart failure (HF), the heart reacts by repressing adult genes and expressing fetal genes, thereby returning to a more fetal-like gene profile. To identify genes involved in this process, we carried out transcriptional analysis on murine hearts at different stages of development and on hearts from adult mice with HF. Our screen identified Oplah, encoding for 5-oxoprolinase, a member of the γ-glutamyl cycle that functions by scavenging 5-oxoproline. OPLAH depletion occurred as a result of cardiac injury, leading to elevated 5-oxoproline and oxidative stress, whereas OPLAH overexpression improved cardiac function after ischemic injury. In HF patients, we observed elevated plasma 5-oxoproline, which was associated with a worse clinical outcome. Understanding and modulating fetal-like genes in the failing heart may lead to potential diagnostic, prognostic, and therapeutic options in HF.

Metabolic acidosis caused by concomitant use of paracetamol (acetaminophen) and flucloxacillin? A case report and a retrospective study

PurposeA patient was identified with severe metabolic acidosis, a high anion gap and 5-oxoproline accumulation, probably caused by the simultaneous use of paracetamol (acetaminophen) and flucloxacillin. We wanted to investigate the necessity to control the interaction between both drugs with an automatic alert system.MethodsTo investigate the relevance of the interaction of paracetamol and flucloxacillin, a retrospective study was conducted. Data on paracetamol and flucloxacillin prescriptions and laboratory data (pH, Na+, HCO3−, Cl−, albumin and 5-oxoproline levels) were combined to assess the prevalence of acidosis, calculate the anion gap and analyse 5-oxoproline levels in clinically admitted patients using both drugs simultaneously.ResultsIn the 2-year study period, approximately 53,000 admissions took place in our hospital. One thousand and fifty-seven patients used paracetamol and flucloxacillin simultaneously, of which 51 patients (4.8%) had a serum pH ≤ 7.35. One patient, the same patient as presented in the case report, had a high anion gap and a toxic level of 5-oxoproline.ConclusionThe prevalence of metabolic acidosis is very low and the only patient identified with the interaction was recognised during normal clinical care. We conclude that automatic alerts based on simultaneous use of paracetamol and flucloxacillin will generate too many signals. To recognise patients earlier and prevent severe outcomes, a warning system (clinical rule) based on paracetamol, flucloxacillin and pH measurement may be helpful. Early calculation of the anion gap can narrow the differential diagnosis of patients with metabolic acidosis and measurement of 5-oxoproline can explain acidosis due the interaction of paracetamol and flucloxacillin.

Metabolic acidosis with a high anion: a drug-drug interaction between Paracetamol and Flucloxacillin

Background: Five-oxoproline is a product of disordered glutathione metabolism in the gamma glutamyl cycle: glutathione deficiency removes the feedback inhibition resulting in the formation of γ -glutamylcysteine and elevated concentrations of γ -glutamylcysteine leading to the formation of 5-oxoproline, which is degraded by 5-oxoprolinase. Both paracetamol and flucloxacillin interact with the gamma glutamyl cyclus. Paracetamol depletes glutathione which leads to the accumulation of γ -glutamylcysteine that is a precursor for 5-oxoproline and flucloxacillin inhibits 5-oxoprolinase which also leads to accumulation of 5-oxoproline. The accumulation of 5-oxoproline, an acid residue, may lead to a high anion gap and a metabolic acidosis. Although a few cases of this drug-drug interaction are published, it is still not included in the summary of product characteristics of paracetamol and flucloxacillin or included in medication safety monitoring systems in hospitals and pharmacies. Material and Methods: We analyzed all submitted reports to the Netherlands' Pharmacovigilance Centre Lareb till 31 December 2014 on this drug-drug interaction. Results: Lareb received 3 reports of metabolic acidosis where both paracetamol and flucloxacillin, used in therapeutic doses, were marked as suspected and interacting drugs. The cases concern 3 females of older age (67, 72 and 78 years). The aberrant mechanism of the 72 year old female was treated with acetyl cysteine; she died. The other 2 women were treated with sodium bicarbonate and recovered. We could not confirm a relationship between the treatment and the outcome of the interaction. Conclusions: Our reported cases contribute to the suspicion of a relationship between metabolic acidosis and concomitantly used paracetamol and flucloxacillin. This drug interaction should be included in the summary of drug characteristics and included in medication monitoring systems in health institutions.

Acetaminophen Toxicity and 5-Oxoproline (Pyroglutamic Acid)

The acquired form of 5-oxoproline (pyroglutamic acid) metabolic acidosis was first described in 1989 and its relationship to chronic acetaminophen ingestion was proposed the next year. Since then, this cause of chronic anion gap metabolic acidosis has been increasingly recognized. Many cases go unrecognized because an assay for 5-oxoproline is not widely available. Most cases occur in malnourished, chronically ill women with a history of chronic acetaminophen ingestion. Acetaminophen levels are very rarely in the toxic range; rather, they are usually therapeutic or low. The disorder generally resolves with cessation of acetaminophen and administration of intravenous fluids. Methionine or N-acetyl cysteine may accelerate resolution and methionine is protective in a rodent model. The disorder has been attributed to glutathione depletion and activation of a key enzyme in the γ-glutamyl cycle. However, the specific metabolic derangements that cause the 5-oxoproline accumulation remain unclear. An ATP-depleting futile 5-oxoproline cycle can explain the accumulation of 5-oxoproline after chronic acetaminophen ingestion. This cycle is activated by the depletion of both glutathione and cysteine. This explanation contributes to our understanding of acetaminophen-induced 5-oxoproline metabolic acidosis and the beneficial role of N-acetyl cysteine therapy. The ATP-depleting futile 5-oxoproline cycle may also play a role in the energy depletions that occur in other acetaminophen-related toxic syndromes.

An unusual cause of high anion gap metabolic acidosis: pyroglutamic acidosis

Metabolic acidosis is a common acid-base disturbance in intensive care. A high anion gap indicates the presence of endogenous acids, which in critically ill patients are most commonly ketones, lactate and those accumulated in renal failure. However, excluding these causes means more rare forms of acid must be considered, including pyroglutamic acidosis. Pyroglutamic acidosis is caused by the accumulation of 5-oxoproline [1] due to the depletion of glutathione. This leads to loss of negative feedback and therefore the build-up of Y-glutamyl cysteine, which is converted to 5-oxoproline.

Paracetamol use and High Anion Gap Metabolic Acidosis

Accumulation of 5-oxoproline (pyroglutamic acid) has been reported as a rare cause of high anion gap metabolic acidosis. Chronic paracetamol ingestion in a susceptible individual can lead to accumulation of 5-oxoproline and a high anion gap metabolic acidosis. The condition resolves with supportive care and discontinuation of paracetamol and, most importantly, it can be prevented. This case report aims to alert clinicians to the condition as well as provide insight into the underlying mechanisms of the disease process. We report two cases of high anion gap metabolic acidosis due to accumulation of 5-oxoproline. Both patients had a recent history of regular paracetamol use for back pain on a background of poor nutrition. Common causes of high anion gap metabolic acidosis were excluded in both patients systematically. The underlying cause was discovered on testing for urinary 5-oxoproline. Both patients improved and the acidosis resolved upon withdrawal of paracetamol and other supportive measures. The need for a high index of suspicion and a detailed patient drug history is highlighted in these case reports, as raised anion gap metabolic acidosis is a common finding in critically ill patients. When lactate and ketones are absent, 5-oxoproline levels should be tested in patients who are taking paracetamol; especially in those who are malnourished or have other predisposing factors to reduced glutathione levels. Once suspected, paracetamol should be stopped, full supportive care should be initiated and treatment with N-acetylcysteine considered.

Metabolic acidosis in late pregnancy due to 5-oxoproline (pyroglutamic acid)—A case report

Introduction: Accumulation of 5-oxoproline (pyroglutamic acid) is a rare cause of severe, high anion gap metabolic acidosis in adults. Case: A 21 year old lady presented at 39 weeks gestation in her first pregnancy with 2 weeks history of shortness of breath. She suffered from ear ache and had been taking Paracetamol on regular basis for a year. She was admitted to having regular alcohol intake until the pregnancy when she stopped. She was not in acute distress and all her observations were stable. The laboratory analysis of renal function was normal. Arterial blood gas showed metabolic acidosis. The anion gap 34 mEq/l which was consistent with metabolic acidosis. Plasma aminoacid screen revealed no abnormality. Chest X-rays showed patchy consolidation keeping with a chest infection. Emergency caesarean section was carried out for fetal distress in first stage of labour. Urine and serum samples were taken which showed an increase in the serum level five Oxoproline to creatinine ratio indicating pyroglutamic metabolic acidosis. Polyglutamate was found in the urine She was admitted to intensive care unit; cardiovascular stable, had no signs of sepsis. She underwent ventilation and haemofiltration. On second day of admission metabolic acidosis was corrected. During the 48 hours treatment with supportive therapy produced general overall improvement. Discussion: Metabolic acidosis that caused by 5-oxoproline results from disruption of the gamma glutamyl cycle. Glutamile synthetase (GS) deficiency is an autosomol recessive disorder. With GS deficiency, reduced glutathione levels increase gamma glutamile synthetase activity, and the resulting gamma—glutamile cystine levels are particularly converted to 5-oxoproline. Intoxication of organic acids is a differential diagnosis of high anion gap metabolic acidosis with no renal impairment, there was no evidence of ethanol, methanol or ethylene glycol ingestion. Suspicion for 5-oxoproline-associated high anion gap metabolic acidosis should be entertained when the cause of high anion gap metabolic acidosis remains poorly defined, the anion gap cannot be explained reasonably by measured organic acids, and there is concomitant acetaminophen use. Conclusion: Clinicians need to be aware of this unusual cause of anion gap acidosis because it may be more common than expected, early discontinuation of the offending agent is therapeutic, and administration of N-acetylcysteine could be beneficial.

Abstract 3653: Cytotoxicity of curcumin combined with docetaxel at low or high dose implicates the antioxidant response and the glutathione cycle in MCF7 tumor cells: A metabolomics analysis

Abstract Curcumin (CCM) has antioxidant and chemopreventive properties at low dose. However, at high dose, it exhibits prooxidant activity. Recently, we showed using pharmacometabolomics that MCF7 cells response to docetaxel (DTX) involved, at low dose (1 nM), blockade of glutathione (GSH) biosynthesis, whereas, at high dose (5 µM), extensive GSH consumption. Cytotoxicity was significant even at low dose DTX. Here, we investigated whether CCM at 10 mg/l, a dose stimulating GSH synthesis, may interfere with GSH metabolism, reactive oxygen species (ROS) production, and cytotoxicity when combined to DTX at low and high doses. MCF7 cells were exposed for 72h to DTX at 1 nM and 5 µM in combination with 10 mg/l CCM as a 24h-pretreatment (PRE), cotreatment (CO) and 24h- and 48h-posttreatment (POST24 and POST48). Cytotoxicity was assessed from DNA content (Hoescht 33342), and ROS production from DNA strand breaks (Comet assay). Metabolomics analysis used high resolution magic angle spinning 1H-NMR spectroscopy, 2D spectral acquisitions and a new 2D-based quantification procedure, enabling to measure 32 metabolites. We focused on the variations of 13 metabolites from the GSH metabolism. Overall cytotoxicity of combinations increased according to POST48&amp;lt;POST24&amp;lt;CO&amp;lt;PRE (all, P&amp;lt;0.05), and ROS production was increased in PRE and CO (both, P&amp;lt;0.05), at low and high dose DTX. Metabolomics analysis of PRE at low and high dose DTX involved the preservation of GSH levels but an accumulation of 5-oxoproline (OP, X3.85 at 1 nM and X5.90 at 5 µM, both P&amp;lt;0.05), suggesting a blockade at oxoprolinase (OPase), step of the GSH cycle. Metabolomics analysis of CO at low dose DTX showed an increase in GSH (X1.25, P&amp;lt;0.05), together with starvation of most GSH precursors: glycine (Gly, X0.26, P&amp;lt;0.05) and homocysteine (Hcy, X0.24, P&amp;lt;0.05)). At high dose DTX, the GSH level was unchanged, but OP was increased (X4.26, P&amp;lt;0.05). Metabolomics analysis of POST24 at low dose DTX involved an increase in GSH (X1.22, P&amp;lt;0.05) suggesting increased biosynthesis of GSH but at the expense of taurine (X0.44, P=NS). At high dose DTX, GSH level was maintained, but associated with an increase in glutamate (Glu, X1.73, P&amp;lt;0.05). Metabolomics analysis of POST48 at low dose DTX showed an increase in GSH (X1.21, P&amp;lt;0.05) without signs of blockade of transsulfuration (Hcy X0.80, P=NS). At high dose DTX, the GSH level was maintained with mild signs of precursor starvation (Gly, X0.27, P&amp;lt;0.05), and decreased Glu derivatives (P&amp;lt;0.05), suggesting increased GSH biosynthesis and consumption. In all combinations, CCM at 10 mg/l generated an antioxidant response in MCF7 cells, with preserved or increased GSH levels. However, the underlying biochemical mechanism was different. Maximal cytotoxicity was obtained in PRE conditions involving ROS production, probable OPase blockade with the accumulation of biomarker OP. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3653.

Increased Anion Gap Metabolic Acidosis as a Result of 5-Oxoproline (Pyroglutamic Acid)

The endogenous organic acid metabolic acidoses that occur commonly in adults include lactic acidosis; ketoacidosis; acidosis that results from the ingestion of toxic substances such as methanol, ethylene glycol, or paraldehyde; and a component of the acidosis of kidney failure. Another rare but underdiagnosed cause of severe, high anion gap metabolic acidosis in adults is that due to accumulation of 5-oxoproline (pyroglutamic acid). Reported are four patients with this syndrome, and reviewed are 18 adult patients who were reported previously in the literature. Twenty-one patients had major exposure to acetaminophen (one only acute exposure). Eighteen (82%) of the 22 patients were women. Most of the patients were malnourished as a result of multiple medical comorbidities, and most had some degree of kidney dysfunction or overt failure. The chronic ingestion of acetaminophen, especially by malnourished women, may generate high anion gap metabolic acidosis. This undoubtedly is an underdiagnosed condition because measurements of serum and/or urinary 5-oxoproline levels are not readily available.

Transient 5-oxoprolinuria (pyroglutamic aciduria) with systemic acidosis in an adult receiving antibiotic therapy

5-Oxoprolinuria is a recognized condition with increased urinary excretion of 5-oxoproline and is associated with a variety of inborn metabolic defects involving the series of enzyme-linked reactions known as the gamma-glutamyl cycle. We report the unusual case of a 35-year-old woman who initially presented with staphylococcal pneumonia but went on to develop a transient high anion gap metabolic acidosis. The development and subsequent complete recovery from this acidosis were subsequently shown to be related in time to the intravenous administration of the antibiotics flucloxacillin and netilmicin. Analysis of the patient's urine for organic acids revealed massively increased excretions of 5-oxoproline at the peak of her acidosis. We suggest that this patient developed a transient disturbance in the gamma-glutamyl cycle involving the 5-oxoprolinase step, which resulted in accumulation of 5-oxoproline that caused a severe high anion gap metabolic acidosis. The administered antibiotics remain as possible causative agents.

Glutathione synthetase deficient human fibroblasts in culture

Cultured skin fibroblasts from patients with 5-oxoprolinuria caused by hereditary deficiency of glutathione synthetase have decreased levels of the corresponding enzyme as well as of glutathione. Fibroblasts from the same patients accumulated γ-glutamyl cysteine, but the levels were lower than those of glutathione in control fibroblasts. The uptake of [ 35S]cystine was equally rapid in control and patient fibroblasts. In the acid-soluble fraction γ-glutamyl-[ 35S]cysteine accumulated in fibroblasts from patients but not from controls. Appreciable turnover of γ-glutamyl cysteine and glutathione in the respective cell strains was observed, the half-lives of these pools being approximately 5 hours. The growth rate of mutant fibroblasts in culture was significantly slower than that of control fibroblasts. There was no significant accumulation of 5-oxoproline in the culture medium.

Studies on γ-Glutamyl Transpeptidase in Human and Rabbit Erythrocytes

Gamma-glutamyl transpeptidase transfers the gamma-glutamyl moiety of glutathione to a variety of acceptor amino acids. Through the operation of the gamma-glutamyl-cyclotransferase cycle, this enzyme has been implicated in the transport of amino acids into cells, especially the cells of the proximal tubules of kidney. It has been reported to be present in rabbit erythrocytes. However, using white cell-free preparations, we have not been able to demonstrate the presence of gamma-glutamyl transpeptidase in human or rabbit erythrocytes either by measuring the utilization of GSH or by following the formation of the product. 14C-L-methionine was used as acceptor amino acid, and the formation of gamma-glutamyl-14C-L-methionine was followed. Using similar conditions, we have been able to demonstrate the presence of gamma-glutamyl transpeptidase in human and rabbit leukocytes and in human kidney. In contrast to a previous report, we were unable to find the accumulation of 5-oxoproline, an intermediate of the gamma-glutamyl-cyclotransferase pathway in human red cells incubated in Krebs-Ringer solution. Immunologic studies demonstrated that human red cell membranes contained no protein antigenically similar to kidney gamma-glutamyl transpeptidase. Thus our studies indicated that in human and rabbit erythrocytes, the gamma-glutamyl transpeptidase-cyclotransferase pathway was not operative.

Studies on gamma-glutamyl transpeptidase in human and rabbit erythrocytes

Gamma-glutamyl transpeptidase transfers the gamma-glutamyl moiety of glutathione to a variety of acceptor amino acids. Through the operation of the gamma-glutamyl-cyclotransferase cycle, this enzyme has been implicated in the transport of amino acids into cells, especially the cells of the proximal tubules of kidney. It has been reported to be present in rabbit erythrocytes. However, using white cell-free preparations, we have not been able to demonstrate the presence of gamma-glutamyl transpeptidase in human or rabbit erythrocytes either by measuring the utilization of GSH or by following the formation of the product. 14C-L-methionine was used as acceptor amino acid, and the formation of gamma-glutamyl-14C-L-methionine was followed. Using similar conditions, we have been able to demonstrate the presence of gamma-glutamyl transpeptidase in human and rabbit leukocytes and in human kidney. In contrast to a previous report, we were unable to find the accumulation of 5-oxoproline, an intermediate of the gamma-glutamyl- cyclotransferase pathway in human red cells incubated in Krebs-Ringer solution. Immunologic studies demonstrated that human red cell membranes contained no protein antigenically similar to kidney gamma- glutamyl transpeptidase. Thus our studies indicated that in human and rabbit erythrocytes, the gamma-glutamyl transpeptidase-cyclotransferase pathway was not operative.