Caenorhabditis elegans as a model for studies on quinolinic acid-induced NMDAR-dependent glutamatergic disorders.

Quinolinic acid (QUIN) is an agonist of the neurotransmitter glutamate (Glu) capable of binding to N-methyl-D-aspartate receptors (NMDAR) increasing glutamatergic signaling. QUIN is known for being an endogenous neurotoxin, able to induce neurodegeneration. In Caenorhabditis elegans, the mechanism by which QUIN induces behavioral and metabolic toxicity has not been fully elucidated. The effects of QUIN on behavioral and metabolic parameters in nmr-1 and nmr-2 NMDA receptors in transgenic and wild-type (WT) worms were performed to decipher the pathway by which QUIN exerts its toxicity. QUIN increased locomotion parameters such as wavelength and movement amplitude medium, as well as speed and displacement, without modifying the number of body bends in an NMDAR-dependent-manner. QUIN increased the response time to the chemical stimulant 1-octanol, which is modulated by glutamatergic neurotransmission in the ASH neuron. Brood size increased after exposure to QUIN, dependent upon nmr-2/NMDA-receptor, with no change in lifespan. Oxygen consumption, mitochondrial membrane potential, and the flow of coupled and unbound electrons to ATP production were reduced by QUIN in wild-type animals, but did not alter citrate synthase activity, altering the functionality but the mitochondrial viability. Notably, QUIN modified fine locomotor and chemosensory behavioral parameters, as well as metabolic parameters, analogous to previously reported effects in mammals. Our results indicate that QUIN can be used as a neurotoxin to elicit glutamatergic dysfunction in C. elegans in a way analogous to other animal models.

Hypermethioninemia induces memory deficits and morphological changes in hippocampus of young rats: implications on pathogenesis.

The aim of this study was to investigate the effect of the chronic administration of methionine (Met) and/or its metabolite, methionine sulfoxide (MetO), on the behavior and neurochemical parameters of young rats. Rats were treated with saline (control), Met (0.2-0.4 g/kg), MetO (0.05-0.1 g/kg), and/or a combination of Met + MetO, subcutaneously twice a day from postnatal day 6 (P6) to P28. The results showed that Met, MetO, and Met + MetO impaired short-term and spatial memories (P < 0.05), reduced rearing and grooming (P < 0.05), but did not alter locomotor activity (P > 0.05). Acetylcholinesterase activity was increased in the cerebral cortex, hippocampus, and striatum following Met and/or MetO (P < 0.05) treatment, while Na+, K+-ATPase activity was reduced in the hippocampus (P < 0.05). There was an increase in the level of thiobarbituric acid reactive substances (TBARS) in the cerebral cortex in Met-, MetO-, and Met + MetO-treated rats (P < 0.05). Met and/or MetO treatment reduced superoxide dismutase, catalase, and glutathione peroxidase activity, total thiol content, and nitrite levels, and increased reactive oxygen species and TBARS levels in the hippocampus and striatum (P < 0.05). Hippocampal brain-derived neurotrophic factor was reduced by MetO and Met + MetO compared with the control group. The number of NeuN-positive cells was decreased in the CA3 in Met + MetO group and in the dentate gyrus in the Met, MetO, and Met + MetO groups compared to control group (P < 0.05). Taken together, these findings further increase our understanding of changes in the brain in hypermethioninemia by elucidating behavioral alterations, biological mechanisms, and the vulnerability of brain function to high concentrations of Met and MetO.

Excessive Methionine Supplementation Exacerbates the Development of Abdominal Aortic Aneurysm in Rats.

OBJECTIVE: The relationship between methionine (Met) and abdominal aortic aneurysm (AAA) has been previously demonstrated, but the mechanisms controlling this association remain unclear. This study investigated the potential contribution of hypermethioninemia (HMet) to the development of AAA. METHODS: A model of AAA was induced by intraluminal porcine pancreatic elastase (PPE) infusion in 60 male Sprague-Dawley rats divided into 4 groups (n = 15 per group). Met was supplied by intragastric administration (1 g/kg body weight/day) from 1 week before surgery until 4 weeks after surgery. The aortic diameter was measured by ultrasound. Aortas were collected 4 weeks after surgery and subjected to biochemical analysis, histological assays, and transmission electron microscopy. RESULTS: After 5 weeks of Met supplementation, HMet increased the dilation ratio of the HMet + PPE group, and hyperhomocysteinemia was also induced in HMet and HMet + PPE rats. Increased matrix metalloproteinase-2 (MMP-2), osteopontin, and interleukin-6 expression was detected in HMet + PPE rats. Furthermore, increased autophagy was detected in the HMet + PPE group. CONCLUSION: This study demonstrates that HMet may exacerbate the formation of AAA due to the increased dilation ratio partially via enhancing MMP-2 and inflammatory responses.

Lesson of the month 1: A rare adverse reaction between flucloxacillin and paracetamol.

Flucloxacillin, a beta-lactam antibiotic, is a commonly prescribed antibiotic for the treatment of infections caused by staphylococci and streptococci, most notably Staphylococcus aureus Paracetamol is one of the most dispensed medications by NHS England and is used for the treatment of fever and pain.1 However most doctors are unaware that concurrent use of these drugs can cause a potentially fatal drug interaction due to pyroglutamic acidosis (PGA), also known as 5-oxoprolinaemia. PGA is a rare cause of raised anion gap metabolic acidosis due to disruption of the γ-glutamyl cycle. We report the case of a patient with multiple comorbidities who developed PGA due to coadministration of paracetamol and flucloxacillin.

Ammonia role in glial dysfunction in methylmalonic acidemia.

Hyperammonemia is a common finding in patients with methylmalonic acidemia. However, its contribution to methylmalonate (MMA)-induced neurotoxicity is poorly understood. The aim of this study was evaluate whether an acute metabolic damage to brain during the neonatal period may disrupt cerebral development, leading to neurodevelopmental disorders, as memory deficit. Mice received a single intracerebroventricular dose of MMA and/or NH4Cl, administered 12 hs after birth. The maze tests showed that MMA and NH4Cl injected animals (21 and 40 days old) exhibited deficit in the working memory test, but not in the reference memory test. Furthermore, MMA and NH4Cl increased the levels of 2',7'-dichlorofluorescein-diacetate (DCF), TNF-α, IL-1ß in the cortex, hippocampus and striatum of mice. MMA and NH4Cl also increased glial proliferation in all structures. Since the treatment of MMA and ammonia increased cytokines levels, we suggested that it might be a consequence of the glial activation induced by the acid and ammonia, leading to delay in the developing brain and contributing to behavioral alterations. However, this hypothesis is speculative in nature and more studies are needed to clarify this possibility.

[Acetaminophen induced 5-oxoproline acidosis: An uncommon case of high anion gap metabolic acidosis]. / Acidose à la 5-oxoproline induite par le paracétamol : une cause rare d'acidose métabolique à trou anionique augmenté.

The most common causes of high anion gap metabolic acidosis (HAGMA) are lactic acidosis, ketoacidosis, and intoxications. Nevertheless, clinicians can be faced with unexplained HAGMA, with a need to look for less common etiologies. We describe a case of 5-oxoproline (pyroglutamate) acidosis due to chronic acetaminophen ingestion at therapeutic dose in a 79-year-old inpatient. The pathophysiology of this condition is detailed, with abnormalities in the gamma-glutamyl cycle due to acetaminophen ingestion and severe chronic morbidities, resulting in glutathione and cysteine deficiency and then accumulation of 5-oxoproline. In HAGMA, when usual causes have been excluded, 5-oxoproline acidosis should be suspected in patients with chronic morbidities and acetaminophen ingestion. This diagnosis should be kept in mind because it generally resolves quickly with cessation of acetaminophen and administration of intravenous fluids.

Methionine Administration in Pregnant Rats Causes Memory Deficit in the Offspring and Alters Ultrastructure in Brain Tissue.

In the present work, we evaluated the effect of gestational hypermethioninemia on locomotor activity, anxiety, memory, and exploratory behavior of rat offspring through the following behavior tests: open field, object recognition, and inhibitory avoidance. Histological analysis was also done in the brain tissue of pups. Wistar female rats received methionine (2.68 µmol/g body weight) by subcutaneous injections during pregnancy. Control rats received saline. Histological analyses were made in brain tissue from 21 and 30 days of age pups. Another group was left to recover until the 30th day of life to perform behavior tests. Results from open field task showed that pups exposed to methionine during intrauterine development spent more time in the center of the arena. In the object recognition memory task, we observed that methionine administration during pregnancy reduced total exploration time of rat offspring during training session. The test session showed that methionine reduced the recognition index. Regarding to inhibitory avoidance task, the decrease in the step-down latency at 1 and 24 h after training demonstrated that maternal hypermethioninemia impaired short-term and long-term memories of rat offspring. Electron microscopy revealed alterations in the ultrastructure of neurons at 21 and 30 days of age. Our findings suggest that the cell morphological changes caused by maternal hypermethioninemia may be, at least partially, associated to the memory deficit of rat offspring.

Maternal Hypermethioninemia Affects Neurons Number, Neurotrophins Levels, Energy Metabolism, and Na+,K+-ATPase Expression/Content in Brain of Rat Offspring.

In the current study, we verified the effects of maternal hypermethioninemia on the number of neurons, apoptosis, nerve growth factor, and brain-derived neurotrophic factor levels, energy metabolism parameters (succinate dehydrogenase, complex II, and cytochrome c oxidase), expression and immunocontent of Na+,K+-ATPase, edema formation, inflammatory markers (tumor necrosis factor-alpha and interleukin-6), and mitochondrial hydrogen peroxide levels in the encephalon from the offspring. Pregnant Wistar rats were divided into two groups: the first one received saline (control) and the second group received 2.68 µmol methionine/g body weight by subcutaneous injections twice a day during gestation (approximately 21 days). After parturition, pups were killed at the 21st day of life for removal of encephalon. Neuronal staining (anti-NeuN) revealed a reduction in number of neurons, which was associated to decreased nerve growth factor and brain-derived neurotrophic factor levels. Maternal hypermethioninemia also reduced succinate dehydrogenase and complex II activities and increased expression and immunocontent of Na+,K+-ATPase alpha subunits. These results indicate that maternal hypermethioninemia may be a predisposing factor for damage to the brain during the intrauterine life.

Chronic administration of methionine and/or methionine sulfoxide alters oxidative stress parameters and ALA-D activity in liver and kidney of young rats.

High levels of methionine (Met) and methionine sulfoxide (MetO) are found in several genetic abnormalities. Oxidative stress is involved in the pathophysiology of many inborn errors of metabolism. However, little is known about the role of oxidative damage in hepatic and renal changes in hypermethioninemia. We investigated the effect of chronic treatment with Met and/or MetO on oxidative stress parameters in liver and kidney, as lipid peroxidation (TBARS), total sulfhydryl content (SH), reactive oxygen species (ROS) and enzymes activities superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and delta aminolevulinic dehydratase (ALA-D). Serum biochemical parameters were evaluated. Wistar rats were treated daily with two subcutaneous injections of saline (control), Met (0.2-0.4 g/kg), MetO (0.05-0.1 g/kg) and the association between these (Met plus MetO) from the 6th to the 28th day of life. Our data demonstrated an increase of glucose and urea levels in all experimental groups. Cholesterol (MetO and Met plus MetO) were decreased and triglycerides (MetO) were increased. SOD (MetO and Met plus MetO) and CAT (Met, MetO and Met plus MetO) activities were decreased, while GPx was enhanced by MetO and Met plus MetO treatment in liver. In kidney, we observed a reduction of SH levels, SOD and CAT activities and an increase of TBARS levels in all experimental groups. ROS levels in kidney were increased in MetO and Met plus MetO groups. ALA-D activity was enhanced in liver (MetO and Met plus MetO) and kidney (Met plus MetO). These findings help to understand the pathophysiology of hepatic and renal alterations present in hypermethioninemia.

Ammonium accumulation is a primary effect of 2-methylcitrate exposure in an in vitro model for brain damage in methylmalonic aciduria.

Using 3D organotypic rat brain cell cultures in aggregates we recently identified 2-methylcitrate (2-MCA) as the main toxic metabolite for developing brain cells in methylmalonic aciduria. Exposure to 2-MCA triggered morphological changes and apoptosis of brain cells. This was accompanied by increased ammonium and decreased glutamine levels. However, the sequence and causal relationship between these phenomena remained unclear. To understand the sequence and time course of pathogenic events, we exposed 3D rat brain cell aggregates to different concentrations of 2-MCA (0.1, 0.33 and 1.0mM) from day in vitro (DIV) 11 to 14. Aggregates were harvested at different time points from DIV 12 to 19. We compared the effects of a single dose of 1mM 2-MCA administered on DIV 11 to the effects of repeated doses of 1mM 2-MCA. Pan-caspase inhibitors Z-VAD FMK or Q-VD-OPh were used to block apoptosis. Ammonium accumulation in the culture medium started within few hours after the first 2-MCA exposure. Morphological changes of the developing brain cells were already visible after 17h. The highest rate of cleaved caspase-3 was observed after 72h. A dose-response relationship was observed for all effects. Surprisingly, a single dose of 1mM 2-MCA was sufficient to induce all of the biochemical and morphological changes in this model. 2-MCA-induced ammonium accumulation and morphological changes were not prevented by concomitant treatment of the cultures with pan-caspase inhibitors Z-VAD FMK or Q-VD-OPh: ammonium increased rapidly after a single 1mM 2-MCA administration even after apoptosis blockade. We conclude that following exposure to 2-MCA, ammonium production in brain cell cultures is an early phenomenon, preceding cell degeneration and apoptosis, and may actually be the cause of the other changes observed. The fact that a single dose of 1mM 2-MCA is sufficient to induce deleterious effects over several days highlights the potential damaging effects of even short-lasting metabolic decompensations in children affected by methylmalonic aciduria.

Chemically induced acute model of sarcosinemia in wistar rats.

In the present study, we developed an acute chemically induced model of sarcosinemia in Wistar rats. Wistar rats of 7, 14 and 21 postpartum days received sarcosine intraperitoneally in doses of 0.5 mmol/Kg of body weight three time a day at intervals of 3 h. Control animals received saline solution (NaCl 0.85 g%) in the same volume (10 mL/Kg of body weight). The animals were killed after 30 min, 1, 2, 3 or 6 h after the last injection and the brain and the blood were collected for sarcosine measurement. The results showed that plasma and brain sarcosine concentrations achieved levels three to four times higher than the normal levels and decreased in a time-dependent way, achieving normal levels after 6 hours. Considering that experimental animal models are useful to investigate the pathophysiology of human disorders, our model of sarcosinemia may be useful for the research of the mechanisms of neurological dysfunction caused by high tissue sarcosine levels.

New developments in diagnosis and treatment update: Schizophrenia/first episode psychosis in children and adolescents.

Childhood onset schizophrenia (COS) is diagnosed before the age of 13 years, and early onset schizophrenia (EOS) is diagnosed before the age of 18 years. EOS is considered extremely rare and its prevalence in comparison to the worldwide prevalence of schizophrenia (1%) has not adequately been studied. Patients who experience the first episode of psychosis need to be treated early and optimally to lessen the morbidity and improve the outcome of the illness. Treatment needs to be a combination of both pharmacological and non-pharmacological modalities. Pharmacological intervention is necessary for remission, improvement of positive symptoms and to aid with the efficacy of psychosocial interventions. There is a lack of efficacy and safety data of the use of antipsychotic medication in children, with most of the information available being extrapolations of adult data. An increased use of atypical antipsychotic drugs in the treatment of EOS has been accompanied by growing concern about the appropriate use and associated side effects in children and adolescents. This update highlights new developments, concepts and treatment trends in EOS.

Development of an animal model for gestational hypermethioninemia in rat and its effect on brain Na⁺,K⁺-ATPase/Mg²âº-ATPase activity and oxidative status of the offspring.

In the present study we developed a chemically induced experimental model for gestational hypermethioninemia in rats and evaluated in the offspring the activities of Na(+),K(+)-ATPase and Mg(2+)-ATPase, as well as oxidative stress parameters, namely sulfhydryl content, thiobarbituric acid-reactive substances and the antioxidant enzymes superoxide dismutase and catalase in encephalon. Serum and encephalon levels of methionine and total homocysteine were also evaluated in mother rats and in the offspring. Pregnant Wistar rats received two daily subcutaneous injections of methionine throughout the gestational period (21 days). During the treatment, a group of pregnant rats received dose 1 (1.34 µmol methionine/g body weight) and the other one received dose 2 (2.68 µmol methionine/g body weight). Control group received saline. After the rats give birth, a first group of pups was killed at the 7th day of life and the second group at the 21th day of life for removal of serum and encephalon. Mother rats were killed at the 21th day postpartum for removal of serum and encephalon. Both doses 1 and 2 increased methionine levels in encephalon of the mother rats and dose 2 increased methionine levels in encephalon of the offspring. Maternal hypermethioninemia also decreased the activities of Na(+),K(+)-ATPase, Mg(2+)-ATPase and catalase, as well as reduced total sulfhydryl content in the encephalon of the pups. This chemical model seems to be appropriate for studies aiming to investigate the effect of maternal hypermethioninemia on the developing brain during gestation in order to clarify possible neurochemical changes in the offspring.

Chronic administration of methylmalonate on young rats alters neuroinflammatory markers and spatial memory.

The methylmalonic acidemia is an inborn error of metabolism (IEM) characterized by methylmalonic acid (MMA) accumulation in body fluids and tissues, causing neurological dysfunction, mitochondrial failure and oxidative stress. Although neurological evidence demonstrate that infection and/or inflammation mediators facilitate metabolic crises in patients, the involvement of neuroinflammatory processes in the neuropathology of this organic acidemia is not yet established. In this experimental study, we used newborn Wistar rats to induce a model of chronic acidemia via subcutaneous injections of methylmalonate (MMA, from 5th to 28th day of life, twice a day, ranged from 0.72 to 1.67 µmol/g as a function of animal age). In the following days (29th-31st) animal behavior was assessed in the object exploration test and elevated plus maze. It was performed differential cell and the number of neutrophils counting and interleukin-1 beta (IL-1ß) and tumor necrosis factor-alpha (TNF-α) levels in the blood, as well as levels of IL-1ß, TNF-α, inducible nitric oxide synthase (iNOS) and 3-nitrotyrosine (3-NT) in the cerebral cortex were measured. Behavioral tests showed that animals injected chronically with MMA have a reduction in the recognition index (R.I.) when the objects were arranged in a new configuration space, but do not exhibit anxiety-like behaviors. The blood of MMA-treated animals showed a decrease in the number of polymorphonuclear and neutrophils, and an increase in mononuclear and other cell types, as well as an increase of IL-1ß and TNF-α levels. Concomitantly, MMA increased levels of IL-1ß, TNF-α, and expression of iNOS and 3-NT in the cerebral cortex of rats. The overall results indicate that chronic administration of MMA increased pro-inflammatory markers in the cerebral cortex, reduced immune system defenses in blood, and coincide with the behavioral changes found in young rats. This leads to speculate that, through mechanisms not yet elucidated, the neuroinflammatory processes during critical periods of development may contribute to the progression of cognitive impairment in patients with methylmalonic acidemia.

Acute renal failure potentiates methylmalonate-induced oxidative stress in brain and kidney of rats.

Tissue methylmalonic acid (MMA) accumulation is the biochemical hallmark of methylmalonic acidemia. The disease is clinically characterized by progressive neurological deterioration and kidney failure, whose pathophysiology is still unclear. In the present work we investigated the effects of acute MMA administration on various parameters of oxidative stress in cerebral cortex and kidney of young rats, as well as the influence of acute renal failure on MMA-elicited effects on these parameters. Acute renal failure was induced by gentamicin, an aminoglycoside antibiotic whose utilization over prolonged periods causes nephrotoxicity. The administration of gentamicin alone increased carbonyl content and inhibited superoxide dismutase (SOD) activity in cerebral cortex, as well as increased thiobarbituric acid-reactive substances (TBA-RS) and sulfhydryl levels and diminished glutathione peroxidase activity in kidney. On the other hand, MMA administration increased TBA-RS levels in cerebral cortex and decreased SOD activity in kidney. Furthermore, the simultaneous administration of MMA and gentamicin to the rats provoked an augment in TBA-RS levels and superoxide generation in cerebral cortex and in TBA-RS, carbonyl and sulfhydryl levels in kidney, while diminished SOD activity in both studied tissues. Finally, nitrate/nitrite content, reduced glutathione levels, 2',7'-dihydrodichlorofluorescein oxidation and catalase activity were not affected by this animal treatment in either tissue. In conclusion, our present data are in line with the hypothesis that MMA acts as a toxin in brain and kidney of rats and suggest that renal injury potentiates the toxicity of MMA on oxidative stress parameters in brain and peripheral tissues.

Impairment of brain redox homeostasis caused by the major metabolites accumulating in hyperornithinemia-hyperammonemia-homocitrullinuria syndrome in vivo.

Ornithine, ammonia and homocitrulline are the major metabolites accumulating in hyperornithinemia-hyperammonemia-homocitrullinuria syndrome, a genetic disorder characterized by neurological regression whose pathogenesis is still not understood. The present work investigated the in vivo effects of intracerebroventricular administration of ornithine and homocitrulline in the presence or absence of hyperammonemia induced by intraperitoneal urease treatment on a large spectrum of oxidative stress parameters in cerebral cortex from young rats in order to better understand the role of these metabolites on brain damage. Ornithine increased thiobarbituric acid-reactive substances (TBA-RS) levels and carbonyl formation and decreased total antioxidant status (TAS) levels. We also observed that the combination of hyperammonemia with ornithine resulted in significant decreases of sulfhydryl levels, reduced glutathione (GSH) concentrations and the activities of catalase (CAT) and glutathione peroxidase (GPx), highlighting a synergistic effect of ornithine and ammonia. Furthermore, homocitrulline caused increases of TBA-RS values and carbonyl formation, as well as decreases of GSH concentrations and GPx activity. Hcit with hyperammonemia (urease treatment) decreased TAS and CAT activity. We also showed that urease treatment per se was able to enhance TBA-RS levels. Finally, nitric oxide production was not altered by Orn and Hcit alone or in combination with hyperammonemia. Our data indicate that the major metabolites accumulating in hyperornithinemia-hyperammonemia-homocitrullinuria syndrome provoke lipid and protein oxidative damage and a reduction of the antioxidant defenses in the brain. Therefore, it is presumed that oxidative stress may represent a relevant pathomechanism involved in the brain damage found in patients affected by this disease.

Chronic postnatal ornithine administration to rats provokes learning deficit in the open field task.

Hyperornithinemia is the biochemical hallmark of hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, an inherited metabolic disease clinically characterized by mental retardation whose pathogenesis is still poorly known. In the present work, we produced a chemical animal model of hyperornithinemia induced by a subcutaneous injection of saline-buffered Orn (2-5 µmol/g body weight) to rats. High brain Orn concentrations were achieved, indicating that Orn is permeable to the blood brain barrier. We then investigated the effect of early chronic postnatal administration of Orn on physical development and on the performance of adult rats in the open field, the Morris water maze and in the step down inhibitory avoidance tasks. Chronic Orn treatment had no effect on the appearance of coat, eye opening or upper incisor eruption, nor on the free-fall righting reflex and on the adult rat performance in the Morris water maze and in the inhibitory avoidance tasks, suggesting that physical development, aversive and spatial localization were not changed by Orn. However, Orn-treated rats did not habituate to the open field apparatus, implying a deficit of learning/memory. Motor activity was the same for Orn- and saline- injected animals. We also verified that Orn subcutaneous injections provoked lipid peroxidation in the brain, as determined by a significant increase of thiobarbituric acid-reactive substances levels. Our results indicate that chronic early postnatal hyperornithinemia may impair the central nervous system, causing minor disabilities which result in specific learning deficiencies.

5-oxoprolinemia causing elevated anion gap metabolic acidosis in the setting of acetaminophen use.

BACKGROUND: Anion gap metabolic acidosis is typically encountered in the emergency department (ED) setting as the result of shock, other endogenous metabolic derangements, or from exogenous toxicants. The differential diagnosis for toxicant-related acidosis (exemplified by common mnemonics) emphasizes acute overdose. CASE REPORT: The case we present manifested an anion gap (AG) metabolic acidosis due to a chronic intoxication: acetaminophen (APAP) overuse over a period of weeks. Lactic acidemia did not account for the AG. In this case, chronic APAP overuse, combined with decreased caloric intake and weight loss, was associated with excess 5-oxoproline (pyroglutamic acid), an organic acid accounting for the AG metabolic acidosis. Overproduction of 5-oxoproline is attributed to depleted glutathione stores, leading to perturbation in the γ-glutamyl cycle. The patient was treated with supportive care and with N-acetylcysteine (NAC). By repleting glutathione, NAC may facilitate the resolution of excess 5-oxoproline. CONCLUSIONS: The ED differential diagnosis of AG metabolic acidosis in chronic APAP overuse, especially with concomitant nutritional compromise, should include 5-oxoprolinemia.

Experimental hyperprolinemia induces mild oxidative stress, metabolic changes, and tissue adaptation in rat liver.

The present study investigated the effects of chronic hyperprolinemia on oxidative and metabolic status in liver and serum of rats. Wistar rats received daily subcutaneous injections of proline from their 6th to 28th day of life. Twelve hours after the last injection the rats were sacrificed and liver and serum were collected. Results showed that hyperprolinemia induced a significant reduction in total antioxidant potential and thiobarbituric acid-reactive substances. The activities of the antioxidant enzymes catalase and superoxide dismutase were significantly increased after chronic proline administration, while glutathione (GSH) peroxidase activity, dichlorofluorescin oxidation, GSH, sulfhydryl, and carbonyl content remained unaltered. Histological analyses of the liver revealed that proline treatment induced changes of the hepatic microarchitecture and increased the number of inflammatory cells and the glycogen content. Biochemical determination also demonstrated an increase in glycogen concentration, as well as a higher synthesis of glycogen in liver of hyperprolinemic rats. Regarding to hepatic metabolism, it was observed an increase on glucose oxidation and a decrease on lipid synthesis from glucose. However, hepatic lipid content and serum glucose levels were not changed. Proline administration did not alter the aminotransferases activities and serum markers of hepatic injury. Our findings suggest that hyperprolinemia alters the liver homeostasis possibly by induction of a mild degree of oxidative stress and metabolic changes. The hepatic alterations caused by proline probably do not implicate in substantial hepatic tissue damage, but rather demonstrate a process of adaptation of this tissue to oxidative stress. However, the biological significance of these findings requires additional investigation.