Caroline Paula Mescka

In vivo neuroprotective effect of L-carnitine against oxidative stress in maple syrup urine disease

Maple syrup urine disease (MSUD) is an autosomal recessive inborn error of metabolism caused by deficiency of the activity of the mitochondrial enzyme complex branched-chain α-keto acid dehydrogenase (BCKAD) leading to accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine and valine and their corresponding branched-chain α-keto acids. Affected patients present severe brain dysfunction manifested such as ataxia, seizures, coma, psychomotor delay and mental retardation. The mechanisms of brain damage in this disease remain poorly understood. Recent studies have shown that oxidative stress may be involved in neuropathology of MSUD. L-Carnitine (L-Car) is considered a potential antioxidant through its action against peroxidation as a scavenger of reactive oxygen species and by its stabilizing effect of damage to cell membranes. In this study we evaluate the possible neuroprotective in vivo effects of L-Car against pro-oxidative effects of BCAA in cerebral cortex of rats. L-Car prevented lipoperoxidation, measured by thiobarbituric acid-reactive substances, protein damage, measured by sulfhydryl and protein carbonyl content and alteration on catalase and glutathione peroxidase activity in rat cortex from a chemically-induced model of MSUD. Our data clearly show that L-Car may be an efficient antioxidant, protecting against the oxidative stress promoted by BCAA. If the present results are confirmed in MSUD patients, this could represent an additional therapeutic approach to the patients affected by this disease.

Neurological Damage in MSUD: The Role of Oxidative Stress

Maple syrup urine disease (MSUD) is a metabolic disease caused by a deficiency in the branched-chain α-keto acid dehydrogenase complex, leading to the accumulation of branched-chain keto acids and their corresponding branched-chain amino acids (BCAA) in patients. Treatment involves protein-restricted diet and the supplementation with a specific formula containing essential amino acids (except BCAA) and micronutrients, in order to avoid the appearance of neurological symptoms. Although the accumulation of toxic metabolites is associated to appearance of symptoms, the mechanisms underlying the brain damage in MSUD remain unclear, and new evidence has emerged indicating that oxidative stress contributes to this damage. In this context, this review addresses some of the recent findings obtained from cells lines, animal studies, and from patients indicating that oxidative stress is an important determinant of the pathophysiology of MSUD. Recent works have shown that the metabolites accumulated in the disease induce morphological alterations in C6 glioma cells through nitrogen reactive species generation. In addition, several works demonstrated that the levels of important antioxidants decrease in animal models and also in MSUD patients (what have been attributed to protein-restricted diets). Also, markers of lipid, protein, and DNA oxidative damage have been reported in MSUD, probably secondary to the high production of free radicals. Considering these findings, it is well-established that oxidative stress contributes to brain damage in MSUD, and this review offers new perspectives for the prevention of the neurological damage in MSUD, which may include the use of appropriate antioxidants as a novel adjuvant therapy for patients.

Protein and lipid damage in maple syrup urine disease patients: l-carnitine effect

Maple syrup urine disease (MSUD) is an inborn error of metabolism biochemically characterized by elevated levels of the branched chain amino acids (BCAA) leucine, isoleucine, valine and the corresponding branched‐chain α‐keto acids. This disorder is clinically characterized by ketoacidosis, seizures, coma, psychomotor delay and mental retardation whose pathophysiology is not completely understood. Recent studies have shown that oxidative stress may be involved in neuropathology of MSUD. l‐Carnitine (l‐Car) plays a central role in the cellular energy metabolism because it transports long‐chain fatty acids for oxidation and ATP generation. In recent years many studies have demonstrated the antioxidant role of this compound. In this work, we investigated the effect of BCAA‐restricted diet supplemented or not with l‐Car on lipid peroxidation and in protein oxidation in MSUD patients. We found a significant increase of malondialdehyde and of carbonyl content in plasma of MSUD patients under BCAA‐restricted diet compared to controls. Furthermore, patients under BCAA‐restricted diet plus l‐Car supplementation presented a marked reduction of malondialdehyde content in relation to controls, reducing the lipid peroxidation. In addition, free l‐Car concentrations were negatively correlated with malondialdehyde levels. Our data show that l‐Car may have an antioxidant effect, protecting against the lipid peroxidation and this could represent an additional therapeutic approach to the patients affected by MSUD.

Oxidative stress in Niemann-Pick type C patients: a protective role of N-butyl-deoxynojirimycin therapy.

Niemann‐Pick type C (NPC) is a rare neurodegenerative disorder biochemically characterized by the accumulation of cholesterol and glycosphingolipids in late endosomes and lysosomes of the affected patients. N‐butyl‐deoxynojirimycin is the only approved drug for patients with NPC disease. It inhibits glycosphingolipid synthesis, therefore reducing intracellular lipid storage. Although the mechanisms underlying the neurologic damage in the NPC disease are not yet well established, in vitro and in vivo studies suggest an involvement of reactive species in the pathophysiology of this disease. In this work we aimed to evaluate parameters of lipid and protein oxidation, measured by thiobarbituric acid‐reactive species (TBA‐RS) and protein carbonyl formation, respectively, as well as the enzymatic and non‐enzymatic antioxidant defenses in plasma, erythrocytes and fibroblasts from NPC1 patients, at diagnosis and during treatment with N‐butyl‐deoxynojirimycin. We found a significant increase of TBA‐RS in plasma and fibroblasts, as well as increased protein carbonyl formation and decreased total antioxidant status (TAS) in plasma of untreated NPC1 patients as compared to the control group. In addition, erythrocyte glutathione peroxidase (GSH‐Px) activity was increased, whereas CAT and SOD activities were normal in these patients. We also observed that patients treated with N‐butyl‐deoxynojirimycin normalized plasma TBA‐RS and TAS, as well as erythrocyte GSH‐Px activity. Taken together, the present data indicate that oxidative stress is increased in patients with NPC1 disease and that treatment with N‐butyl‐deoxynojirimycin is able to confer protection against this pathological process.

Oxidative Stress Parameters in Urine from Patients with Disorders of Propionate Metabolism: a Beneficial Effect of l -Carnitine Supplementation

Propionic (PA) and methylmalonic (MMA) acidurias are inherited disorders caused by deficiency of propionyl-CoA carboxylase and methylmalonyl-CoA mutase, respectively. Affected patients present acute metabolic crises in the neonatal period and long-term neurological deficits. Treatments of these diseases include a protein restricted diet and l-carnitine supplementation. l-Carnitine is widely used in the therapy of these diseases to prevent secondary l-carnitine deficiency and promote detoxification, and several recent in vitro and in vivo studies have reported antioxidant and antiperoxidative effects of this compound. In this study, we evaluated the oxidative stress parameters, isoprostane and di-tyrosine levels, and the antioxidant capacity, in urine from patients with PA and MMA at the diagnosis, and during treatment with l-carnitine and protein-restricted diet. We verified a significant increase of isoprostanes and di-tyrosine, as well as a significant reduction of the antioxidant capacity in urine from these patients at diagnosis, as compared to controls. Furthermore, treated patients presented a marked reduction of isoprostanes and di-tyrosine levels in relation to untreated patients. In addition, patients with higher levels of protein and lipid oxidative damage, determined by di-tyrosine and isoprostanes levels, also presented lower urinary concentrations of total and free l-carnitine. In conclusion, the present results indicate that treatment with low protein diet and l-carnitine significantly reduces urinary biomarkers of protein and lipid oxidative damage in patients with disorders of propionate metabolism and that l-carnitine supplementation may be specially involved in this protection.

Urinary biomarkers of oxidative damage in Maple syrup urine disease: The l-carnitine role

Maple syrup urine disease (MSUD) is a disorder of branched‐chain amino acids (BCAA). The defect in the branched‐chain α‐keto acid dehydrogenase complex activity leads to an accumulation of these compounds and their corresponding α‐keto‐acids and α‐hydroxy‐acids. Studies have shown that oxidative stress may be involved in neuropathology of MSUD. l‐carnitine (l‐car), which has demonstrated an important role as antioxidant by reducing and scavenging free radicals formation and by enhancing the activity of antioxidant enzymes, have been used in the treatment of some metabolic rare disorders. This study evaluated the oxidative stress parameters, di‐tyrosine, isoprostanes and antioxidant capacity, in urine of MSUD patients under protein‐restricted diet supplemented or not with l‐car capsules at a dose of 50 mg kg−1 day−1. It was also determined urinary α‐keto isocaproic acid levels as well as blood free l‐car concentrations in blood. It was found a deficiency of carnitine in patients before the l‐car supplementation. Significant increases of di‐tyrosine and isoprostanes, as well as reduced antioxidant capacity, were observed before the treatment with l‐car. The l‐car supplementation induced beneficial effects on these parameters reducing the di‐tyrosine and isoprostanes levels and increasing the antioxidant capacity. It was also showed a significant increase in urinary of α‐ketoisocaproic acid after 2 months of l‐car treatment, compared to control group. In conclusion, our results suggest that l‐car may have beneficial effects in the treatment of MSUD by preventing oxidative damage to the cells and that urine can be used to monitorize oxidative damage in patients affected by this disease.

Brain effect of insulin and clonazepam in diabetic rats under depressive-like behavior

Diabetes mellitus is characterized by hyperglycemia resulting from defects on insulin secretion, insulin action, or both. It has recently become clear that the central nervous system is not spared from the deleterious effects of diabetes, since diabetic encephalopathy was recognized as a complication of this heterogeneous metabolic disorder. There is a well recognized association between depression and diabetes, once prevalence of depression in diabetic patients is higher than in general population, and clonazepam is being used to treat this complication. Oxidative stress is widely accepted as playing a key mediatory role in the development and progression of diabetes and its complications. In this work we analyzed DNA damage by comet assay and lipid damage in prefrontal cortex, hippocampus and striatum of streptozotocin-induced diabetic rats submitted to the forced swimming test. It was verified that the diabetic group presented DNA and lipid damage in the brain areas evaluated, when compared to the control groups. Additionally, a significant reduction of the DNA and lipid damage in animals treated with insulin and/or clonazepam was observed. These data suggest that the association of these two drugs could protect against DNA and lipid damage in diabetic rats submitted to the forced swimming test, an animal model of depression.

Urinary biomarkers of oxidative stress and plasmatic inflammatory profile in phenylketonuric treated patients

Oxidative stress has been proposed as an important pathophysiologic feature of various inborn errors of metabolism, including phenylketonuria (PKU). Considering that there are few studies relating oxidative stress and inflammation directly in PKU disease, the aim of this study was to evaluate and correlate oxidative damage to biomolecules, antioxidant defenses, pro‐inflammatory cytokines, phenylalanine (Phe) and its metabolites (phenyllactic acid—PLA and phenylacetic acid—PAA) levels in urine and plasma from patients with PKU under dietary treatment. We observed a marked increase of isoprostanes, which is a lipid peroxidation biomarker, in urine from these treated patients. Next, we demonstrated that protein oxidative damage, measured by di‐tyrosine formation, was significantly increased in urine from PKU treated patients and that decreased urinary antioxidant capacity was also observed. Our findings concerning to the inflammatory cytokines interleukin‐6 and interleukin‐1β, both significantly increased in these patients, provide evidence that the pro‐inflammatory state occurs. Besides, interleukin‐1β was positively correlated with isoprostanes. We observed a negative correlation between interleukin‐6 and interleukin‐10, an anti‐inflammatory cytokine. Di‐tyrosine was positively correlated with Phe, which indicates oxidative damage to proteins, as well as with PAA. These findings may suggest that the protein damage may be induced by Phe and its metabolite PAA in PKU. Our results indicate that pro‐oxidant and pro‐inflammatory states occur and are, in part, correlated and protein oxidation seems to be induced by Phe and PPA in PKU patients.

Acute administration of 5-oxoproline induces oxidative damage to lipids and proteins and impairs antioxidant defenses in cerebral cortex and cerebellum of young rats

Abstract5-Oxoproline accumulates in glutathione synthetase deficiency, an autossomic recessive inherited disorder clinically characterized by hemolytic anemia, metabolic acidosis, and severe neurological symptoms whose mechanisms are poorly known. In the present study we investigated the effects of acute subcutaneous administration of 5-oxoproline to verify whether oxidative stress is elicited by this metabolite in vivo in cerebral cortex and cerebellum of 14-day-old rats. Our results showed that the acute administration of 5-oxoproline is able to promote both lipid and protein oxidation, to impair brain antioxidant defenses, to alter SH/SS ratio and to enhance hydrogen peroxide content, thus promoting oxidative stress in vivo, a mechanism that may be involved in the neuropathology of gluthatione synthetase deficiency.

Hypermethioninemia provokes oxidative damage and histological changes in liver of rats

In the present study we evaluated the effect of chronic methionine administration on oxidative stress and biochemical parameters in liver and serum of rats, respectively. We also performed histological analysis in liver. Results showed that hypermethioninemia increased chemiluminescence, carbonyl content and glutathione peroxidase activity, decreased total antioxidant potential, as well as altered catalase activity. Hypermethioninemia increased synthesis and concentration of glycogen, besides histological studies showed morphological alterations and reduction in the glycogen/glycoprotein content in liver. Serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and glucose were increased in hypermethioninemic rats. These findings suggest that oxidative damage and histological changes caused by methionine may be related to the hepatic injury observed in hypermethioninemia.