Inhibition of Na+, K+-ATPase activity in rat striatum by the metabolites accumulated in Lesch-Nyhan disease

Kidney Bean Protein Prevents High-Fat and High-Fructose Diet-Induced Obesity, Cognitive Impairment, and Disruption of Gut Microbiota Composition

A long-term intake of a high-fat and high-fructose diet (HFFD), even a high-fat, high-fructose but low-protein diet (HFFD + LP), could cause obesity associated with cognitive impairments. In the present study, rats were subjected to a normal diet (ND), an HFFD diet, an HFFD + LP diet, and an HFFD with kidney bean protein (KP) diet for 8 weeks to evaluate the effect of KP on HFFD- or HFFD + LP-induced obesity and cognitive impairment. The results demonstrated that compared with the HFFD diet, KP administration significantly decreased the body weight by 7.7% and the serum Angiotensin-Converting Enzyme 2 (ACE-2) and Insulin-like Growth Factor 1 (IGF-1) levels by 14.4% and 46.8%, respectively (p < 0.05). In addition, KP suppressed HFFD-induced cognitive impairment, which was evidenced by 8.7% less time required to pass the water maze test. The 16s RNA analysis of the colonic contents showed that the relative abundance of Bifidobacterium, Butyricimonas, and Alloprevotella was increased by KP by 5.9, 44.2, and 79.2 times. Additionally, KP supplementation primarily affected the choline metabolic pathway in the liver, and the synthesis and functional pathway of neurotransmitters in the brain, thereby improving obesity and cognitive function in rats.

Metabolic fingerprints of fear memory consolidation during sleep

Metabolites underlying brain function and pathology are not as well understood as genes. Here, we applied a novel metabolomics approach to further understand the mechanisms of memory processing in sleep. As hippocampal dentate gyrus neurons are known to consolidate contextual fear memory, we analyzed real-time changes in metabolites in the dentate gyrus in different sleep-wake states in mice. Throughout the study, we consistently detected more than > 200 metabolites. Metabolite profiles changed dramactically upon sleep-wake state transitions, leading to a clear separation of phenotypes between wakefulness and sleep. By contrast, contextual fear memory consolidation induced less obvious metabolite phenotypes. However, changes in purine metabolites were observed upon both sleep-wake state transitions and contextual fear memory consolidation. Dietary supplementation of certain purine metabolites impaired correlations between conditioned fear responses before and after memory consolidation. These results point toward the importance of purine metabolism in fear memory processing during sleep.

Serum antioxidant levels associated with subcortical ischemic vascular disease

OBJECTIVE

We aimed to examine changes in serum bilirubin and uric acid (ua) levels in subcortical ischemic vascular disease (Sivd). in addition, we investigated if altered serum bilirubin and ua levels correlate with the subtypes of Sivd as well as the severity of leukoaraiosis (la).

METHODS

this cross-sectional study included 1098 consecutive patients with slight symptoms, such as dizziness, vertigo etc. according to magnetic resonance imaging (Mri) appearances, they were divided into either Sivd group or controls (Cn), and the Sivd group was further grouped in lacunar infarction (li) and la subtypes, as well as different grades. Serum bilirubin and ua levels were determined by the vanadate oxidase method and enzymatic method respectively, after at least an eight hour overnight fasting, in all subjects.

RESULTS

the bilirubin level was obviously lower while the ua level was significantly higher in the Sivd group when compared with the controls. Moreover, the la subgroup presented more significant changes in bilirubin and ua when compared to the li subgroup in both males and females. the correlation was positive between the ua levels and the la severity (r=0.134, p=0.006). Multivariate regression analysis revealed that the odds ratio (95% Ci) for Sivd in the lowest tertile of total bilirubin (tbil<9.58 μmol/l) and highest tertile of ua (ua>339 μmol/l) were 2.702(1.936-3.770) and 2.135(1.521-2.996) respectively after adjusting for confounding variables.

CONCLUSION

Serum bilirubin levels were lower, whereas ua levels were higher in Sivd patients when compared with controls in both males and females, especially in la patients. Moreover, serum ua levels positively correlated to la severity.

An amperometric hypoxanthine biosensor based on Au@FeNPs for determination of hypoxanthine in meat samples

A xanthine oxidase (XOD) from buttermilk was immobilized covalently onto boronic acid functionalized gold coated iron nanoparticles (Au@FeNPs) electrodeposited on pencil graphite (PG) electrode, via the boroester linkages, between free hydroxyl groups of boronic acid, α-COOH and -NH2 groups of enzyme. The surface functionalization of Fe/Au nanoparticles with boronic acid (Au@FeNPs) on pencil graphite (PG) electrode was characterized by Fourier transform infrared (FTIR), cyclic voltammetry (CV), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Electrochemical impedance spectroscopy (EIS) before and after immobilization of XOD. The biosensor exhibited optimum response within 3s at pH 7.2 and 30 °C and linearity in the range, 0.05 μM to 150 μM for hypoxanthine with a detection limit of 0.05 μM (S/N=3). Apparent Michaelis Menten constant (Km(app)) for hypoxanthine was 40 μM and Imax 0.125 mA. The biosensor was employed to determine hypoxanthine in fish, chicken, pork, beef meat and lost 50% of its initial activity after its 200 uses over 100 days, when stored at 4 °C.

Effect of uric acid on gentamicin-induced nephrotoxicity in rats - role of matrix metalloproteinases 2 and 9

In this work, we aimed to study the effect of uric acid on gentamicin-induced nephrotoxicity. Male Sprague-Dawley rats were assigned to one of six groups (six rats each) which received intraperitoneal injections for 9 days: (S) saline; (UA) Uric acid alone; (G) Gentamicin alone; (G + UA) Gentamicin + uric acid; (G rec) Gentamicin recovery and (G + UA rec) Gentamicin + uric acid recovery. In (G rec) and (G + UA rec), rats recovered for 7 days after the last injection. Urine and blood samples were taken on day 0 and at the end of every stage. Kidneys were harvested for histological scoring, determination of renal malondialdehyde (MDA), zymography and western blots for matrix metalloprotease (MMP)-2 and MMP-9. Uric acid alone did not provoke changes in biochemical and histological parameters when compared to controls. Gentamicin alone increased significantly plasma creatinine and blood urea nitrogen and caused a moderate histological damage. When combined with uric acid, these conditions worsened. MMP-9 activity and expression was decreased in rats from group G + UA as compared with rats from group G, while activity of MMP-2 was similarly increased in both groups when compared to controls. The increase in renal MDA induced by gentamicin was not altered when it was combined with uric acid. During the recovery stage, all biochemical parameters returned to normal levels, though a trend for delay of tubular damage recovery was observed in group G + UA rec when compared with group G rec. The results indicate that uric acid worsens gentamicin-induced nephrotoxicity. The mechanism is likely to implicate down-regulation of MMP-9.

Na,K-ATPase activity regulates AMPA receptor turnover through proteasome-mediated proteolysis

Neuronal activity largely depends on two key components on the membrane: the Na,K-ATPase (NKA) that maintains the ion gradients and sets the foundation of excitability, and the ionotropic glutamatergic AMPA receptors (AMPARs) through which sodium influx forms the driving force for excitation. Because the frequent sodium transients from glutamate receptor activity need to be efficiently extruded, a functional coupling between NKA and AMPARs should be a necessary cellular device for synapse physiology. We show that NKA is enriched at synapses and associates with AMPARs. NKA dysfunction induces a rapid reduction in AMPAR cell-surface expression as well as total protein abundance, leading to a long-lasting depression in synaptic transmission. AMPAR proteolysis requires sodium influx, proteasomal activity and receptor internalization. These data elucidate a novel mechanism by which NKA regulates AMPAR turnover and thereby synaptic strength and brain function.

Uric acid inhibits placental system A amino acid uptake

Hyperuricemia, a common clinical characteristic of preeclamptic pregnancies, has historically been considered a marker of reduced renal function in preeclamptic women. More recently it has been suggested that uric acid may directly contribute to pathological cell signaling events involved in disease progression as well as maternal and fetal pregnancy outcomes including fetal growth restriction. We hypothesize that the increased frequency of restricted fetal growth seen in relation to increasing uric acid concentrations in preeclamptic women is in part the result of uric acid-induced reductions in amino acid transport across the placenta. The objective of the current study was to examine the effects of uric acid on human placental System A amino acid transport using a primary placental villous explant model. Further, we examined the necessity of uric acid uptake and the role of redox signaling as a potential mechanism through which uric acid may attenuate System A activity. Placental uptake of a radiolabeled amino acid analogue, specific to the System A transporter, was reduced in a concentration-dependent fashion with increasing uric acid (0-7 mg/dL), corresponding to uric acid concentrations measured in healthy pregnant and preeclamptic women in the third trimester. Uric acid-induced reduction in System A activity was partially reversed by NADPH oxidase inhibition and completely eliminated by antioxidant treatment. This study demonstrates inhibition of placental System A amino acid transport with uric acid treatment, as a result of uric acid-induced stimulation of intracellular redox signaling cascades. These findings may be relevant to the increased frequency of fetal growth restriction observed in hyperuricemic preeclampsia. Additionally the results of this study, indicating a detrimental effect of hyperuricemia on amino acid transport in the placenta, at concentrations present in women with preeclampsia, also suggest a role for uric acid in the pathophysiology of preeclampsia.

Intrastriatal injection of hypoxanthine alters striatal ectonucleotidase activities: a time-dependent effect

The aim of this study was to investigate the effects of intrastriatal injection of hypoxanthine on ectonucleotidase (E-NTPDases and ecto-5'-nucleotidase) activities and expressions in the striatum of rats. The effect of pre-treatment with vitamins E and C on the effects elicited by this oxypurine on enzymatic activities and on thiobarbituric reactive substances (TBARS) was also investigated. The effect of pre-incubation with hypoxanthine on nucleotide hydrolysis in striatum homogenate was also determined. Adult Wistar rats were divided into (1) control and (2) hypoxanthine-injected groups. For ectonucleotidase activity determination, the animals were sacrificed at 30 min, 24 h and 7 days after drug infusion. For the evaluation of the expression of NTPDase 1-3 and also ecto-5'-nucleotidase, TBARS assay and the influence of the pre-treatment with vitamins on ectonucleotidase activities, the animals were sacrificed 24 h after hypoxanthine infusion. Results show that hypoxanthine infusion significantly inhibited ectonucleotidase activities and increased TBARS only 24 h after administration. Pre-treatment with vitamins was able to prevent these effects. Moreover, ecto-5'-nucleotidase expression was increased (80%) at 24 h after hypoxanthine infusion. We suggest that these hypoxanthine-induced biochemical modifications could, at least in part, participate in the pathophysiology of Lesch Nyhan disease.

Intrastriatal injection of hypoxanthine reduces striatal serotonin content and impairs spatial memory performance in rats

The aim of this study was to investigate the effects of intrastriatal injection of hypoxanthine, a metabolite accumulated in Lesch-Nyhan disease, on rats' performance in the Morris water maze tasks, along with the monoamine content in striatum of rats. Male adult Wistar rats were divided in two groups: (1) saline-injected and (2) hypoxanthine-injected group. Seven days after solutions infusion, animals were trained in the Morris Water Maze or were sacrificed for evaluation of the striatal monoamine content. Results show that hypoxanthine administration caused impairment on spatial navigation in the acquisition phase in reference memory task in the Morris Water Maze, as well as in the latency to cross over the platform location in probe trial, when compared to the saline group (control). Hypoxanthine also altered rat performance in the working memory. Although striatal dopamine metabolites content did not change, treated animals showed a reduction of tissue levels of serotonin (5-HT) and 5- hydroxyl-indoleacetic acid (5-HIAA). These results show that intra-striatal hypoxanthine administration provoked impairment of spatial learning/memory in rats without affecting striatal dopaminergic system, although serotonergic pathways seem to have been affected.

Intrastriatal hypoxanthine reduces Na(+),K (+)-ATPase activity and induces oxidative stress in the rats

The main objective of this study was to investigate the effects of a single intrastriatal injection of hypoxanthine, a metabolite accumulated in Lesch Nyhan disease and possibly involved in its neuropathology, on Na(+),K(+)-ATPase activity, as well as on some parameters of oxidative stress, namely chemiluminescence (an index of lipid peroxidation), total radical-trapping antioxidant parameter--TRAP (an index of total antioxidant capacity of the tissue) and total thiol protein membrane content, in striatum, cerebral cortex and hippocampus of rats. Results show that hypoxanthine significantly decreased Na(+),K(+)-ATPase activity and TRAP while increased chemiluminescence in all ipsislateral structures tested. However, no effect on total thiol protein membrane content was detected. We suggest that hypoxanthine induces oxidative stress in all cerebral structures studied (striatum, hippocampus and cerebral cortex) and that the reduction of Na(+),K(+)-ATPase activity was probably mediated by reactive oxygen species.

Synaptic plasma membrane Na(+), K (+)-ATPase activity is significantly reduced by the alpha-keto acids accumulating in maple syrup urine disease in rat cerebral cortex

The objective of the present study was to investigate the in vitro effects of the branched-chain alpha-keto acids accumulating in maple syrup urine disease, namely L-2-ketoisocaproic acid, L-2-keto-3-methylvaleric acid and L-2-ketoisovaleric acid on Na(+), K(+)-ATPase activity in synaptic plasma membranes from cerebral cortex of 35-day-old rats. All keto acids significantly inhibited Na(+), K(+)-ATPase activity at concentrations similar (1 mM) or even lower (0.5 mM) than those found in blood and cerebrospinal fluid of maple syrup urine disease patients. We also tested the effects of alanine on this enzyme activity. Alanine per se did not alter Na(+), K(+)-ATPase activity, but totally prevented the branched-chain alpha-keto acids-induced Na(+), K(+)-ATPase inhibition, indicating that alanine and the keto acids may possibly bind to the same site on the enzyme. We also observed that the branched-chain amino acids leucine, isoleucine and valine also inhibited Na(+) K(+)-ATPase activity to a similar degree as that of the branched-chain alpha-keto acids and that alanine was able to fully prevent these effects. Considering that Na(+), K(+)-ATPase is a critical enzyme for normal brain development and functioning, it is presumed that these findings may be involved in the pathophysiology of the neurological dysfunction of maple syrup urine disease.

Intrastriatal hypoxanthine administration affects Na+,K+‐ATPase, acetylcholinesterase and catalase activities in striatum, hippocampus and cerebral cortex of rats

The aim of this study was to investigate the effects of a single intrastriatal injection of hypoxanthine, the major metabolite accumulating in Lesch-Nyhan disease, on Na(+),K(+)-ATPase, acetylcholinesterase and catalase activities in striatum, cerebral cortex and hippocampus of rats at different post-infusion periods. Adult Wistar rats were divided in two groups: (1) vehicle-injected group (control) and (2) hypoxanthine-injected group. For Na(+),K(+)-ATPase activity determination, the animals were sacrificed 3h, 24h and 7 days after drug infusion. For the evaluation of acetylcholinesterase and catalase activities, the animals were sacrificed 30min, 3h, 24h and 7 days after hypoxanthine infusion. Results show regional and time dependent effects of hypoxanthine on Na(+),K(+)-ATPase, acetylcholinesterase and catalase activities. The in vitro effect of hypoxanthine on the same enzymes in striatum was also investigated. Results showed that hypoxanthine inhibited Na(+),K(+)-ATPase, but not the activities of acetylcholinesterase and catalase in rat striatum. We suggest that these modification on cerebral biochemical parameters (Na(+),K(+)-ATPase, acetylcholinesterase and catalase activities) induced by intrastriatal administration of hypoxanthine in all cerebral structures studied, striatum, hippocampus and cerebral cortex, could be involved in the pathophysiology of Lesch-Nyhan disease.

Effect of hypoxanthine on Na+,K+-ATPase activity and some parameters of oxidative stress in rat striatum

The main objective of this study was to investigate the effects of preincubation of rat striatum homogenate in the presence of hypoxanthine, a metabolite accumulated in Lesch-Nyhan disease, on Na+,K+-ATPase activity and on some parameters of oxidative stress namely thiobarbituric acid-reactive substances (TBA-RS), total radical-trapping antioxidant parameter (TRAP) and membrane protein thiol content. Results showed that hypoxanthine significantly increased TBA-RS and reduced Na+,K+-ATPase activity, TRAP and membrane protein thiol content. In addition, we also evaluated the effect of glutathione, trolox, allopurinol and Nvarpi-nitro-L-arginine methyl ester (L-NAME) on the inhibitory effect of hypoxanthine on Na+,K+-ATPase activity in the same rat cerebral structure. All tested compounds per se did not alter Na+,K+-ATPase activity, but only glutathione and trolox prevented the effect of hypoxanthine on the enzyme activity. The effect of glutathione and trolox on hypoxanthine-induced increase of TBA-RS levels was also investigated. These antioxidants alone or combined with hypoxanthine reduced TBA-RS levels. Our present findings show that hypoxanthine induces oxidative stress in rat striatum and that the inhibition of Na+,K+-ATPase activity caused by this oxypurine was probably mediated by reactive oxygen species. It is presumed that these results might be associated with the neuronal dysfunction of patients affected by Lesch-Nyhan disease.

BSE and vCJD cause disturbance to uric acid levels

Bovine spongiform encephalopathy (BSE) and variant Creutzfeldt-Jakob disease (vCJD) are two new members of the family of neurodegenerative conditions termed prion diseases. Oxidative damage has been shown to occur in prion diseases and is potentially responsible for the rapid neurodegeneration that is central to the pathogenesis of these diseases. An important nonenzymatic antioxidant in the brain is uric acid. Analysis of uric acid in the brain and cerebrospinal fluid (CSF) of cases of BSE and CJD showed a specific reduction in CSF levels for both BSE and variant CJD, but not sporadic CJD. Further studies based on cell culture experiments suggested that uric acid in the brain was produced by microglia. Uric acid was also shown to inhibit neurotoxicity of a prion protein peptide, production of the abnormal prion protein isoform (PrP(Sc)) by infected cells, and polymerization of recombinant prion protein. These findings suggest that changes in uric acid may aid differential diagnosis of vCJD. Uric acid could be used to inhibit cell death or PrP(Sc) formation in prion disease.