Effect of thyroid hormones on the glycolytic enzyme activity in brain areas of the rat

The glycolytic metabolism through the key enzymes, hexokinase, phosphofructokinase, pyruvate kinase and lactate dehydrogenase, have been studied in the brain areas: anterior cortex, amygdala, hypothalamus, septum and hippocampus in adult rats with pharmacologically induced hyperthyroidism. The oxidative metabolism of glucose is accelerated in most brain areas by treatment with high doses of T3, as is shown by the increase in HK activity, approaching normality on reducing the dose. This decrease can also by observed in the PFK activity through the effect of assayed doses of thyroxine. The anterior cortex is the only brain area that does not show significant variations of PK activity through the effects of treatment with thyroid hormones. On the other hand, a general inhibition of the glycolytic anaerobic pathway by treatment with T3 was observed.     

Cytochemical research on the effect of a synthetic enkephalin analog on the protein content and enzyme activity of neurons

Using quantitative cytochemical technique a study was made of the effect of the synthetic analog of the Tyr-D-Ala-Gly-Phe-NH2 on the content and concentration of proteins and on the activity of enzymes (aminopeptidase, glutamate dehydrogenase and acid phosphatase) in neurons of the brain motor cortex and nucleus caudatus of rabbits and rats. The essential changes of the parameters used were registered 3 days after neuropeptide injection. A 30 minutes effects of the synthetic analog of enkephalins in protein metabolism was not so pronounced as a 3 days effect, the former being observed only in neurons of the brain motor cortex. Long-lasting effects of the neuropeptide Tyr-D-Ala-Gly-Phe-NH2 on the metabolism in brain are discussed.     

Enzyme Activities in Regions of the Hypothalamus

Abstract: The activities of certain key enzymes have been measured in the ventral medial and ventral lateral areas of the hypothalamus, which are implicated in feeding behaviour, and compared with enzyme activities in the cortex and brainstem. The enzymes measured are concerned with glucose metabolism [hexokinase (EC 2.7.1.1) and glucosesphosphate dehydrogenase (EC 1.1.1.49)], ketone body metabolism [3-hydroxybutyrate dehydrogenase (EC 1.1.1.30)], fatty acid utilisation [carnitine palmitoyl transferase (EC 2.3.1.7)], citric acid cycle activity [pyruvate dehydrogenase (EC 1.2.4.2) and citrate synthase (EC 4.1.3.7)] and neurotransmitter synthesis [glutamate dehydrogenase (EC 1.4.1.3)].     

Effect of Leucine Administration to Female Rats During Pregnancy and Lactation on Oxidative Stress and Enzymes Activities of Phosphoryltransfer Network in Cerebral Cortex and Hippocampus of the Offspring

Maple Syrup Urine Disease is an inborn error of metabolism caused by severe deficiency in the activity of branched-chain α-keto acid dehydrogenase complex. Neurological disorder is common in patients with maple syrup urine disease. Although leucine is considered the main toxic metabolite, the mechanisms underlying the neuropathology of brain injury are poorly understood. In the present study, we evaluated the possible preventive effect of the co-administration of creatine plus pyruvate on the effects elicited by leucine administration to female Wistar rats during pregnancy and lactation on some oxidative stress parameters as well as the activities of some enzymes involved in the phosphoryltransfer network in the brain cortex and hippocampus of the offspring at 21 days of age. Leucine administration induced oxidative stress and altered the activities of pyruvate kinase, adenylate kinase, mitochondrial and cytosolic creatine kinase. Co-administration of creatine plus pyruvate was partially effective in the prevention of some alterations provoked by leucine administration on the oxidative stress but not in the enzymes of phosphoryltransfer network. These results suggest that non-treated maternal hyperleucinemia may be toxic to the brain of the offspring.     

Metabolite of tryptophan promoting changes in EEG signal and the oxidative status of the brain

Tryptophan is an essential amino acid precursor of neurotransmitter serotonin and triptamine. During its metabolism, indole‐3‐acetic acid (IAA) is generated; this substance presents both antioxidant and prooxidant effects in different biological systems in addition to hipoglicemic effects. To date, electroencephalography (EEG) has been used to evaluate the temporal effect of several substances in neurotransmission. The goal of this study was to characterize the effect of IAA in the brain by analysing the EEG signal and evaluate the oxidative status by means of biochemical parameters. The EEG was acquired by using a noninvasive method, and the brain electric signal was analysed by advanced digital signal processing techniques to determinate the energy signal filtered in different band frequencies. Furthermore, the oxidative status of the brain was investigated by measuring the activity of antioxidant enzymes and lipid peroxidation as well as blood glucose rates of the animals treated with different doses of IAA. Our results showed the relationship of IAA administration with changes in EEG signals. The oxidative status of the brain was modified by IAA after 14 days of treatment. Copyright © 2014 John Wiley & Sons, Ltd.     

Oxidation-reduction enzymes in the cyst stages of the sarcosporidian, Sarcocystis ovifelis

Using methods of light microscope cytochemistry, the availability of oxidative enzymes were examined in the cyst stages (merozoites) of Sarcocystis ovifelis. Enzymes of glycolysis, Krebs' cycle and pentose--phosphate way of oxidation were detected suggesting a mixed character of merozoite's oxidative metabolism. A weak activity of glutamate dehydrogenase (an enzyme involved in protein metabolism) was shown in merozoites in addition to the absence of beta-hydroxybutyrate dehydrogenase (an enzyme of lipid metabolism).     

Effect ot tuftsin on cerebral monoamine oxidase and acetylcholinesterase activity

The administration of a tetrapeptide tuftsin at a dose of 300 mkg/kg body weight for 30, 75 min or 3 days leads to the changes in specific activity of monoamine oxidase, forms A and B, and acetylcholinesterase in synaptosomal and cellular mitochondrial subfractions from the rabbit sensorimotor cortex and nucleus caudatus. The reciprocity of neuro-transmitter systems and specific peptide effects on the brain structures have been demonstrated. The results suggest that tuftsin has an activating effect on dopamine metabolism.     

Adaptive changes induced by high altitude in the development of brain monoamine enzymes

Exposure to high altitude (HA) affects neurotransmitter levels in the adult brain and induces a number of neurologic and behavioral disturbances. The present work was undertaken to investigate the effects of chronic exposure to a moderate hypoxic environment (natural altitude of 3800 m, 12.8% O₂ in inspired air) on the development from birth until adulthood of brain monoamine enzymes in rats. The activity of synthesizing (tyrosine and tryptophan hydroxylase) and catabolizing (catechol-O-methyl transferase and monoamine oxidase) enzymes was studied in discrete brain areas (cerebral cortex, cerebellum, mesodiencephalon, hypothalamus, corpus striatum, and pons medulla) and was shown to be selectively affected by HA, depending on the age of the animal and the brain region. In general, enzyme activity was less susceptible to HA during the first week after birth than at later ages, some brain areas such as the hypothalamus showing significant alterations in some enzymes throughout development, and in all enzymes at adulthood. Furthermore, in all brain areas and at all ages, tyrosine and tryptophan hydroxylase were more affected by HA than the catabolizing enzymes, and their activity was increased in some areas (e.g., cerebral cortex and cerebellum) but decreased in other areas (e.g., hypothalamus, mesodiencephalon, corpus striatum). These enzymatic changes and the corresponding alterations in precursor amino acids, particularly tryptophan, seem to be due more to the direct effect of hypoxia on oxygen-dependent enzymes, than to the stress. It appears that an hypoxic environment may provoke both early and long-term alterations in catecholamine and serotonin metabolism, thus neurotransmitter imbalances may explain some of the alterations in neurologic and endocrine development characteristic of the hypoxic animal.Part of this report was presented at the Sixth International Meeting of the International Society of Neurochemistry, Copenhagen, 1977.     

Changes in the dehydrogenase and GABA transaminase activity in the cerebral cortex during corazol kindling

The experiments on (CBA X C57BL/6)F1 mice have shown that regular corazol injections in subliminal doses stimulated seizure susceptibility (pharmacological kindling). Cytophotometric assay of the activity of oxidative metabolism enzymes (glutamate dehydrogenase, malate dehydrogenase, succinate dehydrogenase, alpha-oxoglutarate dehydrogenase, lactate dehydrogenase) and GABA-transaminase in the sensorimotor cortex of kindled mice in post-convulsive period, and 24 hours or 30 days after corazol injections were discontinued, has revealed some specific alterations of the enzymes under study, that suggest the existence of two phases of energy metabolism disturbances. The first phase (24 hours after corazol injections were discontinued) is characterized by intensified succinic acid oxidation, while the second phase (30 days after the last injection) is characterized by anaerobic glycolysis in neuronal and glial cells. Inhibition of GABA-transaminase activity was particularly marked in postconvulsive period. From a molecular point of view these data may be considered as enzyme disturbances during stimulation of seizure susceptability or seizure activity and as a compensation component ensuring anticonvulsive mechanisms and reparative processes (antagonistic principle of molecular mechanism regulation) during activation of antiepileptic system.     

Glutamate dehydrogenase in brain mitochondria: do lipid modifications and transient metabolon formation influence enzyme activity?

Metabolism of glutamate, the primary excitatory neurotransmitter in brain, is complex and of paramount importance to overall brain function. Thus, understanding the regulation of enzymes involved in formation and disposal of glutamate and related metabolites is crucial to understanding glutamate metabolism. Glutamate dehydrogenase (GDH) is a pivotal enzyme that links amino acid metabolism and TCA cycle activity in brain and other tissues. The allosteric regulation of GDH has been extensively studied and characterized. Less is known about the influence of lipid modifications on GDH activity, and the participation of GDH in transient heteroenzyme complexes (metabolons) that can greatly influence metabolism by altering kinetic parameters and lead to channeling of metabolites. This review summarizes evidence for palmitoylation and acylation of GDH, information on protein binding, and information regarding the participation of GDH in transient heteroenzyme complexes. Recent studies suggest that a number of other proteins can bind to GDH altering activity and overall metabolism. It is likely that these modifications and interactions contribute additional levels of regulation of GDH activity and glutamate metabolism.     

Comparative analysis of the morphochemical changes in the visual and sensorimotor cortical neurons of rats exposed to taftsin

White rats were treated with a single administration of immunostimulator tuftsin (Thr-Lys-Pro-Arg, in the dose 300 mcg/kg b. w.). By interferometry protein content and concentration and the area of neuron cytoplasm and nucleus were assessed 15 minutes after injection, significant alterations in protein content and cellular area were detected in one type neurons of visual and sensomotor cortex. A possible interrelation is discussed between tuftsin action and the functional activity of neurons, and between the level of their protein metabolism and establishment of emotional and motor response.     

Chronic hypoxia in development selectively alters the activities of key enzymes of glucose oxidative metabolism in brain regions

The immature brain is more resistant to hypoxia/ischemia than the mature brain. Although chronic hypoxia can induce adaptive-changes on the developing brain, the mechanisms underlying such adaptive changes are poorly understood. To further elucidate some of the adaptive changes during postnatal hypoxia, we determined the activities of four enzymes of glucose oxidative metabolism in eight brain regions of hypoxic and normoxic rats. Litters of Sprague-Dawley rats were put into the hypoxic chamber (oxygen level maintained at 9.5%) with their dams starting on day 3 postnatal (P3). Age-matched normoxic rats were use as control animals. In P10 hypoxic rats, lactate dehydrogenase (LDH) activity in cerebral cortex, striatum, olfactory bulb, hippocampus, hypothalamus, pons and medulla, and cerebellum was significantly increased (by 100%–370%) compared to those in P10 normoxic rats. In P10 hypoxic rats, hexokinase (HK) activity in hypothalamus, hippocampus, olfactory bulb, midbrain, and cerebral cortex was significantly decreased (by 15%–30%). Neither -ketoglutarate dehydrogenase complex (KGDHC, which is believed to have an important role in the regulation of the tricarboxylic acid [TCA] cycle flux) nor citrate synthase (CS) activity was significantly decreased in the eight regions of P10 hypoxic rats compared to those in P10 normoxic rats. In P30 hypoxic rats, LDH activity was only increased in striatum (by 19%), whereas HK activity was only significantly decreased (by 30%) in this region. However, KGDHC activity was significantly decreased in olfactory bulb, hippocampus, hypothalamus, cerebral cortex, and cerebellum (by 20%–40%) in P30 hypoxic rats compared to those in P30 normoxic rats. Similarly, CS activity was decreased, but only in olfactory bulb, hypothalamus, and midbrain (by 9%–21%) in P30 hypoxic rats. Our results suggest that at least some of the mechanisms underlying the hypoxia-induced changes in activities of glycolytic enzymes implicate the upregulation of HIF-1. Moreover, our observation that chronic postnatal hypoxia induces differential effects on brain glycolytic and TCA cycle enzymes may have pathophysiological implications (e.g., decreased in energy metabolism) in childhood diseases (e.g., sudden infant death syndrome) in which hypoxia plays a role.     

Regional enzyme development in rat brain. Enzymes of energy metabolism.

The development of several key enzymes of pyruvate and 3-hydroxybutyrate metabolism and of the tricarboxylic acid cycle was studied in six regions (cerebellum, medulla oblongata and pons, hypothalamus, striatum, mid-brain and cortex) of the neonatal, suckling and adult rat brain (2 days before birth to 60 days after birth). The enzymes whose developmental patterns were studied were: pyruvate dehydrogenase (EC 1.2.4.1), 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30), citrate synthase (EC 4.1.3.7), NAD-linked isocitrate dehydrogenase (EC 1.1.1.41) and fumarase (EC 4.2.1.2). Citrate synthase, isocitrate dehydrogenase and pyruvate dehydrogenase develop as a cluster in each region, although the pyruvate dehydrogenase appears to lag slightly behind the others. As with the glycolytic-enzyme cluster [Leong & Clark (1984) Biochem. J. 218, 131-138] the timing of the development of the activity of this group of enzymes varies from region to region; 50% of the adult activity developed first in the medulla oblongata, followed by the hypothalamus, striatum and mid-brain, and then in the cortex and cerebellum respectively. The 3-hydroxybutyrate dehydrogenase activity also develops earlier in the medulla oblongata than in the other regions. The results are discussed with respect to the neurophylogenetic development of the brain regions studied and the importance of the development of the enzymes of aerobic glycolysis in relationship to the development of neurological maturation.     

The effect of low doses of x-rays on the biochemical processes in the brain and on urinary metabolites in fasted rats

The effect of mild doses of X-rays (three fractions, each of 100 R) on energy metabolism of the brain of starved rats has been investigated. It is inferred that X-radiation may cause serious detrimental changes of enzymes involved in glucose metabolism (glucose-6-phosphate dehydrogenase and fructose diphosphate aldolase) and in peroxidation (of catalase and lipid peroxidase), and of the acetylcholine activity which is determined by the cholinesterase level. Dynamics of changes in the protein and nucleic acid content of the brain has been studied. It has been shown that the level of 4-HIAA and 3M4HMA in the brain increases after irradiation of starved and normally fed rats.     

Enzymes of Fatty Acid β-Oxidation in Developing Brain

Developmental profiles were determined for the activities of eight enzymes involved in fatty acid beta-oxidation in rat brain. The enzymes studied were the palmitoyl-CoA, octanoyl-CoA, butyryl-CoA, glutaryl-CoA, and 3-hydroxyacyl-CoA dehydrogenases, the enoyl-CoA hydratase (crotonase), and the C4- and C10-thiolases. With the exception of the thiolases, all of the activities (expressed on the basis of brain weight) increased during the postnatal period of brain maturation. The activity of octanoyl-CoA dehydrogenase was elevated markedly compared to that of palmitoyl-CoA dehydrogenase at all developmental stages and in all brain regions in the rat. A similar relationship between these enzymes was observed in various regions of adult human brain. Comparisons of the activities of the beta-oxidation enzymes in human brain versus human skeletal muscle and in cultured neural cell lines (neuroblastoma and glioma) versus cultured skin fibroblasts revealed that the elevated activity of octanoyl-CoA dehydrogenase relative to palmitoyl-CoA dehydrogenase was specific to the neural tissues. This relationship was particularly evident when the enzyme activities were normalized to the activity of crotonase. The data support previous findings with radiochemical tracers, indicating that the brain is capable of utilizing fatty acids as substrates for oxidative energy metabolism. The relatively high activity of the medium-chain fatty acyl-CoA dehydrogenase in neural tissue may represent an adaptive mechanism to protect the brain from the known encephalopathic effects of octanoate and other medium-chain fatty acids that readily cross the blood-brain barrier.     

Protective Effects of 28-O-Caffeoyl Betulin (B-CA) on the Cerebral Cortex of Ischemic Rats Revealed by a NMR-Based Metabolomics Analysis

28-O-caffeoyl betulin (B-CA) has been demonstrated to reduce the cerebral infarct volume caused by transient middle cerebral artery occlusion (MCAO) injury. B-CA is a novel derivative of naturally occurring caffeoyl triterpene with little information associated with its pharmacological target(s). To date no data is available regarding the effect of B-CA on brain metabolism. In the present study, a ¹H-NMR-based metabolomics approach was applied to investigate the therapeutic effects of B-CA on brain metabolism following MCAO in rats. Global metabolic profiles of the cortex in acute period (9 h after focal ischemia onset) after MCAO were compared between the groups (sham; MCAO?+?vehicle; MCAO?+?B-CA). MCAO induced several changes in the ipsilateral cortex of ischemic rats, which consequently led to the neuronal damage featured with the downregulation of NAA, including energy metabolism dysfunctions, oxidative stress, and neurotransmitter metabolism. Treatment with B-CA showed statistically significant rescue effects on the ischemic cortex of MCAO rats. Specifically, treatment with B-CA ameliorated the energy metabolism dysfunctions (back-regulating the levels of succinate, lactate, BCAAs, and carnitine), oxidative stress (upregulating the level of glutathione), and neurotransmitter metabolism disturbances (back-regulating the levels of γ-aminobutyric acid and acetylcholine) associated with the progression of ischemic stroke. With the administration of B-CA, the levels of three phospholipid related metabolites (O-phosphocholine, O-phosphoethanolamine, sn-glycero-3-phosphocholine) and NAA improved significantly. Overall, our findings suggest that treatment with B-CA may provide neuroprotection by augmenting the metabolic changes observed in the cortex following MCAO in rats.

     

Metabolic effects of hydrocortisone in mouse brain

The effect of intramuscular administration of hydrocortisone (10 mg/day per animal) for 5 days has been studied on the content of the amino acids belonging to the glutamate family, in the different regions of the mouse brain, along with the activities of glutamine synthetase, glutamate dehydrogenase, and aspartate, alanine, tyrosine, and ornithine aminotransferases. Further, since proline too is related to glutamate metabolism, the activity of proline oxidase was also studied in these regions. As hydrocortisone is known to influence the ionic fluxes in different tissues and the nitrogen metabolism, the activities of Na⁺,K⁺-ATPase together with the content of RNA and protein have also been estimated. A fall in the amino acids of the glutamate family in all three regions was observed with an increase in glutamate dehydrogenase activity in cerebral cortex. A significant fall in the protein content was also observed, mainly in the brain stem. A universal increase in Na⁺,K⁺-ATPase activity was observed in all three regions, with the highest in the cerebral cortex. The results indicate that hydrocortisone triggers increased utilization of glutamate in brain as an alternative to glucose, thereby shifting the nitrogen metabolism toward catabolism. The increased activity of Na⁺,K⁺-ATPase under these conditions would further aggravate the same and may lead to membrane stabilization.     

Focal neurometabolic alterations in mice deficient for succinate semialdehyde dehydrogenase

Metabolite profiling in succinate semialdehyde dehydrogenase (SSADH; Aldh5a1-/-) deficient mice previously revealed elevated gamma-hydroxybutyrate (GHB) and total GABA in urine and total brain and liver extracts. In this study, we extend our metabolic characterization of these mutant mice by documenting elevated GHB and total GABA in homogenates of mutant kidney, pancreas and heart. We quantified beta-alanine (a GABA homolog and putative neurotransmitter) to address its potential role in pathophysiology. We found normal levels of beta-alanine in urine and total homogenates of mutant brain, heart and pancreas, but elevated concentrations in mutant kidney and liver extracts. Amino acid analysis in mutant total brain homogenates revealed no abnormalities except for significantly decreased glutamine, which was normal in mutant liver and kidney extracts. Regional amino acid analysis (frontal cortex, parietal cortex, hippocampus and cerebellum) in mutant mice confirmed glutamine results. Glutamine synthetase protein and mRNA levels in homogenates of mutant mouse brain were normal. We profiled organic acid patterns in mutant brain homogenates to assess brain oxidative metabolism and found normal concentrations of Kreb's cycle intermediates but increased 4,5-dihydroxyhexanoic acid (a postulated derivative of succinic semialdehyde) levels. We conclude that SSADH-deficient mice represent a valid metabolic model of human SSADH deficiency, manifesting focal neurometabolic abnormalities which could provide key insights into pathophysiologic mechanisms.     

Influence of intermittent hypoxia and pyrimidinic nucleosides on cerebral enzymatic activities related to energy transduction

The effect of intermittent normobaric hypoxia and of biological pyrimidines (uridine and cytidine) on the specific activities of some enzymes related to cerebral energy metabolism were studied. Measurement were carried out on the following: (a) homogenate in toto; (b) purified mitochondrial fraction; (c) crude synaptosomal fraction, in different areas of rat brain: cerebral cortex, hippocampus, corpus striatum, hypothalamus, cerebellum, and medulla oblongata. Intermittent normobaric hypoxia (12 hours daily for 5 days) caused modifications of the enzyme activities in the homogenate in toto (decrease of hexokinase in cerebellum; increase of pyruvate kinase in medulla oblongata), in the purified mitochondrial fraction (increase of succinate dehydrogenase in the corpus striatum) and in the crude synaptosomal fraction (decrease of cytochrome oxidase activity in cerebral cortex, hippocampus, and cerebellum; decrease of malate dehydrogenase in hippocampus and cerebellum; decrease of lactate dehydrogenase in cerebellum). Daily treatment with cytidine or uridine altered some enzyme activities either affected or unaffected by intermittent hypoxia.     

Chronic metabolic effects of ammonia in mouse brain.

Chronic ammonia toxicity in experimental mice was induced by exposing them for 2 and 5 days to 5 % (v/v) ammonia solution. The enzymes concerned with glutamate metabolism (aspartate-, alanine- and tyrosine aminotransferases, glutamate dehydrogenase and glutamine synthetase) and (Na+ + K+)-ATPase were estimated in the three regions of brain (cerebellum, cerebral cortex and brain stem) and in liver. Glutamate, aspartate, alanine, glutamine and GABA, RNA and protein were also estimated in the three regions of brain and liver. A significant rise in the activity of (Na+ + K+)-ATPase in all the three regions of brain along with a fall in the activity of alanine aminotransferase was noticed. Changes in the activities of other enzymes were also observed. A significant increase in alanine and a decrease in glutamic acid was observed while no change was observed in the content of other amino acids belonging to the glutamate family. As a result of this, changes in the ratios of glutamate/glutamine and glutamate + aspartate/GABA was observed. The results indicated that the brain was in a state of more depression and less of excitation. Under these conditions the liver tissue was showing a profound rise in the activity of the enzymes of glutamate metabolism. The results are further discussed.