glycogen and Brain-Ischemia

The astrocyte-neuron lactate transfer shuttle (ANLS) is one of the important metabolic systems that provides a physiological infrastructure for glia-neuronal interactions where specialized architectural organization supports the function. Perivascular astrocyte end-feet take up glucose via glucose transporter 1 to actively regulate glycogen stores, such that high ambient glucose upregulates glycogen and low levels of glucose deplete glycogen stores. A rapid breakdown of glycogen into lactate during increased neuronal activity or low glucose conditions becomes essential for maintaining axon function. However, it fails to benefit axon function during an ischemic episode in white matter (WM). Aging causes a remarkable change in astrocyte architecture characterized by thicker, larger processes oriented parallel to axons, as opposed to vertically-transposing processes. Subsequently, aging axons become more vulnerable to depleted glycogen, although aging axons can use lactate as efficiently as young axons. Lactate equally supports function during aglycemia in corpus callosum (CC), which consists of a mixture of myelinated and unmyelinated axons. Moreover, axon function in CC shows greater resilience to a lack of glucose compared to optic nerve, although both WM tracts show identical recovery after aglycemic injury. Interestingly, emerging evidence implies that a lactate transport system is not exclusive to astrocytes, as oligodendrocytes support the axons they myelinate, suggesting another metabolic coupling pathway in WM. Future studies are expected to unravel the details of oligodendrocyte-axon lactate metabolic coupling to establish that all WM components metabolically cooperate and that lactate may be the universal metabolite to sustain central nervous system function.

Topics: Aging; Axons; Brain; Brain Ischemia; Cell Communication; Glucose; Glycogen; Lactic Acid; Oligodendroglia

In the mammalian white matter, glycogen-derived lactate from astrocytes plays a critical role in supporting axon function using the astrocyte-neuron lactate transfer shuttle (ANLTS) system with specialized monocarboxylate transporters (MCTs). A rapid breakdown of glycogen to lactate during increased neuronal activity or low glucose conditions becomes essential to maintain axon function. Therefore astrocytes actively regulate their glycogen stores with respect to ambient glucose levels such that high ambient glucose upregulates glycogen and low levels of glucose depletes glycogen stores. Although lactate fully supports axon function in the absence of glucose and becomes a preferred energy metabolite when axons discharge at high frequency, it fails to benefit axon function during an ischemic episode in white matter. Emerging evidence implies a similar lactate transport system between oligodendrocytes and the axons they myelinate, suggesting another metabolic coupling pathway in white matter. Therefore the conditions that activate this lactate shuttle system and the signaling mechanisms that mediate activation of this system are of great interest. Future studies are expected to unravel the details of oligodendrocyte-axon lactate metabolic coupling to establish how white matter components metabolically cooperate and that lactate may be the universal metabolite to sustain CNS function.

Topics: Animals; Astrocytes; Axons; Biological Transport; Brain Ischemia; Cell Communication; Energy Metabolism; Glucose; Glycogen; Homeostasis; Humans; Lactic Acid; Mice; Models, Neurological; Monocarboxylic Acid Transporters; Oligodendroglia; Optic Nerve; Sodium-Potassium-Exchanging ATPase; White Matter

Brain ischemia resulting from multiple disease states including cardiac arrest, stroke and traumatic brain injury, is a leading cause of death and disability. Despite significant resources dedicated to developing pharmacological interventions, few effective therapeutic options are currently available. The basic consequence of cerebral ischemia, characterized by energy failure and subsequent brain metabolic abnormalities, enables the protective effects by pharmacological manipulation of brain metabolism. We present here the important roles of brain glycogen metabolism and propose inhibition of glycogenolysis as a therapeutic approach to cerebral ischemia.

Topics: Animals; Brain; Brain Ischemia; Glycogen; Glycogenolysis; Indoles; Magnesium Sulfate; Phenylbutyrates; Triterpenes

Astrocytic glycogen works as an essential energy reserve for surrounding neurons and is reported to accumulate excessively during cerebral ischemia/reperfusion (I/R) injury. Our previous study found that accumulated glycogen mobilization exhibits a neuroprotective effect against I/R damage. In addition, ischemia could transform astrocytes into A1-like (toxic) and A2-like (protective) subtypes. However, the underlying mechanism behind accumulated glycogen mobilization-mediated neuroprotection in cerebral reperfusion injury and its relationship with the astrocytic A1/A2 paradigm is unknown.. Astrocytic glycogen phosphorylase, the rate-limiting enzyme in glycogen mobilization, was specifically overexpressed and knocked down in mice and in cultured astrocytes. The I/R injury was imitated using a middle cerebral artery occlusion/reperfusion model in mice and an oxygen-glucose deprivation/reoxygenation model in cultured cells. Alterations in A1-like and A2-like astrocytes and the expression of phosphorylated nuclear transcription factor-κB (NF-κB) and phosphorylated signal transducer and activator of transcription 3 (STAT3) were determined by RNA sequencing, immunofluorescence and immunoblotting. Metabolites, including glycogen, NADPH, glutathione and reactive oxygen species (ROS), were analyzed by biochemical analysis.. Here, we observed that astrocytic glycogen mobilization inhibited A1-like astrocytes and enhanced A2-like astrocytes after reperfusion in an experimental ischemic stroke model in vivo and in vitro. In addition, glycogen mobilization could enhance the production of NADPH and glutathione by the pentose phosphate pathway (PPP) and reduce ROS levels during reperfusion. NF-κB inhibition and STAT3 activation caused by a decrease in ROS levels were responsible for glycogen mobilization-induced A1-like and A2-like astrocyte transformation after I/R. The astrocytic A1/A2 paradigm is closely correlated with glycogen mobilization-mediated neuroprotection in cerebral reperfusion injury.. Our data suggest that ROS-mediated NF-κB inhibition and STAT3 activation are the key pathways for glycogen mobilization-induced neuroprotection and provide a promising metabolic target for brain reperfusion injury in ischemic stroke.

Topics: Animals; Animals, Newborn; Astrocytes; Brain Ischemia; Coculture Techniques; Female; Glycogen; Ischemic Stroke; Male; Mice; Mice, Inbred C57BL; Neuroprotection; Reactive Oxygen Species; Reperfusion Injury

Imaging energy metabolites as markers of the energy shuttle between glia and neurons following ischemia is an ongoing challenge. Traditional microscopies in combination with histochemistry reveal glycogen accumulation within glia following ischemia, indicating an altered metabolic profile. Although semiquantitative histochemical glycogen analysis is possible, the method suffers from typical confounding factors common to histochemistry, such as variation in reagent penetration and binding. In addition, histochemical detection of glycogen does not reveal information on the metabolic fate of glycogen (i.e., lactate production). Therefore, validation of a direct semiquantitative method to simultaneously image both brain glycogen and lactate in the same tissue section would benefit this research field. In this study, we demonstrate the first application of Fourier transform infrared (FTIR) spectroscopy for simultaneous direct spectroscopic imaging of brain glycogen and lactate, in situ within ex vivo tissue sections. Serial tissue sections were analyzed with anti-glial fibrillary acidic protein (GFAP) immunohistochemistry to provide a comparison between the glycogen and lactate distribution revealed by FTIR and the glial distribution revealed by GFAP immunohistochemistry. The distribution of glycogen revealed by FTIR spectroscopic imaging has been further compared with histochemical detection of glycogen on the adjacent tissue sections. This approach was then applied to study spatiotemporal disturbances in metabolism, relative to glia and neuronal populations, following cerebral ischemia in a murine model of stroke.

Topics: Animals; Brain Ischemia; Glycogen; Immunohistochemistry; Lactic Acid; Male; Mice; Mice, Inbred BALB C; Neuroglia; Spectroscopy, Fourier Transform Infrared

In isolated white matter, ischemic tolerance changes dramatically in the period immediately before the onset of myelination. In the absence of an extrinsic energy source, postnatal day 0 to 2 (P0 to P2) white matter axons are here shown to maintain excitability for over twice as long as axons >P2, a differential that was dependent on glycogen metabolism. Prolonged withdrawal of extrinsic energy supply tended to spare axons in zones around astrocytes, which are shown to be the sole repository for glycogen particles in developing white matter. Analysis of mitochondrial volume fraction revealed that neither axons nor astrocytes had a low metabolic rate in neonatal white matter, while oligodendroglia at older ages had an elevated metabolism. The astrocyte population is established early in neural development, and exhibits reduced cell density as maturation progresses and white matter expands. The findings show that this event establishes the necessary conditions for ischemia sensitivity in white matter and indicates that astrocyte proximity may be significant for the survival of neuronal elements in conditions associated with compromised energy supply.

Topics: Animals; Astrocytes; Axons; Brain; Brain Diseases; Brain Ischemia; Energy Metabolism; Female; Glycogen; Male; Myelin Sheath; Rats; White Matter

Transient carotid artery occlusion causes ischemia/reperfusion (I/R) injury resulting in neuron and pancreatic β-cell death with consequential post-stroke hyperglycemia, which can lead to diabetes and may accelerate the development of Alzheimer's disease. Antioxidants have been shown to protect against the I/R injury and destruction of neurons. However, it is unknown whether the protection against I/R injury extends to the pancreatic β-cells. Therefore, we investigated whether treatment with ebselen, a glutathione peroxidase mimic, prevents neuronal and β-cell death following I/R in gerbils susceptible to stroke. After 28 days post artery occlusion, there was widespread neuronal cell death in the CA1 of the hippocampus and elevated IL-1β and TNF-α levels. Pretreatment with ebselen prevented the death by 56% and attenuated neurological damage (abnormal eyelid drooping, hair bristling, muscle tone, flexor reflex, posture, and walking patterns). Ischemic gerbils also exhibited impaired glucose tolerance and insulin sensitivity which induced post-stroke hyperglycemia associated with decreased β-cell mass due to increased β-cell apoptosis. Ebselen prevented the increased β-cell apoptosis, possibly by decreasing IL-1β and TNF-α in islets. Ischemia also attenuated hepatic insulin signaling, and expression of GLUT2 and glucokinase, whereas ebselen prevented the attenuation and suppressed gluconeogenesis by decreasing PEPCK expression. In conclusion, antioxidant protection by ebselen attenuated I/R injury of neurons and pancreatic β-cells and prevented subsequent impairment of glucose regulation that could lead to diabetes and Alzheimer's disease.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Azoles; Brain Ischemia; Cell Survival; Cytokines; Gerbillinae; Glycogen; Hyperglycemia; Insulin; Insulin-Secreting Cells; Isoindoles; Liver; Male; Organoselenium Compounds; Random Allocation; Reperfusion Injury; Signal Transduction

Ischemic stroke is the combinatorial effect of many pathological processes including the loss of energy supplies, excessive intracellular calcium accumulation, oxidative stress, and inflammatory responses. The brain's ability to maintain energy demand through this process involves metabolism of glycogen, which is critical for release of stored glucose. However, regulation of glycogen metabolism in ischemic stroke remains unknown. In the present study, we investigate the role and regulation of glycogen metabolizing enzymes and their effects on the fate of glycogen during ischemic stroke.. Ischemic stroke was induced in rats by peri-vascular application of the vasoconstrictor endothelin-1 and forebrains were collected at 1, 3, 6 and 24 hours post-stroke. Glycogen levels and the expression and activity of enzymes involved in glycogen metabolism were analyzed. We found elevated glycogen levels in the ipsilateral hemispheres compared with contralateral hemispheres at 6 and 24 hours (25% and 39% increase respectively; P<0.05). Glycogen synthase activity and glycogen branching enzyme expression were found to be similar between the ipsilateral, contralateral, and sham control hemispheres. In contrast, the rate-limiting enzyme for glycogen breakdown, glycogen phosphorylase, had 58% lower activity (P<0.01) in the ipsilateral hemisphere (24 hours post-stroke), which corresponded with a 48% reduction in cAMP-dependent protein kinase A (PKA) activity (P<0.01). In addition, glycogen debranching enzyme expression 24 hours post-stroke was 77% (P<0.01) and 72% lower (P<0.01) at the protein and mRNA level, respectively. In cultured rat primary cerebellar astrocytes, hypoxia and inhibition of PKA activity significantly reduced glycogen phosphorylase activity and increased glycogen accumulation but did not alter glycogen synthase activity. Furthermore, elevated glycogen levels provided metabolic support to astrocytes during hypoxia.. Our study has identified that glycogen breakdown is impaired during ischemic stroke, the molecular basis of which includes reduced glycogen debranching enzyme expression level together with reduced glycogen phosphorylase and PKA activity.

Topics: Animals; Astrocytes; Brain Ischemia; Cell Hypoxia; Cell Survival; Cyclic AMP-Dependent Protein Kinases; Energy Metabolism; Gene Expression Regulation, Enzymologic; Glycogen; Glycogen Debranching Enzyme System; Glycogen Phosphorylase; Male; Protein Kinase Inhibitors; Rats; Rats, Wistar; Reperfusion; Stroke

Glucose is a necessary source of energy to sustain cell activities and homeostasis in the brain, and enhanced glucose transporter (GLUT) activities are protective of cells during energy depletion including brain ischemia. Here we investigated whether and if so how the astrocytic expression of GLUTs crucial for the uptake of glucose changes in ischemic conditions. Under physiological conditions, cultured astrocytes primarily expressed GLUT1, and GLUT3 was only detected at extremely low levels. However, exposure to ischemic stress increased the expression of not only GLUT1 but also GLUT3. During ischemia, cultured astrocytes significantly increased production of the transcription factor nuclear factor-κB (NF-κB), leading to an increase in GLUT3 expression. Moreover, astrocytic GLUT3 was responsible for the enhanced storage of intracellular glucose during reperfusion, resulting in increased resistance to lethal ischemic stress. These results suggested that astrocytes promptly increase GLUT3 production in situations such as ischemia, and much glucose is quickly taken up, possibly contributing to the protection of astrocytes from ischemic damage.

Topics: Animals; Astrocytes; Base Sequence; Brain Ischemia; DNA Primers; Glucose Transport Proteins, Facilitative; Glycogen; Immunohistochemistry; Polymerase Chain Reaction; Rats

Maslinic acid (MA), a natural triterpene from Olea europaea L., is a well-known inhibitor of glycogen phosphorylase and elicits multiple biological activities. The purpose of this study was to evaluate the effects of MA on focal cerebral ischemia in hyperglycemic rats. Adult rats were made hyperglycemic by intraperitoneal injection of streptozotocin and were given MA (50 mg/kg or 5 mg/kg) intragastrically for 14 consecutive days. Transient middle cerebral artery occlusion/reperfusion was then induced by a suture insertion technique. Results showed that diabetic rats pretreated with high-dose MA had lower blood glucose levels, but both doses reduced infarct volumes and improved neurological scores. Less glutamate overflow was also observed in MA-treated rats after 2 hr of ischemia followed by 24 hr and 72 hr reperfusion. In addition, MA treatment enhanced the glial glutamate transporter GLT-1 expression at the protein and mRNA levels. However, the injection of dihydrokainate, a GLT-1 glutamate transporter inhibitor, reversed the effect of MA. Previous studies have shown that suppression of glutamate uptake via nuclear factor-κB (NF-κB) activation is an important contributory factor in ischemia-triggered glutamate excitotoxicity, and inhibition of NF-κB could prevent ischemic suppression of glutamate uptake and GLT-1 expression. In the present study, we showed that MA pretreatment attenuated ischemia-induced translocation of NF-κB p65 subunit to the nucleus. In conclusion, these findings demonstrate that, in addition to showing promising antidiabetic properties, MA has a direct beneficial effect in cerebral ischemic injury, which may be correlated with the promotion of glutamate clearance by NF-κB-mediated GLT-1 up-regulation.

Topics: Animals; Blood Glucose; Brain; Brain Ischemia; Diabetes Mellitus, Experimental; Enzyme Inhibitors; Excitatory Amino Acid Transporter 2; Glycogen; Glycogen Phosphorylase; Hyperglycemia; Liver; Male; Neuroglia; Rats; Rats, Sprague-Dawley; Streptozocin; Triterpenes; Up-Regulation

Phosphorylated fructose compounds have been reported to lessen neuronal injury in in vitro models of hypoxia and in vivo models of ischemia. Although a variety of mechanisms have been proposed to account for this finding, it is unknown if intracellular uptake and incorporation of these compounds into the glycolytic pathway contribute to the benefit. We evaluated phosphorylated fructose administration in an adult rat model of transient, near-complete cerebral ischemia to determine its impact on brain metabolism before, during, and after ischemia. Fifty-four pentobarbital anesthetized rats were randomly assigned to receive IV infusions of either fructose-1,6-bisphosphate, fructose-2,6-bisphosphate, or 0.9% saline. After 2 hours of infusion, 18 rats (6/treatment group) were subjected to brain harvesting before any ischemia, 18 additional rats had brain harvesting at the completion of 10 minutes of forebrain ischemia (2-vessel occlusion plus induced hypotension), and 18 rats had harvesting after ischemia and 15 minutes of reperfusion. Cortical brain samples were analyzed for ATP, ADP, AMP, phosphocreatine, glucose, and glycogen. When compared with placebo, neither phosphorylated fructose compound altered preischemic, intraischemic, or postischemic concentrations of brain high-energy phosphates, glucose, glycogen, or lactate, nor did they influence the intraischemic metabolism of endogenous brain glucose or glycogen. On the basis of these results, we conclude that mechanisms other than augmented carbohydrate metabolism are responsible for previous reports of neuronal protection by the bisphosphonates.

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Anesthesia; Anesthetics; Animals; Blood Glucose; Brain Chemistry; Brain Ischemia; Carbohydrate Metabolism; Cerebrovascular Circulation; Electroencephalography; Fructosediphosphates; Glycogen; Hemodynamics; Lactic Acid; Phosphocreatine; Prosencephalon; Rats; Rats, Sprague-Dawley; Reperfusion Injury

Spreading depression (SD) has been demonstrated following focal ischemia, and the additional workload imposed by SD on a tissue already compromised by a marked reduction in blood flow may contribute to the evolution of irreversible damage in the ischemic penumbra. SD was elicited in one group of rats by injecting KCl directly into a frontal craniectomy and the wave of depolarization was recorded in two craniectomies 3 and 6 mm posterior to the first one. In a second group, the middle cerebral artery was occluded using the monofilament technique and a recording electrode was placed 5 mm lateral to the midline and 0.2 mm posterior to bregma. To determine the metabolic response in the penumbral region of the cortex ipsilateral to the occlusion, brains from both groups were frozen in situ when the deflection of the SD was maximal. The spatial metabolic response of SD in the ischemic cortex was compared to that in the non-ischemic cortex. Coronal sections of the brains were lyophilized, pieces of the dorsolateral cortex were dissected and weighed, and analyzed for ATP, P-creatine, inorganic phosphate (Pi), glucose, glycogen and lactate at varying distances anterior and posterior to the recording electrode. ATP and P-creatine levels were significantly decreased at the wavefront in both groups and the levels recovered after passage of the wavefront in the normal brain, but not in the ischemic brain. Glucose and glycogen levels were significantly decreased and lactate levels significantly increased in the tissue after the passage of the wavefront. While the changes in the glucose-related metabolites persisted during recovery even in anterior portions of the cortex in both groups in the aftermath of the SD, the magnitude of the changes was greater in the penumbra than in the normal cortex. SD appears to impose an equivalent increase in energy demands in control and ischemic brain, but the ability of the penumbra to recover from the insult is compromised. Thus, increasing the energy imbalance in the penumbra after multiple SDs may hasten the deterioration of the energy status of the tissue and eventually contribute to terminal depolarization and cell death, particularly in the penumbra.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cerebral Cortex; Cerebral Infarction; Cortical Spreading Depression; Energy Metabolism; Glucose; Glycogen; Lactic Acid; Male; Membrane Potentials; Phosphates; Phosphocreatine; Potassium Chloride; Rats; Rats, Wistar; Recovery of Function

Previous studies have demonstrated that traumatic brain injury (TBI) increases the vulnerability of the brain to an acute episode of hypoxia-ischemia. The objective of the present study was to determine whether TBI alters the vulnerability of the brain to a delayed episode of ischemia and, if so, to identify contributing mechanisms. Sprague-Dawley rats were subjected to lateral fluid-percussion (FP) brain injury (n = 14) of moderate severity (2.3-2.5 atm), or sham-injury (n = 12). After recovery for 24 h, all animals underwent an 8-min episode of forebrain ischemia, followed by survival for 6 days. Ischemic damage in the hippocampus and cerebral cortex of the FP-injured hemisphere was compared to that in the contralateral hemisphere and to that in sham-injured animals. Remarkably, the number of surviving CA(1) neurons in the middle and lateral segments of the hippocampus in the FP-injured hemisphere was significantly greater than that in the contralateral hemisphere and sham-injured animals (p < 0.05). Likewise, in the cerebral cortex the number of damaged neurons tended to be lower in the FP-injured hemisphere than in the contralateral hemisphere. These results suggest that TBI decreased the vulnerability of the brain to a delayed episode of ischemia. To determine whether TBI triggers protective metabolic alterations, glycogen levels were measured in cerebral cortex and hippocampus in additional animals 24 h after FP-injury (n = 13) or sham-injury (n = 7). Cortical glycogen levels in the ipsilateral hemisphere increased to 12.9 +/- 6.4 mmol/kg (mean +/- SD), compared to 6.4 +/- 1.8 mmol/kg in the opposite hemisphere and 5.7 +/- 1.3 mmol/kg in sham-injured animals (p < 0.001). Similarly, in the hippocampus glycogen levels in the FP-injured hemisphere increased to 13.4 +/- 4.9 mmol/kg, compared to 8.1 +/- 2.4 mmol/kg in the contralateral hemisphere (p < 0.004) and 6.2 +/- 1.5 mmol/kg in sham-injured animals (p < 0.001). These results demonstrate that TBI triggers a marked accumulation of glycogen that may protect the brain during ischemia by serving as an endogenous source of metabolic energy.

Topics: Animals; Brain Injuries; Brain Ischemia; Cerebral Cortex; Glucose; Glycogen; Hippocampus; Male; Rats; Rats, Sprague-Dawley; Time Factors

Brain infarction was induced in rats by injection of microspheres through the right internal carotid artery, and structural changes in the astrocytes were observed during the early period following the infarction. Necrotic foci, varying in size and shape, were found in the right hemisphere. After immunohistochemical staining for GFAP, GFAP-positive astrocytes in the perinecrotic area known as the ischemic penumbra had distinctly increased in number and size with elongation of cytoplasmic processes 3 days after infarction. Electron microscopic observation revealed that glycogen granules had markedly accumulated in the cytoplasm of astrocytes located in the ischemic penumbra 3 and 5 days after infarction. Seven days after infarction, however, the glycogen granules disappeared from the astrocytes. Intermediate filaments increasingly appeared in the protoplasmic astrocytes after 3 days and were abundant in the activated and hypertrophied astrocytes after 7 days. As a result of our present study, we conclude that: (1) the function of glucose uptake from blood vessels was not impaired in the astrocytes under hypoxic conditions; (2) the astrocytes actively ingested blood glucose through the endothelial cells and accumulated it as glycogen for activation of their functions, and the cell volume increased under hypoxic conditions; (3) the depression of energy metabolism and the decrease in the uptake of energy sources in the nerve cells promoted glycogen accumulation in the astrocytes under hypoxic conditions; (4) intermediate filaments (GFAP filaments) increased in number, coincident with the activation and enlargement of the astrocytes; and (5) protoplasmic astrocytes were transformed into fibrous astrocytes in the ischemic penumbra of the brain infarction.

Topics: Animals; Astrocytes; Brain; Brain Infarction; Brain Ischemia; Glial Fibrillary Acidic Protein; Gliosis; Glycogen; Immunohistochemistry; Male; Microscopy, Electron; Neurons; Rats; Rats, Wistar

The primary objective of this study was to attempt to induce excessive intraglial acidosis during ischemia by subjecting rats to an initial insult which leads to post insult accumulation of glycogen, presumed to accumulate primarily in astrocytes. The initial insults were 15 min of transient forebrain ischemia, 30 min of hypoglycemic coma, and intraperitonial injection of methionine-sulphoximine (MSO). In the first two of these insults, glycogen content in neocortex increased to 6-7 mM kg(-1) after 6 h of recovery, and in MSO-treated animals even higher values were measured 24 h after administration ( 12 mM kg(-1)). In spite of this glycogen loading, the amount of lactate formed during a subsequent ischemic insult (of 5-30 min duration) did not exceed values usually obtained during complete ischemia in animals with normal glycogen contents (tissue lactate contents of 15 mM kg(-1)) This was because appreciable amounts of glycogen (3-7 mM kg(-1)) remained undegraded even after 30 min of ischemia. The undigested part largely reflected the extra amount of glycogen accumulated after the initial insults. It is discussed whether this part is unavailable to degradation by phosphorylase.

Topics: Acidosis; Animals; Astrocytes; Brain; Brain Ischemia; Coma; Energy Metabolism; Glycogen; Hypoglycemia; Ischemic Attack, Transient; Male; Methionine Sulfoximine; Phosphorylation; Rats; Rats, Wistar; Reperfusion Injury; Seizures

Increases in brain glucose will worsen outcome after global cerebral ischemia, and some experimental evidence suggests that the duration of hyperglycemia also may influence outcome. Different types of hyperglycemia were studied to identify metabolic differences that might account for alterations in postischemic outcome.. Ninety pentobarbital-anesthetized Sprague-Dawley rats were divided into three groups: normoglycemic nondiabetic rats (N) (n = 30), chronically hyperglycemic diabetic rats (HD) (n = 30), and acutely hyperglycemic, glucose-infused nondiabetic rats (HN) (n = 30). These groups were further subdivided into groups of six rats each that received 0, 2.5, 5, 10, or 15 min of complete cerebral ischemia (potassium chloride--induced cardiac arrest). Brains were excised after 10-kW focused microwave radiation and metabolites were measured using enzymatic fluorometric techniques.. At all study intervals, plasma glucose concentrations in HD and HN were fourfold greater than in N. Before ischemia, brain glucose concentrations in all groups were proportional to plasma glucose concentrations; however, brain glycogen concentrations did not differ among groups. After the onset of ischemia, there was an immediate diminution of brain glucose, glycogen, adenosine triphosphate (ATP), and phosphocreatine that in all cases was most pronounced during the initial 2.5 min of ischemia. Consumption of carbohydrate stores and lactate production were greater in HD and HN than in N. HD had lesser preischemic ATP concentrations and energy charges relative to N and HN (P < 0.05), perhaps reflecting their disease state; however, at 2.5 min of ischemia, the relationship of ATP concentrations and energy charges was HN > HD > N (P < 0.05 among all). In all groups, ATP and phosphocreatine were more than 96% depleted by 10 min of ischemia. With few exceptions (ATP concentrations and energy charges before ischemia and at 2.5 min, and lactate concentration in HD < HN at 15 min), there were no measured metabolic differences between HD and HN.. In these studies, the duration of hyperglycemia did not affect intraischemic carbohydrate consumption. At short durations of ischemia (2.5 min), both HD and HN groups had greater intraischemic ATP concentrations and energy charges than N; however, at longer durations of ischemia (> 5.0 min), high-energy phosphate depletion was similarly severe in all groups. These studies suggest that energy failure is not the origin of worse postischemic neurologic injury in hyperglycemic subjects, nor does energy failure readily explain reported differences between acutely and chronically hyperglycemic subjects exposed to global cerebral ischemia.

Topics: Adenine Nucleotides; Animals; Blood Glucose; Blood Pressure; Brain; Brain Ischemia; Diabetes Mellitus, Experimental; Energy Metabolism; Glucose; Glycogen; Hyperglycemia; Lactates; Rats; Rats, Sprague-Dawley

Impairment of energy metabolism is the fundamental mechanism leading to cell death in ischemia. Using the middle cerebral artery (MCA) occlusion model in cats, we studied the effect of Duxil (almitrine and raubasine combination), which was given either before and after or only after MCA occlusion, on ischemia in terms of neurological function and histological changes. Neurological function was assessed consecutively for 7 days after MCA occlusion using a categorical rating scale in 18 cats. Neurological function was significantly improved in treated animals than in non-treated controls regarding to the motor and sensory function, walking, posture and stepping reflex. Animals were killed on the 8th day and histological changes were examined by light and electron microscopies. Significant improvement in the morphological scores based on the light-microscopy changes were found in animals treated with Duxil compared to non-treated ones. Under the electron microscopy, the protective effects of Duxil were characterized by retaining glycogen and mitochondria. Morphological improvement was associated with the recovery of neurological function and especially profound in penumbra areas of MCA infarction. These results suggest that Duxil has a protective effect against ischemic damage induced by occlusion of MCA in cats.

Topics: Almitrine; Animals; Anti-Inflammatory Agents, Non-Steroidal; Behavior, Animal; Brain; Brain Chemistry; Brain Ischemia; Cats; Cerebral Arteries; Female; Glycogen; Male; Mitochondria; Secologanin Tryptamine Alkaloids; Yohimbine

Bilateral ischemia has been shown to alter the net brain levels of energy metabolites such as ATP, phosphocreatine, glucose, and glycogen. The amino acid neurotransmitter gamma-aminobutyric acid (GABA) exerts a tonic inhibitory influence on neural activity. The present studies were designed to evaluate the influence of elevated GABA levels on the metabolic sequelae of ischemia. The GABA transaminase inhibitor gamma-vinyl-GABA (GVG; vigabatrin) was administered to Mongolian gerbils before the production of a bilateral ischemic incident. GABA levels were elevated in all regions assayed. Levels of energy metabolites were also increased, an indication of reduced energy utilization. In control animals, in the absence of GVG, 1 min of bilateral ischemia produced decreases in the levels of all metabolites. In animals pretreated with GVG, the effects of 1 min of bilateral ischemia were attenuated. These data suggest that the level of ongoing activity may affect the response to an ischemic insult. Furthermore, GVG may have a clinical indication in reducing the effect of minor ischemic incidents.

Topics: Adenosine Triphosphate; Aminocaproates; Animals; Body Temperature; Brain; Brain Ischemia; Energy Metabolism; GABA Antagonists; gamma-Aminobutyric Acid; Gerbillinae; Glycogen; Phosphocreatine; Tissue Distribution; Vigabatrin

We tested the efficacy of various putative neuroprotective agents in the gerbil model of delayed neuronal death. The selective loss of anterior CA1 neurons of the hippocampus 4 days after 5 minutes of bilateral ischemia was complete in greater than 90% of the gerbils examined. We tested 11 agents for their ability to protect against neuronal loss. Only those agents that were associated with the GABAergic system exhibited protection and only when administered before the ischemic insult. The possibility that delayed neuronal death is the result of a primary defect in inhibitory neurotransmission is considered.

Topics: Animals; Brain Ischemia; Cell Survival; Disease Models, Animal; Female; gamma-Aminobutyric Acid; Gerbillinae; Glycogen; Hippocampus; Neurons; Time Factors; Tissue Distribution

Serum lactic acidosis is characterized by a pH less than 7.25 and lactate greater than 5 mEq. Although sodium bicarbonate (NaHCO3) is standard treatment for this condition, clinical and experimental studies suggest that high doses of NaHCO3 may be ineffectual or even detrimental to brain, cardiovascular, and respiratory function, as well as survival. For this reason, low dose therapy with NaHCO3 has been recommended. Sodium dichloroacetate (NaDCA) has been used successfully to treat clinical and experimentally-induced lactic acidosis. The present study was designed to compare the effects of low dose NaHCO3 with NaDCA on blood pressure, blood chemistries and brain metabolites in rats with a low flow-induced (Type A, the most common type) lactic acidosis. Fasted male Wistar rats were subjected to cerebral ischemia and systemic hypotension for 30 min at which time, if the pH or HCO-3 fell to 7.2 or 10, respectively, the rat was treated with NaHCO3, NaDCA, or an equal volume of sterile water. Over the 30 min of recirculation that followed ischemia, treatment had no effect on blood pressure or glucose or on brain glucose or glycogen. NaHCO3 had no effect on lactate but appeared to stabilize pH and increase HCO3- more than in sham- or NaDCA-treated rats. Although NaDCA caused a greater increase in HCO3- than sham treatment, pH continued to decline. However, lactate decreased more in NaDCA- than in sham- or NaHCO3- treated rats. These results suggest that low dose NaHCO3 is not detrimental in this model; however, although NaHCO3 stabilized pH, it did not rapidly correct the acidosis. NaDCA at this dose had no effect on the acidosis but was effective in decreasing lactate. Since serum lactate has previously correlated with survival and since higher doses of NaDCA have corrected lactic acidosis in other studies, future evaluation of postischemic treatment with higher doses of NaDCA is warranted.

Topics: Acetates; Acidosis, Lactic; Animals; Bicarbonates; Blood Glucose; Brain Chemistry; Brain Ischemia; Dichloroacetic Acid; Glycogen; Lactates; Male; Rats; Rats, Inbred Strains; Resuscitation; Sodium; Sodium Bicarbonate

The CA 1 neurons of the gerbil hippocampus die at 4 days following 5 min of bilateral ischemia. The fiber and somal layers of the CA 1 region of the gerbil hippocampus were analyzed for high-energy phosphates, glucose-related metabolites, and amino acids from 0.75 hr to 4 days of postischemia. The results were compared to those from two layers of the CA 3 region and the cerebral cortex. The metabolite changes in the fiber layers of the CA 1 region were qualitatively similar to those in the somal layer. The energy status of the tissues taken from the CA 1 region was never compromised for up to 2 days of recirculation, after which the ATP and P-creatine in the somal layer decreased to 43 and 56% of the control, respectively, whereas the average decreases in the CA 1 fiber layers were only 71 and 88% of the control, respectively. Thus, the high-energy phosphate response of the neuronal elements in the fiber layers was temporally similar to that found in the somal layer of the CA 1 region. The biphasic increases in glycogen, glucose, glucose-6-phosphate, and high-energy phosphates to values greater than the control indicated that the metabolic restoration following transient ischemia is a dynamic process which persists for up to 2 days of recirculation, even in resistant tissues. A similar pattern of delayed changes was observed in glutamate, gamma-aminobutyric acid (GABA), and glutamine, but the change in each amino acid appeared to be independent of the others despite their close metabolic relationship. The delayed decreases in GABA would favor a loss of inhibition to the CA 1 neurons and may be related to the phenomenon of delayed neuronal death.

Topics: Adenosine Triphosphate; Amino Acids; Animals; Brain Ischemia; Cerebral Cortex; Energy Metabolism; gamma-Aminobutyric Acid; Gerbillinae; Glucose; Glutamine; Glycogen; Hippocampus; Nerve Fibers; Neurons; Phosphates

Elevated cerebral lactate levels following cerebral ischemia have been associated with brain cell damage and death. We previously found that pre- or postischemia treatment with dichloroacetate (DCA), presumably by its activation of brain pyruvate dehydrogenase, effectively lowers cerebral lactate levels in rats subjected to 30 minutes of partial global ischemia (PGI) followed by 30 minutes of recirculation. The goal of the present study was to determine the effects of preischemia DCA treatment on cortical lactate levels during the ischemia period or during early recirculation. Rats (four in each group) received preischemia treatment with DCA and were then subjected to 0, 10, or 30 minutes of PGI or 30 minutes of PGI followed by 15 minutes of recirculation. Cortical lactate levels in pretreated animals were not significantly different from lactate levels of untreated rats at any time during PGI, but were significantly lower than levels in untreated rats at 15 minutes of recirculation (P less than .05, ANOVA). These results suggest that preischemia treatment with DCA does not limit the accumulation of cortical lactate during PGI but may promote its clearance during recirculation following PGI. If reperfusion events influence the degree of brain cell injury, DCA may enhance cell recovery by lower cortical lactate levels in the reperfusion period.

Topics: Acetates; Animals; Blood Glucose; Brain; Brain Ischemia; Cerebral Cortex; Cerebrovascular Circulation; Dichloroacetic Acid; Glucose; Glycogen; Lactates; Male; Rats; Rats, Inbred Strains; Time Factors

This study addresses the question of whether the cyclooxygenase inhibitors indomethacin and diclofenac and the glucocorticosteroid dexamethasone ameliorate neuronal necrosis following cerebral ischemia. In addition, since these drugs inhibit the production of prostaglandins and depress phospholipase A2 activity, respectively, the importance of free fatty acids (FFAs) on the development of ischemic neuronal damage was assessed. Neuronal damage was determined in the rat brain at 1 week following 10 min of forebrain ischemia. The cyclooxygenase inhibitors, whether given before or after ischemia, failed to alter the brain damage incurred. Animals given dexamethasone were divided into three groups and the drug was administered at a constant dosage of 2 mg/kg: (a) 2 days, 1 day, and 3 h intraperitoneally before (chronic pretreatment), (b) 3 h intraperitoneally before (acute pretreatment), and (c) 5 min intravenously and 6 h and 1 day intraperitoneally after (chronic posttreatment) induction of ischemia. Acute pretreatment did not affect the histopathological outcome. Chronic posttreatment of animals with dexamethasone ameliorated the damage inflicted on the caudate nucleus, but had no effect on other brain areas investigated. Unexpectedly, the chronic pretreatment aggravated the brain damage and caused seizures following ischemia. Histopathological data showed massive neuronal damage in these brains. The accumulation of FFA levels during ischemia was markedly suppressed, and the decrease in the energy charge was curtailed by chronic pretreatment with dexamethasone. However, brain glucose levels in control animals and lactic acid concentrations following 10 min of ischemia were significantly higher both in the cerebral cortex and in the hippocampus of dexamethasone-treated animals. These results suggest that aggravation of neuronal necrosis by chronic dexamethasone pretreatment could be ascribed to lactic acidosis due to hyperglycemia in combination with an action of dexamethasone on glucocorticoid receptors in the brain.

Topics: Animals; Blood Glucose; Brain Chemistry; Brain Ischemia; Cyclooxygenase Inhibitors; Dexamethasone; Diclofenac; Electroencephalography; Energy Metabolism; Fatty Acids, Nonesterified; Glycogen; Indomethacin; Male; Necrosis; Neurons; Rats; Rats, Inbred Strains

Cerebral ischemic insult is one of the most clinically significant conditions leading to irreversible brain cell damage and death. Animal studies have suggested that lowered intracellular pH due to the severe brain lactic acidosis following ischemia interferes with normal cell structure and function and leads to brain cell necrosis. Therefore, efforts directed to decreasing brain lactate may be beneficial in preventing brain cell damage and death. The goal of our study was to evaluate the effectiveness of postinsult treatment with dichloroacetate (DCA) in controlling increases in brain lactate following partial global ischemia (PGI) in rats. PGI was induced by bilateral carotid artery occlusion and induced hypotension. Animals that received DCA immediately after a 30-minute ischemic insult (n = 5) or 15 minutes after the end of an ischemic insult (n = 5) had cortical lactate levels that were significantly lower (P less than .005) than lactate levels in untreated insulted animals and that were not significantly different than those previously obtained with preinsult DCA treatment in rats subjected to 30 minutes of PGI. Treatment of rats with DCA following PGI may be effective in reducing cortical lactate levels and hence may limit irreversible damage to brain cells following cerebral ischemia.

Topics: Acetates; Acidosis; Animals; Blood Glucose; Blood Pressure; Brain; Brain Chemistry; Brain Ischemia; Dichloroacetic Acid; Electroencephalography; Glucose; Glycogen; Hydrogen-Ion Concentration; Lactates; Male; Rats; Rats, Inbred Strains

The influence of a new eburnamenine derivative RU 24722 [(3 beta, 14 alpha, 16 alpha)-(+/-)-14,15-dihydro-20,21-dinoreburnamenin -14-ol] on post-ischemic EEG recovery was studied in N2O anesthetized rats subjected to 1 min of global-compression cerebral ischemia. RU 24722 was compared with vincamine, dihydroergotoxine mesylate and nicergoline. Treatment with RU 24722 (2 mg/kg i.v.) significantly decreased the EEG recovery time and increased the electrocortical activity during the first phase of the post-ischemic recovery. Vincamine (2 mg/kg i.v.), dihydroergotoxine mesylate (0.5 mg/kg i.v.) and nicergoline (0.5 mg/kg i.v.) were devoid of activity. In an attempt to elucidate its mechanism of action, the influence of RU 24722 on changes in the cerebral metabolic energy reserves was studied in mouse brain after different periods of decapitation ischemia. The changes occurring during the first 10 s of ischemia were used to calculate the baseline cerebral metabolic rate (CMR). The activity of RU 24722 was compared with that of vincamine and pentobarbital. RU 24722 (10 mg/kg i.p.) significantly retarded glucose, phosphocreatine and adenosine triphosphate utilisation and lactate production. Vincamine (10 mg/kg i.p.) had no effect on cerebral energy substrates. Pentobarbital (100 mg/kg i.p.) markedly increased the tissue concentration of glucose and phosphocreatine and decreased lactate levels before and after ischemia. The improvement of EEG recovery suggests that RU 24722 may be therapeutically effective in cerebral insufficiency, and the decreased brain energy demand may be one of the mechanisms by which RU 24722 has a protective effect against cerebral ischemic damage.

Topics: Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Dihydroergotoxine; Electroencephalography; Energy Metabolism; Glucose; Glycogen; Lactates; Lactic Acid; Male; Mice; Nicergoline; Phosphocreatine; Rats; Vasodilator Agents; Vinca Alkaloids; Vincamine

Norepinephrine (NE) depletion of the cerebral cortex after lesion of the ipsilateral locus ceruleus (LC) causes abnormalities of cerebral oxidative metabolism when the cortex is stimulated to increased energy demand (Harik, S. I., J. C. LaManna, A. I. Light, and M. Rosenthal (1979) Science 206: 69-71; LaManna, J. C., S. I. Harik, A. I. Light, and M. Rosenthal (1981) Brain Res. 204: 87-101). These abnormalities were exhibited as decreased mitochondrial reducing equivalent flow. One possible cause of this would be the decreased availability of oxidative metabolic substrates in the NE-depleted cortex. We therefore investigated the effect of unilateral LC lesion and the resultant depletion of ipsilateral endogenous NE on glycogen and other energy metabolites in the cerebral cortex of rats under three conditions: (1) at "rest," (2) when energy demand is inncreased markedly by seizures, and (3) during total cerebral ischemia. We report no differences in cerebral metabolites between NE-depleted and control hemispheres at "rest." In seizures and ischemia, however, the increase in the level of adenosine 3':5'-monophosphate (cyclic AMP) and the breakdown of glycogen were impaired considerably in the NE-depleted cortex. The data suggest that depletion of central NE impairs cerebral glycogenolysis in response to increased energy demands and ischemia. Such impairment may be mediated via a cyclic AMP-related mechanism.

Topics: Animals; Brain Ischemia; Cerebral Cortex; Cyclic AMP; Electroencephalography; Energy Metabolism; Glycogen; Male; Norepinephrine; Oxidation-Reduction; Rats; Rats, Inbred Strains; Seizures

Microanalysis methods were used to determine the effect of bilateral carotid occlusion on net levels of energy metabolites in discrete cellular regions of the hippocampus and dentate gyrus of the Mongolian gerbil. Glucose, glycogen, ATP and phosphocreatine levels were not decreased after one minute of bilateral occlusion. Three minutes of ischemia, however, produced a dramatic fall in net levels with no further decrease observed at fifteen minutes. Re-establishment of blood flow for five minutes after a fifteen minute ischemic episode resulted in replenishment of metabolites to pre-ischemic levels. Glucose was increased two to three times in sham-operated animals as compared to control (non-operated) animals. The increase was the result of the Na-pentobarbital anesthetic employed. The present data indicate that regions of the hippocampus and dentate gyrus respond in a uniform manner to bilateral occlusion of the carotid arteries. Further, most cells maintained enough viability to resume production of high-energy phosphate and carbohydrate metabolites.

Topics: Adenosine Triphosphate; Animals; Blood Glucose; Brain Ischemia; Dominance, Cerebral; Energy Metabolism; Gerbillinae; Glycogen; Hippocampus; Phosphocreatine

Topics: Adenine Nucleotides; Animals; Brain Ischemia; Cerebral Cortex; Energy Metabolism; Glycogen; Hypoxia; Kinetics; Lactates; Phosphocreatine; Potassium; Pyruvates; Rats

The ischemic effect on cerebral enzymes and glycogen content was histochemically evaluated in mongolian gerbils subjected to unilateral common carotid artery occlusion for various periods of time from 1/2 to 9 h. In early stages (up to 2 h), the only enzyme affected was the phosphorylase which revealed a decreased activity. Thereafter, the observed changes inclusive of glycogen and other enzymes such as the dehydrogenase, nonspecific acid and alkaline phosphatases, leucine aminopeptidase and thiamine pyrophosphatase progressed proportionally to the duration of ischemia. There was an overall inverse appearance of histochemically demonstrated enzymatic disturbances between the severely damaged ischemic regions and its marginal zones; the former revealing a conspicuous decrease and/or loss of enzymatic activities while the latter showing an increase of the same enzymes. Correlating the various ischemic responses of the intracellular organelles it appears that the changes in the lysosomes and Golgi apparatus occurred slower than those of mitochondria.

Topics: Acid Phosphatase; Alkaline Phosphatase; Animals; Brain; Brain Chemistry; Brain Ischemia; Female; Gerbillinae; Glycogen; Golgi Apparatus; Leucyl Aminopeptidase; Lysosomes; Male; Mitochondria; Oxidoreductases; Thiamine Pyrophosphatase

The behaviour of fuels (glycogen, glucose), of glycolytic pathway intermediates (glucose-6-phosphate, pyruvate) and end-product (lactate), as well as the pool of labile phosphates (ATP, ADP, AMP, creatine phosphate) and the energy charge of the brain were studied in the motor area of the cerebral cortex of beagle dogs in hypovolaemic hypotension. These parameters were evaluated after acute hypoxia (obtained by altering the composition of the inhalation mixture), after acute hypoxia plus incomplete ischaemia, after acute hypoxia plus complete ischaemia, during post-hypoxic recovery (3, 15 or 30 min after the restoration of normal ventilation), during post-hypoxic recovery and recirculation. A comparative examination of the different conditions showed that the most dramatic fall in the cerebral energy state took place in hypoxia plus complete ischaemia followed, in the order, by hypoxia plus incomplete ischaemia and simple hypoxia. However, reversal was most difficult in hypoxia plus incomplete ischaemia. The different situations are discussed in this paper with regard to the changes taking place in cerebral biochemical events.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Dogs; Energy Metabolism; Female; Glucose; Glycogen; Hypoxia, Brain; Lactates; Models, Biological; Phosphocreatine; Pyruvates

The effect of (-)eburnamonine, papaverine and UDP-glucose intracarotid perfusion has been evaluated in the brain of beagle dogs during various conditions of cerebral damage (hypoxia, hypoxia plus incomplete ischaemia, hypoxia plus complete ischaemia), and after 3, 15 or 30 min of the post-hypoxic recovery and recirculation. The behaviour of fuels (glycogen, glucose), of glycolytic pathway intermediates (glucose-6-phosphate, pyruvate) and end-product (lactate), of the pool of labile phosphates (ATP, ADP, AMP, creatine phosphate) and the energy charge potential of the brain were evaluated in the motor area of the cerebral cortex. The different pharmacological effects of (-)eburnamonine, papaverine and UDP-glucose are discussed with regard to the biochemical changes taking place during the physiopathological conditions tested.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Brain; Brain Ischemia; Dogs; Energy Metabolism; Female; Glucose; Glycogen; Hypoxia, Brain; Lactates; Papaverine; Phosphocreatine; Pyruvates; Uridine Diphosphate Glucose; Uridine Diphosphate Sugars; Vasodilator Agents; Vinca Alkaloids

Effects of controlled hypoxemia on cerebral functional activity were studied in rats using cyclic adenosine monophosphate (cAMP) and aminergic neurotransmitters in the brain tissue as special references. Evidence is presented that: (1) mild hypoxemic stress (PaO2 60 to 40 torr) may activate cerebral glycolysis with no evidence of anaerobic metabolism but that further reduction of PaO2 impairs cellular respiration, as evidenced by accumulation of glycolytic products; (2) glycogenolysis in the brain tissue, leakage of potassium ions from the brain cell, increase in brain water, and suppression of neural functional activity occur concomitant with accumulation of cAMP and prior to the fall of adenosine triphosphate; (3) the diminution of cerebral high-energy phosphates during hypoxia is associated with and may be caused by hypoxemia-induced neuroglycopenia and occurs at PaO2 15 torr; (4) induced hypoxemia per se does not affect the level or aminergic neurotransmitter substances in brain tissue.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Blood Glucose; Brain; Brain Ischemia; Carbon Dioxide; Cyclic AMP; Dopamine; Electroencephalography; Evoked Potentials; Glycogen; Lactates; Male; NAD; Norepinephrine; Oxygen; Phosphocreatine; Pyruvates; Rats; Serotonin