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Neurons are metabolically handicapped in the sense that they are not able to perform de novo synthesis of neurotransmitter glutamate and gamma-aminobutyric acid (GABA) from glucose. A metabolite shuttle known as the glutamate/GABA-glutamine cycle describes the release of neurotransmitter glutamate or GABA from neurons and subsequent uptake into astrocytes.(More)
Protoplasmic astrocytes are critically important to energy metabolism in the CNS. Our current understanding of the metabolic interactions between neurons and glia is based on studies using cultured cells, from which mainly inferential conclusions have been drawn as to the relative roles of neurons and glia in brain metabolism. In this study, we used(More)
The malate-aspartate shuttle and the glycerol phosphate shuttle act to transfer reducing equivalents from NADH in the cytosol to the mitochondria since the inner mitochondrial membrane is impermeable to NADH and NAD+. This transfer of reducing equivalents is essential for maintaining a favorable NAD+/NADH ratio required for the oxidative metabolism of(More)
Studies in different preparations of neurons and astrocytes of alanine transport and activities of its metabolizing enzyme alanine aminotransferase have led to the proposal that this amino acid is preferentially synthesized in astrocytes and transferred from the astrocytic to the neuronal compartment. From a functional point of view this may well be the(More)
Primary cultures of mouse cerebral cortical neurons (GABAergic) were incubated for 4 hours in media without glucose containing 1.0 mmol/L [U-13C]lactate in the absence or presence of 0.5 mmol/L glutamine. Redissolved, lyophilized cell extracts were analyzed by 13C nuclear magnetic resonance spectroscopy to investigate neuronal metabolism of lactate and by(More)
Glycogen is a complex glucose polymer found in a variety of tissues, including brain, where it is localized primarily in astrocytes. The small quantity found in brain compared to e.g., liver has led to the understanding that brain glycogen is merely used during hypoglycemia or ischemia. In this review evidence is brought forward highlighting what has been(More)
Net synthesis of the neurotransmitter amino acids glutamate and GABA can take place either from glutamine or from alpha-ketoglutarate or another tricarboxylic acid (TCA) cycle intermediate plus an amino acid as donor of the amino group. Since neurons lack the enzymes glutamine synthetase and pyruvate carboxylase that are expressed only in astrocytes,(More)
UNLABELLED Studies have shown decreased cerebral oxygen metabolism (CMRO(2)) and blood flow (CBF) in patients with cirrhosis with hepatic encephalopathy (HE). It remains unclear, however, whether these disturbances are associated with HE or with cirrhosis itself and how they may relate to arterial blood ammonia concentration and cerebral metabolic rate of(More)
The significance and functional roles of glycogen shunt activity in the brain are largely unknown. It represents the fraction of metabolized glucose that passes through glycogen molecules prior to entering the glycolytic pathway. The present study was aimed at elucidating this pathway in cultured astrocytes from mouse exposed to agents such as a high [K+],(More)
BACKGROUND & AIMS It is unclear whether patients with hepatic encephalopathy (HE) have disturbed brain oxygen metabolism and blood flow. METHODS We measured cerebral oxygen metabolism rate (CMRO(2)) by using (15)O-oxygen positron emission tomography (PET); and cerebral blood flow (CBF) by using (15)O-water PET in 6 patients with liver cirrhosis and an(More)