Brain carbohydrate metabolism

Other strategies include detailed studies of the changes in brain carbohydrate metabolism in ageing and how this may differ in patients with Alzheimer s disease. Changes in the composition and biophysical properties of neuronal membranes may also be of crucial importance in regulating the cytosolic free calcium, which could affect cellular homeostasis. 

Hormones have a profound effect on carbohydrate metabolism. Great interest has been aroused by reports of hormonal control of hexokinase activity by specific proteins in animal tissues.99- 100 Hexokinase action is the rate-limiting step in the uptake of D-glucose by muscle. Hexokinase is inhibited in diabetic muscle, but the inhibition can be partially reversed by insulin. A protein fraction from the anterior pituitary gland will inhibit the hexokinase of extracts of brain and muscle, and the effect of this... 

Major metabolic pathways in brain in the absorptive state. [Note The numbers in circles, which appear both on the figure and in the text, indicate important pathways for carbohydrate metabolism.]... 

The neonate is at risk for kemicterus if the serum unconjugated bilirubin level is higher than 17 mg/dL. Kemicterus is characterized by yellow staining of clusters of neuronal cell bodies in the basal ganglia, cerebellum, and brain stem, leading to motor and cognitive deficits or death. Immaturity and f)erhaps hypoxia make the blood-brain barrier permeable to bilirubin and contribute to the likelihood of kemictems. The biochemical basis of bilirubin encephalopathy is due to many causes inhibition of RNA and protein synthesis, carbohydrate metabolism (both cAMP-mediated and Ca " -activated), phospholipid-dependent protein kinases, enzymes involved in the electron transport system, and impaired nerve conduction. 

Lipid and carbohydrate metabolism occur to different extents in different organs. The liver regulates the flow of metabolites to brain, muscle, and adipose tissue and ultimately controls the concentration of blood glucose. Adipose tissue is the major storage depot for fatty acids. Triglycerides... 

This reaction, which produces oxaloacetate from pyruvate, provides a connection between the amphibolic citric acid cycle and the anabolism of sugars by gluconeogenesis. On this same topic of carbohydrate anabolism, we should note again that pyruvate cannot be produced from acetyl-GoA in mammals. Because acetyl-GoA is the end product of catabolism of latty acids, we can see that mammals could not exist with fats or acetate as the sole carbon source. The intermediates of carbohydrate metabolism would soon be depleted. Garbohydrates are the principal energy and carbon source in animals (Figure 19.11), and glucose is especially critical in humans because it is the preferred fuel for our brain cells. Plants can carry out the conversion of acetyl-GoA to pyruvate and oxaloacetate, so they can exist without carbohydrates as a carbon source. The conversion of pyruvate to acetyl-GoA does take place in both plants and animals (see Section 19.3). 

The thyroid hormones, T4 and T3, play numerous, profound roles in regulating metabolism, growth, and development and in maintaining homeostasis. Their reactions and products influence carbohydrate metabolism, protein synthesis and breakdown, and cardiovascular, renal, and brain function. It generally is believed that these actions result from effects of thyroid hormones on protein synthesis. 

Effect of Insulin on Glucose Uptake in Brain, Lens, and Tumor Cells Site of Action of Insulin on Carbohydrate Metabolism Transport Theory... 

The primary function of B vitamins is to help body cells produce energy through metabolism of carbohydrate, fat and protein. These vitamins are required for brain energy metabolism, neurotransmitter synthesis and functioning, and myelination of the spinal cord and brain cells. More specifically, folic acid, vitamin Bg and Bj2 deficiencies or congenital defects in enzymes that are involved in the metabolism of these B vitamins, are known to be associated with impaired brain function (Rosenberg 2001). Folic acid, vitamin Bg and B2 are also involved in homocysteine metabolism known to be important for cardiovascular function. 

In vitro studies of LSD with purified calf thymus DNA showed that it might cause changes In the conformation of DNA and thus make It more susceptible to enzymatic attack and breakage. Glycolysis was observed to be significantly Increased In the rat brain. In a study of the effect of LSD on carbohydrate metabolism. 

Disturbances in lipid and carbohydrate metabolism in relation to the brain. In Mental retardation, p. 277. Eds. P. W. Bowman and H. V. Mantuer. New York-London Grune and Stratton 1960. 

Disturbances in lipid and carbohydrate metabolism in relation to the brain. In Mental Retardation. New York Grune Stratton 1960. 

Impaired brain. Abnormal carbohydrate metabolism may affect the structure and function of the brain. 

Aldehydes derived from monoamines, especially 5-hydroxyindolacetyl-aldehyde (5-HIAAld), are quite reactive intermediates and make covalent bonds by a SchifTs base with free amino groups of dibasic amino adds of brain proteins. This mechanism explains why aldehydes play some important regulatory actions on carbohydrate metabolism and on sleep induction (see Fig. 8). However, aldehydes derived from biogenic amines are quite inactive on smooth-muscles contractions and MAO can therefore be considered as a significant means of termination of 5-HT actions. 

Tbiamine, aneurin or vitamin Bj is directly concerned with intermediate carbohydrate metabolism, and the extensive work of R. Peters has shown that in the form of its diphosphoric ester (co-carboxylase), it works in conjunction with the dicarboxylic acid system of Szent-Gy5rgyi in brii ing about the characteristic oxidation of pyruvate in brain tissue. 

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