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Treatment of Chronic Fatigue Syndrome
Published in Jay A. Goldstein, Chronic Fatigue Syndromes, 2020
Other treatment possibilities include (a) substances which increase levels of NADPH, since nitric oxide synthase is NADPH-diaphorase,98 (b) tetrahydrobiopterin, a cofactor in nitric oxide biosynthesis; and (c) nicotinic and muscarinic cholinergic agonists, since the vasodilatation that occurs during mental work is dependent on acetylcholine stimulation of nitric oxide.99,100 Ravin adenine dinucleotide and mononucleotide are also nitric oxide synthase cofactors.
Hyperphenylalaninemia and defective metabolism of tetrahydrobiopterin
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
Each of these defects leads to a situation in which phenylalanine cannot be converted to tyrosine, even though the phenylalanine hydroxylase apoenzyme is normal. Tetrahydrobiopterin is also the cofactor for the hydroxylation of tryptophan and tyrosine. Thus, its deficiency interferes with the synthesis of serotonin, DOPA, and norepinephrine. Data have been obtained that indicate that this is the case, since levels of 5-hydroxyindoleacetic acid, vanillylmandelic acid, and homovanillic acid in CSF are considerably lower than normal [6, 23]. Low levels of dopamine and serotonin have also been documented in urine [8, 29]. Since it is possible in these disorders to have severe neurologic disease in the presence of only mild HPA, levels of BH4 may be relatively more sufficient for phenylalanine hydroxylation than that of tryptophan or tyrosine [7, 36, 37]. Defective neurotransmitter metabolism is doubtless related to the genesis of neurologic abnormalities.
Ascorbate as an Enzyme Cofactor
Published in Qi Chen, Margreet C.M. Vissers, Vitamin C, 2020
Margreet C.M. Vissers, Andrew B. Das
Ascorbate provides reducing equivalents for the recycling of that tetrahydrobiopterin, the cofactor for tyrosine hydroxylase that synthesizes dihydroxyphenylalanine (L-dopa), the precursor of dopamine, and tryptophan hydroxylase, which is involved in the synthesis of serotonin [282,283]. In addition, tetrahydrobiopterin is a cofactor for the nitric oxide synthases, and ascorbate-mediated recycling has been suggested to be a mechanism for observed cardiovascular health benefits of supplementation [284].
Development of gamma-tocotrienol as a radiation medical countermeasure for the acute radiation syndrome: current status and future perspectives
Published in Expert Opinion on Investigational Drugs, 2023
Still yet another distinct radioprotective feature of GT3 relates to its capacity to ameliorate radiation-induced GI injury by improving the survival of crypts, improving the mucosal surface area, and by reducing the HMG-CoA reductase independent vascular oxidative stress after radiation exposure. It is important to note that the ability of GT3 to decrease radiation-induced oxidative stress was reversed by the use of mevalonate. This observation has important implications for GT3, specifically for its development for injury where vascular damage is expected to play an important role (intestinal and lung injury). GT3 decreases vascular peroxynitrite production through HMG-CoA reductase inhibition. Such inhibitors mediate their efficacy by endothelial nitric oxide synthase, with tetrahydrobiopterin (BH4) as an important cofactor.
Mental energy: plausible neurological mechanisms and emerging research on the effects of natural dietary compounds
Published in Nutritional Neuroscience, 2021
Patrick J. O’Connor, David O. Kennedy, Stephen Stahl
In addition to their role in oxidative metabolism, B vitamins are important for one-carbon metabolism and neurochemical synthesis and regulation [125]. Pyridoxal phosphate (vitamin B6) is a rate-limiting cofactor in synthesizing neurotransmitters (e.g. serotonin, GABA). Vitamin B6 deficiencies downregulate GABA and serotonin synthesis, causing disruptions in behavior (e.g. sleep) and physiology (e.g. cardiovascular function; hypothalamus-pituitary control of hormone excretion) that could influence mental energy [125]. Folate and vitamins B2, B3, B6, and B12 are critical to producing neurotransmitters through the folate and methionine cycles (Figure 3). These processes are important for synthesizing and regenerating tetrahydrobiopterin, an essential cofactor that converts amino acids to serotonin, melatonin, dopamine, and noradrenaline, which are pivotal for synthesizing the vasodilatory molecule nitric oxide [125]. Vitamin C acts as a free radical scavenger in the citric acid cycle and central nervous system and is highly expressed in neuronal tissue, acting as a modulator of neurotransmitters including dopamine, glutamate, and acetylcholine [126].
A pilot study on machine learning approach to delineate metabolic signatures in intellectual disability
Published in International Journal of Developmental Disabilities, 2021
Vidya Nikam, Suvidya Ranade, Naushad Shaik Mohammad, Mohan Kulkarni
In the present study, the technique of tandem mass spectrometry was successfully used to screen the children with the ID for IEM. No classical IEM was detected in 20 individuals screened. However, the comparison of each analyte in ID individuals with controls revealed that proline, phenylalanine, ornithine, and alanine were elevated in the ID group while arginine levels were found to be decreased. Although we have not observed any classical case of hyperprolinemia (OMIM 239500; 239510) presenting with seizures along with ID (Evers et al.2015), proline levels were higher in ID individuals. There are reports on the association of ID and hyperalaninemia associated with Leigh’s syndrome (OMIM 256000) (Tada et al.1973). Hyperornithinemia–hyperammonemia–homocitrullinuria (HHH) syndrome (OMIM 238970) is one of the commonest disorders associated with ornithine elevation resulting in growth and developmental delays, learning disabilities, periodic confusion, and ataxia (Martinelli et al.2015). High levels of phenylalanine in ID persons substantiate that there could be hydroxylation defects due to tetrahydrobiopterin resulting in low tyrosine levels.