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Fuel Metabolism in the Fetus
Published in Emilio Herrera, Robert H. Knopp, Perinatal Biochemistry, 2020
Ketone bodies can be utilized by the developing brain as a source of energy, especially in the case of maternal food deprivation (see Section III.A). In the human, the enzymes of ketone body metabolism are present and active as early as 22 weeks of gestation. During late gestation ketone body concentration increases in maternal and fetal blood and, as a consequence, the quantitative importance of these substrates for fuel metabolism may also increase. Moreover, ketone bodies and ketogenic amino acids are used as precursors for fatty acid synthesis and, therefore, for the formation of a myelin sheath.
Protein and amino acids
Published in Geoffrey P. Webb, Nutrition, 2019
Surplus amino acids generated from protein breakdown are used as an energy source; in adults, almost all of the dietary protein is used as an energy source either directly or when body protein is catabolised. The nitrogen-containing amino group is removed to leave a moiety called the keto acid. For the so-called glucogenic amino acids, this keto acid is converted to either pyruvate or one of the intermediaries of the Krebs cycle. For the so-called ketogenic amino acids, the keto acid is converted to acetyl coenzyme A or acetoacetyl coenzyme A. The amino group can be converted to the waste product urea or it can be transferred to another keto acid and thus produce another amino acid, a process called transamination.
Metabolic Diseases
Published in Stephan Strobel, Lewis Spitz, Stephen D. Marks, Great Ormond Street Handbook of Paediatrics, 2019
Stephanie Grünewald, Alex Broomfield, Callum Wilson
Ketone bodies acetoacetate and 3-hydroxybutyric acid are metabolites derived from fatty acids and ketogenic amino acids, such as leucine. They are mainly produced in the liver, via reactions catalysed by the ketogenic enzymes HMG CoA synthase and HMG CoA lyase. After prolonged starvation, ketone bodies can provide up to two-thirds of the brain’s energy requirements. The rate-limiting enzyme of ketone body utilisation (ketolysis) is succinylcoenzyme A: 3-oxoacid coenzyme A transferase. The subsequent step of ketolysis is catalysed by 2-methylactoacetyl-coenzyme A thiolase (beta-ketothiolase), which is also involved in isoleucine catabolism.
The place of a ketogenic diet in the treatment of resistant epilepsy: a comprehensive review
Published in Nutritional Neuroscience, 2023
Recent studies describe a new mechanism for the ketogenic diet in preventing seizures by altering the gut microbiota in animals and humans [30,31]. In mouse models, KD is hypothesized to increase the intestinal population of Akkermansia muciniphila and Parabacteroides merda, most likely providing seizure prevention [32]. These bacteria have been found to reduce gamma-glutamylated ketogenic amino acids, which leads to neurotransmitter modulation, which has anti-seizure effects [31]. Olson et al. [33] found that Akkermansia muciniphila increased from 2.8% to 36.3% during 4 and 14 days of dietary treatment. Parabacteroides merdae, Sutterella, and Erysipelotrichaceae were also significantly increased, while Allobaculum, Bifidobacterium, and Desulfovibrio were lower in ketogenic-fed mice compared to mice fed the control diet. Akkermansia muciniphila and Parabacteroides merdae have been shown to be essential for achieving the anti-seizure effect of a ketogenic diet. Studies have revealed that KD alters the gut microbiome to varying degrees. In individuals with good seizure control, it is a selective increase in Bacteroids and a decrease in Firmicutes and Actinobacteria [30,31]. With these changes, it was hypothesized that KD could exert anti-seizure effects by modulation of the gut microbiota [13].
A comprehensive proteomics analysis of the response of Pseudomonas aeruginosa to nanoceria cytotoxicity
Published in Nanotoxicology, 2023
Lidija Izrael Živković, Nico Hüttmann, Vanessa Susevski, Ana Medić, Vladimir Beškoski, Maxim V. Berezovski, Zoran Minić, Ljiljana Živković, Ivanka Karadžić
The presence of NC caused significant changes in amino acid metabolism, in particular in their anabolism. Biosynthesis of the glucogenic amino acids was intensified, according to the upregulation of their biosynthesis enzymes. Furthermore, the biosynthesis of aromatic amino acids and isoleucine, both considered as glucogenic and ketogenic, was enhanced (Table 1). In particular, proteins involved in the synthesis of the ketogenic amino acid lysine were significantly upregulated. Enzymes involved in lysine degradation were also upregulated, along with glutarate-semialdehyde dehydrogenase that catalyzes the conversion of glutarate-semialdehyde to glutarate and NADPH, where the latter protects cells from redox stress. Upregulation of enzymes involved in arginine and histidine degradation was also noticed. Arginine deiminase, which regulates L-arginine degradation, is involved in the first step of the sub-pathway (ADI) that synthesizes carbamoyl phosphate from L-arginine and can serve as a non-redox, ATP producing process that can be induced under various stress conditions (White 2000; Eschbach 2004). Histidine ammonia-lyase catalyzes the synthesis of N-formimidoyl-L-glutamate from L-histidine, as a part of the pathway degrading L-histidine into L-glutamate, which after transformation, can replenish the TCA cycle through α-ketoglutarate. In addition, upregulation of glycine dehydrogenase, as a part the glycine cleavage system that is highly sensitive to alterations in the oxidation–reduction state of the respiratory chain, was observed. Upregulated aromatic-amino-acid aminotransferase is related to chorismate, which is a branch-point metabolite used for the synthesis of aromatic amino acids and phenazine metabolites such as pyocyanin.
Vitamin B12, homocysteine, and folic acid in patients suffering from bipolar disorders: Relationship with suicide
Published in The World Journal of Biological Psychiatry, 2023
Paola Mangiapane, Manuel Glauco Carbone, Alessandro Arone, Lucia Massa, Stefania Palermo, Walter Flamini, Elisabetta Parra, Benedetto Morana, Florinda Morana, Giovanni Bertini, Donatella Marazziti
Vitamin B12 is a crucial cofactor of two different enzymes: methionine synthase and methylmalonyl CoA mutase. The former is a cytoplasmic enzyme that, by the transfer of a methyl group from methyltetrahydrofolate, leads to the conversion of homocysteine to methionine. The latter, located in the mitochondria, is essential for the conversion of methylmalonyl CoA to succinyl CoA, a process taking part in the oxidation of odd-chain fatty acids and the catabolism of ketogenic amino acids. As a result, B12 is overall fundamental for DNA synthesis (Green and Miller 2007).