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Emerging ergogenic aids for strength/power development
Published in Jay R Hoffman, Dietary Supplementation in Sport and Exercise, 2019
Betaine acts as a methyl donor in one-carbon metabolism (16). In the cytoplasm, betaine is required for remethylation of homocysteine to methionine, which serves as a precursor to the universal methyl donor S-adenosylmethionine (SAM) (Figure 14.2). Methyl groups are transferred to homocysteine in a reaction catalyzed by the enzyme BHMT. Betaine increases serum methionine, transmethylation rate, homocysteine remethylation and methionine oxidation. Betaine supplementation decreases plasma homocysteine concentrations (51). Reduced homocysteine and homocysteine thiolactone (i.e., a thioester of homocysteine) have been suggested to enhance insulin signalling and possibly increase muscle protein synthesis (10). SAM-dependent reactions include DNA methylation, synthesis of PC, proteins, neurotransmitters, creatine and other compounds. However, consumption of 2 g of betaine per day for ten days did not increase muscle phosphocreatine (PCr) content, nor did the addition of 2 g of betaine to creatine augment muscle PCr content (17), so betaine’s role in creatine metabolism remains to be determined.
Spinal Cord Disease
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
SAM is used for methylation in the nervous system and is essential for, among other things, the production of myelin basic protein. SAM is produced from methionine by methionine synthetase, which requires vitamin B12 and folate as cofactors. The exact mechanism by which the cofactor deficiency produces neuropathologic changes in myelinated fibers has not been definitively determined.
Obesity enriches for tumor protective microbial metabolites and treatment refractory cells to confer therapy resistance in PDAC
Published in Gut Microbes, 2022
Kousik Kesh, Roberto Mendez, Beatriz Mateo-Victoriano, Vanessa T Garrido, Brittany Durden, Vineet K Gupta, Alfredo Oliveras Reyes, Nipun Merchant, Jashodeep Datta, Santanu Banerjee, Sulagna Banerjee
The role of microbial metabolites in tumor progression is one aspect of microbiome-cancer research field that has remained underexplored. While some studies show the role of short chain fatty acid (SCFA) in colon cancer progression, their role in cancers that are more remote and not exposed to the microbial milieu is not clear. Certain microbial metabolites like polyamines supplement the host metabolic pool and contribute to tumor cell proliferation by feeding into nucleotide and protein synthesis pathways.15–17 Among metabolites, S-adenosyl methionine or SAM has emerged as the one that regulates the balance between cell survival and cell death. Produced by bacteria as well as by mammalian cells, SAM regulates cysteine-methionine metabolism, immune response and methylation of nucleotides thus controlling transcriptional processes. SAM has been used as an anti-tumor agent as well.18,19 Among metabolites solely made by bacteria is a t-RNA homolog, Queuosine (Q). Q cannot be synthesized by mammalian cells; however, it is required by mammalian cells for tRNA modifications.20–22
Changes at global and site-specific DNA methylation of MLH1 gene promoter induced by waterpipe smoking in blood lymphocytes and oral epithelial cells
Published in Inhalation Toxicology, 2020
Salsabeel H. Sabi, Omar F. Khabour, Karem H. Alzoubi, Caroline O. Cobb, Thomas Eissenberg
How waterpipe can lead to alterations in the epigenome is unknown, but oxidative stress was suggested as a mechanism that can cause loss or gain of DNA methylation (Valinluck et al. 2006). Tobacco smoking has been shown to induce reactive oxidants that can lead to damage of macromolecules in exposed cells. In addition, tobacco smoking triggers increases of leukocytes and platelets that produce oxidative stress (Csiszar et al. 2009). In addition, smoking causes a reduction in B12, which is required for S-Adenosylmethionine (SAM) (Fragou et al.) synthesis. SAM is a methyl donor involved in methyl-transferase pathway (Gabriel et al. 2006). Moreover, smoking has been shown to alter the expression of DNA Methyl Transferase gene, which is highly expressed in lung tumors (Lin et al. 2007). A previous study that was conducted on animals has shown that exposure of rats to waterpipe smoke can cause oxidative damage and gene expression changes in the lung (Khabour et al. 2012; Alqudah et al. 2018). Furthermore, waterpipe tobacco smoke contains toxicants such as organic compounds (aromatic hydrocarbons and volatile aldehydes), carbon monoxides, heavy metals and others (Sepetdjian et al. 2008; Jawad et al. 2019; El Hourani et al. 2020). Exposure to such toxicants in the waterpipe smoke might contribute to the altered DNA methylation observed in the current study (Caffo et al. 2015; White et al. 2016; de Souza et al. 2018; Kahl et al. 2018). More studies are required to determine the mechanism by which waterpipe smoking can alter global DNA methylation.