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Methionine dependence in tumor cells: The potential role of cobalamin and MMACHC.
Sorin, M, Watkins, D, Gilfix, BM, Rosenblatt, DS
Molecular genetics and metabolism. 2021;(3):155-161
Abstract
Methionine dependence of tumor cell lines, the inability to grow in tissue culture media lacking methionine but supplemented with homocysteine, has been known for decades, but an understanding of the mechanism underlying this phenomenon remains incomplete. Methionine dependence of certain glioma and melanoma cell lines has been linked to alterations in the metabolism of cobalamin (vitamin B12). In the MeWo LC1 melanoma line, complementation analysis demonstrated that the genetic defect affected the same locus mutated in the cblC inborn error of cobalamin metabolism; hypermethylation of the MMACHC promoter was subsequently demonstrated. Analysis of data in the Cancer Cell Line Encyclopedia showed increased MMACHC methylation levels in melanoma lines compared to other types of cancer. RNA sequencing data from isolated tumors, tabulated at the cBioPortal for Cancer Genomics website, showed decreased MMACHC expression compared to other tumors; and methylation data tabulated at the TGGA Wanderer website demonstrated increased MMACHC methylation. These data suggest that disruptions in cobalamin metabolism might play a more general role in methionine dependence, and potentially in the pathogenesis of melanoma cell lines and primary tumors.
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2.
Vitamin B12 deficiency: case report and review of literature.
Hasbaoui, BE, Mebrouk, N, Saghir, S, Yajouri, AE, Abilkassem, R, Agadr, A
The Pan African medical journal. 2021;:237
Abstract
Vitamin B12 deficiency in early childhood is an important cause of neurodevelopmental delay and regression. Most of these cases occur in exclusively breast-fed infants of deficient mothers. Symptoms and signs of vitamin B12 deficiency appear between the ages of 2 to 12 months and include vomiting, lethargy, failure to thrive, hypotonia, and arrest or regression of developmental skills. Approximately one half of this cases exhibit abnormal movements, variously described as tremors, twitches, chorea, or myoclonus. Urinary concentrations of methylmalonic acid and homocysteine are characteristically elevated in vitamin B12 deficiency. Hyperglycinuria is sometimes present. The early diagnosis and treatment of vitamin B12 deficiency is crucial for significant neurological impairment and long-term prognosis. Treatment with vitamin B12 corrects these metabolic abnormalities very rapidly (within a few days). Vitamin B12 supplementation of pregnant women may prevent neurological and neuroradiological findings of the infants. Because of the importance of vitamin B12 in the development of the foetal and neonatal brain, vegetarian and vegan mothers should be aware of the severe and not fully-reversible damages caused by insufficient nutritional intake of vitamin B12 during pregnancy and lactation. Therefore, efforts should be directed to prevent its deficiency in pregnant and breastfeeding women on vegan diets and their infants. It is also important to take the nutritional history of both infants and their mothers for the early prevention and treatment. Here an interesting case of vitamin B12 deficiency in a 10-month-old boy presented with psychomotor regression, hypotonia and lethargy.
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3.
Genetic, epigenetic and genomic mechanisms of methionine dependency of cancer and tumor-initiating cells: What could we learn from folate and methionine cycles.
Guéant, JL, Oussalah, A, Zgheib, R, Siblini, Y, Hsu, SB, Namour, F
Biochimie. 2020;:123-128
Abstract
Methionine-dependency is a common feature of cancer cells, which cannot proliferate without constant inputs of exogenous methionine even in the presence of its precursor, homocysteine. The endogenous synthesis of methionine is catalyzed by methionine synthase, which transfers the methyl group of 5-methyltetrahydrofolate (5-methylTHF) to homocysteine in the presence of vitamin B12 (cobalamin, cbl). Diverse mechanisms can produce it, including somatic mutations, aberrant DNA methylation (epimutations) and altered expression of genes. Around twenty somatic mutations have been reported as a cause of methionine dependency. Some of them are contributors but not sufficient on their own to cause methionine dependency. Epigenetic invalidation of MMACHC gene expression triggers methionine dependency of the MeWo-LC1 melanoma cancer cell line. This epimutation is generated by aberrant antisense transcription of the adjacent gene PRDX1. Methionine dependency involves the abnormal expression of 1-CM genes in cancer stem cells. It is related to an increased demand for methionine and SAM, which is not compensated by the increased production of formate by glycine decarboxylase pathway in lung cancer tumor spheres. Tumor spheres of glioblastoma U251 are methionine-dependent through disruption of folate metabolism. The rescue of the growth of glioblastoma stem cells by folate shows the considerable importance to evaluate the influence of supplements and dietary intake of folate on the risk of tumor development, in particular in countries subjected to mandatory food fortification in folic acid. Dietary methionine restriction or the use of methioninase represent promising anticancer therapeutic strategies that deserve to be explored in combination with chemotherapy.
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4.
Alterations in Sulfur Amino Acids as Biomarkers of Disease.
Stabler, SP
The Journal of nutrition. 2020;(Suppl 1):2532S-2537S
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Abstract
Homocysteine (Hcy) is methylated by methionine synthase to form methionine with methyl-cobalamin as a cofactor. The reaction demethylates 5-methyltetrahydrofolate to tetrahydrofolate, which is required for DNA and RNA synthesis. Deficiency of either of the cobalamin (Cbl) and/or folate cofactors results in elevated Hcy and megaloblastic anemia. Elevated Hcy is a sensitive biomarker of Cbl and/or folate status and more specific than serum vitamin assays. Elevated Hcy normalizes when the correct vitamin is given. Elevated Hcy is associated with alcohol use disorder and drugs that target folate or Cbl metabolism, and is a risk factor for thrombotic vascular disease. Elevated methionine and cystathionine are associated with liver disease. Elevated Hcy, cystathionine, and cysteine, but not methionine, are common in patients with chronic renal failure. Higher cysteine predicts obesity and future weight gain. Serum S-adenosylhomocysteine (AdoHcy) is elevated in Cbl deficiency and chronic renal failure. Drugs that require methylation for catabolism may deplete liver S-adenosylmethionine and raise AdoHcy and Hcy. Deficiency of Cbl or folate or perturbations of their metabolism cause major changes in sulfur amino acids.
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5.
Fallacies of clinical studies on folic acid hazards in subjects with a low vitamin B12 status.
van Gool, JD, Hirche, H, Lax, H, Schaepdrijver, L
Critical reviews in toxicology. 2020;(2):177-187
Abstract
A 2016 plea for revision of the 1 mg/day upper level of folic acid intake prompted us to comprehensively review the 1945-2017 literature on folic acid hazards in subjects with low cyanocobalamin. The concept of folic acid treatment 'masking' the anemia in undiagnosed cyanocobalamin deficiency, thereby delaying the diagnosis of neuropathy, does not account for the dissociation between the deficiency's hematologic and neurologic manifestations. Possible risks of this concept were addressed by 1963-1971 FDA rulings, classifying all folic acid preparations as prescription-only drugs, delivering ≤1 mg daily. The neuropathy in folic acid trials for 'pernicious anemia' is due to the singular use of folic acid-neuropathy improved or disappeared with replacement of folic acid by liver extract or cyanocobalamin. The hypothesis that cognitive impairment in 'subclinical' cyanocobalamin deficiency is folate-mediated is untenable. Of 6 papers specifically investigating this, none could prove that increased cognitive impairment was related to high folate intake. This review fully supports the safety of the 1 mg/day upper level for folic acid intake.
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6.
Acne related to dietary supplements.
Zamil, DH, Perez-Sanchez, A, Katta, R
Dermatology online journal. 2020;(8)
Abstract
Multiple prescription medications may cause or aggravate acne. A number of dietary supplements have also been linked to acne, including those containing vitamins B6/B12, iodine, and whey, as well as "muscle building supplements" that may be contaminated with anabolic-androgenic steroids (AAS). Acne linked to dietary supplements generally resolves following supplement discontinuation. Lesions associated with high-dose vitamin B6 and B12 supplements have been described as monomorphic and although pathogenesis is unknown, a number of hypotheses have been proposed. Iodine-related acne may be related to the use of kelp supplements and has been reported as monomorphic, inflammatory pustules on the face and upper trunk. Whey protein supplements, derived from milk and used for bodybuilding, are associated with papulonodular acne involving the trunk and sometimes the face. Finally, AAS-induced acne has been described as acne fulminans, acne conglobata, and acne papulopustulosa. With studies indicating that about half of US adults report using dietary supplements, it is important that dermatologists directly ask acne patients about their supplement use and educate them on the potential risks of even seemingly innocuous dietary supplements.
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Vitamin B Supplementation and Nutritional Intake of Methyl Donors in Patients with Chronic Kidney Disease: A Critical Review of the Impact on Epigenetic Machinery.
Cappuccilli, M, Bergamini, C, Giacomelli, FA, Cianciolo, G, Donati, G, Conte, D, Natali, T, La Manna, G, Capelli, I
Nutrients. 2020;(5)
Abstract
Cardiovascular morbidity and mortality are several-fold higher in patients with advanced chronic kidney disease (CKD) and end-stage renal disease (ESRD) than in the general population. Hyperhomocysteinemia has undoubtedly a central role in such a prominent cardiovascular burden. The levels of homocysteine are regulated by methyl donors (folate, methionine, choline, betaine), and cofactors (vitamin B6, vitamin B12,). Uremia-induced hyperhomocysteinemia has as its main targets DNA methyltransferases, and this leads to an altered epigenetic control of genes regulated through methylation. In renal patients, the epigenetic landscape is strictly correlated with the uremic phenotype and dependent on dietary intake of micronutrients, inflammation, gut microbiome, inflammatory status, oxidative stress, and lifestyle habits. All these factors are key contributors in methylome maintenance and in the modulation of gene transcription through DNA hypo- or hypermethylation in CKD. This is an overview of the epigenetic changes related to DNA methylation in patients with advanced CKD and ESRD. We explored the currently available data on the molecular dysregulations resulting from altered gene expression in uremia. Special attention was paid to the efficacy of B-vitamins supplementation and dietary intake of methyl donors on homocysteine lowering and cardiovascular protection.
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8.
B Vitamins and One-Carbon Metabolism: Implications in Human Health and Disease.
Lyon, P, Strippoli, V, Fang, B, Cimmino, L
Nutrients. 2020;(9)
Abstract
Vitamins B9 (folate) and B12 are essential water-soluble vitamins that play a crucial role in the maintenance of one-carbon metabolism: a set of interconnected biochemical pathways driven by folate and methionine to generate methyl groups for use in DNA synthesis, amino acid homeostasis, antioxidant generation, and epigenetic regulation. Dietary deficiencies in B9 and B12, or genetic polymorphisms that influence the activity of enzymes involved in the folate or methionine cycles, are known to cause developmental defects, impair cognitive function, or block normal blood production. Nutritional deficiencies have historically been treated with dietary supplementation or high-dose parenteral administration that can reverse symptoms in the majority of cases. Elevated levels of these vitamins have more recently been shown to correlate with immune dysfunction, cancer, and increased mortality. Therapies that specifically target one-carbon metabolism are therefore currently being explored for the treatment of immune disorders and cancer. In this review, we will highlight recent studies aimed at elucidating the role of folate, B12, and methionine in one-carbon metabolism during normal cellular processes and in the context of disease progression.
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9.
Laboratory approach to investigation of anemia with a focus on pyruvate kinase deficiency.
Agarwal, AM, Rets, A
International journal of laboratory hematology. 2020;:107-112
Abstract
Anemia is a major health burden worldwide and affects approximately one-third of world's population. It is not a diagnosis; it is a manifestation of an underlying pathophysiology leading to either decreased hemoglobin (Hb), hematocrit (Hct), or red blood cells (RBCs). Iron deficiency anemia is still the most common cause of anemia worldwide. The symptoms are usually due to the underlying compensatory responses to decrease in oxygen delivery to the tissues. Laboratory investigation should start with complete blood count (CBC), reticulocyte count (RC), and peripheral smear evaluation. Further testing depends on these indices, that is, iron parameters and hemoglobinopathies/thalassemia evaluation in microcytic hypochromic anemia, vitamin B12, and folic acid level in macrocytic anemia. Increased RC denotes adequate bone marrow response and points toward hemolytic process and vice versa. Anemia diagnosis can be complex and confusing for the practicing physician. This review tries to give a practical simplistic approach to the diagnosis, focusing mainly on the basic parameters, that is, CBC, RC, and peripheral smear etc. Moreover, we have also tried to provide an update on the pyruvate kinase deficiency, as there has been recent exciting development in the management of these patients.
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10.
Persistently increased vitamin B12 concentration due to cobalamin macrocomplexes: a case report and review of the literature.
Rodríguez, JAD, García, MIP, Bauça, JM, Mullor, RV, Barceló, A
Clinical chemistry and laboratory medicine. 2020;(10):e237-e239