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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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Biomarkers of oxidative stress, inflammation, and vascular dysfunction in inherited cystathionine β-synthase deficient homocystinuria and the impact of taurine treatment in a phase 1/2 human clinical trial.
Van Hove, JLK, Freehauf, CL, Ficicioglu, C, Pena, LDM, Moreau, KL, Henthorn, TK, Christians, U, Jiang, H, Cowan, TM, Young, SP, et al
Journal of inherited metabolic disease. 2019;(3):424-437
Abstract
STUDY OBJECTIVE A phase 1/2 clinical trial was performed in individuals with cystathionine β synthase (CBS) deficient homocystinuria with aims to: (a) assess pharmacokinetics and safety of taurine therapy, (b) evaluate oxidative stress, inflammation, and vascular function in CBS deficiency, and (c) evaluate the impact of short-term taurine treatment. METHODS Individuals with pyridoxine-nonresponsive CBS deficiency with homocysteine >50 μM, without inflammatory disorder or on antioxidant therapy were enrolled. Biomarkers of oxidative stress and inflammation, endothelial function (brachial artery flow-mediated dilation [FMD]), and disease-related metabolites obtained at baseline were compared to normal values. While maintaining current treatment, patients were treated with 75 mg/kg taurine twice daily, and treatment response assessed after 4 hours and 4 days. RESULTS Fourteen patients (8-35 years; 8 males, 6 females) were enrolled with baseline homocysteine levels 161 ± 67 μM. The study found high-dose taurine to be safe when excluding preexisting hypertriglyceridemia. Taurine pharmacokinetics showed a rapid peak level returning to near normal levels at 12 hours, but had slow accumulation and elevated predosing levels after 4 days of treatment. Only a single parameter of oxidative stress, 2,3-dinor-8-isoprostaglandin-F2α, was elevated at baseline, with no elevated inflammatory parameters, and no change in FMD values overall. Taurine had no effect on any of these parameters. However, the effect of taurine was strongly related to pretreatment FMD values; and taurine significantly improved FMD in the subset of individuals with pretreatment FMD values <10% and in individuals with homocysteine levels >125 μM, pertinent to endothelial function. CONCLUSION Taurine improves endothelial function in CBS-deficient homocystinuria in patients with preexisting reduced function.
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Choline intakes exceeding recommendations during human lactation improve breast milk choline content by increasing PEMT pathway metabolites.
Davenport, C, Yan, J, Taesuwan, S, Shields, K, West, AA, Jiang, X, Perry, CA, Malysheva, OV, Stabler, SP, Allen, RH, et al
The Journal of nutritional biochemistry. 2015;(9):903-11
Abstract
Demand for the vital nutrient choline is high during lactation; however, few studies have examined choline metabolism and requirements in this reproductive state. The present study sought to discern the effects of lactation and varied choline intake on maternal biomarkers of choline metabolism and breast milk choline content. Lactating (n=28) and control (n=21) women were randomized to 480 or 930 mg choline/day for 10-12 weeks as part of a controlled feeding study. During the last 4-6 weeks, 20% of the total choline intake was provided as an isotopically labeled choline tracer (methyl-d9-choline). Blood, urine and breast milk samples were collected for choline metabolite quantification, enrichment measurements, and gene expression analysis of choline metabolic genes. Lactating (vs. control) women exhibited higher (P < .001) plasma choline concentrations but lower (P ≤ .002) urinary excretion of choline metabolites, decreased use of choline as a methyl donor (e.g., lower enrichment of d6-dimethylglycine, P ≤ .08) and lower (P ≤ .02) leukocyte expression of most choline-metabolizing genes. A higher choline intake during lactation differentially influenced breast milk d9- vs. d3-choline metabolite enrichment. Increases (P ≤ .03) were detected among the d3-metabolites, which are generated endogenously via the hepatic phosphatidylethanolamine N-methyltransferase (PEMT), but not among the d9-metabolites generated from intact exogenous choline. These data suggest that lactation induces metabolic adaptations that increase the supply of intact choline to the mammary epithelium, and that extra maternal choline enhances breast milk choline content by increasing supply of PEMT-derived choline metabolites. This trial was registered at clinicaltrials.gov as NCT01127022.
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Pregnancy alters choline dynamics: results of a randomized trial using stable isotope methodology in pregnant and nonpregnant women.
Yan, J, Jiang, X, West, AA, Perry, CA, Malysheva, OV, Brenna, JT, Stabler, SP, Allen, RH, Gregory, JF, Caudill, MA
The American journal of clinical nutrition. 2013;(6):1459-67
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Abstract
BACKGROUND Although biomarkers of choline metabolism are altered by pregnancy, little is known about the influence of human pregnancy on the dynamics of choline-related metabolic processes. OBJECTIVE This study used stable isotope methodology to examine the effects of pregnancy on choline partitioning and the metabolic activity of choline-related pathways. DESIGN Healthy third-trimester pregnant (n = 26; initially week 27 of gestation) and nonpregnant (n = 21) women consumed 22% of their total choline intake (480 or 930 mg/d) as methyl-d9-choline for the final 6 wk of a 12-wk feeding study. RESULTS Plasma d9-betaine:d9-phosphatidylcholine (PC) was lower (P ≤ 0.04) in pregnant than in nonpregnant women, suggesting greater partitioning of choline into the cytidine diphosphate-choline (CDP-choline) PC biosynthetic pathway relative to betaine synthesis during pregnancy. Pregnant women also used more choline-derived methyl groups for PC synthesis via phosphatidylethanolamine N-methyltransferase (PEMT) as indicated by comparable increases in PEMT-PC enrichment in pregnant and nonpregnant women despite unequal (pregnant > nonpregnant; P < 0.001) PC pool sizes. Pregnancy enhanced the hydrolysis of PEMT-PC to free choline as shown by greater (P < 0.001) plasma d3-choline:d3-PC. Notably, d3-PC enrichment increased (P ≤ 0.011) incrementally from maternal to placental to fetal compartments, signifying the selective transfer of PEMT-PC to the fetus. CONCLUSIONS The enhanced use of choline for PC production via both the CDP-choline and PEMT pathways shows the substantial demand for choline during late pregnancy. Selective partitioning of PEMT-PC to the fetal compartment may imply a unique requirement of PEMT-PC by the developing fetus.
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Maternal choline intake modulates maternal and fetal biomarkers of choline metabolism in humans.
Yan, J, Jiang, X, West, AA, Perry, CA, Malysheva, OV, Devapatla, S, Pressman, E, Vermeylen, F, Stabler, SP, Allen, RH, et al
The American journal of clinical nutrition. 2012;(5):1060-71
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Abstract
BACKGROUND In 1998 choline Adequate Intakes of 425 and 450 mg/d were established for nonpregnant and pregnant women, respectively. However, to our knowledge, no dose-response studies have been conducted to evaluate the effects of pregnancy or maternal choline intake on biomarkers of choline metabolism. OBJECTIVE We sought to quantify the effects of pregnancy and maternal choline intake on maternal and fetal indicators of choline metabolism. DESIGN Healthy pregnant (n = 26; 27 wk gestation) and nonpregnant (n = 21) women were randomly assigned to receive 480 or 930 mg choline/d for 12 wk. Fasting blood samples and placental tissue and umbilical cord venous blood were collected and analyzed for choline and its metabolites. RESULTS Regardless of the choline intake, pregnant women had higher circulating concentrations of choline (30%; P < 0.001) but lower concentrations of betaine, dimethylglycine, sarcosine, and methionine (13-55%; P < 0.001). Obligatory losses of urinary choline and betaine in pregnant women were ∼2-4 times as high (P ≤ 0.02) as those in nonpregnant women. A higher choline intake yielded higher concentrations of choline, betaine, dimethylglycine, and sarcosine (12-46%; P ≤ 0.08) in both pregnant and nonpregnant women without affecting urinary choline excretion. The higher maternal choline intake also led to a doubling of dimethylglycine in cord plasma (P = 0.002). CONCLUSION These data suggest that an increment of 25 mg choline/d to meet the demands of pregnancy is insufficient and show that a higher maternal choline intake increases the use of choline as a methyl donor in both maternal and fetal compartments. This trial was registered at clinicaltrials.gov as NCT01127022.
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MTHFR C677T genotype influences the isotopic enrichment of one-carbon metabolites in folate-compromised men consuming d9-choline.
Yan, J, Wang, W, Gregory, JF, Malysheva, O, Brenna, JT, Stabler, SP, Allen, RH, Caudill, MA
The American journal of clinical nutrition. 2011;(2):348-55
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Abstract
BACKGROUND Homozygosity for the variant 677T allele in the methylenetetrahydrofolate reductase (MTHFR) gene increases the requirement for folate and may alter the metabolic use of choline. The choline adequate intake is 550 mg/d for men, although the metabolic consequences of consuming extra choline are unclear. OBJECTIVE Deuterium-labeled choline (d9-choline) as tracer was used to determine the differential effects of the MTHFR C677T genotype and the effect of various choline intakes on the isotopic enrichment of choline derivatives in folate-compromised men. DESIGN Mexican American men with the MTHFR 677CC or 677TT genotype consumed a diet providing 300 mg choline/d plus supplemental choline chloride for total choline intakes of 550 (n = 11; 4 with 677CC and 7 with 677TT) or 1100 (n = 12; 4 with 677CC and 8 with 677TT) mg/d for 12 wk. During the last 3 wk, 15% of the total choline intake was provided as d9-choline. RESULTS Low but measurable enrichments of the choline metabolites were achieved, including that of d3-phosphatidylcholine (d3-PtdCho)--a metabolite produced in the de novo pathway via choline-derived methyl groups. Men with the MTHFR 677TT genotype had a higher urinary enrichment ratio of betaine to choline (P = 0.041), a higher urinary enrichment of sarcosine (P = 0.041), and a greater plasma enrichment ratio of d9-betaine to d9-PtdCho with the 1100 mg choline/d intake (P = 0.033). CONCLUSION These data show for the first time in humans that choline itself is a source of methyl groups for de novo PtdCho biosynthesis and indicate that the MTHFR 677TT genotype favors the use of choline as a methyl donor.
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S-adenosyl-L-methionine treatment for alcoholic liver disease: a double-blinded, randomized, placebo-controlled trial.
Medici, V, Virata, MC, Peerson, JM, Stabler, SP, French, SW, Gregory, JF, Albanese, A, Bowlus, CL, Devaraj, S, Panacek, EA, et al
Alcoholism, clinical and experimental research. 2011;(11):1960-5
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Abstract
BACKGROUND S-adenosyl-L-methionine (SAM) is the methyl donor for all methylation reactions and regulates the synthesis of glutathione, the main cellular antioxidant. Previous experimental studies suggested that SAM may benefit patients with established alcoholic liver diseases (ALDs). The aim of this study was to determine the efficacy of SAM in treatment for ALD in a 24-week trial. The primary endpoints were changes in serum aminotransferase levels and liver histopathology scores, and the secondary endpoints were changes in serum levels of methionine metabolites. METHODS We randomized 37 patients with ALD to receive 1.2 g of SAM by mouth or placebo daily. Subjects were required to remain abstinent from alcohol drinking. A baseline liver biopsy was performed in 24 subjects, and a posttreatment liver biopsy was performed in 14 subjects. RESULTS Fasting serum SAM levels were increased over timed intervals in the SAM treatment group. The entire cohort showed an overall improvement of AST, ALT, and bilirubin levels after 24 weeks of treatment, but there were no differences between the treatment groups in any clinical or biochemical parameters nor any intra- or intergroup differences or changes in liver histopathology scores for steatosis, inflammation, fibrosis, and Mallory-Denk hyaline bodies. CONCLUSIONS Whereas abstinence improved liver function, 24 weeks of therapy with SAM was no more effective than placebo in the treatment for ALD.
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Impaired homocysteine transsulfuration is an indicator of alcoholic liver disease.
Medici, V, Peerson, JM, Stabler, SP, French, SW, Gregory, JF, Virata, MC, Albanese, A, Bowlus, CL, Devaraj, S, Panacek, EA, et al
Journal of hepatology. 2010;(3):551-7
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BACKGROUND & AIMS Although abnormal hepatic methionine metabolism plays a central role in the pathogenesis of experimental alcoholic liver disease (ALD), its relationship to the risk and severity of clinical ALD is not known. The aim of this clinical study was to determine the relationship between serum levels of methionine metabolites in chronic alcoholics and the risk and pathological severity of ALD. METHODS Serum levels of liver function biochemical markers, vitamin B6, vitamin B12, folate, homocysteine, methionine, S-adenosylmethionine, S-adenosylhomocysteine, cystathionine, cysteine, alpha-aminobutyrate, glycine, serine, and dimethylglycine were measured in 40 ALD patients, of whom 24 had liver biopsies, 26 were active drinkers without liver disease, and 28 were healthy subjects. RESULTS Serum homocysteine was elevated in all alcoholics, whereas ALD patients had low vitamin B6 with elevated cystathionine and decreased alpha-aminobutyrate/cystathionine ratios, consistent with decreased activity of vitamin B6 dependent cystathionase. The alpha-aminobutyrate/cystathionine ratio predicted the presence of ALD, while cystathionine correlated with the stage of fibrosis in all ALD patients. CONCLUSIONS The predictive role of the alpha-aminobutyrate/cystathionine ratio for the presence of ALD and the correlation between cystathionine serum levels with the severity of fibrosis point to the importance of the homocysteine transsulfuration pathway in ALD and may have important diagnostic and therapeutic implications.
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Sex and menopausal status influence human dietary requirements for the nutrient choline.
Fischer, LM, daCosta, KA, Kwock, L, Stewart, PW, Lu, TS, Stabler, SP, Allen, RH, Zeisel, SH
The American journal of clinical nutrition. 2007;85(5):1275-85
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Plain language summary
Choline is used to form cell membranes, and it is a precursor for the neurotransmitter acetylcholine. Other than from the diet, choline can also be derived from the de novo biosynthesis of phosphatidylcholine. The current Adequate Intake for choline is considered sufficient to prevent deficiency, however an Estimated Average Requirement cannot be generated due to lack of availability of adequate human data. The aim of this study was to evaluate the dietary choline requirement in healthy men and women (pre- and postmenopausal), and to identify the clinical and metabolic sequelae of choline deficiency. Fifty-seven adult participants (26 healthy men, 16 premenopausal women and 15 postmenopausal women) were recruited for the study. A randomised double-blind protocol was followed to assign participants in one of the 2 arms; folate only (100 DFE) vs a dietary supplement of 400μg folic acid/d (768 DFE). Results show that independent of folate status, most men and postmenopausal women developed liver or muscle dysfunction when fed a low-choline diet, whereas premenopausal women were more resistant to developing such organ dysfunction. AP activity increased in all subjects in response to the low-choline diet regardless of whether they manifested organ dysfunction. Liver and muscle dysfunction occurred in response to a low-choline diet in both men and women. The current AI for choline was not be sufficient for some of the participants who became depleted despite this level of intake.
Abstract
BACKGROUND Although humans require dietary choline for methyl donation, membrane function, and neurotransmission, choline can also be derived from the de novo synthesis of phosphatidylcholine, which is up-regulated by estrogen. A recommended Adequate Intake (AI) exists for choline; however, an Estimated Average Requirement has not been set because of a lack of sufficient human data. OBJECTIVE The objective of the study was to evaluate the dietary requirements for choline in healthy men and women and to investigate the clinical sequelae of choline deficiency. DESIGN Fifty-seven adult subjects (26 men, 16 premenopausal women, 15 postmenopausal women) were fed a diet containing 550 mg choline x 70 kg(-1) x d(-1) for 10 d followed by <50 mg choline x 70 kg(-1) x d(-1) with or without a folic acid supplement (400 microg/d per randomization) for up to 42 d. Subjects who developed organ dysfunction during this diet had normal organ function restored after incremental amounts of choline were added back to the diet. Blood and urine were monitored for signs of toxicity and metabolite concentrations, and liver fat was assessed by using magnetic resonance imaging. RESULTS When deprived of dietary choline, 77% of men and 80% of postmenopausal women developed fatty liver or muscle damage, whereas only 44% of premenopausal women developed such signs of organ dysfunction. Moreover, 6 men developed these signs while consuming 550 mg choline x 70 kg(-1) x d(-1), the AI for choline. Folic acid supplementation did not alter the subjects' response. CONCLUSION Subject characteristics (eg, menopausal status) modulated the dietary requirement for choline, and a daily intake at the current AI was not sufficient to prevent organ dysfunction in 19 of the subjects.
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High- but not low-dose folic acid improves endothelial function in coronary artery disease.
Moat, SJ, Madhavan, A, Taylor, SY, Payne, N, Allen, RH, Stabler, SP, Goodfellow, J, McDowell, IF, Lewis, MJ, Lang, D
European journal of clinical investigation. 2006;(12):850-9
Abstract
BACKGROUND While folic acid (FA) reduces plasma homocysteine (Hcy), whether the simultaneous improvement in endothelial function is dependent on Hcy lowering per se is questionable. In the present study the relationship between FA dose, Hcy lowering and endothelial function in patients with coronary artery disease (CAD) was investigated. MATERIALS AND METHODS Eighty-four patients with CAD received either 400 microg FA or 5 mg placebo daily for a 6-week treatment period. A further 44 patients with CAD received either 100 mg kg(-1) day(-1) of betaine or placebo for a 6-week treatment period. Flow-mediated dilatation (FMD), a measure of endothelial function, was assessed before and after the 6-week periods. Isometric tension and Western blotting were used to investigate the effect of FA on endothelial function and endothelial nitric oxide synthase (eNOS) dimerization in isolated rabbit aortic rings and cultured porcine aortic endothelial cells (PAEC), respectively. RESULTS Both 400 micro g day(-1) and 5 mg day(-1) FA significantly increased plasma folate and decreased plasma Hcy. The FMD improved significantly after 6 weeks' treatment of 5 mg day(-1) FA but did not correlate with the reduction in Hcy. There was no change in FMD in either the 400 micro g FA or placebo group. In a subgroup analysis of 11 patients in the betaine group, despite a reduced Hcy, a significant impairment in FMD was observed. In the in vitro studies FA, but not betaine, reversed methionine-induced endothelial dysfunction. Moreover, the FA promoted eNOS dimerization in cultured PAEC. CONCLUSIONS These data suggest that FA dose-dependently improves endothelial function in CAD via a mechanism independently of Hcy lowering. It may involve promotion of eNOS dimerization.