Total homocysteine

Moller j, Rasmussen K, Christensen L (1999) External quality assessment of methylmalonic acid and total homocystein. Clin Chem 45 1536-1542. 

Nygird 0, Refsum H, Ueland PM, Stensvold I, Nordrehaug JE, Kv le G, Vollset SE. (1997). Coffee consumption and plasma total homocysteine the Hordaland Homocysteine Study. Am J Clin Nutr. 65(1) 136-43. 

Nhgard, O., H. Refsum, P. M. Ueland, et al. Coffee consumption and plasma total homocysteine the hordaland and... 

Fig. 2.2.3 Standard curve of total homocysteine (tHcy) in human plasma. IS Internal standard...

Table 2.2.1 Reference values. tHcy Total homocysteine ... 

Stabler SP, Marcell PD, Podell ER, Allen RH, Savage DG, Lindenbaum J (1988) Elevation of total homocysteine in the serum of patients with cobalamin or folate deficiency detected by capillary gas chromatography-mass spectrometry. J Clin Invest 81 466-474... 

Refsum H, Smith AD, Ueland PM, Nexo E, Clarke R, McPartlin J, Johnston C, Engbaek F, Schneede J, McPartlin C, Scott JM (2004) Facts and recommendations about total homocysteine determinations an expert opinion. Clin Chem 50 3-32... 

Araki A, Sako Y (1987) Determination of free and total homocysteine in human plasma by high-performance liquid chromatography with fluorescence detection. J Chromatogr 422 43-52... 

Ubbink JB, Hayward Vermaak WJ, Bissbort S (1991) Rapid high-performance liquid chromatographic assay for total homocysteine levels in human serum. J Chromatogr 565 441-446... 

Ueland PM, Refsum H, Stabler SP, Malinow MR, Andersson A, Allen RH (1993) Total homocysteine in plasma or serum methods and clinical applications. Clin Chem 39 1764-79... 

Vilaseca MA, Moyano D, Ferrer I, Artuch R (1997) Total homocysteine in pediatric patients. Clin Chem 43 690-692... 

Clarke R, Smith AD, Jobst KA, Refsum H, Sutton L, Ueland PM. Folate, vitamin B12, and serum total homocysteine levels in confirmed Alzheimer disease. Arch Neurol 1998 55(11) 1449-1455. 

Nedrebo BG, et al. Plasma total homocysteine levels in hyperthyroid and hypothyroid patients. Metabolism 1998 47(1) 89-93. 

Voutilainen S, et al. Enhanced in vivo lipid peroxidation at elevated plasma total homocysteine levels. Arterioscler Thromb Vase Biol 1999 19(5) 1263-1266. 

Podda G, et al. No effect of fasting plasma total homocysteine on protein C activity in vitro. Blood 2003 101 (6) 2446-2447. 

Giltay EJ, Hoogeveen EK, Elbers JM, Gooren U, Asscheman H, Stehouwer CD. 1998. Insulin resistance is associated with elevated plasma total homocysteine levels in healthy, non obese subjects. Atherosclerosis 139 197-198. 

He was diagnosed with moderate hyperhomocysteinemia and treated with 2.0 mg folic acid daily. He continued to take warfarin and clopidogrel. After 1 month, his plasma total homocysteine level had decreased to 9 pmol/L. He had no further episodes of weakness or other neurological symptoms during the ensuing 12 months. 

An alternative reaction for the remethylation of homocysteine to methionine can be accomplished by betaine homocysteine methyltrans-ferase, which uses betaine instead of 5-MTHF as the methyl donor. Unlike the MS reaction, which is believed to be ubiquitously present in all tissues, the betaine homocysteine methyl-transferase reaction occurs only in the liver and kidney. Betaine is not a required nutrient since the liver can synthesize betaine from choline. Betaine supplements, however, have been shown to lower plasma total homocysteine concentrations successfully in subjects with deficient homocysteine remethylation due to defects in MTHFR or MTRR and in those with deficient CBS activity. 

The fraction of intracellular homocysteine that does not undergo transsulfuration or remethylation is secreted into the extracellular space and ultimately finds its way into the blood. One major source of blood homocysteine is the liver, but some homocysteine is secreted into the blood by endothelial cells, circulating blood cells, and other tissues. Only about 2% of homocysteine in blood remains in its reduced, thiol form. The remainder circulates as a variety of different oxidation adducts, which include the disulfide, homocystine, as well as homocysteine-cysteine mixed disulfide and several protein-bound disulfides.About 70% of total homocysteine in blood is bound to the protein albumin through a disulfide linkage.When blood homocysteine is measured in the clinical laboratory, a reducing agent is added to the sample... 

Table 21-1. Factors Influencing Plasma Levels of Total Homocysteine ...

V5. Voutilainen, S., Morrow, J. D., Roberts, L. J., II, Alfthan, G., Alho, H., Nyyssonen, K., and Salonen, J. T., Enhanced in vivo lipid peroxidation at elevated plasma total homocysteine levels. Arterioscler. Thromb. Vase. Biol. 19, 1263-1266 (1999). 

Serum cystatin C has also been described to be a better predictor than serum creatinine of fasting total homocysteine serum levels, probably because of its closer correlation to GFR (B23, N7). 

Bates CJ, Mansoor MA, van der Pols J, Prentice A, Cole TJ, Finch S (1997) Plasma total homocysteine in a representative sample of972 British men and women aged 65 and over. Eur J Chn Nutr 51(10) 691-697... 

Normal endothelial cells modulate the effects of homocysteine by facilitating the S-nitrosilation of homocysteine by nitric oxide. The formed S-nitrosothiol adduct is a potent vasorelaxing substance [2,108]. So, when high levels of homocysteine occur, they may overcome or impair the endothelial capacity for NO synthesis. Endothelial cell damage may result from increased production of reactive oxygen species or from impaired production of nitric oxide [3,102]. In endothelial cells, total homocysteine reduces the levels of tetra-hydrobiopterin (BH4), relative to dihydrobiopterin (BH ), thereby creating a dysfunctional eNOS causing a reduced amount of nitric oxide [1,101],... 

M. Amadottir, B. Hultberg, P. Nilsson-Ehle and H. Tysell, The Effect of Reduced Glomerular Filtration Rate on Plasma Total Homocysteine Concentration, Journal of Clinical Laboratory Investigations 56 (1996) 41-46. 

Sumner, A. E., Chin, M. M., Abrahm, J. L., Berry, G. T., Cracely, E. J., Allen, R. H and Stabler, S. P. (1996). F.levated methylmalonic acid and total homocysteine levels show-high prevalence of vitamin deficiency after gastric surgery. Ami. inicrn. Med. 124, 469-476. 

Jacques PF, Selhub J, Bostom AG, Wilson PW, Rosenberg IH. The effect of folic acid fortification on plasma folate and total homocysteine concentrations. N Engl J Med 1999 340(19) 1449-54. 

Garcia, A.J. Apitz-Castro, R. Plasma total homocysteine quantitation An improvement of the classical high-... 

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