title: Genotype-independent in vivo oxidative stress following a methionine loading test: maximal platelet activation in subjects with early-onset thrombosis.
abstract: BACKGROUND
  Methionine ingestion (100mg/kg) identifies subjects in whom fasting total homocysteine (tHcy) may be normal but the post-methionine load (PML) tHcy is abnormally high.
  
  
  METHODS
  In 96 subjects [54 M/42 F, 40.4 ± 12.3 yrs old; 28 with the 68 bp844 ins of the cystathionine-β-synthase gene (CBSins+); 20 homozygotes for the C677T mutation of the methylene-tetrahydrofolate reductase gene (MTHFR++); 13 with the combination of the two, and 35 without any of them], we have evaluated in vivo oxidative stress and platelet activation, as reflected by urinary excretions of 8-iso-PGF(2α) and of 11-dehydro-TXB(2) respectively, before and after a methionine load test (PML). A history of early-onset thrombosis (18 arterial, 32 venous, 2 both) was present in 52/96 of them.
  
  
  RESULTS
  Baseline; tHcy was highest in MTHFR++ carriers (p < 0,05); 8-iso-PGF(2α) and 11-dehydro-TXB(2) levels were independent of sex, MTHFR++ and/or CBSins + (p > 0.05). PML; The ~3-fold increase (p < 0.01 vs baseline) in tHcy reached a plateau within 6-8 hrs. Mean PML tHcy was maximal in MTHFR++ carriers (p = 0.000). 8-iso-PGF(2α) and 11-dehydro-TXB(2) increase reached a maximum within 4 hrs. 11-dehydro-TXB(2) increase was highest (p = 0.023 vs baseline) in subjects with a history of thrombosis. Baseline 11-dehydro-TXB(2) and a history of thrombosis independently predicted PML 11-dehydro-TXB(2) (β = 0.287, p = 0.000 and β = 0.308, p = 0.026, respectively).The PML increase in 8-iso-PGF(2α) or in 11-dehydro-TXB(2) were comparable in the different genotypes (p > 0.05).
  
  
  CONCLUSIONS
  Regardless genotypes associated with moderate hyperhomocysteinemia, following a methionine loading test, in vivo oxidative stress and platelet activation occur, being the latter maximal in subjects with a history of early-onset thrombosis.
authors.affiliation: Regional Reference Centre for Coagulation Disorders, Department of Clinical and Experimental Medicine, Federico II University, Naples, Italy.
authors.forename: Matteo Nicola Dario
authors.initials: MN
authors.lastname: Di Minno
authors.forename: Salvatore
authors.initials: S
authors.lastname: Pezzullo
authors.forename: Vittorio
authors.initials: V
authors.lastname: Palmieri
authors.forename: Antonio
authors.initials: A
authors.lastname: Coppola
authors.forename: Armando
authors.initials: A
authors.lastname: D'Angelo
authors.forename: Francesca
authors.initials: F
authors.lastname: Sampietro
authors.forename: Viviana
authors.initials: V
authors.lastname: Cavalca
authors.forename: Elena
authors.initials: E
authors.lastname: Tremoli
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Minno
mesh_terms: D000328:Adult; D017668:Age of Onset; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood / Q000652:urine; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003541:Cystathionine beta-Synthase / Q000235:genetics / Q000378:metabolism; D015237:Dinoprost / Q000031:analogs & derivatives / Q000652:urine; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006720:Homozygote; D006801:Humans; D020138:Hyperhomocysteinemia / Q000097:blood / Q000175:diagnosis* / Q000235:genetics; D007558:Italy; D016014:Linear Models; D008297:Male; D008715:Methionine; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D009154:Mutation; D018384:Oxidative Stress / Q000235:genetics*; D010641:Phenotype; D015539:Platelet Activation / Q000235:genetics; D010979:Platelet Function Tests; D013927:Thrombosis / Q000097:blood / Q000175:diagnosis* / Q000235:genetics; D013929:Thromboxane B2 / Q000031:analogs & derivatives / Q000652:urine; D013997:Time Factors
chemical_list: D015415:Biomarkers; D006710:Homocysteine; C075750:8-epi-prostaglandin F2alpha; D013929:Thromboxane B2; C049235:11-dehydro-thromboxane B2; D008715:Methionine; D015237:Dinoprost; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D003541:Cystathionine beta-Synthase