title: Effect of L-methionine supplementation on plasma homocysteine and other free amino acids: a placebo-controlled double-blind cross-over study.
abstract: OBJECTIVE
  The essential amino acid L-methionine is a potential compound in the prophylaxis of recurrent or relapsing urinary tract infection due to acidification of urine. As an intermediate of L-methionine metabolism, homocysteine is formed. The objective was to study the metabolism of L-methionine and homocysteine, and to assess whether there are differences between patients with chronic urinary tract infection and healthy control subjects.
  
  
  METHODS
  A randomized placebo-controlled double-blind intervention study with cross-over design.
  
  
  METHODS
  Department of Nutritional Physiology, Institute of Nutrition in cooperation with the Department of Internal Medicine III, Friedrich Schiller University of Jena, Germany.
  
  
  METHODS
  Eight female patients with chronic urinary tract infection and 12 healthy women (controls).
  
  
  METHODS
  After a methionine-loading test, the volunteers received 500 mg L-methionine or a placebo three times daily for 4 weeks.
  
  
  METHODS
  Serum and urinary concentrations of methionine, homocysteine, cystathionine, cystine, serine, glycine and serum concentrations of vitamin B12, B6 and the state of folate.
  
  
  RESULTS
  Homocysteine plasma concentrations increased from 9.4+/-2.7 micromol/l (patients) and 8.9+/-1.8 micromol/l (controls) in the placebo period to 11.2+/-4.1 micromol/l (P=0.031) and 11.0+/-2.3 micromol/l (P=0.000), respectively, during L-methionine supplementation. There were significant increases in serum methionine (53.6+/-22.0 micromol/l; P=0.003; n=20) and cystathionine (0.62+/-0.30 micromol/l; P=0.000; n=20) concentrations compared with the placebo period (33.0+/-12.0 and 0.30+/-0.10 micromol/l; n=20). Simultaneously, renal excretion of methionine and homocysteine was significantly higher during L-methionine intake.
  
  
  CONCLUSIONS
  Despite an adequate vitamin status, the supplementation of 1500 mg of L-methionine daily significantly increases homocysteine plasma concentrations by an average of 2.0 micromol/l in patients and in control subjects. An optimal vitamin supplementation, especially with folate, might prevent such an increase.
authors.affiliation: Department of Nutritional Physiology, Institute of Nutrition, Friedrich Schiller University of Jena, Jena, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Ditscheid
authors.forename: R
authors.initials: R
authors.lastname: Fünfstück
authors.forename: M
authors.initials: M
authors.lastname: Busch
authors.forename: R
authors.initials: R
authors.lastname: Schubert
authors.forename: J
authors.initials: J
authors.lastname: Gerth
authors.forename: G
authors.initials: G
authors.lastname: Jahreis
mesh_terms: D000328:Adult; D000368:Aged; D000596:Amino Acids / Q000097:blood* / Q000652:urine; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005492:Folic Acid / Q000097:blood; D006710:Homocysteine / Q000097:blood* / Q000378:metabolism / Q000652:urine; D006801:Humans; D008715:Methionine / Q000097:blood / Q000494:pharmacology* / Q000652:urine; D008875:Middle Aged; D014552:Urinary Tract Infections / Q000097:blood / Q000517:prevention & control* / Q000652:urine; D014805:Vitamin B 12 / Q000097:blood; D025101:Vitamin B 6 / Q000097:blood
chemical_list: D000596:Amino Acids; D006710:Homocysteine; D025101:Vitamin B 6; D005492:Folic Acid; D008715:Methionine; D014805:Vitamin B 12