title: Reduced urinary excretion of homocysteine could be the reason of elevated plasma homocysteine in patients with psychiatric illnesses.
abstract: OBJECTIVE
  Although increased plasma total homocysteine (tHcy) concentrations were reported in psychiatric diseases, currently the reasons of elevated tHcy levels were not clearly understood. In this study we aimed to investigate the contribution of renal clearance of homocysteine on plasma tHcy load in patients with depression and first episode psychosis.
  
  
  METHODS
  Thirty depression, 14 first episode psychosis patients and 34 healthy individuals (control group) were involved in the study. In patients and control groups, plasma and urine tHcy levels, urine methylmalonic acid (uMMA), serum vitamin B12 and folate concentrations were measured.
  
  
  RESULTS
  Although there was not any difference between depression, psychosis and control groups with respect to mean (SD) values of vitamin B12 (289(131), 230 (72) and 249(79) pg/mL, respectively) and folate (6.4(4.0), 5.3(2.3) and 5.7(2.3) ng/mL, respectively), plasma tHcy levels of depression and psychosis group were higher than the control values (16.3(6.2), 15.5(4.3) and 9.9(2.1) micromol/L, respectively). Urine tHcy values of patient groups were significantly lower than those in the control group (14.5(7.6), 15.8(6.8) and 29.6(16.9) micromol/g creatinine, respectively). There were elevated uMMA levels in depression and psychosis groups compared with control group (4.9(2.4), 6.6(3.2) and 2.8(1.2) mmol/mol creatinine, respectively). There were a significant and negative correlation between urinary tHcy and plasma tHcy levels (r=-0.258 and p=0.011).
  
  
  CONCLUSIONS
  In conclusion, reduced urinary tHcy levels in psychiatric patients could be one of the reasons of plasma tHcy elevations with normal folate and vitamin B12 levels. Altered renal handling mechanisms of homocysteine may lead to elevated plasma tHcy levels by reduced clearance of homocysteine via glomerular filtration.
authors.affiliation: Department of Biochemistry and Clinical Biochemistry, GATA Haydarpasa Training Hospital, Uskudar, Istanbul, Turkey. osmetip@yahoo.com
authors.forename: Osman Metin
authors.initials: OM
authors.lastname: Ipcioglu
authors.forename: Omer
authors.initials: O
authors.lastname: Ozcan
authors.forename: Mustafa
authors.initials: M
authors.lastname: Gultepe
authors.forename: Alpay
authors.initials: A
authors.lastname: Ates
authors.forename: Cengiz
authors.initials: C
authors.lastname: Basoglu
authors.forename: Erdinc
authors.initials: E
authors.lastname: Cakir
mesh_terms: D000208:Acute Disease; D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D002908:Chronic Disease; D005260:Female; D005492:Folic Acid / Q000097:blood; D006710:Homocysteine / Q000097:blood* / Q000652:urine*; D006801:Humans; D008297:Male; D015201:Meta-Analysis as Topic; D008875:Middle Aged; D011618:Psychotic Disorders / Q000097:blood* / Q000652:urine*; D014805:Vitamin B 12 / Q000097:blood
chemical_list: D015415:Biomarkers; D006710:Homocysteine; D005492:Folic Acid; D014805:Vitamin B 12