title: The usefulness of γ-glutamyltransferase as a marker of cardiovascular function in Africans and Caucasians: the SABPA study.
abstract: OBJECTIVE
  Serum γ-glutamyltransferase (GGT) is increasingly regarded as a marker of vascular function. However, the usefulness of this marker is in dispute. Gender and ethnic differences, as well as the serum level range where correlations with vascular function will emerge, may complicate the usefulness of GGT. The aim is to compare correlations with markers of vascular function between African and Caucasian groups.
  
  
  METHODS
  This cross-sectional target population study involved four groups of African and Caucasian men and women of 100 participants each. Fasting lipids, GGT, C-reactive protein (CRP), reactive oxygen species, and glycosylated hemoglobin (HbA1c) were determined as well as blood pressure, carotid intima-media thickness (CIMT), and left ventricular hypertrophy.
  
  
  RESULTS
  γ-Glutamyltransferase levels were significantly higher in Africans compared with Caucasians and also higher in men than in women. γ-Glutamyltransferase correlated with triglycerides in all four groups and after adjusting the correlations sustained in the male groups but disappeared in women. Correlations existed between GGT and blood pressure, except for the African women. After adjustments, CIMT correlated with GGT in Caucasian men (r = 0.29; P < .01). Glycosylated hemoglobin was associated with GGT in Caucasian women (r = 0.26; P = .01) as well as CRP (r = 0.36; P < .01). When the groups were divided into low and high GGT groups by median split, most of the correlations disappeared in the high GGT groups.
  
  
  CONCLUSIONS
  Gender and ethnic-specific associations occurred regarding GGT and variables associated with cardiovascular function. With high levels of GGT the correlations diminished. The usefulness of GGT as a marker of vascular dysfunction seems limited.
authors.affiliation: Hypertension in Africa Research Team, School for Physiology, North-West University, Potchefstroom Campus, Potchefstroom, South Africa. Hugo.Huisman@nwu.ac.za
authors.forename: Hugo Willem
authors.initials: HW
authors.lastname: Huisman
authors.forename: Rudolph
authors.initials: R
authors.lastname: Schutte
authors.forename: Aletta Elisabeth
authors.initials: AE
authors.lastname: Schutte
authors.forename: Johannes Marthinus
authors.initials: JM
authors.lastname: van Rooyen
authors.forename: Nicolaas Theodore
authors.initials: NT
authors.lastname: Malan
authors.forename: Carla Maria Theresia
authors.initials: CM
authors.lastname: Fourie
authors.forename: Matthew Colin
authors.initials: MC
authors.lastname: Glyn
authors.forename: Leone
authors.initials: L
authors.lastname: Malan
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D044383:Black People / Q000706:statistics & numerical data*; D002318:Cardiovascular Diseases / Q000097:blood / Q000175:diagnosis / Q000208:ethnology; D002320:Cardiovascular Physiological Phenomena; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D017678:Sex Distribution; D013019:South Africa / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data*; D005723:gamma-Glutamyltransferase / Q000097:blood*
chemical_list: D015415:Biomarkers; D005723:gamma-Glutamyltransferase