title: Bioavailable IGF-1 and its relationship with endothelial damage in a bi-ethnic population: The SABPA study.
abstract: BACKGROUND
  Insulin-like growth factor-1 (IGF-1) has vasculoprotective effects and can directly oppose endothelial dysfunction in several ways. To improve our understanding on the potential contribution of reduced IGF-1 to the development of vascular endothelial damage, we investigated the link between bioavailable IGF-1 and von Willebrand factor (vWF) as a marker of endothelial damage. We performed this study in black South African school teachers, known to be prone to hypertension.
  
  
  METHODS
  From the larger Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA) study we included 179 black and 207 white non-diabetic men and women (aged 44.5 ± 9.96 years). We measured ambulatory blood pressure and determined IGF-1, insulin-like growth factor binding protein 3 (IGFBP-3) and vWF antigen from blood samples. We used the molar IGF-1/IGFBP-3 ratio as an estimate of bioavailable IGF-1.
  
  
  RESULTS
  Black individuals presented higher blood pressure and vWFag and lower IGF-1 than the white group (all p < 0.001). In multivariate-adjusted analyses, vWFag was inversely associated with IGF-1 (R(2) = 0.18; β = -0.17; p = 0.044) and IGF-1/IGFBP-3 (R(2) = 0.18; β = -0.17; p = 0.030) in blacks, with no associations in whites. Since IGF-1 is attenuated and vWFag elevated in diabetes, we included patients with diabetes (n = 38) and the aforementioned associations found in blacks remained robust.
  
  
  CONCLUSIONS
  The inverse association between bioavailable IGF-1 and vWF in black South Africans suggests that suppressed IGF-1 may result in endothelial damage independent of traditional risk factors.
authors.affiliation: Hypertension in Africa Research Team (HART), North-West University, South Africa.
authors.forename: A S E
authors.initials: AS
authors.lastname: Koegelenberg
authors.affiliation: Hypertension in Africa Research Team (HART), North-West University, South Africa; MRC Research Unit for Hypertension and Cardiovascular disease, North-West University, South Africa.
authors.forename: R
authors.initials: R
authors.lastname: Schutte
authors.affiliation: Hypertension in Africa Research Team (HART), North-West University, South Africa.
authors.forename: W
authors.initials: W
authors.lastname: Smith
authors.affiliation: Hypertension in Africa Research Team (HART), North-West University, South Africa; MRC Research Unit for Hypertension and Cardiovascular disease, North-West University, South Africa. Electronic address: alta.schutte@nwu.ac.za.
authors.forename: A E
authors.initials: AE
authors.lastname: Schutte
mesh_terms: D000328:Adult; D042783:Endothelial Cells / Q000378:metabolism*; D005006:Ethnicity; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors
chemical_list: D007334:Insulin-Like Growth Factor I
keywords: Insulin-like growth factor binding protein-3; Insulin-like growth factor-1; von Willebrand factor