The association of factor VIIa, factor XIIa and beta2-glycoprotein-1 with triglyceride-rich lipoproteins in normolipidaemic subjects.
The activation of factors XII (FXII) and VII (FVII) has been shown to occur on the surface of lipoproteins in the presence of lipoprotein lipase and may be modulated by beta2glycoprotein-1 (beta2GP1). In the postprandial state FVII is activated without apparent activation of FXII in plasma. We investigated whether beta2GP1, FXIIa and FVIIa are associated with triglyceride-rich lipoproteins in the fasting and postprandial state. Six normal subjects were studied while fasting and 1, 2 and 4 h after ingestion of 100 g fat. We confirmed that plasma FVIIa activity, but not FXIIa antigen, was increased in the postprandial period. FXIIa, FVIIa and beta2GP1 were associated with chylomicra-rich lipoproteins, and lipase or Triton X-100 treatment caused an increase in FXIIa in plasma and chylomicra without an increase in FVIIa. This suggests that FXIIa may be formed in the postprandial period, but its antigenic determinants are masked by the association with lipoprotein particles, although it could still express proteolytic activity. Alternatively a FXII-independent mechanism or surface other than triglyceride-rich lipoproteins may be responsible for FVII activation in the postprandial state.
Department of Haematology, University College London Medical School, UK. r.cardigan@ucl.ac.uk
R A
RA
Cardigan
S
S
Donohoe
G
G
Purdy
I J
IJ
Mackie
S J
SJ
Machin
D002914:Chylomicrons / Q000097:blood / Q000187:drug effects / Q000302:isolation & purification; D015942:Factor VIIa / Q000032:analysis* / Q000187:drug effects; D015956:Factor XIIa / Q000032:analysis* / Q000187:drug effects; D005215:Fasting / Q000097:blood; D006023:Glycoproteins / Q000097:blood* / Q000187:drug effects; D006801:Humans; D008049:Lipase / Q000494:pharmacology; D008074:Lipoproteins / Q000097:blood* / Q000737:chemistry / Q000187:drug effects; D008562:Membrane Glycoproteins / Q000097:blood / Q000187:drug effects; D011092:Polyethylene Glycols / Q000494:pharmacology; D019518:Postprandial Period / Q000502:physiology; D012016:Reference Values; D014280:Triglycerides / Q000097:blood*; D053482:beta 2-Glycoprotein I
D002914:Chylomicrons; D006023:Glycoproteins; D008074:Lipoproteins; D008562:Membrane Glycoproteins; D014280:Triglycerides; D053482:beta 2-Glycoprotein I; D011092:Polyethylene Glycols; D008049:Lipase; D015942:Factor VIIa; D015956:Factor XIIa