Elevated high density lipoprotein cholesterol levels correlate with decreased apolipoprotein A-I and A-II fractional catabolic rate in women.
High levels of HDL-cholesterol (HDL-C) protect against coronary heart disease susceptibility, but the metabolic mechanisms underlying elevated HDL-C levels are poorly understood. We now report the turnover of isologous radioiodinated HDL apolipoproteins, apo A-I and apo A-II, in 15 female subjects on a metabolic diet with HDL-C levels ranging from 51 to 122 mg/dl. The metabolic parameters, fractional catabolic rate (FCR) and absolute synthetic rate (SR), were determined for apo A-I and apo A-II in all subjects. There was an inverse correlation between plasma HDL-C and the FCR of apo A-I and apo A-II (r = -0.75, P less than 0.001, and r = -0.54, P = 0.036, respectively), but no correlation with the SR of either apo A-I or apo A-II (r = 0.09, and r = -0.16, respectively, both P = NS). Apo A-I levels correlated inversely with apo A-I FCR (r = -0.64, P = 0.01) but not with apo A-I SR (r = 0.30, P = NS). In contrast, plasma levels of apo A-II did not correlate with apo A-II FCR (r = -0.38, P = 0.16), but did correlate with apo A-II SR (r = 0.65, P = 0.009). Further analysis showed that apo A-I and apo A-II FCR were inversely correlated with the HDL-C/apo A-I + A-II ratio (r = -0.69 and -0.61, P = 0.005 and 0.015, respectively). These data suggest that: (a) low HDL apolipoprotein FCR is the predominant metabolic mechanism of elevated HDL-C levels; (b) apo A-I FCR is the primary factor in controlling plasma apo A-I levels, but apo A-II SR is the primary factor controlling plasma apo A-II levels; (c) low HDL apolipoprotein FCR is associated with a lipid-rich HDL fraction. These findings elucidate aspects of HDL metabolism which contribute to high HDL-C levels and which may constitute mechanisms for protection against coronary heart disease.
Brinton
E A
EA
Laboratory of Biochemical Genetics and Metabolism, Rockefeller University, New York 10021.
Eisenberg
S
S
Breslow
J L
JL
D000328:Adult; D000368:Aged; D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A / Q000378:metabolism*; D008076:Cholesterol, HDL / Q000097:blood*; D002853:Chromatography, Liquid; D005260:Female; D006801:Humans; D008049:Lipase / Q000378:metabolism; D008875:Middle Aged
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A; D008076:Cholesterol, HDL; D008049:Lipase