Increased hepatic secretion of very-low-density-lipoprotein apolipoprotein B-100 in heterozygous familial hypercholesterolaemia: a stable isotope study.
We have measured the hepatic secretion of very-low-density-lipoprotein apolipoprotein B-100 (VLDL apo B) in 6 patients with heterozygous familial hypercholesterolaemia (FH) (4 males, 2 females, age 47.0 +/- 2.7 years (mean +/- S.E.M.), weight 71.0 +/- 5.3 kg) and 6 normocholesterolaemic subjects matched for age, weight and sex (4 males, 2 females, age 47.5 +/- 3.1 years, weight 70.0 +/- 4.4 kg) using a stable isotope method. Each subject received a primed, constant infusion of [I-13C]leucine and isotopic enrichment of VLDL apo B was determined using gas-chromatography mass-spectrometry (GCMS). Mean plasma low-density-lipoprotein (LDL) cholesterol and apo B concentrations in the FH group were more than twice that in the control group (FH, 8.5 +/- 0.5 mmol/l vs. controls, 3.3 +/- 0.2 mmol/l, P < 0.001; and FH, 2.0 +/- 0.1 g/l vs. controls, 1.0 +/- 0.04 g/l, P < 0.0001, respectively). Plasma triglyceride (TG) and high-density-lipoprotein (HDL) cholesterol concentrations were not significantly different between the two groups. Although the fractional secretion rates of VLDL apo B were similar (FH, 14.3 +/- 3.6 pools/day vs. controls, 11.6 +/- 1.7 pools/day, P = 0.53), VLDL apo B pool size and VLDL apo B absolute secretion rates (ASR) were significantly higher in the FH group (FH, 234.2 +/- 27.8 mg vs. controls, 66.3 +/- 13.5 mg, P < 0.001; and FH, 51.4 +/- 17.9 mg/kg per day vs. controls, 9.4 +/- 1.1 mg/kg per day, P < 0.02, respectively). We conclude that FH is associated with increased hepatic secretion of VLDL apo B and that this may contribute to the elevated concentration of LDL-cholesterol. The findings are also consistent with the hypothesis that in FH increased hepatic cholesterol availability (due to increased uptake of LDL-cholesterol via the receptor-independent pathway) stimulates hepatic secretion of VLDL apo B.
Cummings
M H
MH
Department of Medicine, St. Thomas' Hospital (UMDS), London, UK.
Watts
G F
GF
Umpleby
M
M
Hennessy
T R
TR
Quiney
J R
JR
Sönksen
P H
PH
D000328:Adult; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000097:blood / Q000378:metabolism*; D002247:Carbon Isotopes; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006579:Heterozygote; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D014280:Triglycerides / Q000097:blood
D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D002247:Carbon Isotopes; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D014280:Triglycerides