High‐density lipoprotein apolipoprotein A‐I kinetics: comparison of radioactive and stable isotope studies

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Abstract
Background To compare the kinetic determinants of high‐density lipoprotein (HDL) apolipoprotein A‐I (apoA‐I) concentration in lean normolipidaemic subjects using radioisotope and stable isotope studies. Materials and methods We pooled data from 16 radioisotope and 13 stable isotope studies to investigate the kinetics of apoA‐I in lean normolipidemic individuals. We also examined the associations of HDL kinetic parameters with age, sex, body mass index (BMI) and concentrations of apoA‐I, triglycerides, HDL cholesterol and low‐density lipoprotein (LDL) cholesterol. Results Lean subjects from radioisotope and stable isotope studies were matched for age, gender, BMI and lipid profile. The apoA‐I concentration was significantly lower in the radioisotope group than the stable isotope group (P = 0·031). There was no significant difference in HDL apoA‐I fractional catabolic rate (FCR) and production rate (PR) between the groups. In the radioisotope group, HDL apoA‐I FCR was significantly associated with apoA‐I and HDL cholesterol concentrations (r = −0·681, P < 0·001 and r = −0·542, P < 0·001, respectively), whereas in the stable isotope group, only HDL apoA‐I PR was significantly associated with apoA‐I concentration (r = 0·455, P = 0·004). Conclusions Our findings suggest that HDL apoA‐I FCR is the primary determinant of apoA‐I concentrations in lean subjects in studies using radiotracer techniques. By contrast, HDL apoA‐I PR is the primary determinant of apoA‐I concentration in lean subject in studies employing stable isotope methods. These discrepancies may be reconciled by differences in methodologies and/or study population characteristics.

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