Lipoprotein profiles in children with two common cholesteryl ester transfer protein gene mutations, D442G and I14A, during the first year of life

A two-step homogeneous assay for apolipoprotein E-containing high-density lipoprotein-cholesterol

BACKGROUND

Apolipoprotein E-containing high-density lipoprotein shows antiatherogenic properties in vitro. There is a need for a homogeneous assay to determine the concentration of apolipoprotein E-containing high-density lipoprotein for in vivo studies.

METHODS

In the proposed homogeneous assay, lipoproteins other than apolipoprotein E-containing high-density lipoprotein were eliminated in the first step. Apolipoprotein E-containing high-density lipoprotein-cholesterol was measured in the second step. The control study used a 13% polyethylene glycol precipitation assay (control assay).

RESULTS

The homogeneous assay showed good performance in validation studies. In subjects with normal liver function ( n = 78), a significant correlation was found between the control assay and the homogeneous assay ( r = 0.824). Serum apolipoprotein E-containing high-density lipoprotein cholesterol concentrations, determined by the control assay and the homogeneous assay, respectively, were 0.05 (0.04-0.10) (median [25th-75th percentile]) mmol/L and 0.10 (0.06-0.13) mmol/L for healthy individuals ( n = 12), and 0.03 (0.01-0.13) mmol/L and 0.02 (0.01-0.02) mmol/L for patients with cholestasis ( n = 6). The results indicate that the homogeneous assay recovers cholesterol contained in physiological apolipoprotein E-containing high-density lipoprotein, but not in pathological apolipoprotein E-containing high-density lipoprotein from cholestatic patients.

CONCLUSIONS

The proposed two-step homogeneous assay enables selective measurement of physiological apolipoprotein E-containing high-density lipoprotein cholesterol in common autoanalysers. This assay might uncover a role for apolipoprotein E-containing high-density lipoprotein in physiological conditions.

Development of homogeneous assay for simultaneous measurement of apoE-deficient, apoE-containing, and total HDL-cholesterol

BACKGROUND

Pathophysiological role for high-density lipoprotein (HDL) subclasses remains to be elucidated. Homogeneous assay for simultaneous measurements of apoE-deficient HDL-cholesterol (HDL-C), apoE-containing HDL-C, and total HDL-C is desired, because apoE plays important roles in lipid metabolism.

METHODS

The proposed assay consists of a primary reaction to remove non-HDL-C, a secondary reaction to measure apoE-deficient HDL-C, and a tertiary reaction to measure apoE-containing HDL-C. The assay is completed within 10 min. For control study, 13% polyethylene glycol precipitation assay and phosphotungstate-dextran sulfate-magnesium precipitation assay were carried out.

RESULTS

Good correlations between the control assays and the proposed assay was obtained in serum samples from patients without liver disease (n=33): r=0.987, 0.957, and 0.991 for apoE-deficient, apoE-containing, and total HDL-C, respectively. ApoE-containing HDL-C by the proposed method in healthy individuals (n=12) and patients with hyper-HDL-cholesterolemia (n=5) were 0.11±0.03 and 0.26±0.05 mmol/l (4.1±1.3 and 10.1±2.0 mg/dl), respectively. ApoE-containing HDL-C increased rapidly at >2.59 mmol/l (100 mg/dl) of total HDL-C, suggesting a unique regulating mechanism of apoE-containing HDL-C.

CONCLUSIONS

The established homogeneous assay might be useful for clinical and epidemiological studies on apoE-deficient and apoE-containing HDL subclasses.

Early postnatal changes of lipoprotein subclass profile in late preterm infants

BACKGROUND

Late preterm infants (LPIs; 34-37 gestational weeks at birth) have higher risk for several morbidities than do term infants (TIs). It has been suggested that a cholesterol and fatty acid supply may improve their outcomes. We investigated the lipoprotein subclass profile in LPIs to evaluate their early postnatal lipid metabolism.

METHODS

Eighty-one infants (25 LPIs, 56 TIs) were included. Cholesterol and triglyceride (TG) concentrations in 12 lipoprotein subclasses were measured at birth and at 1 month using HPLC.

RESULTS

In LPIs, the cord blood exhibited higher cholesterol concentrations in medium and large subclasses of very low-density lipoprotein (VLDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) compared to the values in TIs. During the first month of life, LPIs had greater increases in cholesterol concentrations of medium and large subclasses of VLDL than TIs, whereas postnatal increases in cholesterol concentrations of medium and large subclasses of LDL and HDL were smaller. TG concentrations were not different in each VLDL subclass at birth and at 1 month.

CONCLUSIONS

In LPIs, cord blood lipoprotein subclass profiles and the early postnatal change exhibited different, especially in cholesterol concentrations.