Storage of human plasma samples leads to alterations in the lipoprotein distribution of apoC-III and apoE.
The effect of frozen storage on lipoprotein distribution of apolipoprotein C-III (apoC-III) and apoE was investigated by measuring apoC-III and apoE by ELISA in HDL and apoB-containing lipoproteins of human plasma samples (n = 16) before and after 2 weeks of frozen storage (-20 degrees C). HDLs were separated by heparin-manganese precipitation (HMP) or by fast-protein liquid chromatography (FPLC). Total plasma apoC-III and apoE levels were not affected by frozen storage. HDL-HMP apoC-III and apoE levels were significantly higher in frozen versus fresh samples: 7.7 +/- 0.7 versus 6.7 +/- 0.7 mg/dl (P < 0.05) and 2.0 +/- 0.1 versus 1.2 +/- 0.1 mg/dl (P < 0.001), respectively. HDL-FPLC apoC-III and apoE, but not triglyceride (TG) or cholesterol, levels were also higher in frozen samples: 12.0 +/- 1.2 versus 7.5 +/- 0.6 mg/dl (P < 0.001) and 2.7 +/- 0.2 versus 1.6 +/- 0.2 mg/dl (P < 0.001), respectively. Frozen storage led to a decrease in apoC-III (-17 +/- 9%) and apoE (-19 +/- 9%) in triglyceride-rich lipoprotein. Redistribution of apoC-III and apoE was most evident in samples with high TG levels. HDL apoC-III and apoE levels were also significantly higher when measured in plasma stored at -80 degrees C. Our results demonstrate that lipoprotein distribution of apoC-III and apoE is affected by storage of human plasma, suggesting that analysis of frozen plasma should be avoided in studies relating lipoprotein levels of apoC-III and/or apoE to the incidence of coronary artery disease.
Cohn
Jeffrey S
JS
Clinical Research Institute of Montreal, Quebec, Canada. cohnj@ircm.qc.ca
Rodriguez
Claudia
C
Jacques
Hélène
H
Tremblay
Michel
M
Davignon
Jean
J
D053305:Apolipoprotein C-III; D001056:Apolipoproteins C / Q000097:blood*; D001057:Apolipoproteins E / Q000097:blood*; D002784:Cholesterol / Q000097:blood; D002853:Chromatography, Liquid; D015925:Cryopreservation / Q000379:methods; D006801:Humans; D010949:Plasma / Q000378:metabolism*; D013048:Specimen Handling / Q000379:methods*; D014280:Triglycerides / Q000097:blood
D053305:Apolipoprotein C-III; D001056:Apolipoproteins C; D001057:Apolipoproteins E; D014280:Triglycerides; D002784:Cholesterol