In Vitro Effects of Lipoprotein Deficient Serum Containing Normal Lecithin: Cholesterol Acyltransferase Activity on Serum Lipoproteins in Patients with Chronic Renal Failure

Abstract

It is well known that uremic serum lipoprotein abnormalities are associated with a decrease in serum lecithin: cholesterol acyltransferase (LCAT) activity but the precise mechanism is not yet clear.
Thus, we investigated the in vitro effects of LCAT containing lipoprotein deficient fraction (LPDF) from a normal control on uremic lipoprotein fraction (LP). The incubation with the LPDF and LP was carried out for 12 hours, at 37°C. The resulting mixture was isolated by isopycnic density gradient ultracentrifugation and the pooled fraction corresponding each lipoprotein was used for the chemical determination and the quantitation of apoprotein (apo) A-I and apo A-II in high density lipoproteins (HDL). Consequently, the following findings were summerized.
1) In the absorbance of lipoprotein profiles, LPDF caused an increase in low density lipoproteins (LDL) and HDL₂, and a decrease in very low density lipoproteins (VLDL)-intermediate density lipoproteins (IDL) and HDL₃.
2) LPDF brought about an increase in total amounts of LDL and HDL₂, and a decrease in those of VLDL-IDL and HDL₃.
3) With respect to the chemical compositions, LPDF caused an increase in percent cholesteryl ester and a decease in phospholipid content in any lipoprotein fraction.
4) There was an increase in total amounts of apo A-I and apo A-II, and apo A-I/A-II ratio in HDL₂ and a reverse change in HDL₃ after the incubation of LPDF with the uremic LP.
These in vitro results strongly suggest that low LCAT activity in uremia may be related to a decrease in HDL₂.