Insect lipophorin conversions. Compositional analysis of high- and low-density lipophorin of Acherontia atropos and Locusta migratoria.

Abstract

The formation of low-density lipophorin (LDLp) in insect hemolymph, resulting from association of high-density lipophorin (HDLp) with both lipid and apolipophorin III, is considered to provide a reutilizable lipid shuttle for flight muscle energy supply. The changes in lipid and apolipoprotein composition of LDLp, isolated after flight activity, compared to that of HDLp in the hemolymph at rest, were studied in two evolutionary divergent insects, the hawkmoth Acherontia atropos and the migratory locust, Locusta migratoria. Using FPLC on Superose 6 prep grade as a novel technique to separate the apolipophorins of HDLp and LDLp, the ratio of apolipoprotein I, II, and III in HDLp of both species was demonstrated to be 1:1:1, whereas flight activity resulted in a ratio of 1:1:10 in LDLp. Injection of adipokinetic hormone into resting moths showed that, depending on the dose, the number of apolipophorin III molecules in LDLp can exceed that recovered after the physiological condition of flight. Analysis of the lipophorin lipids demonstrated that in addition to the considerable increase in diacylglycerol in the LDLp particle, which is consistent with the role LDLp in energy supply, particularly the hydrocarbons were increased compared to HDLp, rendering the mechanism of LDLp formation from HDLp even more complex.