An insect lipid transfer particle promotes lipid loading from fat body to lipoprotein

The role of Manduca sexta lipid transfer particle (LTP) in the transport of lipid from fat body to lipophorin was investigated in vitro. Fat body that contained radiolabeled lipid was incubated with either high density lipophorin or low density lipophorin, and it was shown that lipid was transferred from fat body to lipophorins. The transfer of diacylglycerol was blocked by preincubating fat body with LTP antibody. Furthermore, transfer was restored by the addition of LTP, indicating that LTP promotes the transfer of lipid from fat body to lipophorins. Using lipophorins radio-labeled in their lipid moiety, transfer of lipid from lipophorin to fat body was demonstrated. This transfer was not mediated by LTP. The adipokinetic hormone induced diacylglycerol mobilization from the fat body and the concomitant interconversion of high density lipophorin to low density lipophorin were performed in vitro and were shown to require the presence of LTP.