Studies On The Metabolic Characteristics Of Drosophila To Long Chain Polyunsaturated Fattv Acids (AA/EPA)

Eicosanoids are mainly formed from C20 polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA,20:4n-6) and eicosapentaenoic acid (EPA,20:5n-3) through cyclooxygenases (COX-1/2), lipoxygenases (LOXs) and cytochrome P450(CYPs) pathways. These derivatives include prostaglandins (PGs), thromboxanes (TXs) and the lipoxin/leukotriene family of eicosanoids such as hydroperoxyeicosatetraenoic acids (HPETEs), hydroxyeicosatetraenoic acids (HETEs), and epoxyeicosatrienoic acids (EETs). Numerous studies have demonstrated that Drosophila melanogaster does not require nor biosynthesize C20 PUFAs. It was reported that some kinds of eicosanoids, the derivatives of C20 PUFAs, are of important physiological functions for Drosophila. This study was designed to detect the fatty acids compositions (FACs) of Drosophila and assess the generation capacity of eicosanoids derived from AA and EPA in Drosophila.This study was divided into three aspects. First, the FACs of Canton-S Drosophila fed with base diet, diet added with 1 g/kg AA or 1 g/kg EPA were detected by gas chromatography (GC). Analysis results showed that the FACs of Drosophila fed with base diet included 12:0,14:0,14:1n-5,16:0,16:1n-7,18:0,18:1n-9,18:2n-6 and 18:3n-3, and the Drosophila fed with AA or EPA contained the both PUFAs respectively. The relative amount of AA in the whole body, head and abdomen in Drosophola fed with AA are 2.35±0.45%,2.92±0.39% and 1.39±0.23%, respectively.The relative amount of EPA in the whole body, head and abdomen in Drosophola fed with EPA are 1.98±0.57%,2.92±0.39% and 1.39±0.23%, respectively. These results suggest that AA and EPA can be absorbed into body in Drosophlia from diet, but the both PUFAs cannot be endogenously synthesized by Drosophila. The the content of AA and EPA in head of Drosophila is more than those in thorax-abodoman of the fly.Second, a high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) determining 15 metabolites of AA and EPA produced by human in COX, LOX and CYP pathway was established. The results showed that the calibration curves were of good linearity for 15 metabolites in the range of 2.5-100 ng/mL, with correlation coefficient greater than 0.9900. The limits of detection (LOD) was about 0.1-2.6 ng/g. Spiked recovery experiments showed that both recoveries (89.3%-111.5%) and relative standard deviations (1.0%-15.0%) met the requirements of analytical methods.Third, the chosen eicosanoids in flies fed with AA or EPA and fly homogenates cultivated with AA or EPA were detected, respectively. No any selected metabolites were found in control fly fed with base diet. While 15(S)-HETE the derivatives of AA and 15(S)-HEPE the derivatives of EPA were found from the Drosophila fed both PUFAs and homogenates incubated with both PUFAs, respectively.15(S)-HETE and 15(S)-HEPE were the metabolites corresponding to human 15-LOX pathway. However, the precursors,15(S)-HpETE and 15(S)-HpEPE of 15(S)-HETE and 15(S)-HEPE in human were not be found, which suggests that metabolism pathways of AA and EPA in Drosophila are different with those of the both PUFAs in human in some aspects. The metabolites of AA in human, PGH2、PGF2 and PGE2 in COX pathway,5(S)-HpETE and LTB4 in 5-LOX pathwas of AA,20-HETE and 11(12)-EET in CYP pathway, and the metabolites of EPA, PGF3a and PGE3 in COX pathway, 17(18)-EpETE and 17,18-DiHETE in CYP pathway were all not be found in Drosophiala. These findings demonstrate that Drosophlia might lack the metabolic enzymes with similar functions of those in pathways of COX,5-LOX and CYP of human.