Quantitative analysis of branched amino acids in a single fruit fly by LC-ICP-MS after pre-column derivatization with a metal tag reagent

Water accounts for about 60% of the human body. About a half of the remaining part consists of amino acids (including proteins). Amino acids are essential for nutrition and they work as hub compounds in metabolic pathways. Therefore, their concentrations in the biofluids could reflect various diseases (hepatocellular carcinoma, malignant melanoma, liver disease, coronary heart disease, rheumatoid arthritis, chronic renal failure, diabetes mellitus, Alzheimer's disease) and metabolic conditions. Especially, branched amino acids (BCAAs) are frequently affected. It is very important to analyze the concentration of BCAAs. The fruit fly, Drosophila melanogaster, is one of the most valuable organisms in biological research, particularly in genetics and developmental biology. Mutant flies, with defects in any of several thousand genes, are available, and the entire genome has been sequenced. The fly's genome is in good agreement with those of other eukaryotic organisms, including human. In the future, the fly will be used in other omics studies, such as metabolomics. However, since the fly is very small, it is quite difficult to analyze the metabolites in its body. To obtain an aminogram of the fly, a large sample pool is required. However, the pooled results can lead to the conclusion that the fly's aminogram is equalized, and the various important distinctions are lost. To address this issue, in this study, we have used a highly sensitive analytical method for a single fly sample. The method involves LC-ICP-MS after pre-column derivatization with a metal tag reagent. We could determine the quantities of free BCAAs in a single adult fly, the pupa, the larva and the ovary. In addition, we have found that the quantity of free BCAAs in the body of the mated female fly becomes increased.