Fasting experiments in Drosophila with concentrations of yeast extract to quantify the optimal number of Drosophila for food consumption assay

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Panalee Petcharat
Krieng Kanchanawatee

Abstract

Background Dietary restriction is a reduction in food consumption confirmed to extend lifespan.
However, due to the different nutrient compositions of each type of food, the consumption
reduction that yields the most efficient life extension is varied. Experiments were carried out
with Drosophila food – with a reduced concentration of yeast extract (to maximize lifespan),
which is different from other types of protein sources. Furthermore, the types and quantities
of food may affect the consumption level of Drosophila. Therefore, an optimized method for
quantifying consumption is required.
Objective To investigate the optimal yeast extract concentrations used in both restricted and
fully fed Drosophila diets, and to optimize a method for quantifying Drosophila consumption.
Materials and Methods The survival ratios of Drosophila fed with diets containing 0.25, 0.5,
1, 5 and 10 percent (w/v) yeast extracts were compared with Drosophila on a restricted diet
control using only 10 percent (w/v) dried yeast. The log-rank test was used to compare the
survival distributions. The Gompertz model was adopted to calculate aging rates. The Brilliant
Blue FCF No.1 previously fed to Drosophila was extracted from 10, 20 and 30 flies in 300 μL
of phosphate buffered saline with measured absorbance at 625 nm.
Results The medians and log-rank tests compared between the survival distributions of each
diet regimen revealed the ranges in yeast extract concentration in correspondence with the
dietary restriction theory were 1 – 5 percent (w/v) in females and 0.5 – 10 percent (w/v) in
males. However, the ageing rates calculated from the Gompertz model did not coincide with
the medians. Only the ageing rates of the treatments with 0.25 percent (w/v) yeast extract in
both female and male flies matched the medians. For the consumption assay, ten fly extracts
gave the absorbance at 0.539.
Conclusion The proper yeast extract concentrations that could be implemented in both female
and male Drosophila as restricted and fully fed diets were 1 and 5 percent (w/v), respectively.
The appropriate number of Drosophila for the consumption assay was ten flies.

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