Dietary protein-to-carbohydrate ratio effects development and metabolism in Drosophila larvae and imago

Abstract

Background. Nutrition during growth and development affects various traits not only in larvae but also imago including lifespan, reproduction, feeding, metabolism, and stress resistance. In this study, we have tested the hypothesis of whether the dietary protein-to-carbohydrate (P:C) ratio in the developmental diet could be related to subsequent changes in metabolic profile and physiological parameters in Drosophila larvae and imago. Materials and Methods. Drosophila melanogaster Canton-S strain were used in this study. Larvae were fed diets with different P:C ratios. Experimental media were composed of either 2 % or 5 % dry yeast and 0 %, 1 %, or 10 % of sucrose. We tested developmental rate, wet or dry body weight and the levels of certain metabolites inclu­ding glucose, glycogen, triacylglycerides and total lipids. The developmental rate was assessed by counting the number of generated pupae every 6/6/12 hours. For wet or dry weight measurement, 20 larvae or flies were weighed and transferred to plastic vial with a cut bottom. The flies were dried at 60 °C with the subsequent weighing after two days. Another two-day flies cohort were separated by sex and frozen in liquid nitrogen for further biochemical assays. Hemolymph glucose, total lipid concentration, triacyl­glycerides (TAG), body glucose and glycogen contents were determined spectrophotometrically. Results. We found that a low 0.08 P:C ratio in the diet slowed down pupation by ~20 % and decreased body weight in larvae. Hemolymph glucose levels in both larvae and imago were inversely associated with dietary P:C. Larvae developing on a diet with a low P:C ratio displayed a lower level of glycogen pool, but a higher level of lipids. Developmental dietary P:C ratio also influences metabolic traits such as hemolymph glucose, glycogen, TAG and total lipids in male and female imago. A higher total protein intake combined with restriction of sucrose consumption had glucose-lowering and lipids-lowering effects. Conclusions. Our study demonstrated that nutritional conditions during larval development trigger adaptive changes that provide a level of regulation necessary to surpass dietary stress in Drosophila imago.