Evolving resistance to obesity in an insect

Abstract

Failure to adapt to a changing nutritional environment comes at a cost, as evidenced by the modern human obesity crisis. Consumption of energy-rich diets can lead to obesity and is associated with deleterious consequences not only in humans but also in many other animals, including insects. The question thus arises whether animals restricted over multiple generations to high-energy diets can evolve mechanisms to limit the deposition of adverse levels of body fat. We show that Plutella xylostella caterpillars reared for multiple generations on carbohydrate-rich foods (either a chemically defined artificial diet or a high-starch Arabidopsis mutant) progressively developed the ability to eat excess carbohydrate without laying it down as fat, providing strong evidence that excess fat storage has a fitness cost. In contrast, caterpillars reared in carbohydrate-scarce environments (a chemically defined artificial diet or a low-starch Arabidopsis mutant) had a greater propensity to store ingested carbohydrate as fat. Additionally, insects reared on the low-starch Arabidopsis mutant evolved a preference for laying their eggs on this plant, whereas those selected on the high-starch Arabidopsis mutant showed no preference. Our results provide an experimental example of metabolic adaptation in the face of changes in the nutritional environment and suggest that changes in plant macronutrient profiles may promote hostassociated population divergence.geometric framework ͉ nutrition ͉ Plutella

Genotype-by-Diet Interactions Drive Metabolic Phenotype Variation inDrosophila melanogaster

“…The negative correlation between weight and larval survival reported above could be the mechanism of selection for lower weight on a laboratory diet. This observation is consistent with observed rapid adaptation to laboratory diets seen in other systems (Warbrick-Smith et al 2006). However, also note that the canonical lab strains (Oregon R and Canton S, Figures 1 and 2) tended to have relatively high weights and pupal survival and low triglyceride content, hemolymph sugar concentration, and larval survival, which cautions against the assumption that metabolic regulation in standard lab strains is fully representative of the normal range of physiologies found in nature.…”

Dietary protein content affects evolution for body size, body fat and viability in Drosophila melanogaster

“…One mechanism that may have allowed such change could be selection for different utilization efficiency of carbohydrates [16]. Flies maintained on the protein-enriched diet have experienced relatively low access to easy accessible energy sources (carbohydrates).…”

“…Artificial selection experiments have also shown that the selection response is dependent on the nutritional environment, for instance in mice selected for larger body size [15]. Within insects, studies have used experimental evolution to study the impact of diet composition and it has been shown that rearing under alternative diet regimes for multiple generations results in genetically based changes in life-history traits [16,17].…”

The nature of nutrition: a unifying framework

“…An example of how postingestive responses can change over generations in response to a shift in the nutritional environment comes from the work of Warbrick- Smith et al (2006), who reared multiple lines of the diamondback moth, Plutella xylostella, for eight generations either on a carbohydrate-rich or a protein-rich diet. The carbohydrate-rich diet comprised either chemically defined artificial food or a high-starch mutant of the plant Arabidopsis.…”