Hormetic Effect of Combined Stresses on Drosophila melanogaster Cardiac Performance and Mobility: A Comparative Study

Abstract

Mild stresses cause adaptive response by enhancing the ability to resist other stresses. Some of the most ubiquitous causes of stress in animals are cold and starvation. It is well known that exercise improves both skeletal muscle and cardiac function in vertebrates. However, the effect of cold stress on endurance training has not been studied thoroughly. Therefore, we used the Drosophila model to describe the effects of mild stress on some physiological indices. We hypothesized that the survival benefit displayed by cold stress would be associated with deleterious effect on health, such as depression in cardiac function and that endurance training is capable of rescuing the deleterious effect caused by cold stress.
A number of techniques and assays, including starvation resistant assay, negative geotaxis assay, cold stress treatment, biochemical parameter measurement and qPCR, were employed.
Survival was higher in all pretreatment groups compared to the no-pretreatment counterparts. We observed increased climbing ability in both sexes selected for starvation resistance. However, we found no significant difference in climbing between cold-pretreated and non-treated flies. There was a significant increase in the climbing index of flies subjected to exercise regimen in both wild-type male and female.
The down-regulation of FKBP12, Lamin-C, CaMKII, PP2A-C and SERCA observed in the starvation-resistant flies is a characteristic of deteriorating heart function. Furthermore, the mRNA levels of the female flies were up-regulated in both control and starvation-resistant groups, except in SERCA genes. The outcome strengthens our understanding on the effect of starvation on cardiac function.
Keywords: cold stress, Drosophila, endurance training, hormesis, starvation