Effects of dietary restriction and β-hydroxy-β- methylbutyrate supplementation on spontaneous locomotor activity in Drosophila melanogaster

Dietary restriction (DR) has been shown in a wide variety of model organisms, including Drosophila melanogaster, to increase lifespan and health span. It is unclear how much of this effect is due to a DR-induced increase in physical activity. β-hydroxyβ-methylbutyrate (HMB) supplementation has been shown in improve health span in Drosophila. The exact mechanism of this effect has not yet been elucidated but it is possible that, like DR, HMB increases health span through increased physical activity. In this study, the spontaneous flight activity (SFA) and spontaneous walking (activity) was measured at one and five weeks after eclosion for flies raised on low yeast, HMB-supplemented, and normal laboratory diet. To see if any effects of diet were immediate or occurred from life-long consumption, flies were switched to a new diet and their SWA and SFA was measured. Also, to see if age had any effects on the association between diet and physical activity, SFA and SWA were measured in flies one week (young) and five weeks (old) after eclosion. We hypothesized that (i) HMB and dietary restriction will increase SFA and SWA activity compared to a standard laboratory diet in young flies and that the effect of dietary restriction would be immediate; and (ii) HMB and dietary restriction will increase SFA and SWA compared to a standard laboratory diet in old flies and that this effect would be more pronounced than that in younger flies. No association between spontaneous activity and diet was found, either in young flies or in older flies. In switching experiments, no significant change in spontaneous activity was found, concluding that there was no immediate or long-term effect of diet on physical activity. From this, we concluded that DR-induced increased lifespan and HMBinduced increased health span are likely not due to increased physical activity.