The influence of sirtuin-controlled circadian rhythmicity anddiet on lifespan in the honey bee, Apis mellifera

Abstract

This thesis explores the role of sirtuin controlled circadian rhythmicity and diet on honey bee longevity. By manipulating the circadian period of newly emerged honey bees and using qPCR to measure the expression of metabolic and circadian genes, we attempt to understand the effect of non-24 h circadian periods on longevity. We found evidence that altering the circadian period to 20 h or 28 h resulted in reduced longevity and a 1.6-fold increase in mortality, disruption to circadian clockwork and observed that this effect was not additive with that of a high-EAA diet, suggesting a potential shared pathway (Chapter 3). Rapamycin is an inhibitor of the mTOR pathway and has been shown to extend lifespan across species. We investigate the effect of rapamycin on longevity and appetite in the honey bee. We also observe the effects of rapamycin in combination with high-EAA diets. We found no evidence of any life extending effects and in some cases a reduction in longevity as well as polyphagic behaviour common in metabolic diseases (Chapter 4). Methylation plays an important role in sirtuin controlled mediation of lifespan, however the study of methylation in insects is time consuming and costly due to low global methylation levels. In this study we aim to test the viability and suitability of common methods of measuring global and site-specific methylation changes. We determine that methylation levels were too low to effectively measure with generic ELISA-kits in the honey bee and this also made site specific analysis for circadian genes challenging (Chapter 5). In the final chapter we analyse the effect of methionine on longevity and behaviour in the honey bees. By varying the dietary methionine content and analysing key metabolic genes FOXO and Sir2 we attempt to determine the mechanisms controlling these effects. We found that a high methionine diet reduced lifespan, appetite and lead to upregulation of FOXO but not Sir2 (Chapter 6).