Metabolomics and proteomics of dietary restriction in Drosophila

The life-extending paradigm of Dietary Restriction (DR) is one of the most powerful yet poorly understood geroprotective mechanisms known to modern man. DR restricts a specific dietary component, often total protein content, to reduce mortality without malnutrition. Though progress continues to be made in disentangling the multi-faceted effects of dietary restriction, not one mechanism associated with DR physiology recapitulates its benefit in totality. Therefore, my focus is to better understand the mechanisms underpinning the DR effect. In this thesis, I employ a mechanistic approach combining demographic, metabolomic, and proteomic approaches to better understand the biology of DR. I begin with the introduction, discussing aspects of ageing and the current state of DR within the current literature and discusses how genomic approaches have become relatively commonplace, whilst mass-spectrometry-based technologies continue to be underutilised. In chapter one, I explore the demographic response to the application of short- and long-term DR within Drosophila melanogaster. I discuss the immediate reduction in age-specific mortality in response to DR and the recently discovered mortality overshoot phenomenon. In chapter two, I explore the metabolomic mechanisms which underpin the switching paradigm in Drosophila melanogaster and identify known (ceramide, NAD+ and uridine) and potentially novel (xylitol, palmitate) mediaries of DR. In chapter three, I compare the effects of DR on the metabolome across a
further three species of fly (Drosophila ananassae, Drosophila biarmipes and Drosophila virilis), identifying conserved interspecies mediators of longevity (palmitate and uridine). In chapter four, I return to the switching paradigm, investigating the proteomic responses to short- and long-term DR in Drosophila melanogaster to complement the metabolomic findings identified previously. We discover a significant (>50% proteome) long-term adjustment to DR and a strong response to refeeding. Surprisingly, we find no evidence of proteomic change in response to DR which contravenes biological expectations. Finally, I critically evaluate and discuss my research findings within the context of the current literature and highlight the overall importance of the work.