39 research outputs found
Understanding the mechanisms of dietary restriction to extend healthy lifespan in Drosophila melanogaster.
No full textDietary restriction (DR), defined as a moderate reduction in food intake short of malnutrition, has been shown to extend healthy lifespan in a diverse range of organisms, from yeast to primates. In this work we aim to uncover the mechanism by which DR extends lifespan. The prevailing theory of somatic maintenance by resource reallocation proposes that the balance of nutrient allocation is weighted either towards reproduction, when environmental nutrients are abundant, or towards maintenance of the soma when food is limited, thereby aiding organismal survival during food shortages. This theory has found support in reports that dietary restricted Drosophila melanogaster (fruit fly) benefit from increased lifespan but have compromised reproduction, and that the inverse is true of fully fed flies. It has recently been found that addition of the ten essential amino acids (EAA) to a DR diet is sufficient to decrease lifespan and increase fecundity to the same degree as full feeding, implicating EAAs as the dietary mediators of the responses of lifespan and fecundity to DR. In this thesis I characterise the physiological and metabolic parameters that define DR flies, fully fed flies and EAA-supplemented DR flies, with the aim of identifying candidate factors that consistently correlate with lifespan for the three treatments in order to identify the causes of longer life in response to DR. We also use genetic tools to explore the role of nutrient signalling pathways in mediating the relationship between nutrition and ageing, with special focus on the amino acid sensitive target of rapamycin (TOR) pathway, the insulin/insulin-like growth factor signalling (IIS) pathway, and the general amino acid control (GAAC) pathway. These studies find a role for TOR signalling in mediating the effects of DR on lifespan and this effect appears to be different from those caused by altered IIS and GAAC pathways. These data also implicate accumulation of fat as consistently correlated with, and so possibly causal for, longer life. Finally, I investigated the potential roles that these nutrient sensing/signalling pathways might play in modifying feeding behaviour in response to changes in dietary nutrient quality. Here, the GAAC pathway proved to play an important and specific role in the way single amino acid deficient foods are detected to alter feeding behavior. These data are somewhat consistent with mammalian studies on nutrient-specific feeding alterations and establish the groundwork for detailed studies into the molecular processes involved. As a combined body of work, this thesis outlines important data on the mechanisms of DR to extend life as well as new information about the nutrients and molecular signals involved in shaping feeding choices
Quantification of food intake in Drosophila
No full textMeasurement of food intake in the fruit fly Drosophila melanogaster is often necessary for studies of behaviour, nutrition and drug administration. There is no reliable and agreed method for measuring food intake of flies in undisturbed, steady state, and normal culture conditions. We report such a method, based on measurement of feeding frequency by proboscis-extension, validated by short-term measurements of food dye intake. We used the method to demonstrate that (a) female flies feed more frequently than males, (b) flies feed more often when housed in larger groups and (c) fly feeding varies at different times of the day. We also show that alterations in food intake are not induced by dietary restriction or by a null mutation of the fly insulin receptor substrate chico. In contrast, mutation of takeout increases food intake by increasing feeding frequency while mutation of ovoD increases food intake by increasing the volume of food consumed per proboscis-extension. This approach provides a practical and reliable method for quantification of food intake in Drosophila under normal, undisturbed culture conditions
Holidic media (HM) preparation v1
No full textThis protocol is part of the manuscript: Gonçalves et al. Commensal bacteria and essential amino acids control food choice behavior and reproduction. Plos Biology. 2017 Apr 18. Holidic media (HM) were developed in collaboration with the laboratories of Linda Partridge at UCL and Matthew Piper at Monash University. The publications describing the holidic medium development are: Piper MDW, Blanc E, Leitão-Gonçalves R, Yang M, He X, Linford NJ, et al. A holidic medium for Drosophila melanogaster. Nat Methods. 2013;11: 100–105. doi:10.1038/nmeth.2731 Piper MD, Soultoukis GA, Blanc E, Mesaros A, Herbert SL, Juridic P, et al. Matching Dietary Amino Acid Balance to the In Silico Translated Exome Optimizes Growth and Reproduction without Cost to Lifespan. Cell Metab. 2017;25: 610-621. doi:10.1016/j.cmet.2017.02.005 </p
Multi-disciplinary work [~ tværfagligligt samarbejde] in Denmark:an overview of the literature
No full textThis article reviews literature on Multi-Disciplinary Work (MDW) for children and young people in need of special support, as defined by the Danish Social Services Act. The focus is on frontline workers’ everyday encounters with each other. The author reviews all significant Danish publications between 1999 and until the middle of 2008. The publications are categorised as one of the following: primary research, secondary research, and practice and commentary literature. Although there has been an increase in the promotion of MDW with an emphasis on early intervention and prevention during the last 30 years, this literature review reveals a lack of research publications. Even though the literature review advocates that the quality of existing Danish research literature is varying, it also demonstrates that there are several good sources which can be used when writing theoretically about MDW or for enhancing MDW on a practice level in Denmark as well in other Nordic countries
Drosophila as a model for ageing
No full textDrosophila melanogaster has been a key model in developing our current understanding of the molecular mechanisms of ageing. Of particular note is its role in establishing the evolutionary conservation of reduced insulin and IGF-1-like signaling in promoting healthy ageing. Capitalizing on its many advantages for experimentation, more recent work has revealed how precise nutritional and genetic interventions can improve fly lifespan without obvious detrimental side effects. We give a brief summary of these recent findings as well as examples of how they may modify ageing via actions in the gut and muscle. These discoveries highlight how expanding our understanding of metabolic and signaling interconnections will provide even greater insight into how these benefits may be harnessed for anti-ageing interventions
Dietary restriction in Drosophila: delayed aging or experimental artefact?
No full textLifespan can be extended by reduction of dietary intake. This practice is referred to as dietary restriction (DR), and extension of lifespan by DR is evolutionarily conserved in taxonomically diverse organisms including yeast, invertebrates, and mammals. Although these two often-stated facts carry the implication that the mechanisms of DR are also evolutionarily conserved, extension of lifespan could be a case of evolutionary convergence, with different underlying mechanisms in different taxa. Furthermore, extension of lifespan by different methods of DR in the same organism may operate through different mechanisms. These topics remain unresolved because of the very fact that the mechanisms of DR are unknown. Given these uncertainties, it is essential that work on the mechanisms of DR is not clouded by imprecise descriptions of methods or by technical problems. Here we review the recent literature on DR in Drosophila to point out some methodological issues that can obscure mechanistic interpretations. We also indicate some experiments that could be performed to determine if DR in Drosophila operates through similar mechanisms to the process in rodents
Protocols to Study Aging in Drosophila
No full textThe fruit fly Drosophila melanogaster offers a host of advantages for studying the biology of aging: a well-understood biology, a wide range of genetic reagents, well-defined dietary requirements, and a relatively short life span, with a median of ~80 days and maximum ~100 days. Several phenotypes can be used to assess the aging process, but the simplest and most widely used metric is length of life. Here we describe a standard life span assay for Drosophila housed on a simple sugar/yeast diet
The problem with the revitalization of waterways - economic and ecological aspect of the example of the lower Vistula
No full textThe paper presents the status of river valleys floor, resulting in various forms of human activity on the natural background conditions. Author proposed the most rational spatial organization of lower Vistula valley, as a part of the International Waterway (MDW) E40, the Trans-European system of waterways
Target of Rapamycin Drives Unequal Responses to Essential Amino Acid Depletion for Egg Laying in Drosophila Melanogaster
No full textNutrition shapes a broad range of life-history traits, ultimately impacting animal fitness. A key fitness-related trait, female fecundity is well known to change as a function of diet. In particular, the availability of dietary protein is one of the main drivers of egg production, and in the absence of essential amino acids egg laying declines. However, it is unclear whether all essential amino acids have the same impact on phenotypes like fecundity. Using a holidic diet, we fed adult female Drosophila melanogaster diets that contained all necessary nutrients except one of the 10 essential amino acids and assessed the effects on egg production. For most essential amino acids, depleting a single amino acid induced as rapid a decline in egg production as when there were no amino acids in the diet. However, when either methionine or histidine were excluded from the diet, egg production declined more slowly. Next, we tested whether GCN2 and TOR mediated this difference in response across amino acids. While mutations in GCN2 did not eliminate the differences in the rates of decline in egg laying among amino acid drop-out diets, we found that inhibiting TOR signalling caused egg laying to decline rapidly for all drop-out diets. TOR signalling does this by regulating the yolk-forming stages of egg chamber development. Our results suggest that amino acids differ in their ability to induce signalling via the TOR pathway. This is important because if phenotypes differ in sensitivity to individual amino acids, this generates the potential for mismatches between the output of a pathway and the animal's true nutritional status
Effect of a standardised dietary restriction protocol on multiple laboratory strains of Drosophila melanogaster
No full textBackground:
Outcomes of lifespan studies in model organisms are particularly susceptible to variations in technical procedures. This is especially true of dietary restriction, which is implemented in many different ways among laboratories.
Principal Findings:
In this study, we have examined the effect of laboratory stock maintenance, genotype differences and microbial infection on the ability of dietary restriction (DR) to extend life in the fruit fly Drosophila melanogaster. None of these factors block the DR effect.
Conclusions:
These data lend support to the idea that nutrient restriction genuinely extends lifespan in flies, and that any mechanistic discoveries made with this model are of potential relevance to the determinants of lifespan in other organisms
