Dietary protein restriction deciphers new relationships between lifespan, fecundity and activity levels in fruit flies Drosophila melanogaster

Abstract

Drosophila melanogaster has been used in Diet Restriction (DR) studies for a few decades now, due to easy diet implementation and its short lifespan. Since the concentration of protein determines the trade-offs between lifespan and fecundity, it is important to understand the level of protein and the extent of its influence on lifespan, fecundity and activity of fruit flies. In this study, we intend to assess the effect of a series of protein restricted diets from age 1 day of the adult fly on these traits to understand the possible variations in trade-off across tested diets. We found that lifespan under different protein concentrations remains unaltered, even though protein restricted diets exerted an age-specific influence on fecundity. Interestingly, there was no difference in lifetime activity of the flies in most of the tested protein restricted (PR) diets, even though a sex-dependent influence of protein concentrations was observed. Additionally, we report that not all concentrations of pR diet increase activity, thereby suggesting that the correlation between lifespan and the lifetime activity can be challenged under protein-restricted condition. Therefore, the PR does not need to exert its effect on lifespan and fecundity only but can also influence activity levels of the flies, thereby emphasizing the role of nutrient allotment between lifespan, fecundity and activity. Lifespan and fecundity are major fitness parameters that can assess the rate of aging and healthspan of organisms. It is suggested that lifespan and healthspan are no longer equivalent parameters and hence do not allow us to use lifespan alone to assess aging and fitness of an individual 1. For the past two decades, studies on the role of nutrition in the regulation of fitness and its related traits have been studied to understand the intricate process of aging. Nutritional studies employ techniques like calorie restriction, Diet Restriction (DR; henceforth), food dilution, intermittent feeding, etc., for a long time in a variety of animal models such as mice, fruit flies and nematodes 2-4. Since the validity of calorie restriction and food dilution has been debatable 5,6 , intermittent feeding and DR (involving restriction of one or more nutrients in the food, without causing malnutrition) have gained momentum in nutritional geometry studies. Numerous DR and aging studies have been done using fruit flies Drosophila melanogaster because of their ability to cater to a wide range of researches due to its shorter lifespan, well-understood genetics, and the presence of many equivalent genes in humans. Implementing reduced yeast (protein source in fly food) can be termed as Protein Restriction (PR; a type of DR). Several studies have shown that PR can extend lifespan and also result in a possible trade-off in fecundity 2,5. PR imposed on fruit flies D. melanogaster enables us to assess the effect of protein alone on fitness and fitness-related traits. Apart from the interplay between lifespan and fecundity upon DR, the locomotor activity of fl...

DO‐SRS imaging of diet regulated metabolic activities in Drosophila during aging processes

“…The dietary balance of protein to carbohydrate (P:C) ratio has been shown the predominant determinant for the lifespan (Lee, 2015 ). For example, increase in the yeast to sucrose ratio can decrease the life span of Drosophila (Krittika & Yadav, 2020 ; Lee, 2015 ; Zid et al, 2009 ).…”

Dietary restriction fails to extend life in stressful environments

“…Consequently, physiological responses (such as reduced metabolic rate) and behavioural strategies (such as reduced activity) that can be deployed to reduce mortality risk during cold‐season diapause might be limited or impossible during the breeding season, regardless of nutrition. Moreover, protein restriction induces increased activity levels in D. melanogaster (Ghimire & Kim, 2015; Krittika & Yadav, 2020), and this behavioural response could elevate risk of predation for protein‐restricted animals in the wild.…”

Dietary restriction fails to extend life in stressful environments

“…Consequently, physiological responses (such as reduced metabolic rate) and behavioural strategies (such as reduced activity) that can be deployed to reduce mortality risk during cold-season diapause might be limited or impossible during the breeding season, regardless of nutrition. Moreover, protein restriction induces increased activity levels in D. melanogaster (Ghimire & Kim 2015; Krittika & Yadav 2020), and this behavioural response could elevate risk of predation for protein-restricted animals in the wild.…”