Molecular Mechanisms Of The Nutritional Regulation In Developmental Stages For Health Span In Male Drosophila

Aging is a process of gradual loss of physiological integrity and functional degradation,which is largely impacted by both genetic and environmental factors.Environmental factors are considered to make a greater contribution to regulate human life expectancy,among which the nutrition is one of the important environmental factors.Achieving extension of healthspan was defined as slowing or delaying the loss of physiological function with advancing age.Although numerous nutritional interventions have been reported to effectively delay aging,extend lifespan or health span,most of which are only focused on adulthood,a relatively few studies are found on how developmental nutrition affects aging and lifespan.Nutrition during developmental stages has long-term effects on adult physiology,disease and lifespan,which is termed as the nutritional programming.However,the underlying molecular mechanisms of nutritional programming are not yet well understood.To investigate the nutritional programming on long-term or lifelong health and lifespan and its molecular mechanisms,we used Drosophila as a model organism to carry out such a study.We have mainly explored the changes in the fly lifespan,physiological health status and potential mechanisms caused by changing the yeast concentration of diets（0.05SY,0.2SY,1SY,3SY.SY,Sugar-yeast）in larval stage and adulthood.As the larval stage of Drosophila are not disturbed by the maternal environment,and its aging-related signaling pathways are highly conserved with humans,therefore,using the Drosophila to investigate the effects and mechanism of developmental nutrition on health and lifespan can provide important references for early nutrition and anti-aging research in humans.The main results of this study are as follows:（1）Larval diets significantly regulate body weight and fecundity of adult Drosophila.Specifically,adult male and female flies reached their maximum body weight,and female flies reached their maximum fecundity under normal nutrition（1SY）during the larval stage.When the larval nutrition was under-or over-1SY,the body weight of adult male and female flies,and the fecundity of female flies significantly decreased.（2）Larval diets regulate the lifespan of adult Drosophila in a way that interacts with adult diets.Importantly,we demonstrated that larval low-nutrient diet（0.2SY）extended both the health span and lifespan in male flies under nutrient-replete conditions in adulthood through nutritional programming.（3）The larval low-nutrient diet has a general genetic effect on extending the lifespan of male flies.Both wild type Dahomey and wild type W¹¹¹⁸ in larval low-nutrient conditions have significantly longer lifespans,compared to the control groups.（4）The larval low-nutrient diet improves the health of male flies during adulthood.Males in larval low nutrition had higher lipid storage,better resistance to starvation and lessened the decline of climbing ability with age in adulthood.In addition,the larval low-nutrient diet improved glucose metabolism in adult males,including reduced systemic glucose levels and reduced expression levels of dilp3 and dilp5.（5）Nutrient-sensing pathways,including the insulin signaling（IIS）and the mechanistic target of rapamycin（m TOR）,were significantly affected in adult male flies developed under low-nutrient conditions.The phosphorylation level of the key protein AKT in the IIS pathway was significantly reduced in male flies of larval low nutrition under nutrient-replete conditions（1SY and 3SY）in adulthood.The phosphorylation level of the key protein S6K in the m TOR signaling pathway was significantly reduced within 12 hours of eclosion in male flies of larval low nutrition.（6）The lifespan extending effects of the larval low-nutrient diet is partly dependent on the IIS pathway and the m TOR signaling pathway,which was reduced in AKT heterozygous mutation males（a key gene of IIS pathway）and in Thor homozygous mutation males（a key gene in the m TOR signaling pathway）,and was almost abolished in S6K heterozygous mutation males（another key gene of m TOR signaling pathway）,compared with wild type males under the larval low-nutrient diet.（7）The larval low-nutrient diet reshaped the innate immune system of male Drosophila.Transcriptome data analysis showed that Toll and Imd signaling pathways were significantly down-regulated,while the expression of stress response genes was significantly up-regulated in males of larval low nutrition.The q PCR results revealed that males in larval low nutrition maintained a lower expression of antimicrobial peptides（AMPs）in all ages.In addition,the lifespan extending effects of the larval low nutrition diet does not depend on the Relish（NF-κB like transcription factor）dependent innate immune signaling pathway.（8）The larval low-nutrient diet stimulates the activity of Drosophila transcription factor FOXO（d FOXO）in adult,which is required for the improvement of the physiological health and the lifespan-extending effect in male flies.Heterozygous mutation of d FOXO,fat body-specific knockdown or overexpression of d FOXO in Drosophila can completely abolish the lifespan extending effect from the larval low nutrition.Taken together,this study investigates the molecular mechanisms of nutritional programming in larval Drosophila from physiological phenotypes,nutrient-sensing pathways and transcriptomic levels.Importantly,our findings uncovered that the larval low-nutrient diet can prolong the health span of male Drosophila under nutrient-replete conditions in adulthood through nutritional programming.This effect is achieved through the modulation of the key transcription factor d FOXO activity.The results provide experimental data that nutrition in the early life of animals could program the health of their later life and longevity.We also reveal the molecular mechanism of nutritional programming from the perspective of aging biology.