Diet Restriction And The Effect And Mechanism Of The High-nutrition On The Aging And Reproduction Of Male Flies

The fruit fly Drosophila is an ideal model organism for studying ageing. Its relatively short life span, powerful fecundity, knowledge of the complete genomic sequence, accessibility of stocks with many different genetic alterations are useful for studying ageing. Besides, two other features of Drosophila stand out as advantageous for ageing studies, one is that, it is able to reproduce within 24 hours after eclosion, the other is that except for many cells in gonads and some cells in the gastrointestinal system, there do not appear to be any new cells added to the adult body. In addition to these, many genes, basic signal pathway and biochemical processes are highly conserved in human and Drosophila. These advantages made the Drosophila widely used in the field of ageing studies.Dietary restriction (DR) or caloric restriction (CR) can extend life-span in many organisms including mammals by reduction of nutrient intake without malnutrition. DR is correlative to energy metabolism, because it can reduce the active oxygen production in mitochondrion and lead to the extension of maximum life-span and mean life-span by reduceing the energy metabolism to decrease the use of oxygen and function of mitochondrion. At present, DR research is mainly on mammals in domestic, and the foreign researches focus on the ageing mechanisms of Drosophila. The research how DR effect the Drosophila development is mainly on the female, it is few report of the effects of DR on male reproduction. Yeast contains abundant nutrition, and it is one of the basic ingredients in Drosophila culture medium and plays an important role in Drosophila growth, development and reproduction. We therefore confine our attention to the effects and mechanisms of DR and high nutrition (HN) on ageing and reproduction as well as the relationship of them. We select the culture media contained 0.5 %, 2 % and 8 % yeast concentration as the DR, control and HN group on the base of experiment we did before in our lab.Here, we studied the survivorship, mean life-span, maximum life-span of male Drosophila, and the climbing ability, cold endurance, activity or content of superoxied dismutase (SOD), alondialdehyed (MDA), mitochondrial cytochrome c oxidase (MCO), Succinate dehydrogenase (SDH) of seven different ages in conditions of above nutritions. The morphological changes of male Drosophila reproductive system in the seven ages were also observed by paraffin section and fluorescent labeling of DAPI, Anti-β2-tubulin and Mito Tracker Green FM. At last, we analysed the effects and mechanisms of DR and HN on ageing and reproduction as well as the relationship of them. The results show:1. HN reduced the survival rate; mean life-span, maximum life-span of male Drosophila, whereas DR extended the maximum life-span.2. HN accelerated the ageing of male Drosophila and reduced its climbing ability, whereas DR delayed the reducing of climbing ability. HN and DR can also improve the cold endurance of male Drosophila during the middle age.3. DR improved the level of SOD expressed in male Drosophila body, whereas HN reduced it but prolonged the time of SOD expression. The age-dependent variation of SOD activity is complex. The MDA content in DR group was higher than those in the other two groups, which suggests it is not certain that HN produces high content of MDA. The changes of MDA content didn't show increasing along with ageing. All of these suggest that the level of SOD and MDA can't determine the life-span, whereas the homeostasis of them may be the important factor effecting ageing.4. DR improved the level of MCO expressed in male Drosophila body, whereas HN reduced it but prolonged the time of MCO expression. DR can make Drosophila express more SDH than the other two before age of 20 days, but reduced its maximum activity, whereas HN can prolong the time of SDH expression. The level of MCO and SDH decreased in the aged Drosophila, and it showed the function of mitochondrion declined in conditions of ageing, which support the mitochondrial-free radical theory.5. HN can increase the number of sperm bundles, strengthen the ability of germ stem cell mitosis, improve the volume of testis, all of these demonstrate HN can increase the reproductive ability in male Drosophila, whereas DR decreased the male Drosophila's reproductive ability. The acceleration of reproductive ageing was realized in DR and HN groups in the aged condition.6. DR can decrease the reproductive ability in male Drosophila and lead to the extension of life span, whereas the HN had the opposite effect. And these suggest there is a energy allocation and trad e-off between survive and reproduction.