Mechanisms of Lifespan Modulation by Diet

衰老是由遗传和环境因素共同调节的。膳食营养素已被证明是对健康寿命和寿命有重大影响的最有力的环境因素之一。许多药物和营养保健品已被确定对模式生物有延长寿命的作用。由植物制成的营养保健品富含植物化学物质，具有多种生物活性，并具有许多健康益处，包括抗衰老作用。然而，膳食营养素是否以及如何影响促进健康衰老的干预措施的延长寿命效果仍然是难以捉摸的。这是老龄化领域的一个重要问题，考虑到不同地理来源的人群中不同的饮食习惯。包括蠕虫和苍蝇在内的无脊椎动物是研究药物和营养品延长寿命效应的理想模式生物，至少部分原因是它们的寿命短，遗传资源丰富。我们利用无脊椎动物模型总结了延年益寿营养保健品的研究进展，并在《氧化医学与细胞长寿》（2013）上发表综述。本研究为进一步研究营养保健品延缓衰老和提高健康水平的机制提供了有价值的指导。

Aging is modulated by both genetic and environmental factors. Dietary nutrients have been shown to be among the most potent environmental factors that have significant impact on healthspan and lifespan. A number of pharmaceuticals and nutraceuticals have been identified to have prolongevity effects in model organisms. Nutraceuticals made from plants are rich in phytochemicals, which possess diverse bioactivities and exert numerous health benefits, including anti-aging effects. However, whether and how dietary nutrients influence the prolongevity effects of interventions for promoting healthy aging remains elusive. This is an important issue in the aging field to address considering diverse dietary customs among human populations of different geographic origins. Invertebrates including worms and flies are ideal model organisms to investigate the prolongevity effect of pharmaceuticals and nutraceuticals at least partially due to their short lifespan and rich genetic resources. We have summarized the research progress on prolongevity nutraceuticals using invertebrate models and published a review in Oxidative Medicine and Cellular Longevity (2013). This work should provide valuable guidance for future mechanistic studies on the effect of nutraceutical supplementation in delaying aging process and improve healthspan. To investigate the interaction between nutraceuticals and macronutrients in lifespan modulation, we have investigated the effect of cranberry-derived nutraceuticals on lifespan and determined the impact of dietary macronutrient composition on the prolongevity effect of cranberry in Drosophila. We have found that cranberry can extend lifespan of flies fed a diet with modest amount of sugar and protein, and increase lifespan more prominently in flies fed a high sugar-low protein diet, but does not extend or shorten lifespan of flies fed a low sugar-high protein diet. We have further demonstrated that lifespan extension induced by cranberry supplementation is associated with increased lifetime reproductive output and higher expression of stress response genes. We have also shown that cranberry can improve the survival of flies fed a high-fat diet. This study reveals the critical role of dietary macronutrients in the prolongevity effect of cranberry supplementation and points out the importance of take into account diet composition in implementing interventions for promoting healthy aging. This line of the work has been accepted for publication in Journal of Gerontology Biological Sciences (2013). Future work will be directed more to understand the molecular mechanisms underlying the prolongevity effect of cranberry supplementation and its interaction between dietary macronutrients in modulating lifespan. This will provide a comprehensive view of and help improve interventions for promoting healthy aging. An important issue in aging studies is to assess healthspan since a fundamental goal of aging research is to not just increase lifespan but significantly improve healthspan through the preservation of function. Aging is associated with numerous behavioral changes, such as gradual decline of locomotor activity, which is a parameter for healthspan. Many tools are available for measuring locomotor activity in model organisms and humans. However, age-related behavioral changes remain poorly understood mainly due to the lack of tools capable of recording lifelong behavioral changes in a high resolution in any organism. We have previously developed a behavior monitor system (BMS) that can record six types of behaviors in a fine resolution over the lifetime of Mexican fruit flies (mexflies). Mexflies have been used extensively in demographic and aging intervention studies. In collaboration with Drs. Pablo Liedo at Mexico, Joanne Chiu and James Carey at UC Davis and Donald Ingram at Pennington, we have taken advantage of the BMS to investigate the impact of diet on age-related changes in locomotor activity, sleep quantity and quality using the high resolution lifelong behavior recording data in mexflies. We have found that flies under a nutritionally balanced diet have little age-related change in activity profile, while flies on suboptimal diet have a significant decrease of activity in amplitude and lower sleep quality at old age. This line of work has been published in Scientific Reports (2013). Future work will be to use the BMS to evaluate lifelong behavioral changes induced by any prolongevity interventions to shed light on the impact of aging interventions on healthspan. We will also develop a similar BMS for Drosophila in order to investigating molecular mechanisms underlying the lifelong behavioral changes. In summary, we have determined the impact of dietary macronutrients on the prolongevity effect of a cranberry-containing nutraceutical in Drosophila. We have assessed the impact of diet on healthspan by analyzing lifelong behavioral changes in mexflies under different dietary conditions. These findings provide the foundation for our future research directed towards understanding the molecular mechanisms underlying the interplay between dietary macronutrients and nutraceuticals or pharmaceuticals in modulating lifespan and healthspan. These studies should provide valuable information for developing efficient interventions for promoting healthy aging in humans. This project should advance the objectives of the Translational Gerontology Branch and overall missions of the National Institute on Aging.