Dietary nutrients are among the most potent environmental factors involved in modulating lifespan. Dietary restriction (DR) without malnutrition is well known to increase lifespan and promote health span in divergent species. Our understandings of molecular mechanisms of DR come primarily from studies of genetically amenable systems, including yeast, worms, and flies, where DR has been imposed by either diluting the food source or by using genetic mutations that reduce feeding efficiency. However, a major drawback of these approaches is that it remains substantially uncertain in determining the exact caloric intake of individual organisms under the DR paradigms. It is, therefore, critical to measure food intake in dietary studies in invertebrate models. Further, accurate measurement of food intake is essential to assess the dosage effect of any aging intervention using pharmaceutical and nutraceutical compounds. Several methods have been developed to measure food intake in flies. These methods, however, overlook the amount of the food excreted out of the flies as feces or deposited in eggs. We have developed a feeding method using a radioactive tracer to account for all the ingested food. We have found that most of the ingested food is retained in the fly bodies and 8% is excreted out of the flies as feces and eggs. Under a DR condition, flies increase food intake in volume to compensate for the reduction of calorie content in the diet and also slightly increase the excretion. Under an oxidative stress condition, flies reduce both food intake and excretion. In general, males ingest and excrete 3-5 folds less amount of the food than females. This work has been published in Fly (2011). Taken together, our method provides an accurate way to measure food intake and facilitates studying the mechanisms underlying lifespan extension by DR and pharmaceutical or nutraceutical interventions in invertebrates. Characterization of lifetime behavioral changes is essential for understanding aging and aging-related diseases. However, such studies are scarce partly due to the lack of efficient tools. To this end, we have established an international and interdisciplinary collaboration with biologists, physicists and computer engineers from the United States, Mexico and Greece. We have developed a stereo vision system that automatically classifies and records at an extremely fine scale six different behaviors (resting, micro-movement, walking, flying, feeding and drinking) and 3-dimension location of individual Mexican fruit flies (Mexflies) throughout their lives. Using this system, we have determined for the first time lifetime behavioral changes and location preference of Mexflies under different dietary conditions at a high resolution. In addition, we have developed a behavioral informatics method to perform clustering analyses of daily behavioral patterns of flies, which has revealed three distinct young, middle-aged and old behavioral clusters for flies under different diet conditions. This work has been published in PLoS ONE (2011). Future research and development will be directed to further development of the software and hardware of this behavioral system to allow tracking other invertebrate flying species, such as Drosophila, house flies and honey bees. This technology provides research opportunities for using a behavioral informatics approach to understand the complexity of aging in model organisms. Botanical extracts are rich with phytochemicals and have been shown to exert numerous health benefits. Considering diverse dietary customs among human populations in different geographic regions, it is important to assess the effectiveness of an aging intervention using pharmaceutical and nutraceutical compounds in humans under different dietary condition. To this end, we have investigated the interaction between botanicals and DR, and the age-dependent effect of botanicals on lifespan and reproduction. We previously demonstrated that an oregano-cranberry (OC) mixture could promote longevity in the Mexfly. We have now assessed the effect of OC supplementation on lifespan and reproduction of Mexflies under a DR condition. We have also determined the effect of short-term OC supplementation on lifespan and reproduction by implementing the supplementation at three age intervals--young, middle, and old age. Our findings suggest that OC extends lifespan and promotes reproduction partly through DR-independent pathways. Our results also indicate that short-term supplementation has varied effects on longevity and reproduction depending on the period of supplementation. This work has been published in AGE (2011). Future studies will be directed to determine whether the response to OC supplementation in Mexflies is conserved in D. melanogaster and then investigate the underlying molecular mechanisms in Drosophila, a genetically amenable model organism. Together, these studies should shed light on the interaction between non-genetic and genetic factors in promoting longevity and provide guidance for using botanicals as aging interventions in humans. In summary, we have addressed several issues related to dietary modulation of lifespan in this project. We have developed an accurate method to measure food intake in Drosophila. We have also developed a high resolution system to automatically monitor lifetime behavioral changes in the Mexfly. In addition, we have determined the impact of dietary nutrients and implementing periods on the prolongevity effect of a botanical extract in Mexflies. These studies provide a basis to investigate mechanisms underlying lifespan modulation by dietary nutrients and their interactions with genetic and non-genetic factors. Together, this project should advance the objectives of the Laboratory of Experimental Gerontology and the National Institute on Aging, and provide valuable information for understanding human aging and more importantly for developing efficient aging intervention strategies in humans.
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