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The effect of green tea polyphenols on Drosophila melanogaster lifespan and healthspan

  • Author(s): Lopez, Terry Enriquez
  • Advisor(s): Jafari, Mahtab
  • et al.
Abstract

Green tea is a popular beverage believed to have many health benefits including reducing the risks of neurodegenerative disorders, cardiovascular disease, and some cancers. As such, it has been suggested as a candidate life-extending natural product. Rich in polyphenolic compounds known as catechins, green tea has been shown to increase the lifespan of various animal models including the fruit fly,Drosophila melanogaster. Despite this, inconsistencies in reported data have been cited. In this dissertation, green tea’s life extension mechanisms were explored in a standard laboratory Drosophila strain, w1118.

Green tea was found to increase male Drosophila lifespan by 19%, but had no effect on female lifespan. Interestingly, this effect was associated with a reduction in male fly fertility. This is important as impairments in reproduction can modulate fruit fly lifespan. Moreover,green tea showed a modest protection against iron-induced oxidative stress, likely by its ability to bind iron. Since iron has been evidenced to play an essential role in male fly fertility, this dissertation explored the unique interplay of green tea on iron homeostasis, fertility and Drosophila lifespan. Processes that can modulate fly healthspan,such as development and reproduction, were evaluated. Green tea was found to delay larval development, reduce offspring sizes, and atrophied reproductive organs. From this it was suggested that green tea is toxic to Drosophila’s physiological processes. Green tea’s ability to chelate iron and modulate iron metabolism was evaluated using hypomorph mutants of iron-regulating proteins. Specifically, the lifespan and fertility of mitoferrin, a mitochondrial iron transporter, transferrin, an extracellular iron binding protein, and Malvolio, the fly homolog of the divalent-metal transporter-1, were characterized. Hypomorph flies displayed increased lifespans and reduced fertility than normal flies. Interestingly, green tea could no longer increase the lifespan of mitoferrin and Malvolio flies but did rescue the reduced male fertility phenotype. This was associated with an up-regulation of mitoferrin and Malvolio expression. Combined, these results support the possibility that green tea increases male Drosophila lifespan in part by the modulation of iron homeostasis that is essential for male fly fertility.

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