Tea and its ingredients have aging-slowing or lifespan-extending properties in various experimental animal models. Using Caenorhabditis elegans as a model organism, we found that epigallocatechin-3-gallate (EGCG), the major bioactive polyphenol in green tea, affected longevity in an inverted U-shaped dose-response manner. A moderate level of EGCG extended healthy lifespan mainly during early-to-mid adulthood. This occurred somewhat counter-intuitively through the transient induction of reactive oxygen species (ROS), and subsequent activation of an antioxidant response. Interestingly, EGCG also caused an increase in endogenous ROS of E. coli OP50, the bacterial diet of C. elegans, suggesting EGCG might play a conserved role in different species. We also show that AAK-2/AMPK acted as a feedback regulator that modulated longevity in response to transiently increased ROS. This triggered SIR-2.1/SIRT1-NAD+- and DAF-16/FOXO-dependent activation. Moreover, EGCG improved mitochondrial biogenesis and restored mitochondrial function. However, aging decreased the response to EGCG and progressively neutralized its longevity benefits. Theanine, a characteristic compound of tea, extend C. elegans’ lifespan under heat or oxidative stress, without life-extension under normal environments at dosages we used. During its anti-heat shock processing, theanine up-regulates the expression of the HSP-16.2/sHSP16, a very important chaperone protein involved in stress resistance. Black tea extracts (BTE) could increase C. elegans’ resistance to osmosis, heat, and UV irradiation treatments. However, BTE could not increase C. elegans’ lifespan under normal cultural conditions and MnCl2-induced toxicity at concentrations we used. BTE decreased ROS and up-regulated some antioxidant genes, such as sod-3. However, only a slight mean lifespan extension in mev-1 mutants, a model to identify antioxidant, was observed without significance, indicating that the antioxidant activity of BTE might be necessary but not sufficient to protect against aging to C. elegans. Our results suggested BTE improved heat and UV stress resistance in a SIR-2.1-dependent manner. In addition, BTE concentration is very important for C. elegans’ survival under stress. Collectively, our findings validate a link between tea and healthy lifespan, which should warrant further research into tea and ways of applying its ingredients to improve healthy aging or for other therapeutic indications.

Promotion of healthy lifespan by tea in Caenorhabditis elegans

256th National Meeting (2018)

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