The mechanisms and pathways involved in the health and aging benefits conveyed by green tea were investigated in C. elegans.
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Boiled or iced with water or milk, blended in smoothies, condensed into shots or even baked into pastries—humans are infatuated with green tea. Today, green tea is one of the most widely consumed beverages in the world. Molecules found in this plant, named catechins, are known to have numerous evidence-based health benefits, including weight loss and age delaying properties. However, the mechanism by which these effects take place have yet to be fully elucidated.
“The popularity of green tea makes it crucial to study its impact on health and aging.”
Researchers from Friedrich Schiller University Jena, Huazhong Agricultural University, ETH Zurich, and the Medical University of Graz investigated green tea catechins and their effects in roundworms, known as Caenorhabditis elegans (C. elegans), and isolated rodent mitochondria. Their trending paper was published in October of 2021 by Aging (Aging-US), and entitled, “Green tea catechins EGCG and ECG enhance the fitness and lifespan of Caenorhabditis elegans by complex I inhibition.”
“We have designed the current study to investigate the impact and to unveil the target of the most abundant green tea catechins, epigallocatechin gallate (EGCG) and epicatechin gallate (ECG).”
In this study, the researchers focused on testing two of the most common green tea catechins, epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), in isolated mitochondria from murine liver and C. elegans. C. elegans are approximately one millimeter long nematodes, or roundworms, and have been used in a variety of biomedical studies. The reason C. elegans were chosen for this study is likely due to the fact that many genes in C. elegans have functional counterparts in humans. (C. elegans also have the ability to “smell” cancer.)
Over the course of 24 hours or seven days, C. elegans and rodent mitochondria were treated with 2.5 μM of EGCG and/or ECG compounds. To analyze the green tea catechins’ effects on cellular metabolism, reactive oxygen species (ROS) homeostasis, stress resistance, physical exercise capacity, health- and lifespan, and on the underlying signaling pathways, the researchers conducted lifespan analyses, locomotion assay, paraquat stress resistance assay, basal oxygen consumption rate, ROS quantification, glucose oxidation assay, ATP quantification, activity assays for catalase and superoxide dismutase, fat content analysis, quantification of complex I activity in mitochondria, quantification of oxygen consumption rate in mitochondria, and statistical analyses.
“We conclude that applying the green tea catechins EGCG and ECG at a low dose extends the lifespan of C. elegans via inducing a mitohormetic response.”
They found that the catechins hindered mitochondrial respiration in C. elegans after 6–12 hours, the activity of complex I in isolated rodent mitochondria and temporarily increased ROS levels. Then, after 24 hours and through adaptive responses, catechins reduced fat content, enhanced ROS defense and, in the long term, improved healthspan in C. elegans.
Mechanisms and pathways observed to be involved in this process of C. elegans fitness and lifespan extension by green tea were further described in the paper. The researchers note that additional studies will be required to determine the best timing and dosage for administering catechins. They also acknowledge that the low bioavailability of green tea catechins may limit the lifespan extending effects of green tea in humans, despite the promising effects demonstrated in C. elegans.
“Despite the promising results obtained in animal experiments, the low bioavailability of EGCG  still raises the question of whether green tea catechins can reliably provoke beneficial effects in humans. Consequently, additional efforts might be needed to identify complex I inhibitors with increased bioavailability.”
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