Investigation of the effects of fisetin and myricetin flavonoids on lifespan and stress resistance in Caernorhabditis elegans

As organisms age, the function of cells decrease and they accumulate signs of aging. Aging is the gradual decrease in cell and tissue functions that occurs over time in almost all organisms, and a decrease in the ability to respond to stress is also observed in this process. Aging is senescence in biology, its biological causes such as DNA damage in cells, telomere shortening, epigenetic factors, mitochondrial dysfunction, proteostatic dysfunction, nutrient signal dysfunction, decrease in stem cells and increase in chronic inflammation in the body have been defined. Some potentially dangerous molecules, such as various types of free reactive oxygen or nitrogen species that are either produced endogenously by targeted or as undesired by-products, or exposed exogenously, are known causes of aging and disease. These molecules are tried to be neutralized both by antioxidant enzymes and other small molecules which are produced in the body, and by vitamins and polyphenolic compounds are taken from the outside. However, increase in oxidative stress in cells/body, decrease in antioxidant capacity or both increase oxidative stress. In addition to the body's own antioxidants, vitamins or polyphenolic compounds taken from outside help to delay or prevent aging and diseases related to aging by reducing the increase in oxidative stress. Myricetin and fisetin, which are in the flavonoids group of polyphenolic compounds, are compounds with antioxidant effects. As natural antioxidants such as myricetin and fisetin reduce the effects of aging, interest in studies in this area is increasing. Caenorhabditis elegans is the most preferred in vivo model organism because its genes show approximately 44% homology with human genes, its life cycle is short, it shows signs of aging similar to humans, and rapid experimental results can be obtained. The aim of this study is to investigate whether fisetin and myricetin (which are two separate compounds with natural antioxidant effects in the flavonoids group of polyphenols), applied separately and/or in combination, increases life expectancy, thermal stress response and oxidative stress response in C. elegans in vivo model organism and whether they also affect the reactive oxygen species levels. In this context, 5 different groups were formed: a control group, a 1% DMSO control group, and 100 μM fisetin, 100 μM myricetin and 100 μM myricetin + 100 μM fisetin containing experimental groups. Each experimental group was studied in three sets in each study. The normal temperature longevity experiment was carried out by keeping the C. elegans culture at 20 °C. In the temperature stress response experiment, the nematodes were placed in 37 °C environment and thus stress induction was achieved. In the oxidative stress response experiment, oxidative stress was induced by the oxidant substance paraquat. In the experiment of determining the level of total reactive oxygen species in the body by fluorescent dye, the increase in reactive oxygen species against time was measured at 37 °C after 24 hours of flavonoid administration. In the lifespan experiment performed at 20 °C, it was found that only myricetin increased the longevity of the nematodes. According to the oxidative stress tolerance experiment, it was observed that the combination of myricetin + fisetin increased the tolerance of nematodes to oxidative stress and therefore, the lifespan of the nematodes. According to the temperature stress tolerance tested at 37 ºC, it was observed that the lifespan of nematodes in the fisetin and myricetin + fisetin groups increased, while the lifespan decreased in the myricetin group. According to the ROT level measurement, it was found that the application of the compounds alone (myricetin and fisetin) or together (myricetin + fisetin) did not contribute to the reduction of nematodes' ROT levels. Although it is known that myricetin and fisetin compounds have antioxidant properties, it is not known whether the co-administration and/or use of these two flavonoids has the ability to increase their antioxidant properties and/or delay the aging process and its signs. In this regard, this is the first study shows that combined use of myricetin + fisetin is more effective in reducing the effects of aging than the use of myricetin and fisetin separately. This study reveals the importance of antioxidants in nutrition once again. It is clear that antioxidants support healthy life span. However, to be able to use as an antiaging agent and therapeutic for human health, higher amounts may be needed. In this context, it is possible to develop nutritional supplements or drugs containing these antioxidants in order to reduce aging and aging-related problems.