**4. Discussion**

The improved living conditions, reduced rate of child mortality and advances in the medical field have led to an increased life expectancy compared to past decades. Despite this, aging and in particular age-related diseases are still major causes of mortality worldwide. Aging is characterized by a loss of fitness over time, with a series of molecular and macromolecular damages over the course of a lifetime. Faulty regulation of cellular processes could damage physiological integrity of cells and let to accumulation of damaged bioproducts. Among the various phenomena associated with aging, there is oxidative stress, characterized by the loss of balance of antioxidants/reactive oxygen species, with an accumulation of ROS at the cellular level. At the molecular level, there is a progressive shortening of the telomeres that, reached a threshold level, lead to cellular senescence and/or apoptosis. Crucial is the role of telomerase, a polymerase that can elongate telomeres by de novo addition of TTAGGG sequence repeated in telomeres.

In this study, we evaluated the effect of FPP® on redox balance (antioxidant and ROS levels) together with an anti-aging effect on telomerase concentration and telomeres length in a mice model of aging treated with FPP®-supplemented water from 6 weeks of age (early treatment) and from 51 weeks of age (late treatment). Interestingly, we showed that FPP® dissolved in water had a higher Total Antioxidant Power and it contains measurable amount of Ascorbic Acid and we were able to measure the daily dose of ascorbic acid taken by the FPP®-treated mice. The dual action of ascorbic acid as scavenging antioxidant and pro-antioxidant and the direct correlation between ascorbic acid dietary intake and the increased amount of antioxidants levels (i.e. glutathione) have been previously demonstrated [56–60].

Our data are consistent with previous works, where the correlation between dietary antioxidants from fruits and vegetables and the effects on the increase of antioxidant levels in the treated subjects has been extensively studied [9,10]. Our results showed that the daily intake of FPP® significantly increased the levels of antioxidants in the blood (Total Antioxidant Power, GSH and SOD-1) and decreased the levels of total ROS, together with a clear anti-aging effect as shown by the length of telomeres and telomerase quantification in FPP® treated mice. These results are consistent with previous studies where the crucial role of FPP® in reducing oxidative stress and inducing the antioxidant defense response have been extensively investigated [22–29,37,38,61]. Previous reports have shown that FPP® is able to modulate characteristic phenomena of elderly people, such as the

pro-inflammatory profile [31] and the oxidative damage [44,45]. Moreover, FPP ® supplementation induced several beneficial e ffects in patients with neurodegenerative diseases and Electromagnetic Field Intolerance Syndrome [21,43,47,48]. Supporting these reports we have shown that plasmatic telomerase concentration and the telomeres length in bone marrow and ovarian germ cells, are significantly increased by the daily FPP ® administration. In our experiment, we have shown that although papaya has an e ffect even in beginning treatment later in life, the early treatment is far more effective. This is conceivably due to the fact that the anti-aging action of FPP ® in maintaining telomeres length and mitigating progressive age-related shortening, is reduced when at a later age the telomeres have reached a shorter length. These results are consistent with previous reports on the attenuation of telomere length by antioxidants during aging [62,63] and on FPP ® action in modulating aging mechanisms [44–47,49].

Similarly considering the redox balance, in ET-FPP ® mice we have much higher antioxidants levels and a greater reduction of ROS than in LT-FPP ® mice. The plasma levels of antioxidants, in particular GSH and SOD-1, usually decrease with increasing age [64–67], therefore in the case of LT-FPP ® mice, FPP ® induces an increase in GSH and SOD-1, but starting from lower basal levels, thus failing to trigger a minimally comparable anti-aging action.
