Introduction
Aging is an inevitable process characterized by a gradual decline in the physiological function of organs and increased vulnerability to death (Guo et al., 2022). The aging of the brain is strongly linked to the development of several neurodegenerative diseases (Fricker, Tolkovsky, Borutaite, Coleman & Brown, 2018; Gorman, 2008). In this context, targeting brain aging may present an opportunity to counter the development of age-related neurodegenerative diseases. Among several hallmarks of aging, brain aging and neurodegenerative diseases, mitochondrial dysfunction is one of the most significant factors (Mattson & Arumugam, 2018; Wilson, Cookson, Van Den Bosch, Zetterberg, Holtzman & Dewachter, 2023). Mitochondrial dysfunction plays a vital role in reducing the availability of energy metabolites in the brain and other organs of the body (Boveris & Navarro, 2008; Johri & Beal, 2012). The proper functioning of mitochondrial ETC requires a continuous supply of oxygen, which acts as a final acceptor of electrons (Johri & Beal, 2012; Mitchell, 1970; Wilkins & Swerdlow, 2021). However, its availability to the tissues is reduced significantly during aging due to various factors like reduced lung capacity, anemia, COPD, compromised microvascular network, and other age-related changes leading to hypoxia and mitochondrial dysfunction (Borson et al., 2008; Dodd, Getov & Jones, 2010; Hong et al., 2013; Lowery, Brubaker, Kuhlmann & Kovacs, 2013; Moeini et al., 2018; Snyder, Simone, Giovannetti & Floyd, 2021). Additionally, chronic hypoxia is a strong trigger for the development of neurodegenerative diseases (Li et al., 2022; Webster, Green, Settle, Peers & Vaughan, 2004), which can be reversed by oxygenation therapy (Arjun, Acharya, Shender, Rorres, Hrebien & Kam, 2019; Ferrari et al., 2017; Kim et al., 2013; Shapira et al., 2021). Therefore, to stop the development of pathological conditions, one of the possible ways to overcome the shortfall of oxygen may be to supplement the oxygen. Pharmacologically, a class of molecules called oxygen diffusion enhancers (ODEs) (Shah, Jain, Joshi & Kharkar, 2021) can be considered potential drug candidates to help overcome chronic hypoxia and related diseases. In this study, we used trans-crocetin’s oxygen diffusion-enhancing property to restore ETC activity in aged mice and its effect on brain and body aging. Trans sodium crocetinate (TSC) is reported to alter the molecular arrangement of blood plasma’s water molecules, creating a more ordered water structure (Stennett, Dempsey & Gainer, 2006). Oxygen diffuses faster in plasma with this altered water structure because of its low density. Thus, more oxygen can reach oxygen-deprived tissues, which has been proved in pre-clinical and clinical studies (Okonkwo et al., 2003) (NCT04808622). The oxygen-enhancing effect of TSC has been tested in several conditions responsible for low oxygen saturation, which include stroke (NCT03763929), hemorrhage shock (Wang, Schretter, Clarke & Lee, 2015; Wang et al., 2014), and high-altitude exercise (NCT05036980).
In this study, we investigated the efficacy of trans- crocetin to prevent or delay brain and body aging in 16-18 months old C57BL/6J mice. We treated the mice for four months and analyzed various parameters that could be affected by aging with a primary focus on the brain. This included memory behavior, hematology, biochemistry, and gene expression profile of hippocampi and analysis of energy metabolites (Supplementary Figure S2). We observed several interesting changes in the behavior and gene profile of the mice treated with crocetin, data of which are presented here.