Nutritional supplement containing a nuclear fraction of bovine thymus gland increases the circulating levels of spermidine

Polyamines (PAs), including spermidine, spermine and their precursor, putrescine, are ubiquitous molecules that are vital for a variety of physiological processes. Recently, PAs gained research attention because of their roles in promoting longevity and preventing age-related diseases. Circulating and tissue levels of PAs appear to decline with age, while higher intake of PAs in humans is correlated with better health during aging. Many foods, including plants and offal (organ meats), are good sources of dietary PAs, but are consumed much less in regions with prevailing Western diets. Elevating the circulating levels of PAs through dietary supplementation with PA-rich plant extracts or foods, on the other hand, has proven to be challenging, most likely due to their low bioavailability. In this study, we evaluated the effectiveness of nutritional supplements derived from bovine glandular tissues and/or plant material in elevating blood and tissue levels of spermidine, spermine and putrescine in adult rats. We detected appreciable amounts of PAs in the following materials: 1) spermidine-rich supplement (SRS), containing wheat germ, 2) a cytosolic fraction extract of bovine thymus gland (Thymus Cytosolic Fraction - TCF) and 3) a nuclear fraction extract of bovine thymus gland (Thymus Nuclear Fraction - TNF). We showed that all three PA-containing supplements also contain liposomes, with TNF displaying the largest amounts of liposomal PAs, as well as RNAs, among the tested supplements. We demonstrated that oral administration of SRS, TCF and TNF induce rapid changes in blood PA concentrations. Finally, we showed that TNF supplement is superior to SRS and TCF in elevating the levels of spermidine in the blood, liver and heart following a 28-day supplementation period. Considering the importance of PAs in prevention of age-related disease, supplementation with TNF could be a plausible approach towards the maintenance of proper cellular PA homeostasis during aging.