Uridine is a molecule (known as a nucleoside) that is formed when uracil is attached to a ribose ring (also known as a ribofuranose) via a β-N1-glycosidic bond.

If uracil is attached to a deoxyribose ring, it is known as a deoxyuridine.

Dietary sources of uridine

Uridine is one of the four basic components of ribonucleic acid (RNA); the other three are adenosine, guanosine, and cytidine. Upon digestion of foods containing RNA, uridine is released from RNA and is absorbed intact in the gut. Some common food sources of uridine are:

• sugarcane extract [1] • tomatoes (0.5 to 1.0 g uridine per kilogram dry weight)[2] • brewer’s yeast (3% uridine by dry weight)[3] • beer [4] • broccoli[3]

• organ meats (liver, pancreas, etc.)[3]

Consumption of RNA-rich foods may lead to high levels of purines (adenosine and guanosine) in blood. High levels of purines are known to increase uric acid production and may aggravate or lead to conditions such as gout. Moderate consumption of yeast, about 5 grams per day, should provide adequate uridine for improved health with minimal side effects.[citation needed]

Note: It has been suggested that the RNA content of yeast products should be chemically reduced if these products are to be consumed in high amounts (50 grams or more per day) as a source of protein. However, such processing is expensive and, as of 2008, commonly available brewer's yeast products were not RNA-reduced.[citation needed]

Harvard researchers report that supplementation in rats with a combination of uridine and EPA/DHA omega-3 fatty acids has antidepressant activity equivalent to that of commonly prescribed antidepressant medications, such as Prozac and other SSRIs.[5]

Uridine in the Glycolysis Pathway

Uridine plays a role in the glycolysis pathway of galactose[6]. There is no catabolic process to metabolize galactose. Therefore, galactose is converted to glucose and metabolized in the common glucose pathway. Once the incoming galactose has been converted into galactose-1-phosphate (Gal-1-P), it is involved in a reaction with UDP-glucose, a glucose molecule bonded to a UDP (uridine-di-phosphate) molecule. This process is catalyzed by the enzyme galactose-1-phosphate uridyl transferase, and transfers the UDP to the galactose molecule. The end result is a UDP-galactose molecule and a glucose-1-phosphate molecule. This process is continued to allow the proper glycolysis of the galactose molecule.

References

1. ^ http://www.thebody.com/content/art30244.html
2. ^ http://www.aseanfood.info/Articles/11018411.pdf
3. ^ a b c Jonas DA, Elmadfa I, Engel KH, Heller KJ, Kozianowski G, König A, Müller D, Narbonne JF, Wackernagel W, Kleiner J (2001). "Safety considerations of DNA in food". Ann Nutr Metab 45 (6): 235–54. doi:10.1159/000046734. PMID 11786646.
4. ^ Yamamoto T, Moriwaki Y, Takahashi S, Tsutsumi Z, Ka T, Fukuchi M, Hada T (October 2002). "Effect of beer on the plasma concentrations of uridine and purine bases". Metab Clin Exp 51 (10): 1317–23. doi:10.1053/meta.2002.34041. PMID 12370853.
5. ^ Carlezon WA, Mague SD, Parow AM, Stoll AL, Cohen BM, Renshaw PF (February 2005). "Antidepressant-like effects of uridine and omega-3 fatty acids are potentiated by combined treatment in rats". Biol Psychiatry 57 (4): 343–50. doi:10.1016/j.biopsych.2004.11.038. PMID 15705349.
6. ^ The Entry of Fructose and Galactose into Glycolysis, Biochemistry, Stryer, Berg and Tymoczko, 5th edition.