Uridine belongs to the group of pyrimidine nucleotides, which are ingredients of nucleic acids. It is made of uracil, nitrogenous basis and ribose. Uridine is associated with maintaining body homeostasis and it regulates glucose, lipid and amino acid metabolism and other vital processes. Uridine occurs in the highest numbers from among all pyrimidine products.

Uridine – source and absorption

Uridine is produced in the liver in some amounts. Uridine-rich products include (beef and pork) liver, beer yeast, beer, oats, fish (particularly herring), mushrooms (common mushrooms and boletus mushrooms) and vegetables, in particular cabbages and broccoli. Uridine is absorbed from the alimentary tract by diffusion or by specific uridine transporters. The substance is more bioavailable in the form of uridine monophosphate, or uridine nucleotide combined with phosphate residue, compared to pure uridine. Uridine levels are regulated by different factors: eating habits, uridine phosphorylase (UPase) and ATP depletion.

Uridine – health benefits

Uridine participates in galactose transformation. In the form of uridine diphosphate glucose (UDP-glucose), it is the donor of glucose molecules used in glycogen synthesis. Phosphatidylcholine, one of the major membrane-building lipids – including nervous cell membranes, is formed from uridine. In turn, phosphatidylcholine underlies acetylcholine, neurotransmitter which is responsible for memorisation, for instance. Delivering phosphatidylcholine, uridine helps not only create membranes, but also dendrites (nervous branches), which may promote synaptic function. It has been shown that supplementation with uridine supports the process of memorising new information and its recall later on. In addition, taking uridine with choline improves logical thinking and visual memory. One study has shown that uridine can boost cognitive function even in patients with damaged hippocampus. Furthermore, clinical trials have proven that supplementation with uridine improves sleep quality. uridine and its derivatives also reduce cytotoxicity and inhibit drug-induced liver fat buildup.

Uridine has been reported to regulate the mitochondrial respiratory chain with the enzyme called dihydroorotate dehydrogenase (DHODH). Mitochondrial dysfunction is one of the causes of various diseases, so uridine can be used as a therapeutic agent in mitochondrial diseases. The said compound participates, for instance, in formation of new connections between nervous cells. Even though pyrimidine nucleotides, including uridine, do not exhibit a direct analgesic or anti-inflammatory effect, they have been shown to improve patient status in the peripheral nervous system in the case of nerve damage. Studies with animals with induced crushing injury have shown that administration of nucleotides speeds up repair of the axons and myelin sheath of regenerating nervous and muscular fibres, which resulted in better conduction rate in nervous fibres. Pre-clinical studies have shown that nucleotide administration is followed by increase in the surface are and thickness of axonal myelin, increase in the number of neuritic protein neurofilaments and increase in the concentration of phospholipids of the neural cell membrane, phosphatidylethanolamine and phosphatidylcholine. Uridine is a biologically active molecule within the brain, and affects both the brain structures and functions. Aside from the formation of the neuronal membrane, uridine interacts with specific uridine-nucleotide receptors (P2Y2 brain receptors), which deal with neuronal differentiation control. The P2Y2 receptor involves structural patterns that promote interactions with the receptors of the growth factor, whose stimulation activates NGF/TrkA signaling, which in turn has neuroprotective effect. Such properties are beneficial in the context of neurodegenerative disorders, including Alzheimer’s disease, and uridine deficiency may result from neurological symptoms. Studies have shown that patients with Alzheimer’s disease have lower plasma/brain uridine levels compared to healthy individuals at similar age. A controlled study on 17 healthy individuals have shown that administration of uridine increases brain membrane phospholipid precursors, which may have a positive effect on cognitive function.

In their study on 212 patients with carpal tunnel syndrome treated with the combination of uridine monophosphate, folic acid and vitamin B12, Negrão et al. observed pain reduction from pain score of 17.5 down to 8.8 over 2 months and NSAID administration was reduced or discontinued in 77.4% of the patients. The conclusion is that the said substances, if administered in combination, reduce the intensity and extent of the affected areas and pain radiation. Moreover, a 6-week uridine supplementation (500 mg two times a day) in children with bipolar affective disorder led to considerable relief of depressive symptoms compared to baseline.

Uridine – dosage

The recommended dose of pure uridine, uridine monophosphate and triacetyluridine is 500–1,000, 250–500 mg and 25–100 mg per day, respectively.

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