Nucleosides and nucleotides: natural bioactive substances in milk and colostrum

Abstract

Nucleotides, nucleosides and nucleobases belong to the non-protein-nitrogen (NPN) fraction of milk. The largest amounts of ribonucleosides and ribonucleotides ± ribose forms only were considered in this review ± were measured directly after parturition in bovine milk and other ruminants as well as in the milk of humans. Generally, concentrations of most of the nucleos(t)ides tend to decrease gradually with advancing lactation period or nursing time. The species-specific pattern of these minor constituents in milk from different mammals is a remarkable property and confirms, at least, the specific physiological impact of these minor compounds in early life. The physiological capacity of these compounds in milk is given by the total potentially available nucleosides. The main dietary sources of nucleos(t)ides are nucleoproteins and nucleic acids which are converted in the course of intestinal digestion into nucleosides and nucleobases the preferred forms for absorption in the intestine. Thus, nucleosides and nucleobases are suggested to be the acting components of dietary and/or supplemented nucleic acid-related compounds in the gut. They are used by the body as exogenous trophochemical sources and can be important for optimal metabolic functions. Up to 15 % of the total daily need for a breast-fed infant was calculated to come from this dietary source. Concerning their biological role they not only act as metabolites but are also involved as bioactive substances in the regulation of body functions. Dietary nucleotides affect immune modulation, e.g. they enhance antibody responses of infants as shown by a study with more than 300 full-term healthy infants. Dietary nucleos(t)ides are found to contribute to iron absorption in the gut and to influence desaturation and elongation rates in fatty acid synthesis, in particular long-chain polyunsaturated fatty acids in early stages of life. The in vitro modulation of cell proliferation and apoptosis has been described by ribonucleosides, in particular by modified components using human cell culture models. Due to the bio-and trophochemical properties of dietary nucleos(t)ides, the European Commission has allowed the use of supplementation with specific ribonucleotides in the manufacture of infant and follow-on formula. From the technochemical point of view, the ribonucleoside pattern is influenced by thermal treatment of milk. In addition ribonucleosides are useful indicators for quantifying adulterations of milk and milk products.

Nucleotides in broiler chicken diet: effect on breast muscles quality

“…Whereas, nucleotides administration influenced significantly (P < 0.001) the ether extract content, showing higher values in the N group than in the C group; this could be related to the physiologic effect of nucleotides to stimulate the plasmatic α-lipoprotein synthesis (Schlimme et al 2000;Mateo & Stein 2007) and to increase the haematic levels of high density lipoprotein during the neonatal period (Sanchez-Pozo et al 1996).…”

“…A hypothesis could be considered that nucleotide supplementation stimulated the intestinal or he- patic synthesis of the elongation enzymes and all the desaturase enzymes (∆9-,∆6-, ∆5-desaturase) as a result of increased protein synthesis (Gil et al 1986;Garcia-Molina et al 1991) for the metabolic conversion of acidic products as reported by Schlimme et al (2000) but: (i) in relation to the individual fatty acid levels and (ii) in relation to the affinity of the desaturase enzymes with the fatty acid classes, the effect of stimulation was remarkable only for the ∆-9-desaturase. These findings suggest that no induction occurred of long chain polyunsaturated fatty acid accumulation in Pectoralis major muscle owing to the dietary supplementation with nucleotides in accordance to Gibson et al (2005) observations.…”

Composition and properties of bovine colostrum: a review

“…Nucleotides and nucleosides comprise part of the non-protein-nitrogen (NPN) fraction of milk and are present in the sub-milligram range per litre (Schlimme et al 2000); they have important roles in biochemical synthesis, i.e. nucleic acid synthesis, enhancement of immune response (Schaller et al 2004), influence the metabolism of fatty acids, contribute to iron absorption in the gut and improve gastrointestinal tract repair after damage (Sanchez-Pozo and Gill 2002).…”

Ribonucleic Acid Hydrolysis by Intestinal Explants of Neonatal Piglets

“…Human milk contains at least 13 acid-soluble nucleotides, cytidine and uridine derivatives being quantitatively the most important. It also contains minor amounts of free nucleosides (15). In contrast, bovine milk has a low content of nucleotides (13).…”