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Nucleotides are low-molecular-weight intracellular compounds. They are the building blocks for nucleic acids and play a key role in many biochemical pathways. They are phosphoric nucleoside esters, made up of three components: a weakly basic nitrogenous compound, a pentose sugar, and one or more phosphate groups. They are the basic units of the nucleic acids DNA and RNA. The most important nucleotides are adenosine, guanosine, inosine, cytidine and uridine monophosphates.
Nucleotides are considered ‘semi-essential’ nutrients. This means that endogenous production satisfies requirements in the maintenance condition, but exogenous administration is needed in childhood, in stress conditions or when tissues are damaged .
Every new cell requires around 1 billion nucleotides in order to duplicate. Some tissues have a limited capacity for de novo nucleotide synthesis, and thus require exogenously supplied bases that can be utilized by a salvage pathway. For example, the intestinal mucosa, haematopoietic cells of the bone marrow, leucocytes, erythrocytes and lymphocytes are incapable of de novo synthesis, and thus utilize the salvage pathway, suggesting that an exogenous supply of nucleotides via the diet might be important for these cells .
For over 15 years, Prosol has provided a benchmark in nucleotide blends, sold under the Ribocare® brand, for infant formula application. Following this success story, the company decided to deploy its extensive knowledge in the field of yeast cell extracts and, after years of trials, has launched Ribodiet®, a combination of natural nutritional ingredients that can have positive effects on different body tissues.
Composition and technical specifications
Ribodiet® is a natural product extracted from yeast cells with a gentle, standardized and highly controlled process which is free of chemical solvents. Ribodiet® is a source of nucleotides, nucleosides, oligo nucleotides, ribonucleic acid fragments, amino acids, minerals and group B vitamins (Table 1). It is derived from Kluyveromyces fragilis or Saccharomyces cerevisiae yeast cells.
Yeast RNA, extracted from the cell only by physical means, is concentrated, and free nucleotides are obtained via enzymatic hydrolysis. The product is then spray-dried in order to maintain its chemical and physical characteristics and make it stable and storable at room temperature. The concentration process, complete standardization, and the hydrolysis of nucleic acids allows Prosol to obtain an ingredient with a high content of free nucleotides (>40%), qualitatively and quantitatively standardized.
Ribodiet® is a gluten-free product and suitable for vegans. It is certified halal and kosher. The Ribodiet® trade mark is registered in the European Union. Table 2 summarizes the technical features of Ribodiet®.
Mechanism of action
Nucleotides are mainly used in infant foods because research in human nutrition has demonstrated that the inclusion of nucleotides in parenteral and infant milk formulas improves intestinal health and the development of the immune system .
Nucleotides do not all have the same effect, so a mixture of nucleotides is used to provide the best result. Many studies in healthy term infants have demonstrated that nucleotide supplementation may reduce the risk of diarrhoea by approximately one quarter because immune maturation is enhanced .
Nucleotides have a direct effect on the maintenance of intestinal mucosal integrity. It has been demonstrated that nucleotide supplementation in young rats increases the weight of the intestinal mucosa, villus height (by 25%), and the activity of brush border enzymes (maltase, sucrase and lactase), suggesting acceleration of gut growth and differentiation .
Supplementation with a nucleoside–nucleotide mixture increases recovery after food deprivation, infection or protein deficiency. Small intestine atrophy and decreased activity of brush border enzymes in rats quickly resolved with nucleotide supplementation .
As regards microbiota health status, in vivo studies show that dietary supplementation with nucleotides improves the intestinal flora and stimulates the growth of bifidobacteria . Dietary nucleotides favour the development of faecal flora with a predominance of bifidobacteria and lactobacilli and lower percentage of Gram-negative enterobacteria.
Finally, in relation to immune system modulation, nucleotides influence both humoral and cell-mediated immunity: they accelerate T-cell-dependent antibody production and seem to exert actions on T-helper cells at antigen presentation, perhaps during cognitive cell–cell interactions.
A nucleoside-nucleotide mixture stimulates the proliferation, differentiation and maturation of neutrophils . Nucleotides cause a transient increase in natural killer cell cytotoxicity, interleukin-2 production and interferon-gamma secretion, and lower macrophage activation .
Supplementation with dietary nucleotides increases resistance to bacterial infection in animals and humans.
Two pre-clinical trials have been performed on Ribodiet® at the Food Chemistry and Nutraceuticals laboratories (Department of Drug Sciences – Pavia – Italy) to evaluate efficacy in modulating some parameters involved in the immune response. The cell line used in this assay was THP-1, a human monocytic cell line, which was incubated for 24 hours in a complete medium plus a non-cytotoxic concentration (1.25 mg/ml) of Ribodiet®. Before the end of the treatment, a lipo-polysaccharide (LPS), one of the best characterized macrophage-activating factors, was added to the samples to promote the inflammatory response.
The following markers of the inflammatory process were detected:
– TNF-α, a pro-inflammatory cytokine recognized as a central mediator of inflammation;
– IL-10, a cytokine that down-regulates the production of the pro-inflammatory cytokines;
– NO (nitric oxide), a compound generated endogenously as part of the inflammatory response against pathogens, such as bacteria and viruses;
– ROS (reactive oxygen species) secreted upon macrophage activation as part of the host cell defence mechanism.
The results are summarized in Fig. 1.
Ribodiet® treatment induced a significant reduction of over 90% in TNF-α expression compared to the control group. The yeast product also modulated oxidative process markers. After inflammation was induced, the nucleotide complex reduced NO levels by 22.5% and ROS levels by 55%. However, the anti-inflammatory IL-10 cytokine was significantly increased by 23.5% compared to control.
The reported results indicate that Ribodiet®, in the investigated in vitro system, exerts an anti-inflammatory, anti-oxidant and immuno-modulatory action on the cell line stimulated with LPS.
A second pre-clinical study was carried out to evaluate Ribodiet® efficacy in combination with a source of zinc, an ingredient with European Food Safety Authority (EFSA) – approved claims regarding the immune system (Commission Regulation (EU) no.432/2012).
A THP-1 human monocyte line was treated with LPS to induce an inflammatory response at the end of 24 hours of incubation in the culture media (Fig. 2). The zinc source (0.039 mg/ml, Zn at 20%) alone reduced TNF-α levels by 16.8%. However, when combined with Ribodiet® (1.25 mg/ml), the zinc reduced TNF-α expression by 91.6% compared to control.
The results demonstrate that Ribodiet® significantly boosts the anti-inflammatory activity of zinc, thus reducing TNF-α expression induced by LPS.
Nucleotides are ingredients generally recognized as safe. The use of nucleotides in infant formulas has not been reported to cause an increase in gastro-intestinal intolerance. Furthermore, elderly residents in a long-term care facility were fed enterally for 12 weeks with either a standard formula without any added nucleotides or an immune-modulating formula that contained 1.3 g/l of nucleotides as yeast RNA. No differences related to feeding parameters or safety measures were observed .
Applications and usage
In light of the above evidence, Ribodiet® is an interesting ingredient for addition to products targeted at immune system functionality.
Other potential applications are to improve:
– Gut barrier health
– Sports nutrition (recovery after performance)
– Cognition/concentration (lack of synthesis of nucleotides in brain tissue)
– Iron absorption.
The suggested daily dosage is 50-350 mg. The ingredient can be used in both solid and liquid formulations.
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