Introduction to Nicotinamide Riboside (NR) and its Role in Human Metabolism

Nicotinamide riboside (NR) is gaining increasing interest as a dietary supplement that can support metabolic health and delay the aging process. As a precursor to the important cofactor nicotinamide adenine dinucleotide (NAD+), NR plays a key role in many cellular processes, including energy metabolism and DNA repair. In this article, we will introduce the topic of nicotinamide riboside, discuss its mechanisms of action, and outline what health benefits NR supplementation can provide.

Introduction to NAD+ and its Biological Significance

Nicotinamide adenine dinucleotide (NAD+) is a coenzyme present in all living cells, essential for energy production. NAD+ plays a key role in the process of cellular respiration by transferring electrons in the electron transport chain, which leads to the production of ATP - the main source of energy for cells. In addition, NAD+ acts as a cosubstrate for many enzymes, including sirtuins and ADP-ribosyltransferases, which are involved in regulating aging, repairing DNA and maintaining genome stability.
As the body ages, the levels of NAD+ in cells gradually decrease, leading to a decline in regenerative capacity, increased oxidative stress and general deterioration of health. Therefore, maintaining adequate NAD+ levels is crucial for health and longevity.

Characteristics of Nicotinamide Riboside (NR)

Nicotinamide riboside (NR) is one form of vitamin B3 and acts as an NAD+ precursor. Unlike other NAD+ precursors, such as niacin or nicotinamide, NR is thought to be more effective in raising NAD+ levels in cells. NR is rapidly converted to nicotinamide mononucleotide (NMN) by nicotinamide riboside kinases (NRK1 and NRK2) and then to NAD+.

Mechanisms of NR Action

There are three main pathways of NAD+ biosynthesis in organisms: the Preiss-Handler pathway, the de novo pathway and the rescue pathway. NR enters the rescue pathway, bypassing the earlier steps and allowing it to rapidly increase NAD+ levels in cells. This makes it a potentially more effective supplement compared to other precursors.

The Preiss-Handler pathway involves the conversion of nicotinic acid (NA) via nicotinic acid mononucleotide (NAMN) and nicotinic acid adenine dinucleotide (NAAD) to NAD+. The de novo pathway begins with tryptophan, which through a series of transformations also leads to NAD+ production. The rescue pathway is the most direct pathway, in which nicotinamide (NAM) is converted to NMN and then to NAD+. NR, as a precursor to NMN, rapidly raises NAD+ levels in the body.

Importance of NR in the Context of Aging and Metabolic Health

Preclinical studies suggest that NR may have beneficial effects on aging and metabolic health. NR supplementation has shown promise in reducing inflammation, improving mitochondrial function and potentially treating metabolic and neurodegenerative diseases. Studies in animal models have shown that NR can reduce oxidative stress and improve tissue regeneration after radiation damage, which is particularly important in the context of aging.

However, human clinical studies show mixed results. Some studies have shown that NR supplementation increases levels of NAD+ and some of its metabolites in the blood, and can reduce markers of inflammation. However, clinical effects, such as effects on blood pressure, insulin sensitivity and improved cognitive function, are less clear and require further research.

Summary

Nicotinamide riboside (NR) is a promising dietary supplement with potential health benefits associated with raising NAD+ levels in the body. Its unique ability to rapidly increase NAD+ makes it an interesting candidate for research on aging and metabolic diseases. Although clinical studies show mixed results, there is potential for further research that could provide clearer evidence of its efficacy. Understanding the role of NR and its impact on human health requires further, more rigorous clinical studies.

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