What is NAD (NAD+ and NADH)?

NAD (Nicotinamide Adenine Dinucleotide) is present in all living cells in our bodies.

The coenzyme functions by transporting electrons within a cell, driving mitochondrial activity.

Mitochondria, also referred to as the “powerhouses of cells”, turn the proteins, fats and sugars we eat into energy we use to function. [1] 
mrc-mbu.cam.ac.uk/what-are-mitochondria

NAD+ is important in:

  • Fuelling reduction-oxidation reactions i.e. carrying electrons from one reaction to another
  • Acting as a co-substrate for enzyme production such as sirtuins
  • Sirtuins are proteins regulating healthy cell function

NAD+ has a lot of potential for improving many aspects of metabolism.

There is a lot of new research into NAD+ and precursor supplementation and their effect on aging. [2]
science.sciencemag.org/content/350/6265/1208

 

The molecular structure of NAD (NAD+ and NADH):NAD+ Structure

NAD+ Research Summary

  1. NAD (NAD+ and NADH) depletion plays a major role in the aging process
  2. NAD+ declines drastically with age in the brain
  3. Elysium trial - NR increases NAD+ levels in humans
  4. NAD+ levels restored mitochondrial function in mice
  5. NAD+ precursor improves muscle function in mice
  6. NAD+ precursor increases DNA damage repair in mice
  7. NAD+ precursor supplemented mice had improved cognitive function
  8. Sirtuins & NAD+ in the Development & Treatment of Metabolic & Cardiovascular Diseases
  9. NAD+ and sirtuins in aging/longevity control
  10. Regulatory Effects of NAD+ Metabolic Pathways on Sirtuin Activity

NAD (NAD+ and NADH) Key Facts

  1. NAD is a coenzyme - synthesised via the De Novo and Salvage Pathways
  2. NAD is a key for molecule for cellular respiration and mitochondrial function
  3. NAD is a co-substrate for many enzymes
  4. Maintaining optimal levels of NAD+ in the body is essential for health
  5. NAD+ is a key substrate for the production of sirtuins involved in DNA regulation
  6. A decline in NAD+ is associated with the aging process

NAD Scientific Studies and Trials

Age-associated changes in oxidative stress & NAD+ metabolism in human tissue

ABSTRACT

This 2012 study provides quantitative evidence of the importance of NAD+ the aging process, DNA repair and cell health.  
ncbi.nlm.nih.gov/pubmed/22848760

 

In vivo NAD assay reveals the intracellular NAD contents and redox state in healthy human brain and their age dependences

ABSTRACT

This study provides a first insight into the cellular NAD (NAD+ and NADH) concentrations and redox state in the brain of healthy volunteers. The findings provide straight evidence of declines in mitochondrial function and altered NAD homeostasis which is a natural consequence of aging. Moreover, it elucidates the merits and potentials of NAD (NAD+ and NADH) metabolism and redox state in the normal or diseased human brain or other organs in situ. 
ncbi.nlm.nih.gov/pubmed/25730862

 

Repeat dose NRPT (nicotinamide riboside and pterostilbene) increases NAD+ levels in humans safely and sustainably:

A randomized, double-blind, placebo-controlled study

ABSTRACT

This is the first human, placebo-controlled study which assesses the safety and efficacy of taking repeat doses of Basis - NR and pterostilbene - in a population of 120 healthy adults between 60-80 years old.

The results are extraordinary: regular doses of NR and pterostilbene increased NAD+ levels by 40%. 
nature.com/articles/s41514-017-0016-9

 

Declining NAD+ Induces a Pseudohypoxic State Disrupting Nuclear -Mitochondrial Communication during Aging

ABSTRACT

A 2013 study demonstrating when we age there is mitochondrial dysfunction - causes are debated.

The mitochondrial loss is encoded by OXPHOS subunits. In this study, there is an explanation of the cause to an alternate PGC-1α/β-independent pathway of nuclear-mitochondrial communication that is induced by a decline in nuclear NAD+ and the accumulation of HIF-1α under normoxic conditions.

Deleting SIRT1 accelerates this process, whereas raising NAD+ levels in old mice restores mitochondrial function to that of a young mouse in a SIRT1-dependent manner. 
ncbi.nlm.nih.gov/pmc/articles/PMC4076149/

 

NAD+ repletion improves muscle function in muscular dystrophy and counters global PARylation

ABSTRACT

This 2016 study demonstrates that NAD+ precursors such as NMN and NR, improve muscle function and strength in aging mice. 
sciencemag.org/content/8/361/361ra139

 

Conserved NAD+ binding pocket regulates protein-protein interactions during aging

ABSTRACT

A 2017 study where 2 year old mice tissues were given an NAD+ precursor. The tissues looked identical to tissues in 3 month old mice.

NAD+ regulates protein-protein interactions, which may protect against cancer, radiation, and aging. 
sciencemag.org/content/355/6331/1312

 

NAD+ supplementation normalizes key Alzheimer's features and DNA damage responses in a new AD mouse model with introduced DNA repair deficiency

ABSTRACT

This 2018 study demonstrates that mice supplemented with an NAD+ precursor had improved cognitive function, showing the therapeutic potential for treatment of Alzheimer’s disease. 
ncbi.nlm.nih.gov/pubmed/29432159

 

Sirtuins and NAD+ in the Development and Treatment of Metabolic and Cardiovascular Diseases

ABSTRACT

The sirtuin family of NAD (NAD+ and NADH) dependent deacylases (SIRT1–7) are thought to be responsible for the cardiometabolic benefits of a lean diet and exercise.

  • When upregulated can delay key aspects of aging.

When we age, NAD (NAD+ and NADH) levels decrease together with sirtuin activity.

  • Further exacerbated by an high-fat diet and a sedentary lifestyle.

The activation of NAD (NAD+ and NADH) and sirtuins repletion induces angiogenesis, insulin sensitivity, and other health benefits in a wide range of age-related cardiovascular and metabolic disease models.

Human clinical trials testing agents that activate SIRT1 or boost NAD (NAD+ and NADH) levels show premises in their ability to enhance the health of the heart and metabolic disease patients. 
ahajournals.org/doi/10.1161/CIRCRESAHA.118.312498

 

It Takes Two to Tango: NAD+ and Sirtuins in Aging/Longevity Control

ABSTRACT

Recent studies have shown the importance of sirtuins as conserved aging/longevity regulators.

There is a deep connection between NAD+ and sirtuins, regulated at several different levels, which add further complexity to their coordination in metabolic and aging/longevity control.

In addition, it has been demonstrated that NAD+ levels decrease over age

  • reducing sirtuin activities
  • affecting communication between nucleus and mitochondria at a cellular level
  • affecting communication between hypothalamus and adipose tissue at a systemic level

These dynamic cellular and systemic processes contribute to the development of age-associated functional decline and the pathogenesis of diseases we get when we aging.

Thus, NAD+ supplementation is becoming more and more significant to preserve the health of the body and to prevent age-associated disease. 
nature.com/articles/npjamd201617

 

Regulatory Effects of NAD+ Metabolic Pathways on Sirtuin Activity

ABSTRACT

NAD+ is fundamental to regulate cell physiology and it is an integral participant in cellular metabolism. In addition, it serves as a well-known metabolic cofactor whose function is a redox- active substrate. It can also function as a substrate for signaling enzymes, such as sirtuins, poly (ADP-ribosyl) polymerases, mono (ADP-ribosyl) transferases, and CD38.

Sirtuins function as NAD+-dependent protein deacetylases (deacylases) and catalyze the reaction of NAD+ with acyllysine groups to remove the acyl modification from substrate proteins. This provides a regulatory function and integrates cellular NAD+ metabolism into a wide spectrum of cellular processes such as cell metabolism, cell survival, cell cycle, apoptosis, DNA repair, mitochondrial homeostasis and mitochondrial biogenesis, and lifespan. Thus, there is increasing attention on how to regulate NAD+ levels and on how pharmacological changes in NAD+ can influence sirtuins activities.

This study focuses on how NAD+ metabolic pathways regulate sirtuin activities and how regulating NAD+ levels can impact cell physiology. Finally, there is discussion on how NAD+ precursors are beneficial to treat the diseases related to aging. 
ncbi.nlm.nih.gov/pubmed/29413178

NAD (NAD+ and NADH) has several essential roles in metabolism [3]

en.wikipedia.org/wiki/Nicotinamide_adenine_dinucleotide

  • Coenzyme in reactions forming ATP
    • Via reduction and oxidization
  • Substrate for many enzymes and sirtuins
  • Donor in ADP-ribosylation reactions
  • Precursor of cyclic ADP-ribose
  • Cellular signaling and neurotransmission

NAD+ plays critical roles in several signaling pathways involved in healthy aging. [4]
neurohacker.com/nad-introduction-to-an-important-healthspan-molecule

 

NAD (NAD+ and NADH) Structure

NAD+ is a dinucleotide – it consists of two nucleotides joined via their phosphate groups.

One nucleotide contains an adenine base, and the other contains nicotinamide.

NAD (NAD+ and NADH) can be found as two forms in the cell:

  • An oxidizing agent (NAD+) - takes electrons from molecules
  • A reducing agent (NADH) - can donate electrons to molecules

The movement of electrons is one of the key functions of NAD (NAD+ and NADH) [5]
leafscience.org/nmn-crosses-cell-membrane/ 
 

NAD (NAD+ and NADH) redox reaction:

NAD Redox Reaction

NAD (NAD+ and NADH) Synthesis

NAD+ is synthesised in the body via two different pathways.

NAD+ can be created via food that contains NAD+ precursors such as NR and NMN.

E.g. The De Novo Pathway – NAD+ is created using tryptophan / 5HTP (an essential amino acid).

NAD De Novo Pathway

These feed into the Salvage Pathway:

Which recycles components back into active NAD+ for use again. [6] 
leafscience.org/nmn-crosses-cell-membrane/

NAD Salvage Pathway

Cellular Respiration

Cellular respiration - converts food and oxygen into Adenosine Trisphosphate (ATP).

ATP is the usable energy for our cells.

Cellular respiration:

Cellular Respiration

The process involves catabolic reactions - the break down of large molecules into smaller ones.

NAD+ plays a vital role in all: [7]
wikipedia.org/wiki/Cellular_respiration#cite_note-1

  1. Glycolysis
  2. Oxidative Decarboxylation
  3. The Citric Acid Cycle / Krebs Cycle
  4. Oxidative Phosphorylation 

Glycolysis

Occurs in the cytosol of all living cells.

In aerobic conditions (with oxygen), glucose is converted to pyruvate.

Glucose + 2 NAD+ + 2 Pi + 2 ADP → 2 Pyruvate + 2 NADH + 2 ATP + 2 H+ + 2 H2O + heat

NAD+ is essential for the final step, converting glyceraldehyde 3-phosphate to pyruvate.

Two NAD+ molecules must be present to accept electrons, for the process to complete. [8]
khanacademy.org/science/biology/cellular-respiration-and-fermentation/glycolysis/a/glycolysis

 

Glycolysis
Oxidative Decarboxylation

Pyruvate must be oxidized by the pyruvate dehydrogenase complex (PDC) to form acetyl-CoA.

This reaction also requires a NAD+ to accept electrons.

The Krebs Cycle

The Krebs Cycle, also known as the Citric Acid Cycle, is an essential pathway in cellular respiration.

Acetyl-CoA is utilised as the starting material and is transformed in a series of redox reactions.

The energy produced is harvested in the form of NADH, FAHD2 and ATP. 

The reduced electron carriers, including NADH, will pass their electrons into the transport chain, through oxidative phosphorylation. [9]
khanacademy.org/science/biology/cellular-respiration-and-fermentation/pyruvate-oxidation-and-the-citric-acid-cycle/a/the-citric-acid-cycle?modal=1

Krebs Cycle

Oxidative Phosphorylation

This process takes place in the mitochondria.

ATP is formed as a result of the transfer of electrons from NADH to O2 by a series of electron carriers. [10]
ncbi.nlm.nih.gov/books/NBK21208/

Oxidative Phosphorylation

     

    [1] mrc-mbu.cam.ac.uk/what-are-mitochondria

    [2] science.sciencemag.org/content/350/6265/1208

    [3] en.wikipedia.org/wiki/Nicotinamide_adenine_dinucleotide

    [4] neurohacker.com/nad-introduction-to-an-important-healthspan-molecule

    [5] leafscience.org/nmn-crosses-cell-membrane/

    [6] leafscience.org/nmn-crosses-cell-membrane/

    [7] wikipedia.org/wiki/Cellular_respiration#cite_note-1

    [8] khanacademy.org/science/biology/cellular-respiration-and-fermentation/glycolysis/a/glycolysis

    [9] khanacademy.org/science/biology/cellular-respiration-and-fermentation/pyruvate-oxidation-and-the-citric-acid-cycle/a/the-citric-acid-cycle?modal=1

    [10] ncbi.nlm.nih.gov/books/NBK21208/