- NAD Depletion Plays A Major Role In The Aging Process
- NAD+ Declines Drastically With Age In The Brain
- NR Increases NAD+ Levels In Humans
- NAD+ Restores Mitochondrial Function
- NAD+ Precursors Improve Muscle Function
- NAD+ Precursors Increase DNA Damage Repair
- NAD+ Precursors Improved Cognitive Function
- Sirtuins & NAD+ In The Treatment Of Metabolic & Cardiovascular Diseases
- Sirtuins & NAD+ In Aging And Longevity Control
- Positive Effects Of NAD+ Metabolic Pathways On Sirtuin Activity
WHAT IS NAD+?
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. 
NAD+ is important in:
- Fuelling reduction-oxidation reactions i.e. carrying electrons from one reaction to another
- Acting as a co-substrate for enzymes such as sirtuins
- Sirtuins are proteins regulating healthy cell function
NAD+ is in the headlines – with its superb potential for improving the metabolism.
There is a lot of new research into NAD+ precursor supplementation and its effects on ageing. 
NAD+ ESSENTIAL ROLES IN METABOLISM 
- Coenzyme in reactions forming ATP
- via reduction and oxidization
- Substrate for enzymes sirtuins
- Donor in ADP-ribosylation reactions
- Precursor of cyclic ADP-ribose
- Bacterial DNA ligase substrate
- Extracellular signaling and neurotransmission
NAD+ plays critical roles in several signaling pathways involved in HEALTHY AGEING. 
NAD+ is a dinucleotide – two nucleotides joined via their phosphate groups.
One nucleotide contains an adenine base, and the other contains nicotinamide.
NAD 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 Redox Reaction:
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).
These feed into the Salvage Pathway
Which recycles components back into active NAD+ for use again. 
Cellular respiration - converts food and oxygen into Adenosine Trisphosphate (ATP).
ATP is the usable energy for our cells.
The process involves catabolic reactions - the breakdown of large molecules into smaller ones.
NAD+ plays a vital role in all: 
- Oxidative Decarboxylation
- The Krebs / Citric Acid Cycle
- Oxidative Phosphorylation
Occurs in the cytosol of all living cells.
Glucose is converted to pyruvate in aerobic conditions:
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. 
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. 
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. 
NAD+ KEY FACTS
- NAD is a coenzyme - synthesised via the De Novo and Salvage Pathways
- NAD is a key for molecule for cellular respiration and mitochondrial function
- NAD is a co-substrate for many enzymes
- Maintaining optimal levels of NAD+ in the body is essential for health
- NAD+ is a key substrate for the production of sirtuins involved in DNA regulation
- A decline in NAD+ is associated with the aging process
NAD+ SCIENTIFIC STUDIES AND TRIALS
Age associated changes in Oxidative Stress & NAD+ metabolism
This 2012 study provides evidence of NAD+ importance in the Aging Process, DNA repair and cell health.
Human Brain: intracellular NAD contents & redox state and its age dependences
This study provides an insight into cellular NAD concentrations and redox state in the brain.
Providing evidence of declines in mitochondrial function and altered NAD homeostasis in aging.
It elucidates the merits and potentials of NAD metabolism and redox state in the normal or diseased human brain or other organs in situ.
Nicotinamide riboside & pterostilbene increases NAD+ levels in humans safely
This is the first human, placebo-controlled study which assesses the safety and efficacy of taking repeat doses of 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%.
Declining NAD+ Induces a Pseudohypoxic State Disrupting Nuclear Mitochondrial Communication during Aging
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.
NAD+ repletion Improves Muscle Function in Muscular Dystrophy
& Counters Global PARylation
This 2016 study demonstrates that NAD+ precursors such as NMN & NR, improve muscle function and strength in aging mice.
NAD+ binding pocket regulates protein-protein interactions during aging
A 2017 study in which 2 years old mice tissues were given an NAD+ precursor:
The tissues looked identical to tissues in 3 months old mice.
NAD+ regulates protein-protein interactions, which may protect against cancer, radiation, and aging.
NAD+ supplementation normalizes key Alzheimer's features
& DNA damage responses
This 2018 study demonstrates that mice supplemented with a NAD+ precursor had improved cognitive function, showing the therapeutic potential for treatment of Alzheimer’s disease.
NAD+ Development and Treatment of Metabolic & Cardiovascular Diseases
The sirtuin family of NAD 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 levels decrease together with sirtuin activity
- Further exacerbated by a high-fat diet and a sedentary lifestyle.
The activation of NAD and sirtuins repletion induces angiogenesis, insulin sensitivity, and other health benefits in a wide range of age-related cardiovascular and metabolic disease models.
Human trials testing agents that activate SIRT1 or boost NAD levels, show promise in their ability to enhance both heart health and the health of metabolic disease patients.
NAD+ and Sirtuins in Aging and Longevity
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 age.
Thus, NAD+ supplementation is becoming more and more significant to preserve the health of the body and to prevent age associated disease.
Regulatory Effects of NAD+ Metabolic Pathways on Sirtuin Activity
NAD+ is fundamental to regulate cell physiology and it is an integral participant in cellular metabolism.
In addition, it serves as a metabolic cofactor whose function is a redox- active substrate.
It can also function as a substrate for signalling 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.
How NAD+ precursors are beneficial to treat the diseases related to aging.
GLOSSARY OF TERMS
NAD – Nicotinamide adenine dinucleotide (NAD) – coenzyme in all living cells
NAD+ – oxidized form – accepts electrons
NADH – reduced form - .donates electrons
NA / Nicotinic Acid / Vit B3 / Niacin – precursor of Nicotinamide thus NAD
NAM - Nicotinamide - water soluble vitamin B, precursor of NAD, however inhibits the sirtuins and their health-producing properties.
NR - Nicotinamide riboside – a precursor of NAD, and is a source of Vitamin B3
NMN - Nicotinamide mononucleotide – derivative of niacin, precursor of NAD
NAMPT – Nicotinamide phosphoribosyltransferase - enzyme involved in NAD synthesis. NAMPT is the rate-limiting enzyme of the NAD salvage pathway.
NMNAT – Nicotinamide/nicotinic acid mononucleotide adenylyltransferase - enzyme in NAD synthesis
ATP – Adenosine triphosphate – energy currency of cell
ADP – Adenosine diphosphate – cleavage of phosphate from ATP results in energy release, forming by-product ASP.
Sirtuins - family of proteins that act predominantly as nicotinamide adenine dinucleotide (NAD)-dependent deacetylases