Does NAD+ cross the cell membrane?

Nicotinamide Adenide Dinucleotide (NAD+) and its immediate precursor Nicotinamide Mononucleotide (NMN) have both been shown to quickly elevate levels of NAD+ in various tissues and organs throughout the body.

There is some controversy as to the mechanism on the path these molecules may take to enter cells.

As Dr Sinclair says in the most recent review of NR, NMN, and NAD+ :

“Whether or not NMN is taken up by a transporter is currently the subject of debate (Mills et al., 2016; Ratajczak et al., 2016).

Dr Imai argues that this is likely a cell-type-specific phenomenon and that some cell types can rapidly take up NMN (Mills et al., 2016).

the identification of the putative transporter will help resolve the debate and help identify which cell types and tissues are able to transport NMN across the plasma membrane.

Research that NMN or NAD+ enter tissues directly:

Exogenous nicotinamide adenine dinucleotide regulates energy metabolism via hypothalamic Connexin 43 (Roh, 2018)

In conclusion, our results demonstrate that exogenous NAD is effectively imported into the hypothalamus and increases hypothalamic NAD content. Therefore, NAD supplement can constitute a therapeutic method for metabolic disorders characterized by hypothalamic NAD depletion in humans.

In this study published in September 2018, administration of LABELED NAD+ by IP and IV injection demonstrated that exogenous NAD+ crosses the blood brain barrier to enter the hypothalamus INTACT, reduces hunger and weight gain, and increases energy expenditure and fat burning in mice.

This study also shows that NR and NMN can not utilize the cd43 gap to cross the blood brain barrier!

This might explain why NAD+ clinics have found success treating addictions and other brain imbalances, but NR and NMN have not been used in similar fashion.

Exogenous NAD Blocks Cardiac Hypertrophic Response via Activation of the SIRT3-LKB1-AMP-activated Kinase Pathway (Pillai, 2009)

Bruzzone et al. (21) have shown that connexin 43 (Cx43) channels are permeable to extracellular NAD

Pharmacological effects of exogenous NAD on mitochondrial bioenergetics, DNA repair, and apoptosis.

“Taken together, our findings strengthen the hypothesis that eNAD crosses the plasma membrane intact”

“In the present study we report that exposure to eNAD substantially increases the dinucleotide cellular pool, suggesting plasma membrane permeability”

Nicotinamide adenine dinucleotide is transported into mammalian mitochondria (Baur, 2018)

Here we present evidence that mitochondria directly import NAD

Taken together, our experiments confirm that despite the lack of any recognized transporter, mammalian mitochondria, like their yeast and plant counterparts, are capable of importing NAD

at least two studies have previously reported evidence for uptake of NAD, leading the authors to propose that intact NAD crosses the plasma membrane and subsequently enters the mitochondria directly

This observation suggests that a mitochondrial transporter for NMN may also await discovery

In summary, we show that mammalian mitochondria are capable of directly importing NAD (or NADH). This finding strongly suggests the existence of an undiscovered transporter in mammalian mitochondria

Detection and pharmacological modulation of nicotinamide mononucleotide (NMN) in vitro and in vivo (Fermenting, 2009)

evidence that intracellular NMN contents promptly increase when the nucleotide is added to the culture media indicates that plasma membrane is permeable to this nucleotide

More research on exogenous NAD+ for combating illness and disease

Exogenous NAD+ crosses the BLOOD BRAIN BARRIER intact, increases NAD content in Hypothalamus,  increases energy and decreases appetite

Exogenous nicotinamide adenine dinucleotide regulates energy metabolism via hypothalamic Connexin 43

In this study, administration of LABELED NAD+ by IP and IV injection demonstrated that exogenous NAD+ crosses the blood brain barrier to enter the hypothalamus INTACT, reduces hunger and weight gain, and increases energy expenditure and fat burning in mice.

This study shows that NAD+ levels in the blood have a direct effect on the levels of metabolic activity in the body.

They also show that NR and NMN can not utilize the cd43 gap to cross the blood brain barrier.

This might explain why NAD+ clinics have found success treating addictions and other brain imbalances, but NR and NMN have not been used in similar fashion.

In mice, exogenous NAD may be transported to the hypothalamus via Cx43 at the blood-brain barrier [48] thereby increasing hypothalamic NAD content and decreasing food intake and weight gain.

Boosting NAD⁺ levels is beneficial for health and lifespan (Pittelli, 2011)

Increased NAD⁺ levels protects against mitochondrial and age-related disorders (Srivastava,2016)

Reduced NAD⁺/NADH ratio is strongly implicated in mitochondrial disorders and, age-related disorders including diabetes, obesity, neurodegeneration and cancer [26, 53, 60, 71].

NAD⁺ levels also decline during aging in multiple models including worms, rodents and human tissue [17, 45, 67, 72].

Increasing evidence suggests that boosting NAD⁺ levels could be clinically beneficial, as it activates the NAD⁺/sirtuin pathway which yields beneficial effects on multiple metabolic pathways

Exogenous NAD+ crosses the plasma membrane intact, increases NAD content,  and  mitochondrial bioenergetics.

Pharmacological Effects of Exogenous NAD on Mitochondrial Bioenergetics, DNA Repair and Apoptosis

Although the canonical view considers NAD unable to permeates lipid bilayers (Di Lisa and Ziegler, 2001), several studies report evidence for exogenous NAD (eNAD) uptake by different cells “

These findings are at odds with the hypothesis that eNAD increase iNAD contents because of extracellularly-formed NAD precursors

Nicotinamide adenine dinucleotide is transported into mammalian mitochondria

mitochondria do not synthesize NAD at all, but rather take it up intact from the cytosol, which in turn, can take up NAD from the extracellular space 
While mammalian mitochondria are generally considered to be impermeable to pyridine nucleotides (32,33), at least two studies have previously reported evidence for uptake of NAD

leading the authors to propose that intact NAD crosses the plasma membrane and subsequently enters the mitochondria directly

Protects against  liver damage

NAD+ administration decreases doxorubicin-induced liver damage of mice by enhancing antioxidation capacity and decreasing DNA damage.

NAD+ at the doses of 100 or 200 mg/kg was also injected intraperitoneally 1 h before the DOX administration.

NAD(+) is capable of increasing the antioxidation capacity of tissues.

NAD(+) can significantly decrease DOX-induced liver damage

can also selectively decrease tumor cell survival, NAD(+)

Treat Multiple Sclerosis autoimmune-related neurodegeneration

Treatment with NAD(+) inhibited experimental autoimmune encephalomyelitis by activating AMPK/SIRT1 signaling pathway and modulating Th1/Th17 immune responses in mice (Wang, 2016)

NAD(+) could be an effective and promising agent to treat multiple sclerosis

Prevents heart disease

Exogenous NAD Blocks Cardiac Hypertrophic Response via Activation of the SIRT3-LKB1-AMP-activated Kinase Pathway (Pillai, 2009)

Mice were simultaneously treated with NAD at 1 mg/kg/day for 2 weeks 

NAD treatment was capable of maintaining cellular NAD levels 

Exogenous supplementation of NAD restores the intracellular levels of NAD and blocks the cardiac hypertrophic response. 

These results indicated that NAD treatment prevented the development of cardiomyocyte hypertrophy 

NAD treatment restored the cellular NAD levels 

NAD treatment may become a panacea for prevention and cure of many diseases in the future

Prevents heart damage from Stroke

Exogenous NAD+ administration significantly protects against myocardial ischemia/reperfusion injury in rat model (Zhang, 2016)

NAD+ produced 85% decrease in the infarct size

NAD+ is one of the drugs that have greatest capacity to decrease myocardial ischemia

NAD+ dose dependently decreased infarct formation

Decreased brain damage

Intranasal administration with NAD+ profoundly decreases brain injury in a rat model of transient focal ischemia (Ying,2007)

The profound protective effects of the intranasal NAD+ administration were also observed at 72 hrs after ischemia.

intranasal administration with 10 mg / kg NAD+, but not with 5 mg / kg NAD+, significantly attenuated the ischemia / reperfusion-produced neurological deficits

NAD+ administration can profoundly decrease brain damage under certain pathological conditions

Investigated as a potential anti-aging treatment

Promotes mitochondrial health,

Enhances fat oxidation

Protects against metabolic disease