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Effect of nicotinamide mononucleotide on brain mitochondrial respiratory deficits in an Alzheimer's disease-relevant murine model.

Long AN, Owens K, Schlappal AE, Kristian T, Fishman PS, Schuh RA - BMC Neurol (2015)

Bottom Line: Student t-test was used for direct comparison of two groups.Levels of SIRT1 and CD38 change with age and NMN treatment.This is the first study to directly examine amelioration of NAD(+) catabolism and changes in mitochondrial morphological dynamics in brain utilizing the immediate precursor NMN as a potential therapeutic compound.

View Article: PubMed Central - PubMed

Affiliation: Research Service, VAMHCS, 10 North Greene Street, Baltimore, MD, 21201, USA. Aaron.Long@va.gov.

ABSTRACT

Background: Mitochondrial dysfunction is a hallmark of neurodegenerative diseases including Alzheimer's disease (AD), with morphological and functional abnormalities limiting the electron transport chain and ATP production. A contributing factor of mitochondrial abnormalities is loss of nicotinamide adenine dinucleotide (NAD), an important cofactor in multiple metabolic reactions. Depletion of mitochondrial and consequently cellular NAD(H) levels by activated NAD glycohydrolases then culminates in bioenergetic failure and cell death. De Novo NAD(+) synthesis from tryptophan requires a multi-step enzymatic reaction. Thus, an alternative strategy to maintain cellular NAD(+) levels is to administer NAD(+) precursors facilitating generation via a salvage pathway. We administered nicotinamide mononucleotide (NMN), an NAD(+) precursor to APP(swe)/PS1(ΔE9) double transgenic (AD-Tg) mice to assess amelioration of mitochondrial respiratory deficits. In addition to mitochondrial respiratory function, we examined levels of full-length mutant APP, NAD(+)-dependent substrates (SIRT1 and CD38) in homogenates and fission/fusion proteins (DRP1, OPA1 and MFN2) in mitochondria isolated from brain. To examine changes in mitochondrial morphology, bigenic mice possessing a fluorescent protein targeted to neuronal mitochondria (CaMK2a-mito/eYFP), were administered NMN.

Methods: Mitochondrial oxygen consumption rates were examined in N2A neuroblastoma cells and non-synaptic brain mitochondria isolated from mice (3 months). Western blotting was utilized to assess APP, SIRT1, CD38, DRP1, OPA1 and MFN2 in brain of transgenic and non-transgenic mice (3-12 months). Mitochondrial morphology was assessed with confocal microscopy. One-way or two-way analysis of variance (ANOVA) and post-hoc Holm-Sidak method were used for statistical analyses of data. Student t-test was used for direct comparison of two groups.

Results: We now demonstrate that mitochondrial respiratory function was restored in NMN-treated AD-Tg mice. Levels of SIRT1 and CD38 change with age and NMN treatment. Furthermore, we found a shift in dynamics from fission to fusion proteins in the NMN-treated mice.

Conclusions: This is the first study to directly examine amelioration of NAD(+) catabolism and changes in mitochondrial morphological dynamics in brain utilizing the immediate precursor NMN as a potential therapeutic compound. This might lead to well-defined physiologic abnormalities that can serve an important role in the validation of promising agents such as NMN that target NAD(+) catabolism preserving mitochondrial function.

No MeSH data available.


Related in: MedlinePlus

Full-length, transgene-derived amyloid precursor protein (APP) levels in brain homogenates following NMN treatment. (A) Representative Western blots of homogenates isolated from the brains of AD-Tg and non-transgenic (NTG) mice (3 months) probed with 6E10 antibody. (B) Transgene-derived full-length APP (~106kD) is observed in AD-Tg mice with negligible levels in the NTG mice. Full-length APP levels (ratio of APP:β-Actin) are significantly decreased in NMN-treated transgenic (AD-Tg NMN) mice compared to AD-Tg vehicle-treated. Data are presented as the average full-length APP ± SE. N = 6 separate animals per group. *p < 0.05.
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Fig2: Full-length, transgene-derived amyloid precursor protein (APP) levels in brain homogenates following NMN treatment. (A) Representative Western blots of homogenates isolated from the brains of AD-Tg and non-transgenic (NTG) mice (3 months) probed with 6E10 antibody. (B) Transgene-derived full-length APP (~106kD) is observed in AD-Tg mice with negligible levels in the NTG mice. Full-length APP levels (ratio of APP:β-Actin) are significantly decreased in NMN-treated transgenic (AD-Tg NMN) mice compared to AD-Tg vehicle-treated. Data are presented as the average full-length APP ± SE. N = 6 separate animals per group. *p < 0.05.

Mentions: Forebrain homogenates were assessed for relative transgene-derived full-length APP expression in both APP(swe)/PS1(ΔE9) transgenic (AD-Tg) and non-transgenic (NTG) mice (3 months). There were significantly (p < 0.05) increased mutant full-length APP levels in the brain homogenates from the AD-Tg mice regardless of treatment when compared to non-transgenic littermates. There was a significant (p ≤ 0.05) decrease (38%) in full-length mutant APP levels in brain homogenates of AD-Tg mice treated with NMN as compared to AD-Tg vehicle-treated mice (Figure 2).Figure 2


Effect of nicotinamide mononucleotide on brain mitochondrial respiratory deficits in an Alzheimer's disease-relevant murine model.

Long AN, Owens K, Schlappal AE, Kristian T, Fishman PS, Schuh RA - BMC Neurol (2015)

Full-length, transgene-derived amyloid precursor protein (APP) levels in brain homogenates following NMN treatment. (A) Representative Western blots of homogenates isolated from the brains of AD-Tg and non-transgenic (NTG) mice (3 months) probed with 6E10 antibody. (B) Transgene-derived full-length APP (~106kD) is observed in AD-Tg mice with negligible levels in the NTG mice. Full-length APP levels (ratio of APP:β-Actin) are significantly decreased in NMN-treated transgenic (AD-Tg NMN) mice compared to AD-Tg vehicle-treated. Data are presented as the average full-length APP ± SE. N = 6 separate animals per group. *p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4358858&req=5

Fig2: Full-length, transgene-derived amyloid precursor protein (APP) levels in brain homogenates following NMN treatment. (A) Representative Western blots of homogenates isolated from the brains of AD-Tg and non-transgenic (NTG) mice (3 months) probed with 6E10 antibody. (B) Transgene-derived full-length APP (~106kD) is observed in AD-Tg mice with negligible levels in the NTG mice. Full-length APP levels (ratio of APP:β-Actin) are significantly decreased in NMN-treated transgenic (AD-Tg NMN) mice compared to AD-Tg vehicle-treated. Data are presented as the average full-length APP ± SE. N = 6 separate animals per group. *p < 0.05.
Mentions: Forebrain homogenates were assessed for relative transgene-derived full-length APP expression in both APP(swe)/PS1(ΔE9) transgenic (AD-Tg) and non-transgenic (NTG) mice (3 months). There were significantly (p < 0.05) increased mutant full-length APP levels in the brain homogenates from the AD-Tg mice regardless of treatment when compared to non-transgenic littermates. There was a significant (p ≤ 0.05) decrease (38%) in full-length mutant APP levels in brain homogenates of AD-Tg mice treated with NMN as compared to AD-Tg vehicle-treated mice (Figure 2).Figure 2

Bottom Line: Student t-test was used for direct comparison of two groups.Levels of SIRT1 and CD38 change with age and NMN treatment.This is the first study to directly examine amelioration of NAD(+) catabolism and changes in mitochondrial morphological dynamics in brain utilizing the immediate precursor NMN as a potential therapeutic compound.

View Article: PubMed Central - PubMed

Affiliation: Research Service, VAMHCS, 10 North Greene Street, Baltimore, MD, 21201, USA. Aaron.Long@va.gov.

ABSTRACT

Background: Mitochondrial dysfunction is a hallmark of neurodegenerative diseases including Alzheimer's disease (AD), with morphological and functional abnormalities limiting the electron transport chain and ATP production. A contributing factor of mitochondrial abnormalities is loss of nicotinamide adenine dinucleotide (NAD), an important cofactor in multiple metabolic reactions. Depletion of mitochondrial and consequently cellular NAD(H) levels by activated NAD glycohydrolases then culminates in bioenergetic failure and cell death. De Novo NAD(+) synthesis from tryptophan requires a multi-step enzymatic reaction. Thus, an alternative strategy to maintain cellular NAD(+) levels is to administer NAD(+) precursors facilitating generation via a salvage pathway. We administered nicotinamide mononucleotide (NMN), an NAD(+) precursor to APP(swe)/PS1(ΔE9) double transgenic (AD-Tg) mice to assess amelioration of mitochondrial respiratory deficits. In addition to mitochondrial respiratory function, we examined levels of full-length mutant APP, NAD(+)-dependent substrates (SIRT1 and CD38) in homogenates and fission/fusion proteins (DRP1, OPA1 and MFN2) in mitochondria isolated from brain. To examine changes in mitochondrial morphology, bigenic mice possessing a fluorescent protein targeted to neuronal mitochondria (CaMK2a-mito/eYFP), were administered NMN.

Methods: Mitochondrial oxygen consumption rates were examined in N2A neuroblastoma cells and non-synaptic brain mitochondria isolated from mice (3 months). Western blotting was utilized to assess APP, SIRT1, CD38, DRP1, OPA1 and MFN2 in brain of transgenic and non-transgenic mice (3-12 months). Mitochondrial morphology was assessed with confocal microscopy. One-way or two-way analysis of variance (ANOVA) and post-hoc Holm-Sidak method were used for statistical analyses of data. Student t-test was used for direct comparison of two groups.

Results: We now demonstrate that mitochondrial respiratory function was restored in NMN-treated AD-Tg mice. Levels of SIRT1 and CD38 change with age and NMN treatment. Furthermore, we found a shift in dynamics from fission to fusion proteins in the NMN-treated mice.

Conclusions: This is the first study to directly examine amelioration of NAD(+) catabolism and changes in mitochondrial morphological dynamics in brain utilizing the immediate precursor NMN as a potential therapeutic compound. This might lead to well-defined physiologic abnormalities that can serve an important role in the validation of promising agents such as NMN that target NAD(+) catabolism preserving mitochondrial function.

No MeSH data available.


Related in: MedlinePlus