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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

Changes in mitochondrial dynamics following NMN treatment in CA1 hippocampal neurons from CAMK-eYFP mice. Representative confocal images of control (A) and NMN-treated (B) neuronal mitochondria in the CA1 hippocampal sub-region. The fluorescent mitochondria appear more fragmented (see white arrows) in the control image compared to NMN treatment that clearly demonstrates more elongated mitochondria. Graphs (C, D) show the relative shape distribution and the relative mitochondrial length distribution (E, F) of different mitochondrial populations. Scale bar in panels (A) and (B) represents 5 μm. **p < 0.05; *p < 0.01.
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Fig6: Changes in mitochondrial dynamics following NMN treatment in CA1 hippocampal neurons from CAMK-eYFP mice. Representative confocal images of control (A) and NMN-treated (B) neuronal mitochondria in the CA1 hippocampal sub-region. The fluorescent mitochondria appear more fragmented (see white arrows) in the control image compared to NMN treatment that clearly demonstrates more elongated mitochondria. Graphs (C, D) show the relative shape distribution and the relative mitochondrial length distribution (E, F) of different mitochondrial populations. Scale bar in panels (A) and (B) represents 5 μm. **p < 0.05; *p < 0.01.

Mentions: Brain mitochondrial respiratory rates in CaMK2a-mito/eYFP mice have been previously determined to be similar to the rates in wildtype mice [21] and therefore can be utilized as an important tool to examine morphology. Following the same protocol for NMN treatment as described in the AD animals above, CaMK2a-mito/eYFP mice given vehicle had more fragmented neuronal mitochondria in the CA1 region of the hippocampus when compared to CaMK2a-mito/eYFP animals given NMN (Figure 6A). The CaMK2a-mito/eYFP mice given NMN had far less fragmented mitochondria, but had longer neuronal mitochondria in the CA1 region (Figure 6B).Figure 6


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)

Changes in mitochondrial dynamics following NMN treatment in CA1 hippocampal neurons from CAMK-eYFP mice. Representative confocal images of control (A) and NMN-treated (B) neuronal mitochondria in the CA1 hippocampal sub-region. The fluorescent mitochondria appear more fragmented (see white arrows) in the control image compared to NMN treatment that clearly demonstrates more elongated mitochondria. Graphs (C, D) show the relative shape distribution and the relative mitochondrial length distribution (E, F) of different mitochondrial populations. Scale bar in panels (A) and (B) represents 5 μm. **p < 0.05; *p < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig6: Changes in mitochondrial dynamics following NMN treatment in CA1 hippocampal neurons from CAMK-eYFP mice. Representative confocal images of control (A) and NMN-treated (B) neuronal mitochondria in the CA1 hippocampal sub-region. The fluorescent mitochondria appear more fragmented (see white arrows) in the control image compared to NMN treatment that clearly demonstrates more elongated mitochondria. Graphs (C, D) show the relative shape distribution and the relative mitochondrial length distribution (E, F) of different mitochondrial populations. Scale bar in panels (A) and (B) represents 5 μm. **p < 0.05; *p < 0.01.
Mentions: Brain mitochondrial respiratory rates in CaMK2a-mito/eYFP mice have been previously determined to be similar to the rates in wildtype mice [21] and therefore can be utilized as an important tool to examine morphology. Following the same protocol for NMN treatment as described in the AD animals above, CaMK2a-mito/eYFP mice given vehicle had more fragmented neuronal mitochondria in the CA1 region of the hippocampus when compared to CaMK2a-mito/eYFP animals given NMN (Figure 6A). The CaMK2a-mito/eYFP mice given NMN had far less fragmented mitochondria, but had longer neuronal mitochondria in the CA1 region (Figure 6B).Figure 6

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