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. 2019 Dec;18(6):e13037.
doi: 10.1111/acel.13037. Epub 2019 Sep 27.

Lifelong Choline Supplementation Ameliorates Alzheimer's Disease Pathology and Associated Cognitive Deficits by Attenuating Microglia Activation

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Free PMC article

Lifelong Choline Supplementation Ameliorates Alzheimer's Disease Pathology and Associated Cognitive Deficits by Attenuating Microglia Activation

Ramon Velazquez et al. Aging Cell. .
Free PMC article

Abstract

Currently, there are no effective therapies to ameliorate the pathological progression of Alzheimer's disease (AD). Evidence suggests that environmental factors may contribute to AD. Notably, dietary nutrients are suggested to play a key role in mediating mechanisms associated with brain function. Choline is a B-like vitamin nutrient found in common foods that is important in various cell functions. It serves as a methyl donor and as a precursor for production of cell membranes. Choline is also the precursor for acetylcholine, a neurotransmitter which activates the alpha7 nicotinic acetylcholine receptor (α7nAchR), and also acts as an agonist for the Sigma-1 R (σ1R). These receptors regulate CNS immune response, and their dysregulation contributes to AD pathogenesis. Here, we tested whether dietary choline supplementation throughout life reduces AD-like pathology and rescues memory deficits in the APP/PS1 mouse model of AD. We exposed female APP/PS1 and NonTg mice to either a control choline (1.1 g/kg choline chloride) or a choline-supplemented diet (5.0 g/kg choline chloride) from 2.5 to 10 months of age. Mice were tested in the Morris water maze to assess spatial memory followed by neuropathological evaluation. Lifelong choline supplementation significantly reduced amyloid-β plaque load and improved spatial memory in APP/PS1 mice. Mechanistically, these changes were linked to a decrease of the amyloidogenic processing of APP, reductions in disease-associated microglial activation, and a downregulation of the α7nAch and σ1 receptors. Our results demonstrate that lifelong choline supplementation produces profound benefits and suggest that simply modifying diet throughout life may reduce AD pathology.

Keywords: APP/PS1 mice; Alzheimer's disease; Aβ; Sigma-1 receptor; alpha7 nicotinic acetylcholine receptor; choline supplementation; microglia activation; spatial memory.

Conflict of interest statement

None declared.

Figures

Figure 1
Figure 1
Experimental design. Starting at 2.5 months of age, female APP/PS1 and NonTg mice (APP/PS1 CTL = 10, NonTg CTL = 7, APP/PS1 Ch+ = 10, NonTg Ch+ = 7) were assigned to receive one of two concentrations of choline in diet; a diet containing 1.1 g/kg of choline (CTL) or a choline supplemented diet containing 5.0 g/kg of choline (Ch+). All mice were aged to 10 months and behaviorally tested in the hippocampal dependent Morris water maze task. Mice were subsequently sacrificed, and their brains were prepared for neuropathological assays
Figure 2
Figure 2
Lifelong choline supplementation significantly reduces spatial reference memory deficits. (a) Body weight analysis revealed that APP/PS1 mice are significantly heavier than NonTg (p < .0001), with no effect of diet (APP/PS1 CTL = 10, NonTg CTL = 7, APP/PS1 Ch+ = 10, NonTg Ch+ = 7). (b‐c) Escape latency and distance traveled to the platform during the learning phases of the Morris water maze (MWM). (d‐e) During the probe trial, we find that the APP/PS1 Ch+ mice cross the platform location significantly more times (p < .01) and first cross the platform location significantly faster (p < .01) than APP/PS1 mice on the CTL diet. (f) No differences in swim speed were detected among the four groups. Data are presented as box plots. The center line represents the median value, the limits represent the 25th and 75th percentile, and the whiskers represent the minimum and maximum value of the distribution. **p < .01, ***p < .001
Figure 3
Figure 3
Lifelong choline supplementation significantly reduces Aβ pathology. (a‐b) Photomicrographs of Aβ42 plaques within the hippocampus of APP/PS1 CTL and Ch+ mice (n = 6 mice/group). (c‐e) Quantitative analysis reveals that lifelong Ch+ significantly reduces the number of Aβ42 plaques within the hippocampus of APP/PS1 mice (p < .05). Both soluble and insoluble forms of Aβ40 and Aβ42 were reduced in APP/PS1 Ch+ mice (n = 7 mice/group). (f‐i) Representative Western blot of APP processing. Quantitative analysis reveals that APP/PS1 Ch+ mice have significantly decreased levels of C99 compared to APP/PS1 mice on the CTL diet (n = 5 mice/group), illustrating a reduction in amyloidogenic processing of APP (p < .05). Data are presented as box plots. The center line represents the median value, the limits represent the 25th and 75th percentile, and the whiskers represent the minimum and maximum value of the distribution. *p < .05
Figure 4
Figure 4
Lifelong choline supplementation reduces activated microglia. (a) Photomicrographs depicting the Cornus Ammonis 1 (CA1) of the hippocampus from APP/PS1 and NonTg mice fluorescently stained for CD68 and Iba1. Images taken at 10X; Scale bar = 150 µm (n = 6 mice/group). Arrows illustrate colocalization of CD68/Iba1. (b) Quantitative analysis reveals a significant main effect of genotype, where the APP/PS1 mice have a significantly higher intensity of yellow pixels of CD68/Iba1 colocalization than the NonTg mice (p < .05). Additionally, we find a significant main effect of diet, where the Ch+ groups show a significant reduction in CD68/Iba1 colocalization than the CTL groups (p < .001). Data are presented as box plots. The center line represents the median value, the limits represent the 25th and 75th percentile, and the whiskers represent the minimum and maximum value of the distribution. *p < .05, ***p < .001
Figure 5
Figure 5
Lifelong choline supplementation alters the expression of the alpha7 nicotinic acetylcholine receptor (α7nAchR) within microglia. (a) Photomicrographs depicting the Cornus Ammonis 1 (CA1) of the hippocampus from APP/PS1 and NonTg mice fluorescently stained for α7nAchR and Iba1. Images taken at 40X; scale bar = 25 µm (n = 6 mice/group). (b) Quantitative analysis reveals a significant main effect of genotype, where the APP/PS1 mice have a significantly higher intensity of yellow pixels of α7nAchR/Iba1 colocalization than the NonTg mice (p < .01). Additionally, we find a significant main effect of diet, where the Ch+ groups show a significant reduction in α7nAchR/Iba1 colocalization than the CTL groups (p < .05). A genotype by diet interaction was found, where the APP/PS1 Ch+ mice show a significant reduction of α7nR/Iba1 colocalization compared to the CTL counterparts (p < .001). The center line represents the median value, the limits represent the 25th and 75th percentile, and the whiskers represent the minimum and maximum value of the distribution. **p < .01, ***p < .001
Figure 6
Figure 6
Lifelong choline supplementation alters the expression of the Sigma‐1 receptor (σ1R) within microglia. (a‐b) Representative Western blot of σ1R levels. Quantitative analysis of σ1R protein levels reveals a significant reduction with Ch+ (p < .05; n = 5/APP group; n = 4/NonTg group). (c‐d) Quantitative analysis reveals a significant main effect of genotype, where the APP/PS1 mice have a significantly higher intensity of yellow pixels of σ1R/Iba1 colocalization than the NonTg mice (p < .05, n = 6 APP/PS1 CTL, n = 5 APP/PS1 Ch+, n = 6 NonTg CTL, n = 6 NonTg Ch+). Additionally, we find a significant genotype by diet interaction where the APP/PS1 Ch+ mice show a significant reduction in σ1R/Iba1 colocalization than the APP/PS1 CTL mice (p < .001). Photomicrographs depicting the Cornus Ammonis 1 (CA1) of the hippocampus from APP/PS1 and NonTg mice fluorescently stained for the σ1R and Iba1; images taken at 40×; scale bar = 25 µm. Data are presented as box plots. The center line represents the median value, the limits represent the 25th and 75th percentile, and the whiskers represent the minimum and maximum value of the distribution. *p < .05, ***p < .001

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