Evaluating the Effects of Grain of Isogenic Wheat Lines Differing in the Content of Anthocyanins in Mouse Models of Neurodegenerative Disorders

Abstract

Functional foods enriched with plant polyphenols and anthocyanins in particular attract special attention due to multiple beneficial bioactive properties of the latter. We evaluated the effects of a grain diet rich in anthocyanins in a mouse model of Alzheimer's disease induced by amyloid-beta (Aβ) and a transgenic mouse model of Parkinson's disease (PD) with overexpression of human alpha-synuclein. The mice were kept at a diet that consisted of the wheat grain of near isogenic lines differing in anthocyanin content for five-six months. The anthocyanin-rich diet was safe and possessed positive effects on cognitive function. Anthocyanins prevented deficits in working memory induced by Aβ or a long-term grain mono-diet; they partially reversed episodic memory alterations. Both types of grain diets prolonged memory extinction and rescued its facilitation in the PD model. The dynamics of the extinction in the group fed with the anthocyanin-rich wheat was closer to that in a group of wild-type mice given standard chow. The anthocyanin-rich diet reduced alpha-synuclein accumulation and modulated microglial response in the brain of the transgenic mice including the elevated expression of arginase1 that marks M2 microglia. Thus, anthocyanin-rich wheat is suggested as a promising source of functional nutrition at the early stages of neurodegenerative disorders.

Keywords: Barnes test; T-maze; alpha-synuclein; animal models; bioflavonoids; cognitive; functional food; neurodegeneration; neuroinflammation; passive avoidance.

Figure 1

Effects of the type of diet and treatment duration (a) or of the type of diet and overexpression of α-synuclein (genetic Parkinson’s disease (PD) model) (b) on body weight gain in mice. Data are presented as the mean ± S.E.M. of the values obtained in an independent group of animals (n = 6–15 per group). Statistically significant differences: ### p < 0.001 vs. a respective group given the standard diet (St. diet); *** p < 0.001 vs. a respective group given the same type of diet for six months.

Figure 2

Effects of the type of diet and Aβ25-35 administration (Alzheimer’s disease (AD) model) (a) or of the type of diet and overexpression of α-synuclein (genetic PD model) (b) on the working memory in mice evaluated in the T-maze test. Data are presented as the mean ± S.E.M. of the values obtained in an independent group of animals (n = 5–11 per group). Statistically significant differences: * p < 0.05 vs. a respective control group (in the experiment with AD model); # p < 0.05 vs. a respective group given the standard diet (St. diet); + p < 0.05 vs. a respective group given the control grain diet (CGr).

Figure 3

Effects of the type of diet and Aβ25-35 administration (AD model) on the episodic memory measured during the first day of training (a) or long-term spatial memory and learning estimated during four days of training (b) in Barnes test, or of the type of diet and overexpression of α-synuclein (genetic PD model) on the contextual memory retrieval and memory extinction evaluated in the passive avoidance test (c) in mice. Data are presented as the means of the values obtained in an independent group of animals (n = 5–12 per group). Statistically significant differences: ^ p < 0.05, ^^ p < 0.01, ^^^ p < 0.001 compared to values of the same group in the first session (a), on the first day of training (b), on the training day (c); & p < 0.05, && p < 0.01, &&& p < 0.001 compared to values of the same group on the test day; * p < 0.05, ** p < 0.01 vs. a respective control (in the experiment with AD model) or wild-type (WT) (in the experiment with PD model) group; # p < 0.05, ## p < 0.01, ### p < 0.001 vs. a respective group given the standard diet (St. diet); + p < 0.05, ++ p < 0.01 vs. a respective group given the control grain diet (CGr).

Figure 4

Effects of the type of diet and overexpression of α-synuclein (genetic PD model) on the α-synuclein accumulation in the frontal cortex in mice. (a) Quantitative results. The data are expressed as the means ± SEMs of the values obtained in an independent group of animals (n = 3–4 per group). Statistically significant differences: ** p < 0.01, *** p < 0.001 vs. a respective WT group; ## p < 0.01 vs. a respective group of mut(PD) mice given the standard diet (“mut(PD)+St. diet”); +++ p < 0.001 vs. a respective group of mut(PD) mice given the control grain diet (“mut(PD)+CGr”). (b) α-synuclein immunoreactivity in the frontal cortex. Magnification, 100×; bar, 100 μm.

Figure 5

Effects of the type of diet and overexpression of α-synuclein (genetic PD model) on the expression of microglial marker IBA1 in the mouse brain. (a) Quantitative results. CA1–CA1 hippocampal area, CA3–CA3 hippocampal area, DG–dentate gyrus. The data are expressed as the means ± SEMs of the values obtained in an independent group of animals (n = 3–4 per group). Statistically significant differences: ** p < 0.01, *** p < 0.001 vs. respective WT groups; # p < 0.05, ### p < 0.001 vs. a respective group of mut(PD) mice given the standard diet (“mut(PD) + St. diet”); + p < 0.05, +++ p < 0.001 vs. a respective group of mut(PD) mice given the control grain diet (“mut(PD) + CGr”). (b) IBA1 immunoreactivity in the frontal cortex. Magnification, 200×; bar, 50 μm.

Figure 6

Effects of the type of diet and overexpression of α-synuclein (genetic PD model) on the expression of arginase 1 in the frontal cortex in mice. (a) Quantitative results. The data are expressed as the means ± SEMs of the values obtained in an independent group of animals (n = 3–4 per group). Statistically significant differences: * p < 0.05, ** p < 0.01 vs. a respective WT group; # p < 0.05 vs. a respective group of mut(PD) mice given the standard diet (“mut(PD)+St. diet”); ++ p < 0.01 vs. a respective group of mut(PD) mice given the control grain diet (“mut(PD)+CGr”). (b) Arginase 1 immunoreactivity in the frontal cortex. Magnification, 200×; bar, 50 μm. High magnification images (630×) of arginase 1-positive cells are shown in the insets.