Cacao Ameliorates Amyloid Beta-Induced Cognitive and Non-Cognitive Disturbances

Abstract

Background: Alzheimer's disease (AD) is a progressive neurological disorder characterized by a wide range of cognitive and non-cognitive impairments. The present study was designed to investigate the potential effects of cacao on cognitive and non-cognitive performance and to identify the role of oxidative stress in an AD animal model induced by unilateral intracerebroventricular (U-ICV) injection of amyloid beta_1-42 (Aβ_1-42).

Methods: Oral administration of cacao (0.5 g/kg/day) was performed for 60 consecutive days. Following 60 days, the open-field (OF) test, elevated plus-maze (EPM) test, novel object recognition (NOR) test, Barnes maze (BM) test, and Morris water maze (MWM) test were used to evaluate locomotor activity, anxiety-like behavior, recognition memory, and spatial memory, respectively. Total oxidant status (TOS) and total antioxidant capacity (TAC) in plasma were also examined. Furthermore, the number of healthy cells in the hippocampus's dentate gyrus (DG), CA1, and CA3 regions were identified using hematoxylin and eosin staining.

Results: The results indicated that the injection of Aβ_1-42 in rats led to recognition memory and spatial memory impairments, as well as increased anxiety. This was accompanied by decreased total antioxidant capacity (TAC), increased total oxidative stress (TOS), and increased neuronal death. Conversely, cacao treatment in AD rats improved memory function, reduced anxiety, modulated oxidative stress balance, and decreased neuronal death.

Conclusion: The findings suggest that cacao's ability to improve the balance between oxidants and antioxidants and prevent neuronal loss may be the mechanism underlying its beneficial effect against AD-related cognitive and non-cognitive impairments.

Keywords: Alzheimer’s disease; anxiety; cacao; oxidative stress; recognition memory; spatial memory.

Figure 1.

After 1 week of adaptation to the laboratory environment, before (Aβ-Pre group) and after (Aβ-Post group) unilateral intracerebroventricular (U-ICV) injection of a 5 µL solution of Aβ_1-42 (1 mg/mL), cacao was administered orally at a dose of 0.5 g/kg daily for 60 consecutive days. Anxiety, recognition memory, and spatial memory tests were performed afterward. At the end of the experiment, plasma biomarkers (TAC and TOS) were measured and hematoxylin and eosin staining was performed on the hippocampal tissue.

Figure 2.

Samples of recorded activities of rats in the OF test (a). The effects of cacao administration on the locomotor activity (b), time spent in the central square (c) in the open-field test, and discrimination index of the novel objective recognition (d). Data is presented as means ± SD of 8 animals per group (one-way ANOVA, Tukey’s post-hoc test). Abbreviation: ns, no significance. *P < .05. **P < .01. *** P < .001.

Figure 3.

Samples of recorded activities of rats in the EPM (a). The effects of cacao administration on the open arms entries (b), time spent in open arms (c) of the elevated plus maze Test. Data is presented as means ± SD of 8 animals per group (one-way ANOVA, Tukey’s post-hoc test). **P < .01, ***P < .001.

Figure 4.

Samples of recorded activities of rats in the BM test (a). The effects of cacao administration on the distance traveled (b), escape latency (c), search errors of the training days (d), time spent in the target zone (e), and search errors of the probe day (f) in the Barnes maze test. Data is presented as means ± SD of 8 animals per group (two and one-way ANOVA, Tukey’s post-hoc test). Abbreviation: ns, no significance. *P < .05. **P < .01. ***P < .001.

Figure 5.

Samples of recorded activities of rats in the MWM test (a). The effects of cacao administration on the swimming distance (b), escape latency to the hidden platform in the training trials (c), and time spent in the target zone (d) in the Morris water maze Test. Data is presented as means ± SD of 8 animals per group (two and one-way ANOVA, Tukey’s post-hoc test). Abbreviation: ns, no significance. *P < .05. ** P < .01. ***P < .001.

Figure 6.

The effects of cacao administration on the plasma parameters of total oxidant status (TOS) (a) and total antioxidant capacity (TAC) (b) of rats using assay kits. Data is presented as means ± SD of 8 animals per group (one-way ANOVA, Tukey’s post-hoc test. **P < .01. ***P < .001.

Figure 7.

Effects of cacao and Aβ on histological changes in the hippocampal CA1, CA3, and DG regions of rats. (a) figure illustrates intact neurons (identified by black arrows) and dark neurons (identified by blue arrows, H & E stain, ×400 magnification). (b) represents the quantitative data of the number of intact neurons. Data is presented as means ± SD of 4 animals per group (one-way ANOVA, Tukey’s post-hoc test). *P < .05. ***P < .001.