Activity of Natural Cocoa on Markers of Brain Health in Exercise Trained Rats

ABSTRACT

Exercise training enhances healthy brain function by regulating inflammation and oxidative stress and promotes the production of growth factors including brain-derived neurotrophic factor (BDNF). BDNF is essential for neuronal growth and survival in deleterious neurological conditions such as stroke, Parkinson’s and Alzheimer’s. Moreover, dietary nutrients in cocoa reduces oxidative stress and inflammation and may have a protective effect that affects the growth and survival of neurons. 

Aim: To assess whether ingestion of natural cocoa additively affects structural and biochemical indices of brain health produced by regular exercise training in healthy rats. 

Methodology:  Five rats were randomly assigned in to four groups: Exercise + Natural cocoa (G1), Exercise only (G2), Cocoa only (G3), No exercise and No cocoa (G4). Exercised rats were subjected to running training for 6 weeks on a running wheel. Natural cocoa was administered as 2% (w/v) suspension which the rats drunk in place of water for 12 hours. Rats in G4 were given tap water and all rats were fed with standard chow. Rats in group 1 and 2 were subjected to a six-day pre-training period on the running wheel to help accustom them to the apparatus and reduce stress associated with novelty. Blood samples were collected at the beginning and end of the study via tail snipping and milking to assess the biochemical indices of oxidative stress (SOD), inflammation (IL-6) and neurotrophic growth factors (BDNF). The brains were harvested at the end of experiment and processed histologically for morphometric analysis by stereological methods. 

Results: Stereological analysis showed that the volume density of unhealthy pyramidal neurons in G1(0.111±0.02×103µm3), G2(0.085±0.01×103µm3) and G3(0.046±0.01×103µm3) was significantly lower (0.0002) when compared to G4(0.186±0.04×103µm3). Activity of SOD was significantly increased in G2 (p value= 0.016) and G4 (p=0.0091) with mean SOD activity values of (0.449±0.016 U/ml) and (0.343±0.0091U/ml) respectively. GSH activity was found by paired t-test to be statistically significant in G3 (p value = 0.0474) and a mean activity value of 3.39 (SD1.27) mmol/g).  ANOVA of post treatment levels of IL-6 showed significant difference (p = 0.0484) between the groups.  G1 (33.9625, SD 11.9), G2 (38.6425, SD 10.8), G3 (37.9425, SD 8.6) showing higher levels of IL6 compared to G4 (19.565, SD 2.6). There was a significant difference in the post treatment levels of BDNF among the groups. However, G1 (1292.500, SD 149.30) recorded the highest mean BDNF when compared to G4 (760.333, SD 172.92).

Conclusion: Exercise training and cocoa individually as well as when combined exert potentiating benefits on selected markers of brain health by reducing oxidative stress, increasing anti-inflammatory markers as well as maintaining the structural integrity of the neurons.