Mitigating Age-Related Cognitive Decline and Oxidative Status in Rats Treated with Catechin and Polyphenon-60

Abstract

Aging is a normal physiological process influenced by the combination of multiple mechanisms, primarily oxidative stress and neuroinflammation, which impact general physiology and brain function. Phenolic compounds have demonstrated the ability to slow down the aging process of the brain due to their antioxidant and anti-inflammatory effects. This study assessed the protective properties of catechin and polyphenon-60 in non-pathologically aged rats regarding visuo-spatial learning and the oxidative status of the frontal cortex. Old animals were treated with catechin or green tea extract (polyphenon-60) for 36 days, daily. Healthy old and young rats were used as controls. During the first training phase, treated rats executed the test better, locating the target in less time compared with the controls. Biomarkers of oxidative stress (catalase activities, superoxide dismutase, glutathione reductase, and glutathione S-transferase) were reduced in the brain of old animals, although their activities were partially improved after both antioxidant treatments. Furthermore, the rise in the production of reactive oxygen species and malondialdehyde levels-a marker of lipid peroxidation-in the frontal cortex of aged animals was significantly ameliorated after the interventions. In conclusion, old rats exhibited enhanced cognitive function and reduced stress levels following the administration of catechin and polyphenon-60.

Keywords: Barnes maze test; antioxidant enzymes; cognitive decline; lipidic damage; polyphenols.

Figure 1

Effects on visuo-spatial learning ability of rats evaluated by means of the Barnes maze test. (A) Latency: time spend to finish the test; (B) number of errors committed during the test; (C) strategy used to find the target in percentage. Latency and number of errors are represented as mean ± SEM and strategy by %. Two-way analysis of variance (ANOVA) and chi-square test. * p < 0.05 with respect to young control; and # p < 0.05; ## p < 0.01; ### p < 0.001 with respect to old control. T: Training (performed the same day of the test).

Figure 2

Antioxidant enzyme response in frontal cortexes of young control, old control, and treated rats (catechin and polyphenon-60) (3 and 20 months old, respectively). Data is expressed as mean ± SEM. * p < 0.05; ** p < 0.01; *** p < 0.001 respect to young control; and # p < 0.05 respect to old control rats. One-way analysis of variance (ANOVA) and Bonferroni post hoc test. CAT: catalase; SOD: superoxide dismutase; GPX: glutathione S-transferase; GR: glutathione reductase.

Figure 3

GSH and GSSG levels in frontal cortexes of young control, old control, and treated rats (catechin and polyphenon-60) (3 and 20 months old, respectively). Bars represent mean ± SEM. * p < 0.05 and *** p < 0.001 respect to young control; and ## p < 0.01 and ### p < 0.001 respect to old control rats. One-way analysis of variance (ANOVA) and Bonferroni post hoc test.

Figure 4

Western blot analysis of cortical levels of MnSOD young control, aged control, and treated rats (catechin and polyphenon-60) (3 and 20 months old, respectively). Data is represented as mean ± SEM of protein levels expressed as percentage relative to the young control group. ** p < 0.01 compared to the young control; and # p < 0.05 with respect to old control rats. One-way analysis of variance (ANOVA) and Bonferroni post hoc test.