Cognitive and Neurochemical Changes Following Polyphenol-Enriched Diet in Rats

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

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.

Influence of Supplementation of Ecklonia cava Polyphenols on Learning, Memory, and Brain Fatty Acid Composition in Mice

AIMS

The objective of this study was to determine the effects of intake of polyphenols from Ecklonia cava on spatial task performance and nervous fatty acid composition in mice fed with a high-fat diet.

METHODS

Thirty mice were randomly divided into three groups; each group consisted of ten mice. The control group was fed 5% soybean oil as a fat source, whereas the high fat (HF) group was fed a 15% lard diet and the polyphenol (ECP) group was maintained on the HF diet plus 1% E. cava polyphenols.

RESULTS

The ECP group exhibited a short escape latency and better memory retention in the Morris water maze test compared with the control and HF groups (P<0.05). In addition, the ECP group showed a greater increase in avoidance latency than that of the HF group (P<0.05). Moreover, the consumption of polyphenols from E. cava presented higher levels of DHA in the brain and retina (P<0.05).

CONCLUSION

This study suggested the positive effects of polyphenols from E. cava on memory retention, which might be partially attributed to the increased levels of DHA in the brain.

Dietary Polyphenols as a Protection against Cognitive Decline: Evidence from Animal Experiments; Mechanisms and Limitations

Emerging evidence suggests that cognitive impairments may result from various factors, such as neuroinflammation, oxidative stress, mitochondrial damage, impaired neurogenesis, synaptic plasticity, blood-brain barrier (BBB) disruption, amyloid β protein (Aβ) deposition, and gut dysbiosis. Meanwhile, dietary polyphenol intake in a recommended dosage has been suggested to reverse cognitive dysfunction via various pathways. However, excessive intake of polyphenols could trigger unwanted adverse effects. Thus, this review aims to outline possible causes of cognitive impairments and how polyphenols alleviate memory loss via various pathways based on in vivo experimental studies. Thus, to identify potentially relevant articles, the keywords (1) nutritional polyphenol intervention NOT medicine AND neuron growth OR (2) dietary polyphenol AND neurogenesis AND memory impairment OR (3) polyphenol AND neuron regeneration AND memory deterioration (Boolean operators) were used in the Nature, PubMed, Scopus, and Wiley online libraries. Based on the inclusion and exclusion criteria, 36 research papers were selected to be further reviewed. The outcome of all the studies included supports the statement of appropriate dosage by taking into consideration gender differences, underlying conditions, lifestyle, and causative factors for cognitive decline, which will significantly boost memory power. Therefore, this review recapitulates the possible causes of cognitive decline, the mechanism of polyphenols involving various signaling pathways in modulating the memory, gut dysbiosis, endogenous antioxidants, bioavailability, dosage, and safety efficacy of polyphenols. Hence, this review is expected to provide a basic understanding of therapeutic development for cognitive impairments in the future.

Mediterranean Diet on Sleep: A Health Alliance

The Mediterranean diet is a plant-based, antioxidant-rich, unsaturated fat dietary pattern that has been consistently associated with lower rates of noncommunicable diseases and total mortality, so that it is considered one of the healthiest dietary patterns. Clinical trials and mechanistic studies have demonstrated that the Mediterranean diet and its peculiar foods and nutrients exert beneficial effects against inflammation, oxidative stress, dysmetabolism, vascular dysfunction, adiposity, senescence, cognitive decline, neurodegeneration, and tumorigenesis, thus preventing age-associated chronic diseases and improving wellbeing and health. Nocturnal sleep is an essential physiological function, whose alteration is associated with health outcomes and chronic diseases. Scientific evidence suggests that diet and sleep are related in a bidirectional relationship, and the understanding of this association is important given their role in disease prevention. In this review, we surveyed the literature concerning the current state of evidence from epidemiological studies on the impact of the Mediterranean diet on nighttime sleep quantity and quality. The available studies indicate that greater adherence to the Mediterranean diet is associated with adequate sleep duration and with several indicators of better sleep quality. Potential mechanisms mediating the effect of the Mediterranean diet and its foods and nutrients on sleep are described, and gap-in-knowledge and new research agenda to corroborate findings are discussed.

Neurochemical and Cognitive Beneficial Effects of Moderate Physical Activity and Catechin in Aged Rats

A healthy aging process is a requirement for good life quality. A relationship between physical activity, the consumption of antioxidants and brain health has been stablished via the activation of pathways that reduce the harmful effects of oxidative stress, by inducing enzymes such as SIRT1, which is a protector of brain function. We analyzed the cognitive and neurochemical effects of applying physical exercise in elderly rats, alone or in combination with the antioxidant catechin. Several tests of spatial and episodic memory and motor coordination were evaluated. In addition, brain monoaminergic neurotransmitters and SIRT1 protein levels were assessed in the brains of the same rats. The results show that physical activity by itself improved age-related memory and learning deficits, correlating with the restoration of brain monoaminergic neurotransmitters and SIRT1 protein levels in the hippocampus. The administration of the antioxidant catechin along with the exercise program enhanced further the monoaminergic pathways, but not the other parameters studied. These results agree with previous reports revealing a neuroprotective effect of physical activity, probably based on its ability to improve the redox status of the brain, demonstrating that exercise at an advanced age, combined with the consumption of antioxidants, could produce favorable effects in terms of brain health.