The impact of a diphenyl diselenide-supplemented diet and aerobic exercise on memory of middle-aged rats

Ageing, Cognitive Decline, and Effects of Physical Exercise: Complexities, and Considerations from Animal Models

In our ageing global population, the cognitive decline associated with dementia and neurodegenerative diseases represents a major healthcare problem. To date, there are no effective treatments for age-related cognitive impairment, thus preventative strategies are urgently required. Physical exercise is gaining traction as a non-pharmacological approach to promote brain health. Adult hippocampal neurogenesis (AHN), a unique form of brain plasticity which is necessary for certain cognitive functions declines with age and is enhanced in response to exercise. Accumulating evidence from research in rodents suggests that physical exercise has beneficial effects on cognition through its proneurogenic capabilities. Given ethical and technical limitations in human studies, preclinical research in rodents is crucial for a better understanding of such exercise-induced brain and behavioural changes. In this review, exercise paradigms used in preclinical research are compared. We provide an overview of the effects of different exercise paradigms on age-related cognitive decline from middle-age until older-age. We discuss the relationship between the age-related decrease in AHN and the potential impact of exercise on mitigating this decline. We highlight the emerging literature on the impact of exercise on gut microbiota during ageing and consider the role of the gut-brain axis as a future possible strategy to optimize exercise-enhanced cognitive function. Finally, we propose a guideline for designing optimal exercise protocols in rodent studies, which would inform clinical research and contribute to developing preventative strategies for age-related cognitive decline.

Differences in learning and memory between middle-aged female and male rats

We observed differences in cognitive functions between middle-aged female and male Wistar rats. Both (like youngsters) discriminated new versus familiar objects, showing similar short- and long-term memory (STM and LTM, respectively). Only females show robust LTM for new location of an object. Both successfully form LTM of inhibitory avoidance, though males appeared to be amnesic for memory persistence. Habituation, locomotion, horizontal exploration, "stereotypies," fear, and anxiety-like behavior were similar for both, while vertical exploration was significantly higher in middle-aged and younger females. Therefore, sex-dependent differences in some cognitive functions and behaviors must be considered when designing and interpreting learning and memory studies.

Swimming Improves Memory and Antioxidant Defense in an Animal Model of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a genetic disease associated with progressive skeletal muscle degeneration. In humans, DMD has an early onset, causes developmental delays, and is a devastating disease that drastically diminishes the quality of life of young individuals affected. The objective of this study was to evaluate the effects of a swimming protocol on memory and oxidative stress in an animal model of DMD. Male mdx and wild-type mice aged ≥ 28 days were used in this study. The animals were trained for a stepped swimming protocol for four consecutive weeks. The swimming protocol significantly reduced the levels of lipid peroxidation and protein carbonylation in the gastrocnemius, hippocampus, and striatum in the exercised animals. It also prevented lipid peroxidation in the diaphragm. Moreover, it increased the free thiol levels in the gastrocnemius, the diaphragm, and all central nervous system structures. The results showed that the protocol that applied swimming as a low-intensity aerobic exercise for 4 weeks prevented aversive memory and habituation in mdx mice.

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Neurobiological effects of forced swim exercise on the rodent hippocampus: a systematic review

Forced swimming is a common exercise method used for its low cost and easy management, as seen in studies with the hippocampus. Since it is applied for varied research purposes many protocols are available with diverse aspects of physical intensity, time and periodicity, which produces variable outcomes. In the present study, we performed a systematic review to stress the neurobiological effects of forced swim exercise on the rodent hippocampus. Behavior, antioxidant levels, neurotrophins and inflammatory markers were the main topics examined upon the swimming effects. Better results among these analyses were associated with forced exercise at moderate intensity with an adaptation period and the opposite for continuous exhausting exercises with no adaptation. On further consideration, a standard swimming protocol is necessary to reduce variability of results for each scenario investigated about the impact of the forced swimming on the hippocampus.

Forced swimming is a common exercise method used for its low cost and easy management, as seen in studies with the hippocampus. Since it is applied for varied research purposes many protocols are available with diverse aspects of physical intensity, time and periodicity, which produces variable outcomes. In the present study, we performed a systematic review to stress the neurobiological effects of forced swim exercise on the rodent hippocampus. Behavior, antioxidant levels, neurotrophins and inflammatory markers were the main topics examined upon the swimming effects. Better results among these analyses were associated with forced exercise at moderate intensity with an adaptation period and the opposite for continuous exhausting exercises with no adaptation. On further consideration, a standard swimming protocol is necessary to reduce variability of results for each scenario investigated about the impact of the forced swimming on the hippocampus.

Mitochondrial dynamics, a key executioner in neurodegenerative diseases

Neurodegenerative diseases (NDs) are the group of disorder that includes brain, peripheral nerves, spinal cord and results in sensory and motor neuron dysfunction. Several studies have shown that mitochondrial dynamics and their axonal transport play a central role in most common NDs such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and Amyotrophic Lateral Sclerosis (ALS) etc. In normal physiological condition, there is a balance between mitochondrial fission and fusion process while any alteration to these processes cause defect in ATP (Adenosine Triphosphate) biogenesis that lead to the onset of several NDs. Also, mitochondria mediated ROS may induce lipid and protein peroxidation, energy deficiency environment in the neurons and results in cell death and defective neurotransmission. Though, mitochondria is a well-studied cell organelle regulating the cellular energy demands but still, its detail role or association in NDs is under observation. In this review, we have summarized an updated mitochondria and their possible role in different NDs with the therapeutic strategy to improve the mitochondrial functions.

Sex differences in aerobic exercise efficacy to improve cognition: A systematic review and meta-analysis of studies in older rodents

Research in humans indicates that women may show greater cognitive benefits from aerobic training (AT) than men. To determine whether this sex difference extends to rodents, we conducted a systematic review and meta-analysis of studies in healthy, older rodents. Results indicate that compared to controls, AT improved hippocampus-dependent and -independent learning and memory. A sex difference was found with males showing larger benefits from AT on conditioned-avoidance and non-spatial memory tasks. AT also increased brain-derived neurotrophic factor compared to controls, with larger effects in females. As an exploratory analysis, sex differences in voluntary AT were examined separately from forced AT. Voluntary AT enhanced non-spatial memory to a greater extent in males. Forced AT enhanced hippocampus-dependent learning and memory more so in females. These findings suggest that sex is an important factor to consider, and studies directly assessing sex differences in the ability of exercise to improve brain function are needed.

Effects of Physical Exercise Combined with Nutritional Supplements on Aging Brain Related Structures and Functions: A Systematic Review

Age-related decline in gray and white brain matter goes together with cognitive depletion. To influence cognitive functioning in elderly, several types of physical exercise and nutritional intervention have been performed. This paper systematically reviews the potential additive and complementary effects of nutrition/nutritional supplements and physical exercise on cognition. The search strategy was developed for EMBASE, Medline, PubMed, Cochrane, CINAHL, and PsycInfo databases and focused on the research question: “Is the combination of physical exercise with nutrition/nutritional supplementation more effective than nutrition/nutritional supplementation or physical exercise alone in effecting on brain structure, metabolism, and/or function?” Both mammalian and human studies were included. In humans, randomized controlled trials that evaluated the effects of nutrition/nutritional supplements and physical exercise on cognitive functioning and associated parameters in healthy elderly (>65 years) were included. The systematic search included English and German language literature without any limitation of publication date. The search strategy yielded a total of 3129 references of which 67 studies met the inclusion criteria; 43 human and 24 mammalian, mainly rodent, studies. Three out of 43 human studies investigated a nutrition/physical exercise combination and reported no additive effects. In rodent studies, additive effects were found for docosahexaenoic acid supplementation when combined with physical exercise. Although feasible combinations of physical exercise/nutritional supplements are available for influencing the brain, only a few studies evaluated which possible combinations of nutrition/nutritional supplementation and physical exercise might have an effect on brain structure, metabolism and/or function. The reason for no clear effects of combinatory approaches in humans might be explained by the misfit between the combinations of nutritional methods with the physical interventions in the sense that they were not selected on sharing of similar neuronal mechanisms. Based on the results from this systematic review, future human studies should focus on the combined effect of docosahexaenoic acid supplementation and physical exercise that contains elements of (motor) learning.