Difference of brain-derived neurotrophic factor expression and pyramid cell count during mastication of food with varying hardness

Early Childhood Caries, Masticatory Function, Child Early Cognitive, and Psychomotor Development: A Narrative Review

Dental caries is known as a global public health issue that has been affecting general health apart from its painful nature. Hence, it is undeniable that caries affecting young children or known as early childhood caries, also have an effect on children's general health. One of the interesting findings about caries is that it can also affect child growth and development, specifically on their cognitive and psychomotor ability. Untreated caries are linked to cognitive development through both neural and vascular pathways, with masticatory function as the key. Meanwhile, its effect on psychomotor development might be related to nutritional intake, which might slightly decline on those with caries. This review is aimed to describe the current findings of caries effect on early child development, from masticatory disturbance to further impacts on cognitive and psychomotor development. The overall conclusion of this review is that untreated severe caries in children are potentially associated negatively with their growth and development.

Mastication stimuli regulate the heartbeat rate through rhythmic regulation by the hypothalamic-autonomic system; molecular and telemetric studies in weaning-stage rats

Mastication stimuli have been demonstrated to affect memory function and autonomic nerve activity; however, this process has not been well studied during weaning compared to old age. Previously, we conducted molecular analyses of the thalamus and hippocampus to elucidate the mechanisms underlying this memory-enhancing effect in weaning-stage rats. In this study, we aimed to evaluate the effect of masticatory stimuli on the regulation of heartbeat rate (HR) through the hypothalamic-autonomic system. Three-week-old male rats were administered a powdered diet (P group) or chow-diet (C group) for 10 days. Thereafter, transcriptome analysis was performed. Vasopressin, cocaine-amphetamine-regulated transcript prepropeptide, corticotropin-releasing hormone, and thyrotropin-releasing hormone, which are involved in sympathetic activation of heart rate, were downregulated in the C group. Electrocardiograms were recorded continuously for 12 days under the same condition. Interestingly, rats in the C group had a significantly lower HR than those in the P group on day 11. We checked several parameters representing the autonomic regulation of HR. The C group had higher values for the high-frequency band integration of the HR power spectrum (parasympathetic marker) and root mean square successive difference of R-wave intervals (parasympathetic marker) relative to the P group. Such findings provide a molecular and physiological basis for understanding the regulation of cardiovascular function in response to masticatory stimuli in the autonomic nervous system.

Mastication stimuli enhance the learning ability of weaning-stage rats, altering the hippocampal neuron transcriptome and micromorphology

Mastication stimuli are known to relieve senile dementia in human and animal studies. However, few studies have focused on its effect on weaning-stage animals and the underlying molecular processes. In this study, 3-week-old male rats were raised on a powdered (P-group) or chow (C-group) diet for 8 days, and their behavior was examined using the Y-maze and novel object recognition tests. In the Y-maze test, the C-group rats showed a larger alternation ratio than the P-group rats. In the novel object recognition test, the C-group rats exhibited a significantly larger discrimination index for novel objects than for familiar objects, but the P-group rats did not. We then compared the hippocampal neuron morphology and transcriptome between the groups. C-group rats exhibited larger dendrite branch numbers in the apical dendrites of pyramidal cells in the cornu ammonis 1 (CA1) region and a larger spine density in the basal dendrites of CA1 neurons than the P-group rats. Using DNA microarray analysis, we identified 621 (P < C) and 96 (P > C) genes that were differentially expressed between the groups. These genes were enriched in functional terms related to dendrite growth and included the Igf2, RhoA, and Rho GEF genes, most of which were upregulated in the C-group. These results suggest that the mastication stimuli during the weaning period can enhance the learning ability of rats by increasing the dendrite branches of hippocampal CA1 neurons and by regulating genes related to dendrite growth.

Musculoskeletal Deficits and Cognitive Impairment: Epidemiological Evidence and Biological Mechanisms

PURPOSE OF REVIEW

Cognitive impairment is associated with obesity, sarcopenia, and osteoporosis. However, no critical appraisal of the literature on the relationship between musculoskeletal deficits and cognitive impairment, focusing on the epidemiological evidence and biological mechanisms, has been published to date. Herein, we critically evaluate the literature published over the past 3 years, emphasizing interesting and important new findings, and provide an outline of future directions that will improve our understanding of the connections between the brain and the musculoskeletal system.

RECENT FINDINGS

Recent literature suggests that musculoskeletal deficits and cognitive impairment share pathophysiological pathways and risk factors. Cytokines and hormones affect both the brain and the musculoskeletal system; yet, lack of unified definitions and standards makes it difficult to compare studies. Interventions designed to improve musculoskeletal health are plausible means of preventing or slowing cognitive impairment. We highlight several musculoskeletal health interventions that show potential in this regard.

Tooth Loss-Associated Mechanisms That Negatively Affect Cognitive Function: A Systematic Review of Animal Experiments Based on Occlusal Support Loss and Cognitive Impairment

Background

There is a dose-response relationship between tooth loss and cognitive impairment, while tooth loss can be an independent risk factor for Alzheimer's disease (AD) and vascular dementia (VaD). Tooth loss can also accelerate nerve damage and neurodegeneration. However, the associated mechanisms remain poorly understood.

Objective

To conduct a systematic review of animal experiments on cognitive decline caused by the loss of occlusal support performed over the past 10 years and summarize the possible underlying mechanisms.

Methods

“Tooth Loss,” “Edentulous,” “Tooth Extraction and Memory Loss,” “Cognition Impairment,” and “Dementia” were used as keywords to search PubMed, Embase, SCI, ScienceDirect, and OpenGrey. A total of 1,317 related articles from 2010 to 2021 were retrieved, 26 of which were included in the review after screening according to predetermined inclusion and exclusion criteria. Comprehensiveness was evaluated using ARRIVE guidelines and the risk of bias was assessed using SYCLE'S risk of bias tool.

Results

The putative mechanisms underlying the cognitive impairment resulting from the loss of occlusal support are as follows: (1) The mechanical pathway, whereby tooth loss leads to masticatory motor system functional disorders. Masticatory organ activity and cerebral blood flow decrease. With reduced afferent stimulation of peripheral receptors (such as in the periodontal membrane) the strength of the connections between neural pathways is decreased, and the corresponding brain regions degenerate; (2) the aggravation pathway, in which tooth loss aggravates existing neurodegenerative changes. Tooth loss can accelerates nerve damage through apoptosis and mitochondrial autophagy, increases amyloid deposition in the brain; and (3) the long-term inflammatory stress pathway, which involves metabolic disorders, microbial-gut-brain axis, the activation of microglia and astrocytes, and inflammatory cascade effect in central nervous system.

Conclusion

The loss of occlusal support may lead to cognitive dysfunction through the reduction of chewing-related stimuli, aggravation of nerve damage, and long-term inflammatory stress.

The impact of oral health on physical fitness: A systematic review

Background

Oral health problems may have numerous effects on general health, including physical fitness and performance. In this review, we aimed to systematically review the available evidence to assess the effect of oral health on general physical fitness.

Methods

We systematically performed a literature search in two different databases (PUBMED and EMBASE) without restriction to the year of publication. Articles were included if the subjects were humans and the primary aim was to assess the effects of dental and/or oral health problems on physical activity using either objective physical measurements or physical performance tests. The quality of the studies was then assessed using a Joanna Briggs Institute (JBI) Critical Appraisal tool.

Results

A total of 2651 articles were initially retrieved from the systematic search of the literature. Of these, a final total of 11 articles following the inclusion criteria were included in the review. All of the 11 articles included in the review had good methodological quality. Of the 11 articles, ten articles suggested a correlation between dental and oral condition toward physical fitness, body balance, cardiorespiratory function, and also cognitive function. Only one article found contradictory results, which showed that periodontal conditions did not correlate with the cardiorespiratory function. Malocclusion, including the number of remaining teeth, was reported in five studies (45.4%), periodontal disease was evaluated in six studies (54.5%), along with slight evaluation of periapical inflammation.

Conclusion

This review suggests that there is a negative effect of poor dental and/or oral health on physical fitness and performance.