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Int J Mol Sci. 2017 Aug 3;18(8). pii: E1687. doi: 10.3390/ijms18081687.

Association between Mastication, the Hippocampus, and the HPA Axis: A Comprehensive Review.

Author information

1
Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, Fukuoka 807-8555, Japan. kazuma@med.uoeh-u.ac.jp.
2
Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, Fukuoka 807-8555, Japan. zhou@med.uoeh-u.ac.jp.
3
Department of Radiology, JA Gifu Welfare Federation Ibi Welfare Hospital, 2547-4, Miwa Ibigawa-cho, Ibi-gun, Gifu 501-0696, Japan. m7niwa@poem.ocn.ne.jp.
4
Department of Food Science and Nutrition, Faculty of Human Life and Environmental Science, Nagoya Women's University, 3-40 Shioji-cho, Mizuho-ku, Nagoya, Aichi 467-8610, Japan. kubo@nagoya-wu.ac.jp.

Abstract

Mastication is mainly involved in food intake and nutrient digestion with the aid of teeth. Mastication is also important for preserving and promoting general health, including hippocampus-dependent cognition. Both animal and human studies indicate that mastication influences hippocampal functions through the end product of the hypothalamic-pituitary-adrenal (HPA) axis, glucocorticoid (GC). Epidemiologic studies suggest that masticatory dysfunction in aged individuals, such as that resulting from tooth loss and periodontitis, acting as a source of chronic stress, activates the HPA axis, leading to increases in circulating GCs and eventually inducing various physical and psychological diseases, such as cognitive impairment, cardiovascular disorders, and osteoporosis. Recent studies demonstrated that masticatory stimulation or chewing during stressful conditions suppresses the hyperactivity of the HPA axis via GCs and GC receptors within the hippocampus, and ameliorates chronic stress-induced hippocampus-dependent cognitive deficits. Here, we provide a comprehensive overview of current research regarding the association between mastication, the hippocampus, and HPA axis activity. We also discuss several potential molecular mechanisms involved in the interactions between mastication, hippocampal function, and HPA axis activity.

KEYWORDS:

HPA axis; chewing; hippocampus; masticatory dysfunction

PMID:
28771175
PMCID:
PMC5578077
DOI:
10.3390/ijms18081687
[Indexed for MEDLINE]
Free PMC Article

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