title: Hard-diet feeding recovers neurogenesis in the subventricular zone and olfactory functions of mice impaired by soft-diet feeding.
abstract: The subventricular zone (SVZ) generates an immense number of neurons even during adulthood. These neurons migrate to the olfactory bulb (OB) and differentiate into granule cells and periglomerular cells. The information broadcast by general odorants is received by the olfactory sensory neurons and transmitted to the OB. Recent studies have shown that a reduction of mastication impairs both neurogenesis in the hippocampus and brain functions. To examine these effects, we first measured the difference in Fos-immunoreactivity (Fos-ir) at the principal sensory trigeminal nucleus (Pr5), which receives intraoral touch information via the trigeminal nerve, when female adult mice ingested a hard or soft diet to explore whether soft-diet feeding could mimic impaired mastication. Ingestion of a hard diet induced greater expression of Fos-ir cells at the Pr5 than did a soft diet or no diet. Bromodeoxyuridine-immunoreactive (BrdU-ir) structures in sagittal sections of the SVZ and in the OB of mice fed a soft or hard diet were studied to explore the effects of changes in mastication on newly generated neurons. After 1 month, the density of BrdU-ir cells in the SVZ and OB was lower in the soft-diet-fed mice than in the hard-diet-fed mice. The odor preferences of individual female mice to butyric acid were tested in a Y-maze apparatus. Avoidance of butyric acid was reduced by the soft-diet feeding. We then explored the effects of the hard-diet feeding on olfactory functions and neurogenesis in the SVZ of mice impaired by soft-diet feeding. At 3 months of hard-diet feeding, avoidance of butyric acid was reversed and responses to odors and neurogenesis were recovered in the SVZ. The present results suggest that feeding with a hard diet improves neurogenesis in the SVZ, which in turn enhances olfactory function at the OB.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Asahikawa Medical University, Asahikawa, Japan; Department of Sensory Physiology, Asahikawa Medical University, Asahikawa, Japan.
authors.forename: Chizuru
authors.initials: C
authors.lastname: Utsugi
authors.affiliation: Department of Sensory Physiology, Asahikawa Medical University, Asahikawa, Japan.
authors.forename: Sadaharu
authors.initials: S
authors.lastname: Miyazono
authors.affiliation: Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Tohbetu, Japan.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Osada
authors.affiliation: Department of Sensory Physiology, Asahikawa Medical University, Asahikawa, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sasajima
authors.affiliation: Department of Sensory Physiology, Asahikawa Medical University, Asahikawa, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Noguchi
authors.affiliation: Department of Oral and Maxillofacial Surgery, Asahikawa Medical University, Asahikawa, Japan.
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Matsuda
authors.affiliation: Department of Sensory Physiology, Asahikawa Medical University, Asahikawa, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Kashiwayanagi
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001973:Bromodeoxyuridine; D020148:Butyric Acid / Q000378:metabolism; D004032:Diet; D005260:Female; D007150:Immunohistochemistry; D020547:Lateral Ventricles / Q000166:cytology*; D008409:Mastication / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D055495:Neurogenesis / Q000502:physiology*; D009830:Olfactory Bulb / Q000166:cytology / Q000502:physiology; D012903:Smell / Q000502:physiology*; D013268:Stimulation, Chemical; D013997:Time Factors; D014278:Trigeminal Nuclei / Q000378:metabolism
chemical_list: D020148:Butyric Acid; D001973:Bromodeoxyuridine