OBJECTIVES:Masticatory function may influence the gut microbial metabolism via mechanical and neurohumoral mechanisms. However, the relationship between microbial metabolites and systemic indicators in healthy adults remains unclear. METHODS:This cross-sectional study included 20 healthy young adults (mean age: 27.6 ± 2.5 years). Masticatory performance was assessed using a validated chewing examination with gummy jelly as the test food. Fecal short-chain fatty acids were quantified by gas chromatography. Microbial metabolic functions were inferred using PICRUSt2 based on 16S rRNA gene sequences. Defecation frequency and body mass index were assessed using questionnaires and anthropometry, respectively. Correlation, regression, and mediation analyses were performed using 2,000 bootstrap samples. RESULTS:Masticatory performance showed nominal positive associations with several microbial metabolic pathways (p < 0.05), but none remained significant after false discovery rate correction (q ≥ 0.05). Propionate concentration and masticatory performance showed trends toward associations with defecation frequency, although these associations did not reach statistical significance. The mediation pathway involving propionate and defecation frequency was suggested but not significant. CONCLUSION:Overall, masticatory performance was associated with fecal propionate levels in healthy young adults. Associations among defecation frequency, BMI, and predicted microbial metabolic pathways are exploratory and require confirmation in larger studies.
OBJECTIVES:Hypophosphatasia (HPP) is a congenital disease caused by mutations in the tissue non-specific alkaline phosphatase gene. HPP is characterized by impaired hard tissue mineralization and premature tooth loss. Mild-type HPP includes childhood-, adult, and odonto-HPP. Mild-type HPP is difficult to diagnose because individuals with mild-type HPP do not have characteristic symptoms. The effects of applying mechanical stress, such as that caused by orthodontic force, on the teeth and jawbones of patients with mild-type HPP are unknown; therefore, in this study these effects were examined in mild-type HPP model mice. METHODS:A 10 gf nickel-titanium closed-coil spring was placed on the maxillary incisors and left first molar (M1) of mild-type HPP model mice (Akp2+/-). The M1 moved mesially to the maxillary incisors 14 days before sampling. RESULTS:Tooth movement distance, serum alkaline phosphatase (ALP) and serum C-terminal telopeptide of Type I collagen (CTX-1) levels did not differ between Akp2+/- and normal (Akp2+/+) mice. However, alveolar bone resorption on the compressed side was higher in Akp2+/- mice than that in normal mice. The cancellous bone quality on the compressed was side was lower in Akp2+/- than in Akp2+/+ mice. Fibrous structures infiltrated the bone resorption sites, and the number of osteoclasts was markedly higher in Akp2+/- mice. CONCLUSIONS:The application of orthodontic force to mice with mild-type HPP did not affect the serum ALP and bone resorption marker CTX-1 levels, or tooth movement. However, compression induced alveolar bone resorption due to an increase in osteoclasts. These findings support the importance of differentially diagnosing mild-type HPP before initiating treatment.
BACKGROUND:Leptin receptor (LepR)+ stromal cells are widely recognized as skeletal stem/progenitor cells (SSPCs) in the bone marrow that generate osteolineage cells, and contribute to skeletal homeostasis under steady-state conditions and tissue repair. By expressing representative niche factors, including stem cell factor and C-X-C motif chemokine ligand 12, LepR+ SSPCs function as key microenvironmental components of the hematopoietic stem cell (HSC) niche. Over the past decade, genetic cell-labeling studies have identified LepR+ SSPCs in craniofacial tissues, including in the periodontal ligament and alveolar bone marrow, where they differentiate into osteoblasts and cementoblasts. HIGHLIGHT:Emerging evidence indicates that periodontal LepR + cells contribute to orthodontic remodeling, periodontal repair, and extraction socket healing. Independent SSPC populations may coexist with LepR+ SSPCs in oral tissues and contribute in parallel to tissue homeostasis. Periodontal LepR+ cells also express HSC niche-associated factors, suggesting their possible role in the regulation of local immune and hematopoietic environments. Because oral tissues are continuously exposed to mechanical forces and the oral microbiome, LepR+ SSPCs in the oral environment may function through unique regulatory mechanisms that influence skeletal homeostasis and hematopoiesis. CONCLUSION:In this review, current knowledge regarding LepR+ SSPCs in periodontal tissues is summarized, and their emerging roles in skeletal maintenance, tissue repair, and hematopoietic regulation is discussed. Further elucidation of the regulatory mechanisms governing these cells will advance understanding of oral skeletal and hematopoietic biology, and may provide new insights into oral health and regenerative strategies.
Objectives Sodium chloride (NaCl), an important mineral for human homeostasis, is perceived by taste receptors. The objective of this study was to investigate how perceived intensity and preference for NaCl by taste receptors were affected after mixing with thickeners in electrophysiological and behavioral experiments in Wistar/ST rats. Methods Chorda tympani nerve responses to 0.1 M NaCl, 0.1 M sucrose, 3 mM hydrochloride, and 1 mM quinine hydrochloride, with and without thickeners, were measured by electrophysiology. Commercially available grades of 3% xanthan gum-based (X), 2% guar gum-based (G), and 4.7% starch-based (S) thickeners were used. To investigate the effect of thickener concentration, responses to 0.1 M NaCl mixed with 1%, 2%, and 3% X were measured. A two-bottle preference test and a brief-access test were performed using the following stimuli: 0.1 M NaCl, distilled water, and their mixture with one of the three thickeners. Results The degree of suppression varied depending on taste stimuli and thickeners; however, in most instances, chorda tympani nerve responses to the tested taste stimuli were suppressed by mixing with thickeners. The response and preference for 0.1 M NaCl were suppressed by mixing with X and G. The brief-access test demonstrated that the suppression was caused by the taste effect. Conclusion Mixing thickeners, such as X and G, but not S, with NaCl, suppressed perceived intensity and preference for NaCl.
Objectives Circadian rhythms in peripheral organs undergo dynamic reorganization during postnatal development. However, the mechanisms underlying the maturation of circadian clocks in the salivary glands, particularly in relation to feeding behavior, remain poorly understood. In this study, we aimed to characterize the developmental maturation of circadian rhythms in the mouse submandibular gland (SMG). Methods PERIOD2::LUCIFERASE bioluminescence rhythms were recorded from cultured suprachiasmatic nucleus (SCN) and SMG tissues isolated from mice at postnatal days 0, 1, 7, 14, 21, and 28, and 8 weeks. Maternal behavior and pup feeding activity were continuously monitored using infrared video recording. Peak phases and circadian periods were analyzed to evaluate developmental changes. Results Robust circadian oscillations were observed in the SCN tissue at all developmental stages, with stable periods and peak phases. In contrast, rhythms in the SMG were rapidly damped in culture, and exhibited a progressive phase shift from the light phase to the middle of the dark phase during postnatal development. Circadian periods in both tissues remained close to 24 h throughout development. Behavioral analyses revealed that developmental changes in maternal care and feeding activity were closely associated with the phase realignment of SMG rhythms. After weaning, SMG peak phases resembled those in adult mice. Conclusions Postnatal maturation of circadian rhythms in the SMG is characterized by progressive phase realignment that parallels the transition from suckling to independent feeding. These findings suggest that developmental coordination between feeding behavior and peripheral clock machinery contributes to the establishment of circadian regulation of salivary function.
