Impact of Habitual Yogurt Intake in Mother-Child Dyads on Incidence of Childhood Otitis Media: The Japan Environment and Children's Study (JECS).

Otitis media, one of the most common childhood diseases, is characterized by inflammation or infection of the middle ear. Due to their ease of access, daily probiotics are recommended for the prevention of early childhood otitis media. This study aimed to assess the impact of probiotics on the incidence of otitis media using a dataset (n = 95,380) from the Japan Environment and Children's Study, a nationwide birth cohort study. After multiple imputations, the association between the incidence of otitis media in early childhood and the daily frequency of yogurt intake in children and mothers was examined using a generalized linear model after adjusting for several confounders. Repeated incidence of otitis media during the 2 years after birth was found in 14,874 participants (15.6%). Based on participants with the lowest frequency of yogurt intake ("almost never") as the reference group, risk ratios for otitis media incidence decreased with higher frequencies of yogurt intake in children at one year of age, but also independently in mothers during pregnancy. The lowest risk ratio (95% confidence interval) for otitis media incidence at six months of age was observed with the most frequent yogurt intake (once/day or more) (0.54 [0.46-0.63]). Additionally, although a similar association was observed in the subgroup of those with cleft lip and/or palate (CL/P), a high-risk group for severe recurrent otitis media, no statistical significance was observed. Thus, increased regular yogurt intake in both children and mothers was associated with a decrease of otitis media during early childhood.

Impact of habitual chewing on gut motility via microbiota transition.

The gut environment, including the microbiota and its metabolites and short-chain fatty acids (SCFA), is essential for health maintenance. It is considered that functional recovery treatment for masticatory dysphagia affects the composition of the gut microbiota, indicating that habitual mastication, depending on the hardness of the food, may affect the gut microbiota and environment. However, the impact of chronic powdered diet feeding on the colonic condition and motility remains unclear. Here, we evaluated various colonic features in mice fed with powdered diets for a long-term and a mouse model with masticatory behavior. We observed a decreased abundance of the SCFA-producing bacterial genera in the ceca of the powdered diet-fed mice. Based on the importance of SCFAs in gut immune homeostasis and motility, interestingly, powdered diet feeding also resulted in constipation-like symptoms due to mild colitis, which were ameliorated by the administration of a neutrophil-depleting agent and neutrophil elastase inhibitors. Lastly, the suppressed colonic motility in the powdered diet-fed mice was significantly improved by loading masticatory activity for 2 h. Thus, feeding habits with appropriate masticatory activity and stimulation may play a key role in providing a favorable gut environment based on interactions between the gut microbiota and host immune system.

Prospective association of short sleep duration in newborns with bruxism behavior in children: The Japan Environment and Children's Study (JECS).

BACKGROUND: Bruxism is defined as a repetitive masticatory muscle activity, characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. Although the bruxism etiology can be bidirectionally described with sleep disorders, there are few studies available to understand the association of sleep duration with bruxism behavior in early childhood. METHODS: A dataset of children (n = 90,148) from the Japan Environment and Children's Study (JECS) - an ongoing nationwide, prospective birth cohort study - was used to investigate the prospective association of the infant's sleep duration with bruxism behavior, which were acquired using self-reported questionnaire. After multiple imputation of data, the association between sleep duration and bruxism behavior in early childhood was examined using a binomial logistic regression analysis. It was conducted with adjustments for several maternal (e.g., age at delivery and sleep duration) and child-related (e.g., sex and sleep position) variables. RESULTS: The prevalence of bruxism behavior at the ages of two and four were 16.2% and 22.5%, respectively. Using the shortest sleep duration group's participants (≤13 h) as the reference, the odds ratio (95% confidence interval) for prevalence of bruxism behavior decreased with longer sleep duration at one month of age, but not at 36 months of age, after covariate adjustments. Furthermore, in comparison with the impacts between daytime and nighttime sleep, nighttime sleep with longer duration were dominantly associated with bruxism behavior. CONCLUSION: The sleep duration in infant stage, especially during newborn stage was associated with the prevalence of bruxism behavior in children.

Neurodevelopmental trajectories in children with cleft lip and palate: A longitudinal study based on the Japan Environment and Children's Study.

Cleft lip and/or palate (CL/P), the most prevalent congenital anomaly, is understood to negatively affect a wide range of child development. Since the concept remains controversial, because most published work is from cross-sectional studies, we examined the neurodevelopmental trajectories in participants with CL/P through a longitudinal comparison with the general population during early childhood using data from a nationwide birth cohort study in Japan. The linear mixed models for each domain of the Ages and Stages Questionnaire, third edition (ASQ-3), were used to detect differences in standardised mean scores between groups. The ASQ-3 is a general neurodevelopmental screening tool comprising communication, gross motor, fine motor, problem-solving, and personal-social domains. Participants' neurodevelopment was determined semi-annually from 6 to 36 months of age. The trajectories of standardised mean scores in each domain showed several significant differences between the control and CL/P groups, with the maximum difference at 24 months of age in the communication domain. Indeed, CL/P was associated with significantly lower scores in the communication (coefficient: -3.31, 95% CI: -5.09 to -1.14), problem-solving (coefficient: -3.13, 95% CI: -5.07 to -1.18), and personal-social domains (coefficient: -1.99, 95% CI: -3.87 to -0.11). Trajectories of ASQ-3 scores suggest neurodevelopmental delays in children with CL/P.

Influence of maternal postpartum depression on children's toothbrushing frequency.

OBJECTIVES: Daily toothbrushing behaviour is very effective for the prevention of early childhood dental caries (ECC), but is mostly dependent upon parental management. Intrapersonal association between lower toothbrushing frequency and depression is well known; however, the impact of maternal postpartum depression on child toothbrushing behaviour within the mother-child dyad remains unknown. The aim of this study was to determine the association between the prevalence of maternal postpartum depression and lower toothbrushing frequency in children aged two years. METHODS: A secondary analysis of a data set from the Japan Environment and Children's Study was performed. A total of 104 062 fetuses were enrolled after obtaining informed written parental consent, in which 84 533 mother-infant pairs were included after applying exclusion criteria. The Edinburgh Postpartum Depression Scale (EPDS) was used to evaluate maternal postpartum depression (a total score of ≥9 in EPDS) at one and six months postpartum. Indeed, the participants were classified based on the persistence of postpartum depression: 'Resilient' (no prevalence); 'Improving' (prevalence only at one month postpartum); 'Emergent' (prevalence only at six months postpartum); and 'Chronic' (prevalence at both time points). The association between postpartum depression and a toothbrushing frequency in children (the reference group: more than once per day, the low group: once per day, and the very-low group: less than once per day) was examined using Poisson regression models with adjustments for maternal and child characteristics after multiple imputations for missing data. RESULTS: The prevalence of maternal postpartum depression at one and six months postpartum was 13.9% and 11.4%, respectively; the proportions of each persistence group were 81.1% ('Resilient'), 7.5% ('Improving'), 5.0% ('Emergent') and 6.4% ('Chronic'). Concerning children's toothbrushing frequency, 51.6% and 0.5% of participants self-reported frequencies of once per day and less than once per day, respectively. The association of maternal postpartum depression with a lower toothbrushing frequency in children consistently had higher relative risks (RRs). However, these associations were weakened when adjusting for whether the child could self-perform toothbrushing or whether this was done under parental supervision. A key result is that participants with persistent postpartum depression at both one and six month(s) postpartum showed the highest adjusted RRs (95% CI) for lower toothbrushing frequency in children (1.08 [1.04-1.12] with a decrease in children's toothbrushing frequency). CONCLUSION: Maternal mental health provides valuable screening information for children with lower toothbrushing frequency for the purpose of preventing ECC.

Prospective association between maternal bonding disorders and child toothbrushing frequency: A cross-sectional study of the Japan Environment and Children's Study.

BACKGROUND: Daily toothbrushing prevents early childhood caries, but reinforcement depends on facilitative parenting behaviours. Mother-to-infant bonding, the maternal affection towards the infant, is an environmental factor that strongly influences parenting. AIM: This study examined the association between maternal bonding and children's daily toothbrushing frequency. DESIGN: The sample consisted of 83 954 mother-infant pairs at two years postpartum, derived from the initial sample of JECS (cohort study), which included 104 062 foetuses. Maternal bonding disorders were assessed using the Mother-to-Infant Bonding Scale (MIBS). After multiple imputation for missing data, a multinomial logistic regression analysis was conducted with adjustments for several maternal (eg, age at delivery) and child-related (eg, self-performed toothbrushing) variables. RESULTS: The odds ratio (95% confidence interval) for the association of maternal bonding disorders with the low (once per day) and the very low child toothbrushing frequency (<1 per day) was 1.12 (1.07-1.17) and 1.23 (0.91-1.66), respectively, after covariate adjustments. Furthermore, the univariate general linear model showed that the mean MIBS scores significantly decreased as the daily child toothbrushing frequency increased. CONCLUSIONS: The prevalence of maternal bonding disorders at one year postpartum was prospectively associated with a lower frequency of child toothbrushing at two years of age.

Association of cleft lip and palate on mother-to-infant bonding: a cross-sectional study in the Japan Environment and Children's Study (JECS).

BACKGROUND: Cleft lip and/or palate is among the most prevalent congenital birth defects, and negatively affects maternal psychological status and may consequently result in higher prevalence of child maltreatment. However, the association of childbirths of infants with cleft lip and/or palate with maternal emotional involvement still remains unclear. We examined the association between childbirths of infants with cleft lip and/or palate and mother-to-infant bonding, using data from the Japan Environment and Children's Study, a nationwide birth cohort study. METHODS: A cross-sectional study using the jecs-an-20,180,131 dataset was performed. A total 104,065 fetuses in 15 regional centres in Japan were enrolled after obtaining informed written consent. The Mother-to-Infant Bonding Scale, a self-report scale consisting of 10 items, was used to evaluate maternal bonding at one year after childbirth. Finally, the participants consisted of 79,140 mother-infant pairs, of which 211 mothers of infants with cleft lip and/or palate were included in our analyses. Multivariable logistic regression analysis using multiple imputation for missing data was performed to calculate the odds ratio and 95% confidence interval in the estimation of the association between bonding disorders and childbirths with cleft lip and/or palate. RESULTS: No increased risk of bonding disorders was observed among all the mothers of infants with cleft lip and/or palate (odds ratio [95% confidence interval]; 0.97 [0.63-1.48], p = 0.880), however, advanced maternal age or multiple parity may adversely affect the associations between bonding disorders and cleft lip and/or palate, respectively. After stratification with a combination of maternal age and parity, a significant association of cleft lip and/or palate with bonding disorders was found only among advanced-age multiparae (odds ratio [95% confidence interval] = 2.51 [1.17-5.37], p = 0.018), but it was weakened after additional adjustment for maternal depression. CONCLUSIONS: Childbirths of infants with cleft lip and/or palate may increase the risk of bonding disorders among advanced-age multiparae, possibly through maternal depression. This finding provides valuable information for the provision of multidisciplinary cleft care.

Factors associated with sports-related dental injuries among young athletes: a cross-sectional study in Miyagi prefecture.

BACKGROUND: Sports-related dental injuries, such as tooth fracture, loosening, and avulsion, are a major concern among young athletes because they directly impair oral function. Although the preventive efficacy of mouthguards has been well established, the prevalence of sports-related dental injuries remains high among young athletes. The aim of this study is to identify the variables contributing to the risk of sports-related dental injuries by conducting a survey on large population of young athletes in Miyagi prefecture. METHODS: A cross-sectional study was conducted with school-aged athletes (aged 6-15 years, n = 5735) using a self-reported questionnaire. The questionnaire examined general variables, including sex, age, and body mass index; sports-related variables, including sports-type, team level, activity schedule, break time, and verbal/physical abuse by coaches; and lifestyle variables related to free time, including screen-time and sleep duration. Their associations with sports-related dental injuries were examined using multivariate logistic regression models. RESULTS: The prevalence of sports-related dental injuries was 13.3% (763 of 5735 young athletes) and was higher in males (14.3%, 592 of 4132) than in females (10.7%, 171 of 1603; adjusted odds ratios [ORs] and 95% confidence intervals [CIs]: 1.48 [1.22-1.79], p < 0.001). After stratification according to sex, significant associations with the prevalence of sports-related dental injuries were evident for three variables-insufficient break time, verbal abuse, and physical punishment-in males (adjusted ORs [95% CI]: 1.35 [1.03-1.77], p = 0.032; 1.31 [1.05-1.62], p = 0.015; and 1.36 [1.06-1.75], p = 0.016, respectively) but not in females (adjusted ORs [95% CI]: 0.88 [0.53-1.47], p = 0.623; 1.29 [0.87-1.91], p = 0.206; and 0.97 [0.57-1.63], p = 0.894, respectively). CONCLUSIONS: Although our results might be based on the individual athlete's self-perception to the sports-related variables, our results suggest that insufficient break time, verbal abuse, and physical punishment from coaches are positively associated with the prevalence of sports-related dental injuries in young male athletes.

Transfer of the bone morphogenetic protein 4 gene into rat periodontal ligament by in vivo electroporation.

OBJECTIVE: Regulation of alveolar bone metabolism is required in clinical dentistry. The aim of the present study was to establish a method for gene transfer into the periodontal ligament (PDL) by in vivo electroporation with a plasmid vector and to investigate the effects of BMP-4 transfer into the PDL. DESIGN: Plasmids containing mouse BMP-4 cDNA (pCAGGS-BMP4) were transfected into cultured rat PDL cells by in vitro electroporation, and BMP-4 production and secretion were detected by immunocytochemistry and western blotting. Next, pCAGGS-BMP4 was injected into the PDL of rats, and electroporation was performed in vivo, using original paired-needle electrodes. BMP-4 expression was examined by immunohistochemical staining 3, 7, 14, 21, and 28days after electroporation. Control groups were injected with pCAGGS by electroporation, injected with pCAGGS-BMP4 without electroporation, or subjected to neither injection nor electroporation. RESULTS: In vitro-transfected rat PDL cells exhibited production and secretion of the mature-form BMP-4. After in vivo electroporation of pCAGGS-BMP4, site-specific BMP-4 expression peaked on day 3, gradually decreased until day 14, and was absent by day 21. We observed no unfavorable effects such as inflammation, degeneration, or necrosis. CONCLUSIONS: Gene transfer by electroporation with plasmid DNA vectors has several advantages over other methods, including the non-viral vector, non-immunogenic effects, site-specific expression, simplicity, cost-effectiveness, and limited histological side effects. Our results indicate that the method is useful for gene therapy targeting the periodontal tissue, which regulates alveolar bone remodeling.

Long-term feeding on powdered food causes hyperglycemia and signs of systemic illness in mice.

AIMS: Dietary habits are crucial factors affecting metabolic homeostasis. However, few animal experiments have addressed the effects of long-term feeding with soft food on parameters reflecting systemic health. MAIN METHODS: Using mice, we compared the effects of short (3 days) and long (17 weeks from weaning) feeding periods between powdered food and normal pellet food on the levels of blood glucose, serum levels of insulin, catecholamines, and corticosterone, blood pressure, and/or social interaction behaviors. In addition, the effects of a human glucagon-like peptide-1 analog, liraglutide (a new drug with protective effects against neuronal and cardiovascular diseases), were compared between the powder and pellet groups. KEY FINDING: (i) Powdered food, even for such a short period, resulted in a greater glycemic response than pellet food, consistent with powdered food being more easily digested and absorbed. (ii) Long-term feeding on powdered food induced hyperglycemia and related systemic signs of illness, including increases in serum adrenaline, noradrenaline, and corticosterone, higher blood pressures (especially diastolic), and increased social interaction behaviors. (iii) Liraglutide, when administered subcutaneously for the last 2 weeks of the 17-week period of feeding, improved these changes (including those in social interaction behaviors). SIGNIFICANCE: The hyperglycemia associated with long-term powdered-food feeding may lead to certain systemic illness signs, such as elevations of blood glucose, hypertension, and abnormal behaviors in mice. Mastication of food of adequate hardness may be very important for the maintenance of systemic (physical and mental) health, possibly via reduction in the levels of blood glucose and/or adrenal stress hormones (catecholamines and glucocorticoids).

Physiological distal drift in rat molars contributes to acellular cementum formation.

Occlusal forces may induce the physiological teeth migration in humans, but there is little direct evidence. Rat molars are known to migrate distally during aging, possibly caused by occlusal forces. The purpose of this study was to determine if a reduction in occlusion would decrease teeth migration and affect associated periodontal structures such as cementum. To reduce occlusal forces, the right upper first molar (M1) in juvenile rats was extracted. The transition of the position of upper second molar (M2) and formation of M2 cementum was followed during aging. From the cephalometric analyses, upper M2 was located more anterior compared with the original position with aging after M1 extraction. Associated with this "slowing-down" of the physiological drift, cementum thickness on distal surface, but not on mesial surface, of M2 root was significantly increased. The accumulation of alizarin red as vital stain indicative of calcification, was observed in the distal cementum of M2 root only on the side of M1 extraction. Extraction of M1 that results in less functional loading, distinctly attenuates the physiological drift only in the upper dentition. The decreased physiological drift appears to activate acellular cementum formation only on distal surface of M2 root, perhaps due to reduced mechanical stress associated with the attenuated distal drift. In conclusion, the physiological distal drift in rat molars appears to be largely driven by the occlusal force and also affects the formation of acellular cementum. These findings provide additional direct evidence for an important role of occlusal forces in tooth migration.

Interleukin-6 maintains glucose homeostasis to support strenuous masseter muscle activity in mice.

The cytokine interleukin-6 (IL-6) is released from working skeletal muscles and reportedly plays key roles in their glucose homeostasis. However, it is unclear whether IL-6 plays such roles in the masseter muscle (MM), which is important in normal and pathological chewing behaviors, such as bruxism and/or prolonged clenching. When restrained (R+) in a narrow cylinder blocked at the front end with a thin plastic strip, a mouse gnaws away (G+) the strip to escape. The absolute weight of plastic gnawed away serves as an index of MM activity. Using this model, we examined the roles of IL-6 in MM with the following results. R+G+ increased the expression levels of IL-6 and glucose transporter 4 (Glut4) mRNAs in MM and the serum level of IL-6 protein. IL-6-deficient mice exhibited about 60% less gnawing activity than wild-type mice at 3-4 h after the start of R+G+, slower recovery of glycogen levels (indicating poorer glucose supply) in MM after R+G+, and no significant change in Glut4 mRNA in MM upon R+G+. During an R+G+ test conducted after "training" (repeated R+G+ sessions), wild-type mice exhibited greater gnawing activity than untrained controls, but no increase in IL-6 mRNA in MM. IL-6 mRNA increased in MM when hard food was eaten by mice raised on soft food for 3 weeks from weaning, but not in those raised on (accustomed to) hard food. Thus, IL-6 may maintain glucose homeostasis in MM in support of unusually strenuous activity, but not of accustomed activity levels.

Synthesis and intracellular transportation of type I procollagen during functional differentiation of odontoblasts.

The expression of type I collagen, the most component of dentin extracellular matrix proteins (ECMs) in odontoblast is correlated with the activity of dentin formation. Since odontoblast possesses a distinct cellular process for protein transport into the dentinal tubule, it is important to examine the intracellular protein localization. However, a study focusing on odontoblast processes has not been performed. Type I collagen is synthesized as procollagen, which is immediately converted to collagen upon secretion. After characterization of antiserum to rat type I procollagen, we investigated the intracellular localization of type I procollagen in odontoblasts during and after dentinogenesis, using immunohistochemistry and in situ hybridization. The level of mRNA expression decreased during dentinogenesis, whereas the intracellular localization of type I procollagen in odontoblast processes become more distinct. The percentage of dentinal tubules with type I procollagen increased significantly with aging. Odontoblasts in pulp horn, in particular, showed moderate expression of type I procollagen after dentinogenesis. Since loss of occlusion also caused a significant decrease in type I procollagen, we concluded that occlusal stimulation activated type I procollagen synthesis in odontoblasts. We also suggest that analysis of intracellular transport of type I procollagen via odontoblast processes may be a new approach to evaluation of odontoblast function.

Comparison of expression patterns of cathepsin K and MMP-9 in odontoclasts and osteoclasts in physiological root resorption in the rat molar.

Root resorption lacunae are principally formed by odontoclasts. While these cells develop from the same origin as osteoclasts, odontoclasts normally have fewer nuclei and a less clear zone compared with osteoclasts. We therefore, hypothesized that odontoclasts possess less differentiation in matrix resorption characteristics than osteoclasts. To test our hypothesis, we compared the TRAP-positive area and the expression patterns of two important proteolytic enzymes, cathepsin K and matrix metalloproteinase-9 (MMP-9), between odontoclasts and osteoclasts. We focused on physiological root resorption in the rat molar, which is a useful experimental model for estimating odontoclasts and osteoclasts. Observations showed the number of nuclei and the TRAP-positive area of odontoclasts to be significantly less compared with osteoclasts. Using in situ hybridization and double labeling fluorescence in situ hybridization showed the majority of odontoclasts to express both cathepsin K and MMP-9, especially 4 and 5 weeks of age, when physiological root resorption occurs actively. Moreover, putative precursor cells of odontoclasts, which typically appeared in the middle of the periodontal ligament at 3 weeks of age, expressed both enzymes. In contrast, the majority of matured osteoclasts expressed only cathepsin K but not MMP-9. We suggest that odontoclasts are comparable to osteoclasts with less differentiation with regard to the expression of proteolytic enzymes.