Melatonin expression in periodontitis and obesity: An experimental in-vivo investigation.

BACKGROUND AND OBJECTIVE: Melatonin deficiency has been associated with obesity and systemic inflammation. This study aims to evaluate whether melatonin could interfere with the mechanisms of co-morbidity linking obesity and periodontitis. MATERIAL AND METHODS: Twenty-eight male Wistar rats were randomly divided in 4 groups: control group (Con) (fed with standard diet); high-fat diet group (HFD) (fed with a diet containing 35.2% fat); Con group with induced periodontitis (Con-Perio) and HFD group with induced periodontitis (HFD-Perio). To induce periodontitis, the method of oral gavages with Porphyromonas gingivalis ATCC W83K1 and Fusobacterium nucleatum DMSZ 20482 was used. Circulating melatonin levels were analyzed by multiplex immunoassays. Periodontitis was assessed by alveolar bone loss (micro-computed tomography and histology) and by surrogate inflammatory outcomes (periodontal pocket depth, modified gingival index and plaque dental index). RESULTS: Plasma melatonin levels were significantly decreased (P < .05) in the obese rats with periodontitis when compared with controls or with either obese or periodontitis rats. Alveolar bone loss increased 27.71% (2.28 µm) in HFD-Perio group compared with the Con group. The histological analysis showed marked periodontal tissue destruction with osteoclast activity, particularly in the HFD-Perio group. A significant negative correlation (P < .05) was found between periodontal pocket depth, modified gingival index and circulating melatonin levels. CONCLUSION: Obese and periodontitis demonstrated significantly lower melatonin concentrations when compared with controls, but in obese rats with periodontitis these concentrations were even significantly lower when compared with either periodontitis or obese rats. These results may indicate that melatonin deficiency could be a key mechanism explaining the co-morbidity effect in the association between obesity and periodontitis.

Parotid gland tissue is able partially to assume pituitary functions under the influence of hypothalamic factors: in vivo and in vitro studies.

To test whether salivary tissue can secrete pituitary hormones, female Sprague-Dawley rats were hypophysectomized (hypox) and the following were transplanted to the sella turcica: parotid gland (group 3, n=33), adrenal gland (group 4, n=30), muscle (group 5, n=24). Group 2 (n=21) had the sella turcica filled with dentist's cement. In addition a group of rats (group 1, n=22) remained intact as controls. All groups were followed for 8 months. Daily vaginal smears showed normal cyclicity in controls and constant dioestrus in all hypox groups. Blood samples, taken once every 30 days before and after LHRH stimulation, showed significantly lower (P<0.001) plasma LH values in all hypox groups compared with controls. In group 3, a gradual and significant increase (P<0.05) was observed in the LH response to LHRH in parallel with a partial recovery of oestrous smears. No LH modification was observed in the other hypox groups. Plasma prolactin (PRL) levels were also very low in all hypox groups and were unaltered throughout the study. At the end of the experiments, half the animals were killed by decapitation and the hypothalamic-pituitary areas carefully dissected, homogenized and analysed for LH and PRL content. The remaining animals were perfused with 4% paraformaldehyde to obtain fixing of the whole body tissues. Hypothalamic and transplant areas were carefully dissected, frozen, cut and submitted to immunochemical procedures. LH content in the graft of group 3 animals was markedly (P<0.001) lower than in the control pituitary, but significantly higher (P<0.05) than in the other hypox groups. Immunochemistry showed LH and PRL positive cells in the graft of group 3 animals, whereas neither positive cells, nor LH content were observed in the parotid gland in situ. Experiments were completed with in vitro cultures of parotid glands in the presence or absence (controls) of synthetic hypothalamic hormones or rat hypothalamic extracts. After 1.5 weeks of culture, a significantly higher LH concentration (P<0.05) was observed in the wells treated with synthetic hypothalamic hormones (216+/-46 pg/ml vs 41+/-6 pg/ml in controls). When hypothalamic extracts were used, the LH levels increased more markedly (1834+/-190 pg/ml vs 36+/-6 pg/ml in controls) and those values were maintained during 3 weeks of culture. Immunostaining of these cultures showed a positive LH reaction in the epithelial cells found in the hypothalamic extract-treated wells. Both in vivo and in vitro studies confirm the transdifferentiation of parotid gland tissue to pituitary hormone-producing cells under hypothalamic influence.

Point mutations and deletion responsible for the Bombay H null and the Reunion H weak blood groups.

OBJECTIVE: Definition of the molecular basis of the Reunion and the Bombay red cell and salivary H-deficient phenotypes. METHODS: Sequence and expression of FUT1 and FUT2 genes from H-deficient individuals. Family segregation analysis of the mutations responsible for the fucosyltransferase defects of H, secretor and Lewis systems. RESULTS: The Indian red cell H null Bombay phenotype depends on a new mutation of the FUT1 gene. T725-->G changing Leu242-->Arg. Their salivary nonsecretor phenotype is secondary to a complete deletion of the FUT2 gene. The red cell H weak Reunion phenotype depends on another new mutation of FUT1, C349-->T which induces a change of His117-->Tyr. Their salivary nonsecretor phenotype is due to the known Caucasian inactivating mutation G428-->A. CONCLUSION: Single prevalent FUT1 and FUT2 point mutations and a deletion are responsible for the Indian Bombay H null and the Reunion H weak phenotypes found on Reunion island. This is in contrast with other H-deficient phenotypes where sporadic nonprevalent inactivating mutations are the rule.

Advances in molecular genetics of alpha-2- and alpha-3/4-fucosyltransferases.

Fucosyltransferases are involved in the last steps of the biosynthesis of ABH and Lewis oligosaccharide antigens. Seven human genes (FUT1 to FUT7) and one pseudogene (Sec 1) have been cloned and localized on different chromosomes (9q34.3; 11q21; 19p13.3 and 19q13.3). Their locations and their high degree of primary sequence identity, suggest that they have appeared by successive duplications followed by translocation and divergent evolution. Their expression is tissue specific and they present a switch during human embryo-foetal development similar to that of hemoglobins. Polymorphic genes FUT1-FUT2 and FUT3-FUT5-FUT6 are organized in two clusters and each gene is partially or totally inactivated by different types of point mutations (nonsense, missense and frame shift), complete gene deletion or a fusion gene. The products of the monomorphic genes FUT4 and FUT7 seem implicated in cell-cell interactions during embryo-foetal development and in the leukocyte adhesion phenomena to endothelial cells in the adult. A phylogenetic tree of the 28 available nucleotide coding sequences of fucosyltransferases has allowed us to situate the duplication events with respect to the separation of species from the main evolutionary path (nematods, birds, mammals, primates and humans). Recently, using a computer approach a general structure of fucosyltransferases has been proposed, inspired from the crystalline structure of the beta-glucosyltransferase of bacteriophage T4. This folding contains two domains with an alternate succession alpha and beta chains. In this model the GDP-fucose binding site would be located between the two domains.

Choline-acetyltransferase-like immunoreactivity in the organ of Corti of the rat during postnatal development.

The mammalian cochlea receives efferent innervation from neurons located in the superior olivary complex. This efferent olivocochlear innervation is divided in two separate systems, lateral and medial, which mainly innervate afferent dendrites connected to inner hair cells and the cell body of outer hair cells, respectively. Besides other substances, lateral and medial efferent terminals of the adult cochlea use acetylcholine (ACh) as a neurotransmitter. In this study, we have used immunocytochemistry to detect the presence of choline acetyltransferase (ChAT), the synthesizing enzyme of ACh, in efferent olivocochlear terminals during the development of the rat. The appearance and distribution of immunoreactivity to ChAT has been studied in developing rat cochleas from birth (postnatal day 1, P1) to adulthood. Attention was paid to the temporal relationships between the expression of ChAT, the presence of other putative neuroactive substances, the onset of hearing and other developmental phenomena. Our results indicate that ChAT-like immunoreactivity is already present at birth (P1) in the region of inner hair cells, that it appears at P3 in the outer hair cell area and that it reaches an adult pattern of distribution by P15. ACh may thus be present early in the developing cochlea, before the onset of hearing, as it also occurs with other putative transmitters/modulators such as enkephalins, CGRP or GABA. It is suggested that ACh could be involved in the modulation of sound-evoked potentials as soon as they appear, and in the regulation of other developmental phenomena such as neurite outgrowth or synaptogenesis.

Piribedil affects dopamine turnover in cochleas stimulated by white noise.

The presence of dopamine (DA) within the cochlea has been previously reported, indicating that its turnover increases under noise stimulation. In the present report, piribedil, a dopaminergic D2 agonist, was used in order to provide evidence of the activity of D2 receptors in the turnover of DA under noise stimulation. Long-Evans rats were intraperitoneally injected with distilled water or with a solution of piribedil one hour previously to either noise or silence exposure. Noise stimulation was performed in an anechoic chamber at 70, 90 or 110 dB SPL for one hour. The animals were then sacrificed and the cochlear contents of DA and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were quantified by HPLC with electrochemical detection. The administration of piribedil to animals kept in silence did not modify the cochlear DA, DOPAC and HVA content. Noise stimulation resulted in a decrease of the cochlear DA content and an increase of the cochlear DOPAC and HVA contents in vehicle treated animals. The administration of piribedil resulted in a blockade of this noise induced cochlear DA turnover. These results suggest that piribedil stimulates cochlear D2 receptors controlling the cochlear DA release. Piribedil action on D2 receptors could explain the improvement observed in some cochleo-vestibular diseases signs after piribedil treatment.

Effects of noise stimulation on cochlear dopamine metabolism.

Dopamine (DA) appears to be one of the putative neurotransmitters of the lateral efferent olivocochlear fibers. However, its role in the cochlear physiology remains unknown. In this study, animals were exposed for 1 h to white noise at 70, 90 or 110 dB SPL or were kept in silence conditions. Afterwards, the cochlear content of DA and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were analyzed using HPLC coupled to electrochemical detection. Cochlear DA concentration decreased with the noise intensity, while cochlear DOPAC and HVA concentrations increased. Males presented higher cochlear DOPAC contents and lower HVA contents than females. This sexual dimorphism could be related to the link between DA and gonadal steroids. Present results show that DA, as other lateral efferent neurotransmitters, is released and metabolized in relationship with the noise stimulation, and suggest that DA could be involved in the modulation of the type I afferent fiber activity.