Dipeptidyl peptidase-4 inhibitor enhances restoration of salivary glands impaired by obese-insulin resistance

ObjectiveChronic high-fat diet consumption causes not only obese- insulin resistance, but also leads to pathological changes in salivary glands, including increased mitochondrial dysfunction, apoptosis, oxidative stress, and inflammation. Dipeptidyl peptidase-4 inhibitor (vildagliptin) is an oral anti-diabetic drug, using for treatment of type 2 diabetes. Vildagliptin has been shown to exert beneficial effects on several organs in cases of obese-insulin resistant condition. However, the effect of vildagliptin on salivary glands impaired by obese-insulin resistance has not been investigated. The hypothesis in this study is that vildagliptin confers beneficial effects on the salivary gland impaired by obese-insulin resistance via decreasing mitochondrial dysfunction, apoptosis, oxidative stress, and inflammation.DesignTwenty-four male Wistar rats were divided into two groups. Each group was fed with either a normal (ND; n = 8) or a high fat diet (HFD; n = 16) for 16 weeks. At week 13, the HFD-fed rats were subdivided into 2 subgroups to receive either a vehicle or vildagliptin (3 mg/kg/day) for 28 days via gavage feeding. ND-fed rats were treated with the vehicle. At the end of treatment, metabolic parameters were examined, and rats were killed. Submandibular glands were removed to appraise inflammatory markers, apoptosis and mitochondrial function.ResultsVehicle-treated HFD-fed rats developed obese-insulin resistance with an increase in oxidative stress, inflammation, apoptosis, and mitochondrial dysfunction in the salivary glands. Vildagliptin therapy reduced oxidative stress, inflammation, apoptosis and mitochondrial dysfunction in salivary gland of HFD-fed rats.ConclusionVildagliptin prevented salivary gland injury occurring due to obese-insulin resistance.     

Saliva secretion in engrafted mouse bioengineered salivary glands using taste stimulation

PurposeThe aim of this study was to compare saliva flow and protein composition induced using five basic taste stimulations between natural and bioengineered salivary glands.Materials and methodsWe developed a mouse saliva secretion model using taste stimulation and analyzed the saliva secretion from natural and bioengineered salivary glands using an assay. The protein components and alpha-amylase in the natural and bioengineered saliva were analyzed by gel electrophoresis and Western blotting.ResultsThe salivary flow responses induced by sour (citric acid) and bitter (quinine-HCl) stimuli were significantly high in the natural and bioengineered salivary glands. Although the protein concentrations in the natural and bioengineered saliva induced using five basic taste stimulations were similar, the protein composition and the amylase concentration in the natural saliva after taste stimulation had different profiles. Sympathetic and non-sympathetic nerves were observed around the acini and ducts in the natural and bioengineered salivary glands. However, the frequency of neuropeptide Y-positive sympathetic nerves in the bioengineered gland was relatively high compared to that in the natural gland.ConclusionsThese results suggest that the signal balance between the sympathetic and parasympathetic components of the efferent nerves in an engrafted bioengineered salivary gland may differ from that in a natural salivary gland.     

Protein expression in submandibular glands of young rats is modified by a high-fat/high-sugar maternal diet

ObjectiveMaternal diet has consequences on many organs of the offspring, but salivary glands have received little attention despite the importance of the saliva secretory function in oral health and control of food intake. The objective of this work was therefore to document in rats the impact of maternal high-fat/high-sugar diet (Western Diet) on submandibular glands of the progeny.DesignSprague-Dawley rat dams were fed either a Western diet or control diet during gestation and lactation and their pups were sacrificed 25 days after birth. The pups’ submandibular gland protein content was characterized by means of 2D-electrophoresis followed by LC–MS/MS. Data were further analyzed by Gene Ontology enrichment analysis and protein-protein interactions mapping. The expression of two specific proteins was also evaluated using immunohistochemistry.ResultsCombining both male and female pups (n = 18), proteome analysis revealed that proteins involved in protein quality control (e.g. heat shock proteins, proteasome sub-units) and microtubule proteins were over-expressed in Western diet conditions, which may translate intense metabolic activity. A cluster of proteins controlling oxidative stress (e.g. Glutathione peroxidases, peroxiredoxin) and enhancement of the antioxidant activity molecular function were also characteristic of maternal Western diet as well as under-expression of annexin A5. The down-regulating effect of maternal Western diet on Annexin A5 expression was significant only for males (p < 0.05).ConclusionsA maternal Western diet modifies the protein composition of the offspring’s salivary glands, which may have consequences on the salivary function.     

Effect of feeding different levels of corn oil on the composition of submandibular salivary gland fatty acids in rats

Male, weanling rats were fed synthetic diets containing 0, 3, 10 and 20 per cent corn oil. Rats were killed after 3 weeks, their plasma and submandibular salivary glands were extracted for lipids, and the fatty acid composition was determined. There were significant changes in the fatty acid composition of both plasma and submandibular salivary glands as a result of feeding different levels of corn oil in the diet. The proportions of monoenoic fatty acids (16:1, 18:1) decreased whereas those of linoleic acid increased as the level of corn oil was increased from 0 to 20 per cent. Arachidonic acid level was the lowest in the fat-free group as compared with the other groups. Plasma and submandibular salivary gland lipids of rats fed 0 per cent corn oil in their diet contained another fatty acid which appears to be eicosadicnoic fatty acid. The changes in submandibular salivary gland fatty acids were correlated with the changes in plasma fatty acids. Fractions of neutral lipids and phospholipids which were isolated from the submandibular salivary glands showed changes in their fatty acid composition similar to those observed in the total lipid extract.     

Interobserver and intraobserver variability in the radiological assessment of sialolithiasis using cone beam computed tomography

Background Data regarding the inter- and intraobserver variability in the radiological assessment of sialolithiasis using cone beam computed tomography are missing in the current literature. This study assessed the inter- and intraobserver variability in the radiological assessment of sialolithiasis using cone beam computed tomography (CBCT).Material and Methods In 107 patients, 130 salivary glands (65 parotid and 65 submandibular) with clinical signs of obstruction were assessed by four independent observers; 2 residents OMFS and 2 experienced OMFS. The observers analyzed the CBCT images and determined the absence or presence of one or more salivary stones in the affected gland. This procedure was repeated after three months.Results Interobserver agreements showed kappa values of 0.84 for the parotid gland, and 0.93 for the submandibular gland. Intraobserver agreements for the whole group reported kappa values between 0.83 - 0.95. There was no significant difference between residents and experienced OMFS.Conclusions Due to the good inter- and intraobserver agreement, CBCT appears to be a reproducible imaging modality for detecting salivary stones in patients with signs and symptoms of obstructed parotid and submandibular glands. Key words:Salivary gland calculi, cone-beam computed tomography, observer variation.     

Responses of salivary glands to intake of soft diet

BackgroundModernization has made individuals prefer processed and cooked foods (soft food), but this eating habit may have negative effects on the oral cavity. However, laboratory animals fed with soft diet are commonly used in an attempt to clarify this issue, and various oral tissues, including the salivary glands have been examined. In this review, we summarize the findings of previous studies concerning the responses of salivary glands to daily intake of soft diet.HighlightThe weight of the parotid glands decreased in rodents fed with soft diet (liquid or powder). In atrophic parotid glands, acinar cell shrinkage is histologically observed and the DNA content is reduced, showing that the atrophy is caused by a decrease in the size and number of acinar cells. Immunohistochemical examinations showed that the decrease in the acinar cell number was induced by suppression of acinar cell proliferation and acceleration of apoptosis. The atrophic parotid glands recovered following a change from soft to pellet diet. Other salivary glands, such as the submandibular, sublingual, and palatine glands, responded only slightly to the soft diet feeding.ConclusionAccumulated research data showed that a soft diet negatively affects the parotid glands much more than other salivary glands and that atrophic parotid glands are able to recover by switching to a hard diet. Therefore, it should be emphasized that good eating habits are important for not only digestion but also the health of oral tissues, including the salivary glands.     

Effects of hyperleptinemia in rat saliva composition,histology and ultrastructure of the major salivary glands

ObjectiveTo study the effect of the satiety hormone, leptin, in saliva proteome and salivary gland histology and ultrastructure.DesignIncreases in blood leptin levels were induced through mini-pump infusion in male Wistar rats, during a period of 7 days. Saliva was collected before and at the end of the experimental period, for proteomic analysis, and major salivary glands were collected, at the end, for biochemical, histological and ultrastructural analysis.ResultsImmunohistochemistry revealed the presence of leptin receptors in major salivary glands. Salivary amylase levels and enzymatic activity were decreased in saliva, whereas the enzymatic activity of this protein was increased in the cytosol of parotid gland cells. Transmission electron microscopy allowed the observation of high number of electron-dense granules in cytosol of parotid acinar cells, from leptin treated animals.ConclusionsIncreased levels of plasmatic leptin result in changes in saliva composition and salivary glands function. To our knowledge, this is the first study providing evidences for a potential role of leptin in salivary gland secretion and saliva composition. An understanding of how appetite/satiety factors influence saliva composition and how this composition influences food processing in mouth may be relevant in understanding ingestivebehaviour.     

Salivary gland progenitor cell biology provides a rationale for therapeutic salivary gland regeneration

Oral Diseases (2011) 17 , 445–449 An irreversible loss of salivary gland function often occurs in humans after removal of salivary tumors, after therapeutic radiation of head and neck tumors, as a result of Sjögren’s syndrome and in genetic syndromes affecting gland development. The permanent loss of gland function impairs the oral health of these patients and broadly affects their quality of life. The regeneration of functional salivary gland tissue is thus an important therapeutic goal for the field of regenerative medicine and will likely involve stem/progenitor cell biology and/or tissue engineering approaches. Recent reports demonstrate how both innervation of the salivary gland epithelium and certain growth factors influence progenitor cell growth during mouse salivary gland development. These advances in our understanding suggest that developmental mechanisms of mouse salivary gland development may provide a paradigm for postnatal regeneration of both mice and human salivary glands. Herein, we will discuss the developmental mechanisms that influence progenitor cell biology and the implications for salivary gland regeneration.     

Changes of salivary functions in experimental periodontitis model rats

ObjectiveThis study was designed to investigate the mechanism of salivary dysfunction in an experimental periodontitis rat model and to examine the improvements in salivary secretion following treatment of the experimental periodontitis.MethodsIn the experimental periodontitis rat model, which included a unilateral ligature for 4 weeks around the second upper molar, several salivary functions were investigated. Changes in the salivary function were evaluated 4 weeks after removal of the ligature in some rats.ResultsThe periodontitis model showed significant reductions in the weight of the bilateral major salivary glands and pilocarpine-induced salivary secretion. The model also showed an increase in the number of apoptotic cells in bilateral salivary glands. According to Ca²⁺ imaging and Western blotting, there were no differences in the muscarine-induced intracellular Ca²⁺ mobilization in acinar cells or in the M3 receptor and AQP5 expression levels in the salivary glands between the sham and the periodontitis model. Following removal of the ligature, differences in the weights of salivary glands and pilocarpine-induced salivary secretion between the sham and the periodontitis model animals were not found.ConclusionThese results suggest that experimental periodontitis leads to hyposalivation and that relief from it improves salivary function. It is likely that lower levels of salivary secretion are caused by the decrease of functional acinar cells in salivary glands in the experimental periodontitis model, and the bilateral gland effects in the unilateral periodontitis model are caused by systemic rather than by local effects.     

Development of rampant dental caries, and composition of plaque fluid and saliva in irradiated primates

Abstract Co-60 gamma irradiation of the salivary glands of Macaca mulata monkeys fed a cariogenic diet led to the rapid onset of dental caries resembling that in irradiated human patients. Plaque fluid and saliva were sampled from irradiated monkeys, nonirradiated controls and a group of animals fed a noncariogenic diet in order to look for changes which might occur in inorganic composition related to the caries development and to dietary differences. Salivary calcium and phosphate levels were not markedly changed after irradiation: iodide levels were raised, while thiocyanate levels fell. In plaque fluid, calcium concentrations were not affected by irradiation, but were higher in animals fed a noncariogenic diet. Phosphate levels were higher with a cariogenic diet and further increased in irradiated animals. Magnesium levels were occasionally higher than those of calcium. Other differences in plaque fluid composition may be related to secondary effects of the concomitant gingival disease. The results do not point clearly at a specific change in the quality of the saliva produced by the residual gland tissue after irradiation which precipitates the rampant caries. II is more likely that the great reduction in the quantity of saliva with its protective constituents is responsible.     

Control of amylase secretion in the rat parotid gland during feeding.

The object was to determine the relative importance of the sympathetic and parasympathetic innervation of the rat parotid gland in (a) the secretion of amylase during natural feeding (b) the synthesis of amylase during fasting and (c) the production of saliva.Under Avertin anaesthesia, the preganglionic cervical sympathetic or auriculo-temporal nerve was sectioned on the right. Glands on the left acted as controls. Amylase was determined in gland homogenates prepared in aqueous Triton X-100. Sympathectomy markedly prevented the amylase depletion seen in control glands after $\text{1–1}\text{1}\text{2}\text{hr}$ feeding in previously fasted animals, but did not impair resynthesis during fasting. Parasympathectomy also restricted amylase release during feeding, but to a smaller extent. This finding was attributed to the large reduction in salivary secretion rate. Sympathectomy did not reduce flow-rates in response to gustatory stimulation in conscious rats.A technique was developed which allowed saliva to be collected during feeding. Although Sympathectomy reduced the amylase concentration in saliva, the secretion of amylase under these conditions seemed less dependent upon an intact sympathetic innervation than in the gland analyses. The most probable explanation for this is that in rats with cannulated ducts the pattern of eating might be different from normal because of a drying of the mouth and discomfort when chewing and also that the duration of feeding was short.     

Salivary gland tumours: 25 years of experience from a single institution in Croatia

IntroductionThe aim of this study was to determine the types, frequency, distribution, and demographic characteristics of salivary gland tumours in a large representative sample.Patients and methodsWe retrospectively analysed the medical records of 779 patients with tumours of the salivary glands surgically treated from 1985 to 2009 at a single institution.ResultsThere were 500 benign and 279 malignant tumours. The average age of patients with benign tumours was 50 years and of malignant salivary gland tumours 56 years. No differences in age and incidence of tumours existed between males and females. The majority of the tumours occurred in the parotid gland (509), followed by the minor salivary glands (212), the submandibular gland (51) and lastly, the sublingual gland (7). Minor salivary gland tumours occurred most frequently on the palate, the pleomorphic adenoma being the most frequent benign tumour type and the adenoid cystic carcinoma being the commonest malignant tumour. Tumours of the sublingual gland were rare, but all were malignant. Malignant tumours were more common in the minor salivary glands and the submandibular gland.ConclusionThis large study of salivary gland tumours in Croatia could improve our understanding of the significant differences in the global distribution of salivary gland tumours which have been reported.     

Unilateral maxillary molar extraction influences AQP5 expression and distribution in the rat submandibular salivary gland

ObjectiveMastication has been regarded as a crucial factor for maintaining the morphology and function of secretion in salivary glands. Although it is known that occlusion affects mastication, the detailed process for how occlusal changes affect the secretory function of salivary glands is still unknown. Aquaporin 5 (AQP5) is a membrane protein that forms water channels, and plays an important role in water transport. In this study, we investigated the structural changes and alterations in the expression and distribution of AQP5 in the rat submandibular salivary gland (SMG) under occlusal hypofunction after unilateral molar extraction.MethodsSeven-week-old male Wistar rats (n = 36) were used in the study. In the experimental group, all of the right maxillary molars were extracted. Rats with no molar extraction were used as the control group. The rats were euthanized at 7, 14 or 28 days after the procedure, and the right SMGs were isolated and subjected to histological analyses. The expression and distribution of AQP5 were detected by immunohistochemistry.ResultsMorphological analyses revealed hypertrophic changes in the acinar cells in the experimental group. Immunohistochemical staining of AQP5 was detected in the apical membrane (APM) and intercellular secretory canaliculi of acinar cells in both groups. On the other hand, the AQP5 expression in the APM and intercellular secretory canaliculi of acinar cells was less prominent in the experimental group than in the control group.ConclusionsThe present findings suggest that unilateral molar extraction has significant influences on the function of water transport in the rat SMG.     

Long- and short-term diabetes mellitus type 1 modify young and elder rat salivary glands morphology

ObjectiveIn this study we performed a temporal analysis of the effects of Diabetes Mellitus on morphology and laminin deposition in salivary glands of young (2 months-old) and aging (12 months-old) male Wistar rats, using immunohistochemistry.Materials and methodsThe animals were divided in control and diabetic (Streptozotocin induced) groups and euthanized after short and long-term diabetes induction.ResultsShort-term induction led to vacuolization of parotid acinar cells and increased laminin deposition in both animal ages. In young rats, no difference was observed between short or long-term diabetes regarding laminin deposition, but parotid acinar cells vacuolization was more discrete after long-term diabetes. A slight decrease of submandibular gland convoluted granular ducts was observed in young and elder diabetic animal ages. In diabetic aging rats was observed an increase of laminin content only in the parotid gland.ConclusionsThese results suggest that some Diabetes Mellitus effects on salivary glands are not progressive over time, possibly due to the existence of adaptive mechanisms in response to chronic hyperglycemia. They also show that the duration of the disease was more relevant to the morphological effects than the age, although it is known that aging per se affects salivary gland morphology and function.     

Hypertriglyceridemia-induced brain-derived neurotrophic factor in rat submandibular glands

ObjectivesSalivary glands produce brain-derived neurotrophic factor (BDNF), which increases plasma BDNF content. Salivary BDNF influences the hippocampus and enhances anxiety-like behaviors. Dyslipidemia affects the brain, promoting depression and anxiety-like behaviors. This study was performed to investigate whether hypertriglyceridemia influences salivary BDNF expression.MethodsHypertriglyceridemia was induced in rats by high-fat diet intake for 10 weeks. BDNF protein levels in the saliva and submandibular glands were measured using enzyme-linked immunosorbent assay (ELISA). Bdnf mRNA levels in the submandibular gland were determined using real-time polymerase chain reaction.ResultsA hypertriglyceridemia rat model was established. Body weight did not differ between the control and hypertriglyceridemia groups. Bdnf mRNA and protein expression was increased in the submandibular gland in the hypertriglyceridemia group compared to the control group. BDNF expression was also significantly increased in the saliva of the hypertriglyceridemia group.ConclusionsThis is first study to show that hypertriglyceridemia induces BDNF expression in the rat submandibular gland and suggests that salivary BDNF is associated with lipid metabolism.     

Histamine deficiency inhibits lymphocyte infiltration in the submandibular gland of aged mice via increased anti-aging factor Klotho

ObjectivesHistidine decarboxylase (HDC), a histamine synthase, is expressed in various tissues and is induced by proinflammatory cytokines such as TNFα. As they age, C57BL/6 mice show auto-antibody deposition and lymphocyte infiltration into various tissues, including salivary glands. However, the mechanism underlying cell infiltration and the change in HDC expression in salivary glands with aging remain unclear. Thus, we aimed to elucidate the relationship between histamine and inflammaging.MethodsWe investigated the change in histology and HDC expression in the major salivary glands (parotid, submandibular, and sublingual) of 6-week- and 9-month-old wild-type mice. We also determined the histological changes, cytokine expression, and anti-aging factor Klotho in the salivary glands of 9-month-old wild-type and HDC-deficient (HDC-KO) mice.ResultsCell infiltration was observed in the submandibular gland of 9-month-old wild-type mice. Although most cells infiltrating the submandibular glands were CD3-positive and B220-positive lymphocytes, CD11c-positive and F4/80-positive monocyte lineages were also detected. HDC, TNFα, and IL-1β mRNA expression increased in the submandibular gland of 9-month-old wild-type mice. The expression of PPARγ, an anti-inflammatory protein, declined in 9-month-old wild-type mice, and Klotho expression increased in 9-month-old HDC-KO mice. Immunohistochemistry showed that Klotho-positive cells disappeared in the submandibular gland of 9-month-old wild-type mice, while Klotho was detected in all salivary glands in HDC-KO mice of the same age.ConclusionOur findings demonstrate the multifunctionality of histamine and can aid in the development of novel therapeutic methods for inflammatory diseases such as Sjogren's syndrome and age-related dysfunctions.     

Establishment of ex vivo mucocele model using salivary gland organ culture

A mucocele is a common lesion originating from the minor salivary glands and frequently seen in children. For this study, we established an ex vivo mucocele model using a mouse salivary gland organ culture method.ResultsFirst, medium from the upper portion of salivary gland organ cultures was either removed or not, then culturing was continued for 10 days. After that 10-day period, 13 of 21 specimens (61.9%) in the medium removed group showed mucocele-like mucus restoration, while only 1 of 15 (6.7%) in the non-medium removed group showed restoration. Next, we examined mucocele type in the ex vivo salivary gland organ cultures and found mucous retention type mucocele formation in only the main duct of most of the cultures. Other types were observed in the main excretory and intercalated ducts, but not exclusively in the intercalated duct. We also investigated the effect of duct cutting on mucocele recrudescence. Mucoceles that developed in the cultures were cut with stainless needles under a stereomicroscope and mucus was promptly discharged. At 7 days after duct cutting, 5 of 19 specimens (26.3%) showed recrudescence mucus retention.ConclusionsThis is the first report of establishment of an ex vivo pathogenic condition for examination of salivary glands. Our model may be useful to establish mucocele treatment options including drug screening and surgical procedures.