A tentative model for (D)-glucose turnover in human saliva.

OBJECTIVE: The aim of the present study is to propose a tentative model for d-glucose turnover in human saliva. The whole saliva and the saliva from parotid and submandibular/sublingual glands were collected by use of the Salivette™. RESULTS: The saliva glucose concentration was measured by the hexokinase method, saliva bacteria glycolysis by use of d-[5-(3)H] glucose, and the saliva ATP content by the luciferase method. The concentration of glucose amounted to 43.9±6.3 (n=29), 197.5±17.3 (n=29), 104.0±12.4 (n=27) µM in whole saliva, parotid saliva and submandibular/sublingual saliva, respectively. The rate of d-glucose utilization by oral bacteria at a physiological concentration of d-glucose in saliva (50µM) was estimated at 0.047±0.003 (n=11) nmol/min per 10(6) bacteria. Unstimulated salivary d-glucose turnover rate, as calculated from the amount of glucose secreted in saliva which comes from parotid and submandibular and sublingual glands represented 214.6±19.1%/min. In order for salivary d-glucose production to match bacterial utilization of the hexose, the total number of oral bacteria was estimated at about 2.0×10(9) bacteria, in fair agreement with previously published data. CONCLUSION: This study thus provides support for a tentative model for d-glucose turnover in human saliva.

Comparison of GLUT1, GLUT2, GLUT4 and SGLT1 mRNA expression in the salivary glands and six other organs of control, streptozotocin-induced and Goto-Kakizaki diabetic rats.

BACKGROUND/AIMS: The expression and localization of several distinct glucose transporters (GLUT1, GLUT2, GLUT4, and SGLT1) was recently characterized in the parotid gland of normal rats by quantitative real-time PCR analysis, immunohistochemistry and Western blotting. The major aims of the present study was to compare the mRNA expression of these glucose transporters in both the parotid gland and submaxillary gland of control rats, streptozotocin-induced diabetic rats and hereditarily diabetic Goto-Kakizaki rats. METHODS: Quantitative real-time PCR analysis was performed in the parotid and submaxillary salivary glands and, for purpose of comparison, also in the heart, kidney, liver, lung, muscle and pancreas from control animals and either streptozotocin-treated or Goto-Kakizaki rats. RESULTS: The expression of GLUT4, but not GLUT1 or SGLT1, mRNA was decreased in the diabetic rats. The results also allow comparing both the mRNA expression level of the four glucose transporters in salivary glands and six other organs, and the diabetes-induced changes in such an expression in distinct locations. CONCLUSION: The mRNA expression of the insulin-dependent GLUT4 transporter was the sole to be significantly decreased in the salivary glands of diabetic animals. The possible consequence of such a decrease in terms of the control of salivary glucose concentration requires further investigation.

Uptake and efflux of 3-O-methyl-D-glucose in rat parotid cells.

In the framework of recent investigations on the regulation of D-glucose production by salivary glands, the aim of the present study was to compare the uptake of 3-O-[14C]methyl-D-glucose by rat parotid cells over a 6-min incubation period at 37°C to its efflux from prelabelled parotid cells, also incubated for 6 min at 37°C. It was first assessed that the intracellular 3HOH water space, whether expressed in absolute terms or relative to the total 3HOH distribution space, is not significantly different between parotid cells obtained from either control rats or streptozotocin-induced diabetic rats. In the control rats, the uptake of 3-O-[14C]methyl-D-glucose corresponded, following correction for extracellular contamination, to a mean distribution space of 0.44±0.05 nl/103 cells, representing 29.8±3.4% of the intracellular water space. The efflux of 3-O-[14C]methyl-D-glucose from prelabelled parotid cells, expressed relative to their initial radioactive content, averaged 82.9±4.8 and 84.1±2.5% in control and diabetic rats, respectively. These findings suggest that the increased production of salivary D-glucose in diabetic subjects may be attributable to hyperglycemia, rather than to any major perturbation of the intrinsic processes involved, at least in parotid cells, in hexose handling.

Biodentine used as a pulp-capping agent in primary pig teeth.

PURPOSE: The purpose of this study was to assess and compare, in primary pig teeth, the pulp response after a pulpotomy using either Biodentine (a new tricalcium-silicate cement), white mineral trioxide aggregate (WMTA), or formocresol (FC) and repeat the same after direct pulp capping using either Biodentine, WMTA, or calcium hydroxide. METHODS: A total of 180 primary teeth from 9 healthy 4-month-old female pigs were divided into 3 experimental periods (7, 28, and 90 days) for each material used for the pulpotomy and direct pulp capping treatments. Seven, 28, and 90 days later, the animals were euthanized and the specimens were prepared for histological examination and evaluation. The data collected from the histological examinations were statistically analyzed using Kruskal-Wallis and Dunn multiple comparison tests. RESULTS: In pulpotomy groups, there was a significant difference between Biodentine and WMTA vs FC in terms of inflammatory cell response and hard tissue formation. In direct pulp capping groups, there was only a significant difference between Biodentine and calcium hydroxide in terms of hard tissue formation in a 7-day period. CONCLUSIONS: Biodentine and white mineral trioxide aggregate are both suitable, biocompatible materials for pulp capping in primary teeth of pigs.

Glucose transport by acinar cells in rat parotid glands.

BACKGROUND/AIMS: Salivary glucose is often considered as being from glandular origin. Little information is available, however, on the possible role of glucose transporters in the secretion of the hexose by salivary glands. The major aim of the present study was to investigate the expression and localization of several distinct glucose transporters in acinar cells of rat parotid glands. METHODS: Quantitative real-time PCR analysis, immunohistochemistry and western blotting techniques were used to assess the presence of SGLT1, GLUT1, GLUT2 and GLUT4 in acinar cells of rat parotid glands. RESULTS: Quantitative real-time PCR documented the expression of SGLT1 and GLUT1 in parotid tissues, with a much lower level of GLUT4 mRNA and no expression of GLUT2 mRNA. Western blot analysis revealed the presence of SGLT1, GLUT1 and GLUT4 proteins, but not GLUT2 proteins in the parotid extract. Immunohistochemistry confirmed these findings. SGLT1 was specifically located at the baso-lateral membrane, co-localizing with Na(+)/K(+) ATPase. GLUT1 was found both at the baso-lateral and apical level. GLUT4 appeared to be also located at the baso-lateral level. However, too little GLUT4 was present to allow co-localization labeling. CONCLUSION: Based on these findings, a model is proposed for the transport of glucose into the acinar cells and thereafter into the acinar lumen.

Salivary glucose concentration and excretion in normal and diabetic subjects.

The present report aims mainly at a reevaluation of salivary glucose concentration and excretion in unstimulated and mechanically stimulated saliva in both normal and diabetic subjects. In normal subjects, a decrease in saliva glucose concentration, an increase in salivary flow, but an unchanged glucose excretion rate were recorded when comparing stimulated saliva to unstimulated saliva. In diabetic patients, an increase in salivary flow with unchanged salivary glucose concentration and glucose excretion rate were observed under the same experimental conditions. Salivary glucose concentration and excretion were much higher in diabetic patients than in control subjects, whether in unstimulated or stimulated saliva. No significant correlation between glycemia and either glucose concentration or glucose excretion rate was found in the diabetic patients, whether in unstimulated or stimulated saliva. In the latter patients, as compared to control subjects, the relative magnitude of the increase in saliva glucose concentration was comparable, however, to that of blood glucose concentration. The relationship between these two variables was also documented in normal subjects and diabetic patients undergoing an oral glucose tolerance test.

Altered fatty acid pattern of phospholipids and triglycerides in the submandibular gland of omega3-depleted rats.

Alteration of the phospholipid (PL) and triglyceride (TG) fatty acid pattern was recently documented in several organs of rats depleted in long-chain polyunsaturated omega3 fatty acid (omega3 rats). This study extends such a knowledge to the submandibular gland. The total PL and TG content of the salivary gland was not different in control and omega3 rats. The sole omega3 fatty acids found in omega3 rats (C22:5omega3 and C22:6omega3) were present at levels 3-12 times lower than in control rats. The C22:5omega3/C22:6omega3 ratio was increased threefold in omega3 rats. The PL and TG C16:0/C16:1omega7 and C18:0/C18:1omega9 ratios were decreased in omega3 rats. The conversion of C18:2omega6 to C20:4omega6 and C22:4omega6 appeared facilitated in the omega3 rats. Some of these rats were injected intravenously, 60-120 min before killing, with either a medium-chain triglyceride:fish oil emulsion or a control medium-chain triglyceride:olive oil emulsion. The former emulsion increased the PL C22:5omega3 and C22:6omega3 content and prevented the age-related decrease in C16:0/C16:1omega7 and C18:0/C18:1omega9 ratios otherwise also recorded in PL. In conclusion, these findings document an increased activity of Delta9-desaturase, a more efficient conversion of C18:2omega6 to its metabolites, and an impaired generation of C22:6omega3 from C22:5omega3 in omega3 rats.

Quantitative and qualitative alterations of intestinal mucins in BioBreeding rats.

In diabetes-prone BioBreeding rats, an enteropathy often precedes the onset of auto-immune insulitis. The present study draws attention to quantitative and qualitative alterations of intestinal mucins in this animal model of type 1 diabetes mellitus. Male and female diabetes-resistant (BBc) and diabetes-prone (BBdp) BioBreeding rats fed, from one to two weeks after weaning onwards, either a plant-based diabetes-promoting diet (NTP) or a hydrolysed casein diabetes-protective diet (HC), were sacrificed at 11-14 weeks of age. Proteins and total mucins, as well as acid and neutral mucins, were measured in a segment of the intestinal tract, located 25-30 cm below the pylorus. No significant difference between BBc and BBdp rats was found when fed the HC diet. However, the NTP diet lowered both total and neutral mucins, whilst failing to affect significantly acidic mucins. The effects of the NTP diet were more pronounced in BBdp rats than in BBc rats. It is speculated that the quantitative and qualitative changes evoked by the NTP diet in BBdp rats may play a role in the alteration of gut permeability found under the same experimental conditions.