Altered glycogen metabolism in the submandibular and parotid salivary glands of rats with streptozotocin-induced diabetes

Effect of Tungstate Administration on the Lipid Peroxidation and Antioxidant Parameters in Salivary Glands of STZ-Induced Diabetic Rats

Sodium tungstate is an alternative to reduce hyperglycemia for the treatment of diabetes. In previous work, we showed that the administration of sodium tungstate increased the specific activity of salivary amylase in the parotid gland. Here, we investigated the effect of the administration of sodium tungstate on the lipid peroxidation and some antioxidant parameters in the submandibular (SM) and parotid (PA) salivary glands of streptozotocin (STZ)-induced diabetic rats. Thirty-two male Wistar rats were divided into four groups (n = 8, each): control (C), control treated with sodium tungstate (CT), diabetic (D), and diabetic treated with sodium tungstate (CT). Sodium tungstate (2 mg/ml) was administered to the STZ-induced diabetic rats for 15 days. Malondialdehyde (MDA), reduced (GSH) and oxidized (GSSG) glutathione, and blood glucose concentrations were quantified. In addition, superoxide dismutase (SOD) and catalase (CAT) activities were assessed. Results revealed that diabetes caused an increase in MDA concentration in both glands, a reduction in the SOD activity in SM, and an increase in catalase activity in PA glands. Administration of sodium tungstate reduced the blood glucose levels and normalized the SOD activity in the SM and MDA levels in both glands of the STZ-induced diabetic rats. Catalase activity was increased in PA glands of diabetic and tungstate-treated animals (p < 0.05). The GSH/GSSG ratio was increased in SM glands of tungstate-treated animals (p < 0.05). Overall, the reduction of hyperglycemia by sodium tungstate reduced lipid peroxidation and caused alterations in the antioxidant system in the salivary glands of STZ-induced diabetic rats.

Effect of vitamin C and E on oxidative stress and antioxidant system in the salivary glands of STZ-induced diabetic rats

OBJECTIVE

We examined the effects of vitamin C and E supplementation in the prevention of oxidative stress in the salivary glands of STZ-induced diabetic rats.

DESIGN

Forty-eight male Wistar rats were divided into six groups (n = 8 in each): control (C), control supplemented with vitamin C (Cvc) and E (Cve), diabetic (D), and diabetic supplemented with vitamin C (Dvc) and E (Dve). Vitamin C (150 mg/kg) and E (300 mg/kg) were daily administered for 21 days. Serum ascorbic acid and α-tocopherol levels were quantified. Glandular levels of hydrogen peroxide (H₂O₂), superoxide anion (O₂^-), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), malondialdehyde (MDA) and the total antioxidant status (TAS) were estimated.

RESULTS

Vitamin C and E levels were reduced in D group. Vitamin C decreased the levels of O₂^- in the salivary gland of diabetic rats. Vitamin E increased the concentration of O₂^- in PA gland of diabetic animals. In the SM gland of the diabetic group, MDA, SOD, GPx and TAS increased. Dve presented reduced SOD activity and increased GR, GPx, and MDA. Dve increased GPx, Gr and TAS levels. In the PA gland, MDA, SOD, CAT, GPx, GR, and TAS were similar in C and D. TAS, SOD, CAT, GPx, and GR increased in Dvc. Vitamin E supplementation resulted in increased MDA and CAT levels and reduced SOD activity.

CONCLUSION

In the SM glands of the diabetic rats, vitamin C supplementation improved the antioxidant system, while vitamin E acted as pro-oxidant.

Salivary gland metabolism in an animal model of chronic kidney disease

OBJECTIVE

The aim of this study was to determine the effects of experimental CKD into the metabolism of parotid and submandibular glands of rats. CKD was induced by 5/6 nephrectomy.

DESIGN

Serum analyses of BUN (Blood Urea Nitrogen) and creatinine concentrations were performed. Major salivary glands metabolism was investigated in vivo, both at rest and during salivary stimulation conditions by NMR isotopomer analysis, using [U-¹³C]glucose as metabolic tracer.

RESULTS

CKD increases BUN and serum creatinine concentrations (p < 0.001). Multiple metabolic alterations were detected in the parotid glands of this animal model, including decreased concentrations of alanine (p < 0.05) and creatine (p < 0.05) and increased lactate/alanine ratios (p < 0.05). The salivary stimulus fostered accumulations of acetate at both analyzed glands of the CKD model (p < 0.05), indicative of disruption of the oxidative metabolic process.

CONCLUSIONS

Experimental CKD induced by 5/6 nephrectomy altered the parotid salivary gland function, since glucose metabolism is clearly affected after stimulation for salivation in this gland.

Postnatal changes in the development of rat submandibular glands in offspring of diabetic mothers: Biochemical, histological and ultrastructural study

Development and maturation of submandibular salivary glands are influenced by intrauterine diabetic environment. Several studies investigated the effects of diabetes on the salivary glands. However, the effects of maternal diabetes on the submandibular glands of the offspring was not properly examined. Therefore, the present study was designed to describe the changes in the development of the submandibular glands of the offspring of diabetic mothers. The submandibular glands of the offspring of Streptozotocin (STZ)-induced diabetic female rats were examined at two and four weeks after birth. Detection of mRNA demonstrated that maternal diabetes affects the level of different indicators. The reduction of expression of epidermal growth factor (EGF); a protein mitogen, cytokeratin 5 (CK5); an epithelial cell progenitor, CK7 and aquaporin 5 (AQP5); differentiation markers and B cell lymphoma 2 (Bcl2); an antiapoptotic marker were found. Increase in Bcl2-associated X protein (Bax); an apoptotic marker was detected. These changes indicate their effects on saliva secretion, glands tumorigenesis, growth of normal oral flora and oral microbes, with decreased protein synthesis and production of xerostomia and dental caries. Loss of normal glandular architecture, significant increase in fibrosis, by the detection of collagen fibers, and stagnation of secretory granules were found with atrophic changes in the acinar cells. Marked defect of polysaccharides in the acinar cells, denoting functional changes, was manifested by significant reduction of the intensity of periodic acid-Schiff (PAS) reaction. The positive immunoreactivity of caspase-3, denoting cellular apoptosis, and minimal reaction of alpha-smooth muscle actin (α SMA) and proliferating cell nuclear antigen (PCNA) were evident in the offspring of diabetic mothers. We conclude that maternal diabetes produces degenerative effects in the structure and function of the submandibular salivary glands of the offspring, reflecting possible influences on their secretory activity affecting oral and digestive health.

Low-power laser irradiation decreases lipid droplet accumulation in the parotid glands of diabetic rats

Lipid droplet accumulation has been related to salivary gland hypofunction in diabetes. In this study, the effect of laser irradiation on the parotid glands (PGs) of diabetic rats was analyzed with regard to its effect on lipid droplet accumulation, intracellular calcium concentration and calmodulin expression. The animals were distributed into 6 groups: D0, D5, D20 and C0, C5, C20, for diabetic (D) and control animals (C), respectively. Twenty-nine days following diabetes induction, PGs of groups D5 and C5; D20 and C20 were irradiated with 5 and 20 J/cm² of a red diode laser at 100 mW, respectively. After 24 hours, PGs were removed for histological, biochemical, and western blotting analysis. The diabetic animals showed lipid droplet accumulation, which was decreased after irradiation. Ultrastructurally, the droplets were nonmembrane bound and appeared irregularly located in the cytoplasm. Moreover, diabetic animals showed an increased intracellular calcium concentration. In contrast, after laser irradiation a progressive decrease in the concentration of this ion was observed, which would be in agreement with the results found in the increased expression of calmodulin in D20. These data are promising for using laser to decrease lipid droplet accumulation in PGs, however, more studies are necessary to better understand its mechanisms. Micrographs showing decreased lipid accumulation after laser irradiation in light micrographs (LM), and morphology of lipid droplet in transmission electron microscopic (TEM). LM: (A) PGs from nondiabetic rats that did not receive Laser irradiation (LI), (B) PGs from nondiabetic rats that received a dose of 20 J/cm² , (C) lipid accumulation (arrows) in the secretory cells from diabetic rats that did not receive irradiation, (D) reduction of lipid accumulation in the secretory cells from diabetic rats that received a dose of 20 J/cm² and TEM: (E) scale bar = 5 μm, (F) scale bar = 1 μm, and (G) scale bar = 0.5 μm.

Sphingolipids metabolism in the salivary glands of rats with obesity and streptozotocin induced diabetes

Diabetes is considered a major public health problem affecting millions of individuals worldwide. Remarkably, scientific reports regarding salivary glands sphingolipid metabolism in diabetes are virtually non‐existent. This is odd given the well‐established link between the both in other tissues (e.g., skeletal muscles, liver) and the key role of these glands in oral health preservation. The aim of this paper is to examine sphingolipids metabolism in the salivary glands in (pre)diabetes (evoked by high fat diet feeding or streptozotocin). Wistar rats were allocated into three groups: control, HFD‐, or STZ‐diabetes. The content of major sphingolipid classes in the parotid (PSG) and submandibular (SMSG) glands was assessed via chromatography. Additionally, Western blot analyses were employed for the evaluation of key sphingolipid signaling pathway enzyme levels. No changes in ceramide content in the PSG were found, whereas an increase in ceramide concentration for SMSG of the STZ group was observed. This was accompanied by an elevation in SPT1 level. Probably also sphingomyelin hydrolysis was increased in the SMSG of the STZ‐diabetic rats, since we observed a significant drop in the amount of SM. PSG and SMSG respond differently to (pre)diabetes, with clearer pattern presented by the later gland. An activation of sphingomyelin signaling pathway was observed in the course of STZ‐diabetes, that is, metabolic condition with rapid onset/progression. Whereas, chronic HFD lead to an inhibition of sphingomyelin signaling pathway in the salivary glands (manifested in an inhibition of ceramide de novo synthesis and accumulation of S1P).

Metabolic remodeling triggered by salivation and diabetes in major salivary glands

The metabolic profile of major salivary glands was evaluated by ¹³ C nuclear magnetic resonance isotopomer analysis (¹³ C NMR-IA) following the infusion of [U-¹³ C]glucose in order to define the true metabolic character of submandibular (SM) and parotid (PA) glands at rest and during salivary stimulation, and to determine the metabolic remodeling driven by diabetes. In healthy conditions, the SM gland is characterized at rest by a glycolytic metabolic profile and extensive pyruvate cycling. On the contrary, the PA gland, although also dominated by glycolysis, also possesses significant Krebs' cycle activity and does not sustain extensive pyruvate cycling. Under stimulation, both glands increase their glycolytic and Krebs' cycle fluxes, but the metabolic coupling between the two pathways is further compromised to account for the much increased biosynthetic anaplerotic fluxes. In diabetes, the responsiveness of the PA gland to a salivary stimulus is seriously hindered, mostly as a result of the incapacity to burst glycolytic activity and also an inability to improve the Krebs' cycle flux to compensate. The Krebs' cycle activity in the SM gland is also consistently compromised, but the glycolytic flux in this gland is more resilient. This diabetes-induced metabolic remodeling in SM and PA salivary glands illustrates the metabolic need to sustain adequate saliva production, and identifies glycolytic and oxidative pathways as key players in the metabolic dynamism of salivary glands.

Lithium Induces Glycogen Accumulation in Salivary Glands of the Rat

Lithium is administered for the treatment of mood and bipolar disorder. The aim of this study was to verify whether treatment with different concentrations of lithium may affect the glycogen metabolism in the salivary glands of the rats when compared with the liver. Mobilization of glycogen in salivary glands is important for the process of secretion. Two sets of experiments were carried out, that is, in the first, the rats received drinking water supplemented with LiCl (38,25 and 12 mM of LiCl for 15 days) and the second experiment was carried out by intraperitoneal injection of LiCl solution (12 mg/kg and 45 mg LiCl/kg body weight) for 3 days. The active form of glycogen phosphorylase was not affected by treatment with LiCl considering the two experiments. The active form of glycogen synthase presented higher activity in the submandibular glands of rats treated with 25 and 38 mM LiCl and in the liver, with 25 mM LiCl. Glycogen level was higher than that of control in the submandibular glands of rats receiving 38 and 12 mM LiCl, in the parotid of rats receiving 25 and 38 mM, and in the liver of rats receiving 12 mM LiCl. The absolute value of glycogen for the submandibular treated with 25 mM LiCl, and the liver treated with 38 mM LiCl, was higher than the control value, although not statistically significant for these tissues. No statistically significant difference was found in the submandibular and parotid salivary glands for protein concentration when comparing experimental and control groups. We concluded that LiCl administered to rats influences the metabolism of glycogen in salivary glands.

Laser irradiation affects enzymatic antioxidant system of streptozotocin-induced diabetic rats

The aim of the present study was to analyze the effect of low-power laser irradiation in the antioxidant enzymatic system of submandibular (SMG) and parotid (PG) salivary glands of streptozotocin-induced diabetic rats. The animals were randomly divided into six groups: three diabetic groups (D0, D5, and D20) and three non-diabetic groups (C0, C5, and C20), according to laser dose received (0, 5, and 20 J/cm(2), respectively). Areas of approximately 1 cm(2) were demarcated in the salivary glands (each parotid and both submandibular glands) and after irradiated according to Simões et.al. (Lasers Med Sci 24:202-208, 2009). A diode laser (660 nm/100 mW) was used, with laser beam spot of 0.0177 cm(2). The group treated with 5 J/cm(2) laser dose was subjected to irradiation for 1 min and 4 s (total irradiation time) and the group treated with 20 J/cm(2) laser dose was subjected to irradiation for 4 min and 16 s. Twenty-four hours after irradiation the animals were euthanized and the salivary glands were removed for biochemical analysis. The total antioxidant values (TA), the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase enzymes were determined. SOD and CAT activities, as well as TA were higher in SMG of irradiated diabetic rats. However, in SMG of non-diabetic rats, laser irradiation decreased TA values and led to an increase in the CAT activity. In addition, there was a decrease in the activity of CAT in PG of diabetic and non-diabetic animals after laser irradiation. According to the results of the present study, low-power laser irradiation can affect the enzymatic antioxidant system of salivary glands of streptozotocin-induced diabetic rats.

Antioxidant enzymatic defense in salivary glands of streptozotocin-induced diabetic rats: a temporal study

Hyperglycemia induces overproduction of superoxide and it is related to diabetic complications. In this study, we analyzed the antioxidant enzymatic defense and the lipid peroxidation of rat salivary glands in six different periods of diabetic condition. Ninety-six rats were divided into 12 groups: C7/14/21/28/45/60 (non-diabetic animals) and D7/14/21/28/45/60 (diabetic animals). Diabetes was induced by streptozotocin and the rats were euthanized after 7, 14, 21, 28, 45, or 60 days. Their parotid (PA) and submandibular (SM) glands were removed soon after the sacrifice and the total protein and malondialdehyde (MDA) concentrations, as well as, the superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activities were determined. Twenty-one days after the diabetes induction, the SM glands showed an increase in SOD, CAT, and GPx activities, as well as, MDA concentration. Concerning the PA glands, an increase in the CAT activity and MDA content was observed throughout the observation period. The results suggest that diabetes can cause alterations on the salivary glands and that PA and SM glands react differently when exposed to diabetes condition. However, no impairment of antioxidant system was observed in the group whose diabetic condition had been induced 60 days earlier, herein named 60-day group.

Astaxanthin restores the enzymatic antioxidant profile in salivary gland of alloxan-induced diabetic rats

OBJECTIVE

To evaluate the effect of astaxanthin on antioxidant parameters of salivary gland from diabetic rats. The hypothesis of the study was whether the supplementation of diabetic rats with astaxanthin might antagonize, or at least prevent, the defect in their antioxidative status.

DESIGN

Wistar rats (n=32) were divided in 4 groups: untreated control, treated control, untreated diabetic and treated diabetic rats. Astaxanthin (20mg/kg body weight) was administered daily by gavage for 30 days. On day 23, diabetes was induced by injection of alloxan (60 mg/kg body weight). After 7 days of diabetes induction, the rats were killed and submandibular and parotid removed. Superoxide dismutase (SOD), catalase, glutathione peroxidase and reductase activities and the content of thiol groups were determined. Data were compared by ANOVA and the Tukey test (p<0.05).

RESULTS

Diabetes caused a reduction of SOD, and thiol content and increase of catalase and glutathione peroxidase activities of submandibular gland whilst in the parotid gland diabetes caused an increase of thiol content and no effect in the antioxidant system. The astaxanthin restores the enzymatic activities in the salivary gland, however does not prevent its oxidative damage.

CONCLUSION

The submandibular gland presented more susceptibility to oxidative alterations induced by diabetes. Astaxanthin presented a positive effect on the oxidative protection of the salivary gland from diabetic rats.

Diode laser decreases the activity of catalase on submandibular glands of diabetic rats

OBJECTIVE

The aim of this study was to evaluate the effect of laser irradiation on the amylase and the antioxidant enzyme activities, as well as on the total protein concentration of submandibular glands (SMG) of diabetic and non-diabetic rats.

BACKGROUND

Laser has been used aiming to improve some biochemical alterations observed in salivary glands of streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

Ninety-six female rats were divided into eight groups: D0, D5, D10, and D20 (diabetic animals), and C0, C5, C10, and C20 (non-diabetic animals), respectively. Diabetes was induced by administering streptozotocin and confirmed later by the glycemia results. Twenty-nine days after diabetes induction, the SMG of groups D5 and C5, D10 and C10, and D20 and C20 were irradiated with 5, 10, and 20 J/cm(2), respectively. A diode laser (660 nm/100 mW) was used. On the day after irradiation, the rats were euthanized and the SMG were removed. Catalase, peroxidase, and amylase activities, as well as protein concentration, were assayed.

RESULTS

Diabetic rats without irradiation (D0) showed higher catalase activity (p < 0.05) when compared to C0 (0.16 +/- 0.05 and 0.07 +/- 0.01 U/mg protein, respectively). However, laser irradiation of 5, 10, and 20 J/cm(2) reduced the catalase activity of diabetic groups (D5 and D20) to non-diabetic values (p > 0.05).

CONCLUSION

Based on the results of this study, laser irradiation decreased catalase activity in diabetic rats' SMG.

Ionic and histological studies of salivary glands in rats with diabetes and their glycemic state after laser irradiation

OBJECTIVES

To evaluate the effect of laser irradiation (LI) on the glycemic state and the histological and ionic parameters of the parotid and submandibular glands in rats with diabetes.

METHODS

One hundred twenty female rats were divided into eight groups. Diabetes was induced by administration of streptozotocin and confirmed later according to results of glycemia testing. Twenty-nine days after the induction, the parotid and submandibular glands of the rats were irradiated with 5, 10, and 20 J/cm2 using a laser diode (660 nm/100 mW) (without diabetes: C5, C10, and C20; with diabetes: D5, D10, and D20, respectively). On the following day, the rats were euthanized, and blood glucose determined. Histological and ionic analyses were performed.

RESULTS

Rats with diabetes without irradiation (D0) showed lipid droplets accumulation in the parotid gland, but accumulation decreased after 5, 10, and 20 J/cm2 of laser irradiation. A decrease in fasting glycemia level from 358.97+/-56.70 to 278.33+/-87.98 mg/dL for D5 and from 409.50+/-124.41 to 231.80+/-120.18 mg/dL for D20 (p<0.05) was also observed.

CONCLUSION

LI should be explored as an auxiliary therapy for control of complications of diabetes because it can alter the carbohydrate and lipid metabolism of rats with diabetes.

Alteration of Ca(2+)-ATPase activity in the homogenate, plasma membrane and microsomes of the salivary glands of streptozotocin-induced diabetic rats

Diabetes has been implicated in the dryness of the mouth, loss of taste sensation, sialosis, and other disorders of the oral cavity, by impairment of the salivary glands. The aim of the present study was to examine the plasma membrane, microsomal, and homogenate Ca(2+)-ATPase activity in the rat submandibular and parotid salivary glands of streptozotocin-induced diabetes. We have also examined the influence of the acidosis state on this parameter. Diabetes was induced by an intraperitoneal injection of streptozotocin and acidosis was induced by daily injection of NH(4)Cl. At 15 and 30 days after diabetes induction, the animals were euthanized and the submandibular and parotid salivary glands were removed and analyzed. Ca(2+)-ATPase (total, independent, and dependent) was determined in the homogenate, microsomal, and plasma membranes of the salivary glands of diabetic and control rats. Calcium concentration was also determined in the glands and showed to be higher in the diabetic animals. Ca(2+)-ATPase activity was found to be reduced in all cell fractions studied in the diabetic animals compared with control. Similar results were obtained for the submandibular salivary glands of acidotic animals; however in the parotid salivary glands it was found an increase in the enzyme activity.

Vascular endothelial growth factor expression (VEGF) in salivary glands of diabetic rats

This study is aimed at evaluating vascular endothelial growth factor (VEGF) expression in the salivary glands of diabetic rats. Our study was carried out on 1 group of male Wistar rats and 1 group of male Bio Breeding Wistar (BB/W) pre-diabetic rats. The first group (control) was composed of 11 rats (4 months old), and the other (test) of 11 rats (4 months old) which showed diabetes at day 85 of life. This kind of diabetes can be compared to human diabetes mellitus type 1. The submandibular glands were removed and processed for immunohistochemical analysis of VEGF. Diabetes increased salivary gland VEGF expression in the rats. The tissues analyzed (vascular endothelium, ductal endothelium, mucinous glands) always expressed VEGF, thus demonstrating that not only vascular endothelial cells, but also the other elements evaluated, have a role in the neoangiogenesis process. In both control and diabetic rats, the VEGF expression was constantly negative only in serous acini; thus demonstrating that serous acini are not involved in the neoangiogenetic processes. The vascular growth is a fundamental part of normal salivary gland development, therefore we speculate that strategies aimed at preservation or promotion of salivary gland VEGF expression may mitigate or attenuate diabetic-induced gland microvascular injury.