Role of GAD peptides p217 and p290 in the repair of INS receptor in salivary tissues of type 1 diabetic mice.

Glutamate decarboxylase or glutamic acid decarboxylase (GAD) is a protein associated with autoimmune diseases, including type-1 diabetes. This disease is primarily associated with the occurrence of a specific isoform: GAD65. Conversely, some specific peptides of this protein may block autoimmunity in diabetes. In this respect, understanding the relationship between GAD and the development of diabetes is important, and it is necessary to understand the role of each GAD peptide to design effective autoimmune diabetes treatments. The purpose of the present study was to analyze the effects of treatment with GAD-derived peptides p217 and p290 on INS receptors in the salivary epithelium of nonobese diabetic (NOD) animals. Three groups of 7 mice each were studied: I, BALB/c mice (control); II, NOD mice; and III, NOD mice treated with peptides p290 and p217. Groups I and II only received buffered saline solution. Glucose levels were measured daily during the 21 days of the experiment. After the study, the animals were euthanized and the parotid and submandibular glands were removed for the analysis of INS-R by fluorescence microscopy. Therapy with two peptides together was associated with reduced glucose levels in NOD mice and intense INS-R expression in both salivary organs. Our approach of combining GAD p217 and p290 peptides contributed to hormonal balance and promoted the repair of INS-R.

Hypoglycemic effects of an aqueous extract of Bauhinia forficata on the salivary glands of diabetic mice.

The objective of this study was to evaluate the salivary glands in diabetic mice, analyzing alterations in the secretory epithelium and interactions with the stromal compartment acquired during a prolonged period of treatment with Bauhinia forficata extract. Female mice were divided into two groups: Nonobese diabetic (NOD) mice treated with Bauhinia forficata (I), and NOD mice not treated with the hypoglycemic agent (II). After treatment, the salivary glands were collected for analysis by transmitted and polarized light microscopy, complemented by three-dimensional analysis of these tissues. The results showed weight loss in animals of group II and weight recovery in treated animals. Glucose levels were elevated in group II, but declined in group I. In the two groups, the salivary glands were characterized by involution of the secretory epithelium, presence of an inflammatory infiltrate and an increase of extracellular fibrillar components. It can be concluded that treatment with Bauhinia forficata reduced glucose levels and contributed to weight recovery in treated animals. However, the observation of tissue destructuring and compromised epithelial-stromal interactions, with consequent impairment of glandular function, demonstrates that Bauhinia forficata exerts an effect on the recovery of body metabolism but this improvement does not influence in the tissue recovery.

Dipeptidyl peptidase IV inhibitor improves the salivary gland histology of spontaneously diabetic mice.

OBJECTIVES: The incretin-based therapy might be effective in patients possessing certain levels of preserved pancreatic beta-cells. However, doubts still exist regarding the efficacy of this atment in the recovery of tissues damaged by type 1 diabetes. Thus, the objective of this study was to evaluate the treatment with MK0431 in salivary glands of spontaneously diabetic mice, focusing mainly on the possible therapeutic and hypoglycaemic effects of this dipeptidyl peptidase IV inhibitor in the recovery of these salivary tissues. METHODS AND RESULTS: Twenty mice were divided into two groups of 10 animals each: group I (NOD diabetic/untreated) and group II (NOD diabetic MK0431/treated). The group II was treated during 4 weeks with MK0431 mixed in the food. The group I was maintained in the same way without receiving, however, any treatment. Glucose levels were monitored during treatment and salivary glands samples were collected at the end of treatment for the histological examination under both transmitted and polarized light microscopy. High glucose levels were observed in untreated animals, while in animals with treatment, reduction of these levels was observed. Tissue restructuring was also observed in animals submitted to therapy with MK0431, mainly in relation to the attempt to extracellular matrix reorganization. CONCLUSIONS: According to results, the treatment with this dipeptidyl peptidase IV inhibitor contributed to the general homeostasis of the organism and to the reestablishment of both epithelial and stromal compartments which were damaged by the hyperglycaemic condition, demonstrating that the incretin-based therapy may be an important complementary treatment for the type 1 diabetic condition.