Background: Diabetes is usually associated with impaired function of salivary glands, by both histolological deterioration and altered salivary composition. Abnormal apoptosis has been recognized in salivary glands of diabetic rats. Amyloidosis constitutes a group of diseases in which proteins deposit in tissues as insoluble fibrils, causing progressive organ dysfunction. Insulin and oral hypoglycemic agents are the widely used in diabetes treatment, but they have undesirable sequelae and fail to completely alter the course of diabetic complications. Cod liver oil (CLO) as an important source of omega-3 (ω-3) fatty acid, has been documented to have a powerful antioxidant effect on several tissues.
Objective: The present study was carried out to study the possible effect of CLO combined with insulin in regeneration of the exceretory duct of sublingual salivary glands in streptozotocin (STZ)-induced diabetic rats.
Design: forty adult male albino rats (200-250 gm) were selected for this study. The animals were randomly divided into four groups (ten rats each): Group I (Control group), Group II (Diabetic untreated group), Group III (Insulin treated group) and Group IV (Cod liver oil - insulin treated group). At the end of the experimental period (four weeks), the rats were killed and the sublingual salivary glands were dissected out. The sections were examined histologically, immunohistochemically, histomorphometrically and by fluorescence staining technique.
Statistical analysis: Data obtained from histomorphometric analysis were statistically described in terms of mean ± standard deviation (± SD).
Results: Histopathologic examination of Group I showed the normal histological features of the gland΄s duct system. Group II revealed disturbed ductal outlines, ill-defined ductal cells boundaries, nuclear changes, ductal cells degeneration and stagnated salivary secretion in the lumina. Moreover apparent decrease, hyalinization and degeneration in the surrounding connective tissue (C.T) stroma; fibroblasts showed signs of degeneration and dilated blood vessels (BVs) with swollen endothelial cells. Group III showed better histological features than those of Group II, while Group IV showed histological features nearly resembling those of the control group (Group I). The least immuno-expression for caspase-3 (apoptosis marker) and the minimum fluorescence with thioflavin-T (amyloidosis marker) stain were demonstrated in Group I, followed by Group IV, then Group III and subsequently Group II. The histomorphometric analysis supported the previous results. On the other hand, Group I showed the least mean area percentage of both caspase-3 immunoreactivity and thioflavin-T fluorescence, followed by Group IV, then Group III and the highest values were for Group II. There was statistically highly significant difference between the studied groups.
Conclusions: Diabetes has deleterious effect on the structure of the exceretory duct of sublingual salivary glands. Moreover, it has a major role in tissue damage through development of amyloidosis. Insulin as a sole treatment, couldn't completely inhibit the complications of diabetes. However, CLO- insulin combination had great potential to minimize the abnormalities caused by diabetes.