Background: The diabetic condition is frequently associated with impaired functions of salivary glands, testified by both morphological deterioration of the gland and by altered salivary composition. Abnormal apoptosis has been implicated in salivary glands of diabetic rat models. Amyloidosis constitutes a group of diseases in which proteins deposit in tissues as insoluble fibrils, causing progressive organ dysfunction. Although insulin and oral hypoglycemic agents are the mainstays of diabetes treatment, they have prominent side effects and fail to alter the course of diabetic complications. Cod liver oil (CLO) is an important source of long-chain omega-3 (ω-3) fatty acids as well as vitamins A, E and D. CLO has antioxidant effect especially on parotid salivary glands.
Objective: The present study was undertaken to investigate the possible role of CLO versus insulin supplementation in enhancement of parotid salivary glands in streptozotocin (STZ)-induced diabetic rats.
Design: Sixty adult male Swiss albino rats (200-250 gm) were selected for this study. The animals were randomly divided into four groups (fifteen rats each): Group I (Control group), Group II (Diabetic untreated group), Group III (Insulin treated group) and Group IV (Cod liver oil treated group). At the end of the experimental period (four weeks), the rats were sacrificed and the parotid 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 parotid gland. Group II revealed apparent reduction in acinar size, ill-defined acinar and ductal cells outlines, nuclear changes, acinar and ductal cells degeneration, lipid droplets, dilatation of the duct system lumina and stagnated salivary secretion in the lumina of striated and excretory ducts. Moreover apparent decrease, hyalinization and degeneration in the fibrous connective tissue (C.T) fibroblasts showing signs of degeneration and dilated blood vessels (BVs) with swollen endothelial cells were noticed. Group III showed better histological features than those of Group II, while Group IV showed histological features resembling nearly those of the control group (Group I). The least immuno-expression for caspase-3 and the minimum fluorescence with thioflavin-T stain were demonstrated in Group I, followed by Group IV, then Group III and subsequently Group II. The histomorphometric analysis supported the previous results as Group I showed the highest mean acinar area fraction, followed by Group IV, then Group III and the least value was for Group II. 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 and function of parotid salivary glands. Moreover, it has a major role in tissue damage through development of amyloidosis. Insulin can't completely inhibit the complications of diabetes. However, CLO has great potential to inhibit the abnormalities caused by diabetes.