Abstract
Objectives: This study aimed to assess the impact of high cholesterol diet (HCD)-induced hypercholesterolemia on the rat thyroid gland and investigate the role of grape juice (GJ) in reducing such impact through biochemical and histopathological methods. Materials and Methods: Thirty male Wistar rats sorted into three groups (the control, HCD-fed group, and the HCD+GJ fed group for 13 weeks) were used in this study. Lipid profile, blood glucose and insulin, thyroid hormones, some oxidants/antioxidants parameters were assessed. After the end of the experiment, thyroid glands were dissected out and processed for histopathological assessment using the light and electron microscopy. Results: Based on the lipid profile, HCD induced hypercholesterolemia in rats after 13 weeks. This resulted in significant (p<0.001) increase of the levels of insulin, blood glucose, thyroid-stimulating hormone (TSH) (596.4 +/- 17 IU/mL), thyroxine (T4) (202.8 +/- 14.1 ng/mL) and malondialdehyde (MDA) (21.2 +/- 4.9 nmol/mg protein), while the levels of triiodothyronine (T3) (12.6 +/- 1.9 ng/mL) and total antioxidant capacity (TAOC) (21.2 +/- 4.9 U/mg protein) decreased in HCD-fed rats compared to that of the controls. Structurally, thyroid gland follicles of HCD-fed rats showed cytoplasmic vacuolation, stratification and increased thickness of some lining cells. Ultrastructurally, some of follicular and parafollicular cells showed heterochromatic nuclei, degenerated mitochondria, intracytoplasmic lipid droplets and deposition of collagen fibers between the follicles. GJ could improve the lipid and antioxidants profiles, reduced blood glucose level, thyroid hormones, and alleviated the HCD-induced structural changes in the thyroid. Conclusions: GJ administrated simultaneously with HCD ameliorated the negative impact of the function and structure of the thyroid.