Possible Cardio-protective Effect of Olive Oil in Experimentally Induced Hyperthyroidism in Rats
Authors: Mousa Eman Mohammed Ali , Daoud Nermine Kamal Mohamed Saleh , Mohamed Abd El-Hamid A , El Hamid Manal Said Abd , Abou-Bakr Doaa Ahmed , saleh Hanan A 
Published: October 2021

Abstract

Background
Hyperthyroidism is an endocrine disorder that causes both functional and structural changes in the cardiovascular system. Untreated hyperthyroidism and even persistent subclinical thyroid hyperactivity has been associated with the development of Heart failure by inducing atrial fibrillation, chronic hemodynamic overload, oxidative stress and activation of renin-angiotensin pathway. HF secondary to hyperthyroidism is a reversible cause of cardiomyopathy, which highlights the importance of its prompt diagnosis and treatment. Olive oil with its phenolic compounds are powerful antioxidant that may serve as potential therapeutic agents to reduce cardiovascular hazardous effect of hyperthyroidism and intake of virgin olive oil provides benefits on cardiovascular disease.

Aim of the work
The aim of the present study is to evaluate the possible cardio-protective effects of olive oil, as a natural antioxidant, in experimentally induced hyperthyroidism in rats.
Also, to elucidate the underlying mechanism(s), if any, of its effects.

Materials and Methods
Animals used were 30 adult male albino rats, which were randomly allocated into three groups. Control group(n = 10): received intraperitoneal (i.p.) injection of the solvent of L-thyroxine daily for 4 consecutive weeks. Hyperthyroid group (n = 10): received i.p. injection of L-thyroxine 100μg/kg daily for 4 consecutive weeks. Olive oil-treated hyperthyroid group (n = 10): received i.p. L-Thyroxine as in group II. By the beginning of the third week, 1 ml/100 g B.W extra virgin olive oil was given daily by gavage for 2 weeks. At the end of the study, the overnight fasted rats were subjected to collection of retroorbital blood samples for determination of T3, T4, TSH serum levels. Rats were then weighed and anaesthetized with thiopental sodium (EIPICO, Egypt), IP (40 mg/kg B.W). Then, ECG was recorded. The heart was then subjected to In vitro study of isolated hearts perfused in langendorff preparation. Hearts chambers were then weighed. Apex of left ventricle was used in histopathological examination.

Results
The induction of hyperthyroidism was confirmed by T3 and T4 levels that were significantly increased, while TSH was significantly decreased in hyperthyroid group as well as olive oil-treated hyperthyroid group compared to control group. Compared to control group, both hyperthyroid and olive oil-treated hyperthyroid groups showed significant decrease in FBW, FBMI, BW% and BMI%. The absolute weights of RV, LV, WH, as well as, their relative weights RV/BW, LV/BW and WH/BW all were significantly increased. Compared to hyperthyroid group, olive oil-treated hyperthyroid group showed significant decrease in FBW as well as FBMI. The LV/BW and WH/BW were significantly increased. As regard ECG findings, HR, QRS duration and amplitude were significantly increased in both hyperthyroid and olive oil-treated hyperthyroid groups as compared to control rats. In the hyperthyroid group the PR interval was significantly shortened compared to control group, after olive oil-treatment PR interval increased significantly compared to hyperthyroid group, and became insignificant from control group. The baseline values in isolated perfused hearts study showed, significant increase in spontaneous beating rate in both hyperthyroid and olive oil-treated hyperthyroid groups as compared to control group. Hyperthyroid group showed non-significant decrease in TG/unit time and significant decrease in HRT compared to control group Olive oil-treated hyperthyroid group TG/unit time was non-significantly increased compared to control group and significantly increased compared to hyperthyroid group. HRT was the same as hyperthyroid group while. Isoprotrenol infusion showed early toxicity in hyperthyroid group indicated by reduced TG/unit time and HRT compared to control group. Olive oil-treated hyperthyroid group TG/unit time maximal response was significantly increased compared to hyperthyroid group, being non-significant from control group. The hematoxylin and eosin study of the left ventricular cardiac muscle, the hyperthyroid group showed apparent structural changes that were partially reversed by olive oil treatment.

Conclusion
Olive oil was able to impose partial improvement on cardiac systolic function at baseline condition, also, in response to the beta adrenergic agonist, isoproterenol, even though this improvement did not reach control levels.