Olive oil improved the impairment of in vitro insulin-stimulated glucose uptake by diaphragm in ovariectomized female Wistar rats

This work was carried out to examine the impact of ovariectomy in female Wistar rats on in vitro basal and insulin-stimulated glucose uptake by diaphragm, and the possible beneficial effects of olive oil supplementation in these rats. Methods: we studied 21 female Wistar rats aged 12–14 months, divided into three groups: sham-operated control (SHAM), ovariectomized (OVX), and ovariectomized rats supplemented with extravirgin olive oil (Olive–OVX) orally for 12 weeks; 4 weeks before ovariectomy and 8 weeks after. At the end of the experiment, blood samples were collected for lipid profile assays. Malondialdehyde (MDA) in soleus muscles was assayed. The diaphragms were collected for determination of glucose uptake by the muscles. Soleus muscles and pancreas were processed for histological examination. Results: ovariectomy impaired insulin-stimulated glucose uptake by diaphragm of female rats, induced abnormalities of lipid metabolism, and increased the oxidative stress marker, MDA level in soleus muscles. Olive oil supplementation to ovariectomized rats resulted in an enhancement of insulin-stimulated glucose uptake by diaphragm and a better lipid profile, as well as a decrease in the MDA level in soleus muscles. Histological study in OVX rats revealed a decrease in the size and number of islets of Langerhans in the pancreatic tissue, and decreases in both glycogen content, and in mitochondrial density in the soleus muscles. In Olive–OVX rats the size of islets of Langerhans was normal, and muscle glycogen, and muscle mitochondrial density were increased as compared to OVX rats. Conclusion: ovariectomy impaired in vitro insulin-stimulated glucose uptake by diaphragm. The improvement of this impairment by olive oil supplementation could be attributed to its antioxidant properties, its high content of monounsaturated fatty acids, as well as, its enhancement effect on mitochondrial density in skeletal muscles.

Research Highlights►Ovariectomy impaired in vitro insulin-stimulated glucose uptake by diaphragm. ►Olive oil improved the impairment of in vitro insulin-stimulated glucose uptake by diaphragm induced by ovariectomy. ►The improvement of ovariectomy-induced impairment of glucose homeostasis by olive oil could be attributed to its antioxidant properties, its high content of monounsaturated fatty acid, as well as, its enhancement effect on mitochondrial density in skeletal muscles.