The 17β-oestradiol treatment minimizes the adverse effects of protein restriction on bone parameters in ovariectomized Wistar rats

Abstract

Objectives Insufficient protein ingestion may affect muscle and bone mass, increasing the risk of osteoporotic fractures in the elderly, and especially in postmenopausal women. We evaluated how a low-protein diet affects bone parameters under gonadal hormone deficiency and the improvement led by hormone replacement therapy (HRT) with 17β-oestradiol. Methods Female Wistar rats were divided into control (C), ovariectomized (OVX), and 17β-oestradioltreated ovariectomized (OVX-HRT) groups, which were fed a control or an isocaloric lowprotein diet (LP; 6.6% protein; seven animals per group). Morphometric, serum, and body composition parameters were assessed, as well as bone parameters, mechanical resistance, and mineralogy. Results The results showed that protein restriction negatively affected body chemical composition and bone metabolism by the sex hormone deficiency condition in the OVX group. The association between undernutrition and hormone deficiency led to bone and muscle mass loss and increased the fragility of the bone (as well as decreasing relative femoral weight, bone mineral density, femoral elasticity, peak stress, and stress at offset yield). Although protein restriction induced more severe adverse effects compared with the controls, the combination with HRT showed an improvement in minimizing these damaging effects, as it was seen that HRT had some efficacy in maintaining muscle and bone mass, preserving the bone resistance and minimizing some deleterious processes during the menopause. Conclusion Protein restriction has adverse effects on metabolism, leading to more severe menopausal symptoms, and HRT could minimize these effects. Therefore, special attention should be given to a balanced diet during menopause and HRT.