Avaliação do efeito anabólico ósseo do Kefir associado ao exercício resistido no fêmur de ratos com osteoporose induzida por glicocorticoide

Abstract

Osteoporosis is a multifactorial skeletal disease that alters microarchitecture and reduces bone mass, causing loss of mechanical strength and increased risk of fracture. Among the forms of osteoporosis, glucocorticoid-induced (GIO) is the most frequent type of secondary osteoporosis. Knowing that the prevention and treatment of GIO will still remain a challenge, natural products and physical exercises have been the focus of study. In this context, Kefir, an oral probiotic, stands out for presenting benefits to the bone and minimizing the pharmacological effects of medications. Thus, this study aimed to evaluate the effect of physical exercise on osteoporosis and the effect of kefir associated with resistance exercise on bone tissue in the GIO. Initially, 2 systematic reviews were evaluated, with preclinical and clinical studies, to analyze the effects of exercise on bone tissue during osteoporosis. It was observed that exercise for enhanced bone mineral strength (BMD), bone and trabecular volume (BV/TV) and decreased trabecular separation (Tb.Sp), beneficial effects of exercise for bone tissue in animal models. 60% of clinical studies confirm a positive association between decreased bone resorption markers and exercise, suggesting reduced resorption in patients with osteoporosis. Finally, to analyze the effect of the association of exercise + kefir on bone tissue submitted to OIG, 60 male Wistar rats were divided into 2 groups: normal (N), and performing GIO, which was subdivided into 4 groups according to treatment: control (C), Kefir (K), Exercise (Ex) and Exercise+Kefir (ExK). GIO was induced by dexamethasone (7mg/kg; i.m.). Kefir was administered by gavage (0.7 ml/animal/day) for 16 weeks. The exercise was performed 3 days/week, with an intensity of 20% to 80% of the maximum individual load, for 16 weeks. After euthanasia, the femur was collected for macro and microscopic analyses, imaging examinations and biomechanical tests. In light of our knowledge, this is the first time that an in vivo evaluation of exercise + Kefir in bone tissue from rats with GIO has been performed. GIO reduced by 35% BV/TV, 33% trabecular thickness (Tb.Th), 26% mineral and collagen content (56%). There is also a reduction in flexion strength (81%), fracture load (80%) and number of osteocytes (84%) after GIO. Glucocorticoids altered bone remodeling (p < 0.05), marked by a reduction in the number of osteoblasts while an increased number of osteoclasts, and roughness of bone tissue. After the 16-week intervention, association of ExK improved microarchitecture evolution and bone quality, marked by an increase in fractal dimension (38%), cortical volume (34%), 13 BV/TV (34%), Tb.Th (33%), mineral content and collagen maturity, while reducing Tb.Sp (34%) and bone roughness. Thus, ExK improved bone strength and biomechanics, in addition to stimulating bone formation and modular bone remodeling. It is concluded that exercise had antiresorptive effects on bone tissue and that kefir potentiated the beneficial effects of exercise on bone tissue, improving microarchitecture, femur quality and biomechanical properties and stimulated bone formation. Thus, treatment with kefir and physical exercises are provided as adjuvant tools to improve the bone loss picture caused by GIO.