Avaliação biomecânica e morfométrica dos efeitos da natação em fêmures de camundongos knockout para o gene do receptor de LDL (LDLr-/-)

Abstract

Hyperlipidemias trigger changes in plasma lipoprotein concentrations, favoring the development of chronic diseases. High levels of cholesterol and triglycerides may cause changes in bone tissue. For the treatment of metabolic diseases, such as hyperlipidemia and osteoporosis, physical exercises are indicated, including swimming, and low-impact exercise, which may promote muscle contractions that stimulate bone remodeling. Therefore, the present study analyzed the effects of swimming on the morphology and biomechanics of femurs from wild-type and LDL receptor gene knockout (LDLr-/-) mice. Mice were divided into sedentary and

swimming groups, and subdivided in those fed with standard rodent chow or high- fat diet. The group submitted to swimming underwent daily sessions lasting 40

min. each, which were performed in individual tanks with controlled temperature, for 60 days. After this period, the animals were anesthetized and euthanized for collection of whole blood samples for biochemical analysis. Femurs were collected for histological processing and biomechanical analysis. The results demonstrate that LDLr-/- mice represent a good experimental model for hyperlipidemia and that swimming, combined or not with a high-fat diet, established a relationship with the reduction of plasma concentrations of total cholesterol and triglycerides, as well as with increased levels of plasma HDL and calcium. The morphometric and biomechanical findings showed more pronounced alterations in the cortical and trabecular bones of the femurs obtained from LDLr-/- mice that received the high-fat diet and were not submitted to swimming. Changes in plasma levels of calcium, triglycerides and cholesterol

and their fractions were also more marked in this group. In contrast, wild-type and LDLr-/- mice submitted to aquatic training, regardless of the diet consumed, showed high plasma levels of HDL, which probably protected against mechanical and morphological bone alterations. In conclusion, the biomechanical and morphometric evaluations carried out in the present study suggest that swimming and a balanced lipid diet can prevent the harmful effects of hyperlipidemia on bone tissue.