Effect of exercising in water on the fibrocartilage of the deep digital flexor tendon in rats with induced diabetes

Abstract

Individuals with diabetes mellitus (DM) are affected four times more by tendinopathies than non-diabetics. On the other hand, physical activity helps to DM control. However, the effects of physical exercise in water (PEW) on the fibrocartilages present in the tendons of animals affected by DM are unknown. In this sense, the aim of this study was to analyze the structural organization and chemical composition of fibrocartilage present in the intermediate region of the deep digital flexor tendon (DDFT) of Wistar rats with alloxan-induced DM. Diabetic and non-diabetic animals were randomly separated into four experimental groups (n = 10): Non-Trained Control (NTC), Trained Control (TC), Non-Trained Diabetic (NTD), and Trained Diabetic (TD). TC and TD animals underwent the exercise protocol (total weekly training load - week 1: 14,375; 2: 16,500; 3: 18,375; 4: 20,000) and then were euthanized to collect tendon samples for analysis. The matrix basophilia was more intense in the TC and TD groups. The Decorin immunohistochemical test results showed greater intensity in the NTD and TD groups. The wet weight of the fibrocartilaginous region of the tendon (NTC:19.9 ± 0.06; TC:22.3 ± 0.05; NTD:20.3 ± 0.08; TD:21.8 ± 0.04 mg - p = 0.048), glycosaminoglycan amounts (NTC:3.21 ± 0.18; TC:3.98 ± 0.44; NTD:3.32 ± 0.19; TD:3.79 ± 0.28 μg/mg of fresh tissue - p = 0.046), and intumescence in water (NTC:13.8 ± 3.8; TC:24.3 ± 3.9; NTD:14.9 ± 3.9; TD:28.2 ± 5.3 % w/w - p = 0.042) were higher in the TC and TD groups. The TD group showed the highest levels of type I collagen and matrix metalloproteinase (MMP)-13. The TC group showed the highest and TD the lowest TGF-β1 levels. In conclusion, the PEW was able to stimulate the deposition of proteoglycans, without inducing chemical changes that would cause histopathological modifications in fibrocartilage in the DDFT of adult rats. Thus, PEW preserves the structural organization of these tissues in tendons of animals affected by DM.

Keywords: Extracellular matrix; Hyperglycemia; Proteoglycan; Swimming.