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Cocoa polyphenols increase catalase, superoxide dismutase and glutathione peroxidase activities of skeletal muscles in diabetic rats

Introduction: Oxidative stress (OS) in diabetes mellitus (DM) can modify a number of the signaling pathways within a cell, and in this way, ultimately lead to insulin resistance as well as to diabetic complications. Diabetes, type 1 is the endocrinologic disorder characterized by inflammatory processes in the ß-cells of the pancreas. The nerve cells of the pancreatic islets insufficient release neurotransmitters for the necessary signaling ß-cells to produce insulin, and in this way blocks the secretion of insulin. Treatment with insulin is an only possible way to sustain life. Exposure to high glucose also causes cumulative changes in long-lived macromolecules. Skeletal muscles play an important role in maintaining glucose homeostasis. The inability to repair damaged skeletal muscle is one of a characteristic feature of uncontrolled diabetes. Dietary polyphenols are recognized to control OS at different levels, including modulating the expression of multiple regulatory elements comprised of antioxidants (e.g., glutathione) and enzymes (e.g., superoxide dismutase, catalase). Cocoa is a rich source of flavanols, which have a beneficial effect on many disorders caused by the OS, also improve blood lipid profiles and reduce insulin resistance in diabetes. The purpose of this work is to investigate the effect of cocoa on superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) levels in skeletal muscles of diabetic rats. Materials & methods. DM was induced by a single administration of streptozotocin (SZT) in male Wistar rats. The blood glucose was monitored at set time intervals. In the group treated with cocoa, drinking water was replaced with a cocoa drink (0.5%, w/v, cocoa powder in water) during one month (ad libitum) after SZT-induced DM. The activities of CAT, SOD, and GPx were determined in rat soleus and tibialis muscles. Differences between the groups assessed by an ANOVA one-way, and p<0.05 were considered to be statistically significant. Results. DM and posttreatment with 0.5% cocoa drink have affected on CAT, SOD and GPx activities in both skeletal muscles, tibialis and soleus. DM reduced significantly SOD, CAT and GPx activities in soleus. Cocoa significantly elevated SOD, CAT and GPx activities in tibialis and soleus of diabetic rats. SOD and CAT activities were significantly higher in the group treated with cocoa than in control in tibialis. CAT activity was markedly higher, and SOD activity, lower in the group treated with cocoa in soleus. Conclusions: Cocoa has a modulated expression of enzymes and antioxidants in rat skeletal muscles, soleus, and tibialis, so allows muscle dysfunction repair in diabetic rats. This study suggested an important role of polyphenols which acting through a redox-modulating mechanism.

diabetes mellitus; cocoa polyphenols; skeletal muscle; oxidative stress

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