Date Published: November 7, 2008
Publisher: BioMed Central
Author(s): Gonzalo Marañón, Bárbara Muñoz-Escassi, William Manley, Cruz García, Patricia Cayado, Mercedes Sánchez de la Muela, Begoña Olábarri, Rosa León, Elena Vara.
Exercise induces changes in several organs and tissues, and this process might be due to oxidative damage caused by free radicals and inflammatory mediators. Methyl Sulphonyl Methane, better known as MSM, is a naturally occurring sulphur compound with well-known antioxidant properties. On the other hand, Vitamin C is important in limiting free radical damage in the aqueous phase of the cell, and cellular vitamin C status may be linked to the mechanisms involved in quenching cellular reactive oxygen species. The aim of this study was to determine if supplementation with MSM and vitamin C could alleviate exercise-induced oxidative stress in horses undergoing jumping competition.
Twenty four jumping horses involved in competition were used. Horses were given the following three treatment diets: control (without supplementation), MSM 8 mg/kg, and combined supplements (MSM 8 mg/kg + Vit-C 5 mg/kg). EDTA blood samples were collected before exercise, upon arrived to the schooling area (control), and each week after last show. Nitric oxide, carbon monoxide, lipid hydroperoxides and the antioxidant enzymes, glutathione peroxidase, glutathione transferase and glutathione reductase, plasma levels were determined.
Competition induced a significant increase in lipid peroxidation, nitric oxide and carbon monoxide. By contrary, reduced glutathione as well as antioxidant enzyme activities, were decreased. MSM administration significantly ameliorated all these exercise-related changes, and this effect was potentiated by Vit C reaching values in some of the parameters similar to those found before competition.
These results suggest that jumping exercise could induce harmful effects on horses, probably due to an increase in oxidative damage and proinflammatory molecules. In addition, we have demonstrated that MSM could exert some protective effect on oxidative and inflammatory exercise-induced injury.
Exercise is accompanied by several changes in the morphology and physiology of different organs and tissues. One of the theories that tries to explain the exercise effects defends that it may be in part due to the accumulation of oxidative damage induced by reactive oxygen species (ROS) and reactive nitrogen species (RNS) to cells and macromolecules [1-3]. ROS are highly reactive molecules which are mainly generated in mitochondria during oxygen metabolism . Approximately 95% of the oxygen consumed is reduced to water during aerobic metabolism, but the remaining fraction may be converted to reactive oxygen species and other free radicals, inducing oxidative stress. There may be a number of sources of this oxidative stress, including mitochondrial superoxide production, ischemia-reperfusion mechanisms and auto-oxidation of catecholamines. Severe or prolonged exercise can overwhelm antioxidant defences, which include vitamins E and C and thiol antioxidants, which are interlinked in an antioxidant network, as well as antioxidant enzymes. Evidence for oxidative stress and damage during exercise comes from direct measurement of free radicals, from measurement of damage to lipids and DNA, and from measurement of antioxidant redox status, especially glutathione. There is little evidence that antioxidant supplementation can improve performance, but a large body of work suggests that bolstering antioxidant defences may ameliorate exercise-induced damage.
Twenty for jumping horses (8–13 years old; 2 stallions, 13 geldings, 9 mares) competing in the south of Spain (Winter Sunshine Tour) during 5 weeks (3–4 days/week), were used in the present study. All horses were apparently healthy and showed a good performance condition, Horses were randomly assigned to one of three experimental groups: MSM group (8 mg/Kg of MSM, Alefa Aesar, Germany: 98–99% purity, daily); MSM+Vit C group (8 mg/Kg of MSM plus 5 mg/Kg of vitamin C, daily) and Control (no supplementation). Supplements (one daily oral dose mixed in the morning feed), were administered in spaced doses, 7 days before arrived to the schooling area and every day until the end.
As shown in figure 1, exercise decreased all antioxidant enzymes studied. GR activity was reduced by exercise in a time-dependent manner, while no changes were observed in GPx and GST activities during time. These effects were partially prevented by MSM, although levels remain lower than those observed on week 0, before starting competition. When MSM was combined with Vit C, the three enzymatic activities were restored reaching normal values (before starting competition).
The role of ROS in the exercise-induced damage is supported by many studies. ROS production has been found to increase with exercise, thus augmenting the amount of oxidative damage induced to lipids, proteins and DNA [1,2,22,23]. The control of ROS is important to the athlete because they interfere with the rebuilding process which is so necessary after strenuous competition. Therefore, many studies have focused their attention on the search of substances that could restrain this increase in exercise-induced oxidative stress.
These results suggest that jumping exercise could induce harmful effects on horses, probably due to an increase in oxidative damage and proinflammatory molecules. In addition, we have demonstrated that MSM could exert some protective effect on oxidative and inflammatory exercise-induced injury. All these findings suggest the necessity of investigating the mechanisms of the protective effect of MSM, in order to develop strategies capable to increase performance in sport horses.
MSM: methyl sulphonyl methane; Vit C: vitamin C; GPx: glutathione peroxidise; GST: glutathione transferase; GR: glutathione reductase; HO: heme oxygenase; ROS: reactive oxygen species; RNS: reactive nitrogen species; NO: nitric oxide; CO: carbon monoxide; GSH: glutathione.
The authors declare that they have no competing interests.
GM: Participated in the design of the study and performed the statistical analysis. BME, WM, MSM, PC, BO, RL and CG: Participated in the recovery of blood samples and carried out the biochemistry determinations. EV: Conceived the study, participated in its design and coordination and helped to draft the manuscript. All authors read and approved the final manuscript.