Effects of vitamin E supplementation and training on oxidative stress parameters measured in exercising horses

Validation of a commercially available photometric analytical system for assessment of plasma oxidative status in healthy horses

Reactive oxygen species (ROS) are the end-products of physiologic functions in health. Oxidative stress occurs when endogenous antioxidants are insufficient to neutralize ROS in the system. As a result, ROS can damage DNA, RNA, proteins, lipids, and cell organelles. To obtain accurate measurements of plasma oxidative stress, levels of both oxidants and antioxidants must be measured. This study validates a commercially available, semi-quantitative, photometric analytical system that measures systemic determinants of reactive oxygen metabolites (dROM) and plasma antioxidant capacity (PAC) in stored equine plasma. The objectives of this work were: 1) to validate a photometric analytical system to quantify dROM and PAC in equine plasma; and 2) to determine expected results for these tests in healthy adult horses. We hypothesized that this system would reliably and reproducibly assess dROM and PAC in equine plasma. We observed expected, dose-dependent increases in dROM generated by adding increasing concentrations of H2O2 or ascorbic acid to equine plasma to provide samples containing a known quantity of oxidants or antioxidants respectively. Mean dROM value in healthy horses was 103.3 ±20.7 U. Carr and mean PAC was 2881.0 ± 313.9 U. Cor. This system reliably and reproducibly quantified dROM and PAC in equine plasma samples.

Effects of Vitamin E and Coenzyme Q10 Supplementation on Oxidative Stress Parameters in Untrained Leisure Horses Subjected to Acute Moderate Exercise

The effects of antioxidant supplements on exercise-induced oxidative stress have not been investigated in untrained leisure horses. We investigated the effects of 14-day supplementation with vitamin E (1.8 IU/kg/day), coenzyme Q₁₀ (CoQ₁₀; ubiquinone; 800 mg/day), and a combination of both (the same doses as in mono-supplementation) on the blood levels of CoQ₁₀, vitamin E, and oxidative stress parameters in untrained leisure horses subjected to acute moderate exercise. Correlations between lipid peroxidation and muscle enzyme leakage were also determined. Forty client-owned horses were included in the study, with 10 horses in each of the antioxidant and placebo (paraffin oil) groups. Blood parameters were measured before supplementation, before and immediately after exercise, and after 24 h of rest. The differences in individual parameters between blood collection times and groups were analysed with linear mixed models (p ˂ 0.05). None of the supplemented antioxidants affected vitamin E and CoQ₁₀ concentrations, oxidative stress parameters, or serum muscle enzymes. Lipid peroxidation occurred in horses supplemented with placebo and CoQ₁₀ but not in horses supplemented with vitamin E or the combination of both antioxidants. These results suggest that vitamin E alone or in combination with CoQ₁₀ prevented lipid peroxidation in untrained leisure horses subjected to acute moderate exercise.

Form of Vitamin E Supplementation Affects Oxidative and Inflammatory Response in Exercising Horses

Vitamin E is an essential antioxidant that may benefit athletes by reducing oxidative stress and influencing cytokine expression. Supplements can be derived from natural or manufactured synthetic sources. This study aimed to determine (1) if supplemental vitamin E is beneficial to exercising horses and (2) if there is a benefit of natural versus synthetic vitamin E. After 2 weeks on the control diet (vitamin E-deficient grain and hay), 18 horses were divided into three groups and fed the control diet plus (1) 1000 IU/d synthetic α-tocopherol (SYN-L), (2) 4000 IU/d synthetic α-tocopherol (SYN-H), or (3) 4000 IU/d RRR-α-tocopherol (natural source [NAT]). On day 7, horses began a 6-week training protocol, with standard exercise tests (SETs) performed before and after the 6-week protocol. Venous blood samples were collected on days 0, 7, 29, and 49. Horses fed NAT had higher α-tocopherol (P < .05) at post-SET1 through post-SET2. Plasma thiobarbituric acid-reactive substance levels were lower in NAT versus SYN-L horses after SET2 (P = .02). Serum aspartate aminotransferase was lower after exercise in NAT horses versus SYN-L and SYN-H (P = .02), and less reduction in stride duration was seen after exercise in NAT as compared with SYN-L and SYN-H (P = .02). Gene expression of tumor necrosis factor α was lower in NAT compared with SYN-H (P = .01) but not SYN-L. In conclusion, feeding higher levels of natural vitamin E source resulted in higher serum α-tocopherol levels as well as some improvement in oxidative and inflammatory response and improved functional outcomes in response to an exercise test.

Efeito da suplementação com vitamina E sobre os metabolismos oxidativo e cardíaco em equinos submetidos a exercício de alta intensidade

A suplementação antioxidante visa prevenir os danos oxidativos induzidos pelo exercício físico em diversos tecidos, como o miocárdio. Nesse contexto, este estudo objetivou avaliar os marcadores cardíacos e a lipoperoxidação em equinos no teste de exercício de rápida aceleração e curta duração (TRA), em esteira de alta velocidade, antes e após a suplementação com vitamina E. Para tanto, foram utilizados 10 equinos sem treinamento, que realizaram o primeiro TRA (TRA1) com carga de trabalho fundamentada no consumo máximo de oxigênio individual (VO2max) e que induziu a concentração de lactato maior que 4mmol/L, sendo considerado predominantemente anaeróbico. Em seguida, os equinos receberam vitamina E (dl-alfa-tocoferol) na dose de 1.000UI/dia, por via oral, durante 52 dias, e, posteriormente, realizaram um segundo TRA (TRA2) com o mesmo protocolo de TRA1. As amostras de sangue foram colhidas nos momentos antes do exercício, imediatamente após o término do teste e em 1h, 3h, 6h, 12h e 24h subsequentes. Determinou-se o malondialdeído (MDA) plasmático como índice de lipoperoxidação, e as concentrações séricas de troponina I cardíaca (cTnI), isoenzima MB da creatinoquinase (CK-MB) e mioglobina, como marcadores cardíacos. Como efeito do exercício, observou-se aumento discreto de MDA, de cTnI e de CK-MB, sendo significativo apenas para CK-MB. A suplementação foi capaz de amenizar a produção das espécies reativas de oxigênio, evidenciada pela menor concentração de MDA em TRA2, em 24h, além de causar um efeito protetor no miocárdio, devido ao menor valor de cTnI em 6h no TRA2 em relação ao TRA1. Não houve grandes alterações na concentração de mioglobina. Concluiu-se que o exercício de alta intensidade promoveu estresse no miocárdio nos equinos avaliados, bem como houve efeito benéfico da vitamina E na proteção miocárdica e sobre a lipoperoxidação.

Short- and long-term effect of oral administration of micellized natural vitamin E (D-α-tocopherol) on oxidative status in race horses under intense training

This study tested the effect of micellized vitamin E (D-α-tocopherol; 1,400 IU/d) administered 12 and 1 h orally before training for 1 d (ST-VitE) or 8 d (LT-VitE) compared with an unsupplemented control (CONTROL) on plasma α-tocopherol, thiobarbithuric acid-reactive substances (TBARS), total glutathione (GSHt), and trolox equivalent antioxidant capacity (TEAC) in 10 race horses. Different sampling times [immediately before training (BEF) and after intense training (END) or 8 h after recovery (+8h)] were investigated. Plasma α-tocopherol concentration was greater in the ST-VitE group than the CONTROL group at +8h (P < 0.05). Natural vitamin E supplementation increased plasma α-tocopherol (P < 0.001) in the LT-VitE group by approximately 1.6-fold at BEF, END, and +8h. In all groups, TBARS tended to be slightly greater (P = 0.087) immediately after training when compared with values BEF or +8h and the lowest TBARS values were observed at +8h in LT-VitE. Vitamin E supplementation did not affect the GSHt concentrations at BEF, END, or +8h. The TEAC values were modified by the vitamin E administration (P = 0.010). The greatest TEAC was found in the LT-VitE group at all sampling times and similar concentrations were reached in the ST-VitE group at +8h. The CONTROL group was not able to maintain TEAC after training (P < 0.001), indicating consumption of antioxidants (mainly vitamin E) and consequently oxidative stress because of the antioxidant system being overwhelmed by a reduced antioxidant supply. In conclusion, micellized natural vitamin E at 1,400 IU/d for 8 d efficiently increased plasma α-tocopherol concentration of race horses undergoing intense training conditions and maintained the general oxidative status.