Original ResearchEffects of β-Hydroxy-β-Methylbutyrate and γ-Oryzanol on Blood Biochemical Markers in Exercising Thoroughbred Race Horses
Introduction
β-Hydroxy-β-methylbutyrate (HMB) and γ-oryzanol (GO) are supplements used to enhance the effects of training in exercising humans, dogs, and horses. A metabolite of the amino acid leucine, HMB is produced endogenously in small amounts and has been shown to improve gains in strength and lean body mass in humans when associated with resistance training [1], [2]. The efficacy of HMB has been demonstrated in pathological conditions, where it has been reported to reduce muscle wasting associated with AIDS, trauma, and cancer cachexia [3], [4], [5]. More recently, HMB has been shown to decrease protein degradation and increase protein synthesis [6]. In decreasing muscle damage, HMB may also provide a source of cytosolic HMG-coenzyme A for cholesterol synthesis and increase the availability of cholesterol for cell membrane synthesis. This may result in an overall reinforcement of the sarcolemma as well as the provision of valuable substrate for its repair following muscle damage or injurious exercise [7]. This is evidenced by studies demonstrating that HMB leads to decreased markers of muscle damage following mechanically strenuous exercise, including lower activity of creatine kinase (CK), lactate dehydrogenase, and a decrease in muscle protein breakdown as indicated by serum 3-methylhistidine, a direct marker of muscle protein degradation [8], [9], [10]. Other studies have shown that HMB reduces cancer-induced muscle weight loss through attenuation of the ubiquitin-proteasome proteolytic pathway [11], suggesting that HMB functions predominantly as an anticatabolic, rather than anabolic compound. However, a recent study has shown that HMB supplementation induces muscle hypertrophy in the extensor digitorum longus and soleus muscles in rats via mammalian target of rapamycin pathway [12], in addition to attenuating the depression in protein synthesis induced by the proteolysis-inducing factor [6]. In geldings fed an alfalfa-based supplement containing 10 g of HMB per day during 6 weeks of low to moderate-intensity training followed by 6 weeks of high-intensity training, HMB supplementation resulted in a 10% improvement in treadmill endurance [13]. This was followed by a study in racing Thoroughbreds where HMB-supplemented horses had reduced serum CK, maintained body weight better, needed less recovery time between races, and had a better win rate. These effects were most likely through a decrease in training and race-related muscle damage and increased aerobic ability, which allowed for a quicker recovery after racing.
GO is a mixture of ferulic acid esters of sterol and triterpene alcohols extracted from rice bran, and is known to be a powerful inhibitor of iron-driven hydroxyl radical formation; it has also been reported to possess antioxidant activity in stabilizing lipids [14]. Because GO is insoluble in water, a GO emulsion is used in supplementing humans, dogs, and horses. There are few studies in the peer-reviewed literature on GO, despite its apparent use as an ergogenic aid. One study looked at resistance-weight-trained male athletes supplemented with 500 mg/d GO or a placebo [15]. However, this study failed to show an effect of GO on training performance.
Thoroughbred horses undergo intensive training starting at a young age. The results of this training and their race performance may be improved by the use of dietary supplementation. The use of supplementation may not only improve performance but also improve muscle recovery after a race or heavy training period. Therefore, the main objective of this study was to evaluate the effect of dietary supplementation of HMB and GO on exercise parameters in horses trained from winter break to their maximal physical performance at the start of the racing season. Our hypothesis is that one or both supplements, either alone or in combination, will decrease muscle damage and improve recovery, and thus improve overall performance.
Section snippets
Horses
Twenty-four Thoroughbred racehorses ranging in age from 3-6 years (12 mares and 12 stallions) and weighing 520 ± 50 kg were studied at the Sluzewiec Racetrack training center (Warsaw, Poland). The horses were privately owned, and the experimental design and all procedures were approved by the Ethical Committee in Warsaw and by the owners of horses. The horses were selected on the basis of a clinical examination and hematological analysis, and horses with pathological conditions were excluded.
Exercise Monitoring
Resting and peak HR as well as maximum speed did not differ between placebo and experimental groups (Fig. 2). Resting HR during all exercise sessions was in the range of 32-37 beats/min. Average peak HR was approximately 200 beats/min for all exercised horses and was not affected by the length of training. Maximal speed increased from average 38 km/hr at the beginning of training to about 50 km/hr at the end of the racing season. These data confirm that training exertion was similar and intense
Discussion
The present study was the first study to determine whether dietary supplementation with either HMB or GO alone, or in combination, would affect indirect markers of muscle damage and fatigue in Thoroughbred horses during 16 weeks of training in preparation for the racing season. Currently, little data are available on the effects of these supplements in horses, with only one study describing the effect of HMB on the physiological response to exercise in horses. Miller et al. [13] fed horses an
Conclusion
This field study, performed on 22 trained Thoroughbred horses, is the first showing that dietary supplementation with GO and HMB may significantly improve training results by decreasing muscle damage caused as a result of the intensity of the training. The current study has shown that GO does not significantly affect performance-related physiological parameters in training Thoroughbred race horses; however, when GO is supplemented with HMB, the training results in increased performance
Acknowledgments
The study was supported by the State Committee for Scientific Research, Poland (grant number N N308 3076 33 for P.O.). The authors thank Mrs Małgorzata Podgurniak and Dr John C. Fuller for their assistance with the manuscript preparation.
References (36)
- et al.
Reversal of cancer-related wasting using oral supplementation with a combination of β-hydroxy-β-methylbutyrate, arginine and glutamine
Am J Surg
(2002) - et al.
Nutritional role of the leucine metabolite β-hydroxy-β-methylbutyrate (HMB)
J Nutr Biochem
(1997) Hematologic and serum biochemical responses to exercise and training
Exercise testing in the field
- et al.
Effect of high intensity training on anerobic capacity of middle gluteal muscle in thoroughbred horses
Res Vet Sci
(2004) - et al.
Role of exercise and ascorbate on plasma antioxidant capacity in Thoroughbred race horses
Comp Biochem Physiol
(2001) - et al.
Effect of dietary supplements on lean mass and strength gains with resistance exercise: a meta-analysis
J Appl Physiol
(2003) - et al.
Nutritional supplementation of the leucine metabolite β-hydroxy-β-methylbutyrate (hmb) during resistance training
Nutrition
(2000) - et al.
Nutritional treatment for acquired immunodeficiency virus-associated wasting using β-hydroxy-β-methylbutyrate, glutamine and arginine: a randomized, double-blind, placebo-controlled study
J Parenter Enteral Nutr
(2000) - et al.
β-hydroxy-β-methylbutyrate supplementation in critically ill trauma patients
J Trauma
(2007)