A Review of the Effects of Leucine Metabolite (β-Hydroxy-β-methylbutyrate) Supplementation and Resistance Training on Inflammatory Markers: A New Approach to Oxidative Stress and Cardiovascular Risk Factors

Abstract

β-hydroxy β-methylbutyrate (HMB) is a bioactive metabolite formed from the breakdown of the branched-chain amino acid, leucine. Given the popularity of HMB supplements among different athletes, specifically, those who participate in regular resistance training, this review was performed to summarize current literature on some aspects of HMB supplementation that have received less attention. Because of the small number of published studies, it has not been possible to conclude the exact effects of HMB on cardiovascular parameters, oxidative stress, and inflammatory markers. Thus, the interpretation of outcomes should be taken cautiously. However, the data presented here suggest that acute HMB supplementation may attenuate the pro-inflammatory response following an intense bout of resistance exercise in athletes. Also, the available findings collectively indicate that chronic HMB consumption with resistance training does not improve cardiovascular risk factors and oxidative stress markers greater than resistance training alone. Taken together, there is clearly a need for further well-designed, long-term studies to support these findings and determine whether HMB supplementation affects the adaptations induced by resistance training associated with the body's inflammatory condition, antioxidative defense system, and cardiovascular risk factors in humans.

Keywords: HMB; branched-chain amino acid; inflammation; sports nutrition; strength training.

Figure 1

Pathways of HMB metabolism from the amino acid, leucine. Modified from Nissen and Abumrad [31]. HMB: Beta-hydroxy-beta-methylbutyrate, KIC: Alpha-ketoisocaproic acid, HB: Beta-hydroxybutyrate, HMG-CoA: 3-hydroxy-3-methyl-glutaryl-CoA, Ala: Alanine, Pyr: Pyruvate, 1: branched-chain amino acid (BCAA) aminotransferase, 2: KIC dioxygenase, 3: Branched-chain alpha-keto acid dehydrogenase (BCKAD), 4: Glutamine synthetase, 5: Alanine aminotransferase.