title: [β-hydroxy-β-methylbutyrate as a dietary supplement (II): cell and molecular mechanism of action].
abstract: BACKGROUND
  In recent years, several investigations have related -hydroxy--methylbutyrate (HMB) to a reduced muscle proteolysis and to an increase in muscle mass. Therefore, a number of studies focused on the cellular and molecular mechanisms regulating these effects have been carried out.
  
  
  OBJECTIVE
  The objectives of this review are: to know both HMB metabolism and toxicity, and to identify HMB cellular and molecular mechanisms of action when used as a dietary supplement.
  
  
  METHODS
  A search was performed in the Web of Science, Pubmed and SportDiscus data bases. RESULTS were divided into two parts; this article presents aspects referring to HMB mechanisms of action.
  
  
  RESULTS
  There is insufficient evidence that HMB intake increases muscle cholesterol synthesis. It probably has positive effects on muscle metabolism through both the mTOR and ubiquitin-proteasome pathways, although the mechanism of action is unknown. HMB may increase blood levels of -hydroxybutyrate and this could explain the main effects of HMB on muscle proteolysis.
  
  
  CONCLUSIONS
  According to these results, the possibility of justifying the action of HMB through the beta-hydroxybutyrate pathway opens an interesting line of research for future studies.
authors.affiliation: Licenciatura en Cultura Física y Deporte, Facultad de Ciencias de la Conducta, Universidad Autónoma del Estado de México (UAEMex). Toluca, México. Instituto de Biomedicina (IBIOMED), Universidad de León. León, España,. ialvor@unileon.es.
authors.forename: Rafael
authors.initials: R
authors.lastname: Manjarrez-Montes-de-Oca
authors.affiliation: Licenciatura en Biología, Facultad de Ciencias, UAEMex. Toluca, México.. ialvor@unileon.es.
authors.forename: Mateo
authors.initials: M
authors.lastname: Torres-Vaca
authors.affiliation: Instituto de Biomedicina (IBIOMED), Universidad de León. León, España,. ialvor@unileon.es.
authors.forename: Javier
authors.initials: J
authors.lastname: González-Gallego
authors.affiliation: Instituto de Biomedicina (IBIOMED), Universidad de León. León, España,. ialvor@unileon.es.
authors.forename: Ildefonso
authors.initials: I
authors.lastname: Alvear-Ordenes
mesh_terms: D000818:Animals; D019587:Dietary Supplements; D006801:Humans; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D014631:Valerates / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000633:toxicity
chemical_list: D009124:Muscle Proteins; D014631:Valerates; C004961:beta-hydroxyisovaleric acid