beta-Hydroxy beta-methylbutyric acid

β-Hydroxy β-methylbutyric acid^[1]

Names
IUPAC name 3-hydroxy-3-methylbutanoic acid
Other names β-Hydroxyisovaleric acid 3-Hydroxyisovaleric acid
Identifiers
CAS Number	625-08-1 Y
Abbreviations	HMB
ChEBI	CHEBI:37084 Y
ChemSpider	62571 Y
Jmol interactive 3D	Image
PubChem	69362
UNII	3F752311CD N
InChI InChI=1S/C5H10O3/c1-5(2,8)3-4(6)7/h8H,3H2,1-2H3,(H,6,7) Y Key: AXFYFNCPONWUHW-UHFFFAOYSA-N Y InChI=1/C5H10O3/c1-5(2,8)3-4(6)7/h8H,3H2,1-2H3,(H,6,7) Key: AXFYFNCPONWUHW-UHFFFAOYAC
SMILES O=C(O)CC(O)(C)C
Properties
Chemical formula	C5H10O3
Molar mass	118.131 g/mol
Density	0.938 g/mL
Melting point	−80 °C (−112 °F; 193 K)
Boiling point	88 °C (190 °F; 361 K) at 1 mmHg
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

β-Hydroxy β-methylbutyric acid (HMB), or β-hydroxy β-methylbutyrate, is a metabolite of the essential amino acid leucine and is synthesized in the human body. Its part in protein synthesis was discovered by Steven L. Nissen at Iowa State University.^[2] It has been used in scientific studies to purportedly increase muscle mass and decrease muscle breakdown. Nissen held the original patent on the metabolite as a nutritional supplement. It was discovered in pigs and small quantities can also be found in grapefruit, alfalfa, and catfish. As a supplement it is usually sold as the calcium salt calcium beta-hydroxy-beta-methylbutyrate.

Research published in the Journal of Applied Physiology has shown that HMB may have an effect on increasing muscle weight and strength.^[2] A review in Nutrition & Metabolism provides an in depth and objective analysis of HMB research. ^[3] The same study lists as HMB's proposed mechanisms of action the following:

• Increased sarcolemmal integrity via conversion to HMG-CoA
• Enhanced protein synthesis via the mTOR pathway
• Depression of protein degradation through inhibition of the ubiquitin pathway

The human body produces about 0.2-0.4 grams per day. Standard doses in research studies have been 1.5 to 3.0 grams per day, usually divided into two doses. Toxicity at these doses is unlikely, as the no-observed-adverse-event-level (NOAEL) in rats is between 2.48 to 2.83 g/kg BW per day, roughly equivalent to 70 to 100 g/day in humans.^[4]

References

1. ↑ β-Hydroxyisovaleric acid at Sigma-Aldrich
2. 1 2 Nissen S, Sharp R, Ray M; et al. (November 1996). "Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistance-exercise training". J. Appl. Physiol. 81 (5): 2095–104. PMID 8941534. 
3. ↑ Wilson GJ, Wilson JM, Manninen AH. (2008). "Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise performance and body composition across varying levels of age, sex, and training experience: A review.". Nutrition & Metabolism 5: 1. doi:10.1186/1743-7075-5-1. PMC 2245953. PMID 18173841. 
4. ↑ Fuller JC Jr, Arp LH, Diehl LM, Landin KL, Baier SM, Rathmacher JA. (February 2014). "Subchronic toxicity study of β-hydroxy-β-methylbutyric free acid in Sprague-Dawley rats". Food Chem Toxicol. 67: 145–53. doi:10.1016/j.fct.2014.02.025. PMID 24576552.