β-Hydroxy-β-methylbutyrate (HMB)

β-Hydroxy-β-methylbutyrate (HMB) is a small molecule metabolite formed from the breakdown of the amino acid leucine in the human body[3]. It is best known as a dietary supplement used to improve muscle mass and strength, particularly in older adults or those with muscle wasting. HMB does not function as a receptor, enzyme, or traditional therapeutic target; rather, it acts indirectly to stimulate protein synthesis (via mTORC1 pathway) and inhibit muscle protein breakdown. It is commonly formulated as calcium β-hydroxy-β-methylbutyrate (HMB-Ca) for supplementation[1][2][3][4].

Other names

HMBβ-hydroxy β-methylbutyratebeta-hydroxy beta-methylbutyratehydroxymethylbutyrate3-hydroxy-3-methylbutyric acidbeta-hydroxyisovaleric acid

Increases protein synthesis (via mTORC1 activation), decreases protein breakdown