β-hydroxy β-methylbutyrate (HMB), a metabolite of the essential amino acid leucine, has been shown to preserve muscle mass and strength during aging. The signaling mechanism by which HMB elicits its favorable effects on protein metabolism in ...

TLDR: Middle-aged rats who were given varying doses of β-hydroxy β-methylbutyrate (HMB), a metabolite of the essential amino acid leucine showed improvements in memory.

However the doses are ridiculously high IMO: 225 (low), 450 (medium), and 900 (high) mg/kg body weight/day.