β-Hydroxy--methylbutyrate modulates lipid metabolism in adipose tissues of growing pigs

Background: The effects and roles of the leucine (Leu) metabolite -hydroxy--methylbutyrate (HMB) in lipid metabolism in adipose tissues of pigs are still unknown. Objectives: This study was conducted to investigate the effects of excess Leu versus HMB on growth, carcass traits, and lipid metabolism in adipose tissues of growing pigs. Methods and results: Compared to control, the Leu/HMB group significantly increased/reduced weight of total fat mass, respectively, with a concurrent increase of serum adiponectin concentration (P < 0.05). Moreover, dietary HMB supplementation regulated the expression of genes involved in adipose tissue function, accompanied by increases/decreases in the phosphorylation of AMPK/mTOR in perirenal adipose tissue, respectively (P < 0.05). Serum IL-15 concentration and the mRNA abundance of IL-15, PGC-1, and NRF-1 were also increased in the HMB group (P < 0.05). Conclusions: HMB supplementation can regulate adipose tissue function including fatty acid oxidation, lipolysis, and adipokine secretion. These effects may be partly mediated by AMPK-mTOR pathway and associated with mitochondrial biogenesis, the AMPK-PGC-1 axis, and myokines secreted by muscle tissues.