3-hydroxy-3-methylbutyrate (HMB) is a leucine metabolite with protein anabolic action which may be employed in treatment of proteocatabolic illness and in endurance training. We examined the effects of exogenous HMB on protein synthesis and proteolysis in whole body and selected tissues of laboratory rat.
Rats were administered by HMB at a dose of 0.1 g/kg b.w. (s.c. and i.v., 1:1) or by saline (control). The parameters of whole-body protein metabolism were evaluated 24 hours later using L-[1-14C]leucine and L-[3,4,5-3H]phenylalanine. Changes in proteasome dependent proteolysis and protein synthesis in selected tissues were determined according the chymotrypsin-like activity and labeled leucine and phenylalanine incorporation into the protein. The results were analyzed using Mann-Whitney test.
A decrease in whole-body proteolysis and protein synthesis was observed in HMB treated rats. Proteasome-dependent proteolysis decreased significantly in skeletal muscle, changes in heart, liver, jejunum, colon, kidney, and spleen were insignificant. Decrease in protein synthesis was observed in the heart, colon, kidney, and spleen, while an increase was observed in the liver.
We conclude that protein anabolic effect of HMB in skeletal muscle is related to inhibition of proteolysis in proteasome. Alterations in protein synthesis in visceral tissues may affect several important functions and the metabolic status of the whole body.
Supported by PRVOUK P37/02.