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09.01.2009


HMB inhibits protein metabolism, animal study shows

Publicity for HMB, full name beta-hydroxy-beta-methylbutyrate, it most certainly isn't, this Czech study. The researchers pumped rats full of HMB and then studied the effect of this amino acid metabolite on the rats' protein metabolism. And, although the researchers themselves state with a note of satisfaction that they have uncovered the way in which HMB works with their animal study, we the compilers of this critical web magazine are scratching our heads in confusion.

What effect?

The Czechs put the animals on a drip, with 0.1 g HMB per kilo bodyweight. A control group was given salt instead. Then the researchers waited a day before giving the rats labelled amino acids leucine and phenylalanine. By tracking the amino acids, the researchers were able to determine the effect of HMB on protein synthesis and breakdown.


HMB inhibits protein metabolism, animal study shows


HMB reduces the protein breakdown, but also the production of protein. In fact the entire protein metabolism process is lowered by HMB. The table below shows the 'fractional rate of protein synthesis' in various body tissues. Protein metabolism is reduced in all of them except the liver.


HMB inhibits protein metabolism, animal study shows


The most important route for protein breakdown in the muscle cells is via the proteasome, which is where the enzyme chymotrypsin breaks proteins down into fragments. HMB considerably reduces the activity of this enzyme.


HMB inhibits protein metabolism, animal study shows


And this is what makes the Czechs suspect that they have discovered how HMB's anti-catabolic effect works. Voila! That's good for a publication in Food and Chemical Toxicology. But, we ask ourselves, what use is an anti-catabolic supplement that also inhibits anabolic processes to power athletes?

By the way, there are studies that show that HMB does work. A lot of these come from the HMB manufacturers' own box, and most of the time there's something fishy about them. We are not convinced.

Sources:
Food Chem Toxicol. 2008 Nov 21. [Epub ahead of print].