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11.10.2014

HMB inhibits muscle atrophy by corticosteroids

Corticosteroids such as dexamethason and prednison are powerful anti-inflammatories, but they also cause muscles to atrophy – and that's less good news. Should you ever need to use corticosteroids, it might be worth considering using HMB. According to researchers at Pusan National University in South Korea, HMB can reduce muscle atrophy caused by corticosteroids.

HMB

Dexamethasone Prednisone HMB Leucine

HMB is a metabolite of leucine, and muscle cells have a kind of inbuilt sensor for this amino acid. The more leucine muscle cells 'see', the more they do their best to grow.

HMB has a similar effect on muscle cells, but we don't know exactly how HMB actually works. A not particularly new theory suggests that it's not leucine that muscle cells 'see', but its metabolite HMB. Recent studies suggest however that HMB and leucine induce muscle growth in two different ways.

Study
The Koreans wanted to know whether patients who had to take corticosteroids would retain muscle mass by taking either leucine or HMB. They performed an animal study in which they gave rats dexamethasone, a corticosteroid, for 5 days. Dexamethasone is five times stronger than prednisone. A control group [Con] was given no active substances.

One group of rats was given only dexamethasone. [Dexa]

Another group was given a hefty dose of leucine on top of this. [Dexa + Leu] The human equivalent of this dose would be about 8 g per day, based on a person weighing 80 kg.

Another group of rats was given a modest dose of HMB in addition to the dexamethasone. [Dexa +HMB 150] The human equivalent of this dose would be about 2 g per day.

Yet another group of rats was given a hefty dose of HMB in addition to the dexamethasone. [Dexa + HMB 600] The human equivalent of this dose would be about 8 g per day.

Less muscle loss
At the end of the five days the dexamethasone had reduced the weight of the rats' gastrocnemius muscle, but HMB supplementation had reduced the level of atrophy. The figure below shows the weight of the gastrocnemius as a proportion of the rats' bodyweight.

Dexamethason also reduced the rats' muscle strength and boosted the concentration of creatine kinase in the blood. The latter is an indication of muscle damage.

Mechanism
The Koreans think that HMB sabotages the forkhead box protein O1 [FOXO1]. The receptor to which corticosteroid hormones attach themselves doesn't function properly without this protein.

Conclusion
"Our in vivo data show that HMB protects against glucocorticoid-induced muscle atrophy and suggest that HMB supplementation be considered a potential treatment for muscle atrophy", the Koreans write.

Source:
PLoS One. 2014 Jul 17;9(7):e102947.

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