Researchers Find that Smoking Wastes Muscle Away

It is well known that smoking causes a number of detrimental physiological effects. Now in a new study from the UK published in the Journal of American Physiology, scientists have found that smoking also has a direct and damaging effect on muscle mass.

The study was conducted by Anne Marie Winter Peterson, academic at the Copenhagen Research Muscle Center in Denmark and Bettina Mittendorfer from the School of Biomedical Sciences at the University of Nottingham in Derby, United Kingdom.

The research was prompted by questions of the uncertainty if smoking had any direct effect on skeletal muscle. Previous studies had demonstrated that smokers had a decreased muscle mass, but the underlying mechanism of action was unknown.

The research team studied 8 smokers (four men and four women) who had a documented smoking history of at least 20 cigarettes per day for a minimum of twenty years. Their physiological function was directly compared to non-smokers that were matched by gender and age. The average age of study participants was 65±3 in the smoking group and 63±3 in the control group. The researchers also made sure the study volunteers were matched for body habitus (size) with the smokers having a body mass index (BMI) of 25.9±0.9 and the non-smokers averaging a BMI of 25.1±1.2.

In their study, each participant was administered an intravenous infusion of a non-dangerous radioactive amino acid (leucine) to assess muscle metabolism. Blood and muscle samples were then subsequently obtained from each individual.

The muscle tissue was tested via indices of muscle formation and muscle breakdown. The team also measured the expression of genes that are involved in the regulation of muscle mass, such as myostatin (an inhibitor of muscle growth), MAFBx/MurRF-1 (metabolic enzymes) and TNF-alpha (a mediator of inflammation).

When the research team compared the lab values between groups, they found that there were no major differences in the inflammatory factor levels. However, the biological marker of muscle formation (FSR) was almost 40% less in smokers than in non-smokers (0.037 vs 0.059).

When they evaluated the markers that inhibit muscle growth (myostatin, MAFB-X), they found that smokers exhibited much higher levels than the non-smokers by 33 and 45%, respectively.

With these data, the team arrived at the conclusion that smoking directly impairs the generation of muscle protein, and at the same time, increases the expression of genes that encode for proteins that compromise adequate muscle turnover and preservation.

In the University of Nottingham's press release, the researchers involved with the study stated that "from our tests, we can conclude that smoking slows the muscle protein synthesis machinery. We are all well aware of the ill affects of smoking on the lungs but our study reveals yet another cause of ill-health associated with smoking. Hopefully the UK smoking ban will encourage people to quit while they are still young, helping them to keep in good health in later life".

Sources:

American Journal of Physiology/Endocrinology and Metabolism:

http://ajpendo.physiology.org/cgi/content/abstract/00301.2007v1?maxtoshow=&HITS=&hits=&RESULTFORMAT=&author1=Rennie&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT

University of Nottingham News: http://www.nottingham.ac.uk/public-affairs/press-releases/index.phtml?menu=pressreleases&code=MOR-127/07&create_date=09-jul-2007