Protein metabolism in rheumatoid arthritis and aging. Effects of muscle strength training and tumor necrosis factor alpha.
OBJECTIVE
To determine the effects of rheumatoid arthritis (RA) on whole-body protein metabolism.


METHODS
We examined protein metabolism and its hormonal and cytokine mediators before and 12 weeks after progressive resistance muscle strength training in 8 healthy young (mean +/- SD age 25 +/- 2 years) and 8 healthy elderly (70 +/- 5 years) men and women, and in 8 adults with RA (42 +/- 13 years). An additional 6 healthy elderly subjects (69 +/- 3 years) served as a swimming-only control group.


RESULTS
Subjects with RA had higher rates of protein breakdown than did young or elderly healthy subjects (79.9 +/- 17.2 versus 60.3 +/- 5.8 and 63.7 +/- 12.4 mumoles/gm total body potassium/hour, respectively, P < 0.05), while there was no effect of age per se. Patients treated with methotrexate had normal rates of protein breakdown (P < 0.01 versus RA without methotrexate; P not significant versus healthy young subjects). Increased protein catabolism in RA was no longer evident after strength training. In multiple regression analysis, levels of tumor necrosis factor alpha (TNF alpha) (r = 0.47, P = 0.01) and growth hormone (r = -0.51, P = 0.006) were associated with protein breakdown, and plasma glucagon levels were inversely correlated with protein synthesis (r = -0.45, P = 0.02). Growth hormone (r = -0.56, P = 0.002) and glucagon (r = 0.45, P = 0.04, levels were associated with protein oxidation.


CONCLUSIONS
Adults with RA have increased whole-body protein breakdown, which correlates with growth hormone, glucagon, and TNF alpha production.
Rall
L C
LC
USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts 02111, USA.
Rosen
C J
CJ
Dolnikowski
G
G
Hartman
W J
WJ
Lundgren
N
N
Abad
L W
LW
Dinarello
C A
CA
Roubenoff
R
R
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005934:Glucagon / Q000097:blood*; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007930:Leucine / Q000378:metabolism; D008297:Male; D008727:Methotrexate / Q000627:therapeutic use; D008875:Middle Aged; D011506:Proteins / Q000378:metabolism*; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D018501:Antirheumatic Agents; D011506:Proteins; D014409:Tumor Necrosis Factor-alpha; D013006:Growth Hormone; D005934:Glucagon; D007930:Leucine; D008727:Methotrexate