Effects of aging and cytokine blockade on inflammatory cachexia.
OBJECTIVE
To evaluate the role of aging and specific cytokine blockade in the etiology of cachexia caused by adjuvant arthritis (AA), a model of cytokine-associated cachexia.


METHODS
AA was induced in Lewis rats using CFA. In Experiment 1, severity of AA and inflammatory cachexia was assessed in young (Y, age 2-6 months, n = 132) and old rats (O, age 18-22 months, n = 40). In Experiment 2, young rats were divided into 5 different intervention groups: Saline-injected (n = 66); CFA-injected (n = 78); CFA-injected and treated with IL-1 receptor antagonist (IL-1Ra, n = 18); CFA-injected and treated with soluble TNF receptor type I (sTNFrI, n = 27); and CFA-injected and treated with both IL-1Ra and sTNFrI (both treatments, n = 8).


RESULTS
In Experiment 1, young Lewis rats developed more severe arthritis (mean joint score on day 21 = 5.1 +/- 0.3) compared to the old group (0.6 +/- 0.6, p < 0.0001). The young group with AA lost 2.1% of baseline total body weight loss compared to 13.8% total body weight gain in controls (p < 0.0001). In contrast, old rats injected with CFA lost as much weight (-11%) as age-matched saline injected controls (-13%, p > 0.05, n = 18, age 18-22 months). In Experiment 2, mean joint scores in rats treated with IL-1Ra, sTNFrI or both were higher then untreated rats injected with CFA (p < 0.0001). Despite this, rats given both IL-1Ra and sTNFrI lost less weight on day 16 (p < 0.01) and 21 (p < 0.002) than untreated rats or those rats treated with either IL-1Ra or sTNFrI.


CONCLUSIONS
Lewis rats aged 2-6 months are more susceptible to developing AA than older rats (age range 18-22 months). Inhibition of both IL-1 and TNF is needed to mitigate AA-associated weight loss, and this effect is dissociated from the effect of such inhibition on joint inflammation.
Fathalla
B
B
Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts-New England Medical Center, Boston, Massachusetts, USA.
Hamada
K
K
Vannier
E
E
Smith
D
D
Edwards
C
C
Roubenoff
R
R
D000375:Aging / Q000502:physiology*; D000818:Animals; D001169:Arthritis, Experimental / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D001835:Body Weight / Q000187:drug effects; D002100:Cachexia / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D004195:Disease Models, Animal; D005260:Female; D005620:Freund's Adjuvant / Q000494:pharmacology; D053590:Interleukin 1 Receptor Antagonist Protein; D007596:Joints / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew; D018124:Receptors, Tumor Necrosis Factor / Q000627:therapeutic use*; D012795:Sialoglycoproteins / Q000627:therapeutic use*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors
D053590:Interleukin 1 Receptor Antagonist Protein; D018124:Receptors, Tumor Necrosis Factor; D012795:Sialoglycoproteins; D014409:Tumor Necrosis Factor-alpha; D005620:Freund's Adjuvant