Cachexia in rheumatoid arthritis is associated with inflammatory activity, physical disability, and low bioavailable insulin-like growth factor.
OBJECTIVE
To examine the impact of inflammation, insulin-like growth factor (IGF-1) and its regulating binding protein (IGFBP-1) on lean body mass (LBM) in patients with rheumatoid arthritis (RA).


METHODS
In 60 inpatients (50 women), inflammatory activity was measured by Disease Activity Score 28 (DAS28), C-reactive protein (CRP), and interleukin (IL)-6, and physical disability by the Health Assessment Questionnaire (HAQ). LBM was assessed by dual-energy X-ray absorptiometry (DXA) and fat free mass index (FFMI; kg/m(2)) and fat mass index (FMI; kg/m(2)) were calculated.


RESULTS
Median age was 65 years and disease duration 13 years. Fifty per cent of the patients had FFMI below the 10th percentile of a reference population and 45% had FMI above the 90th percentile, corresponding to the condition known as rheumatoid cachexia (loss of muscle mass in the presence of stable or increased FM). DAS28, CRP, and IL-6 correlated negatively with LBM (p = 0.001, 0.001, and 0.018, respectively), as did HAQ (p = 0.001). Mean (confidence interval) IGF-1 was in the normal range, at 130 (116-143) microg/L. IGFBP-1 levels were elevated in patients (median 58 microg/L in women and 59 microg/L in men) compared with a normal population (33 microg/L in women and 24 microg/L in men). The ratio IGF-1/IGFBP-1, which reflects bioavailable IGF-1, was low (2.0 microg/L) and was positively correlated with LBM (p = 0.015). In multiple regression analysis, 42% of the LBM variance was explained by IGF-1/IGFBP-1, HAQ score, and DAS28.


CONCLUSIONS
A large proportion of RA inpatients, mainly women, had rheumatoid cachexia. The muscle wasting was explained by inflammatory activity and physical disability as well as low bioavailable IGF-1.
Engvall
I-L
IL
Department of Rheumatology, the Karolinska Institute, Karolinska University Hospital Huddinge, Stockholm, Sweden. inga-lill.engvall@karolinska.se
Elkan
A-C
AC
Tengstrand
B
B
Cederholm
T
T
Brismar
K
K
Hafstrom
I
I
D000368:Aged; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology*; D001682:Biological Availability; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000378:metabolism; D002100:Cachexia / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology*; D016022:Case-Control Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012720:Severity of Illness Index; D013851:Thinness / Q000503:physiopathology
D018970:Insulin-Like Growth Factor Binding Protein 1; D015850:Interleukin-6; D007334:Insulin-Like Growth Factor I; D002097:C-Reactive Protein