Relationship of Adiposity to Inflammatory Components of Knee Osteoarthritis: The MOST Study

Title:

Relationship of Adiposity to Inflammatory Components of Knee Osteoarthritis: The MOST Study

Author(s):

Laura B. Hughes¹, Robert B. Wallace², Jingbo Niu³, David Felson³, Kassim Javaid⁴, Krishna Chaganti⁵, Cora Lewis¹. ¹The University of Alabama at Birmingham, Birmingham, AL; ²The University of Iowa, Iowa City, IA; ³Boston University School of Medicine, Boston, MA; ⁴The Botnar Research Centre, University of Oxford, Southampton, United Kingdom; ⁵Hospital for Special Surgery, New York, NY

Purpose: Increased body mass index (BMI) is associated with incident knee osteoarthritis (OA) and knee pain severity. Biomechanical factors play a role in this association, but inflammatory mediators have also been implicated, and visceral adipose tissue is an important site of cytokine production. The Multicenter Osteoarthritis Study (MOST) is a NIH-funded longitudinal study of subjects who either have knee OA or are at high risk of developing it. Demographic and radiographic data, whole body DEXA scans and Gd-DTPA enhanced MRI of one knee were obtained. We tested for association of adipose tissue as well as weight, BMI, lean body mass (LBM)), and whole body bone mineral density (BMD) measures with MRI evidence of synovitis. Methods: 30 month Gd-DTPA enhanced MRI images and baseline whole body DEXA (Hologic QDR-4500W) were available on 521 subjects. Fat mass (total and trunk), LBM, and total BMD were calculated utilizing DEXA. MRI synovitis (range 0-3) was scored from 6 compartments of the knee and categorized as: 0-normal; 1-mild; 2-moderate; 3-severe. BMI and weight were obtained at baseline. Predictor variables were separated into sex-specific quartiles and analyzed comparing the highest to lowest quartiles. Sex-specific univariate and multivariate ordinal logistic regression were performed.

Results: The mean age of subjects was 59.6 ± 7.2; 50.5% were female, and 86.5% were Caucasian. Mean baseline BMI was 29.5 + 4.7, weight 190.7 + 36.3 lbs, % fat mass total 32.0 + 8.4, abdominal fat mass/total fat mass 49.3% + 7.1%, LBM 56,563 +12,694 gms, and total BMD 1.16 + 0.13 gm/cm2. MRI evidence of synovitis was present in 75% of subjects.

In women, synovitis was positively associated with % fat mass total (*); however, this lost significance when adjusting for weight (**) (see Table 1). In men there was no significant association between % fat mass total and synovitis in the univariate analysis (*), but a significant inverse association was present in the model adjusted for weight (**). BMI, weight and LBM were positively associated with synovitis in women. In men, only LBM and total BMD were positively associated with synovitis.

Conclusions: We did not find an independent positive association between fat mass and knee synovitis. The sex-based differences in our study highlight the possibility of different pathological pathways in men and women with knee synovitis.

* Adj. for age, race, height
** Adj. for age, race, height, and weight

Disclosures:

L.B. Hughes, None; R.B. Wallace, None; J. Niu, None; D. Felson, None; K. Javaid, None; K. Chaganti, None; C. Lewis, None.