Associations between body composition, metabolic mediators and osteoarthritis in cats.

Background: Osteoarthritis (OA) is a common, age-related joint disease in cats. The common finding of bilateral symmetric joint involvement may suggest influence from systemic factors, and could imply that body parameters such as excess body fat and cat size are important for OA development. We aimed to investigate associations between body composition and whole-body OA scores in 72 cats, using whole-body computed tomography (CT), and if serum concentrations of the metabolic mediators leptin, adiponectin and insulin-like growth factor-1 (IGF-1) reflected the total OA load. In addition, associations between body composition and metabolic mediators were determined. For data analyses, cats were grouped as smaller or larger according to the median value of the total body bone volume (body size), and as leaner or fatter cats according to the median of the total body fat volumes normalized for body size (nBFV).

Results: Computed tomography-detected OA changes were present in 94% of cats. In appendicular joints, OA was most commonly detected in hip joints followed by elbow, stifle, carpal, tarsal and shoulder joints, whereas in axial joints, OA was most commonly detected in the thoracic region. Groupwise comparisons showed that whole-body OA scores were higher for fatter compared to leaner cats (p = 0.012), and larger fatter cats had higher whole-body OA scores compared to smaller leaner cats (p = 0.021). Whole-body OA scores were associated with IGF-1 concentrations (p = 0.0051). Leptin concentrations were strongly associated with nBFV (p < 0.0001), whereas IGF-1 concentrations were weakly associated with total body bone volumes (p = 0.0134). Individual joint region OA scores were higher in carpal, elbow, stifle and hip joints in fatter cats, in carpal joints in larger and larger fatter cats, in elbow joints in larger leaner cats, and in stifle joints in smaller fatter cats.

Conclusions: In cats, increased body fat is a risk factor for having a higher load of OA, particularly in carpal, elbow, stifle and hip joints. Increased body size is additionally a risk factor for having carpal OA. The total OA load is reflected in serum IGF-1 concentrations, but underlying mechanisms for this association are unclear.