Phenotypic Differences in Inflammatory, Metabolic, and Biochemical Biomarkers in Dogs with Osteoarthritis According to Body Condition and Sex

Osteoarthritis (OA) in dogs is increasingly recognized as a condition with systemic inflammatory and metabolic components, potentially influenced by body condition and sex. This study aimed to characterize phenotypic differences in circulating inflammatory, metabolic, and biochemical biomarkers in dogs with OA according to body condition and sex. In this cross-sectional study, client-owned dogs were classified as healthy controls, thin dogs with OA (TOA), or obese dogs with OA (OOA). Circulating cytokines, adipokines, cartilage degradation markers, and routine biochemical parameters were measured in blood samples, including interleukin-1 beta, interleukin-4, interleukin-10, adiponectin, C-terminal telopeptide of type II collagen, and standard metabolic and hepatic markers. Data were analyzed using linear models fitted on log-transformed values, with group and sex as fixed effects, complemented by adjusted and sensitivity analyses. TOA dogs showed significantly higher interleukin-1 beta concentrations compared with controls (multiplicative effect 1.39, 95% confidence interval 1.05-1.82), indicating increased systemic inflammatory activity. In contrast, OOA dogs exhibited predominantly metabolic-associated alterations, including higher gamma-glutamyl transferase activity (multiplicative effect 1.22, 95% confidence interval 1.03-1.46) and higher cholesterol concentrations (multiplicative effect 1.22, 95% confidence interval 1.03-1.46). Several other biomarkers showed no clear group-related differences. Overall, these findings demonstrate that systemic biomarker profiles in canine OA vary primarily according to body condition, with secondary sex-related patterns, supporting the existence of biologically distinct OA phenotypes relevant for future diagnostic and therapeutic strategies.