Investigating inflammation of adipose tissue in a diet induced obesity model of OA in female sprague dawley rats

This study was aimed at evaluating the disturbance of mesenteric fat, and the infrapatellar fat pad (IFP) of the knee, and their potential contribution to systemic inflammation and local inflammation in the knee, and the development of knee joint OA in female Sprague-Dawley rats.Female rats were randomized into two groups; a Chow-fed group (Chow) and rats fed a high-fat and high-sucrose diet (HFS). Body composition, serum lipid profile, insulin resistance, serum and synovial fluid inflammatory markers, knee joint degeneration, and adipocyte size in the two fat depots were assessed after 12 weeks of the diet interventions. Mesenteric fat macrophage infiltration and infrapatellar fat pad fibrosis were also quantified.Rats from the HFS group had higher body fat, serum triglycerides levels, serum cholesterol levels, insulin resistance, increases in selected serum biomarkers such as TNF-α, leptin, MCP-1, and MIP-1α, and more severe cartilage degeneration and subchondral bone lesions than did the Chow-fed control rats. However, no increase in macrophage infiltration and fibrosis in the fat tissues were observed in the HFS group compared to the chow-fed group.The mesenteric fat and IFP were protected from inflammation associated with the HFS diet in the female rats, indicating a sex-based difference in the response to the HFS diet. However, cartilage degeneration and subchondral bone lesions were increased in the HFS compared to the control group rats, suggesting that the mechanisms resulting in knee OA development and progression in female rats may distinctly differ from that of male rats.