gene expression in infrapatellar fat pad is correlated with fat mass in obese patients with end-stage knee osteoarthritis.

OBJECTIVE

To investigate associations between obesity-linked systemic factors and gene expression indicative for the inflammatory and fibrotic processes in the infrapatellar fat pad (IFP), in a population of obese patients with end-stage knee osteoarthritis (KOA).

METHODS

We collected human IFPs from 48 patients with a mean body mass index (BMI) of 35.44 ​kg/m during total knee replacement procedures. These patients were part of a randomized controlled trial and met the criteria of having OA and a BMI of ≥30 ​kg/m. Blood samples were collected to assess serum levels of glucose, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, and leptin. Total body composition was measured using dual-energy X-ray absorptiometry. Gene expressions of in the IFP were analyzed.

RESULTS

Univariate analysis resulted in a positive correlation between BMI and procollagen-lysine,2-oxoglutarate 5-dioxygenase 2 () expression ( ​= ​0.13). In univariate analyses of obesity-linked systemic factors and , significant correlations were found for lean mass ( ​= ​0.20), fat mass ( ​= ​0.20), serum cholesterol ( ​= ​0.17), serum triglycerides ( ​= ​0.19) and serum leptin ( ​= ​0.10). A multiple linear regression model indicated fat mass to be a strong predictor of PLOD2 production in the IFP ( ​= ​0.22,  ​= ​0.003).

CONCLUSION

Our study demonstrates the positive association between fat mass and expression in the IFP of obese end-stage knee OA patients. This may indicate that within this patient population the fibrotic process in the IFP is influenced by systemic adipose tissue, next to local inflammatory processes.