A. Joint circumference were calculated in CIA mice that were fed on regular diet (RD) (n=13 mice) or 60% high fat diet (HFD) (n=12 mice) for 8 weeks. B. CIA ankles harvested on day 29 from mice fed on RD and HFD were H&E stained (orig. mag. x 200), and C. inflammation (inflam), lining thickness (lining) and bone erosion (erosion) were quantified on a 0-5 scale, n=5 mice, 10 back paws. Synovial tissues (STs) obtained from the back paws of day 29 CIA mice fed on RD and HFD were stained with anti-GR1 antibody (orig. mag. x 200) (D) and GR1 staining was quantified on a 0-5 scale, (E) n=8. F. Joint MIP2, TNF, IL-6, IL-1 and IL-17 protein levels were assessed by ELISA from the front (carpal joints) and back paws of day 29 CIA mice fed on RD and HFD and normalized by joint weight, n=8. G. Joint circumference is shown from day 31 to day 55 in CIA mice that were fed on RD or HFD for up to 12 weeks, n=12-13 mice. H. CIA ankles harvested on day 55 from mice fed on RD and HFD were H&E stained (orig. mag. x 200), and I. inflammation, lining thickness and bone erosion were quantified on a 0-5 scale, n=8. J. % lean and fat mass or H&E staining of liver samples from day 55 CIA mice on RD and HFD were measured by dual-energy x-ray absorptiometry (DXA) or scored for fatty liver on a 0-4 scale, n=12-13. K. The frequency of CD3, B220, F480, F480+CD80+ as well as TH1 and TH17 cells was assessed in splenocytes harvested on day 55 from CIA mice fed on RD and HFD, n=7. L. Changes in joint MIP2, TNF, IL-6, IL-1 and IL-17 were determined by ELISA from day 55 CIA mice fed on RD and HFD, n=7. Values are mean ± SE. * indicates p<0.05.