In animal research, 4E1RCat prevented upregulation of fibronectin and Nr4a and delayed cartilage degeneration in a rat osteoarthritis model after an intra-articular injection [34]; it also regulated obesity via inhibition of protein tyrosine phosphatase 1B activity (US Patent No. 2006/070135 A1). Here, FN1 is linked to obesity due to melanocortin 4 receptor deficiency.