Treg cells in adipose tissue express the enzyme hydroxyprostaglandin dehydrogenase (HPGD), which converts prostaglandin E2 (PGE2) into 15-keto PGE2, and Treg cell-specific loss of HPGD exacerbates adipose inflammation and insulin resistance in response to diet-induced obesity [47]. The gene discussed is HPGD; the disease is obesity due to melanocortin 4 receptor deficiency.