摘要To the Editor:Iroquois-related Homeobox 3 (IRX3) is a member of the Iroquois homeobox gene family that encodes a protein known for its essential role in spinal cord development.[1] Recent studies reported that the expression level of this gene in hypothalamus is related to calorie intake and body composition.[1,2] There are some evidences that polymorphisms of IRX3 gene and the level of IRX3 gene expression are both related to obesity through various mechanisms.An interesting point is that in some studies,upregulation ofIRX3 was related to obesity,[2] while in some other studies,decrease of its expression was related to obesity.[1,3] Several mechanisms have been identified for the association between IRX3 gene and obesity.Knockout of IRX3 expression in brain resulted in a decrease of body fat mass by increasing basal metabolism rate and browning white adipose tissue.Knockout of IRX3 expression in mice caused an increase in uncoupling protein 1 (UCP1) gene expression in white adipose cells which is an important factor of browning white adipocytes.[2] However,contradictory results were found in this area.In the study by Zou eta/.,[1] it was observed that increasing the expression level of IRX3 is positively related with browning adipocytes.In this study,the researchers reported that IRX3 knockdown could decrease the expression of UCP 1 and thermogenesis and increase obesity.It seems that some metabolic factors influence the effect of IRX3 on body weight that may lead to contradictory results.