LEP and obesity due to melanocortin 4 receptor deficiency: In this study, immunohistochemical analysis of the hypothalamic leptin receptor in obese rats induced by high-fat diet was conducted, and it was found that the expression of the hypothalamic leptin receptor was significantly decreased in the obesity model group, indicating that the leptin resistance in obese rats may be caused by the lack of receptors in the central part and the decreased expression of the hypothalamic receptor.