FTO and obesity due to melanocortin 4 receptor deficiency: The literature showed that gga-miR-33 can participate in lipid metabolism by targeting fat mass and obesity-associated (FTO) genes associated with obesity in chicken liver [1], and miR-33 can regulate cholesterol and fatty acid metabolism in mammals (humans and mice), which corresponds to the function of the host gene sterol regulatory element binding transcription factor 2 (SREBP2), which can regulate the synthesis and uptake of triglycerides and cholesterol [62,63], it can be seen that miR-33 functions similarly in chickens and mammals (humans and mice).