PNPLA2 and obesity due to melanocortin 4 receptor deficiency: The PI3K/AKT pathway can be activated to mediate SREBP regulation of fatty acid synthesis and FOXO1 signal pathway for fatty triglyceride lipase (ATGL) regulation of lipolysis, increasing glucose utilization and body fat deposition and reducing insulin resistance caused by obesity (Zhang et al., 2018; Savova et al., 2023).