PNPLA2 and obesity due to melanocortin 4 receptor deficiency: Interestingly, the metabolic actions of ATGL in metabolic tissues complicate the relationship between ATGL and inflammation in vivo, as evidenced in adipose-specific Atgl-KO mice that have reduced immune cell infiltration and improved insulin signaling in the liver (likely due to less adipose FA delivery), but greater proinflammatory gene expression and immune cell infiltration in adipose tissue in response to high-fat diet–induced obesity (17).