CCL4 and obesity due to melanocortin 4 receptor deficiency: Obesity was associated with significant alterations in GPCR ligand mRNA expression in visceral adipose tissue, some of which encode for peptides with established effects on islet function (e.g. neuropeptide Y), or for GPCR ligands that have not previously been investigated for their effects on islets (e.g. (C‐C motif) ligand 4; Ccl4).