INS and obesity due to melanocortin 4 receptor deficiency: While mice possessing global deletions of p85α/β and p55α/p50α exhibit improved insulin sensitivity (88–90) and mice with global deletions in p110α and p110β display impaired insulin sensitivity (91, 92), given that these subunits are deleted in all insulin sensitive tissues the exact function of myeloid cell specific PI3Ks during obesity and insulin resistance remains an enigma.