EXT1 and obesity due to melanocortin 4 receptor deficiency: White adipose tissue (WAT) macrophages exhibit lower HS levels, resulting in reduced intercellular mitochondrial transfer from adipocytes to macrophages in mice with obesity or deletion of the myeloid-cell HS biosynthesis gene exostosin-1 (Ext1), which increases body weight and obesity and decreases glucose tolerance and insulin sensitivity [125].