SLC6A2 and obesity due to melanocortin 4 receptor deficiency: Sympathetic neuron-associated macrophages (SAMs), a macrophage population involved in norepinephrine clearance via the transporter Slc6a2, are upregulated in the sympathetic fibers of obese mice—deletion of Slc6a2 gene rescues the thermogenic capacities and promotes fat browning in obesity [134].