Additionally, NPY is co-expressed with noradrenaline in central noradrenergic neurons and peripheral sympathetic nervous system (SNS) (Ekblad et al., 1984), where NPY promotes weight gain by inhibiting lipolysis, and stimulating adipogenesis and angiogenesis in the adipose tissue, and is indispensable for stress-induced obesity (Zukowska-Grojec et al., 1998; Bradley et al., 2005; Kuo et al., 2007; Zhang et al., 2014). Here, NPY is linked to obesity due to melanocortin 4 receptor deficiency.