NNAT and obesity due to melanocortin 4 receptor deficiency: Nnat mainly expresses in adult cerebral cortex, endocrine tissue, placenta, and adipose tissue, and its abnormal expression is associated with diabetes, obesity, and Lafora disease, which may be caused by an Nnat-mediated abnormality in Ca signaling abnormality, inflammation response, glucose exchange, or Nnat misfolding (16, 17).