APLN and obesity due to melanocortin 4 receptor deficiency: In addition to TNF-α, IL-6, adiponectin, resistin, or leptin that are involved in obesity, other biomarkers are included, such as the retinol-binding protein-4 (RBP-4), visfatin, adipocyte fatty acid-binding protein (AFAABP), and some novel proteins like visceral adipose tissue-derived serpin A12 (vaspin) [130], apelin [131], and omentin, which may be involved in the development of GDM and in the progression of obesity [132].