NRG4 and type 2 diabetes mellitus: Among the very first studies assessing the serum Nrg4 levels in people with diabetes, two case-control studies by Kang et al. [63] and Chen et al. [64] reported that serum Nrg4 levels were elevated in newly diagnosed T2DM, however, they were correlated with FPG but not glycated haemoglobin A1c (HbA1c).