NRDC and type 1 diabetes mellitus: Unlike the reduction in islet B7-H4 protein expression in T1D through the proteolytic cleavage of the B7-H4 protein from the cell membrane by the metalloproteinase nardilysin (NRD1) [21,22], we found that the expression of the islet B7-H4 protein was increased in HFD-induced obese and genetically modified T2D mice.