LCN2 and diabetic kidney disease: DKD is a complication with multifaceted pathogenesis, therefore it is possible to consider biomarkers related to the different mechanisms involved in kidney injury, such as oxidative stress (i.e., 8-hydroxyseoxy-guanosine—8-OHdG), glomerular (i.e., nephrin) and tubular damage (i.e., urinary neutrophil gelatinase-associated lipocalin—NGAL—and urinary kidney injury molecule 1—KIM-1), inflammation (i.e., interleukin-6—IL-6), and fibrosis (i.e., type IV collagen) [3,14,15,16].