PLAU and obesity due to melanocortin 4 receptor deficiency: The development of kidney and spleen abnormalities seen in cDNA-uPA/SCID mice is a limitation for future development of a humanized mouse model of obesity and insulin resistance, a lengthy process that entails first, engraftment of human hepatocytes for approximately 3 months, and then, feeding special diets for 10–12 weeks to promote the development of metabolic disease, bringing mouse age to >6 months at the end of the experimentation.