KO mice display no deficiency at young age (3–4 months) but have impaired insulin production and glucose tolerance later (13–14 months). No difference in the symptom severity in either STZ-induced diabetes (8- to 10-week-old), or caerulein-induced pancreatitis (6- to 8-week-old). After high-fat diet for 19 weeks, islet mass expansion and serum insulin level were reduced in KO vs. WT. Blood glucose is significantly lower in KO mice vs. WT from 11 to 19 weeks. The gene discussed is INS; the disease is diabetes mellitus.