DHPS and obesity due to melanocortin 4 receptor deficiency: A study investigating the onset of facultative β cell mass expansion during obesity/insulin resistance using an inducible β cell-specific Dhps knockout mouse demonstrated that DHPS activity is increased in islets in response to a high-fat diet (HFD) and facilitates the induction of β cell proliferation and the maintenance of normal glucose homeostasis after HFD feeding [20].