Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by many cells and tissues including pancreatic b-cells, liver, skeletal muscle, and adipocytes. This study investigates the potential role of MIF in carbohydrate homeostasis in a physiological setting outside of severe inflammation, utilizing Mif knockout (MIFK/K) mice. Compared with wild-type (WT) mice, MIFK/K mice had a lower body weight, from birth until 4 months of age, but subsequently gained weight faster, resulting in a higher body weight at 12 months of age. The lower weight in young mice was related to a higher energy expenditure, and the higher weight in older mice was related to an increased food intake and a higher fat mass. Fasting blood insulin level was higher in

MIFK/K mice compared with WT mice at any age. After ip glucose injection, the elevation of blood insulin level was higher in MIFK/K mice compared with WT mice, at 2 months of age, but was lower in 12-month-old MIFK/K mice. As a result, the glucose clearance during intraperitoneal glucose tolerance tests was higher in MIFK/K mice compared with WT mice until 4 months of age, and was lower in 12-month-old MIFK/K mice. Insulin resistance was estimated (euglycemic–hyperinsulinemic clamp tests), and the phosphorylation activity of AKTwas similar in MIFK/K mice and WT mice. In conclusion, this mouse model provides evidence for the role of MIF in the control of glucose homeostasis.