Transient postweaning expression of excessive fat deposition and diabetes mellitus in ob/ob mice

Growth, glucose levels and body composition of male and female C57BL/6 ob/ob and lean (?/+) mice were examined between 17 days and 1 year of age. Obese mice displayed three distinct periods of growth with each phase characterized by a different pattern of glucoregulation. Until 4 weeks of age, ob/ob mice had slightly higher rates of weight gain and fat accretion than littermate lean mice. Glycemia was in the normal range and insulin levels were elevated. Shortly after the transition to solid food, ob/ob mice displayed several weeks of increased body growth and very high rates of fat deposition. During this period of rapid weight gain, hyperglycemia arose despite progressively increasing IRI concentrations. Examination of individual obese mice at this time revealed that glycemia was highly correlated with the rate of body fat deposition. The final phase of the ob/ob syndrome began at 3 months of age, as rates of fat deposition abruptly slowed to values slightly less than those of lean mice and glucose values declined to normal although hyperinsulinemia and glucose intolerance persisted. The present results show that ob/ob mice, although characterized throughout life by many metabolic and growth disturbances, only display diabetes mellitus and exaggerated fat deposition during a 6 to 8 week period just after weaning.