Spontaneous obesity and weight loss: insulin binding and lipogenesis in the dormouse

Obese dormice (Glis glis) become anorexic during the weight loss phase of the 2-mo (infradian) body weight cycle. We have shown previously that this phase is characterized by severe insulin resistance, manifested by impaired insulin-stimulated glucose utilization in isolated adipocytes. Contrary to other obesity models, the insulin resistance was not accompanied by hyperinsulinism. In the present study, impaired lipogenesis was associated with decreased maximal insulin-binding capacity (due to a reduction in receptor concentration) and a postreceptor defect, which were exacerbated rather than attenuated during weight loss.