Molecular and metabolic changes in white adipose tissue of the rat during development of ventromedial hypothalamic obesity

We have previously shown that rats made obese by lesion of ventromedial hypothalamus (VMH) nuclei, demonstrate an hyper-responsiveness to insulin with regard to whole-body glucose utilization one week after injury. This is mainly due to an increased glucose uptake in white adipose tissue. Six weeks after the lesion, glucose utilization in white adipose tissue returns to normal values. These modifications in insulin responsiveness could be mediated by altered activity and/or concentration of intracellular insulin effectors. In this study, we have measured the expression of the insulin-sensitive glucose transporter, Glut 4 and the activities and expression of key lipogenic enzymes (fatty-acid synthase and acetyl-CoA carboxylase) in white adipose tissue, one and six weeks after the lesion. All these parameters, as well as glucose transport and metabolism determined in white adipocytes, were markedly increased one week after the lesion. They returned to control values within six weeks in VMH-lesioned rats. These results indicate the existence of an increased expression of Glut 4 and lipogenic enzymes in white adipose tissue of VMH-lesioned rats which decreased with time and were parallel to glucose utilization determined in vivo.