C/EBP alpha expression in adipose tissue of genetically obese Zucker rats.

The adipose tissue of genetically obese Zucker rats is characterized by coordinated tissue specific overtranscription of a subset of genes related to lipid storage such as Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH). We show that CCAAT/Enhancer Binding Protein alpha (C/EBP alpha) is an activator of GAPDH proximal promoter in transiently transfected mature rat adipocytes. C/EBP alpha mRNA levels were increased in adipose tissue but not in liver of obese as compared to lean rats at 30 days of age, i.e., when obesity is fully expressed. Nevertheless at 16 days of age, although overdevelopment of adipose tissue could be detected in preobese rats, C/EBP alpha mRNA levels were similar whatever the genotype. In conclusion C/EBP alpha mRNA is overexpressed in adipose tissue of obese rats, suggesting a possible role for this factor in the activation of lipid storage-related genes in adipose tissue of obese rats. However, C/EBP alpha overexpression is not temporally related to the onset of obesity.