Gene expression of albumin and liver-specific nuclear transcription factors in liver of protein-deprived rats

Abstract

Protein-energy malnutrition causes hypoalbuminemia. Recent work has suggested that this may be partly due to decreased transcription of the albumin gene. This study examined the role of cis-acting and transacting elements of the albumin gene during protein deprivation. Mate 7-wk-old Donryu rats were fed a protein-free diet (0% casein diet) for 10 d or given restricted (pair-fed control) or free access (freely fed control) to a 25% casein diet. Serum albumin concentrations were significantly lower in the protein-deprived rats (29 ± 1 g/L) than in the pair-fed controls (42 ± 3 g/L) or the freely fed controls (45 ± 3 g/L). The albumin mRNA level was also significantly lower in livers of protein-deprived rats (36% of pair-fed control). However, gel mobility shift analysis using river nuclear extracts did not show any significant difference between the protein-deprived rats and the pair-fed controls in the binding activity to the B and D sites of the albumin promoter. Furthermore, gel mobility shift-Western blot analysis showed no significant difference between the two groups in the protein levels of nuclear transcription factors binding to the D sites. The amounts of mRNA of hepatocyte nuclear factor-1 binding to the B site were not significantly different between these two groups. These results suggest that the proximal promoter region may not play a major role in the down-regulation of the albumin gene during protein deprivation.