Effects of cyclic and continuous parenteral nutrition on albumin gene transcription in rat liver

Abstract

To evaluate schedule-dependent effects of parenteral nutrition on albumin gene expression and regulation, mRNA levels for albumin and its promoter-binding nuclear factors in the liver were measured in rats receiving cyclic or continuous parenteral nutrition. Rats were divided into three groups: the control group (n = 5) received a nonpurified diet, the continuous parenteral nutrition group (n = 5) received a continuous infusion of a defined parenteral nutrition formula, and the cyclic parenteral nutrition group (n = 5) received a cyclic (between 2000 and 0800) infusion of the same formula. After 7 d, rats were killed to obtain serum and liver. The serum albumin concentrations were 44 +/- 3 g/L in the controls, 31 +/- 2 g/L in the continuous parenteral nutrition group, and 33 +/- 3 g/L in the cyclic parenteral nutrition group. The mRNA for albumin and D site binding protein (DBP) was more abundant and mRNA for CCAAT/enhancer binding protein beta (C/EBP beta) was less abundant in the cyclic parenteral nutrition group than in the continuous parenteral nutrition group. Gel-shift assay for D site and gel-shift Western blotting of DBP carried out using another three rats in each group revealed an increase of DBP in rats receiving cyclic parenteral nutrition compared with continuous parenteral nutrition. In conclusion, although parenteral nutrition decreases serum albumin concentrations, cyclic parenteral nutrition maintains transcription of the albumin gene to a greater extent than does continuous parenteral nutrition. Cyclic parenteral nutrition, in contrast with continuous parenteral nutrition, sustains the mRNA and concentrations of DBP.