Regulatory Effect of Nutritional Status on Albumin Synthesis

(Young Investigator Award of JSNFS (2010))

Abstract

Serum albumin has become an indispensable factor for evaluation of nutritional status. In the regulation of albumin synthesis, stimulation resulting from ingestion of a meal is one of the most important factors. Transcription of the albumin gene is known to be influenced by protein nutrition status, and we have shown that modulation of albumin gene expression by amino acid supply in rat liver is mediated through the intracellular concentration of pyridoxal 5′-phosphate. We suggest that pyridoxal 5′-phosphate interacts directly with a tissue-specific transcription factor and modulates binding to the albumin gene. Post-transcriptional regulation plays an important role in the reduction of albumin synthesis under fasting conditions. Polypyrimidine tract-binding protein (PTB) is an abundant eukaryotic RNA-binding protein. We have shown that binding of PTB to the coding region of albumin mRNA suppresses its translation. We suggest that alterations in the level of the albumin mRNA-PTB complex are involved in the regulation of albumin synthesis in fasted rats.