Adverse Effects of Excessive Leucine Intake Depend on Dietary Protein Intake: A Transcriptomic Analysis to Identify Useful Biomarkers

DOI PubMed 2 Citations 29 References
  • IMAMURA Wataru
    Corporate Sponsored Research Program “Food for Life,” Organization for Interdisciplinary Research Projects, The University of Tokyo
  • YOSHIMURA Ryoji
    Laboratory of Molecular Nutrition, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University
  • TAKAI Marie
    Laboratory of Molecular Nutrition, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University
  • YAMAMURA Junki
    Corporate Sponsored Research Program “Food for Life,” Organization for Interdisciplinary Research Projects, The University of Tokyo
  • KANAMOTO Ryuhei
    Laboratory of Molecular Nutrition, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University

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Abstract

The present study was conducted to identify reliable gene biomarkers for the adverse effects of excessive leucine (Leu) in Sprague-Dawley rats by DNA microarray. It has long been known that the adverse effects of excessive amino acid intake depend on dietary protein levels. Male rats were divided into 12 groups (n=6) and fed for 1 wk a diet containing low (6%), moderate (12%) or high (40%) protein. Different levels of Leu (0, 2, 4, and 8%) were added to the diets. Consumption of diets containing more than 4% Leu in 6% protein resulted in growth retardation and reduced liver weight, whereas the administration of the same dose of Leu with 12% or 40% protein did not affect them. By a process of systematic data extraction, 6 candidate gene markers were identified. The liver gene expression data obtained from another experiment with 0, 2, 3, 4, and 8% Leu in a low-protein diet was used to examine the validity of these biomarker candidates with receiver operating characteristic (ROC) curve analysis. All of AUC values of the biomarker candidates were more than 0.700, suggesting the effectiveness of the marker candidates as the indices of Leu excess. The cut-off value for the ROC curve of the gene-marker panel, which was obtained by multiple regression analysis of gene markers, indicated that Leu levels higher than 3% have adverse effects. In conclusion, the gene-marker panel suggested that for male rats dietary Leu supplementation of 2% is the NOAEL dose in low-protein (6%) diets.

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