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Dietary soya protein concentrate enriched with isoflavones reduced fatty liver, increased hepatic fatty acid oxidation and decreased the hepatic mRNA level of VLDL receptor in obese Zucker rats

Published online by Cambridge University Press:  08 March 2007

Oddrun A. Gudbrandsen*
Affiliation:
Institute of Medicine, Section of Medical Biochemistry, University of Bergen, Haukeland University Hospital, N-5021 Bergen, Norway
Hege Wergedahl
Affiliation:
Institute of Medicine, Section of Medical Biochemistry, University of Bergen, Haukeland University Hospital, N-5021 Bergen, Norway
Sverre Mørk
Affiliation:
Gade Institute, Department of Pathology, University of Bergen, Haukeland University Hospital, N-5021 Bergen, Norway
Bjørn Liaset
Affiliation:
National Institute of Nutrition and Seafood Research, Box 2029 Nordnes, N-5817 Bergen, Norway
Marit Espe
Affiliation:
National Institute of Nutrition and Seafood Research, Box 2029 Nordnes, N-5817 Bergen, Norway
Rolf K. Berge
Affiliation:
Institute of Medicine, Section of Medical Biochemistry, University of Bergen, Haukeland University Hospital, N-5021 Bergen, Norway
*
*Corresponding author: Dr Oddrun A. Gudbrandsen, fax +47 55973115, email nkjgu@uib.no
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Abstract

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Casein-based diets containing a low (LDI) or high (HDI) dose of soya protein concentrate enriched with isoflavones were fed to obese Zucker rats for 6 weeks. HDI feeding, but not LDI feeding, reduced the fatty liver and decreased the plasma levels of alanine transaminase and aspartate transaminase. This was accompanied by increased activities of mitochondrial and peroxisomal β-oxidation, acetyl-CoA carboxylase, fatty acid synthase and glycerol-3-phosphate acyltransferase in liver and increased triacylglycerol level in plasma. The decreased fatty liver and the increased plasma triacylglycerol level appeared not to be caused by an increased secretion of VLDL, as HDI decreased the hepatic mRNA levels of apo B and arylacetamide deacetylase. However, the gene expression of VLDL receptor was markedly decreased in liver, but unchanged in epididymal white adipose tissue and skeletal muscle of rats fed HDI, indicating that the liver may be the key organ for the reduced clearance of triacylglycerol-rich lipoproteins from plasma after HDI feeding. The n−3/n−6, 20:4n-/8:2n−6 and (20:5n−3+22:6n−3)/18:3n−3 ratios were increased in liver triacylglycerol by HDI. The phospholipids in liver of rats fed HDI contained a low level of 20:4n−6 and a high level of 20:5n−3, favouring the production of anti-inflammatory eicosanoids. When obese Zucker rats were fed soya protein, this also resulted in reduced fatty liver, possibly through reduced clearance of VLDL by the liver. We conclude that the isoflavone-enriched soya concentrate as well as soya protein may be promising dietary supplements for treatment of non-alcoholic fatty liver.

Type
Research Article
Copyright
Copyright © The Nutrition Society 2006

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