Abstract
This study reports on a comprehensive comparison of the effects of soy and meat proteins given at the recommended level on physiological markers of metabolic syndrome and the hepatic transcriptome. Male rats were fed semi-synthetic diets for 1 wk that differed only regarding protein source, with casein serving as reference. Body weight gain and adipose tissue mass were significantly reduced by soy but not meat proteins. The insulin resistance index was improved by soy, and to a lesser extent by meat proteins. Liver triacylglycerol contents were reduced by both protein sources, which coincided with increased plasma triacylglycerol concentrations. Both soy and meat proteins changed plasma amino acid patterns. The expression of 1571 and 1369 genes were altered by soy and meat proteins respectively. Functional classification revealed that lipid, energy and amino acid metabolic pathways, as well as insulin signaling pathways were regulated differently by soy and meat proteins. Several transcriptional regulators, including NFE2L2, ATF4, Srebf1 and Rictor were identified as potential key upstream regulators. These results suggest that soy and meat proteins induce distinct physiological and gene expression responses in rats and provide novel evidence and suggestions for the health effects of different protein sources in human diets.
Highlights
For panel (A), linear regression was performed for body weight of rats
We are the first to report on a comprehensive comparison of the effects of dietary soy and meat proteins given at the recommended level on markers of the metabolic syndrome and hepatic mRNA expression
Our work relates to some previously published papers that reported on the effects of dietary proteins, but most of these studies only focused on lipid metabolism and applied high fat diets in their studies[12,13,14,15], or focused on only one kind of dietary protein, mostly soy protein[15] or fish protein[13,14]
Summary
For panel (A), linear regression was performed for body weight of rats. The intercept representing initial body weight of rats was not different for three groups. This showed that mRNA expression of 68 PPARα target genes were significantly reduced by meat protein (P value < 0.05 & fold change > 2.0) but not by soy protein (see Supplementary Table S3 online). Unlike these studies, by measuring and comparing the widespread responses on plasma, hepatic gene expression and physiological markers, our study provides a comprehensive comparison between two different protein sources (soy and meat) versus casein, all provided at the recommended level.
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