Comparative Proteomics Provides Insights into Metabolic Responses in Rat Liver to Isolated Soy and Meat Proteins

It has been reported
that isolated dietary soy and meat proteins
have distinct effects on physiology and liver gene expression, but
the impact on protein expression responses are unknown. Because these
may differ from gene expression responses, we investigated dietary
protein-induced changes in liver proteome. Rats were fed for 1 week
semisynthetic diets that differed only regarding protein source; casein
(reference) was fully replaced by isolated soy, chicken, fish, or
pork protein. Changes in liver proteome were measured by iTRAQ labeling
and LC–ESI–MS/MS. A robust set totaling 1437 unique
proteins was identified and subjected to differential protein analysis
and biological interpretation. Compared with casein, all other protein
sources reduced the abundance of proteins involved in fatty acid metabolism
and Pparα signaling pathway. All dietary proteins, except chicken,
increased oxidoreductive transformation reactions but reduced energy
and essential amino acid metabolic pathways. Only soy protein increased
the metabolism of sulfur-containing and nonessential amino acids.
Soy and fish proteins increased translation and mRNA processing, whereas
only chicken protein increased TCA cycle but reduced immune responses.
These findings were partially in line with previously reported transcriptome
results. This study further shows the distinct effects of soy and
meat proteins on liver metabolism in rats.