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ARS Home » Southeast Area » Little Rock, Arkansas » Arkansas Children's Nutrition Center » Research » Publications at this Location » Publication #208295
Title: Colonic Fatty Acid Synthase is Down-regulated in Sprague-Dawley Rats Fed Soy Protein Isolate

Author
item XIAO, RIJIN - ACNC/UAMS
item SIMMEN, FRANK - ACNC/UAMS

Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/15/2007
Publication Date: 4/28/2007
Citation: Xiao, R., Simmen, F.A. 2007. Colonic fatty acid synthase is down-regulated in Sprague-Dawley rats fed soy protein isolate [abstract]. The FASEB Journal. 21(6):A1103.

Interpretive Summary: We have a long-standing interest in soy foods, primarily because about 25% of American infants are fed soy formula. In addition, soy foods have been associated with beneficial health outcomes, as well as potential adverse effects. Previous work from our lab has demonstrated that animals fed soy protein are partially protected against colon cancer. In this study, we evaluated the dietary effects of soy protein on the presence of an important enzyme in fat metabolism, and which may also be important to cancer development. This enzyme is called fatty acid synthase. Our data show that a soy protein-based diet suppresses fatty acid synthase production in the large intestine and suggest that this may occur because of effects on insulin. This is associated with the insulin-lowering effects of soy foods. Our data suggest that there is a positive relationship between soy, fatty acid synthase, and lowering of risk of developing colon cancers. Future studies will be aimed at determining if early soy exposure, such as occurs with infant formula, can influence colon cancer later in life.

Technical Abstract: Fatty Acid Synthase (FAS), a key enzyme in the fatty acid biosynthetic pathway, is over-expressed in multiple cancers. The aim of this study was to evaluate the effects of dietary proteins [soy protein isolate (SPI) and casein (CAS), latter is the control] on the expression of FAS in the colonic mucosa of male rats. Animals were fed AIN93G diets containing CAS (20%) or SPI (20%) over a lifetime. Results indicated that soy protein consumption decreased circulating insulin concentration, compared to casein (P<0.05); a similar effect on serum C-peptide was observed. FAS mRNA abundance in colon mucosa was decreased in SPI-fed rats (P<0.05). Relative expression of sterol regulatory element binding protein-1c (SREBP-1c), an insulin-responsive transcription factor that regulates FAS expression, was also suppressed with SPI diet (P<0.05). Immunohistochemistry identified FAS in crypt absorptive cells, with strong staining detected in basal regions of crypts; weaker staining was observed in luminal epithelium. Overall tissue staining of FAS was reduced with SPI diet. In summary, soy protein consumption decreased colon mucosa FAS gene and protein expression, probably via decreases in circulating insulin/C-peptide and colonic SREBP-1c. The relative impact of these effects on soy protein’s colon cancer-preventive actions is currently under investigation.