|HAKKAK, REZA - University Arkansas For Medical Sciences (UAMS)|
|KOROURIAN, SOHEILA - University Arkansas For Medical Sciences (UAMS)|
Submitted to: Journal of Medicinal Food
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2015
Publication Date: 7/17/2015
Publication URL: http://handle.nal.usda.gov/10113/61174
Citation: Hakkak, R., Zeng, H., Korourian, S. 2015. Short and long-term soy diet vs. casein protects liver steatosis independent of the arginine content. British Journal of Nutrition [epub ahead of print]. http://online.liebertpub.com/doi/10.1089/jmf.2015.0002.
Interpretive Summary: Non-alcoholic fatty liver disease (NAFLD), the major cause of abnormal liver function, is often associated with obesity. It is known that long term consumption of soy protein can decrease serum cholesterol and triglycerides and also reduce accumulation of cholesterol and triglycerides in the liver which can lead to reduction of NAFLD. The identification that soy protein is rich in bioactive molecules (e.g., arginine) added a fascinating new aspect to the soy protein. Arginine (ARG) plays a role in modulating body weight/fat, but there are limited data as to the role that ARG may play in soy protein’s ability to protect from NAFLD. The objective of this study was to determine the role of short term consumption of soy protein isolate (SPI) and native ARG in SPI in protecting from NAFLD in male obese Zucker rats. Our results suggest that both short and long term SPI consumption can reduce NAFLD and inflammation, but longer period of SPI consumption results in lower NAFLD. The protective effect of SPI on NAFLD does not appear to be due to its ARG. The information will be useful for scientists, health-care and food-production professionals who are interested in soy consumption and obesity prevention.
Technical Abstract: Non-alcoholic fatty liver disease (NAFLD), the major cause of abnormal liver function, is often associated with obesity. Arginine (ARG) plays a role in modulating body weight/fat, but there are limited data as to the role that ARG may play in soy protein’s ability to protect from liver steatosis. The objective of this study was to determine the role of native ARG in soy protein isolate (SPI) in reducing liver steatosis in male obese Zucker rats. Rats (N=49; 6 weeks old) were acclimatized for one week on ad libitum were randomly assigned to one of three diets for 8 or 16 weeks: casein (CAS) diet as control (0.6% ARG), a CAS diet supplemented to contain 1.3% ARG, or a SPI diet containing naturally occurring isoflavones (SPI) (1.3% ARG). SPI and ARG rats gained more weight (P<0.05) than CAS rats after 16 weeks only. The SPI rats had lower liver steatosis scores after 8 and 16 weeks (P<0.05 and P<0.001, respectively) compared to CAS and ARG rats. SPI rats had lower serum alanine amino transferase (ALT) and aminotransferase (AST) levels (P<0.05) compared to CAS after 16 weeks, and AST was lower (P<0.05) compared to ARG rats. After 16 weeks, the SPI rats had lower (P<0.05) serum ALT and AST levels than SPI rats at 8 weeks. Our results suggest that longer period of SPI feeding results in lower liver steatosis and serum ALT and AST levels while ARG diet had no effect on steatosis or ALT and AST levels. Our results shows that SPI diet reduced (P<0.001) serum TNF-a compared to CAS and ARG diet after 8 and 16 weeks. Also, SPI diet significantly reduced (P<0.001) IL-6 when compared to CAS diet at 8 weeks but there was no significant difference at 16 weeks. The protective effect of SPI to reduce liver steatosis does not appear to be due to its ARG content.