Effects of high isoflavone soy diet vs casein or arginine‐supplemented casein diet on liver steatosis

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 reducing body fat, but there is limited data as to the role that Arg may play in soy protein's ability to protect from fatty liver. The objective of this study was to find the role of native Arg in soy to protect from fatty liver in male obese Zucker rats (N=49; 6 weeks old). Rats had ad libitum access to water and were randomly assigned to one of 3 diets for 8 or 16 weeks: Casein (CAS) diet as control (0.6% Arg) or a casein diet supplemented to contain 1.3% Arg (ARG) or a soy protein isolate diet with high 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 after 8 and 16 weeks (P<0.05 and P<0.001, respectively) compared to CAS & ARG rats. SPI rats had lower serum alanine amino transferase (ALT) & 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. The protective effect of soy protein to reduce fatty liver does not appear to be due to its arginine content. Supported by ABI to RH