Dietary modulation of apolipoprotein serum amyloid A (apoSAA) metabolism and prevention of amyloidosis in aging C57BL/6J and SJL/J mice

Abstract The specific effect of acute inflammation on apoSAA and lipoprotein metabolism was determined in two strains of mice that are prone to develop spontaneous age-associated systemic amyloidosis. C57BL6J and SJLJ mice were maintained on purified diets, relatively rich in fat and differing only with respect to protein constituents, i.e., casein (20%) versus soy protein (20%). After 18 months, aging mice of either strain and on either diet were injected subcutaneously with AgNO 3 thus inducing a powerful acute phase response as evidenced by increases in plasma LDL and apoSAA-rich HDL. None of the mice in each of the dietary groups developed amyloidosis. Cholesterol levels were elevated during the acute phase response in both mouse strains, although the hypercholesterolemia was less pronounced in C57BL6J mice and in SJLJ mice fed soy protein compared with casein. Control plasma triglyceride levels were lower in C57BL6J mice in both dietary groups compared to the SJLJ strain. By contrast, C57BL6J mice fed either protein increased the triglyceride concentration, whereas in SJLJ mice, triglyceride levels were not altered by casein but were decreased significantly by soy protein diets. Oir findings show for the first time that dietary protein intake modulates the acute phase response in rodents. Furthermore, the data support the concept that alterations in lipid metabolism during the acute phase response may represent a protective mechanism whereby HDL-cholesterol and phospholipids are directed to sites of inflammation for connective tissue repair.