DIFFERENTIAL-EFFECTS OF FAT AND SUCROSE ON BODY-COMPOSITION IN A J AND C57BL/6 MICE/

The C57BL/6 (B6) mouse is more sensitive to the effects of a high-fat diet than the A/J strain. The B6 mouse develops severe obesity, hyperg lycemia, and hyperinsulinemia when fed this dietary regimen. This stud y was conducted to determine the effects of dietary fat and sucrose co ncentrations on body composition and intestinal sucrase (EC 3.2.1.48) and maltase (EC 3.2.1.20) activity in these two mouse strains. High-fa t diets, regardless of sucrose content, resulted in significant weight gain, higher body fat, and lower body protein and water content in bo th strains of mice. The shift toward higher body fat and lower protein and water content was far greater in the B6 strain. Low-fat, high-suc rose diets resulted in lower body weight in both strains, as well as s ignificantly greater body protein content in B6 mice. Analysis of inte stinal sucrase showed that the enzyme was less active in B6 mice when the diet was high in sucrose. Both sucrase and maltase had lower activ ity in the presence of high dietary fat in both mouse strains. The per cent reduction of intestinal enzyme activity due to dietary fat was si milar in both strains. The B6 mouse exhibits disproportionate weight g ain and altered body composition on a high-fat diet. This coupled with the reduced body weight and increased body protein on a low-fat, high sucrose diet suggests that factors relative to fat metabolism rather than sucrose metabolism are responsible for obesity. Copyright (C) 199 8 by W.B. Saunders Company.