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,
hyperglycemia, and
hyperinsulinemia when fed this dietary regimen. This study was conducted to determine the effects of
dietary fat and
sucrose concentrations 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-fat diets, regardless of
sucrose content, resulted in significant
weight gain, higher body fat, and lower body
protein and water content in both 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-
sucrose diets resulted in lower
body weight in both strains, as well as significantly greater body
protein content in B6 mice. Analysis of intestinal
sucrase showed that the
enzyme was less active in B6 mice when the diet was high in
sucrose. Both
sucrase and
maltase had lower activity in the presence of high
dietary fat in both mouse strains. The percent reduction of intestinal
enzyme activity due to
dietary fat was similar in both strains. The B6 mouse exhibits disproportionate
weight gain 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.