Effects of Soy Protein Isolate on Fragile X Phenotypes in Mice.

Obesity is a pediatric epidemic that is more prevalent in children with developmental disabilities. We hypothesize that soy protein-based diets increase weight gain and alter neurobehavioral outcomes. Our objective herein was to test matched casein- and soy protein-based purified ingredient diets in a mouse model of fragile X syndrome, mice. The experimental methods included assessment of growth; 24-7 activity levels; motor coordination; learning and memory; blood-based amino acid, phytoestrogen and glucose levels; and organ weights. The primary outcome measure was body weight. We find increased body weight in male from postnatal day 6 (P6) to P224, male wild type (WT) from P32-P39, female from P6-P18 and P168-P224, and female from P9-P18 as a function of soy. Activity at the beginning of the light and dark cycles increased in female and mice fed soy. We did not find significant differences in rotarod or passive avoidance behavior as a function of genotype or diet. Several blood-based amino acids and phytoestrogens were significantly altered in response to soy. Liver weight was increased in WT and adipose tissue in mice fed soy. Activity levels at the beginning of the light cycle and testes weight were greater in versus WT males irrespective of diet. DEXA analysis at 8-months-old indicated increased fat mass and total body area in females and lean mass and bone mineral density in males fed soy. Overall, dietary consumption of soy protein isolate by C57BL/6J mice caused increased growth, which could be attributed to increased lean mass in males and fat mass in females. There were sex-specific differences with more pronounced effects in versus WT and in males versus females.