Effects of aging, phenotype and carbohydrate feeding on caloric efficiency and adiposity in the LA/Ntul//-cp (corpulent) rat

Abstract

Obesity develops in the obese phenotype of the LA/Ntul//-cp (corpulent) specific pathogen-free rat strain by 5 to 6 weeks of age. Groups [n=12 -20 rats/phenotype] of female congenic lean and obese LA/Ntul//-cp (corpulent) rats were fed ad libitum standardized Purina diets for 4, 14, or 24 months or the same diet plus a 16% (w/v) sucrose solution supplement from 12 weeks of age, and measures of body weight, caloric intake, and caloric efficiency (CE) determined at each age group. Body weights of lean animals remained similar at all ages studied, while body weights of obese phenotype were significantly greater than their lean littermates at each age studied. The sucrose supplement was without significant effect on final body weights in the lean phenotypes at all ages studied (p=n.s.) but were associated with greater body weights at ages 4, 14 and 24 months of age in the obese phenotype (p=<0.05). CE was determined as the ratio of kcal/gram of body weight per day remained relatively constant in lean animals throughout the age range, but CE was more efficient in the obese phenotype at all ages studied and became progressively more efficient with the sucrose supplement feeding with increasing age. The results of this study indicate that CE is associated with the predisposition for the development of obesity in the obese phenotype of this strain and likely implicates multiple metabolic factors that contribute to a greater efficiency of energy utilization and or energy conservation in the obese than in the lean phenotype of this strain, and the metabolic impact of added sucrose was associated with an additive impact on the CE of weight gain and adiposity in the obese phenotype of this congenic rodent strain