The Metabolic Effects of Aging, Phenotype and Carbohydrate Feeding on Caloric Efficiency and Adiposity in the LA/Ntul//-Cp Rat
The goal of this work was to see if the decreased responses to diet in the obese phenotype were connected with corresponding alterations in CE, which could be correlated with the increased adiposity associated with the (-cp) trait. Obesity develops at 5 to 6 weeks of age in the obese phenotype of the LA/Ntul/-cp (corpulent) specific pathogen-free rat strain. Female congenic lean and obese LA/Ntul/-cp (corpulent) rats were fed ad libitum standardised Purina diets for 4, 14, or 24 months, or the same diet plus a 16 percent (w/v) sucrose solution supplement from 12 weeks of age, and body weight, caloric intake, and caloric efficiency (CE) were measured at each age group. Body weights of lean animals remained consistent across all ages tested, whereas body weights of obese phenotypes were considerably higher than those of their lean littermates across all years studied. The sucrose supplement had no influence on ultimate body weights in the lean phenotypes at all years tested (p=n.s. ), but was linked with higher body weights in the obese phenotype at ages 4, 14, and 24 months (p=0.05). CE was calculated as the ratio of kcal/gram of body weight per day, which stayed essentially constant in lean animals across the age range, but CE was more efficient in the obese phenotype at all ages investigated and grew progressively more efficient with sugar supplement feeding as age increased. The results of this study show that CE is associated with greater efficiency of energy utilisation and/or energy conservation in the obese phenotype of this strain than in the lean phenotype, and that the metabolic impact of added sucrose was associated with an additive effect on the CE of weight gain and adiposity in the obese. It was concluded that the -cp trait’s autosomal recessive nature was associated with a greater economy of caloric efficiency and marked adiposity, which was exacerbated by ageing and compounded by the addition of a sucrose supplement, but was independent of derangements in appetite dysregulation per se.
Orien L. Tulp
University of Science Arts and Technology, Montserrat, British West Indies, USA.