Effects of Glucose and Fructose on Production Traits, Organ Weights and Metabolomic Indices in Rats on Different Energy and Nutrient Dense Diets

The objectives of this study were to determine the dose effect/s of glucose (G) and fructose (F) at different energy densities (ED) of diets on feed intake, body and organ weights, chemical composition of liver, feed conversion, and metabolomic indices (enzymes and hormones). Methods: Seventy-two 10-week-old male Wistar SPF rats were divided into 9 dietary groups and housed individually in metabolic cages. The control group was on a carbohydrate-free high lard diet (L), and for the other 8 treatment groups, the L content of the control diet was gradually replaced by G or F to decrease the dietary ED, in such a way that the nutrients (protein, minerals and vitamins) to energy ratio of the feeds remained constant. These experimental diets were fed to rats for 28 days. Feed intake and body weight were measured twice weekly. On the 28th day of the experiment, the rats were euthanized, and blood and organ samples were collected for further tests. Results and conclusions: The effects of F and G on twenty-six parameters were measured at different EDs of diets. Significant specific F effects (SFE) over the rats on G diets were found in case of feed intake (statistics with pooled data of feed intake (Fi) showed ~7% more feed intake of F rats: 10.8, 6.4, 9.5 and 2.0% at 5.28, 4.70, 4.23 and 3.85 kcal/g ED, respectively); body weight gain (the relation is polynomial; 8.0, 10.3, 0.1, and -10.2% at 5.28, 4.70, 4.23, and 3.85 kcal/g ED; it related to the weight change of viscera: liver, kidney and RWAT); liver fat (3.98, 21.42, 49.20 and 11.05% at 5.28, 4.70, 4.23, and 3.85 kcal/g ED, respectively); serum triglyceride (the relation is polynomial; 63.2, 88.1, 79.2 and 42.6% at 5.28, 4.73, 4.23, and 3.85 kcal/g ED, respectively); serum glucagon (-1.2, 380.2, 248.3 and 74.7% at 5.28, 4.70, 4.23, and 3.85 kcal/g ED, respectively), and serum leptin (9.59, 30.53, 72.64, and -46.49% at 5.28, 4.70, 4.23, and 3.85 kcal/g ED, respectively). An important conclusion is that in several cases, the effects of F and G were similar in the direction of change, but the magnitude of the effects was different. In case of feed conversion rate, there was no difference between the effect of G and F, however it is important to note that the higher the dietary energy and nutrient density, the better the feed conversion rate (FCR); The potential mechanism(s) of effect for each parameter is discussed and, where appropriate, the clinical relevance of the data compared to the known literature.