Effect of a high fat intake on protein utilization during ontogenetic development.
Male rats (Wistar strain, Velaz, Prague) aged 30, 90 and 150 days were fed 14 days ad libitum on a high fat diet (containing 40% margarine) and their growth (PER, NPR) and utilization (NPU, LPU) parameters of protein (casein) biological value were compared with those of animals given a standard gel containing 10% margarine (the diets were isoenergetic). The course of gluconeogenesis in their liver was also determined by measuring phosphoenolpyruvate carboxykinase (PEPCK) activity. A high fat intake had a negative effect on the growth parameters of protein biological value, PER and NPR, in all three age groups and on the utilization parameters NPU and LPU in 30- and 90-day-old rats. The nonsignificant increase in NPU and LPU in the oldest animals was evidently related to the equal protein intake compared with the control, indicating that proteins need to be utilized more economically in the presence of a raised fat intake; owing to their far lower fat intake compared with 90-day-old animals on a high fat diet, the fat had a less negative effect on their protein utilization than in the younger age group. The negative effect of a high fat intake was confirmed by high activation of gluconeogenesis in 30- and 90-day-old animals and by raised phosphoenolpyruvate carboxykinase activity in 150-day-old rats, in which the supposition that gluconeogenesis would be highly activated if the diet were administered for a period other than 14 days cannot be ignored. The biological and biochemical methods employed in this study can be used with a wider perceptual range of dietary nutrients to determine optimum nutrient values under different conditions.
D000375:Aging; D000818:Animals; D001835:Body Weight; D004041:Dietary Fats / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D005943:Gluconeogenesis; D008099:Liver / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats
D004041:Dietary Fats; D004044:Dietary Proteins; D011506:Proteins; D009584:Nitrogen