Bone growth in nonorganic nutritional dwarfing rats

Since no data are available to characterize mandibular growth in nonorganic nutritional dwarfing (ND), the purpose of the present study was to describe the effects of a diet on mandible and femur growth in a nutritional dwarfish animal model. Male Wistar rats were divided into two groups of 10 animals each: Control (C) and Experimental (E80: diet-restricted group). C rats were fed a standard diet ad libitum. E80 rats received 80% of the amount of standard diet eaten by group C. Food intake and body weight (Wt) and length (Lt) were recorded periodically. Growth data (Wt and Lt) were expressed as a Z-score of weight-for-length (WLZ) ratio, an index of body size. Five animals of each group were selected at random at 4 and 8 weeks and sacrificed. Additionally at t = 0, 5 animals were sacrificed for baseline measurements. Mandibular growth was estimated directly on the right mandible by measuring ten dimensions. Femur growth was estimated from Wt and Lt measurements of the bone. Mandibular weight, area, length and height were negatively affected by dietary restriction during the first 4 weeks of the experimental period. Mandibular growth ceased after this point. Dimensions corresponding to the alveolar unit did not change with time. However, all other dimensions were negatively influenced but not to the same extent. Femur rather than mandibular weight was severely affected. Therefore, the negative effects of the nutritional stress that occurs after weaning would be stronger for the femur, than for the mandible. Femur length was also negatively affected by suboptimal nutrition. In summary, the results of the present study showed that mandible and femur growth respond differently to mild chronic food restriction. These observations could be explained in terms of the different critical bone growth periods and of the time at which nutritional stress was imposed.