In children, inappropriate eating habits can induce a disease known as nutritional dwarfing (ND). Due to the link between nutritional condition and bone growth, the effects induced by a 20 % reduction of food intake on bone competence were assessed in an animal model of ND. Bone status during catch-up growth was also analysed. Male Wistar rats were divided into control (C) and ND groups. C rats were fed ad libitum. ND received 80 % of the diet consumed by C for 4 weeks (T4); thereafter, they were fed ad libitum for 8 weeks. Results, expressed as mean (SEM) for ND v. C, were as follows. At T4, body weight (g) and length (cm) and femur weight (g) and length (mm) were 97.35 (SEM 5.89) v. 199.07 (SEM 9.24), 16.91 (SEM 0.41) v. 20.26 (SEM 0.31), 0.30 (SEM 0.01) v. 0.46 (SEM 0.01) and 23.09 (SEM 0.29) v. 26.98 (SEM 0.26), respectively (P<0.001); bone mineral content (g) and density (g/cm(2)) were 0.014 (SEM 0.002) v. 0.030 (SEM 0.002) and 0.061 (SEM 0.004) v. 0.080 (SEM 0.003), respectively (P<0.001); load-bearing capacity (N), yielding load (N) and elastic stiffness (N/mm) were 25.06 (SEM 1.24) v. 50.34 (SEM 2.94), 23.72 (SEM 1.02) v. 46.97 (SEM 1.75) and 65.98 (SEM 4.42) v. 115.07 (SEM 3.85), respectively (P<0.001); cross-sectional area (mm(2)) and moment of inertia (mm(4)) were 2.86 (SEM 0.19) v. 4.54 (SEM 0.17) and 1.27 (SEM 0.08) v. 3.03 (SEM 0.16), respectively (P<0.001). Significant effects were not evident in material properties. Parameters assessed normalized during re-feeding. These results suggest that the impaired mechanical femur competence in ND rats could be due to an altered bone mass and architectural distribution rather than to intrinsic quality. Re-feeding caused a reversal of the effects of food restriction on growth and bone parameters in ND rats.

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The anorexic effect of exposure to high altitude may be related to the reduction in the arterial oxygen content (Ca(O2)) induced by hypoxemia and possibly the associated decreased convective oxygen transport (COT). This study was then performed to evaluate the effects of either transfusion-induced polycythemia or previous acclimation to hypobaria with endogenously induced polycythemia on the anorexic effect of simulated high altitude (SHA) in adult female rats. Food consumption, expressed in g/d/100 g body weight, was reduced by 40% in rats exposed to 506 mbar for 4 d, as compared to control rats maintained in room air. Transfusion polycythemia, which significantly increased hematocrit, hemoglobin concentration, Ca(O2), and COT, did not change the anorexic response to the exposure to hypobaric air. Depression of food intake during exposure to SHA also occurred in rats fasted during 31 h before exposure and allowed to eat ad libitum for 2 h during exposure. Body mass loss was similar in 48-h fasted rats that were either hypoxic or normoxic. Body mass loss was similar in normoxic and hypoxic rats, the former eating the amount of food freely eaten by the latter. Hypoxia-acclimated rats with endogenously induced polycythemia taken to SHA again had diminished food intake and lost body mass at rates that were very close to those found in nonacclimated ones. Exposure to SHA also led to a decrease in food consumption, body weight, and plasma leptin in adult female mice. Analysis of data suggest that body mass loss that accompanies SHA-induced hypoxia is due to hypophagia and that experimental manipulation of the blood oxygen transport capacity cannot ameliorate it. Leptin does not appear to be an inducer of the anorexic response to hypoxia, at least in mice and rats.

Bozzini, Clarisa, Graciela M. Champin, Rosa M. Alippi, and Carlos E. Bozzini. Static biomechanics in bone from growing rats exposed chronically to simulated high altitudes. High Alt Med Biol 14:367-374, 2013.-Biomechanical behavior of bone is related to the amount (bone mass) and its architectural distribution, as well as the mechanical quality of bone material. This investigation reports the effects of exposure to different simulated high altitudes (SHA) (1850, 2900, 4100, and 5450 m) on femur biomechanical properties in female growing rats exposed to SHA (22-23 h/d) between the 32°and the 74°days of life. The ex vivo right femur was mechanically tested in three-point bending. The left femur was ashed at 600°C and the ash weight obtained. Final body weight and structural (loads at yielding and fracture, stiffness, and elastic energy absorption) and architectural (diaphyseal cross-sectional area, cortical area, and cross-sectional moment of inertia) were negatively affected in the animals exposed to the two highest SHA. Material properties of the mineralized tissue (Young's modulus and limit elastic stress) and the degree of mineralization were unaffected. In conclusion, hypoxic bone is weaker than normoxic one because of its smaller bone mass, which appear to have been negatively influenced by SHA in relation to its effects on overall body mass.