Bone status in an animal model of chronic sub-optimal nutrition: a morphometric, densitometric and mechanical study

Abstract

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.

Effect of chronic undernutrition on body mass and mechanical bone quality under normoxic and altitude hypoxic conditions

“…Undernutrition (in response to either food restriction or exposure to hypoxia), which mainly affects protein and energy availability, affects bone biomechanical properties (21,29,(32)(33)(34)(35)(36) in growing rats by adapting the growth of the bone mass to that of the body mass. Bone mechanical quality of a whole bone (structural properties) depends on the integration of the 'mechanical quality of the mineralised tissue' (material stiffness mainly associated with collagen mineralisation) and the 'architectural quality of the structural bone design' (shape, size, architectural distribution of mineralised tissue) (37) .…”

“…Both NxGR and HxC rats also have in common important changes in the mechanical properties of the appendicular skeleton. Biomechanical tests performed on femur diaphyseal shafts (21,23) revealed a lower than normal bone mass and changes in the geometric properties of the bone, without alterations in the material properties of the bone tissue. The studied bones, because of the subnormal strength and stiffness, were thus structurally incompetent for sex and age.…”

“…The above explanation indicates that increase in body mass is negatively affected by either an 'imposed' or a 'voluntary' restriction of food consumption, as occurs in both the normoxic growth-restricted (NxGR) rat and the hypoxic control (HxC) rat, respectively. Catch-up growth, defined as growth with a velocity above the statistical limits of normality for age during a defined period of time, which follows a period of impaired growth (21) , was observed in both models (19,22) . Both NxGR and HxC rats also have in common important changes in the mechanical properties of the appendicular skeleton.…”

Hypothalamic Noradrenergic Hyperactivity and Detrimental Bone Status in an Animal Model of Nutritional Growth Retardation

“…However, this adaptive responsed to caloric restriction would be predicted to be deleterious to bone status. In fact, previous studies performed in our laboratory showed impaired mechanical femoral competence in ND rats that may result from altered bone mass and architectural distribution rather than its intrinsic quality, a suggestion supported by the high correlation found between bone mineral content and bone mineral density v. body weight, and ultimate load and yielding load v. moment of inertia [16,17].…”

Effects of physical exercise during pregnancy and protein malnutrition during pregnancy and lactation on the development and growth of the offspring’s femur

“…Semelhantemente, foi demonstrado por Boyer et al 20 em cujo estudo o peso femoral também sofreu diminuição com o déficit nutricional. É conhecido que a desnutrição ocorrida durante essas importantes fases do desenvolvimento provoca, em ratos, falha na recuperação óssea completa ao menos até os 100 dias de vida 21 e até os 6 meses de vida em humanos 22 .…”