title: Growth-dependent effects of dietary protein concentration and quality on the biomechanical properties of the diaphyseal rat femur.
abstract: OBJECTIVE
  This study compares the effects of feeding growing rats with increasing concentrations of casein (C) and wheat gluten (G), proteins that show different biological qualities, on the morphometrical and biomechanical properties of the femoral diaphysis.
  
  
  METHODS
  Female rats were fed with one of ten diets containing different concentrations (5-30%) of C and G between the 30th and 90th days of life (Control=C-20%). Biomechanical structural properties of the right femur middiaphysis were estimated using a 3-point bending mechanical test with calculation of some indicators of bone material properties.
  
  
  RESULTS
  Body weight and length were affected by treatments, values being highest in rats fed the C-20% diet. G diets affected negatively both parameters. Changes in cross-sectional geometry (mid-diaphyseal cross-sectional and cortical areas, femoral volume, and rectangular moment of inertia) were positively related to the C content of the diet, while they were severely and negatively affected by G diets. Similar behaviors were observed in the bone structural properties (fracture load, yielding load, diaphyseal stiffness and elastic energy absorption). When values of strength and stiffness were normalized for body weight, the differences disappeared. The bone material quality indicators (elastic modulus, yielding stress, elastic energy absorption/volume) did not differ significantly among all studied groups. Femoral calcium concentration in ashes was not significantly different among groups.
  
  
  CONCLUSIONS
  The clear differences in strength and stiffness of bone beams induced by dietary protein concentration and quality seemed to be the result of an induced subnormal gain in bone structural properties as a consequence of a correlative subnormal gain in bone growth and mass, yet not in bone material properties.
authors.affiliation: Department of Physiology, Faculty of Odontology, University of Buenos Aires, Buenos Aires 1122, Argentina.
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Alippi
authors.forename: Emilio
authors.initials: E
authors.lastname: Picasso
authors.forename: Patricia
authors.initials: P
authors.lastname: Huygens
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Bozzini
authors.forename: Clarisa
authors.initials: C
authors.lastname: Bozzini
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001699:Biometry; D015519:Bone Density / Q000187:drug effects; D001846:Bone Development / Q000187:drug effects; D002364:Caseins / Q000008:administration & dosage / Q000494:pharmacology*; D004044:Dietary Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D055119:Elastic Modulus; D005260:Female; D005269:Femur / Q000737:chemistry / Q000254:growth & development / Q000503:physiopathology*; D005983:Glutens / Q000008:administration & dosage / Q000494:pharmacology*; D006130:Growth Disorders / Q000209:etiology* / Q000503:physiopathology; D011488:Protein Deficiency / Q000150:complications*; D051381:Rats; D014908:Triticum; D016474:Weight-Bearing
chemical_list: D002364:Caseins; D004044:Dietary Proteins; D005983:Glutens