title: Influence of high and low protein intakes on age-related bone loss in rats submitted to adequate or restricted energy conditions.
abstract: Low energy and protein intake has been suggested to contribute to the increased incidence of osteoporosis in the elderly. The impact of dietary protein on bone health is still a matter of debate. Therefore, we examined the effect of the modulation of protein intake under adequate or deficient energy conditions on bone status in 16-month-old male rats. The animals were randomly allocated to six groups (n = 10/group). Control animals were fed a diet providing either a normal-protein content (13%, C-NP) or a high-protein content (26%) (C-HP). The other groups received a 40% protein/energy-restricted diet (PER-NP and PER-HP) or a normal protein/energy-restricted diet (ER-NP and ER-HP). After 5 months of the experiment, protein intake (13% or 26%) did not modulate calcium retention or bone status in those rats, although a low-grade metabolic acidosis was induced with the HP diet. Both restrictions (PER and ER) decreased femoral bone mineral density and fracture load. Plasma osteocalcin and urinary deoxypyridinoline levels were lowered, suggesting a decrease in bone turnover in the PER and ER groups. Circulating insulin-like growth factor-I levels were also lowered by dietary restrictions, together with calcium retention. Adequate protein intake in the ER condition did not elicit any bone-sparing effect compared to PER rats. In conclusion, both energy and protein deficiencies may contribute to age-related bone loss. This study highlights the importance of sustaining adequate energy and protein provision to preserve skeletal integrity in the elderly.
authors.affiliation: Unité de Nutrition Humaine UMR1019, Institut National de la Recherche Agronomique Clermont-Ferrand/Theix, Saint Genes Champanelle, France. juliemardon@hotmail.com
authors.forename: Julie
authors.initials: J
authors.lastname: Mardon
authors.forename: Véronique
authors.initials: V
authors.lastname: Habauzit
authors.forename: Anna
authors.initials: A
authors.lastname: Trzeciakiewicz
authors.forename: Marie-Jeanne
authors.initials: MJ
authors.lastname: Davicco
authors.forename: Patrice
authors.initials: P
authors.lastname: Lebecque
authors.forename: Sylvie
authors.initials: S
authors.lastname: Mercier
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Tressol
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Horcajada
authors.forename: Christian
authors.initials: C
authors.lastname: Demigné
authors.forename: Véronique
authors.initials: V
authors.lastname: Coxam
mesh_terms: D000138:Acidosis / Q000139:chemically induced / Q000378:metabolism; D000596:Amino Acids / Q000652:urine; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001862:Bone Resorption / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism; D031204:Caloric Restriction; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000008:administration & dosage*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005269:Femur / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D015675:Osteocalcin / Q000097:blood; D010024:Osteoporosis / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D011859:Radiography; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D004044:Dietary Proteins; D015675:Osteocalcin; D007334:Insulin-Like Growth Factor I; C036020:deoxypyridinoline; D002118:Calcium