title: Impact of energy and casein or whey protein intake on bone status in a rat model of age-related bone loss.
abstract: In the elderly, nutritional deficiencies, such as low energy and protein intake, are suggested to increase the risk of osteoporotic fractures. Modulation of the amount and quality of protein intake under energy deficient conditions represents an interesting strategy to prevent aged-related bone loss. We investigated the effect of a 5-month dietary restriction on bone status in 16-month-old male rats. Rats were randomised into six groups (n 10 per group). Control animals were fed a normal diet containing either casein (N-C) or whey protein (N-WP). The other groups received a 40 % protein and energy-restricted diet with casein or whey protein (PER-C and PER-WP) or a normal protein and energy-restricted diet (ER-C and ER-WP). Both restrictions (PER and ER) induced a decrease in femoral bone mineral density (BMD), consistent with impaired biomechanical properties and a reduced cortical area at the diaphysis. Plasma osteocalcin and urinary deoxypyridinoline levels suggested a decrease in bone turnover in the PER and ER groups. Interestingly, circulating insulin-like growth factor 1 (IGF-1) levels were also lowered. Overall, normal protein intake did not elicit any bone sparing effect in energy-deficient rats. Regarding protein quality, neither casein nor WP appeared to significantly prevent the BMD decrease. This study confirms that nutritional deficiencies may contribute to osteopenia through decreased IGF-1 levels. Moreover, it seems that impaired bone status could not be significantly prevented by modulating the amount and quality of dietary proteins.
authors.affiliation: Unité de Nutrition Humaine UMR1019, INRA Clermont-Ferrand / Theix, 63122 Saint Genès Champanelle, France. jmardon@clermont.inra.fr
authors.forename: J
authors.initials: J
authors.lastname: Mardon
authors.forename: A
authors.initials: A
authors.lastname: Zangarelli
authors.forename: S
authors.initials: S
authors.lastname: Walrand
authors.forename: M J
authors.initials: MJ
authors.lastname: Davicco
authors.forename: P
authors.initials: P
authors.lastname: Lebecque
authors.forename: C
authors.initials: C
authors.lastname: Demigné
authors.forename: M N
authors.initials: MN
authors.lastname: Horcajada
authors.forename: Y
authors.initials: Y
authors.lastname: Boirie
authors.forename: V
authors.initials: V
authors.lastname: Coxam
mesh_terms: D000596:Amino Acids / Q000652:urine; D000818:Animals; D015415:Biomarkers / Q000097:blood / Q000652:urine; D015519:Bone Density; D001862:Bone Resorption; D001842:Bone and Bones / Q000503:physiopathology*; D002118:Calcium / Q000652:urine; D031204:Caloric Restriction; D002364:Caseins / Q000008:administration & dosage*; D019587:Dietary Supplements; D005269:Femur; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D020738:Leptin / Q000097:blood; D008297:Male; D008894:Milk Proteins / Q000008:administration & dosage*; D023421:Models, Animal; D015675:Osteocalcin / Q000097:blood; D010024:Osteoporosis / Q000378:metabolism* / Q000503:physiopathology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D000067816:Whey Proteins
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D002364:Caseins; D020738:Leptin; D008894:Milk Proteins; D000067816:Whey Proteins; D015675:Osteocalcin; D007334:Insulin-Like Growth Factor I; C036020:deoxypyridinoline; D002118:Calcium