title: Low protein intake magnifies detrimental effects of ovariectomy and vitamin D on bone.
abstract: Protein-induced changes in bone and calcium homeostasis could potentially be greater in the elderly and in women at risk for osteoporosis. We hypothesize that a low protein intake would magnify the negative changes in bone metabolism seen in vitamin D (vitD) insufficiency and/or estrogen deficiency. The present study was undertaken to better understand how a low protein diet along with vitD insufficiency could affect bone metabolism using a rodent ovariectomized (OVX) model. Rats (n = 60) underwent ovariectomy (OVX) or sham operation. The first 15 days after surgery, all rats were fed a standard rodent diet. Thereafter, rats (n = 10/group) were fed a low protein diet (LP; 2.5 %) or a control diet (NP; 12.5 %) with 100 IU% vitD (+D; cholecalciferol) or without vitD (-D) for 45 days. The groups were as follows: SHAM + NP + D (control); SHAM + LP + D; SHAM + LP - D; OVX + NP + D; OVX + LP + D; OVX + LP - D. Body weight (BW) of control and OVX + NP + D groups increased while those feeding the LP diet, independently of vitD feedings, decreased (p < 0.05). The OVX + LP - D group presented the lowest serum Ca, phosphorus and osteocalcin levels and the highest CTX levels (p < 0.05). At the end of the study, total skeleton bone mineral content, proximal tibia bone mineral density, bone volume and trabecular number levels decreased as follows: SHAM + NP + D (controls) > SHAM + LP + D > OVX + NP + D > SHAM + LP - D > OVX + LP + D > OVX + LP - D (p < 0.05). A low protein diet negatively affected bone mass and magnified the detrimental effects of vitD and/or estrogen deficiencies.
authors.affiliation: Metabolic Bone Diseases Laboratory, Clinical Hospital, Immunology, Genetic and Metabolism Institute (INIGEM), National Council for Scientific and Technologic Research (CONICET), Buenos Aires University, Buenos Aires, Argentina.
authors.forename: Clarisa
authors.initials: C
authors.lastname: Marotte
authors.forename: Macarena M S
authors.initials: MM
authors.lastname: Gonzales Chaves
authors.forename: Gretel G
authors.initials: GG
authors.lastname: Pellegrini
authors.forename: Silvia M
authors.initials: SM
authors.lastname: Friedman
authors.forename: Fima
authors.initials: F
authors.lastname: Lifshitz
authors.forename: Patricia
authors.initials: P
authors.lastname: Mandalunis
authors.forename: Susana N
authors.initials: SN
authors.lastname: Zeni
mesh_terms: D000821:Animal Feed; D000818:Animals; D001835:Body Weight; D015519:Bone Density; D001842:Bone and Bones / Q000473:pathology*; D002118:Calcium / Q000097:blood* / Q000378:metabolism; D002136:Calcium, Dietary / Q000494:pharmacology; D018753:Diet, Protein-Restricted / Q000009:adverse effects*; D005247:Feeding Behavior; D005260:Female; D006706:Homeostasis; D010006:Osteoblasts / Q000187:drug effects; D015675:Osteocalcin / Q000737:chemistry / Q000378:metabolism; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar; D014807:Vitamin D / Q000008:administration & dosage*
chemical_list: D002136:Calcium, Dietary; D015675:Osteocalcin; D014807:Vitamin D; D002118:Calcium