Purpose To investigate the effects of dietary restriction on the growth plate and long bone tissue in growing rats. Methods Sixty male Wistar rats were randomly assigned to two groups: Control (Con) and Diet-restricted (Res). After weaning, the Res rats were offered 50% of the chow ingested by the control ( ad libitum food intake). The animals were subdivided into two subgroups with follow-ups up to 56 or 70 days. After euthanasia, the growth plate of tibias was analyzed by histomorphometry, micro-computed tomography, and mechanical test. The trabecular and compact bones were evaluated by histomorphometry, dual-energy X-ray absorptiometry, and micro-computed tomography (μCT). Real-time PCR was used to analyze gene expression. Results Although dietary restriction did not alter gene expression, several phenotypic changes were seen in the growth plate; i.e., decrease in volume, reduction in total area and height, decrease in the area ossified zones, mechanical weakening, reduction in mass of trabecular and cortical bone, lower bone density, deterioration of the trabecular and cortical microarchitecture, and trabeculae with lower collagen deposition. Conclusion Dietary restriction had severe detrimental effects on the growth plate and trabecular and cortical bone.

Purpose To evaluate the effects of food restriction on fracture healing in growing rats. Methods Sixty-eight male Wistar rats were assigned to two groups: (1) Control and (2) Dietary restriction. After weaning the dietary restricted animals were fed ad libitum for 42 days with 50% of the standard chow ingested by the control group. Subsequently, the animals underwent bone fracture at the diaphysis of the right femur, followed by surgical stabilization of bone fragments. On days 14 and 28 post-fracture, the rats were euthanized, and the fractured femurs were dissected, the callus was analyzed by dual-energy X-ray absorptiometry, micro-computed tomography, histomorphometry, mechanical tests, and gene expression. Results Dietary restriction decreased body mass gain and resulted in several phenotypic changes at the bone callus (a delay in cell proliferation and differentiation, lower rate of newly formed bone and collagen deposition, reductions in bone callus density and size, decrease in tridimensional callus volume, deterioration in microstructure, and reduction in bone callus strength), together with the downregulated expression of osteoblast-related genes. Conclusion Dietary restriction had detrimental effects on osseous healing, with a healing delay and a lower quality of bone callus formation.

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sempre me foi muito prestativa na orientação geral das normas e procedimentos do programa. À Dra. Ariane Zamarioli, que foi a porta de entrada ao programa de pós-graduação, dando oportunidade de cursar o mestrado, auxiliando-me e orientando-me na realização deste trabalho. Ao professor Dr. Alceu Afonso Jordão Júnior pela orientação quanto a dieta restritiva, por ser solícito e ajudar no estabelecimento da metodologia aplicada.