Date Published: March 18, 2019
Publisher: Sociedade Brasileira para o Desenvolvimento da Pesquisa em
Author(s): Patrícia Madalena San Gregório Guedes, Ariane Zamarioli, Iara Inácio Botega, Raquel Assed Bezerra da Silva, João Paulo Mardegan Issa, Mariana Maloste Butezloff, Yara Terezinha Corrêa Silva Sousa, João Paulo Bianchi Ximenez, José Batista Volpon.
To investigate the effects of dietary restriction on the growth plate and
long bone tissue in growing rats.
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.
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.
Dietary restriction had severe detrimental effects on the growth plate and
trabecular and cortical bone.
Growth plate is a specialized structure which is responsible for the longitudinal
growth of long bones as it promotes ossification, thus resulting a cumulative bone
deposition at the metaphysis. Growth plate cells proliferate, differentiate, and
undergo hypertrophy and apoptosis with replacement by newly formed trabecular
bone1. During skeletal growth, several structural changes occur to meet the
demands during the bone growth period2. Therefore, a balanced food intake with specific nutrients such as proteins,
minerals, and vitamins are essential not only for the optimum development of
skeletal tissues, but also for the maturation of several tissues and organs (i.e.,
neurological function, and hormonal and endocrine activity)3-7.
In this study, the effects of undernutrition on the growth plate, trabecular and
compact bones of growing rats were investigated by several approaches. Our overall
results show that undernutrition causes a harmful impact in weight increase and long
bone growth. In our experiment the animals were followed up to 13 weeks of age but
were still growing when they were euthanized20. Therefore, our results do not permit extrapolation of data to the end of
the skeletal maturity, nor if these changes are reversible because we did not
introduced a normal diet to the undernourished rats. However, from clinical studies
it is known that undernutrition may cause irreversible changes not only in the
skeleton, but also in all organs and systems during all life21-24.
50% dietary restriction had detrimental effects on growth plate, trabecular bone,
and cortical shaft bone with anatomical and functional repercussions. Although
undernutrition did not result in changes in expression of the genes studied, several
phenotypic changes were seen in the growth plate.