Efeitos da restrição alimentar sobre marcadores bioquímicos da remodelação óssea e sobre as propriedades biométricas, biofísicas, densitométricas, bioquímicas e biomecânicas de fêmures e vértebras de ratos de diferentes idades
Resumen
The food restriction promotes adaptive mechanisms that have beneficial effects on
diseases and longevity. Also, bone is target of effects provided by the reduction of diet
intake. However, there are controversies about the responses that this intervention can
result on bone quantity and quality. The aim of this study was to evaluate the effect of
food restriction 30% on bone parameters of femurs and vertebrae from rats of different
ages. Male Rattus novegicus albinus rats, Holtzman lineage, aged 38 days, 4 and 16
months of age were used. The animals were divided into six groups (n=8-10 per group),
three being control groups (C38, C4 and C16) and three groups on restricted diet (R38,
R4 on R16). The control animals had free access to food and water. The restricted animals
were submitted to food restriction of 30% being fed with 70% of the ad libitium
consumption of the control group. The experimental period for all groups was 6 weeks.
Analysis was performed in biochemical markers of formation (osteocalcin) and bone
resorption (TRAP), and in parameters biometric (length, largest and smallest diameter of
the femur, vertebral height), biophysical (wet, dry and immersed weight, and of ashes,
bone volume, bone and mineral density, percentage of water, mineral and organic matter),
biochemical (calcium and phosphorus content), densitometric (aDMO of the femur [all
bone, proximal epiphysis, diaphysis and epiphysis distal] and the vertebra),
biomechanical properties (maximum load, maximum load until fracture, displacement
until fracture, femoral tenacity and stiffness; spinal maximum load, tenacity and
stiffness), in addition to body mass and abdominal fat mass. The body mass and fat mass
gain in restricted animals was lower than that of animals which had food ad libitium. The
food restriction in animals with 38 days and 4 months of age presented decreased bone
formation, while the ones with 16 months presented decreased bone resorption. Food
restriction induced reduction of the biometric parameters, biophysical weights, femoral
bone volume and calcium and phosphorous content in the restricted group aged 38 days.
In addition, femoral length and calcium content were reduced in the restricted group aged
4 months. The restricted diet induced reduced areal density in femurs and femoral
diaphyseal of 38 days rats, and increased aDMO of femoral epiphysis proximal from 16
months rats. The femoral biomechanical properties were not affected by the food
restriction diet in any of the experimental groups. As regards the vertebral analysis,
vertebral height, wet weight, immersed weight, bone volume and percentage of water
were lower in the restricted group aged 38 days. Moreover, vertebral height was reduced
in the restricted group aged 4 months. However, mineral density, percentage of mineral
matter and maximum load were higher in the restricted group aged 38 days. The areal
density, vertebral tenacity and stiffness were not altered by the food restriction. The food
restriction diet resulted in damage to femoral bone development with remarkable loss in
prepubertal rats, inconsistent alterations in young adult rats and potential benefits to bones
of elderly rats. In addition, restriction had a positive influence on vertebral bone
properties.