A high-salt diet alters mandibular bone homeostasis. An experimental study across different growth stages

Abstract

OBJECTIVE: To study the effect of a high-salt diet (HSD) on mandibular bone homeostasis in growing rats.

METHODS: Male Wistar rats were assigned at weaning to one of four diet groups for 4 or 8 weeks. Control diets, C4 (n=4) and C8 (n=5), fed a commercial diet; HSD, HSD4 (n=5) and HSD8 (n=6), fed a high-salt diet (8% NaCl). At t=final, 24-hour urine collection was performed in metabolic cages. Animals were euthanized, and hemimandibles were removed. Mandible biomechanical competence was assessed to estimate the structural properties of the bone (fracture strength (Wf max), load bearing capacity (Wf) and stiffness (Wy/dy) using an Instrom 4442. Mandible histological study included interradicular bone volume BV/TV (%), periodontal ligament thickness, density of osteocyte and osteocyte empty lacunae, in sections stained with hematoxylin-eosin.RESULTS: HSD4 and HSD8 presented increased urinary excretion of sodium (p<0.01), calcium (p<0.01), phosphate (p<0.01) and creatinine clearance (p<0.001) than C4 and C8, respectively. In HSD8, an increase in serum ALP (p<0.05), lower Wf max (p=0.038), Wy (p=0.029) and VO/VT% (p=0.007), with an increase in the number of empty osteocytic lacunae compared to C8. In HSD4, there were no differences in the biomechanical properties and histological characteristics versus C4; however, empty osteocytic lacunae were evident. CONCLUSIONS: A high-salt diet during growth negatively affects mandibular bone by promoting early urinary excretion of calcium and phosphate. This study highlights osteocytes as a valuable target for assessing alterations in bone homeostasis induce by unhealthy dietary habits.