An experimental model of vitamin D insufficiency and established osteopenia.

ZENI SUSANA N; MASTAGLIA SILVINA; MANDALUNIS PATRICIA; DE GRANDI MARIA C; OLIVERI BEATRIZ; SOMOZA JULIA; FRIEDMAN SILVIA M

Buenos Aires

Congreso; XXI Reunión Anual de la Asociacion Argentina de Osteologia y Metabolismo Mineral.; 2004

Asociacion Argentina de Osteologia y Metabolismo Mineral.

The present study was carried out to obtain an experimental model of vitamin D (vit D) insufficiency and established osteopenia (experiment1), to then investigate whether vit D status, i.e. normal or insufficient, interferes with bone mass recovery resulting from bisphosphonate therapy (experiment 2). Rats (n=40) underwent OVX (n=32) or a SHAM operation (n=8). The first fifteen days post-surgery, all groups were kept under fluorescent tube lighting and fed a diet containing 200 IU% vit D (+D). They were then assigned during an additional 45-days to receive either +D or a diet lacking vit D (–D) and kept under 12 h. light/dark cycles using fluorescent or red lighting. Serum 25HOD was significantly lower in -D rats (p<0.0001). The type of lighting did not induce differences in 25OHD, calcium (sCa), phosphorus (sP), bone alkaline phosphatase (b-AL), CTX, bone density, or histology. No osteoid was observed in undecalcified bone sections. Experiment 2 (105 days): rats were fed either +D or –D according to experiment 1, and were treated with either placebo or 16 ug olpadronate (OPD)/100g rat/week during the last 45 days. Whereas 25HOD was significantly lower (p<0.0001) in –D/OPD than in +D/OPD rats, no significant differences in sCa, sP, bAL or CTX were observed.  OPD prevented the loss of lumbar spine (LS) and proximal tibia (PT) BMD, and the decrease in bone volume (BV/TV) (p<0.05) and in the number of trabeculae observed in untreated rats. However, +D/OPD animals presented significantly higher values of LS BMD, PT BMD and BV/TV than –D/OPD rats (p<0.05).  No osteoid was observed in undecalcified sections of bone. In summary, this is the first experimental study to provide evidence that differences in vit D status may affect the anticatabolic response to bisphosphonate treatment. However, the molecular mechanism through which vit D insufficiency reduces the effect of the aminobisphosphonate remains to be defined.