DXA is a reliable and precise method to evaluate the bone mass in rabbits. Our results also suggest that subchondral bone is a bone of mixed densitometric characteristics with marked cortical bone predominance.

To characterize an experimental model of osteoporosis in rabbits induced either by ovariectomy (OVX), glucocorticoids, or by a combination of both. Thirty-five rabbits were randomly allocated into five groups: bilateral OVX, daily methylprednisolone hemisuccinate (MPH) injections at a 1.5 mg/kg/day dose for 4 consecutive weeks (MPH group), or variable dose of MPH between 0.5 and 2 mg/kg/day in combination with OVX (OVX + MPH at low, medium, and high dose). Twenty-two animals were killed 6 weeks after OVX, and 13 were killed 16 weeks later. Dual-energy X-ray absorptiometry was obtained at baseline and 6 and 16 weeks after OVX. High-resolution magnetic resonance imaging (MRI) was carried out at 0 and 6 weeks after OVX. Glucose, total cholesterol, triglyceride, and oestradiol blood levels before and 16 weeks after OVX were determined. Bone mineral density (BMD) decreased significantly at lumbar spine in MPH and OVX + MPH medium-dose groups, and at global knee and subchondral bone of the knee in MPH, OVX + MPH low- and medium-dosage groups (P < 0.05). BMD variations in OVX rabbits were not significant in any of the three anatomical locations analyzed. BMD variation 16 weeks after OVX was significant at lumbar spine and global knee in the OVX + MPH medium-dose group and only at global knee in the OVX + MPH low-dose group (P < 0.05). MRI did not show bone or cartilage changes. Osteoporosis can be induced experimentally in rabbits through isolated MPH or by a combination of OVX and medium dose corticosteroid for 4 weeks. OVX alone was not sufficient to induce osteoporosis.

At present there are many techniques available for determining bone mass, measurement of which is essential for monitoring osteopenia. Rats are preferred to other laboratory species when designing animal studies on osteoporosis. The precision and accuracy of dual energy X-ray absorptiometry (DXA) for the assessment of bone mineral density (BMD) and bone mineral content (BMC) in laboratory animals were assessed. Precision, expressed as a coefficient of variation (CV), was measured, making five determinations (Hologic QDR-1000) on lumbar spine (in vivo) and femur (in vitro), both with and without repositioning. The correlation (r) between densitometric parameters and mineral content of bone ashes was calculated both in lumbar spine (in vivo) and in femur (in vitro). In our study, DXA had good precision, better in femur (CV 0.53%) than in lumbar spine (L2-L4) (CV 1.0%). Repositioning did not increase significantly the coefficients of variation (CV 0.61% and 1.2%, respectively). The linear regression between BMD and ash weight, calcium and phosphorous content showed high correlation coefficients (r = 0.64-0.85, p < 0.05). Although we found an overestimate of values of BMC with respect to ash weight (21% in lumbar spine and 31% in femur), the correlation between BMC and mineral content was high (r = 0.96-0.99, p < 0.05). The results suggest that the DXA technique has the precision necessary when used to assess BMD and BMC in small laboratory animals.

Some patients sustain fractures while on antiresorptives. Whether this represents an inadequate response (IR) to treatment or a chance event has not been elucidated. We performed a study to identify which patients are more likely to fracture while on treatment. This is a multicentric, cross-sectional study of postmenopausal women on antiresorptives for osteoporosis in 12 Spanish hospitals, classified as adequate responders (ARs) if on treatment with antiresorptives for 5 years with no incident fractures or inadequate responders (IRs) if an incident fracture occurred between 1 and 5 years on treatment. Poor compliance, secondary osteoporosis, and previous antiosteoporosis treatment other than the assessed were exclusion criteria. Clinical, demographic, analytical, dual-energy X-ray absorptiometry (DXA) variables, and proximal femur structure analysis (ImaTx TM ) and structural/fractal analyses of distal radius were performed. A total of 179 women (76 IRs; mean (SD): age 68.2 (9.0) years; 103 ARs, age 68.5 (7.9) years) were included. History of prior fracture ( p ¼ 0.005), two or more falls in the previous year ( p ¼ 0.032), low lumbar spine bone mineral density (BMD) ( p ¼ 0.02), 25 hydroxyvitamin D ( p ¼ 0.017), and hip ImaTx fracture load index ( p ¼ 0.004) were associated with IR. In the logistic regression models a fracture before treatment (odds ratio [OR], 3.60; 95% confidence interval [CI], 1.47-8.82; p ¼ 0.005) and levels of 25 hydroxyvitamin D below 20 ng/mL (OR, 3.89; 95% CI, 1.55-9.77; p ¼ 0.004) significantly increased risk for IR, while increased ImaTx fracture load (OR, 0.96; 95% CI,; p ¼ 0.006; per every 100 units) was protective, although the latter became not significant when all three variables were fitted into the model. Therefore, we can infer that severity of the disease, with microarchitectural and structure deterioration, as shown by previous fracture and hip analysis, and low levels of 25 hydroxy vitamin D carry higher risk of inadequate response to antiresorptives. More potent regimes should be developed and adequate supplementation implemented to solve this problem. ß

In obese postmenopausal Caucasian women, type 2 DM produces an increase in BMD of the lumbar spine without changes in BMD of the proximal femur or in QUS measurements of the heel. The prevalence of vertebral, hip and non-vertebral fractures did not increase in type 2 DM.

ObjectivesThe aim of the study was to determine the factors that may contribute to decreases in bone mineral density (BMD) in patients with AIDS. MethodsThis was a prospective, non-randomized study. Dual X-ray absorptiometry (DXA) was used to determine the BMD of the lumbar spine, femoral neck and distal radius in treatment-naïve HIV-infected male patients with AIDS before and after 1 year of treatment with zidovudine (ZDV)/lamivudine (3TC) plus abacavir (ABC) or lopinavir/ritonavir (LPV/r). ResultsBasal DXA was performed in 50 patients with CD4 counts o200 cells/mL and/or any AIDS-defining condition. Thirty-two patients completed 1 year with full adherence (17 on ABC and 15 on LPV/r) and a second DXA was then performed. At baseline, 19% had osteopenia at the lumbar spine and 19% at the femoral neck. Low body weight was related to low BMD. After 48 weeks, BMD loss was significant at the three locations. The percentage of BMD loss at the femoral neck tended to be greater in the lopinavir group (5.3 vs. 3.2%, P 5 0.058). The differences became significant at the lumbar spine (5.7 vs. 2.7%, P 5 0.044). In the multivariate analysis, the treatment with LPV/r remained associated with bone loss at the lumbar spine. ConclusionsOsteopenia is frequent in treatment-naïve HIV-infected men with AIDS. Bone loss is higher with LPV/r-based regimens compared with triple nucleoside reverse transcriptase inhibitors.

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To clarify the relationship of sex male hormones and bone in men, we studied in 140 healthy elderly men (aged 55-90 years) the relation between serum levels of androgens and related sex hormones, bone mineral density (BMD) at different sites, and other parameters related to bone metabolism. Our results show a slight decrease of serum-free testosterone with age, with an increase of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in a third of the elderly subjects studied. BMD decreased significantly with age in all regions studied, except in the lumbar spine. We found a positive correlation between body mass index (BMI) and BMD at the lumbar spine and femoral neck (P < 0.001). No relationship was found (uni- and multivariate regression analysis) between serum androgens or sex hormone-binding globulin (SHBG) and BMD. We found a positive correlation of vitamin D binding protein (DBP) and osteocalcin with lumbar spine BMD and with BMI, DBP, IGF-1, and PTH with femoral neck BMD. In conclusion, there is a slight decline in free testosterone and BMD in the healthy elderly males. However, sex male hormones are not correlated to the decrease in hip BMD. Other age-related factors must be associated with bone loss in elderly males.