Bone density, microarchitecture and estimated strength in stone formers: a cross-sectional HR-pQCT study.

BACKGROUND: Low areal bone mineral density (BMD), increased fracture risk and altered bone remodeling have been described among stone formers (SFs), but the magnitude of these findings differs by age, sex, menopausal status and urinary calcium (uCa). This study aimed to investigate volumetric BMD (vBMD), bone microarchitecture and biomechanical properties by high-resolution peripheral quantitative computed tomography (HR-pQCT) and finite element analysis (FEA) in young SFs, irrespective of calciuria, further distinguishing trabecular from cortical compartments. METHODS: HR-pQCT/FEA was performed at the distal tibia (DT) and distal radius (DR) in 106 SFs (57 males and 49 premenopausal females; median age 37 years) and compared with 106 non-SFs (NSFs) retrieved from an existing database, matched for age, sex and body mass index (BMI). Biochemical/hormonal serum and urinary parameters were obtained from SFs. RESULTS: SFs exhibited significantly lower trabecular number (TbN) and higher trabecular separation (TbSp) than NSFs at both anatomical sites and lower cortical porosity in the DR. In a subgroup analysis separated by sex, female SFs presented significantly lower TbvBMD, relative bone volume fraction (BV/TV) and TbN and higher TbSp than NSFs at both sites, while male SFs showed significantly lower stiffness and failure load. Multivariate analysis showed TbN to be independently associated with sex and BMI at both sites and with uCa at the DR. CONCLUSIONS: The present findings suggest that bone disease represents an early event among SFs, associated at least in part with calcium excretion and mainly characterized by trabecular bone microarchitecture impairment, especially among women, but with reduced bone strength parameters in men.

Expression of vitamin D receptor, CYP27B1 and CYP24A1 hydroxylases and 1,25-dihydroxyvitamin D3 levels in stone formers.

The expression of vitamin D receptor (VDR) and 1,25-dihydroxyvitamin D3 [1,25(OH)D] levels exceed the values of controls in some but not all hypercalciuric stone formers (HSF). We aimed to evaluate serum 1,25(OH)D levels, the expression of VDR, CYP27B1, and CYP24A1 hydroxylases in HSF in comparison with normocalciuric stone formers (NSF) and healthy subjects (HS). Blood samples, 24-h urine collections and a 3-day dietary record were obtained from 30 participants from each of the groups. The expression of VDR, CYP27B1, and CYP24A1 was measured by flow cytometry. HSF presented significantly higher urinary volume, sodium, magnesium, oxalate, uric acid, and phosphorus than NSF and HS. Calcium intake was lower in HSF versus NSF and HS (442 ± 41 vs 594 ± 42 and 559 ± 41 mg/day, respectively, p = 0.027). Ionized calcium was significantly lower in HSF than NSF (1.29 ± 0.0 vs 1.31 ± 0.0 mmol/L, p < 0.01). Serum 1,25(OH)D was significantly higher in HSF and NSF than HS (22.5 ± 1.2; 22.2 ± 1.2 vs 17.4 ± 1.2 pg/ml, p = 0.007) but serum 25(OH)D, PTH, klotho and plasma FGF-23 did not differ between groups. VDR expression was higher in HSF and NSF than HS (80.8 ± 3.2; 78.7 ± 3.3 vs 68.6 ± 3.2%, p = 0.023). Although CYP27B1 and CYP24A1 expressions were similar among all groups, the ratio of 1,25(OH)D/CYP24A1 was higher in HSF and NSF than in HS (1.43 ± 0.25 and 0.56 ± 0.10 vs 0.34 ± 0.06, p = 0.00). Stone formers, regardless of urinary calcium excretion, had higher VDR expression and 1,25(OH)D levels than HS, even in ranges considered normal. Higher 1,25(OH)D/CYP24A1 ratio suggested a lower degradation of 1,25(OH)D by CYP24A1 in HSF and NSF.

Bone turnover after bariatric surgery.

OBJECTIVE: The aim of the present study was to evaluate parameters of bone and mineral metabolism after bariatric surgery. SUBJECTS AND METHODS: This sectional study included data from medical records from 61 bariatric surgery (BS) patients (minimum period of 6 months after the procedure) and from 30 class II and III obese patients as a control group (Cont), consisting of daily dietary intake of macronutrients, calcium and sodium, serum 25(OH)D and parathyroid hormone (PTH) and other biochemical serum and urinary parameters. Bone alkaline phosphatase (BAP), leptin, fibroblast growth factor-23 (FGF-23) and deoxypyridinoline (DPYD) were determined from available banked serum and urinary samples. RESULTS: Mean body mass index (BMI), median energy, carbohydrate, protein and sodium chloride consumption were significantly lower in the BS versus Cont, but calcium and lipids were not. No significant differences were found in ionized calcium, 25(OH)D, PTH and fibroblast growth factor 23 (FGF-23) between groups. Mean serum BAP was significantly higher for BS versus Cont and had a positive correlation with time after the surgical procedure. Mean serum leptin was significantly lower and median urinary DPYD higher in BS versus Cont. CONCLUSION: The present study showed an increase in bone markers of both bone formation and resorption among bariatric patients up to more than 7 years after the surgical procedure, suggesting that an increased bone turnover persists even at a very long-term follow-up in such patients.

Bone turnover after bariatric surgery

ABSTRACT Objective The aim of the present study was to evaluate parameters of bone and mineral metabolism after bariatric surgery. Subjects and methods This sectional study included data from medical records from 61 bariatric surgery (BS) patients (minimum period of 6 months after the procedure) and from 30 class II and III obese patients as a control group (Cont), consisting of daily dietary intake of macronutrients, calcium and sodium, serum 25(OH)D and parathyroid hormone (PTH) and other biochemical serum and urinary parameters. Bone alkaline phosphatase (BAP), leptin, fibroblast growth factor-23 (FGF-23) and deoxypyridinoline (DPYD) were determined from available banked serum and urinary samples. Results Mean body mass index (BMI), median energy, carbohydrate, protein and sodium chloride consumption were significantly lower in the BS versus Cont, but calcium and lipids were not. No significant differences were found in ionized calcium, 25(OH)D, PTH and fibroblast growth factor 23 (FGF-23) between groups. Mean serum BAP was significantly higher for BS versus Cont and had a positive correlation with time after the surgical procedure. Mean serum leptin was significantly lower and median urinary DPYD higher in BS versus Cont. Conclusion The present study showed an increase in bone markers of both bone formation and resorption among bariatric patients up to more than 7 years after the surgical procedure, suggesting that an increased bone turnover persists even at a very long-term follow-up in such patients.