High dietary calcium intake decreases bone mobilization during pregnancy in humans / Alto consumo de calcio en la dieta, disminuye la movilización ósea durante el embarazo en seres humanos

Calcium metabolism of the mother is modified during pregnancy because of the mineralization of the fetus skeleton. OBJECTIVE: To evaluate the association of calcium intake and bone demineralization during pregnancy. MATERIAL AND METHODS: At each trimester of pregnancy a validated food frequency intake questionnaire was administered to assess individual daily calcium intake in a cohort of 206 pregnant women, residents of Mexico City. Samples of urine were collected to measure levels of the cross-linked N-telopeptide of type I collagen (NTx), which is a biomarker of bone resorption. The association between calcium ingestion and bone resorption was analyzed using random effects models; non-linear associations were explored using generalized additive models. RESULTS: Progressive increases in NTx levels were observed during pregnancy; with mean and standard deviation (SD) values during the first, second and third trimester of 76.50 (SD=38), 101.02 (SD=48.86) and 144.83 (SD=61.33) nmol BCE/mmol creatinine, respectively. Higher dietary calcium intake was associated with lower bone resorption (β=-0.015; p<0.05). The association between age and NTx showed a non-linear trend with an inflexion point around 33 years: increase in maternal age below that point was associated with a decrease in bone resorption, while in older women the increase in age was associated with an increased resorption. CONCLUSIONS: Our results suggest that calcium ingestion, specifically from dairy products, reduces bone resorption during pregnancy. For each 300mg (a glass of milk) of calcium intake there is an estimated reduction in NTx level of 4.8 nmol BCE/mmol of creatinine (p<0.05).

El metabolismo de calcio es modificado durante el embarazo debido a la mineralización del esqueleto del feto. OBJETIVO: Evaluar la asociación entre la ingesta de calcio y la desmineralización ósea durante el embarazo. MATERIAL Y MÉTODOS: Se administró un Cuestionario de Frecuencia de Consumo de alimentos en cada trimestre del embarazo para evaluar el consumo de calcio en una cohorte de 206 mujeres residentes de la Ciudad de México. Se recolectaron muestras de orina para medir los niveles de N-telopéptido de colágeno tipo I (NTx), biomarcador de resorción. Se hicieron modelos de efectos aleatorios; se estudiaron asociaciones no lineales utilizando modelos aditivos generalizados. RESULTADOS: Se observó aumento progresivo en los niveles de NTx durante el embarazo. El mayor consumo de calcio se asoció con una menor resorción ósea (β=- 0.015, p<0,05). CONCLUSIONES: Los resultados sugieren que la ingestión de calcio reduce la resorción ósea en el embarazo.

Influence of Ovariectomy on Bone Turnover and Trabecular Bone Mass in Mature Cynomolgus Monkeys

PURPOSE: To examine the influence of ovariectomy (OVX) on bone turnover and trabecular bone mass at the 3 clinically important skeletal sites in mature cynomolgus monkeys. MATERIALS AND METHODS: Six female cynomolgus monkeys, aged 17-21 years, were randomized into 2 groups by the stratified weight: the OVX and sham-operation groups (n = 3 in each group). The experimental period was 16 months. Lumbar bone mineral density (BMD) in vivo and serum and urinary bone turnover markers were longitudinally measured, and peripheral quantitative computed tomographic and bone histomorphometric analyses were performed on trabecular bone of the lumbar vertebra, femoral neck, and distal radius at the end of the experiment. RESULTS: OVX induced in a reduction in lumbar BMD compared with the sham controls and the baseline, as a result of increased serum levels of bone-specific alkaline phosphatase and urinary levels of cross-lined N- and C-terminal telopeptides of type I collagen. Furthermore, OVX induced reductions in trabecular volumetric BMD and trabecular bone mass compared with the sham controls, with increased bone formation rate at the lumbar vertebra, femoral neck, and distal radius. CONCLUSION: The results indicated that OVX in mature cynomolgus monkeys (17-21 years of age) increased bone turnover and induced trabecular bone loss at the three skeletal sites compared with the sham controls. Thus, mature cynomolgus monkeys could be utilized for preclinical studies to examine the effects of interventions on bone turnover and trabecular bone mass at the 3 clinically important skeletal sites.

Bone and Cartilage Turnover Markers, Bone Mineral Density, and Radiographic Damage in Men with Ankylosing Spondylitis

PURPOSE: To determine the levels of bone and cartilage turnover markers in men with ankylosing spondylitis (AS) and to investigate their associations with disease activity, bone mineral density, and radiographic damage of the spine. PATIENTS AND METHODS: This cross-sectional study enrolled 35 men with newly diagnosed AS. The bone mineral densities (BMD) of their lumbar spines and proximal femurs, Bath AS Disease Activity Index (BASDAI), and Bath AS Radiographic Index (BASRI) were evaluated. Urinary C-terminal telopeptide fragments of type I collagen (CTX-I) and type II collagen (CTX-II) levels were determined by enzyme-linked immunosorbent assay, and serum levels of bone-specific alkaline phosphatase (BALP) and osteocalcin were determined by an enzyme immunoassay. Levels of biochemical markers were compared with those of 70 age-matched healthy men. RESULTS: Patients with AS had significantly higher mean urinary CTX-I and CTX-II levels than control subjects (p < 0.05). Elevated urinary CTX-I levels correlated well with BASDAI, femoral BMD, and femoral T score (p < 0.05), and elevated urinary CTX-II levels correlated well with spinal BASRI (p < 0.05) in patients with AS. Mean serum BALP and osteocalcin levels did not differ between patients and controls and did not show any significant correlations with BMD, BASDAI, or BASRI in men with AS. Conclusions: Elevated CTX-I reflects disease activity and loss of femoral BMD while elevated CTX-II levels correlate well with radiographic damage of the spine, suggesting the usefulness of these markers for monitoring disease activity, loss of BMD, and radiographic damage in men with AS.