BMC) And Density Research Articles

Effects of dietary restriction on total body, femoral, and vertebral bone in SENCAR, C57BL/6, and DBA/2 mice

Dietary restriction (DR) increases the life span and retards aging, in part, by limiting free radical generation and oxidative damage. DR also reduces body mass, a major determinant of bone mass across the life span. We tested the hypothesis that DR has its most beneficial effects on bone in mouse strains with high free radical generation (sensitive to carcinogenesis [SENCAR] > C57 > DBA) versus the hypothesis that bone mass at weight-bearing sites is determined by body mass in DR and ad libitum (AL)-fed mice. Male mice of each strain were killed at 10 weeks of age (t 0) or randomized to an AL-fed or 30% DR feeding regimen for 6 months. Food consumption by AL-fed mice was measured daily, and DR mice received 70% of the amount of food consumed by their respective AL-fed mice the previous day. Body fat (%) and bone mineral density (BMD) and content (BMC) were determined by PIXImus densitometry. There were strain-dependent effects on body mass, crown-to-rump length, percent body fat, and total body, femoral, and vertebral BMD and BMC under all conditions. SENCAR mice were heavier, longer, had larger bones, and generally exhibited higher total body, femoral, and vertebral BMC and BMD than C57 and DBA mice. DR had beneficial effects on BMD and BMC in the vertebrae of the SENCAR mouse model of high free radical generation and in the obese, diabetes-prone C57 mouse model of high end-stage protein glycation. DR DBA and SENCAR mice had lower femoral BMDs and BMCs than their respective AL-fed controls. Regression analysis confirmed linear relationships between total and lean body mass and total body and femoral BMDs and BMCs, suggesting that physiologic adaptation to a lower body mass accounts for the lower femoral bone mineral values observed in DR versus AL-fed mice. Thus, both hypotheses are, at least, partially valid. DR is beneficial in the trabeculae-rich vertebrae of animal models of high oxidant stress, and total/lean body mass determines BMD and BMC in the weight-bearing femur in DR and AL-fed mice.

Soy protein consumption and bone mass in early postmenopausal Chinese women.

Recent interest has been shown in the potential beneficial effects of phytoestrogens on bone health. As the early years of menopause are a period of rapid bone loss, and the risk for osteoporosis increases substantially, the habitual intake of soy protein and isoflavones may play a role in the retardation of bone loss. This paper reports the results of the baseline cross-sectional analysis of the association between dietary soy protein intake and bone mineral density/content in a population-based study of Chinese women. The sample comprised 454 healthy Chinese women (mean age 55.1 +/- 3.57) within the first 12 years of postmenopause. We estimated the dietary intake of soy protein and isoflavones, and other key nutrients, including dietary protein and calcium, using the quantitative food frequency method. Bone mineral density (BMD) and content (BMC) at the spine, hip and total body were measured with a dual energy X-ray densitometer (Hologic 4500A). Soy protein consumption was categorized as quartiles of intake, and related to BMD values at the spine and hip, and BMC of total body. Stratified analyses were carried out among women within or at least 4 years postmenopausal. We observed few differences in BMD/BMC values among the intake quartiles in women within the first 4 years of menopause. However, among the later postmenopausal women, we noted a dose-response relationship with increasing higher BMD values at the trochanter, intertrochanter as well as the total hip and total body with increasing soy protein intake quartiles (P<0.05 from tests for trend). The BMD values differed by about 4-8% between the first and fourth soy protein intake quartiles. Though women from the fourth intake quartile had a 2.9% higher BMD value compared with those from the first intake quartile, the difference was not statistically significant. Stepwise multiple linear regression analyses showed the association between soy intake quartiles and hip BMD as well as total body BMC values remained after adjusting for body weight, which was retained in the final model. Analyses based on soy isoflavones content yielded similar results. This study demonstrated that, among women after the initial few years postmenopausal, soy protein/isoflavones intake had a modest but significant association with hip BMD as well as total body BMC. The effects of soy protein and soy isoflavones on bone health should be further explored in populations with habitual dietary soy intake.

INFLUENCE OF CLOTHING ON DUAL ENERGY X-RAY ABSORPTIOMETRY MEASURES OF BONE MINERAL CONTENT, DENSITY AND BODY COMPOSITION

PURPOSE Recently, Dual-Energy X-Ray Absorptiometry (DXA) measures of bone mineral content (BMC) and density (BMD) were reportedly altered by adding 6 kg of lard to the extremities of subjects. Further, clothing has been shown to affect body fat measurements obtained by both air displacement plethysmography and hydrodensitometry. This investigation sought to determine if wearing loose-fitting clothes (LFC) or tight-fitting clothes (TFC) affects DXA measures of BMD, BMD and body composition. METHODS Thirty-five females underwent two DXA scans (Lunar DPX-L) while wearing; 1) a hospital gown(LFC), and 2) full-body Danskins tights (TFC) affects DXA measures of bone mineral content, density and body composition. RESULTS Wearing TFC resulted in significantly higher values for BMC (TFC = 2.62±0.35kg; LFC = 2.6±0.33kg, P = 0.017) and BMD (TFC = 1.21±0.068g/cm2; LFC = 1.206±0.066g/cm2, P = 0.015). However, clothing did not affect measurments of %body fatness (TFC = 29.1 ±8.7%; LFC = 29.2±8.3%, P = 0.69), fat weight (TFC = 17.8±7.6kg; LFC = 18.1±7.5kg, P = 0.18) or lean body mass (TFC = 39.5±4.5kg; LFC = 39.6 4.7kg, P = 0.37). CONCLUSIONS These results indicate that clothing affects DXA measurements of BMC and BMD, but not body fatness or LBM. While the magnitude of difference in BMC and BMD measures was very small between the two conditions, it does raise questions and concerns regarding the use DXA to clinically assess both bone mineral health and the efficacy of treatments to increase BMC and BMD. These concerns are further enforced by recent studies that have demonstrated considerable discrepancies between volumetric measures of BMD (g/cm3) obtained via CT scans and the planar measures (g/cm2) provided by DXA. While clothing does not affect DXA measures of body fatness and lean body mass, these results raise questions regarding the appropriateness of using DXA measurements of BMC and BMD to clinically assess bone mineral health.

GRATER BONE MASS IN PREPUBESCENT FOOTBALLERS

Previous studies provide evidence that long-term football participation increase bone mass in male football players (Calbet et al 2001). PURPOSE To determine whether the effect of football participation is already detectable in prepubescent boys. METHODS One hundred and four prepubescent boys (Tanner ≤ 2) were divided into two groups depending on the level of their physical activity. Fifty three were ascribed to the football group as they trained football regularly (at least 3 h per week). The other 51, whose physical activities were limited to those programmed during the compulsory physical education curriculum, composed the control group. Both groups had similar age (9.3 ± 0.2 and 9.3 ± 0.2 years, mean ± ± sem) and height. Lean mass (LM), bone mineral content (BMC) and density (BMD) were calculated from total and regional analysis of the whole body, femoral and lumbar scans (DXA). RESULTS Footballers had 10% lower body mass due to reduced fat mass (p ≤ 0.05). Total and regional lean mass, as well as the BMC of the whole body, head, pelvic, upper limbs, femoral region and lumbar spine were similar in both groups. However, the footballers showed a 17% higher BMC of the trochanter and significant greater BMC and BMD (∼5–6%, p ≤ 0.05) in the lower limbs. Proximal femur, lumbar spine, pelvic, trochanter and femoral neck BMD were also greater in the football players (p ≤ 0.05). CONCLUSION The beneficial effect of football participation on BMC and BMD accrual starts at prepubescent ages. Granted by Ministerio de Educación, Cultura y Deportes (AP2000–3652), Universidad de Las Palmas de Gran Canaria, Gobierno de Canarias (PI2000/067), y Consejo Superior de Deportes (27/UNI10/00).

EFFECTS OF INCREASING FLUID MILK INTAKE ON BONE MINERAL DENSITY IN RESPONSE TO RESISTANCE TRAINING IN ADOLESCENT FEMALES

Inadequate consumption of dairy products can compromise development of peak bone mass in adolescent women. PURPOSE The primary purpose of this study was to examine the effects of increasing fluid milk on bone health in girls engaged in a resistance training program. METHODS Thirty-two girls (13 to 17 yrs) who habitually consumed less than 3 servings of fluid milk per day were matched and then randomly assigned into either a milk (MG; n = 16) or juice (JG; n = 16) supplementation group. Subjects consumed 236 mL (24 oz) per day of either 1% fluid milk or juice in addition to the their habitual diet. Both groups completed a 12-wk heavy-resistance training program (3 days/wk). Whole body and regional bone mineral density (BMD) and content (BMC) were assessed at 0, 6, and 12 wks. Data were analyzed using a 2x3 ANOVA with supplement group (MG and JG) and time (weeks 0, 6, and 12) as main effects. RESULTS There were significant interaction (group × time) effects for whole body BMD (P £ 0.05) and lumbar spine BMD (P £ 0.05). The MG group demonstrated a nearly two-fold greater increase than the JG in whole body BMD (DMG = +0.013 vs. DJG = +0.007 g/cm2) and the magnitude of difference was greater for spine BMD (DMG = +0.029 vs. DJG = −0.015 g/cm2). CONCLUSION These findings indicate that providing 3 additional servings of milk per day in adolescent girls engaged in a resistance training program has favorable effects on whole body BMD, especially in the lumbar spine region. Supported by the National Dairy Council, Rosemont, IL.

Growth hormone predicts bone density in elderly women

Evidence is accumulating that the risk of osteoporosis may be influenced by environmental factors during intrauterine and early postnatal life; such programming might be mediated through modification of the GH/IGF-1 axis during critical periods in its development. To address this issue, we explored the relationships among birth weight, circulating GH profile, bone density, and bone loss rate in a group of British women. The study population consisted of 38 women 60–75 years old resident in Hertfordshire for whom detailed birth records were available. Twenty-four-hour circulating GH profiles were obtained during an inpatient stay on a metabolic ward, after an overnight rest. The circulating profile of GH was characterised by estimating the peak, median, trough, and total concentrations from 72 samples measured sequentially over 24 h in each subject. Bone mineral density was assessed at the lumbar spine and femoral neck at baseline and at follow-up 4 years later. Lumbar spine bone mineral content (BMC) and density (BMD) were positively associated with all measures of GH concentration, although relationships were strongest for BMC with trough GH ( r = 0.47, P < 0.01). Associations persisted after adjustment for age, body mass index, smoking, alcohol consumption, physical activity, and osteoarthritis score in multiple regression models. However, associations of GH concentration with femoral neck BMC were weak, and there was no association between any measure of GH concentration and bone loss at either site. Total (integrated) daily GH concentration tended to increase ( P = 0.08) with rising birth weight, while IGF-1 concentration fell ( P = 0.05) with rising birth weight, suggesting a role for the GH/IGF-1 axis in the programming of adult bone mass among women.

Effects of nicotine on bone mass and strength in aged female rats

This study investigated the effects of nicotine on bone mass and biomechanical properties in aged, estrogen-replete (sham-operated) and estrogen-deplete (ovariectomized) female rats. Eight month old, retired breeder, sham-operated and ovariectomized Sprague-Dawley rats were left untreated for 12 weeks to establish cancellous osteopenia in the ovariectomized group. The animals were then administered saline, low dose nicotine (6.0 mg/kg/day) or high dose nicotine (9.0 mg/kg/day) via osmotic minipumps for 12 weeks. Vertebrae and femora were collected at necropsy for determination of bone mass and strength. As expected, ovariectomy had a negative effect on most endpoints evaluated. Vertebral body bone mineral content (BMC) and density (BMD) and the structural (ultimate load and yield load) and material (ultimate stress, yield stress, and flexural modulus of elasticity) strength properties were lower in the OVX rats than in the sham-operated rats. Femoral diaphysis BMC, BMD, ultimate load, and flexural modulus were also lower in the OVX rats than in the sham-operated rats. The nicotine doses administered resulted in serum nicotine levels that averaged 1.5–4.5-fold greater than those observed in heavy smokers. Despite the high doses used, nicotine had no effect on vertebral BMC, BMD, or any of the structural and material strength properties in either the OVX or the Sham rats. In addition, nicotine had no effect on femoral diaphysis BMC, BMD, ultimate load, stiffness, ultimate stress, or flexural modulus. Femoral yield load and stress were lower in low dose nicotine-treated rats than in vehicle-treated rats. However, differences were not detected between the high dose nicotine- and vehicle-treated rats for either femoral yield load or stress. The results suggest that tobacco agents other than nicotine are responsible for the decreased bone density and increased fracture risk as observed in smokers.

Influence of a Vegetarian Diet Versus a Diet with Fishmeal on Bone in Growing Pigs

This study was conducted to examine if substantial bone loss occurs in growing pigs fed a vegetarian diet in comparison with a diet containing fishmeal. Twelve 6-week-old weaned pigs were assigned to two groups: group V [vegetarian diet; 0.61% phosphorus (P) in dry matter until 25 kg and 0.46% P until the end of the experiment] and group F (fishmeal diet; 0.61% P in dry matter until 25 kg and 0.46% P until the end of the experiment). Phytase was added to both diets. These two diets were fed to the two groups for a period of 6 weeks. Blood samples were collected weekly, faeces were collected three times a week. Concentrations of osteocalcin (OC) and carboxyterminal telopeptide of type I collagen (ICTP) were measured in serum, using a radioimmunoassay, and bone-specific alkaline phosphatase (bAP) was measured using an enzyme immunoassay. Bone mineral density (BMD) and content (BMC) were determined by peripheral quantitative computer tomography (pQCT) in the tibia and phalanx. In addition, 1,25-dihydroxyvitamin D (VitD) and parathyroid hormone (PTH) were measured in serum. The digestibility of P was significantly decreased in group V. Significant changes in bAP activities and OC concentrations occurred with time during the 6 weeks. ICTP concentrations were significantly higher in group V. Total BMC and BMD in the tibia and BMD in the phalanx significantly decreased in group V. The results show that a vegetarian diet induces a significant loss of bone and a higher bone formation in group V compared with group F, although phytase was added to both diets. The dietary requirements for P in pigs, especially in the context of feeding vegetarian diets and adding an appropriate amount of phytase, should be investigated further.

CIGARETTE SMOKING, SECOND-HAND-SMOKE, AND ADOLESCENT BONE MASS IN WUHAN, CHINA

Research addressing the role of lifestyle and environmental factors on bone development during times of peak bone acquisition in adolescence is limited. Although the relationship between cigarette smoking and bone loss during adulthood is well established, the effect of smoking and second-hand-smoke on bone mass in adolescents is unknown. The high prevalence of smoking among the adults living in China, and the adolescent period being a critical time for both bone accretion and smoking initiation, were the incentives for this investigation. To determine whether these factors were detrimental to the adolescent skeletal system, we measured cortical (forearm) and trabecular (os calcis) bone mineral density (BMD) and content (BMC) using peripheral dual energy x-ray absorptiometry (DXA) in 466 girls and boys ages 10 to 16 years and living in Wuhan, China. In 166 girls, forearm BMC was best predicted by body mass index (24%), age (5%), and menarche (2%) for a combined variance of 31%, while 8% of the variance in os calcis BMC was predicted by body mass index (BMI) alone with no contribution by age or menarche. In 300 boys, a total of 24% of the variance in forearm BMC was explained by BMI (18%) and age (6%); os calcis BMC was only predicted by BMI (21%). The addition of active cigarette smoking and second-hand-smoke into the multiple linear regression models for forearm and os calcis bone mineral contant did not make significant contributions to the variances in either girls or boys. The reasons may have been due to the low levels and duration of tobacco use and exposure among the adolescents we studied. Selecting an older sample of adolescents who smoke more frequently and for a long duration may have uncovered a different relationship. Nevertheless, this was the first study that investigated the role of smoking and second-hand-smoke on bone mass during adolescence.

Lumbar bone mineral content and density measured using a Lunar DPX densitometer in healthy full‐term infants during the first year of life

This cross-sectional study provides values for lumbar spine bone mineral content (BMC) and density (BMD) in 41 healthy full-term born Finnish infants, 19 boys and 22 girls, during the first year of life measured by dual energy X-ray absorptiometry (DXA) using the Lunar DPX densitometer. Lumbar BMC correlated with the weight (r=0.733; P=0.000), length (r=0.677; P=0.000), standardized length (r=0.315; r=0.045) and age at examination (r=0.314; P=0.045), and with the bone area (r=0.736; P=0.000). Infants with < or =-1 SD scores for lengths at examination had significantly lower BMC values [mean (SD); 1.79 (0.66) g] than infants with SD scores above -1 SD [2.27 (0.46) g] (P=0.011). Exclusive breast feeding did not correlate with the lumbar BMC values (r=-0.039; P=0.811). No differences were found in lumbar spine BMC (P=0.097), BMD (P=0.254) and bone area (P=0.094) values between boys and girls. In order to determine the predictive value of the anthropometric measurements on lumbar BMC, stepwise multiple regression analysis were performed, bone area and present weight were the only independent variables which explained 67.6% of the variance in the BMC values. The present cross-sectional data imply that, in healthy term infants, patterns of relative linear growth during the first year of life are related to the lumbar BMC values. In future, careful longitudinal measurements of linear growth are needed to study connections between growth patterns and bone mineral status in infancy.

Relationship between physical activity and bone mineral status in young adults: the Northern Ireland young hearts project

Physical activity during the first three decades of life may increase peak bone mass and reduce future osteoporosis risk. The aim of this study was to determine the extent to which different components of physical activity may influence bone mineral status within a representative population sample of young men and women. Bone mineral density (BMD) and content (BMC) were determined at the lumbar spine and femoral neck in 242 men and 212 women, aged 20–25 years, by dual-energy X-ray absorptiometry. Physical activity was assessed by a self-report questionnaire designed to measure the frequency and duration of physical activity and its components (i.e., work, non-sports leisure, sports-related activities, and peak strain sports activities). Potential confounding factors such as height, weight, diet, and smoking habits were also assessed. In multivariate linear regression models, sports activity and peak strain sports activity undertaken by men were strongly associated with both lumbar spine BMD (β = 0.35 [0.21, 0.49] and β = 0.31 [0.17, 0.44], respectively) and BMC (β = 0.33 [0.21, 0.45] and β = 0.26 [0.14, 0.38], respectively) and femoral neck BMD (β = 0.35 [0.21, 0.48] and β = 0.27 [0.14, 0.40], respectively) and BMC (β = 0.32 [0.19, 0.44] and β = 0.29 [0.17, 0.41], respectively) (all p < 0.01), but work and non-sports leisure activities were not. In women, there were no associations between bone measurements and any component of physical activity. In models involving all subjects the gender/sports activity, but not the gender/peak strain, interaction term was statistically significant. Sports activity explained 10.4% of the observed variance in lumbar spine BMD in men, but <1% in women. These results demonstrate the importance of sports activities, especially those involving high peak strain, in determining peak bone status in young men. Failure to observe this association in women reflects their lower participation in such activities, but they may have the same capacity to benefit from these activities as men. Intervention studies are warranted to determine whether peak bone density in women can be improved by participating, during childhood and adolescence, in sports activities involving high peak strain.

Influence of dietary phosphorus deficiency with or without addition of fumaric acid to a diet in pigs on bone parameters.

The purpose of this study was to examine if substantial bone loss occurs in weaned pigs by feeding a phosphorus-deficient diet with or without fumaric acid. Eighteen weaned pigs were used. The animals were assigned to three groups: group C (control; 0.65% P on DM basis), group LP (low phosphorus; 0.37% P on DM basis) and group LPF (low phosphorus plus fumaric acid; 0.35% P on DM basis plus 2% fumaric acid). These three diets were fed to the groups for a period of four weeks after a two-week adaptation period. Blood samples were collected once a week. Carboxyterminal telopeptide of type I collagen (ICTP) in serum was used as a bone resorption marker. Osteocalcin (OC) and bone-specific alkaline phosphatase (bAP) were used as bone formation markers. Bone mineral density (BMD) and content (BMC) were determined by peripheral quantitative computer tomography. BAP activities significantly increased (24%) in group LPF, and at the last sampling day group LPF had significantly increased activities in comparison to group C. In contrast, ICTP concentrations significantly increased with time in group LP and LPF, and at the last sampling day group LPF had significantly increased activities in comparison to group C. BMD and BMC in femur and tibia significantly decreased in group LP and LPF. The results show that P-deficient diets induce a bone loss. Fumaric acid did not influence the degree of bone loss. With a better understanding of its effect on bone, dietary phosphorus requirements in pigs could be more precisely defined.

Bone mineral content and collagen metabolites in children receiving steroid treatment for nephrotic syndrome.

Bone mineral density (BMD) and content (BMC) were measured in nine children treated with corticosteroids for nephrotic syndrome and in age-matched controls, using dual-energy X-ray absorptiometry (DEXA). The urinary excretion of cross-linked N-telopeptide (NTx) released from collagen type I as a specific marker of bone resorption was also measured. There were no significant differences in body size, BMD results or NTx urinary concentrations between patients and controls, nor could any significant differences be found when the six patients given a cumulative corticosteroid dose of >15 g were analysed separately. The lack of significant differences could be due to the small number of patients included in the study. But when the measured BMD and BMC were analysed according to methods that corrected for body size and puberty stage, values well within the normal range were found in patients as well as in controls. There was, however, a significant, negative correlation between the urinary excretion of NTx and the cumulative dose of corticosteroids. Despite treatment for long periods with high, cumulative doses of corticosteroids, the skeletons of the patients had a normal mineral content, which is encouraging for all those in need of steroids for nephrotic syndrome. A negative correlation between urinary collagen degradation products and the cumulative steroid dose might point to a reduced growth velocity in patients on high doses of steroids earlier than an effect on bone mineralization.

Bone mineral content and collagen metabolites in children receiving steroid treatment for nephrotic syndrome

Bone mineral density (BMD) and content (BMC) were measured in nine children treated with corticosteroids for nephrotic syndrome and in age‐matched controls, using dual‐energy X‐ray absorptiometry (DEXA). The urinary excretion of cross‐linked N‐telopeptide (NTx) released from collagen type I as a specific marker of bone resorption was also measured. There were no significant differences in body size, BMD results or NTx urinary concentrations between patients and controls, nor could any significant differences be found when the six patients given a cumulative corticosteroid dose of &lt; 15 g were analysed separately. The lack of significant differences could be due to the small number of patients included in the study. But when the measured BMD and BMC were analysed according to methods that corrected for body size and puberty stage, values well within the normal range were found in patients as well as in controls. There was, however, a significant, negative correlation between the urinary excretion of NTx and the cumulative dose of corticosteroids. Conclusion: Despite treatment for long periods with high, cumulative doses of corticosteroids, the skeletons of the patients had a normal mineral content, which is encouraging for all those in need of steroids for nephrotic syndrome. A negative correlation between urinary collagen degradation products and the cumulative steroid dose might point to a reduced growth velocity in patients on high doses of steroids earlier than an effect on bone mineralization.

Dietary restraint, exercise, and bone density in young women: are they related?

Women with high scores for dietary restraint have been found to have higher 24-h urinary cortisol excretion and a higher prevalence of subclinical ovulatory disturbances, both of which may be risk factors for bone loss. The purpose of this study was to explore relationships between dietary restraint and bone health in regularly menstruating young women. 62 women (age: 21.7 +/- 2.5 yr) had body composition and total body and lumbar spine bone mineral density (BMD) and content (BMC) assessed using dual-energy x-ray absorptiometry. Dietary restraint was assessed using the restraint subscale from the Three-Factor Eating Questionnaire: 29 women had low restraint (LR; restraint score 0--5), 33 had high restraint (HR; restraint score 13--21). Exercise (h x wk(-1)) was assessed by questionnaire on two occasions. LR and HR women were similar in age and body composition (fat mass = 15.0 +/- 4.7 kg, lean mass = 40.9 +/- 4.9 kg), but HR women exercised more (3.4 +/- 1.7 vs 2.2 +/- 1.8 h x wk(-1), P < 0.05). Exercise was correlated with BMD and BMC, and when it was included as a covariate, total body BMC was significantly lower in HR than LR women. In multiple regression analysis, weekly hours of exercise and restraint score were significant predictors of total body BMD and BMC. The observations of this cross-sectional study suggest that high levels of cognitive dietary restraint, or associated factors such as higher cortisol, may attenuate the positive effects of exercise on bone in young women.

Effects of nicotine on bone mass, turnover, and strength in adult female rats.

This study investigated the effects of nicotine, the chemical responsible for tobacco addiction, on bone and on serum mineral and calcitropic hormone levels in adult, female rats to help resolve a current controversy regarding the impact of nicotine on bone health. Seven-month-old rats received either saline (n = 12), low-dose nicotine (4.5 mg/kg/day, n = 2), or high-dose nicotine (6.0 mg/kg/day, n = 12) administered subcutaneously via osmotic minipumps for 3 months. Blood, femora, tibiae, and lumbar vertebrae (3-5) were collected at necropsy for determination of serum mineral and hormonal concentrations, bone density (femora and vertebrae), bone turnover (tibiae), and bone strength (femora). The presence of nicotine in serum (111 +/- 7 and 137 +/- 10 ng/ml for the low- and high-dose nicotine groups, respectively) confirmed successful delivery of the drug via osmotic minipumps. Nicotine-induced treatment differences were not detected in serum calcium, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D. However, serum phosphorus and parathyroid hormone (PTH) were higher in rats treated with high-dose nicotine, and serum calcitonin was lower in rats treated with both high- and low-dose nicotine than in control rats. Nicotine treatment had no effect on tibial cancellous or cortical bone turnover or femoral bone mineral content (BMC) and density (BMD). Femoral ultimate load and vertebral BMC were lower in rats treated with high-dose nicotine than in control rats. We conclude that nicotine at serum concentrations 2.5-fold greater than the average in smokers has limited detrimental effects on bone in normal, healthy female rats.

Bone mineral content and density in asymptomatic children with coeliac disease on a gluten-free diet.

Osteoporosis is a complication of coeliac disease. A gluten-free diet improves but does not normalize bone mineral density in adult patients. Only limited data are available regarding the influence of the disease and diet on bone mineralization in children. The aim of this study was to evaluate the radial bone mineral content and density in children and adolescents who are asymptomatic on a gluten-free diet. The bone mineral content (BMC) and density (BMD) values of the non-dominant radius midshaft in 91 children (53 girls, 38 boys, mean age 11.7 years, mean duration of disease 8.7 years) were determined by single-photon absorptiometry. At the diagnosis and at least three years after commencement of a gluten-free diet, serum calcium, phosphorus, albumin concentrations and alkaline phosphatase activities were measured in all patients, and intact parathormone concentrations in 16 patients. The mean BMC Z-score value in the female adolescent group only was significantly lower than normal (mean Z-score -1.04, P < 0.01). In contrast, the mean BMD Z-score was significantly higher compared to a healthy population both in girls (mean Z-score +1.36, P < 0.001) and in boys (mean Z-score +0.53, P < 0.02), as well as in the total patient group (mean Z-score +1.01, P < 0.001). The radial diameter was significantly smaller than normal in both pre-pubertal and adolescent groups. Serum laboratory parameters of asymptomatic patients were in the normal range. The parathormone mean value was significantly lower after at least three years of gluten-free diet than at diagnosis (mean +/- SD 3.77 +/- 1.07 versus 7.89 +/- 2.54 pmol/l, P < 0.01), but significantly higher compared to controls (2.89 +/- 0.90 pmol/l, P < 0.05). These data indicate that treated, asymptomatic coeliac children and adolescents have normal or even higher radius mineral density values than controls, but the bone size remains reduced. Although there is no direct evidence of calcium malabsorption in this cohort of coeliac patients, the slightly higher parathormone levels, together with some other factors, particularly delayed puberty, may result in reduced bone size.

Effects of sodium bicarbonate supplementation on axial and peripheral bone mass in rats on strenuous treadmill training exercise.

We observed the effects of sodium bicarbonate supplement on bone mass in rats on strenuous treadmill training. Sixty female Wistar rats (93-days-old; mean initial weight 261 +/- 16 g) were studied. One group of 15 rats was killed at the beginning of the experiments (basal control group), while another group of 15 rats was not manipulated (Exer-NaB-). Another group of 15 rats was exercised but did not receive sodium bicarbonate (Exer+NaB-), while the final group of 15 rats exercised and received sodium bicarbonate (Exer+NaB+) at a dose of 0.05 mg/kg/day, administered by esophageal catheter on exercise days. These rats were killed at the end of 11 weeks. Femoral and vertebral length, weight, and bone mineral content (BMC) and density (BMD) were measured. According to ANOVA with the Tukey-Kramer test, femur length and weight, vertebral weight, femur BMC and BMD, vertebral BMC and BMD and the ratio between femur and vertebral BMC and final body weight, and plasma bicarbonate were lower in the basal control and Exer+NaB- groups than in the two other groups (P < 0.005-0.0001). Overall, there was a positive correlation between femur and vertebral BMC and femur BMC and length (P < 0.0001 for all). Only in the Exer+NaB- group was there a positive association between plasma bicarbonate levels and femur length (r = 0.78; P < 0.0005). Our study demonstrates the adverse effects of strenuous exercise on bone, and the usefulness of sodium bicarbonate supplements in preventing and minimized these effects.

Bone Densitometry: Assessing the Effects of Growth Hormone Treatment in Adults

Dual-energy X-ray absorptiometry (DXA) is the reference method for the measurement of bone mineral mass at different skeletal sites. It has been widely used in recent years to assess the effects of growth hormone (GH) treatment on bone metabolism. In normal individuals, bone mineral content (BMC) and density (BMD), as assessed using DXA, correlate with body size. Therefore, using DXA in patients with congenital GH deficiency (GHD), who have a smaller body frame, would be expected to result in lower bone mass. Thus, comparisons with reference data derived from populations of normal body size are invalid. The evaluation of the effects of GH administration should take into account the possible effects of GH on bone size, not only in children, but also in adults. The enlargement of bone, due to stimulation of the periosteal apposition, may partially mask an increase in BMC, resulting in little or no change in BMD. The ability of GH to affect bone area therefore requires analysis of the possible changes in bone area and BMC, as well as BMD. This issue has been poorly handled in the studies published to date. Lastly, the acceleration of bone turnover induced by GH leads to an increase in bone remodelling space, which in turn is associated with a reduction in BMC and BMD, independent of the net balance between breakdown and formation in each metabolic unit. This bone loss is completely reversible when the remodelling space returns to previous levels. This phenomenon must be taken into account when analysing the effects of GH treatment on bone mass, because a net gain in bone mass may be found in long-term GH treatment or after GH discontinuation, even if bone loss was evident during the first 6 months of treatment. In conclusion, the interpretation of bone density data in patients with GHD, and after GH administration, should take into account some of the methodological aspects of bone densitometry, as well as the specific actions of GH on bone metabolism and body composition.

Influence of strontium on bone mineral density and bone mineral content measurements by dual X-ray absorptiometry.

The presence of Sr in bone influences bone mineral density (BMD) and content (BMC) measurements by dual-energy X-ray absorptiometry (DXA). This interaction is of interest, since strontium ranelate (S12911) demonstrated positive effects on bone metabolism in various animal models of osteoporosis, and is currently being evaluated for treatment of postmenopausal osteoporosis. The present in vitro study aimed to determine adjustment factors for DXA measurements of BMC and BMD at different Sr concentrations in order to estimate the corresponding values that would have been measured without Sr. A series of mixtures of Ca and Sr hydroxyapatites were prepared, with biologically relevant Sr/Ca ratios ranging from 0 to 3.5 mol/mol%, and a constant total concentration of divalent cations (145 mmol). The mixtures were conditioned in plastic dishes 4.5 cm in diameter, to obtain an areal density close to the human vertebral mineral density of 0.7-1.1 g/cm(2). DXA measurements of the mixtures were made with a wide range of different instruments and various acquisition modes. A direct linear relationship (r(2) > 0.99) was found between strontium content and overestimation of BMD and BMC. There were no significant differences in adjustment factors for BMC or BMD between the different machines or acquisition modes, and the presence of Sr in the water bath used to mimic soft tissues did not affect the accuracy and precision of the method. This demonstrates that reliable DXA determinations of BMD may be carried out in the presence of Sr, and may be interpreted in terms of calcium hydroxyapatite equivalent if the bone Sr content of the measured bone is known. The same adjustment factor (10% overestimation for 1 mol/mol% Sr) can be used for all presently available types of instrument and acquisition modes.