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Although body mass is known to be related to bone mass, defined as bone mineral density (BMD) and bone mineral content (BMC), little is known about the effects of body mass reduction programs on bone mass. This study assessed bone mass changes in response to four body mass reduction programs that utilized diet and/or exercise. Ninety-four obese or overweight women (age 49.3±7.1 years, body mass 68.5±7.7 kg) were randomly assigned 4 groups (2 intervention forms × 2 trials) : diet in trial 1 (D<SUB>1</SUB>, n=27), diet plus exercise in trial 1 (DE<SUB>1</SUB>, n=28), diet in trial 2 (D<SUB>2</SUB>, n=21), and diet plus exercise in trial 2 (DE<SUB>2</SUB>, n=18) . Body mass, body mass index (BMI), absolute and relative (%fat) fat mass, lean mass, BMC, and BMD were measured by dual energy X-ray absorptiometry before and after the 3-month intervention program. Body mass loss was similar in DI (-9.7%) and D<SUB>2</SUB> (-11.6%), and in DE<SUB>1</SUB> (-13.8%) and DE<SUB>2</SUB> (-12.2%) . However, BMC loss was different (<I>P</I><0.05) between trial 1 and trial 2 for each intervention form (D<SUB>1</SUB>: -3.2% vs D<SUB>2</SUB> ; -0.9%, DE<SUB>1</SUB>: -4.5% vs DE<SUB>2</SUB>: -0.8%) . With this in mind, multiple regression analyses were applied, with either change in BMC or BMD as the dependent variable, and other physical characteristics measured before and after the intervention program as independent variables. Results indicated that multiple correlation coefficients were statistically significant (R=0.61 with BMC, R=0.49 with BMD) . BMI after the intervention program and change in body mass were identified as the significant contributors to the change in BMC, while change in %fat and age were identified as the significant contributors to the change in BMD. These results suggest that, during body mass reduction, (1) physical characteristics are the significant contributors to changes in BMC and BMD and (2) exercise may not prevent the loss of bone mass.
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The purpose of this study was to examine the relationships between peak bone mass and genetic and environmental factors. We measured whole-body bone mineral density (BMD), lumbar spine BMD, and radius BMD with dual-energy X-ray absorptiometry (DXA) and analyzed eight genetic factors: vitamin D receptor (VDR)-3', VDR-5', estrogen receptor (ER), calcitonin receptor (CTR), parathyroid hormone (PTH), osteocalcin (OC), apolipoprotein E (ApoE), and fatty acid binding protein 2 (FABP2) allelic polymorphisms using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLPs). We also surveyed menstrual history, food intake, and history of physical activity using questionnaires. After adjusting for age, body mass index (BMI), current smoking status, current Ca intake, alcohol intake, menoxenia, and physical activity, the mean BMD in subjects with the HH/Hh genotype was significantly higher than that of subjects with the hh genotype for whole-body BMD (mean±SD, 1.20±0.10 vs. 1.18 ±0.09 g/cm2; HH/Hh vs. hh, p=0.04) and at lumbar spine BMD (mean±SD, 1.18±0.14 vs. 1.14±0.12 g/cm2; HH/Hh vs. hh, p=0.02) in OC allelic polymorphism. Furthermore, the results of multiple regression analyses taking the 8 genetic factors plus the 7 environmental factors listed above into account showed that the strongest factor contributing to BMD was BMI at any site (whole-body and lumbar BMD p<0.0001, radius BMD p=0.0029). In addition, OC polymorphism (p=0.0099), physical activity (p=0.0245), menoxenia (p=0.0384), and PTH polymorphism (p=0.0425) were independent determinants for whole-body BMD, and OC polymorphism (p=0.0137) and physical activity (p=0.0421) were independent determinants for lumbar BMD and radius BMD, respectively.
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Exercício FísicoRESUMO
Objectives: The goal of the present study was to investigate the relationship between occlusal function and body composition in 108 premenopausal healthy Japanese women aged 20−45 years. Methods: Pressure-sensitive sheets were used to measure occlusal function. Whole fat mass and lean mass, fat-free mass, and whole-bone mineral content were measured by dual-energy X-ray absorptiometry (DXA). Results: After being adjusted for age and the square of height, the whole lean mass and grip strength of the large occlusal contact-area group were found to be significantly higher than those of the small occlusal area groups (p<0.05, respectively). In the 1-year follow-up study, changes in weight in the small-occlusal contact-area group and the low-occlusal force group were significantly larger than other occlusal-contact area or occlusal-force groups. The mean occlusal-contact area and occlusal force were both significantly smaller in subjects with partial dentures than in those without (p<0.05). Conclusion: Large occlusal contact-area, high occlusal force, and no dentures may be associated with some good health conditions in premenopausal Japanese women.
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Composição CorporalRESUMO
The purposes of this study were to examine the loss of bone mineral density (BMD) with increasing age and to investigate the relationship between the BMD and body composition. Cross-sectional measurements of total body and regional (head, arms, legs, trunk, ribs, pelvis and spine) BMD and body composition were made in 112 Japanese healthy women, aged 20 to 87 years, by dual-energy X-ray absorptiometry (DXA) . The mean peak BMD for the trunk, ribs, and pelvis was observed at the age of 40-49 years, in the arms and spine at the age of 30-39 years, and in the head, legs, and total body at the age of 20-29 years. The loss of spine BMD appears to begin prior to BMD loss in other regions and the rate of bone loss as a function of aging was readily apparent. Appendicular bone loss did not occur until age 49 yr, accelerated from ages 50 to 69 yr, and then decelerated somewhat after age 70 yr. In this cross-sectional analysis, we found cumulative loss of BMD from peak to 80-89 yr of age was 31.2% for the spine, 25.0% for the total body, and 21.5% for the ribs. To examine the relationship between the BMD and body composition, multiple regression analysis was performed with total body and regional BMD as the dependent variable and fat-free mass (FFM) and fat mass as the independent variable. From this analysis, the results indicated that FFM was a significant predictor of total body and regional BMD but did not evaluate the effects of exercise or other potential variables that might affect BMD. In conclusion, our findings indicate that spine bone loss begins prior to the loss of compact bone, and the rate of bone loss in the spine due to aging was greater than that of other specific regions. Secondly, FFM and fat mass are related to total and regional BMD in Japanese women with the strongest relationship being FFM.
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Bone (tibia, femur, and lumbar spine) and blood samples were obtained from 100 (50 males and 50 females) Wistar-Imamichi rats in groups aged 3, 5, 7, 9, 12, 15 and 20 weeks old to investigate the changes in bone mass during puberty in relation to insulin-like growth factor 1 (IGF-1), IGF binding protein (IGFBP) -3, osteocalcin (OC) and sex steroids in normal rats.<BR>Sharp increases in BMD (bone mineral density) in the tibia, femur and lumbar appeared earlier in female than in male rats, and the BMD in females tended to be higher than in males between 5 and 9 weeks old. After 9 weeks old, BMD in males was higher than that in females, as BMD in males continued to increase whereas that in females tended to remain in a steady state after this stage. This sex-related difference in changes in BMD pattern is probably related to the serum concentrations of IGF-1, IGFBP-3, testosterone, and 17β-estradiol with maturation. In males, marked increases in serum IGF-1 and IGFBP-3 concentrations appeared earlier than that in serum testosterone level. IGF-1 and testosterone peaked at 9 weeks of age, and thereafter remarked in a steady state, whereas IGFBP-3 reached a peak at 7 weeks of age, and then declined gradually. In females, the changes in patterns of serum 17β-estradiol, IGF-1, and IGFBP-3 levels were very similar. The levels increased gradually from 3-5 weeks old, peaked at 9 weeks, and then decreased slowly thereafter. In contrast, serum OC concentrations remain relatively high from 3 to 9 and from 3 to 7 weeks old in males and females, respectively, although OC in both sexes declined gradually with aging.<BR>These observations suggest that BMD development occurs earlier in female than in male rats. This sex-related difference in changes in the BMD pattern may result from the earlier onset of puberty in females, and from the sex-specific differences in concentrations of IGF-1, IGFBP-3 and sex steroids with maturation.
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Measurement of bone mass (BM), especially in the lumbar vertebrae, is very important for diagnosis of osteoporosis. In this study, we compared BM values measured by computed X-ray densitometry (CXD) with those by quantitative computed tomography (QCT), and discussed differences between the two methods.<BR>The subjects were 90 women and 3 men, aged 42-86 years, who visited our outpatient department of osteoporosis. Metacarpal bone density (ΣGS/D) and metacarpal index (MCI) in the second metacarpal bone were measured by CXD. QCT was uesd for measurement of bone mineral density (BMD) in the lumbar trabecular bone, where pronounced osteoporotic changes occur early. The mineral values of L3 were expressed as mineral equivalent of CaCO<SUP>3</SUP> in mg/ cm<SUP>3</SUP>, and≤75 mg/cm<SUP>3</SUP> of L3 values were judged to be loss of lumbar BMD.<BR>There were negative correlations between age and ΣGS/D, MCI or L3 value, and positive correlations were found between ΣGS/D or MCI and L3 value. Based on the above criterion of lumbar BMD loss, sensitivity and specificity of ΣGS/D for lumbar bone loss were examined. If ΣGS /D of 2.30 (T score -2.7) was used as the cut-off point, the sensitivity was 69.8% and the specificity was 75.0%, and if ΣGS/D of 2.37 (T score -2.3) and 2.40 (T score -2.1) were employed, the sensitivity was 79.1% and 79.1%, while the specificity was 64.5% and 62.5%, respectively. We concluded that BM values of cortical bone and trabecular bone decrease with age, and that sensitivity and specificity of GS/D for diagnosis of lumbar BMD loss are not very high.
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Physical activity in the growing period has been shown to be effective for increasing bone mass because immature bones are more sensitive than mature adult bones to the stimulation with mechanical stress. However, bone growth is not uniform and changes markedly at puberty. Therefore, the response of bone to exercise may differ according to the growth process. The purpose of the present study was to investigate the process of the bone response to running training, and the relationship between the bone response and serum insulin-like growth factor-I (IGF-I) and IGF binding protein-3 (IGFBP-3) levels in female rats. Thirty-three female Wistar-Imamichi rats 4 weeks of age were divided randomly into control (CON) and running training (RUN) groups for 6 and 12 weeks. Training consisted of running on a flatbed treadmill at 30 m/min for 60 min/day, 5 days/week. The bone mineral content (BMC) and bone mineral density (BMD) in the whole and five parts of the tibia were measured by a dual-energy X-ray absorptiometer (DXA) . Simultaneously, we measured serum concentrations of IGF-I, IGFBP-3, osteocalcin and 17β-estradiol. The whole tibial BMD was significantly higher in the RUN groups than in the age-matched CON groups. When BMD was analyzed at five different studied parts within the same tibia, the increase of BMD. was noted in the proximal and distal cancellous bone in the 6-week RUN group, and in the diaphysial, cortical bone, in the 12-week RUN group. Serum concentrations of osteocalcin, a marker of bone formation, were not altered by training, whereas they decreased with aging. Serum IGF-I levels in the training groups were not changed, but IGFBP-3 levels were increased significantly only in 6-week RUN rats. As a complex between IGFBP-3 and IGF-I may be more improve than free IGF-I in the bone formation, the high levels of IGFBP-3 in the 6-week RUN group may induce an increase in the activity of IGF-I. There was a significant positive relationship between serum IGF-I concentration and BMD of the whole tibia in the 6-week study, and between the IGFBP-3 level and BMD in both the 6 and 12-week studies.<BR>In conclusion, 1) the process of the skeletal response to running training is site-specific within the same bone, and 2) the increment of the IGFBP-3 level with training in the growth period may reflect the increment of tibial BMD through training.
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The effects of running exercise on bone histomorphometric parameters were examined in sham-treated (Sham) and ovariectomized (OVX) rats. The rats were either kept sedentary (C) or trained (T) on a rodent treadmill at 25 m/min, 30 min/day, 5 days/week for 10 weeks. Fat-free dry bone weight, bone mineral content (BMC), and histomorphometric parameters were assessed after excision of the tibiae at sacrifice. The results are summarized as follows<BR>1) There were no significant differences in fat-free dry bone weight and BMC between OVX-C and Sham-C rats. However, BMC/body weight in OVX-C rats was significantly lower than in Sham-C animals. OVX-C rats had significantly lower trabecular bone volume at the proximal tibial metaphysis than Sham-C animals. Values of bone formation parameters were significantly higher in OVX-C rats than in Sham-C animals.<BR>2) BMC/body weight in OVX-T rats was significantly higher than in OVX-C animals. OVX-T rats had a significantly higher trabecular bone volume at the proximal tibial metaphysis than OVX-C animals. There were no significant differences in bone formation parameters between OVX-T and OVX-C rats.<BR>3) No significant differences were found in any parameters between sham-C and Sham-T rats.<BR>These results suggest that (1) running exercise has a suppressive effect on bone loss after OVX, and (2) training-induced reduction of bone loss by OVX does not seam to be associated with facilitation of bone formation but with suppression of bone resorption.
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The purpose of this study was to investigate the effects of running training on bone formation in rats in relation to the age training started. The first experimental period was set from 6 to 12 weeks (wks) old and the second from 12 to 19 wks old. Sixty-four Wistar strain 6-wk-old male rats were initially divided into a non-exercise (N) and an exercise (E) group. At 12 wks old, each group was subdivided into two groups, providing four groups: non-exercise·non-exercise (NN), non-exercise·exercise (NE), exercise·non-exercise (EN) and exercise·exercise (EE) . Exercise consisted of treadmill running at a speed of 30 m/min, 60 mm day, 5 days wk. The animals were sacrificed before the experiment (6 wks old), post-first experiment (12wks old) and postexperiment (19 wks old), the bilateral tibiae were removed and their lengths, bone mineral content (BMC), bone mineral density (BMD) and bone histomorphometric parameters were measured. The tibial length was significantly shorter in 12-wk-old E than N rats and in 19-wk-old EE than NN. At 19 wks old, the total tibial BMD values were significantly higher in EE than NN, and the BMD values of the proximal and distal tibiae, where the cancellous bone was the main component, had increased markedly, whereas no differences between the diaphyseal BMD of each group were noted. Bone histomorphometry at 12 wks old, considered the immature period, showed that the osteoid surfaces and labeled surfaces tended to be increased by running training, but the bone volume was unchanged. In contrast, at 19 wks old, considered the early mature period, the osteoid surfaces showed a tendency to decrease and labeled surfaces to increase and consequently the bone volume increased albeit not significantly. These results suggest that: 1) running training started in immature rats represses longitudinal tibial growth, 2) the cancellous bone is more sensitive then the cortical bone to this type of training and 3) training of early mature rats increases bone volume by increasing the efficiency of osteoid calcification.
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The effects of exercise training on bone development in growing rats were studied using the photon-absorption method and histomorophological analyses. Thirty-seven male Wistar strain rats at 4 wks of age were divided into five groups : sedentary control (C; N=7), 15 min/day training (T 15 ; N=6), 30 min/day training (T 30 ; N=8), 60 min/day training (T 60 ; N=8) and 120 min/day training (T 120 ; N=8) . All rats in these training groups were subjected to a treadmill running at a speed of 30 m/min, 5 days/wk for 11 wks. The results of our study were summarized as follows :<BR>1) Fat-free dry weight of the tibia was significantly heavier in T 30, T 60 and T 120 than C and T 15, respectively.<BR>2) Bone mineral content (mg/cm) of tibial midshaft in all T groups was significantly higher than that in C group, respectively, while no differences were found between any of the training groups.<BR>3) On histological parameters of cross-sectional samples from tibia, such as cortical area, total area and appositional growth rate on periosteum, higher values were observed in T groups compared with C group.<BR>These results suggest that physical training induce markedly facilitative girth growth associated with elevated bone formation of periosteum in the tibia, and moreover, the daily exercise duration does not change the degree of bone hypertrophy.