Correlation of obesity and osteoporosis: effect of fat mass on the determination of osteoporosis

The Impact of Body Weight Change on Bone Mineral Density of the Lumbar Spine in Perimenopausal Women: A Retrospective, One-year Follow-up Study

Background

Low body weight was one of the risk factors of osteoporosis. Little is known about the correlation between body weight change and bone mineral density (BMD) in Korean women. Therefore, this study was designed to reveal the impact of body weight change on BMD of the lumbar spine in perimenopausal women.

Methods

105 healthy perimenopausal women aged between 44 and 50 years old were enrolled from August 2002 to March 2009. BMD was measured by dual energy X-ray absorptiometry. Partial correlation coefficients between body weight change and BMD change were calculated after the adjustments for several variables. BMD changes among groups based on BMI and the percentage change in body weight during 1-year follow-up period were compared.

Results

At both baseline and year 1, BMD of lumbar spine tended to be associated more with body weight. There was a significant association between body weight change and BMD change in lumbar spine during 1-year follow-up period. The weight gain group relatively showed an increase in BMD of lumbar spines than weight loss group. There was no BMD change in BMI less than 23 kg/m² group, but in case of BMI more than 23 kg/m² group, BMD in weight gain group increased more than the weight maintaining group.

Conclusion

This study demonstrated that body weight change is associated with change in BMD of lumbar spine in perimenopausal women especially if they are overweight.

The peroxisome proliferator-activated receptor (PPAR) alpha agonist fenofibrate maintains bone mass, while the PPAR gamma agonist pioglitazone exaggerates bone loss, in ovariectomized rats

BACKGROUND

Activation of peroxisome proliferator-activated receptor (PPAR)gamma is associated with bone loss and increased fracture risk, while PPARalpha activation seems to have positive skeletal effects. To further explore these effects we have examined the effect of the PPARalpha agonists fenofibrate and Wyeth 14643, and the PPARgamma agonist pioglitazone, on bone mineral density (BMD), bone architecture and biomechanical strength in ovariectomized rats.

METHODS

Fifty-five female Sprague-Dawley rats were assigned to five groups. One group was sham-operated and given vehicle (methylcellulose), the other groups were ovariectomized and given vehicle, fenofibrate, Wyeth 14643 and pioglitazone, respectively, daily for four months. Whole body and femoral BMD were measured by dual X-ray absorptiometry (DXA), and biomechanical testing of femurs, and micro-computed tomography (microCT) of the femoral shaft and head, were performed.

RESULTS

Whole body and femoral BMD were significantly higher in sham controls and ovariectomized animals given fenofibrate, compared to ovariectomized controls. Ovariectomized rats given Wyeth 14643, maintained whole body BMD at sham levels, while rats on pioglitazone had lower whole body and femoral BMD, impaired bone quality and less mechanical strength compared to sham and ovariectomized controls. In contrast, cortical volume, trabecular bone volume and thickness, and endocortical volume were maintained at sham levels in rats given fenofibrate.

CONCLUSIONS

The PPARalpha agonist fenofibrate, and to a lesser extent the PPARaplha agonist Wyeth 14643, maintained BMD and bone architecture at sham levels, while the PPARgamma agonist pioglitazone exaggerated bone loss and negatively affected bone architecture, in ovariectomized rats.

Obesity, diabetes mellitus and last but not least, osteoporosis

Knowledge about the influence of bone on intermediary metabolism corresponds to a developing area that has gained prominence. The old concept of bone and adipose tissues as inert metabolic tissues, with minor contributions to metabolic adaptations has been reconsidered in light of findings that bone is involved in the development of insulin sensitivity. Similarly adipose tissue exerts important influences on bone mass development and maintenance. Moreover, the use of drugs in the treatment of metabolic disorders such as diabetes mellitus can impact bone metabolism. These networks linking osteoporosis to obesity and diabetes mellitus have reinvigorated investigations in the pathophysiology of osteoporosis. The present review examines this aspect and calls attention to health care providers and potential treatments of skeletal disorder.

Inactivation of SPARC enhances high-fat diet-induced obesity in mice

Secreted protein, acidic and rich in cysteine (SPARC), a matricellular protein, modulates extracellular matrix assembly and turnover in many physiological processes. SPARC-null mice exhibit an increased accumulation of adipose tissue. To distinguish between the functions of SPARC in adipogenesis during development and adulthood, we studied wild-type (WT) and SPARC-null mice maintained on a normal (low-fat) or high-fat (HF) diet. On an HF diet, SPARC-null mice exhibited significantly greater weight gain, in comparison to their WT counterparts, and had an enhanced cortical bone area that was likely due to increased mechanical loading. Diet-induced obesity (DIO) was also associated with an increase in vertebral trabecular bone in WT mice, but a significant change in this parameter was not observed in SPARC-null animals. We show that SPARC inhibits mitotic clonal expansion of preadipocytes at an early stage of adipogenesis. Moreover, there were substantially diminished levels of type I collagen in SPARC-null adipose tissue, as well as a reduction in the number of cross-linked, mature collagen fibers. In the absence of SPARC, mice show enhanced DIO. In adult animals, SPARC functions in the production and remodeling of adipose tissue, as well as in the regulation of preadipocyte differentiation.

Relationship of body composition with prevalence of osteoporosis in central south Chinese postmenopausal women

OBJECTIVES

To elucidate the relationship between body composition and bone mineral density (BMD) and the prevalence of osteoporosis in central south Chinese postmenopausal women.

METHODS

A cross-sectional study was conducted on 954 healthy central southern Chinese postmenopausal women, aged 50-82. Total body, lumbar spine and left femur BMD and total body soft tissue composition were measured by dual X-ray absorptiometry.

RESULTS

Among the study population, 578 (60.5%) subjects were without osteoporosis and 376 (39.4%) subjects were osteoporotic. The osteoporotic women were older, shorter and thinner, had an earlier age at menopause, a lower BMD and bone mineral content (BMC) of the total body and at different sites, and had lower body mass and body mass components than the women without osteoporosis. Both fat mass and lean mass were positively correlated with age at menopause, height, weight, body mass index (BMI) and BMD at all sites. Fat mass and lean mass were also inversely correlated with age and years since menopause (P<0.05). After controlling for age, age at menopause and height, both fat mass and lean mass were positively correlated with BMD at the lumbar(1-4) spine, the femoral neck and the total hip. Fat mass was the most significant determinant of BMD at the lumbar(1-4) spine with a higher R(2) change and a partial R(2) compared with that of lean mass, while lean mass had more impact on the total hip values. Either a fat mass below 18.4 kg or a lean mass below 33.9 kg was correlated with a higher prevalence of osteoporosis at the lumbar spine or total hip.

CONCLUSIONS

In central south Chinese postmenopausal women, both fat mass and lean mass are correlated with BMD at the lumbar spine and hip. Fat mass was the most significant determinant of BMD at the lumbar spine, while lean mass had more impact on the total hip value. Both lower values of fat mass and lean mass are related to a higher prevalence of osteoporosis at either the lumbar spine or the total hip. Thus, it is important to maintain a reasonable body weight to balance bone health and other metabolic disorders.

Ultrasound bone measurement in an older population with metabolic syndrome

BACKGROUND AND AIMS

Metabolic syndrome and osteoporosis are recognized as major public health problems in many countries. This study investigated the association between bone quality and components of metabolic syndrome in an elderly population.

METHODS

The study included a population sample of 211 men and women, of mean age 77.9 ± 4.5 years. Anthropometry, blood pressure, serum levels of lipoproteins (HDL and LDL), triglycerides and glucose were measured, and ultrasound bone densitometry was performed in all subjects. Information on lifestyle habits, including physical activity, smoking and alcohol consumption, were obtained by a questionnaire.

RESULTS

Metabolic syndrome, defined by the criteria of the International Diabetes Federation, was determined in 59% of men and 65% of women. The quantitative ultrasound index (QUI) was significantly correlated with serum glucose in men (r=-0.31; p=0.005) and with body mass index (BMI) in women (r=0.39; p<0.0001). QUI was significantly lower in men with metabolic syndrome (F=7.57; p<0.007) and significantly higher in women with it (F=6.47; p=0.012) compared with controls. When QUI was adjusted for body mass index in women and for serum glucose in men, it was no longer significantly different from values for controls. Other covariates such as cholesterol, blood pressure, smoking, alcohol, and physical activity did not change the difference in QUI between patients with metabolic syndrome and controls. Diabetes in men (p=0.005) and obesity and waist circumference in women (p<0.05) were also significant predictors of QUI in regression analysis.

CONCLUSIONS

The association between metabolic syndrome and bone stiffness in elderly people may be explained by increased BMI in women and high serum glucose in men.

Obesity alters cortical and trabecular bone density and geometry in women

The goal in this study was to determine the relationship between body mass index and trabecular and cortical bone using quantitative computed tomography. A higher body mass index (BMI) was positively associated with trabecular and cortical bone parameters, and serum parathyroid hormone, and negatively associated with cortical volumetric bone mineral density (vBMD) and serum 25-hydroxy-vitamin D. When BMI is greater than 35 kg/m(2), adiposity affects vBMD and may explain the higher fracture risk in this population without low BMD.

INTRODUCTION

The influence of adult obesity on the trabecular and cortical bone, geometry, and strength has not been fully addressed. The goal in this study was to determine the relationship between body mass index and trabecular and cortical bone mass and geometry, over a wide range of body weights.

METHODS

We examined 211 women (25-71 years; BMI 18-57 kg/m(2)) who were classified into three categories of BMI (kg/m(2)) including normal-weight (BMI<25), overweight and obese-class I (BMI 25-35) and obese-class II-III (BMI>35), and also by menopausal status. Volumetric bone mineral density (mg/cm(3)), trabecular, and cortical components as well as geometric characteristics at the 4%, 38%, and 66% from the distal tibia were measured by peripheral quantitative computed tomography, and serum was analyzed for parathyroid hormone (PTH) and 25-hydroxy-vitamin D (25OHD).

RESULTS

Higher BMI was associated with greater values of trabecular bone and cortical BMC and area and PTH (r>0.39, p<0.001), but lower cortical vBMD and 25OHD (r>-0.27, p<0.001). When controlling for lower leg muscle area, fat area was inversely associated with cortical vBMD (r=-0.16, p<0.05). Premenopausal obese women with both higher BMI and PTH had lower cortical vBMD (r<-0.40, p<0.001). While age is a predictor for most bone variables, fat mass explains more variance for vBMD, and lean mass and 25OHD explain greater variance in geometric and strength indices (p<0.05).

CONCLUSIONS

Severe obesity (BMI>35) increases trabecular vBMD and in the presence of a higher PTH is associated with a lower cortical vBMD without compromising bone geometry and strength. Whether or not a lower cortical vBMD in obesity influences fracture risk over time needs to be further explored.

HIV type 1 alters mesenchymal stem cell differentiation potential and cell phenotype ex vivo

An increased incidence of bone and lipid toxicities is associated with HIV-1 infection and its treatment. Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into both osteoblasts (OB) and adipocytes (AC). We hypothesize that the interaction of MSC and HIV-1 underlie these toxicities. Serum was collected from uninfected control and HIV-infected, antiviral-naive patients. Sera were divided into three groups: HIV-negative sera (n = 5), HIV-positive low viral load (LVL) (VL range 120; 4000, n = 5) or high viral load (HVL) (VL range 100,000; 500,000, n = 5). MSCs were exposed to these sera (5%) in an adipogenic/osteogenic condition and in nondifferentiating conditions in acute and chronic exposure models. Markers of adipogenesis/osteogenesis were examined in both MSCs induced to differentiated and nondifferentiating cells. Sera from HVL HIV-1-infected individuals induced a clear proadipogenic phenotype, as evidenced by an increase in adipocyte formation and the induction of increased expression of adipogenic markers including LPL and PPARγ. Both CD4 receptor blockade and treatment with the antiretroviral AZT attenuated these proadipogenic effects, suggesting that an infection event may underlie the observed phenomena. Finally, inhibition of COUP TF-1 by HIV-1 TAT was identified as a potential molecular mechanism for these effects. These results suggest that HIV-1 directly interacts with and may infect MSCs resulting in alterations of their differentiation potential, findings that significantly enhance our understanding of HIV-1-associated bone and fat toxicities.

Effects of diet-induced obesity and voluntary wheel running on the microstructure of the murine distal femur

Background

Obesity and osteoporosis, two possibly related conditions, are rapidly expanding health concerns in modern society. Both of them are associated with sedentary life style and nutrition. To investigate the effects of diet-induced obesity and voluntary physical activity we used high resolution micro-computed tomography (μCT) together with peripheral quantitative computed tomography (pQCT) to examine the microstructure of the distal femoral metaphysis in mice.

Methods

Forty 7-week-old male C57BL/6J mice were assigned to 4 groups: control (C), control + running (CR), high-fat diet (HF), and high-fat diet + running (HFR). After a 21-week intervention, all the mice were sacrificed and the left femur dissected for pQCT and μCT measurements.

Results

The mice fed the high-fat diet showed a significant weight gain (over 70% for HF and 60% for HFR), with increased epididymal fat pad mass and impaired insulin sensitivity. These obese mice had significantly higher trabecular connectivity density, volume, number, thickness, area and mass, and smaller trabecular separation. At the whole bone level, they had larger bone circumference and cross-sectional area and higher density-weighted maximal, minimal, and polar moments of inertia. Voluntary wheel running decreased all the cortical bone parameters, but increased the trabecular mineral density, and decreased the pattern factor and structure model index towards a more plate-like structure.

Conclusions

The results suggest that in mice the femur adapts to obesity by improving bone strength both at the whole bone and micro-structural level. Adaptation to running exercise manifests itself in increased trabecular density and improved 3D structure, but in a limited overall bone growth

Depression and percent body fat in American women, ages 39-49

I investigated the association between depression and percent body fat, two major global problems. Participants are 1,704 American women, ages 39-49, who responded to a detailed self-administered mailed questionnaire. My results showed a positive correlation; the adjusted OR = 1.70, 95% CI (1.20, 2.39), p = .002. Percent body fat was estimated from age, height, and weight, a cost-free method that may be useful in areas in which dual energy X-ray absorptiometry, or other procedures are too costly or unavailable. My findings may aid health and mental health care providers in the management and treatment of patients seen in settings with limited resources.

DXA surrogates for visceral fat are inversely associated with bone density measures in adolescent athletes with menstrual dysfunction

OBJECTIVE

Lean mass is associated with bone mineral density (BMD) in athletes, attributable to the anabolic pull of muscle on bone. Fat mass is also important, and subcutaneous fat positively and visceral fat negatively correlates with BMD in obese adolescents. The contribution of regional body composition to low BMD in amenorrheic athletes (AA) has not been elucidated. We hypothesized that in adolescent athletes (runners), BMD is associated positively with total fat (surrogate for subcutaneous fat) and lean mass, and inversely with percent trunk fat and trunk-to-extremity fat ratio (surrogates for visceral fat).

DESIGN

Cross-sectional study.

SUBJECTS AND METHODS

We examined BMD and body composition using dual energy X-ray absorptiometry (DXA) in 21 AA and 19 eumenorrheic athletes (EA) (12-18 years) (runners). We report total hip and height-adjusted BMD [lumbar bone mineral apparent density (LBMAD) and whole body bone mineral content/height (WBBMC/Ht)].

RESULTS

AA had lower BMD than EA. Lean mass was less strongly associated with hip BMD in AA than EA; fat mass was positively associated with LBMAD in EA. Percent trunk fat and trunk-to-extremity fat ratio were inversely associated with lumbar and WB measures in AA. In a regression model, lean and fat mass were positively, and percent trunk fat and trunk-to-extremity fat ratio negatively associated with LBMAD and WBBMC/Ht for all athletes, even after controlling for serum estradiol.

CONCLUSIONS

DXA surrogates for visceral fat are inversely associated with bone density in athletes.

Adiponectin and bone mass density: The InCHIANTI study

INTRODUCTION

Adiponectin serum concentration has been reported to be inversely correlated with bone mineral density (BMD) in humans. The data on this issue, however, are biased by small study sample size and lack of controlling for body composition.

METHODS

We used data from the third follow-up of the InCHIANTI study, which included measurements of BMD using quantitative CT of the tibia and of body composition using bioimpedenziometry. Serum adiponectin was measured using radioimmunoassay. We excluded participants with diabetes, hyperthyroidism, using hormone replacement or corticosteroid therapy. We evaluated the correlation of adiponectin with total, trabecular, and cortical BMD using Pearson's coefficient, and linear regression models to estimate the association between adiponectin and BMD controlling for potential confounders (age, body mass index, alcohol intake, fat mass, smoking).

RESULTS

Our sample was made up of 320 men (mean age: 67 years, SD: 15.8, range: 29-97 years) and 271 postmenopausal women (mean age: 76 years, SD: 8.2, range: 42-97 years). In men, serum adiponectin was not independently associated with BMD. In women, after correction for potential confounders, adiponectin was associated with total (β=-0.626, P<0.001), trabecular (β=-0.696, P<0.001), and cortical (β=-1.076, P=0.001) BMD.

CONCLUSION

Our results show that adiponectin is inversely associated with bone mass in women. Further studies are needed to confirm these findings prospectively and then to clarify the explanatory mechanisms.

Women with primary ovarian insufficiency have lower bone mineral density

The aim of the present study was to assess the prevalence of osteoporosis in a sample of 32 patients with spontaneous primary ovarian insufficiency (POI) in comparison to reference groups of 25 pre- and 55 postmenopausal women. Hip (lumbar) and spinal bone mineral density (BMD) measurements were performed by dual-energy X-ray absorptiometry in the three groups. The median age of POI patients at the time of diagnosis was 35 years (interquartile range: 27-37 years). The mean ± SD age of postmenopausal reference women (52.16 ± 3.65 years) was higher than that of POI (46.28 ± 10.38 years) and premenopausal women (43.96 ± 7.08; P = 0.001) at the time of BMD measurement. Twenty-seven (84.4%) POI women were receiving hormone replacement therapy (HRT) at the time of the study. In the postmenopausal reference group, 30.4% were current users of HRT. Lumbar BMD was significantly lower in the POI group (1.050 ± 0.17 g/cm²) compared to the age-matched premenopausal reference group (1.136 ± 0.12 g/cm²; P = 0.040). Moreover, 22 (68.7%) POI women had low bone density (osteopenia/osteoporosis by World Health Organization criteria) versus 47.3% of the postmenopausal reference group (P = 0.042). In conclusion, the present data indicate that BMD is significantly lower in patients with POI than in age-matched premenopausal women. Also, the prevalence of osteopenia/osteoporosis is higher in POI women than in women after natural menopause. Early medical interventions are necessary to ensure that women with POI will maintain their bonemass.

Fat mass accumulation compromises bone adaptation to load in Finnish women: a cross-sectional study spanning three generations

Body weight and lean mass correlate with bone mass, but the relationship between fat mass and bone remains elusive. The study population consisted of 396 girls and 138 premenopausal mothers and 114 postmenopausal grandmothers of these girls. Body composition and tibial length were assessed using dual-energy X-ray absorptiometry (DXA), and bone traits were determined at the tibia using peripheral quantitative computed tomography (pQCT) in the girls at the ages of 11.2 ± 0.8, 13.2 ± 0.9, and 18.3 ± 1.0 years and in the mothers (44.7 ± 4.1 years) and grandmothers (70.7 ± 6.3 years). The values of relative bone strength index (RBSI), an index reflecting the ratio of bone strength to the load applied on the tibia, were correlated among family members (all p < .05). The mean values of RBSI were similar among 11- and 18-year-old girls and premenopausal women but significantly lower in 13-year-old girls and postmenopausal women. However, in each age group, subjects in the highest BMI tertiles had the lowest RBSI values (all p < .01). RBSI was inversely associated with body weight (all p < .01), indicating a deficit in bone strength relative to the applied load from greater body weight. RBSI was inversely associated with fat mass (all p < .001) across age groups and generations but remained relatively constant with increasing lean mass in girls and premenopausal women (all p > .05), indicating that the bone-strength deficit was attributable to increased fat mass, not lean mass. Moreover, the adverse effect of fat mass was age-dependent, with every unit increase in fat mass associated with a greater decrease in RBSI in pre- and postmenopausal women than in girls (all p < .001). This is largely due to the different capacity of young and adult bones to increase diaphyseal width by periosteal apposition in response to increased load. In summary, increasing body weight with fat accumulation is accompanied by an age-dependent relative bone-strength deficit in women because the beneficial effects of increased fat mass on bone, if any, do not compensate for the mechanical burden that it imposes.

Obesity reduces bone density associated with activation of PPARγ and suppression of Wnt/β-catenin in rapidly growing male rats

BACKGROUND

It is well established that excessive consumption of a high fat diet (HFD) results in obesity; however, the consequences of obesity on postnatal skeletal development have not been well studied.

METHODOLOGY AND PRINCIPAL FINDINGS

Total enteral nutrition (TEN) was used to feed postnatal day 27 male rats intragastrically with a high 45% fat diet (HFD) for four weeks to induce obesity. Fat mass was increased compared to rats fed TEN diets containing 25% fat (medium fat diet, MFD) or a chow diet (low fat diet, LFD) fed ad libitum with matched body weight gains. Serum leptin and total non-esterified fatty acids (NEFA) were elevated in HFD rats, which also had reduced bone mass compared to LFD-fed animals. This was accompanied by decreases in bone formation, but increases in the bone resorption. Bone marrow adiposity and expression of adipogenic genes, PPARγ and aP2 were increased, whereas osteoblastogenic markers osteocalcin and Runx2 were decreased, in bone in HFD rats compared to LFD controls. The diversion of stromal cell differentiation in response to HFD stemmed from down-regulation of the key canonical Wnt signaling molecule β-catenin protein and reciprocal up-regulation of nuclear PPARγ expression in bone. In a set of in vitro studies using pluripotent ST2 bone marrow mesenchymal stromal cells treated with serum from rats on the different diets or using the free fatty acid composition of NEFA quantified in rat serum from HFD-fed animals by GC-MS, we were able to recapitulate our in vivo findings.

CONCLUSIONS/SIGNIFICANCE

These observations strongly suggest that increased NEFA in serum from rats made obese by HFD-feeding impaired bone formation due to stimulation of bone marrow adipogenesis. These effects of obesity on bone in early life may result in impaired attainment of peak bone mass and therefore increase the prevalence of osteoporosis later on in life.

Obesity-mediated inflammatory microenvironment stimulates osteoclastogenesis and bone loss in mice

Clinical evidence indicates that fat is inversely proportional to bone mass in elderly obese women. However, it remains unclear whether obesity accelerates bone loss. In this report we present evidence that increased visceral fat leads to inflammation and subsequent bone loss in 12-month-old C57BL/6J mice that were fed 10% corn oil (CO)-based diet and a control lab chow (LC) for 6 months. As expected from our previous work, CO-fed mice demonstrated increased visceral fat and enhanced total body fat mass compared to LC. The adipocyte-specific PPARγ and bone marrow (BM) adiposity were increased in CO-fed mice. In correlation with those modifications, inflammatory cytokines (IL-1β, IL-6, TNF-α) were significantly elevated in CO-fed mice compared to LC-fed mice. This inflammatory BM microenvironment resulted in increased superoxide production in osteoclasts and undifferentiated BM cells. In CO-fed mice, the increased number of osteoclasts per trabecular bone length and the increased osteoclastogenesis assessed ex-vivo suggest that CO diet induces bone resorption. Additionally, the up-regulation of osteoclast-specific cathepsin k and RANKL expression and down-regulation of osteoblast-specific RUNX2/Cbfa1 supports this bone resorption in CO-fed mice. Also, CO-fed mice exhibited lower trabecular bone volume in the distal femoral metaphysis and had reduced OPG expression. Collectively, our results suggest that increased bone resorption in mice fed a CO-enriched diet is possibly due to increased inflammation mediated by the accumulation of adipocytes in the BM microenvironment. This inflammation may consequently increase osteoclastogenesis, while reducing osteoblast development in CO-fed mice.

Adipose tissue and volumetric bone mineral density of older Afro-Caribbean men

Although low body weight is a risk factor for osteoporosis-related fractures, conflicting data exist for the association between adiposity and bone mineral density (BMD). Studies examining these relationships have measured body fat and BMD with dual-energy X-ray absorptiometry (DXA), which cannot distinguish subcutaneous adipose tissue area (SAT) from total adiposity or trabecular from cortical bone. To investigate the relationship between adiposity and BMD further, we analyzed body composition and adipose tissue distribution by quantitative computed tomography (QCT) in 1829 Afro-Caribbean men aged 40 years and older from a population-based sample. Cortical volumetric BMD, muscle cross-sectional area, total adipose tissue area (TAT), and percentage SAT were measured at the proximal tibia. Trabecular volumetric BMD was measured at the distal tibia. We used analysis of covariance to test for associations between quartile of the adipose tissue measures and BMD, adjusting for anthropometric, health, and lifestyle factors. Higher TAT was associated with lower cortical BMD in both unadjusted and adjusted models (p < .001). Men with a higher percentage SAT had greater cortical BMD (p < .001). Similar associations were seen between percent SAT and trabecular BMD at the distal tibia. These results indicate that total adiposity is a potentially important correlate of bone mass in older men and that different fat depots may have opposing associations with bone mass. Additional research is needed to better understand the mechanisms underlying the relationship between body fat distribution and bone mass.

Apolipoprotein E-dependent inverse regulation of vertebral bone and adipose tissue mass in C57Bl/6 mice: modulation by diet-induced obesity

The long prevailing view that obesity is generally associated with beneficial effects on the skeleton has recently been challenged. Apolipoprotein E (apoE) is known to influence both adipose tissue and bone. The goal of the current study was to examine the impact of apoE on the development of fat mass and bone mass in mice under conditions of diet-induced obesity (DIO). Four week-old male C57BL/6 (WT) and apoE-deficient (apoE(-/-)) mice received a control or a diabetogenic high-fat diet (HFD) for 16 weeks. The control-fed apoE(-/-) animals displayed less total fat mass and higher lumbar trabecular bone volume (BV/TV) than WT controls. When stressed with HFD to induce obesity, apoE(-/-) mice had a lower body weight, lower serum glucose, insulin and leptin levels and accumulated less white adipose tissue mass at all sites including bone marrow. While WT animals showed no significant change in BV/TV and bone formation rate (BFR), apoE deficiency led to a decrease of BV/TV and BFR when stressed with HFD. Bone resorption parameters were not affected by HFD in either genotype. Taken together, under normal dietary conditions, apoE-deficient mice acquire less fat mass and more bone mass than WT littermates. When stressed with HFD to develop DIO, the difference of total body fat mass becomes larger and the difference of bone mass smaller between the genotypes. We conclude that apoE is involved in an inverse regulation of bone mass and fat mass in growing mice and that this effect is modulated by diet-induced obesity.

Moderate weight gain does not influence bone metabolism in skeletally mature female rats

Bone mass is correlated with body weight during growth. However, it is unclear how bone mass is influenced by weight gain following skeletal maturity. The purpose of this study was to determine the effects of weight maintenance and two rates of weight gain on bone metabolism using skeletally mature female rats. Eight-month-old female rats were fed one of 3 diets for 13 weeks: Lieber-DeCarli liquid diet ad lib (control diet), the same diet with caloric restriction to maintain initial body weight (calorie-restricted diet), and the same diet fed ad lib with the exception that appetite was enhanced (calorie-increased diet) by replacing a small quantity of maltose-dextran isocalorically with ethanol (0.5% caloric intake). Compared to baseline, rats fed the calorie-restricted, control, and calorie-increased diets changed in weight by -1+/-2% (mean+/-SE), 10+/-3%, and 21+/-2%, respectively. Weight gain was associated with a significant increase in serum leptin, a putative regulator of bone formation. In contrast, significant differences in tibial bone mineral content and density were not detected among treatments groups following dietary intervention or between treatment groups and the baseline group. Similarly, indices of cancellous bone architecture (area, trabecular number, thickness, and separation) and bone turnover (mineralizing perimeter, mineral apposition rate, and bone formation rate) did not differ among groups following dietary intervention. Our findings suggest that neither weight gain nor increased serum leptin levels, over the range evaluated, influence bone metabolism in skeletally mature female rats.

Relationship between visceral adiposity and bone mineral density in Korean adults

The objective of the study was to investigate the relationship between visceral and subcutaneous adiposity measured by computed tomography and bone mineral density (BMD) and to identify the metabolic factors associated with BMD. We studied 461 subjects recruited from the health-care center at Severance Hospital, Yonsei University College of Medicine. Multivariate regression analyses were conducted to examine the cross-sectional associations between body composition-related or metabolic parameters and BMD. After adjusting for body weight and other confounders, visceral fat area had an inverse association with BMD in men (beta = -0.133, P = 0.049 for lumbar spine; beta = -0.135, P = 0.037 for femoral neck; beta = -0.179, P = 0.005 for total hip) and women (beta = -0.424, P < 0.001 for lumbar spine; beta = -0.302, P = 0.005 for femoral neck; beta = -0.274, P = 0.014 for total hip). However, the subcutaneous fat area showed no statistically significant relationship with BMD at most sites. Among the metabolic parameters, HDL cholesterol was positively associated with BMD, while LDL cholesterol was negatively associated with BMD in men. In women, total and LDL cholesterol were negatively associated with BMD at the lumbar spine. We conclude that visceral adiposity is inversely associated with BMD after adjusting for confounders and that metabolic factors may partly contribute to this inverse relation.

ALOX12 polymorphisms are associated with fat mass but not peak bone mineral density in Chinese nuclear families

OBJECTIVE

Arachidonate 12-lipoxygenase (ALOX12) is a member of the lipoxygenase superfamily, which catalyzes the incorporation of molecular oxygen into polyunsaturated fatty acids. The products of ALOX12 reactions serve as endogenous ligands for peroxisome proliferator-activated receptor γ (PPARG). The activation of the PPARG pathway in marrow-derived mesenchymal progenitors stimulates adipogenesis and inhibits osteoblastogenesis. Our objective was to determine whether polymorphisms in the ALOX12 gene were associated with variations in peak bone mineral density (BMD) and obesity phenotypes in young Chinese men.

METHODS

All six tagging single-nucleotide polymorphisms (SNPs) in the ALOX12 gene were genotyped in a total of 1215 subjects from 400 Chinese nuclear families by allele-specific polymerase chain reaction. The BMD at the lumbar spine and hip, total fat mass (TFM) and total lean mass (TLM) were measured using dual-energy X-ray absorptiometry. The pairwise linkage disequilibrium among SNPs was measured, and the haplotype blocks were inferred. Both the individual SNP markers and the haplotypes were tested for an association with the peak BMD, body mass index, TFM, TLM and percentage fat mass (PFM) using the quantitative transmission disequilibrium test (QTDT).

RESULTS

Using the QTDT, significant within-family association was found between the rs2073438 polymorphism in the ALOX12 gene and the TFM and PFM (P=0.007 and 0.012, respectively). Haplotype analyses were combined with our individual SNP results and remained significant even after correction for multiple testing. However, we failed to find significant within-family associations between ALOX12 SNPs and the BMD at any bone site in young Chinese men.

CONCLUSIONS

Our present results suggest that the rs2073438 polymorphism of ALOX12 contributes to the variation of obesity phenotypes in young Chinese men, although we failed to replicate the association with the peak BMD variation in this sample. Further independent studies are needed to confirm our findings.

Combination of conjugated linoleic acid with fish oil prevents age-associated bone marrow adiposity in C57Bl/6J mice

The inverse relationship between fat in bone marrow and bone mass in the skeleton of aging subjects is well known. However, there is no precise therapy for the treatment of bone marrow adiposity. We investigated the ability of conjugated linoleic acid (CLA) and fish oil (FO), alone or in combination, to modulate bone loss using 12 months old C57Bl/6J mice fed 10% corn oil diet as control or supplemented with 0.5% CLA or 5% FO or 0.5% CLA+5% FO for 6 months. We found, CLA-fed mice exhibited reduced body weight, body fat mass (BFM) and enhanced hind leg lean mass (HLLM) and bone mineral density (BMD) in different regions measured by dual energy x-ray absorptiometry (DXA); however, associated with fatty liver and increased insulin resistance; whereas, FO fed mice exhibited enhanced BMD, improved insulin sensitivity, with no changes in BFM and HLLM. Interestingly, CLA+FO fed mice exhibited reduced body weight, BFM, peroxisome proliferator-activated receptor gamma and cathepsin K expression in bone marrow with enhanced BMD and HLLM. Moreover, CLA+FO supplementation reduced liver hypertrophy and improved insulin sensitivity with remarkable attenuation of bone marrow adiposity, inflammation and oxidative stress in aging mice. Therefore, CLA with FO combination might be a novel dietary supplement to reduce fat mass and improve BMD.

Percent fat mass is inversely associated with bone mass and hip geometry in rural Chinese adolescents

This study was an attempt to examine the phenotypic, genetic, and environmental correlations between percent fat mass (PFM) and bone parameters, especially hip geometry, among 786 males and 618 females aged 13 to 21 years from a Chinese twin cohort. PFM, bone area (BA), bone mineral content (BMC), cross-sectional area (CSA), and section modulus (SM) were obtained by dual-energy X-ray absorptiometry. Multiple linear regression models were used to assess the PFM-bone relationships. A structural equation model for twin design was used to estimate genetic/environmental influences on individual phenotype and phenotypic correlations. After controlling for body weight and other pertinent covariates, we observed inverse associations between PFM and bone parameters: Compared with the lowest age- and gender-specific tertile of PFM, males in the highest tertile of PFM had lower measures of whole-body-less-head BA (WB-BA), lumbar spine BA (L(2)-L(4)-BA), total-hip BA (TH-BA), total-hip BMC, CSA, and SM (p < .005 for all, adjusted p < .05). Similar inverse associations were observed in females for all the preceding parameters except WB-BA and L2-L(4)-BA. These associations did not vary significantly by Tanner stages. In both genders, the estimated heritabilities were 80% to 86% for BMC, 67% to 80% for BA, 74% to 77% for CSA, and 64% for SM. Both shared genetics and environmental factors contributed to the inverse PFM-bone correlations. We conclude that in this sample of relatively lean Chinese adolescents, at a given body weight, PFM is inversely associated with BA, BMC, and hip geometry in both genders, and such associations are attributed to both shared genetic and environmental factors.

Correlation of obesity and osteoporosis: Effect of free fatty acids on bone marrow-derived mesenchymal stem cell differentiation

Studies on the relationship between obesity and bone have recently become widespread. The aim of this study was to investigate the effect of obesity on bone, utilizing a diet-induced obese mouse model, and to explore the role of free fatty acids (FFAs) in the osteogenesis/adipogenesis of mouse bone marrow-derived mesenchymal stem cells (BMSCs). An obese mouse model was established by a high-fat diet (HFD). Proximal femurs were collected at sacrifice, and bone mineral density (BMD) in the proximal femurs was measured by dual-energy X-ray absorptiometry. Bone histomorphometry was performed using undecalcified sections of the proximal femurs. The effect of obesity on the differentiation of mouse BMSCs was assessed by colony formation assays and gene expression analysis. In vitro, various osteogenic and adipogenic genes were determined by real-time quantitative PCR in mouse BMSCs after exposure to conditioned medium (CM) from FFA-treated 3T3-L1 adipocytes. Western blotting was further performed to analyze the representative protein expression of PPARγ and Runx2. BMD and trabecular thickness were significantly greater in the HFD mice than in the control mice. CFU-osteo assay showed significantly increased osteogenesis of BMSCs. The mRNA level of Runx2 was significantly higher, while PPARγ and Pref-1 were significantly lower in BMSCs from the HFD mice compared to the control mice. In mouse BMSCs, the Sox9 and Runx2 genes were significantly up-regulated after exposure to CM from FFA-treated adipocytes, while PPARγ and CEBP-α were significantly down-regulated. Osteogenesis was significantly increased, while adipogenesis was significantly decreased. In conclusion, HFD-induced obesity may play a protective role in bone formation by concomitantly promoting osteogenic and suppressing adipogenic differentiation of BMSCs through factors secreted by FFA-treated adipocytes.

Percent body fat, fractures and risk of osteoporosis in women

OBJECTIVES

Globally, in an aging population, osteoporosis and fractures are emerging as major public health problems; accessible and affordable recognition, prevention and treatment strategies are needed. Percent body fat is known to be associated with bone mineral density and fractures. This paper uses an innovative, virtually cost-free method to estimate percent body fat from age, height and weight, and assesses its validity by examining the association between percent body fat and fractures among women 39 and older.

DESIGN

An epidemiologic study.

PARTICIPANTS

3940 college alumnae, median age 53.6, participated by responding to a mailed questionnaire covering medical history, behavioral factors, birth date, weight and height.

STATISTICAL METHODS

T-tests, chi-square and multivariable logistic regression.

MEASUREMENTS

Percent body fat estimated from age, weight, height and gender.

RESULTS

Associations of fractures with percent body fat are expressed as odds ratios: for osteoporotic (wrist, hip and/or x-ray confirmed vertebral), the adjusted OR = 2.41, 95% CI (1.65, 3.54), P < 0.0001; for wrist fractures, the adjusted OR = 2.56, 95% CI (1.65, 3.96), P < 0.0001; for x-ray confirmed vertebral fractures the adjusted OR = 4.69, 95% CI (2.05, 10.77), P=0.0003).; and for non-osteoporotic, he adjusted OR= 1.00, 95% CI (0.76 1.32), P=0.999.

CONCLUSION

The findings are consistent with methods using DXA and/or other technologies that show percent body fat is associated with fractures of the wrist and vertebrae. Identification of risk factors is necessary for the prevention and treatment of osteoporosis and osteoporotic fractures. Estimation of percent body fat from age, height and weight may be a valid, cost-saving, and cost-effective alternative tool for screening and assessing risk of osteoporosis in settings where Dual x-ray absorptiometry (DXA) or other radiological techniques are too costly or unavailable.

Men with metabolic syndrome have lower bone mineral density but lower fracture risk--the MINOS study

Data on the association of the metabolic syndrome (MetS) with bone mineral density (BMD) and fracture risk in men are inconsistent. We studied the association between MetS and bone status in 762 older men followed up for 10 years. After adjustment for age, body mass index, height, physical activity, smoking, alcohol intake, and serum 25-hydroxycholecalciferol D and 17beta-estradiol levels, men with MetS had lower BMD at the hip, whole body, and distal forearm (2.2% to 3.2%, 0.24 to 0.27 SD, p < .05 to .005). This difference was related to abdominal obesity (assessed by waist circumference, waist-hip ratio, or central fat mass) but not other MetS components. Men with MetS had lower bone mineral content (3.1% to 4.5%, 0.22 to 0.29 SD, p < .05 to 0.001), whereas differences in bone size were milder. Men with MetS had a lower incidence of vertebral and peripheral fractures (6.7% versus 12.0%, p < .05). After adjustment for confounders, MetS was associated with a lower fracture incidence [odds ratio (OR) = 0.33, 95% confidence interval (CI) 0.15-0.76, p < .01]. Among the MetS components, hypertriglyceridemia was most predictive of the lower fracture risk (OR = 0.25, 95%CI 0.10-0.62, p < .005). Lower fracture risk in men with MetS cannot be explained by differences in bone size, rate of bone turnover rate and bone loss, or history of falls or fractures. Thus older men with MetS have a lower BMD related to the abdominal obesity and a lower risk of fracture related to hypertriglyceridemia. MetS probably is not a meaningful concept in the context of bone metabolism. Analysis of its association with bone-related variables may obscure the pathophysiologic links of its components with bone status.

Is obesity protective for osteoporosis? Evaluation of bone mineral density in individuals with high body mass index

BACKGROUND

Obese individuals often present comorbidities while they appear protected against the development of osteoporosis. However, few and contradictory data are now available on skeletal modifications in obese patients. The aim of this study was to characterise bone mineral density (BMD) in overweight (BMI > 25 < 29.9) and obese (BMI > 30) patients.

METHODS

We selected 398 patients (291 women, 107 men, age 44.1 + 14.2 years, BMI 35.8 + 5.9 kg/m(2)) who underwent clinical examination, blood tests and examination of body composition. Subjects with chronic conditions or taking medications interfering with bone metabolism, hormonal and nutritional status and recent weight loss were excluded.

RESULTS

Interestingly, 37% (n = 146) of this population showed a significantly lower than expected lumbar BMD: 33% (n = 98) of women showed a T-score -1.84 +/- 0.71, and 45% (n = 48) of men showed a T-score -1.88 +/- 0.64. When the population was divided into subgroups based on different BMI, it was noted that overweight (BMI > 25 < 29.9) was neutral or protective for BMD, whereas obesity (BMI > 30) was associated with a low bone mass, compatible with a diagnosis of osteoporosis. No differences were observed in hormones and lipid profiles among subgroups.

CONCLUSIONS

Our results indicate that a subpopulation of obese patients has a significant low lumbar BMD than expected for age. Thus, a careful characterisation of skeletal metabolism might be useful in all obese individuals to avoid fragility fractures later in life.

Prevalence and risk factors of vertebral fractures in women with rheumatoid arthritis using vertebral fracture assessment

OBJECTIVE

To study the prevalence and risk factors of vertebral fractures (VFs) in a large cohort of patients with RA using VF assessment (VFA).

METHODS

We enrolled 172 women with RA, none of whom were taking osteoporosis medications. Patients underwent dual X-ray absorptiometry at the hip and spine and VFA, and completed a questionnaire. Radiological status was assessed by the modified Sharp erosion and narrowing score. VFA was classified using a combination of Genant semi-quantitative approach and morphometry.

RESULTS

Patients had a mean (s.d.) disease duration of 8.4 (5.2) years. VFs were detected in 36% (62/172). This group of women had a statistically significant lower weight, height and lumbar spine and total hip BMD and T-scores than those without a VFA-identified VF. They also had more long-standing and severe disease and a greater consumption of corticosteroids. Stepwise regression analysis showed that the presence of VFs was independently associated with low weight and total hip T-score and long disease duration, CRP and Sharp erosion score.

CONCLUSION

RA is a risk factor on its own for the development of osteoporosis and VFs and this risk increases more with low weight, disease duration and severe course of disease. These findings may suggest that to prevent the development of VFs, precautions should be taken immediately to suppress the disease activity and correct the weight loss in patients with RA.

Regulation of neural crest cell fate by the retinoic acid and Pparg signalling pathways

Although the regulation of osteoblast and adipocyte differentiation from mesenchymal stem cells has been studied for some time, very little is known about what regulates their appearance in discrete regions of the embryo. Here we show that, as in other vertebrates, zebrafish osteoblasts and adipocytes originate in part from cephalic neural crest (CNC) precursors. We investigated the roles that the retinoic acid (RA) and Peroxisome proliferator-activated receptor gamma (Pparg) pathways play in vivo and found that both pathways act on CNC to direct adipocyte differentiation at the expense of osteoblast formation. In addition, we identify two distinct roles for RA in the osteoblast lineage: an early role in blocking the recruitment of osteoblasts and a later role in mature osteoblasts to promote bone matrix synthesis. These findings might help to increase our understanding of skeletal and obesity-related diseases and aid in the development of stem cell-based regenerative therapies.

High fat diet-induced animal model of age-associated obesity and osteoporosis

Osteoporosis and obesity remain a major public health concern through its associated fragility and fractures. Several animal models for the study of osteoporotic bone loss, such as ovariectomy (OVX) and denervation, require unique surgical skills and expensive set up. The challenging aspect of these age-associated diseases is that no single animal model exactly mimics the progression of these human-specific chronic conditions. Accordingly, to develop a simple and novel model of post menopausal bone loss with obesity, we fed either a high fat diet containing 10% corn oil (CO) or standard rodent lab chow (LC) to 12-month-old female C57Bl/6J mice for 6 months. As a result, CO fed mice exhibited increased body weight, total body fat mass, abdominal fat mass and reduced bone mineral density (BMD) in different skeletal sites measured by dual energy X-ray absorptiometry. We also observed that decreased BMD with age in CO fed obese mice was accompanied by increased bone marrow adiposity, up-regulation of peroxisome proliferator-activated receptor γ, cathepsin k and increased proinflammatory cytokines (interleukin 6 and tumor necrosis factor α) in bone marrow and splenocytes, when compared to that of LC fed mice. Therefore, this appears to be a simple, novel and convenient age-associated model of post menopausal bone loss, in conjunction with obesity, which can be used in pre-clinical drug discovery to screen new therapeutic drugs or dietary interventions for the treatment of obesity and osteoporosis in the human population.

Serum markers of bone turnover are increased at six and 18 months after Roux-en-Y bariatric surgery: correlation with the reduction in leptin

OBJECTIVE

The aim of the study was to examine serum markers of bone turnover at 6 and 18 months after Roux-en-Y gastric bypass surgery.

PARTICIPANTS

Ten women and 10 men [body mass index (BMI), 50.2 +/- 8.4 kg/m(2)] were studied at 6 months; 10 women and nine men (BMI, 47.2 +/- 6.6 kg/m(2)) were studied at 18 months after surgery.

MAIN OUTCOME MEASURES

Serum osteocalcin, bone specific alkaline phosphatase (BAP), N-telopeptide of type 1 collagen (NTX), PTH, 25-hydroxy vitamin D, and leptin were measured.

RESULTS

BMI was reduced 32.7 +/- 6.2% at 6 months after surgery. Serum osteocalcin (6.9 +/- 2.4 to 10.9 +/- 2.6 ng/ml; P < 0.0001), BAP (14.2 +/- 3.7 to 16.4 +/- 4.5 ng/ml; P = 0.04), and NTX (10.9 +/- 1.7 to 19.6 +/- 5.3 nm bone collagen equivalents; P < 0.0001) were increased. Calcium, phosphate, and PTH were unchanged, but 25-hydroxy vitamin D increased (16.0 +/- 8.9 vs. 26.9 +/- 10.6 ng/ml; P <0.0001). The increase in NTX correlated with reduction in serum leptin (r = 0.58; P = 0.007). BMI was reduced 40.9 +/- 7.5% at 18 months after surgery. Serum BAP (17.6 +/- 5.3 to 22.2 +/- 7.8 ng/ml; P = 0.0017) and NTX (10.8 +/- 2.7 to 16.9 +/- 5.5 nm bone collagen equivalents; P < 0.0001) were increased. Calcium, phosphate, and PTH were unchanged, but 25-hydroxy vitamin D increased (17.7 +/- 7.6 to 25.6 +/- 6.8 ng/ml; P < 0.0001). The increase in NTX correlated with reduction in BMI (r = 0.58; P = 0.009) and leptin (r = 0.45; P = 0.04) and the increase in serum 25-hydroxy vitamin D (r = 0.43; P = 0.05). In multiple regression (adjusted model R(2) 0.263; P = 0.013), reduction in leptin was a significant predictor of increase in NTX (P = 0.016), but changes in BMI and 25-hydroxy vitamin D were not.

CONCLUSIONS

Weight loss after bariatric surgery is associated with long-term increase in serum markers of bone turnover. The increase in NTX is related to the decrease in leptin, which may signal caloric restriction to the skeleton.

High weight or body mass index increase the risk of vertebral fractures in postmenopausal osteoporotic women

In the general population, low body weight and body mass index (BMI) are significant risk factors for any fracture, but the specific association between body weight, BMI, and prevalence of vertebral fractures in osteoporotic women is not fully recognized. Hence, the association between body weight, BMI, and prevalent vertebral fractures was investigated in 362 women with never-treated postmenopausal osteoporosis. All participants underwent measurement of BMI, bone mineral density (BMD), and semiquantitative assessment of vertebral fractures. Thirty percent of participants had > or =1 vertebral fracture. Body weight and BMI were associated with L1-L4 BMD (R = 0.29, P < 0.001 and R = 0.17, P = 0.009, respectively). In logistic regression analysis, BMI was positively associated with the presence of vertebral fractures independent of age and other traditional risk factors for fractures. Including weight and height instead of BMI in the multivariate model, showed weight as a positive and significant covariate of the presence of vertebral fractures (OR = 1.045; P = 0.016; 95% CI 1.008-1.084). BMI was associated with the number of vertebral fractures (rho = 0.18; P = 0.001), this association being confirmed also in the multivariate analysis (beta = 0.14; P = 0.03) after correction for smoking, early menopause, family history of fragility fractures and BMD. In conclusion, among postmenopausal women with osteoporosis, body weight and BMI are associated with a higher likelihood of having a vertebral fracture, irrespective of the positive association between weight and BMD.

Adiponectin stimulates osteoblast differentiation through induction of COX2 in mesenchymal progenitor cells

In bone marrow, osteoblasts and adipocytes are differentiated from mesenchymal progenitor cells and their differentiation is reciprocally regulated by largely unknown mechanisms. In this study, we investigated downstream signaling cascades of adiponectin, a member of the adipocytokine family, in the regulation of osteoblast differentiation. Adiponectin augmented expression of several osteogenic marker genes and increased osteoblast differentiation in mesenchymal progenitor cells. The expression of cyclooxygenase-2 (COX2) was potently increased by adiponectin, whereas inhibition of COX2 activity abolished the effect of adiponectin on osteogenesis. In addition, adiponectin rapidly stimulated p38 mitogen-activated protein kinase via the adiponectin receptor, AdipoR1, which resulted in c-Jun activation for COX2 expression. Adiponectin also stimulated BMP2 expression in a COX2-dependent manner. Moreover, Runx2, a key osteogenic transcription factor, contributed to the acceleration of osteogenesis in the presence of adiponectin. Collectively, the finding that adiponectin could promote osteogenesis through an intracellular signaling cascade in mesenchymal progenitor cells suggests that adiponectin would be a potential therapeutic target for bone-related diseases.

Relative contributions of multiple determinants to bone mineral density in men

SUMMARY

Focus on individual risk factors for osteoporosis could allocate disproportionate attention to trivial relationships. We tested many recognized risk factors of osteoporosis for their association with bone mineral density (BMD) in multivariate models among men. Lean mass accounted for the most variance, with substantially less accounted for by demographic, strength, and health factors.

INTRODUCTION

Osteoporosis in men has gained recognition as a public health problem, generating an interest in the search for risk factors. Isolation of individual risk factors could allocate disproportionate attention to relationships that may be of limited consequence.

METHODS

The Boston Area Community Health/Bone (BACH/Bone) Survey is a population-based study of randomly selected community-dwelling men (age, 30-79 years). BMD and lean mass were measured by dual X-ray absorptiometry. Socioeconomic status, health history, and lifestyle factors were obtained via interview. Hormone levels and markers of bone turnover were obtained from non-fasting blood samples. Multivariate analyses measured relative contributions of covariates to femoral neck (hip), one-third distal radius (wrist), and lumbar spine BMD.

RESULTS

Factors positively associated with BMD in multivariate models at the three sites were black race and appendicular lean mass. Asthma was consistently negatively associated. Various other risk factors also contributed significantly to each of the individual sites. R (2) values for the hip, wrist, and spine were 41%, 30%, and 24%, respectively. Lean mass accounted for the most explained variance at all three sites.

CONCLUSIONS

These data emphasize the limitation of focusing on individual risk factors and highlight the importance of potentially modifiable lean mass in predicting BMD.

Modeling pathways for low bone mass in children with malignancies

Children with malignancies have low bone mass. Pathways for metabolic bone disease were investigated in children with cancer by concomitantly assessing lifestyle, clinical, and biochemical predictors of bone mass. Forty-one children who were receiving cancer therapy for 61 weeks and 39 controls were studied. Data on lifestyle factors, biochemical and hormonal parameters, dual-energy X-ray absorptiometry bone mass measurements, body composition, and bone age were obtained. Compared with controls, patients had higher weight percentile and fat mass, a 6-month delay in bone age, and lower estradiol levels. They also had higher parathyroid hormone levels and lower bone remodeling markers and bone mass. Age, height, lean mass, fat mass, and bone maturation correlated positively with several bone mass variables, so did serum estradiol, testosterone, and markers of bone remodeling. Conversely, corticosteroids, methotrexate (MTX), and intrathecal therapy negatively correlated with bone mass at the spine and hip (R = -0.33 to 0.40, p < 0.04). In the adjusted analyses, bone maturation, serum osteocalcin level, MTX, and intrathecal therapy were significant predictors of lumbar spine and total body Z-scores, bone maturation accounting for the largest proportion in Z-score variance. Chemotherapy-induced delay in bone maturation and suppression of bone modeling are major pathophysiologic pathways predicting bone mass in children with malignancies.

Does obesity really make the femur stronger? BMD, geometry, and fracture incidence in the women's health initiative-observational study

Heavier individuals have higher hip BMD and more robust femur geometry, but it is unclear whether values vary in proportion with body weight in obesity. We studied the variation of hip BMD and geometry across categories of body mass index (BMI) in a subset of postmenopausal non-Hispanic whites (NHWs) from the Women's Health Initiative Observational Cohort (WHI-OS). The implications on fracture incidence were studied among NHWs in the entire WHI-OS. Baseline DXA scans of hip and total body from 4642 NHW women were divided into BMI (kg/m(2)) categories: underweight (<18.5), healthy weight (18.5-24.9), overweight (25-29.9), and mild (30-34.9), moderate (35-39.9), and extreme obesity (>40). Femur BMD and indices of bone axial (cross-sectional area [CSA]) and bending strength (section modulus [SM]) were extracted from DXA scans using the hip structure analysis (HSA) method and compared among BMI categories after adjustment for height, age, hormone use, diabetes, activity level, femur neck-shaft angle, and neck length. The association between BMI and incident fracture was studied in 78,013 NHWs from the entire WHI-OS over 8.5 +/- 2.6 (SD) yr of follow-up. Fracture incidence (cases/1000 person-years) was compared among BMI categories for hip alone, central body (hip, pelvis, spine, ribs, and shoulder girdle), upper extremity (humerus and distal), and lower extremity (femur shaft and distal but not hip). Femur BMD, CSA, and SM were larger in women with higher BMI, but values scaled in proportion to lean and not to fat or total body mass. Women with highest BMI reported more falls in the 12 mo before enrollment, more prevalent fractures, and had lower measures of physical activity and function. Incidence of hip fractures and all central body fractures declined with BMI. Lower extremity fractures distal to the hip trended upward, and upper extremity incidence was independent of BMI. BMD, CSA, and SM vary in proportion to total body lean mass, supporting the view that bones adapt to prevalent muscle loads. Because lean mass is a progressively smaller fraction of total mass in obesity, femur BMD, CSA, and SM decline relative to body weight in higher BMI categories. Traumatic forces increase with body weight, but fracture rates at the hip and central body were less frequent with increasing BMI, possibly because of greater soft tissue padding. There was no evident protective effect in fracture rates at less padded distal extremity sites. Upper extremity fractures showed no variation with BMI, and lower extremity fracture rates were higher only in the overweight (BMI = 25-29.9 kg/m(2)).

Metabolic diseases and associated complications: sex and gender matter!

BACKGROUND

Clinicians and health professionals are increasingly challenged to understand and consider the different health needs of women and men. The increase of gender awareness and the expanding science of gender medicine will affect more and more clinical practice. This review addresses gender-specific aspects in metabolic disorders and related complications, which represent an increasing burden of this century and a great challenge to public health.

DESIGN

There is increasing evidence of gender-related differences in risk factors, clinical manifestation and sequelae of obesity and diabetes and increasing knowledge that prevention, detection and therapy of illness affect men and women differently.

RESULTS

Some gender-specific aspects, especially regarding cardiovascular disease, have been studied in more detail, but for many complications sex-related analyses of the results of both clinical trials and basic science are still missing or disregarded. Impaired glucose and lipid metabolism as well as dysregulation of energy balance and body fat distribution have a great impact on overall health via neuroendocrine changes and inflammatory pathways and deteriorate the course of many diseases with particular harm for women. Metabolic diseases dramatically affect life of men and women from infancy up to old age and are a major challenge for women during pregnancy. Great impact is attached to the intrauterine period and the lifelong implications of fetal programming.

CONCLUSIONS

Initiation of prospective studies on the impact of gender as primary outcome and investigation of gender-related pathophysiological mechanisms of chronic diseases will help to improve patient care and to implement evidence-based gender-specific prevention programs and clinical recommendations in future.

Bivariate association analyses for the mixture of continuous and binary traits with the use of extended generalized estimating equations

Genome-wide association (GWA) study is becoming a powerful tool in deciphering genetic basis of complex human diseases/traits. Currently, the univariate analysis is the most commonly used method to identify genes associated with a certain disease/phenotype under study. A major limitation with the univariate analysis is that it may not make use of the information of multiple correlated phenotypes, which are usually measured and collected in practical studies. The multivariate analysis has proven to be a powerful approach in linkage studies of complex diseases/traits, but it has received little attention in GWA. In this study, we aim to develop a bivariate analytical method for GWA study, which can be used for a complex situation in which continuous trait and a binary trait are measured under study. Based on the modified extended generalized estimating equation (EGEE) method we proposed herein, we assessed the performance of our bivariate analyses through extensive simulations as well as real data analyses. In the study, to develop an EGEE approach for bivariate genetic analyses, we combined two different generalized linear models corresponding to phenotypic variables using a seemingly unrelated regression model. The simulation results demonstrated that our EGEE-based bivariate analytical method outperforms univariate analyses in increasing statistical power under a variety of simulation scenarios. Notably, EGEE-based bivariate analyses have consistent advantages over univariate analyses whether or not there exists a phenotypic correlation between the two traits. Our study has practical importance, as one can always use multivariate analyses as a screening tool when multiple phenotypes are available, without extra costs of statistical power and false-positive rate. Analyses on empirical GWA data further affirm the advantages of our bivariate analytical method.

Fat mass is negatively associated with cortical bone size in young healthy male siblings

CONTEXT

Body weight has been associated with bone mass and bone size through shared genetic determination and environmental influences. Whereas lean mass exerts a positive influence on bone size, the relationship between fat and bone remains unclear.

OBJECTIVE

The objective of the present study was to investigate the individual influence of fat mass and lean mass on volumetric bone density and size in young healthy male siblings at age of peak bone mass.

DESIGN

This was a cross-sectional, population-based sibling pair study.

PARTICIPANTS

A total of 677 men (25-45 yr) were included in this study with 296 independent pairs of brothers.

MAIN OUTCOME MEASURES

Areal and volumetric bone parameters were determined using dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). Body composition was determined by DXA. Sex steroids, leptin, and adiponectin were determined by immunoassay.

RESULTS

Total and regional fat mass were found to be inversely associated with areal bone mass and bone size, independent from lean mass (radius periosteal circumference beta: -0.29 +/- 0.04; P < 0.001). Lean mass was positively associated with bone size but inversely with cortical density at both tibia and radius (P < 0.01). The negative association between total fat mass and bone size was independent from sex steroid concentrations. Leptin but not adiponectin was inversely associated with bone size, but this was no longer significant after adjustment for body fat.

CONCLUSIONS

Increased fat mass is associated with smaller bone size, challenging the view of a high bone mass index as a protective factor for osteoporosis, whereas lean mass was a consistent positive determinant of bone size.

Disordered-eating attitudes in relation to bone mineral density and markers of bone turnover in overweight adolescents

PURPOSE

To examine the relationships between cognitive eating restraint and both bone mineral density (BMD) and markers of bone turnover in overweight adolescents.

METHODS

One hundred thirty-seven overweight (BMI 39.1 +/- 6.8 kg/m(2)) African American and Caucasian adolescent (age = 14.4 +/- 1.4 years) girls (66.4%) and boys were administered the Eating Disorder Examination (EDE) interview and Eating Inventory (EI) questionnaire and underwent dual energy X-ray absorptiometry (DXA) to measure total lumbar spine BMD. Markers of bone formation (serum bone specific alkaline phosphatase and osteocalcin), bone resorption (24-hour urine N-telopeptides), and stress (urine free cortisol) were measured.

RESULTS

After accounting for the contribution of demographics, height, weight, serum 25-hydroxyvitamin D, and depressive symptoms, adolescents' weight concern, as assessed by interview, was a significant contributor to the model of urine free cortisol (beta = .30, p < .05). Shape concern, as also assessed by interview, was significantly associated with lumbar spine bone mineral density (beta = -.15, p < .05). Dietary restraint was not a significant predictor in any of these models.

CONCLUSIONS

These findings suggest that among severely overweight adolescents, dissatisfaction with shape and weight may be salient stressors. Future research is required to illuminate the relationship between bone health and disordered-eating attitudes in overweight adolescents.

Relationships between body composition, muscular strength, and bone mineral density in estrogen-deficient postmenopausal women

The purpose of this study was to examine relationships between muscular strength, body composition, and bone mineral density (BMD) in untrained postmenopausal women who are not on hormone replacement therapy (HRT). Fifty-five women (age: 63.3+/-0.6yr) completed menstrual history, physical activity, and calcium intake questionnaires. Total and regional body composition and total body, anteroposterior lumbar spine, nondominant forearm, and right proximal femur BMD were measured using dual-energy X-ray absorptiometry (DXA) (GE Lunar Prodigy, Prodigy enCORE software version 10.50.086, Madison, WI). Participants performed strength tests for 3 upper body and 5 lower body resistance exercises. Women with a relative skeletal muscle mass index (RSMI) value less than 5.45 kg/m(2) were defined as a sarcopenia group (SAR). SAR had significantly (p < 0.05) lower total body and forearm BMD compared with those who were not sarcopenic. BMD sites were significantly correlated with upper body strength (UBS) and lower body strength (LBS) (r = 0.28-0.50, p < 0.01), with the strength of relationship being site specific. Strength and fat mass (FM) significantly predicted total body BMD (R(2) = 0.232-0.241, p < 0.05), FM variables predicted spine BMD (R(2) = 0.109-0.140, p < 0.05), and LBS and RSMI predicted hip BMD sites (R(2) = 0.073-0.237, p < 0.05). Body composition variables failed to significantly predict LBS. In conclusion, the contribution of body composition and strength variables to BMD varied by site as FM was more important for total body, forearm and spine BMD, and LBS exerted greater influence on the hip sites.

High-fat diet decreases cancellous bone mass but has no effect on cortical bone mass in the tibia in mice

Body mass has a positive effect on bone health. Whether mass derived from an obesity condition or excessive fat accumulation is beneficial to bone has not been established; neither have the mechanisms by which obesity affects bone metabolism. The aim of this study was to examine the effects of obesity on bone structure and osteoblastic expression of key markers involved in bone formation and resorption in a diet-induced obesity mouse model. Six-wk-old male C57BL/6 mice (n=21) were assigned to two groups and fed either a control (10 kcal% energy as fat) or high-fat diet (HFD, 45 kcal% energy as fat) for 14 weeks. Bone marrow stromal/osteoblastic cells (BMSC) were cultured. Osteoprogenitor activity [alkaline phosphatase (ALP) positive colonies] and mineralization (calcium nodule formation) were determined. Gene expression was measured using quantitative real-time PCR. Bone structure of proximal and midshaft tibia was evaluated by micro-computed tomography. Mice fed the HFD were 31% heavier (P<0.01) than those fed the control diet. There were more ALP positive colony forming units at d 14 and calcium nodules at d 28 of culture by BMSC from HFD mice than from control mice (P<0.01). Receptor activator of NF-kappaB ligand (RANKL) mRNA levels and the ratio of RANKL to osteoprotegerin expression in HFD animals was higher (P<0.01) than in control diet animals. Serum tartrate-resistant acid phosphatase levels were higher in HFD fed mice when compared to control diet fed mice (P<0.05). There were no significant differences in tibial fat-free weight, length, and cortical parameters of midshaft between the two groups. Compared with control mice, tibial trabecular bone volume was reduced, and trabecular separation was increased in HFD mice. Trabecular number was lower (P<0.05) and connectivity density tended to be less (P=0.07) in HFD mice than in control mice. In conclusion, our data indicate that obesity induced by a high-fat diet decreases cancellous bone mass but has no effect on cortical bone mass in the tibia in mice.

Cysteine, homocysteine and bone mineral density: a role for body composition?

BACKGROUND

Plasma total cysteine (tCys) and homocysteine (tHcy) are associated with body composition, which in turn affects bone mineral density (BMD).

OBJECTIVES

To investigate whether associations of tCys and tHcy with BMD are mediated through body composition (fat mass and/or lean mass).

DESIGN

Using data from 5238 Hordaland Homocysteine Study participants, we fit multiple linear regression models and concentration-response curves to explore the relationships between tCys, tHcy, and BMD, with and without adjustment for body mass index (BMI), lean mass and/or fat mass.

RESULTS

All associations were stronger in women. tCys was positively associated with BMD (women, partial r=0.11; men, partial r=0.07, p<or=0.001 for both), but this association was markedly attenuated after adjustment for fat mass. tHcy showed an inverse association with BMD in women (partial r=-0.09, p<0.001), which remained significant after adjustment for lean mass and fat mass. In men and women, changes in tCys or tHcy during 6 years were not associated with BMD at follow-up. Weight gain during 6 years predicted higher BMD at follow-up (p<or=0.009) independent of nutrient intakes, physical activity and baseline BMI. Baseline tHcy inversely predicted BMD measured 6 years later (partial r=-0.11, p<0.001 in women; partial r=-0.07, p=0.002 in men) independent of baseline BMI, while a positive association of baseline tCys with BMD at follow-up (partial r=0.10 in women, 0.09 in men, p<or=0.001) disappeared after adjustment for baseline BMI.

CONCLUSION

tHcy is inversely associated with BMD independent of body composition, while the positive association of tCys with BMD appears to be mainly mediated through fat mass.

Relationship between nutrition factors and osteopenia: Effects of experimental diets on immature bone quality

To investigate the influence of experimental diets on morphological and mechanical characteristics of immature bone, this study thoroughly examined the nutrition-bone connection. A non-destructive evaluation method involving high-resolution in-vivo micro-computed tomography and finite element (FE) analysis was used to investigate the relationship between obesity and osteopenia-two disorders of body composition. Correlation of nutritional deficiency with bone characteristics was also investigated. Some recent studies have shown that both obesity and osteopenia share several common genetic and environmental factors. However, there have been few studies correlating these pathologies in-vivo from a structural and biomechanical point of view. In the present study, detailed changes in morphological and mechanical characteristics of trabecular bone architecture were detected and tracked by longitudinal studies of morphometric parameters and simulated compression testing. Rats were randomized into three groups: overeaten diet (OD) for formation of obesity, normal diet (ND), and restricted diet (RD) in which rats received 65% of the normal diet. In the OD and ND groups, all structural parameters changed significantly (p<0.05). The degree of alteration in the structural parameters of the ND group was similar to that of the RD group (p<0.05). In simulated compression tests using FE models, the effective modulus of the OD group significantly decreased, depending on measuring time (p<0.05), whereas that of the ND and RD groups significantly increased (p>0.05). The key finding of the present study is that fat mass is morphologically and mechanically inversely correlated with bone mass when the mechanical loading effects of greater body weight on bone mass are applied.

Bivariate whole-genome linkage scan for bone geometry and total body fat mass

To quantify the genetic correlations between total body fat mass (TBFM) and femoral neck geometric parameters (FNGPs) and, if possible, to detect the specific genomic regions shared by them, bivariate genetic analysis and bivariate whole-genome linkage scan were carried out in a large Caucasian population. All the phenotypes studied were significantly controlled by genetic factors (P < 0.001) with the heritabilities ranging from 0.45 to 0.68. Significantly genetic correlations were found between TBFM and CSA (cross-section area), W (sub-periosteal diameter), Z (section modulus) and CT (cortical thickness) except between TBFM and BR (buckling ratio). The peak bivariate LOD scores were 3.23 (20q12), 2.47 (20p11), 3.19 (6q27), 1.68 (20p12), and 2.47 (7q11) for the five pairs of TBFM and BR, CSA, CT, W, and Z in the entire sample, respectively. Gender-specific bivariate linkage evidences were also found for the five pairs. 6p25 had complete pleiotropic effects on the variations of TBFM & Z in the female sub-population, and 6q27 and 17q11 had coincident linkages for TBFM & CSA and TBFM & Z in the entire population. We identified moderate genetic correlations and several shared genomic regions between TBFM and FNGPs in a large Caucasian population.

Is PPARγ a prospective player in HIV-1-associated bone disease?

Currently infection with the human immunodeficiency virus-1 (HIV-1) is in most instances a chronic disease that can be controlled by effective antiretroviral therapy (ART). However, chronic use of ART has been associated with a number of toxicities; including significant reductions in bone mineral density (BMD) and disorders of the fat metabolism. The peroxisome proliferator-activated receptor γ (PPARγ) transcription factor is vital for the development and maintenance of mature and developing adipocytes. Alterations in PPARγ expression have been implicated as a factor in the mechanism of HIV-1-associated lipodystrophy. Both reduced BMD and lipodystrophy have been well described as complications of HIV-1 infection and treatment, and a question remains as to their interdependence. Interestingly, both adipocytes and osteoblasts are derived from a common precursor cell type; the mesenchymal stem cell. The possibility that dysregulation of PPARγ (and the subsequent effect on both osteoblastogenesis and adipogenesis) is a contributory factor in the lipid- and bone-abnormalities observed in HIV-1 infection and treatment has also been investigated. This review deals with the hypothesis that dysregulation of PPARγ may underpin the bone abnormalities associated with HIV-1 infection, and treats the current knowledge and prospective developments, in our understanding of PPARγ involvement in HIV-1-associated bone disease.

How does body fat influence bone mass in childhood? A Mendelian randomization approach

Fat mass may be a causal determinant of bone mass, but the evidence is conflicting, possibly reflecting the influence of confounding factors. The recent identification of common genetic variants related to obesity in children provides an opportunity to implement a Mendelian randomization study of obesity and bone outcomes, which is less subject to confounding and several biases than conventional approaches. Genotyping was retrieved for variants of two loci reliably associated with adiposity (the fat mass and obesity-related gene FTO and that upstream of the MC4R locus) within 7470 children from the Avon Longitudinal Study of Parents and Children (ALSPAC) who had undergone total body DXA scans at a mean of 9.9 yr. Relationships between both fat mass/genotypes and bone measures were assessed in efforts to determine evidence of causality between adiposity and bone mass. In conventional tests of association, both with and without height adjustment, total fat mass was strongly related to total body, spinal, and upper and lower limb BMC (ratio of geometric means [RGM]: 1.118 [95% CI: 1.112, 1.123], 1.110 [95% CI: 1.102, 1.119], 1.101 [95% CI: 1.093, 1.108], 1.146 [95% CI: 1.143, 1.155]; p < 10(-10) [adjusted for sex, height, and sitting height]). Equivalent or larger effects were obtained from instrumental variable (IV) regression including the same covariates (1.139 [95% CI: 1.064, 1.220], 1.090 [95% CI: 1.010, 1.177], 1.142 [95% CI: 1.049, 1.243], 1.176 [95% CI: 1.099, 1.257]; p = 0.0002, 0.03, 0.002, and 2.3(-6) respectively). Similar results were obtained after adjusting for puberty, when truncal fat mass was used in place of total fat, and when bone area was used instead of bone mass. In analyses where total body BMC adjusted for bone area (BA) was the outcome (reflecting volumetric BMD), linear regression with fat mass showed evidence for association (1.004 [95% CI: 1.002, 1.007], p = 0.0001). IV regression also showed a positive effect (1.031 [95% CI: 1.000, 1.062], p = 0.05). When MC4R and FTO markers were used as instruments for fat mass, similar associations with BMC were seen to those with fat mass as measured by DXA. This suggests that fat mass is on the causal pathway for bone mass in children. In addition, both directly assessed and IV-assessed relationships between fat mass and volumetric density showed evidence for positive effects, supporting a hypothesis that fat effects on bone mass are not entirely accounted for by association with overall bone size.