The association of obesity and glucose and insulin concentrations with bone density in premenopausal and postmenopausal women

Causal relationship between glycemic traits and bone mineral density in different age groups and skeletal sites: a Mendelian randomization analysis

INTRODUCTION

Previous research has confirmed that patients with type 2 diabetes mellitus tend to have higher bone mineral density (BMD), but it is unknown whether this pattern holds true for individuals without diabetes. This Mendelian randomization (MR) study aims to investigate the potential causal relationship between various glycemic trait (including fasting glucose, fasting insulin, 2-h postprandial glucose, and glycated hemoglobin) and BMD in non-diabetic individuals. The investigation focuses on different age groups (15-30, 30-45, 45-60, and 60 + years) and various skeletal sites (forearm, lumbar spine, and hip).

MATERIALS AND METHODS

We utilized genome-wide association study data from large population-based cohorts to identify robust instrumental variables for each glycemic traits parameter. Our primary analysis employed the inverse-variance weighted method, with sensitivity analyses conducted using MR-Egger, weighted median, MR-PRESSO, and multivariable MR methods to assess the robustness and potential horizontal pleiotropy of the study results.

RESULTS

Fasting insulin showed a negative modulating relationship on both lumbar spine and forearm. However, these associations were only nominally significant. No significant causal association was observed between blood glucose traits and BMD across the different age groups. The direction of fasting insulin's causal effects on BMD showed inconsistency between genders, with potentially decreased BMD in women with high fasting insulin levels and an increasing trend in BMD in men.

CONCLUSIONS

In the non-diabetic population, currently available evidence does not support a causal relationship between glycemic traits and BMD. However, further investigation is warranted considering the observed gender differences.

Metabolic associated fatty liver disease and bone mineral density: a cross-sectional study of the National Health and Nutrition Examination Survey 2017-2018

This research is a cross-sectional study based on the participants aged 50 years and older from National Health and Nutrition Examination Survey (NHANES) database. The metabolic associated fatty liver disease (MAFLD) population has higher BMD and a lower risk of osteoporosis than those without MAFLD.

INTRODUCTION

MAFLD is a new definition presented by panel of experts based on non-alcoholic fatty liver disease in 2020. However, the link between MAFLD and bone mineral density (BMD) is uncertain. Thus, the present study aimed to investigate the relationship between MAFLD and BMD.

METHODS

This cross-sectional study included subjects aged ≥ 50 years from the National Health and Nutrition Examination Survey 2017-2018. Multivariate linear regression models were performed to investigate the association between MAFLD and BMD. Moreover, the relationship between MAFLD and osteoporosis was assessed using multiple logistic regression models.

RESULTS

Finally, 817 participants (non-MAFLD, n = 436; MAFLD, n = 381) were included in the final analysis. The results demonstrated that participants with MAFLD showed higher femoral BMDs than those without MAFLD, especially among males aged ≥ 50 years and females aged ≥ 65 years. Moreover, the results showed that obese men (BMI ≥ 30 kg/m²) with MAFLD had higher femoral BMDs than the control group according to subgroup analyses stratified by BMI, but this trend was not present in women. In addition, multiple logistic regression models showed that participants with MAFLD had no increased risks of osteoporosis.

CONCLUSION

The present study found that the MAFLD population has higher BMD and a lower risk of osteoporosis than those without MAFLD. Because the present study was a cross-sectional study, we could not identify the cause-effect relation between MAFLD and BMD. Therefore, additional research needs to be performed to explore the influences of MAFLD on bone metabolism in the future.

Relationship Between Visceral Adipose Tissue and Bone Mineral Density in Older People: Results from AHAP Study

INTRODUCTION

Due to discrepancy of the relationship between visceral adipose tissue (VAT) and bone mineral density (BMD), this study was performed to determine the relationship between BMD and VAT in the elderly.

METHODOLOGY

This cross-sectional study is part of the second wave of Amirkola Health and Ageing Project (AHAP), including 1,200 people aged 60 years and older. BMD and VAT were measured by dual-energy X-ray absorptiometry (DXA) in Hologic equipment. Based on the amount of VAT, individuals were divided into four quartiles. Then, the data were statistically analyzed by SPSS22 software using chi-square, ANOVA, Pearson correlation coefficient and logistic regression.

RESULTS

The mean age of the participants was 69.6 ± 6.9 year and the mean VAT was 862.6 ± 337.8 gram. In this study, people with osteoporosis had less VAT (p<0.0001). Furthermore, with the increase in the amount of VAT, BMD increased in the femoral region and lumbar spine (p<0.0001). There was a positive and significant correlation between VAT and BMD in the femoral region (r = 0.267) and lumbar spine (r = 0.197) (p<0.0001). After performing multiple logistic regression analysis in the presence of factors such as age, gender, body mass index and especially lean mass, the protective role of VAT against osteoporosis was maintained (OR=0.510, CI_95% (0.290-0.895)) (P = 0.019).

CONCLUSIONS

This study has shown that VAT can independently have a positive association with BMD in the elderly.

Associations between markers of glucose metabolism and bone measures among diabetic and non-diabetic adults

Purpose

To investigate the relationships between bone measures, vitamin D status and markers of glucose metabolism among diabetic and non-diabetic adults.

Methods

Cross sectional study with 298 adults (mean age 57.5 years, SD = 14.8; 44.3% male, 16.9% diabetic) participants of the Health Survey-São Paulo (ISA-Capital) 2014-2015. Blood samples were collected to assess serum glucose, insulin and 25 hydroxyvitamin D [25(OH)D] concentrations. Dual-energy x-ray absorptiometry (DXA) was performed to determine total body fat; total lean mass; full body bone mineral density (BMD); lumbar spine BMD and bone mineral content (BMC); and femur BMD and BMC. Fat mass index (FMI), lean mass index (LMI), quantitative insulin sensitivity check index (QUICKI), homeostasis model assessment of insulin resistance (HOMA-IR) and of β-pancreatic cell function (HOMA-β) were calculated. Linear regression analysis were performed.

Results

Multiple bone measures were associated with markers of glucose metabolism in analyses adjusted by age and sex. However, after additional adjustments by LMI, FMI and serum 25(OH)D, only associations of lumbar spine BMC with HOMA-IR (β = 0.167; p = 0.035) and QUICKI (β = -1.879; p = 0.027) persisted, in the subgroup of diabetic participants. Analysis restricted to diabetic subjects revealed stronger correlations between bone parameters and markers of glucose metabolism.

Conclusions

Our study observed positive associations between BMD and markers of insulin resistance among a sample of adults. Correlations were stronger among diabetic subjects, and some associations between bone and glucose metabolism were independent of adiposity. Findings reinforce the need of further research for better understanding the bidirectional and multifactorial crosstalk between glucose homeostasis and bone metabolism.

Relationship between Insulin Resistance (HOMA-IR), Trabecular Bone Score (TBS), and Three-Dimensional Dual-Energy X-ray Absorptiometry (3D-DXA) in Non-Diabetic Postmenopausal Women

BACKGROUND

Insulin may play a key role in bone metabolism, where the anabolic effect predominates. This study aims to analyze the relationship between insulin resistance and bone quality using the trabecular bone score (TBS) and three-dimensional dual-energy X-ray absorptiometry (3D-DXA) in non-diabetic postmenopausal women by determining cortical and trabecular compartments.

METHODS

A cross-sectional study was conducted in non-diabetic postmenopausal women with suspected or diagnosed osteoporosis. The inclusion criteria were no menstruation for more than 12 months and low bone mass or osteoporosis as defined by DXA. Glucose was calculated using a Hitachi 917 auto-analyzer. Insulin was determined using an enzyme-linked immunosorbent assay (EIA). Insulin resistance was estimated using a homeostasis model assessment of insulin resistance (HOMA-IR). DXA, 3D-DXA, and TBS were thus collected. Moreover, we examined bone parameters according to quartile of insulin, hemoglobin A1C (HbA1c), and HOMA-IR.

RESULTS

In this study, we included 381 postmenopausal women. Women located in quartile 4 (Q4) of HOMA-IR had higher values of volumetric bone mineral density (vBMD) but not TBS. The increase was higher in the trabecular compartment (16.4%) than in the cortical compartment (6.4%). Similar results were obtained for insulin. Analysis of the quartiles by HbA1c showed no differences in densitometry values, however women in Q4 had lower levels of TBS. After adjusting for BMI, statistical significance was maintained for TBS, insulin, HOMA-IR, and HbA1c.

CONCLUSIONS

In non-diabetic postmenopausal women there was a direct relationship between insulin resistance and vBMD, whose effect is directly related to greater weight. TBS had an inverse relationship with HbA1c, insulin, and insulin resistance unrelated to weight. This might be explained by the formation of advanced glycosylation products (AGEs) in the bone matrix, which reduces bone deformation capacity and resistance, as well as increases fragility.

The effect of adolescent inhalant abuse on energy balance and growth

The abuse of volatile solvents such as toluene is a significant public health concern, predominantly affecting adolescents. To date, inhalant abuse research has primarily focused on the central nervous system; however, inhalants also exert effects on other organ systems and processes, including metabolic function and energy balance. Adolescent inhalant abuse is characterized by a negative energy balance phenotype, with the peak period of abuse overlapping with the adolescent growth spurt. There are multiple components within the central and peripheral regulation of energy balance that may be affected by adolescent inhalant abuse, such as impaired metabolic signaling, decreased food intake, altered dietary preferences, disrupted glucose tolerance and insulin release, reduced adiposity and skeletal density, and adrenal hypertrophy. These effects may persist into abstinence and adulthood, and the long-term consequences of inhalant-induced metabolic dysfunction are currently unknown. The signs and symptoms resulting from chronic adolescent inhalant abuse may result in a propensity for the development of adult-onset metabolic disorders such as type 2 diabetes, however, further research investigating the long-term effects of inhalant abuse upon energy balance and metabolism are needed. This review addresses several aspects of the short- and long-term effects of inhalant abuse relating to energy and metabolic processes, including energy balance, intake and expenditure; dietary preferences and glycemic control; and the dysfunction of metabolic homeostasis through altered adipose tissue, bone, and hypothalamic-pituitary-adrenal axis function.

Longitudinal 5-Year Evaluation of Bone Density and Microarchitecture After Roux-en-Y Gastric Bypass Surgery

CONTEXT

Bone health declines in the initial years after Roux-en-Y gastric bypass (RYGB), but long-term skeletal effects are unclear.

OBJECTIVE

To document longitudinal changes in bone mineral density (BMD) and microarchitecture 5 years after RYGB.

DESIGN, SETTING, AND PARTICIPANTS

Prospective 5-year observational study of 21 adults with severe obesity receiving RYGB at an academic medical center.

MAIN OUTCOME MEASURES

Spine and hip areal BMD were measured by dual-energy X-ray absorptiometry, and trabecular volumetric BMD (vBMD) of the spine was assessed by quantitative CT (QCT). We measured vBMD and microarchitecture of the distal radius and tibia by high-resolution peripheral QCT in a subset of subjects. Serum type I collagen C-terminal telopeptide (CTX) and procollagen type I N-terminal propeptide (P1NP) were also measured.

RESULTS

Areal BMD declined by -7.8% ± 7.6% at the spine and -15.3% ± 6.3% at the total hip by 5 years after RYGB (P ≤ 0.001), although the rate of bone loss slowed in later years. Trabecular spine vBMD decreased by -12.1% ± 12.3% by 5 years (P ≤ 0.001). At peripheral sites, vBMD continued to decrease steadily throughout 5 years, with parallel declines in cortical and trabecular microarchitecture, leading to decreases in estimated failure load of -20% and -13% at the radius and tibia, respectively (P < 0.001). Five years after RYGB, CTX and P1NP were 150% and 34% above baseline (P < 0.001 and P = 0.017, respectively).

CONCLUSIONS

Sustained high-turnover bone loss and bone microarchitectural deterioration occur in the 5 years after RYGB. Adults receiving RYGB warrant assessment of bone health.

Positive Association of Obesity and Insulin Resistance With Bone Mineral Density in Tunisian Postmenopausal Women

The association of bone mineral density (BMD) with obesity and insulin resistance remains unclear. This study aimed to explore these associations in Tunisian menopausal women. Eighty-one postmenopausal women were recruited. Data were analyzed for obese (N = 57) and non-obese women (N = 24) and for insulin-resistant (N = 43) and non insulin-resistant women (N = 36). Anthropometric and biochemical parameters were recorded. BMD in different sites and body composition were measured using dual-energy X-ray absorptiometry. Higher BMD was observed in obese women than those non-obese in the left femur (p = 0.0067), right femur (p = 0.0108), total hip (p = 0.0077), and the whole body (p = 0.0276). Also BMD was significantly greater in insulin-resistant women than in non-insulin-resistant women when measured in the left femur and total hip. Positive correlations were recorded between BMD and anthropometric parameters, body composition parameters, and glycemia (r = 0.249, p < 0.05). Multiple linear regression analysis shows that only trunk fat (p < 0.05) and lean mass (p < 0.05) were independently and positively related to BMD, and the waist circumference was the only anthropometric parameter independently and negatively associated to BMD. BMD is improved in obese and insulin-resistant women. Also, trunk fat and lean mass are likely to be key positive independent factors for BMD.

Effects of reduced energy availability on bone metabolism in women and men

BACKGROUND

The short-term effects of low energy availability (EA) on bone metabolism in physically active women and men are currently unknown.

PURPOSE

We evaluated the effects of low EA on bone turnover markers (BTMs) in a cohort of women and a cohort of men, and compared effects between sexes.

METHODS

These studies were performed using a randomised, counterbalanced, crossover design. Eleven eumenorrheic women and eleven men completed two 5-day protocols of controlled (CON; 45kcal·kgLBM^-1·d^-1) and restricted (RES; 15kcal·kgLBM^-1·d^-1) EAs. Participants ran daily on a treadmill at 70% of their peak aerobic capacity (VO₂ peak) resulting in an exercise energy expenditure of 15kcal·kgLBM^-1·d^-1 and consumed diets providing 60 and 30kcal·kgLBM^-1·d^-1. Blood was analysed for BTMs [β-carboxyl-terminal cross-linked telopeptide of type I collagen (β-CTX) and amino-terminal propeptide of type 1 procollagen (P1NP)], markers of calcium metabolism [parathyroid hormone (PTH), albumin-adjusted calcium (ACa), magnesium (Mg) and phosphate (PO₄)] and regulatory hormones [sclerostin, insulin-like growth factor 1 (IGF-1), triiodothyronine (T₃), insulin, leptin, glucagon-like-peptide-2 (GLP-2)].

RESULTS

In women, β-CTX AUC was significantly higher (P=0.03) and P1NP AUC was significantly lower (P=0.01) in RES compared to CON. In men, neither β-CTX (P=0.46) nor P1NP (P=0.12) AUCs were significantly different between CON and RES. There were no significant differences between sexes for any BTM AUCs (all P values>0.05). Insulin and leptin AUCs were significantly lower following RES in women only (for both P=0.01). There were no differences in any AUCs of regulatory hormones or markers of calcium metabolism between men and women following RES (all P values>0.05).

CONCLUSIONS

When comparing within groups, five days of low EA (15kcal·kgLBM^-1·d^-1) decreased bone formation and increased bone resorption in women, but not in men, and no sex specific differences were detected.

Association Between Insulin Resistance and Bone Structure in Nondiabetic Postmenopausal Women

CONTEXT

The clinical consequences of insulin resistance and hyperinsulinemia on bone remain largely unknown.

OBJECTIVE

The objective of the study was to evaluate the effect of insulin resistance on peripheral bone geometry, volumetric bone mineral density (vBMD), bone microarchitecture, and estimated bone strength.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study included 146 postmenopausal, nondiabetic Caucasian women (mean age 60.3 ± 2.7 y) who were participating in the Study of Women's Health Across the Nation.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

High-resolution peripheral quantitative computed tomography was used to assess bone density and microstructure at the distal radius and tibia. Fasting insulin and glucose were measured and insulin resistance was estimated using homeostasis model assessment of insulin resistance (HOMA-IR), with higher values indicating greater insulin resistance.

RESULTS

There was a negative association between HOMA-IR and bone size and a positive association between HOMA-IR and total vBMD, trabecular vBMD, trabecular thickness, and cortical thickness at the radius and tibia. These relationships remained, even after adjusting for body weight and other potential covariates (eg, time since menopause, cigarette smoking, physical activity, prior use of osteoporosis medications or glucocorticoids).

CONCLUSIONS

In nondiabetic, postmenopausal women, insulin resistance was associated with smaller bone size, greater volumetric bone mineral density, and generally favorable bone microarchitecture at weight-bearing and nonweight-bearing skeletal sites. These associations were independent of body weight and other potential covariates, suggesting that hyperinsulinemia directly affects bone structure independent of obesity and may explain, in part, the higher trabecular bone density and favorable trabecular microarchitecture seen in individuals with type 2 diabetes mellitus.

BMI and BMD: The Potential Interplay between Obesity and Bone Fragility

Recent evidence demonstrating an increased fracture risk among obese individuals suggests that adipose tissue may negatively impact bone health, challenging the traditional paradigm of fat mass playing a protective role towards bone health. White adipose tissue, far from being a mere energy depot, is a dynamic tissue actively implicated in metabolic reactions, and in fact secretes several hormones called adipokines and inflammatory factors that may in turn promote bone resorption. More specifically, Visceral Adipose Tissue (VAT) may potentially prove detrimental. It is widely acknowledged that obesity is positively associated to many chronic disorders such as metabolic syndrome, dyslipidemia and type 2 diabetes, conditions that could themselves affect bone health. Although aging is largely known to decrease bone strength, little is yet known on the mechanisms via which obesity and its comorbidities may contribute to such damage. Given the exponentially growing obesity rate in recent years and the increased life expectancy of western countries it appears of utmost importance to timely focus on this topic.

Dietary restrictions, bone density, and bone quality

Caloric restriction (CR), protein restriction (PR), and specific amino acid restriction (e.g., methionine restriction (MR)) are different dietary interventions that have been confirmed with regard to their comprehensive benefits to metabolism and health. Based on bone densitometric measurements, weight loss induced by dietary restriction is known to be accompanied by reduced areal bone mineral density, bone mass, and/or bone size, and it is considered harmful to bone health. However, because of technological advancements in bone densitometric instruments (e.g., high-resolution X-ray tomography), dietary restrictions have been found to cause a reduction in bone mass/size rather than volumetric bone mineral density. Furthermore, when considering bone quality, bone health consists of diverse indices that cannot be fully represented by densitometric measurements alone. Indeed, there is evidence that moderate dietary restrictions do not impair intrinsic bone material properties, despite the reduction in whole-bone strength because of a smaller bone size. In the present review, we integrate research evidence from traditional densitometric measurements, metabolic status assays (e.g., energy metabolism, oxidative stresses, and inflammatory responses), and biomaterial analyses to provide revised conclusions regarding the effects of CR, PR, and MR on the skeleton.

Effects of Gastric Bypass and Gastric Banding on Bone Remodeling in Obese Patients With Type 2 Diabetes

CONTEXT

Roux-en-Y gastric bypass (RYGB) leads to high-turnover bone loss, but little is known about skeletal effects of laparoscopic adjustable gastric banding (LAGB) or mechanisms underlying bone loss after bariatric surgery.

OBJECTIVE

To evaluate effects of RYGB and LAGB on fasting and postprandial indices of bone remodeling.

DESIGN AND SETTING

Ancillary investigation of a prospective study at 2 academic institutions.

PARTICIPANTS

Obese adults aged 21-65 years with type 2 diabetes who underwent RYGB (n = 11) or LAGB (n = 8).

OUTCOMES

Serum C-terminal telopeptide (CTX), procollagen type 1 N-terminal propeptide (P1NP), and PTH were measured during a mixed meal tolerance test at baseline, 10 days and 1 year after surgery. Changes in 25-hydroxyvitamin D, polypeptide YY (PYY), glucagon-like peptide-1, glucose-dependent insulinotropic peptide, and insulin were also assessed.

RESULTS

Fasting CTX increased 10 days after RYGB but not LAGB (+69 ± 23% vs +12±12%, P < .001), despite comparable weight loss at that time. By 1 year, fasting CTX and P1NP increased more after RYGB than LAGB (CTX +221 ± 60% vs +15 ± 6%, P<0.001; P1NP +93 ± 25% vs -9 ± 10%, P < .001) and weight loss was greater with RYGB. Changes in CTX were independent of PTH and 25-hydroxyvitamin D but were associated with increases in fasting PYY. Postprandial suppression of CTX was more pronounced after RYGB than LAGB at 10 days and 1 year postoperatively.

CONCLUSIONS

RYGB is accompanied by early increases in fasting indices of bone remodeling, independent of weight loss or changes in PTH or 25-hydroxyvitamin D. LAGB did not affect bone markers. PYY and other enterohormonal signals may play a role in RYGB-specific skeletal changes.

Type 2 diabetes and the skeleton: new insights into sweet bones

Substantial evidence shows that skeletal fragility should be considered among the complications associated with type 2 diabetes. Individuals with type 2 diabetes have increased fracture risk, despite normal bone mineral density (BMD) and high BMI-factors that are generally protective against fractures. The mechanisms underlying skeletal fragility in diabetes are not completely understood, but are multifactorial and likely include effects of obesity, hyperglycaemia, oxidative stress, and accumulation of advanced glycation end products, leading to altered bone metabolism, structure, and strength. Clinicians should be aware that BMD measurements underestimate fracture risk in people with type 2 diabetes, and that new treatments for diabetes, with neutral or positive effects on skeletal health, might play a part in the management of diabetes in those at high risk of fracture. Data for the optimum management of osteoporosis in patients with type 2 diabetes are scarce, but in the absence of evidence to the contrary, physicians should follow guidelines established for postmenopausal osteoporosis.

Is the negative relationship between obesity and bone mineral content greater for older women?

Obesity and osteoporosis are two important body composition problems with increasing prevalences in aged populations. Traditionally, obesity has been regarded as being beneficial to bone health. However, the protective effect of obesity on osteoporosis has been questioned. In some recent studies, obesity, as defined by percentage body fat, was regarded as a risk factor for osteoporosis. The purpose of this study was to (1) evaluate the effect of waist circumference, a surrogate measure for abdominal obesity, on bone mineral content (BMC) and (2) examine whether the effect of waist circumference increases with advancing age. The study population is made up of women aged over 45 years who completed the body composition and bone mineral density examinations in the fifth Korea National Health and Nutrition Examination Survey in 2010. Subjects who take estrogen or are under medical treatment for osteoporosis were excluded. Stroke patients are also excluded. Femoral neck, total-hip, and whole-body BMC were measured by dual-energy X-ray absorptiometry. A total of 1,434 subjects were included in the analysis. Waist circumference was negatively associated with BMC in all tested regions after correction for weight, menopausal status, smoking, drinking, and exercise. In addition, the negative association between waist circumference and BMC in the femoral neck and total hip increases with age, after correction for confounding factors, showing an interaction effect between waist circumference and age on BMC. In conclusion, this study shows that the negative relationship between waist circumference and BMC in the femoral neck and total hip is greater for older women.

Insulin resistance and bone strength: findings from the study of midlife in the United States

Although several studies have noted increased fracture risk in individuals with type 2 diabetes mellitus (T2DM), the pathophysiologic mechanisms underlying this association are not known. We hypothesize that insulin resistance (the key pathology in T2DM) negatively influences bone remodeling and leads to reduced bone strength. Data for this study came from 717 participants in the Biomarker Project of the Midlife in the United States Study (MIDUS II). The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated from fasting morning blood glucose and insulin levels. Projected 2D (areal) bone mineral density (BMD) was measured in the lumbar spine and left hip using dual-energy X-ray absorptiometry (DXA). Femoral neck axis length and width were measured from the hip DXA scans, and combined with BMD and body weight and height to create composite indices of femoral neck strength relative to load in three different failure modes: compression, bending, and impact. We used multiple linear regressions to examine the relationship between HOMA-IR and bone strength, adjusted for age, gender, race/ethnicity, menopausal transition stage (in women), and study site. Greater HOMA-IR was associated with lower values of all three composite indices of femoral neck strength relative to load, but was not associated with BMD in the femoral neck. Every doubling of HOMA-IR was associated with a 0.34 to 0.40 SD decrement in the strength indices (p<0.001). On their own, higher levels of fasting insulin (but not of glucose) were independently associated with lower bone strength. Our study confirms that greater insulin resistance is related to lower femoral neck strength relative to load. Further, we note that hyperinsulinemia, rather than hyperglycemia, underlies this relationship. Although cross-sectional associations do not prove causality, our findings do suggest that insulin resistance and in particular, hyperinsulinemia, may negatively affect bone strength relative to load.

Chronic risperidone exposure does not show any evidence of bone mass deterioration in animal model of schizophrenia

BACKGROUND

It has been shown that bone mass is centrally regulated. Thus schizophrenia being a disease of the central nervous system is an interesting model for studying bone. Most second generation antipsychotic drugs including risperidone are used in the treatment of schizophrenia. Weight gain and metabolic disturbances are common side effects.

OBJECTIVE

The aims of this study were to investigate bone mass, body composition and light microscopic pathology examinations of femur in an animal model of schizophrenia (pharmacologically induced by postnatally administered phencyclidine-PCP) and to further examine the effects of chronic treatment with risperidone on these parameters in rats.

METHODS

Four groups of male rats were studied:1) control group-NaCl postnatally administered, n=9; 2) PCP group-postnatal PCP administration to rat pups (on day 2,6,9 and 12), n=6; 3) risperidone group-rats treated with risperidone alone for 9weeks from day 35 (NaCl-RSP group, n=7); 4) PCP rats treated with risperidone for 9weeks from day 35 (PCP-RSP group, n=7). Bone mass and body composition were measured in vivo by dual X ray absorptiometry (areal DXA and fat mass). Light microscopic analysis of the femoral metaphysis was performed in all groups after sacrificing the animals.

RESULTS

Postnatal phencyclidine (PCP) administration to rat pups caused a long lasting reduction of total bone mass versus control animals (aDXA 128±2mg/cm(2) vs 139±5mg/cm(2), p<0.05). Examination of the femoral bone revealed a decrease in the number and thickness of the metaphyseal trabecule and cortical thinning. There was a decrease in total and retroperitoneal fat. Nine weeks of administration of risperidone alone to rats, resulted in significant weight gain and had no effect on bone mass versus control animals (aDXA was 136±7mg/cm(2) vs 139±5mg/cm(2), p>0.05). Furthermore, there were no changes in the light microscopic analysis of femoral metaphysis in comparison with controls. When PCP rats were treated with risperidone, they did not change their body weight nor bone mass versus PCP alone (aDXA 126±2mg/cm(2) vs 128±2mg/cm(2), p>0.05) but intriguingly on examination of the femoral bone an increase in the number and thickness of the metaphyseal trabecule was found (trabecular thickness 0.6±0.1μm vs 0.35±0.1μm, p<0.01).

CONCLUSION

This study shows that in the PCP rat model of schizophrenia bone mass is reduced. When PCP rats were treated with risperidone bone mass remained unchanged but intriguingly and unexpectedly light microscopic examination of femoral metaphysis showed an increase in thickness of metaphyseal trabeculae. The mechanism of risperidone's action on bone remains to be clarified.

Correlation between metabolic syndrome and knee osteoarthritis: data from the Korean National Health and Nutrition Examination Survey (KNHANES)

BACKGROUND

This study was designed to investigate the correlations of knee osteoarthritis (OA) with metabolic syndrome (MetS) and MetS parameters in Korean subjects.

METHODS

This study included data from 270 subjects with knee OA and 1964 control subjects with a mean age of 54.56 (SD 11.53) years taken from the Korean National Health and Nutritional Examination Survey (KNHANES) 2008. Multivariate logistic regression analysis was conducted to examine possible associations for knee OA with MetS and MetS parameters.

RESULTS

MetS was shown to be associated with an increased risk of knee OA in female subjects in unadjusted analysis (OR 1.798, 95% CI 1.392, 2.322), but this significance disappeared when adjusted for confounding factors (OR 1.117, 95% CI 0.805, 1.550). No significant association between MetS and knee OA was found in male subjects. Among parameters of MetS, only high waist circumference (WC) in female subjects was significantly associated with an increased prevalence of knee OA, even after adjusting for confounding factors, while no other significant associations were found in both male and female subjects.

CONCLUSION

We found that WC was associated with knee OA in female subjects, but neither MetS nor any parameters thereof were shown to be associated with knee OA in the Korean subjects of this study. Although we found no relationship between a pre-inflammatory state of MetS and knee OA, we believe further investigation of this relationship in various aspects is warranted, as MetS may also be a risk factor for complications in knee OA related procedures.

Bone metabolism and the 10-year probability of hip fracture and a major osteoporotic fracture using the country-specific FRAX algorithm in men over 50 years of age with type 2 diabetes mellitus: a case-control study

The aim of the study was to evaluate the 10-year probability of hip fracture and a major osteoporotic fracture using the FRAX algorithm, vitamin D status, bone mineral density (BMD), and biochemical markers of bone turnover in men over 50 years of age with type 2 diabetes mellitus (T2DM). We estimated FRAX-predicted 10-year fracture probability, levels of 25-hydroxyvitamin D (25-OH-D), markers of bone turnover, and bone mineral density at the L1-L4 (lumbar spine (LS)) and femur neck (FN) in 68 men with T2DM and compared these with an age-matched group (n = 68). The mean (range) age of the T2DM group was 61.4 (51-78) years. The prevalence of hypovitaminosis D (25-OH-D <75 nmol/L) was 59 %. The mean (range) FRAX hip fracture and FRAX major osteoporotic fracture was 0.7 (0-2.8) and 3.2 (0-8.5) %, respectively. BMD at the FN (0.974 vs. 0.915 g/cm(2), p = 0.008) and LS (1.221 vs. 1.068 g/cm(2), p < 0.001) was significantly higher in the T2DM cohort as compared to the healthy age-matched males. 25-OH-vitamin D (67.7 vs.79.8 nmol/L, p < 0.001), crosslaps (0.19 vs. 0.24 μg/L, p = 0.004), and osteocalcin (13.3 vs. 15.7 μg/L, p = 0.004) were significantly lower in the T2DM group. There was no difference in FRAX-related fracture probability between the two groups. Acknowledging the limitations of our study size, we suggest that the increased BMD in T2DM and the noninclusion of T2DM as a secondary risk factor in the FRAX algorithm may be probable explanations for the discordance between literature-observed and FRAX-related fracture probabilities.

Bone metabolism and the 10-year probability of hip fracture and a major osteoporotic fracture using the country-specific FRAX algorithm in men over 50 years of age with type 2 diabetes mellitus: a case-control study

The aim of the study was to evaluate the 10-year probability of hip fracture and a major osteoporotic fracture using the FRAX algorithm, vitamin D status, bone mineral density (BMD), and biochemical markers of bone turnover in men over 50 years of age with type 2 diabetes mellitus (T2DM). We estimated FRAX-predicted 10-year fracture probability, levels of 25-hydroxyvitamin D (25-OH-D), markers of bone turnover, and bone mineral density at the L1-L4 (lumbar spine (LS)) and femur neck (FN) in 68 men with T2DM and compared these with an age-matched group (n = 68). The mean (range) age of the T2DM group was 61.4 (51-78) years. The prevalence of hypovitaminosis D (25-OH-D <75 nmol/L) was 59 %. The mean (range) FRAX hip fracture and FRAX major osteoporotic fracture was 0.7 (0-2.8) and 3.2 (0-8.5) %, respectively. BMD at the FN (0.974 vs. 0.915 g/cm(2), p = 0.008) and LS (1.221 vs. 1.068 g/cm(2), p < 0.001) was significantly higher in the T2DM cohort as compared to the healthy age-matched males. 25-OH-vitamin D (67.7 vs.79.8 nmol/L, p < 0.001), crosslaps (0.19 vs. 0.24 μg/L, p = 0.004), and osteocalcin (13.3 vs. 15.7 μg/L, p = 0.004) were significantly lower in the T2DM group. There was no difference in FRAX-related fracture probability between the two groups. Acknowledging the limitations of our study size, we suggest that the increased BMD in T2DM and the noninclusion of T2DM as a secondary risk factor in the FRAX algorithm may be probable explanations for the discordance between literature-observed and FRAX-related fracture probabilities.

The association of fasting insulin, glucose, and lipids with bone mass in adolescents: findings from a cross-sectional study

CONTEXT

It is unclear whether variation in insulin resistance mediates the positive association of fat mass with bone mass in children/adolescents.

OBJECTIVE

Our objective was to examine whether markers linked to insulin resistance [fasting insulin, glucose, triglycerides, and high-density lipoprotein cholesterol (HDLc)] are associated with bone mass in adolescents, and if they are, to examine whether they mediate the fat mass-bone mass association.

DESIGN AND SETTING

We conducted a cross-sectional analysis in participants from the Avon Longitudinal Study of Parents and Children.

PARTICIPANTS

Participants included 2305 (1100 male) individuals of mean age 15.5 yr.

OUTCOME MEASURES

We evaluated total body less head bone mineral content (BMC) (grams), bone area (BA) (square centimeters), and bone mineral density (BMD) (grams per square centimeter) from a dual-energy x-ray absorptiometry scan.

RESULTS

Fat mass, fasting insulin, and triglycerides were positively associated with BMD, BMC, and BA; HDLc was inversely associated with these outcomes. For example, the adjusted mean difference in BMC per 1 sd fasting insulin was 45 g (95% confidence interval = 17-73 g) in males and 50 g (95% confidence interval = 28-72 g) in females. When the associations of fat mass with outcomes were adjusted for markers of insulin resistance, they were largely unchanged. Associations of triglycerides and HDLc with outcomes were attenuated to the null when they were adjusted for fat mass, whereas those of insulin changed direction; i.e. with adjustment for fat mass, higher fasting insulin was associated with lower BMD, BMC, and BA.

CONCLUSIONS

Fasting insulin, glucose, and lipids do not appear to mediate the positive association of fat mass with bone mass in children/adolescents. The inverse association of fasting insulin with BMD, BMC, and BA once fat mass has been controlled for needs further study.

Osteoporosis and type 2 diabetes mellitus: what do we know, and what we can do?

Diabetes mellitus (DM) is a pandemic and chronic metabolic disorder with substantial morbidity and mortality. In addition, osteoporosis (OP) is a silent disease with a harmful impact on morbidity and mortality. Therefore, this systematic review focuses on the relationship between OP and type 2 diabetes mellitus (T2DM). Systematic reviews of full-length articles published in English from January 1950 to October 2010 were identified in PubMed and other available electronic databases on the Universiti Sains Malaysia Library Database. The following keywords were used for the search: T2DM, OP, bone mass, skeletal. Studies of more than 50 patients with T2DM were included. Forty-seven studies were identified. The majority of articles (26) showed increased bone mineral density (BMD), while 13 articles revealed decreased BMD; moreover, eight articles revealed normal or no difference in bone mass. There were conflicting results concerning the influence of T2DM on BMD in association with gender, glycemic control, and body mass index. However, patients with T2DM display an increased fracture risk despite a higher BMD, which is mainly attributable to the increased risk of falling. As a conclusion, screening, identification, and prevention of potential risk factors for OP in T2DM patients are crucial and important in terms of preserving a good quality of life in diabetic patients and decreasing the risk of fracture. Patients with T2DM may additionally benefit from early visual assessment, regular exercise to improve muscle strength and balance, and specific measures for preventing falls. Patient education about an adequate calcium and vitamin D intake and regular exercise is important for improving muscle strength and balance. Furthermore, adequate glycemic control and the prevention of diabetic complications are the starting point of therapy in diabetic patients.

Osteoporosis in men with diabetes mellitus

Osteoporosis is more common in women than in men. The prevalence in men is not defined yet; however it is becoming much more recognized as its prevalence and impact have become explicable. It is estimated that around 1% of bone mineral density is lost in men every year. Studies show that secondary osteoporosis is the major cause thus, making it important to define the disorders associated with male osteoporosis. Diabetes is a risk factor for bone fractures. In male patients with diabetes measures should be undertaken such as encouraging exercise, assuring adequate calcium and vitamin D intake, and treating diabetic complications.

Bone remodeling, bone mass and weight gain in patients with stabilized schizophrenia in real-life conditions treated with long-acting injectable risperidone

BACKGROUND

Prolactin-raising antipsychotics, risperidone (antidopaminergic activity), may be associated with low bone mass. On the other hand, risperidone may cause an increase in body weight thought to be favorable for bone.

OBJECTIVES

(1) To determine bone remodeling parameters and bone mass in patients with schizophrenia on long-term treatment with long-acting injectable risperidone (LAIR) in naturalistic settings, and (2) to evaluate the change in body weight, metabolic profile and neuroendocrine status in these patients.

DESIGN

This was a prospective, cross-sectional study.

PATIENTS

Patients included 26 outpatients with controlled schizophrenia in real-life conditions (age 31.3 ± 1.3 years, BMI 28.1 ± 1.0) on long-term maintenance therapy with LAIR for a mean of 18.0 ± 1.6 months (range 6-36) with a mean dose of 38 ± 2 mg. 35 subjects matched for sex, age, BMI and education served as healthy controls.

METHODS

Serum osteocalcin, C-terminal telopeptide of type I collagen (CTx), vitamin D, leptin, prolactin, sex steroids, and parathyroid hormone were assessed. Indices of insulin sensitivity and resistance were determined following an oral glucose tolerance test (OGTT). Bone mineral density (BMD) was measured by dual X-ray absorptiometry at the lumbar spine (LS) and femoral neck (FN).

RESULTS

Mild to moderate hyperprolactinemia (1,000-2,000 mU/l) was associated with asymptomatic hypogonadism. Prolactin values >2,000 mU/l occurred in a few female patients. Hypogonadism leads to a slight increase (upper limit of normal) in bone resorption marker (CTx) in patients with schizophrenia (p = 0.023). As for bone mass, although lower at the spine than in healthy subjects, it did not reach statistical significance (p = 0.094), while at the FN, BMD was not different from healthy subjects. Body weight increased on average 8.7 ± 1.6 kg in more than 50% of patients. Leptin levels adjusted for BMI in females were significantly higher in patients than in healthy female subjects (p = 0.018), while in males there was no difference between the groups (p = 0.833). A high prevalence of low vitamin D levels and more current smokers were found in patients with schizophrenia. As for the metabolic profile during treatment with risperidone, the low Matsuda index of insulin sensitivity (p = 0.039) confirmed insulin resistance in these patients.

CONCLUSION

A potential long-term consequence of asymptomatic hypogonadism due to risperidone-induced hyperprolactinemia might cause a slight rise in bone resorption marker (CTx). On the other hand, by increasing body weight, risperidone could have a protective effect on the bone and thus no change in bone mass was recorded when compared with healthy controls.

Adiponectin and its association with bone mass accrual in childhood

Circulating adiponectin levels are inversely related to bone mineral density (BMD) in humans and animal models. Previous studies in humans have been confined largely to adult populations, and whether adiponectin influences bone mass accrual in childhood is unclear. We examined this question using the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort by investigating relationships between circulating adiponectin levels at a mean age of 9.9 years, indices of bone mass as measured by total-body dual-energy X-ray absorptiometry (DXA) at ages 9.9 and 15.5 years, and cortical bone parameters as measured by peripheral quantitative computed tomography (pQCT) of the midtibia at age 15.5 years. A total of 4927 children were included at age 9.9 years, of whom 97% and 90% of boys and girls, respectively, were in prepuberty or early puberty, as defined by Tanner stage 1-2. A total of 2754 children were included at age 15.5 years, of whom 95% and 97% of boys and girls, respectively, were in late puberty, as defined by Tanner stage 4-5. Circulating adiponectin was found to be related to fat mass, lean mass, and, to a lesser extent, height, so analyses were adjusted for these three variables to identify possible independent effects of adiponectin on bone development. Adiponectin was inversely related to total-body-less-head bone mineral content (BMC; -3.0%), bone area (BA; -1.8%), BMC divided by BA (BMD; -4.8%), and BMC adjusted for BA by linear regression (aBMC; -5.6%), as measured at age 9.9 years (coefficients show change per doubling in adiponectin concentration, p < .001). Consistent with these results, inverse associations also were seen between adiponectin and cortical BMC (-4.8%) and cortical bone area (-4.7%), as measured by tibial pQCT at age 15.5 years (p < .001). Further pQCT results suggested that this inverse association of adiponectin with skeletal development predominantly involved a negative association with endosteal relative to periosteal expansion, as reflected by cortical thickness (-6.0%, p < .001). We conclude that, independent of fat mass, lean mass, and height, adiponectin is associated with lower bone mass in childhood predominantly owing to an influence on relative endosteal expansion. Since these associations were observed before and after puberty, this suggests that setting of adiponectin levels in midchildhood has the potential to exert long-term effects on bone strength and fracture risk.

The effect of diabetes mellitus on osseous healing

Diabetes mellitus and, in particular, type 1 diabetes has been associated with impaired osseous wound healing properties. The scope of the present review is to discuss the clinical evidence supporting a higher rate of complications during fracture healing in diabetic patients and the histological evidence indicating impaired potential for intramembranous and endochondral ossification in the presence of uncontrolled experimental diabetes. The article further provides a synthesis of our current understanding of the plausible molecular mechanisms underlying the diabetic bone healing pathophysiology and of the role of insulin treatment in promoting osseous healing in the diabetic status.

Bone health in diabetes: considerations for clinical management

BACKGROUND

The metabolic and endocrine alterations of diabetes adversely affect bone quantity and/or quality and may increase fracture risk.

SCOPE

A survey of the scientific literature on diabetes and bone cited on PubMed/MEDLINE and published in English from January 1970 to November 2008.

FINDINGS

Subjects with type 1 diabetes have reduced bone mass and increased risk of fragility fracture, while those with type 2 diabetes, despite having normal or above-normal bone mineral density (BMD), are susceptible to low-trauma fractures, especially hip fractures. A recent meta-analysis, involving 836 000 subjects and 139 000 incident cases of fracture, found that type 2 diabetes was associated with significantly increased risks of non-vertebral (relative risk 1.2), hip (relative risk 1.7) and foot (relative risk 1.3) fracture. The association with hip fracture persisted after adjustment for age, physical activity and body weight, and was more pronounced in men and in those with long-standing diabetes. Insulin has an anabolic effect on bone, and the qualitatively different effects of type 1 and type 2 diabetes on bone mass are consistent with the opposing insulin-secretory states (hypoinsulinaemia vs. hyperinsulinaemia). However, the existence of an elevated fracture risk in type 2 diabetes, despite the underlying hyperinsulinaemia, suggests the involvement of other potential pathogenic influences (e.g., hyperglycaemia, diabetic complications and lifestyle factors) on bone. Animal studies suggest that diabetic bone may be more fragile than non-diabetic bone. Falls arising from diabetes-related comorbidities are another possible cause of low-trauma fracture. Clinical trial findings, supported by bone marker and bone density data, suggest that the oral antidiabetic agents metformin and glibenclamide significantly lower fracture risk, whereas the thiazolidinediones slightly increase fracture risk in postmenopausal women, but not in men, with type 2 diabetes. Recent preclinical studies have helped elucidate the mechanisms underlying the dynamics of bone remodelling, but more research is needed to improve outcomes for patients.

CONCLUSIONS

Bone health is an important consideration in diabetes, and caution should be exercised in prescribing thiazolidinediones to postmenopausal women with low BMD and patients with prior fracture.

Prevalence of osteoporosis and factors affecting bone mineral density among postmenopausal Turkish women with type 2 diabetes

OBJECTIVES

Controversy remains as to the effects of type 2 diabetes on bone metabolism. The aims of this study were to assess the association between type 2 diabetes and bone mineral density (BMD) and to evaluate the possible relationship between chronic diabetic complications and bone density.

METHODS

Bone mineral densities at the lumbar spine, femur, and radius in 206 postmenopausal Turkish women with type 2 diabetes were evaluated by dual-energy X-ray absorptiometry and compared with those in 61 age-matched postmenopausal nondiabetic women. Medical and lifestyle characteristics, body mass index (BMI), hemoglobin A1c level, and status of microvascular and macrovascular diabetic complications were recorded. Frequency of osteoporosis and that of osteopenia as well as the relationship between microvascular and macrovascular complications and BMD were evaluated.

RESULTS

The groups did not differ on BMDs and T scores at the hip, lumbar spine, and radius. Patients with radial and/or lumbar and/or hip osteoporosis had a longer duration of diabetes (P=.000), were older (P=.000), and had a lower BMI (P=.000). No correlation was found between osteopenia or osteoporosis and hemoglobin A1c level, presence of microalbuminuria, retinopathy, neuropathy, peripheral artery disease, cerebrovascular event, and coronary artery disease. Among the three sites, BMD at the hip was positively correlated with BMI (P=.000) but negatively correlated with age (P=.000) and duration of diabetes (P=.000). Presence of microalbuminuria revealed a negative correlation with BMD at the femoral neck (P=.042).

CONCLUSION

There is no evidence that type 2 diabetes influenced BMD in our postmenopausal patient group.

Calorie restriction and bone health in young, overweight individuals

BACKGROUND

Calorie restriction (CR) is promoted to increase longevity, yet this regimen could lead to bone loss and fracture and therefore affect quality of life.

METHODS

Forty-six individuals were randomized to 4 groups for 6 months: (1) healthy diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 25% energy deficit by a combination of CR and increased aerobic exercise (CR + EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group). Bone mineral density (total body and hip by dual-energy x-ray absorptiometry) and serum bone markers (bone-specific alkaline phosphatase, osteocalcin, cross-linked C-telopeptide of type I collagen, and cross-linked N-telopeptide of type I collagen) were measured at baseline and after 6 months.

RESULTS

Mean +/- SE body weight was reduced by -1.0% +/- 1.1% (control), -10.4% +/- 0.9% (CR), -10.0% +/- 0.8% (CR + EX), and -13.9% +/- 0.7% (LCD). Compared with the control group, none of the groups showed any change in bone mineral density for total body or hip. Bone resorption by serum cross-linked C-telopeptide of type I collagen was increased in all 3 intervention groups, with the largest change observed in the LCD group (CR, 23% +/- 10%; CR + EX, 22% +/- 9%; and LCD, 74% +/- 16% vs control, 4% +/- 10%). Serum levels of cross-linked N-telopeptide of type I collagen were also increased in the LCD group. With regard to bone formation, bone alkaline phosphatase levels were decreased in the CR group (-23% +/- 10%) but were unchanged in the CR + EX, LCD, and control groups.

CONCLUSIONS

Moderate CR, with or without exercise, that preserves calcium intake for 6 months leads to large changes in body composition without significant bone loss in young adults. Longer studies with assessments of bone architecture are needed to confirm that CR nutrient-dense diets have no deleterious effect on bone health.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00099151.

Diabetes and osteoporosis

Care of patients with diabetes should include assessment of bone health. The extension of the average life expectancy of people with diabetes, which has accompanied improvements in medical care, has also increased the significance of osteoporosis. In addition to the usual causes of osteoporosis associated with aging, bone health is also compromised by diabetes. Studies on bone involvement in patients with diabetes mellitus have generated conflicting results, largely because of the pathogenetic complexity of the condition. It is now clear that patients with type 1 diabetes have lower bone mineral density (BMD) and a higher risk of fractures. Evidence is emerging that patients with type 2 diabetes who have complications are also at increased risk of certain types of osteoporotic fractures, despite having a higher BMD when compared to patients with type 1 diabetes. Although many factors, including number and type of falls, visual impairment, neuropathy, and reduced muscle strength, influence the probability of fractures, the most significant factor seems to be the strength of the bone itself. Thus, sarcopenia, a reduction in muscle mass and muscle strength, is considered one of the main determinants of bone fragility. The aim of this review is to examine the occurrence of osteoporosis in type 1 and type 2 diabetes.

Relationships between fat and bone

Body weight impacts both bone turnover and bone density, making it, therefore, an important risk factor for vertebral and hip fractures and ranking it alongside age in importance. The effect of body weight is probably contributed to by both fat mass and lean mass, though in postmenopausal women, fat mass has been more consistently demonstrated to be important. A number of mechanisms for the fat-bone relationship exist and include the effect of soft tissue mass on skeletal loading, the association of fat mass with the secretion of bone active hormones from the pancreatic beta cell (including insulin, amylin, and preptin), and the secretion of bone active hormones (e.g., estrogens and leptin) from the adipocyte. These factors alone probably do not fully explain the observed clinical associations, and study of the actions on bone of novel hormones related to nutrition is an important area of further research. An understanding of this aspect of bone biology may open the way for new treatments of osteoporosis. More immediately, the role of weight maintenance in the prevention of osteoporosis is an important public health message that needs to be more widely appreciated.

Understanding the pathology and mechanisms of type I diabetic bone loss

Type I (T1) diabetes, also called insulin dependent diabetes mellitus (IDDM), is characterized by little or no insulin production and hyperglycemia. One of the less well known complications of T1-diabetes is bone loss which occurs in humans and animal models. This complication is receiving increased attention because T1-diabetics are living longer due to better therapeutics, and are faced with their existing health concerns being compounded by complications associated with aging, such as osteoporosis. Both male and female, endochondrial and intra-membranous, and axial and appendicular bones are susceptible to T1-diabetic bone loss. Exact mechanisms accounting for T1-diabetic bone loss are not known. Existing data indicate that the bone defect in T1-diabetes is anabolic rather than catabolic, suggesting that anabolic therapeutics may be more effective in preventing bone loss. Potential contributors to T1-diabetic suppression of bone formation are discussed in this review and include: increased marrow adiposity, hyperlipidemia, reduced insulin signaling, hyperglycemia, inflammation, altered adipokine and endocrine factors, increased cell death, and altered metabolism. Differences between T1-diabetic- and age-associated bone loss underlie the importance of condition specific, individualized treatments for osteoporosis. Optimizing therapies that prevent bone loss or restore bone density will allow T1-diabetic patients to live longer with strong healthy bones.

Influence of obesity on bone density in postmenopausal women

OBJECTIVE: To evaluate the influence of obesity, age, and years since menopause on bone density. METHODS: A retrospective analysis of bone mineral density (BMD) obtained from 588 women, 41 to 60 years, previously menopaused (1-10 years before). RESULTS: Positive influence of obesity was confirmed by the significant differences in BMD at lumbar spine, femoral neck (FN), and trochanter (TR) between the groups (p < 0.01). Age and years since menopause (YSM) were negatively correlated with BMD at all sites (p = 0.000). Comparing patients within 1 to < 6 YSM versus 6 to 10 YSM, BMD was higher in the former at LS and FN (p < 0.005), despite the higher BMI in the older group (p = 0.01). Obese patients had a lower prevalence of osteoporosis at LS and FN (p = 0.009). Regression analysis identified BMI as the strongest determinant of FN and TR BMD, while YSM was the strongest determinant of LS BMD. CONCLUSION: The protective effect of obesity is overtaken by age and estradiol deficiency. We recommend that even obese postmenopausal women should be screened for osteoporosis.

Influences of diabetes (db/db), obese (ob/ob) and dystrophic (dy/dy) genotype mutations on hind limb bone maturation: a morphometric, radiological and cytochemical indices analysis

The influences of single-gene missense mutations expressing diabetes (db/db), obese (ob/ob) or dystrophia (dy/dy) dysregulated metabolic syndromes on hind limb bone maturation and cytodevelopment in C57BL/KsJ mice were evaluated by radiological, macro- and cytomorphometric analysis of the resulting variances in os coxae, femur and tibia osteodevelopment indices relative to control parameters between 8 and 16 weeks of age. Associated with obesity and hyperglycaemic/hyperinsulinaemic states, both db/db and ob/ob mutants demonstrated significant suppression of hind limb maturation (length) and cytodensity indices relative to control growth parameters. By contrast, skeletal growth suppression induced by dy/dy mutation expression was associated with lean body mass and normoglycaemic/hypoinsulinaemic systemic endometabolic indices. In both db/db and ob/ob mutation syndromes, osteovascular, -interstitial and -cytolipidaemia were prominent cytochemical aberrations of the osteopaenic states relative to the dyslipidaemia/fibrodysplasia characteristic of dy/dy osteomaturation. Between 8 and 16 weeks of age, both ob/ob and db/db groups demonstrated extensive cortical interstitial (laminal) osteolipidaemia and suppressed cytodensities compared to control indices. These data demonstrate that the abnormal hyperglycaemic/hyperinsulinaemic endometabolic states associated with the expression of db/db and ob/ob genomutations promote extensive lipidaemia-induced osteopaenia, compromising hind limb osteomaturation and cytodensity indices, as compared to the hyperfibritic osteopaenia characteristic of dy/dy mutation syndromes. Recognized therapeutic modulation of the hypercytolipidaemic component of diabetes-obesity syndromes may prove to be effective towards amelioration of the deleterious influences of these expressed hyperglycaemic, dysregulated lipometabolic conditions on osteomaturation and cytodevelopment.

Normal bone density obtained in the absence of insulin receptor expression in bone

Type I diabetes is characterized by little or no insulin production and hyperglycemic conditions. It is also associated with significant bone loss and increased bone marrow adiposity. To examine the role of reduced insulin signaling in type I diabetic bone loss without inducing hyperglycemia, we used genetically reconstituted insulin receptor knockout mice (IRKO-L1) that are euglycemic as a result of human insulin receptor transgene expression in the pancreas, liver, and brain. RT-PCR analyses demonstrated undetectable levels of insulin receptor expression in IRKO-L1 bone, yet IRKO-L1 bones exhibit similar (and trend toward greater) bone density compared with wild-type animals as determined by microcomputed tomography. More detailed bone analyses indicated that cortical bone area was increased in tibias of IRKO-L1 mice. Osteoblast markers (osteocalcin and runx2 mRNA levels) and resorption markers (serum pyridinoline levels) were similar in wild-type and IRKO-L1 bones. When marrow adiposity was examined, we noticed a decrease in adipocyte number and fatty-acid-binding protein 2 expression in IRKO-L1 mice compared with wild-type mice. Bone marrow stromal cell cultures obtained from wild-type and IRKO-L1 mice demonstrated similar adipogenic and osteogenic potentials, indicating that systemic factors likely contribute to differences in marrow adiposity in vivo. Interestingly, IGF-I receptor mRNA levels were elevated in IRKO-L1 bones, suggesting (in combination with hyperinsulinemic conditions) that increased IGF-I receptor signaling may represent a compensatory response and contribute to the changes in cortical bone. Taken together, these results suggest that reduced insulin receptor signaling in bone is not a major factor contributing to bone loss in type I diabetes.

Chronic hyperglycemia modulates osteoblast gene expression through osmotic and non-osmotic pathways

Insulin dependent diabetes mellitus (IDDM; type I) is a chronic disease stemming from little or no insulin production and elevated blood glucose levels. IDDM is associated with osteoporosis and increased fracture rates. The mechanisms underlying IDDM associated bone loss are not known. Previously we demonstrated that osteoblasts exhibit a response to acute (1 and 24 h) hyperglycemia and hyperosmolality. Here we examined the influence of chronic hyperglycemia (30 mM) and its associated hyperosmolality on osteoblast phenotype. Our findings demonstrate that osteoblasts respond to chronic hyperglycemia through modulated gene expression. Specifically, chronic hyperglycemia increases alkaline phosphatase activity and expression and decreases osteocalcin, MMP-13, VEGF and GAPDH expression. Of these genes, only MMP-13 mRNA levels exhibit a similar suppression in response to hyperosmotic conditions (mannitol treatment). Acute hyperglycemia for a 48-h period was also capable of inducing alkaline phosphatase and suppressing osteocalcin, MMP-13, VEGF, and GAPDH expression in differentiated osteoblasts. This suggests that acute responses in differentiated cells are maintained chronically. In addition, hyperglycemic and hyperosmotic conditions increased PPARgamma2 expression, although this increase reached significance only in 21 days chronic glucose treated cultures. Given that osteocalcin is suppressed and PPARgamma2 expression is increased in type I diabetic mouse model bones, these findings suggest that diabetes-associated hyperglycemia may modulate osteoblast gene expression, function and bone formation and thereby contribute to type I diabetic bone loss.

Early manifestation of type 1 diabetes in children is a risk factor for changed bone geometry: data using peripheral quantitative computed tomography

OBJECTIVE

Normal to severely decreased bone mineral density has been reported in children with type 1 diabetes. To detect possible abnormalities in bone mineralization, geometry, and muscle bone unit, we measured selective parameters in children with type 1 diabetes using peripheral quantitative computed tomography.

METHODS

Measurements of the radius by peripheral quantitative computed tomography were made to assess cortical and trabecular bone characteristics as well as muscle mass in 88 patients (42 girls, 46 boys) at a mean age of 11.7 +/- 3.0 years, a mean disease duration of 5.6 +/- 3.7 years, and a mean manifestation age of type 1 diabetes of 6.1 +/- 3.5 years. Height, weight, Tanner stage, insulin regimen, and glycosylated hemoglobin values were recorded. Bone metabolism was studied by measurement of bone formation and bone resorption parameters. Dynamic muscle force was measured using a grip strength device.

RESULTS

Overall, cortical, trabecular, and total bone mineral density were within the reference range. Total and cortical bone cross-sectional area and muscle mass were low in prepubertal patients, and total cross-sectional area was low in early puberty. Adolescent patients showed normal bone and muscle parameters. Grip strength and recreational physical activity were normal in all in relation to a healthy reference population. In a subgroup of 18 patients, early manifestation of type 1 diabetes was detected as a risk factor for altered bone development with significantly reduced cortical bone mineral density and total, cortical, and muscle cross-sectional area (-0.9 +/- 1.3 SD, -2.1 +/- 1.3 SD, -1.6 +/- 0.7 SD, and -1.0 +/- 0.7 SD, respectively). Bone characteristics were not influenced by metabolic control, disease duration, or insulin regimen.

CONCLUSIONS

Manifestation of type 1 diabetes at an early age may impair bone development. Longitudinal data are needed to determine whether this impairment persists into adolescence and adulthood.

Glucose is a key metabolic regulator of osteoclasts; glucose stimulated increases in ATP/ADP ratio and calmodulin kinase II activity

Glucose-stimulated increases in osteoclast activity are mediated, at least in part, by transcriptional regulation of H+-ATPase expression through a mechanism involving p38 mitogen-activated protein kinase. We hypothesized that early events in the glucose-dependent signaling pathway would be similar to those identified in other glucose-sensitive cells, such as islet beta-cells, including rapid changes in the cellular ATP/ADP ratio and mobilization of intracellular Ca2+. We demonstrate that glucose stimulates a prolonged 50% increase in the ATP/ADP ratio that was maximal 30 s after glucose concentrations were increased. Glucose stimulated a transient 30% increase in calcium/calmodulin-dependent kinase II (CaMK II) activity that was maximal 3 min after the glucose concentration was increased. CaMK II was activated maximally by 3 mmol D-glucose/L in 3-min assays. Activation of CaMK II in the presence of the nonmetabolizable glucose analog 2-deoxyglucose was 2-fold greater than with D-glucose but was unchanged by glucosamine. Pretreatment of osteoclasts with the intracellular Ca2+ chelator BAPTA-AM inhibited glucose transport by 75%. BAPTA-AM treatment also prevented glucose-dependent stimulation of CaMK II. The data indicate that osteoclasts utilize a glucose-sensing mechanism similar to that of beta-cells and that glucose-stimulated signaling in osteoclasts involves changes in the ATP/ADP ratio and mobilization of intracellular Ca2+, resulting in activation of CaMK II.

Influences of obese (ob/ob) and diabetes (db/db) genotype mutations on lumber vertebral radiological and morphometric indices: skeletal deformation associated with dysregulated systemic glucometabolism

Background

Both diabetes and obesity syndromes are recognized to promote lumbar vertebral instability, premature osteodegeneration, exacerbate progressive osteoporosis and increase the propensity towards vertebral degeneration, instability and deformation in humans.

Methods

The influences of single-gene missense mutations, expressing either diabetes (db/db) or obese (ob/ob) metabolic syndromes on vertebral maturation and development in C57BL/KsJ mice were evaluated by radiological and macro-morphometric analysis of the resulting variances in osteodevelopment indices relative to control parameters between 8 and 16 weeks of age (syndrome onset @ 4 weeks), and the influences of low-dose 17-B-estradiol therapy on vertebral growth expression evaluated.

Results

Associated with the indicative genotypic obesity and hyper-glycemic/-insulinemic states, both db/db and ob/ob mutants demonstrated a significant (P ≤ 0.05) elongation of total lumbar vertebrae column (VC) regional length, and individual lumbar vertebrae (LV1-5) lengths, relative to control VC and LV parameters. In contrast, LV1-5 width indices were suppressed in db/db and ob/ob mutants relative to control LV growth rates. Between 8 and 16 weeks of age, the suppressed LV1-5 width indices were sustained in both genotype mutant groups relative to control osteomaturation rates. The severity of LV1-5 width osteosuppression correlated with the severe systemic hyperglycemic and hypertriglyceridemic conditions sustained in ob/ob and db/db mutants. Low-dose 17-B-estradiol therapy (E2-HRx: 1.0 ug/ 0.1 ml oil s.c/3.5 days), initiated at 4 weeks of age (i.e., initial onset phase of db/db and ob/ob expressions) re-established control LV 1–5 width indices without influencing VC or LV lengths in db/db groups.

Conclusion

These data demonstrate that the abnormal systemic endometabolic states associated with the expression of db/db and ob/ob genomutation syndromes suppress LV 1–5 width osteomaturation rates, but enhanced development related VC and LV length expression, relative to control indices in a progressive manner similar to recognized human metabolic syndrome conditions. Therapeutic E2 modulation of the hyperglycemic component of diabetes-obesity syndrome protected the regional LV from the mutation-induced osteopenic width-growth suppression. These data suggest that these genotype mutation models may prove valuable for the evaluation of therapeutic methodologies suitable for the treatment of human diabetes- or obesity-influenced, LV degeneration-linked human conditions, which demonstrate amelioration from conventional replacement therapies following diagnosis of systemic syndrome-induced LV osteomaturation-associated deformations.

Is insulin an anabolic agent in bone? Dissecting the diabetic bone for clues

Diabetic osteoporosis is increasingly recognized as a significant comorbidity of type 1 diabetes mellitus. In contrast, type 2 diabetes mellitus is more commonly associated with modest increases in bone mineral density for age. Despite this dichotomy, clinical, in vivo, and in vitro data uniformly support the concept that new bone formation as well as bone microarchitectural integrity are altered in the diabetic state, leading to an increased risk for fragility fracture and inadequate bone regeneration following injury. In this review, we examine the contribution that insulin, as a potential anabolic agent in bone, may make to the pathophysiology of diabetic bone disease. Specifically, we have assimilated human and animal data examining the effects of endogenous insulin production, exogenous insulin administration, insulin sensitivity, and insulin signaling on bone. In so doing, we present evidence that insulin, acting as an anabolic agent in bone, can preserve and increase bone density and bone strength, presumably through direct and/or indirect effects on bone formation.

Decreased bone mineral density at the distal radius, but not at the lumbar spine or the femoral neck, in Japanese type 2 diabetic patients

The purpose of this study is to assess the association between type 2 diabetes and bone mineral density. This study included 145 Japanese patients (64 men and 81 women) with type 2 diabetes and 95 non-diabetic control subjects (41 men and 54 women) of similar age. We measured bone mineral density (BMD) at the sites with different cortical/cancellous bone ratio (lumbar spine, femoral neck, and distal radius) using dual-energy X-ray absorptiometry. BMD and Z score at the distal radius were significantly lower in type 2 diabetic patients than those in control subjects, and in type 2 diabetic patients, the Z score at the distal radius was lower than that at their own lumbar spine and femoral neck. In type 2 diabetic patients, negative correlation between BMD and the mean HbA1c during the previous 2 years was found significantly at the distal radius in both genders and at the femoral neck in women. These results indicate the selective cortical bone loss in type 2 diabetes and suggest the importance of also determining BMD at the radius and keeping good metabolic control to prevent bone loss in type 2 diabetic patients.

Evidence for bone mass and body fat distribution relationship in postmenopausal obese women

The measurement of bone mass, a reliable predictor of osteoporotic fractures, in obese subjects has yielded conflicting results and bone mass has been reported to be elevated, normal or decreased. These observations indicate that factors other than body weight may be involved in the less risk for osteoporosis in obese subjects. In order to clarify the role of body fat distribution on bone density we studied sixty postmenopausal overweight/obese women with Body Mass Index (BMI) over 25 kg/m(2). Thirty five age-matched, nonobese postmenopausal women, served as controls. Bone mineral density (BMD) was measured at the proximal and ultradistal non dominant forearm using a double energy X-ray absorption (DEXA) apparatus. The waist/hip circumferences ratio (WHR) was used, in obese group, as an anthropometric estimation of the abdominal (WHR>0.85) to lower-extremity (WHR>0.85) fat proportion. The results were analyzed by Student t-test, ANOVA, and multiple linear regression analysis. No difference was found in BMD between obese group and controls, but a highly significant (P<0.001) positive correlation has been documented between proximal and ultradistal radius bone mineral density and waist/hip ratio in the obese group. Instead not significant correlation was found with BMI. Regional fat topography may influence the bone mass independently of total adiposity and visceral fat was the primary parameter accounting for higher bone mineral density values. These finding suggest that women with android-like obesity are protected from osteoporosis.

Clinical significance of alendronate in postmenopausal type 2 diabetes mellitus

OBJECTIVES

To examine early changes in biochemical markers of bone turnover and bone mineral density (BMD) in a clinical trial of anti-resorptive agent alendronate versus alfacalcidol in postmenopausal women with type 2 diabetes mellitus.

METHODS

12 subjects (mean age; 73.1 +/- 6.3 yrs, duration of diabetes; 13.2 +/- 3.7 yrs) were administered alendronate sodium (5 mg/day) and 12 subjects (mean age; 70.7 +/- 7.8 yrs, duration of diabetes; 12.8 +/- 2.0 yrs) were administered alfacalcidol (0.5 microg/day) for 12 months. Urinary N-telopeptide cross-linked collagen type I (NTx), one of biochemical markers, and radial bone mineral density (BMD) were measured as a marker of bone turnover.

RESULTS

After 12 months, urinary NTx did not change in women with alfacalcidol treatment, however urinary NTx significantly decreased after alendronate treatment. The BMD significantly decreased by 3.33% (p<0.05) in women with alfacalcidol treatment, while the BMD did not decrease in women with alendronate treatment.

CONCLUSION

Alendronate that produces reduction in urinary NTx and inhibition of decrease in BMD may have a clinical significance to reduce the risk of bone fracture in postmenopausal type 2 diabetic women.

Diabetes is associated independently of body composition with BMD and bone volume in older white and black men and women: The Health, Aging, and Body Composition Study

The association between type 2 diabetes, BMD, and bone volume was examined to determine the effect of lean and fat mass and fasting insulin in the Health, Aging, and Body Composition Study, which included white and black well-functioning men and women 70-79 years of age (N = 2979). Diabetes predicted higher hip, whole body, and volumetric spine BMD, and lower spine bone volume, independent of body composition and fasting insulin.

INTRODUCTION

The purpose of this study was to determine if the association between type 2 diabetes and higher BMD observed in older white women is seen in elderly white men and blacks and to evaluate if higher BMD in diabetic individuals is accounted for by lean mass, fat mass, or fasting insulin differences.

MATERIALS AND METHODS

In the Health, Aging, and Body Composition Study, which included white and black well-functioning men and women 70-79 years of age (N = 2979), 19% of participants had diabetes at baseline. Of those with diabetes, 57% were men, and 62% were black. Multivariate linear regression models examined independent effects of diabetes, lean mass, fat mass, visceral fat, and fasting insulin on BMD and bone volume while adjusting for relevant covariates.

RESULTS AND CONCLUSIONS

Fasting insulin, visceral fat, and volumetric spine BMD, assessed by CT, and lean mass, fat mass, and total hip and whole body BMD, assessed by DXA, were higher (p < or = 0.05 for all) for those with diabetes. Hip BMD was higher in white men (0.99 +/- 0.14 versus 0.93 +/- 0.14 g/cm2, p < 0.001), black men (1.06 +/- 0.17 versus 1.00 +/- 0.15 g/cm2, p < 0.001), white women (0.83 +/- 0.13 versus 0.76 +/- 0.13 g/cm2, p < 0.001), and black women (0.90 +/- 0.15 versus 0.85 +/- 0.15 g/cm2, p < 0.001) with diabetes compared with those without diabetes, although the relationship was attenuated by body composition. In multiple regression models, diabetes was an independent predictor of higher hip, whole body, and volumetric spine BMD in all participants (p < or = 0.001), but lower spine volume (p = 0.01) and higher hip BMD for each race-gender group (p < or = 0.01). Type 2 diabetes was associated with a 4-5% higher total hip BMD in all race-gender groups of elderly adults, independent of body composition and fasting insulin levels.