Relations between bone status and glucose metabolism with progression of insulin resistance

Suboptimal bone microarchitecure in adolescent girls with obesity compared to normal-weight controls and girls with anorexia nervosa

BACKGROUND

Despite their higher areal bone mineral density (aBMD), adolescents with obesity (OB) have an increase in fracture risk, particularly of the extremities, compared with normal-weight controls. Whereas bone parameters that increase fracture risk are well characterized in anorexia nervosa (AN), the other end of nutritional spectrum, these data are lacking in adolescents with obesity.

OBJECTIVE

Our objective was to compare bone parameters in adolescent girls across the nutritional spectrum, to determine whether suboptimal bone adaptation to increased body weight may explain the increased fracture risk in OB.

METHODS

We assessed bone endpoints in 153 adolescent girls 14-21 years old: 50 OB, 48 controls and 55 AN. We used (i) DXA to assess aBMD at the lumbar spine, proximal femur and whole body, and body composition, (ii) high resolution peripheral quantitative CT (HRpQCT) to assess bone geometry, microarchitecture and volumetric BMD (vBMD), and (iii) finite element analysis to assess failure load (a strength estimate) at the distal radius and tibia. All aBMD, microarchitecture and FEA analyses were controlled for age and race.

RESULTS

Groups did not differ for age or height. Areal BMD Z-scores at all sites were highest in OB, intermediate in controls and lowest in AN (p < 0.0001). At the radius, cortical area and thickness were higher in OB compared to AN and control groups (p = 0.001) while trabecular area did not differ across groups. Compared to controls, OB had higher cortical porosity (p = 0.003), higher trabecular thickness (p = 0.024), and higher total, cortical and trabecular vBMD and rod BV/TV (p < 0.04). Plate BV/TV did not differ in OB vs. controls, but was higher than in AN (p = 0.001). At the tibia, total, cortical, and trabecular area and cortical thickness were higher in OB vs. controls and AN (p < 0.005). OB also had higher cortical porosity (p < 0.007) and lower trabecular thickness (p < 0.02) than the other two groups. Trabecular number, total and trabecular vBMD, and rod BV/TV were higher in OB vs. controls and AN (p < 0.02), while cortical vBMD and plate BV/TV did not differ in OB vs. the other two groups. Finally, failure load (a strength estimate) was higher in OB at the radius and tibia compared to controls and AN (p < 0.004 for all). However, after adjusting for body weight, failure load was lower in OB vs. controls at both sites (p < 0.05), and lower than in AN at the distal tibia.

CONCLUSION

Not all bone parameters demonstrate appropriate adaptation to higher body weight. Cortical porosity and plate BV/TV at the radius and tibia, and cortical vBMD and trabecular thickness at the tibia are particularly at risk. These effects may contribute to the higher risk for fracture reported in OB vs. controls.

Association between site-specific bone mineral density and glucose homeostasis and anthropometric traits in healthy men and women

OBJECTIVE

Patients with type 2 diabetes mellitus have an increased risk of fracture despite normal or increased bone mineral density (BMD). Studies on the relationship of glucose homeostasis with BMD phenotypes have been inconclusive because distinguishing the roles of insulin resistance and hyperglycaemia in bone remodelling is challenging. In this study, we sought to define the relationship of site-specific BMD with glucose homeostasis traits and anthropometric traits.

DESIGN/PATIENTS/MEASUREMENTS

In a cross-sectional study, we examined 787 subjects from the Mexican-American Coronary Artery Disease (MACAD) cohort who had undergone euglycaemic-hyperinsulinaemic clamps, oral glucose tolerance testing and dual X-ray absorptiometry. Glucose homeostasis traits included insulinogenic index (IGI30), insulin sensitivity (M value), insulin clearance (MCRI), fasting insulin, fasting glucose and 2-hour glucose. Univariate and multivariate analyses were performed to assess the association of glucose homeostasis and anthropometric traits with site-specific BMD.

RESULTS

Two-hour glucose was negatively associated with arm BMD in women, which remained significant in multivariate analysis (β = -.15, P = .0015). Positive correlations between fasting insulin and BMD at weight-bearing sites, including pelvis (β = .22, P < .0001) and legs (β = .17, P = .001) in women and pelvis (β = .33, P < .0001) in men, lost significance after multivariate adjustment. Lean mass exhibited strong independent positive associations with BMD at multiple sites in both sexes.

CONCLUSION

Our findings suggest that (i) anabolic effects of insulin might work via mechanical loading from lean mass; (ii) a direct negative effect of increasing glucose might be more prominent at cortical-bone-rich sites in women; and (iii) lean mass is a strong positive predictor of bone mass.

Insulin resistance in type 2 diabetes mellitus may be related to bone mineral density

The mechanism of bone mineral density (BMD) changes in type 2 diabetes mellitus is not clear. We aimed to investigate the effect of insulin resistance in type 2 diabetics on BMD. Insulin resistance was determined using the homeostasis model assessment index (HOMA-IR). Nineteen type 2 diabetic patients with a HOMA-IR <2.7 (mean age, 51.5±9.6yr; body mass index [BMI], 27.3±5.1kg/m(2); duration of diabetes, 10.5±7.3yr) were included in Group A, and 30 BMI- and age-matched type 2 diabetic patients with a HOMA-IR ≥2.7 were included in Group B. The BMD was measured with dual-energy X-ray absorptiometry. Independent t-test was used for statistical analysis. The Group A values for mean fasting glucose and insulin levels were 160.1±77.0mg/dL and 4.79±2.89μU/L, respectively, whereas the Group B values were 195.1±58.9mg/dL (p>0.05) and 19.30±16.89μU/L (p=0.0001). Significantly higher total lumbar vertebra T-score (p=0.02) and total lumbar vertebra BMD in Group A were determined than Group B (p=0.033). The lumbar vertebra total Z-score was significantly lower in Group B (p=0.042). Marked insulin resistance may have a negative effect on BMD in type 2 diabetics, while the presence of hyperinsulinemia may be associated with the low BMD.

Association between bone mineral density and type 2 diabetes mellitus: a meta-analysis of observational studies

Type 2 diabetes mellitus (T2DM) influences bone metabolism, but the relation of T2DM with bone mineral density (BMD) remains inconsistent across studies. The objective of this study was to perform a meta-analysis and meta-regression of the literature to estimate the difference in BMD (g/cm²) between diabetic and non-diabetic populations, and to investigate potential underlying mechanisms. A literature search was performed in PubMed and Ovid extracting data from articles prior to May 2010. Eligible studies were those where the association between T2DM and BMD measured by dual energy X-ray absorptiometry was evaluated using a cross-sectional, cohort or case–control design, including both healthy controls and subjects with T2DM. The analysis was done on 15 observational studies (3,437 diabetics and 19,139 controls). Meta-analysis showed that BMD in diabetics was significantly higher, with pooled mean differences of 0.04 (95% CI: 0.02, 0.05) at the femoral neck, 0.06 (95% CI: 0.04, 0.08) at the hip and 0.06 (95% CI: 0.04, 0.07) at the spine. The differences for forearm BMD were not significantly different between diabetics and non-diabetics. Sex-stratified analyses showed similar results in both genders. Substantial heterogeneity was found to originate from differences in study design and possibly diabetes definition. Also, by applying meta-regression we could establish that younger age, male gender, higher body mass index and higher HbA_1C were positively associated with higher BMD levels in diabetic individuals. We conclude that individuals with T2DM from both genders have higher BMD levels, but that multiple factors influence BMD in individuals with T2DM.

Association between bone mineral density and type 2 diabetes mellitus: a meta-analysis of observational studies

Type 2 diabetes mellitus (T2DM) influences bone metabolism, but the relation of T2DM with bone mineral density (BMD) remains inconsistent across studies. The objective of this study was to perform a meta-analysis and meta-regression of the literature to estimate the difference in BMD (g/cm(2)) between diabetic and non-diabetic populations, and to investigate potential underlying mechanisms. A literature search was performed in PubMed and Ovid extracting data from articles prior to May 2010. Eligible studies were those where the association between T2DM and BMD measured by dual energy X-ray absorptiometry was evaluated using a cross-sectional, cohort or case-control design, including both healthy controls and subjects with T2DM. The analysis was done on 15 observational studies (3,437 diabetics and 19,139 controls). Meta-analysis showed that BMD in diabetics was significantly higher, with pooled mean differences of 0.04 (95% CI: 0.02, 0.05) at the femoral neck, 0.06 (95% CI: 0.04, 0.08) at the hip and 0.06 (95% CI: 0.04, 0.07) at the spine. The differences for forearm BMD were not significantly different between diabetics and non-diabetics. Sex-stratified analyses showed similar results in both genders. Substantial heterogeneity was found to originate from differences in study design and possibly diabetes definition. Also, by applying meta-regression we could establish that younger age, male gender, higher body mass index and higher HbA(1C) were positively associated with higher BMD levels in diabetic individuals. We conclude that individuals with T2DM from both genders have higher BMD levels, but that multiple factors influence BMD in individuals with T2DM.

Association between bone mineral density and type 2 diabetes mellitus: a meta-analysis of observational studies

Type 2 diabetes mellitus (T2DM) influences bone metabolism, but the relation of T2DM with bone mineral density (BMD) remains inconsistent across studies. The objective of this study was to perform a meta-analysis and meta-regression of the literature to estimate the difference in BMD (g/cm(2)) between diabetic and non-diabetic populations, and to investigate potential underlying mechanisms. A literature search was performed in PubMed and Ovid extracting data from articles prior to May 2010. Eligible studies were those where the association between T2DM and BMD measured by dual energy X-ray absorptiometry was evaluated using a cross-sectional, cohort or case-control design, including both healthy controls and subjects with T2DM. The analysis was done on 15 observational studies (3,437 diabetics and 19,139 controls). Meta-analysis showed that BMD in diabetics was significantly higher, with pooled mean differences of 0.04 (95% CI: 0.02, 0.05) at the femoral neck, 0.06 (95% CI: 0.04, 0.08) at the hip and 0.06 (95% CI: 0.04, 0.07) at the spine. The differences for forearm BMD were not significantly different between diabetics and non-diabetics. Sex-stratified analyses showed similar results in both genders. Substantial heterogeneity was found to originate from differences in study design and possibly diabetes definition. Also, by applying meta-regression we could establish that younger age, male gender, higher body mass index and higher HbA(1C) were positively associated with higher BMD levels in diabetic individuals. We conclude that individuals with T2DM from both genders have higher BMD levels, but that multiple factors influence BMD in individuals with T2DM.

Serum adiponectin in elderly men does not correlate with fracture risk

CONTEXT

Recent evidence suggests that adiponectin may play a role in bone metabolism, but studies of the correlation between serum adiponectin and bone mineral density (BMD) have given conflicting results, and the impact on fracture risk is unknown.

OBJECTIVE

Our objective was to investigate the association between serum adiponectin levels and BMD and fracture risk. DESIGN, SETTING, PARTICIPANTS, MAIN OUTCOME MEASURES: We used regression analyses to estimate the relationship between adiponectin and BMD in the Prospective Investigation of the Vasculature in Uppsala Seniors cohort of 441 men and 457 women aged 70 yr. The association was thereafter analyzed in the Uppsala Longitudinal Study of Adult Men (ULSAM), in which adiponectin was analyzed at age 70 yr and BMD at 82 yr in 507 men. Fractures in the ULSAM were documented in 314 men during 15 yr follow-up. Cox regression analysis was used to determine the risk of fracture according to serum adiponectin levels.

RESULTS

In multivariable analysis a negative association between adiponectin and BMD was found in both cohorts. When individuals in the highest quintile of adiponectin were compared with those in the lowest quintile, adjusted BMD was 9.7% lower at the lumbar spine, 7.1% lower at the proximal femur, and 5.2% lower for total body in the Prospective Investigation of the Vasculature in Uppsala Seniors (P < 0.001 for all three), and 8.1, 5.1, and 4.1% (P < 0.003 for all three), respectively, in the ULSAM. However, the hazard ratio for fracture per 1 sd of serum adiponectin was 0.99 (95% confidence interval 0.89-1.11).

CONCLUSION

Although adiponectin was a negative determinant of BMD in two independent cohorts, it was not associated with fracture risk in men.

[Diabetes mellitus--a risk factor for the development of osteoporosis]

<zakljucak> Osteoporoza je vazan zdravstveni problem. Prisutan je kod svake trece zene u postmenopauzi i povezuje se sa znacajnim morbiditetom i mortalitetom. Zene sa dijabetesom u postmenopauzi imaju povecan rizik od preloma kuka nego zene koje nisu dijabeticari, tako da strategija prevencije osteoporoze kod svih bolesnika sa dijabetesom ima smisla, narocito kod zena obolelih od dijabetesa. Dokazi da populacija starih sa dijabetesom ima povecan rizik od fraktura kosti daju novi podsticaj za dalja istrazivanja fokusirana na kost i dijabetes. Ona bi trebala da razjasne uticaj razlicitih aspekata dijabetesnog metabolizma, poboljsanja kontrole glikemije i uticaja lecenja dijabetesa na kosti. Odredjivanje (procena) kvaliteta kosti ukljucivala bi standarde merenja BMD, kao i razvoj novih pristupa merenju glikoziliranog kolagena. Bolje shvatanje i sagledavanje uticaja dijabetesa na kost povecava mogucnost ocuvanja kosti i preveniranja pojave fraktura kod osoba sa dijabetesom. Takodje, neophodno je ustanoviti optimalni izbor ispitivanih biohemijskih markera i napraviti standardizaciju merenja kostane mase kod obolelih od dijabetesa. U klinickoj praksi pristup bolesniku sa dijabetesnom osteopatijom trebalo bi da bude individualan, prema stanju promena i profilu rizika, a da dijagnostikovanje i terapijski postupci postanu rutina.