Long-term bone loss in insulin-dependent diabetic patients with microvascular complications

Reduction of the trans-cortical vessel was associated with bone loss, another underlying mechanism of osteoporosis

RATIONALE

Numerous studies have established a robust association between bone morrow microvascular diseases and osteoporosis. This study sought to investigate the relationship between alterations in trans-cortical vessel (TCVs) and the onset of osteoporosis in various mouse models.

METHODS

Aged mice, ovariectomized mice, and db/db mice, were utilized as osteoporosis models. TCVs in the tibia were detected using tissue clearing and light sheet fluorescence microscopy imaging. Femurs bone mass were analyzed using micro-CT scanning. Correlations between the number of TCVs and bone mass were analyzed using Pearson correlation analysis.

RESULTS

All osteoporosis mouse models showed a significant reduction in the number of TCVs compared to the control group. Correlation analysis revealed a positive association between the number of TCVs and bone mass. TCVs were also expressed high levels of CD31 and EMCN proteins as type H vessels.

CONCLUSIONS

This study underscores a consistent correlation between the number of TCVs and bone mass. Moreover, TCVs may serve as a potential biomarker for bone mass evaluation.

Fracture patterns in adult onset type 1 diabetes and associated risk factors - A nationwide cohort study

OBJECTIVE

This study aimed to determine the hazard ratios (HR) for various fracture sites and identify associated risk factors in a cohort of relatively healthy adult people with newly diagnosed type 1 diabetes (T1D).

METHODS

The study utilized data from the UK Clinical Practice Research Datalink GOLD (1987-2017). Participants included people aged 20 and above with a T1D diagnosis code (n = 3281) and a new prescription for insulin. Controls without diabetes were matched based on sex, year of birth, and practice. Cox regression analysis was conducted to estimate HRs for any fracture, major osteoporotic fractures (MOFs), and peripheral fractures (lower-arm and lower-leg) in people with T1D compared to controls. Risk factors for T1D were examined and included sex, age, diabetic complications, medication usage, Charlson comorbidity index (CCI), hypoglycemia, previous fractures, falls, and alcohol consumption. Furthermore, T1D was stratified by duration of disease and presence of microvascular complications.

RESULTS

The proportion of any fracture was higher in T1D (10.8 %) than controls (7.3). Fully adjusted HRs for any fracture (HR: 1.43, CI95%: 1.17-1.74), MOFs (HR: 1.46, CI95%: 1.04-2.05), and lower-leg fractures (HR: 1.37, CI95%: 1.01-1.85) were statistically significantly increased in people with T1D compared to controls. The primary risk factor across all fracture sites in T1D was a previous fracture. Additional risk factors at different sites included previous falls (HR: 1.64, CI95%: 1.17-2.31), antidepressant use (HR: 1.34, CI95%: 1.02-1.76), and anxiolytic use (HR: 1.54, CI95%: 1.08-2.29) for any fracture; being female (HR: 1.65, CI95%: 1.14-2.38) for MOFs; the presence of retinopathy (HR: 1.47, CI95%: 1.02-2.11) and previous falls (HR: 2.04, CI95%: 1.16-3.59) for lower-arm and lower-leg fractures, respectively. Lipid-lowering medication use decreased the risk of MOFs (HR: 0.66, CI95%: 0.44-0.99). Stratification of T1D by disease duration showed that the relative risk of any fracture in T1D did not increase with longer diabetes duration (0-4 years: HR: 1.52, CI95%: 1.23-1.87; 5-9 years: HR: 1.30, CI95%: 0.99-1.71; <10 years: HR: 1.07, CI95%: 0.74-1.55). Similar patterns were observed for other fracture sites. Moreover, the occurrence of microvascular complications in T1D was linked to a heightened risk of fractures in comparison to controls. However, when considering the T1D cohort independently, the association was not statistically significant.

CONCLUSION

In a cohort of relatively healthy and newly diagnosed people with T1D HRs for any fracture, MOFs, and lower-leg fractures compared to controls were increased. A previous fracture was the most consistent risk factor for a subsequent fracture, whereas retinopathy was the only diabetes related one. We postulate a potential initial fracture risk, succeeded by a subsequent risk reduction, which might potentially increase in later years due to the accumulation of complications and other factors.

Childhood type 1 diabetes is associated with abnormal bone development

OBJECTIVE

To describe bone mineral density (BMD), bone structure, and fracture prevalence in adolescents with type 1 diabetes (T1D) and explore their associations with glycemic control and microvascular complications.

RESEARCH DESIGN AND METHODS

Cross sectional study of 64 adolescents (38 males) with T1D duration >10 years who underwent dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), fracture survey, plantar fascia thickness, and microvascular complications assessment.

RESULTS

Mean age was 16.6 ± 2.1 years, diabetes duration 12.8 ± 2.2 years and HbA1c 8.9 ± 1.7% (74 mmol/mol). Fracture prevalence was 50%. DXA areal BMD (Z-score) was reduced for femoral neck (-0.5 ± 1.3, p = 0.008) and arm (-0.4 ± 1.0, p < 0.001), while total areal BMD and lumbar spine BMD were normal. In pQCT (Z-score), trabecular volumetric BMD (vBMD) was reduced for tibia (-0.4 ± 0.8, p < 0.001) and radius (-0.8 ± 1.4, p < 0.001) whereas cortical vBMD was increased at both sites (tibia: 0.5 ± 0.6, p < 0.001, radius: 0.7 ± 1.5, p < 0.001). Muscle cross-sectional area (CSA) was reduced for upper (-0.6 ± 1.2, p < 0.001) and lower (-0.4 ± 0.7, p < 0.001) limbs. DXA total areal BMD was positively correlated with BMI (p < 0.01) and age at T1D diagnosis (p = 0.04). Lower radial bone CSA, total and lumbar spine BMD were associated with autonomic nerve dysfunction. HbA1c, diabetes duration, fracture history and other microvascular complications were not significantly associated with bone parameters.

CONCLUSIONS

Adolescents with childhood-onset T1D have site-specific bone deficits in upper and lower limbs but normal total and lumbar spine BMD. T1D appears to have differential effects on trabecular and cortical bone compartments. Future longitudinal analysis is warranted to examine whether these changes translate in to increased fracture risk.

Associations of insulin resistance and insulin secretion with bone mineral density and osteoporosis in a general population

We investigated the associations of insulin resistance and β-cell secretion with bone mineral density (BMD) and osteoporosis using data from the National Health and Nutrition Examination Survey. Data on BMD assessed using dual-energy x-ray absorptiometry from 5292 participants were analyzed. Insulin resistance and β-cell secretion were assessed using the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and β-cell function (HOMA-β), respectively. We divided the study population into four groups according to HOMA-IR (<2 vs. ≥ 2) and HOMA-β (<100 vs. ≥ 100). BMD and T score at the lumbar spine, hip joint, and femur were used for analyses. Osteoporosis was defined as a T score ≤ -2.5. Logistic regression analyses were conducted to examine the associations of HOMA-IR and HOMA-β with osteoporosis, and the joint effects of HOMA-IR and HOMA-β on osteoporosis. We found a positive association between HOMA-IR and osteoporosis in participants with a HOMA-β ≥ 100 (OR 8.773, 95% CI 2.160-35.637, p=0.002 at the femoral neck). A negative association between HOMA-β and osteoporosis was noted in those with a HOMA-IR <2 (OR 0.183, 95% CI 0.038-0.882, p=0.034 at the femoral neck). Compared with participants who had HOMA-IR <2 and HOMA-β <100, those with HOMA-IR <2 and HOMA-β ≥ 100 had a lower risk of osteoporosis (OR 0.126, 95% CI 0.020-0.805, p=0.032 at the femoral neck). In conclusion, the association between HOMA-β and BMD/osteoporosis changed as HOMA-IR increased. HOMA-β was negatively associated with osteoporosis when HOMA-IR <2. The association was not significant when HOMA-IR ≥ 2.

Are diabetes microvascular complications risk factors for fragility fracture?

PURPOSE OF REVIEW

We describe relationships between microvascular complications and bone fragility fracture in the context of diabetes. We highlight gaps in knowledge and suggest areas of further study.

RECENT FINDINGS

Evidence in type 1 diabetes (T1D) demonstrates that low bone mineral density (BMD) is associated with microvascular complications and linked to increased fracture risk. Of note, the low BMD does not solely explain bone fragility. Microvascular disease also has been linked to compromised bone microarchitecture and poorer bone quality. Moreover, microvascular complications may indirectly increase the rate of fragility fracture through increasing fall propensity; however, to date no conclusive studies have assessed microvascular disease and fracture risk independent of falls.In the other hand, individuals with type 2 diabetes (T2D) have increased fracture risk despite high BMD. Data suggest microvascular disease mediates microarchitectural changes by increasing cortical porosity and is associated with lower bone turnover. There is no direct evidence linking microangiopathy to fracture incidence.

SUMMARY

Taken together present evidence suggests associations between diabetic bone disease, fragility fracture, and microvascular disease. Data are more convincing for T1D than T2D. Further studies are required to confirm whether microvascular disease is itself causative of fracture or merely a contributory factor to fragility fracture for persons with diabetes.

Bone turnover markers in children and adolescents with type 1 diabetes-A systematic review

Type 1 diabetes (T1D) is associated with impaired bone health and both osteocalcin (OCN) and procollagen type 1 amino terminal propetide (P1NP) (markers of bone formation) and C-terminal cross-linked telopeptide (CTX) (marker of bone resorption) are decreased in adult patients with T1D. We review the existing literature characterizing these bone turnover markers in children and adolescents with T1D and by meta-analysis examine whether alterations in OCN, P1NP, and CTX are evident and if potential changes correlate to the metabolic control (hemoglobin A1c, HbA1c). Systematic searches at MEDLINE and EMBASE were conducted in January 2018 identifying all studies describing OCN, P1NP, or CTX in children and adolescents with T1D. A total of 26 studies were included, representing data from more than 1000 patients with T1D. Pooled analyses of standard mean difference and summary effects analysis were performed when sufficient data were available. Pooled analysis revealed mean OCN to be significantly lower in children and adolescents with T1D compared to healthy controls (standard mean difference: -1.87, 95% confidence interval, CI: -2.83; -0.91) whereas both P1NP and CTX did not differ from the controls. Only data on OCN was sufficient to make pooled correlation analysis revealing a negative correlation between OCN and HbA1c (-0.31 95% CI: -0.45; -0.16). In conclusion, OCN is decreased in children and adolescents with T1D, whether CTX and P1NP are affected as well is unclear, due to very limited data available. New and large studies including OCN, P1NP, and CTX (preferably as z-scores adjusting for age variability) is needed to further elucidate the status of bone turnover in children and adolescents with T1D.

Association Between Glycemic Control and Risk of Fracture in Diabetic Patients: A Nested Case-Control Study

CONTEXT

Diabetes mellitus (DM) has been associated with an increased risk of fractures. However, the effect of glycemic control on the risk of fracture is not well understood.

OBJECTIVE

To evaluate the association between glycemic control and the risk of low-trauma fractures in patients with type 1 DM (T1DM) and type 2 DM (T2DM).

DESIGN

Nested case-control analysis.

SETTING

UK-based Clinical Practice Research Datalink.

PATIENTS OR OTHER PARTICIPANTS

The study population was patients whose T1DM or T2DM had been newly diagnosed between 1995 and 2015. The cases were patients with a low-trauma fracture after DM onset. We matched four controls to each case by age, sex, general practice, fracture date, and DM type and duration.

STATISTICAL ANALYSIS

Conditional logistic regression analyses were performed, adjusted for covariates, including body mass index, smoking, DM complications and medications.

RESULTS

The study population included 3329 patients with T1DM and 44,275 patients with T2DM. The median duration between DM onset and fracture date was 4.5 years for both T1DM and T2DM. The risk of fracture was increased in the patients with T1DM with a mean hemoglobin A1c >8.0% (adjusted OR, 1.39; 95% CI, 1.06 to 1.83) compared with those patients with T1DM and a mean hemoglobin A1c ≤7.0%. No such effect was found in the patients with T2DM. Independently of glycemic control, the risk of fracture was elevated in patients with T2DM and the current use of rosiglitazone and pioglitazone.

CONCLUSIONS

The effect of glycemic control on the risk of low-trauma fracture differs between patients with T1DM and T2DM. Poor glycemic control increased the risk of fractures in patients with T1DM but not in those with T2DM.

Cardiovascular autonomic neuropathy and bone metabolism in Type 1 diabetes

AIM

To investigate the association between cardiovascular autonomic neuropathy and bone metabolism in people with Type 1 diabetes.

METHODS

We assessed cardiovascular autonomic neuropathy in 329 people with Type 1 diabetes according to heart rate response to deep breathing, to standing and to the Valsalva manoeuvre, and 2-min resting heart rate. More than one pathological non-resting test was defined as cardiovascular autonomic neuropathy. Bone mineral density of the femoral neck (BMDfn) was assessed by dual energy X-ray absorptiometry. Serum parathyroid hormone levels and other bone markers were measured.

RESULTS

The mean (sd) age of the participants was 55.6 (9.4) years, 52% were men, and the mean (sd) diabetes duration was 40 (8.9) years, HbA_1c 62 (9) mmol/mol and estimated GFR 78 (26) ml/min/1.73m² . In all, 36% had cardiovascular autonomic neuropathy. Participants with cardiovascular autonomic neuropathy had 4.2% (95% CI -8.0 to -0.2; P=0.038) lower BMDfn and 33.6% (95% CI 14.3 to 53.8; P=0.0002) higher parathyroid hormone levels compared with participants without cardiovascular autonomic neuropathy in adjusted models. Higher resting heart rate remained associated with higher parathyroid hormone level and lower BMDfn after additional adjustment for eGFR (P<0.0001 and P = 0.042, respectively).

CONCLUSIONS

The presence of cardiovascular autonomic neuropathy was associated with reduced BMDfn and increased levels of parathyroid hormone. Kidney function may either confound or mediate these findings. Cardiovascular autonomic neuropathy could be associated with increased risk of osteoporosis in Type 1 diabetes. Whether cardiovascular autonomic neuropathy directly affects bone metabolism detrimentally or if this association is mediated via decreased kidney function should be investigated further.

Bone disease in diabetes: another manifestation of microvascular disease?

Type 1 and type 2 diabetes are generally accepted to be associated with increased bone fracture risk. However, the pathophysiological mechanisms of diabetic bone disease are poorly understood, and whether the associated increased skeletal fragility is a comorbidity or a complication of diabetes remains under debate. Although there is some indication of a direct deleterious effect of microangiopathy on bone, the evidence is open to question, and whether diabetic osteopathy can be classified as a chronic, microvascular complication of diabetes remains uncertain. Here, we review the current knowledge of potential contributory factors to diabetic bone disease, particularly the association between diabetic microangiopathy and bone mineral density, bone structure, and bone turnover. Additionally, we discuss and propose a pathophysiological model of the effects of diabetic microvascular disease on bone, and examine the progression of bone disease alongside the evolution of diabetes.

Diabetes and Bone Disease

The World Health Organization estimates that diabetes mellitus occurs in more than 415 million people; this number could double by the year 2040. Epidemiologic data have shown that the skeletal system may be a target of diabetes-mediated damage, leading to the development of diabetes-induced osteoporosis. T1D and T2D have been associated with an increased risk of fracture. Bone mineral density and fracture risk prediction tools developed for the general population capture some of the risk associated with diabetes. Recent adaptations to these tools have improved their efficacy in patients with diabetes.

Low-level laser therapy associated to a resistance training protocol on bone tissue in diabetic rats

Objective

The present study aimed to evaluate the in vivo response of a resistance training and low-level laser therapy (LLLT) on tibias and femurs of rats with diabetes mellitus (DM).

Materials and methods

Forty male Wistar rats were randomly distributed into four experimental groups: control group (CG), diabetic group (DG), diabetic trained group (TG) and diabetic trained and laser irradiated group (TLG). DM was induced by streptozotocin (STZ) and after two weeks laser and resistance training started, performed for 24 sessions, during eight weeks. At the end of the experiment, animals were euthanized and tibias and femurs were removed for analysis. Histological, histomorphometrical, immunohistochemistry and mechanical analyses were performed.

Results

Trained groups, with or without laser irradiation, showed increased cortical area, bone density and biomechanical properties. The immunohistochemical analysis revealed that TG and TLG demonstrated an increased RUNX2 expression. RANK-L immunoexpression was similar for all experimental groups.

Conclusion

In conclusion, it can be suggested that the resistance exercise program stimulated bone metabolism, culminating in increased cortical tibial area, bone mineral content, bone mineral density and biomechanical properties. Furthermore, the association of physical exercises and LLLT produced higher values for bone mineral content and stiffness. Consequently, these data highlight the potential of physical exercise in the management of bone loss due to DM and the possible extra osteogenic stimulus offered by lasertherapy. Further long-term studies should be carried out to provide additional information.

Bilateral Calcaneal Avulsion Fracture Complicated with a Delayed Achilles Tendon Rupture in a Patient with Diabetes: A Case Report

CASE

A sixty-five-year-old man with diabetes mellitus had bilateral calcaneal avulsion fracture without a history of trauma. Both fractures were treated surgically with modified tension-band wiring, cerclage wiring, and screws. Six months after the surgery on the left side, the patient had a left Achilles tendon rupture proximal to its insertion into the calcaneus.

CONCLUSION

Calcaneal avulsion fractures are rare but often have complications. Even if these fractures are managed by well-established treatment methods, an unanticipated complication, namely a delayed Achilles tendon rupture, can occur in patients with diabetes.

The alliance of mesenchymal stem cells, bone, and diabetes

Bone fragility has emerged as a new complication of diabetes. Several mechanisms in diabetes may influence bone homeostasis by impairing the action between osteoblasts, osteoclasts, and osteocytes and/or changing the structural properties of the bone tissue. Some of these mechanisms can potentially alter the fate of mesenchymal stem cells, the initial precursor of the osteoblast. In this review, we describe the main factors that impair bone health in diabetic patients and their clinical impact.

The effects of low-level laser irradiation on bone tissue in diabetic rats

Diabetes mellitus (DM) leads to a decrease in bone mass and increase the risk of osteoporosis and in this context, many treatments have shown to accelerate bone metabolism. It seems that low-level laser therapy (LLLT) is able of stimulating osteoblast activity and produced increased biomechanical properties. However, its effects on bone in diabetic rats are not fully elucidated. The aim of this study was to evaluate the effects of LLLT on bone formation, immunoexpression of osteogenic factors, biomechanical properties and densitometric parameters in diabetic rats. Thirty male Wistar rats were randomly distributed into three experimental groups: control group, diabetic group, and laser-treated diabetic group. DM was induced by streptozotocin (STZ) and after 1 week laser treatment started. An 830-nm laser was used, performed for 18 sessions, during 6 weeks. At the end of the experiment, animals were euthanized and tibias and femurs were defleshed for analysis. Extensive resorptive areas as a result of osteoclasts activity were noticed in DG when compared to control. Laser-treated animals showed an increased cortical area. The immunohistochemical analysis revealed that LLLT produced an increased RUNX-2 expression compared to other groups. Similar RANK-L immunoexpression was observed for all experimental groups. In addition, laser irradiation produced a statistically increase in fracture force, bone mineral content (BMC) and bone mineral density compared to DG. The results of this study indicate that the STZ model was efficient in inducing DM 1 and producing a decrease in cortical diameter, biomechanical properties and in densitometric variables. In addition, it seems that LLLT stimulated bone metabolism, decreased resorptive areas, increased RUNX-2 expression, cortical area, fracture force, BMD, and BMC. Further studies should be developed to provide additional information concerning the mechanisms of action of laser therapy in diabetic bone in experimental and clinical trials.

Serum vitamin D levels are lower in Australian children and adolescents with type 1 diabetes than in children without diabetes

Vitamin D is synthesised in the skin through the action of UVB radiation (sunlight), and 25-hydroxy vitamin D (25OHD) measured in serum as a marker of vitamin D status. Several studies, mostly conducted in high latitudes, have shown an association between type 1 diabetes mellitus (T1DM) and low serum 25OHD. We conducted a case-control study to determine whether, in a sub-tropical environment with abundant sunlight (latitude 27.5°S), children with T1DM have lower serum vitamin D than children without diabetes. Fifty-six children with T1DM (14 newly diagnosed) and 46 unrelated control children participated in the study. Serum 25OHD, 1,25-dihydroxy vitamin D (1,25(OH)(2) D) and selected biochemical indices were measured. Vitamin D receptor (VDR) polymorphisms Taq1, Fok1, and Apa1 were genotyped. Fitzpatrick skin classification, self-reported daily hours of outdoor exposure, and mean UV index over the 35 d prior to blood collection were recorded. Serum 25OHD was lower in children with T1DM (n = 56) than in controls (n = 46) [mean (95%CI) = 78.7 (71.8-85.6) nmol/L vs. 91.4 (83.5-98.7) nmol/L, p = 0.02]. T1DM children had lower self-reported outdoor exposure and mean UV exposure, but no significant difference in distribution of VDR polymorphisms. 25OHD remained lower in children with T1DM after covariate adjustment. Children newly diagnosed with T1DM had lower 1,25(OH)(2) D [median (IQR) = 89 (68-122) pmol/L] than controls [121 (108-159) pmol/L, p = 0.03], or children with established diabetes [137 (113-153) pmol/L, p = 0.01]. Children with T1DM have lower 25OHD than controls, even in an environment of abundant sunlight. Whether low vitamin D is a risk factor or consequence of T1DM is unknown.

Albuminuria and rapid loss of GFR and risk of new hip and pelvic fractures

BACKGROUND AND OBJECTIVES

The microvascular circulation plays an important role in bone health. This study examines whether albuminuria, a marker of renal microvascular disease, is associated with incident hip and pelvic fractures.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study reanalyzed data from the Ongoing Telmisartan Alone and in combination with Ramipril Global End Point Trial/Telmisartan Randomized Assessment Study in Angiotensin-Converting Enzyme Intolerant Subjects with Cardiovascular Disease trials, which examined the impact of renin angiotensin system blockade on cardiovascular outcomes (n=28,601). Albuminuria was defined as an albumin-to-creatinine ratio≥30 mg/g (n=4597). Cox proportional hazards models were used to determine the association of albuminuria with fracture risk adjusted for known risk factors for fractures, estimated GFR, and rapid decline in estimated GFR (≥5%/yr).

RESULTS

There were 276 hip and pelvic fractures during a mean of 4.6 years of follow-up. Participants with baseline albuminuria had a significantly increased risk of fracture compared with participants without albuminuria (unadjusted hazard ratio=1.62 [1.22, 2.15], P<0.001; adjusted hazard ratio=1.36 [1.01, 1.84], P=0.05). A dose-dependent relationship was observed, with macroalbuminuria having a large fracture risk (unadjusted hazard ratio=2.01 [1.21, 3.35], P=0.007; adjusted hazard ratio=1.71 [1.007, 2.91], P=0.05) and microalbuminuria associating with borderline or no statistical significance (unadjusted hazard ratio=1.52 [1.10, 2.09], P=0.01; adjusted hazard ratio=1.28 [0.92, 1.78], P=0.15). Estimated GFR was not a predictor of fracture in any model, but rapid loss of estimated GFR over the first 2 years of follow-up predicted subsequent fracture (adjusted hazard ratio=1.47 [1.05, 2.04], P=0.02).

CONCLUSIONS

Albuminuria, especially macroalbuminuria, and rapid decline of estimated GFR predict hip and pelvic fractures. These findings support a theoretical model of a relationship between underlying causes of microalbuminuria and bone disease.

Use of thiazolidinediones and risk of osteoporotic fracture: disease or drugs?

PURPOSE

Clinical and observational studies suggest that use of thiazolidinediones (TZDs) is associated with an increased fracture risk. In addition, type 2 diabetes mellitus (T2DM) is a risk factor for osteoporotic fracture. Our aim was to estimate fracture risks in TZD users and users of other antidiabetic drugs, classified according to proxies of disease severity.

METHODS

We conducted a population-based cohort study utilizing the Dutch PHARMO database (1998-2008). PHARMO links pharmacy-dispensing data to the National Hospital Registry. Oral antidiabetic users (n = 123,452) were matched 1:4 by year of birth and sex to non-users. Cox proportional hazards models were used to estimate hazard ratios (HRs) of fracture in TZD users. We created a proxy indicator for disease severity. The first stage was defined as current use of either a biguanide or a sulfonylureum, the second stage as current use of a biguanide and a sulfonylureum at the same time, the third stage was assigned to patients using TZDs and the fourth stage to patients using insulin.

RESULTS

The risk of osteoporotic fracture was increased 1.5-fold (HR 1.49, 95%CI 1.28-1.73) in patients who currently used TZDs (stage 3), and for patients using insulin (stage 4), the risk was increased 1.2-fold (HR 1.24, 1.14-1.36), as compared with controls. In the first and second stages, risks were lower: HR 1.11 (1.06-1.17) for stage 1 and HR 1.03 (0.96-1.11) for stage 2.

CONCLUSIONS

When observational studies assess risk of fracture in patients with TZDs, the severity of T2DM should be taken into account.

Review: The diabetic bone: a cellular and molecular perspective

With the increasing worldwide prevalence of diabetes the resulting complications, their consequences and treatment will lead to a greater social and financial burden on society. One of the many organs to be affected is bone. Loss of bone is observed in type 1 diabetes, in extreme cases mirroring osteoporosis, thus a greater risk of fracture. In the case of type 2 diabetes, both a loss and an increase of bone has been observed, although in both cases the quality of the bone overall was poorer, again leading to a greater risk of fracture. Once a fracture has occurred, healing is delayed in diabetes, including nonunion. The reasons leading to such changes in the state of the bone and fracture healing in diabetes is under investigation, including at the cellular and the molecular levels. In comparison with our knowledge of events in normal bone homeostasis and fracture healing, that for diabetes is much more limited, particularly in patients. However, progress is being made, especially with the use of animal models for both diabetes types. Identifying the molecular and cellular changes in the bone in diabetes and understanding how they arise will allow for targeted intervention to improve diabetic bone, thus helping to counter conditions such as Charcot foot as well as preventing fracture and accelerating healing when a fracture does occur.

Osteoporosis and risk of fracture in patients with diabetes: an update

Diabetes mellitus (DM) and osteoporotic fractures are two of the most important causes of mortality and morbidity in older subjects. Recent data report a close association between fragility fracture risk and DM of both type 1 (DM1) and type 2 (DM2). However, DM1 is associated with reduced bone mineral density (BMD), whereas patients with DM2 generally have normal or increased BMD. This apparent paradox may be explained by the fact that, at a given level of BMD, diabetic patients present lower bone quality with respect to non-diabetics, as shown by several studies reporting that diabetes may affect bone tissue by means of various mechanisms, including hyperinsulinemia, deposition of advanced glycosylation endproducts (AGEs) in collagen, reduced serum levels of IGF-1, hypercalciuria, renal failure, microangiopathy and inflammation. In addition, the propensity to fall and several comorbidities may further explain the higher fracture incidence in DM patients with respect to the general population. It is reasonable to expect that close metabolic control of diabetes may improve bone status, although its effect on reduction of fracture risk has not yet been demonstrated. However, metformin has a direct effect on bone tissue by reducing AGE accumulation, whereas insulin acts directly on osteoclast activity, and thiazolidinediones (TZD) may have a negative effect by switching mesenchymal progenitor cells to adipose rather than bone tissue. New prospects include the incretins, a class of antidiabetic drugs which may play a role linking nutrition and bone metabolism. Better knowledge on how diabetes and its treatments influence bone tissue may lie at the basis of effective prevention of bone fracture in diabetic patients. Thus, close glycemic control, adequate intake of calcium and vitamin D, screening for low BMD, and prevention and treatment of diabetic complications are key elements in the management of osteoporosis in both DM1 and DM2. Attention should be paid to treating diabetes with TZD in women with DM2, particularly if elderly. Lastly, patients with osteoporosis and diabetes should be offered the same pharmacological treatments as non-diabetics, although specific trials on the effects of anti-osteoporotic drugs in the diabetic population are lacking.

Enhanced excretion of vitamin D binding protein in type 1 diabetes: a role in vitamin D deficiency?

CONTEXT

Vitamin D deficiency is an increasingly recognized comorbidity in patients with both type 1 (T1D) and type 2 diabetes, particularly associated with the presence of diabetic nephropathy.

OBJECTIVE

Because we have previously reported enhanced excretion of megalin in the urine of T1D patients with microalbuminuria, we hypothesized that concurrent urinary loss of the megalin ligand, vitamin D binding protein, might contribute mechanistically to vitamin D deficiency.

DESIGN AND PARTICIPANTS

Examining a study cohort of 115 subjects with T1D, aged 14-40 yr, along with 55 age-matched healthy control subjects, we measured plasma and urine concentrations of vitamin D binding protein (VDBP) along with serum concentrations of total calcium, parathyroid hormone, 25-hydroxyvitamin D, and 1, 25-dihydroxyvitamin D; these results were compared between groups and investigated for relationships with metabolic control status or with albuminuria.

MAIN OUTCOME MEASURE

Between-group differences in urinary VDBP concentration were the main outcome measures.

RESULTS

A marked increase in the urinary excretion of VDBP was apparent in subjects with T1D, compared with control subjects. Using multivariate regression modeling, significant correlates of urinary VDBP excretion included microalbuminuria (P = 0.004), glycosylated hemoglobin (P = 0.010), continuous glucose monitoring system average capillary glucose (P = 0.047), and serum 1,25(OH)(2)D concentrations (P = 0.037). Vitamin D deficiency or insufficiency was slightly more prevalent in diabetic subjects with albuminuria, coincident with the increase in urine VDBP excretion.

CONCLUSIONS

These findings suggest that, theoretically, exaggerated urinary loss of VDBP in T1D, particularly in persons with albuminuria, could contribute mechanistically to vitamin D deficiency in this disease.

Autonomic nerve fiber function and bone mineral density in individuals with type 1 diabetes: a cross-sectional study

AIMS

Experimental models support a role for the sympathetic nervous system in bone metabolism. Beta-adrenoreceptors have been demonstrated on osteoblast-like cells. Beta-blocker use is associated with higher bone mineral density (BMD) in some epidemiologic studies. The aim of this study was to determine if measures of the autonomic nervous system (ANS) were associated with reduced BMD in type 1 diabetes.

METHODS

We studied 66 individuals with type 1 diabetes. Dual-energy X-ray absorptiometry was used to measure BMD and bone mineral content (BMC). Measures of heart rate variability (HRV) (e.g., power spectral analysis, mean circular resultant) and circulating norepinephrine levels were used to evaluate autonomic function.

RESULTS

BMD/BMC were examined by gender for individuals with a normal versus elevated low-frequency (LF) band (expressed in normalized units). No significant differences in BMD/BMC were shown for individuals with an elevated LF band. Direct-entry linear regression models with BMD/BMC as the dependent variable were performed. Duration, gender, BMI, HbA(1c), insulin dose/kg, activity energy expenditure, and measures of HRV were entered as potential independent variables. No measures of HRV, or norepinephrine, were independently associated with BMD/BMC.

CONCLUSIONS

The ANS, as assessed by measures of HRV, does not appear to impact BMD/BMC in type 1 diabetes.

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.

Diabetes and its complications and their relationship with risk of fractures in type 1 and 2 diabetes

This case-control study sought to assess the effects of diabetes and its complications on the risk of fractures. There were 124,655 fracture cases and 373,962 age- and sex-matched controls. The main exposure was diabetes and its complications, and the main confounders were use of insulin and oral antidiabetic agents, presence of cardiovascular disease, and use of drugs for cardiovascular disease, along with a number of other confounders. In the crude analysis, diabetes and all complications was associated with a statistically significantly increased overall risk of fractures. The increase in risk of fractures was higher in type 1 diabetes (T1D) than in type 2 diabetes (T2D). However, after adjustment for confounders, the difference between T1D and T2D disappeared, and only diabetic kidney disease in T1D retained a significantly increased risk of fractures. There was a time dependency in the risk of fractures with an early increase at <2.5 years after diagnosis. followed by a decrease to the level of the background population from 2.5 to 5 years after diagnosis, and a limited increase in T1D but not T2D at >5 years after diagnosis. We conclude that diabetes, whether T1D or T2D, seems to carry an increased risk of fractures, and complications to diabetes except for diabetic kidney disease add little to the overall risk of fracture, perhaps pointing at a common risk factor linked to the high blood glucose levels, which may weaken bone strength.

Lower bone mineral content in children with type 1 diabetes mellitus is linked to female sex, low insulin-like growth factor type I levels, and high insulin requirement

CONTEXT

Studies on bone mineral characteristics in children with type 1 diabetes mellitus (T1DM) have generated conflicting results.

OBJECTIVE

Our objective was to investigate bone mineral characteristics in children with T1DM and to analyze their associations with bone metabolism and the IGF-I system.

DESIGN

We recruited a cohort of Caucasian patients with T1DM for at least 3 yr and healthy children between January 2003 and June 2004.

SETTING

This was a university hospital-based study.

PARTICIPANTS

A total of 127 patients and 319 controls aged 6 to 20 yr participated.

METHODS

Dual-energy x-ray absorptiometry was performed in patients and controls. Serum bone alkaline phosphatase, CrossLaps, IGF-I, and IGF-binding protein 3 levels were determined in patients with values analyzed using our normative data from 1150 healthy children.

RESULTS

After adjustment for age, sex, pubertal stage, and body mass index sd score, total body bone mineral content (BMC)/lean body mass was significantly lower in patients than in controls (P < 0.04). This difference was a result of the differences between the girls of the two groups. Girls with T1DM had significantly lower lumbar spine and total body BMC than control girls (P = 0.002), whereas no such difference was observed in boys. Serum bone alkaline phosphatase level was significantly lower in girls than in boys (P = 0.04). Low serum IGF-I levels and the administration of large amounts of insulin were found to have independent deleterious effects on BMC for children of all ages and both sexes, whereas disease duration and glycosylated hemoglobin levels did not.

CONCLUSIONS

A sex-related difference in the impairment of bone mineral characteristics was identified in children with T1DM. Longitudinal studies are required to investigate whether boys may gain slightly less bone mass during skeletal growth.

Prospective study of diabetes and risk of hip fracture: the Nurses' Health Study

OBJECTIVE

The purpose of this study was to determine whether women with type 1 and type 2 diabetes are at higher risk of hip fractures.

RESEARCH DESIGN AND METHODS

A total of 109,983 women aged 34-59 years in 1980 were followed through 2002 for the occurrence of hip fracture. At baseline and through biennial follow-up, women were asked about their history and treatment of diabetes and other potential risk factors for hip fracture.

RESULTS

During 2.22 million person-years of follow-up, 1,398 women had a hip fracture. Compared with women without diabetes, the age-adjusted relative risk (RRs) of hip fracture was 7.1 (95% CI 4.4-11.4) for women with type 1 diabetes and 1.7 (1.4-2.0) for those with type 2 diabetes. After further adjustment for BMI, smoking, physical activity, menopausal status, daily intake of calcium, vitamin D, protein, and postmenopausal hormone use, the multivariate RR of incident hip fracture in individuals with type 1 diabetes compared with individuals without diabetes was 6.4 (3.9-10.3) and with type 2 diabetes was 2.2 (1.8-2.7). The RRs increased with longer duration of type 2 diabetes (3.1 [2.3-4.0] for >or=12 years compared with no diabetes, P for trend < 0.001) and ever use of insulin.

CONCLUSIONS

These data indicate that both type 1 and type 2 diabetes are associated with an increased risk of hip fracture. The results of this study highlight the need for fracture-prevention strategies in women with diabetes.

Elevated hip fracture risk in type 1 diabetic patients: a population-based cohort study in Sweden

OBJECTIVE

Patients with type 1 diabetes often have low bone mineral density, but epidemiological data on fracture risk are sparse and imprecise, particularly for men.

RESEARCH DESIGN AND METHODS

In the Swedish Inpatient Register, we identified a population-based cohort of 24,605 patients (12,551 men and 12,054 women) who were hospitalized for diabetes before age 31 years during 1975 through 1998. Follow-up for hip fracture was accomplished through cross-linkage in the Inpatient Register until the end of 1998. Censoring information was obtained from the registers of Death and Migration. Using the Kaplan-Meier method, we calculated the cumulative probability of getting a hip fracture. Standardized hospitalization ratios and their 95% CIs estimated relative risks with the age-, sex-, and calendar period-matched Swedish general population as reference.

RESULTS

In total, 70 and 51 first hip fractures were ascertained in men and women, respectively, corresponding to a cumulative probability (both sexes) of 65.8/1,000 until age 65 years. Markedly elevated risks were observed in both men and women (standardized hospitalization ratios = 7.6 [95% CI 5.9-9.6] and 9.8 [7.3-12.9], respectively), increasing with follow-up time. Ophthalmic, nephropathic, neurological, and cardiovascular complications were indicators of particularly high risks.

CONCLUSIONS

Both male and female type 1 diabetic patients are at increased risk for hip fracture. Although optimal preventive measures still need to be defined, the co-occurrence with other diabetes complications suggests that tighter metabolic control might reduce the risk.

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.

Musculoskeletal disorders in diabetes mellitus: an update

Diabetes mellitus (DM) is associated with several musculoskeletal disorders. The incidence of DM and the life expectancy of the diabetic patient have both increased, resulting in the increased prevalence and clinical importance of musculoskeletal alterations in diabetic subjects. The exact pathophysiology of most of these musculoskeletal disorders remains obscure. Connective tissue disorders, neuropathy, vasculopathy or combinations of these problems, may underlie the increased incidence of musculoskeletal disorders in DM. The development of musculoskeletal disorders is dependent on age and on the duration of DM; however, it has been difficult to show a direct correlation with the metabolic control of DM. Most of these disorders can be diagnosed clinically, but some radiological examination may help, especially in differential diagnosis. No specific treatment is available, and treatments used in the general population are also recommended for diabetic subjects. Infectious complications affecting the musculoskeletal system are common in DM subjects, and these, possibly life-threatening, complications should be systematically discussed.

Type 2 diabetes is associated with increased bone mineral density in Mexican-American women

BACKGROUND

Our purpose was to determine whether type 2 diabetes is associated with altered bone mineral density (BMD) and whether fasting serum insulin levels are correlated with BMD.

METHODS

In a population-based family study of Mexican-Americans, we obtained measurements of BMD, diabetes status (by 2-h oral glucose tolerance test), obesity, and serum insulin concentrations in 600 subjects from 34 families. Analyses were stratified by sex and conditioned on the pedigree structure to account for residual correlations among related individuals.

RESULTS

Women with diabetes had significantly higher BMD at hip than women without diabetes (p=0.03) even after adjustment for age, body mass index (BMI), and menopause status. BMD at spine was also higher in diabetic women than in nondiabetic women, although the association was no longer statistically significant after adjustment for BMI. Diabetes was not associated with BMD in men. In nondiabetic men and women, insulin levels were significantly correlated with BMD after adjustment for age and other lifestyle covariates, but correlations were diminished and were no longer statistically significant after further adjustment for body mass index.

CONCLUSIONS

These results suggest that Mexican-American women with type 2 diabetes have higher BMD compared to their nondiabetic counterparts, with the association independent of obesity at hip, although not at spine or forearm. Increased BMD was also correlated with serum insulin levels, although this association was not independent of obesity. Longitudinal studies may be required to better define the mechanisms underlying the observed association between BMD and diabetes.

Diabetes Mellitus: Does it Affect Bone?

Both diabetes and fractures affect a large proportion of older adults. Recent cohort studies indicate that diabetes itself is associated with increased risk of fracture of the hip, proximal humerus, and foot. Observational studies and animal models suggest that decreased bone strength in diabetes may contribute to fracture risk but this remains a controversial issue. Type 1 diabetes is associated with modest reductions in bone mineral density (BMD) but type 2 diabetes is often characterized by elevated BMD. This paradox of higher BMD but increased fracture risk in type 2 diabetes may be explained by a combination of more frequent falls and poorer bone quality. Diabetes can impact bone through multiple pathways, some with contradictory effects, including obesity, changes in insulin levels, higher concentrations of advanced glycation end products in collagen, hypercalciuria associated with glycosuria, reduced renal function, lower insulin-like growth factor-I, microangiopathy, and inflammation. A better understanding of how diabetes metabolism and treatments affect bone would improve fracture prevention efforts in older diabetic adults.

Rheumatologic manifestations of diabetes mellitus

Diabetes mellitus has been linked to disorders of bones and joints, including neuroarthropathy, limited joint mobility, and hyperostosis. Some of the relations have known pathogenic mechanisms, but most are based on epidemiologic findings. This article reviews the associations between diabetes mellitus and its putative rheumatologic manifestations, and proposes a classification composed of four categories: consequences of diabetic complications, consequences of metabolic derangements inherent to diabetes, syndromes that may share etiologic mechanisms with microvascular disease, and probable associations. This approach may facilitate a clearer understanding of the musculoskeletal conditions that are prevalent in patients with diabetes mellitus.

Serum interleukin-6 levels and bone mineral density at the femoral neck in post-menopausal women with Type 1 diabetes

BACKGROUND

Although osteopenia is often reported in Type 1 diabetes mellitus, the pathogenic mechanisms are not fully understood. Oestrogen deficiency also leads to decreased bone mineral density (BMD). Enhanced interleukin-6 (IL-6) production among Type 1 diabetic patients could be involved in the pathogenesis of diabetic bone loss since it is a potent bone resorbing cytokine.

AIMS

To evaluate the relationship between serum bioactive IL-6 levels and BMD at the femoral neck of post-menopausal women with Type 1 diabetes.

METHODS

We studied BMD, urine excretion of deoxypirydynoline crosslinks, serum bioactive IL-6 and soluble IL-6 receptor (sIL-6R) levels in 20 post-menopausal women with Type 1 diabetes mellitus, and compared these results with 20 matched healthy post-menopausal controls.

RESULTS

Post-menopausal women with Type 1 diabetes had significantly lower BMD at the femoral neck and increased serum bioactive IL-6 levels compared with the control group, but no relationship was observed between these variables in a multiple regression analysis. Using BMD at the femoral neck of diabetic women as the dependent variable in the multiple step regression analysis model, we found that independent variables that were strongly associated with bone mass at the femoral neck in this group were: time since menopause and duration of diabetes.

CONCLUSIONS

Although our study had a small sample size, we found that post-menopausal women with Type 1 diabetes mellitus present lower bone mass and higher serum bioactive IL-6 levels than matched healthy controls, but we were unable to find a correlation between these two parameters.

Hypoxia decreases Runx2/Cbfa1 expression in human osteoblast-like cells

To elucidate the molecular mechanism in relation to vascular supply and osteoporosis, we investigated the effect of hypoxia on Runx2 expression in MG63 cells. Also investigated was expression of type I collagen and osteocalcin, which are regulated by Runx2, alkaline phosphatase (ALPase) to see if they are affected by hypoxia. Quiescent cultures of MG63 cells were exposed to hypoxia (2% O(2)) and normoxia (18% O(2)) for 24, 48, 72 and 96 h. In cells exposed to hypoxia, reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that mRNA expression of Runx2, type I collagen, osteocalcin, and ALPase were decreased in a time dependent manner to 96 h. Activity of ALPase was also reduced in the same manner. Western blotting showed a marked decrease in Runx2 protein at 96 h in cells under hypoxia compared to normoxia. These data indicate that Runx2 expression in osteoblasts is reduced by hypoxia, and may be a mechanism of osteoporosis by decreased vascular supply.

Calcaneal fractures in diabetic patients

We would like to present 23 calcaneal fractures in 22 patients of whom 21 had type I diabetes mellitus. There appear to be three basic fracture types: (1) a superiorly displaced extra-articular avulsion fracture of the posterior calcaneus (or Iowa fracture), which occurred in 12 patients (five men, seven women); (2) a mid-calcaneal compression fracture in six patients (four men, two women), and (3) a cleavage or "wedge" type fracture in four patients extending from the calcaneal tubercle (one man, 3 women). All four of this last group of patients had a history of a chronic penetrating ulcer, and this is noteworthy since only one other patient out of the remaining 18 in groups 1 and 2 had a similar history. Most patients had decreased bone mineralization: 15 patients were on long-term, high-dose steroids, and 18 patients had either poor renal function or complete renal failure (11 of 12). Fourteen patients had received either renal or pancreas transplants. Eight patients were on restricted weight bearing prior to their fractures. We believe that diabetic patients are more prone to calcaneal fractures than the general population, and early diagnosis is imperative, followed by early treatment to prevent significant bony deformity.

Advanced glycation endproducts stimulate interleukin-6 production by human bone-derived cells

Advanced glycation endproducts (AGEs), which result from nonenzymatic reactions of glucose with tissue proteins, have been shown to accumulate on long-lived proteins in advanced aging and diabetes mellitus. Thus, AGEs have been implicated in some of the chronic complications associated with these disorders. In this study, we investigated the effects of the glucose-modified protein on the production of the potent bone resorption factors by cells derived from explants of human bone. AGEs stimulated the release of interleukin-6 (IL-6) in the culture supernatants from the bone-derived cells and increased the levels of IL-6 mRNA in the cells. By contrast, the levels of IL-11 in the culture supernatants were not altered by AGEs, and the other bone resorption factors IL-1 alpha and IL-1 beta were undetectable (< 1.0 pg/ml) either without or with the treatment of AGEs. Electrophoretic mobility-shift assays revealed that the transcription nuclear factor-kappa B, which is critical for the inducible expression of IL-6, was activated in the nuclear extracts from mouse osteoblastic MC3T3-E1 cells treated with AGEs. These results suggest that AGEs are involved in bone remodeling modulation by stimulating IL-6 production in human bone-derived cells.

Bone mineral density measured by dual X-ray absorptiometry in Spanish patients with insulin-dependent diabetes mellitus

Previous studies suggest that low bone mass is a potential complication of insulin-dependent diabetes mellitus. Nevertheless, the factors that influence diabetic osteopenia are not well established. In order to evaluate the prevalence and magnitude of diabetic osteopenia and its association with clinical and metabolic variables, we studied 94 consecutive patients with insulin-dependent diabetes mellitus. Their age ranged from 20 to 56 years and duration of diabetes varied from 1 to 35 years. Bone mineral density (BMD) was measured by dual X-ray absorptiometry at lumbar spine and proximal femur and the values were expressed as z-score. The presence and extent of microvascular complications, degree of metabolic control, and other risk factors for osteoporosis were recorded and some biochemical markers of bone metabolism were assessed. Diabetic patients showed reduced BMD in all sites (lumbar spine: -0.89 +/- 1.21; femoral neck: -0.99 +/- 1.24; Ward triangle: -1.05 +/- 1.24; P < 0.0001). Of the 94 patients 19.1% met diagnostic criteria for osteoporosis. BMD correlated with body mass index in all sites and with the duration of disease in Ward's triangle. Presence and extent of diabetic complications were associated with lower BMD, as was smoking. No correlation was found between BMD and biochemical markers. In conclusion, osteopenia is a common complication in patients with insulin-dependent diabetes mellitus. Microvascular complications are a critical point in the progression of diabetic osteopenia. Other risk factors for osteoporosis (nutritional status and smoking) must be taken into account.

Peripheral osteopenia in adult patients with insulin-dependent diabetes mellitus

Alterations in bone metabolism in diabetes mellitus is a topic of special interest. Bone blood flow is increased in the distal limb of diabetic patients, which is believed to increase osteoclastic activity. We measure bone mineral density using dual-photon absorptiometry in the distal lower limb, the femoral neck, and the lumbar spine in 41 IDDM patients and in 30 control persons. In the diabetic group there was a 10% reduction of bone mineral density in the femoral neck (p < 0.01) and a 12% reduction in the distal limb (p < 0.001) compared with the control group. No significant difference was found in the lumbar spine (p = 0.22). Our data yield incidence for peripheral osteopenia in IDDM-patients, independent of any systemic bone disease such as osteoporosis. A link between decreased bone mineral density and diabetic neuropathy has been observed for the femoral neck (p < 0.001), but not for the distal limb or axial skeleton. Whether there is a common aetiological link or a casual connection between diabetic neuropathy and bone mineral density has still to be determined.

Bone densitometry and biochemical bone remodeling markers in type 1 diabetes mellitus

Bone mineral density (BMD) at the lumbar spine, quantified by dual energy X-ray absorptiometry, and biochemical bone remodeling markers (serum alkaline phosphatase, osteocalcin, tartrate-resistant acid phosphatase and urinary hydroxyproline) have been studied in 94 patients with diabetes mellitus aged 18-62 years. BMD was normal (1.13 +/- 0.02 g/cm2 in patients vs. 1.16 +/- 0.12 g/cm2 in controls), although it was found to be negatively correlated with HbA1, microalbuminuria, age and the duration of the disease. Serum alkaline phosphatase (188 +/- 75 I.U./l vs. 168 +/- 42 I.U./1; P < 0.03), serum tartrate-resistant acid phosphatase (14.3 +/- 4.3 I.U./l vs. 11.7 +/- 3.7 I.U./l; P < 0.0001) and urinary hydroxyproline (0.018 +/- 0.016 mmol/mmol creatinine vs. 0.011 +/- 0.008 mmol/mmol creatinine; P < 0.001) were higher in diabetics than in controls. Serum osteocalcin was lower (2.5 +/- 1.3 ng/ml vs. 3.4 +/- 1.2 ng/ml; P < 0.0001). No relationship was found between bone remodeling markers and BMD. It is concluded that lumbar BMD is normal in type 1 diabetic patients, although the degree of metabolic control, age and duration of the disease may affect it. In the light of the biochemical markers, bone remodeling may be disturbed in diabetes, but such disturbance seems to be unimportant regarding BMD.

Diabetic and age-related enhancement of collagen-linked fluorescence in cortical bones of rats

Nonenzymatic collagen cross-linking occurs in a variety of connective tissues as a result of formation of advanced glycosylation end products. Diabetes and aging significantly increase levels of nonenzymatic collagen cross-linking in connective tissues. This study was undertaken to determine whether nonenzymatic collagen cross-linking occurs in rat cortical bone and if these levels are increased in diabetic and aged rats. Collagen-linked fluorescence, a measurement of nonenzymatic collagen cross-linking, was significantly increased in rat cortical bone with diabetes and age. In addition, incubation of bone powder with glucose resulted in a similar increase in collagen-linked fluorescence. These changes in bone collagen may contribute to alterations observed in bone with diabetes and age by influencing bone cell function and the ability of the matrix to be responsive to bone cells.