Diabetes and osteoporosis

Investigation of the relationship between serum sclerostin and dickkopf-1 protein levels with bone turnover in children and adolescents with type-1 diabetes mellitus

OBJECTIVES

Diabetes mellitus (DM) is widely known to have a detrimental effect on bone health and is associated with increased fracture risk. Recently, the Wnt/beta-catenin signaling pathway and its inhibitors sclerostin and dickkopf-1 (Dkk-1) were found to be involved in the control of bone mass. The present study aimed to measure serum sclerostin and Dkk-1 protein levels in children and adolescents with type-1 DM and compare with other bone turnover markers and bone mineral density (BMD).

METHODS

This study was performed on 40 children and adolescents with type-I DM and 40 healthy children and adolescents. Anthropometric measurements and pubertal examination were done. In addition to laboratory analysis, dickkopf-1, sclerostin, cross-linked N-telopeptides of type I collagen (NTx), bone alkaline phosphatase (bALP), and osteocalcin levels were studied. BMD of the participants was measured by calcaneus ultrasonography.

RESULTS

Dickkopf-1 levels of the children and adolescents with type-1 DM were significantly higher, vitamin D, NTx, osteocalcin, and phosphorus levels were significantly lower than those of the controls (p<0.001). Fasting blood glucose, HbA1c, and insulin were significantly higher in the type 1 DM group (p<0.01).

CONCLUSIONS

Both bone remodeling and its compensatory mechanism bone loss are lower in children and adolescents with type-1 DM than in the controls. Also, higher levels of Dkk-1 play a role in decreased bone turnover in these patients. Since Dkk-1 and sclerostin seem to take a role in treating metabolic bone diseases in the future, we believe that our findings are significant in this respective.

Association Between Osteoporosis and Refracture Rate Among Patients With Hip Fractures at King Abdulaziz Medical City, Saudi Arabia

Background

Hip fracture is a major medical and surgical topic and is a significant cause of morbidity and mortality. Older women, especially those with osteoporosis, are at an increased risk for hip fractures. Multiple studies have shown the effect of osteoporosis on the refracture rate among the elderly population. Therefore, selecting a targeted population for screening and treating osteoporosis has an essential role in decreasing the hip fracture rate. This study aimed to determine the association between osteoporosis treatment and refracture rate among patients with hip fractures at King Abdulaziz Medical City, Jeddah, Saudi Arabia.

Methods

Collected data included patient demographics (men: ≥55 years old; women: ≥50 years old), the used osteoporosis investigation method, osteoporosis treatment history, presence of comorbidities, and refracture as a primary outcome. The refracture rate among patients with hip fracture was calculated and used to determine the association between hip refracture and osteoporosis.

Results

Our study included a total of 292 patients who presented to our hospital due to hip fractures. The patients were divided into two groups, the osteoporotic and non-osteoporotic groups. These groups were then compared. There was no statistical significance between osteoporosis and hip refracture (p = 0.721), and there was no association between the treatment of osteoporosis and hip refracture (p = 0.493). Statistical difference was found between patients who had undergone dual-energy X-ray absorptiometry scan and were not treated for osteoporosis (p = 0.00). Lastly, the mortality of the refracture group was 10%, while it was 11% in the no-refracture group (p = 1.00).

Conclusion

Morbidity and mortality rates are higher among patients with hip fractures. Our study showed that there was no association between hip refracture rate and osteoporosis whether the patient is treated for osteoporosis or not. We recommend a systematic review that can include more studies in this field to acquire more definitive results regarding this topic.

Increasing fasting glucose and fasting insulin associated with elevated bone mineral density-evidence from cross-sectional and MR studies

We performed a cross-sectional study using the National Health Examination and Nutrition Survey (NHANES) data and a Mendelian randomisation (MR) study using the GWAS summary statistics from European populations. The T2D-related indices (fasting plasma glucose (FPG), fasting insulin (FI), and insulin resistance (IR)) were found to associate with elevated bone mineral density (BMD).

INTRODUCTION

The known associations amongst FPG, FI, IR, and BMD remain inconsistent. This study aims to explore the abovementioned associations by using cross-sectional and MR designs.

METHODS

Data from adults aged ≥ 20 years (n = 7170) in four rounds of the U.S. NHANES (2005-2010 and 2013-2014) were analysed in this cross-sectional study. Multiple linear and logistic regression models were used for statistical analyses. A two-sample MR study was performed using the genome-wide association study summary statistics obtained from the Meta-analyses of Glucose and Insulin-related traits Consortium (n = 108,557) and Genetic Factors for Osteoporosis Consortium (n = 32,735) to examine the causality of the FI-BMD association.

RESULTS

Multiple linear regression revealed that FPG was positively associated with the BMDs at the hip, femur neck, and 1st lumbar spine (L1). Multiple logistic regressions revealed that FPG levels were associated with elevated BMDs at the hip and L1, and FI and IR levels were associated with elevated BMD at the hip. Patients with type 2 diabetes had higher hip BMD than those without diabetes. In the MR study, the lumbar spine BMD increased by 0.49 g/cm² (95% confidence interval: 0.01, 0.97) in response to per unit increase in log-transformed FI.

CONCLUSION

Findings from our cross-sectional and MR studies revealed the associations between the studied diabetic indices and BMD measurements in the US and European adults.

Aptamer selection and aptasensor construction for bone density biomarkers

Osteoporosis (OP) is a bone disease involved in dysregulation of one of the bone metabolism arms, formation, or desorption cause a porous bone. Osteocalcin (OC) and beta-crosslap (BC), are the well-known markers for OP, which are connected to bone formation and desorption, respectively. In addition to the OP biomarker, BC is also used as an estrogen replacement therapeutic monitoring. ELISA and other antibody-based detection methods are routinely used for measuring OC and BC. These methods have limitations that include thermostability, sensitivity, sacrificing animals, and cost of production. However, aptamer-based-assays are of interest to overcome these drawbacks and achieve the most specific and robust application. Herein, specific aptamers for OC and BC were selected by the systematic evolution of ligands by exponential enrichment (SELEX) method from the pool of ssDNA library with 60 random sequences. The binding affinity (K_d) of the selected aptamers were evaluated against the respective biomarkers. The high-affinity aptamers of OC and BC showed the K_d values of 59 and 55 nM respectively. A graphene oxide-based aptasensors were fabricated from the high-affinity aptamers, and the detection limits of OC and BC were found to be 0.4 pg/ml and 0.21 pg/ml, respectively. These aptasensors have been tested with OC and BC spiked buffer samples and validated using serum samples collected from osteoporotic rats.

Antidiabetic and antiosteoporotic pharmacotherapies for prevention and treatment of type 2 diabetes-induced bone disease: protocol for two network meta-analyses

INTRODUCTION

Patients with type 2 diabetes mellitus (T2DM) are at risk for a variety of severe debilitating effects. One of the most serious complications experienced by patients with T2DM are skeletal diseases caused by changes in the bone microenvironment. As a result, patients with T2DM are at risk for higher prevalence of fragility fractures. There are a variety of treatments available for counteracting this effect. Some antidiabetic medications, such as metformin, have been shown to have a positive effect on bone health without the addition of additional drugs into patients' treatment plans. Chinese randomised controlled trial (RCT) studies have also proposed antiosteoporotic pharmacotherapies as a viable alternative treatment strategy. Previous network meta-analyses (NMAs) and meta-analyses regarding this topic did not include all available RCT trials, or only performed pairwise comparisons. We present a protocol for a two-part NMA that incorporates all available RCT data to provide the most comprehensive ranking of antidiabetics (part I) and antiosteoporotic (part II) pharmacotherapies in terms of their ability to decrease fracture incidences, increase bone mineral density (BMD) and improve indications of bone turnover markers (BTMs) in adult patients with T2DM.

METHODS AND ANALYSIS

We will search Medical Literature Analysis and Retrieval System Online, Excerpta Medica Database, PubMed, Web of Science, Cumulative Index to Nursing and Allied Health Literature, Cochrane Central Register of Controlled Trials and Chinese literature sources (China National Knowledge Infrastructure, Chongqing VIP Information, Wanfang Data, Wanfang Med Online) for RCTs, which fit our criteria. We will include adult patients with T2DM who have taken antidiabetics (part I) or antiosteoporotic (part II) therapies with relevant outcome measures in our study. We will perform title/abstract and full-text screening as well as data extraction in duplicate. Risk of bias will be evaluated in duplicate for each study, and the quality of evidence will be examined using Confidence in Network Meta-Analysis in accordance to the Grading of Recommendations Assessment, Development and Evaluation framework. We will use R and gemtc to perform the NMA. We will report changes in BMD and BTMs in either weighted or standardised mean difference, and we will report fracture incidences as ORs. We will use the Surface Under the Cumulative Ranking Curve scores to provide numerical estimates of the rankings of interventions.

ETHICS AND DISSEMINATION

The study will not require ethics approval. The findings of the two-part NMA will be disseminated in peer-reviewed journals and presented at conferences. We aim to produce the most comprehensive quantitative analysis regarding the management of T2DM bone disease. Our analysis should be able to provide physicians and patients with up-to-date recommendations for antidiabetic medications and antiosteoporotic pharmacotherapies for maintaining bone health in patients with T2DM.

PROSPERO REGISTRATION NUMBER

CRD42019139320.

Effects of Glycated Hemoglobin Level on Bone Metabolism Biomarkers in Patients with Type 2 Diabetes Mellitus

PURPOSE

We aimed to determine the relationship between the levels of glycated hemoglobin (HbA1c) and biomarkers of bone metabolism in patients with type 2 diabetes mellitus (T2DM), and whether HbA1c independently influences any of these biomarkers.

PATIENTS AND METHODS

A cohort study of 240 patients with T2DM was performed. Serum was obtained and used to measure HbA1c, total cholesterol (TC), triglycerides, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol (LDL-C), very-low-density lipoprotein-cholesterol, apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), total protein, albumin, blood urea nitrogen (BUN), creatinine, serum 25-hydroxyvitamin D (25OHD), osteocalcin (OC), β-C-terminal cross-linked telopeptide of type I collagen (β-CTX), procollagen type 1 N-terminal propeptide (P1NP), or parathyroid hormone (PTH) concentrations. The participants were divided into three study groups according to HbA1c level: <7%, 7-9% and ≥9%. Chi-square testing and one-way analysis of variance were used to compare groups. The relationships between HbA1c and bone metabolism biomarker values were analyzed using linear correlation analysis and multiple linear regression analysis.

RESULTS

Age, duration of T2DM, and the concentrations of TC, LDL-C, apolipoprotein B, albumin, and BUN showed significant difference among the <7%, 7-9% and ≥9% HbA1c groups. Of the bone metabolism biomarkers, there were significant differences in serum 25-hydroxyvitamin D (25OHD) and osteocalcin (OC) among the groups. The correlation coefficients (r) for the relationships of HbA1c with 25OHD and OC were -0.200 and -0.183, respectively (P <0.05). Regardless of adjustment for none, some, or all of the confounding factors (age, sex, and duration of T2DM), the 25OHD and OC concentrations were significantly lower in the HbA1c ≥9% group than in the HbA1c <7% group. HbA1c showed no relationship with β-CTX, PINP, or PTH.

CONCLUSION

T2DM patients with poorer glycemic control had lower concentrations of serum 25OHD and OC, suggesting that HbA1c is an independent risk factor for low 25OHD and OC.

Charcot Neuroarthropathy Advances: Understanding Pathogenesis and Medical and Surgical Management

Understanding new theories of the epidemiology of Charcot neuroarthropathy is practice changing. Treatment of Charcot neuroarthropathy is evolving from a passive approach to one that sees the urgency of proactive, early recognition, thereby avoiding the cascading events that lead to the complex, limb-threatening deformities. Preventive medicine is the most efficient at avoiding severe deformity, with prolonged offloading and immobilization as the current mainstay of treatment. However, with recent advancements in medical and surgical modalities, this may become the treatment of the past as clinicians begin to favor medical management and early surgical intervention.

A review of bone metabolism and developments in medical treatment of the diabetic Charcot foot

Charcot foot is a rare but severe, and possibly limb-threatening, complication to neuropathy and diabetes mellitus. The current treatment consists of long-term off-loading, and has a large negative impact on the patient's life. Much research has gone into understanding the condition and its biochemical mechanisms, however, the underlying pathogenesis of a Charcot foot is not yet fully understood. In the recent decades several key advances in our understanding of the Charcot foot have been made, both in regards to the changes in bone metabolism and structure an acute Charcot foot can cause, and to the molecular pathways involved in this. This review summerizes the available research into the bone metabolism around a Charcot foot, with an emphasis on the biochemical profile. The existing data regarding attempts at medical treatment is also reviewed, including novel trials targetting specific inflammatory pathways upregulated in the acute diabetic Charcot foot.

Imaging of diabetic bone

Diabetes is an important concern in terms of medical and socioeconomic costs; a high risk for low-trauma fractures has been reported in patients with both type 1 and type 2 diabetes. The mechanism involved in the increased fracture risk from diabetes is highly complex and still not entirely understood; obesity could play an important role: recent evidence suggests that the influence of fat on bone is mainly dependent on the pattern of regional fat deposition and that an increased amount of visceral adipose tissue negatively affects skeletal health.Correct and timely individuation of people with high fracture risk is critical for both prevention and treatment: Dual-energy X-ray Absorptiometry (currently the "gold standard" for diagnosis of osteoporosis) underestimates fracture risk in diabetic patients and therefore is not sufficient by itself to investigate bone status. This paper is focused on imaging, covering different modalities involved in the evaluation of skeletal deterioration in diabetes, discussing the limitations of conventional methods and exploring the potential of new tools and recent high-resolution techniques, with the intent to provide interesting insight into pathophysiology and fracture risk.

Vitamin D deficiency aggravates diabetes-induced muscle wasting in female mice

We recently reported that vitamin D deficiency aggravates diabetic bone loss in mice. Although vitamin D affects both muscle and bone, the role of the vitamin D state in diabetic muscle loss and muscle-bone relationships remains unclear. In the present study, we examined the effects of vitamin D deficiency on muscle mass, muscle differentiation and muscle-derived humoral factors linking muscle to bone in diabetic female mice. Diabetes was induced in mice by streptozotocin (STZ) injection after feeding with a normal or vitamin D-deficient diet for 6 weeks. Quantitative computed tomography analysis showed that tibial muscle mass was significantly decreased in diabetic mice compared with control mice 4 weeks after induction of diabetes. Vitamin D deficiency accelerated muscle loss in diabetic mice. Vitamin D deficiency augmented the decreases in Pax7 mRNA levels and the increases in muscle RING-Finger Protein-1 and atrogin-1 mRNA levels induced by diabetes in the gastrocnemius muscle of mice. Moreover, vitamin D deficiency decreased the mRNA levels of insulin-like growth factor-1, fibroblast growth factor-2 and osteoglycin in muscle of diabetic mice. In conclusion, we demonstrated that vitamin D deficiency aggravates muscle loss induced by diabetes in female mice. Vitamin D may exert significant effects on the maintenance of the musculoskeletal system partly through the muscle-bone relationships in diabetic state.

Expression pattern of CYP24 in liver during ageing in long-term diabetes

Association of liver calcitriol (active vitamin D metabolite) catabolism with osteomalacia during prolonged use of certain drugs was reported in several recent studies. To examine whether the increased calcitriol catabolism could be a potential link between ageing/diabetes mellitus (DM) and bone loss, we studied the dynamic of expression of CYP24, the main calcitriol catabolising enzyme in the liver of rats during ageing and a long-term experimental DM1. DM1 model was induced with intraperitoneally injected streptozotocin (STZ) (55mg/kg). Sprague-Dawley rats were sacrificed 6 and 12 months after the DM1 induction. The immunohistochemical analyses of CYP24 and transforming growth factor β 1 (TGF-β1) expression in the liver were performed. We found that ageing and long-term DM1 resulted in a significantly increased expression of CYP24 in hepatocytes, as well as in non-hepatocyte liver cells (Kupffer cells, hepatic stellate cells and sinusoidal endothelial cells). Ageing and long-term DM1 resulted in an increased expression of TGF-β1 as well. Expression of CYP24 coexisted with the expression of TGF-β1 in all types of hepatic cells. We concluded that liver has the capacity for an active vitamin D catabolism in different populations of liver cells, especially in sinusoidal endothelial cells, through an expression of CYP24. That capacity is substantially increased during ageing and long-term diabetes mellitus. Increased liver calcitriol catabolism could be one of the mechanisms of the bone metabolism impairment related to ageing and diabetes.

Effect of exenatide, insulin and pioglitazone on bone metabolism in patients with newly diagnosed type 2 diabetes

AIM

Preclinical studies suggested that insulin, incretin and thiazolidinediones had effect on regulation of bone metabolism. But clinical evidence is limited. We assessed the effects of these antihyperglycemic agents on bone metabolism in patients with newly diagnosed type 2 diabetes.

METHODS

The present study was a two-center, randomized, parallel-group clinical trial. Sixty-two newly diagnosed and drug-naïve patients with type 2 diabetes were randomized to exenatide (EXE, n = 20), mixed protamine zinc recombinant human insulin lispro injection (25R; INS, n = 21) or pioglitazone (PIO, n = 21) group for a 24-week treatment. Glycosylated hemoglobin A1c (HbA1c), body weight, body mineral density (BMD) and fasting serum concentration of bone turnover markers including osteocalcin (OC), C-telopeptide of type I collagen (CTX) and tartrate-resistant alkaline phosphatase 5b (TRAcP5b) were assessed at baseline and week 24.

RESULTS

Baseline characteristics were similar among groups. At week 24, HbA1c improved in all patients (EXE:-2.4 ± 0.3 %, INS:-2.4 ± 0.3 %, PIO:-2.0 ± 0.2 %; p > 0.05 among groups). Patients treated with exenatide lost body weight remarkably (-4.7 ± 0.8 kg). In spite of the amelioration of glucose control, no significant improvement of OC, CTX or TRAcP5b was observed at week 24 (EXE: OC -0.619 ± 0.728 ng/ml, CTX 0.147 ± 0.046 ng/ml, TRAcP5b 0.302 ± 0.149 U/L;INS: OC 0.637 ± 0.787 ng/ml, CTX -0.012 ± 0.074 ng/ml, TRAcP5b 0.124 ± 0.395 U/L; PIO: OC -0.150 ± 0.691 ng/ml, CTX 0.073 ± 0.094 ng/ml, TRAcP5b 0.586 ± 0.183 U/L; p > 0.05), as well as BMD measurement, regardless of the treatments.

CONCLUSIONS

Twenty-four-week treatment with exenatide, insulin and pioglitazone improved glucose control in patients with newly diagnosed type 2 diabetes, but had no impact on bone turnover markers or BMD.

Association of haematological parameters with bone mineral density in elderly diabetic women

OBJECTIVES

In this study, we aimed to evaluate whether an association exists between complete blood count (CBC) parameters and bone mineral density (BMD) in elderly females with type 2 diabetes mellitus (T2DM) and to estimate the differences in BMD in T2DM.

METHODS

The medical records of female patients who had been referred for BMD analysis to a tertiary hospital in Ankara, Turkey were reviewed.

RESULTS

A total of 275 women (66 with T2DM, 209 without T2DM; mean age 72.1 ± 5.4 years) were included in study. White blood cell (WBC) counts, lumbar spine BMD (LSBMD) and femoral neck BMD (FNBMD) were found to be significantly higher in T2DM. There was an inverse association between haematocrit (Hct) and LSBMD in diabetic group (r =  - 0.330; P = 0.008).

CONCLUSION

Diabetic patients had higher BMD levels. Regardless of the mechanisms, Hct could be a readily available potential candidate to identify diabetic patients with osteoporosis.

The prevention of fragility fractures in diabetic patients

Patients with diabetes mellitus (DM) are at greater risk of fractures mostly due to not only extraskeletal factors, such as propensity to falls, but also to bone quality alteration, which reduces bone strength. In people with DM, insulin deficit and hyperglycemia seem to play a role in determining bone formation alteration by AGE accumulation which directly influences osteoblast activity. Although there are conflicting data in the literature, adequate glycemic control with hypoglycemic treatment may be an important element in preventing bone tissue alterations in both type 1 and type 2 DM. Diabetes status is a predictive of future hip and major osteoporosis fractures independently of BMD and FRAX probability. Attention should be paid to the use of thiazolidinediones, especially in older women, because the direct negative effect on bone could exceed the positive effect of glycemic control. Systematic screening for complications and fall prevention efforts, along with calcium and vitamin D repletion and adequate physical activity, represents the mainstay of fracture prevention in DM patients. All anticatabolic drugs (raloxifene, bisphosphonates, denosumab) seem to be effective in DM patients. On the basis of pathophysiological evidence that suggests low bone formation in DM patients, osteoanabolic therapies such as teriparatide might represent an important therapeutic option for DM patients with severe osteoporosis and/or multiple fractures. The search for better methods for the identification of fragility fracture risk in the growing population of adult and elderly subjects with DM might be considered a clinical priority which could improve the prevention of fracture in DM patients.

Diabetes reduces mesenchymal stem cells in fracture healing through a TNFα-mediated mechanism

AIMS/HYPOTHESIS

Diabetes interferes with bone formation and impairs fracture healing, an important complication in humans and animal models. The aim of this study was to examine the impact of diabetes on mesenchymal stem cells (MSCs) during fracture repair.

METHODS

Fracture of the long bones was induced in a streptozotocin-induced type 1 diabetic mouse model with or without insulin or a specific TNFα inhibitor, pegsunercept. MSCs were detected with cluster designation-271 (also known as p75 neurotrophin receptor) or stem cell antigen-1 (Sca-1) antibodies in areas of new endochondral bone formation in the calluses. MSC apoptosis was measured by TUNEL assay and proliferation was measured by Ki67 antibody. In vitro apoptosis and proliferation were examined in C3H10T1/2 and human-bone-marrow-derived MSCs following transfection with FOXO1 small interfering (si)RNA.

RESULTS

Diabetes significantly increased TNFα levels and reduced MSC numbers in new bone area. MSC numbers were restored to normal levels with insulin or pegsunercept treatment. Inhibition of TNFα significantly reduced MSC loss by increasing MSC proliferation and decreasing MSC apoptosis in diabetic animals, but had no effect on MSCs in normoglycaemic animals. In vitro experiments established that TNFα alone was sufficient to induce apoptosis and inhibit proliferation of MSCs. Furthermore, silencing forkhead box protein O1 (FOXO1) prevented TNFα-induced MSC apoptosis and reduced proliferation by regulating apoptotic and cell cycle genes.

CONCLUSIONS/INTERPRETATION

Diabetes-enhanced TNFα significantly reduced MSC numbers in new bone areas during fracture healing. Mechanistically, diabetes-enhanced TNFα reduced MSC proliferation and increased MSC apoptosis. Reducing the activity of TNFα in vivo may help to preserve endogenous MSCs and maximise regenerative potential in diabetic patients.

Role of sclerostin in the bone loss of postmenopausal chinese women with type 2 diabetes

OBJECTIVE

To evaluate the role of sclerostin in bone loss of postmenopausal Chinese women with type 2 diabetes mellitus.

METHODS

The postmenopausal patients suffering from type 2 diabetes mellitus and age, body mass index, and duration of menopause matched healthy controls were enrolled into this cross-sectional study according to criteria of inclusion and exclusion. The serum sclerostin level and bone mineral density of the anterior-posterior lumbar spine (L1-L4), femoral neck, and total hip were determined by using a quantitative sandwich ELISA kit and dual X-ray absorptiometry, respectively. Meanwhile, the clinical and laboratory indexes of bone mineral metabolism were analyzed. Associations between serum sclerostin level and bone mineral density as well as bone turnover markers were evaluated by linear regression analysis.

RESULTS

Finally, 265 postmenopausal women with type 2 diabetes and 225 non-diabetic women were recruited in the diabetic group and control group, respectively. Serum sclerostin level of the diabetic group was significantly higher than that of the control group (48.2±19.4 vs. 37.2±18.6 pmol/L, P<0.001) and was increased with age in both groups (diabetic group, r=0.374, P<0.001; control group, r=0.312, P<0.001). In type 2 diabetes patients, serum sclerostin concentration was positively correlated with hemoglobin A1c level (r=0.237; P=0.021). Biochemical bone turnover markers, intact parathyroid hormone and bone-specific alkaline phosphatase, were negatively associated with serum sclerostin level (r=-0.138, P=0.078 and r=-0.265, P<0.001). Conversely, the positive correlation between sclerostin and C-terminal cross-linking telopeptide of type I collagen was found in diabetic patients (r=0.354, P<0.001). Serum sclerostin levels of the diabetic group were positively correlated with bone mineral density of the lumbar spine, femoral neck, and total hip (r=0.324, 0.367, and 0.416, respectively; all P<0.001).

CONCLUSIONS

Sclerostin might participate in the pathogenesis of bone loss of type 2 diabetes. The high sclerostin level might serve as a marker of increased osteocyte activity in postmenopausal patients with type 2 diabetes mellitus.

Fracture risk in kidney transplant recipients: a systematic review

BACKGROUND

Fractures in men and women after kidney transplantation are associated with morbidity (including acute and chronic pain), mortality, and high economic costs.

METHODS

We systematically reviewed cohort studies that provided estimates on incidence and risk factors for fracture in kidney transplant recipients. We abstracted data in duplicate and assessed the methodological quality of each study on a 17-point scale (17 representing the highest quality).

RESULTS

We screened 2715 articles, reviewed 81, and included 10 studies totaling 262,678 recipients (study mean, 26,268 recipients; range, 61-77,430). The average follow-up ranged from 1.7 to 5.3 years. The study quality scores ranged from 8 to 13. Fracture sites varied by study resulting in a highly variable incidence rate ranging from 3.3 to 99.6 fractures per 1000 person-years. Similarly, the 5-year cumulative incidence for fracture varied ranging from 0.85% to 27%. Common factors associated with an increased fracture risk were older age, female sex, the presence of diabetes, and receipt of dialysis before transplantation. Other less common but statistically significant risk factors were a previous history of fracture and receipt of a kidney from a deceased (vs. living) donor.

CONCLUSIONS

There is poor consensus on the incidence and risk factors for fractures in kidney transplant recipients. Previous studies vary substantially in quality, fracture definitions, and the characteristics of recipients studied. Future research should clarify fracture incidence and risk, which will inform the design of future prevention trials and guide prognostication.

Prevalence of Osteoporosis and Its Associated Factors among Older Men with Type 2 Diabetes

This study investigated the prevalence of osteoporosis and its associated factors in old men with T2DM to identify risk factors for low BMD. We enrolled 93 old men (≥60 years of age) with T2DM and 125 healthy old men (controls) and collected data of their lifestyle, medical history, bone densitometry, body weight, height, and blood pressure. Blood samples were collected for biochemical analyses. Urine samples were collected to determine 24 h urinary creatinine, albumin, and protein. Although no differences in age, blood pressure, waist-to-hip ratio, body mass index (BMI), and testosterone levels were observed, the prevalence of low BMD was significantly higher in the T2DM group compared to the control group. The risk of developing low BMD and fracture in T2DM subjects was increased by 46- and 26-fold, respectively, compared to control subjects. BMD of total spine and hip was positively correlated with BMI and negatively correlated with age, duration of diabetes, creatinine, and 24 h urinary albumin. So old men with T2DM have a greater risk of developing low BMD than old men without 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/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.

Borage and fish oils lifelong supplementation decreases inflammation and improves bone health in a murine model of senile osteoporosis

Fats are prevalent in western diets; they have known deleterious effects on muscle insulin resistance and may contribute to bone loss. However, relationships between fatty acids and locomotor system dysfunctions in elderly population remain controversial. The aim of this study was to analyze the impact of fatty acid quality on the age related evolution of the locomotor system and to understand which aging mechanisms are involved. In order to analyze age related complications, the SAMP8 mouse strain was chosen as a progeria model as compared to the SAMR1 control strain. Then, two months old mice were divided in different groups and subjected to the following diets : (1) standard "growth" diet - (2) "sunflower" diet (high ω6/ω3 ratio) - (3) "borage" diet (high γ-linolenic acid) - (4) "fish" diet (high in long chain ω3). Mice were fed ad libitum through the whole protocol. At 12 months old, the mice were sacrificed and tissues were harvested for bone studies, fat and muscle mass measures, inflammation parameters and bone cell marker expression. We demonstrated for the first time that borage and fish diets restored inflammation and bone parameters using an original model of senile osteoporosis that mimics clinical features of aging in humans. Therefore, our study strongly encourages nutritional approaches as relevant and promising strategies for preventing aged-related locomotor dysfunctions.

Alteration of vitamin D metabolic enzyme expression and calcium transporter abundance in kidney involved in type 1 diabetes-induced bone loss

This study aimed to delineate the mechanism involved in type 1 diabetes-induced bone loss. The results revealed the alteration of vitamin D metabolic enzyme expression and the downregulation of renal calcium transporter abundance in type 1 diabetic mice.

INTRODUCTION

The purpose of this study was to investigate the changes of the expression of vitamin D metabolic enzymes and transcellular calcium-transporting proteins in kidneys from mice with experimentally induced diabetes.

METHODS

Male DBA/2J mice were injected with either vehicle (control) or streptozotocin (STZ) daily for five consecutive days. Bone mineral density was measured by peripheral quantitative computerized tomography, and bone histomorphology was analyzed by Safranin O staining. Real-time PCR and Western blotting were applied to determine the expression of target genes and proteins.

RESULTS

Type 1 diabetes produced high urinary calcium excretion and loss of trabecular bone measured at the proximal metaphysis of the tibia and the distal femur. Bone loss was associated with deterioration of trabecular bone microstructure. Quantified PCR results showed that mRNA expression level in the kidney of diabetic mice for 25-hydroxyvitamin D-24-hydroxylase was downregulated at week 10, while those for 25-hydroxyvitamin D-1α-hydroxylase were upregulated at week 20. In addition, mRNA expression levels for renal transient receptor potential V6, plasma membrane Ca-ATPase (PMCA)1b, and vitamin D receptor (VDR) genes were decreased in STZ-treated mice. Western blot analysis showed that protein expression of PMCA1b and VDR was significantly decreased in kidneys from STZ-treated mice compared to that of controls.

CONCLUSIONS

The limitation in this study is the lack of vitamin D, parathyroid hormone, and phosphorus levels in serum. However, the present study supports the conclusion that the underlying mechanism contributing to type 1 diabetes-associated bone loss may be alterations of vitamin D metabolic enzyme expression and associated decreases in expression of renal calcium transporters.

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.

Elevated incidence of fractures in solid-organ transplant recipients on glucocorticoid-sparing immunosuppressive regimens

This study was conducted to assess the occurrence of fractures in solid-organ transplant recipients. Methods. Medical record review and surveys were performed. Patients received less than 6 months of glucocorticoids. Results. Of 351 transplant patients, 175 patients provided fracture information, with 48 (27.4%) having fractured since transplant (2-6 years). Transplants included 19 kidney/liver (50% male), 47 kidney/pancreas (53% male), 92 liver (65% male), and 17 pancreas transplants (41% male). Age at transplant was 50.8 ± 10.3 years. Fractures were equally seen across both genders and transplant types. Calcium supplementation (n = 94) and bisphosphonate therapy (n = 52) were observed, and an association with a lower risk of fractures was noted for bisphosphonate users (OR = 0.45 95% C.I. 0.24, 0.85). Fracture location included 8 (16.7%) foot, 12 (25.0%) vertebral, 3 (6.3%) hand, 2 (4.2%) humerus, 5 (10.4%) wrist, 10 (20.8%) fractures at other sites, and 7 (14.6%) multiple fractures. The estimated relative risk of fracture was nearly seventeen-times higher in male liver transplant recipients ages 45-64 years compared with the general male population, and comparable to fracture rates on conventional immunosuppressant regimens. Conclusion. We identify a high frequency of fractures in transplant recipients despite limited glucocorticoid use.

Management of osteoporosis in CKD Stages 3 to 5

Osteoporosis and chronic kidney disease (CKD) are both common conditions of older adults and both may be associated with substantial morbidity. However, biochemical and histologic changes that occur with progressive kidney disease require specific interventions, some of which may be concordant with osteoporosis management in the general population, whereas others may be less relevant or perhaps even harmful. In this article, we review the diagnosis of and management strategies for osteoporosis in individuals with CKD, placing these into perspective with the recently published KDIGO (Kidney Disease: Improving Global Outcomes) guidelines for treatment of CKD-mineral and bone disorder (CKD-MBD). Specifically, we highlight osteoporosis treatment recommendations by CKD stage and discuss new avenues for osteoporosis treatment that may be useful in individuals with CKD.

Insulin receptor substrate 2 plays important roles in 17beta-estradiol-induced bone formation

BACKGROUND

Discovering the mechanisms of the estrogen effects on the osteoblasts is very important for the development of new agents which have the clear-cut beneficial effects of estrogen while free of adverse effect.

AIM

The aim of this study was to investigate the differential gene expression of 17beta-estradiol (E2)-treated osteoblast-like cells, and the effect of E2 on the insulin receptor substrate 2 (IRS- 2) expression in human cultured osteoblast-like cells and the osteoblasts of ovariectomized (OVX) rats.

MATERIAL AND METHODS

The differential gene expression of E2-treated osteoblast- like cells was analyzed by cytokine expression array and validated by RT-PCR and Western blot analysis. The protein expression and phosphorylation of one of the differentially expressed gene, IRS-2, treated at different times with E2 were analyzed. The Sprague-Dawley rats were ovariectomized and then treated with E2, the IRS-2 expression was analyzed by immunohistochemistry analysis.

RESULTS

E2 upregulated the mRNA expression of IRS-2, bone morphogenetic protein 9, and connective tissue growth factor expression, down-regulated the mRNA expression of matrix metalloproteinase 15 and some tumor suppressor genes. Peak expression of IRS-2 was observed at 12-24 h of treatment by 10-8M E2. E2 can also increase the phosphorylation of IRS-2. The IRS-2 expression was down-regulated in the osteoblasts and bone marrow cells of the OVX rats, which had lower bone mineral density (BMD) than the normal rats. However, both BMD and IRS-2 expression can be rescued by 10-8M E2 in the OVX rats.

CONCLUSION

IRS-2 in osteoblast is up-regulated by E2 and plays important roles in the estrogen- induced bone formation.

Association between osteoprotegerin G1181C and T245G polymorphisms and diabetic charcot neuroarthropathy: a case-control study

OBJECTIVE

Charcot neuroarthropathy is a disabling complication of diabetes. Although its pathogenesis remains unknown, we suppose that genetics may play a relevant role.

RESEARCH DESIGN AND METHODS

We performed a case-control study with 59 subjects with diabetic Charcot neuroarthropathy (Ch group), 41 with diabetic neuropathy without Charcot neuroarthropathy (ND group), and 103 healthy control subjects (H group) to evaluate the impact of two single nucleotide polymorphisms (SNPs) of the osteoprotegerin gene (G1181C and T245G) on the risk of Charcot neuroarthropathy.

RESULTS

Regarding the SNPs of G1181C, we found a significant linkage between the G allele and Charcot neuroarthropathy (Ch vs. ND, odds ratio [OR] 2.32 [95% CI 1.3-4.1], P = 0.006; Ch vs. H, 2.10 [1.3-3.3], P = 0.002; and ND vs. H, 0.90 [0.7-1.9], P = 0.452); similarly, we found a linkage with the G allele of T245G (Ch vs. ND, 6.25 [2.2-19.7], P < 0.001; Ch vs. H, 3.56 [1.9-6.7], P = 0.001; and ND vs. H, 0.54 [0.6-5.7], P = 0.304), supporting a protective role for the allele C and T, respectively. For this reason we investigated the frequency of the protective double homozygosis CC + TT (7% in Ch) that was significantly lower in Ch compared with H (0.18 [0.06-0.5], P = 0.002) and with ND (0.17 [0.05-0.58], P = 0.006), whereas there was no difference between H and ND (1.05 [0.43-2.0], P = 0.468). In a multivariate logistic backward regression model, only weight and the lack of CC and TT genotypes were independently associated with the presence of Charcot neuroarthropathy.

CONCLUSIONS

This is the first study that shows an association between genetic regulation of bone remodeling and Charcot neuroarthropathy.