Lower bone turnover and relative bone deficits in men with metabolic syndrome: a matter of insulin sensitivity? The European Male Ageing Study

Novel Associations of Dyslipidaemia with Vitamin D and Bone Metabolism in Elderly Patients with Diabetes: A Cross-Sectional Study

Objective

Little is known about whether diabetic dyslipidaemia contributes to increased bone fragility in patients with diabetes. This study aimed to explore the potential effects of dyslipidaemia on vitamin D and bone metabolism in elderly subjects with type 2 diabetes (T2D).

Methods

A total of 1479 male patients and 1356 female patients 50 years or older with T2D were included in Shanghai, China. Lipid profiles, 25-hydroxyvitamin D (25(OH)D), serum procollagen type I N-terminal propeptide (P1NP), β-C-terminal telopeptide (β-CTX) and other parameters were measured. Principal component regression (PCR) and mediation analysis were used to estimate the associations of lipid profile, 25(OH)D and bone turnover levels.

Results

Female patients presented with higher blood lipids, lower 25(OH)D, and higher P1NP and β-CTX levels than male patients with T2D. TC was associated with P1NP in males and females (β=0.056, P<0.05; β=0.095, P<0.01, respectively), and 25(OH)D fully mediated the associations in males and mediated approximately 17.89% of the effects in females. LDL-C was associated with P1NP in males and females (β=0.072 and 0.105 respectively, all P<0.01), and 25(OH)D mediated the relationships approximately 20.83% in males and 14.29% in females. TG was negatively associated with P1NP (in males, β= -0.063, P<0.05; in females, β= -0.100, P<0.01) and β-CTX (in males, β= -0.108; in females, β= -0.128, all P<0.01) independent of 25(OH)D, while HDL-C was not associated with P1NP or β-CTX in diabetic patients.

Conclusion

Hypercholesterolemia and hypertriglyceridaemia might affect bone metabolism by distinguishing pathways in diabetes patients. Ameliorating lipid control in elderly diabetes patients, especially female patients, will benefit both vitamin D and bone metabolism.

Effect of insulin resistance on gonadotropin and bone mineral density in nondiabetic postmenopausal women

Objective

The effects of insulin resistance (IR) on bone mineral density (BMD) are unclear. This investigation aimed to assess the impact of IR and hyperinsulinemia on bone health. Determine whether IR mediates the link between follicle-stimulating hormone (FSH) and bone mass in nondiabetic postmenopausal women.

Design

Retrospective cross-sectional study.

Setting

Health checkup center of Hangzhou Women's Hospital.

Methods

This study comprised 437 nondiabetic postmenopausal women. BMD was evaluated using dual-energy X-rays. Fasting sera were analyzed for insulin and glucose levels, and indicators related to IR were determined. By pathway analysis, we examined the indirect effects of FSH on BMD via the mediators Homeostatic Model Assessment for insulin resistance (HOMA-IR) and fasting insulin (FINS) after correction for confounding factors.

Result

After adjusting for age and body mass index (BMI) in linear regression, HOMA-IR and FINS were linked with FSH (P<0.05). IR was stronger among women in the normal BMD group than those in the osteoporosis or osteopenia group. In unadjusted models, BMD was greater in those with higher HOMA-IR and FINS (β=0.027, P=0.006 and β=0.033, P=0.003, respectively). After correcting for BMI and other possible variables, these associations remained. In addition, path models for FSH demonstrated a negative association with BMD by HOMA-IR (95% confidence interval [CI]: -0.0174 to -0.0014) and FINS (95% CI: -0.0188 to -0.002).

Conclusion

Greater IR was associated with increased BMD in nondiabetic postmenopausal women, regardless of BMI and other variables. HOMA-IR or FINS could play a novel mediating role in FSH-induced BMD suppression.

The Impact of Metabolic Syndrome on Bone Mass in Men: Systematic Review and Meta-Analysis

Studies to date have yielded conflicting results on associations between components of metabolic syndrome (MetS) and bone mineral density (BMD), particularly in men. This current systematic review and meta-analysis addresses the existing gap in the literature and aims to evaluate bone mineral density (BMD) at the femoral neck (FN) and lumbar spine (LS) in men diagnosed with MetS. The two study authors independently searched PubMed, Cinahl, Embase, and Web of Science up to 8 February 2022 for studies in English. The inclusion criteria were (i) diagnosis of MetS according to the NCEP-ATP III 2001 criteria; (ii) adult male demographic; (iii) analyzable data on BMD in at least two sites using dual-energy X-ray absorptiometry (DXA), and (iv) original observational studies. Case reports and non-English articles were excluded. We analyzed the results of seven studies providing data on bone density in men with MetS. Results: Based on random effect weights, the mean BMD of the femoral neck and lumbar spine were 0.84 and 1.02, respectively. The mean lumbar spine T-score was -0.92. In meta-regression analysis, the variances in mean BMD in the lumbar spine and femoral neck could not be significantly explained by BMI (lumbar BMD: Q = 1.10, df = 1, p = 0.29; femoral neck BMD: Q = 0.91, df = 1, p = 0.34). Our meta-analysis suggests normal bone mass in adult males with MetS. Due to the high heterogeneity in the seven analyzed studies and the lack of control groups in these studies, further research is needed to fully elucidate the associations between MetS and its components and BMD in men.

Sarcopenia, osteoporosis and frailty

Muscles and bones are intricately connected tissues displaying marked co-variation during development, growth, aging, and in many diseases. While the diagnosis and treatment of osteoporosis are well established in clinical practice, sarcopenia has only been classified internationally as a disease in 2016. Both conditions are associated with an increased risk of adverse health outcomes such as fractures, dysmobility and mortality. Rather than focusing on one dimension of bone or muscle mass or weakness, the concept of musculoskeletal frailty captures the overall loss of physiological reserves in the locomotor system with age. The term osteosarcopenia in particular refers to the double jeopardy of osteoporosis and sarcopenia. Muscle-bone interactions at the biomechanical, cellular, paracrine, endocrine, neuronal or nutritional level may contribute to the pathophysiology of osteosarcopenia. The paradigm wherein muscle force controls bone strength is increasingly facing competition from a model centering on the exchange of myokines, osteokines and adipokines. The most promising results have been obtained in preclinical models where common drug targets have been identified to treat these conditions simultaneously. In this narrative review, we critically summarize the current understanding of the definitions, epidemiology, pathophysiology, and treatment of osteosarcopenia as part of an integrative approach to musculoskeletal frailty.

Biochemical Markers of Bone Fragility in Patients with Diabetes. A Narrative Review by the IOF and the ECTS

CONTEXT

The risk of fragility fractures is increased in both type 1 and type 2 diabetes. Numerous biochemical markers reflecting bone and/or glucose metabolism have been evaluated in this context. This review summarizes current data on biochemical markers in relation to bone fragility and fracture risk in diabetes.

METHODS

Literature review by a group of experts from the International Osteoporosis Foundation (IOF) and European Calcified Tissue Society (ECTS) focusing on biochemical markers, diabetes, diabetes treatments and bone in adults.

RESULTS

Although bone resorption and bone formation markers are low and poorly predictive of fracture risk in diabetes, osteoporosis drugs seem to change bone turnover markers in diabetics similarly to non-diabetics, with similar reductions in fracture risk. Several other biochemical markers related to bone and glucose metabolism have been correlated with BMD and/or fracture risk in diabetes, including osteocyte-related markers such as sclerostin, HbA1c and advanced glycation end products (AGEs), inflammatory markers and adipokines, as well as IGF-1 and calciotropic hormones.

CONCLUSION

Several biochemical markers and hormonal levels related to bone and/or glucose metabolism have been associated with skeletal parameters in diabetes. Currently, only HbA1c levels seem to provide a reliable estimate of fracture risk, while bone turnover markers could be used to monitor the effects of anti-osteoporosis therapy.

Diabetes and Impaired Fracture Healing: A Narrative Review of Recent Literature

PURPOSE OF THE REVIEW

Diabetes mellitus is a chronic metabolic disorder commonly encountered in orthopedic patients. Both type 1 and type 2 diabetes mellitus increase fracture risk and impair fracture healing. This review examines complex etiology of impaired fracture healing in diabetes.

RECENT FINDINGS

Recent findings point to several mechanisms leading to orthopedic complications in diabetes. Hyperglycemia and chronic inflammation lead to increased formation of advanced glycation end products and generation of reactive oxygen species, which in turn contribute to the disruption in osteoblast and osteoclast balance leading to decreased bone formation and heightening the risk of nonunion or delayed union as well as impaired fracture healing. The mechanisms attributing to this imbalance is secondary to an increase in pro-inflammatory mediators leading to premature resorption of callus cartilage and impaired bone formation due to compromised osteoblast differentiation and their apoptosis. Other mechanisms include disruption in the bone's microenvironment supporting different stages of healing process including hematoma and callus formation, and their resolution during bone remodeling phase. Complications of diabetes including peripheral neuropathy and peripheral vascular disease also contribute to the impairment of fracture healing. Certain diabetic drugs may have adverse effects on fracture healing. The pathophysiology of impaired fracture healing in diabetic patients is complex. This review provides an update of the most recent findings on how key mediators of bone healing are affected in diabetes.

Relationships of Serum Bone Turnover Markers With Metabolic Syndrome Components and Carotid Atherosclerosis in Patients With Type 2 Diabetes Mellitus

Objective

This study aimed to investigate the association of serum bone turnover markers (BTMs) with metabolic syndrome components and carotid atherosclerosis in patients with type 2 diabetes mellitus (T2DM).

Methods

We performed a cross-sectional based study in T2DM populations. Serum BTMs including N-terminal osteocalcin (N-MID), β-cross-linked C-telopeptide of type I collagen (β-CTX), and procollagen type I N-terminal propeptide (PINP) were measured by immunoassay method. Carotid artery intima-media thickness and carotid artery plaque (CAP) were measured by B-mode ultrasound.

Results

The serum N-MID, PINP, and β-CTX levels significantly lower in the CAP group compared with the non-CAP group. N-MID and PINP levels were inversely associated with fasting blood glucose, HOMA-IR, CRP, eGFR, and triglycerides (all P < 0.05), whereas β-CTX levels were negatively associated with triglycerides (P < 0.05). After multiple adjustment, the odds ratios (ORs) were substantially higher for CAP with decreased N-MID level (OR = 0.958; 95% CI = 0.926–0.991; P = 0.013). However, serum levels of PINP and β-CTX were not associated with the presence of CAP. Multivariate logistic regression analysis further revealed that serum N-MID, PINP, and β-CTX levels were significantly associated with hypertriglyceridemia, whereas serum N-MID and β-CTX levels were associated with overweight/obesity risk.

Conclusions

These findings indicated that serum N-MID level was an independent risk factor for carotid atherosclerosis, whereas BTM levels were associated with other metabolic syndrome components in a T2DM population.

Bone Density and Structure in Overweight Men With and Without Diabetes

OBJECTIVE

Metabolic syndrome (MetS), type 1 diabetes (T1D), and type 2 diabetes, are associated with an increased risk of fractures; however, the impact of obesity on bone deficits in diabetes is unknown. We aimed to compare markers of bone structure, bone density, and bone turnover in non-diabetic overweight men with MetS and overweight men with T1D or T2D.

METHODS AND RESEARCH DESIGN

In this cross-sectional study we included participants from two previously described study cohorts consisting of participants with diabetes and participants with MetS. Participants underwent dual-energy X-ray absorptiometry measuring areal bone mineral density (aBMD) at the hip and lumbar spine, High Resolution peripheral Quantitative (HRpQCT) scan of the tibia and radius and measurement of circulating bone turnover markers. We compared groups with unpaired t test and performed multiple linear regression with adjustment for age, body mass index, and smoking.

RESULTS

We included 33 participants with T1D, 25 participants with T2D, and 34 participants with MetS. Bone turnover markers levels were comparable between T1D and MetS. aBMD at the hip was lower in T1D compared to MetS, also after adjustment. P1NP and Osteocalcin levels were lower among individuals with T2D compared to MetS, whereas aBMD were similar between the groups after multiple adjustments. We observed no difference in volumetric BMD at the tibia or radius between MetS and T1D and T2D, respectively. Participants with T2D had a higher trabecular number and lower trabecular separation compared to individuals with MetS at the tibia, which remained signficant after multiple adjustments.

CONCLUSION

In conclusion, we observed no clinically important differences in bone density or structure between men with T2D, T1D, or MetS. However, men with T2D displayed lower bone turnover compared to MetS highlighting that T2D per se and not obesity, is associated with low bone turnover.

Osteocalcin Is Independently Associated with C-Reactive Protein during Lifestyle-Induced Weight Loss in Metabolic Syndrome

Bone-derived osteocalcin has been suggested to be a metabolic regulator. To scrutinize the relation between osteocalcin and peripheral insulin sensitivity, we analyzed changes in serum osteocalcin relative to changes in insulin sensitivity, low-grade inflammation, and bone mineral density following lifestyle-induced weight loss in individuals with metabolic syndrome (MetS). Participants with MetS were randomized to a weight loss program or to a control group. Before and after the 6-month intervention period, clinical and laboratory parameters and serum osteocalcin levels were determined. Changes in body composition were analyzed by dual-energy X-ray absorptiometry (DXA). In participants of the intervention group, weight loss resulted in improved insulin sensitivity and amelioration of inflammation. Increased serum levels of osteocalcin correlated inversely with BMI (r = −0.63; p< 0.001), total fat mass (r = −0.58, p < 0.001), total lean mass (r = −0.45, p < 0.001), C-reactive protein (CRP) (r = −0.37; p < 0.01), insulin (r = −0.4; p < 0.001), leptin (r = −0.53; p < 0.001), triglycerides (r = −0.42; p < 0.001), and alanine aminotransferase (ALAT) (r = −0.52; p < 0.001). Regression analysis revealed that osteocalcin was independently associated with changes in CRP but not with changes in insulin concentration, fat mass, or bone mineral density, suggesting that weight loss-induced higher serum osteocalcin is primarily associated with reduced inflammation.

Impact of metabolic syndrome and its components on bone remodeling in adolescents

INTRODUCTION

Osteoporosis and metabolic syndrome (MetS) are diseases that have serious public health consequences, reducing the quality of life of patients and increasing morbidity and mortality, with substantial healthcare expenditures.

OBJECTIVE

To evaluate the impact of MetS on bone mineral density (BMD) and biochemical markers of bone formation and resorption in adolescents with excess weight.

METHOD

A descriptive and analytical cross-sectional study was performed that evaluated 271 adolescents of both sexes (10 to 16 years). From the total sample, 42 adolescents with excess weight and the presence of MetS (14%) were selected. A further 42 adolescents with excess weight and without MetS were chosen, matched for chronological age, bone age, and pubertal developmental criteria to those with MetS, for each sex. Anthropometric measurements, blood pressure collection, and biochemical tests were performed in all adolescents, as well as evaluation of BMD and the bone biomarkers osteocalcin (OC), bone alkaline phosphatase (BAP), and carboxy-terminal telopeptide (S-CTx).

RESULTS

The adolescents with excess weight and MetS exhibited significantly lower transformed BMD and concentrations of BAP, OC, and S-CTx compared to the matched group, except for OC in boys. A negative and significant correlation was observed between total body BMD and BAP (r = -0.55568; p = 0.005), OC (r = -0.81760; p = < .000), and S-CTx (r = -0.53838; p = 0.011) in girls.

CONCLUSION

Metabolic syndrome may be associated with reduced bone mineral density and biochemical markers of bone formation and resorption in adolescents with excess weight.

Consumption of nutrients and insulin resistance suppress markers of bone turnover in subjects with abdominal obesity

OBJECTIVE

Abdominal obesity and type 2 diabetes are associated with insulin resistance and low bone turnover along with an increased fracture risk. The mode of action is poorly understood. The bone resorption marker, C-terminal telopeptide type 1 collagen (CTX), and to a lesser extent, the bone formation marker, Procollagen type 1 N-terminal propeptide (P1NP) appear to be inhibited by food consumption. The link between food consumption, insulin resistance and bone turnover remains to be clarified. Primarily we aimed to compare the postprandial CTX, P1NP and PTH responses by two frequently applied methods in assessing metabolic health; oral glucose tolerance test (OGTT) and mixed meal tolerance test. Secondly, we explored the effect of insulin resistance on bone marker responses.

METHODS

We enrolled 64 subjects with abdominal obesity. Following 10 h of fasting, subjects initially underwent a standard OGTT (300 kcal) and approximately one week later a mixed meal tolerance test (1130 kcal). Circulating CTX, P1NP and PTH were assessed on both days at time = 0, after 30 min and after 90 min for comparison of the two interventions. We analyzed glucose and insulin levels for the assessment of insulin resistance. Additionally, we measured plasma calcium levels along with the gut hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like-peptide 2 (GLP-2) in an attempt to identify possible mediators of the postprandial bone response.

RESULTS

CTX, P1NP and PTH were suppressed by OGTT and the mixed meal; the latter induced a more pronounced suppression after 90 min. Calcium levels were similar between OGTT and meal. GIP and GLP-2 levels increased after both interventions, although only the meal induced a sustained increase after 90 min. Fasting P1NP was inversely associated with insulin resistance. The meal-induced suppression of P1NP (but not CTX or PTH) was inversely associated with level of insulin resistance.

CONCLUSION

The acute postprandial suppression of bone turnover markers is extended after ingestion of a mixed meal compared to an OGTT. The response appears to be independent of gender and prompted by a reduction in PTH. The study additionally indicates a possible link between the development of insulin resistance and low bone turnover - which may be of key essence in the development of the fragile bone structure and increased fracture risk demonstrated in subjects with abdominal obesity and T2D.

GIP's involvement in the pathophysiology of type 2 diabetes

During the past four decades derangements in glucose-dependent insulinotropic polypeptide (GIP) biology has been viewed upon as contributing factors to various parts of the pathophysiology type 2 diabetes. This overview outlines and discusses the impaired insulin responses to GIP as well as the effect of GIP on glucagon secretion and the potential involvement of GIP in the obesity and bone disease associated with type 2 diabetes. As outlined in this review, it is unlikely that the impaired insulinotropic effect of GIP occurs as a primary event in the development of type 2 diabetes, but rather develops once the diabetic state is present and beta cells are unable to maintain normoglycemia. In various models, GIP has effects on glucagon secretion, bone and lipid homeostasis, but whether these effects contribute substantially to the pathophysiology of type 2 diabetes is at present controversial. The review also discusses the substantial uncertainty surrounding the translation of preclinical data relating to the GIP system and outline future research directions.

Metabolomics analysis in adults with high bone mass identifies a relationship between bone resorption and circulating citrate which replicates in the general population

OBJECTIVE

Bone turnover, which regulates bone mass, may exert metabolic consequences, particularly on markers of glucose metabolism and adiposity. To better understand these relationships, we examined cross-sectional associations between bone turnover markers (BTMs) and metabolic traits in a population with high bone mass (HBM, BMD Z-score ≥+3.2).

DESIGN

β-C-terminal telopeptide of type-I collagen (β-CTX), procollagen type-1 amino-terminal propeptide (P1NP) and osteocalcin were assessed by electrochemiluminescence immunoassays. Metabolic traits, including lipids and glycolysis-related metabolites, were measured using nuclear magnetic resonance spectroscopy. Associations of BTMs with metabolic traits were assessed using generalized estimating equation linear regression, accounting for within-family correlation, adjusting for potential confounders (age, sex, height, weight, menopause, bisphosphonate and oral glucocorticoid use).

RESULTS

A total of 198 adults with HBM had complete data, mean [SD] age 61.6 [13.7] years; 77% were female. Of 23 summary metabolic traits, citrate was positively related to all BTMs: adjusted ββ-CTX  = 0.050 (95% CI 0.024, 0.076), P = 1.71 × 10-4 , βosteocalcin  = 6.54 × 10-4 (1.87 × 10-4 , 0.001), P = .006 and βP1NP  = 2.40 × 10-4 (6.49 × 10-5 , 4.14 × 10-4 ), P = .007 (β = increase in citrate (mmol/L) per 1 µg/L BTM increase). Inverse relationships of β-CTX (β = -0.276 [-0.434, -0.118], P = 6.03 × 10-4 ) and osteocalcin (-0.004 [-0.007, -0.001], P = .020) with triglycerides were also identified. We explored the generalizability of these associations in 3664 perimenopausal women (age 47.9 [4.4] years) from a UK family cohort. We confirmed a positive, albeit lower magnitude, association between β-CTX and citrate (adjusted βwomen  = 0.020 [0.013, 0.026], P = 1.95 × 10-9 ) and an inverse association of similar magnitude between β-CTX and triglycerides (β = -0.354 [-0.471, -0.237], P = 3.03 × 10-9 ).

CONCLUSIONS

Bone resorption is positively related to circulating citrate and inversely related to triglycerides. Further studies are justified to determine whether plasma citrate or triglyceride concentrations are altered by factors known to modulate bone resorption, such as bisphosphonates.

Bone health in diabetes and prediabetes

Bone fragility has been recognized as a complication of diabetes, both type 1 diabetes (T1D) and type 2 diabetes (T2D), whereas the relationship between prediabetes and fracture risk is less clear. Fractures can deeply impact a diabetic patient’s quality of life. However, the mechanisms underlying bone fragility in diabetes are complex and have not been fully elucidated. Patients with T1D generally exhibit low bone mineral density (BMD), although the relatively small reduction in BMD does not entirely explain the increase in fracture risk. On the contrary, patients with T2D or prediabetes have normal or even higher BMD as compared with healthy subjects. These observations suggest that factors other than bone mass may influence fracture risk. Some of these factors have been identified, including disease duration, poor glycemic control, presence of diabetes complications, and certain antidiabetic drugs. Nevertheless, currently available tools for the prediction of risk inadequately capture diabetic patients at increased risk of fracture. Aim of this review is to provide a comprehensive overview of bone health and the mechanisms responsible for increased susceptibility to fracture across the spectrum of glycemic status, spanning from insulin resistance to overt forms of diabetes. The management of bone fragility in diabetic patient is also discussed.

Relationship of cardiometabolic risk biomarkers with DXA and pQCT bone health outcomes in young girls

BACKGROUND

Excess weight exerts the positive effect of mechanical loading on bone during development whereas obesity-related metabolic dysfunction may have a detrimental impact. In adults, the presence of metabolic syndrome and type 2 diabetes has been associated with compromised bone density, quality, and strength, and an increased incidence of fractures. The few studies that have investigated the role of cardio-metabolic disease risk biomarkers (CMR) on bone strength in children have given conflicting results. The aim of this study was to assess the combined and independent relationships of cardio-metabolic biomarkers with total body and regional bone parameters in young girls.

METHODS

In 306, 9-12 year old girls, measures of whole body fat and lean mass, areal bone mineral density (aBMD), bone mineral content (BMC), and bone area (BA) were obtained by dual-energy x-ray absorptiometry (DXA). Bone mineral density (vBMD), geometry, and strength of metaphyseal and diaphyseal regions of the femur and tibia and a diaphyseal region of the radius were measured using peripheral quantitative computed tomography (pQCT). Fasting serum measures of CMRs included, fasting glucose, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), high-density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triglyceride (TG), systolic and diastolic blood pressure (SBP and DBP), and C-reactive protein (CRP). Multiple linear regression was used to assess the independent associations of a single CMR with total body and peripheral measures of bone strength after controlling for the other CMRs, plus total body soft tissue, and other relevant covariates. Also, a standardized total CMR composite score, calculated by standardizing to z-scores and then summing z-scores of each CMR biomarker, was regressed with total body and regional bone measures to assess the relationship of a cluster of risk factors with bone health.

RESULTS

Total CMR composite score had inverse associations (p < 0.001) with DXA total BMC and BA. Inverse associations (p < 0.05) of CMR risk score with pQCT regional bone measures occurred with total and trabecular BA at the 4% tibia. Of the individual CMRs, HOMA-IR and CRP were significant predictors of total body bone measures by DXA accounting for ~1-5% of the variance in BMC, BA, and/or aBMD. HOMA-IR was the main predictor of regional pQCT bone outcomes, accounting for the most variance in trabecular vBMD (2.6%) and BSI (3.8%) at the 4% tibia. Most markers of dyslipidemia (TG, HDL-C, LDL-C) and hypertension (SBP, DBP) were not associated (p > 0.05) with any total body or regional bone outcomes with the exception of the inverse relationship of LDL-C with total and trabecular BA and the positive relationship of DBP with cortical vBMD at the radius.

CONCLUSION

Of the obesity-related metabolic impairments, insulin resistance and chronic inflammation may compromise whole body bone development in young girls. In particular, trabecular bone, such as that found at the metaphysis of long bones, may be more susceptible to the detrimental effects associated with obesity-related metabolic dysfunction.

Effect of Sodium-Glucose Co-transporter 2 Inhibitors on Bone Metabolism and Fracture Risk

The effect of anti-diabetic medications on bone metabolism has received increasing attention, considering that type 2 diabetes mellitus is a common metabolic disorder with adverse effects on bone metabolism. Sodium-glucose co-transporter 2 (SGLT2) inhibitors are novel anti-diabetic medications that prevent glucose resorption at the proximal convoluted tubules in the kidney, increasing urinary glucose excretion, and decreasing the blood glucose level. The superiority of SGLT2 inhibitors shows in reducing the glucose level independent of insulin secretion, lowering the risk of hypoglycemia, and improving cardiovascular outcomes. SGLT2 inhibitors have been associated with genital mycotic infections, increased risk of acute kidney injury, dehydration, orthostatic hypotension, and ketoacidosis. Moreover, the effect of SGLT2 inhibitors on bone metabolism and fracture risk has been widely taken into consideration. Our review summarizes the results of current studies investigating the effects of SGLT2 inhibitors on bone metabolism (possibly including increased bone turnover, disrupted bone microarchitecture, and reduced bone mineral density). Several mechanisms are probably involved, such as bone mineral losses due to the disturbed calcium and phosphate homeostasis, as confirmed by an increase in fibroblast growth factor 23 and parathyroid hormone levels and a decrease in 1,25-dihydroxyvitamin D levels. SGLT2 inhibitors might indirectly increase bone turnover by weight loss. Lowering the blood glucose level might ameliorate bone metabolism impairment in diabetes. The effect of SGLT2 inhibitors on bone fractures remains unclear. Evidence indicating the direct effect of SGLT2 inhibitors on fracture risk is lacking and increased falls probably contribute to fractures.

Type 2 Diabetes in Relation to Hip Bone Density, Area, and Bone Turnover in Swedish Men and Women: A Cross-Sectional Study

Men and women with type 2 diabetes mellitus (T2DM) have higher risk of hip fracture, but the mechanisms are not fully understood. We aimed to investigate how T2DM, glucose, and insulin were associated with femoral bone mineral density (BMD), bone mineral area (BMA), and bone turnover markers. We used two cross-sectional cohorts: the Uppsala Longitudinal Study of Adult Men (ULSAM, n = 452, mean age 82 years) and the Swedish Mammography Cohort Clinical (SMCC, n = 4713, mean age 68 years). We identified men and women with normal fasting glucose (NFG), impaired fasting plasma glucose (IFG), and T2DM. BMD and BMA at the total hip and femoral shaft were measured using dual energy X-ray absorptiometry (DXA). Bone turnover markers; CrossLaps and osteocalcin were measured in women. Linear regression models were applied. Men and women showed a progressively higher BMD following the clinical cutoffs of fasting glucose from NFG to IFG to T2DM. In contrast, there was a progressively lower BMA. Men and women with T2DM, compared to those with NFG, had lower BMA at the total hip (- 1.7%; 95% CI - 3.2, - 0.2 and - 1.0%; 95% CI - 1.6, - 0.4) and the femoral shaft (- 2.0%; 95% CI - 3.5, - 0.4 and - 0.6%; 95% CI - 1.2, - 0.01), respectively. T2DM was associated with lower concentrations of CrossLaps (- 8.1%; 95% CI - 12.7, - 3.6) and osteocalcin (- 15.2%; 95% CI - 19.0, - 11.2). These cross-sectional results indicate that those with T2DM have smaller bone area and lower bone turnover, which could increase the risk of hip fracture.

Novel insights into the relationship between nonalcoholic fatty liver disease and osteoporosis

Excess fat deposition and insulin resistance are considered the main risk factors for nonalcoholic fatty liver disease (NAFLD), and therefore, not surprisingly, the global prevalence of NAFLD increases in parallel with both obesity and type 2 diabetes. Although deterioration of bone homeostasis in patients with NAFLD is commonly observed, its etiology has not been fully elucidated yet. It was shown in several studies that bone tissue seems to be independently associated with NAFLD. A mechanistic perspective puts the liver at the center of mutual interdependencies obviously involving adipose tissue and muscles and also the bone matrix and bone cells, which are relatively novel. In this review, various pathophysiological mechanisms and possible mediating molecules that may interplay between NAFLD and bone tissue are described. Chronic inflammation, vitamin D3, growth hormone, insulin-like growth factor 1, osteopontin, fetuin-A, irisin, osteocalcin, and osteoprotegerin from osteoblasts have been proposed as mediators of mutual interactions among the skeleton, fatty tissue, and liver. Although to date there are still many issues that have not been elucidated, growing evidence suggests that screening and surveillance of bone mineral density in patients with NAFLD should be considered in future strategies and guidelines for NAFLD management.

The effect of meals on bone turnover - a systematic review with focus on diabetic bone disease

INTRODUCTION

Type 2 diabetes is associated with an increased risk of bone fractures. Bone mineral density (BMD) is increased and bone turnover is low in type 2 diabetes and the increased BMD does not explain the increased fracture risk. However, the low bone turnover may lead to insufficient bone renewal with unrepaired micro-cracks and thus increase fracture risk. Ingestion of food acutely decreases bone resorption markers and the macronutrient composition of meals and meal frequency may influence bone metabolism adversely in subjects with unhealthy eating patterns, e.g., patients with type 2 diabetes.

AREAS COVERED

The treatment strategy of bone disease in type 2 diabetics is covered in this review. The current management of diabetic bone disease consists of anti-osteoporotic treatment. However, anti-resorptives may further reduce an already low bone turnover with uncertain effects. Furthermore, the acute and long-term effects of meal ingestion, weight loss alone and in combination with exercise as well as the possible underlying mechanisms are covered in this systematic review.

EXPERT COMMENTARY

Current management of diabetic bone disease is based on principles of anti-osteoporotic treatment in non-diabetic subjects. However, studies are urged to investigate whether anti-resorptives are equally beneficial in type 2 diabetes as in non-diabetic individuals.

Skeletal Fragility in Type 2 Diabetes Mellitus

Type 2 diabetes (T2D) is associated with an increased risk of fracture, which has been reported in several epidemiological studies. However, bone mineral density in T2D is increased and underestimates the fracture risk. Common risk factors for fracture do not fully explain the increased fracture risk observed in patients with T2D. We propose that the pathogenesis of increased fracture risk in T2D is due to low bone turnover caused by osteocyte dysfunction resulting in bone microcracks and fractures. Increased levels of sclerostin may mediate the low bone turnover and may be a novel marker of increased fracture risk, although further research is needed. An impaired incretin response in T2D may also affect bone turnover. Accumulation of advanced glycosylation endproducts may also impair bone strength. Concerning antidiabetic medication, the glitazones are detrimental to bone health and associated with increased fracture risk, and the sulphonylureas may increase fracture risk by causing hypoglycemia. So far, the results on the effect of other antidiabetics are ambiguous. No specific guideline for the management of bone disease in T2D is available and current evidence on the effects of antiosteoporotic medication in T2D is sparse. The aim of this review is to collate current evidence of the pathogenesis, detection and treatment of diabetic bone disease.

Bone Turnover in Young Adult Men: Cross-Sectional Determinants and Associations With Prospectively Assessed Bone Loss

Biochemical markers of bone turnover are higher in young adult men than in middle-aged men or young adult women. Nonetheless, little is known about the determinants and clinical significance hereof. The present study examined determinants of serum bone turnover markers in men around peak bone mass age, and explored whether bone turnover at this age predicts subsequent changes in bone mass. We used cross-sectional and longitudinal data from 973 and 428 healthy men, respectively, aged 25 to 45 years at baseline, including baseline procollagen type I amino-terminal propeptide (P1NP), osteocalcin, and C-terminal telopeptide of type I collagen (CTX) from fasting serum samples, baseline questionnaire-assessed physical activity levels, and baseline and follow-up dual-energy X-ray absorptiometry-derived areal bone mineral density (aBMD) and body composition. Mean follow-up time was 12.4 ± 0.4 years. At baseline, all bone turnover markers were inversely associated with total body fat mass (β ≤ -0.20, p < 0.001), and positively with physical activity during sports activities (β ≥ 0.09, p ≤ 0.003), and, albeit not independently from fat mass, total body lean mass (β ≥ 0.20, p ≤ 0.003). Mean annual aBMD changes in the longitudinal cohort were -0.19% ± 0.24% at the total body, -0.14% ± 0.42% at the spine, -0.49% ± 0.47% at the femoral neck, and -0.25% ± 0.37% at the total hip (all p < 0.001). Higher bone turnover markers at baseline were associated with larger decreases in aBMD at all measurement sites (β ≤ -0.08, p ≤ 0.081 for P1NP; β ≤ -0.16, p ≤ 0.002 for osteocalcin; and β ≤ -0.21, p < 0.001 for CTX). In conclusion, our findings show that sports activities and body composition, primarily fat mass, are the main identified determinants of bone turnover in men around peak bone mass age. Further, bone turnover at this age is an important determinant of subsequent changes in bone mass, with higher levels of bone turnover markers being associated with greater decreases in aBMD. © 2017 American Society for Bone and Mineral Research.

Metabolic milieu associates with impaired skeletal characteristics in obesity

High leptin concentration, low-grade inflammation, and insulin resistance often coexist in obese subjects; this adverse metabolic milieu may be the main culprit for increased fracture risk and impaired bone quality seen in patients with type 2 diabetes. We examined the associations of leptin, hs (high sensitivity)- CRP and insulin resistance with bone turnover markers (BTMs) and bone characteristics in 55 young obese adults (median BMI 40 kg/m²) and 65 non-obese controls. Mean age of the subjects was 19.5 ± 2.5 years (mean ± SD). Concentrations of leptin, adiponectin, hs-CRP, MMP-8 and TIMP-1, fasting plasma glucose and insulin (to calculate HOMA), BTMs (BAP, P1NP, CTX-1, and TRAC5b) were measured. Bone characteristics were determined with pQCT at radius and tibia, and with DXA for central sites. Leptin, hs-CRP and HOMA correlated inversely with BTMs: the partial coefficients were 1.5–1.9 fold higher in males than in females. After adjusting for age, BMI, and other endocrine factors, leptin displayed an independent effect in males on radial bone mass (p = 0.019), tibial trabecular density (p = 0.025) and total hip BMD (p = 0.043), with lower densities in males with high leptin. In females, the model adjusting for age, BMI, and other endocrine factors, revealed that hs-CRP had independent effects on radial bone mass (p = 0.034) and lumbar spine BMD (p = 0.016), women with high hs-CRP having lower values. Partial correlations of adiponectin and TIMP-1 with bone characteristics were discrepant; MMP-8 showed no associations. In conclusion, in young obese adults and their controls, leptin, hs-CRP and HOMA associate inversely with BTMs and bone characteristics. Leptin appears to be the key independent effector in males, whereas hs-CRP displayed a predominant role in females.

Insulin Resistance Is Associated With Smaller Cortical Bone Size in Nondiabetic Men at the Age of Peak Bone Mass

CONTEXT

In type 2 diabetes mellitus, fracture risk is increased despite preserved areal bone mineral density. Although this apparent paradox may in part be explained by insulin resistance affecting bone structure and/or material properties, few studies have investigated the association between insulin resistance and bone geometry.

OBJECTIVE

We aimed to explore this association in a cohort of nondiabetic men at the age of peak bone mass.

DESIGN, SETTING, AND PARTICIPANTS

Nine hundred ninety-six nondiabetic men aged 25 to 45 years were recruited in a cross-sectional, population-based sibling pair study at a university research center.

MAIN OUTCOME MEASURES

Insulin resistance was evaluated using the homeostasis model assessment of insulin resistance (HOMA-IR), with insulin and glucose measured from fasting serum samples. Bone geometry was assessed using peripheral quantitative computed tomography at the distal radius and the radial and tibial shafts.

RESULTS

In age-, height-, and weight-adjusted analyses, HOMA-IR was inversely associated with trabecular area at the distal radius and with cortical area, periosteal and endosteal circumference, and polar strength strain index at the radial and tibial shafts (β ≤ -0.13, P < 0.001). These associations remained essentially unchanged after additional adjustment for dual-energy X-ray absorptiometry-derived body composition, bone turnover markers, muscle size or function measurements, or adiponectin, leptin, insulin-like growth factor 1, or sex steroid levels.

CONCLUSION

In this cohort of nondiabetic men at the age of peak bone mass, insulin resistance is inversely associated with trabecular and cortical bone size. These associations persist after adjustment for body composition, muscle size or function, or sex steroid levels, suggesting an independent effect of insulin resistance on bone geometry.

MECHANISMS IN ENDOCRINOLOGY: Diabetes mellitus, a state of low bone turnover - a systematic review and meta-analysis

OBJECTIVE

To investigate the differences in bone turnover between diabetic patients and controls.

DESIGN

A systematic review and meta-analysis.

METHODS

A literature search was conducted using the databases Medline at PubMed and EMBASE. The free text search terms 'diabetes mellitus' and 'bone turnover', 'sclerostin', 'RANKL', 'osteoprotegerin', 'tartrate-resistant acid' and 'TRAP' were used. Studies were eligible if they investigated bone turnover markers in patients with diabetes compared with controls. Data were extracted by two reviewers.

RESULTS

A total of 2881 papers were identified of which 66 studies were included. Serum levels of the bone resorption marker C-terminal cross-linked telopeptide (-0.10 ng/mL (-0.12, -0.08)) and the bone formation markers osteocalcin (-2.51 ng/mL (-3.01, -2.01)) and procollagen type 1 amino terminal propeptide (-10.80 ng/mL (-12.83, -8.77)) were all lower in patients with diabetes compared with controls. Furthermore, s-tartrate-resistant acid phosphatase was decreased in patients with type 2 diabetes (-0.31 U/L (-0.56, -0.05)) compared with controls. S-sclerostin was significantly higher in patients with type 2 diabetes (14.92 pmol/L (3.12, 26.72)) and patients with type 1 diabetes (3.24 pmol/L (1.52, 4.96)) compared with controls. Also, s-osteoprotegerin was increased among patients with diabetes compared with controls (2.67 pmol/L (0.21, 5.14)).

CONCLUSIONS

Markers of both bone formation and bone resorption are decreased in patients with diabetes. This suggests that diabetes mellitus is a state of low bone turnover, which in turn may lead to more fragile bone. Altered levels of sclerostin and osteoprotegerin may be responsible for this.