Lean mass predicts hip geometry in men and women with non-insulin-requiring type 2 diabetes mellitus

Associations of Type 2 Diabetes, Body Composition, and Insulin Resistance with Bone Parameters: The Dubbo Osteoporosis Epidemiology Study

Type 2 diabetes (T2D) may be associated with increased risk of fractures, despite preserved bone mineral density (BMD). Obesity and insulin resistance (IR) may have separate effects on bone turnover and bone strength, which contribute to skeletal fragility. We characterized and assessed the relative associations of obesity, body composition, IR, and T2D on bone turnover markers (BTMs), BMD, and advanced hip analysis (AHA). In this cross-sectional analysis of Dubbo Osteoporosis Epidemiology Study, 525 (61.3% women) participants were grouped according to T2D, IR (homeostasis model assessment insulin resistance [HOMA-IR] Collapse

Key Words

• BIOCHEMICAL MARKERS OF BONE TURNOVER
• BONE‐FAT INTERACTIONS
• DUAL‐ENERGY X‐RAY ABSORPTIOMETRY
• FRACTURE RISK ASSESSMENT
• STATISTICAL METHODS

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MESH Headings Collapse

Grants

• St. Vincent's Clinic Foundation

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Affiliation(s)

Angela Sheu Skeletal Diseases ProgramGarvan Institute of Medical ResearchSydneyNSWAustralia School of Clinical Medicine, UNSW Medicine and Health, St Vincent's Clinical Campus, Faculty of Medicine and HealthUNSW SydneySydneyNSWAustralia Department of Endocrinology and DiabetesSt Vincent's HospitalSydneyNSWAustralia
Robert D. Blank Skeletal Diseases ProgramGarvan Institute of Medical ResearchSydneyNSWAustralia
Thach Tran Skeletal Diseases ProgramGarvan Institute of Medical ResearchSydneyNSWAustralia School of Clinical Medicine, UNSW Medicine and Health, St Vincent's Clinical Campus, Faculty of Medicine and HealthUNSW SydneySydneyNSWAustralia
Dana Bliuc Skeletal Diseases ProgramGarvan Institute of Medical ResearchSydneyNSWAustralia School of Clinical Medicine, UNSW Medicine and Health, St Vincent's Clinical Campus, Faculty of Medicine and HealthUNSW SydneySydneyNSWAustralia
Jerry R. Greenfield Skeletal Diseases ProgramGarvan Institute of Medical ResearchSydneyNSWAustralia School of Clinical Medicine, UNSW Medicine and Health, St Vincent's Clinical Campus, Faculty of Medicine and HealthUNSW SydneySydneyNSWAustralia Department of Endocrinology and DiabetesSt Vincent's HospitalSydneyNSWAustralia
Christopher P. White School of Clinical Medicine, Prince of Wales Clinical Campus, Faculty of Medicine and HealthUNSW SydneySydneyNSWAustralia Department of Endocrinology and MetabolismPrince of Wales HospitalSydneyNSWAustralia
Jacqueline R. Center Skeletal Diseases ProgramGarvan Institute of Medical ResearchSydneyNSWAustralia School of Clinical Medicine, UNSW Medicine and Health, St Vincent's Clinical Campus, Faculty of Medicine and HealthUNSW SydneySydneyNSWAustralia Department of Endocrinology and DiabetesSt Vincent's HospitalSydneyNSWAustralia

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Contributors to impaired bone health in type 2 diabetes

Type 2 diabetes (T2D) is associated with numerous complications, including increased risk of fragility fractures, despite seemingly protective factors [e.g., normal bone mineral density and increased body mass index(BMI)]. However, fracture risk in T2D is underestimated by current fracture risk calculators. Importantly, post-fracture mortality is worse in T2D following any fracture, highlighting the importance of identifying high-risk patients that may benefit from targeted management. Several diabetes-related factors are associated with increased fracture risk, including exogenous insulin therapy, vascular complications, and poor glycaemic control, although detailed comprehensive studies to identify the independent contributions of these factors are lacking. The underlying pathophysiological mechanisms are complex and multifactorial, with different factors contributing during the course of T2D disease. These include obesity, hyperinsulinaemia, hyperglycaemia, accumulation of advanced glycation end products, and vascular supply affecting bone-cell function and survival and bone-matrix composition. This review summarises the current understanding of the contributors to impaired bone health in T2D, and proposes an updated approach to managing these patients.

Diabetes and Osteoporosis: Part II, Clinical Management

Diabetes-induced osteoporosis is characterized by an increase in fracture risk. FRAX, the most widely used tool, underestimates the risk of fracture in both type 1 and type 2 diabetes. Specific adjustments to FRAX can help to better identify patients with diabetes at increased risk of fracture and select those at high fracture risk for treatment. Although clinical trial data are limited, the available evidence indicates that the presence of diabetes does not alter antiosteoporotic treatment response in patients with diabetes.

Bone tissue material composition is compromised in premenopausal women with Type 2 diabetes

Type 2 diabetes mellitus (T2DM) patients are at an increased risk of fracture despite normal to high bone mineral density (BMD) values. In this cross-sectional study we establish bone compositional properties in tetracycline labeled iliac crest biopsies from premenopausal women diagnosed with T2DM (N = 26). Within group comparisons were made as a function of tissue age (TA), presence of chronic complications (CC), glycosylated haemoglobin (HbA1c) levels, and morphometric fracture (MFx). We also compared these data at actively trabecular bone forming surfaces against sex- and age-matched healthy controls (N = 32). The bone quality indices determined by Raman microspectroscopic analysis were: mineral/matrix (MM), tissue water content (nanoporosity; NanoP), mineral maturity/crystallinity (MMC), and glycosaminoglycan (GAG), pyridinoline (Pyd), N-(carboxymethyl)lysine (CML), and pentosidine (PEN) content. Within the T2DM group, at the oldest tissue, CML and PEN contents were significantly elevated in the cancellous compared to cortical compartment. The outcomes were not dependent on MFx. On the other hand, both were significantly elevated in patients with CC, as well as those with HbA1c levels > 7%. At actively forming surfaces, the cortical compartment had higher NanoP compared to cancellous. Still within the T2DM group, patients with MFx had significantly elevated MM and GAGs compared to the ones that did not. At actively forming trabecular surfaces, compared to healthy women, T2DM patients had elevated GAGs content and MMC. The results of this study indicate increased AGEs in those with poor glycation control and chronic complications. Additionally, T2DM patients had elevated MMC and decreased GAGs content compared to healthy controls. These alterations may be contributing to the T2DM inherent elevated fracture risk and suggest a role for hyperglycemia on bone quality.

A genome-wide association study identifies new genes associated with developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is one of the most common congenital malformations and covers a spectrum of hip disorders from mild dysplasia to irreducible dislocation. The pathological mechanisms of DDH are poorly understood, which hampers the development of diagnostic tools and treatments. To gain insight into its disease mechanism, we explored the potential biological processes that underlie DDH by integrating pathway analysis tools and performing a genome-wide association study (GWAS). A total of 406 DDH-associated genes (P < 0.001) were identified by our GWAS using a Chinese Han cohort consisting of 386 DDH cases and 500 healthy controls (Set A). We verified the significant loci (P < 10^-5 ) in another Chinese Han cohort consisting of 574 DDH patients and 569 healthy controls (Set B). An intronic Single Nucleotide Polymorphism (SNP) (rs61930502) showed significant association in Set A and Set B (P = 2.65 × 10^-7 and 2.0 × 10^-4 , respectively). The minor allele, rs61930502-A, which tended to prevent DDH showed a dominant effect. Heat shock 70 kDa protein 8 (HSPA8) showed the most direct interactions with other proteins which were coded by DDH-associated genes in the protein-protein interaction analysis. Interestingly, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis suggested a relation between DDH and the genes involved in type II diabetes mellitus pathway (P = 0.0067). Our genetic and protein interaction evidence could open avenues for future studies of DDH.

Working to Increase Stability through Exercise (WISE): Study protocol for a pragmatic randomized controlled trial of a coached exercise program to reduce serious fall-related injuries

Approximately one-third of older adults fall each year and fall-related injuries are a leading cause of death and disability among this rapidly expanding age group. Despite the availability of bisphosphonates to reduce fractures, concerns over side effects have dramatically reduced use, suggesting that other treatment options are needed. Though many smaller studies have shown that physical activity programs can reduce falls, no study has been adequately powered to detect a reduction in fall-related injuries. We present the design of a three-year randomized controlled clinical trial of 1130 adults age 65 and older with a past history of fragility fractures (e.g., vertebral, fall-related). The main aim is to determine the impact of a community-based multicomponent (strength, balance, aerobic) physical activity program led by trained volunteers (or delivered via DVD) and accompanied by coaching and oversight, by telephone and in-person, by a fitness professional. The main outcome measure is serious fall-related injuries. Secondary outcomes include health care utilization, bone and muscle mass, loneliness, health-related quality of life and mood. The study represents the first large clinical trial of a comprehensive physical activity program to reduce secondary injuries among patients with a history of fragility fracture.

Association of Insulin Resistance with Bone Strength and Bone Turnover in Menopausal Chinese-Singaporean Women without Diabetes

Insulin resistance (IR) is accompanied by increased areal or volumetric bone mineral density (aBMD or vBMD), but also higher fracture risk. Meanwhile, imbalances in bone health biomarkers affect insulin production. This study investigates the effect of IR on proximal femur and lumbar spine BMD, femoral neck bending, compressive and impact strength indices (Composite Strength Indices) and circulating levels of parathyroid hormone (PTH), C-telopeptide of Type I collagen (CTx-1) and 25(OH) Vitamin D₃, in a cohort of 97 healthy, non-obese, menopausal Chinese-Singaporean women. Lumbar spine aBMD was inversely associated with IR and dependent on lean body mass (LBM) and age. No such associations were found for vBMD of the third lumbar vertebra, aBMD and vBMD of the proximal femur, or circulating levels of PTH, CTx-1 and 25(OH) Vitamin D₃. Composite Strength Indices were inversely associated with IR and independent of LBM, but after adjusting for fat mass and age, this association remained valid only for the impact strength index. Composite Strength Indices were significantly lower in participants with a high degree of IR. Our findings on IR and Composite Strength Indices relationships were in agreement with previous studies on different cohorts, but those on IR and BMD associations were not.

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.

DXA-Based Measurements in Diabetes: Can They Predict Fracture Risk?

In the absence of a fragility fracture, osteoporosis is usually diagnosed from bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA). Osteoporosis is an increasingly prevalent disease, as is diabetes [in particular type 2 diabetes (T2D)], in part due to aging populations worldwide. It has been suggested that an increased risk of fracture may be another complication ensuing from longstanding diabetes. The purpose of this review is to concentrate on skeletal parameters and techniques readily available from DXA scanning, and their utility in routine clinical practice for predicting fracture risk. In addition to BMD, other applications and measures from DXA include trabecular bone score (TBS), skeletal geometry and DXA-based finite-element analysis, vertebral fracture assessment, and body composition. In type 1 diabetes (T1D), BMD and FRAX^R (when secondary osteoporosis is included without BMD) only partially account for the excess risk of fracture in T1D. Consistent data exist to show that BMD and FRAX^R can be used to stratify fracture risk in T2D, but do not account for the increased risk of fracture. However, several adjustments to the FRAX score can be made as proxies for T2D to inform the use of FRAX by primary care practitioners. Examples include using the rheumatoid arthritis input (as a proxy for T2D), lumbar spine TBS (to adjust FRAX probability) or an altered hip T-score (lowered by 0.5 units). These adjustments can improve fracture risk prediction in T2D and help to avoid systematically underestimating the risk of osteoporosis-related fractures in those with diabetes.

The genetics of bone mass and susceptibility to bone diseases

Osteoporosis is characterized by low bone mass and an increased risk of fracture. Genetic factors, environmental factors and gene-environment interactions all contribute to a person's lifetime risk of developing an osteoporotic fracture. This Review summarizes key advances in understanding of the genetics of bone traits and their role in osteoporosis. Candidate-gene approaches dominated this field 20 years ago, but clinical and preclinical genetic studies published in the past 5 years generally utilize more-sophisticated and better-powered genome-wide association studies (GWAS). High-throughput DNA sequencing, large genomic databases and improved methods of data analysis have greatly accelerated the gene-discovery process. Linkage analyses of single-gene traits that segregate in families with extreme phenotypes have led to the elucidation of critical pathways controlling bone mass. For example, components of the Wnt-β-catenin signalling pathway have been validated (in both GWAS and functional studies) as contributing to various bone phenotypes. These notable advances in gene discovery suggest that the next decade will witness cataloguing of the hundreds of genes that influence bone mass and osteoporosis, which in turn will provide a roadmap for the development of new drugs that target diseases of low bone mass, including osteoporosis.

Sex-specific differences in progressive glucose intolerance and hip geometry: the Baltimore Longitudinal Study of Aging

Fracture risk is increased in type 2 diabetes mellitus (T2DM). The effect of pre-diabetes and T2DM on bone macroarchitecture and strength has not been well investigated. In this study, we show that in women only, both pre-diabetes and T2DM are associated with decreased hip bending strength and mineralization which might lead to skeletal weakness.

INTRODUCTION

Older men and women with T2DM are at increased risk for fracture despite normal bone mineral density (BMD). The discordance between bone quantity and skeletal fragility has driven investigation into additional determinants of fracture resistance in T2DM. Additionally, the effect of pre-diabetes on bone strength has not been well described. The aim of this study was to determine differences in bone macroarchitecture and strength, measured by hip geometry, in persons with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and T2DM.

METHODS

We performed cross-sectional analyses of older (age >55 years) men (n = 472) and women (n = 473) participating in the Baltimore Longitudinal Study of Aging (BLSA) classified as NGT, IGT, or T2DM based on oral glucose tolerance testing. Bone strength measures included the hip geometry parameters of section modulus (Z), cross-sectional area (CSA), and buckling ratio (BR). Sex-stratified analyses were conducted using adjusted stepwise regression models.

RESULTS

In women, IGT and T2DM were negatively associated with hip geometry parameters including mineralization in cross section (CSA, ß -0.076 and -0.073, respectively; both p < 0.05) and hip bending strength (Z, ß -0.097 and -0.09, respectively; both p < 0.05); conversely, IGT and T2DM were associated with improved compressive strength (BR, ß -0.31 and -0.29, respectively; both p < 0.05). There was no significant association between glycemic status and hip geometry in men.

CONCLUSIONS

In women only, both IGT and T2DM were inversely associated with bone macroarchitecture and measures of bone mineralization and bending strength. The same association between worsening glycemic status and bone strength was not observed in men. These data suggest a differential effect of sex on hip geometry with evolving glucose intolerance.

Effects of leucine-rich protein supplements on anthropometric parameter and muscle strength in the elderly: a systematic review and meta-analysis

OBJECTIVE

The primary objective of the present systematic review and meta-analysis was to synthesize the available literature relating to leucine supplementation in the elderly with respect to its effects on anthropometrical parameters and muscle strength. The secondary aim was to perform a selective subgroup analysis when possible differentiating between healthy and sarcopenic subjects.

METHODS

Literature search was performed using the electronic databases MEDLINE, EMBASE, SportDiscus, and the Cochrane Central Register of trials with restrictions to randomized controlled trials or studies following a cross-over design. Parameters taken into account were body weight, body mass index, lean body mass, fat mass, percentage of body fat, hand grip strength, and knee extension strength. Moreover, biomarkers of glucose metabolism (fasting glucose, fasting insulin, albumin, and HOMA index) were extracted when possible. For each outcome measure of interest, a meta-analysis was performed in order to determine the pooled effect of the intervention in terms of weighted mean differences between the post-intervention (or differences in means) values of the leucine and the respective control groups. Data analysis was performed using the Review Manager 5.2.4. software.

RESULTS

A total of 16 studies enrolling 999 subjects met the inclusion criteria. Compared with control groups, leucine supplementation significantly increased gain in body weight [mean differences 1.02 kg, 95%-CI (0.19, 1.85), p=0.02], lean body mass [mean differences 0.99 kg, 95%-CI (0.43, 1.55), p=0.0005], and body mass index [mean differences 0.33 kg/m2, 95%-CI (0.13, 0.53), p=0.001], when compared to the respective control groups. With respect to body weight and lean body mass, leucine supplementation turned out to be more effective in the subgroup of study participants with manifested sarcopenia. All other parameters under investigation were not affected by leucine supplementation in a fashion significantly different from controls.

CONCLUSIONS

It is concluded that leucine supplementation was found to exert beneficial effects on body weight, body mass index, and lean body mass in older persons in those subjects already prone to sarcopenia, but not muscle strength. However, due to the heterogeneity between the trials included in this systematic review, further studies adopting a homogenous design with respect to participant characteristics duration as well as the kind and amount of daily supplement in use are required.

Increased fracture risk in patients with type 2 diabetes mellitus: an overview of the underlying mechanisms and the usefulness of imaging modalities and fracture risk assessment tools

Type 2 diabetes mellitus has recently been linked to an increased fracture risk. Since bone mass seems to be normal to elevated in patient with type 2 diabetes, the increased fracture risk is thought to be due to both an increased falling frequency and decreased bone quality. The increased falling frequency is mainly a result of complications of the disease such as a retinopathy and polyneuropathy. Bone quality is affected through changes in bone shape, bone micro-architecture, and in material properties such as bone mineralization and the quality of collagen. Commonly used methods for predicting fracture risk such as dual energy X-ray absorptiometry and fracture risk assessment tools are helpful in patients with type 2 diabetes mellitus, but underestimate the absolute fracture risk for a given score. New imaging modalities such as high resolution peripheral quantitative computed tomography are promising for giving insight in the complex etiology underlying the fragility of the diabetic bone, as they can give more insight into the microarchitecture and geometry of the bone. We present an overview of the contributing mechanisms to the increased fracture risk and the usefulness of imaging modalities and risk assessment tools in predicting fracture risk in patients with type 2 diabetes.

Hip geometry in diabetic women: implications for fracture risk

OBJECTIVE

Women with type 2 diabetes mellitus (T2DM) have a higher risk of fractures despite increased bone mineral density (BMD) as compared to women without diabetes. We hypothesized that bone strength is diminished in women with T2DM after accounting for lean body mass, which may contribute to their increased fracture risk.

METHODS

Participants from Women's Health Initiative Observational Study were included in this cross-sectional study. These analyses include 3 groups of women: 1) T2DM women on diet or oral hypoglycemic agents (n=299); 2) T2DM women on insulin therapy (with or without oral agents) (n=128); and 3) Non-diabetic control women (n=5497). Hip structural analyses were done using the validated Beck's method on hip scans from dual energy x-ray absorptiometry (DXA). We compared BMD and section modulus (bending strength) at the narrow neck with and without correcting for total body DXA lean body mass.

RESULTS

Women in all three groups were of similar ages (63.7, 64.6 and 64.2 years, respectively) and heights, but those with T2DM were heavier, with greater lean body weight vs controls (P<.001). In both diabetic groups, absolute BMD and section modulus were higher compared with controls. However, after adjusting for total lean body weight, diabetic women on insulin had significantly lower BMD and section modulus.

CONCLUSION

Adjusted for lean body weight, the BMD and bending strength in the femoral neck are significantly lower in insulin-treated diabetic women vs controls. This may represent altered adaptation of bone modeling and explain the higher fracture risk in patients with T2DM.

The genetic pleiotropy of musculoskeletal aging

Musculoskeletal aging is detrimental to multiple bodily functions and starts early, probably in the fourth decade of an individual's life. Sarcopenia is a health problem that is expected to only increase as a greater portion of the population lives longer; prevalence of the related musculoskeletal diseases is similarly expected to increase. Unraveling the biological and biomechanical associations and molecular mechanisms underlying these diseases represents a formidable challenge. There are two major problems making disentangling the biological complexity of musculoskeletal aging difficult: (a) it is a systemic, rather than "compartmental," problem, which should be approached accordingly, and (b) the aging per se is neither well defined nor reliably measurable. A unique challenge of studying any age-related condition is a need of distinguishing between the "norm" and "pathology," which are interwoven throughout the aging organism. We argue that detecting genes with pleiotropic functions in musculoskeletal aging is needed to provide insights into the potential biological mechanisms underlying inter-individual differences insusceptibility to the musculoskeletal diseases. However, exploring pleiotropic relationships among the system's components is challenging both methodologically and conceptually. We aimed to focus on genetic aspects of the cross-talk between muscle and its "neighboring" tissues and organs (tendon, bone, and cartilage), and to explore the role of genetics to find the new molecular links between skeletal muscle and other parts of the "musculoskeleton." Identification of significant genetic variants underlying the musculoskeletal system's aging is now possible more than ever due to the currently available advanced genomic technologies. In summary, a "holistic" genetic approach is needed to study the systems's normal functioning and the disease predisposition in order to improve musculoskeletal health.

Type 2 diabetes and bone fractures

PURPOSE OF REVIEW

To discuss current literature and hypotheses pertaining to the pathophysiology of increased bone fragility and fracture in men and women with type 2 diabetes mellitus.

RECENT FINDINGS

Despite high bone mineral density, studies have shown that men and women with type 2 diabetes mellitus (T2DM) are at increased risk for fracture. Complications of T2DM including retinopathy and autonomic dysfunction may contribute to bone fracture by increasing fall risk. Nephropathy may lead to renal osteodystrophy. Lean mass and potentially fat mass, may additionally contribute to skeletal health in diabetes. There is increasing acknowledgement that the marrow microenvironment is critical to efficient bone remodeling. Medications including thiazolidinediones and selective serotonin reuptake inhibitors may also impair bone remodeling by acting on mesenchymal stem cell differentiation and osteoblastogenesis. T2DM is associated with significant alterations in systemic inflammation, advanced glycation end-product accumulation and reactive oxygen species generation. These systemic changes may also directly and adversely impact the remodeling cycle and lead to bone fragility in T2DM, though more research is needed.

SUMMARY

Fracture is a devastating event with dismal health consequences. Identifying the extrinsic and intrinsic biochemical causes of bone fracture in T2DM will speed the discovery of effective strategies for fracture prevention and treatment in this at-risk population.