There is an increase in the risk of bone fracture with aging and adult diabetes, and this increase cannot be solely explained by changes in bone mineral density (BMD). One barrier to new diagnostic tools and treatments is that the underlying cause for the disproportionate increase in fracture risk among diabetics and the elderly is currently unknown. Consequently, there is a need to identify the biophysical basis of the age- and diabetes-related changes in bone that decrease fracture resistance, not just bone strength. Addressing this, the proposal aims to determine whether increases in advanced glycation end-products (AGEs) explain the effect of diabetes and aging on the fracture resistance of bone (as characterized by fracture properties) and to determine whether an AGE inhibitor and/or an antioxidant can both improve the quality of bone structure and increase the fracture properties of bone.
Aim 1 will determine the role of bone structure, BMD, and AGEs in the effect of Type 2 Diabetes (T2D) and aging on the fracture properties of bone. In the first experiment, bones will be collected from T2D rats and non-diabetic rats at 24 weeks and 32 weeks of age. In the second experiment, bones will be harvested from aging rats at 4 months (young), 12 months (adult), and 24 months (old) of age. All the bones will undergo extensive analysis in order to identify the relative contribution of compositional properties such as BMD and AGEs and structural properties such as moment of inertia to a set of biomechanical properties including traditional measurements of strength and new measurements of fracture toughness and fatigue life.
Aim 2 will evaluate how exogenous glycation of collagen affects the fracture properties of bone.
This aim i nvestigates whether the direct accumulation of AGEs within the extracellular matrix of bone decreases the fracture resistance of bone and whether the AGE inhibitor pyridoxamine, a B6 vitamin, protects against such a change. With appropriate controls, both human cortical bone and rodent bone will be incubated in diabetic concentrations of glucose with and without the inclusion of pyridoxamine. After quantifying the concentration of pentosidine, a biomarker for AGEs, and BMD, each specimen will be subjected to a mechanical test. In the case of the human bone, tests will determine the effects of increasing AGE on bone strength, post-yield energy dissipation, fatigue life, and crack-initiation &crack-growth toughness. For the rodent bones, tests will determine the effect of increasing AGE on fatigue life and fracture toughness, the ability to resist crack propagation.
Aim 3 will assess the efficacy of pyridoxamine and N-acetylcysteine to increase fracture resistance of bone in an aging rat model of T2D through changes in bone structure, BMD, and AGEs. In this translation aim, the role of oxidative stress and AGE accumulation in the aging and diabetic effects on bone will be investigated using these two compounds. Starting at 4 months of age, non-diabetic and T2D rats will drink water, water with pyridoxamine, or water with N-acetylcysteine, an antioxidant. After 4 months, 8 months, and 14 months (aging) of treatment, bones will be harvested for extensive analysis to determine the effects of treatment on the structural, compositional, and biomechanical properties of bone. Additionally, histological and cell culture assays will assess the biological effects of the compounds on oxidative stress and osteoblast differentiation. To achieve these aims, Micro-Computed Tomography will quantify volumetric BMD;high performance liquid chromatography will quantify the concentration of crosslinks and collagen content;and thermal gravimetric analysis will quantify the collagen and mineral fractions as well as water content. Statistical models will determine the relative contribution of the structural and the compositional properties to the fracture properties of bone. This will address the relevance of targeting oxidative stress and AGEs to improve the bone health of Veterans and prevent bone fractures. The long-term goal is to identify the factors affecting the important determinants of fracture resistance and developing accurate diagnostic assessments of fracture risk.

Public Health Relevance

The incidence of bone fractures increases with age and diabetes, and this phenomenon cannot be attributed to a decrease in bone mineral density (BMD). Greater numbers of Veterans are living longer, and many Veterans are developing type 2 diabetes. Thus, the number of fractures will increase. This is a rather significant problem because 1) current clinical tools based on BMD measurements do not necessarily identify individuals at risk of a fracture, 2) fracture resistance is more than just a problem of low BMD and low bone strength, 3) fractures are costly to repair and are associated with a high mortality rate, and 4) current osteoporosis drugs targeted to increasing BMD may not reduce the fracture risk of diabetics. Thus, there is a need to identify new mechanisms that affect the quality of bone tissue. The proposed research therefore explores oxidative stress and the accumulation of non-enzymatic crosslinks as factors underlying the biophysical changes that reduce the fracture resistance of bone.

National Institute of Health (NIH)
Veterans Affairs (VA)
Non-HHS Research Projects (I01)
Project #
Application #
Study Section
Endocriniology A (ENDA)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Veterans Health Administration
United States
Zip Code
Unal, Mustafa; Creecy, Amy; Nyman, Jeffry S (2018) The Role of Matrix Composition in the Mechanical Behavior of Bone. Curr Osteoporos Rep 16:205-215
Unal, Mustafa; Uppuganti, Sasidhar; Leverant, Calen J et al. (2018) Assessing glycation-mediated changes in human cortical bone with Raman spectroscopy. J Biophotonics 11:e201700352
Nyman, Jeffry S; Kalaitzoglou, Evangelia; Clay Bunn, R et al. (2017) Preserving and restoring bone with continuous insulin infusion therapy in a mouse model of type 1 diabetes. Bone Rep 7:1-8
Makowski, Alexander J; Granke, Mathilde; Ayala, Oscar D et al. (2017) Applying Full Spectrum Analysis to a Raman Spectroscopic Assessment of Fracture Toughness of Human Cortical Bone. Appl Spectrosc 71:2385-2394
Thrailkill, Kathryn M; Nyman, Jeffry S; Bunn, R Clay et al. (2017) The impact of SGLT2 inhibitors, compared with insulin, on diabetic bone disease in a mouse model of type 1 diabetes. Bone 94:141-151
Mitra, Debika; Fatakdawala, Hussain; Nguyen-Truong, Michael et al. (2017) Detection of Pentosidine Cross-Links in Cell-Secreted Decellularized Matrices Using Time Resolved Fluorescence Spectroscopy. ACS Biomater Sci Eng 3:1944-1954
Uppuganti, Sasidhar; Granke, Mathilde; Manhard, Mary Kate et al. (2017) Differences in sensitivity to microstructure between cyclic- and impact-based microindentation of human cortical bone. J Orthop Res 35:1442-1452
Thrailkill, Kathryn M; Clay Bunn, R; Nyman, Jeffry S et al. (2016) SGLT2 inhibitor therapy improves blood glucose but does not prevent diabetic bone disease in diabetic DBA/2J male mice. Bone 82:101-7
Nyman, Jeffry S; Granke, Mathilde; Singleton, Robert C et al. (2016) Tissue-Level Mechanical Properties of Bone Contributing to Fracture Risk. Curr Osteoporos Rep 14:138-50
Granke, Mathilde; Makowski, Alexander J; Uppuganti, Sasidhar et al. (2016) Prevalent role of porosity and osteonal area over mineralization heterogeneity in the fracture toughness of human cortical bone. J Biomech 49:2748-2755

Showing the most recent 10 out of 18 publications