In Vivo Removal of Advanced Glycation End-products Rescues Type-II Diabetes Skeletal Fragility
Bone fracture, a serious diabetic complication, contributes significantly to health care costs and affect quality of life including increased morbidity and mortality. Risk of fracture is increased 3-folds in patients with type-II diabetes (T2D) despite normal to high bone mineral density (BMD). Consequently, the increase fracture risk in T2D patients is paradoxical and suggests that there may be diabetes-associated detrimental alterations within bone extracellular matrix. This study seeks to determine and remove such modifications to rescue T2D associated bone fragility. In particular, non-enzymatic glycation (NEG) of bone, a post translational modification of long-lived extracellular matrix proteins by sugars, is associated with T2D and linked to fragility fractures. Pentosidine (PEN) is the only established clinical marker of NEG in bone but it represents <1% of total fluorescent Advanced Glycation End-products (fAGEs). Here for the first time, we show that Carboxymethyl-lysine (CML), a non-fluorescent AGE, is 40-100 times more prevalent in bone matrix than PEN, and CML is highly correlated to bone toughness (a measure of bone fracture). More importantly, AGEs in bone can be cleaved in-vitro by phenacylthiazolium-based compounds. However, AGE based prediction and rescue of T2D bone fragility needs to be established in a relevant in-vivo model in order to pursue a larger (R01) federally funded investigation. Thus, the overall goal of the proposed pilot and feasibility study is to determine the contribution of AGEs to diabetic fractures and rescue T2D bone fragility by removal of AGEs. Using a validated preclinical diet-induced rat model, we will test whether removal of AGEs with phenacylthiazolium chloride (PTC) in-vivo rescues T2D bone fragility by measuring CML, PEN, and fAGEs (by UPLC and fluorometric assays), bone strength, and fracture toughness. The findings of our pilot study will provide a new understanding of the role of AGEs in T2D-induced skeletal fragility and establish feasibility of new strategies to predict, manage, and mitigate T2D fractures.