Long-duration type 1 diabetes is associated with deficient cortical bone mechanical behavior and altered matrix composition in human femoral bone

Abstract

Type 1 diabetes (T1D) is associated with an increased risk of hip fracture beyond what can be explained by reduced bone mineral density, possibly due to changes in bone material from accumulation of advanced glycation end products (AGEs) and altered matrix composition, though data from human cortical bone in T1D are limited. The objective of this study was to evaluate cortical bone material behavior in T1D by examining specimens from cadaveric femora from older adults with long-duration T1D (≥50 years; n = 20) and age- and sex-matched non-diabetic controls (n = 14). Cortical bone was assessed by mechanical testing (4-point bending, cyclic reference point indentation, impact microindentation), AGE quantification (total fluorescent AGEs, pentosidine, carboxymethyl-lysine (CML)), and matrix composition via Raman spectroscopy. Cortical bone from older adults with T1D had diminished post-yield toughness to fracture (-30%, P=.036), elevated levels of AGEs (pentosidine, +17%, P=.039), lower mineral crystallinity (-1.4%, P=.010), greater proline hydroxylation (+1.9%, P=.009), and reduced glycosaminoglycan (GAG) content (-1.3%, P<.03) compared to non-diabetics. In multiple regression models to predict cortical bone toughness, cortical tissue mineral density (Ct.TMD), CML, and Raman spectroscopic measures of enzymatic collagen crosslinks and GAG content remained highly significant predictors of toughness, while diabetic status was no longer significant (adjusted R2 > 0.60, P<.001). Thus, impairment of cortical bone to absorb energy following long-duration T1D is well explained by AGE accumulation and modifications to the bone matrix. These results provide novel insight into the pathogenesis of skeletal fragility in individuals with T1D.