Biochemical Markers of Bone Turnover in Older Adults With Type 1 Diabetes

Context Type 1 diabetes (T1D) is characterized by high fracture risk, yet little is known regarding diabetes-related mechanisms or risk factors. Objective Determine whether glycemic control, advanced glycation end products (AGEs), and microvascular complications are associated with bone turnover markers among older T1D adults. Design Cross-sectional. Setting Epidemiology of Diabetes Interventions and Complications study (6 of 27 clinical centers). Participants 232 T1D participants followed for >30 years. Exposures Glycemic control ascertained as concurrent and cumulative hemoglobin A1c (HbA1c); kidney function, by estimated glomerular filtration rates (eGFR); and AGEs, by skin intrinsic fluorescence. Main Outcome Measures Serum procollagen 1 intact N-terminal propeptide (PINP), bone-specific alkaline phosphatase (bone ALP), serum C-telopeptide (sCTX), tartrate-resistant acid phosphatase 5b (TRACP5b), and sclerostin. Results Mean age was 59.6 +/- 6.8 years, and 48% were female. In models with HbA1c, eGFR, and AGEs, adjusted for age and sex, higher concurrent HbA1c was associated with lower PINP [beta -3.4 pg/mL (95% CI -6.1, -0.7), P = 0.015 for each 1% higher HbA1c]. Lower eGFR was associated with higher PINP [6.9 pg/mL (95% CI 3.8, 10.0), P < 0.0001 for each -20 mL/min/1.73 m(2) eGFR], bone ALP [1.0 U/L (95% CI 0.2, 1.9), P = 0.011], sCTX [53.6 pg/mL (95% CI 32.6, 74.6), P < 0.0001], and TRACP5b [0.3 U/L (95% CI 0.1, 0.4), P = 0.002]. However, AGEs were not associated with any bone turnover markers in adjusted models. HbA1c, eGFR, and AGEs were not associated with sclerostin levels. Conclusions Among older adults with T1D, poor glycemic control is a risk factor for reduced bone formation, while reduced kidney function is a risk factor for increased bone resorption and formation.