Adolescents with long-duration type 1 diabetes have low bone mass and reduced levels of bone indices reflecting altered bone resorption.

The prevalence of type 1 diabetes (T1D) is increasing globally and is associated with severe complications, including an increased risk of fractures. This case-control study investigated whether young individuals with well-controlled, long-duration T1D have differences in bone mass and bone biomarkers in comparison with healthy matched controls. Fifty individuals, aged 15.0-17.9 years, with a T1D duration of at least 8 years and (mean ± SD) 10.6 ± 2.1 years were included, hence the participants had diabetes throughout most part of their puberty and growth spurt. The mean HbA1c since diabetes diagnosis was 56 ± 6 mmol/mol (7.3 ± 0.6 %). Bone mass was assessed by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography (pQCT). Clinical follow-up data were retrieved from the Swedish National Diabetes Registry. The control group comprised 50 healthy matched adolescents, aged 15.1-17.9 years. The groups were well-matched with no significant differences in age, sex, weight, height, body mass index and the self-reported physical activity. Total body less head aBMD and Z-scores were significantly lower in T1D individuals, p < 0.05. Total tibia density and trabecular density, by pQCT, were also lower in the T1D group, p < 0.05. There were no differences between the groups for parathyroid hormone, 25-hydroxyvitamin D, bone-specific alkaline phosphatase (BALP), intact procollagen type I N-propeptide (PINP), sclerostin, bioactive sclerostin and osteoprotegerin. However, individuals with T1D had reduced levels of C-terminal telopeptide of type I collagen (CTX) (p < 0.001) and nuclear factor κB ligand (a.k.a. RANKL) (p = 0.01), indicating altered regulation of osteoclasts. In conclusion, young individuals with well-controlled, long-duration T1D have subnormal bone mass accrual, impaired microstructure at several sites and suppressed RANKL-mediated osteoclastogenesis resulting in reduced bone resorption. Based on these findings, we suggest that bone health should be monitored in pediatric diabetes care to potentially intervene early in life in susceptible individuals to achieve optimal peak bone mass.