Diabetes Care. 2020 Oct;43(10):25442552. doi: 10.2337/dc19-2164. PMID: 32778556.
In brief: This cross-sectional study compared bone mineral density (BMD), lean body mass and abdominal visceral fat between 180 individuals with T2DM, 226 with obesity, and 238 with normal weight, aged 1023 years. The findings suggest that T2DM in youth may have a detrimental effect on bone accrual during the critical window of peak bone mass attainment, irrespective of obesity. Individuals with T2DM and with increased abdominal visceral fat tended to have lower BMD.
Comment: Data regarding bone quantity (BMD) are obtained by the gold standard method of dual X-ray absorptiometry (DXA) and are used to diagnose osteoporosis and assess future risk of fracture. Areal BMD (aBMD), defined as bone mineral content (BMC) per unit area (g/cm2) is preferred, as it is corrected for body size. Data from adults with T2DM show increased fracture risk despite normal or increased aBMD. This is the first study to assess bone health in youth with T2DM. Whole-body (excluding the head) BMC and aBMD, lean mass, abdominal visceral (cm2) and subcutaneous (cm2) fat area, and lean body mass index (LBMI, a measure of skeletal muscle calculated as lean mass (kg)/height (m2)) were assessed in three groups of youth: normal weight, obesity and T2DM.
Across the age range, BMC and aBMD Z scores were higher in the T2DM and obese groups than in healthy weight controls. However, while the bone Z scores were consistent across the age range in the obese and healthy weight groups, the T2DM group showed an age-related decline in bone Z scores. This finding suggests an adverse impact of diabetes on aBMD during the critical period of bone mass attainment. Longer diabetes duration, nutritional inadequacies, physical inactivity and pharmacologic interventions are factors that may affect this age-related decline. The LBMI Z score as a marker for skeletal muscle mirrored the BMD findings. Accordingly, a higher LBMI Z score was observed in T2DM, but age-related trends resulted in compromised muscle-bone relations in youth with obesity and youth with T2DM.
A multivariate regression model including age, ancestry and sex showed that visceral fat was negatively associated with BMC and aBMD Z scores. This suggests a potential adverse influence of central fat depots on bone development. Skeletal muscle showed no difference between the groups. However, in both the T2DM and obese groups, aBMD Z scores were lower for a given LBMI Z score than compared to healthy-weight controls. Dietary factors including calcium, vitamin D and physical activity differed between the groups. This suggests that poor diet and physical inactivity might contribute to poor bone health in youth with T2DM. In conclusion, bone assessment in youth with T2DM appears to be an important component of follow-up.