Bone turnover and metabolite responses to exercise in people with and without long-duration type 1 diabetes: a case-control study

INTRODUCTION: Exercise acutely alters markers of bone resorption and formation. As risk of fracture is increased in patients with type 1 diabetes, understanding if exercise-induced bone turnover is affected within this population is prudent. We assessed bone turnover responses to acute exercise in individuals with long-duration type 1 diabetes and matched controls. RESEARCH DESIGN AND METHODS: Participants with type 1 diabetes (n=15; age: 38.7±13.3; glycosylated hemoglobin: 60.5±6.7 mmol/mol; diabetes duration: 19.3±11.4 years) and age-matched, fitness-matched, and body mass index-matched controls (n=15) completed 45 min of incline walking (60% peak oxygen uptake). Blood samples were collected at baseline and immediately, 30 min, and 60 min postexercise. Markers of bone resorption (β-C-terminal cross-linked telopeptide of type 1 collagen, β-CTx) and formation (procollagen type-1 amino-terminal propeptide, P1NP), parathyroid hormone (PTH), phosphate, and calcium (albumin-adjusted and ionized) were measured. Data (mean±SD) were analyzed by a mixed-model analysis of variance. RESULTS: Baseline concentrations of P1NP and β-CTx were comparable between participants with type 1 diabetes and controls. P1NP did not change with exercise (p=0.20) but β-CTx decreased (p<0.001) in both groups, but less so in participants with type 1 diabetes compared with controls (-9.2±3.7%; p=0.02). PTH and phosphate increased immediately postexercise in both groups; only PTH was raised at 30 min postexercise (p<0.001), with no between-group differences (p>0.39). Participants with type 1 diabetes had reduced albumin and ionized calcium at all sample points (p<0.01). CONCLUSIONS: Following exercise, participants with type 1 diabetes displayed similar time-course changes in markers of bone formation and associated metabolites, but an attenuated suppression in bone resorption. The reduced albumin and ionized calcium may have implications for future bone health. Further investigation of the interactions between type 1 diabetes, differing modalities and intensities of exercise, and bone health is warranted.