Background: Down syndrome (DS) is a risk factor for metabolic syndrome and cardiovascular disease. The greater oxidative stress described in DS can increase this risk owing to its potential deleterious effects on insulin sensitivity. We hypothesized that metabolic syndrome or its markers, at rest and during exercise, are more pronounced in young adults with DS.
Design: The study design is that of a controlled study.
Methods: Thirteen physically active young adults with DS, after overnight polysomnography, plasma-lipid profile, and insulin-resistance [Homeostasis Model Assessment Insulin Resistance (HOMA-IR)] assessments, underwent a submaximal progressive treadmill exercise (10 min at 30 and 50%, and 20 min at 75% of V O2max), allowing for maximal fat-oxidation rate and blood-oxidative stress determinations. They were compared with 15 healthy control participants (C).
Results: V O2max of DS participants was lower than that of C (60.8+/-2.4 versus 44.4+/-3.3 ml/kg/min; P<0.001) but was close to the predicted value (95+/-6%). In DS participants, as expected, oxidative stress was greater than in C (+15%; P<0.001) at rest and all through the exercise protocol. Although a greater fat mass (DS: 19.9+/-1.3%; C: 13.5+/-0.9%; P<0.001), and a lower insulin sensitivity (HOMA-IR in DS: 1.09+/-0.16; in C: 0.64+/-0.13; P<0.05) was observed for DS participants, a metabolic syndrome could not be shown. Maximal fat-oxidation rate was lower in DS participants (394.2+/-69.9 versus 486.1+/-134.8 mg/min in C; P<0.01), but it was in the normal range.
Conclusion: Despite greater oxidative stress and lower insulin sensitivity, the DS group involved in our study did not display clear metabolic abnormalities. The young age and lifestyle of this group might, partially, have accounted for this apparently healthy metabolic status.