Author(s): GARTHWAITE, T., SJOROS, T., LAINE, S., KOIVUMAKI, M., VAHA-YPYA, H., NEUVONEN, J., NORHA, J., HOUTTU, N., LAITINEN, K., KALLIOKOSKI, K., VASANKARI, T., KNUUTI, J., HEINONEN, I., Institution: UNIVERSITY OF TURKU, Country: FINLAND, Abstract-ID: 1660

INTRODUCTION:
Sedentary behavior (SB) and physical inactivity are associated with insulin resistance, and regular physical activity (PA) is known to improve whole-body glucose metabolism. It is not clear whether reducing SB and increasing PA can improve tissue-specific insulin sensitivity in adipose tissue. The purpose was to investigate the effects of reducing SB on glucose uptake (GU) in adipose tissue in adults at risk of type 2 diabetes in a 6-month randomized controlled trial.
METHODS:
Forty-four sedentary inactive middle-aged adults with metabolic syndrome were randomized into intervention (INT, n=23) and control (CON, n=21) groups. INT aimed to limit SB by 1 h/day and CON was instructed to maintain usual habits. SB and PA were measured with hip-worn accelerometers for six months. Insulin-stimulated GU in visceral (VAT) and abdominal and femoral subcutaneous adipose tissue (SAT) was determined with (18F)FDG-PET imaging and hyperinsulinemic euglycemic clamp. VAT and abdominal SAT masses were determined with MRI.
RESULTS:
INT reduced SB by 51 min/day and increased moderate-to-vigorous PA by 22 min/day, with no changes in CON. Both groups increased light-intensity PA by 11 min/day on average. Steps also increased in both groups, but the increase was greater in INT compared to CON (+3200 vs. +1700 steps/day). VAT GU and abdominal SAT GU did not change during the intervention in either group, but femoral SAT GU increased from 6.5 (95 % CI 5.8, 7.3) umol/kg tissue/min at baseline to 7.7 (6.8, 8.7) umol/kg tissue/min at six months, with no difference between groups (time p=0.02, group x time p=0.66). VAT and abdominal SAT mass (kg) also decreased slightly in both groups (time p<0.05). The decrease in SAT mass was greater in INT compared to CON, but the difference was not significant (-0.43 kg vs. -0.02 kg, group x time p=0.07). GU per total abdominal VAT and SAT mass did not change in either group. Among all participants, changes in adipose tissue GU correlated with changes in body composition and circulating lipids (p<0.05).
CONCLUSION:
A reduction in daily SB did not have an effect on adipose tissue GU. However, reducing SB and increasing PA might improve adipose tissue GU indirectly through their positive effects on body composition.