Session: FP15-Adipocyte Biology
Bench to Bedside
Room 303 (Moscone Center)
Poster Board SUN-678
Methods: Twenty-four hour EE was measured with whole room indirect calorimetry in 18 healthy subjects (2NA/3C/5H/8AA; 11M/7F; mean±SD: age 30.2±9.5 y; %body fat 28.7±13.6%) during energy balance (EB), during 24h of fasting (FST) and during 24h of OF with 200% of energy requirements using a high fat (60%), normal protein (20%) diet. Body composition was measured using DXA. While on a weight maintaining diet and after an overnight fast, all subjects had an 18-fluorodeoxyglucose (FDG)-PET-CT scan after exposure to at least one hour of cool temperatures (16˚C) to determine cold-induced BAT activity. PET and CT images were co-registered and BAT quantified using SPM8 software (Statistical Parametric Mapping) with an individualized mask extending from the base of the cerebellum to the apex of the heart. BAT was defined in cool scans as the collection of voxels with standard uptake value (SUV) ≥ 2.0 in areas with Hounsfield units between -250 and -10. Subjects were then divided into 2 cohorts: 6 subjects had a second scan at 23˚C after FST, and 8 had a second scan at 23˚C after 24h of OF. The SUV of the defined BAT areas from the cool scan was then determined in corresponding FST or OF scans.
Results: Visible cold-induced BAT activity was present in 13/18 subjects (72%). Cold-induced BAT activity was negatively correlated with fat free mass (ρ=−0.56, p=0.02) but not with fat mass (ρ=0.19, p=0.5) or %body fat (ρ=0.33, p=0.2). Cold-induced BAT activity was higher than the measured SUV of BAT after FST at 23˚C (n=6; 3.5±0.7 v 1.2±0.2 SUV; p<0.01). With OF, 24h EE increased by 7.5±5.7% above EE in EB (p<0.01). Compared to cold-induced BAT activity, mean SUV of BAT was lower after 24h of OF at 23˚C (n=8; 2.9±0.5 v 0.9±0.1 SUV; p<0.01), with a mean SUV similar to that observed in the FST cohort. In 12 subjects with a 6m follow-up visit, cold-induced BAT activity was negatively associated with the 6m changes in body weight (ρ=−0.58, p=0.06) and fat mass (ρ=−0.66, p=0.02).
Conclusion: OF did not increase BAT activity compared to cold-induced BAT activation, thus the increase in EE in response to overfeeding is not driven by BAT. Despite this, higher cold-induced BAT activity was negatively related to weight change at 6 months.
Nothing to Disclose: MS, PP, PT, EMR, KC, CL, JK, MST
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