Oral Presentation Abstracts Brown adipose tissue impact on vascular function through an anti-contractile effect and redox-sensitive mechanisms. Malou Friederich-Persson1, Aurelie Nguyen Dinh Cat1, Augusto Montezano1, Rhian Touyz1, 1University of Glasgow, Institute of Cardiovascular and Medical Sciences, Glasgow, UK Introduction: White (WAT) and brown (BAT) adipose tissue are phenotypically different. Under physiological conditions, WAT secretes “adipocyte-derived relaxing factors” (ADRF) and promotes vasorelaxation, an effect that is lost during pathological conditions such as obesity. Whether BAT influences vascular function remains unclear. In this study, we investigated whether BAT regulates vascular reactivity. Methods: Vascular reactivity of wild-type mouse mesenteric arteries to acetylcholine (Ach) and noradrenaline (NA) was performed by wire myography. Vessels were studied in the absence of perivascular adipose tissue (PVAT) and were incubated for 30 minutes with BAT (obtained from the interscapular region) alone or in combination with inhibitors of nitric oxide synthase (L-NAME, 100 µM), cyclooxygenase (indomethacin, 10 µM), voltage-gated K-channels (4-aminopyridine, 0.1-2 mM) or the scavenger of hydrogen peroxide (PEG-catalase, 300 U/ml). Fitted curves were evaluated for EC50 and maximal contraction (MC). Results: BAT exerts a strong anti-contractile effect (P<0.0001 EC50 and MC vs. PVAT-denuded arteries, N=10-11). There was no effect of BAT on vascular relaxation (N=4, all NS). The anti-contractile effect of BAT also remained unaffected with L-NAME, indomethacin or 4-aminopyridine (BAT+drug P<0.0001 EC50 and MC vs. PVAT-denuded arteries and NS vs. BAT alone, N=3-11) but was completely blocked by PEG-catalase (N=3-11). Conclusion and discussion: Our results indicate that BAT mediates an anti-contractile effect and may impact on vascular function through hydrogen peroxide-dependent mechanisms. Indeed, hydrogen peroxide is a suggested candidate for the ADRF and it is of interest to note that mRNA expression of NOX-4, a hydrogen peroxide producer, is approximately 8-fold higher in BAT compared to WAT (N=4). Importantly, the present study suggests that BAT may influence vascular function through processes that involve hydrogen peroxide. Precise molecular mechanisms and targets underlying these phenomena await clarification. Our findings may be important in obesity/adiposity where BAT could be of interest for new therapeutic strategies as it could play an important role to attenuate the vascular complications in obesity. The association of sedentary behaviour with adiposity-related markers differ in population of White-European, South Asians and Black ethnic background: Findings from 224,395 UK Biobank participants Carlos Celis-Morales1, Uduakobong Tuk2, Jana Anderson2, Daniel Mackay2, Naveed Sattar1, Jill Pell2, Jason Gill1, 1BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK, 2Institute of Health and Wellbeing, University of Glasgow, Glasgow, UK Background: Adults spend ~55% of their waking time sedentary. However, there is limited evidence on whether the effect of sedentary behaviour (SB) on adiposity-related markers differs by ethnicity. Therefore, the aim of this study was to investigate the association between SB and adiposity-related markers in adults of White-European, South Asians (SAs) and Black ethnic background. Methods: A cross-sectional analysis was conducted in 224,395 individuals recruited in the UK Biobank, with ages ranging from 40 to 73 years. Linear regression analyses were used to explore the association between SB and adiposity-related markers (body mass index (BMI), waist circumference (WC) and % body fat). SB was derived from self-reported spent watching TV, sitting in front of a computer or driving (hours/day). Results: Mean ± SD self-reported total SB was 5.31±2.5, 5.26±2.9 and 6.07±3.2 hours per day for white, SAs and black population, respectively. Significant SB*ethnicity interaction effect were found for BMI, WC and Body fat (p<0.0001 for all). SB (hours/day) was significantly associated with an increase in BMI (β±SE) [white: 0.32±0.01 kg.m-2, p<0.0001; SAs: 0.23±0.03 kg.m-2, p<0.0001 and Black: 0.55±0.03 kg.m-2, p<0.0001], WC [white: 0.81±0.03 cm, p<0.0001; SAs: 0.69±0.08 cm, p<0.0001 and Black: 1.12 ±0.07 cm, p<0.0001] and % of body fat [white: 0.51±0.02, p<0.0001; SAs: 0.69±0.04, p<0.0001 and Black: 0.79 ±0.04, p<0.0001]. All analysis was adjusted for age, sex, education level, total physical activity and total energy intake. Main Findings: Our results revealed that SB is associated with an increased BMI, WC and body fat in populations of different ethnic background independent of physical activity and energy intake. Moreover, the detrimental effect of SB on adiposity-related markers differ by ethnicity, with Black population showing a higher increase in adiposity compare to Whites and SAs for BMI, WC and % body fat. However, SAs shows a higher effect of SB on % of body fat than the White-European population. UKCO2015 September 9-11, 2015 35

UKCO 2015 2nd UK congress on Obesity