Author(s): STELZER, T., MOITZI, A., KÖNIG, D., WAGNER, K.H., Institution: UNIVERSTIY OF VIENNA, Country: AUSTRIA, Abstract-ID: 1134

INTRODUCTION:
Moderately elevated unconjugated bilirubin (UCB) levels, as observed in people with Gilberts syndrome (GS) have previously been described to have beneficial effects on metabolic health. A specific metabolomics profile was identified for GS subjects, where downstream metabolites associated with ketogenesis, and fatty acid oxidation were significantly increased. However, until now there is no data on exercise performance or substrate utilization during exercising. We therefore determined maximal fat oxidation (MFO), Fatmax and ventilatory thresholds during a graded step protocol
METHODS:
41 male (n=24) and female (n=17) GS subjects (UCB>17μmol/l) between 18 and 65 years of age as well as their 41 age and gender matched healthy controls (UCB <17μmol/l) were included. Participants were moderately physically active. After a 12h overnight fast, all subjects completed a graded exercise test on a cycle ergometer until reaching a RER of 1.00 to determine MFO, Fatmax and ventilatory thresholds (VT1, VT2). 48h prior to the exercise test subjects were asked to avoid strenuous physical activity and consume carbohydrates only at moderate amounts the day before. During the exercise test heart rate and gas exchange were continuously collected. Body composition (fat mass, FM, fat free mass, FFM, skeletal muscle mass, SMM, and total body water TBW) and body weight (BW) were determined using bioelectric impedance. VO2max was calculated using a regression model designed by Nunes et al. in 2018. UCB was measured via high performance liquid chromatography (HPLC).
RESULTS:
BMI tended to be lower in GS subjects (p=0.065). FM (kg) was significantly lower in subjects with GS over 35 years of age (p=0.037). No significant difference was found in absolute MFO (g/min) between groups (p=0.143), or Fatmax (p=0.358). However, MFO relative to BW (p=0.042) and FFM (p=0.043) was significantly higher in the GS group (g/min/kg BW: 0.0040±0.0011; g/min/kg FFM: 0.0053±0.0015) compared to controls (g/min/kg BW: 0.0034±0.0014; g/min/kg FFM: 0.0045±0.0016). Between MFO and FFM (kg) as well as SMM (kg) there was a significant positive correlation (p<0.001). Power (W/kg BW) at VT1 was significantly (p=0.023) higher in GS (1.1±0.4) compared to controls (0.9±0.3). Power output (W/kg BW) at VT2 tended to be higher in GS subjects (p=0.062), while oxygen uptake (ml/min/kg BW) was significantly higher (p=0.021) in GS (32.1±8.0) compared to controls (27.5±9.2). Predicted VO2max was higher in GS (41.1±9.5) than in controls (37.0±9.9) but not significant (p=0.058). However, in GS over the age of 35 predicted VO2max was (p=0.003) significantly higher
CONCLUSION:
Even though, there is no significant difference in absolute MFO, MFO relative to BW and FFM is significantly higher in the GS group. Together with the higher performance at VT1 and VT2, this indicates that moderately elevated UCB levels seem to somehow enhance metabolic health and exercise performance.