Abstract
PurposeThe metabolic consequences of carrying a FTO obesity-promoting risk allele have not been fully elucidated and may be confounded by obesity per se. Against this background, we investigated the impact of FTO allele (SNP rs9939609) on fasting and postprandial energy expenditure and fasting substrate expenditure in a study population of uniformly and similarly obese individuals. ProceduresWe studied a similar number of participants with BMI classes 2–3 (median BMI 42.8 kg/m2) who were either homozygote for the non-risk allele TT (n = 33, numbers increased by enrichment), heterozygote (AT) (n = 32), or homozygote for the risk allele AA (n = 35). Major findingsBasal metabolic rate and postprandial energy expenditure did not differ between FTO-groups. However, fasting respiratory quotient (RQ) was increased in those carrying ≥1 risk allele (p = 0.008), whereas postprandial RQ was not. ConclusionIn this study population, the FTO-risk allele associates with fasting reduced fat and increased carbohydrate oxidation.
Highlights
Numerous studies have reported on the fat mass and obesityassociated gene (FTO) risk allele's impact on obesity
Our study brings out novel findings
Our study population is rather unique as it compares the impact of the FTO gene on metabolic parameters in subjects who are uniformly obese, obviating a confounding influence of obesity per se
Summary
The obesity-promoting effects of the fat mass and obesityassociated gene (FTO), risk allele is well studied, but the mechanisms behind effects are not fully elucidated [1]. One reason for remaining uncertainties might be the confounding influence of overweight per se on metabolic and behavioral parameters To minimize such confounding we assessed energy expenditure (EE) and substrate utilization in FTO tested individuals with body mass index (BMI) obesity class 2e3. Oxygen consumption (VO2), carbon dioxide production (VCO2), and respiratory quotient (RQ) were measured pre- and postprandially by indirect calorimetry using a ventilated hood system (Vmax Encore 29, CareFusion, Hoechberg, Germany), with recordings every 30sec for 15min per session. We calculated fasting carbohydrate and fat oxidation using each participant's basal metabolic rate (BMR) (kcal), RQ value, and a revised table of non-protein RQ [6]. We controlled for gender in selected models due to significant gender differences on some outcomes
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