Brown Adipose Tissue as Nutrient Buffer Through Diet Induced Thermogenesis
Brown Adipose Tissue as Nutrient Buffer Through Diet Induced Thermogenesis
To test the hypothesis that active BAT improves metabolic health by buffering postprandial metabolites plasma metabolites and energy expenditure will be compared in volunteers with and without active BAT. Both groups will receive test meals with protein, fat and carbohydrates separately, so that the individual impacts of these macronutrients on diet induced thermogenesis and the buffering function of BAT can be derived. BAT biopsies will be taken before and after the test meals for molecular analysis.
In this prospective interventional study healthy individuals will be screened for presence of active BAT: Maximal BAT activity will be achieved by a mild cold stimulus over 2 hous and quantified by 18F-FDG-PET/CT 30 min after injection of 75 MBq of 18F-FDG.
Individuals with FDG-PET positive BAT will be included as BAT-positive subjects (n=15) and individuals with absence of FDG-positive BAT will be included as BAT-negative subjects (n=15) and then take part in three study visits in random order.
During the study visits participants will consume a standardized isocaloric liquid meal consisting of A) glucose (OGTT) B) fat and C) protein.
Energy expenditure will be measured by indirect calorimetry before as well as hourly after the meal for 5 hours. Blood samples will be taken before and at 30 minute intervals after the meal for 5 hours for analysis of blood glucose, triglycerides, FAAs, representative amino acids, insulin and noradrenaline.
Subjects will undergo ultrasound-guided biopsy of the supraclavicular fat depot in the fasting state and after one of the test meals so that biopsies from 5 individuals in each group after each test meal will be obtained.
Inclusion Criteria:
Exclusion Criteria:
Concomitant medication other than prescription free analgesics (paracetamol and NSAID) and oral contraceptives
Other clinically significant concomitant disease states (e.g., renal failure, hepatic dysfunction, cardiovascular disease, diabetes mellitus)
Hyper- or hypothyroidism
Smoker / habitual tobacco use
Weight change of >5% within 3 months prior to inclusion
Hypersensitivity to cold (e.g. Raynaud syndrome)
Known or suspected non-compliance, drug or alcohol abuse
Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant
Enrolment of the investigator, his/her family members, employees and other dependent persons
Enrolment into another study using ionizing radiation within the previous 12 months
Enrolment into another study including a pharmacological or nutritional intervention
Pregnancy or lactation
Lab parameters