The activation of brown adipose tissue in response to glyceroltrinitrate as compared to cold exposure will be studied in an open-label, cross-over trial in healthy volunteers with random sequence of the two study periods (treatment and control) seperated by a washout period of 7 days.~In the treatment phase all participants will receive Nitroderm® TTS (glyceroltrinitrate) for a total of 15 days. For better tolerability, it will be will started with a lower dose of 5mg/24h (Nitroderm® TTS) the first 5 days and after that a change to Nitroderm® TTS 10mg/24h for another 10 days will be done. Each transdermal patch will be applied for 12 hours per day (overnight) to avoid development of nitrate tolerance.~Energy expenditure will be measured by indirect calorimetry before and after a mild cold exposure by placing a medical cooling system around their midsection. Additionally brown adipose tissue activity will determined by 18F-FDG-PET/CT 30 min after injection of 75 MBq of 18F-FDG. To analyse changes in BAT and muscle which are caused by glyceroltrinitrate as compared with cold stimulus, a tissue biopsie of supraclavicular BAT and skeletal muscle (musculus vastus lateralis) will be performed.~To measure changes in glucose tolerance and triglyceride levels a mixed meal test will be performed during control and treatment phase respectively. Additionally, a indirect calorimetry will be conducted before and after mixed meal test to assess diet-induced thermogenesis, i.e. the increase in REE due to ingestion of nutrients~In control phase the same examinations will be performed, but without glyceroltrinitrat.
The aim of this study is to evaluate the efficacy of glyceroltrinitrate (Nitroderm® TTS) to activate and expand human BAT as compared to mild cold exposure.