Cold Induced Activation of Brown Adipose Tissue in Humans

The field of human brown adipose tissue (BAT) research is focused on activation of BAT as a means of manipulating energy expenditure and potentially anti-obesity and anti-diabetic properties of the tissue. This is well established in rodent studies and explained as due to the specific brown fat uncoupling protein 1 (UCP1). Despite increasing evidence that indicates a metabolic regulatory role of BAT in humans, BAT activation/recruitment is not fully understood and even less is known about the endocrine capacities of human BAT.

Cold induced brown fat activity will be assessed with PET/MR scans and validate an infra-red thermography camera, as well as perform a proteomic screening using blood samples under these two intervention days.

15 healthy lean male subjects will serve as their own control in a cross-over randomized control study, including a pre-examination day, a thermoneutral-day and a cooling test-day with cold exposure followed by a PET/MR scan to determine BAT activity. An extra cooling day is applied for the external validation of the infrared thermography camera. Blood samples and abdominal fat-biopsies will be taken at thermoneutral condition and under cold stimulation of brown fat.

Inclusion criteria

• Age 18-30 years.
• Men
• Caucasian white
• Body Mass Index 19-25 kg/m2.
• Moderate physical activity level (not more than 8-10 hours of training pr. Week)
• Ability to give informed consent.
• Ability to follow verbal and written instructions in Danish.
• Body fat percent under 21% measured at the pre-examination day.

Exclusion criteria

• Chronic diseases: Hormonal: Metabolic Diseases mb. Graves, hypothyroidism, myxedema and goiter. Diabetes Melitus, Coronary heart disease (history of myocardial infarction, unstable angina pectoris, or congestive heart failure), cancer treated within last 3 years.
• Tobacco, marijuana or intravenous drug use within 1 year of screening.
• Dieting, recent weight loss (>3 kg within 3 month) or a history of an eating disorder.
• Dietary supplements.
• History of depression, psychosis, or other psychiatric illness requiring hospitalization.
• Alcohol consumption >14 units/week.
• History of alcohol abuse within the past 3 years.
• Known liver disease or elevated liver biomarkers more than 2 times upper normal levels in the preliminary investigation.
• Known kidney disease or elevated kidney biomarkers, eCRF <60 ml/min, in the preliminary investigation.
• Use of daily medications, except for seasonal use of antihistamines.
• Diagnosed sleep disturbances.
• Pacemaker or other electronics implanted in the body.
• Magnetic impressionable metal implants or foreign objects in the body inconsistent with completion of MR.
• Claustrophobia
• Communication problems, including understanding the experimental protocol
• History of contrast allergy.
• Winter swimmers.