Adaptive Thermogenesis and Obesity - The role of the sympathetic nervous system

Obesity is an increasing problem in the western society. This study aims at
identifying the mechanisms behind the large inter-individual differences in
cold-induced adaptive thermogenesis. This leads to an increased insight in the
development and treatment of obesity.

To anwer the question: Is the elevation of energy expenditure and mitochondrial
uncoupling smaller in obese than in lean subjects after mild cold exposure and
what is the role of the sympathetic nervous system?

Subjects will stay twice for 84 hours in the respiration chamber of the
department of Human Biology in which 24h Energy Expenditure is measured under
standardised conditions. The first 36 hours of the stay will be at an
environmental temperature of 22°C, the last 48 hours at 16°C. At the end of
each visit three tubes of venous blood and a muscle biopsy will be taken. In
one of the stays, subjects will not undergo any pharmacological intervention,
in the other stay the subjects will be administred the beta-blocker
propranolol. Two visits will be seperated by at least 14 days. In between, a
body composition measurement will be carried out for standardisation purposes.
From the muscle biopsies changes in gene expression, protein expression, and
mitochondrial respiration will be determined. From the fat biopsies, the amount
of the protein PRDM16 will be determinded.

see study design

All measurement are easy to undergo and there are no extra riscs. Taking the
biopsies might cause local bruises. The main load for the subjects is the time
consumed by the study, two times 84 hours in the respiration chamber.