The long-term effects of bariatric surgery on metabolism, behavior and striatal dopamine receptors

Obesity induces a series of metabolic alterations and increase the risk for
cardiovascular diseases. Bariatric surgery is the most effective way to induce
sustained weight loss and reversal of the obesity-induced changes in lipid and
glucose metabolism. Insight into the mechanisms underlying these highly
desirable effects is crucial in the development of future treatment modalities
for metabolic syndrome that do not involve the risks associated with surgery.
For this reason, we recently performed a study called ' The pleiotropic
metabolic effects of bariatric surgery' in which we studied the short-term
effects of bariatric surgery on amongst others striatal dopamine D2/3 receptor
availability, behavioral parameters and hormones involved in metabolism. After
completion of this study (6 weeks after surgery) subjects had lost significant
amounts of weight, but they were still obese and body weight had not stabilized
yet. Striatal D2/3 receptor availability did not change despite this
significant change in weight. At present, more than a year has passed since the
surgery and body weight has stabilized during this time. In the present
follow-up study we want to determine the long-term effects of bariatric surgery
in these patients. Gaining insight into the association between obesity and
reduced striatal D2/3 receptor availability in these patients will provide
valuable insight into the development of obesity and the metabolic syndrome. In
addition, studying the long-term effects of bariatric surgery on
(eating)behavior and hormones known to be involved in the regulation of
appetite and glucose metabolism will aid the development of future treatment
modalities for obesity and the metabolic syndrome.

Determining the effect of long-term weight loss after bariatric surgery on:
- striatal dopamine D2/3 receptor availability
- behavioral parameters
- plasma hormones, metabolites and peptides involved in appetite regulation,
and glucose metabolism

Subjects that took part in our previous study examining the short-term effects
of bariatric surgery will visit the AMC once after an overnight fast. On this
day the following procedures will be performed (total duration approximately 5
hrs):
- Measurement of B-HCG in urine to exclude pregnancy
- Determination of body weight and -composition, BMI and resting energy
expenditure
- Fasting blood sample
- Brain imaging: [123I]IBZM SPECT imaging.
- A questionnaire and a computer task will be assessed during the waiting time
required for the SPECT imaging.

The radiation committee considers the risk to exposure during the SPECT scans
as intermediate.