Functional MRI of satiety, the interaction between gastric and oral stimulation and related hormones in healthy men

The amount and kind of food which are ingested influences the regulation of
meal size. Neural signals from the gastrointestinal tract travel via the vagus
nerve to the brain stem and thalamus, which projects to the rest of the brain,
in particular the hypothalamus, amygdala and primary sensory cortices. In
studies, in which the stomach was distended with a gastric balloon, activation
was observed in the insula, amygdala, posterior insula, left inferior frontal
gyrus and anterior cingulate cortex (Wang et al 2007; Stephan et al 2003). So
far, no study has examined the effects of ingestion or infusion of a food in
the stomach on the brain. In addition to neural signals, hormonal signals are
important for meal termination. Hormones like insulin, ghrelin and CCK interact
with gastric as well as sensory signals in the process of satiation, which
ultimately leads to meal termination.

Our main goal is to investigate the interaction between food administration,
hormone responses and brain responses.

A randomized crossover intervention study

Subjects will undergo a MRI scan (3 times). They will consume 500ml of
chocolate milk (twice oral, once only gastric load) and once 500ml of water
with an thinking agent (guarum). An naso-gastric tube will be placed 4 times.
An IV will be placed during all MRI-scans (3 times total), and blood will be
drawn 8 times during one session. A breakfast will be consumed three times
(after every frmi session), it will consist of bread with toppings.

The experiment is non-therapeutic to the subjects and consists of one
trainings-session and three study days. The risk associated with participation
is negligible and the burden can be considered as low.
Although subjects will be screened for claustrophobia prior to participation in
this study, occasionally people experience some claustrophobia*like symptoms
when they enter the MRI scanner. Subjects will be informed beforehand about the
details of the scanning procedure to ensure that this potential problem is
minimized.
Subjects might perceive the drawing of the blood sample as an uncomfortable
procedure. To minimize the discomfort, blood sampling will be performed by an
experienced nurse, who will be present during the entire study session.
Ingestion of a naso-gastric tube has been considered a low risk; it can be
experienced as uncomfortable when ingested and when removed. A subject can have
the feeling he has to vomit or a bleeding noose can appear. In rare cases an
inflammation in the larynx can occur. In some cases the tube can be placed in
the bronchus; this has serious consequences when food will be ingested in the
bronchus, which can lead to pneumonia. This can easily be tested by a nurse,
and is part of the procedure when placing the tube ("maag-sonde protocol UMC
Utrecht"). If a nurse is not sure if the gastric tube is placed right, the food
ingestion will not be started. An experienced/qualified nurse will be there to
assist during the whole procedure.
There is a small chance that aspiration occurs during the scan. A researcher
will be next to the subject the whole experiment to help immediately if this
occurs.