Pilot Study: are human intestinal biopsies usefull as in vitro model for the small intestine

Obesity is a growing problem throughout the world. The most commonly used
measure of obesity is the Body Mass Index (BMI): body weight in kilograms
divided by height in metres square. A person with a BMI of more than 25.0 kg/m2
is considered too heavy (overweight), a BMI of more than 30.0 kg/m2 is
considered overweight (obesity). Several epidemiological studies have shown
that obesity increases complications, such as diabetes, high blood pressure,
elevated cholesterol and cardiovascular disease.

Obesity is regulated by eating patterns, related to hunger or appetite and
saturation (the feeling of enough). The regulation of appetite and satiety in
general is very complex and includes several signalling systems, organs and
processes. Hormones in the gastrointestinal tract are part of these regulation
processes by reducing or increasing food intake. Important research focuses on
the phase of recognition of food in the gastrointestinal tract. Many
researchers involved stress the importance of using a good intestinal model to
study this phase. A good intestinal model will enable futher research to study
the integrity and functionality of the gut epithelium, and to sreen for
nutrients and potential drug candidates for obesity. Also the impact of satiety
hormones on the intestinal function can then be studied. however this pig model
needs first to be validated in comparison with the human intestine.

Human intestinal biopsies will be used to further develop an in vitro
intestinal model. This model will the be used for future research to study the
effect of nutreints and drugs on intestinal function. The human biopsies will
be compared with intestinal segments of a pig.

For this study, biopsies will be taken from the small intestine from patients
already scheduled to undergo an endoscopy. These biopsies will be used for
various in vitro experiments. The biopsies will be cultured for up to 24 hours
for the measurements of various satiety hormones.

To measure the satiety hormones biopsies will be exposed to a concentration
gradient of casein hydrosolate. Casein hydrosolate is a positive control for
the release of satiety hormones. This will be performed in 24-wells plates and
ussing chambers.

24-well plates
After 1-hour incubation with casein medium will be collected and stored until
measurement of the released satiety hormones. Two important satiety hormones
will be measured via a radio immuno assay (RIA); CCK and GLP-1.

Ussing chambers
To determine if there is active or passive transport of the satiety hormones
biopsies will be placed in an ussing chamber. Hereby the apical and basolateral
side will be determined. The biopsy will be exposed on the apical side.
Subsequently the transport from the apical side to the basolateral side can be
determined due to the separation of the compartments. In the medium the
concentration of CCK and GLP-1 will be determined via RIA assay. As comparison
the reference compounds mannitol and caffeine as markers for paracellular and
transcellular transport in gut epithelium will be determined as well.

These studies will run in parallel with experiment performed in gut segments of
the pig. These results will be compared with each other in order to validate
the model in pig. Subsequently future experiments with other drugs and
nourishment components will be performed in the pig model.

The endoscopy that patients will undergo is already scheduled, unrelated to
this study. To take an extra 6 biopsies is considered a minimal burden for the
participating patients.