STUDY BACKGROUND INFORMATION AND RATIONALE
Crohn's disease (CD) patients can present with a variety of luminal and extra-luminal symptoms but nutritional abnormalities are a very common but poorly studied \[1\] problem in this disease \[2\]. Apart from disease burden and repeated surgery, reduced appetite \[3\] and associated symptoms such as nausea undoubtedly contribute, with a major impact on quality of life.
Appetite and satiation, the processes by which a meal is terminated, involve complex interactions of homeostatic and hedonic factors. While the hypothalamus is central in the homeostatic control of food intake, other neural circuits integrate environmental and emotional cues to constitute the hedonic drive of appetite regulation. The homeostatic control of food intake is governed by the enteroendocrine-gut brain axis. Enteroendocrine cells (EC) play a pivotal role in orchestrating physiological functions in the gastrointestinal (GI) tract. Sensing the nutrient content of the lumen, they secrete multiple peptides and amines that control gut secretory and motor functions. Gut hormones act on vagal afferents in the GI tract, directly relaying to key central nervous system (CNS) nuclei that interface within the hypothalamus and other cortical areas to regulate food intake. CD patients with active small bowel inflammation show significant up-regulation of EC cells with an increase in ileal expression of chromogranin A \[4, 5\], glucagon-like peptide-1 (GLP-1) \[4\], key transcription factors in the stem cell to EC differentiation pathway \[4\] , plasma polypeptide YY (PYY) \[3\], cholecystokinin (CCK) \[6\] levels and a reduction in the key enzyme dipeptidyl peptidase-4 expression \[7\]. This increase in plasma peptide levels is associated with the symptoms of nausea and anorexia, with both symptoms, and tissue and plasma EC-peptide expression decreasing to normality in remission \[3\].
An increase in EC expression at the tissue and plasma level might affect appetite regulation through an increase in CNS signalling.
Fatty-acids infused in the gut, lead to a CCK-dependent increase in CNS activity in areas related to homeostatic control of feeding such as the brainstem, the pons, hypothalamus, cerebellum and the motor cortical areas \[8\]. Glucose has been shown to decrease the response in the upper hypothalamus \[9\], possibly via a GLP-1-mediated pathway \[10\]. Ghrelin and PYY have known homeostatic CNS signalling properties but play a hedonic role in the control of food intake \[11\]. In effect, the increase in plasma PYY and GLP-1 seen after Roux-en-Y gastric bypass surgery in obese subjects or after parenteral administration \[12\] is associated with a lower activation in brain-hedonic food responses and a healthier eating behaviour \[13\]. In CD, we expect a subdued reward value of food, but postulate that this would be aversive, and inappropriately impairing appetite and food intake.
We hypothesize that in CD and small bowel inflammation we will observe a change in eating behaviour with loss of hedonic drives and food reward responses and an accentuated homeostatic response.
STUDY OBJECTIVES AND PURPOSE
PURPOSE The overall purpose of the study is to quantify food intake in patients with active Crohn's disease and compare it to when they are in remission and to healthy age, BMI and gender-matched healthy cohort of volunteers. We will quantify eating behaviour traits in the same patient cohort when in active disease and repeat when in remission. These data will be compared to that of healthy volunteers.
PRIMARY OBJECTIVE The primary objective is to quantify food intake in patients with active CD and compare this to HV.
SECONDARY OBJECTIVES The secondary objectives of this study are to a) quantify food intake in patients with active CD and compare that when in inactive disease. b) quantify changes in appetite and eating behaviour in patients with active CD and compare these to those in HV and inactive CD as measured by the appetite-related questionnaires
