Phenotyping of Adult Crohn's Focusing on Sarcopenia

Inflammatory bowel disease (IBD) includes two idiopathic chronic relapsing and remitting inflammatory conditions affecting the gastrointestinal (GI) tract: Crohn's disease (CD) and ulcerative colitis (UC)Malnutrition and significant alteration of body composition are common in inflammatory bowel disease patients, whereby the prevalence of malnutrition may be up to 82.8% in CD patients with active disease, and up to 38.9% in CD patients in remission. Many CD patients have low muscle mass and function (sarcopenia) with drivers of such pathophysiology unknown. 41.6% of CD patients with sarcopenia require surgery, with the surgical trauma and resulting inactivity leading to further muscle mass loss such that the chronic inflammatory insult associated with refractory disease may be linked to advanced muscle mass depletion. The majority of adult CD patients have low muscle mass even in clinical remission indicating the poorly reversible nature of this phenomenon. Chronic disease burden may therefore be important in the accentuation of muscle loss. Muscle mass is maintained through the daily balance of MPS and muscle protein breakdown (MPB), with the essential amino acid (EAA) components of a meal and muscle contraction being the primary stimulators of MPS. Patients with active CD show a significant decrease in the expression of proteins in hypertrophic signalling pathways (Akt, P70S6K1) with no change in the expression of atrophic signalling (MAFbx, MuRF1). Also, adult CD patients with established disease consume less protein compared to matched healthy volunteers (HV). Furthermore, the intestinal motility, measured using cine-MRI, is reduced in active CD, possibly further decreasing intestinal digestion and absorption of dietary peptides. In general, the malabsorption is a major contributing factor to malnourishment in CD. It has been shown that in male paediatric patients with long-term CD, muscle metabolism is perturbed by a negative branched-chain amino acid balance