Serum citrulline levels as a marker of enterocyte function in patients after allogeneic hematopoietic stem cells transplantation – a pilot study

BACKGROUND Citrulline is an amino acid produced by enterocytes. Serum citrulline concentration has been proposed as a marker of enterocyte mass and function. Our study focused on evaluation of citrulline levels in patients with diarrhea related to toxic intestinal damage (mucositis), intestinal graft versus host disease (GVHD), and other etiology of diarrhea (e.g., dysmicrobia) after allogeneic stem cells transplantation (SCT). MATERIAL AND METHODS This was a prospective study in 11 adults (18 blood samples) with diarrhea developed after allogeneic SCT in 4/2011-1/2012 compared to twenty healthy control samples. RESULTS The median (interquartile range) of citrulline levels was significantly lower in the transplanted patients group compared to healthy controls: 9.3 (3.62-15.38) vs. 33.3 (26.82-36.23) µmol/L, p<0.0001. The median values of citrulline in patients with post-transplant toxic intestinal mucositis (n=8, days 1-22 post-transplant) vs. intestinal GVHD (n=7, day 43-142) vs. other etiology of diarrhea (e.g., dysmicrobia) (n=3, day 120-127) were: 9.55 (2.95-12.03) vs. 5 (3.85-9.05) vs. 15.6 (15.45-18.3) mol/L resp. Serum citrulline levels were significantly higher in other (eg, dysmicrobic) etiology of diarrhea in comparison with mucositis (p=0.0336) and GVHD (p=0.0152). CONCLUSIONS Citrulline levels are very low shortly after the myeloablative FLU/MEL or BuCY2 conditioning allogeneic SCT due to the toxic intestinal damage. Significantly low levels of citrulline were also in patients with intestinal GVHD later on. Other observations in larger groups of patients are necessary before any specific recommendation for citrulline levels monitoring in intestinal GVHD can be made.