Small Bowel Enterocytes Research Articles

Intestinal Inflammation Modulates the Expression of ACE2 and TMPRSS2 and Potentially Overlaps With the Pathogenesis of SARS-CoV-2–related Disease

Background and AimsThe presence of gastrointestinal symptoms and high levels of viral RNA in the stool suggest active severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication within enterocytes.MethodsHere, in multiple, large cohorts of patients with inflammatory bowel disease (IBD), we have studied the intersections between Coronavirus Disease 2019 (COVID-19), intestinal inflammation, and IBD treatment.ResultsA striking expression of ACE2 on the small bowel enterocyte brush border supports intestinal infectivity by SARS-CoV-2. Commonly used IBD medications, both biologic and nonbiologic, do not significantly impact ACE2 and TMPRSS2 receptor expression in the uninflamed intestines. In addition, we have defined molecular responses to COVID-19 infection that are also enriched in IBD, pointing to shared molecular networks between COVID-19 and IBD.ConclusionsThese data generate a novel appreciation of the confluence of COVID-19– and IBD-associated inflammation and provide mechanistic insights supporting further investigation of specific IBD drugs in the treatment of COVID-19. Preprint doi: https://doi.org/10.1101/2020.05.21.109124

Fat rich diet-induced steatosis and changes in the gut–liver axis

Fatty liver can develop as a result of diseases, surgical procedures, medicaments, malnutrition or excessive alcohol consumption, however, fat and poor fiber feeding can be attributed as the primary cause. Non-alcoholic fatty liver can be found in 20-30% of the population. Generally, alimentary-induced fatty liver in early state is described as uncomplicated liver injury. The aim of our research was to study the effect of fat rich nutrition on the gut-liver axis by routine laboratory, analytical and histological methods in rats. We also examined the redox parameters of the liver and of the bowel. Fatty acid composition and element content of liver were measured. Significant changes were found in parameters of redox homeostasis as well as alterations in liver enzymes and metabolites. The changes could be detected in the liver, blood and bowel parts. The development of fatty liver is associated with the decrease of transmethylation capacity. Fatty acid composition and metal ion homeostasis were also altered in liver. Histological examinations showed that hepatocytes were swollen in the central part of the liver lobules, showed droplets and pycnotic nuclei, which were characterized by fatty degeneration. Small and large bowel enterocytes were damaged, sometimes pushed from the surface, and sometimes inflammatory reactions in the mucous membrane were observed. Our results suggest that alimentary fatty liver in early state is not considered simply as a reversible alteration because it alters the entire body's redox homeostasis and establishes heart and serious metabolic diseases as well as hasten the development of gastrointestinal tumors. Orv Hetil. 2020; 161(35): 1456-1465.

Intestinal Fatty Acid Binding Protein is Associated With Mortality in Patients With Acute Heart Failure or Cardiogenic Shock.

Acute heart failure and cardiogenic shock are associated with an impaired intestinal perfusion, which may lead to a release of cytoplasmatic proteins by hypoxic epithelial injury. Intestinal fatty acid binding protein (iFABP), highly specific for the small bowel enterocyte, may pose a useful novel and very sensitive biomarker for predicting outcome of these patients.The aim of this study was to investigate whether circulating levels of iFABP are associated with mortality in patients with acute heart failure or cardiogenic shock requiring intensive care unit (ICU) admission. We included 90 consecutive patients with cardiogenic shock (74.4%) or severe acute heart failure (25.6%) admitted to a cardiac ICU. Blood samples were taken at day 0 and day 3. Median age was 64.7 (49.4-74.3), 76.7% of patients were male and median NT-proBNP levels were 4,986 (1,525-23,842) pg/mL. 30-day survival was 64.4%. Patients with serum levels of iFABP at day 0 in the highest quartile (iFABP ≥ 588.4 pg/mL) had a 2.5-fold risk (P = 0.02) of dying independent of demographics, NT-proBNP levels, and vasopressor use. Extensively elevated admission levels of iFABP above the 90th percentile (iFABP ≥ 10208.4 pg/mL) were associated with an excessive mortality rate of 88.9%. In contrast, iFABP levels at day 3 were not associated with outcome. Circulating levels of iFABP at admission predict mortality. This suggests that early inadequate perfusion of the small intestine may be associated with a dramatically decreased survival in patients with cardiogenic shock or severe acute heart failure.

Plasma citrulline levels as a biomarker for bowel toxicity in prostate stereotactic radiotherapy with or without pelvic nodal radiation.

73 Background: Plasma levels of citrulline, an amino acid, are derived mainly from small bowel enterocytes. Decreased levels occur in a range of bowel conditions and citrulline has been proposed as a biomarker of bowel toxicity in pelvic radiotherapy. In a prospective study, we identify no correlation between plasma citrulline and toxicity in men receiving prostate stereotactic radiotherapy randomized to receive either pelvic nodal irradiation or not. Furthermore, citrulline levels were not significantly different between these two groups. Methods: As part of an approved clinical trial, men with intermediate to high risk prostate cancer were randomised 1:1 to prostate only or prostate + pelvic nodal radiotherapy, delivered with a rectal spacer gel in situ. The prostate and proximal seminal vesicles received 40 Gy in 5 fractions. Those randomised to the pelvic nodal arm also received 25 Gy in 5 fractions to pelvic nodes. Citrulline was measured at 10 points during treatment – consent, before fraction 1, 1 and 24 hours following fraction 1, prior to each fraction 2 – 5 and at 6 weeks’ and 3 months’ follow up. Bowel toxicity was measured by EPIC patient reported scores. Results: 16 men with follow up of at least 3 months (median 9, maximum 18 months) were analysed. Reported toxicity was significantly higher in the prostate and pelvis arm: 5 of 9 men showed a decrease in EPIC bowel domain summary score of 10 points or more compared to 0 of 7 in the prostate-only arm (p = 0.0337, two tailed Fisher’s exact test). No significant correlation between toxicity and citrulline levels was seen, nor did citrulline vary significantly between arms or fall as treatment progressed. Data analysis for a further 8 men already recruited to the study is ongoing. Conclusions: Toxicity was more commonly reported by men randomised to receive pelvic radiotherapy, suggesting that the small bowel irradiated in pelvic fields plays a role in bowel toxicity experienced during stereotactic radiotherapy. Citrulline levels showed no significant correlation with toxicity or radiation dose to small bowel. We propose that citrulline is not a useful biomarker of small bowel toxicity in this setting. Clinical trial information: NCT03253978.

Erratum: Effects of roux-en-Y gastric bypass surgery on postprandial fructose metabolism.

Objective Fructose is partly metabolized in small bowel enterocytes, where it can be converted into glucose or fatty acids. It was therefore hypothesized that Roux-en-Y gastric bypass (RYGB) may significantly alter fructose metabolism. Methods We performed a randomized clinical study in eight patients 12-17 months after RYGB and eight control (Ctrl) subjects. Each participant was studied after ingestion of a protein and lipid meal (PL) and after ingestion of a protein+lipid+fructose+glucose meal labeled with 13C-fructose (PLFG). Postprandial blood glucose, fructose, lactate, apolipoprotein B48 (apoB48), and triglyceride (TG) concentrations, 13C-palmitate concentrations in chylomicron-TG and VLDL-TG, fructose oxidation (13CO2 production), and gluconeogenesis from fructose (GNGf) were measured over 6 hours. Results After ingestion of PLFG, postprandial plasma fructose, glucose, insulin, and lactate concentrations increased earlier and reached higher peak values in RYGB than in Ctrl. GNGf was 33% lower in RYGB than Ctrl (P = 0.041), while fructose oxidation was unchanged. Postprandial incremental areas under the curves for total TG and chylomicrons-TG were 72% and 91% lower in RYGB than Ctrl (P = 0.064 and P = 0.024, respectively). ApoB48 and 13C-palmitate concentrations were not significantly different. Conclusions Postprandial fructose metabolism was not grossly altered, but postprandial lipid concentrations were markedly decreased in subjects having had RYGB surgery.

Effects of roux-en-Y gastric bypass surgery on postprandial fructose metabolism.

Fructose is partly metabolized in small bowel enterocytes, where it can be converted into glucose or fatty acids. It was therefore hypothesized that Roux-en-Y gastric bypass (RYGB) may significantly alter fructose metabolism. We performed a randomized clinical study in eight patients 12-17 months after RYGB and eight control (Ctrl) subjects. Each participant was studied after ingestion of a protein and lipid meal (PL) and after ingestion of a protein+lipid+fructose+glucose meal labeled with (13) C-fructose (PLFG). Postprandial blood glucose, fructose, lactate, apolipoprotein B48 (apoB48), and triglyceride (TG) concentrations, (13) C-palmitate concentrations in chylomicron-TG and VLDL-TG, fructose oxidation ((13) CO2 production), and gluconeogenesis from fructose (GNGf) were measured over 6 hours. After ingestion of PLFG, postprandial plasma fructose, glucose, insulin, and lactate concentrations increased earlier and reached higher peak values in RYGB than in Ctrl. GNGf was 33% lower in RYGB than Ctrl (P = 0.041), while fructose oxidation was unchanged. Postprandial incremental areas under the curves for total TG and chylomicrons-TG were 72% and 91% lower in RYGB than Ctrl (P = 0.064 and P = 0.024, respectively). ApoB48 and (13) C-palmitate concentrations were not significantly different. Postprandial fructose metabolism was not grossly altered, but postprandial lipid concentrations were markedly decreased in subjects having had RYGB surgery.

Intestinal fatty acid-binding protein as a diagnostic marker for complicated and uncomplicated necrotizing enterocolitis: a prospective cohort study.

BackgroundEarly NEC symptoms are non-specific and diagnostic tests lack discriminative power. Intestinal fatty acid-binding protein (I-FABP), mainly located in small bowel enterocytes, is released into the blood following NEC-associated enterocyte disruption. Aim of this prospective cohort trial was to determine the diagnostic value of I-FABP measured in plasma (I-FABPp) and urine (I-FABPu) for the presence of NEC, to evaluate I-FABP levels during NEC development, and to assess its prognostic value for the progression from suspected to complicated disease.MethodsBetween 2010 and 2012 we prospectively enrolled neonates with suspected NEC. We measured I-FABP levels eight-hourly from onset of suspected NEC for at least 48 hours, or until surgery. NEC diagnosis was confirmed radiologically or during operation. We defined NEC as complicated if it resulted in surgery and/or death. We determined disease course and diagnostic I-FABP cut-off points.ResultsThe study comprised 37 neonates (24M, 13F), gestational age 28 (24–36) weeks, birth weight 1190 (570–2,400) grams. We found significantly higher I-FABPp and I-FABPu levels in NEC patients (n = 22) than in patients with other diagnoses (n = 15). Cut-off values for diagnosing NEC were 9 ng/mL I-FABPp and 218 ng/mL I-FABPu, with corresponding likelihood ratios (LRs) of 5.6 (95% CI 0.89–35) and 5.1 (95% CI 0.73–36), respectively. I-FABP levels were highest in the first eight hours after symptom onset and gradually decreased over time. Cut-off values for complicated disease were 19 ng/mL I-FABPp and 232 ng/mL I-FABPu, with LRs of 10 (95% CI 1.6–70) and 11 (95% CI 1.6–81), respectively.ConclusionsBoth plasma and urinary I-FABP levels specifically identify NEC in preterm infants prior to appearance of diagnostic radiological signs suggestive for NEC. Moreover, serial I-FABP measurements accurately predict development of complicated disease.

Intestinal lengthening and reversed segment in a piglet short bowel syndrome model

BackgroundTreatment of short bowel syndrome (SBS) remains difficult, entailing severe morbidity and mortality. Accepted surgical treatment modalities for SBS are the Bianchi intestinal lengthening procedure and reversed-segment procedure. We seek to investigate the short-term effects regarding growth, nutrition, and microscopic and functional adaptation after the intestinal lengthening and RS procedures in a piglet SBS-model. Material and methodsTwenty-four piglets (Sus scrofa, ±30 kg) were divided into four groups (n = 6 each) as follows: sham, SBS, Bianchi lengthening procedure (BIA), and reversed-segment (RS). At day one either sham laparotomy (sham) or 75% small bowel resection (SBS, BIA, and RS) was performed. After 2 wk sham laparotomy (sham and SBS), BIA, or RS procedure was performed. After 8 wk all animals were terminated. During the experimental time course, the following parameters were assessed: body weight, intestinal length, diameter, and weight, fat absorption, and biochemical parameters from serum and urine. Citrulline was used as a marker of absorptive enteral mass to demonstrate massive functional bowel loss. Intestinal biopsies were obtained for histologic analysis and electrophysiological measurements to analyze glucose absorptive capacity. ResultsEight weeks after bowel resection, piglet growth was reduced in SBS, BIA, and RS piglets as demonstrated by reduced weight (51 ± 4 kg, 47 ± 2 kg, and 53 ± 1 kg, respectively) compared with sham (69 ± 3 kg; P < 0.01), with no demonstrable difference between SBS and treatment groups. Malabsorption and malnutrition occurred in SBS, BIA, and RS piglets reflected by increased fecal fat loss per 24 h (35 ± 4%, 30 ± 2%, and 32 ± 4%, respectively versus 18 ± 1% in sham; P < 0.01) and reduced serum albumin levels (24 ± 1 g/L, 22 ± 1 g/L, and 24 ± 1 g/L, respectively versus sham 33 ± 1 g/L; P < 0.01), but there was no significant difference between SBS and treatment groups. Serum citrulline levels reflected massive functional bowel loss (SBS 36 ± 7 μmol/L, BIA 23 ± 1 μmol/L, and RS 24 ± 2 μmol/L) compared with sham (64 ± 5 μmol/L; P < 0.01). Electrophysiological measurements demonstrated reduced glucose absorption after intestinal resection, which did not return to base levels within the experimental time course. However, the intestine of BIA and RS piglets adapted more profoundly than SBS piglets, as reflected by a greater crypt depth (490 ± 25 μm and 492 ± 21 μm versus 388 ± 20 μm; P < 0.01); and BIA piglets showed greater villus length (884 ± 58 μm) than RS or SBS piglets (715 ± 30 μm and 737 ± 64 μm, respectively; P < 0.01) after 8 wk. ConclusionsDespite increased histologic intestinal adaptation, neither intestinal lengthening nor RS procedure demonstrated significantly improved absorption, nutrition, or weight gain for the treatment of SBS during the study period. Reduced glucose uptake on electrophysiology measurements and persistent low levels of citrulline may indicate reduced small bowel enterocyte functioning during the initial phase of intestinal adaptation.

Plasma citrulline level as a biomarker for cancer therapy-induced small bowel mucosal damage.

Regimen-related mucosal toxicity is extremely common following cytotoxic chemotherapy and radiotherapy. Mucositis is as an important determinant of the inflammatory response and infectious complications in cancer treated patients. Most assessment scales for mucosal damage are focussed on oral mucositis, since it is easy to evaluate. Measuring gastrointestinal musocal damage objectively remains difficult because it cannot be seen directly or readily detected. One of potential non-invasive biomarkers of gastrointestinal mucosal damage is plasma citrulline level. Citrulline is an amino acid produced by small bowel enterocytes. Low concentration of free circulating citrulline signifies severe intestinal mucosal damage in humans with nonmalignant disorders, such as villous atrophy-associated diseases, short bowel syndrome, Crohn's disease, and is used in follow-up after small bowel transplantation. The plasma citrulline level is a reliable and objective biochemical marker of enterocyte mass and function in humans, and therefore can be used to monitor enterocyte toxicity resulting from chemotherapy and radiotherapy during anticancer therapy in patients with severely disturbed gut integrity.

Serum Citrulline as a Biomarker of Gastrointestinal Function During Hematopoietic Cell Transplantation in Children

We sought to determine whether serum citrulline (CIT), an amino acid produced by small bowel enterocytes, was associated with clinical and biochemical markers of gastrointestinal function in children undergoing hematopoietic cell transplantation (HCT). We conducted a multicenter, prospective cohort study of 26 children to define time-related changes in serum CIT during the course of HCT. Markers of gastrointestinal function including oral energy intake, emesis, stool volume, presence of graft-versus-host disease (GVHD), oral mucositis severity, and cytokine and neurohormone levels were measured. Weekly serum CIT concentrations were obtained from 10 days prior until 30 days after HCT. Mean baseline CIT concentration was 22.7 μmol/L (95% confidence interval [CI] 17.7-27.6) on day -10, which decreased to a nadir of 7.5 μmol/L (95% CI 3.1-18.0, P = 0.017) on day 8 following HCT before returning to baseline by day 30. After adjustment for IL-6 level (1.0% lower CIT per 10% increase in interleukin-6, P = 0.004), presence of acute GVHD (27% lower CIT, P = 0.025), and oral energy intake (2.1% lower CIT per 10% decrease in energy intake, P = 0.018), the nadir shifted to day 10, when mean CIT concentration was lower in patients with severe oral mucositis (6.7 μmol/L, 95% CI 3.4-13.1) than in those without severe mucositis (11.9 μmol/L, 95% CI 5.8-24.4, P = 0.003). Change in CIT was not correlated with stool volume, C-reactive protein, tumor necrosis factor-α, leptin, or ghrelin. In children undergoing HCT, serum CIT correlates with measures of gastrointestinal function (oral mucositis severity, dietary intake, acute GVHD) and may reflect mucosal injury to the gastrointestinal tract.

Changes in serum citrulline during hematopoietic cell transplantation (HCT) in children

Children undergoing HCT may experience gastrointestinal side effects that limit oral intake and enteral absorption. Serum citrulline (CIT), a non‐essential amino acid produced by small bowel enterocytes, is a marker of intestinal mass. We sought to determine if serum CIT was associated with clinical markers of gastrointestinal health in children undergoing HCT. We conducted a multi‐center, prospective cohort study of 26 children to define time related changes in serum CIT over the course of HCT. Enteral intake, emesis, days on parenteral nutrition, stool volume, IL‐6 levels, and oral mucositis severity were measured. Weekly serum CIT concentrations were obtained from 10 days prior until 30 days after HCT. Mean baseline CIT concentration was 25.1 μmol/L (95% CI 7.5–83.5), decreasing to a nadir on day +8 that was lower with severe oral mucositis (6.2 μmol/L, 95% CI 3.1– 12.2) than without (11.5 μmol/L, 95% CI 5.5–23.9), before returning to baseline by day 30 (p=0.005). CIT was inversely associated with IL‐6 (1% lower CIT per 10% increase in IL‐6, p=0.016) but was not correlated with TNF‐alpha, leptin, or ghrelin. In children undergoing HCT, serum CIT is valid marker for oral mucositis severity and may indicate more extensive mucosal injury to the gastrointestinal tract. Supported by the Massachusetts Vitamin Litigation Grant and NIH grants M01‐RR02172, UL1 RR025758–01, M01‐RR00865, M01‐RR00188, and K24 HD 058795.

Observations on Serial Plasma Citrulline Concentrations in a Patient With Intestinal Ischemia and Full-Thickness Necrosis After Severe Thermal Injury

Abstract : Recent critical car literature by Piton et al has demonstrated that plasma citrulline may be a helpful adjunct in determining prognosis as well as determining intestinal dysfunction and failure. Citrulline is an amino acid produced by mitochondria within small bowel enterocytes. Citrulline is not incorporated into any protein, its plasma concentration is entirely derived from enterocyte production, and it is metabolized by the kidneys to arginine. Decreased plasma citrulline levels correlate with loss of enterocyte mass in short bowel syndrome and are associated with poor outcomes in radiation enteritis, sepsis, and critical illness. We compared their findings with our own recent observations of serial plasma citrulline levels in a severely burned adult who ultimately died from nonocclusive mescenteric ischemia leading to full-thickness small bowel necrosis.

The glycan-binding protein galectin-1 controls survival of epithelial cells along the crypt-villus axis of small intestine

Intestinal epithelial cells serve as mechanical barriers and active components of the mucosal immune system. These cells migrate from the crypt to the tip of the villus, where different stimuli can differentially affect their survival. Here we investigated, using in vitro and in vivo strategies, the role of galectin-1 (Gal-1), an evolutionarily conserved glycan-binding protein, in modulating the survival of human and mouse enterocytes. Both Gal-1 and its specific glyco-receptors were broadly expressed in small bowel enterocytes. Exogenous Gal-1 reduced the viability of enterocytes through apoptotic mechanisms involving activation of both caspase and mitochondrial pathways. Consistent with these findings, apoptotic cells were mainly detected at the tip of the villi, following administration of Gal-1. Moreover, Gal-1-deficient (Lgals1−/−) mice showed longer villi compared with their wild-type counterparts in vivo. In an experimental model of starvation, fasted wild-type mice displayed reduced villi and lower intestinal weight compared with Lgals1−/− mutant mice, an effect reflected by changes in the frequency of enterocyte apoptosis. Of note, human small bowel enterocytes were also prone to this pro-apoptotic effect. Thus, Gal-1 is broadly expressed in mucosal tissue and influences the viability of human and mouse enterocytes, an effect which might influence the migration of these cells from the crypt, the integrity of the villus and the epithelial barrier function.

Acute intestinal failure in critically ill patients: is plasma citrulline the right marker?

Small bowel functions are more complex than colon functions, and short bowel conditions are associated with increased mortality. Gastrointestinal dysfunction in critically ill patients is common, probably underestimated, and associated with a poor prognosis. However, a validated definition of acute intestinal failure is lacking, in absence of a marker to measure it. Consequently, small bowel dysfunction is not clearly integrated into the overall approach used to treat ICU patients. Review of the literature on gastrointestinal dysfunction in critically ill patients, and proposition of a definition of acute intestinal failure. On the one hand, small bowel ischemia is related to acute reduction of enterocyte mass and loss of gut barrier function by epithelial lifting of villi. On the other hand, systemic inflammatory response syndrome (SIRS) and sepsis could be linked to an acute dysfunction of enterocytes without enterocyte reduction. Citrulline is an amino acid mainly synthesized by small bowel enterocytes. Various contexts of chronic and acute reduction of enterocyte mass have been correlated with low plasma citrulline concentration. Critically ill patients with shock have an acute reduction of enterocyte mass and reduced gut citrulline synthesis, leading to a low plasma citrulline concentration. Acute intestinal failure could be defined as an acute reduction of enterocyte mass and/or acute dysfunction of enterocytes, associated or not with loss of gut barrier function. The influence of SIRS and acute renal failure on plasma citrulline concentration and the value of this concentration as an indicator of acute intestinal failure in critically ill patients must be further evaluated.

Light Microscopic Diagnosis of Microvillus Inclusion Disease on Colorectal Specimens Using CD10

Microvillus inclusion disease (MID) is a rare neonatal enteropathy that is typically diagnosed using electron microscopy to show characteristic inclusions in conjunction with light microscopy and periodic acid-Schiff staining to show lack of the normal brush border on biopsies obtained endoscopically from the small bowel. MID has also been diagnosed using CD10 immunoreactivity that shows abnormal intense cytoplasmic staining in absorptive small bowel enterocytes. As ultrastructural studies also show abnormal microvillus inclusions in absorptive colonocytes in these patients, we investigated the use of CD10 immunoreactivity on colon specimens. We studied the CD10 staining pattern in 4 colon specimens from patients with MID and in colon biopsy specimens from pediatric control patients with and without histopathologic abnormalities. All MID cases had cytoplasmic CD10 staining in absorptive colonocytes in contrast to the control patients who did not show any epithelial CD10 staining. We conclude that abnormal cytoplasmic CD10 staining of absorptive colonocytes can aid in the diagnosis of MID, which may be invaluable in the situations where only colon biopsy specimens are available for examination.

Gut commensal Lactobacillus reuteri 100‐23 stimulates an immunoregulatory response

Lactobacillus reuteri 100-23 is a bacterial commensal of the gastrointestinal tract of mice. Previous studies have shown that colonization of the murine gut by this strain stimulates small-bowel enterocytes to produce proinflammatory cytokines. This is associated with a mild, transitory inflammatory response 6 days after inoculation of formerly Lactobacillus-free animals. The inflammation subsides by 21 days after colonization, although lactobacilli continue to be present in the bowel. To determine the immunological mechanisms that underpin tolerance to bowel commensals, we investigated cytokine responses of dendritic cells and T cells after exposure to cells of L. reuteri 100-23. Interleukin-10 (IL-10), IL-2 and transforming growth factor-beta (TGF-beta) concentrations in supernatants of cultured immune cells, as well as the results of proliferative assays of mesenteric lymph node (MLN) cells and quantification of Foxp3-positive cells in MLN and spleen, indicated that L. reuteri 100-23 stimulated the development of an increased number of regulatory T cells.

Serum Citrulline Is A Simple Quantitative Marker for Small Intestinal Enterocytes Mass and Absorption Function in Short Bowel Patients

To investigate the clinical significance of serum citrulline in evaluating the remnant small bowel enterocytes mass and absorptive function in short bowel (SB) patients. Serum citrulline concentrations were determined using high-performance liquid chromatography (HPLC) in 22 SBS patients and 33 healthy controls. Five-hour urine D-xylose excretion and digestive protein absorption were measured using HPLC and micro-Kjeldahl method, respectively. Small bowel length and surface area were assessed on X-ray radiograph. Correlations between serum citrulline levels and small bowel length, small bowel surface, and nutritional substrate digestive absorption percentage were analyzed. For six patients receiving bowel rehabilitation therapy, serum citrulline, D-xylose excretion, and intestinal protein absorption were measured pre- and immediately postmanagement, and their correlations were analyzed. Serum citrulline levels were significantly lower in SB patients compared with healthy controls. In SB patients, they correlated well with remnant small bowel length (r = 0.82, P < 0.001), surface area (r = 0.86, P < 0.001), 5-h urine D-xylose excretion (r = 0.56, P = 0.007), and digestive protein absorption (r = 0.48, P = 0.046). The increased percentage of serum citrulline level in six patients receiving rehabilitation therapy followed a trend of correlating with that of intestinal protein absorption (r = 0.79, P = 0.063) and urine D-xylose excretion (r = 0.81, P = 0.053). In patients with short bowel syndrome, serum citrulline is a simple and accurate biomarker for the severity of intestinal failure and may be a candidate marker for the gut-trophic effects of bowel rehabilitation therapies.

Plasma citrulline concentration: A surrogate end point for radiation-induced mucosal atrophy of the small bowel. A feasibility study in 23 patients

Purpose Plasma citrulline, a nitrogen end product of glutamine metabolism in small-bowel enterocytes, was suggested as a marker of radiation-induced small-bowel epithelial cell loss in mice after single-dose whole-body irradiation. Our objective was to evaluate the feasibility of citrulline as a marker for radiation-induced small-intestinal mucosal atrophy in patients during and after abdominal fractionated radiotherapy. Methods and materials Twenty-three patients were studied weekly during treatment and at intervals of 2 weeks and 3 and 6 months after treatment by postabsorptive plasma citrulline concentration and clinical toxicity grading. The interrelationship between these variables and the correlation with small-bowel dose and volume parameters were investigated. Results During fractionated radiotherapy, citrulline concentration significantly decreased as a function of the radiation dose ( p < 0.001) and the volume of small bowel treated ( p = 0.001). The plasma citrulline concentration correlated with clinical toxicity during the last 3 weeks of treatment. As a whole, citrulline concentration correlated better with radiation dose and volume parameters than clinical toxicity grading. Conclusions In patients treated with fractionated radiation therapy for abdominal or pelvic cancer sites, plasma citrulline concentration may be a simple objective marker for monitoring epithelial cell loss, a major event in acute radiation-induced small-bowel toxicity.

Citrulline: a potentially simple quantitative marker of intestinal epithelial damage following myeloablative therapy.

We noted a significant decline in the serum concentrations of citrulline of 32 haematopoietic stem cell transplant recipients following intensive myeloablative therapy during the first 3 weeks after transplantation when patients have oral mucositis, a markedly disturbed gut integrity (L/R ratio) and are most at risk of infection and other severe complications. Closer inspection of the citrulline concentrations of 12 patients confirmed that the decline did indeed correspond to the onset of oral mucositis and altered gut integrity. Since serum citrulline is a reliable biochemical marker of small bowel enterocyte mass in humans with villous-atrophy-associated diseases, it may prove a useful marker for intestinal mucosal damage induced by chemotherapy, allowing the relationship between gut mucosal damage and post-transplant complications including infections to be explored more readily.

Citrulline: A physiologic marker enabling quantitation and monitoring of epithelial radiation-induced small bowel damage

Purpose Small bowel irradiation results in epithelial cell loss and consequently impairs function and metabolism. We investigated whether citrulline, a metabolic end product of small bowel enterocytes, can be used for quantifying radiation-induced epithelial cell loss. Methods and materials NMRI mice were subjected to single-dose whole body irradiation (WBI). The time course of citrullinemia was assessed up to 11 days after WBI. A dose–response relationship was determined at 84 h after WBI. In addition, citrullinemia was correlated with morphologic parameters at this time point and used to calculate the dose-modifying factor (DMF) of glutamine and amifostine on acute small bowel radiation damage. Results After WBI, a time- and dose-dependent decrease in plasma citrulline level was observed with a significant dose–response relationship at 84 h. At this time point, citrullinemia significantly correlated with jejunal crypt regeneration ( p < 0.001) and epithelial surface lining ( p = 0.001). A DMF of 1.0 and 1.5 was computed at the effective dose 50 (ED50) level for glutamine and amifostine, respectively. Conclusions Citrullinemia can be used to quantify acute small bowel epithelial radiation damage after single-dose WBI. Radiation-induced changes in citrullinemia are most pronounced at 3 to 4 days postirradiation. At this time point, citrullinemia correlates with morphologic endpoints for epithelial radiation damage.