Citrulline evaluation in bowel transplantation

The role of citrulline, intestinal fatty acid-binding protein, and D-dimer as potential biomarkers in the diagnosis of internal herniation after Roux-en-Y gastric bypass

BACKGROUND

Diagnosing internal herniation (IH) in Roux-en-Y gastric bypass (RYGB) patients with acute abdominal pain poses a diagnostic challenge. Diagnostic laparoscopy is often required for a definitive diagnosis. We hypothesized that intestinal ischemia biomarkers would aid in the diagnosing of IH.

OBJECTIVES

To explore intestinal ischemia biomarkers in diagnosing IH.

SETTING

University Hospital, Sweden.

METHODS

Prospective inclusion of 46 RYGB patients admitted for acute abdominal pain between June 2015 and December 2017. Blood samples for analysis of citrulline, intestinal fatty acid-binding protein (I-FABP), and D-dimer were drawn <72 hours from admission and compared between patients with IH (n = 8), small bowel obstruction (SBO) (n = 5), other specified diagnoses (n = 12), or unspecified abdominal pain (n = 21). Levels of white blood cell count (WBC), C-reactive protein (CRP), and lactate at admission were compared. A prospective pain questionnaire for time of pain onset and level of pain at onset and at admission was analyzed.

RESULTS

None of the investigated biomarkers differed significantly between diagnosis categories. Most patients with IH had normal CRP, WBC, and D-dimer levels while their lactate levels were significantly lower (P = .029) compared with the rest of the cohort. Neither pain level nor pain duration differed between the groups.

CONCLUSION

This study shows that citrulline, I-FABP, and D-dimer cannot be used to diagnose IH and indicates that CRP, D-dimer, and lactate are rarely elevated by an IH. Furthermore, pain intensity and duration cannot differentiate patients with IH. A diagnostic laparoscopy remains the gold standard to diagnose and rule out an IH.

Gastrointestinal Failure in Critically Ill Patients With Cirrhosis

Gastrointestinal failure (GIF) is frequent in patients managed in the intensive care units and manifests as gut paralysis or ileus. GIF is often associated with sepsis or multiorgan failure. In critically ill patients, the precipitating causes of GIF include inflammation, sepsis, electrolyte abnormalities, and acidosis. It is possible that GIF is associated with an increase in bacterial translocation, especially in those with cirrhosis and portal hypertension, and this may play a significant pathogenic or prognostic role in acute-on-chronic liver failure (ACLF). The critical care literature suggests that GIF is associated with a higher mortality risk. In this review, we summarize the evidence for a potential association between GIF and ACLF and propose treatment options for the management of GIF. Moreover, we suggest GIF to be considered as another organ failure when the severity of ACLF is assessed.

Serological biomarkers for acute mesenteric ischemia

Acute mesenteric ischemia (AMI) defines a complex of conditions characterized by an interruption of the splanchnic circulation, leading to insufficient oxygen delivery or utilization to fill the metabolic needs of the visceral organs. Early diagnosis and immediate therapy are the cornerstones of early ischemia to reach a successful outcome and are necessary to reduce the high mortality. Although there is still lack of specific biomarkers to assist the diagnosis of AMI in clinical practice, there are several biomarkers with high specificity, may become a potential tools in early diagnosis of AMI, including intestinal fatty acid binding protein (I-FABP), a-glutathione S-transferase (a-GST), D-dimer, L- and D-lactate, citrulline, ischemia modified albumin, procalcitonin (PCT). However, they use in clinical limited duo to the many studies about these makers finished with small patient populations, and heterogeneous among these populations. This review describes the etiology of AMI, the current most studied promising biomarkers, the current research situation and future of biomarker research.

Screening and combining serum biomarkers to improve their diagnostic performance in the detection of intestinal barrier dysfunction in patients after major abdominal surgery

Background

The aim of this prospective study was to screen and combine effective biomarkers to improve their diagnostic performance in detecting intestinal barrier dysfunction in patients after major abdominal surgery.

Methods

Patients undergoing major abdominal surgery were enrolled after signing informed consent in this study. The serum concentrations of α-GST, DAO, D-lactate, citrulline and I-FABP were detected 24 hours before and after surgery. The diagnostic performance of five biomarkers on intestinal barrier dysfunction was assessed using logistic regression models and receiver operating characteristic (ROC) curve analyses.

Results

Thirty-nine patients with major abdominal surgery were enrolled in and successfully completed this study. ROC analysis revealed that the sensitivities of D-lactate, citrulline and I-FABP were very high (0.91, 0.91 and 1.00, respectively), but the specificities of these biomarkers were less than 0.70. The sensitivity of DAO was very low [0.25; 95% confidence interval (CI), 0.05-0.57], but its specificity was high (0.92; 95% CI, 0.75-0.99). The accuracies of D-lactate and I-FABP were very high, and the areas under the curves (AUCs) of the biomarkers were 0.84 (95% CI, 0.68-0.93) and 0.81 (95% CI, 0.65-0.92), respectively. Different combinations of five biomarkers were also analysed. The sensitivity, specificity and AUC values of the combination of I-FABP, citrulline and D-lactate were 1.00, 0.74 and 0.89, respectively. These results were similar to those derived from the combination of α-GST, DAO, D-lactate, citrulline and I-FABP (P=1.000).

Conclusions

The combination of serum D-lactic acid, citrulline and I-FABP greatly improved the diagnostic performance for identifying intestinal barrier dysfunction in patients after major abdominal surgery.

Characterization of T cell immunophenotypes in intestinal transplantation: A pilot study

Immunophenotyping of peripheral blood mononuclear cells has been shown to be a useful, non-invasive method of predicting acute cellular rejection (ACR) following intestinal transplantation (ITx). Our objectives were to characterize differences in the T cell immunophenotype of ITx recipients in peripheral blood samples (1) collected late versus early after ITx and (1) associated with episodes of ACR and infectious enteritis. An IRB-approved, cross-sectional study of ITx recipients was performed. Peripheral blood samples were collected during normal visits and episodes of allograft dysfunction. A total of 38 patients were included in the analysis: 31 ITx recipients (87% liver-inclusive allografts) and 7 intestinal failure control patients. Of the ITx patients, 26 patients were pediatric patients (<21 years). A total of 70 samples were analyzed from ITx recipients, including 51 during normal visits and 19 during episodes of allograft dysfunction (median of 2 samples per patient; range of 1-6 samples per patient). In the late (n = 32) versus early post-ITx (n = 19) normal samples, there was a significantly higher percentage of central memory CD4 T cells (p = .001). In the ACR (n = 5) versus infectious enteritis (n = 14) samples, there was a higher percentage of CD8 T cells expressing HLA-DR (p = .002), CD57 (p < .001), and KLRG1 (p < .001) and a higher percentage of CD4 T cells expressing CD57 (p = .03). Additional studies are needed with larger cohorts to validate these changes in the T cell immunophenotype. Further elucidating T cell immunophenotypes in ITx will lead to a better understanding of immune mechanisms of allograft dysfunction, identification of potential biomarkers in ITx, and optimized selection of immunosuppressive therapies.

Endoscopic Follow-up of Intestinal Transplant Recipients

The growing population of intestinal transplant recipients present a unique challenge to the gastroenterologists responsible for their support and evaluation. Improvements in patient and graft survival are largely attributed to surgical advancements, refined antirejection therapy, and enhanced endoscopic surveillance protocols that better perceive rejection and other complications. This article reviews the endoscopic management and interventions provided for transplant recipients at the University of Illinois Hospital with complications, such as acute rejection, ischemia, bleeding, fistula, post-transplant lymphoproliferative disorder, and gastroparesis. Further research is needed on promising strategies currently used for related diseases to treat and sustain the intestinal graft.

Citrulline as a marker of intestinal function and absorption in clinical settings: A systematic review and meta-analysis

Background

Citrulline has been described as a marker of intestinal function or absorption but evidence varies according to clinical settings.

Objective

The objective of this article is to examine the evidence of plasma citrulline as a marker of intestinal function and absorption in various clinical settings.

Methods

Studies were examined for p values, means and standard deviations, correlation coefficients or other metrics depicting the association of citrulline with intestinal function. A random effects model was used to produce a pooled estimate. A hierarchical summary receiver operating curve model was fitted for diagnostic accuracy measures.

Results

Citrulline levels are correlated strongly with small bowel length in short bowel syndrome patients (r = 0.67). Citrulline is strongly negatively correlated (r = -0.56) with intestinal disease severity with regards to enteropathies (coeliac disease, tropical enteropathy, Crohn's disease, mucositis, acute rejection in intestinal transplantation). Citrulline cut-off levels have an overall sensitivity and specificity of 80% and 84% respectively. Citrulline levels in untreated coeliac patients compared to controls were reduced by 10 µmol/l. Citrulline levels increase with gluten-free diet and with improvement of enteropathy. Citrulline is decreased in critical illness and sepsis.

Conclusion

These findings allow us to advocate quite reasonably that citrulline is a marker of acute and chronic intestinal insufficiency.

Diagnostic accuracy of novel serological biomarkers to detect acute mesenteric ischemia: a systematic review and meta-analysis

Laparotomy remains the gold standard for diagnosis of acute mesenteric ischemia (AMI), but is often unhelpful or too late due to non-specific clinical and radiological signs. This systematic review and meta-analysis aims to evaluate the diagnostic accuracy of the novel serological biomarkers intestinal fatty acid-binding protein (I-FABP), α-glutathione S-transferase (α-GST), D-lactate, ischemia modified albumin (IMA), and citrulline to detect AMI. A systematic search of electronic databases was performed to identify all published diagnostic accuracy studies on I-FABP, α-GST, D-lactate, IMA, and citrulline. Articles were selected based on pre-defined inclusion and exclusion criteria. Risk of bias and applicability were assessed. Two-by-two contingency tables were constructed to calculate accuracy standards. Summary estimates were computed using random-effects models. The search yielded 1925 papers, 21 were included in the final analysis. Pooled sensitivity and specificity for investigated biomarkers were: I-FABP (Uden); 79.0 (95% CI 66.5-88.5) and 91.3 (87.0-94.6), I-FABP (Osaka); 75.0 (67.9-81.2) and 79.2 (76.2-82.0), D-lactate; 71.7 (58.6-82.5) and 74.2 (69.0-79.0), α-GST; 67.8 (54.2-79.5) and 84.2 (75.3-90.9), IMA; 94.7 (74.0-99.9) and 86.4 (65.1-97.1), respectively. One study investigated accuracy standards for citrulline: sensitivity 39% and specificity 100%. The novel serological biomarkers I-FABP, α-GST, IMA, and citrulline may offer improved diagnostic accuracy of acute mesenteric ischemia; however, further research is required to specify threshold values and accuracy standards for different aetiological forms.

Plasma citrulline measurement in the diagnosis of acute mesenteric ischaemia

BACKGROUND

The differential diagnosis in acute mesenteric ischaemia (AMI) is essential and sometimes life-saving. A marker for early diagnosis is lacking. Citrulline is an amino acid mainly synthesized by small bowel enterocytes from glutamine. In this study, we aimed to evaluate the diagnostic and prognostic values of citrulline with those of the D-dimer in patients with AMI.

METHODS

The patients were divided into two groups; group 1: patients with acute abdominal findings which were attributed preoperatively to AMI, and group 2: patients with acute abdominal findings which were attributed preoperatively to causes other than AMI. All patients underwent surgical exploration. Blood samples were taken before surgery. The demographic features, laboratory examinations, citrulline concentration, D-dimer level and surgical findings were evaluated.

RESULTS

Overall, 48 patients were enrolled in the study. AMI was diagnosed in 23 of the 48 patients. There was no significant difference between the groups with regard to gender, leucocyte count and creatinine levels but group 1 was significantly older than group 2. Citrulline, D-dimer and lactate levels were also significantly higher in group 1. Age, lactate, D-dimer and citrulline levels were statistically significant for mortality. The most significant factor was increased lactate level at admission.

CONCLUSION

Plasma citrulline level may be helpful in the diagnosis of patients with AMI.

Serum citrulline as a diagnostic marker of sepsis-induced intestinal dysfunction

OBJECTIVE

To investigate the use of citrulline as an indicator for diagnosing septic acute intestinal dysfunction (SAID) in a rat model.

METHODS

SD rats were divided into three groups: a normal group (A), a model group (B), and a glutamine group (C). Group B was divided into a 36-h group (B1) and a 72-h feeding group (B2). The concentrations of serum citrulline, intestinal fatty acid-binding protein (I-FABP) and intestinal glutamine and histopathological changes were measured.

RESULTS

The lengths of the villus and thicknesses of the mucosal layer in groups B1, B2 and C were significantly different from those in group A. Citrulline concentrations in groups B1, B2 and C were lower than in group A; the serum concentrations in group C were significantly greater than in groups B1 and B2. The I-FABP levels of groups B1, B2 and C were higher than group A; I-FABP levels of groups B1 and B2 were higher than group C. Intestinal glutamine levels of groups B1 and B2 were lower than groups A and C. The serum citrulline of group C was negatively correlated with I-FABP and Chiu's score.

CONCLUSIONS

Serum citrulline could be used as the diagnostic indicator of SAID.

Utility of an immune cell function assay to differentiate rejection from infectious enteritis in pediatric intestinal transplant recipients

The Cylex Immune Cell Function Assay measures cell-mediated immunity based on ATP production by stimulated CD4 + cells. We hypothesized that this test would discriminate acute cellular rejection (ACR) from infectious enteritis (IE) in pediatric intestinal transplant (ITx) recipients with allograft dysfunction. We retrospectively analyzed 224 Cylex assays drawn in 47 children who received 53 ITx. Samples were classified as stable, ACR, or IE based on clinical status. ATP values were analyzed using Kruskal-Wallis and t-tests. Overall, there was a statistically significant difference in ATP values based on clinical status (p = 0.03); however, overlap was observed between groups. The median ATP value during ACR was significantly greater than during stable periods (p = 0.02). No difference was seen in IE vs. stability (p = 0.8). The difference in median ATP value in ACR vs. IE approached significance (p = 0.1). Relative to previous levels, ACR episodes were associated with a median ATP increase of 101 ng/mL and IE episodes with a decrease of 3 ng/mL (p = 0.3). These data indicate that the Cylex assay has limited utility in differentiating ACR from IE, largely due to interpatient variability. Following longitudinal intrapatient trends may be an adjunctive tool in discriminating IE from ACR and guiding immunosuppression adjustments in select patients.

The evolving concepts of haemodynamic support: from pulmonary artery catheter to echocardiography and theragnostics

Echocardiography is a non-invasive tool, aimed towards the anatomical and functional characterization of the heart. In Intensive Care it is considered nowadays as a necessary tool for patient evaluation. However, the information obtained using echocardiography is not the same as provided by other means, namely the invasive ones. In recent years there has been a significant evolution in the general concepts of haemodynamic support for the critically ill patient. In this new environment, echocardiography has gained particular relevance. In this text the new positioning of echocardiography in the light of the new concepts for hemodynamic support is described, as well as, the need for a specific formative program directed towards Intensive Care physicians. A new generation of biomarkers can also add relevant information and start a new era in haemodynamic support. They may help to further characterize the disease process, identifying patients at risk, as well as, characterize specific organ failure as well as monitoring therapy.

Citrulline level is a potent indicator of acute rejection in the long term following pediatric intestinal/multivisceral transplantation

Citrulline has been advocated as a marker for acute cellular rejection (ACR) in intestinal transplantation; however, its significance as a forewarning in the long-term follow-up remains unknown. This study aimed to investigate the association between citrulline levels and the grading of ACR to establish a cutoff point that accurately predicts ACR beyond 3 months posttransplant in the pediatric patient population. During a 16-year period (1995-2011), a total of 13 499 citrulline samples were prospectively collected from 111 consecutive pediatric intestinal/multivisceral transplant recipients: 2155 were obtained concurrently with intestinal biopsies. There were 185 ACR episodes observed among 74/111 (67%) patients (median follow-up: 4.4 years). Citrulline levels were inversely proportional to the severity of ACR. Negative predictive values for any type of ACR (cutoff, 20 μmol/L) and moderate/severe ACR (cutoff, 10 μmol/L) were 95% and 99%, respectively. When patients were divided according to graft size, diagnostic accuracy using the same cutoff was identical. Similarly, subgroup analysis by the timing of citrulline measurement prior to biopsy varying from 1 to 7 days demonstrated comparable results. Citrulline is a potent indicator as a danger signal for ACR, being an exclusionary, noninvasive biomarker with excellent negative predictive values in the long term after pediatric intestinal/multivisceral transplant.

Plasma citrulline may be a good marker of intestinal functions in intestinal dysfunction

BACKGROUND

Plasma citrulline has been reported to be a good indicator of intestinal functional volume in patients with intestinal dysfunction. We reconfirmed the facts and also investigated the dynamic changes of plasma citrulline in acute-phase patients with intestinal dysfunction.

METHODS

We measured plasma citrulline in six patients with intestinal dysfunction who were in the acute and chronic phase for more than 6 months.

RESULTS

Four patients out of six could be withdrawn from total parenteral nutrition, and their plasma citrulline level dynamically changed according to their intestinal states and finally increased up to 15 nmol/mL. Two patients, who could not be withdrawn from parenteral nutrition, showed very low levels of plasma citrulline throughout the treatment course (under 15 nmol/mL).

CONCLUSION

The cut-off level of plasma citrulline indicating permanent intestinal dysfunction may be 15 nmol/mL in our data. In the acute phase, plasma citrulline changed dynamically according to the intestinal state and may be a good indicator of fluctuating intestinal functions. Thus, although only a few patients were enrolled in this study, plasma citrulline may be a good indicator of stable-state as well as acute-unstable-state intestinal functions.

Nonsurgical care of intestinal and multivisceral transplant recipients: a review for the intensivist

Intestinal and multivisceral transplantation has evolved from an experimental procedure to the treatment of choice for patients with irreversible intestinal failure and serious complications related to long-term parenteral nutrition. Increased numbers of transplant recipients and improved survival rates have led to an increased prevalence of this patient population in intensive care units. Management of intestinal and multivisceral transplant recipients is uniquely challenging because of complications arising from the high incidence of transplant rejection and its treatment. Long-term comorbidities, such as diabetes, hypertension, chronic kidney failure, and neurological sequelae, also develop in this patient population as survival improves. This article is intended for intensivists who provide care to critically ill recipients of intestinal and multivisceral transplants. As perioperative care of intestinal/multivisceral transplant recipients has been described elsewhere, this review focuses on common nonsurgical complications with which one should be familiar in order to provide optimal care. The article is both a review of the current literature on multivisceral and isolated intestinal transplantation as well as a reflection of our own experience at the University of Miami.

Plasma citrulline concentration as a biomarker for bowel loss and adaptation in hospitalized pediatric patients requiring parenteral nutrition

BACKGROUND

Citrulline is a nonessential amino acid produced solely in the enterocyte. Plasma citrulline concentration has been proposed as a noninvasive biomarker for bowel length, function, and dependency on parenteral nutrition (PN). The purpose of this study was to determine if citrulline concentrations differed between pediatric patients with and without small bowel loss requiring specialized nutrition support.

METHODS

This was a retrospective categorical analysis of citrulline concentrations from previously published studies. Patients were included if they were receiving PN, more than 30 days of age, and if they had at least 2 plasma citrulline concentrations. Patients with renal insufficiency and who received outpatient PN treatment were excluded. Patients were categorized as either having or not having small bowel loss.

RESULTS

Thirty-six patients were included for analysis (18 per category). The median citrulline concentration was significantly lower in the group with bowel loss, 8.4 µmol/L vs 10.5 µmol/L (P < .0005), and undetectable citrulline concentrations occurred more often in the bowel loss group, 40% vs 8% (P < .0005). In 13 patients who received enteral nutrition during the study periods, plasma citrulline concentrations increased only in patients without bowel loss.

CONCLUSIONS

These data confirm previous studies and identify decreased citrulline concentrations in pediatric patients with bowel dysfunction in the absence of bowel loss. These data also represent the first serial citrulline concentrations over a 21-day period. The increase in citrulline concentrations only in fed patients without bowel loss suggests that citrulline concentrations could provide a biomarker for bowel function and adaptation.

Biomarkers of immunosuppressant organ toxicity after transplantation: status, concepts and misconceptions

INTRODUCTION

A major challenge in transplantation is improving long-term organ transplant and patient survival. Immunosuppressants protect the transplant organ from alloimmune reactions, but sometimes also exhibit limiting side effects. The key to improving long-term outcome following transplantation is the selection of the correct immunosuppressive regimen for an individual patient for minimizing toxicity while maintaining immunosuppressive efficacy.

AREAS COVERED

Proteomics and metabolomics have the potential to develop sensitive and specific diagnostic tools for monitoring early changes in cell signal transduction, regulation and biochemical pathways. Here, we review the steps required for the development of molecular markers from discovery, mechanistic and clinical qualification to regulatory approval, and present a critical discussion of the current status of molecular marker development as relevant for the management and individualization of immunosuppressive drug regimens.

EXPERT OPINION

Although metabolomics and proteomics-based studies have yielded several candidate molecular markers, most published studies are poorly designed, statistically underpowered and/or often have not gone beyond the discovery stage. Most molecular marker candidates are still at an early stage. Due to the high complexity of and the resources required for diagnostic marker development, initiatives and consortia organized and supported by funding agencies and regulatory agencies will be critical.

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

INTRODUCTION

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.

MATERIALS AND METHODS

Review of the literature on gastrointestinal dysfunction in critically ill patients, and proposition of a definition of acute intestinal failure.

CONCLUSION

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.