Low Energy Availability, Menstrual Dysfunction, and Low Bone Mineral Density in Individuals with a Disability: Implications for the Para Athlete Population

Low energy availability, functional hypothalamic amenorrhea, and low bone mineral density are three interrelated conditions described in athletic women. Although described as the female athlete triad (Triad), males experience similar health concerns. The literature suggests that individuals with a disability may experience altered physiology related to these three conditions when compared with the able-bodied population. The goal of this review is to describe the unique implications of low energy availability, low bone mineral density, and, in females, menstrual dysfunction in individuals with a disability and their potential impact on the para athlete population. A literature review was performed linking search terms related to the three conditions with six disability categories that are most represented in para sport. Few articles were found that directly pertained to athletes, therefore, the review additionally characterizes literature found in a non-athlete population. Review of the available literature in athletes suggests that both male and female athletes with spinal cord injury demonstrate risk factors for low energy availability. Bone mineral density may also show improvements for wheelchair athletes or athletes with hemiplegic cerebral palsy when compared with a disabled non-athlete population. However, the prevalence of the three conditions and implications on the health of para athletes is largely unknown and represents a key gap in the sports medicine literature. As participation in para sport continues to increase, further research is needed to understand the impact of these three interrelated health concerns for athletes with a disability, accompanied by educational initiatives targeting athletes, coaches, and health professionals.

Citrulline Generation Test: What Does It Measure?

BACKGROUND

The citrulline generation test (CGT) has been proposed as a tool to determine gut function. However, the increase in plasma citrulline concentration that follows a bolus dose of alanyl-glutamine may also result from a reduction in citrulline clearance due to competition with glutamine for transport.

MATERIALS AND METHODS

A swine model was developed, and stable isotope tracers were used to determine the mechanism behind the increase in plasma citrulline that follows a bolus dose of alanyl-glutamine. Plasma concentrations and enrichments were determined, and a non-steady-state model was used to calculate rates of appearance, disappearance, and conversion.

RESULTS

The pig model recapitulated the increase in plasma citrulline observed in humans after a dose of alanyl-glutamine. The dipeptide was rapidly hydrolyzed to its constitutive amino acids. Both citrulline plasma concentration and citrulline rate of appearance increased by ≈45% after the bolus dose of alanyl-glutamine. The conversion of citrulline to arginine and the rate of appearance of arginine also increased. Glutamine contributed up to 25% ± 2% of the rate of appearance of citrulline. No changes in the rate of disappearance of citrulline were observed.

CONCLUSION

Our results indicate that a single bolus dose of alanyl-glutamine increases plasma citrulline concentration by increasing citrulline production without any effect on citrulline disposal. Our findings strongly indicate that the CGT assesses the metabolic response of the gut and that CGT can become a useful tool to evaluate gut mass and function.

Plasma citrulline concentration, a marker for intestinal functionality, reflects exercise intensity in healthy young men

BACKGROUND & AIMS

Plasma citrulline concentration is considered to be a marker for enterocyte metabolic mass and to reflect its reduction as may occur during intestinal dysfunction. Strenuous exercise can act as a stressor to induce small intestinal injury. Our previous studies suggest that this comprises the intestinal ability to produce citrulline from a glutamine-rich protein bolus. In this study we investigated the effects of different exercise intensities and hydration state on citrulline and iFABP levels following a post-exercise glutamine bolus in healthy young men.

METHODS

Fifteen healthy young men (20-35 yrs, VO₂ max 56.9 ± 3.9 ml kg^-1 min^-1) performed in a randomly assigned cross-over design, a rest (protocol 1) and four cycle ergometer protocols. The volunteers cycled submaximal at different percentages of their individual pre-assessed maximum workload (Wmax): 70% Wmax in hydrated (protocol 2) and dehydrated state (protocol 3), 50% Wmax (protocol 4) and intermittent 85/55% Wmax in blocks of 2 min (protocol 5). Immediately after 1 h exercise or rest, subjects were given a glutamine bolus with added alanine as an iso-caloric internal standard (7.5 g of each amino acid). Blood samples were collected before, during and after rest or exercise, up to 24 h post onset of the experiment. Amino acids and urea were analysed as metabolic markers, creatine phosphokinase and iFABP as markers of muscle and intestinal damage, respectively. Data were analysed using a multilevel mixed linear statistical model. p values were corrected for multiple testing.

RESULTS

Citrulline levels already increased before glutamine supplementation during normal hydrated exercise, while this was not observed in the dehydrated and rest protocols. The low intensity exercise protocol (50% Wmax) showed the highest increase in citrulline levels both during exercise (43.83 μmol/L ± 2.63 (p < 0.001)) and after glutamine consumption (50.54 μmol/L ± 2.62) compared to the rest protocol (28.97 μmol/L ± 1.503 and 41.65 μmol/L ± 1.96, respectively, p < 0.05). However, following strenuous exercise at 70% Wmax in the dehydrated state, citrulline levels did not increase during exercise and less after the glutamine consumption when compared to the resting condition and hydrated protocols. In line with this, serum iFABP levels were the highest with the strenuous dehydrated protocol (1443.72 μmol/L ± 249.9, p < 0.001), followed by the high intensity exercise at 70% Wmax in the hydrated condition.

CONCLUSIONS

Exercise induces an increase in plasma citrulline, irrespective of a glutamine bolus. The extent to which this occurs is dependent on exercise intensity and the hydration state of the subjects. The same holds true for both the post-exercise increase in citrulline levels following glutamine supplementation and serum iFABP levels. These data indicate that citrulline release during exercise and after an oral glutamine bolus might be dependent on the intestinal health state and therefore on intestinal functionality. Glutamine is known to play a major role in intestinal physiology and the maintenance of gut health and barrier function. Together, this suggests that in clinical practice, a glutamine bolus to increase citrulline levels after exercise might be preferable compared to supplementing citrulline itself. To our knowledge this is the first time that exercise workload-related effects on plasma citrulline are reported in relation to intestinal damage.

Biochemical markers of acute intestinal ischemia: possibilities and limitations

Acute intestinal ischemia is a relative rare abdominal emergency, associated with considerably high morbidity and mortality rates. Although the conventional diagnostic approach to acute intestinal ischemia entails a preliminary evaluation of signs and symptoms, followed by radiological and laboratory investigations, a definitive diagnosis is can usually be made after laparotomy, which still remains the gold standard diagnostic (and therapeutic) procedure. Several potential laboratory biomarkers have been investigated over the past decades, but none of these seems to reach a suitable diagnostic accuracy for an early and reliable diagnosis of intestinal ischemia. The aim of this narrative review is to provide an overview on traditional laboratory tests for diagnosing acute intestinal ischemia (i.e., complete blood count, D-dimer, blood gas analysis, total lactic acid, C-reactive protein and procalcitonin), and summarize current evidence regarding some emerging and potentially useful biomarkers such as D-lactate, intestinal fatty acid-binding protein (I-FABP), ischemia modified albumin (IMA), α-glutathione S-transferase (α-GST), interleukin-6 (IL-6), citrulline and smooth muscle protein of 22 kDa (SM22). Among the various tests, D-lactate, IMA and I-FABP are perhaps the most promising, since they are characterized by optimal sensitivity and relatively good specificity, early kinetics, and can be measured with assays suited for a rapid diagnosis.

Ex Vivo Enteroids Recapitulate In Vivo Citrulline Production in Mice

Background

The endogenous production of arginine relies on the synthesis of citrulline by enteral ornithine transcarbamylase (OTC). Mutations in the gene coding for this enzyme are the most frequent cause of urea cycle disorders. There is a lack of correlation between in vivo metabolic function and DNA sequence, transcript abundance, or in vitro enzyme activity.

Objective

The goal of the present work was to test the hypothesis that enteroids, a novel ex vivo model, are able to recapitulate the in vivo citrulline production of wild-type (WT) and mutant mice.

Methods

Six-week-old male WT and OTC-deficient mice [sparse fur and abnormal skin (spf-ash) mutation] were studied. Urea and citrulline fluxes were determined in vivo, and OTC abundance was measured in liver and gut tissue. Intestinal crypts were isolated and cultured to develop enteroids. Ex vivo citrulline production and OTC abundance were determined in these enteroids.

Results

Liver OTC abundance was lower (mean ± SE: 0.16 ± 0.01 compared with 1.85 ± 0.18 arbitrary units; P < 0.001) in spf-ash mice than in WT mice, but there was no difference in urea production. In gut tissue, OTC was barely detectable in mutant mice; despite this, a lower but substantial citrulline production (67 ± 3 compared with 167 ± 8 µmol · kg-1 · h-1; P < 0.001) was shown in the mutant mice. Enteroids recapitulated the in vivo findings of a very low OTC content accompanied by a reduced citrulline production (1.07 ± 0.20 compared with 4.64 ± 0.44 nmol · µg DNA-1 · d-1; P < 0.001).

Conclusions

Enteroids recapitulate in vivo citrulline production and offer the opportunity to study the regulation of citrulline production in a highly manipulable system.

Identifying the etiology and pathophysiology underlying stunting and environmental enteropathy: study protocol of the AFRIBIOTA project

BACKGROUND

Globally one out of four children under 5 years is affected by linear growth delay (stunting). This syndrome has severe long-term sequelae including increased risk of illness and mortality and delayed psychomotor development. Stunting is a syndrome that is linked to poor nutrition and repeated infections. To date, the treatment of stunted children is challenging as the underlying etiology and pathophysiological mechanisms remain elusive. We hypothesize that pediatric environmental enteropathy (PEE), a chronic inflammation of the small intestine, plays a major role in the pathophysiology of stunting, failure of nutritional interventions and diminished response to oral vaccines, potentially via changes in the composition of the pro- and eukaryotic intestinal communities. The main objective of AFRIBIOTA is to describe the intestinal dysbiosis observed in the context of stunting and to link it to PEE. Secondary objectives include the identification of the broader socio-economic environment and biological and environmental risk factors for stunting and PEE as well as the testing of a set of easy-to-use candidate biomarkers for PEE. We also assess host outcomes including mucosal and systemic immunity and psychomotor development. This article describes the rationale and study protocol of the AFRIBIOTA project.

METHODS

AFRIBIOTA is a case-control study for stunting recruiting children in Bangui, Central African Republic and in Antananarivo, Madagascar. In each country, 460 children aged 2-5 years with no overt signs of gastrointestinal disease are recruited (260 with no growth delay, 100 moderately stunted and 100 severely stunted). We compare the intestinal microbiota composition (gastric and small intestinal aspirates; feces), the mucosal and systemic immune status and the psychomotor development of children with stunting and/or PEE compared to non-stunted controls. We also perform anthropological and epidemiological investigations of the children's broader living conditions and assess risk factors using a standardized questionnaire.

DISCUSSION

To date, the pathophysiology and risk factors of stunting and PEE have been insufficiently investigated. AFRIBIOTA will add new insights into the pathophysiology underlying stunting and PEE and in doing so will enable implementation of new biomarkers and design of evidence-based treatment strategies for these two syndromes.

Exploring the relationship between environmental enteric dysfunction and oral vaccine responses

Oral vaccines significantly underperform in low-income countries. One possible contributory factor is environmental enteric dysfunction (EED), a subclinical disorder of small intestinal structure and function among children living in poverty. Here, we review studies describing oral vaccine responses and EED. We identified eight studies evaluating EED and oral vaccine responses. There was substantial heterogeneity in study design and few consistent trends emerged. Four studies reported a negative association between EED and oral vaccine responses; two showed no significant association; and two described a positive correlation. Current evidence is therefore insufficient to determine whether EED contributes to oral vaccine underperformance. We identify roadblocks in the field and future research needs, including carefully designed studies those can investigate this hypothesis further.

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.

Determining optimal therapy of dogs with chronic enteropathy by measurement of serum citrulline

Background

Serum concentration of citrulline is a useful biomarker in human intestinal disease and indicates globally reduced enterocyte mass and absorptive function in various disease states.

Objectives

To determine whether serum citrulline concentration is a biomarker in chronic enteropathy (CE) in dogs, to provide useful information regarding optimal treatment or to predict outcome.

Animals

Seventy‐four dogs with CE and 83 breed‐ and age‐matched hospital controls with no clinical signs of intestinal disease.

Methods

Retrospective study. Outcome was determined and dogs were categorized by response to treatment as having food‐responsive enteropathy (FRE), antibiotic‐responsive diarrhea (ARD), or idiopathic inflammatory bowel disease (IBD). Disease severity was quantified by the CIBDAI scoring index.

Results

Serum citrulline concentration did not differ between dogs with CE (median, 8.4 µg/mL, 5th‐95th percentile 2.0‐19.6) and controls (median, 8.1 µg/mL, 5th‐95th percentile 2.2‐19.7, P = .91). Serum citrulline concentration was similar between dogs with FRE (median, 9.1 µg/mL, 5th‐95th percentile 2.0‐18.9), ARD (median, 13.0 µg/mL, 5th‐95th percentile 1.6‐19.2), IBD (median, 8.4 µg/mL, 5th‐95th percentile 2.1‐21.0; P = .91). Serum citrulline did not correlate to CIBDAI or to serum albumin concentration.

Conclusions and Clinical Importance

In our study, serum citrulline concentration was not associated with efficacy of treatment or outcome in dogs with CE.

A Longitudinal Study of Household Water, Sanitation, and Hygiene Characteristics and Environmental Enteropathy Markers in Children Less than 24 Months in Iquitos, Peru

Poor child gut health, resulting from a lack of access to an improved toilet or clean water, has been proposed as a biological mechanism underlying child stunting and oral vaccine failure. Characteristics related to household sanitation, water use, and hygiene were measured among a birth cohort of 270 children from peri-urban Iquitos Peru. These children had monthly stool samples and urine samples at four time points and serum samples at (2–4) time points analyzed for biomarkers related to intestinal inflammation and permeability. We found that less storage of fecal matter near the household along with a reliable water connection were associated with reduced inflammation, most prominently the fecal biomarker myeloperoxidase (MPO) (no sanitation facility compared with those with an onsite toilet had −0.43 log MPO, 95% confidence interval [CI]: −0.74, −0.13; and households with an intermittent connection versus those with a continuous supply had +0.36 log MPO, 95% CI: 0.08, 0.63). These results provide preliminary evidence for the hypothesis that children less than 24 months of age living in unsanitary conditions will have elevated gut inflammation.

Pilot Study of Radiation-induced Gastrointestinal Injury in a Hemi-body Shielded Göttingen Minipig Model

Development of medical countermeasures (MCMs) for gastrointestinal (GI) injury following acute radiation exposure requires well-characterized models that can assess not only survival but also secondary endpoints, including structural and functional characteristics of GI damage and recovery that ultimately contribute to long-term survival. The authors conducted a pilot study in a hemi-body shielded Göttingen minipig model of radiation-induced GI injury that enables radiation damage to the GI tract to be evaluated and reduces the potential for hemorrhage and/or damage in other more sensitive organ systems. With shielding of the head, chest, and front legs, radiation dose levels of 14 Gy were required to see significant GI-related morbidity, while dose levels of 16 Gy resulted in significant mortality by day 45 post-irradiation. Periodic scheduled necropsies showed significant reduction in and slow recovery of intestinal crypt count at 14 and 16 Gy. Intestinal proliferative activity was initially increased and then gradually decreased over the course of the study. Histological evidence of marked inflammatory infiltrates was noted in the GI tract at day 5, while collagen deposition, indicative of fibrosis, was observed as early as day 15, peaking at day 30. The radiation dose-responsive indicators of GI damage identified in this model (i.e., intestinal crypt count and proliferative activity) may serve as useful endpoints for evaluation of the efficacy of potential MCMs.

Amino acid supplements in critically ill patients

Observational studies have associated a low amino acid intake with adverse outcome of critical illness. Although this finding could theoretically be explained by differences in feeding tolerance related to illness severity, guidelines have recommended to administer sufficient amounts of amino acids from early onwards in the disease course. Recently, however, several high quality randomized controlled trials have not shown benefit by early amino acid supplementation and some trials even found potential harm, thus questioning this recommendation. These negative results could be related to amino acid-induced suppression of autophagy, to the inability to suppress bulk catabolism by exogenous amino acids, or to the administration of an amino acid mixture with an inappropriate composition. Currently, there is no evidence supporting administration of individual amino acid supplements during critical illness and glutamine administration may be harmful. The optimal timing, dose and composition of the amino acid mixture for critically ill patients remain unclear.

Biomarkers for visceral hypersensitivity in patients with irritable bowel syndrome

BACKGROUND

Increased visceral sensitivity is observed in up to 60% of patients with Irritable Bowel Syndrome (IBS). Mucosal inflammation, altered neuroendocrine activity and intraluminal metabolic processes may contribute to the development of visceral hypersensitivity. Previously, we demonstrated that biomarkers, indicative for these biological processes, were altered in IBS patients compared to healthy controls. However, how these processes relate to visceral hypersensitivity is unknown.

AIM

The aim of this study was to provide insight in biological processes associated with visceral hypersensitivity. Fecal and plasma biomarkers were measured in normosensitive and hypersensitive IBS patients.

METHODS

A total of 167 IBS patients underwent a rectal barostat procedure to assess visceral sensitivity to pain. Based on the outcome, patients were classified into a normosensitive or hypersensitive group. Calprotectin, human β-defensin 2 (HBD2), chromogranin A (CgA), and short chain fatty acids (SCFAs) were measured in feces, citrulline in plasma, and serotonin and its main metabolite 5-hydroxyindoleacetic acid (5-HIAA) in platelet-poor plasma.

KEY RESULTS

Fecal markers and plasma citrulline were measured in 83 hypersensitive and 84 normosensitive patients, while platelet-poor plasma for the assessment of serotonin and 5-HIAA was available for a subgroup, i.e. 53 hypersensitive and 42 normosensitive patients. No statistically significant differences were found in concentrations of biomarkers between groups. Adjustment of the analyses for potential confounders, such as medication use, did not alter this conclusion.

CONCLUSIONS & INFERENCES

Our findings do not support a role for the biological processes as ascertained by biomarkers in visceral hypersensitivity in IBS patients. This study is registered in the US National Library of Medicine (clinicaltrials.gov, NCT00775060).

The IN-PANCIA Study: Clinical Evaluation of Gastrointestinal Dysfunction and Failure, Multiple Organ Failure, and Levels of Citrulline in Critically Ill Patients

PURPOSE

Gastrointestinal dysfunction and failure (GID and GIF) in critically ill patients are a common, relevant, and underestimated complications in ICU patients. The aims of this study were (1) to determine plasmatic levels of citrulline, glutamine, and arginine as markers of GID/GIF in critically ill patients with or without GID/GIF with or without multiple organ failure (MOF) and (2) to assess the role of intra-abdominal hypertension in these patient groups.

MATERIALS AND METHODS

This is a 1-year, monocentric (Italian hospital), prospective observational study. Inclusion criteria were adult patients with GID/GIF, with or without MOF. The GIF score was daily evaluated in 39 critically ill patients. Amino acids were measured at the time of GID or GIF.

RESULTS

We enrolled 39 patients. Nine patients developed GID and 7 GIF; 6 of patients with GID/GIF developed MOF. Citrulline was lower (P < .001) in patients with GID/GIF (11.3 [4.4] µmol/L), compared to patients without GID/GIF (22.4 [6.8] µmol/L); likewise, glutamine was lower in patients with GID/GIF, whereas arginine was nonstatistically different between the 2 groups. Intra-abdominal pressure was higher in patients affected by MOF (13.0 [2.2] mm Hg) than in patients with GIF/GID without MOF (9.6 [2.6] mm Hg) and compared to patients without GID/GIF (7.2 [2.1] mm Hg).

CONCLUSIONS

Both GID and GIF in critically ill patients are associated with low levels of citrulline and glutamine, which could be considered as markers of small bowel dysfunction. The higher the GIF score, the lower the citrulline levels. Patients affected by MOF had higher levels of intra-abdominal pressure.

Intestinal Fatty Acid Binding Protein and Citrulline as Markers of Gut Injury and Prognosis in Patients With Acute Pancreatitis

OBJECTIVES

Severe acute pancreatitis (AP) is associated with high mortality due to systemic inflammatory response syndrome in the early phase and secondary infection in the later phase. Concomitant intestinal ischemia often results in gut injury. We studied intestinal fatty acid binding protein (IFABP) and citrulline levels as markers of gut injury to predict prognosis in AP.

METHODS

Acute pancreatitis patients at admission and controls were studied. Serum IFABP was measured by enzyme-linked immunosorbent assay and plasma citrulline by high-performance liquid chromatography technique. Ultrastructural changes in duodenal biopsy were also compared between the 2 groups.

RESULTS

The IFABP concentration was significantly higher in AP cases (n = 94) compared with controls (n = 100) (mean [standard deviation], 592.5 [753.6] vs 87.8 [67.6] pg/mL; P < 0.001) and in patients with severe AP versus mild AP (738.3 [955.3] vs 404.0 [263.3] pg/ mL, P = 0.03). Citrulline concentration was lower in AP versus controls (29.9 [33.8] vs 83.9 [60.1] μg/L, P < 0.001). We propose a model by which these biomarkers (IFABP >350 pg/mL and citrulline <18 μg/L) are able to predict poor prognosis in 33.9% of patients with AP. The gut injury was also validated via ultrastructural changes.

CONCLUSIONS

Intestinal fatty acid binding protein is a promising prognostic marker in acute pancreatitis.

The effect of endurance exercise on intestinal integrity in well-trained healthy men

Exercise is one of the external factors associated with impairment of intestinal integrity, possibly leading to increased permeability and altered absorption. Here, we aimed to examine to what extent endurance exercise in the glycogen‐depleted state can affect intestinal permeability toward small molecules and protein‐derived peptides in relation to markers of intestinal function. Eleven well‐trained male volunteers (27 ± 4 years) ingested 40 g of casein protein and a lactulose/rhamnose (L/R) solution after an overnight fast in resting conditions (control) and after completing a dual – glycogen depletion and endurance – exercise protocol (first protocol execution). The entire procedure was repeated 1 week later (second protocol execution). Intestinal permeability was measured as L/R ratio in 5 h urine and 1 h plasma. Five‐hour urine excretion of betacasomorphin‐7 (BCM7), postprandial plasma amino acid levels, plasma fatty acid binding protein 2 (FABP‐2), serum pre‐haptoglobin 2 (preHP2), plasma glucagon‐like peptide 2 (GLP2), serum calprotectin, and dipeptidylpeptidase‐4 (DPP4) activity were studied as markers for excretion, intestinal functioning and recovery, inflammation, and BCM7 breakdown activity, respectively. BCM7 levels in urine were increased following the dual exercise protocol, in the first as well as the second protocol execution, whereas 1 h‐plasma L/R ratio was increased only following the first exercise protocol execution. FABP2, preHP2, and GLP2 were not changed after exercise, whereas calprotectin increased. Plasma citrulline levels following casein ingestion (iAUC) did not increase after exercise, as opposed to resting conditions. Endurance exercise in the glycogen depleted state resulted in a clear increase of BCM7 accumulation in urine, independent of DPP4 activity and intestinal permeability. Therefore, strenuous exercise could have an effect on the amount of food‐derived bioactive peptides crossing the epithelial barrier. The health consequence of increased passage needs more in depth studies.

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.

Effects of Pu-erh ripened tea on hyperuricemic mice studied by serum metabolomics

To evaluate effects of Pu-erh ripened tea in hyperuricemic mice, a mouse hyperuricemia model was developed by oral administration of potassium oxonate for 7 d. Serum metabolomics, based on gas chromatography-mass spectrometry, was used to generate metabolic profiles from normal control, hyperuricemic and allopurinol-treated hyperuricemic mice, as well as hyperuricemic mice given Pu-erh ripened tea at three doses. Pu-erh ripened tea significantly lowered serum uric acid levels. Twelve potential biomarkers associated with hyperuricemia were identified. Pu-erh ripened tea and allopurinol differed in their metabolic effects in the hyperuricemic mice. Levels of glutamic acid, indolelactate, L-allothreonine, nicotinoylglycine, isoleucine, l-cysteine and glycocyamine, all involved in amino acid metabolism, were significantly changed in hyperuricemic mice treated Pu-erh ripened tea. Thus, modulating amino acid metabolism might be the primary mechanism of anti-hyperuricemia by Pu-erh ripened tea.

The intestinal barrier: a fundamental role in health and disease

The gastrointestinal mucosa constitutes a critical barrier where millions of microbes and environmental antigens come in close contact with the host immune system. Intestinal barrier defects have been associated with a broad range of diseases and therefore denote a new therapeutic target. Areas covered: This review is based on an extensive literature search in PubMed of how the intestinal barrier contributes to health and as a trigger for disease. It discusses the anatomy of the intestinal barrier and explains the available methods to evaluate its function. Also reviewed is the importance of diet and lifestyle factors on intestinal barrier function, and three prototypes of chronic diseases (inflammatory bowel disease, celiac disease and nonalcoholic fatty liver disease) that have been linked to barrier defects are discussed. Expert commentary: The intestinal barrier has been investigated by various methods, but correlation of results across studies is difficult, representing a major shortcoming in the field. New upcoming techniques and research on the effect of barrier-restoring therapeutics may improve our current understanding of the gut barrier, and provide a step forward towards personalised medicine.

Markers of enteral adaptation in pediatric short bowel syndrome

BACKGROUND

The aim of this study was to ascertain if prospective determination of specific gut hormones and growth factors could predict bowel adaptation in children with short bowel syndrome (SBS).

METHODS

We studied independence from parenteral nutrition (PN) as the short-term result and discontinuation of enteral nutrition (EN) as the long-term result from a retrospective chart review of seven patients with SBS, who were managed in the absence of growth retardation. The correlation between increased number of enteral feeds or enteral nutrients and fasting serum gastrin, glucagon-like peptide 2 (GLP-2), citrulline, and D-amino acid oxidase (DAO) activity was analyzed. Five patients were weaned from PN, and two from EN.

RESULTS

Fasting serum gastrin was significantly higher and serum GLP-2 lower in the PN-dependent patients than in the patients weaned from EN. The upper limit of fasting serum gastrin for PN independence and for EN independence was 300 and 200 pg/mL, respectively. The lower limit of fasting serum citrulline for PN independence was 15 μmol/L. The relationship between serum citrulline and DAO and the course of bowel adaptation, however, was poor.

CONCLUSIONS

Serum citrulline is a predictor of PN independence in children with SBS. Fasting serum gastrin and GLP-2 are indicators for adaptation of the residual intestine, but this was a small study and further larger prospective trials are required to confirm these results.

Tumor Necrosis Factor-Alpha Inhibitor Etanercept Does Not Alter Methotrexate-Induced Gastrointestinal Mucositis in Rats

OBJECTIVES

Gastrointestinal (GI) mucositis is a severe adverse effect of chemotherapy and radiotherapy. Proinflammatory cytokines are thought to play an important role in the pathophysiology of GI mucositis. We aimed to determine the effect of the tumor necrosis factor-alpha (TNF-α) inhibitor etanercept on the severity of mucositis in a previously established methotrexate (MTX)-induced GI mucositis rat model.

METHODS

Male Wistar rats received 60 mg/kg MTX on day 0 intravenously. Rats were treated daily with either etanercept (TNF-α inhibitor) 5 mg/kg or NaCl 0.9% subcutaneously from day -3 till day 3. Control rats received NaCl 0.9% intravenously and etanercept subcutaneously. The severity of mucositis was determined by intake, bodyweight, plasma citrulline, and by a function test (absorption of an oral glucose bolus). On day 4 and day 10 rats were terminated. Villus length, crypt length, intestinal myeloperoxidase, and plasma etanercept levels were determined.

RESULTS

The administration of MTX induced mucositis in all rats. Etanercept did not cause a change in the degree of mucositis. Bodyweight, intake, and glucose levels were not altered by etanercept; villus length was comparable; and there was no difference in myeloperoxidase and citrulline level. Etanercept levels in plasma were significantly increased in the etanercept rats (P < 0.05).

CONCLUSIONS

TNF-α inhibitor etanercept did not alter the severity of mucositis in the rat, suggesting that targeting only the inflammatory pathway of TNF-α is not effective for decreasing the severity of GI mucositis induced by high-dose MTX. Etanercept alone is not useful for the treatment of MTX-induced GI mucositis.

Citrulline metabolism in plants

Citrulline was chemically isolated more than 100 years ago and is ubiquitous in animals, plants, bacteria, and fungi. Most of the research on plant citrulline metabolism and transport has been carried out in Arabidopsis thaliana and the Cucurbitaceae family, particularly in watermelon which accumulates this non-proteinogenic amino acid to very high levels. Industrially, citrulline is produced via specially optimized microbial strains; however, the amounts present in watermelon render it an economically viable source providing that other high-value compounds can be co-extracted. In this review, we provide an overview of our current understanding of citrulline biosynthesis, transport, and catabolism in plants additionally pointing out significant gaps in our knowledge which need to be closed by future experimentation. This includes the identification of further potential enzymes of citrulline metabolism as well as obtaining a far better spatial resolution of both sub-cellular and long-distance partitioning of citrulline. We further discuss what is known concerning the biological function of citrulline in plants paying particular attention to the proposed roles in scavenging of excess NH₄⁺ and as a compatible solute.

Surface-enhanced Raman spectroscopy competitive binding biosensor development utilizing surface modification of silver nanocubes and a citrulline aptamer

A point-of-care (PoC) device with the ability to detect biomarkers at low concentrations in bodily fluids would have an enormous potential for medical diagnostics outside the central laboratory. One method to monitor analytes at low concentrations is by using surface-enhanced Raman spectroscopy (SERS). In this preliminary study toward using SERS for PoC biosensing, the surface of colloidal silver (Ag) nanocubes has been modified to test the feasibility of a competitive binding SERS assay utilizing aptamers against citrulline. Specifically, Ag nanocubes were functionalized with mercaptobenzoic acid, as well as a heterobifunctional polyethylene glycol linker that forms an amide bond with the amino acid citrulline. After the functionalization, the nanocubes were characterized by zeta-potential, transmission electron microscopy images, ultraviolet/visible spectroscopy, and by SERS. The citrulline aptamers were developed and tested using backscattering interferometry. The data show that our surface modification method does work and that the functionalized nanoparticles can be detected using SERS down to a 24.5 picomolar level. Last, we used microscale thermophoresis to show that the aptamers bind to citrulline with at least a 50 times stronger affinity than other amino acids. Download PDF SAVE FOR LATER

Safety and Efficacy of Teduglutide (Gattex) in Patients With Crohn's Disease and Need for Parenteral Support Due to Short Bowel Syndrome-associated Intestinal Failure

BACKGROUND

Teduglutide is a GLP-2 analogue indicated for treatment of adults with short bowel syndrome (SBS). Because of the rarity of SBS, real-world safety or efficacy data are not available in patients with Crohn's disease (CD) and SBS treated with teduglutide.

AIM

To evaluate teduglutide's safety and efficacy in CD patients with SBS.

METHODS

We conducted a retrospective cohort study at 3 tertiary centers in the United States between 2012 and 2014. Demographic, clinical, and therapeutic data were retrieved from medical record systems.

RESULTS

Thirteen CD patients were included, 8 (62%) of whom were on concomitant immunosuppression. Median duration of teduglutide therapy was 365 days [interquartile range (IQR), 122 to 482 d] and 9/13 patients (69%) remain on therapy. At teduglutide initiation, 69% were on parenteral nutrition. At conclusion of follow-up, 1 patient was on parenteral nutrition. All patients were on intravenous fluids (IVF) before teduglutide; median IVF were 9000 mL/wk (IQR, 7000 to 14,000 mL/wk). IVF requirements decreased by a median of 3100 mL/wk (IQR, 2400 to 8400 mL/wk). Six patients (46%) ceased IVF. Adverse events attributed to teduglutide were obstructive symptoms (n=1), pancreatitis (n=1), asymptomatic lipase and amylase elevation (n=1), nausea (n=1), and abdominal pain (n=1). Catheter-related sepsis occurred in 4 patients.

CONCLUSIONS

This is the first report evaluating the safety and efficacy of teduglutide in a cohort of CD patients with SBS requiring parenteral support. More of half the cohort was on concomitant immunosuppression. Teduglutide seemed to be safe and the majority of patients were weaned off parenteral support.

Biomarkers and non-invasive tests for gastrointestinal mucositis

Gastrointestinal mucositis is a complex inflammatory reaction of the mucous membranes, a side effect of both chemotherapy and radiotherapy. Currently, assessment scales are used to diagnose mucositis. However, a biomarker which would determine whether there is mucositis and thereby establish the severity objectively would be very useful. This will give the opportunity to evaluate studies, to determine risk factors and incidence, and it will make it possible to compare studies. Moreover, this biomarker might improve clinical management for patients. In this paper, we reviewed studies concerning potential biomarkers in blood samples and fecal samples, and potential tests in breath samples and urine samples. We include biomarkers and tests studied in animal models and/or in clinical trials, and discuss the validity, diagnostic accuracy, and applicability.

Intravenous citrulline generation test to assess intestinal function in intensive care unit patients

Background

Assessment of a quantifiable small intestinal function test is cumbersome. Fasting citrulline concentrations have been proposed as a measure of enterocyte function and elaborated into a citrulline generation test (CGT), which is applicable only when glutamine is administered orally. CGT is an oral test, limiting its use, for example, in critically ill patients.

Objective

Assessment of normative values and feasibility of an intravenously performed CGT in intensive care unit (ICU) patients with presumed gastrointestinal motility disturbances, especially when performed intravenously.

Design

CGT reference values were determined in 16 stable ICU patients using two different CGT methods, namely following either enteral or intravenous glutamine administration and both with simultaneous arterial and venous plasma citrulline sampling at six time-points. Plasma amino acid analysis was performed using reverse-phase high-performance liquid chromatography.

Results

The median total generation of citrulline in 90 min (CGT iAUCT90) was markedly higher with arterial citrulline sampling compared with venous citrulline sampling, being 724±585 and 556±418 µmol/L/min for enteral glutamine, respectively (p=0.02) and 977±283 and 769±231 µmol/L/min for intravenous glutamine, respectively (p=0.0004). The median slope (time-dependent increase) for plasma arterial and venous citrulline during the CGT was 0.20±0.16 and 0.18±0.12 µmol/L/min for enteral glutamine, respectively (p=0.004) and 0.22±0.16 and 0.19±0.05 µmol/L/min for intravenous glutamine, respectively (p=0.02).

Conclusion

Intravenous glutamine administration combined with arterial plasma citrulline sampling yielded the least variation in CGT characteristics in stable ICU patients. A 2-point measurement test had comparable test characteristics as a 6-point measurement CGT and seems promising.

Feeding strategies in pediatric cancer patients with gastrointestinal mucositis: a multicenter prospective observational study and international survey

INTRODUCTION

Currently, there is no adequate prevention or treatment for both oral and gastrointestinal mucositis induced by chemotherapy and/or radiotherapy. Supportive care of symptoms plays a primary role during mucositis in the pediatric clinical setting. We aimed to get insight in the currently used feeding strategies in clinical practice in pediatric cancer patients with chemotherapy-induced mucositis.

METHODS

A prospective observational study was performed to identify feeding strategies after chemotherapy courses causing mucositis in almost all patients at the University Medical Center Groningen (UMCG), the Academic Medical Center Amsterdam (AMC), and the Princess Maxima Center Utrecht (PMC). Consecutive patients, aged 0-18 years, either diagnosed with B cell non-Hodgkin lymphoma (B-NHL) or scheduled for autologous stem cell transplantation (SCT) between April 2015 and September 2016 were included in this study. In addition to the observational study in the Netherlands, an international online questionnaire was conducted for pediatric oncology centers.

RESULTS

A total of 13 patients were included, after 21 chemotherapy courses. No nutritional support was administered after 23.8% courses, tube feeding after 19.0% of the courses, TPN in 19.0% of courses, and 38.1% received a combination of tube feeding and TPN. The international survey revealed that 63.2% of the centers administered tube feeding as first choice, 31.6% administered only TPN as first choice, and one center administered a combination as first choice.

CONCLUSIONS

There is a variability in feeding strategies in the clinical practice both in the Netherlands as well as worldwide. This study is a basis for future studies in this important clinical field to develop clinical trials comparing tube feeding and TPN both in adult and pediatric patients.

Citrulline and Monocyte-Derived Macrophage Reactivity before Conditioning Predict Acute Graft-versus-Host Disease

During conditioning, intestinal damage induces microbial translocation which primes macrophage reactivity and leads to donor-derived T cell stimulation. Little is known about the role of intestinal health and macrophage reactivity before conditioning in the development of acute graft-versus-host disease (aGVHD) in patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT). We assessed (1) citrulline, a surrogate marker of functional enterocyte mass and (2) circulating monocyte-derived macrophage reactivity, before allo-HCT. Forty-seven consecutive patients were prospectively included. Citrulline levels from blood samples withdrawn 30 days before transplantation were assessed using liquid chromatography combined with mass spectrometry. Monocyte-derived macrophages were isolated and incubated with 5 pathogen-associated molecular patterns: lipopolysaccharide, PamCSK4, flagellin, muramyl dipeptide, and curdlan. Multiplex fluorescent immunoassay on culture supernatant assessed levels of TNF-α, IL-1β, IL-6, and IL-10 in each condition. Citrulline and cytokine levels were analyzed relatively to aGVHD onset within 100 days after transplantation. Citrulline levels were lower in the aGVHD group (n = 20) than in the no-aGVHD group (n = 27) (P = .005). Conversely, IL-6 and IL-10 were greater in aGVHD group, especially after curdlan stimulation (P = .005 and P = .012). Citrulline levels ≤20 µmol/L, IL-6 ≥ 332 pg/mL, and IL-10 ≥ 90 pg/mL were associated with aGVHD development (log-rank test, P = .002, P = .041, and P < .0001, respectively). In multivariate analysis, IL-10 ≥ 90 pg/mL, myeloablative conditioning, and citrulline ≤20 µmol/L remained independent factors of aGVHD development (hazard ratio [HR],  8.18, P = .0003; HR, 4.28, P = .006; and HR, 4.43, P = .01, respectively). Preconditioning citrulline and monocyte-derived macrophage reactivity are objective surrogate markers suitable to identify patients at risk of developing aGVHD. This work highlights the influence of preconditioning status in aGVHD development.

Accuracy of using serum D-dimer for diagnosis of acute intestinal ischemia: A meta-analysis

OBJECTIVE

The purpose of this meta-analysis is to comprehensively assess the accuracy of serum D-dimer for the diagnosis of acute intestinal ischemia.

METHODS

Diagnostic studies of D-dimer for accurate diagnosis of acute intestinal ischemia were extracted from 6 databases, and prospective and retrospective studies that provided adequate data on sensitivity and specificity were included here. Sensitivity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated. The overall diagnostic performance of D-dimer was assessed by plotting a summary receiver operating characteristic curve (SROC) and calculating the area under the curve (AUC).

RESULTS

A total of 1300 patients with suspected acute intestinal ischemia from 12 studies met the inclusion criteria. The combined sensitivity, specificity, PLR, NLR, and DOR were 0.94 (95% CI: 0.87-0.97), 0.50 (95% CI: 0.40-0.61), 1.9 (95% CI: 1.5-2.3), 0.12 (95% CI: 0.05-0.26), and 16 (95% CI: 7-39), respectively. The AUC was 0.81 (95% CI: 0.78-0.84).

CONCLUSION

The results of this meta-analysis suggested that plasma D-dimer detection might be a useful means of identifying patients with acute intestinal ischemia of the abdomen.

Effect of Oral Insulin on the Severity and Recovery of Methotrexate-Induced Gastrointestinal Mucositis in the Rat

OBJECTIVES

Gastrointestinal (GI) mucositis is an adverse-effect of chemo- and radiotherapy. Oral insulin has been suggested as possible intestinal growth factor and possible intervention for GI mucositis. We aimed to determine the effect of oral insulin on the severity and recovery of mucositis in a methotrexate (MTX)-induced GI mucositis rat model.

METHODS

Male Wistar rats (n = 24) received a single injection of 60 mg/kg MTX intravenously at day 0. From day -3 oral insulin was added to the drinking water. Group MTX received normal drinking water, group MTX+INS0.5 received 0.5 U/mL insulin, and group MTX+INS1 received 1 U/mL insulin in drinking water. The severity of mucositis was determined by intake, bodyweight, illness, and plasma citrulline. In the recovery phase, the function of the gut was tested with an oral glucose tolerance test, and villus and crypt length of the small intestine were measured.

RESULTS

MTX-induced mucositis in all 3 groups and oral insulin did not cause a change in the severity of mucositis, with comparable bodyweight, food intake, and water intake. Oral insulin did not alter the enterocyte mass, determined with plasma citrulline. The glucose level after bolus was higher in the MTX group than the MTX+INS1 group (P < 0.05). Histology was not significant different between all groups.

CONCLUSIONS

Oral insulin does not alter the severity or the acceleration of recovery of mucositis. Therefore, we conclude that it is not useful to further study oral insulin as possible intervention to prevent or treat chemotherapy-induced GI mucositis.

Gastrointestinal failure in the ICU

PURPOSE OF REVIEW

The current review summarizes different aspects of assessment of gastrointestinal function and provides a practical approach to management of adult patients with gastrointestinal dysfunction in the ICU.

RECENT FINDINGS

Different ways to define gastrointestinal failure have been used in the past. Recently, the term 'acute gastrointestinal injury (AGI)' has been proposed to specifically describe gastrointestinal dysfunction as a part of multiple organ dysfunction syndrome. Possible pathophysiological mechanisms and different aspects in assessment of gastrointestinal function in adult ICU patients are presented. Currently, there is no single marker that could reliably describe gastrointestinal dysfunction. Therefore, monitoring and management is still based on complex assessment of different gastrointestinal symptoms and feeding intolerance, even though this approach includes a large amount of subjectivity. The possible role of biomarkers (citrulline, enterohormones, etc.) and additional parameters like intra-abdominal pressure remains to be clarified.

SUMMARY

Defining gastrointestinal failure remains challenging but broad consensus needs to be reached and disseminated soon to allow conduct of interventional studies. A systematic approach to management of gastrointestinal problems is recommended.

Biomarkers of gut barrier failure in the ICU

PURPOSE OF REVIEW

Gut barrier failure is associated with bacterial translocation, systemic inflammation, and is presumed to be associated with the development of multiple organ dysfunction syndrome. As the gut barrier function is carried out by a monolayer of enterocytes, a minimum requirement is the integrity of the enterocytes, and controlled paracellular permeability between adjacent enterocytes. Many factors can cause critically ill patients to lose gut barrier function by a mechanism of enterocyte damage; for example, small bowel ischemia or hypoxia, sepsis, systemic inflammatory response syndrome, or absence of enteral feeding.

RECENT FINDINGS

Two enterocyte biomarkers may help the intensivist to identify enterocyte damage and dysfunction, namely plasma citrulline, a biomarker of functional enterocyte mass, and plasma or urinary intestinal fatty acid-binding protein, a marker of enterocyte damage. This review focuses on results obtained with these biomarkers in the context of critical care, in particular: prevalence of enterocyte biomarker abnormalities; mechanisms associated with enterocyte damage and dysfunction; link with systemic inflammation, bacterial translocation, and clinical intestinal dysfunction; prognostic value of enterocyte biomarkers. Lastly, we also review the limits of these biomarkers.

SUMMARY

Enterocyte biomarkers may help the intensivist to identify patients presenting with intestinal damage, and who are at risk of bacterial translocation and systemic inflammatory response syndrome, as well as those with decreased enterocyte function, at risk of malabsorption. Enterocyte biomarkers should be interpreted with caution in the critically ill and should be interpreted within the overall clinical context of the patient.

Human milk oligosaccharide effects on intestinal function and inflammation after preterm birth in pigs

Human milk oligosaccharides (HMOs) may mediate prebiotic and anti-inflammatory effects in newborns. This is particularly important for preterm infants who are highly susceptible to intestinal dysfunction and necrotizing enterocolitis (NEC). We hypothesized that HMO supplementation of infant formula (IF) improves intestinal function, bacterial colonization and NEC resistance immediately after preterm birth, as tested in a preterm pig model. Mixtures of HMOs were investigated in intestinal epithelial cells and in preterm pigs (n=112) fed IF supplemented without (CON) or with a mixture of four HMOs (4-HMO) or >25 HMOs (25-HMO, 5-10 g/L given for 5 or 11 days). The 25-HMO blend decreased cell proliferation and both HMO blends decreased lipopolysaccharide-induced interleukin-8 secretion in IPEC-J2 cells, relative to control (P<.05). All HMOs were found in urine and feces of HMO-treated pigs, and short-chain fatty acids in the colon were higher in HMO vs. CON pigs (P<.05). After 5 days, NEC lesions were similar between HMO and CON pigs and 25-HMO increased colon weights (P<.01). After 11 days, the 4-HMO diet did not affect NEC (56 vs. 79%, P=.2) but increased dehydration and diarrhea (P<.05) and expression of immune-related genes (IL10, IL12, TGFβ, TLR4; P<.05). Bacterial adherence and diversity was unchanged after HMO supplementation.

CONCLUSION

Complex HMO-blends affect intestinal epithelial cells in vitro and gut gene expression and fermentation in preterm pigs. However, the HMOs had limited effects on NEC and diarrhea when supplemented to IF. Longer-term exposure to HMOs may be required to improve the immature intestinal function in formula-fed preterm neonates.

Circadian and postprandial variation in plasma citrulline concentration in healthy dogs

OBJECTIVE

To evaluate circadian and postprandial variations in plasma citrulline concentration in healthy dogs.

ANIMALS

8 healthy Beagles.

PROCEDURES

Blood samples were collected from dogs after 12 hours of food withholding (0 hours; 8:00 am) and then every 2 hours for 12 hours (until 8:00 pm) and again at 24 hours (8:00 am the next day). The same protocol was repeated, with the only difference being that a meal was given immediately after the 0-hour sample collection point. Plasma citrulline concentration was measured by ion exchange chromatography.

RESULTS

No significant difference in plasma citrulline concentration was identified among measurement points when food was withheld. Mean ± SD plasma citrulline concentration at 4 hours (72.2 ± 12.7 μmol/L) and 24 hours (56.1 ± 12.5 μmol/L) after dogs were fed was significantly different from that at 0 hours (64.4 ± 12.7 μmol/L).

CONCLUSIONS AND CLINICAL RELEVANCE

Plasma citrulline concentration had no circadian variation in unfed dogs but increased significantly in fed dogs 4 hours after a meal. Therefore, food should be withheld from dogs for 8 to 12 hours before blood sample collection for measurement of citrulline concentration.

Citrulline as a biomarker of gastrointestinal toxicity in patients with rectal carcinoma treated with chemoradiation

BACKGROUND

Gastrointestinal toxicity is the principal toxicity of chemoradiation in the treatment of rectal carcinoma. The assessment of this toxicity still relies mostly on the symptoms reported by the patient.

METHODS

Plasma citrulline, serum neopterin and urinary neopterin were followed weekly in 49 patients with rectal carcinoma during chemoradiation.

RESULTS

Citrulline significantly (p<0.05) decreased while serum and urinary neopterin concentrations increased during therapy. Irradiated gut volume correlated significantly inversely with citrulline and positively with urinary neopterin. Statistically significant inverse correlations were also observed between urinary neopterin and plasma citrulline concentrations during the treatment. Urinary neopterin concentrations were significantly higher and citrulline concentrations were lower in patients who experienced grade ≥3 gastrointestinal toxicity.

CONCLUSIONS

Citrulline represents a promising biomarker of gastrointestinal toxicity. Moreover, the volume of irradiated gut correlated with urinary neopterin concentrations and an association was observed between gastrointestinal toxicity evidenced by lower citrulline concentrations and systemic immune activation reflected in increased concentrations of urinary neopterin.

Apo AIV and Citrulline Plasma Concentrations in Short Bowel Syndrome Patients: The Influence of Short Bowel Anatomy

INTRODUCTION

Parenteral nutrition (PN) dependence in short bowel syndrome (SBS) patients is linked to the functionality of the remnant small bowel (RSB). Patients may wean off PN following a period of intestinal adaptation that restores this functionality. Currently, plasma citrulline is the standard biomarker for monitoring intestinal functionality and adaptation. However, available studies reveal that the relationship the biomarker with the length and function of the RSB is arguable. Thus, having additional biomarkers would improve pointing out PN weaning.

AIM

By measuring concomitant changes in citrulline and the novel biomarker apolipoprotein AIV (Apo AIV), as well as taking into account the anatomy of the RSB, this exploratory study aims to a better understanding of the intestinal adaptation process and characterization of the SBS patients under PN.

METHODS

Thirty four adult SBS patients were selected and assigned to adapted (aSBS) and non-adapted (nSBS) groups after reconstructive surgeries. Remaining jejunum and ileum lengths were recorded. The aSBS patients were either on an oral diet (ORAL group), those with intestinal insufficiency, or on oral and home parenteral nutrition (HPN group), those with chronic intestinal failure. Apo AIV and citrulline were analyzed in plasma samples after overnight fasting. An exploratory ROC analysis using citrulline as gold standard was performed.

RESULTS

Biomarkers, Apo AIV and citrulline showed a significant correlation with RSBL in aSBS patients. In jejuno-ileocolic patients, only Apo AIV correlated with RSBL (rb = 0.54) and with ileum length (rb = 0.84). In patients without ileum neither biomarker showed any correlation with RSBL. ROC analysis indicated the Apo AIV cut-off value to be 4.6 mg /100 mL for differentiating between the aSBS HPN and ORAL groups.

CONCLUSIONS

Therefore, in addition to citrulline, Apo AIV can be set as a biomarker to monitor intestinal adaptation in SBS patients. As short bowel anatomy is shown to influence citrulline and Apo AIV plasma values, both biomarkers complement each other furnishing a new insight to manage PN dependence.

Biomarkers of Environmental Enteropathy, Inflammation, Stunting, and Impaired Growth in Children in Northeast Brazil

Critical to the design and assessment of interventions for enteropathy and its developmental consequences in children living in impoverished conditions are non-invasive biomarkers that can detect intestinal damage and predict its effects on growth and development. We therefore assessed fecal, urinary and systemic biomarkers of enteropathy and growth predictors in 375 6–26 month-old children with varying degrees of malnutrition (stunting or wasting) in Northeast Brazil. 301 of these children returned for followup anthropometry after 2-6m. Biomarkers that correlated with stunting included plasma IgA anti-LPS and anti-FliC, zonulin (if >12m old), and intestinal FABP (I-FABP, suggesting prior barrier disruption); and with citrulline, tryptophan and with lower serum amyloid A (SAA) (suggesting impaired defenses). In contrast, subsequent growth was predicted in those with higher fecal MPO or A1AT and also by higher L/M, plasma LPS, I-FABP and SAA (showing intestinal barrier disruption and inflammation). Better growth was predicted in girls with higher plasma citrulline and in boys with higher plasma tryptophan. Interactions were also seen with fecal MPO and neopterin in predicting subsequent growth impairment.

Biomarkers clustered into markers of 1) functional intestinal barrier disruption and translocation, 2) structural intestinal barrier disruption and inflammation and 3) systemic inflammation. Principle components pathway analyses also showed that L/M with %L, I-FABP and MPO associate with impaired growth, while also (like MPO) associating with a systemic inflammation cluster of kynurenine, LBP, sCD14, SAA and K/T. Systemic evidence of LPS translocation associated with stunting, while markers of barrier disruption or repair (A1AT and Reg1 with low zonulin) associated with fecal MPO and neopterin.

We conclude that key noninvasive biomarkers of intestinal barrier disruption, LPS translocation and of intestinal and systemic inflammation can help elucidate how we recognize, understand, and assess effective interventions for enteropathy and its growth and developmental consequences in children in impoverished settings.

Accuracy of the serum intestinal fatty-acid-binding protein for diagnosis of acute intestinal ischemia: a meta-analysis

Numerous studies have investigated the utility of serum intestinal fatty-acid binding protein (I-FABP) in differentiating acute intestinal ischemia from acute abdomen. However, the results remain controversial. The aim of this meta-analysis is to determine the overall accuracy of serum I-FABP in the diagnosis of acute intestinal ischemia. Publications addressing the accuracy of serum I-FABP in the diagnosis of ischemic bowel diseases were selected from databases. The values of true-positive (TP), true-negative (TN), false-positive (FP), and false-negative (FN) were extracted or calculated for each study. Pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated. The overall diagnostic performance was assessed using a summary receiver operating characteristic curve (SROC) and area under curve (AUC). Nine studies that collectively included 1246 patients met the eligible criteria. The pooled sensitivity, specificity, DOR, PLR, and NLR were 0.80 (95% CI: 0.72–0.86), 0.85 (95% CI: 0.73–0.93), 24 (95% CI: 9–65), 5.5 (95% CI: 2.8–10.8) and 0.23 (95% CI: 0.15–0.35), respectively. The AUC was 0.86 (95% CI: 0.83–0.89). The meta-analysis carried out in this report suggests that the I-FABP may be a useful diagnostic tool to confirm acute intestinal ischemia in acute abdomen, but better-designed trials are still required to confirm our findings.

[Current Status of Translational Research on Irritable Bowel Syndrome]

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. The pathophysiology of IBS is not completely understood. Genetic, immune, environmental, inflammatory, neurological and psychological factors contribute to the risk of this condition. Traditional research explored gastrointestinal motor abnormalities, central neural dysregulation, abnormal psychological features, and visceral hypersensitivity. More recent investigations consider bacterial overgrowth, abnormal serotonin pathways, altered gut flora, immune activation and mucosal inflammation. The purpose of this article is to review recent translational research concerning the pathophysiology, biomarker and genetic factors of IBS and to encourage IBS research in Korea.

Identification and Evaluation of Novel MicroRNA Biomarkers in Plasma and Feces Associated with Drug-induced Intestinal Toxicity

Gastrointestinal toxicity is dose limiting with many therapeutic and anticancer agents. Real-time, noninvasive detection of markers of toxicity in biofluids is advantageous. Ongoing research has revealed microRNAs as potential diagnostic and predictive biomarkers for the detection of select organ toxicities. To study the potential utility of microRNA biomarkers of intestinal injury in a preclinical toxicology species, we evaluated 3 rodent models of drug-induced intestinal toxicity, each with a distinct mechanism of toxicity. MiR-215 and miR-194 were identified as putative intestinal toxicity biomarkers. Both were evaluated in plasma and feces and compared to plasma citrulline, an established intestinal injury biomarker. Following intestinal toxicant dosing, microRNA changes in feces and plasma were detected noninvasively and correlated with histologic evidence of intestinal injury. Fecal miR-215 and miR-194 levels increased, and plasma miR-215 decreased in a dose- and time-dependent manner. Dose-dependent decreases in plasma miR-215 levels also preceded and correlated positively with plasma citrulline modulation, suggesting miR-215 is a more sensitive biomarker. Moreover, during the drug-free recovery phase, plasma miR-215 returned to predose levels, supporting a corresponding recovery of histologic lesions. Despite limitations, this study provides preliminary evidence that select microRNAs have the potential to act as noninvasive, sensitive, and quantitative biomarkers of intestinal injury.

Management and Complications of Short Bowel Syndrome: an Updated Review

Short bowel syndrome (SBS) is defined as loss of bowel mass from surgical resection, congenital defects, or disease. Intestinal failure (IF) includes the subset of SBS unable to meet nutrition needs with enteral supplements and requires parenteral nutrition (PN). The parenteral treatment of SBS is now a half-century old. Recent pharmacologic treatment (GLP-2 analogues) has begun to make a significant impact in the care and ultimate management of these patients such that the possibility of reducing PN requirements in formerly PN-dependent patients is a now a real possibility. Finally, newer understanding and possible treatment for some of the complications related to IF have more recently evolved and will be an emphasis of this report. This review will focus on developments over the last 10 years with the goal of updating the reader to new advances in our understanding of the care and feeding of the SBS patient.

Diffuse traumatic brain injury affects chronic corticosterone function in the rat

As many as 20-55% of patients with a history of traumatic brain injury (TBI) experience chronic endocrine dysfunction, leading to impaired quality of life, impaired rehabilitation efforts and lowered life expectancy. Endocrine dysfunction after TBI is thought to result from acceleration-deceleration forces to the brain within the skull, creating enduring hypothalamic and pituitary neuropathology, and subsequent hypothalamic-pituitary endocrine (HPE) dysfunction. These experiments were designed to test the hypothesis that a single diffuse TBI results in chronic dysfunction of corticosterone (CORT), a glucocorticoid released in response to stress and testosterone. We used a rodent model of diffuse TBI induced by midline fluid percussion injury (mFPI). At 2months postinjury compared with uninjured control animals, circulating levels of CORT were evaluated at rest, under restraint stress and in response to dexamethasone, a synthetic glucocorticoid commonly used to test HPE axis regulation. Testosterone was evaluated at rest. Further, we assessed changes in injury-induced neuron morphology (Golgi stain), neuropathology (silver stain) and activated astrocytes (GFAP) in the paraventricular nucleus (PVN) of the hypothalamus. Resting plasma CORT levels were decreased at 2months postinjury and there was a blunted CORT increase in response to restraint induced stress. No changes in testosterone were measured. These changes in CORT were observed concomitantly with altered complexity of neuron processes in the PVN over time, devoid of neuropathology or astrocytosis. Results provide evidence that a single moderate diffuse TBI leads to changes in CORT function, which can contribute to the persistence of symptoms related to endocrine dysfunction. Future experiments aim to evaluate additional HP-related hormones and endocrine circuit pathology following diffuse TBI.

Citrulline as a Biomarker for Gastrointestinal-Acute Radiation Syndrome: Species Differences and Experimental Condition Effects

Animal models of hematopoietic and gastrointestinal acute radiation syndromes (ARS) have been characterized to develop medical countermeasures. Acute radiation-induced decrease of intestinal absorptive function has been correlated to a decrease in the number of intestinal crypt cells resulting from apoptosis and enterocyte mass reduction. Citrulline, a noncoded amino acid, is produced almost exclusively by the enterocytes of the small intestine. Citrullinemia has been identified as a simple, sensitive and suitable biomarker for radiation-induced injury associated with gastrointestinal ARS (GI-ARS). Here we discuss the effect of radiation on plasma citrulline levels in three different species, C57BL/6 mice, Göttingen minipigs and rhesus nonhuman primates (NHPs), measured by liquid chromatography tandem mass spectrometry (LC-MS/MS). The effects of experimental study conditions such as feeding and anesthesia were also examined on plasma citrulline levels in the NHPs. Both the mice and Göttingen minipigs were partial-body irradiated (PBI) with doses from 13-17 Gy and 8-16 Gy, respectively, whereas NHPs were total-body irradiated (TBI) with doses from 6.72-13 Gy. Blood samples were taken at different time points and plasma citrulline levels were measured in the three species at baseline and after irradiation. Basal plasma citrulline concentrations (mean ± SEM) in mice and minipigs were 57.8 ± 2.8 μM and 63.1 ± 2.1 μM, respectively. NHPs showed a basal plasma citrulline concentration of 32.6 ± 0.7 μM, very similar to that of humans (∼40 μM). Plasma citrulline progressively decreased after irradiation, reaching nadir values between day 3.5 and 7. The onset of citrulline recovery was observed earlier at lower radiation doses, while only partial citrulline recovery was noted at higher radiation doses in minipigs and NHPs, complete recovery was noted in mice at all doses. Plasma citrulline levels in NHPs anesthetized with ketamine and acepromazine significantly decreased by 35.5% (P = 0.0017), compared to unanesthetized NHPs. In the postprandial state, citrulline concentrations in NHPs were slightly but significantly decreased by 12.2% (P = 0.0287). These results suggest that plasma citrulline is affected by experimental conditions such as anesthesia and feeding.

Metabolic alterations in children with environmental enteric dysfunction

Environmental enteric dysfunction, an asymptomatic condition characterized by inflammation of the small bowel mucosa, villous atrophy, malabsorption, and increased intestinal permeability, is a major contributor to childhood stunting in low-income countries. Here we report the relationship of increased intestinal permeability with serum metabolites in 315 children without acute malnutrition, aged 12-59 months, in rural Malawi. Increased gut permeability was associated with significant differences in circulating metabolites that included lower serum phosphatidylcholines, sphingomyelins, tryptophan, ornithine, and citrulline, and elevated serum glutamate, taurine, and serotonin. Our findings suggest that environmental enteric dysfunction is characterized by alterations in important metabolites involved in growth and differentiation and gut function and integrity.

A novel biomarker panel for irritable bowel syndrome and the application in the general population

Biological markers that measure gut health and diagnose functional gastro-intestinal (GI) disorders, such as irritable bowel syndrome (IBS), are lacking. The objective was to identify and validate a biomarker panel associated with the pathophysiology of IBS that discriminates IBS from healthy controls (HC), and correlates with GI symptom severity. In a case-control design, various plasma and fecal markers were measured in a cohort of 196 clinical IBS patients and 160 HC without GI symptoms. A combination of biomarkers, which best discriminates between IBS and HC was identified and validated in an independent internal validation set and by permutation testing. The correlation between the biomarker panel and GI symptom severity was tested in IBS patients and in a general population cohort of 958 subjects. A set of 8 biomarker panel was identified to discriminate IBS from HC with high sensitivity (88.1%) and specificity (86.5%). The results for the IBS subtypes were comparable. Moreover, a moderate correlation was found between the biomarker panel and GI symptom scores in the IBS (r = 0.59, p < 0.001) and the general population cohorts (r = 0.51, p = 0.003). A novel multi-domain biomarker panel has been identified and validated, which correlated moderately to GI symptom severity in IBS and general population subjects.

Quantitative Metabolomic Analysis of Urinary Citrulline and Calcitroic Acid in Mice after Exposure to Various Types of Ionizing Radiation

With the safety of existing nuclear power plants being brought into question after the Fukushima disaster and the increased level of concern over terrorism-sponsored use of improvised nuclear devices, it is more crucial to develop well-defined radiation injury markers in easily accessible biofluids to help emergency-responders with injury assessment during patient triage. Here, we focused on utilizing ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to identify and quantitate the unique changes in the urinary excretion of two metabolite markers, calcitroic acid and citrulline, in mice induced by different forms of irradiation; external γ irradiation at a low dose rate (LDR) of 3.0 mGy/min and a high dose rate (HDR) of 1.1 Gy/min, and internal exposure to Cesium-137 ((137)Cs) and Strontium-90 ((90)Sr). The multiple reaction monitoring analysis showed that, while exposure to (137)Cs and (90)Sr induced a statistically significant and persistent decrease, similar doses of external γ beam at the HDR had the opposite effect, and the LDR had no effect on the urinary levels of these two metabolites. This suggests that the source of exposure and the dose rate strongly modulate the in vivo metabolomic injury responses, which may have utility in clinical biodosimetry assays for the assessment of exposure in an affected population. This study complements our previous investigations into the metabolomic profile of urine from mice internally exposed to (90)Sr and (137)Cs and to external γ beam radiation.