Necrotizing enterocolitis in a mouse model leads to widespread renal inflammation, acute kidney injury, and disruption of renal tight junction proteins

Necrotizing Enterocolitis-Associated Acute Kidney Injury-Transforming the Paradigm

Necrotizing enterocolitis (NEC) is one of the most common conditions requiring emergency surgery in the neonatal intensive care unit and is associated with a septic shock-like state contributing to multiorgan dysfunction. NEC affects 6 to 10% of very low-birth-weight infants and remains a leading cause of death. The occurrence of severe acute kidney injury (AKI) following surgical NEC is a harbinger of multiple morbidities. This review presents current evidence about the clinical impact of NEC-associated AKI on the clinical outcomes. Studies evaluating nephroprotective strategies to prevent AKI and its consequences are greatly needed to improve the postoperative recovery and clinical outcomes in neonates with NEC. Future observational studies and clinical trials in preterm infants with NEC prioritize measuring short-term (AKI) and longer term (chronic kidney disease) kidney outcomes. KEY POINTS: · Severe AKI is common following surgical NEC.. · Severe AKI following NEC is associated with poor clinical outcomes.. · Studies evaluating nephroprotective strategies to prevent AKI and its consequences are needed.. IMPACT: · Severe AKI (stage 2 and 3) occurs in 32.6% of neonates after NEC diagnosis and in 58.7% following surgical NEC diagnosis.. · NEC-associated AKI is associated with severe postoperative course, moderate-to-severe bronchopulmonary dysplasia, surgical complications, brain injury, and longer hospital stay in preterm infants.. · Severity of NEC-associated AKI can be utilized by bedside providers for the prognostication of clinical outcomes in preterm infants..

Timing and risk factors associated with acute kidney injury in infants with necrotizing enterocolitis

OBJECTIVE

To evaluate the prevalence, onset, risk factors, and mortality associated with acute kidney injury (AKI) in infants with necrotizing enterocolitis (NEC).

DESIGN/METHODS

Retrospective study at 2 centers in infants with NEC, with/without AKI. AKI assessed by serum creatinine and urine output. Statistical tests used included t, Mann-Whitney U, Chi-square, and Fisher Exact tests.

RESULTS

Among 80 eligible infants with NEC, 56 (70%) had AKI. Median onset of NEC was day 15, with median AKI onset two days (IQR, -5.75 to 0) prior to NEC onset. Vasopressors were significantly more likely to be used in infants with NEC and AKI (p = 0.009). Increased mortality (p = 0.01) was noted in infants with NEC and AKI.

CONCLUSIONS

The onset of AKI mostly precedes NEC onset, with moderate to severe AKI more prevalent than the milder form in infants with NEC. These infants are significantly more likely to be hemodynamically unstable and have increased mortality.

Gestational age-specific clinical correlates of acute kidney injury in preterm infants with necrotizing enterocolitis

BACKGROUND

To study the gestational age-specific risk factors and outcomes of severe acute kidney injury (AKI) in neonates with necrotizing enterocolitis (NEC).

METHODS

Retrospective cohort study comparing gestational age (GA)-specific clinical data between infants without severe AKI (stage 0/1 AKI) and those with severe AKI (stages 2 and 3 AKI) stratified by GA ≤27 and >27 weeks.

RESULTS

Infants with GA ≤27 weeks had double the rate of severe AKI (46.3% vs. 20%). In infants with GA >27 weeks, male sex, outborn, and nephrotoxic medication exposure were associated with severe AKI. On multivariable logistic regression, in infants with GA ≤27 weeks, surgical NEC (OR 35.08 (CI 5.05, 243.73), p < 0.001) and ostomy (OR 6.2(CI 1.29, 29.73), p = 0.027) were associated with significantly higher odds of severe AKI. Surgical NEC infants with GA >27 weeks and severe AKI were significantly more likely to be outborn, have later NEC onset, need dopamine, and have longer hospitalization (158 days [110; 220] vs.75.5 days [38.8; 105]; p = 0.007 than those with non-severe AKI.

CONCLUSION

In neonates with NEC, surgical intervention was associated with moderate-to-severe AKI in infants with GA ≤27 weeks and with longer hospitalization in infants with GA >27 weeks.

IMPACT

In both cohorts need for surgery, stoma, cholestasis, and mechanical ventilation were associated with severe AKI; however, the infants with GA <27 weeks had twice the risk of severe AKI than GA >27 weeks group. The longer exposure to nephrotoxic medication and referral need were significant risk factors for AKI in GA >27 weeks group. GA-specific kidney protective and monitoring strategies to prevent AKI and its consequences are needed to improve the clinical outcomes in neonates with NEC. Understanding the risk factors and short- and long-term outcomes unique to different GA groups will help inform those strategies.

Caveolin-1: A Review of Intracellular Functions, Tissue-Specific Roles, and Epithelial Tight Junction Regulation

Caveolin-1 (Cav1) is a vital protein for many cellular processes and is involved in both the positive and negative regulation of these processes. Cav1 exists in multiple cellular compartments depending on its role. Of particular interest is its contribution to the formation of plasma membrane invaginations called caveolae and its involvement in cytoskeletal interactions, endocytosis, and cholesterol trafficking. Cav1 participates in stem cell differentiation as well as proliferation and cell death pathways, which is implicated in tumor growth and metastasis. Additionally, Cav1 has tissue-specific functions that are adapted to the requirements of the cells within those tissues. Its role has been described in adipose, lung, pancreatic, and vascular tissue and in epithelial barrier maintenance. In both the intestinal and the blood brain barriers, Cav1 has significant interactions with junctional complexes that manage barrier integrity. Tight junctions have a close relationship with Cav1 and this relationship affects both their level of expression and their location within the cell. The ubiquitous nature of Cav1 both within the cell and within specific tissues is what makes the protein important for ongoing research as it can assist in further understanding pathophysiologic processes and can potentially be a target for therapies.

Butyrate induces development-dependent necrotizing enterocolitis-like intestinal epithelial injury via necroptosis

BACKGROUND

The accumulation of short-chain fatty acids (SCFAs) from bacterial fermentation may adversely affect the under-developed gut as observed in premature newborns at risk for necrotizing enterocolitis (NEC). This study explores the mechanism by which specific SCFA fermentation products may injure the premature newborn intestine mucosa leading to NEC-like intestinal cell injury.

METHODS

Intraluminal injections of sodium butyrate were administered to 14- and 28-day-old mice, whose small intestine and stool were harvested for analysis. Human intestinal epithelial stem cells (hIESCs) and differentiated enterocytes from preterm and term infants were treated with sodium butyrate at varying concentrations. Necrosulfonamide (NSA) and necrostatin-1 (Nec-1) were used to determine the protective effects of necroptosis inhibitors on butyrate-induced cell injury.

RESULTS

The more severe intestinal epithelial injury was observed in younger mice upon exposure to butyrate (p = 0.02). Enterocytes from preterm newborns demonstrated a significant increase in sensitivity to butyrate-induced cell injury compared to term newborn enterocytes (p = 0.068, hIESCs; p = 0.038, differentiated cells). NSA and Nec-1 significantly inhibited the cell death induced by butyrate.

CONCLUSIONS

Butyrate induces developmental stage-dependent intestinal injury that resembles NEC. A primary mechanism of cell injury in NEC is necroptosis. Necroptosis inhibition may represent a potential preventive or therapeutic strategy for NEC.

IMPACT

Butyrate induces developmental stage-dependent intestinal injury that resembles NEC. A primary mechanism of cell injury caused by butyrate in NEC is necroptosis. Necroptosis inhibitors proved effective at significantly ameliorating the enteral toxicity of butyrate and thereby suggest a novel mechanism and approach to the prevention and treatment of NEC in premature newborns.

Tight junctions and acute kidney injury

Acute kidney injury (AKI) is characterized by a rapid reduction in kidney function caused by various etiologies. Tubular epithelial cell dysregulation plays a pivotal role in the pathogenesis of AKI. Tight junction (TJ) is the major molecular structure that connects adjacent epithelial cells and is critical in maintaining barrier function and determining the permeability of epithelia. TJ proteins are dysregulated in various types of AKI, and some reno-protective drugs can reverse TJ changes caused by insult. An in-depth understanding of TJ regulation and its causality with AKI will provide more insight to the disease pathogenesis and will shed light on the potential role of TJs to serve as novel therapeutic targets in AKI.

Neonatal AKI: An update

Neonatal acute kidney injury (AKI) is a common complication, especially in the neonatal intensive care unit, that is associated with long term consequences and poor outcomes. Early detection and treatment is critical. Currently, neonatal AKI is defined with urinary markers and serum creatinine, with limitations on early detection and individual treatment. There have been numerous biomarkers and risk factor scores that have been studied for their ability to predict neonatal AKI. To move towards personalized medicine, neonatal AKI must be categorized into phenotypes and subphenotypes that fully encapsulate the diverse causes and specific treatments. This review aims to advance our understanding of neonatal AKI detection through the use of biomarkers, subphenotypes, and phenotypes to move towards personalized treatment strategies.

Clinical impact of severe acute kidney injury on post-operative and brain injury outcomes in preterm infants following surgical necrotizing enterocolitis

BACKGROUND

To evaluate post-operative outcomes and white matter injury (WMI) using brain MRI at term equivalent in neonates with and without severe acute kidney injury (AKI) following surgical necrotizing enterocolitis (NEC).

METHODS

A retrospective cohort study comparing neonates with severe (Stage 2/3) vs. other (no AKI/Stage 1) AKI using KDIGO classification with multivariable models assessing this association in the context of multiple systemic comorbidities.

RESULTS

Of 103 neonates with surgical NEC, 60 (58%) had severe AKI. Those with severe AKI had lower birth weight (BW; 715 vs. 950 g; p = .023), more frequently treated with indomethacin (18.3 vs. 2.4%); p = .014), higher CRP levels at 24 h after NEC onset (14.4 [6.4-19.8] vs. 4.8 [1.6-13.4]; p = .005), higher presence of cholestasis (73.3 vs. 51.2%); p = .023), later age of NEC onset (14 vs. 7 d); p = .004), longer length of bowel resected (14.9 vs. 4.3 cm); p = .011), longer post-operative ileus days (14 vs. 9 d); p < .001), longer post-operative days at starting enteral feedings (15 vs. 10 d; p < .001), longer days of attainment of full enteral feedings (75 vs. 44.5 d; p = .008) and longer length of stay (140.5 vs. 94 d; p = .028) compared to those without severe AKI. Compared to infants without AKI by serum creatinine, those with AKI had significantly more cases of white matter abnormality (WMA; 90 vs. 36.6%; p < .001) and retinopathy of prematurity (63.9 vs. 35.3%; p = .017). In addition, the presence of AKI Stage 2 and 3 by serum creatinine was independently associated with higher odds of sustaining severe WMI level on an ordinal scale (OR = 6.2; 95% CI = (1.1-35.5); p = .041).

CONCLUSIONS

Neonates with severe AKI following surgical NEC were more likely to experience longer post-operative morbidity and higher WMI by MRI at term.

A hydrogen-sulfide derivative of mesalamine reduces the severity of intestinal and lung injury in necrotizing enterocolitis through endothelial nitric oxide synthase

Necrotizing enterocolitis (NEC) remains a devastating disease that affects preterm infants. Hydrogen sulfide (H2S) donors have been shown to reduce the severity of NEC, but the optimal compound has yet to be identified. We hypothesized that oral H2S-Mesalamine (ATB-429) would improve outcomes in experimental NEC, and its benefits would be dependent on endothelial nitric oxide synthase (eNOS) pathways. NEC was induced in 5-day-old wild-type (WT) and eNOS knockout (eNOSKO) pups by formula feeding and stress. Four groups were studied in both WT and eNOSKO mice: 1) breastfed controls, 2) NEC, 3) NEC + 50 mg/kg mesalamine, and 4) NEC + 130 mg/kg ATB-429. Mesalamine and ATB-429 doses were equimolar. Pups were monitored for sickness scores and perfusion to the gut was measured by Laser Doppler Imaging (LDI). After euthanasia of the pups, intestine and lung were hematoxylin and eosin-stained and scored for injury in a blind fashion. TLR4 expression was quantified by Western blot and IL-6 expression by ELISA. P < 0.05 was significant. Both WT and eNOSKO breastfed controls underwent normal development and demonstrated milder intestinal and pulmonary injury compared with NEC groups. For the WT groups, ATB-429 significantly improved weight gain, reduced clinical sickness score, and improved perfusion compared with the NEC group. In addition, WT ATB-429 pups had a significantly milder intestinal and pulmonary histologic injury when compared with NEC. ATB-429 attenuated the increase in TLR4 and IL-6 expression in the intestine. When the experiment was repeated in eNOSKO pups, ATB-429 offered no benefit in weight gain, sickness scores, perfusion, intestinal injury, pulmonary injury, or decreasing intestinal inflammatory markers. An H2S derivative of mesalamine improves outcomes in experimental NEC. Protective effects appear to be mediated through eNOS. Further research is warranted to explore whether ATB-429 may be an effective oral therapy to combat NEC.

Incidence, Risk Factors, and Outcomes of Acute Kidney Injury in Necrotizing Enterocolitis: A Prospective Single-Center Study

Necrotizing enterocolitis (NEC) is a significant cause of morbidity and mortality in the neonatal intensive care unit (NICU). Acute kidney injury (AKI) is considered to be one of the most well-established risk factors for mortality in neonates. The aim of this work was to study the incidence of AKI in neonates with NEC and to determine the associated conditions, risk factors, and outcomes. We carried out this prospective cross-sectional study on 104 neonates treated for NEC from September 2015 to September 2019. Diagnoses of AKI were made using the neonatal modified Kidney Disease: Improved Global Outcome criteria. AKI occurred in 63 neonates (61%), with 32 at Stage 1 (31%), 20 at Stage 2 (19%), and 11 at Stage 3 (11%), including three requiring dialysis. Vancomycin use and positive blood culture were risk factors for developing AKI in our NEC neonates (odds ratio: 2.47 and 2.41; P = 0.03 and 0.04, respectively). Neonates with AKI had a higher mortality rate (47.6% vs. 26.8 %, P = 0.03) and an increased length of stay (LOS) (69.8 days vs. 53.9 days, P <0.01) than the non-AKI group. Surgical intervention was required in 11 (10.5%) of our neonates. We concluded that AKI occurs in about 60% of neonates with NEC and is associated with higher mortality and LOS in the NICU. Therefore, it is very important to identify and manage all neonates who are at a high risk of developing AKI as quickly as possible.

Neonatal Acute Kidney Injury

Acute kidney injury (AKI) is a common occurrence in the neonatal intensive care unit (NICU). In recent years, our knowledge of the incidence and impact of neonatal AKI on outcomes has expanded exponentially. Neonatal AKI has been shown to be associated with adverse outcomes including increased length of mechanical ventilation, prolonged length of stay, and rise in mortality. There has also been increasing work suggesting that neonates with AKI are at higher risk of chronic kidney disease (CKD). In the past, AKI had been defined multiple ways. The utilization of the neonatal modified Kidney Disease: Improving Global Outcomes (KDIGO) criteria as the standard definition for neonatal AKI in research and clinical care has driven the advances in our understanding of neonatal AKI over the last 10 years. This definition has allowed researchers and clinicians to better understand the incidence, risk factors, and outcomes associated with neonatal AKI across populations through a multitude of single-center studies and the seminal, multicenter Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates (AWAKEN) study. As the impacts of neonatal AKI have become clear, a shift in efforts toward identifying those at highest risk, protocolizing AKI surveillance, improving prevention and diagnosis, and expanding kidney support therapy (KST) for neonates has occurred. These efforts also include improving risk stratification (identifying high risk populations, including those with nephrotoxic medication exposure) and diagnostics (novel biomarkers and diagnostic tools). Recent work has also shown that the targeted use of methylxanthines may prevent AKI in a variety of high-risk populations. One of the most exciting developments in neonatal AKI is the advancement in technology to provide KST to neonates with severe AKI. In this comprehensive review we will provide an overview of recent work and advances in the field of neonatal AKI. This will include a detailed review of (1) the definition of neonatal AKI, (2) the epidemiology, risk factors, and outcomes associated with neonatal AKI, (3) improvements in risk stratification and diagnostics, (4) mitigation and treatment, (5) advancements in the provision of KST to neonates, and (6) the incidence and risk of subsequent CKD.

Brain injury in preterm infants with surgical necrotizing enterocolitis: clinical and bowel pathological correlates

BACKGROUND

The objective of this study was to determine the risk factors and outcomes of white matter brain injury (WMBI) on magnetic resonance imaging (MRI) at term-equivalent age in infants with surgical necrotizing enterocolitis (NEC).

METHODS

This retrospective study compared clinical/pathological information between infants with and those without WMBI.

RESULTS

Out of 69 infants with surgical NEC, 17 (24.6%) had mild WMBI, 13 (18.8%) had moderate WMBI, and six (8.7%) had severe WMBI on the brain MRI. Several clinical factors (gestational age, more red blood cell (RBC) transfusions before NEC onset, pneumoperitoneum, earlier NEC onset age, postoperative ileus, acute kidney injury (AKI) by serum creatinine, postnatal steroids, hospital stay) and histopathological findings (necrosis, hemorrhage) had univariate associations with WMBI. Associations with RBC transfusion (odds ratio (OR) 23.6 [95% confidence interval (CI): 4.73-117.97]; p = 0.0001), age at NEC onset (OR 0.30 [95%CI: 0.11-0.84]; p = 0.021), necrosis (OR 0.10 [95%CI: 0.01-0.90]; p = 0.040), and bowel hemorrhage (OR 7.79 [95%CI: 2.19-27.72]; p = 0.002) persisted in multivariable association with grade 3-4 WMBI. The infants with WMBI had lower mean motor, cognitive, language scores, and higher ophthalmic morbidity at 2 years of age.

CONCLUSIONS

The WMBI was most likely associated with earlier NEC onset, higher RBC transfusions, and less necrosis and greater hemorrhage lesions on intestinal pathology in preterm infants with surgical NEC.

IMPACT

In preterm infants with surgical NEC, brain MRI showed injury in the white matter in 52%, gray matter in 10%, and cerebellar region in 30%. Preterm infants with severe WMBI (grade 3-4) had less necrosis and greater hemorrhagic lesions on histopathology of the bowel. Preterm infants with WMBI were more likely to have a more severe postoperative course, AKI, and longer length of hospitalization. Neuroprotective strategies to prevent brain injury in preterm infants with surgical NEC are needed with the goal of improving the neurodevelopmental outcomes.

Physiologically Based Pharmacokinetic Modeling of Meropenem in Preterm and Term Infants

BACKGROUND

Meropenem is a broad-spectrum carbapenem antibiotic approved by the US Food and Drug Administration for use in pediatric patients, including treating complicated intra-abdominal infections in infants < 3 months of age. The impact of maturation in glomerular filtration rate and tubular secretion by renal transporters on meropenem pharmacokinetics, and the effect on meropenem dosing, remains unknown. We applied physiologically based pharmacokinetic (PBPK) modeling to characterize the disposition of meropenem in preterm and term infants.

METHODS

An adult meropenem PBPK model was developed in PK-Sim® (Version 8) and scaled to infants accounting for renal transporter ontogeny and glomerular filtration rate maturation. The PBPK model was evaluated using 645 plasma concentrations from 181 infants (gestational age 23-40 weeks; postnatal age 1-95 days). The PBPK model-based simulations were performed to evaluate meropenem dosing in the product label for infants < 3 months of age treated for complicated intra-abdominal infections.

RESULTS

Our model predicted plasma concentrations in infants in agreement with the observed data (average fold error of 0.90). The PBPK model-predicted clearance in a virtual infant population was successfully able to capture the post hoc estimated clearance of meropenem in this population, estimated by a previously published model. For 90% of virtual infants, a 4-mg/L target plasma concentration was achieved for > 50% of the dosing interval following product label-recommended dosing.

CONCLUSIONS

Our PBPK model supports the meropenem dosing regimens recommended in the product label for infants <3 months of age.

Severe acute kidney injury in neonates with necrotizing enterocolitis: risk factors and outcomes

BACKGROUND

To study the risk factors and outcomes of severe acute kidney injury (AKI) in neonates with necrotizing enterocolitis.

METHODS

Retrospective chart review of 202 neonates with necrotizing enterocolitis (NEC) (Bell stage >IIa) from 2013 to 2018. AKI was defined as per-modified neonatal Kidney Disease: Improving Global Outcomes criteria. Demographic, clinical, and outcome data were compared between neonates without severe AKI (stage 0 and 1 AKI) and those with severe AKI (stage 2 and 3 AKI).

RESULTS

Severe AKI occurred in 66/202 (32.6%) of neonates after NEC diagnosis and after 61/104 (58.7%) of surgical NEC diagnoses. On adjusted model, surgical NEC [adjusted odds ratio (aOR) = 30.6; 95% confidence interval (CI) = 8.9, 130.6], outborn [aOR = 3.9; 95% CI = 1.54, 11.0], exposure to antenatal steroids [aOR = 3.0; 95% CI = 1.1, 8.9], and positive blood culture sepsis [aOR = 3.5; 95% CI = 1.3, 10.0] had increased odds for severe AKI. Those with severe AKI required longer hospitalization [124 days (interquartile range (IQR) 88-187) vs. 82 days (IQR 42-126), p < 0.001].

CONCLUSIONS

Severe AKI is common in neonates with NEC who require surgical intervention, are outborn, have positive blood culture sepsis, and receive antenatal steroids. Severe AKI is associated with a significantly longer length of hospitalization.

IMPACT

Neonates with NEC, who are transferred from outside hospitals, require surgical NEC management, and/or have a positive blood culture at NEC onset are at the highest odds for severe (stages 2 and 3) AKI. Assessment of urine output is important for patients with NEC. Without it, 11% of those with severe AKI would have been misdiagnosed using serum creatinine alone. Kidney-protective strategies in the pre-, peri-, and postoperative period may improve the morbidity and mortality associated with severe AKI in neonates with NEC.

Neonatal Acute Kidney Injury: Understanding of the Impact on the Smallest Patients

The study of neonatal acute kidney injury (AKI) has transitioned from small, single-center studies to the development of a large, multicenter cohort. The scope of research has expanded from assessment of incidence and mortality to analysis of more specific risk factors, novel urinary biomarkers, interplay between AKI and other organ systems, impact of fluid overload, and quality improvement efforts. The intensification has occurred through collaboration between the neonatology and nephrology communities. This review discusses 2 case scenarios to illustrate the clinical presentation of neonatal AKI, important risk factors, and approaches to minimize AKI events and adverse long-term outcomes.

Exogenous Autoinducer-2 Rescues Intestinal Dysbiosis and Intestinal Inflammation in a Neonatal Mouse Necrotizing Enterocolitis Model

Autoinducer-2 (AI-2) is believed to be a bacterial interspecies signaling molecule that plays an important role in the regulation of the physiological behaviors of bacteria. The effect of AI-2 on the process of necrotizing enterocolitis (NEC) is unknown, and the aim of this study was to study the effect of AI-2 in a mouse NEC model. C57BL/6 mouse pups were randomly divided into three groups: the control group, the NEC group, and the NEC+AI-2 (NA) group. Exogenous AI-2 (500 nM) was added to the formula milk of the NA group. The concentrations of fecal AI-2 and flora were tested. The expression of cytokines, TLR4 and NF-κB in intestinal tissue was detected. The AI-2 level was significantly decreased in the NEC group (P<0.05). Compared with the NEC group, the intestinal injury scores, expression of TLR4, NF-kB, and proinflammatory factors (IL-1β, IL-6, IL-8 and TNF-α) were reduced, and expression of anti-inflammatory factor (IL-10) was increased in the NA group mice (P<0.05). At the phylum level, the Proteobacteria abundance in the NA group was significantly increased, while the Bacteroidota abundance in the control group was significantly increased (P<0.05). At the genus level, Helicobacter and Clostridium_sensu_stricto_1 exhibited significantly greater abundance in the NEC group than in the other two groups, while Lactobacillus had the opposite trend (P<0.05). In addition, the abundances of Klebsiella, Rodentibacter and Enterococcus were significantly higher in the NA group than in the NEC and control groups (P < 0.05). Exogenous AI-2 partially reverses flora disorder and decreases inflammation in an NEC mouse model.

Review of claudin proteins as potential biomarkers for necrotizing enterocolitis

Background

Claudin proteins are a component of tight junctions found in cell-cell adhesion complexes. A central feature of necrotizing enterocolitis (NEC) is intestinal permeability, with changes to claudin proteins potentially contributing to intestinal instability, inflammation, and the progression of NEC. A current area of interest is the development of a novel, noninvasive biomarker for the detection of NEC in neonates at risk of developing this disease, in order to reduce morbidity and mortality through earlier intervention.

Aims

This review aims to explore the relevance of claudin proteins in the pathophysiology of NEC and their potential usefulness as a biomarker.

Methods

This review was conducted using the search terms “claudin” + “necrotizing enterocolitis”, with 27 papers selected for review.

Results

Claudin proteins appear to have a role in the stability of the gut epithelium through the regulation of intestinal permeability, maturity, and inflammation. Formula feeding has been shown to promote inflammation and result in changes to claudin proteins, while breastfeeding and certain nutritional supplements lead to reduced inflammation and improved intestinal stability as demonstrated through changes to claudin protein expression. Preliminary studies in human neonates suggest that urinary claudin measurements may be used to predict the development of NEC.

Conclusions

Alterations to claudin proteins may reflect changes seen to intestinal permeability and inflammation in the context of NEC. Further research is necessary to understand the relevance of claudin proteins in the pathophysiology of NEC and their use as a biomarker.

Incidence, risk factors, and outcomes of acute kidney injury in neonates after surgical procedures

BACKGROUND

Acute kidney injury (AKI) is common and associated with poor outcomes in critically ill neonates. The objective of this study was to study the incidence, risk factors, and clinical outcomes of AKI in neonates receiving non-cardiac surgery.

METHODS

We performed a single-center retrospective study between January 2017 and December 2018 of neonates who had received abdominal and thoracic surgical procedures. AKI was defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Patient information, clinical data, and outcomes were collected and analyzed. Logistic regression was used to analyze risk factors of AKI and association between AKI and mortality.

RESULTS

Fifty-four (33.8%) of 160 patients developed AKI after surgical procedures. Compared with neonates without AKI, neonates with AKI had higher mortality rate (18.5% VS 5.7%, p = 0.022), lower gestational age (30.5 weeks, interquartile range [IQR] 28-33.5, VS 34.5 weeks, IQR 33-37.5, p = 0.035), higher rates of very low birth weight (33.3% VS 17.0%, p = 0.019), longer duration of mechanical ventilation (0.5 days, IQR 0-1.5, VS 0 days, IQR 0-1, p = 0.043) and higher rates of sepsis (35.2% VS 19.8%, p = 0.034). Risk factors of AKI included gestational age under 32 weeks (OR 4.8, 95% CI 1.8-12.6; p = 0.001), sepsis (OR 4.3, 95% CI 1.7-11.3; p = 0.003), operation time longer than 120 min (OR 2.7, 95% CI 1.1-6.6; p = 0.024), and diagnosis of necrotizing enterocolitis (OR 3.5, 95% CI 1.3-9.1; p = 0.011). AKI after surgery was significantly associated with mortality (OR 4.3, 95% CI 1.1-16.9; p = 0.036).

CONCLUSIONS

AKI is common and associated with poor outcomes in surgical neonates. Early recognition and intervention of AKI in these patients are important.

Autoinducer-2 May Be a New Biomarker for Monitoring Neonatal Necrotizing Enterocolitis

Autoinducer-2 (AI-2) has a widely accepted role in bacterial intra- and interspecies communication. Little is known about the relationships between AI-2 and NEC. This study found that AI-2 levels in patients and in a NEC mouse model were detected using the Vibrio harveyi BB170 assay system. Bacterial communities of the newborns' stool microbiota (NEC acute group, NEC recovery group, control group, and antibiotics-free group) and of the NEC mouse model (NEC group and control group) were detected by high-throughput sequencing. Intestinal histopathological changes were observed after HE staining. The AI-2 level in the NEC acute group (44.75 [40.17~65.52]) was significantly lower than that in the control group, NEC recovery group and antibiotics-free group. The overall microbiota compositions of each group at the phylum level were not significantly different. The proportions of Enterococcus, Clostridium_sensu_stricto_1, Peptoclostridium, and Veillonella had significant differences among the 4 groups at the genus level. In animal experiments, the AI-2 level in feces of NEC mice (56.89 ± 11.87) was significantly lower than that in the feces of control group mice (102.70 ± 22.97). The microbiota compositions of NEC and control group mice at the phylum level were not significantly different. At the genus level, Klebsiella, Clostridium_sensu_stricto_1, and Peptoclostridium abundances in the NEC group increased significantly compared with those in the control group (P < 0.05). In addition, Lactobacillus, Pasteurella, and Parabacteroides abundances in the NEC group decreased significantly compared with those in the normal control group (P < 0.05), while Lactobacillus, Pasteurella, and Parabacteroides abundances had the opposite trend. The AI-2 concentration decreased significantly in the acute phase of NEC and increased gradually in the convalescent phase. We conclude that the concentration of AI-2 was correlated with intestinal flora disorder and different stages of disease. AI-2 may be a new biomarker for the diagnosis and monitoring of NEC. Trial Registry: ClinicalTrials.gov; ChiCTR-ROC-17013746; URL: www.clinicaltrials.gov.

Caveolin 1 is Associated with Upregulated Claudin 2 in Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal emergency of neonates. Epithelial tight junction (TJ) proteins, such as claudins, are essential for regulation and function of the intestinal barrier. Rho kinase (ROCK) affects cellular permeability and TJ regulation. We hypothesized that TJ protein changes would correlate with increased permeability in experimental NEC, and ROCK inhibitors would be protective against NEC by regulation of key claudin proteins. We tested this hypothesis using an in vivo rat pup model, an in vitro model of experimental NEC, and human intestinal samples from patients with and without NEC. Experimental NEC was induced in rats via hypoxia and bacteria-containing formula, and in Caco-2 cells by media inoculated with LPS. The expression of claudins was measured by gene and protein analysis. Experimental NEC in rat pups and Caco-2 cells had increased permeability compared to controls. Gene and protein expression of claudin 2 was increased in experimental NEC. Sub-cellular fractionation localized increased claudin 2 protein to the cytoskeleton. ROCK inhibition was associated with normalization of these alterations and decreased severity of experimental NEC. Co-immunoprecipitation of caveolin-1 with claudin 2 suggests that caveolin-1 may act as a shuttle for the internalization of claudin 2 seen in experimental NEC. In conclusion, NEC is associated with intestinal permeability and increased expression of claudin 2, increased binding of caveolin-1 and claudin 2, and increased trafficking of claudin 2 to the cytoskeleton.

Late onset neonatal acute kidney injury: results from the AWAKEN Study

BACKGROUND

Most studies of neonatal acute kidney injury (AKI) have focused on the first week following birth. Here, we determined the outcomes and risk factors for late AKI (>7d).

METHODS

The international AWAKEN study examined AKI in neonates admitted to an intensive care unit. Late AKI was defined as occurring >7 days after birth according to the KDIGO criteria. Models were constructed to assess the association between late AKI and death or length of stay. Unadjusted and adjusted odds for late AKI were calculated for each perinatal factor.

RESULTS

Late AKI occurred in 202/2152 (9%) of enrolled neonates. After adjustment, infants with late AKI had higher odds of death (aOR:2.1, p = 0.02) and longer length of stay (parameter estimate: 21.9, p < 0.001). Risk factors included intubation, oligo- and polyhydramnios, mild-moderate renal anomalies, admission diagnoses of congenital heart disease, necrotizing enterocolitis, surgical need, exposure to diuretics, vasopressors, and NSAIDs, discharge diagnoses of patent ductus arteriosus, necrotizing enterocolitis, sepsis, and urinary tract infection.

CONCLUSIONS

Late AKI is common, independently associated with poor short-term outcomes and associated with unique risk factors. These should guide the development of protocols to screen for AKI and research to improve prevention strategies to mitigate the consequences of late AKI.

Necrotizing enterocolitis leads to disruption of tight junctions and increase in gut permeability in a mouse model

Background

Necrotizing enterocolitis (NEC) is a leading cause of death in preterm infants. Neonates weighing <1500 grams are at the highest risk for acquiring NEC, with a prevalence of nearly 7-10%, mortality up to 30%, and several long-term complications among survivors. Despite advancements in neonatal medicine, this disease remains a challenge to treat. The aim of this study is to investigate the effect of NEC on gut epithelial tight junctions and its barrier function using a NEC mouse model.

Methods

Three-day old C57BL/6 mouse pups were fed with Esbilac formula every 3 hours and then subjected to hypoxia twice daily followed by cold stress. Dam fed pups from the same litters served as controls. Pups were observed and sacrificed 96 hours after the treatments and intestines were removed for experiments. The successful induction of NEC was confirmed by histopathology. Changes in tight junction proteins in NEC intestines were studied by western blotting and immunofluorescent microscopy using specific protein markers. The gut leakage in NEC was visualized using biotin tracer molecules.

Results

Our study results demonstrate that we induced NEC in >50% of experimental pups, pups lost nearly 40% of weight and their intestines showed gross changes and microscopic changes associated with NEC. There were inflammatory changes with loss of tight junction barrier function and disruption of tight junction claudin proteins in the intestines of NEC mouse model. We have demonstrated for the first time that NEC intestines develop increased leakiness as visualized by biotin tracer leakage.

Conclusions

NEC leads to breakdown of epithelial barrier due to changes in tight junction proteins with increased leakiness which may explain the transmigration of microbes and microbial products from the gut lumen into the blood stream leading to sepsis like signs clinically witnessed.

Acute kidney injury in preterm infants with necrotizing enterocolitis

Purpose: Acute kidney injury (AKI) is an independent predictor of morbidity and mortality in critically ill infants and children. AKI develops in an estimated one-third of the neonatal intensive care unit (NICU) population; however, literature on the incidence of AKI in premature infants with a diagnosis of necrotizing enterocolitis (NEC) is limited. The objectives of this study were to describe the incidence of AKI in infants with radiographically confirmed NEC, assess these infants for independent risk factors associated with development of AKI and evaluate if the presence of AKI is associated with increased mortality. Study design: We conducted a retrospective chart review of premature infants, gestational age (GA) 23-34 weeks, who developed modified Bell's level 2 or 3 NEC while admitted to two tertiary NICUs within our health system between 2010 and 2015. AKI was defined and staged according to modified Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Results: 77 infants with Bell's level II (63.6%) and III (36.4%) NEC were studied. AKI occurred in 42.9% of infants (Stage 1: 18.2%; Stage 2: 13%; Stage 3: 11.7%). Bell's Stage III NEC, lower GA, maternal preeclampsia/eclampsia, gentamicin/vancomycin exposure, and empiric antibiotic use were independently associated with AKI. AKI was strongly associated with mortality (HR 20.3 95%CI 2.5-162.8, p = .005) in an adjusted Cox model. Conclusions: AKI is common in premature infants who develop NEC. More severe NEC was found to be an independent risk factor for AKI. Additionally, AKI in infants with NEC increases mortality risk significantly.

Acute kidney injury in necrotizing enterocolitis predicts mortality

BACKGROUND

Morbidity and mortality with necrotizing enterocolitis (NEC) remains a significant challenge. Acute kidney injury (AKI) has been shown to worsen survival in critically ill neonates. To our knowledge, this study is the first to evaluate the prevalence of AKI and its impact on outcomes in neonatal NEC.

METHODS

We carried out a single-center retrospective chart review of all neonates treated for NEC between 2003 and 2015 (N = 181). AKI is defined as a rise in serum creatinine (SCr) from a previous trough according to neonatal modified KDIGO criteria (stage 1 = SCr rise 0.3 mg/dL or SCr 150 < 200%, stage 2 = SCr rise 200 < 300%, stage 3 = SCr rise ≥300%, SCr 2.5 mg/dL or dialysis). Primary outcome was in-hospital mortality and secondary outcomes were hospital length of stay (LOS) and need for and type of surgery.

RESULTS

Acute kidney injury occurred in 98 neonates (54%), with 39 stage 1 (22%), 31 stage 2 (18%), and 28 stage 3 (16%), including 5 requiring dialysis. Non-AKI and AKI groups were not statistically different in age, weight, Bell's NEC criteria, and medication exposure (vasopressors, vancomycin, gentamicin, or diuretic). Neonates with AKI had higher mortality (44% vs 25.6%, p = 0.008) and a higher chance of death (HR 2.4, CI 1.2-4.8, p = 0.009), but the effect on LOS on survivors did not reach statistical significance (79 days, interquartile range [IQR] 30-104 vs 54 days, IQR 30-92, p = 0.09). Overall, 48 (27.9%) patients required surgical intervention.

CONCLUSIONS

This study shows that AKI not only occurs in over half of patients with NEC, but that it is also associated with more than a two-fold higher mortality, highlighting the importance of early recognition and potentially early intervention for AKI.

Slow enteral feeding decreases risk of transfusion associated necrotizing enterocolitis

BACKGROUND

Necrotizing Enterocolitis (NEC) is a multifactorial condition where PRBC transfusion is associated with necrotizing enterocolitis (TANEC) in about a third of all cases of NEC. We have investigated the role of feeding practices in incidence of TANEC. We sought to compare infants diagnosed with TANEC versus infants diagnosed with classic NEC and investigated the effects of a standardized slow enteral feeding (SSEF) protocol on TANEC incidence as well as the effects of SSEF on growth of infants with NEC.

METHODS

We conducted a retrospective cohort study, where medical records of infants born in a tertiary care neonatal intensive care unit (level IIIb) from January 1997 to May 2014 with birth weight < 1500 grams and gestational age≤34 weeks with NEC stage IIa or greater according to the modified Bell's staging were reviewed.

RESULTS

During the study period, 111 infants developed NEC, and 41/111 (37%) were diagnosed with TANEC. Infants with TANEC were smaller, more premature, had higher SNAPPE scores and were more anemic prior to transfusion compared with infants with 'classic NEC'. The severity of NEC did not differ between the two groups, however, infants with TANEC had worse outcomes and longer NICU stays. Introduction of SSEF protocol, led to a significant decrease in TANEC. There was no difference in weight and head circumference of infants in the two groups at 2 years corrected age.

CONCLUSION

SSEF led to a significant reduction in the incidence of TANEC without impairing growth at 2 years corrected age.

Animal models for studying epithelial barriers in neonatal necrotizing enterocolitis, inflammatory bowel disease and colorectal cancer

The intestinal epithelial cells line the luminal surface of the entire gastrointestinal tract which is crucial for the absorption of nutrients and prevention of pathogens entering from the external environment. The epithelial barrier plays an important role in organ development, disease pathogenesis, and aging. The major component of an epithelial barrier is the single columnar epithelium and tight junctions. Tight junctions are located at the most apical region of the junctional complex and contain many integral membrane proteins, such as occludin, the claudin family, and junctional adhesion molecules (JAMs). The disruption of intestinal epithelial barriers may lead to several pathophysiological conditions causing malabsorption of nutrition and chronic inflammation. In this review, we provide an update on the alterations of epithelial barriers associated with gut diseases using experimental animal models; we appraise the role of tight junctions in neonatal necrotizing enterocolitis (NEC), inflammatory bowel disease (IBD), and colorectal cancer; we also compare some common features as well as differences and similarities in the pathophysiology of intestinal inflammation in neonatal (NEC) and adult (IBD) gut.

Osthole protects against inflammation in a rat model of chronic kidney failure via suppression of nuclear factor-κB, transforming growth factor-β1 and activation of phosphoinositide 3-kinase/protein kinase B/nuclear factor (erythroid-derived 2)-like 2 signaling

Multiple pharmacological applications of osthole have been previously recognized, including antioxidant, anti-inflammatory, anti‑platelet and estrogenic effects, and resistance to pain. The present study investigated the protective effects of osthole against inflammation in a rat model of chronic kidney failure (CRF) and the underlying mechanisms. Osthole treatment with significantly reversed CRF‑induced changes in serum creatinine, calcium, phosphorus and blood urea nitrogen levels in CRF rats. Male Sprague‑Dawley rats (age, 8 weeks) received 200 mg/kg 2% adenine suspension to induce CRF in the model group. In the osthole‑treated group, rats received 200 mg/kg 2% adenine suspension + osthole (40 mg/kg, intravenously). The results revealed that treatment with osthole significantly inhibited CRF‑induced tumor necrosis factor‑α, interleukin (IL)‑8 and IL‑6 expression, and suppressed nuclear factor‑κB (NF‑κB) protein expression in CRF rats. Osthole treatment significantly attenuated the protein expression of transforming growth factor‑β1 (TGF‑β1), reduced monocyte chemoattractant protein‑1 activity and increased the phosphoinositide 3‑kinase (PI3K)/protein kinase B (Akt) ratio in CRF rats. These results suggested that osthole protects against inflammation in a rat model of CRF via suppression of NF‑κB and TGF‑β1, and activation of PI3K/Akt/nuclear factor (erythroid‑derived 2)‑like 2 signaling. Therefore, osthole may represent a potential therapeutic agent for the treatment of CRF.

Peroxisome proliferator-activated receptor-γ agonist pioglitazone reduces the development of necrotizing enterocolitis in a neonatal preterm rat model

BACKGROUND

Factors affecting innate immunity and acting as inflammatory regulators, such as the nuclear peroxisome proliferator-activated receptors (PPAR) could be crucial in the pathogenesis of necrotizing enterocolitis (NEC). We hypothesized that the PPARγ agonist pioglitazone (PIO) might be effective in preventing the development of NEC and/or reducing its severity.

METHODS

We studied preterm rats in which NEC was induced using the hypoxia-hypothermia model. The treatment group (TG; n = 30) received enteral PIO (10 mg/kg/d) for 72 h and the control group (CG; n = 30) did not. Animals were sacrificed 96 h after birth. NEC was diagnosed evaluating histological ileum changes, and mRNA levels of IL-4, IL-12, IL-6, IL-10, INF-γ, and TNF-α cytokines were measured.

RESULTS

NEC occurrence was higher in the CG (18/30; 60%) than in the TG (5/30; 16.7%) and was more severe. Proinflammatory IL-12 and INF-γ mRNA levels were significantly lower in the TG than in the CG; conversely, the anti-inflammatory IL-4 mRNA level was significantly higher in the TG than in the CG.

CONCLUSION

Our results demonstrate for the first time that PIO is effective in reducing the incidence and severity of NEC and in decreasing renal injuries in a preterm rat model.

Intestinal perforation in the premature infant

OBJECTIVE

To compare demographic data, prenatal and postnatal characteristics, laboratory data, and outcomes in a cohort of premature infants with spontaneous ileal perforation (SIP), surgical necrotizing enterocolitis (sNEC) and matched controls.

METHODS

A retrospective case-control study of infants with intestinal perforation with a birth weight (BW) less than 2,000 grams and gestational age (GA) less than 34 weeks and infants without perforation matched for BW (±150 grams) and GA (±1week).

RESULTS

130 premature infants were included, 30 infants with SIP, 35 infants with sNEC and 65 control infants. The median age of onset was 5 days postnatal age in SIP versus 25 days in sNEC (p < 0.001) and the peak onset was at 26 weeks corrected GA for SIP and 30 weeks corrected GA for sNEC. Infants with perforation had significantly higher rates of mortality (p < 0.001) and common morbidities associated with prematurity. Administration of corticosteroids and indomethacin did not differ among groups. SIP was more common among infants born to young mothers (p = 0.04) and less common in infants receiving caffeine (p = 0.02). sNEC was less common among infants receiving early red cell transfusion (p = 0.01). Perforation and sNEC trended towards less common in infants receiving inhaled nitric oxide.

CONCLUSION

SIP and sNEC are distinct clinical entities. Potential protective effects of caffeine, inhaled nitric oxide, and early transfusion should be further studied.