Alkaline Phosphatase Activity and Endotoxemia After Infant Cardiothoracic Surgery

Increased Drop in Activity of Alkaline Phosphatase in Plasma from Patients with Endocarditis

(1) Infective endocarditis is a severe inflammatory disease associated with substantial mortality and morbidity. Alkaline phosphatase (AP) levels have been shown to change significantly during sepsis. Additionally, we previously found that a higher initial AP drop after cardiac surgery is associated with unfavorable outcomes. Therefore, the course of AP after surgery for endocarditis is of special interest. (2) A total of 314 patients with active isolated left-sided infective endocarditis at the Department of Cardiac Surgery (Medical University of Vienna, Vienna, Austria) between 2009 and 2018 were enrolled in this retrospective analysis. Blood samples were analyzed at different time points (baseline, postoperative days 1-7, postoperative days 14 and 30). Patients were categorized according to relative alkaline phosphatase drop (≥30% vs. <30%). (3) A higher rate of postoperative renal replacement therapy with or without prior renal replacement therapy (7.4 vs. 21.8%; p = 0.001 and 6.7 vs. 15.6%; p = 0.015, respectively) and extracorporeal membrane oxygenation (2.2 vs. 19.0%; p = 0.000) was observed after a higher initial alkaline phosphatase drop. Short-term (30-day mortality 3.0 vs. 10.6%; p = 0.010) and long-term mortality (p = 0.008) were significantly impaired after a higher initial alkaline phosphatase drop. (4) The higher initial alkaline phosphatase drop was accompanied by impaired short- and long-term outcomes after cardiac surgery for endocarditis. Future risk assessment scores for cardiac surgery should consider alkaline phosphatase.

Impact of Venoarterial Extracorporeal Membrane Oxygenation on Alkaline Phosphatase Metabolism after Cardiac Surgery

(1) Alkaline phosphatase (AP) is consumed during cardiopulmonary bypass (CPB). A high AP depletion leads to an impaired outcome after cardiac surgery. However, data is scarce on the postoperative course of AP under venoarterial ECMO (VA-ECMO) support. (2) A total of 239 patients with VA-ECMO support between 2000 and 2019 at the Department of Cardiac Surgery (Vienna General Hospital, Austria) were included in this retrospective analysis. Blood samples were collected at several timepoints (baseline, postoperative day (POD) 1-7, POD 14 and 30). Patients were categorized according to the relative AP drop (<60% vs. ≥60%) and ECMO duration (<5 days vs. ≥5 days). (3) Overall, 44.4% reached the baseline AP values within 5 days-this was only the case for 28.6% with a higher AP drop (compared to 62.7% with a lower drop; p = 0.000). A greater AP drop was associated with a significantly higher need for renal replacement therapy (40.9% vs. 61.9%; p = 0.002) and an impaired 1-year survival (51.4% vs. 66.0%; p = 0.031). (4) CPB exceeds the negative impact of VA-ECMO; still, ECMO seems to delay alkaline phosphatase recovery. A greater initial AP drop bears the risk of higher morbidity and mortality.

Target-induced transcription amplification to trigger the trans-cleavage activity of CRISPR/Cas13a (TITAC-Cas) for detection of alkaline phosphatase

Herein, an ultra-sensitive alkaline phosphatase (ALP) sensing strategy is developed by target-induced transcription amplification to trigger the trans-cleavage activity of Cas13a (TITAC-Cas). A double-stranded DNA duplex integrating a T7 promoter with 5'-phosphate and a transcription template (5'P-dsDNA) serves as the ALP substrate. In the absence of ALP, 5'P-dsDNA can be degraded by the λexo, leading to the subsequent transcription failure. In the presence of ALP, dephosphorylation reaction converts the 5'P-dsDNA to 5'OH-dsDNA and provides the protection for T7 promoter against the λexo-digestion. The intact T7 promoter of 5'OH-dsDNA can activate T7 transcription to produce a mass of single-stranded RNA (ssRNA). The ssRNA products possess a full complementarity to the spacer of crRNA and activate the ssRNase activity of CRISPR/Cas13a. As a result, Cas13a exhibits the indiscriminate cleavage of collateral FQ-reporter to release significant fluorescence signal, realizing the ultra-sensitive detection of ALP. Due to the triple signal amplification (ALP self-catalysis, T7 transcription amplification, and trans-cleavage of CRISPR/Cas13a), TITAC-Cas assay shows the ultra-sensitive detection of ALP activity with a wide linear range from 0.008 to 250 U∙L^-1). The LOD is calculated to be 6 ± 0.52 mU∙L^-1. TITAC-Cas assay is also successfully applied for analysis of ALP activity in HepG2 cell lysate with high fidelity. In addition, this method is employed to screen ALP inhibitor.

Effect of Food Endotoxin on Infant Health

Endotoxin is a complex molecule derived from the outer membrane of Gram-negative bacteria, and it has strong thermal stability. The processing of infant food can kill pathogenic bacteria but cannot remove endotoxin. Because the intestinal structure of infants is not fully developed, residual endotoxin poses a threat to their health by damaging the intestinal flora and inducing intestinal inflammation, obesity, and sepsis, among others. This paper discusses the sources and contents of endotoxin in infant food and methods for preventing endotoxin from harming infants. However, there is no clear evidence that endotoxin levels in infant food cause significant immune symptoms or even diseases in infants. However, in order to improve the safety level of infant food and reduce the endotoxin content, this issue should not be ignored. The purpose of this review is to provide a theoretical basis for manufacturers and consumers to understand the possible harm of endotoxin content in infant formula milk powder and to explore how to reduce its level in infant formula milk powder. Generally, producers should focus on cleaning the milk source, securing the cold chain, avoiding long-distance transportation, and shortening the storage time of raw milk to reduce the level of bacteria and endotoxin. After production and processing, the endotoxin content should be measured as an important index to test the quality of infant formula milk powder so as to provide high-quality infant products for the healthy growth of newborns.

Tissue alkaline phosphatase activity and expression in an experimental infant swine model of cardiopulmonary bypass with deep hypothermic circulatory arrest

Background

Infant cardiac surgery with cardiopulmonary bypass results in decreased circulating alkaline phosphatase that is associated with poor postoperative outcomes. Bovine intestinal alkaline phosphatase infusion represents a novel therapy for post-cardiac surgery organ injury. However, the effects of cardiopulmonary bypass and bovine-intestinal alkaline phosphatase infusion on tissue-level alkaline phosphatase activity/expression are unknown.

Methods

Infant pigs (n = 20) underwent cardiopulmonary bypass with deep hypothermic circulatory arrest followed by four hours of intensive care. Seven control animals underwent mechanical ventilation only. Cardiopulmonary bypass/deep hypothermic circulatory arrest animals were given escalating doses of bovine intestinal alkaline phosphatase infusion (0-25 U/kg/hr.; n = 5/dose). Kidney, liver, ileum, jejunum, colon, heart and lung were collected for measurement of tissue alkaline phosphatase activity and mRNA.

Results

Tissue alkaline phosphatase activity varied significantly across organs with the highest levels found in the kidney and small intestine. Cardiopulmonary bypass with deep hypothermic circulatory arrest resulted in decreased kidney alkaline phosphatase activity and increased lung alkaline phosphatase activity, with no significant changes in the other organs. Alkaline phosphatase mRNA expression was increased in both the lung and the ileum. The highest dose of bovine intestinal alkaline phosphatase resulted in increased kidney and liver tissue alkaline phosphatase activity.

Conclusions

Changes in alkaline phosphatase activity after cardiopulmonary bypass with deep hypothermic circulatory arrest and bovine intestinal alkaline phosphatase delivery are tissue specific. Kidneys, lung, and ileal alkaline phosphatase appear most affected by cardiopulmonary bypass with deep hypothermic circulatory arrest and further research is warranted to determine the mechanism and biologic importance of these changes.

Recent advances in intestinal alkaline phosphatase, inflammation, and nutrition

In recent years, much new data on intestinal alkaline phosphatase (IAP) have been published, and major breakthroughs have been disclosed. The aim of the present review is to critically analyze the publications released over the last 5 years. These breakthroughs include, for example, the direct implication of IAP in intestinal tight junction integrity and barrier function maintenance; chronic intestinal challenge with low concentrations of Salmonella generating long-lasting depletion of IAP and increased susceptibility to inflammation; the suggestion that genetic mutations in the IAP gene in humans contribute to some forms of chronic inflammatory diseases and loss of functional IAP along the gut and in stools; stool IAP as an early biomarker of incipient diabetes in humans; and omega-3 fatty acids as direct inducers of IAP in intestinal tissue. Many recent papers have also explored the prophylactic and therapeutic potential of IAP and other alkaline phosphatase (AP) isoforms in various experimental settings and diseases. Remarkably, nearly all data confirm the potent anti-inflammatory properties of (I)AP and the negative consequences of its inhibition on health. A simplified model of the body AP system integrating the IAP compartment is provided. Finally, the list of nutrients and food components stimulating IAP has continued to grow, thus emphasizing nutrition as a potent lever for limiting inflammation.

Immediate Post-operative Enterocyte Injury, as Determined by Increased Circulating Intestinal Fatty Acid Binding Protein, Is Associated With Subsequent Development of Necrotizing Enterocolitis After Infant Cardiothoracic Surgery

Objectives: 1 Measure serial serum intestinal fatty acid binding protein levels in infants undergoing cardiac surgery with cardiopulmonary bypass to evaluate for evidence of early post-operative enterocyte injury. 2 Determine the association between immediate post-operative circulating intestinal fatty acid binding protein levels and subsequent development of necrotizing enterocolitis. Design: Observational cohort study. Intestinal fatty acid binding protein was measured pre-operatively, at rewarming, and at 6 and 24 h post-operatively. Percent of goal enteral kilocalories on post-operative day 5 and episodes of necrotizing enterocolitis were determined. Multivariable analysis assessed for factors independently associated with clinical feeding outcomes and suspected/definite necrotizing enterocolitis. Setting: Quaternary free-standing children's hospital pediatric cardiac intensive care unit. Patients: 103 infants <120 days of age undergoing cardiothoracic surgery with cardiopulmonary bypass. Interventions: None. Results: Median pre-operative intestinal fatty acid binding protein level was 3.93 ng/ml (range 0.24-51.32). Intestinal fatty acid binding protein levels rose significantly at rewarming (6.35 ng/ml; range 0.54-56.97; p = 0.008), continued to rise slightly by 6 h (6.57 ng/ml; range 0.75-112.04; p = 0.016), then decreased by 24 h (2.79 ng/ml; range 0.03-81.74; p < 0.0001). Sixteen subjects (15.7%) developed modified Bell criteria Stage 1 necrotizing enterocolitis and 9 subjects (8.8%) developed Stage 2 necrotizing enterocolitis. Infants who developed necrotizing enterocolitis demonstrated a significantly higher distribution of intestinal fatty acid binding protein levels at both 6 h (p = 0.005) and 24 h (p = 0.005) post-operatively. On multivariable analysis, intestinal fatty acid binding protein was not associated with percentage of goal enteral kilocalories delivered on post-operative day 5. Higher intestinal fatty acid binding protein was independently associated with subsequent development of suspected/definite necrotizing enterocolitis (4% increase in odds of developing necrotizing enterocolitis for each unit increase in intestinal fatty acid binding protein; p = 0.0015). Conclusions: Intestinal fatty acid binding protein levels rise following infant cardiopulmonary bypass, indicating early post-operative enterocyte injury. Intestinal fatty acid binding protein was not associated with percent of goal enteral nutrition achieved on post-operative day 5, likely due to protocolized feeding advancement based on clinically observable factors. Higher intestinal fatty acid binding protein at 6 h post-operatively was independently associated with subsequent development of necrotizing enterocolitis and may help identify patients at risk for this important complication.

Alkaline Phosphatase Treatment of Acute Kidney Injury in an Infant Piglet Model of Cardiopulmonary Bypass with Deep Hypothermic Circulatory Arrest

Acute kidney injury (AKI) is associated with prolonged hospitalization and mortality following infant cardiac surgery, but therapeutic options are limited. Alkaline phosphatase (AP) infusion reduced AKI in phase 2 sepsis trials but has not been evaluated for cardiac surgery-induced AKI. We developed a porcine model of infant cardiopulmonary bypass (CPB) with deep hypothermic circulatory arrest (DHCA) to investigate post-CPB/DHCA AKI, measure serum/renal tissue AP activity with escalating doses of AP infusion, and provide preliminary assessment of AP infusion for prevention of AKI. Infant pigs underwent CPB with DHCA followed by survival for 4 h. Groups were treated with escalating doses of bovine intestinal AP (1, 5, or 25U/kg/hr). Anesthesia controls were mechanically ventilated for 7 h without CPB. CPB/DHCA animals demonstrated histologic and biomarker evidence of AKI as well as decreased serum and renal tissue AP compared to anesthesia controls. Only high dose AP infusion significantly increased serum or renal tissue AP activity. Preliminary efficacy evaluation demonstrated a trend towards decreased AKI in the high dose AP group. The results of this dose-finding study indicate that AP infusion at the dose of 25U/kg/hr corrects serum and tissue AP deficiency and may prevent AKI in this piglet model of infant CPB/DHCA.

Metabolomic Fingerprinting of Infants Undergoing Cardiopulmonary Bypass: Changes in Metabolic Pathways and Association With Mortality and Cardiac Intensive Care Unit Length of Stay

Background Mortality for infants undergoing complex cardiac surgery is >10% with a 30% to 40% risk of complications. Early identification and treatment of high-risk infants remains challenging. Metabolites are small molecules that determine the minute-to-minute cellular phenotype, making them ideal biomarkers for postsurgical monitoring and potential targets for intervention. Methods and Results We measured 165 serum metabolites by tandem mass spectroscopy in infants ≤120 days old undergoing cardiopulmonary bypass. Samples were collected prebypass, during rewarming, and 24 hours after surgery. Partial least squares-discriminant analysis, pathway analysis, and receiver operator characteristic curve analysis were used to evaluate changes in the metabolome, assess altered metabolic pathways, and discriminate between survivors/nonsurvivors as well as upper/lower 50% intensive care unit length of stay. Eighty-two infants had preoperative samples for analysis; 57 also had rewarming and 24-hour samples. Preoperation, the metabolic fingerprint of neonates differed from older infants ( R2=0.89, Q2=0.77; P<0.001). Cardiopulmonary bypass resulted in progressive, age-independent metabolic disturbance ( R2=0.92, Q2=0.83; P<0.001). Multiple pathways demonstrated changes, with arginine/proline ( P=1.2×10-35), glutathione ( P=3.3×10-39), and alanine/aspartate/glutamate ( P=1.4×10-26) metabolism most affected. Six subjects died. Nonsurvivors demonstrated altered aspartate ( P=0.007) and nicotinate/nicotinamide metabolism ( P=0.005). The combination of 24-hour aspartate and methylnicotinamide identified nonsurvivors versus survivors (area under the curve, 0.86; P<0.01), as well as upper/lower 50% intensive care unit length of stay (area under the curve, 0.89; P<0.01). Conclusions The preoperative metabolic fingerprint of neonates differed from older infants. Large metabolic shifts occurred after cardiopulmonary bypass, independent of age. Nonsurvivors and subjects requiring longer intensive care unit length of stay showed distinct changes in metabolism. Specific metabolites, including aspartate and methylnicotinamide, may differentiate sicker patients from those experiencing a more benign course.