Applied glycoproteomics—approaches to study genetic-environmental collisions causing protein-losing enteropathy

Nutritional Management of Patients with Fontan Circulation: A Potential for Improved Outcomes from Birth to Adulthood

Fontan circulation (FC) is a surgically achieved palliation state offered to patients affected by a wide variety of congenital heart defects (CHDs) that are grouped under the name of univentricular heart. The procedure includes three different surgical stages. Malnutrition is a matter of concern in any phase of life for these children, often leading to longer hospital stays, higher mortality rates, and a higher risk of adverse neurodevelopmental and growth outcomes. Notwithstanding the relevance of proper nutrition for this subset of patients, specific guidelines on the matter are lacking. In this review, we aim to analyze the role of an adequate form of nutritional support in patients with FC throughout the different stages of their lives, in order to provide a practical approach to appropriate nutritional management. Firstly, the burden of faltering growth in patients with univentricular heart is analyzed, focusing on the pathogenesis of malnutrition, its detection and evaluation. Secondly, we summarize the nutritional issues of each life phase of a Fontan patient from birth to adulthood. Finally, we highlight the challenges of nutritional management in patients with failing Fontan.

Protein-losing enteropathy recurrence after pediatric heart transplantation: Multicenter case series

BACKGROUND

Protein-losing enteropathy (PLE) is a devastating complication of the Fontan circulation. Although orthotopic heart transplantation (HTx) typically results in resolution of PLE symptoms, isolated cases of PLE relapse have been described after HTx.

METHODS

Patients with Fontan-related PLE who had undergone HTx at participating centers and experienced relapse of PLE during follow-up were retrospectively identified. Available data related to pre- and post-HTx characteristics and PLE events were collected.

RESULTS

Eight patients from four different centers were identified. Median time from Fontan procedure to the development of PLE was 8 years, and median age at HTx was 17 years (range 7.7-21). In all patients, PLE resolved at a median time of 1 month after HTx (0.3-5). PLE recurrences occurred at a median time of 7.5 months after HTx (2-132). Each occurrence was associated with one or more significant clinical events; most commonly cellular- or antibody-mediated rejection; and less commonly graft dysfunction, infection, thrombosis, and posttransplant lymphoproliferative disease. PLE recurrences resolved after the successful treatment of the concomitant event, after a median time of 2 months in seven cases, while persisted and recurred in one patient in association with atypical mycobacterium infection and subsequent PTLD onset and relapses. Six patients were alive during follow-up at a median time of 4 years (1.3-22.5) after HTx.

CONCLUSIONS

This is the largest series of PLE recurrence after HTx. All cases were associated with one or more concomitant and significant clinical events. PLE typically resolved after resolution of the inciting clinical event.

Management of circulatory failure after Fontan surgery

With improvement in survival after Fontan surgery resulting in an increasing number of older survivors, there are more patients with a Fontan circulation experiencing circulatory failure each year. Fontan circulatory failure may have a number of underlying etiologies. Once Fontan failure manifests, prognosis is poor, with patient freedom from death or transplant at 10 years of only about 40%. Medical treatments used include traditional heart failure medications such as renin-angiotensin-aldosterone system blockers and beta-blockers, diuretics for symptomatic management, antiarrhythmics for rhythm control, and phosphodiesterase-5 inhibitors to decrease PVR and improve preload. These oral medical therapies are typically not very effective and have little data demonstrating benefit; if there are no surgical or catheter-based interventions to improve the Fontan circulation, patients with severe symptoms often require inotropic medications or mechanical circulatory support. Mechanical circulatory support benefits patients with ventricular dysfunction but may not be as useful in patients with other forms of Fontan failure. Transplant remains the definitive treatment for circulatory failure after Fontan, but patients with a Fontan circulation face many challenges both before and after transplant. There remains significant room and urgent need for improvement in the management and outcomes of patients with circulatory failure after Fontan surgery.

Sjögren syndrome associated with protein-losing enteropathy: case-based review

The association between Sjögren's syndrome (SS) and protein-losing enteropathy (PLE) was scarcly reported. To analyze the clinical, therapeutic, and outcome characteristics of patients with SS and PLE and also to delineate the potential mechanisms and pathways connecting the gut to SS targeted organ's pathology. Systematic screening was conducted using PubMed/MEDLINE, LILACS, SciELO, Web of Science, and Cochrane, dating 1980 to 2020. SS and PLE were the key words. Eighteen patients with SS and PLE were summarized. The patient's ages ranged between 20 and 88 years, and only 4 were males. Primary SS was observed in most cases. Anti-Ro was detected in 100% of the cases while anti-La was reported in 64% of them. The clinical manifestations were protein loss, edema of the lower limbs, pleural effusion, ascites, facial edema, anasarca, diarrhea, and weight loss. Among these clinical manifestations, edema of the lower limbs was the most severe. Albumin concentration was 0.9-3.4 g/dL which increased to 2.8-4.3 g/dL after treatment. Small bowel biopsy was performed in all of the cases. Concerning the therapy, all the patients received systemic glucocorticoids. All of them improved. The period of onset of improvement ranged from 3 weeks to 36 months (an average of 3 months). The early diagnosis and appropriate therapy of PLE in patients with anti-Ro positive SS and who present edema, anasarca, or hypoalbuminemia is vital for a beneficial outcome. An excellent clinical improvement in all the cases was observed when treated early enough by cortico-therapy, thus preventing patient's deterioration, complications, and reducing morbidity and potential mortality.

Diagnosis and Management of Lymphatic Disorders in Congenital Heart Disease

Purpose of Review

Lymphatic disorders have received an increasing amount of attention over the last decade. Sparked primarily by improved imaging modalities and the dawn of lymphatic interventions, understanding, diagnostics, and treatment of lymphatic complications have undergone considerable improvements. Thus, the current review aims to summarize understanding, diagnostics, and treatment of lymphatic complications in individuals with congenital heart disease.

Recent Findings

The altered hemodynamics of individuals with congenital heart disease has been found to profoundly affect morphology and function of the lymphatic system, rendering this population especially prone to the development of lymphatic complications such as chylous and serous effusions, protein-losing enteropathy and plastic bronchitis.

Summary

Although improved, a full understanding of the pathophysiology and targeted treatment for lymphatic complications is still wanting. Future research into pharmacological improvement of lymphatic function and continued implementation of lymphatic imaging and interventions may improve knowledge, treatment options, and outcome for affected individuals.

Consensus guideline for the diagnosis and management of mannose phosphate isomerase-congenital disorder of glycosylation

Mannose phosphate isomerase-congenital disorder of glycosylation (MPI-CDG) deficiency is a rare subtype of congenital disorders of protein N-glycosylation. It is characterised by deficiency of MPI caused by pathogenic variants in MPI gene. The manifestation of MPI-CDG is different from other CDGs as the patients suffer dominantly from gastrointestinal and hepatic involvement whereas they usually do not present intellectual disability or neurological impairment. It is also one of the few treatable subtypes of CDGs with proven effect of oral mannose. This article covers a complex review of the literature and recommendations for the management of MPI-CDG with an emphasis on the clinical aspect of the disease. A team of international experts elaborated summaries and recommendations for diagnostics, differential diagnosis, management, and treatment of each system/organ involvement based on evidence-based data and experts' opinions. Those guidelines also reveal more questions about MPI-CDG which need to be further studied.

Evaluation and Management of the Child and Adult With Fontan Circulation: A Scientific Statement From the American Heart Association

It has been 50 years since Francis Fontan pioneered the operation that today bears his name. Initially designed for patients with tricuspid atresia, this procedure is now offered for a vast array of congenital cardiac lesions when a circulation with 2 ventricles cannot be achieved. As a result of technical advances and improvements in patient selection and perioperative management, survival has steadily increased, and it is estimated that patients operated on today may hope for a 30-year survival of >80%. Up to 70 000 patients may be alive worldwide today with Fontan circulation, and this population is expected to double in the next 20 years. In the absence of a subpulmonary ventricle, Fontan circulation is characterized by chronically elevated systemic venous pressures and decreased cardiac output. The addition of this acquired abnormal circulation to innate abnormalities associated with single-ventricle congenital heart disease exposes these patients to a variety of complications. Circulatory failure, ventricular dysfunction, atrioventricular valve regurgitation, arrhythmia, protein-losing enteropathy, and plastic bronchitis are potential complications of the Fontan circulation. Abnormalities in body composition, bone structure, and growth have been detected. Liver fibrosis and renal dysfunction are common and may progress over time. Cognitive, neuropsychological, and behavioral deficits are highly prevalent. As a testimony to the success of the current strategy of care, the proportion of adults with Fontan circulation is increasing. Healthcare providers are ill-prepared to tackle these challenges, as well as specific needs such as contraception and pregnancy in female patients. The role of therapies such as cardiovascular drugs to prevent and treat complications, heart transplantation, and mechanical circulatory support remains undetermined. There is a clear need for consensus on how best to follow up patients with Fontan circulation and to treat their complications. This American Heart Association statement summarizes the current state of knowledge on the Fontan circulation and its consequences. A proposed surveillance testing toolkit provides recommendations for a range of acceptable approaches to follow-up care for the patient with Fontan circulation. Gaps in knowledge and areas for future focus of investigation are highlighted, with the objective of laying the groundwork for creating a normal quality and duration of life for these unique individuals.

Investigation of the Influence of Protein-Losing Enteropathy on Monoclonal Antibody Pharmacokinetics in Mice

Protein losing enteropathy (PLE), which is characterized by substantial loss of plasma proteins into the gastrointestinal (GI) tract, is a complication of a variety of GI diseases, including inflammatory bowel disease. Clinical studies have found that the clearance of monoclonal antibodies (mAb) is often increased in subjects with diseases known to cause PLE; however, direct relationships between PLE and mAb pharmacokinetics have not been demonstrated. This study employed a murine model of colitis to examine the influence of PLE on mAb pharmacokinetics. Mice were given dextran sodium sulfate (DSS, 2% w/v) supplemented tap water as drinking source for 6 days to induce colitis and PLE. Mice were then intravenously injected with 8C2, a murine IgG1 mAb. 8C2 plasma concentrations were measured up to 14 days post injection. Fecal alpha-1-antitrypsin (A1AT) clearance was measured as biomarker for PLE. DSS-treated mice developed PLE of clinically relevant severity. They also showed a transient increase in 8C2 plasma clearance and a decrease in 8C2 plasma exposure. The area under the 8C2 plasma concentration-time curve for the length of the study (AUC_0-14d) reduced from 1368 ± 255 to 594 ± 224 day μg/ml following DSS treatment (p = 0.001). A quantitative relationship between A1AT clearance and 8C2 clearance was obtained via population pharmacokinetic modeling. DSS treatment substantially increased 8C2 clearance and reduced 8C2 exposure. Increased mAb plasma clearance was highly correlated with A1AT fecal clearance, suggesting the possible utility of A1AT fecal clearance as a mechanistic biomarker to predict the pharmacokinetics of therapeutic antibodies.

DMP1-CDG (CDG1e) with Significant Gastrointestinal Manifestations; Phenotype and Genotype Expansion

The literature describes eight cases of mutations in the DPM1 gene generating DMP1-CDG, causing similar phenotype of early onset seizures, microcephaly and developmental delay. Investigations of these patients revealed associated abnormal findings on brain imaging, elevated CK, abnormal clotting factors and mildly deranged serum transaminases. We describe the ninth case of DMP1-CDG, whose clinical presentation includes severe gastrointestinal involvement, i.e. food protein induced enterocolitis syndrome (FPIES). Gastrointestinal manifestations (GIT) of the congenital glycosylation disorders have included deranged liver function, hepatomegaly, liver fibrosis, steatosis and protein-losing enteropathy. This is the first report of a congenital glycosylation disorder being associated with FPIES.

Significance of circulating hepatocyte growth factor in protein-losing enteropathy after Fontan operation

The purpose of this study was to measure serum hepatocyte growth factor (HGF) and elucidate the relationship between HGF and protein-losing enteropathy (PLE) after Fontan operation (FO). Ten patients with PLE (mean age 15.7 ± 8.7 years) who underwent FO were enrolled. Control group 1 comprised 20 patients without PLE after FO, and control group 2 comprised 10 patients with nephrotic syndrome (NS). Serum HGF, vascular endothelial growth factor, albumin, and random stool alpha-1 antitrypsin concentration were measured. Transthoracic echocardiography was completed. Serum HGF level was significantly greater in the PLE patients (0.61 ± 0.27 ng/ml) after FO than in the two control groups (0.41 ± 0.12 ng/ml [P = 0.024] for the Fontan group without PLE and 0.26 ± 0.12 ng/ml [P = 0.002] for the patients with NS). Serum albumin of patients with PLE (2.82 ± 0.96 g/dl) showed significantly lower levels compared with those of patients without PLE after FO (4.30 ± 0.37 g/dl, P < 0.001) but significantly greater levels compared with patients with NS (1.91 ± 0.33 g/dl, P = 0.019). Patients with greater serum HGF levels showed significant correlation with lower serum albumin level (P = 0.006, r = -0.495). Because serum HGF levels were significantly greater in patients with PLE after FO, HGF may play a role in the development of PLE after FO.

Protein-losing enteropathy: integrating a new disease paradigm into recommendations for prevention and treatment

Protein-losing enteropathy is a relatively uncommon complication of Fontan procedures for palliation of complex congenital cardiac disease. However, the relative infrequency of protein-losing enteropathy belies the tremendous medical, psychosocial and financial burdens it places upon afflicted patients, their families and the healthcare system that supports them. Unfortunately, because of the complexity and rarity of this disease process, the pathogenesis and pathophysiology of protein-losing enteropathy remain poorly understood, and attempts at treatment seldom yield long-term success. The most comprehensive analyses of protein-losing enteropathy in this patient population are now over a decade old, and re-evaluation of the prevalence and progress in treatment of this disease is needed. This report describes a single institution experience with the evaluation, management, and treatment of protein-losing enteropathy in patients with congenital cardiac disease in the current era, follows with a comprehensive review of protein-losing enteropathy, focused upon what is known and not known about the pathophysiology of protein-losing enteropathy in this patient population, and concludes with suggestions for prevention and treatment.

Reduced production of sulfated glycosaminoglycans occurs in Zambian children with kwashiorkor but not marasmus

BACKGROUND

Kwashiorkor, a form of severe malnutrition with high mortality, is characterized by edema and systemic abnormalities. Although extremely common, its pathophysiology remains poorly understood, and its characteristic physical signs are unexplained.

OBJECTIVE

Because kwashiorkor can develop in protein-losing enteropathy, which is caused by a loss of enterocyte heparan sulfate proteoglycan (HSPG), and previous observations suggest abnormal sulfated glycosaminoglycan (GAG) metabolism, we examined whether intestinal GAG and HSPG are abnormal in children with kwashiorkor.

DESIGN

Duodenal biopsy samples collected from Zambian children with marasmus (n = 18), marasmic kwashiorkor (n = 8), and kwashiorkor (n = 15) were examined for expression of HSPG, GAGs, and immunologic markers and compared against reference samples from healthy UK control children. GAG and HSPG expression density and inflammatory cell populations were quantitated by computerized analysis.

RESULTS

The kwashiorkor group was less wasted and had a lower HIV incidence than did the other groups. All duodenal biopsy samples showed inflammation compared with the histologically uninflamed control samples. Biopsy samples from marasmic children had greater inflammation and greater CD3+ and HLA-DR (human leukocyte antigen DR)-positive cell densities than did samples from children with kwashiorkor. Expression of both HSPG and GAGs was similar between marasmic and well-nourished UK children but was markedly lower in children with kwashiorkor in both the epithelium and lamina propria. Although underglycosylated and undersulfated, epithelial syndecan-1 protein was normally expressed in kwashiorkor, which confirmed that abnormalities arise after core protein synthesis.

CONCLUSIONS

Intestinal HSPG loss occurs in kwashiorkor, which may precipitate protein-losing enteropathy to cause edema. If occurring systemically, impaired HSPG expression could cause several previously unexplained features of kwashiorkor. We speculate that a genetic predisposition to reduced HSPG biosynthesis may offer a contrasting selective advantage, by both diminishing protein catabolism during transient undernutrition and protecting against specific infectious diseases.

Glycosylation diseases: quo vadis?

About 250 to 500 glycogenes (genes that are directly involved in glycan assembly) are in the human genome representing about 1-2% of the total genome. Over 40 human congenital diseases associated with glycogene mutations have been described to date. It is almost certain that the causative glycogene mutations for many more congenital diseases remain to be discovered. Some glycogenes are involved in the synthesis of only a specific protein and/or a specific class of glycan whereas others play a role in the biosynthesis of more than one glycan class. Mutations in the latter type of glycogene result in complex clinical phenotypes that present difficult diagnostic problems to the clinician. In order to understand in biochemical terms the clinical signs and symptoms of a patient with a glycogene mutation, one must understand how the glycogene works. That requires, first of all, determination of the target protein or proteins of the glycogene followed by an understanding of the role, if any, of the glycogene-dependent glycan in the functions of the protein. Many glycogenes act on thousands of glycoproteins. There are unfortunately no general methods to identify all the potentially large number of glycogene target proteins and which of these proteins are responsible for the mutant phenotypes. Whereas biochemical methods have been highly successful in the discovery of glycogenes responsible for many congenital diseases, it has more recently been necessary to use other methods such as homozygosity mapping. Accurate diagnosis of many recently discovered diseases has become difficult and new diagnostic procedures must be developed. Last but not least is the lack of effective treatment for most of these children and of animal models that can be used to test new therapies.

Protein-losing enteropathy after Fontan operation

Protein-losing enteropathy (PLE) is a poorly understood and enigmatic disease process affecting patients with single ventricle after Fontan operation. In those afflicted, PLE after Fontan operation results in significant morbidity and mortality. The pathophysiology of the disease is unknown; however, a proposed mechanism incorporates a combination of phenomena including: (1) altered hemodynamics, specifically low cardiac output; (2) increased mesenteric vascular resistance; (3) systemic inflammation; and (4) altered enterocyte basal membrane glycosaminoglycan make-up. A paradigm for the clinical management of PLE after Fontan operation is proposed.

Heparan sulfate and syndecan-1 are essential in maintaining murine and human intestinal epithelial barrier function

Patients with protein-losing enteropathy (PLE) fail to maintain intestinal epithelial barrier function and develop an excessive and potentially fatal efflux of plasma proteins. PLE occurs in ostensibly unrelated diseases, but emerging commonalities in clinical observations recently led us to identify key players in PLE pathogenesis. These include elevated IFN-gamma, TNF-alpha, venous hypertension, and the specific loss of heparan sulfate proteoglycans from the basolateral surface of intestinal epithelial cells during PLE episodes. Here we show that heparan sulfate and syndecan-1, the predominant intestinal epithelial heparan sulfate proteoglycan, are essential in maintaining intestinal epithelial barrier function. Heparan sulfate- or syndecan-1-deficient mice and mice with intestinal-specific loss of heparan sulfate had increased basal protein leakage and were far more susceptible to protein loss induced by combinations of IFN-gamma, TNF-alpha, and increased venous pressure. Similarly, knockdown of syndecan-1 in human epithelial cells resulted in increased basal and cytokine-induced protein leakage. Clinical application of heparin has been known to alleviate PLE in some patients but its unknown mechanism and severe side effects due to its anticoagulant activity limit its usefulness. We demonstrate here that non-anticoagulant 2,3-de-O-sulfated heparin could prevent intestinal protein leakage in syndecan-deficient mice, suggesting that this may be a safe and effective therapy for PLE patients.

Using heparin therapy to reverse protein-losing enteropathy in a patient with CDG-Ib

BACKGROUND

A 22-year-old female presented with edema, diarrhea, hypoalbuminemia and pancytopenia. She had previously been diagnosed with congenital disorder of glycosylation type Ib, and had a history of congenital hepatic fibrosis, portal hypertension and esophageal varices. In the past she had refused mannose therapy because of associated diarrhea and abdominal pain.

INVESTIGATIONS

Laboratory examinations, abdominal ultrasonography, bacterial and viral cultures of blood, urine and stools, double-balloon enteroscopy and fecal excretion test using 51Cr-labeled albumin.

DIAGNOSIS

Protein-losing enteropathy.

MANAGEMENT

Infusion of albumin followed by intravenous and subcutaneous therapy with unfractionated heparin.

Agm1/Pgm3-mediated sugar nucleotide synthesis is essential for hematopoiesis and development

Carbohydrate modification of proteins includes N-linked and O-linked glycosylation, proteoglycan formation, glycosylphosphatidylinositol anchor synthesis, and O-GlcNAc modification. Each of these modifications requires the sugar nucleotide UDP-GlcNAc, which is produced via the hexosamine biosynthesis pathway. A key step in this pathway is the interconversion of GlcNAc-6-phosphate (GlcNAc-6-P) and GlcNAc-1-P, catalyzed by phosphoglucomutase 3 (Pgm3). In this paper, we describe two hypomorphic alleles of mouse Pgm3 and show there are specific physiological consequences of a graded reduction in Pgm3 activity and global UDP-GlcNAc levels. Whereas mice lacking Pgm3 die prior to implantation, animals with less severe reductions in enzyme activity are sterile, exhibit changes in pancreatic architecture, and are anemic, leukopenic, and thrombocytopenic. These phenotypes are accompanied by specific rather than wholesale changes in protein glycosylation, suggesting that while universally required, the functions of certain proteins and, as a consequence, certain cell types are especially sensitive to reductions in Pgm3 activity.

Genetic defects in the human glycome

The spectrum of all glycan structures--the glycome--is immense. In humans, its size is orders of magnitude greater than the number of proteins that are encoded by the genome, one percent of which encodes proteins that make, modify, localize or bind sugar chains, which are known as glycans. In the past decade, over 30 genetic diseases have been identified that alter glycan synthesis and structure, and ultimately the function of nearly all organ systems. Many of the causal mutations affect key biosynthetic enzymes, but more recent discoveries point to defects in chaperones and Golgi-trafficking complexes that impair several glycosylation pathways. As more glycosylation disorders and patients with these disorders are identified, the functions of the glycome are starting to be revealed.