Interplay between genetics and the environment in the development of celiac disease: perspectives for a healthy life

Posttranslational modifications as therapeutic targets for intestinal disorders

A variety of biological processes are regulated by posttranslational modifications. Posttranslational modifications including phosphorylation, ubiquitination, glycosylation, and proteolytic cleavage, control diverse physiological functions in the gastrointestinal tract. Therefore, a better understanding of their implications in intestinal diseases, including inflammatory bowel disease, irritable bowel syndrome, celiac disease, and colorectal cancer would provide a basis for the identification of novel biomarkers as well as attractive therapeutic targets. Posttranslational modifications can be common denominators, as well as distinct biomarkers, characterizing pathological differences of various intestinal diseases. This review provides experimental evidence that identifies changes in posttranslational modifications from patient samples, primary cells, or cell lines in intestinal disorders, and a summary of carefully selected information on the use of pharmacological modulators of protein modifications as therapeutic options.

Genome and epigenome analysis of monozygotic twins discordant for congenital heart disease

BACKGROUND

Congenital heart disease (CHD) is the leading non-infectious cause of death in infants. Monozygotic (MZ) twins share nearly all of their genetic variants before and after birth. Nevertheless, MZ twins are sometimes discordant for common complex diseases. The goal of this study is to identify genomic and epigenomic differences between a pair of twins discordant for a form of congenital heart disease, double outlet right ventricle (DORV).

RESULTS

A monoamniotic monozygotic (MZ) twin pair discordant for DORV were subjected to genome-wide sequencing and methylation analysis. We identified few genomic differences but 1566 differentially methylated regions (DMRs) between the MZ twins. Twenty percent (312/1566) of the DMRs are located within 2 kb upstream of transcription start sites (TSS), containing 121 binding sites of transcription factors. Particularly, ZIC3 and NR2F2 are found to have hypermethylated promoters in both the diseased twin and additional patients suffering from DORV.

CONCLUSIONS

The results showed a high correlation between hypermethylated promoters at ZIC3 and NR2F2 and down-regulated gene expression levels of these two genes in patients with DORV compared to normal controls, providing new insight into the potential mechanism of this rare form of CHD.

Infectious Gastroenteritis as a Risk Factor for Tropical Sprue and Malabsorption: A Case-Control Study

BACKGROUND

Previous studies have linked an increase in functional and pathological gastrointestinal (GI) disorders following antecedent infectious gastroenteritis (IGE), yet studies of other chronic GI disorders such as tropical sprue (TS) and intestinal malabsorption (IM) are lacking. This study was performed to evaluate the association between documented IGE and the risk of TS and IM using a matched case-control study.

METHODS

The odds of IGE (exposure) among subjects with TS and IM were compared to the odds of exposure in matched controls. Data were obtained from the Defense Medical Surveillance System. Incidence was estimated based on the number of active duty military personnel, and conditional logistic regression models were used to evaluate the relationship between IGE and TS/IM while adjusting for potential confounders.

RESULTS

The overall incidence of TS and IM was 0.24 and 1.98 per 100,000 person-years, respectively. After adjusting for important covariates, prior IGE was associated with an increase in the odds of TS (odds ratio (OR) 36.64) and IM (OR 3.93) (p < 0.001). Other covariates demonstrating an increased risk were being of Caucasian race, having greater than high school education, and service in military branches other than the Army.

CONCLUSION

Overall, this study demonstrates the first significant estimates that a case of antecedent IGE is associated with an increased risk of TS and IM in an active duty military population. Ultimately, acquisition of TS or IM has the potential to decrease operational efficiency, which may have a significant impact on deployed military missions.

Clinical manifestations of food allergy

Adverse reactions to foods are a diverse group of clinical syndromes resulting from immunologic and non-immunologic responses to food ingestion. Symptoms can range from mild, self-limiting reactions to severe, life-threatening reactions depending on the mechanism. This review primarily focuses on the clinical manifestations of immunologically derived adverse food reactions or food allergies.The true prevalence of food allergy is unknown. Up to 25% of the general population believes that they may be allergic to some food; however, the actual prevalence of food allergy diagnosed by a provider appears to be 1.5% to 2% of the adult population and approximately 6% to 8% of children. This discrepancy makes it imperative that clinicians are aware of the different food allergy syndromes. With a clear understanding of the clinical manifestations of food allergies, an accurate diagnosis and treatment plan can be formulated. Failing to do so may result in unnecessary dietary restrictions that may adversely affect nutritional status, growth, and quality of life.Most food allergic reactions are secondary to a limited number of foods, and the most common foods causing allergic reactions in children include milk, egg, peanuts, tree nuts, and fish. In adolescents and adults, allergies to peanuts, tree nuts, fish, and shellfish are most prevalent. Food allergies can result from immunoglobulin E (IgE)-mediated, non-IGE-mediated, or mixed IgE/non-IgE mechanisms. The purpose of this review is to discuss the clinical manifestations of each of these types of food allergy.

Lower economic status and inferior hygienic environment may protect against celiac disease

BACKGROUND

The populations in adjacent Russian Karelia and Finland are equally exposed to grain products and share partly the same ancestry, but live in completely different socioeconomic environments.

AIM

This creates an ideal epidemiological setting to study gene-environmental interactions in pathogenesis of celiac disease.

METHODS

The prevalence of celiac disease and predisposing human leukocyte antigen (HLA) alleles was compared between Russian Karelia and Finland. Tissue transglutaminase antibodies and HLA-DQ alleles were screened from 1988 schoolchildren from Karelia and 3654 children from Finland. Children with transglutaminase antibodies were invited to small-bowel biopsy. Results. Transglutaminase antibodies were less frequent in Russian Karelia than in Finland (0.6% versus 1.4%, P = 0.005). Immunoglobulin class G (IgG) antigliadin antibodies were also less frequent in Russian Karelia (10.2% versus 28.3%, P<0.0001). Celiac disease was confirmed by duodenal biopsy in four of the eight transglutaminase antibody-positive Karelian children, giving a prevalence of 1 in 496 compared to 1 in 107 children in Finland. The same HLA-DQ alleles were associated with celiac disease and transglutaminase antibody positivity in both populations.

CONCLUSIONS

The prevalence of transglutaminase antibodies and celiac disease is lower in Russian Karelia than in Finland. This may be associated with a protective environment characterized by inferior prosperity and standard of hygiene in Karelia.

Determining IgA and IgG antigliadin, IgA antitransglutaminase, and antiendomysial antibodies in monkey esophagus and in umbilical cord for diagnosis of celiac disease in developing countries

OBJECTIVES

To assess the efficiency of determining IgA and IgG antigliadin antibodies (IgA- and IgG-AGA, respectively), antitransglutaminase (TgA), and anti-endomysial antibodies (AEA) in human umbilical cord (CO) and monkey esophagus for diagnosis of celiac disease; to determine the correlation between serological markers and celiac disease.

PATIENTS AND METHODS

A total of 400 patients were divided in 3 groups: group 1 with 37 patients with celiac disease, group 2 with 208 patients with no enteropathies, and group 3 with 155 patients with other enteropathies. IgA-AGA, IgG-AGA, and TgA were assessed using enzyme-linked immunosorbent assay, whereas AEA was evaluated by indirect immunofluorescence.

RESULTS

Sensitivity and specificity of IgA-AGA were 81.1% and 95.2%, of IgG-AGA 89.2% and 95.2%, of TgA 83.9% and 96.8%, of AEA-CO 87.9% and 100%, and of AEA of monkey esophagus 88.6% and 100%, respectively. Positive predictive values were 75.0%, 76.7%, 83.9%, and 100%. Negative predictive values were 96.6%, 98.0%, 96.8%, and 97.7% for IgA-AGA, IgG-AGA, TgA, and AEA, respectively. Multivariate analysis showed a strong association between AEA-CO and celiac disease and a good correlation with other markers (TgA, IgA-AGA, and IgG-AGA).

CONCLUSIONS

TgA has been recommended for screening patients with celiac disease. Considering the similar sensitivity and specificity of IgA-AGA and TgA and their correlations in the multivariate analysis, both are applicable for this purpose. However, because TgA tests are highly costly and celiac disease is associated with IgA deficiency, the determination of IgA-AGA and IgG-AGA, followed by AEA-CO, is suitable for screening in developing countries, provided a cutoff point for these examinations is established. The results of antiendomysial antibodies in umbilical cord overlapped those in monkey esophagus. Therefore, umbilical cord should be used as a substrate instead of specimens from endangered species.

Genetic and functional analysis of pyroglutamyl-peptidase I in coeliac disease

Coeliac disease (CD) is an enteropathy caused by an immune reaction towards wheat gluten and similar proteins from barley and rye. It was shown that some gluten peptides spontaneously form N-terminal L-pyroglutamate. This modification could potentially make gluten more resistant to proteolytic degradation within the intestine. Pyroglutamyl-peptidase I (PGPEPI) is an enzyme that hydrolytically removes the L-pyroglutamyl residues that render the modified proteins and peptides more sensitive to degradation by other proteases. Interestingly, we found that the PGPEP1 gene is located in a CD susceptibility locus. As an impaired enzyme function caused by genetic alterations might increase the amount of immunogenic gluten peptides, we conducted a comprehensive functional genomics analysis of PGPEP1, including DNA sequencing, genetic association testing, and quantifying RNA expression. We also determined the enzymatic activity of PGPEPI in duodenal biopsies. Our results uniformly indicate that PGPEP1 is not involved in the aetiology and pathology of CD.

Celiac disease: current concepts in diagnosis and treatment

Celiac disease is a complex autoimmune enteropathy that affects the small bowel in genetically predisposed individuals. It is thought that celiac disease is the result of an inappropriate T cell-mediated immune response against ingested gluten protein. The characteristic lesion of the small intestinal mucosa includes loss of absorptive villi and infiltration of the lamina propria with inflammatory cells. The clinical presentation of celiac disease varies greatly depending on patient's age, duration and extent of the disease, and the presence of extraintestinal manifestations. Unfortunately, most patients with celiac disease have either silent or atypical presentations, thus escaping diagnosis for several years. Medical nutrition therapy with lifelong adherence to a strict gluten-free diet is the only accepted treatment of celiac disease. Individuals at risk for this entity should undergo appropriate serologic testing, but there is no evidence to support mass screening.

Prevalence of celiac disease in dyspeptic patients

BACKGROUND

Celiac disease is one of the most common dietary-mediated inflammatory enteropathies that occur in genetically predisposed individuals in response to gluten intolerance. This disorder has become more common than in the past, even if it frequently remains undetected for long periods of time. The screening of patients with dyspepsia, a symptom that can be a manifestation of celiac disease, may allow an early identification of affected individuals. Endoscopy and serological tests may have an important role in the management of these patients.

AIMS

Determining the prevalence of celiac disease in dyspeptic patients submitted to routine diagnostic upper gastrointestinal endoscopy.

PATIENTS/METHODS

Endoscopic findings, duodenal biopsy histological specimens and serological test results were assessed and compared in 142 patients consecutively admitted with dyspeptic symptoms between October 2001 and October 2003.

RESULTS

An endoscopic pattern suggestive of celiac disease was observed in four patients. The IgG-AGA assay was positive in 24 patients. Two of the IgG-AGA positive patients also yielded positive results on the IgA-EMA test and concomitantly disclosed endoscopic pattern and histological features in duodenal biopsy compatible with celiac disease. Abnormal endoscopic findings were notably marked in biopsy proven celiac patients. Therefore, a 1.4% prevalence of celiac disease was observed in this study group.

CONCLUSIONS

The high prevalence of celiac among dyspeptic symptomatic individuals indicates that they are a higher risk group for developing celiac disease. Undiagnosed celiac disease may be inferred by endoscopic markers of duodenal villous atrophy. Endoscopic findings, however, may be inadequate to suitably diagnose this disease and consequently the incorporation of diagnostic serologic assays of celiac disease in routine testing for dyspepsia is strongly recommended.

Gluten: a two-edged sword. Immunopathogenesis of celiac disease

Celiac disease (CD) is a small intestinal disorder caused by adaptive and innate immune responses triggered by the gluten proteins present in wheat. In the intestine, gluten is partially degraded and modified, which results in gluten peptides that bind with high affinity to HLA-DQ2 or HLA-DQ8 and trigger an inflammatory T cell response. Simultaneously, gluten exposure leads to increased production of IL15, which induces the expression of NKG2D on intraepithelial lymphocytes and its ligand MICA on epithelial cells, leading to epithelial cell destruction. The gluten-specific T cell response results in the production of antibodies against tissue transglutaminase and these are specific indicators of disease. CD is one of the most common inherited diseases, the HLA-DQ locus being the major contributing genetic factor. However, as the inheritance does not follow a Mendelian segregation pattern, multiple other genes, each with relative weak effect, contribute to disease development. An important role for environmental factors, however, can not be ignored as the concordance rate in monozygous twins is considerably less than 100%. The identification of these environmental factors and susceptibility genes may allow a better understanding of disease etiology and provide diagnostic and prognostic markers. The current treatment for CD consists of a life-long gluten-free diet. Although long thought to be impossible, recent results suggest that the development of nontoxic wheat varieties may be feasible, which would aid disease prevention and provide an alternative food source for patients.

IL12B and IRF1 gene polymorphisms and susceptibility to celiac disease

Celiac disease (CD) is a common gastro-intestinal disorder resulting from permanent intolerance to wheat gliadins and related proteins in rye and barley. In addition to the strong genetic association with HLA-DQ2 and HLA-DQ8, a genetic region on chromosomes 5 (CELIAC2) has been identified that harbours a susceptibility gene for CD. The gene(s) responsible for this association, however, remains to be identified. In the present study we evaluated polymorphisms in the genes encoding interleukin-12 p40 (IL12B) and interferon regulatory factor 1 (IRF1). Both genes are located in the celiac2 region, and have key roles in inducing interferon (IFN)-gamma secreting T helper 1 (Th1) cells, one of the immunological hallmarks of CD. The frequencies of a TaqI gene polymorphism in the 3' UTR of IL12B and a HinfI gene polymorphism in the 3' UTR of IRF1 were studied in 258 Dutch CD patients and 237 ethnically matched healthy controls. The transmission of the polymorphic variants from parents to affected child was determined in 123 families with at least one affected child. The frequencies of the IL12B TaqI gene polymorphism and the IRF1 HinfI gene polymorphism did not differ significantly between patients and controls. In addition, in the family study, no deviation from the expected transmission from parents to affected child of any of the polymorphic variants was found. The IL12B TaqI and the IRF1 HinfI gene polymorphisms do not appear to be involved in susceptibility to CD. Further studies on the factors that drive the Th1 immunopathology in CD are required.

Hypogalactosylation of serum IgG in patients with coeliac disease

Coeliac disease (CD) is described as an autoimmune enteropathy associated with the presence of IgG and IgA antigliadin and antitransglutaminase autoantibodies. While of diagnostic significance, the role of these autoantibodies in the immunopathogenesis of CD is elucidated. An inappropriate T cell immune response to gluten is also involved in the pathogenesis of CD, as evidenced by autoantibody switching. The N-glycans released from serum IgG of CD patients and three groups of healthy controls, of differing age ranges, were analysed by NH2-high performance liquid chromatography (HPLC). The fucosylated biantennary N- glycans were the most abundant neutral oligosaccharides; in particular, the agalacto form (G0F) showed a mean value of 42% (s.d. +/- 7.4), 30% (s.d. +/- 5.9), 26% (s.d. +/- 4.2) and 35% (s.d. +/- 6.8) for CD patients, healthy children, healthy adults under 40 and healthy adults over 40 years old, respectively. The ratio of asialo agalacto fucosylated biantenna to asialo monogalacto fucosylated biantenna (G0F)/(G1F) for CD patients showed a significant increase compared to healthy children (P < 0.0002), healthy adults under 40 (P < 0.0002) and healthy adults over 40 years old (P < 0.01). Hypogalactosylation was more pronounced for CD patients than for the patients with other autoimmune diseases such as rheumatoid arthritis or psoriatic arthritis.

The molecular basis of celiac disease

Celiac disease is caused by inflammatory, gluten specific T cell responses in the small intestine. Invariably such responses are HLA-DQ2 or HLA-DQ8 restricted, providing an explanation for the strong association between celiac disease and these HLA-class II alleles. It is now clear that some native gluten sequences can bind to HLA-DQ2/8 and induce T cell responses. In addition, modification of gluten peptides by the enzyme tissue transglutaminase results in high affinity HLA-DQ2/8 binding peptides that can induce T cell responses. Thus, gluten molecules contain a large number of immunogenic peptides and this is likely to play an important role in the breaking of oral tolerance to gluten.

Circular dichroism and nuclear magnetic resonance spectroscopic analysis of immunogenic gluten peptides and their analogs

Celiac Sprue, or gluten-sensitive enteropathy, is an inheritable human disease of the small intestine that is triggered by the dietary intake of gluten. Recently, several Pro- and Gln-rich peptide sequences (most notably PQPQLPY and analogs) have been identified from gluten with potent immunogenic activity toward CD4(+) T cells from small intestinal biopsies of Celiac Sprue patients. These peptides have three unusual properties. First, they are relatively stable toward further proteolysis by gastric, pancreatic, and intestinal enzymes. Second, they are recognized and deamidated by human tissue transglutaminase (tTGase) with high selectivity. Third, tTGase-catalyzed deamidation enhances their affinity for HLA-DQ2, the disease-specific class II major histocompatibility complex heterodimer. In an attempt to seek a mechanistic explanation for these properties, we undertook secondary structural studies on PQPQLPY and its analogs. Circular dichroism studies on a series of monomeric and dimeric analogs revealed a strong polyproline II helical propensity in a subset of them. Two-dimensional nuclear magnetic resonance spectroscopic analysis confirmed a polyproline II conformation of PQPQLPY, and was also used to elucidate the secondary structure of the most helical variant, (D-P)QPQLPY. Remarkably, a strong correlation was observed between polyproline II content of naturally occurring gluten peptides and the specificity of human tTGase toward these substrates. Analogs with up to two D-amino acid residues retained both polyproline II helical content and transglutaminase affinity. Since the Michaelis constant (K(m)) is the principal determinant of tTGase specificity for naturally occurring gluten peptides and their analogs, our results suggest that the tTGase binding site may have a preference for polyproline II helical substrates. If so, these insights could be exploited for the design of selective small molecule inhibitors of this pharmacologically important enzyme.

Endocrinological disorders and celiac disease

Celiac disease is a permanent intolerance to dietary gluten. Its well known features are abdominal symptoms, malabsorption of nutrients, and small-bowel mucosal inflammation with villous atrophy, which recover on a gluten-free diet. Diagnosis is challenging in that patients often suffer from subtle, if any, symptoms. The risk of clinically silent celiac disease is increased in various autoimmune conditions. The endocrinologist, especially, should maintain high suspicion and alertness to celiac disease, which is to be found in 2-5% of patients with insulin-dependent diabetes mellitus or autoimmune thyroid disease. Patients with multiple endocrine disorders, Addison's disease, alopecia, or hypophysitis may also have concomitant celiac disease. Similar heredity and proneness to autoimmune conditions are considered to be explanations for these associations. A gluten-free diet is essential to prevent celiac complications such as anemia, osteoporosis, and infertility. The diet may also be beneficial in the treatment of the underlying endocrinological disease; prolonged gluten exposure may even contribute to the development of autoimmune diseases. The diagnosis of celiac disease requires endoscopic biopsy, but serological screening with antiendomysial and antitissue transglutaminase antibody assays is an easy method for preliminary case finding. Celiac disease will be increasingly detected provided the close association with autoimmune endocrinological diseases is recognized.

New developments in childhood celiac disease

Celiac disease (CD) is one of the most common lifelong disorders in Europe and the United States, in both children and adults. It is an immune-mediated enteropathy triggered by the ingestion of gluten in genetically susceptible individuals. This review addresses new developments in CD with respect to pediatric patients and emphasizes the need for awareness among health-care professionals. The epidemiology, pathophysiology, diagnosis, and clinical spectrum of CD in children are highlighted.

Molecular properties of HLA-DQ alleles conferring susceptibility to or protection from insulin-dependent diabetes mellitus: keys to the fate of islet beta-cells

The major histocompatibility complex Class II alleles, HLA-DQ, and the related HLA-DR, are the chief genetic elements of human type 1 diabetes. These genes code for polymorphic heterodimeric proteins, whose chief function is to trap peptide antigens in the endosome and present them on the surface of antigen-presenting cells (dendritic cells, B lymphocytes, monocytes/macrophages) to CD4(+) T helper cells. A systematic investigation of the molecular properties of HLA-DQ alleles linked to susceptibility or resistance to type 1 diabetes has shown that these properties segregate along lines of susceptibility or resistance. A correlation of these features with the function of each particular segment of the HLA-DQ molecule yields interesting insights into the possible pathways leading to type 1 diabetes. There remain, however, areas to be clarified, including mechanisms by which dominant protection is conferred by certain alleles, the interplay between HLA-DQ and the related locus HLA-DR, that also shows autoantigen-specific reactivity, and the cross-Class help delivered to CD8(+) T cells, the final effectors in pancreatic beta-cell destruction. Clarification of these issues may lead to ways to prevent diabetes in predisposed individuals already exhibiting the genetic and immunological characteristics, and perhaps a cure in those with the disease, by means of transplantation, and measures for prevention of disease recurrence.