Managing Cardiovascular Risk in Patients with Autoimmune Diseases: Insights from a Nutritional Perspective

PURPOSE OF REVIEW

Autoimmune diseases manifest as an immune system response directed against endogenous antigens, exerting a significant influence on a substantial portion of the population. Notably, a leading contributor to morbidity and mortality in this context is cardiovascular disease (CVD). Intriguingly, individuals with autoimmune disorders exhibit a heightened prevalence of CVD compared to the general population. The meticulous management of CV risk factors assumes paramount importance, given the current absence of a standardized solution to this perplexity. This review endeavors to address this challenge from a nutritional perspective.

RECENT FINDINGS

Emerging evidence suggests that inflammation, a common thread in autoimmune diseases, also plays a pivotal role in the pathogenesis of CVD. Nutritional interventions aimed at reducing inflammation have shown promise in mitigating cardiovascular risk. The integration of nutritional strategies into the management plans for patients with autoimmune diseases offers a holistic approach to reducing cardiovascular risk. While conventional pharmacological treatments remain foundational, the addition of targeted dietary interventions can provide a complementary pathway to improve cardiovascular outcomes.

Reaction of Lectin-Specific Antibody with Human Tissue: Possible Contributions to Autoimmunity

The aim of this study was to examine the direct reaction of specific lectin/agglutinin antibodies to different tissue antigens to confirm the theory that reactivity between them may contribute to autoimmunities. Lectins are carbohydrate-binding proteins found in nearly all fruits and vegetables. Undigested lectins can penetrate the gut barriers, provoking an immune response that results in the production of antibodies against them. Using an enzyme-linked immunosorbent assay, we reacted lectin-specific antibodies with 62 different tissue antigens. Wheat germ agglutinin-specific antibody was the most reactive with the tissue antigens (37 tissues out of 62), followed by red kidney bean phytohemagglutinin-specific antibody (20), soybean agglutinin-specific antibody (20), and peanut agglutinin-specific antibody (15). This reaction between anti-lectin antibodies and many human tissue antigens may be due to possible molecular mimicry and cross-reactivity. After our results confirmed that anti-lectin antibodies bind with human tissues, we wanted to determine the prevalence of these antibodies in the blood of 500 nominally healthy donors. The percentage elevation of antibodies against different lectins ranged from 12 to 16% (Immunoglobulin G), 9.7-14.7% (Immunoglobulin A), 12-18% (Immunoglobulin M), and 7.8-14.6% (Immunoglobulin E). Serial dilutions and inhibition study confirmed that these reactions were specific. Finally, we tested the lectin-specific antibody level in sera both negative and positive for RF and ANA and found that IgM anti-lectin antibody levels were highly correlated with RF but not with ANA level. The reaction of anti-lectin antibodies with human tissue components and their detection in RF-positive samples may describe mechanisms by which the production of antibodies against undigested lectins may contribute to the pathogenesis of some autoimmune diseases.

Interaction between food antigens and the immune system: Association with autoimmune disorders

It has been shown that environmental factors such as infections, chemicals, and diet play a major role in autoimmune diseases; however, relatively little attention has been given to food components as the most prevalent modifiers of these afflictions. This review summarizes the current body of knowledge related to different mechanisms and associations between food proteins/peptides and autoimmune disorders. The primary factor controlling food-related immune reactions is the oral tolerance mechanism. The failure of oral tolerance triggers immune reactivity against dietary antigens, which may initiate or exacerbate autoimmune disease when the food antigen shares homology with human tissue antigens. Because the conformational fit between food antigens and a host's self-determinants has been determined for only a few food proteins, we examined evidence related to the reaction of affinity-purified disease-specific antibody with different food antigens. We also studied the reaction of monoclonal or polyclonal tissue-specific antibodies with various food antigens and the reaction of food-specific antibodies with human tissue antigens. Examining the assembled information, we postulated that chemical modification of food proteins by different toxicants in food may result in immune reaction against modified food proteins that cross-react with tissue antigens, resulting in autoimmune reactivity. Because we are what our microbiome eats, food can change the gut commensals, and toxins can breach the gut barrier, penetrating into different organs where they can initiate autoimmune response. Conversely, there are also foods and supplements that help maintain oral tolerance and microbiome homeostasis. Understanding the potential link between specific food consumption and autoimmunity in humans may lay the foundation for further research about the proper diet in the prevention of autoimmune diseases.

A combined biochemical, biophysical and immunological approach towards the identification of celiac disease-specific wheat antigens

Celiac disease (CD) is an inflammatory affliction of the small bowel caused by an immunological hypersensitivity to ingested wheat antigens affecting almost 1 % of the population. The gliadin fraction of wheat has been shown to contain the pathogenic antigens which react with antibodies and T cells. However, there is only limited knowledge regarding the precise nature of the wheat antigens recognized by IgA antibodies from CD patients and diagnostic tests based on the gliadin fraction have been demonstrated to give frequently false positive results. The aim of this study was the characterization of wheat antigens specifically recognized by IgA antibodies of CD patients. We developed a combined biochemical, biophysical, and immunological approach for the identification of celiac disease-specific wheat antigens. It is based on sub-fractionation of the wheat gliadin fraction using two ion exchange chromatography steps, the localization of CD-specific antigens by immunoblotting with IgA antibodies from CD patients, subsequent digestion followed by electro spray ionization-liquid chromatography/mass spectrometry (LC-ESI-MS/MS) and N-terminal sequencing by Edman degradation. Through the sub-fractionation procedure it was possible to separate CD-specific IgA-reactive wheat antigens from other wheat antigens which were also recognized by IgA antibodies of individuals without CD or by CD patients on gluten-free diet. Analysis by LC-ESI-MS/MS and N-terminal sequencing of the sub-fractions and the proteins specifically recognized by CD patients identified certain γ-gliadins with molecular mass of 37,000 and 45,000 as CD-specific wheat antigens. The CD-specific γ-gliadins with the molecular mass of 37,000 and 45,000 should be useful to study pathomechanisms of the disease and to improve the specificity of diagnostic tests for CD.

Nuclear fluorescence serum reactivity on monkey oesophagus: a new antibody for the follow-up of coeliac disease?

We have identified previously a nuclear fluorescence reactivity (NFR) pattern on monkey oesophagus sections exposed to coeliac disease (CD) patients' sera positive for anti-endomysium antibodies (EMA). The aim of the present work was to characterize the NFR, study the time-course of NFR-positive results in relation to gluten withdrawal and evaluate the potential role of NFR in the follow-up of CD. Twenty untreated, 87 treated CD patients and 15 healthy controls were recruited and followed for 12 months. Their sera were incubated on monkey oesophagus sections to evaluate the presence of NFR by indirect immunofluorescence analysis. Duodenal mucosa samples from treated CD patients were challenged with gliadin peptides, and thus the occurrence of NFR in culture supernatants was assessed. The NFR immunoglobulins (Igs) reactivity with the nuclear extract of a human intestinal cell line was investigated. Serum NFR was present in all untreated CD patients, persisted up to 151 ± 37 days from gluten withdrawal and reappeared in treated CD patients under dietary transgressions. Serum NFR was also detected in two healthy controls. In culture supernatants of coeliac intestinal mucosa challenged with gliadin peptides, NFR appeared before EMA. The Igs responsible for NFR were identified as belonging to the IgA2 subclass. The NFR resulted differently from EMA and anti-nuclear antibodies, but reacted with two nuclear antigens of 65 and 49 kDa. A new autoantibody, named NFR related to CD, was described. Furthermore, NFR detection might become a valuable tool in monitoring adherence to a gluten-free diet and identifying slight dietary transgressions.

The Immunology of Gluten Sensitivity beyond the Intestinal Tract

Celiac disease and gluten-sensitive enteropathy are terms that have been used to refer to a disease process affecting the small bowel. However, evidence has been accumulated in literature demonstrating that gluten sensitivity or celiac disease can exist even in the absence of enteropathy, but affecting many organs. Based on overwhelming evidence, immunological pathogenesis has been demonstrated in the joint, the heart, thyroid, bone, and, in particular, the brain cerebellum and neuronal synapsin I. When blood samples of patients with celiac disease are tested against gliadin and different tissue antigens, in addition to gliadin antibody, a significant percentage of them exhibit elevation in antibodies against transglutaminase, heat shock protein, collagen, thyroid, myosin, endothelial cell, bone antigen (transglutaminase), myelin basic protein, cerebellar and synapsin. This elevation of autoantibodies in patients with celiac disease may result in neuroimmune disorders. In fact, in comparison to the general population, the incidence of various autoimmune disorders, including gluten ataxia, is increased up to 30-fold in patients with celiac disease. Therefore, immune evaluation of patients with gluten sensitivity or celiac disease, in addition to gliadin and transglutaminase, should include antibody measurement against thyroglobulin, thyroid peroxidase, heat shock protein, bone transglutaminase, myelin basic protein, cerebellar peptide and synapsin. This novel laboratory approach to gluten sensitivity and autoimmunity may enable clinicians to detect markers of autoimmune diseases. Early identification of gluten sensitive and celiac disease patients and implementation of a gluten-free diet may result in significant improvement and control of associated diseases.

Deamidated gliadin peptides form epitopes that transglutaminase antibodies recognize

OBJECTIVE

Deamidated gliadin peptides are efficient antigens in diagnostic tests for celiac disease, and results correlate better with transglutaminase 2-based assays than those with native gliadin. We investigated whether deamidated gliadin antigens are structurally similar to transglutaminase 2 or could mimic transglutaminase epitopes.

PATIENTS AND METHODS

Serum samples from 74 celiac and 65 control patients, and 13 different transglutaminase 2-specific monoclonal mouse antibodies were investigated for their binding to commercially available deamidated gliadin peptides using enzyme-linked immunosorbent assay, competition studies, and molecular modelling.

RESULTS

The enzyme-linked immunosorbent assay with deamidated gliadin peptides had 100% sensitivity and 98.5% specificity in patients. Deamidated gliadin epitopes also were recognized by 3 transglutaminase-specific monoclonal antibodies, and antibodies affinity-purified with deamidated gliadin peptides from celiac patient sera reacted with transglutaminase but did not show endomysial binding. The binding of the monoclonal antibodies to deamidated gliadin was inhibited dose dependently by full-length recombinant human transglutaminase, its fragments containing the binding sites of these monoclonal antibodies, or by celiac patient antibodies. Deamidated gliadin peptides decreased the binding of transglutaminase-specific monoclonal antibodies to transglutaminase. Three different cross-reacting transglutaminase epitopes were found, of which 2 are located in the C-terminal domain and 1 is conformational. The binding of celiac serum samples to deamidated gliadin peptides could not be abolished by transglutaminase or by any of the transglutaminase-specific monoclonals, indicating that celiac sera also contain additional antibodies to gliadin epitopes different from transglutaminase.

CONCLUSIONS

Certain deamidated gliadin-derived peptides and transglutaminase 2 epitopes have similar 3-dimensional appearance. This homology may contribute to the induction of transglutaminase autoantibodies by molecular mimicry.

Associated autoantibodies in celiac disease

Celiac disease (CD) is a life-long inflammatory autoimmune condition of the gastrointestinal tract affecting genetically susceptible individuals. Several autoimmune disorders are more prevalent in patients and their close relatives and that risk is gluten exposure duration related. The most frequent reported CD associated conditions are type 1 diabetes mellitus and autoimmune thyroiditis. Associated autoimmune antibodies are frequent in CD and their first-degree relatives, spanning anti-endocrine, anti-gastrointestinal, anti-nuclear, anti-cytoskeleton and anti-neurological antibodies. More specifically, antibodies against thyroid and the endocrine pancreas, anti-gastric and liver, anti-nuclear constituents, anti-reticulin, actin, smooth muscle, calreticulin, desmin, collagens and bone, anti-brain, ganglioside, neuronal and blood vessel were described in sera of the patients in numerous studies. The common immunogenetic theories for the above associations are: sharing common HLA and non-HLA genes, antigenic mimicry, damage-induced neoantigen exposure, altered intestinal permeability, idiotype network dysregulation and epitope spreading. The CD associated autoantibodies enigma, being an epiphenomenon or pathogenic, remains unresolved and presents a challenging area for future research.

Transglutaminase-independent binding of gliadin to intestinal brush border membrane and GM1 ganglioside

Anti-ganglioside antibodies have been described in celiac disease or gluten sensitivity, in conjunction with the presence of central and peripheral nervous system deficits. The observed antibody reactivity to gangliosides is postulated to be related to the anti-gliadin immune response, either through antigenic mimicry, or by formation of gliadin-ganglioside complexes and haptenization. We examined the possibility of the presence of ganglioside-like epitopes in gliadin, as well as the potential for complex formation between gliadin and GM1 ganglioside. Low levels of glycosylation were present in gliadin, but ganglioside-like carbohydrate epitopes were not detected. However, gliadin was found to bind to GM1 ganglioside and to the GM1-rich intestinal brush border membrane. The described complex formation and possible haptenization of GM1 by gliadin may be responsible for driving the anti-ganglioside antibody response in some patients with gluten sensitivity. Furthermore, binding of gliadin to GM1 on the intestinal epithelium might have a role in the anti-gliadin immune response and contribute to the intestinal inflammatory reaction in celiac disease.

Different profiles of wheat antigens are recognised by patients suffering from coeliac disease and IgE-mediated food allergy

BACKGROUND

Dietary intake of wheat can cause two distinct immunologically mediated diseases with severe gastrointestinal manifestations, coeliac disease (CD) and IgE-mediated food allergy. The pathomechanisms underlying these diseases are different, but the profile of the target antigens in wheat has not been compared for the two diseases.

METHODS

We compared IgA- and IgE-reactive antigens in wheat using sera from patients with coeliac disease (n = 35) and food allergy to wheat (n = 16) by one- and two-dimensional immunoblotting. Furthermore, the IgG subclass (IgG1-IgG4) reactivity to wheat antigens was studied by enzyme-linked immunosorbent assay.

RESULTS

IgA antibodies from CD patients and IgE antibodies from allergic patients recognised distinct profiles of wheat antigens. Furthermore, the IgG subclass responses to wheat antigens were different in CD and wheat-allergic patients.

CONCLUSION

This study thus demonstrates that wheat contains antigens/epitopes which are preferentially recognised by CD patients, whereas others elicit IgE-mediated food allergy. This finding suggests that the nature of a food antigen may influence the quality of the pathological immune response in the gut and has implications for the diagnosis and therapy of hypersensitivity to wheat.

Celiac disease associated with autoimmune myocarditis

BACKGROUND

Both celiac disease (CD) and myocarditis can be associated with systemic autoimmune disorders; however, the coexistence of the 2 entities has never been investigated, although its identification may have a clinical impact.

METHODS AND RESULTS

We screened the serum of 187 consecutive patients with myocarditis (118 males and 69 females, mean age 41.7+/-14.3 years) for the presence of cardiac autoantibodies, anti-tissue transglutaminase (IgA-tTG), and anti-endomysial antibodies (AEAs). IgA-tTG-positive and AEA-positive patients underwent duodenal endoscopy and biopsy and HLA analysis. Thirteen of the 187 patients were positive for IgA-tTG, and 9 (4.4%) of them were positive for AEA. These 9 patients had iron-deficient anemia and exhibited duodenal endoscopic and histological evidence of CD. CD was observed in 1 (0.3%) of 306 normal controls (P<0.003). In CD patients, myocarditis was associated with heart failure in 5 patients and with ventricular arrhythmias (Lown class III-IVa) in 4 patients. From histological examination, a lymphocytic infiltrate was determined to be present in 8 patients, and giant cell myocarditis was found in 1 patient; circulating cardiac autoantibodies were positive and myocardial viral genomes were negative in all patients. HLA of the patients with CD and myocarditis was DQ2-DR3 in 8 patients and DQ2-DR5(11)/DR7 in 1 patient. The 5 patients with myocarditis and heart failure received immunosuppression and a gluten-free diet, which elicited recovery of cardiac volumes and function. The 4 patients with arrhythmia, after being put on a gluten-free diet alone, showed improvement in the arrhythmia (Lown class I).

CONCLUSIONS

A common autoimmune process toward antigenic components of the myocardium and small bowel can be found in >4% of the patients with myocarditis. In these patients, immunosuppression and a gluten-free diet can be effective therapeutic options.

IgA autoreactivity: a feature common to inflammatory bowel and connective tissue diseases

The immunopathogenic mechanisms in inflammatory bowel disease (IBD) are not yet fully established. The aim of this study was to determine the profile and magnitude of IgA and IgG autoantibodies in IBD patients. The autoantigen profile defined by IgA and IgG antibodies from 24 IBD (14 Crohn's disease CD], 10 ulcerative colitis UC]), three coeliac, 12 connective tissue disease (CTD) patients and 10 healthy individuals was studied in human cellular extracts by Western blotting. The magnitude of the IgA and IgG1-4 subclass responses was measured by ELISA. IBD patients could not be distinguished from healthy individuals on the basis of IgG autoantibodies to Western blotted proteins. IgG subclass analysis indicated no clear bias towards Th1 or Th2 immune responses in IBD or CTD. In accordance with previous work, we found that IgA autoreactivity was strongest in coeliac disease patients. Unexpectedly, IBD as well as CTD patients exhibited strong IgA autoantibody reactivities to components of similar molecular weights (16-80 kD) in intestinal and non-intestinal epithelial cell lines. Our data indicate immunopathogenic similarities between IBD and CTD.

Increased levels of IgA antibodies against desmin in children with coeliac disease

BACKGROUND

In addition to IgA anti-endomysial antibodies, IgA anti-smooth muscle antibodies have been observed in a number of patients with coeliac disease (CoD), but only limited data exist on the frequency and antigen specificity of IgA against cytoskeletal proteins in CoD.

METHODS

We evaluated the sera of 42 untreated CoD patients, follow-up sera of 26 CoD patients after treatment, and 116 control sera for IgA reactivity to cytoskeletal proteins from the human umbilical cord (HUC) by immunoblotting, and compared the results with anti-tissue transglutaminase IgA (anti-tTG IgA) ELISA and immunofluorescence results.

RESULTS

Serum IgA from CoD patients most frequently recognized a 57-kD antigen in HUC cytoskeletal extract, identified as desmin using mass spectrometry and internal peptide sequencing. Increased IgA reactivity to the human desmin band was detected in 22 children with untreated CoD (52.4%), in 4 treated CoD patients (15.4%), and in 12 control subjects (10.3%) (p < 0.01); similar results were obtained with anti-chicken desmin IgA ELISA. Anti-tTG IgA levels (increased in 71.4% of untreated CoD patients) correlated significantly with anti-desmin IgA levels in untreated CoD, and both autoantibody reactivities decreased in response to a gluten-free diet. Pre-adsorption experiments and affinity purification of anti-desmin IgA antibodies further confirmed that desmin is an IgA autoantigen in CoD and is recognized by antibodies which are not cross-reactive with tTG.

CONCLUSIONS

Anti-desmin IgA antibodies are frequently occurring if not the predominant cytoskeletal antibodies in children with untreated CoD and could be related to the disease process in the small intestine.