Hypothesis revisited: toothpaste and the cause of Crohn's disease

Trajectories in nanotechnology: embracing complexity, seeking analogies

This account comprises personal reflections on the field of nanosystems primarily designed for the delivery of biologically active agents. It emphasises the colloidal nature of nanoparticles obeying the same physical laws that dictate the behaviour of disperse systems. Research reveals not only intrinsic complexities but a variety of possible trajectories in vivo and ex vivo, issues of stability, interactions and behaviour in a range of often constrained environments. Such are the variations in the chemical and physical nature of the nanosystems and the active agents they carry, their putative "targets" and the many biological systems and models in which they are employed, it is not possible to generalise. Stochastic events may exclude precise prediction or extrapolation of outcomes, but embracing and studying complexity lead to new insights, often aided by consideration of analogies in cognate areas. This is part of the process of illumination. Unexpected results provide the true essence and excitement of scientific endeavour. Simplification is perhaps its antithesis.

Crohn's disease and environmental contamination: Current challenges and perspectives in exposure evaluation

Although the incidence of Crohn's disease has increased worldwide over the past 30 years, the disorder's exact causes and physiological mechanisms have yet to be determined. Given that genetic determinants alone do not explain the development of Crohn's disease, there is growing interest in "environmental" determinants. In medical science, the term "environment" refers to both the ecological and social surroundings; however, most published studies have focused on the latter. In environmental and exposure sciences, the term "environment" mostly relates to contamination of the biotope. There are many unanswered questions on how environmental hazards might contribute to the pathogenesis of Crohn's disease. Which pollutants should be considered? Which mechanisms are involved? And how should environmental contamination and exposure be evaluated? The objective was to perform a systematic review of the literature on Crohn's disease and environmental contamination. We searched the PubMed, Google Scholar, Scopus, ISI Web of Science and Prospero databases. We considered all field studies previous to April 2019 conducted on human health indicators, and evaluating exposure to all type of physical, biological and chemical contamination of the environment. The lack of clear answers to date can be ascribed to the small total number of field studies (n = 16 of 39 publications, most of which were conducted by pioneering medical scientists), methodological differences, and the small number of contaminants evaluated. This make it impossible to conduct a coherent and efficient meta-analysis. Based on individual analysis of available studies, we formulated five recommendations on improving future research: (i) follow up the currently identified leads - especially metals and endocrine disruptors; (ii) explore soil contamination; (iii) gain a better knowledge of exposure mechanisms by developing transdisciplinary studies; (iv) identify the most plausible contaminants by developing approaches based on the source-to-target distance; and (v) develop registries and cohort-based analyses.

History of Inflammatory Bowel Disease and Self-Reported Oral Health: Women's Health Initiative Observational Study

Background and Objective: Both periodontal disease and inflammatory bowel disease (IBD), are chronic inflammatory conditions, which are mediated by a complex interplay among a dysbiotic microbiota, dysregulated host immune-inflammatory responses, and lifestyle factors. Despite substantial differences in physical and chemical environments, rather strong correlations have been detected between microbial compositions of the oral cavity and stool. In this study, we tested the hypothesis that oral health conditions are affected by the presence of IBD. Materials and Methods: We analyzed the data from 73,621 women who were enrolled in the Women's Health Initiative observational cohort study and completed a follow-up questionnaire that surveyed oral health status specifically at year 5. Among these, 880 reported IBD at the baseline, including 47% who were symptomatic cases and 27% who were on immunosuppressive treatment. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) for the association of IBD and medication status for self-reported oral health outcomes, using logistic regression models, adjusted for selected covariates. Results: IBD was not associated with periodontal disease history itself in a multivariable model; however, poorer self-rated oral health was modestly associated with the presence of IBD (OR = 1.15, 95% CI: 1.01-1.30). Likewise, more frequent eating limitations due to teeth were associated with the presence of IBD history (OR = 1.22, 95% CI: 1.07-1.39). When IBD cases were limited to those who were symptomatic, the associations with these two self-rated oral health outcomes were more pronounced with ORs of 1.28 (95% CI: 1.07-1.54) and 1.36 (95% CI: 1.07-1.54), respectively. Immunosuppressive treatment had little effect on these risk estimates. Conclusions: Among this nation-wide cohort of women 50-79 years of age, history of IBD was associated with poorer perceived oral health status.

Development and Validation of Surveys to Estimate Food Additive Intake

(1) Background: The Food Agricultural Organization/World Health Organization (FAO/WHO) International Food Standards Codex Alimentarius CXS 192e International Food Standards (hereafter, CODEX) declares additives non-toxic, but they have been associated with changes to the microbiota changes and thinning of the mucus layer of the gut. Their widespread use has occurred in parallel with increased inflammatory bowel disease (IBD) incidence. This paper reports on the development and validation of surveys to estimate additive intake. (2) Methods: Dietitians created a food-additive database, with a focus on additives that have been associated with IBD. For each additive, information on the CODEX food-category they are permitted in and the associated maximum permissible levels (mg/kg) was recorded. Based on the database, questions to assess early life (part 1) and recent (part 2) additive intake were written. Forward–backward translation from English to Chinese was undertaken. Thirty-one individuals were evaluated to assess understandability. A further fifty-seven individuals completed the tool on two occasions, a fortnight apart; agreement was assessed using Cohen’s kappa coefficient or the intra-class correlation coefficient (ICC). (3) Results: The participants reported that it was difficult to remember food intake and estimate portion sizes. The participants also noted confusion around the term ‘home-grown’. Instructions and definitions were added; after this, respondents judged the questionnaires as clear. The average kappa coefficient for part 1 and part 2 questions were 0.61 and 0.67, respectively. The average ICC ranged from 0.30 to 0.94; three food lists were removed due to low reliability. (4) Conclusions: Two tools have been created and validated, in two languages, that reliably assess remote and recent food additive intake.

Urban-rural environmental exposure during childhood and subsequent risk of inflammatory bowel disease: a meta-analysis

BACKGROUND

The relationship between living conditions in urban and rural areas during childhood and subsequent inflammatory bowel disease (IBD) remains controversial.

AIM

To explore the association between environmental exposures early in life and the subsequent risk of IBD.

METHODS

Literature searches were conducted in the following databases: PubMed, EMBASE, and Conference Proceedings Citation Index. Studies were analyzed separately using rate ratios (RRs) or odds ratios (ORs) with 95% confidence intervals.

RESULTS

The search strategy identified 15 studies. Of these, 9 studies explored the association between urban exposure during childhood and ulcerative colitis (UC), and 12 and 4 studies explored this relationship with Crohn's disease (CD) and IBD, respectively. A meta-analysis showed that the pooled ORs estimated for the case-control studies of UC, CD, and IBD were 1.16 (0.83, 1.61), 1.45 (1.45, 1.85), and 1.34 (1.11, 1.62), respectively. The pooled RR estimated for the cohort studies of CD and IBD was 1.48 (1.17, 1.87). The stratified analysis and meta-regression showed significant relationships between CD and living conditions in case-control studies published during 2010-2017 and in non-European countries (P < 0.05).

CONCLUSIONS

Living conditions during childhood are positively associated with the subsequent development of IBD. Urban living environment is more common among those with CD than UC.

Urbanization and the gut microbiota in health and inflammatory bowel disease

In the 21st century, urbanization represents a major demographic shift in developed and developing countries. Rapid urbanization in the developing world has been associated with an increasing incidence of several autoimmune diseases, including IBD. Patients with IBD exhibit a decrease in the diversity and richness of the gut microbiota, while urbanization attenuates the gut microbial diversity and might have a role in the pathogenesis of IBD. Environmental exposures during urbanization, including Westernization of diet, increased antibiotic use, pollution, improved hygiene status and early-life microbial exposure, have been shown to affect the gut microbiota. The disparate patterns of the gut microbiota composition in rural and urban areas offer an opportunity to understand the contribution of a 'rural microbiome' in potentially protecting against the development of IBD. This Perspective discusses the effect of urbanization and its surrogates on the gut microbiome (bacteriome, virome, mycobiome and helminths) in both human health and IBD and how such changes might be associated with the development of IBD.

Gastrointestinal diseases and their oro-dental manifestations: Part 1: Crohn's disease

Widely varying prevalence rates of oral lesions in patients with Crohn's disease have been reported, ranging from 0.5% to 37%. These manifestations may coincide with or precede intestinal symptoms. Oral manifestations can be classified as specific lesions, when macroscopic examination shows similar changes to those observed endoscopically in the intestine, and non-specific lesions including aphthous ulcerations. The most frequently observed oral lesions are oedema, ulcers and hyperplastic lesions on the buccal mucosa. In most patients these lesions are asymptomatic, however, some patients may experience discomfort. In this review we describe the most relevant oro-dental manifestations observed in patients with Crohn's disease and discuss the potential implications for oro-dental management.

Inverse Association Between Poor Oral Health and Inflammatory Bowel Diseases

BACKGROUND & AIMS

The hygiene hypothesis (a lack of childhood exposure to microorganisms increases susceptibility to allergic diseases by altering immune development) has been proposed as an explanation for the increasing incidence of inflammatory bowel disease (IBD). However, there are few data on the relationship between oral hygiene and development of IBD, and study results have been inconsistent. We investigated the association between poor oral health and risks of IBD, ulcerative colitis (UC), and Crohn's disease (CD).

METHODS

We performed a population-based cohort study of 20,162 individuals followed for 40 years (from 1973 to 2012). Residents of 2 municipalities of Uppsala County, Sweden (N = 30,118), 15 years or older, were invited, and among them 20,333 were examined for tooth loss, dental plaques, and oral mucosal lesions at the time of study entry. Other exposure data were collected from questionnaires. Patients who later developed IBD (UC or CD) were identified by international classification codes from Swedish National Patient and Cause of Death Registers. Cox proportional hazards regression was used to estimate hazard ratios for IBD, UC, and CD.

RESULTS

From National Patient and Cause of Death Registers, we identified 209 individuals who developed IBD (142 developed UC and 67 developed CD), with an incidence rate of 37.3 per 100,000 person-years. We found an inverse relationship between poor oral health and IBD, especially in individuals with severe oral problems. Loss of 5-6 teeth of the 6 teeth examined was associated with a lower risk of IBD (hazard ratio, 0.56; 95% confidence interval, 0.32-0.98). Having dental plaques that covered more than 33% of tooth surface was negatively associated with CD (hazard ratio, 0.32; 95% confidence interval, 0.10-0.97).

CONCLUSIONS

In a population-based cohort study of more than 20,000 people in Sweden, we associated poor oral health with reduced risk of future IBD.

Fluoride: a risk factor for inflammatory bowel disease?

Although the association between inflammatory bowel disease (IBD) and oral hygiene has been noticed before, there has been little research on prolonged fluoride exposure as a possible risk factor. In the presented cases, exposure to fluoride seems indirectly associated with higher incidence of IBD. Fluoride toxicology and epidemiology documents frequent unspecific chronic gastrointestinal symptoms and intestinal inflammation. Efflux genes that confer resistance to environmental fluoride may select for IBD associated gut microbiota and therefore be involved in the pathogenesis. Together these multidisciplinary results argue for further investigation on the hypothesis of fluoride as a risk factor for IBD.

Dietary management of IBD--insights and advice

The current general interest in the use of food choice or diet in maintaining good health and in preventing and treating disease also applies to patients with IBD, who often follow poor or nutritionally challenging dietary plans. Unfortunately, dietary advice plays only a minor part in published guidelines for management of IBD, which sends a message that diet is not of great importance. However, a considerable evidence base supports a focused and serious attention to nutrition and diet in patients with IBD. In this Review, a step-wise approach in the evaluation and management of these patients is proposed. First, dietary intake and eating habits as well as current nutritional state should be documented, and corrective measures instituted. Secondly, dietary strategies as primary or adjunctive therapy for the reduction of inflammation and/or prevention of relapse of IBD should be seriously contemplated. Thirdly, use of diet to improve symptoms or lessen the effects of complications should be considered. Finally, dietary advice regarding disease prevention should be discussed when relevant. An increasing need exists for applying improved methodologies into establishing the value of current and new ways of using food choice as a therapeutic and preventive tool in IBD.

Frequency and risk factors of low immunoglobulin levels in patients with inflammatory bowel disease

Background and aims: Inflammatory bowel diseases (IBD) are considered to be dysregulated, immune-mediated disorders; and immunosuppressive medications are the mainstay of their treatment. Clinically, we have often observed low serum immunoglobulin (Ig) levels in these patients. The aim of this study was to assess the frequency and risk factors of secondary humoral immunodeficiency in IBD patients.

Methods: We conducted a cross-sectional study of eligible IBD patients with Crohn’s disease (CD), ulcerative colitis (UC), indeterminate colitis (IC) or restorative proctocolectomy with ileal pouch, who having serum Ig measured. Demographic and clinical variables were measured. Univariate and multivariate analyses were performed.

Results: A total of 324 patients was included, with a mean age of 38.8 years and 158 (48.8%) being male. Low IgG, IgG1, IgA, and IgM were found in 22.7%, 23.4%, 7.9%, and 10.9% of patients, respectively. The shared risk factors for a low IgG or IgM level were increasing age [odds ratio (OR) = 1.13; 95% confidence interval (CI) 1.03–1.23 for low IgG level and OR = 1.33; 95% CI 1.15–1.56 for low IgM level] and hypoalbuminemia (OR = 1.83; 95% CI 1.01–3.33 for low IgG level and OR = 3.17; 95% CI 1.23–8.15 for low IgM level). In addition, thioprine use was associated with low IgA level (OR = 2.76; 95% CI 1.03–7.39). IBD disease duration was a risk factor for low IgG1 level (OR = 1.40; 95% CI 1.12–1.76). The presence of concurrent primary sclerosing cholangitis (OR = 0.064; 95% CI 0.007–0.60) and the use of biologics (OR = 0.16; 95% CI 0.033–0.79) were associated with normal IgG1 level. IgG level was lower in CD patients than that in UC/IC and ileal pouch patients (P = 0.042). IgG and IgA levels were elevated in patients with inflammatory conditions of the pouch (P = 0.01; P = 0.003, respectively).

Conclusions: Low Ig level appears to be common in IBD patients. Increasing age, disease duration and hypoalbuminemia appeared to be risk factors. The findings may provide rationale for targeted therapy to boost humoral immunity in selected patients with IBD.

The role of oral hygiene in inflammatory bowel disease

BACKGROUND

The 'hygiene hypothesis' suggests that a reduction in the microbial exposure due to improved health measures has contributed to an immunological imbalance in the intestine and increased the incidence of autoimmune diseases such as inflammatory bowel diseases (IBD). Accordingly, we investigated associations between oral hygiene practices and IBD.

METHODS

We developed and administered a multiple choice questionnaire to evaluate oral hygiene and dental care practices of 137 subjects (83 with IBD and 54 healthy controls).

RESULTS

Of the 83 IBD cases, 31% had ulcerative colitis and 69% had Crohn's disease. For subjects with IBD, the frequency of brushing at disease onset was significantly higher than in controls (P=0.005). Also, the frequency of use of dental floss and breath freshener at disease onset was significantly higher in IBD patients (P=0.005 and<0.001, respectively). Also, patients with IBD more frequently visited their dentist at disease onset (P<0.001) and continued to visit their dentist more often (P<0.001). IBD cases had a higher frequency of dental complications such as tooth caries (P=0.007), oral ulcers (P=0.04) and dry mouth (P=0.001).

CONCLUSIONS

These findings suggest that oral hygiene practices may cause alterations in the flora of the oral mucosa, which causes imbalance in the gut microbiome (dysbiosis), and thereby contributes to the pathogenesis of IBD. Conversely, the increased frequency of dental problems in IBD patients might be due, at least in part, to alterations in oral flora or to their disease.

Does evidence exist to include dietary therapy in the treatment of Crohn's disease?

Prescription drugs and surgery are two common medical therapies for Crohn's disease (CD), an inflammatory bowel disease that affects the GI tract. Unfortunately, certain drugs can cause serious side effects, and surgeries must often be repeated. No diet has been established to alleviate the pain and suffering of CD patients. This is curious given the fact that a higher prevalence of food sensitivities exist in this population of patients, and enteral nutrition is not only the first-line of therapy in Japan, but a known research method used to place the majority of CD patients into remission. Although not all patients respond equally to diet, many simply remove symptom-provoking foods, such as dairy, wheat, corn and certain fruits and vegetables. We suggest assisting these patients in their self-assessment of irritating and symptom-provoking foods by educating them in the use of a food-symptom diary followed by a customized elimination diet trialed for 2-4 weeks to determine if there is any benefit to the individual patient.

Hygiene hypothesis in inflammatory bowel disease: A critical review of the literature

The hygiene hypothesis is thought to be a significant contributor to the growing incidence of inflammatory bowel disease (IBD) around the world, although the evidence for specific factors that underlie the hygiene hypothesis in IBD is unclear. We aimed to systematically review the literature to determine which hygiene-related factors are associated with the development of IBD. Publications identified from a broad based MEDLINE and Current Contents search between 1966 and 2007 on key terms relevant to the 'hygiene hypothesis' and IBD including H pylori exposure, helminths, cold chain hypothesis, measles infection and vaccination, antibiotic use, breastfeeding, family size, sibship, urban upbringing, day care attendance and domestic hygiene were reviewed. The literature suggests that the hygiene hypothesis and its association with decreased microbial exposure in childhood probably plays an important role in the development of IBD, although the strength of the supporting data for each of the factors varies considerably. The most promising factors that may potentially be associated with development of IBD include H pylori exposure, helminths, breastfeeding and sibship. However, the vast majority of studies in this area are plagued by serious methodological shortcomings, particularly the reliance on retrospective recall of information making it difficult to truly ascertain the importance of a 'hygiene hypothesis' in IBD. The 'hygiene hypothesis' in IBD is an important area of research that may give clues to the aetiology of this disease. Directions for future research are recommended.

Crohn's disease and its mucocutaneous involvement

Crohn's disease (CD) is a chronic inflammatory disorder primarily affecting the lower gastrointestinal tract but potentially involving the skin, musculoskeletal system, and eyes. The origin remains unknown, although diverse etiologic agents have been proposed. Characteristic pathologic appearances include the formation of "skip" lesions (discrete regions of inflamed bowel separated by uninvolved mucosae), aphthous ulceration, and fistulation; these signs relate to the presence of an underlying granulomatous transmural inflammation. Cutaneous and oral lesions frequently occur in CD. They may be classified as specific manifestations (in particular, perianal fissures, abscesses, sinuses, and fistulae in ano) with a granulomatous noncaseating inflammation on histologic examination, and nonspecific manifestations (eg, erythema nodosum, neutrophilic dermatoses) with a nonspecific histologic pattern. The diagnosis of CD is based on clinical, endoscopic, radiologic, and histopathologic features. Therapy is mainly aimed at the control of the acute disease and prevention of relapse through the use of mesalazine, corticosteroids, immunosuppressive agents and very recently, anti-tumor necrosis factor-alpha antibodies.

Past and current theories of etiology of IBD: toothpaste, worms, and refrigerators

While tremendous advances have improved the understanding of inflammatory bowel disease, with regard to environmental risk factors as well as the biochemical nature of the inflammatory process, a determination of primary etiology remains elusive. Numerous theories have been proposed in the past century concerning the cause of Crohn's disease and ulcerative colitis with implications for specific therapies. On further study, most of these ideas and therapies have failed to be accurate in theory or therapeutic approach. Others remain untested or are the focus of current investigation and controversy. This paper reviews the dominant theories of primary etiology. These hypotheses include infectious causes such as Mycobacteria paratuberculosis and measles. Allergic and nutritionally related causes have been the focus of considerable research. Microparticles, which is part of the concept behind toothpaste as a cause, have been suggested more broadly to be the principal factor initiating Crohn's disease. Several of these concepts rely on the idea that there is an increased intestinal permeability that is the central defect leading to Crohn's disease. Rather than being an excessive T cell driven process, Crohn's has been suggested to be an innate immune deficiency, leading to the use of colony stimulating factors to augment the intestinal barrier function and innate immunity. A variety of changes in the gut flora, ranging from a basic dysbiosis to the absence of helminths, have been proposed as the root cause of inflammatory bowel disease.

Dietary sources of inorganic microparticles and their intake in healthy subjects and patients with Crohn's disease

Dietary microparticles are non-biological, bacterial-sized particles. Endogenous sources are derived from intestinal Ca and phosphate secretion. Exogenous sources are mainly titanium dioxide (TiO2) and mixed silicates (Psil); they are resistant to degradation and accumulate in human Peyer's patch macrophages and there is some evidence that they exacerbate inflammation in Crohn's disease (CD). However, whether their intake differs between those with and without CD has not been studied. We aimed to identify dietary microparticle sources and intakes in subjects with and without CD. Patients with inactive CD and matched general practice-based controls (ninety-one per group) completed 7 d food diaries. Intake data for dietary fibre and sucrose were compared as positive controls. All foods, pharmaceuticals and toothpastes were examined for microparticle content, and intakes of Ca and exogenous microparticles were compared between the two groups. Dietary intakes were significantly different between cases and controls for dietary fibre (12 (SD 5) v. 14 (SD 5) g/d; P=0.001) and sucrose (52 (SD 27) v. 45 (SD 18) g/d; P=0.04) but not for Ca. Estimated median TiO2 and Psil intakes (2.5 and 35 mg/individual per d respectively, totalling 10(12)-10(13) microparticles/individual per d) were broadly similar to per capita estimates and while there was wide variation in intakes between individuals there was no significant difference between subjects with CD and controls. Hence, if exposure to microparticles is associated with the inflammation of CD, then the present study rules out excess intake as the problem. Nonetheless, microparticle-containing foods have now been identified which allows a low-microparticle diet to be further assessed in CD.

Environmental risk factors (excluding tobacco and microorganisms): critical analysis of old and new hypotheses

The increase in incidence in both ulcerative colitis and Crohn's disease during the 20th century has led to an abundance of different hypotheses on what sort of exposures are responsible. There has been a special focus on dietary factors, as well as on other exposures introduced on a population-based level, including fast food, cola drinks, toothpaste, antibiotics and oral contraceptives. The aim of this review is to critically assess the results from the different observational studies that have investigated these hypotheses, and also to propose research agendas that should be pursued in the future. The conclusion is that infectious exposures and early bacterial colonization, which are associated with better hygiene early in life and that influence immune function, and possibly oral contraceptives, remain the only exposures of interest for future research into the aetiology of ulcerative colitis and Crohn's disease.

Oral aspects of Crohn's disease

Crohn's disease is a chronic inflammatory disease, which may involve any part of the gastrointestinal tract, including the oral cavity. This review gives an overview of the oral findings observed in patients with Crohn's disease and the potential implications of the disease for dental management are discussed.

Epidemiology of inflammatory bowel disease--methodological considerations

The causes and mechanisms of action of inflammatory bowel disease have, so far, eluded discovery. Epidemiological studies have shown that ulcerative colitis tends to level off, whereas Crohn's disease tends to increase. Some of these changes may be due to diagnostic practices and increasing awareness of the disease and Crohn's colitis. The disease varies according to geographical location and a distribution along a north-south axis has been suggested. The differences may be due to study design, or may reflect differences in lifestyle, diet or be due to genetic predisposition triggered by environmental factors. Epidemiological studies designed to investigate such interactions may provide clues to its aetiology. Inflammatory bowel disease could, therefore, serve as a model for the importance of epidemiology when to test or reject the hypothesis of aetiology.

Inflammatory bowel disease and environmental influences

Some environmental factors have been established firmly as influences on the development of IBD, such as smoking and appendectomy. Other behaviors, such as oral contraceptive use and sugar intake, have been suggested as risk factors, but he data conflict sharply. The importance of other behaviors, such as breast-feeding, is even murkier with sharply divergent data. Some issues studied may not be factors in themselves but rather markers for other unidentified influences. The conflicting evidence in many of these studies may be clarified as specific genes are identified and the interplay between these environmental factors and genetic subtypes is investigated.

A critical review of epidemiological studies in inflammatory bowel disease

This review addresses the difficulty in interpreting the results of epidemiological studies in IBD and in making meaningful comparisons between studies. Both ulcerative colitis and Crohn disease appear to be more common in some industrialized countries such as Scandinavia, United Kingdom, North America and less common in Central and Southern Europe, Asia and Africa. Given data showing an increased incidence of ulcerative colitis in the United Kingdom, it is crucial that more studies be conducted in developing countries. While the incidence of Crohn disease has increased strikingly in many areas, the incidence of ulcerative colitis has remained fairly stable in most. This could be due to the rising number of community-based studies, as well as the improved accuracy in diagnosing Crohn disease. Although, the incidence of IBD among Blacks in Africa is low, infection rates are high, life expectancy is lower than in developed countries. Data from the USA suggest that rates are similar in Afro-American and Caucasian populations. Rates for Jewish populations may be slightly higher than in non-Jewish populations but this also varies geographically. Careful attention to genetic, environmental, and socioeconomic factors must be accounted for in these studies. There is no strong evidence to support that IBD is more common in urban than in rural settings and migration towards more accessible health care has not been adequately addressed. Recent epidemiological studies suggest that mortality rates for IBD are similar to that of the general population for the majority of patients. However, older patients with IBD and newly diagnosed cases with severe diseases are at increased risk of dying. Epidemiological studies remain important in assisting with health policy planning and in hypothesis testing of etiological factors. As better diagnostic techniques become widely available and public health registries are increasingly used, it is possible that geographic differences will diminish. International collaborative studies will be better equipped to answer research questions addressing risk factors and disease natural history. We have summarized in Table V the essential criteria to conduct a sound epidemiological study, which would permit future testing of hypotheses among different populations.

Review: the role of omega 3 fatty acids in intestinal inflammation

The role of polyunsaturated fatty acids (PUFAs) in inflammatory lesions of the intestines is the subject of increasing research. This review begins with a background discussion of the source, elongation, and desaturation of PUFAs, as well as the role they have played in the human diet through evolution. The available data and hypotheses as to how manipulation of PUFAs might effect the various components of the immune system are then provided. Possible mechanisms by which PUFAs result in immunomodulation include alterations in eicosanoid synthesis, membrane fluidity, signal transduction, intraluminal bacteria, and gene expression. Attention is then turned to the known effects that these polyunsaturated fatty acids have on the various individual components of the immune system including lymphocytes, neutrophils, and antigen presenting cells, as well as the immunoregulatory process of apoptosis. Finally, laboratory data on the role of PUFAs in necrotizing enterocolitis, and to a greater extent inflammatory bowel disease, first as demonstrated in animal models of the disease, and second in human studies are then summarized.

The oral absorption of micro- and nanoparticulates: neither exceptional nor unusual

This mini-review covers some of the historical and recent arguments over the experimental evidence on the uptake by and translocation from the intestinal mucosa of microparticulates after oral administration. It is concluded that there is now no dispute over the fact that this is a normal occurrence. Particulate uptake does take place, not only via the M-cells in the Peyer's patches and the isolated follicles of the gut-associated lymphoid tissue, but also via the normal intestinal enterocytes. Factors affecting uptake include particle size, surface charge and hydrophobicity and the presence or absence of surface ligands. The covalent attachment of lectin or invasion molecules to the surface of carrier particles leads to greater systemic uptake. Whether or not the route can be utilized for the routine administration of therapeutic agents which are not normally absorbed from the gut is not yet proven. Many studies show that 2-3% of the ingested dose of submicron particles can be absorbed. The increasing diversity of carrier systems, which includes dendrimers and liposomes, needs to be exploited fully. More also must be learned about the inter- and intra-subject variability of lymphoid tissue so that appropriate selectivity can be achieved through the design of specific carriers.

Absence of skin sensitivity to oxides of aluminium, silicon, titanium or zirconium in patients with Crohn's disease

BACKGROUND

Some metallic compounds, especially of zirconium, can cause cell mediated granulomatous inflammation of the skin. Pigment granules containing compounds of aluminium, silicon, and titanium have been observed within macrophages in the wall of the small intestine in health and in Crohn's disease. Zirconium compounds can be ingested in toothpaste.

AIM

To determine in a pilot study if granulomatous sensitivity can be detected to compounds of these metals or silicon after injection into the skin of patients with Crohn's disease.

SUBJECTS

Eight patients with Crohn's disease known to have had granulomata in the intestine and not currently treated with corticosteroids, and two healthy controls.

METHOD

Two intradermal injections each of 0.1 ml of a 0.02% suspension of one of the compounds made in the abdominal wall of each subject. The site was marked and full thickness skin biopsy performed six weeks later.

RESULT

A foreign body granuloma was observed on histological examination of two biopsy specimens but no evidence of a cell mediated response in any subject.

CONCLUSION

No support was found for the hypothesis that Crohn's disease is due to a specific sensitivity to ingested metallic or silicon compounds.

Epidemiology of inflammatory bowel disease: an update

What have epidemiologic studies on IBD taught so far? Consistent findings are as follows: A high incidence of both CD and UC in industrialized countries and an increase in these areas of the incidence of CD during the years 1960-80 followed by a plateau phase, and a more stable pattern in UC during the same period have been found. A greater number of mild cases have probably been diagnosed recently. This also helps to explain the differences in severity and survival between community and referral centre groups. The male to female ratio is greater than 1 in UC, and this is the opposite in CD. Mortality of IBD has decreased during the past decades. As young people are especially prone to develop IBD, most of those affected will have their disease for many years. In developing IBD, genetic influences are of importance. However, epidemiologic studies strongly point to possible interactions between genetically determined features and environmental or other factors. Of these exogenic factors smoking is the most consistent, being of negative influence in CD and protective in UC. Diet and oral contraceptives may influence disease expression, and perinatal events such as viral infections may alter adult susceptibility. The question remains open whether UC and CD are one diseases entity. Similarities in the epidemiologic features of UC and CD support the idea of IBD being one disease. Other findings suggest dividing UC and CD into further subgroups: in CD it has been suggested that fibrostenotic, penetrating, and inflammatory behaviour should be considered different disease entities; in UC some groups consider ulcerative proctitis a disease entity on its own, separating it from the proximally extending colitis. In therapeutic trials this approach has proved to be of importance, and it is not inconceivable that in subgroups, with regard to aetiopathogenetic mechanisms, different factors have to be looked for.

Low prevalence of Helicobacter pylori in inflammatory bowel disease: association with sulphasalazine

The prevalence of IgG antibodies to Helicobacter pylori was examined in 110 patients with inflammatory bowel disease (IBD) (63 ulcerative colitis, 47 Crohn's disease) and compared with 100 age and sex matched control patients. The overall prevalence of H pylori seropositivity in the IBD patients was 22%, which was significantly less than that of 52% in the controls (p < 0.002). There was no difference in prevalence between ulcerative colitis and Crohn's patients. The low seropositivity in the IBD patients resulted from a very low prevalence of 10% in those currently receiving sulphasalazine (n = 40) and similarly low prevalence of 7% in those previously receiving sulphasalazine (n = 30). In those receiving olsalazine or mesalazine and who had never had sulphasalazine, the prevalence of seropositivity was 45%. Further studies using 14C urea breath test and microscopy of antral biopsy specimens confirmed that the negative serology in patients receiving sulphasalazine resulted from absence of the infection rather than absence of humoral immune response to it. In six control patients with H pylori infection, a two week course of sulphasalazine (500 mg four times daily) only caused slight suppression of the 14C urea breath test. In vitro studies failed to show any direct antibacterial effect of sulphasalazine on H pylori. These findings indicate that longterm treatment with sulphasalazine leads to eradication of H pylori infection and that this does not result from a direct antibacterial effect. It may be caused by the drug treating the gastritis and thereby depriving the bacterium of essential nutrients exuded by the inflamed mucosa.

M-cells are damaged and increased in number in inflamed human ileal mucosa

Ileocolonoscopy and biopsies of patients with spondylarthropathy reveal gut inflammation in 62% of cases. In order to better understand the pathogenetic mechanisms of spondylarthropathy-related gut inflammation, the follicle-associated epithelium was examined. Biopsies from nine controls and 18 patients with spondylarthropathy were studied by electronmicroscopy. Membranous (M) cells were investigated in normal and inflamed ileum. In normal mucosa, M-cells were scarce whereas in inflamed mucosa their number was increased (up to 24% of follicle-associated epithelial cells). They showed a thin rim of cytoplasm covering groups of lymphocytes. In chronic ileitis, necrotic M-cells, rupture of M-cells and lymphocytes entering the gut lumen were observed. The bursting of M-cells at the top of the lymphoid follicles leads to interruption of the gut epithelial lining and gives the luminal content access to the lymphoid tissue. This pathogenetic mechanism may cause aphthoid ulcers.

Crohn's disease: ancient and modern

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New developments in the pharmacotherapy of inflammatory bowel disease

In this article the clinical features and aetiology of inflammatory bowel diseases are described and current pharmacotherapeutic possibilities are explored. Also reviewed are recent developments and future prospects for the pharmacotherapy of inflammatory bowel diseases, including aminosalicylates, corticosteroids, immunosuppressants, lipoxygenase inhibitors, fish oil, sucralfate, bismuth compounds, free radical scavengers, (hydroxy)chloroquine, sodium cromoglycate and methotrexate.