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Vitamins and Hormones 2022Vitamin B12 is assimilated and transported by complex mechanisms that involve three transport proteins, intrinsic factor (IF), haptocorrin (HC) and transcobalamin (TC)... (Review)
Review
Vitamin B12 is assimilated and transported by complex mechanisms that involve three transport proteins, intrinsic factor (IF), haptocorrin (HC) and transcobalamin (TC) and their respective membrane receptors. Vitamin deficiency is mainly due to inadequate dietary intake in vegans, and B12 malabsorption is related to digestive diseases. This review explores the physiology of vitamin B12 absorption and the mechanisms and diseases that produce malabsorption. In the stomach, B12 is released from food carrier proteins and binds to HC. The degradation of HC by pancreatic proteases and the pH change trigger the transfer of B12 to IF in the duodenum. Cubilin and amnionless are the two components of the receptor that mediates the uptake of B12 in the distal ileum. Part of liver B12 is excreted in bile, and undergoes an enterohepatic circulation. The main causes of B12 malabsorption include inherited disorders (Intrinsic factor deficiency, Imerslund-Gräsbeck disease, Addison's pernicious anemia, obesity, bariatric surgery and gastrectomies. Other causes include pancreatic insufficiency, obstructive Jaundice, tropical sprue and celiac disease, bacterial overgrowth, parasitic infestations, Zollinger-Ellison syndrome, inflammatory bowel diseases, chronic radiation enteritis of the distal ileum and short bowel. The assessment of B12 deficit is recommended in the follow-up of subjects with bariatric surgery. The genetic causes of B12 malabsorption are probably underestimated in adult cases with B12 deficit. Despite its high prevalence in the general population and in the elderly, B12 malabsorption cannot be anymore assessed by the Schilling test, pointing out the urgent need for an equivalent reliable test.
Topics: Adult; Aged; Anemia, Megaloblastic; Humans; Intrinsic Factor; Malabsorption Syndromes; Male; Vitamin B 12; Vitamin B 12 Deficiency
PubMed: 35337622
DOI: 10.1016/bs.vh.2022.01.016 -
BMC Medicine Jul 2019Celiac disease remains a challenging condition because of a steady increase in knowledge tackling its pathophysiology, diagnosis, management, and possible therapeutic... (Review)
Review
BACKGROUND
Celiac disease remains a challenging condition because of a steady increase in knowledge tackling its pathophysiology, diagnosis, management, and possible therapeutic options.
MAIN BODY
A major milestone in the history of celiac disease was the identification of tissue transglutaminase as the autoantigen, thereby confirming the autoimmune nature of this disorder. A genetic background (HLA-DQ2/DQ8 positivity and non-HLA genes) is a mandatory determinant of the development of the disease, which occurs with the contribution of environmental factors (e.g., viral infections and dysbiosis of gut microbiota). Its prevalence in the general population is of approximately 1%, with female predominance. The disease can occur at any age, with a variety of symptoms/manifestations. This multifaceted clinical presentation leads to several phenotypes, i.e., gastrointestinal, extraintestinal, subclinical, potential, seronegative, non-responsive, and refractory. Although small intestinal biopsy remains the diagnostic 'gold standard', highly sensitive and specific serological tests, such as tissue transglutaminase, endomysial and deamidated gliadin peptide antibodies, have become gradually more important in the diagnostic work-up of celiac disease. Currently, the only treatment for celiac disease is a life-long, strict gluten-free diet leading to improvement in quality of life, ameliorating symptoms, and preventing the occurrence of refractory celiac disease, ulcerative jejunoileitis, and small intestinal adenocarcinoma and lymphoma.
CONCLUSIONS
The present review is timely and provides a thorough appraisal of various aspects characterizing celiac disease. Remaining challenges include obtaining a better understanding of still-unclear phenotypes such as slow-responsive, potential (minimal lesions) and seronegative celiac disease. The identification of alternative or complementary treatments to the gluten-free diet brings hope for patients unavoidably burdened by diet restrictions.
Topics: Biopsy; Celiac Disease; Diagnosis, Differential; Diet, Gluten-Free; Humans; Immunity, Innate; Phenotype; Quality of Life; Serologic Tests
PubMed: 31331324
DOI: 10.1186/s12916-019-1380-z -
Gut Nov 2019Lactose is the main source of calories in milk, an essential nutriedigestion, patients with visceral hypersensitivity nt in infancy and a key part of the diet in... (Review)
Review
Lactose is the main source of calories in milk, an essential nutriedigestion, patients with visceral hypersensitivity nt in infancy and a key part of the diet in populations that maintain the ability to digest this disaccharide in adulthood. Lactase deficiency (LD) is the failure to express the enzyme that hydrolyses lactose into galactose and glucose in the small intestine. The genetic mechanism of lactase persistence in adult Caucasians is mediated by a single C→T nucleotide polymorphism at the LCTbo -13'910 locus on chromosome-2. Lactose malabsorption (LM) refers to any cause of failure to digest and/or absorb lactose in the small intestine. This includes primary genetic and also secondary LD due to infection or other conditions that affect the mucosal integrity of the small bowel. Lactose intolerance (LI) is defined as the onset of abdominal symptoms such as abdominal pain, bloating and diarrhoea after lactose ingestion by an individual with LM. The likelihood of LI depends on the lactose dose, lactase expression and the intestinal microbiome. Independent of lactose digestion, patients with visceral hypersensitivity associated with anxiety or the Irritable Bowel Syndrome (IBS) are at increased risk of the condition. Diagnostic investigations available to diagnose LM and LI include genetic, endoscopic and physiological tests. The association between self-reported LI, objective findings and clinical outcome of dietary intervention is variable. Treatment of LI can include low-lactose diet, lactase supplementation and, potentially, colonic adaptation by prebiotics. The clinical outcome of these treatments is modest, because lactose is just one of a number of poorly absorbed carbohydrates which can cause symptoms by similar mechanisms.
Topics: Humans; Lactose Intolerance; Malabsorption Syndromes
PubMed: 31427404
DOI: 10.1136/gutjnl-2019-318404 -
Digestive and Liver Disease : Official... Mar 2020Short bowel syndrome (SBS) is a rare malabsorptive disorder as a result of the loss of bowel mass mostly secondary to surgical resection of the small intestine. Other... (Review)
Review
Short bowel syndrome (SBS) is a rare malabsorptive disorder as a result of the loss of bowel mass mostly secondary to surgical resection of the small intestine. Other causes are vascular diseases, neoplasms or inflammatory bowel disease. The spectrum of the disease is widely variable from single micronutrient malabsorption to complete intestinal failure, depending on the remaining length of the small intestine, the anatomical portion of intestine and the function of the remnant bowel. Over the last years, the management of affected patients has remarkably improved with the increase in patients' quality of life and survival, mainly thanks to advances in home-based parenteral nutrition (PN). In the last ten years new treatment strategies have become available together with increasing experience and the encouraging results with new drugs, such as teduglutide, have added a new dimension to the management of SBS. This review aims to summarize the knowledge available in the current literature on SBS epidemiology, pathophysiology, and its surgical (including intestinal lengthening procedures and intestinal transplantation) and medical management with emphasis on the recent advances. Moreover, this review attempts to provide the new understanding and recent approaches to SBS complications such as sepsis, catheter thrombosis, and intestinal failure-associated liver disease.
Topics: Disease Management; Gastrointestinal Agents; Humans; Intestines; Parenteral Nutrition, Home; Peptides; Quality of Life; Short Bowel Syndrome
PubMed: 31892505
DOI: 10.1016/j.dld.2019.11.013 -
Gastroenterology Clinics of North... Jun 2021The term "small intestinal bacterial overgrowth" (SIBO) has been used to refer to a disorder resulting from the colonization of the small bowel by an increased number of... (Review)
Review
The term "small intestinal bacterial overgrowth" (SIBO) has been used to refer to a disorder resulting from the colonization of the small bowel by an increased number of microorganisms or by the presence of bacteria that are not usual constituents of this part of the gastrointestinal tract. Clinical presentations, often in patients with certain risk factors, can range from a full-blown malabsorption syndrome to such "functional" complaints as bloating and flatulence. SIBO is diagnosed by either culture of a small bowel aspirate or one of several breath tests. Treatment of SIBO entails risk factor modification, correction of nutritional deficiencies, and oral antibiotics.
Topics: Anti-Bacterial Agents; Bacterial Infections; Breath Tests; Humans; Intestine, Small; Malabsorption Syndromes
PubMed: 34024452
DOI: 10.1016/j.gtc.2021.02.008 -
Gastroenterology Jan 2021The incidence of celiac disease is increasing, partly because of improved recognition of, and testing for, the disease. The rise in incidence is also due to a real... (Review)
Review
The incidence of celiac disease is increasing, partly because of improved recognition of, and testing for, the disease. The rise in incidence is also due to a real increase of this immune-based disorder, independent of disease detection. The reasons for this true rise in recent decades are unknown but may be related to environmental factors that may promote loss of tolerance to dietary gluten. Strategies to reduce the development of celiac disease have not been proven successful in randomized trials, but the quantity of early-life gluten exposure has been a major focus of prevention efforts. The criteria for the diagnosis of celiac disease are changing, but in adults, diagnosis still depends on the presence of duodenal villous atrophy while the patient is on a gluten-containing diet, along with findings from serology analysis. Although guidelines in the United States continue to mandate a biopsy at all ages, some children receive a diagnosis of celiac disease without a biopsy. If proven accurate and scalable, assays that detect gluten-HLA tetramer complexes might be used in diagnosis to be made in the context of a gluten-free diet without intestinal biopsy.
Topics: Celiac Disease; Humans; Risk Factors; Symptom Assessment
PubMed: 32950520
DOI: 10.1053/j.gastro.2020.06.098 -
American Family Physician Apr 2020Chronic diarrhea is defined as a predominantly loose stool lasting longer than four weeks. A patient history and physical examination with a complete blood count,...
Chronic diarrhea is defined as a predominantly loose stool lasting longer than four weeks. A patient history and physical examination with a complete blood count, C-reactive protein, anti-tissue transglutaminase immunoglobulin A (IgA), total IgA, and a basic metabolic panel are useful to evaluate for pathologies such as celiac disease or inflammatory bowel disease. More targeted testing should be based on the differential diagnosis. When the differential diagnosis is broad, stool studies should be used to categorize diarrhea as watery, fatty, or inflammatory. Some disorders can cause more than one type of diarrhea. Watery diarrhea includes secretory, osmotic, and functional types. Functional disorders such as irritable bowel syndrome and functional diarrhea are common causes of chronic diarrhea. Secretory diarrhea can be caused by bile acid malabsorption, microscopic colitis, endocrine disorders, and some postsurgical states. Osmotic diarrhea can present with carbohydrate malabsorption syndromes and laxative abuse. Fatty diarrhea can be caused by malabsorption or maldigestion and includes disorders such as celiac disease, giardiasis, and pancreatic exocrine insufficiency. Inflammatory diarrhea warrants further evaluation and can be caused by disorders such as inflammatory bowel disease, Clostridioides difficile, colitis, and colorectal cancer.
Topics: Adult; Celiac Disease; Chronic Disease; Diagnosis, Differential; Diarrhea; Humans; Immunoglobulin A; Inflammatory Bowel Diseases; Malabsorption Syndromes
PubMed: 32293842
DOI: No ID Found -
Nutrition in Clinical Practice :... May 2023Short bowel syndrome (SBS) occurs when a patient loses bowel length or function significantly enough to cause malabsorption, oftentimes requiring lifelong parenteral... (Review)
Review
Short bowel syndrome (SBS) occurs when a patient loses bowel length or function significantly enough to cause malabsorption, oftentimes requiring lifelong parenteral support. In adults, this occurs most commonly in the setting of massive intestinal resection, whereas congenital anomalies and necrotizing enterocolitis predominate in children. Many patients with SBS develop long-term clinical complications over time related to their altered intestinal anatomy and physiology or to various treatment interventions such as parenteral nutrition and the central venous catheter through which it is administered. Identifying, preventing, and treating these complications can be challenging. This review will focus on the diagnosis, treatment, and prevention of several complications that can occur in this patient population, including diarrhea, fluid and electrolyte imbalance, vitamin and trace element derangements, metabolic bone disease, biliary disorders, small intestinal bacterial overgrowth, d-lactic acidosis, and complications of central venous catheters.
Topics: Child; Adult; Humans; Infant, Newborn; Short Bowel Syndrome; Parenteral Nutrition; Enterocolitis, Necrotizing; Acidosis, Lactic; Diarrhea
PubMed: 37115034
DOI: 10.1002/ncp.10978 -
World Journal of Gastroenterology Aug 2022Celiac disease (CeD) is a chronic gluten-induced enteropathy with plethoric manifestations. The typical manifestations of CeD such as chronic diarrhea and malabsorption... (Review)
Review
Celiac disease (CeD) is a chronic gluten-induced enteropathy with plethoric manifestations. The typical manifestations of CeD such as chronic diarrhea and malabsorption are widely recognized, however, many patients have atypical manifestations like iron deficiency anemia, idiopathic short stature, hypertransaminesemia or infertility, These patients often present to the primary care physicians and/or non-gastrointestinal specialties. However, due to a lack of awareness among the healthcare professionals about the various atypical manifestations, many patients are not screened for CeD. In this review, we have summarized the available literature about the prevalence of CeD in various gastrointestinal (chronic diarrhea) and non-gastrointestinal conditions (iron deficiency anemia, short stature, cryptogenic hypertransaminesemia, cryptogenic cirrhosis or idiopathic ataxia ) where the diagnosis of CeD should be con-sidered. In addition, we also discuss special scenarios where screening for CeD should be considered even in absence of symptoms such as patients with type 1 diabetes, Down's syndrome, and first-degree relatives of patients with CeD. Further, we discuss the diagnostic performance and limitations of various screening tests for CeD such as IgA anti-tissue transglutaminase antibodies, anti-endomysial antibodies and anti-deamidated gliadin antibodies. Based on the current recommendations, we propose a diagnostic algorithm for patients with suspected CeD.
Topics: Anemia, Iron-Deficiency; Antibodies, Anti-Idiotypic; Autoantibodies; Celiac Disease; Delivery of Health Care; Diarrhea; Gliadin; Humans; Immunoglobulin A; Protein Glutamine gamma Glutamyltransferase 2; Transglutaminases
PubMed: 36157923
DOI: 10.3748/wjg.v28.i32.4493 -
Gastroenterology Sep 2022The concept of small intestinal bacterial overgrowth (SIBO) arose in the context of maldigestion and malabsorption among patients with obvious risk factors that... (Review)
Review
The concept of small intestinal bacterial overgrowth (SIBO) arose in the context of maldigestion and malabsorption among patients with obvious risk factors that permitted the small bowel to be colonized by potentially injurious colonic microbiota. Such colonization resulted in clinical signs, symptoms, and laboratory abnormalities that were explicable within a coherent pathophysiological framework. Coincident with advances in medical science, diagnostic testing evolved from small bowel culture to breath tests and on to next-generation, culture-independent microbial analytics. The advent and ready availability of breath tests generated a dramatic expansion in both the rate of diagnosis of SIBO and the range of associated gastrointestinal and nongastrointestinal clinical scenarios. However, issues with the specificity of these same breath tests have clouded their interpretation and aroused some skepticism regarding the role of SIBO in this expanded clinical repertoire. Furthermore, the pathophysiological plausibility that underpins SIBO as a cause of maldigestion/malabsorption is lacking in regard to its purported role in irritable bowel syndrome, for example. One hopes that the application of an ever-expanding armamentarium of modern molecular microbiology to the human small intestinal microbiome in both health and disease will ultimately resolve this impasse and provide an objective basis for the diagnosis of SIBO.
Topics: Blind Loop Syndrome; Breath Tests; Humans; Intestine, Small; Irritable Bowel Syndrome; Malabsorption Syndromes
PubMed: 35398346
DOI: 10.1053/j.gastro.2022.04.002