The underappreciated diversity of bile acid modifications.

The repertoire of modifications to bile acids and related steroidal lipids by host and microbial metabolism remains incompletely characterized. To address this knowledge gap, we created a reusable resource of tandem mass spectrometry (MS/MS) spectra by filtering 1.2 billion publicly available MS/MS spectra for bile-acid-selective ion patterns. Thousands of modifications are distributed throughout animal and human bodies as well as microbial cultures. We employed this MS/MS library to identify polyamine bile amidates, prevalent in carnivores. They are present in humans, and their levels alter with a diet change from a Mediterranean to a typical American diet. This work highlights the existence of many more bile acid modifications than previously recognized and the value of leveraging public large-scale untargeted metabolomics data to discover metabolites. The availability of a modification-centric bile acid MS/MS library will inform future studies investigating bile acid roles in health and disease.

High fat intake sustains sorbitol intolerance after antibiotic-mediated Clostridia depletion from the gut microbiota.

Carbohydrate intolerance, commonly linked to the consumption of lactose, fructose, or sorbitol, affects up to 30% of the population in high-income countries. Although sorbitol intolerance is attributed to malabsorption, the underlying mechanism remains unresolved. Here, we show that a history of antibiotic exposure combined with high fat intake triggered long-lasting sorbitol intolerance in mice by reducing Clostridia abundance, which impaired microbial sorbitol catabolism. The restoration of sorbitol catabolism by inoculation with probiotic Escherichia coli protected mice against sorbitol intolerance but did not restore Clostridia abundance. Inoculation with the butyrate producer Anaerostipes caccae restored a normal Clostridia abundance, which protected mice against sorbitol-induced diarrhea even when the probiotic was cleared. Butyrate restored Clostridia abundance by stimulating epithelial peroxisome proliferator-activated receptor-gamma (PPAR-γ) signaling to restore epithelial hypoxia in the colon. Collectively, these mechanistic insights identify microbial sorbitol catabolism as a potential target for approaches for the diagnosis, treatment, and prevention of sorbitol intolerance.

Intestinal Blastocystis is linked to healthier diets and more favorable cardiometabolic outcomes in 56,989 individuals from 32 countries.

Diet impacts human health, influencing body adiposity and the risk of developing cardiometabolic diseases. The gut microbiome is a key player in the diet-health axis, but while its bacterial fraction is widely studied, the role of micro-eukaryotes, including Blastocystis, is underexplored. We performed a global-scale analysis on 56,989 metagenomes and showed that human Blastocystis exhibits distinct prevalence patterns linked to geography, lifestyle, and dietary habits. Blastocystis presence defined a specific bacterial signature and was positively associated with more favorable cardiometabolic profiles and negatively with obesity (p < 1e-16) and disorders linked to altered gut ecology (p < 1e-8). In a diet intervention study involving 1,124 individuals, improvements in dietary quality were linked to weight loss and increases in Blastocystis prevalence (p = 0.003) and abundance (p < 1e-7). Our findings suggest a potentially beneficial role for Blastocystis, which may help explain personalized host responses to diet and downstream disease etiopathogenesis.

De novo and salvage purine synthesis pathways across tissues and tumors.

Purine nucleotides are vital for RNA and DNA synthesis, signaling, metabolism, and energy homeostasis. To synthesize purines, cells use two principal routes: the de novo and salvage pathways. Traditionally, it is believed that proliferating cells predominantly rely on de novo synthesis, whereas differentiated tissues favor the salvage pathway. Unexpectedly, we find that adenine and inosine are the most effective circulating precursors for supplying purine nucleotides to tissues and tumors, while hypoxanthine is rapidly catabolized and poorly salvaged in vivo. Quantitative metabolic analysis demonstrates comparative contribution from de novo synthesis and salvage pathways in maintaining purine nucleotide pools in tumors. Notably, feeding mice nucleotides accelerates tumor growth, while inhibiting purine salvage slows down tumor progression, revealing a crucial role of the salvage pathway in tumor metabolism. These findings provide fundamental insights into how normal tissues and tumors maintain purine nucleotides and highlight the significance of purine salvage in cancer.

Gut microbiota metabolite tyramine ameliorates high-fat diet-induced insulin resistance via increased Ca2+ signaling.

The gut microbiota and their metabolites are closely linked to obesity-related diseases, such as type 2 diabetes, but their causal relationship and underlying mechanisms remain largely elusive. Here, we found that dysbiosis-induced tyramine (TA) suppresses high-fat diet (HFD)-mediated insulin resistance in both Drosophila and mice. In Drosophila, HFD increases cytosolic Ca2+ signaling in enterocytes, which, in turn, suppresses intestinal lipid levels. 16 S rRNA sequencing and metabolomics revealed that HFD leads to increased prevalence of tyrosine decarboxylase (Tdc)-expressing bacteria and resulting tyramine production. Tyramine acts on the tyramine receptor, TyrR1, to promote cytosolic Ca2+ signaling and activation of the CRTC-CREB complex to transcriptionally suppress dietary lipid digestion and lipogenesis in enterocytes, while promoting mitochondrial biogenesis. Furthermore, the tyramine-induced cytosolic Ca2+ signaling is sufficient to suppress HFD-induced obesity and insulin resistance in Drosophila. In mice, tyramine intake also improves glucose tolerance and insulin sensitivity under HFD. These results indicate that dysbiosis-induced tyramine suppresses insulin resistance in both flies and mice under HFD, suggesting a potential therapeutic strategy for related metabolic disorders, such as diabetes.

Modulation of multiple sclerosis risk and pathogenesis by the gut microbiota: Complex interactions between host genetics, bacterial metabolism, and diet.

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, affecting nearly 2 million people worldwide. The etiology of MS is multifactorial: Approximately 30% of the MS risk is genetic, which implies that the remaining ~70% is environmental, with a number of factors proposed. One recently implicated risk factor for MS is the composition of the gut microbiome. Numerous case-control studies have identified changes in gut microbiota composition of people with MS (pwMS) compared with healthy control individuals, and more recent studies in animal models have begun to identify the causative microbes and underlying mechanisms. Here, we review some of these mechanisms, with a specific focus on the role of host genetic variation, dietary inputs, and gut microbial metabolism, with a particular emphasis on short-chain fatty acid and tryptophan metabolism. We put forward a model where, in an individual genetically susceptible to MS, the gut microbiota and diet can synergize as potent environmental modifiers of disease risk and possibly progression, with diet-dependent gut microbial metabolites serving as a key mechanism. We also propose that specific microbial taxa may have divergent effects in individuals carrying distinct variants of MS risk alleles or other polymorphisms, as a consequence of host gene-by-gut microbiota interactions. Finally, we also propose that the effects of specific microbial taxa, especially those that exert their effects through metabolites, are highly dependent on the host dietary intake. What emerges is a complex multifaceted interaction that has been challenging to disentangle in human studies, contributing to the divergence of findings across heterogeneous cohorts with differing geography, dietary preferences, and genetics. Nonetheless, this provides a complex and individualized, yet tractable, model of how the gut microbiota regulate susceptibility to MS, and potentially progression of this disease. Thus, we conclude that prophylactic or therapeutic modulation of the gut microbiome to prevent or treat MS will require a careful and personalized consideration of host genetics, baseline gut microbiota composition, and dietary inputs.

A newborn's perspective on immune responses to food.

In this review, we will highlight infants' immune responses to food, emphasizing the unique aspects of early-life immunity and the critical role of breast milk as a food dedicated to infants. Infants are susceptible to inflammatory responses rather than immune tolerance at the mucosal and skin barriers, necessitating strategies to promote oral tolerance that consider this susceptibility. Breast milk provides nutrients for growth and cell metabolism, including immune cells. The content of breast milk, influenced by maternal genetics and environmental exposures, prepares the infant's immune system for the outside world, including solid foods. To do this, breast milk promotes immune system development through antigen-specific and non-antigen-specific immune education by exposing the newborn to food and respiratory allergens and acting on three key targets for food allergy prevention: the gut microbiota, epithelial cells, and immune cells. Building knowledge of how the maternal exposome and human milk composition influence offspring's healthy immune development will lead to recommendations that meet the specific needs of the developing immune system and increase the chances of promoting an appropriate immune response to food in the long term.

Epigenome-metabolism nexus in the retina: implications for aging and disease.

Intimate links between epigenome modifications and metabolites allude to a crucial role of cellular metabolism in transcriptional regulation. Retina, being a highly metabolic tissue, adapts by integrating inputs from genetic, epigenetic, and extracellular signals. Precise global epigenomic signatures guide development and homeostasis of the intricate retinal structure and function. Epigenomic and metabolic realignment are hallmarks of aging and highlight a link of the epigenome-metabolism nexus with aging-associated multifactorial traits affecting the retina, including age-related macular degeneration and glaucoma. Here, we focus on emerging principles of epigenomic and metabolic control of retinal gene regulation, with emphasis on their contribution to human disease. In addition, we discuss potential mitigation strategies involving lifestyle changes that target the epigenome-metabolome relationship for maintaining retinal function.

Epidermal tyrosine catabolism is crucial for metabolic homeostasis and survival against high-protein diets in Drosophila.

The insect epidermis forms the exoskeleton and determines the body size of an organism. How the epidermis acts as a metabolic regulator to adapt to changes in dietary protein availability remains elusive. Here, we show that the Drosophila epidermis regulates tyrosine (Tyr) catabolism in response to dietary protein levels, thereby promoting metabolic homeostasis. The gene expression profile of the Drosophila larval body wall reveals that enzymes involved in the Tyr degradation pathway, including 4-hydroxyphenylpyruvate dioxygenase (Hpd), are upregulated by increased protein intake. Hpd is specifically expressed in the epidermis and is dynamically regulated by the internal Tyr levels. Whereas basal Hpd expression is maintained by insulin/IGF-1 signalling, Hpd induction on high-protein diet requires activation of the AMP-activated protein kinase (AMPK)-forkhead box O subfamily (FoxO) axis. Impairment of the FoxO-mediated Hpd induction in the epidermis leads to aberrant increases in internal Tyr and its metabolites, disrupting larval development on high-protein diets. Taken together, our findings uncover a crucial role of the epidermis as a metabolic regulator in coping with an unfavourable dietary environment.

Costs of being a diet generalist for the protist predator Dictyostelium discoideum.

Consumers range from specialists that feed on few resources to generalists that feed on many. Generalism has the clear advantage of having more resources to exploit, but the costs that limit generalism are less clear. We explore two understudied costs of generalism in a generalist amoeba predator, Dictyostelium discoideum, feeding on naturally co-occurring bacterial prey. Both involve costs of combining prey that are suitable on their own. First, amoebas exhibit a reduction in growth rate when they switched to one species of prey bacteria from another compared to controls that experience only the second prey. The effect was consistent across all six tested species of bacteria. These switching costs typically disappear within a day, indicating adjustment to new prey bacteria. This suggests that these costs are physiological. Second, amoebas usually grow more slowly on mixtures of prey bacteria compared to the expectation based on their growth on single prey. There were clear mixing costs in three of the six tested prey mixtures, and none showed significant mixing benefits. These results support the idea that, although amoebas can consume a variety of prey, they must use partially different methods and thus must pay costs to handle multiple prey, either sequentially or simultaneously.

Beneficial metabolic effects of PAHSAs depend on the gut microbiota in diet-induced obese mice but not in chow-fed mice.

Dietary lipids play an essential role in regulating the function of the gut microbiota and gastrointestinal tract, and these luminal interactions contribute to mediating host metabolism. Palmitic Acid Hydroxy Stearic Acids (PAHSAs) are a family of lipids with antidiabetic and anti-inflammatory properties, but whether the gut microbiota contributes to their beneficial effects on host metabolism is unknown. Here, we report that treating chow-fed female and male germ-free (GF) mice with PAHSAs improves glucose tolerance, but these effects are lost upon high fat diet (HFD) feeding. However, transfer of feces from PAHSA-treated, but not vehicle-treated, chow-fed conventional mice increases insulin sensitivity in HFD-fed GF mice. Thus, the gut microbiota is necessary for, and can transmit, the insulin-sensitizing effects of PAHSAs in HFD-fed GF male mice. Analyses of the cecal metagenome and lipidome of PAHSA-treated mice identified multiple lipid species that associate with the gut commensal Bacteroides thetaiotaomicron (Bt) and with insulin sensitivity resulting from PAHSA treatment. Supplementing live, and to some degree, heat-killed Bt to HFD-fed female mice prevented weight gain, reduced adiposity, improved glucose tolerance, fortified the colonic mucus barrier and reduced systemic inflammation compared to HFD-fed controls. These effects were not observed in HFD-fed male mice. Furthermore, ovariectomy partially reversed the beneficial Bt effects on host metabolism, indicating a role for sex hormones in mediating the Bt probiotic effects. Altogether, these studies highlight the fact that PAHSAs can modulate the gut microbiota and that the microbiota is necessary for the beneficial metabolic effects of PAHSAs in HFD-fed mice.

A high-fat diet promotes cancer progression by inducing gut microbiota-mediated leucine production and PMN-MDSC differentiation.

A high-fat diet (HFD) is a high-risk factor for the malignant progression of cancers through the disruption of the intestinal microbiota. However, the role of the HFD-related gut microbiota in cancer development remains unclear. This study found that obesity and obesity-related gut microbiota were associated with poor prognosis and advanced clinicopathological status in female patients with breast cancer. To investigate the impact of HFD-associated gut microbiota on cancer progression, we established various models, including HFD feeding, fecal microbiota transplantation, antibiotic feeding, and bacterial gavage, in tumor-bearing mice. HFD-related microbiota promotes cancer progression by generating polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). Mechanistically, the HFD microbiota released abundant leucine, which activated the mTORC1 signaling pathway in myeloid progenitors for PMN-MDSC differentiation. Clinically, the elevated leucine level in the peripheral blood induced by the HFD microbiota was correlated with abundant tumoral PMN-MDSC infiltration and poor clinical outcomes in female patients with breast cancer. These findings revealed that the "gut-bone marrow-tumor" axis is involved in HFD-mediated cancer progression and opens a broad avenue for anticancer therapeutic strategies by targeting the aberrant metabolism of the gut microbiota.

DDID: a comprehensive resource for visualization and analysis of diet-drug interactions.

Diet-drug interactions (DDIs) are pivotal in drug discovery and pharmacovigilance. DDIs can modify the systemic bioavailability/pharmacokinetics of drugs, posing a threat to public health and patient safety. Therefore, it is crucial to establish a platform to reveal the correlation between diets and drugs. Accordingly, we have established a publicly accessible online platform, known as Diet-Drug Interactions Database (DDID, https://bddg.hznu.edu.cn/ddid/), to systematically detail the correlation and corresponding mechanisms of DDIs. The platform comprises 1338 foods/herbs, encompassing flora and fauna, alongside 1516 widely used drugs and 23 950 interaction records. All interactions are meticulously scrutinized and segmented into five categories, thereby resulting in evaluations (positive, negative, no effect, harmful and possible). Besides, cross-linkages between foods/herbs, drugs and other databases are furnished. In conclusion, DDID is a useful resource for comprehending the correlation between foods, herbs and drugs and holds a promise to enhance drug utilization and research on drug combinations.

Obesity Alters POMC and Kisspeptin Neuron Cross Talk Leading to Reduced Luteinizing Hormone in Male Mice.

Obesity is associated with hypogonadism in males, characterized by low testosterone and sperm number. Previous studies determined that these stem from dysregulation of hypothalamic circuitry that regulates reproduction, by unknown mechanisms. Herein, we used mice fed chronic high-fat diet, which mimics human obesity, to determine mechanisms of impairment at the level of the hypothalamus, in particular gonadotropin-releasing hormone (GnRH) neurons that regulate luteinizing hormone (LH), which then regulates testosterone. Consistent with obese humans, we demonstrated lower LH, and lower pulse frequency of LH secretion, but unchanged pituitary responsiveness to GnRH. LH pulse frequency is regulated by pulsatile GnRH secretion, which is controlled by kisspeptin. Peripheral and central kisspeptin injections, and DREADD-mediated activation of kisspeptin neurons, demonstrated that kisspeptin neurons were suppressed in obese mice. Thus, we investigated regulators of kisspeptin secretion. We determined that the LH response to NMDA was lower in obese mice, corresponding to fewer glutamate receptors in kisspeptin neurons, which may be critical for kisspeptin synchronization. Given that kisspeptin neurons also interact with anorexigenic POMC neurons, which are affected by obesity, we examined their cross talk, and determined that the LH response to either DREADD-mediated activation of POMC neurons or central injection of αMSH, a product of POMC, is abolished in obese mice. This was accompanied by diminished levels of αMSH receptor, MC4R, in kisspeptin neurons. Together, our studies determined that obesity leads to the downregulation of receptors that regulate kisspeptin neurons, which is associated with lower LH pulse frequency, leading to lower LH and hypogonadism.

Microglia in Central Control of Metabolism.

Beyond their role as brain immune cells, microglia act as metabolic sensors in response to changes in nutrient availability, thus playing a role in energy homeostasis. This review highlights the evidence and challenges of studying the role of microglia in metabolism regulation.

Emerging Pathophysiological Roles of Ketone Bodies.

The discovery of insulin approximately a century ago greatly improved the management of diabetes, including many of its life-threatening acute complications like ketoacidosis. This breakthrough saved many lives and extended the healthy lifespan of many patients with diabetes. However, there is still a negative perception of ketone bodies stemming from ketoacidosis. Originally, ketone bodies were thought of as a vital source of energy during fasting and exercise. Furthermore, in recent years, research on calorie restriction and its potential impact on extending healthy lifespans, as well as studies on ketone bodies, have gradually led to a reevaluation of the significance of ketone bodies in promoting longevity. Thus, in this review, we discuss the emerging and hidden roles of ketone bodies in various organs, including the heart, kidneys, skeletal muscles, and brain, as well as their potential impact on malignancies and lifespan.

A long journey to the colon: The role of the small intestine microbiota in intestinal disease.

The small intestine represents a complex and understudied gut niche with significant implications for human health. Indeed, many infectious and non-infectious diseases center within the small intestine and present similar clinical manifestations to large intestinal disease, complicating non-invasive diagnosis and treatment. One major neglected aspect of small intestinal diseases is the feedback relationship with the resident collection of commensal organisms, the gut microbiota. Studies focused on microbiota-host interactions in the small intestine in the context of infectious and non-infectious diseases are required to identify potential therapeutic targets dissimilar from those used for large bowel diseases. While sparsely populated, the small intestine represents a stringent commensal bacterial microenvironment the host relies upon for nutrient acquisition and protection against invading pathogens (colonization resistance). Indeed, recent evidence suggests that disruptions to host-microbiota interactions in the small intestine impact enteric bacterial pathogenesis and susceptibility to non-infectious enteric diseases. In this review, we focus on the microbiota's impact on small intestine function and the pathogenesis of infectious and non-infectious diseases of the gastrointestinal (GI) tract. We also discuss gaps in knowledge on the role of commensal microorganisms in proximal GI tract function during health and disease.

AGA Clinical Practice Update on Diet and Nutritional Therapies in Patients With Inflammatory Bowel Disease: Expert Review.

DESCRIPTION: Diet plays a critical role in human health, but especially for patients with inflammatory bowel disease (IBD). Guidance about diet for patients with IBD are often controversial and a source of uncertainty for many physicians and patients. The role of diet has been investigated as a risk factor for IBD etiopathogenesis and as a therapy for active disease. Dietary restrictions, along with the clinical complications of IBD, can result in malnutrition, an underrecognized condition among this patient population. The aim of this American Gastroenterological Association (AGA) Clinical Practice Update (CPU) is to provide best practice advice statements, primarily to clinical gastroenterologists, covering the topics of diet and nutritional therapies in the management of IBD, while emphasizing identification and treatment of malnutrition in these patients. We provide guidance for tailored dietary approaches during IBD remission, active disease, and intestinal failure. A healthy Mediterranean diet will benefit patients with IBD, but may require accommodations for food texture in the setting of intestinal strictures or obstructions. New data in Crohn's disease supports the use of enteral liquid nutrition to help induce remission and correct malnutrition in patients heading for surgery. Parenteral nutrition plays a critical role in patients with IBD facing acute and/or chronic intestinal failure. Registered dietitians are an essential part of the interdisciplinary team approach for optimal nutrition assessment and management in the patient population with IBD. METHODS: This expert review was commissioned and approved by the AGA Clinical Practice Updates Committee and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership and underwent internal peer review by the CPU Committee and external peer review through standard procedures of Gastroenterology. The best practice advice statements were drawn from reviewing existing literature combined with expert opinion to provide practical advice on the role of diet and nutritional therapies in patients with IBD. Because this was not a systematic review, formal rating of the quality of evidence or strength of the presented considerations was not performed. Best Practice Advice Statements BEST PRACTICE ADVICE 1: Unless there is a contraindication, all patients with IBD should be advised to follow a Mediterranean diet rich in a variety of fresh fruits and vegetables, monounsaturated fats, complex carbohydrates, and lean proteins and low in ultraprocessed foods, added sugar, and salt for their overall health and general well-being. No diet has consistently been found to decrease the rate of flares in adults with IBD. A diet low in red and processed meat may reduce ulcerative colitis flares, but has not been found to reduce relapse in Crohn's disease. BEST PRACTICE ADVICE 2: Patients with IBD who have symptomatic intestinal strictures may not tolerate fibrous, plant-based foods (ie, raw fruits and vegetables) due to their texture. An emphasis on careful chewing and cooking and processing of fruits and vegetables to a soft, less fibrinous consistency may help patients with IBD who have concomitant intestinal strictures incorporate a wider variety of plant-based foods and fiber in their diets. BEST PRACTICE ADVICE 3: Exclusive enteral nutrition using liquid nutrition formulations is an effective therapy for induction of clinical remission and endoscopic response in Crohn's disease, with stronger evidence in children than adults. Exclusive enteral nutrition may be considered as a steroid-sparing bridge therapy for patients with Crohn's disease. BEST PRACTICE ADVICE 4: Crohn's disease exclusion diet, a type of partial enteral nutrition therapy, may be an effective therapy for induction of clinical remission and endoscopic response in mild to moderate Crohn's disease of relatively short duration. BEST PRACTICE ADVICE 5: Exclusive enteral nutrition may be an effective therapy in malnourished patients before undergoing elective surgery for Crohn's disease to optimize nutritional status and reduce postoperative complications. BEST PRACTICE ADVICE 6: In patients with IBD who have an intra-abdominal abscess and/or phlegmonous inflammation that limits ability to achieve optimal nutrition via the digestive tract, short-term parenteral nutrition may be used to provide bowel rest in the preoperative phase to decrease infection and inflammation as a bridge to definitive surgical management and to optimize surgical outcomes. BEST PRACTICE ADVICE 7: We suggest the use of parenteral nutrition for high-output gastrointestinal fistula, prolonged ileus, short bowel syndrome, and for patients with IBD with severe malnutrition when oral and enteral nutrition has been trialed and failed or when enteral access is not feasible or contraindicated. BEST PRACTICE ADVICE 8: In patients with IBD and short bowel syndrome, long-term parenteral nutrition should be transitioned to customized hydration management (ie, intravenous electrolyte support and/or oral rehydration solutions) and oral intake whenever possible to decrease the risk of developing long-term complications. Treatment with glucagon-like peptide-2 agonists can facilitate this transition. BEST PRACTICE ADVICE 9: All patients with IBD warrant regular screening for malnutrition by their provider by means of assessing signs and symptoms, including unintended weight loss, edema and fluid retention, and fat and muscle mass loss. When observed, more complete evaluation for malnutrition by a registered dietitian is indicated. Serum proteins are no longer recommended for the identification and diagnosis of malnutrition due to their lack of specificity for nutritional status and high sensitivity to inflammation. BEST PRACTICE ADVICE 10: All patients with IBD should be monitored for vitamin D and iron deficiency. Patients with extensive ileal disease or prior ileal surgery (resection or ileal pouch) should be monitored for vitamin B12 deficiency. BEST PRACTICE ADVICE 11: All outpatients and inpatients with complicated IBD warrant co-management with a registered dietitian, especially those who have malnutrition, short bowel syndrome, enterocutaneous fistula, and/or are requiring more complex nutrition therapies (eg, parenteral nutrition, enteral nutrition, or exclusive enteral nutrition), or those on a Crohn's disease exclusion diet. We suggest that all newly diagnosed patients with IBD have access to a registered dietitian. BEST PRACTICE ADVICE 12: Breastfeeding is associated with a lower risk for diagnosis of IBD during childhood. A healthy, balanced, Mediterranean diet rich in a variety of fruits and vegetables and decreased intake of ultraprocessed foods have been associated with a lower risk of developing IBD.

Nutrition Assessment and Management in Celiac Disease.

Celiac disease (CeD) is the most common immune condition affecting the gastrointestinal tract; it is triggered by gluten and the only available treatment is a strict gluten-free diet (GFD). Therefore, for patients with CeD, adopting a GFD is not a lifestyle choice. The major problem is that a GFD is restrictive and, like all restrictive diets, it has the potential for adverse nutritional outcomes, especially if adopted for a long term. It is well known that GFD can be nutritionally inadequate and is frequently associated with vitamin and mineral deficiencies; it is also associated with excessive sugar and fat intake, particularly when gluten-free substitutes are consumed. Consequently, people with CeD are affected by higher rates of overweight and obesity and metabolic complications, such as fatty liver and cardiovascular disease. Therefore, assessment of nutritional status and diet quality at diagnosis and while on a long-term GFD is key in the management of CeD. This narrative review addresses nutritional considerations in CeD and management of common challenges associated with a GFD.

Non-Host Factors Influencing Onset and Severity of Celiac Disease.

Celiac disease (CeD) is a chronic autoimmune condition driven by gluten ingestion in genetically predisposed individuals, resulting in inflammatory lesions in the proximal small intestine. Although the presence of specific HLA-linked haplotypes and gluten consumption are necessary for disease development, they alone do not account for the variable onset of CeD in susceptible individuals. This review explores the multifaceted role of non-host factors in CeD development, including dietary and microbial influences. We discuss clinical associations and observations highlighting the impact of these factors on disease onset and severity. Furthermore, we discuss studies in CeD-relevant animal models that offer mechanistic insights into how diet, the microbiome, and enteric infections modulate CeD pathogenesis. Finally, we address the clinical implications and therapeutic potential of understanding these cofactors offering a promising avenue for preventive and therapeutic interventions in CeD management.