Small intestinal bacterial overgrowth in systemic sclerosis

Thiamine, gastrointestinal beriberi and acetylcholine signaling

Research has highlighted numerous detrimental consequences of thiamine deficiency on digestive function. These range from impaired gastric and intestinal motility to aberrant changes in pancreatic exocrine function, gastric acidity and disturbances in gut barrier integrity and inflammation. Thiamine and its pharmacological forms, as a primary or adjunctive therapy, have been shown to improve symptoms such as nausea, constipation, dysphagia and intestinal dysmotility, in both humans and animals. This review aims to explore molecular mechanisms underlying the therapeutic action of thiamine in gastrointestinal dysfunction. Our analysis demonstrates that thiamine insufficiency restricted to the gastrointestinal system, i.e., lacking well-known symptoms of dry and wet beriberi, may arise through (i) a disbalance between the nutrient influx and efflux in the gastrointestinal system due to increased demands of thiamine by the organism; (ii) direct exposure of the gastrointestinal system to oral drugs and gut microbiome, targeting thiamine-dependent metabolism in the gastrointestinal system in the first line; (iii) the involvement of thiamine in acetylcholine (ACh) signaling and cholinergic activity in the enteric nervous system and non-neuronal cells of the gut and pancreas, employing both the coenzyme and non-coenzyme actions of thiamine. The coenzyme action relies on the requirement of the thiamine coenzyme form - thiamine diphosphate - for the production of energy and acetylcholine (ACh). The non-coenzyme action involves participation of thiamine and/or derivatives, including thiamine triphosphate, in the regulation of ACh synaptic function, consistent with the early data on thiamine as a co-mediator of ACh in neuromuscular synapses, and in allosteric action on metabolic enzymes. By examining the available evidence with a focus on the gastrointestinal system, we deepen the understanding of thiamine's contribution to overall gastrointestinal health, highlighting important implications of thiamine-dependent mechanisms in functional gastrointestinal disorders.

Understanding the gastrointestinal microbiome in systemic sclerosis: methodological advancements and emerging research

PURPOSE OF REVIEW

This review highlights the role of the gastrointestinal (GI) microbiome in systemic sclerosis (SSc). We describe techniques for evaluating the GI microbiome in humans, and emerging research linking GI microbiome alterations (i.e., dysbiosis) and distinct SSc clinical manifestations. We also address the evolving treatment landscape targeting dysbiosis in SSc.

RECENT FINDINGS

Recent literature brings into focus the complex relationship between the GI microbiome and SSc pathogenesis. Advanced techniques (e.g., shotgun metagenomics, meta-transcriptomics) provide deeper insights into microbial taxonomy and active gene expression, exposing dysbiosis as a potential driver of SSc. New studies demonstrate that SSc patients who possess specific SSc clinical features, (e.g., interstitial lung disease), have unique GI microbiome profiles.

SUMMARY

Dysbiosis is associated with specific clinical features in patients with SSc. New tools for studying the GI microbiome have furthered our understanding of the relationship between dysbiosis and SSc complications. Therapeutic avenues such as dietary adjustments, probiotics, antibiotics, mindfulness practices, and fecal transplants offer potential for managing SSc and preventing its progression through GI microbiome modulation. By clarifying what is known about the relationship between the GI dysbiosis, GI dysfunction, and SSc, this review enhances our understanding of SSc pathogenesis and proposes targeted interventions.

Small Intestinal Bacterial Overgrowth (SIBO) and Twelve Groups of Related Diseases-Current State of Knowledge

The human gut microbiota creates a complex microbial ecosystem, characterized by its high population density, wide diversity, and complex interactions. Any imbalance of the intestinal microbiome, whether qualitative or quantitative, may have serious consequences for human health, including small intestinal bacterial overgrowth (SIBO). SIBO is defined as an increase in the number of bacteria (103-105 CFU/mL), an alteration in the bacterial composition, or both in the small intestine. The PubMed, Science Direct, Web of Science, EMBASE, and Medline databases were searched for studies on SIBO and related diseases. These diseases were divided into 12 groups: (1) gastrointestinal disorders; (2) autoimmune disease; (3) cardiovascular system disease; (4) metabolic disease; (5) endocrine disorders; (6) nephrological disorders; (7) dermatological diseases; (8) neurological diseases (9); developmental disorders; (10) mental disorders; (11) genetic diseases; and (12) gastrointestinal cancer. The purpose of this comprehensive review is to present the current state of knowledge on the relationships between SIBO and these 12 disease groups, taking into account risk factors and the causal context. This review fills the evidence gap on SIBO and presents a biological-medical approach to the problem, clearly showing the groups and diseases having a proven relationship with SIBO, as well as indicating groups within which research should continue to be expanded.

Proton pump inhibitors in systemic sclerosis: a reappraisal to optimise treatment of gastro-oesophageal reflux disease

Gastroesophageal reflux disease (GERD) is associated with significant morbidity in patients with systemic sclerosis (SSc). Although the introduction of proton pump inhibitors (PPIs) into clinical care have represented a major achievement in the management of oesophago-gastric problems in SSc, PPIs are seldom fully effective in SSc patients, and the utilization of maximum PPI dosages is a very frequent clinical practice. However, currently there is little evidence currently to support the empiric use of PPIs in SSc which is especially relevant in regard to safety concerns of long-term exposure with have been raised in the general population. The purpose of this viewpoint is to highlight the significant beneficial impact of PPIs on GERD in SSc, while considering the potential adverse effects in this patient population. Furthermore, we highlight the unmet needs of SSc patients with GERD, and also propose an agenda for future research to optimise the safe and effective use of PPIs in SSc.

Aetiology, diagnosis and management of small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth is a small bowel disorder characterised by excessive amounts of bacteria populating the small intestine leading to symptoms of abdominal pain, bloating and change in bowel habit. This creates some degree of diagnostic uncertainty due to the overlap of these symptoms with numerous other gastrointestinal conditions. Quantitative culture of jejunal aspirates is the gold standard diagnostic test but has largely been replaced by glucose and lactulose breath tests due to their relative ease and accessibility. The approach to treatment centres around reducing bacterial numbers through antibiotic therapy and managing any predisposing factors. Further research is required in order to define the optimum antibiotic choice and duration of therapy as well as the potential diagnostic utility of home breath testing and capsule-based technology.

Ultrasound evaluation of bowel vasculopathy in systemic sclerosis

BACKGROUND

Gastrointestinal (GI) manifestations are frequent in systemic sclerosis (SSc) with an impact on quality of life and morbidity. Bowel vasculopathy is a key pathogenetic factor responsible for GI involvement.

OBJECTIVES

To compare abdominal ultrasound (US) and Color Doppler Ultrasonography (CDU) features of splanchnic vessels of SSc patients with healthy controls.

METHODS

The charts of SSc patients who underwent an abdominal US and CDU study were retrospectively analyzed. For Superior Mesenteric Artery (SMA) and Inferior Mesenteric Artery (IMA) caliber, Peak Systolic Velocity (PSV), Reverse Velocity (RV), End-Diastolic Velocity (EDV), Mean Velocity (mV), Blood-flow, Resistive Index (RI) and Pulsatility Index (PI) were recorded.

RESULTS

28 SSc patients and 28 controls were enrolled. In SSc, caliber of SMA was significantly smaller than in controls (5.75 ± 0.62 mm vs. 6.45 ± 0.60 mm, p < 0.0001 - p adj =0.0002). The flow study of SMA and IMA showed a significant reduction of RV (SMA: 7.25 ± 6.37 cm/s vs. 18.52 ± 6.16 cm/s, p < 0.0001 - p adj <0.0001; IMA: 2.69 ± 6.10 cm/s vs. 17.06 ± 5.75 cm/s, p < 0.0001 - p adj <0.0001) and PI (SMA: 3.33 ± 0.75 vs. 4.53 ± 1.03, p < 0.0001 - p adj =0.0002; IMA: 3.54 ± 0.95 vs. 6.08 ± 1.53, p < 0.0001 - p adj <0.0001) in SSc patients than controls.

CONCLUSION

involvement of splanchnic vessels in SSc may be non-invasively investigated with abdominal US and CDU. Morphological and functional changes of Doppler parameters observed in SMA and IMA clearly demonstrate that these vessels are affected by SSc vasculopathy.

Oral Lactobacillus Species in Systemic Sclerosis

In systemic sclerosis (SSc), the gastrointestinal tract (GIT) plays a central role in the patient's quality of life. The microbiome populates the GIT, where a relationship between the Lactobacillus and gastrointestinal motility has been suggested. In this study, the analysis of oral Lactobacillus species in SSc patients and healthy subjects using culture-independent molecular techniques, together with a review of the literature on microbiota and lactobacilli in SSc, has been carried out. Twenty-nine SSc female patients (mean age 62) and twenty-three female healthy subjects (HS, mean age 57.6) were enrolled and underwent tongue and gum swab sampling. Quantitative PCR was conducted in triplicate using Lactobacillus specific primers rpoB1, rpoB1o and rpoB2 for the RNA-polymerase β subunit gene. Our data show significantly (p = 0.0211) lower LactobacillusspprpoB sequences on the tongue of patients with SSc compared to HS. The mean value of the amount of Lactobacillus ssprpoB gene on the gumsofSSc patients was minor compared to HS. A significant difference between tongue and gums (p = 0.0421) was found in HS but not in SSc patients. In conclusion, our results show a lower presence of Lactobacillus in the oral cavity of SSc patients. This strengthens the hypothesis that Lactobacillus may have both a protective and therapeutic role in SSc patients.