(1) Background: A growing body of evidence highlights that intestinal dysbiosis is associated with the development of psoriasis. The gut–skin axis is the novel concept of the interaction between skin diseases and microbiome through inflammatory mediators, metabolites and the intestinal barrier. The objective of this study was to synthesize current data on the gut microbial composition in psoriasis. (2) Methods: We conducted a systematic review of studies investigating intestinal microbiome in psoriasis, using the PRISMA checklist. We searched MEDLINE, EMBASE, and Web of Science databases for relevant published articles (2000–2020). (3) Results: All of the 10 retrieved studies reported alterations in the gut microbiome in patients with psoriasis. Eight studies assessed alpha- and beta-diversity. Four of them reported a lack of change in alpha-diversity, but all confirmed significant changes in beta-diversity. At the phylum-level, at least two or more studies reported a lower relative abundance of Bacteroidetes, and higher Firmicutes in psoriasis patients versus healthy controls. (4) Conclusions: There is a significant association between alterations in gut microbial composition and psoriasis; however, there is high heterogeneity between studies. More unified methodological standards in large-scale studies are needed to understand microbiota’s contribution to psoriasis pathogenesis and its modulation as a potential therapeutic strategy.

Alterations of intestinal microbiota play a significant role in the pathogenesis of psoriasis. Dysbiosis may cause disruption of the intestinal barrier, which contributes to immune activation by translocation of microbial antigens and metabolites. Intestinal fatty acid binding protein (I-FABP) serves as a biomarker of enterocyte damage. The aim of this study was to investigate clinical and metabolic factors affecting plasma concentration of I-FABP in patients with psoriasis. Eighty patients with psoriasis and 40 control subjects were enrolled in the study. Serum I-FABP (243.00 (108.88–787.10) vs. 114.38 (51.60–241.60) pg/ml, p < 0.001) and neutrophil to lymphocyte ratio (NLR; 2.59 (1.96–3.09) vs. 1.72 (1.36–47 2.11), p < 0.01) were significantly increased in patients with psoriasis compared to controls. A significant positive correlation was found between I-FABP and body mass index (BMI) (r = 0.82, p < 0.001), Psoriasis Area Severity Index (PASI) (r = 0.78, p < 0.001) and neutrophil to lymphocyte ratio (NLR) (r = 0.24, p < 0.001). Rising quartiles of I-FABP were associated with increasing values of BMI, PASI and NLR. The results of the logistic regression model confirmed an increased risk of higher disease severity with I-FABP concentration – odds ratio 3.34 per 100 pg/mL I-FABP increase. In conclusion, intestinal integrity in patients with psoriasis is affected by obesity, severity of the disease and systemic inflammation. The modulation of gut barrier may represent a new therapeutic approach for psoriasis.

Dysbiosis has been identified in many dermatological conditions (e.g., psoriasis, atopic dermatitis, systemic lupus erythematosus). One of the ways by which the microbiota affect homeostasis is through microbiota-derived molecules (metabolites). There are three main groups of metabolites: short-chain fatty acids (SCFAs), tryptophan metabolites, and amine derivatives including trimethylamine N-oxide (TMAO). Each group has its own uptake and specific receptors through which these metabolites can exert their systemic function. This review provides up-to-date knowledge about the impact that these groups of gut microbiota metabolites may have in dermatological conditions. Special attention is paid to the effect of microbial metabolites on the immune system, including changes in the profile of the immune cells and cytokine disbalance, which are characteristic of several dermatological diseases, especially psoriasis and atopic dermatitis. Targeting the production of microbiota metabolites may serve as a novel therapeutic approach in several immune-mediated dermatological diseases.

Introduction: Trimethylamine N-oxide (TMAO), a gut microbiota metabolite from dietary phosphatidylcholine, is involved in the pathogenesis of atherosclerosis and cardiovascular diseases. Psoriasis is associated with increased cardiovascular risk that is not captured by traditional biomarkers. The aim of the present study was to assess TMAO concentration in psoriasis and evaluate the relationship between TMAO and cardiovascular risk in psoriatic patients. Methods: In 72 patients with psoriasis and 40 age-and sex-matched non-psoriatic controls, we evaluated fasting plasma TMAO, measured by high-performance liquid chromatography, and cardiovascular risk assessed by various scoring systems such as Framingham, QRISK2, AHA/ACC, and Reynolds risk scores. Results: In patients with psoriasis, TMAO concentration was significantly higher than in the control group (195.68 [133.54-332.58] ng/ml versus 126. 06 [84.29-156.88] ng/ml, respectively; p \ 0.001). Plasma TMAO concentration was significantly correlated with age, total cholesterol, triglycerides, systolic and diastolic blood pressure. Furthermore, the receiver-operating characteristic (ROC) and multiple regression analysis showed that TMAO is an independent predictor of cardiovascular risk. Conclusion: TMAO is a valuable candidate for biomarker and a translational link between dysbiosis and atherosclerosis in psoriasis.

Background An increasing amount of evidence suggests an association between increased intestinal permeability and the pathogenesis of chronic inflammatory diseases. However, the clinical significance of gut barrier dysfunction in psoriasis remains to be established. Objective To evaluate whether there are differences in disease activity, the severity of gastrointestinal symptoms and the blood concentration of bacterial metabolites in psoriatic patients with a normal and altered intestinal barrier. Patients and Methods Gut barrier integrity was assessed with the serum concentrations of claudin-3, a modulator of intestinal tight junctions and an intestinal fatty acid-binding protein, a marker of enterocyte damage. Gastrointestinal symptoms were evaluated with a validated questionnaire. The concentration of trimethylamine N-oxide (TMAO), a gut microbiota-associated metabolite, was measured with high-performance liquid chromatography. Results One hundred and fourteen patients with psoriasis were finally enrolled in the study – 68 with an altered gut barrier and 46 with a properly functioning intestinal barrier. Patients with an altered gut barrier showed a significantly higher score in the Gastrointestinal Symptom Rating Scale (3.20 vs 1.46, p<0.001). Moreover, patients with psoriasis and a disrupted intestinal barrier demonstrated a higher disease activity (PASI: 19.7 vs 10.3, p<0.001) and systemic inflammatory parameters (neutrophil-to-lymphocyte ratio: 2.86 vs 1.71, p<0.001; C-reactive protein 3.76 vs 1.92; p<0.05). The marker of bacterial translocation was significantly higher in psoriatic patients with damaged gut integrity (TMAO: 375.7±51.9 vs 119.4±27.5 ng/mL; p<0.05). Conclusion The altered gut barrier in psoriasis is associated with gastrointestinal symptoms, systemic inflammatory profile and the increased blood concentration of gut microbiota-derived metabolite – TMAO. Intestinal barrier modulation represents a new promising therapeutic approach.

Introduction: There are several hypotheses of schizophrenia pathogenesis, including the neurodegenerative theory, which is supported by evidence for the decrease of neuroprotective factors’ serum levels. The proteins, that exert a protective effect on neurons and are researched concerning schizophrenia pathogenesis, include the brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin 3 (NT3), and glial cell line-derived neurotrophic factor (GDNF). This review aims to discuss the role of neuroprotective factors in the development of schizophrenia and their relevance in clinical trials. Material and methods: This review was performed by search of the PubMed, Google Scholar, and Science Direct databases from December 25th, 2022, through January 31st, 2023, using keywords: ‘schizophrenia’, ‘schizophrenia pathogenesis’, ‘neuroprotection’, ‘neurodegeneration’, ‘BDNF’, ‘NGF’, ‘NT3’, and ‘GDNF’. We considered original research papers and systematic reviews published in English or Polish. Additionally, clinical trials, which included the assessment of neuroprotective factors’ levels in schizophrenia as outcome measures, were searched for on clinicaltrials.gov. Results: Lower levels of serum BDNF have been linked to cognitive impairment in schizophrenia. In clinical trials, the assessment of serum BDNF is used as a clinical outcome measure for novel schizophrenia therapies. Schizophrenia has also been associated with reduced peripheral NGF levels. During remission, lower NGF levels correlate with higher severity of negative symptoms. Decreased NT3 and GDNF levels can also be seen, but literature reports are inconsistent. Conclusions: Neuroprotective factors are most likely related to the pathogenesis of schizophrenia. Assessing the serum level of these proteins may prove to be an invaluable element of schizophrenia management. Keywords: schizophrenia, brain-derived neurotrophic factor, nerve growth factor,neurotrophin 3, glial cell line-derived neurotrophic factor

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