The prebiotic effects of soluble dietary fiber mixture on renal anemia and the gut microbiota in end-stage renal disease patients on maintenance hemodialysis: a prospective, randomized, placebo-controlled study

The Role of the Gut Microbiota in Complications among Hemodialysis Patients

The composition of the gut microbiota varies among end-stage renal disease (ESRD) patients on the basis of their mode of renal replacement therapy (RRT), with notably more pronounced dysbiosis occurring in those undergoing hemodialysis (HD). Interventions such as dialysis catheters, unstable hemodynamics, strict dietary restrictions, and pharmacotherapy significantly alter the intestinal microenvironment, thus disrupting the gut microbiota composition in HD patients. The gut microbiota may influence HD-related complications, including cardiovascular disease (CVD), infections, anemia, and malnutrition, through mechanisms such as bacterial translocation, immune regulation, and the production of gut microbial metabolites, thereby affecting both the quality of life and the prognosis of patients. This review focuses on alterations in the gut microbiota and its metabolites in HD patients. Additionally, understanding the impact of the gut microbiota on the complications of HD could provide insights into the development of novel treatment strategies to prevent or alleviate complications in HD patients.

Exploring the gut microbiome: probiotics, prebiotics, synbiotics, and postbiotics as key players in human health and disease improvement

The human gut microbiome accompanies us from birth, and it is developed and matured by diet, lifestyle, and environmental factors. During aging, the bacterial composition evolves in reciprocal communication with the host's physiological properties. Many diseases are closely related to the gut microbiome, which means the modulation of the gut microbiome can promote the disease targeting remote organs. This review explores the intricate interaction between the gut microbiome and other organs, and their improvement from disease by prebiotics, probiotics, synbiotics, and postbiotics. Each section of the review is supported by clinical trials that substantiate the benefits of modulation the gut microbiome through dietary intervention for improving primary health outcomes across various axes with the gut. In conclusion, the review underscores the significant potential of targeting the gut microbiome for therapeutic and preventative interventions in a wide range of diseases, calling for further research to fully unlock the microbiome's capabilities in enhancing human health.

Unravelling the Link between the Gut Microbiome and Autoimmune Kidney Diseases: A Potential New Therapeutic Approach

The gut microbiota and short chain fatty acids (SCFA) have been associated with immune regulation and autoimmune diseases. Autoimmune kidney diseases arise from a loss of tolerance to antigens, often with unclear triggers. In this review, we explore the role of the gut microbiome and how disease, diet, and therapy can alter the gut microbiota consortium. Perturbations in the gut microbiota may systemically induce the translocation of microbiota-derived inflammatory molecules such as liposaccharide (LPS) and other toxins by penetrating the gut epithelial barrier. Once in the blood stream, these pro-inflammatory mediators activate immune cells, which release pro-inflammatory molecules, many of which are antigens in autoimmune diseases. The ratio of gut bacteria Bacteroidetes/Firmicutes is associated with worse outcomes in multiple autoimmune kidney diseases including lupus nephritis, MPO-ANCA vasculitis, and Goodpasture's syndrome. Therapies that enhance SCFA-producing bacteria in the gut have powerful therapeutic potential. Dietary fiber is fermented by gut bacteria which in turn release SCFAs that protect the gut barrier, as well as modulating immune responses towards a tolerogenic anti-inflammatory state. Herein, we describe where the current field of research is and the strategies to harness the gut microbiome as potential therapy.

Butyrate Prevents the Pathogenic Anemia-Inflammation Circuit by Facilitating Macrophage Iron Export

Most patients with inflammatory bowel disease (IBD) develop anemia, which is attributed to the dysregulation of iron metabolism. Reciprocally, impaired iron homeostasis also aggravates inflammation. How this iron-mediated, pathogenic anemia-inflammation crosstalk is regulated in the gut remains elusive. Herein, it is for the first time revealed that anemic IBD patients exhibit impaired production of short-chain fatty acids (SCFAs), particularly butyrate. Butyrate supplementation restores iron metabolism in multiple anemia models. Mechanistically, butyrate upregulates ferroportin (FPN) expression in macrophages by reducing the enrichment of histone deacetylase (HDAC) at the Slc40a1 promoter, thereby facilitating iron export. By preventing iron sequestration, butyrate not only mitigates colitis-induced anemia but also reduces TNF-α production in macrophages. Consistently, macrophage-conditional FPN knockout mice exhibit more severe anemia and inflammation. Finally, it is revealed that macrophage iron overload impairs the therapeutic effectiveness of anti-TNF-α antibodies in colitis, which can be reversed by butyrate supplementation. Hence, this study uncovers the pivotal role of butyrate in preventing the pathogenic circuit between anemia and inflammation.

Nutritional Modulation of Hepcidin in the Treatment of Various Anemic States

Twenty years after its discovery, hepcidin is still considered the main regulator of iron homeostasis in humans. The increase in hepcidin expression drastically blocks the flow of iron, which can come from one's diet, from iron stores, and from erythrophagocytosis. Many anemic conditions are caused by non-physiologic increases in hepcidin. The sequestration of iron in the intestine and in other tissues poses worrying premises in view of discoveries about the mechanisms of ferroptosis. The nutritional treatment of these anemic states cannot ignore the nutritional modulation of hepcidin, in addition to the bioavailability of iron. This work aims to describe and summarize the few findings about the role of hepcidin in anemic diseases and ferroptosis, as well as the modulation of hepcidin levels by diet and nutrients.

The associations between dietary fibers intake and systemic immune and inflammatory biomarkers, a multi-cycle study of NHANES 2015-2020

Background

In recent years, there has been considerable growth in abnormal inflammatory reactions and immune system dysfunction, which are implicated in chronic inflammatory illnesses and a variety of other conditions. Dietary fibers have emerged as potential regulators of the human immune and inflammatory response. Therefore, this study aims to investigate the associations between dietary fibers intake and systemic immune and inflammatory biomarkers.

Methods

This cross-sectional study used data from the National Health and Nutrition Examination Survey (2015-2020). Dietary fibers intake was defined as the mean of two 24-h dietary recall interviews. The systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), neutrophil-to-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), red blood cell distribution width-to-albumin ratio (RA), ferritin, high-sensitivity C-reactive protein (hs-CRP), and white blood cell (WBC) count were measured to evaluate systemic immune and inflammatory states of the body. The statistical software packages R and EmpowerStats were used to examine the associations between dietary fibers intake and systemic immune and inflammatory biomarkers.

Results

Overall, 14,392 participants were included in this study. After adjusting for age, gender, race, family monthly poverty level index, alcohol consumption, smoking status, vigorous recreational activity, body mass index, hyperlipidemia, hypertension, diabetes, and dietary inflammatory index, dietary fibers intake was inversely associated with SII (β = -2.19885, 95% CI: -3.21476 to -1.18294, p = 0.000248), SIRI (β = -0.00642, 95% CI: -0.01021 to -0.00263, p = 0.001738), NLR (β = -0.00803, 95% CI: -0.01179 to -0.00427, p = 0.000284), RA (β = -0.00266, 95% CI: -0.00401 to -0.00131, p = 0.000644), ferritin (β = -0.73086, 95% CI: -1.31385 to -0.14787, p = 0.020716), hs-CRP (β = -0.04629, 95% CI: -0.0743 to -0.01829, p = 0.002119), WBC (β = -0.01624, 95% CI: -0.02685 to -0.00563, p = 0.004066), neutrophils (β = -0.01346, 95% CI: -0.01929 to -0.00764, p = 0.000064). An inverse association between dietary fibers and PLR was observed in the middle (β = -3.11979, 95% CI: -5.74119 to -0.4984, p = 0.028014) and the highest tertile (β = -4.48801, 95% CI: -7.92369 to -1.05234, p = 0.016881) and the trend test (βtrend = -2.2626, 95% CI: -3.9648 to -0.5604, Ptrend = 0.0150). The observed associations between dietary fibers intake and SII, SIRI, NLR, RA, ferritin, hs-CRP, WBC, and neutrophils remained robust and consistent in the sensitivity analysis. No significant interaction by race was found.

Conclusion

Dietary fibers intake is associated with the improvement of the parameters of the immune response and inflammatory biomarkers, supporting recommendations to increase dietary fibers intake for enhanced immune health.

Klebsiella quasipneumoniae in intestine damages bile acid metabolism in hematopoietic stem cell transplantation patients with bloodstream infection

BACKGROUND

Bloodstream infection (BSI) is a serious hematopoietic stem cell transplantation (HSCT) complication. The intestinal microbiome regulates host metabolism and maintains intestinal homeostasis. Thus, the impact of microbiome on HSCT patients with BSI is essential.

METHODS

Stool and serum specimens of HSCT patients were prospectively collected from the pretransplant conditioning period till 4 months after transplantation. Specimens of 16 patients without BSI and 21 patients before BSI onset were screened for omics study using 16S rRNA gene sequencing and untargeted metabolomics. The predictive infection model was constructed using LASSO and the logistic regression algorithm. The correlation and influence of microbiome and metabolism were examined in mouse and Caco-2 cell monolayer models.

RESULTS

The microbial diversity and abundance of Lactobacillaceae were remarkably reduced, but the abundance of Enterobacteriaceae (especially Klebsiella quasipneumoniae) was significantly increased in the BSI group before onset, compared with the non-BSI group. The family score of microbiome features (Enterobacteriaceae and Butyricicoccaceae) could highly predict BSI (AUC = 0.879). The serum metabolomic analysis showed that 16 differential metabolites were mainly enriched in the primary bile acid biosynthesis pathway, and the level of chenodeoxycholic acid (CDCA) was positively correlated with the abundance of K. quasipneumoniae (R = 0.406, P = 0.006). The results of mouse experiments confirmed that three serum primary bile acids levels (cholic acid, isoCDCA and ursocholic acid), the mRNA expression levels of bile acid farnesol X receptor gene and apical sodium-dependent bile acid transporter gene in K. quasipneumoniae colonized mice were significantly higher than those in non-colonized mice. The intestinal villus height, crypt depth, and the mRNA expression level of tight junction protein claudin-1 gene in K. quasipneumoniae intestinal colonized mice were significantly lower than those in non-colonized mice. In vitro, K. quasipneumoniae increased the clearance of FITC-dextran by Caco-2 cell monolayer.

CONCLUSIONS

This study demonstrated that the intestinal opportunistic pathogen, K. quasipneumoniae, was increased in HSCT patients before BSI onset, causing increased serum primary bile acids. The colonization of K. quasipneumoniae in mice intestines could lead to mucosal integrity damage. The intestinal microbiome features of HSCT patients were highly predictive of BSI and could be further used as potential biomarkers.

Tryptophan metabolism as bridge between gut microbiota and brain in chronic social defeat stress-induced depression mice

Backgrounds

Gut microbiota plays a critical role in the onset and development of depression, but the underlying molecular mechanisms are unclear. This study was conducted to explore the relationships between gut microbiota and host's metabolism in depression.

Methods

Chronic social defeat stress (CSDS) model of depression was established using C57BL/6 male mice. Fecal samples were collected from CSDS group and control group to measure gut microbiota and microbial metabolites. Meanwhile, tryptophan metabolism-related metabolites in hippocampus were also analyzed.

Results

CSDS successfully induced depressive-like behaviors in CSDS group. The 24 differential bacterial taxa between the two groups were identified, and 14 (60.87%) differential bacterial taxa belonged to phylum Firmicutes. Functional analysis showed that tryptophan metabolism was significantly affected in CSDS mice. Meanwhile, 120 differential microbial metabolites were identified, and two key tryptophan metabolism-related metabolites (tryptophan and 5-hydroxytryptophan (5-HTP)) were significantly decreased in feces of CSDS mice. The correlation analysis found the significant relationships between tryptophan and differential bacterial taxa under Firmicutes, especially genus Lactobacillus (r=0.801, p=0.0002). In addition, the significantly decreased 5-hydroxytryptamine (5-HT) in hippocampus of depressed mice was also observed.

Conclusions

Our results showed that tryptophan metabolism might have an important role in the crosstalk between gut microbioa and brain in depression, and phylum Firmicutes, especially genus Lactobacillus, might be involved in the onset of depression through regulating tryptophan metabolism.