Early life is a critical window for immune system development, during which the gut microbiome shapes innate immunity, antigen presentation, and adaptive immune maturation. Disruptions in microbial colonization—driven by factors such as cesarean delivery, antibiotic exposure, and formula feeding—deplete beneficial early-life taxa (e.g., Bifidobacterium, Bacteroides, and Enterococcus) and impair key microbial functions, including short-chain fatty acid (SCFA) production by these keystone species, alongside regulatory T cell induction. These dysbiosis patterns are associated with an increased risk of pediatric autoimmune diseases, notably type 1 diabetes, inflammatory bowel disease, celiac disease, and juvenile idiopathic arthritis. This review synthesizes current evidence on how the early-life microbiota influences immune maturation, with potential effects on the development of autoimmune diseases later in life. We specifically focus on human observational and intervention studies, where treatments with probiotics, synbiotics, vaginal microbial transfer, or maternal fecal microbiota transplantations have been shown to partially restore a disrupted microbiome. While restoration of the gut microbiome composition and function is the main reported outcome of these studies, to date, no reports have disclosed direct prevention of autoimmune disease development by targeting the early-life gut microbiome. In this regard, a better understanding of the early-life microbiome–immune axis is essential for developing targeted preventive strategies. Future research must prioritize longitudinal evaluation of autoimmune outcomes after microbiome modulation to reduce the burden of chronic immune-mediated diseases.

Although exocrine pancreatic insufficiency (EPI) is thought to be common in type 1 diabetes, little is known about the relationship of EPI with type 1 diabetes parameters or food intake and abdominal complaints. Characterising individuals with EPI could help prevent EPI-related complications such as malabsorption and osteoporosis. In a cross-sectional cohort of 443 individuals with type 1 diabetes (62

Background: Type 1 diabetes (T1D) is a severe chronic T-cell mediated autoimmune disease that attacks the insulin-producing beta cells of the pancreas. The multifactorial nature of T1D involves both genetic and environmental components, with recent research focusing on the gut microbiome as a crucial environmental factor in T1D pathogenesis. The gut microbiome and its metabolites play an important role in modulating immunity and autoimmunity. In recent years, studies have revealed significant alterations in the taxonomic and functional composition of the gut microbiome associated with the development of islet autoimmunity and T1D. These changes include reduced production of short-chain fatty acids, altered bile acid and tryptophan metabolism, and increased intestinal permeability with consequent perturbations of host (auto)immune responses. Methods/Results: In this review, we summarize and discuss recent observational, mechanistic and etiological studies investigating the gut microbiome in T1D and elucidating the intricate role of gut microbes in T1D pathogenesis. Moreover, we highlight the recent advances in intervention studies targeting the microbiota for the prevention or treatment of human T1D. Conclusions: A deeper understanding of the evolution of the gut microbiome before and after T1D onset and of the microbial signals conditioning host immunity may provide us with essential insights for exploiting the microbiome as a prognostic and therapeutic tool.

The human gut microbiome strongly influences host metabolism by fermenting dietary components into metabolites that signal to the host. Our previous work has shown that Intestinimonas butyriciproducens is a prevalent commensal bacterium with the unique ability to convert dietary fructoselysine to butyrate, a well-known signaling molecule with proven health benefits. Dietary fructoselysine is an abundant Amadori product formed in foods during thermal treatment and is part of foods rich in dietary advanced glycation end products which have been associated with cardiometabolic disease. It is therefore of interest to investigate the causal role of this bacterium and fructoselysine metabolism in metabolic disorders. We assessed associations of I. butyriciproducens with metabolic risk biomarkers at both strain and functional levels using a human cohort characterized by fecal metagenomic analysis. We observed that the level of the bacterial strain as well as fructoselysine fermentation genes were negatively associated with BMI, triglycerides, HbA1c, and fasting insulin levels. We also investigated the fructoselysine degradation capacity within the Intestinimonas genus using a culture-dependent approach and found that I. butyriciproducens is a key player in the butyrogenic fructoselysine metabolism in the gut. To investigate the function of I. butyriciproducens in host metabolism, we used the diet-induced obesity mouse model to mimic the human metabolic syndrome. Oral supplementation with I. butyriciproducens counteracted body weight gain, hyperglycemia, and adiposity. In addition, within the inguinal white adipose tissue, bacterial administration reduced inflammation and promoted pathways involved in browning and insulin signaling. The observed effects may be partly attributable to the formation of the short-chain fatty acids butyrate from dietary fructoselysine, as butyrate plasma and cecal levels were significantly increased by the bacterial strain, thereby contributing to the systemic effects of the bacterial treatment. I. butyriciproducens ameliorates host metabolism in the context of obesity and may therefore be a good candidate for new microbiota-therapeutic approaches to prevent or treat metabolic diseases.

Duodenal Mucosal Resurfacing (DMR) is an endoscopic ablation technique aimed at improving glycemia in patients with type 2 diabetes mellitus (T2DM). Although the exact underlying mechanism is still unclear, it is postulated that the DMR-induced improvements are the result of changes in the duodenal mucosa. For this reason, we assessed macroscopic and microscopic changes in the duodenal mucosa induced by DMR + GLP-1RA. We included 16 patients with T2DM using basal insulin that received a combination treatment of a single DMR and GLP-1RA. Endoscopic evaluation was performed before the DMR procedure and 3 month after, and duodenal biopsies were obtained. Histological evaluation was performed and L and K cell density was calculated. In addition, gene-expression analysis and Western blotting was performed. Endoscopic evaluation at 3 month showed duodenal mucosa with a normal appearance. In line, microscopic histological evaluation showed no signs of villous atrophy or inflammation and unchanged L and K cell density. Unbiased transcriptome profiling and western blotting revealed that PDZK1 expression was higher in responders at baseline and after DMR. GATA6 expression was significantly increased in responders after DMR compared to non-responders. The absence of macroscopic and microscopic changes after 3 month suggest that improvements in glycemic parameters after DMR do not result from significant histological changes in duodenal mucosa. It is more likely that these improvements result from more subtle changes in enteroendocrine signaling. PDZK1 and GATA6 expression might play a role in DMR; this needs to be confirmed in pre-clinical studies.

BACKGROUND:Since the existing literature on plasma metabolites and blood pressure (BP) is predominantly focused on populations of European ancestry, we aimed to study associations between metabolite profiles and BP in a multiethnic cohort. METHODS:From the HELIUS study (Healthy Life in an Urban Setting), 369 individuals of Dutch, Ghanaian, African Surinamese, and South-Asian Surinamese ethnicity were included for a cross-sectional analysis. Office BP was recorded, and plasma metabolites were measured using untargeted liquid chromatography tandem mass spectometry. Associations between metabolite profiles and BP were assessed with XGBoost machine learning prediction models, followed by linear regression models. The associations with the highest-ranked metabolite were validated in 2 cohorts, and its effects were investigated in human aortic endothelial and vascular smooth muscle cells. RESULTS:The plasma metabolite N-formylmethionine (fMet) showed the most consistent associations with BP across age, sex, and ethnicity. Notably, fMet was associated with higher systolic (+4.14 mm Hg, 95% CI, 2.11-6.17 per SD increase) and diastolic BP (+2.61 mm Hg, 1.41-3.82), and these associations were validated in 2 independent cohorts. Mechanistically, we found that fMet likely contributes to elevated BP by suppressing endothelial nitric oxide synthase expression, and inducing oxidative stress and mitochondrial dysfunction in endothelial cells. In addition, fMet elicited an early inflammatory response, disrupted the endothelial barrier and upregulated myosin light chain expression in vascular smooth muscle. CONCLUSIONS:We identified the metabolite fMet as a novel independent factor associated with BP in an ethnically diverse population. It likely contributes to higher BP by triggering endothelial cell dysfunction, while augmenting contractile proteins in vascular smooth muscle cells.

BACKGROUND:Sodium-glucose transporter-2 (SGLT2) inhibitors reduced the incidence of acute kidney injury in large cardiovascular outcome trials in patients with chronic heart and kidney failure. Acute kidney injury is a common complication following cardiac surgery. We hypothesized that perioperative SGLT2 inhibition could reduce kidney injury after cardiac surgery, measured with the biomarker neutrophil gelatinase-associated (NGAL). METHODS:In this open-label phase IV, randomized, parallel-group, pilot study, adult patients undergoing elective cardiac surgery with cardiopulmonary bypass were randomized to receive either an SGLT2 inhibitor, empagliflozin (10 mg; oral) once daily, from three days before surgery until postoperative day two, or standard-of-care. The primary outcome was the between-group difference of serum NGAL on the second postoperative day. Moreover, other biomarkers for acute kidney injury were measured, including serum kidney injury molecule-1 (KIM-1), hypoxia-inducible factor-1 alpha (HIF-1α), and urine NGAL/Creatinine and KIM-1/Creatinine ratios. Additional outcomes included acute kidney injury incidence within the first seven days following cardiac surgery according to Kidney Disease: Improving Global Outcomes criteria and metabolic parameters, including ketone body concentrations and glycemic control. RESULTS:Between March 2022 and April 2023, 55 patients were included (sex: 73 % male, age: 66 ± 10 years, BMI: 28 ± 4 kg/m2, empagliflozin n = 25, control n = 30) in the intention-to-treat analysis. There were no significant between-group differences in serum and urine NGAL or KIM-1. However, empagliflozin significantly reduced the incidence of acute kidney injury (20 % vs 66.7 %; absolute difference 46.7 %, 95 % CI, -69.7 - -23.6; P < .001). A significant increase in serum HIF-1α after surgery was solely observed in the control group. We observed no between-group differences in the incidence of (euglycemic) ketoacidosis or hypoglycemic events. CONCLUSIONS:In this pilot study, perioperative SGLT2 inhibition was not associated with lower NGAL levels. We observed that SGLT2 inhibition reduced the incidence of acute kidney injury in this small study population. As the results of this pilot study are hypotheses-generating, further validation is needed in a large-scale, double-blind, placebo-controlled, randomized trial, which is currently ongoing.

AIMS:As compared with C-peptide, plasma proinsulin levels in individuals with long-standing type 1 diabetes mellitus are relatively understudied, but may serve as a marker of stressed, yet alive β-cells. MATERIALS AND METHODS:We measured proinsulin and C-peptide levels (detection limit <0.15 pmol/L and <0.05 nmol/L, respectively) in a cross-sectional cohort of 482 individuals with type 1 diabetes mellitus and measured associations with diabetes duration, HLA haplotype and autoantibodies. RESULTS:Proinsulin showed a biphasic decline with an initial decrease over 15 years followed by a stabilisation period, whereas C-peptide showed a similar pattern but with an inflection point at ~8 years. Proinsulin and the proinsulin-to-C-peptide ratio did not associate with variables associated with insulin resistance (BMI, triglyceride levels, insulin/day/kg). Higher proinsulin- and C-peptide levels correlated with higher levels of anti-GAD antibodies (Spearman ρ = 0.18 and 0.23 respectively, p < 0.05), but not with anti-IA2. A high-risk DR3/3 HLA genotype associated with complete loss of C-peptide (OR 0.34, 95% CI 0.14-0.79) and proinsulin(OR 0.44, 95% CI 0.20-0.92). CONCLUSIONS/INTERPRETATION:In type 1 diabetes mellitus, proinsulin levels remain detectable long after diagnosis, also in the absence of C-peptide, implying the presence of stressed, yet alive β-cells.

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by T-cell-mediated destruction of pancreatic beta cells, resulting in insulin deficiency. Both genetic predisposition and environmental factors contribute to T1D development, with growing evidence implicating the gut microbiome as a critical environmental modulator in disease pathogenesis. Gut microbial composition and derived metabolites influence immune homeostasis and autoimmunity. This review summarizes recent advances elucidating immune dysregulations in T1D and novel therapeutic strategies to preserve beta cell function. We discuss approaches such as immune cell engineering, including CAR-Treg therapy, and targeted modulation of immune signaling pathways like JAK-STAT. Furthermore, we explore the role of the gut microbiota and its metabolites in modulating host immunity and describe emerging microbiome-targeting interventions, including fecal microbiota transplantation and metabolite supplementation. These interventions show promise in modulating disease progression in preclinical and early clinical studies. An integrated understanding of immune and microbiome-related mechanisms is critical for developing next-generation therapies. Further research and clinical trials are needed to optimize these approaches and translate them into durable, personalized treatments for individuals with T1D.

The gut microbiota plays a pivotal role in human health, partly through the production of bioactive metabolites from dietary tryptophan. These indole derivatives have emerged as key modulators of immune function, inflammation, and metabolic health and have been linked to various diseases. In the context of cancer, indole derivatives are increasingly being studied as promising modulators of immune checkpoint inhibitor (ICI) therapy, with accumulating evidence indicating potential for various derivatives to enhance therapeutic efficacy. ICI therapy is associated with various immune-related adverse events, including accelerated progression of atherosclerotic cardiovascular disease. Given their immunomodulatory properties, there is a growing interest in the usage of indole metabolites to mitigate these cardiovascular complications. This mini-review summarizes current knowledge on the roles of microbiota-derived indoles in cancer, ICI therapy, and atherosclerosis. Though direct evidence linking bacterial tryptophan-derived metabolites to ICI-associated atherosclerosis is currently lacking, accumulating evidence indicates that indole derivatives regulate pathways involved in both anti-tumor immunity and atherosclerosis. Advancing our understanding of how the microbiome and its metabolites influence both cancer and cardiovascular disease will be crucial for developing personalized, metabolite-based strategies to improve outcomes in patients undergoing ICI therapy.

BACKGROUND: The microbiota-derived short chain fatty acid butyrate has been shown to lower blood pressure (BP) in rodent studies. Nonetheless, the net effect of butyrate on hypertension in humans remains uncovered. In this study, for the first time, we aimed to determine the effect of oral butyrate on BP in patients with hypertension. METHODS: We performed a double-blind randomized placebo-controlled trial including 23 patients with hypertension. Antihypertensive medication was discontinued for the duration of the study with a washout period of 4 weeks before starting the intervention. Participants received daily oral capsules containing either sodium butyrate or placebo with an equivalent dosage of sodium chloride for 4 weeks. The primary outcome was daytime 24-hour systolic BP. Differences between groups over time were assessed using linear mixed models (group-by-time interaction). RESULTS: Study participants (59.0±3.7 years; 56.5% female) had an average baseline office systolic BP of 143.5±14.6 mm Hg and diastolic BP of 93.0±8.3 mm Hg. Daytime 24-hour systolic and diastolic BP significantly increased over the intervention period in the butyrate compared with the placebo group, with an increase of +9.63 (95% CI, 2.02–17.20) mm Hg in daytime 24-hour systolic BP and +5.08 (95% CI, 1.34–8.78) mm Hg in diastolic BP over 4 weeks. Butyrate levels significantly increased in plasma, but not in feces, upon butyrate intake, underscoring its absorption. CONCLUSIONS: Four-week treatment with oral butyrate increased daytime systolic and diastolic BP in subjects with hypertension. Our findings implicate that butyrate does not have beneficial effects on human hypertension, which warrants caution in future butyrate intervention studies. REGISTRATION: URL: https://onderzoekmetmensen.nl/ ; Unique identifier: NL8924.

Background Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common postoperative complication. Currently, no effective preventative strategies exist to mitigate CSA-AKI. Sodium-glucose transporter-2 (SGLT2) inhibitors reduced acute kidney injury (AKI) incidence in large, randomized placebo-controlled, cardiovascular and kidney outcome trials conducted in patients with chronic kidney disease. We hypothesized that perioperative SGLT2 inhibition could also reduce CSA-AKI. Methods In this open-label phase IV, randomized, parallel-group, pilot study, adult patients undergoing elective cardiac surgery with cardiopulmonary bypass were randomized to receive the SGLT2 inhibitor, empagliflozin (10 mg; oral), once daily three days prior to surgery and continued to two days after surgery compared with standard-of-care. Biomarkers for acute kidney injury (AKI), including serum and urinary neutrophil gelatinase-associated lipocalin (NGAL), serum and urinary kidney injury molecule-1 (KIM-1), and serum hypoxia-inducible factor-1α (HIF-1α) were measured. Additional outcomes included AKI incidence according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria as well as metabolic parameters, including ketone body concentrations and glycemic control. Results Between March 2022 and April 2023, 55 patients were included (sex: 73% male, age: 66 ± 10 years, BMI: 28 ± 4 kg/m2, empagliflozin n = 25, control n = 30) in the intention-to-treat analysis. Empagliflozin significantly reduced the incidence of AKI (20% vs 66.7%; absolute difference 46.7%, 95% CI, –69.7 – –23.6; P=.001). Following surgery, urinary NGAL, and KIM-1 were found to increase in both arms, whereas a significant increment in serum HIF-1α after surgery was solely observed in the control group. We observed no between-group differences in the incidence of (euglycemic) ketoacidosis or hypoglycemic events. Conclusions Perioperative SGLT2 inhibition, compared with standard of care, significantly reduced the incidence of CSA-AKI. These findings warrant validation in large-scale, double-blind, placebo-controlled, randomized trials. Trial Registry Identifier: NL9561 ### Competing Interest Statement DHR has served as a consultant and received honoraria from Boehringer Ingelheim and Lilly, Merck, Novo Nordisk,Sanofi, and AstraZeneca and has received research operating funds from Boehringer Ingelheim and Lilly Diabetes Alliance, AstraZeneca, and NovoNordisk; all honoraria are paid to his employer (Amsterdam University Medical Center, Amsterdam). All other authors declare no conflict of interests. ### Clinical Trial Identifier: NL9561 ### Funding Statement ?This project has received funding from the European Union?s Horizon 2020 research and innovation program under the Marie Sk?odowska-Curie grant agreement No 101024833.? ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: MERC Amsterdam UMC I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data available upon reasonable request. * AKI : Acute kidney injury CI : Confidence interval CKD : Chronic kidney disease CPB : Cardiopulmonary bypass CSA-AKI : Cardiac surgery-associated acute kidney injury eGFR : estimated glomerular filtration rate HIF1α : Hypoxia-inducible factor 1 alpha IU : International units KIM-1 : Kidney injury molecule 1 NGAL : Neutrophil gelatinase-associated lipocalin KDIGO : Kidney Disease: Improving Global Outcomes SGLT2 : Sodium-glucose transporter-2 T1D : Type 1 diabetes T2D : Type 2 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease targeting insulin-producing pancreatic beta cells. T1D is a multifactorial disease incorporating genetic and environmental factors. In recent years, the advances in high-throughput sequencing have allowed researchers to elucidate the changes in the gut microbiota taxonomy and functional capacity that accompany T1D development. An increasing number of studies have shown a role of the gut microbiota in mediating immune responses in health and disease, including autoimmunity. Fecal microbiota transplantations (FMT) have been largely used in murine models to prove a causal role of the gut microbiome in disease progression and have been shown to be a safe and effective treatment in inflammatory human diseases. In this review, we summarize and discuss recent research regarding the gut microbiota-host interactions in T1D, the current advancement in therapies for T1D, and the usefulness of FMT studies to explore microbiota-host immunity encounters in murine models and to shape the course of human type 1 diabetes.

Amino acids, metabolized by host cells as well as commensal gut bacteria, have signaling effects on host metabolism. Oral supplementation of the essential amino acid histidine has been shown to exert metabolic benefits. To investigate whether dietary histidine aids glycemic control, we performed a case-controlled parallel clinical intervention study in participants with type 2 diabetes (T2D) and healthy controls. Participants received oral histidine for seven weeks. After 2 weeks of histidine supplementation, the microbiome was depleted by antibiotics to determine the microbial contribution to histidine metabolism. We assessed glycemic control, immunophenotyping of peripheral blood mononucelar cells (PBMC), DNA methylation of PBMCs and fecal gut microbiota composition. Histidine improves several markers of glycemic control, including postprandial glucose levels with a concordant increase in the proportion of MAIT cells after two weeks of histidine supplementation. The increase in MAIT cells was associated with changes in gut microbial pathways such as riboflavin biosynthesis and epigenetic changes in the amino acid transporter SLC7A5. Associations between the microbiome and MAIT cells were replicated in the MetaCardis cohort. We propose a conceptual framework for how oral histidine may affect MAIT cells via altered gut microbiota composition and SLC7A5 expression in MAIT cells directly and thereby influencing glycemic control. Future studies should focus on the role of flavin biosynthesis intermediates and SLC7A5 modulation in MAIT cells to modulate glycemic control.

Aims/hypothesis The prevalence and severity of metabolic dysfunction-associated steatotic liver disease (MASLD) in type 1 diabetes remain unclear. Therefore, we investigated the prevalence and severity of MASLD in type 1 diabetes and assessed which clinical features are most important in predicting MASLD severity.Methods A total of 453 individuals with type 1 diabetes (41.6 +/- 15.0 years, 64% female, body mass index [BMI] 25.4 +/- 4.2 kg/m2, and HbA1c 55.6 +/- 12 mmol/mol) underwent vibration-controlled transient elastography (VCTE), with a controlled attenuation parameter (CAP) score for steatosis (>= 280.0 dB/m) and a liver stiffness measurement (LMS) for fibrosis (>= 8.0 kPa). A machine learning Extra-Trees classification model was performed to assess the predictive power of the clinical features associated with type 1 diabetes with respect to steatosis and fibrosis.Results The prevalence of hepatic steatosis and fibrosis was 9.5% (95% CI, 6.8-12.2) and 3.5% (95% CI, 1.8-5.2). Higher LMS was associated with a longer duration of type 1 diabetes (median 30.5 [IQR 18.0-39.3] years vs 15.0 [IQR 6.0-27.0] years), and individuals were older, had a higher BMI (mean 27.8 +/- 5.2 vs 25.3 +/- 4.1 kg/m2), and a higher CAP score (mean 211.4 +/- 51.7 dB/m vs 241.4 +/- 75.6 dB/m). The most important predictive features of fibrosis were duration of type 1 diabetes, age, and systolic blood pressure, with a mean +/- SD area under the curve of 0.73 +/- 0.03.Conclusion Individuals with type 1 diabetes and high blood pressure, older age, higher BMI, and longer duration of disease could be considered at high-risk for developing MASLD. Graphical Abstract