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Short-Chain Fatty Acids in Lypopolysaccharide-Induced Inflammation and Executive Function

14 de julio de 2026 actualizado por: Universitaire Ziekenhuizen KU Leuven

Investigating the Role of Short-Chain Fatty Acids in Endotoxemia-Induced Inflammation and Core Executive Functioning: A Randomized, Triple-Blind, Placebo-Controlled Trial

Short-chain fatty acids (SCFAs) are substances produced by gut bacteria when they ferment dietary fiber. They can act as signals between the gut and the brain and may help regulate the body's immune and stress responses. Earlier work has shown that delivering SCFAs to the colon can lower the stress hormone response to a mental stress task in healthy people, and laboratory studies suggest SCFAs can reduce inflammation. However, it is not yet known whether SCFAs can reduce inflammation in humans, or whether doing so protects mental performance.

This study uses a controlled, acute, and short-lasting challenge. Healthy adults receive a single, low dose of a bacterial substance called lipopolysaccharide (LPS) through a vein. LPS briefly activates the immune system and causes mild, flu-like symptoms (such as fatigue, headache, and feeling unwell) that pass on their own within a few hours. It does not cause a real infection.

Participants are randomly assigned to take either SCFA capsules or inactive placebo capsules on the morning of the test day, before the LPS challenge. Neither the participants, the researchers running the visit, nor the researchers analyzing the results know who received which capsules until the study is complete (triple-blind).

The main goal of the study is to test whether SCFAs, compared with placebo, reduce the inflammatory response to LPS, measured by markers of inflammation in the blood. The study also examines whether SCFAs reduce the associated sickness symptoms and whether they protect performance on tasks that measure core executive functions: the ability to keep relevant information in mind (working memory), the ability to hold back automatic responses or thoughts (inhibition), and the ability to switch flexibly between tasks or rules (cognitive flexibility). Blood, saliva, and stool samples are collected to measure inflammation markers, SCFA levels, stress hormones, and gut bacteria.

Participants attend a screening visit, a test day with monitoring for several hours, and a short follow-up visit the next day.

Descripción general del estudio

Estado

Reclutamiento

Condiciones

Intervención / Tratamiento

Descripción detallada

INFLEX is a single-center, randomized, triple-blind, placebo-controlled, parallel-group interventional trial conducted at UZ Leuven / KU Leuven. Its primary aim is to test whether a single acute dose of colon-delivered SCFAs, relative to placebo, attenuates the systemic inflammatory response induced by experimental endotoxemia in healthy adults. Secondary aims are to test whether SCFAs attenuate LPS-induced sickness behaviour and mitigate endotoxemia-induced changes in core executive functioning, and to characterize associations between systemic SCFA uptake, the inflammatory response, and these outcomes.

Eligible participants are randomized to receive SCFA colon-delivery capsule or placebo capsules, taken on the morning of the test day with a standardized low-fiber breakfast. One hour after capsule intake, participants receive a single intravenous bolus of purified Escherichia coli lipopolysaccharide (0.4 ng/kg body weight), which serves as a fixed inflammatory challenge applied to all participants. The timing is designed so that peak circulating SCFA concentrations (approximately 3-4 hours after colonic delivery) coincide with the peak of LPS-induced cytokines and sickness behaviour (approximately 2-3 hours post-injection).

Participants are monitored for a minimum of 6 hours after the LPS challenge. Vital signs, sickness symptoms, and blood and saliva samples are collected hourly to quantify inflammatory markers (including IL-6 and hs-CRP), serum SCFA, cortisol, and ACTH. Core executive-function tasks are administered before and after the LPS challenge and at a 24-hour follow-up visit. A fecal sample collected at home prior to the test day is used for gut microbiota profiling. To standardize endogenous SCFA production, participants follow a low-fiber diet for three days before the test day and avoid caffeine, alcohol, and strenuous exercise beforehand. The night prior to the test day, participants are instructed to consume a standard dinner that is provided to them.

The study comprises three visits: a screening visit (~1 hour), the laboratory test day (~8 hours), and a follow-up visit (~30 minutes) 24 hours after the LPS challenge.

Tipo de estudio

Intervencionista

Inscripción (Estimado)

56

Fase

  • No aplica

Contactos y Ubicaciones

Esta sección proporciona los datos de contacto de quienes realizan el estudio e información sobre dónde se lleva a cabo este estudio.

Estudio Contacto

Copia de seguridad de contactos de estudio

Ubicaciones de estudio

  • Bélgica
      • Leuven, Bélgica, 3000
        • Reclutamiento
        • University Hospital Leuven (UZ Leuven)
        • Contacto:
        • Contacto:

Criterios de participación

Los investigadores buscan personas que se ajusten a una determinada descripción, denominada criterio de elegibilidad. Algunos ejemplos de estos criterios son el estado de salud general de una persona o tratamientos previos.

Criterio de elegibilidad

Edades elegibles para estudiar

  • Adulto

Acepta Voluntarios Saludables

Sí

Descripción

Inclusion Criteria:

  • Voluntary written informed consent obtained prior to any study procedure
  • Healthy, with no gastrointestinal or psychological complaints
  • Age 18-45 years
  • BMI 18.5-27 kg/m2
  • Proficiency in English and/or Dutch

Exclusion Criteria:

  • History of previous or current neurological disorder (e.g., epilepsy, multiple sclerosis, migraine with aura)
  • History of previous or current psychiatric disorder (e.g., depression, anxiety disorders, bipolar disorder, schizophrenia)
  • History of previous or current gastrointestinal disorder (e.g., Crohn's disease, ulcerative colitis, irritable bowel syndrome)
  • History of previous or current endocrine disorder (e.g., diabetes, thyroid disorders, polycystic ovary syndrome)
  • History of immune system disorder, including inflammatory, autoimmune, or severe allergic conditions (e.g., rheumatoid arthritis, lupus, celiac disease, or severe allergies such as anaphylaxis)
  • History of neuropsychiatric disorder (e.g., ADHD, autism spectrum disorder, learning disorder, Tourette's syndrome)
  • History of major head trauma (e.g., concussion with loss of consciousness or long-term symptoms)
  • History of severe infection (e.g., sepsis, pneumonia requiring hospitalization, meningitis, endocarditis, or other systemic infection requiring hospitalization, intravenous antibiotics, or intensive care)
  • One or more diagnoses based on the Mini International Neuropsychiatric Interview (MINI)
  • One or more diagnoses based on ROME-IV criteria for gastrointestinal disorders
  • Any disorder that, in the investigator's opinion, might jeopardise the participant's safety or compliance with the protocol
  • Any prior or concomitant treatment that might jeopardise the participant's safety or compromise the integrity of the study
  • Participation in an interventional trial with an investigational medicinal product (IMP) or device
  • Current or recent (past month) prescribed medication use, with particular attention to cardiovascular drugs, steroids, NSAIDs, and centrally-acting drugs (excluding isolated over-the-counter use such as ibuprofen or paracetamol, and hormonal contraceptives in women)
  • Use of psychotropic medication within the past year (e.g., antidepressants, anxiolytics, antipsychotics)
  • Use of antibiotics within three months preceding the study
  • Use of pre- or probiotics within one month preceding the study
  • Current or recent (past month) infection (e.g., common cold, influenza, COVID-19)
  • Recent (past month) vaccination
  • Pregnant or lactating women
  • Previous or current substance or alcohol dependence or abuse (>2 units/day or >14 units/week)
  • Smoking
  • Night-shift work
  • Adherence to special diets (e.g., vegan, vegetarian, weight-loss, lactose-free, gluten-free)
  • Previous experience with or knowledge of any of the cognitive tasks used in the study (questionnaires excluded)
  • C-reactive protein higher than 0.5mg/dL on the day of the injection.
  • Colour vision deficiency or colour-blindness

Plan de estudios

Esta sección proporciona detalles del plan de estudio, incluido cómo está diseñado el estudio y qué mide el estudio.

¿Cómo está diseñado el estudio?

Detalles de diseño

  • Propósito principal: Ciencia básica
  • Asignación: Aleatorizado
  • Modelo Intervencionista: Asignación paralela
  • Enmascaramiento: Cuadruplicar

Armas e Intervenciones

Grupo de participantes/brazo
Intervención / Tratamiento
Experimental: SCFA Colon-Delivery Capsules
A single acute oral dose of colon-delivery capsules delivering a short-chain fatty acid mixture (approximately 186 mmol total SCFA: 111 mmol acetate, 43 mmol propionate, 32 mmol butyrate; molar ratio approximately 60:23:17), taken on the morning of the test day with a standardized low-fiber breakfast.
Suplemento dietético: Short-Chain Fatty Acid Colon-Delivery Capsules
Single acute oral dose of pH-dependent colon-delivery capsules delivering a short-chain fatty acid mixture to the colon. The mixture comprises sodium acetate,sodium butyrate, and sodium propionate (54.4%, 21.2%, and 24.4% by weight), providing approximately 186 mmol total SCFA per dose (111 mmol acetate, 32 mmol butyrate, 43 mmol propionate). Capsules are sub-coated with hydroxypropylcellulose and coated with a pH-dependent layer (Eudragit FS 30 D with PlasACRYL T20). Taken on the morning of the test day with a standardized low-fiber breakfast.
Biológico: Lipopolysaccharide (LPS)
Single intravenous bolus of purified Escherichia coli-derived lipopolysaccharide (0.4 ng/kg body weight), administered one hour after capsule intake to all participants as a standardized experimental inflammatory challenge common to both study arms.
Otros nombres:
  • LPS
  • Endotoxina
Comparador de placebos: Placebo
Single acute oral dose of placebo capsules containing microcrystalline cellulose and matching excipients, matched in appearance and number to the SCFA capsules.
Biológico: Lipopolysaccharide (LPS)
Single intravenous bolus of purified Escherichia coli-derived lipopolysaccharide (0.4 ng/kg body weight), administered one hour after capsule intake to all participants as a standardized experimental inflammatory challenge common to both study arms.
Otros nombres:
  • LPS
  • Endotoxina
Suplemento dietético: Placebo capsules
Single acute oral dose of placebo capsules containing microcrystalline cellulose and matching excipients, an inert non-fermentable substrate. Matched in appearance and number to the SCFA capsules and taken on the morning of the test day with a standardized low-fiber breakfast.
Otros nombres:
  • Placebo
  • celulosa microcristalina

¿Qué mide el estudio?

Medidas de resultado primarias

Medida de resultado
Medida Descripción
Periodo de tiempo
Serum interleukin-6 (IL-6) response to the LPS challenge
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Effect of SCFA versus placebo on the systemic inflammatory response to experimental endotoxemia, indexed by serum IL-6 concentrations measured at serial timepoints across the test day following the intravenous LPS bolus. The primary analysis evaluates the treatment-by-timepoint interaction on the IL-6 time course using a linear mixed model, with treatment (SCFA vs. placebo) as a between-subject factor and timepoint as a within-subject factor.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection

Medidas de resultado secundarias

Medida de resultado
Medida Descripción
Periodo de tiempo
Serum pro- and anti-inflammatory cytokine response to the LPS challenge
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Effect of SCFA versus placebo on serum concentrations of TNF-alpha, IL-1-beta, IFN-gamma, IL-8, IL-4, and IL-10. Analyzed as treatment-by-timepoint interactions using linear mixed models.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
High-sensitivity C-reactive protein (hs-CRP) response to the LPS challenge
Periodo de tiempo: 2 hours before LPS injection, and at 2, 6, and 24 hours after LPS injection
Effect of SCFA versus placebo on serum high-sensitivity C-reactive protein (hs-CRP) concentrations, measured at selected timepoints on the test day and at the 24-hour follow-up visit.
2 hours before LPS injection, and at 2, 6, and 24 hours after LPS injection
LPS-induced sickness behaviour (SicknessQ)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Effect of SCFA versus placebo on subjective sickness behaviour, assessed with the Sickness Questionnaire (SicknessQ), analyzed across timepoints on the test day.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Body temperature response to the LPS challenge
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Effect of SCFA versus placebo on body temperature (degrees Celsius).
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Heart rate response to LPS challenge
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Effect of SCFA versus placebo on heart rate (beats per minute) across the monitoring period.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Blood pressure response to the LPS challenge
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Effect of SCFA versus placebo on systolic and diastolic blood pressure (mmHg).
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Salivary cortisol response to the LPS challenge
Periodo de tiempo: At 0, 1, 2, 3, 4, and 6 hours after LPS injection
Effect of SCFA versus placebo on salivary cortisol concentrations (ng/ml).
At 0, 1, 2, 3, 4, and 6 hours after LPS injection
Plasma ACTH
Periodo de tiempo: At 0, 1, 2, 3, 4, and 6 hours after LPS injection
Effect of SCFA versus placebo on plasma ACTH concentrations (ng/l)
At 0, 1, 2, 3, 4, and 6 hours after LPS injection
Working memory performance (3-back task)
Periodo de tiempo: 2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Effect of SCFA versus placebo on working memory, assessed with the 3-back task (primary index: d-prime). Assessed at baseline (pre-LPS), post-LPS on the test day, and at the 24-hour follow-up.
2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Response inhibition (Stop Signal Task)
Periodo de tiempo: 2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Effect of SCFA versus placebo on response inhibition, assessed with the Stop Signal Task (outcome: stop-signal reaction time, SSRT, in milliseconds).
2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Cognitive flexibility - task switching (Number-Letter task)
Periodo de tiempo: 2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Effect of SCFA versus placebo on cognitive flexibility, assessed with the Number-Letter task (outcome: switch cost, in milliseconds).
2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Cognitive inhibition (Stroop task)
Periodo de tiempo: 2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Effect of SCFA versus placebo on cognitive inhibition, assessed with the Stroop task (outcome: congruency effect, in milliseconds).
2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Cognitive flexibility - set shifting (Wisconsin Card Sorting Task)
Periodo de tiempo: 2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Effect of SCFA versus placebo on cognitive flexibility, assessed with the Wisconsin Card Sorting Task (outcome: number of perseverative errors).
2 hours before LPS injection, 2.25 hours after LPS injection, and 24 hours after LPS injection
Systemic SCFA uptake (serum SCFA concentrations)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection
Serum concentrations of acetate, propionate, and butyrate, assessed as a measure of systemic SCFA uptake to confirm target engagement of the colon-delivery intervention, and used as a mediator in mechanistic analyses of treatment effects on the inflammatory response.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, and 6 hours after LPS injection

Otras medidas de resultado

Medida de resultado
Medida Descripción
Periodo de tiempo
Baseline gut microbiota composition
Periodo de tiempo: Single fecal sample collected within the 3 days prior to the test day
Baseline fecal gut microbiota composition, characterized by quantitative microbiome profiling from a single fecal sample collected before the test day. Examined in exploratory analyses as a baseline predictor of inter-individual variability in systemic SCFA uptake and treatment response.
Single fecal sample collected within the 3 days prior to the test day
Mood - valence (MDMQ)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported mood valence (good-bad dimension), assessed with the Multidimensional Mood Questionnaire (MDMQ/MDBF). Score range 1-40; higher scores indicate a more positive mood.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Mood - alertness (MDMQ)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported alertness (awake-tired dimension), assessed with the Multidimensional Mood Questionnaire (MDMQ/MDBF). Score range 1-40; higher scores indicate greater alertness.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Mood - calmness (MDMQ)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported calmness (calm-restless dimension), assessed with the Multidimensional Mood Questionnaire (MDMQ/MDBF). Score range 1-40; higher scores indicate greater calmness.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Negative affect (PANAS)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported negative affect, assessed with the negative affect subscale of the Positive and Negative Affect Schedule (10 items, 5-point Likert; score range 10-50). Higher scores indicate greater negative affect.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Positive affect (PANAS)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported positive affect, assessed with the positive affect subscale of the Positive and Negative Affect Schedule (10 items, 5-point Likert; score range 10-50). Higher scores indicate greater positive affect.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
State anxiety (STADI)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported state anxiety, assessed with the anxiety subscale of the State-Trait Anxiety and Depression Inventory (STADI), state form (4-point Likert). Higher scores indicate greater state anxiety.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
State depression (STADI)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported state depression, assessed with the depression subscale of the State-Trait Anxiety and Depression Inventory (STADI), state form (4-point Likert). Higher scores indicate greater state depressive symptoms.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Sleepiness (SSS)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported sleepiness, assessed with the Stanford Sleepiness Scale (single item, range 1-7). Higher scores indicate greater sleepiness.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
State anxiety (STAI-S)
Periodo de tiempo: 2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection
Effect of SCFA versus placebo on self-reported state anxiety, assessed with the state subscale of the State-Trait Anxiety Inventory (20 items, 4-point Likert; score range 20-80). Higher scores indicate greater state anxiety.
2 hours before LPS injection, and at 0, 1, 2, 3, 4, 5, 6 and 24 hours after LPS injection

Colaboradores e Investigadores

Aquí es donde encontrará personas y organizaciones involucradas en este estudio.

Patrocinador

Universitaire Ziekenhuizen KU Leuven

Colaboradores

University Hospital, Essen
Flemish institute of biotechnology (VIB)

Investigadores

  • Investigador principal: Lukas Van Oudenhove, MD, PhD, Laboratory for Brain-Gut Axis Studies, Translational Research Center for Gastrointestinal Disorders, Department of Chronic Diseases and Metabolism, KU Leuven, 3000 Leuven, Belgium
  • Investigador principal: Kristin Verbeke, PhD, Translational Research Center for Gastrointestinal Disorders, Department of Chronic Diseases and Metabolism, KU Leuven, 3000 Leuven, Belgium
  • Investigador principal: Boushra Dalile, PhD, Laboratory for Brain-Gut Axis Studies, Translational Research Center for Gastrointestinal Disorders, Department of Chronic Diseases and Metabolism, KU Leuven, 3000 Leuven, Belgium

Fechas de registro del estudio

Estas fechas rastrean el progreso del registro del estudio y los envíos de resultados resumidos a ClinicalTrials.gov. Los registros del estudio y los resultados informados son revisados ​​por la Biblioteca Nacional de Medicina (NLM) para asegurarse de que cumplan con los estándares de control de calidad específicos antes de publicarlos en el sitio web público.

Fechas importantes del estudio

Inicio del estudio (Actual)

24 de octubre de 2025

Finalización primaria (Estimado)

30 de marzo de 2027

Finalización del estudio (Estimado)

30 de marzo de 2027

Fechas de registro del estudio

Enviado por primera vez

30 de junio de 2026

Primero enviado que cumplió con los criterios de control de calidad

14 de julio de 2026

Publicado por primera vez (Actual)

20 de julio de 2026

Actualizaciones de registros de estudio

Última actualización publicada (Actual)

20 de julio de 2026

Última actualización enviada que cumplió con los criterios de control de calidad

14 de julio de 2026

Última verificación

1 de junio de 2026

Más información

Términos relacionados con este estudio

Palabras clave

Términos MeSH relevantes adicionales

Otros números de identificación del estudio

  • S69844

Plan de datos de participantes individuales (IPD)

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INDECISO

Información sobre medicamentos y dispositivos, documentos del estudio

Estudia un producto farmacéutico regulado por la FDA de EE. UU.

No

Estudia un producto de dispositivo regulado por la FDA de EE. UU.

No

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