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

Summary

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.

Conditions

• Endotoxemia
• Inflammation
• Executive Function (Cognition)

Interventions

DIETARY_SUPPLEMENT

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.

DIETARY_SUPPLEMENT

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.

BIOLOGICAL

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.

Sponsors & Collaborators

• University Hospital, Essen

  collaborator OTHER

• Flemish institute of biotechnology (VIB)

  collaborator OTHER

• Universitaire Ziekenhuizen KU Leuven

  lead OTHER

Principal Investigators

• 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

• Kristin Verbeke, PhD · Translational Research Center for Gastrointestinal Disorders, Department of Chronic Diseases and Metabolism, KU Leuven, 3000 Leuven, Belgium

• 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

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

QUADRUPLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

45 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-10-24

Primary Completion

2027-03-30

Completion

2027-03-30

Countries

• Belgium

Study Locations