Impact of SCFA Supplementation on Metabolic Profiles in Serum and Urine of Kidney Transplant Recipients.

A Randomized, Placebo-controlled Trial Investigating the Effect of Short-chain Fatty Acid (SCFA) Supplementation on Serum and Urinary Metabolome in Kidney Transplant Recipients (METAKID Study)

This is a randomized, double-blind, placebo-controlled clinical trial evaluating the impact of short-chain fatty acid (SCFA) supplementation on the serum and urinary metabolome in stable kidney transplant recipients. A total of eligible patients will be randomized 1:1 to receive either SCFA or placebo for a period of 12 weeks. Metabolomic profiling of serum and urine will be performed at three time points: at baseline, after 12 weeks of intervention, and after a 12-week washout period without supplementation. The primary objective of the study is to investigate whether SCFA supplementation leads to measurable changes in systemic and renal metabolomic profiles. Secondary outcomes include assessment of tolerability, safety, and potential immunometabolic correlations and also impact on the serum level of immunossupresants (tacrolimus). This study aims to explore the potential of microbiota-targeted therapies in modulating post-transplant metabolic homeostasis.

Inclusion Criteria:

• Age ≥ 18 years

Stable kidney transplant recipients (≥ 6 months post-transplantation)

Stable graft function defined as eGFR ≥ 30 mL/min/1.73 m² with no significant change (>15%) in the last 3 months

No episodes of acute rejection within the last 6 months

On stable immunosuppressive therapy for at least 3 months

Ability to provide written informed consent

Willingness and ability to comply with study procedures and sample collection

Exclusion Criteria:

• Use of antibiotics or probiotics within 4 weeks prior to enrollment

Known gastrointestinal disease (e.g. inflammatory bowel disease, celiac disease, short bowel syndrome)

Uncontrolled diabetes mellitus (HbA1c > 9%)

Current infection or active malignancy

Pregnancy or breastfeeding

Participation in another interventional clinical trial within the past 30 days

Known allergy or intolerance to SCFA formulations or study components (lactose intolerance)

Severe hepatic impairment (Child-Pugh class C)

Any condition that, in the opinion of the investigator, may interfere with the participant's ability to complete the study or affect the interpretation of results