Probiotic Supplementation and Metabolic–Immune Biomarkers: 12-Week RCT Findings

Investigators report a 12-week randomized, double-blind, placebo-controlled trial comparing a multi-strain probiotic with placebo in 39 adults with subthreshold depression, focusing on fasting metabolic indices and immune-related biomarkers. Over follow-up, the article describes between-group differences in trajectories for markers related to glucose regulation and incretin signaling, alongside circulating indicators commonly used to track metabolic endotoxemia and systemic inflammation. Circulating short-chain fatty acids (SCFAs) were also assessed as a plasma readout of microbial–host metabolic activity. Results are organized across three domains: glucose and incretins, endotoxemia/inflammation markers, and circulating SCFAs.

The report outlines fasting venous blood collection at baseline, week 6, and week 12, with longitudinal modeling of treatment-by-time effects. Participants received a multi-species probiotic containing Limosilactobacillus fermentum LF16, Lacticaseibacillus rhamnosus LR06, Lactiplantibacillus plantarum LP01, and Bifidobacterium longum 04, or a matching placebo. The methods describe ELISA-based measurements for fasting glucose, insulin, HOMA-IR, glucose-dependent insulinotropic peptide (GIP), and inflammatory/endotoxemia-related peptides including hs-CRP, LBP, and soluble CD14 (sCD14). Plasma SCFAs were quantified using gas chromatography–mass spectrometry (GC–MS), with analyses framed around between-group differences in biomarker change over time.

For glycaemic outcomes, the article reports that fasting glucose decreased more in the probiotic group than placebo by week 12 (−1.8 vs 0.1 mmol/L; p=0.036). Insulin-resistance indices were described as shifting modestly in both groups: fasting insulin and HOMA-IR showed small, non-significant decreases, and neither index had a significant treatment×time interaction. Incretin findings were presented as selective, with greater reductions in fasting GIP in the probiotic group than placebo, with two significant p-values reported for GIP (p=0.012 and p=0.037) over follow-up. GLP-1 was measured but described as below the assay detection limit and therefore not included in analyses.

Markers presented as reflecting metabolic endotoxemia and systemic inflammation were reported to decline in the probiotic arm relative to placebo over follow-up, based on treatment×time interaction testing. Specifically, the article reports significant interaction p-values for LBP (p<0.001), sCD14 (p=0.002 and p=0.001), and hs-CRP (p=0.047). For hs-CRP, the methods note that values were screened for potential acute infection, and the article reports that no participant had hs-CRP >10 mg/L. In the results narrative, these changes are described as concurrent shifts across multiple circulating biomarkers that the authors link to endotoxin exposure and low-grade inflammatory tone.

For circulating SCFAs, the article reports that plasma concentrations were largely unchanged over 12 weeks, with no significant treatment×time interactions for individual SCFAs except for valerate, which was higher at week 12 in the probiotic group (p=0.019). The authors concluded that 12 weeks of multi-species probiotic supplementation improved fasting glucose, reduced incretin and inflammatory biomarkers, and attenuated metabolic endotoxemia, without altering circulating SCFAs.

Key Takeaways:

• The article reports that fasting glucose declined more over 12 weeks in the probiotic group than in the placebo group.
• Investigators report decreased fasting GIP with the probiotic (while GLP-1 was below detection), alongside declines in LBP, sCD14, and hs-CRP compared with placebo.
• Plasma SCFAs were reported as largely unchanged between groups over time, with valerate higher at week 12 in the probiotic group.