Safety and immune-regulating effects of Limosilactobacillus reuteri LR08: Preclinical and clinical evidence from a randomized controlled trial

Abstract

Background and aims: This study aimed to systematically evaluate the genomic safety of Limosilactobacillus reuteri LR08 and to assess its effects on metabolic health, immune function, and gut microbiota composition in healthy adults..

Methods: Whole-genome sequencing and bioinformatics analyses were conducted to assess the presence of genes related to pathogenicity, antibiotic resistance, and biogenic amine synthesis. In vitro assays and animal studies evaluated hemolytic activity, cytotoxicity, and overall biosafety. A randomized, double-blind, placebo-controlled trial was performed in 48 healthy adults, who received either LR08 (30 billion CFU/day) or placebo for 8 weeks. Clinical, biochemical, and immune parameters were measured, and 16S rRNA sequencing was used to assess gut microbiota changes.

Results: Genomic analysis confirmed the absence of pathogenicity-related, antibiotic resistance, or biogenic amine synthesis genes. In vitro and animal tests demonstrated non-hemolytic, non-cytotoxic characteristics and overall safety. Clinically, LR08 significantly reduced serum uric acid (p < 0.001) and LDL-C levels (p = 0.007) compared with baseline. Compared with placebo, LR08 supplementation significantly increased salivary IgA (p = 0.039), IgM (p = 0.029), and calprotectin levels (p < 0.05). Gut microbiota analysis revealed increased α-diversity, enrichment of beneficial genera including Blautia and Romboutsia, and upregulation of pathways related to carbohydrate metabolism and genetic information processing..

Conclusions: L. reuteri LR08 demonstrates robust genomic safety and favorable effects on metabolic, immune, and gut microbiota profiles in healthy adults. These findings support its potential application as a safe probiotic for metabolic regulation, immune enhancement, and microbiota modulation..

Trial registration number: NCT06875362 (ClinicalTrials.gov).

Keywords: Gut microbiota; Immune modulation; Limosilactobacillus reuteri LR08; Metabolic health; Randomized double-blind placebo-controlled trial; Safety assessment.