An exploratory 12-week pilot study of gut microbiota and body-weight patterns during sodium nitrite exposure and Lactobacillus plantarum 299v supplementation in Wistar rats

Sodium nitrite (E250) is a widely used additive in processed meat products and has been reported to disrupt the gut microbiota and exert carcinogenic effects via N-nitroso compounds. This exploratory pilot study examined body-weight and longitudinal gut-microbiota patterns during sodium nitrite exposure and Lactobacillus plantarum 299v supplementation in adolescent Wistar rats. Sixty-four adolescent Wistar rats were allocated to Control, sodium nitrite (SN), Lactobacillus plantarum 299v (LP), or combined SN + LP groups for 12 weeks. Body weight was assessed in the full cohort. The exploratory microbiota component comprised 48 serial fecal samples from eight selected rats, with one male and one female from each treatment group. V3–V4 16S rRNA amplicons were sequenced on an Illumina iSeq 100 using a 2 × 150-bp paired-end configuration. Read 1 (R1) sequences were processed using the single-end DADA2 workflow, and microbiota profiles were analyzed descriptively. Body-weight trajectories varied across groups and sexes in the full cohort. The descriptive relative-abundance profiles varied across sampling times. The sodium nitrite profile showed higher relative Proteobacteria abundance at several post-baseline time points, while longitudinal ordination trajectories overlapped substantially. The exploratory findings describe patterns across sampling times but do not establish group-level treatment effects or probiotic attenuation of nitrite-associated changes. Confirmation in adequately powered studies with independent cage-level replication is required. Not applicable.