Effects of Probiotics Combined with Insulin Therapy on Glycemic Control and Intestinal Microbiota in Children with Type 1 Diabetes Mellitus

Background To explore whether live Clostridium butyricum powder plus insulin modulates glycemic status, inflammatory cytokines and gut microbiota in children with type 1 diabetes mellitus (T1DM), and its potential mechanisms. Methods A case-control study enrolled 77 T1DM children aged 0–16 years hospitalized from September 2023 to December 2025. Subjects were randomized into an observation group (n = 33) and a control group (n = 44). The control group received intensive insulin therapy; the observation group additionally took oral live Clostridium butyricum powder (500 mg sachet, ≥ 7.5×10⁶ CFU viable bacteria, three times daily for 4 weeks). All children were followed for 3 months, and 91 healthy peers served as healthy control group. We compared pre- and post-treatment FBG, HbA1c, fasting C-peptide, fasting insulin, and cytokines (IL-4, IL-6, IL-10, IL-17A, TNF-α, IFN-γ). 16S rRNA V3–V4 sequencing assessed gut microbial α/β-diversity and species composition; Spearman correlation analyzed links between microbiota and clinical markers. Results Both groups showed reduced FBG and HbA1c after treatment, with larger declines in the observation group (FBG: 61.3% vs 47.8%; HbA1c: 3.1% vs 1.35%, P < 0.05). The observation group achieved more prominent drops in pro-inflammatory IL-6, TNF-α, IFN-γ and IL-17A, with significant intergroup differences in IFN-γ (P = 0.002) and IL-17A (P < 0.001). T1DM patients had lower Chao1 index than healthy children (462.56 ± 171.43 vs 696.92 ± 384.29, P = 0.002), while Shannon and Simpson indices were comparable (P > 0.05). PERMANOVA confirmed distinct microbial structures between T1DM and healthy children (R = 0.193, P = 0.001). Post-intervention microbiota in the observation group exhibited concentrated Jaccard similarity coefficients (0.945 vs 0.96), with enriched low-abundance phyla ( Desulfobacterota , Cyanobacteria, Acidobacteriota, P < 0.05). No microbial shift was found in the control group (R = − 0.111, P = 0.992). Conclusions Adjuvant live Clostridium butyricum combined with insulin optimizes glycemic control, alleviates pro-inflammatory response and restores gut microbial homeostasis in pediatric T1DM. The therapeutic effect may rely on short-chain fatty acid-mediated immune regulation and intestinal barrier restoration.