# A Probiotic Fixed Blood Sugar in Old Male Mice, But Did Nothing for Females

_Evidence Level: Preliminary · Jia M et al., Aging cell, DOI 10.1111/acel.70662_

*Lactiplantibacillus plantarum AS21 Attenuates Sex-Biased Glucose Intolerance in Aging Mice via Gut Mucosal Microbiota-Derived Citrulline.*

- **Evidence Level**: Preliminary
- **Why this grade**: Six-month study in naturally aged male and female mice, with no human data yet and no sample size reported.
- **Facts**: Funding: Major Science and Technology Project of Gansu Province
- **Population**: Animal study
- **Publication Types**: Journal Article
- **Journal**: Aging cell
- **Sample Size**: Naturally aged male and female mice (exact number not stated)
- **Authors**: Jia M, Chen M, Chen H, Zhang H, Dou R, Wang C, Ishaq M, Wei X, Ding Z, Guo X
- **Graded and published**: 2026-08-01
- **Last edited**: 2026-09-17
- **Topics**: probiotics, metabolic health, gut microbiome
- **DOI**: https://doi.org/10.1111/acel.70662
- **Free full text**: https://pmc.ncbi.nlm.nih.gov/articles/PMC13473181/
- **Original Source**: https://pubmed.ncbi.nlm.nih.gov/42595959/

## Summary

Older male mice had much worse blood sugar control than females, and they were also low on citrulline (an amino acid made partly by gut bacteria). Feeding them a probiotic called Lactiplantibacillus plantarum AS21 for six months reshaped their gut bacteria, restored citrulline, and improved blood sugar handling. Females, who were already metabolically fine, saw almost no change. Giving citrulline directly produced similar benefits, including more GLP-1 release.

## Practical Takeaway

This early mouse work suggests probiotic benefits for blood sugar may differ by sex.

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