Metformin Eliminates Lymphedema in Mice by Alleviating Inflammation and Fibrosis: Implications for Human Therapy.

Background: Secondary lymphedema is a chronic, disabling disease affecting more than 50% of patients with cancer and lacking effective pharmacologic treatment even for early to middle disease stages. Metformin reportedly exerts anti-inflammatory and antifibrotic effects and is safe, with minimal side effects. The authors investigated the role of metformin in lymphedema mouse models and examined underlying molecular mechanisms.

Methods: Male C57BL/6 mice (6 to 8 weeks old; n = 15/group) received metformin (300 mg/kg/day) by gavage on day 3 after lymphedema surgery; saline and sham groups were administered the same volume of saline. Hindlimb circumference and tail volume were monitored every 2 days. On day 28, samples were collected for histologic assessment, Western blotting, and reverse transcription quantitative polymerase chain reaction analysis of inflammation, fibrosis, and AMP-activated protein kinase (AMPK) expression. AMPK activity was assayed in patients with secondary lymphedema (International Society of Lymphology stage II) and controls following strict inclusion criteria.

Results: Compared with the saline group, the metformin group exhibited hindlimb circumference and tail volume reduced by 469.70% and 305.18%, respectively, on day 28. Dermal thickness was reduced by 38.27% and 72.57% in the hindlimbs and tail, respectively. Metformin decreased CD4+ T-cell infiltration by 19.73%, and decreased expression levels of interleukin-4, interleukin-13, interleukin-17, and transforming growth factor-β1. In addition, it lowered collagen I deposition by 33.18%. Compared with the saline group, the number of lymphatic vessels increased by 229.96% in the metformin group. Both the saline group mice and patients with lymphedema showed reduced AMPK activity; metformin increased p-AMPK expression by 106.12%.

Conclusion: Metformin alleviated inflammation and fibrosis and increased lymphangiogenesis in lymphedema mouse models by activating AMPK signaling.

Clinical Relevance Statement: Metformin provides preliminary evidence as a potential therapeutic option for lymphedema.