Effect of Metformin on Meibomian Gland Epithelial Cells: Implications in Aging and Diabetic Dry Eye Disease.

BACKGROUND

Metformin, a commonly prescribed medication for managing diabetes, has garnered increasing interest as a potential therapeutic option for combating cancer and aging.

METHODS

The current study investigated the effects of metformin treatment on human meibomian gland epithelial cells (hMGECs) at morphological, molecular, and electron microscopy levels. HMGECs were stimulated in vitro with 1 mM, 5 mM, and 10 mM metformin for 24, 48, and 72 h. The assessed outcomes were cell proliferation assays, lipid production, ultrastructural changes, levels of IGF-1, Nrf2, HO-1, apoptosis-inducing factor 1 (AIF1) at the protein level, and the expression of oxidative stress factors (matrix metallopeptidase 9, activating transcription factor 3, CYBB, or NADPH oxidase 2, xanthine dehydrogenase).

RESULTS

Morphological studies showed increased lipid production, the differentiation of hMGECs after stimulation with metformin, and the differentiation effects of undifferentiated hMGECs. Proliferation tests showed a reduction in cell proliferation with increasing concentrations over time. AIF1 apoptosis levels were not significantly regulated, but morphologically, the dying cells at a higher concentration of 5-10 mM showed a rupture and permeabilization of the plasma membrane, a swelling of the cytoplasm, and vacuolization after more than 48 h. The IGF-1 ELISA showed an irregular expression, which mostly decreased over time. Only at 72 h and 10 mM did we have a significant increase. Mitochondrial metabolic markers such as Nrf2 significantly increased over time, while HO-1 decreased partially. The RT-PCR showed a significant increase in MMP9, CYBB, XDH, and ATF with increasing time and metformin concentrations, indicating cell stress.

CONCLUSIONS

Our results using a cell line suggest that metformin affects the cellular physiology of meibomian gland epithelial cells and induces cell stress in a dose- and duration-dependent manner, causing changes in their morphology and ultrastructure.