# Systematic Investigation of Dose-Dependent Protein Thermal Stability Changes to Uncover the Mechanisms of the Pleiotropic Effects of Metformin

## TL;DR

This study explores how metformin affects protein stability at different doses, revealing new insights into its blood sugar-lowering and anti-cancer effects.

## Contribution

The study introduces a systematic analysis of metformin's dose-dependent effects on protein thermal stability, uncovering novel molecular mechanisms.

## Key findings

- Low-dose metformin stabilizes complex IV subunits and ribosomal proteins.
- High-dose metformin affects cell redox responses and membrane protein sorting.
- Metformin impacts mitochondrial and vesicle transport at low concentrations.

## Abstract

Metformin is a widely
used drug to treat type II diabetes. Beyond
lowering blood sugar, it has been reported to have pleiotropic effects
such as suppressing cancer growth and attenuating cell oxidative stress
and inflammation. However, the underlying mechanisms of these effects
remain to be explored. Here, we systematically study the thermal stability
changes of proteins in liver cells (HepG2) induced by a wide dosage
range of metformin by using the proteome integral solubility alteration
(PISA) assay. The current results demonstrate that, besides the most
accepted target of metformin (complex I), low concentrations of metformin
(such as 0.2 μM) stabilize the complex IV subunits, suggesting
its important role in the sugar-lowering effect. Low-dose metformin
also results in stability alterations of ribosomal proteins, correlating
with its inhibitive effect on cell proliferation. We further find
that low-concentration metformin impacts mitochondrial cargo and vesicle
transport, while high-concentration metformin affects cell redox responses
and cell membrane protein sorting. This study provides mechanistic
insights into the molecular mechanisms of lowering blood sugar and
the pleiotropic effects of metformin.