Effects of metformin and other biguanides on oxidative phosphorylation in mitochondria.
Level 5 - mechanism / opinion, no new human data
Preclinical in vitro laboratory study in isolated enzymes, mitochondria, and cultured cells.
PubMed 25017630 · doi:10.1042/BJ20140620
What was done
Researchers evaluated the mechanistic effects of five pharmacologically relevant biguanides (metformin, buformin, phenformin, cycloguanil, and proguanil) on oxidative phosphorylation using isolated mammalian mitochondrial complex I, intact mammalian mitochondria, and cultured cells.
What was found
Biguanides inhibited complex I through non-competitive inhibition of ubiquinone reduction and independently stimulated reactive oxygen species (ROS) production at the complex I flavin site. Biguanides also inhibited mitochondrial ATP synthase, with two compounds selectively inhibiting ATP hydrolysis rather than synthesis. Antidiabetic biguanides (metformin, buformin, phenformin) accumulated in mammalian mitochondria to suppress oxidative phosphorylation, whereas antimalarial biguanides (cycloguanil, proguanil) were excluded from mammalian mitochondria. The abstract reports no numerical values, concentrations, or effect sizes.
Why it matters
This study defines the molecular mechanisms by which biguanides impair mitochondrial respiration and explains why antidiabetic and antimalarial biguanides exhibit divergent cellular pharmacology.
Limits
The study is restricted to cell-free biochemical assays and cultured cells without in vivo validation. Exact compound concentrations, quantitative inhibitory constants (e.g., IC50), and sample sizes are omitted in the abstract.
Cited by
- supports Certain pharmaceutical drugs produce their effects by downregulating complex I of oxidative phosphorylation.