| First Author | Stephenne X | Year | 2011 |
| Journal | Diabetologia | Volume | 54 |
| Issue | 12 | Pages | 3101-10 |
| PubMed ID | 21947382 | Mgi Jnum | J:178126 |
| Mgi Id | MGI:5297319 | Doi | 10.1007/s00125-011-2311-5 |
| Citation | Stephenne X, et al. (2011) Metformin activates AMP-activated protein kinase in primary human hepatocytes by decreasing cellular energy status. Diabetologia 54(12):3101-10 |
| abstractText | AIM/HYPOTHESIS: The glucose-lowering drug metformin has been shown to activate hepatic AMP-activated protein kinase (AMPK), a master kinase regulating cellular energy homeostasis. However, the underlying mechanisms remain controversial and have never been investigated in primary human hepatocytes. METHODS: Hepatocytes isolated from rat, mouse and human livers were treated with various concentrations of metformin. Isoform-specific AMPKalpha abundance and activity, as well as intracellular adenine nucleotide levels and mitochondrial oxygen consumption rates were determined at different time points. RESULTS: Metformin dose- and time-dependently increased AMPK activity in rat and human hepatocytes, an effect associated with a significant rise in cellular AMP:ATP ratio. Surprisingly, we found that AMPKalpha2 activity was undetectable in human compared with rat hepatocytes, while AMPKalpha1 activities were comparable. Accordingly, metformin only increased AMPKalpha1 activity in human hepatocytes, although both AMPKalpha isoforms were activated in rat hepatocytes. Analysis of mRNA expression and protein levels confirmed that only AMPKalpha1 is present in human hepatocytes; it also showed that the distribution of beta and gamma regulatory subunits differed between species. Finally, we demonstrated that the increase in AMP:ATP ratio in hepatocytes from liver-specific Ampkalpha1/2 (also known as Prkaa1/2) knockout mice and humans is due to a similar and specific inhibition of the mitochondrial respiratory-chain complex 1 by metformin. CONCLUSIONS/INTERPRETATION: Activation of hepatic AMPK by metformin results from a decrease in cellular energy status owing to metformin's AMPK-independent inhibition of the mitochondrial respiratory-chain complex 1. The unique profile of AMPK subunits found in human hepatocytes should be considered when developing new pharmacological agents to target the kinase. |
