Metformin induces PGC‐1α expression and selectively affects hepatic PGC‐1α functions. (May 2014)

• Record Type: Journal Article
• Authors: Aatsinki, Sanna‐Mari; Buler, Marcin; Salomäki, Henriikka; Koulu, Markku; Pavek, Petr; Hakkola, Jukka
• Is Part Of: British journal of pharmacology. Volume 171:Number 9(2014:May)
• Page Start: 2351
• Page End: 2363
• Publication Date: 2014-05
• Subjects: Pharmacology -- Periodicals; Chemotherapy -- Periodicals; Drug Therapy -- Periodicals; Pharmacology -- Periodicals; 615.1
• DOI: 10.1111/bph.12585
• Languages: English
• ISSNs: 0007-1188

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="bph12585-sec-0001" sec-type="section"> <title>Background and Purpose</title> <p>The objective of this study was to determine how the AMPK activating antidiabetic drug metformin affects the major activator of hepatic gluconeogenesis, PPARγ coactivator 1α (PGC‐1α) and liver functions regulated by PGC‐1α.</p> </sec> <sec id="bph12585-sec-0002" sec-type="section"> <title>Experimental Approach</title> <p>Mouse and human primary hepatocytes and mice <italic>in vivo</italic> were treated with metformin. Adenoviral overexpression, siRNA and reporter gene constructs were used for mechanistic studies.</p> </sec> <sec id="bph12585-sec-0003" sec-type="section"> <title>Key Results</title> <p>Metformin increased PGC‐1α mRNA and protein expression in mouse primary hepatocytes. 5‐Aminoimidazole‐4‐carboxamide ribonucleotide (AICAR) (another AMPK activator) had the opposite effect. Metformin also increased PGC‐1α in human primary hepatocytes; this effect of metformin was abolished by AMPK inhibitor compound C and sirtuin 1 siRNA. AMPK overexpression by AMPK‐Ad also increased PGC‐1α. Whereas metformin increased PGC‐1α, it down‐regulated gluconeogenic genes phosphoenolpyruvate carboxykinase (PEPCK) and glucose‐6‐phosphatase (G6Pase). Furthermore, metformin attenuated the increase in PEPCK and G6Pase mRNAs induced by PGC‐1α overexpression, but did not affect PGC‐1α‐mediated induction of mitochondrial genes. Metformin down‐regulated several key transcription factors that mediate the effect of PGC‐1α on gluconeogenic genes including Krüppel‐like factor 15, forkhead box protein O1 and hepatocyte NF 4α, whereas it increased nuclear respiratory factor 1, which is involved in PGC‐1α‐mediated regulation of mitochondrial proteins.</p> </sec> <sec id="bph12585-sec-0004" sec-type="section"> <title>Conclusions and Implications</title> <p>Down‐regulation of PGC‐1α is not necessary for suppression of gluconeogenic genes by metformin. Importantly, metformin selectively affects hepatic PGC‐1α‐mediated gene regulation and prevents activation of gluconeogenesis, but does not influence its regulation of mitochondrial genes. These results identify selective modulation of hepatic PGC‐1α functions as a novel mechanism involved in the therapeutic action of metformin.</p> </sec> </abstract>