Project description:Metformin is now the most widely prescribed oral anti-diabetic agent worldwide, taken by over 150 million people annually. Although metformin has been used clinically to treat type 2 diabetes for over 60 years. Its mechanism of action remains only partially understood and controversial. In particular, this includes whether AMPK plays a role in metformin suppression of liver glucose production. To address this issue, we knocked out the AMPK catalytic alpha1 and alpha 2 subunits in the liver of HFD-fed adult homozygous mice. These mice were treated with a physiological relevent metformin dose (50 mg/kg/day) for 3 weeks. Liver samples were collected.
Project description:Trans-10, cis-12 conjugated linoleic acid (t10c12 CLA) causes dramatic reductions in white adipose tissue in mice but has had limited effectiveness in humans. Determination of the signaling pathways involved may lead to better regulation of adiposity. T10c12 CLA was found to activate AMP-activating protein kinase (AMPK), a central regulator of cell metabolism. Compound C, a potent inhibitor of AMPK, prevents many of the typical responses to treatments with t10c12 CLA including the integrated stress response (ISR), the inflammatory response, the reduction in key lipogenic transcription factors, and delipidation. Treatment of adipocytes or mice with t10c12 CLA in conjunction with AMPK activator metformin results in more delipidation than treatment with the individual chemicals. Additionally, the combination showed a reduced inflammatory response relative to a t10c12 CLA treatment alone. The combination of t10c12 CLA and metformin, widely used to treat insulin resistance and Type II diabetes, has potential as a treatment for reducing adiposity in humans. Keywords: control/treatment Mouse 3T3-L1 RNA for was isolated from control linoleic acid (LA) and treatment (CLA, CLA+metformin, metformin) samples for analysis on microarrays with three biological reps.
Project description:Metformin has been used to treat patients with type 2 diabetes for over 60 years, however, its mechanism of action is still not completely understood. Our previous reports showed that high-fat-diet (HFD)-fed mice with liver-specific knockout of both AMPK catalytic ?1 and ?2 subunits exhibited significantly higher fasting blood glucose levels and produced more glucose than floxed AMPK catalytic ?1 and ?2 mice after long-term metformin treatment, and that metformin promotes the formation of the functional AMPK ??? heterotrimeric complex. We tested the importance of each regulatory ? subunit isoform to metformin action in this current study. We found that depletion of ?1, but not ?2 or ?3, drastically reduced metformin activation of AMPK. HFD-fed mice with depletion of the ?1 subunit are resistant to metformin suppression of liver glucose production. Furthermore, we determined the role of each regulatory cystathionine-?-synthase (CBS) domain in the ?1 subunit in metformin action and found that deletion of either CBS1 or CBS4 negated metformin's effect on AMPK? phosphorylation at T172 and suppression of glucose production in hepatocytes. Our data indicate that the ?1 subunit is required for metformin's control of glucose metabolism in hepatocytes. Furthermore, in humans and animal models, metformin treatment leads to the loss of body weight, we found that the decrease in body weight gain in mice treated with metformin is not directly attributable to increased energy expenditure.
Project description:Genes related to AMPK activation, cellular respiration, and metabolism are enriched in the gastric parietal cell population. Metformin is known activator of AMPK. We used microarray analysis to identify metformin targets in mature parietal cells and in parietal cell progenitors.
Project description:Despite being the frontline therapy for Type 2 diabetes, the mechanisms of action of the biguanide drug metformin are still being discovered. In particular, the detailed molecular interplays between the AMPK and the mTORC1 pathway in the hepatic benefits of metformin are still ill-defined. Metformin-dependent activation of AMPK classically inhibits mTORC1 via TSC/RHEB. But several lines of evidence suggest additional mechanisms at play in metformin inhibition of mTORC1. Here we investigated the role of direct AMPK-mediated serine phosphorylation of RAPTOR in a new RaptorAA mouse model, in which AMPK phospho-serine sites Ser722 and Ser792 of RAPTOR were mutated to alanine. Metformin treatment of intact murine liver requires AMPK regulation of both RAPTOR and TSC2 to fully inhibit mTORC1, and this regulation is critical for the transcriptional response to metformin. Transcriptionally, AMPK and mTORC1 were both important for regulation of anabolic metabolism and inflammatory programs triggered by metformin treatment. The hepatic transcriptional response in mice on high fat diet treated with metformin was largely ablated by AMPK-deficiency under the conditions examined, indicating the essential role of this kinase and its targets in metformin action in vivo.
Project description:Despite being the frontline therapy for Type 2 diabetes, the mechanisms of action of the biguanide drug metformin are still being discovered. In particular, the detailed molecular interplays between the AMPK and the mTORC1 pathway in the hepatic benefits of metformin are still ill-defined. Metformin-dependent activation of AMPK classically inhibits mTORC1 via TSC/RHEB. But several lines of evidence suggest additional mechanisms at play in metformin inhibition of mTORC1. Here we investigated the role of direct AMPK-mediated serine phosphorylation of RAPTOR in a new RaptorAA mouse model, in which AMPK phospho-serine sites Ser722 and Ser792 of RAPTOR were mutated to alanine. Metformin treatment of primary hepatocytes and intact murine liver requires AMPK regulation of both RAPTOR and TSC2 to fully inhibit mTORC1, and this regulation is critical for the transcriptional response to metformin. Transcriptionally, AMPK and mTORC1 were both important for regulation of anabolic metabolism and inflammatory programs triggered by metformin treatment.
Project description:Despite being the frontline therapy for Type 2 diabetes, the mechanisms of action of the biguanide drug metformin are still being discovered. In particular, the detailed molecular interplays between the AMPK and the mTORC1 pathway in the hepatic benefits of metformin are still ill-defined. Metformin-dependent activation of AMPK classically inhibits mTORC1 via TSC/RHEB. But several lines of evidence suggest additional mechanisms at play in metformin inhibition of mTORC1. Here we investigated the role of direct AMPK-mediated serine phosphorylation of RAPTOR in a new RaptorAA mouse model, in which AMPK phospho-serine sites Ser722 and Ser792 of RAPTOR were mutated to alanine. Metformin treatment of primary hepatocytes and intact murine liver requires AMPK regulation of both RAPTOR and TSC2 to fully inhibit mTORC1, and this regulation is critical for the translational response to metformin.
Project description:Metformin is the front-line treatment for type 2 diabetes worldwide. It acts via effects on glucose and lipid metabolism in metabolic tissues, leading to enhanced insulin sensitivity. Despite significant effort, the molecular basis for metformin response remains poorly understood, with a limited number of specific biochemical pathways studied to date. To broaden our understanding of hepatic metformin response, we combine phospho-protein enrichment in tissue from genetically engineered mice with a quantitative proteomics platform to enable the discovery and quantification of basophilic kinase substrates in-vivo. We define proteins that binding to 14-3-3 are acutely regulated by metformin treatment and/or loss of the serine/threonine kinase, LKB1. Inducible binding of 250 proteins following metformin treatment is observed, 44% LKB1-dependent. Beyond AMPK, metformin activates Protein Kinase D and MAPKAPK2 in an LKB1-independent manner, revealing additional kinases that may mediate aspects of metformin response. Deeper analysis uncovered substrates of AMPK in endocytosis and calcium homeostasis.
Project description:Trans-10, cis-12 conjugated linoleic acid (t10c12 CLA) causes dramatic reductions in white adipose tissue in mice but has had limited effectiveness in humans. Determination of the signaling pathways involved may lead to better regulation of adiposity. T10c12 CLA was found to activate AMP-activating protein kinase (AMPK), a central regulator of cell metabolism. Compound C, a potent inhibitor of AMPK, prevents many of the typical responses to treatments with t10c12 CLA including the integrated stress response (ISR), the inflammatory response, the reduction in key lipogenic transcription factors, and delipidation. Treatment of adipocytes or mice with t10c12 CLA in conjunction with AMPK activator metformin results in more delipidation than treatment with the individual chemicals. Additionally, the combination showed a reduced inflammatory response relative to a t10c12 CLA treatment alone. The combination of t10c12 CLA and metformin, widely used to treat insulin resistance and Type II diabetes, has potential as a treatment for reducing adiposity in humans. Keywords: control/treatment
Project description:Metformin is the most prescribed anti-diabetic medicine, and has also been shown to have other various benefits, such as anti-aging and anti-cancer effects. For clinical doses of metformin, it is known that AMPK plays a major role; however, the direct molecular target of metformin remains unclear. Here, we found that clinically relevant concentrations of metformin inhibits the lysosomal proton pump (v-ATPase), which has been shown to be a central node for AMPK activation upon glucose starvation. We synthesised a photoactive metformin probe, and identified that PEN2, a subunit of γ-secretases, is a binding partner of metformin with KD at micromolar levels. Metformin-bound PEN2 then forms a complex with ATP6AP1, a subunit of the v-ATPase, leading to inhibition of v-ATPase and activation of AMPK without affecting cellular AMP levels. Knockout of PEN2, or re-introduction of a PEN2 mutant that fails to bind ATP6AP1, blunts AMPK activation. In vivo, liver-specific knockout of PEN2 abolishes metformin-mediated reduction of hepatic fat content, and intestine-specific knockout of PEN2 impairs its glucose-lowering effects. Furthermore, knockdown of PEN2 in Caenorhabditis elegans abrogates metformin-induced extension of lifespan. Together, these findings reveal that metformin binds to PEN2, initiating a signalling route that intersects, via ATP6AP1, the lysosomal glucose-sensing pathway for AMPK activation, ensuring that metformin manifests therapeutic benefits without significant drawbacks in patients.