AMPK Activation through Mitochondrial Regulation Results in Increased Substrate Oxidation and Improved Metabolic Parameters in Models of Diabetes

Abstract

Modulation of mitochondrial function through inhibiting respiratory complex I activates a key sensor of cellular energy status, the 5'-AMP-activated protein kinase (AMPK). Activation of AMPK results in the mobilization of nutrient uptake and catabolism for mitochondrial ATP generation to restore energy homeostasis. How these nutrient pathways are affected in the presence of a potent modulator of mitochondrial function and the role of AMPK activation in these effects remain unclear. We have identified a molecule, named R419, that activates AMPK in vitro via complex I inhibition at much lower concentrations than metformin (IC50 100 nM vs 27 mM, respectively). R419 potently increased myocyte glucose uptake that was dependent on AMPK activation, while its ability to suppress hepatic glucose production in vitro was not. In addition, R419 treatment of mouse primary hepatocytes increased fatty acid oxidation and inhibited lipogenesis in an AMPK-dependent fashion. We have performed an extensive metabolic characterization of its effects in the db/db mouse diabetes model. In vivo metabolite profiling of R419-treated db/db mice showed a clear upregulation of fatty acid oxidation and catabolism of branched chain amino acids. Additionally, analyses performed using both 13C-palmitate and 13C-glucose tracers revealed that R419 induces complete oxidation of both glucose and palmitate to CO2 in skeletal muscle, liver, and adipose tissue, confirming that the compound increases mitochondrial function in vivo. Taken together, our results show that R419 is a potent inhibitor of complex I and modulates mitochondrial function in vitro and in diabetic animals in vivo. R419 may serve as a valuable molecular tool for investigating the impact of modulating mitochondrial function on nutrient metabolism in multiple tissues and on glucose and lipid homeostasis in diabetic animal models.

Novel mitochondrial complex I inhibitors restore glucose-handling abilities of high-fat fed mice

“…The weight gain in the mice was normalized, this was particularly evident in the epididymal fat pad (C Redondo, personal communication), which was greatly increased in the diabetic untreated animals but very similar to chow-fed controls in the compound-treated groups. The ability of these compounds to improve glucose handling in high-fat fed mice is similar to studies carried out with metformin (Matsui et al 2010) and other compounds that target complex I (Jenkins et al 2013).…”

“…Although metformin has some major effects on the liver cells (Bailey & Turner 1996, Madiraju et al 2014, Miller et al 2013, it also affects xmuscle cells to inhibit complex I activity (Brunmair et al 2004, Wessels et al 2014, activate AMPK (Brunmair et al 2004, Li et al 2015, Musi et al 2002 and induce glucose uptake (Kumar & Dey 2002), which are its other important anti-diabetic effects. RTC-1 appears to be more potent in inhibiting mictochondrial complex I, with an IC 50 calculated at 27 µmol L −1 compared with previously stated IC 50 values of between 1.2 and 27 mmol L −1 for metformin (Jenkins et al 2013, Piel et al 2015. One possible drug-dependent side effect of complex I inhibition is reported to be lactic acidosis (Brown et al 1998, Misbin 1977, Wang et al 2003.…”

Targeting AMPK signaling in combating ovarian cancers: opportunities and challenges

“…Understanding of the physiological role of AMPK in cells is, therefore, of the utmost importance, and the approaches can be greatly enhanced by the application of different pharmacological AMPK activators. In fact, the majority of these activators are novel chemicals [99,100] or drugs in clinical use in conventional medicines, while others are some natural compounds found in traditional medicines, food, and drink derivatives [51,[101][102][103]. The mechanisms of most activators can be briefly classified into two categories-those that stimulate AMPK through the major upstream activating kinase LKB1 by increasing the cellular AMP : ATP ratio and those that activate AMPK through alternative pathways, independent of the AMP : ATP ratio [54] (Tables 1 and 2).…”

AMP-activated Protein Kinase Suppresses Arachidonate 15-Lipoxygenase Expression in Interleukin 4-polarized Human Macrophages

“…1A). ALOX15 induction by IL-4 was abolished in the presence of pharmacological AMPK activators of different classes, including the allosteric AMPK activator A-769662, the biguanidine phenformin, a compound decreasing the cellular energy charge, and R419, a novel mitochondrial complex I inhibitor (20) (Fig. 1C).…”