bims-amsmem 2023-05-14 papers

bims-amsmem

Biomed News

on AMPK signaling mechanism in energy metabolism

Issue of 2023–05–14
nine papers selected by
Dipsikha Biswas, Københavns Universitet

Imaging Subcellular AMPK Activity Using an Excitation-Ratiometric AMPK Activity Reporter.
PFKFB2 inhibits ferroptosis in myocardial ischemia/reperfusion injury through AMPK activation.
Exercise improves homeostasis of the intestinal epithelium by activation of APJ-AMPK signaling.
Mechanisms and efficacy of metformin-mediated suppression of established experimental abdominal aortic aneurysms.
Ghrelin improves endothelial function and reduces blood pressure in Ang II-induced hypertensive mice: Role of AMPK.
Diosgenin alleviates the inflammatory damage and insulin resistance in high glucose‑induced podocyte cells via the AMPK/SIRT1/NF‑κB signaling pathway.
d-Glucosamine induces circadian phase delay by promoting BMAL1 degradation through AMPK/mTOR pathway.
Metformin exerts antileukemic effects by modulating lactate metabolism and overcomes imatinib resistance in chronic myeloid leukemia.
Obesity wars: may the smell be with you.

Curr Protoc. 2023 May;3(5): e771

Imaging Subcellular AMPK Activity Using an Excitation-Ratiometric AMPK Activity Reporter.

Danielle L Schmitt.

  Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a master regulator of cellular metabolism, phosphorylating a variety of downstream targets throughout the cell. Subcellular AMPK activity results in regulation of glycolysis, lipid and protein biosynthesis, mitochondrial function, and gene expression. But how AMPK senses and responds to stimuli in a compartment-specific manner is not well understood, leaving an incomplete picture of compartmentalized AMPK activity. Key tools for studying subcellular AMPK activity are genetically encoded AMPK activity reporters (AMPKARs), which allow for the quantitative visualization of subcelluar AMPK activity. However, many AMPKARs suffer from poor dynamic range and sensitivity, limiting their application. I recently reported the development of a new excitation-ratiometric (ExRai) AMPKAR, a single-fluorophore AMPKAR with enhanced dynamic range for detection of subtle, subcellular AMPK activity. I used ExRai AMPKAR to study subcellular AMPK activity at several locations, including the lysosome and mitochondria, identifying new mechanisms for the regulation of AMPK activity. Here, I describe the use of ExRai AMPKAR to image subcellular AMPK activity in mouse embryonic fibroblasts using both widefield and confocal microscopy. I also describe the culture of mouse embryonic fibroblasts. Through the use of ExRai AMPKAR, subcellular AMPK activity can be illuminated to better understand how this central kinase regulates cellular metabolism. © 2023 The Author. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Imaging subcellular AMPK activity using ExRai AMPKAR Support Protocol 1: Culturing of mouse embryonic fibroblasts for live-cell imaging Support Protocol 2: Live-cell imaging of ExRai AMPKAR using confocal microscopy.

Keywords:  AMPK; biosensor; compartmentalized signaling; fluorescence; live-cell imaging

DOI:  https://doi.org/10.1002/cpz1.771
J Cardiovasc Pharmacol. 2023 May 05.

PFKFB2 inhibits ferroptosis in myocardial ischemia/reperfusion injury through AMPK activation.

Caihua Fu, Shengbo Yu, Zhiquan Liu, Jiayu Wang, Ping Liu, Guohai Su.

ABSTRACT: 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 2 (PFKFB2) is a key regulator of glycolytic enzyme. This study identified if PFKFB2 can regulate myocardial ferroptosis in ischemia/reperfusion (I/R) injury. Mice myocardial (I/R) injury and H9c2 cells oxygen-glucose deprivation/reperfusion (OGD/R) models were established. PFKFB2 expression was enhanced in I/R mice and OGD/R H9c2 cells. Overexpression of PFKFB2 improves heart function in I/R mice. Overexpression of PFKFB2 inhibits I/R and OGD/R-induced ferroptosis in mice and H9c2 cells. Mechanistically, overexpression of PFKFB2 activating the adenosine monophosphate activated protein kinase (AMPK). AMPK inhibitor compound C reverses effect of PFKFB2 overexpression in reducing ferroptosis under OGD/R treatment. In conclusion, PFKFB2 protects hearts against I/R-induced ferroptosis through activation of AMPK signaling pathway.

DOI: https://doi.org/10.1097/FJC.0000000000001437
J Physiol. 2023 May 08.

Exercise improves homeostasis of the intestinal epithelium by activation of APJ-AMPK signaling.

Song Ah Chae, Min Du, Jun Seok Son, Mei-Jun Zhu.

  Intestinal remodeling is dynamically regulated by energy metabolism. Exercise is beneficial for gut health, but the specific mechanisms remain poorly understood. Both intestine-specific apelin receptor (APJ) knockdown (KD) and wild-type male mice were randomly divided into two subgroups with/without exercise to obtain four groups: WT, WT with exercise, APJ KD, and APJ KD with exercise. Animals in exercise groups were subjected to daily treadmill exercise for 3 weeks. Duodenum was collected at 48h after the last bout of exercise. AMP-activated protein kinase (AMPK) α1 KD and wild-type mice were also utilized for investigating the mediatory role of AMPK on exercise-induced duodenal epithelial development. AMPK and peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1 α) were upregulated by exercise via APJ activation in the intestinal duodenum. Correspondingly, exercise induced permissive histone modifications in the PR domain containing 16 (PRDM16) promoter to activate its expression, which was dependent on APJ activation. In agreement, exercise elevated the expression of mitochondrial oxidative markers. The expression of intestinal epithelial markers was downregulated due to AMPK deficiency, and AMPK signaling facilitated epithelial renewal. These data demonstrate that exercise-induced activation of APJ-AMPK axis facilitates the homeostasis of the intestinal duodenal epithelium. ONE-SENTENCE SUMMARY: Exercise-induced APJ-AMPK axis upregulated the expression of PGC-1α and PRDM16 to improve homeostasis of intestinal epithelium. KEY POINTS: APJ signaling is required for improved epithelial homeostasis of the small intestine in response to exercise. Exercise intervention activates PRDM16 through inducing histone modifications, improving mitochondrial biogenesis and fatty acid metabolism in duodenum. Structure of intestinal epithelium is improved by muscle-derived exerkine apelin through APJ-AMPK axis. Abstract figure legend. Exercise training increases expression of apelin in muscle and the circulating apelin level. Exercise-induced apelin-APJ signaling enhances villus and crypt structure of the small intestine (duodenum) through the activation of AMPK and stimulation of mitochondrial biogenesis. Of note, exercise program induces histone modifications for PRDM16 expression, which enhances mitochondrial oxidative metabolism, thereby improving intestinal epithelial homeostasis. This article is protected by copyright. All rights reserved.

Keywords:  AMPK, APJ, duodenum, exercise; mitochondrial oxidation, PRDM16

DOI:  https://doi.org/10.1113/JP284552
JVS Vasc Sci. 2023 ;4 100102

Mechanisms and efficacy of metformin-mediated suppression of established experimental abdominal aortic aneurysms.

Baohui Xu, Gang Li, Yankui Li, Hongping Deng, Anna Cabot, Jia Guo, Makoto Samura, Xiaoya Zheng, Tiffany Chen, Sihai Zhao, Naoki Fujimura, Ronald L Dalman.

   Objective: Metformin treatment attenuates experimental abdominal aortic aneurysm (AAA) formation, as well as reduces clinical AAA diameter enlargement in patients with diabetes. The mechanisms of metformin-mediated aneurysm suppression, and its efficacy in suppressing established experimental aneurysms, remain uncertain.
Methods: Experimental AAAs were created in male C57BL/6J mice via intra-aortic infusion of porcine pancreatic elastase. Metformin alone (250 mg/kg), or metformin combined with the 5' AMP-activated protein kinase (AMPK) antagonist Compound C (10 mg/kg), were administered to respective mouse cohorts daily beginning 4 days following AAA induction. Further AAA cohorts received either the AMPK agonist AICA riboside (500 mg/kg) as positive, or vehicle (saline) as negative, controls. AAA progression in all groups was assessed via serial in vivo ultrasonography and histopathology at sacrifice. Cytokine-producing T cells and myeloid cellularity were determined by flow cytometric analyses.
Results: Metformin limited established experimental AAA progression at 3 (-85%) and 10 (-68%) days following treatment initiation compared with saline control. Concurrent Compound C treatment reduced this effect by approximately 50%. In metformin-treated mice, reduced AAA progression was associated with relative elastin preservation, smooth muscle cell preservation, and reduced mural leukocyte infiltration and neoangiogenesis compared with vehicle control group. Metformin also resulted in reduced interferon-γ-, but not interleukin-10 or -17, producing splenic T cells in aneurysmal mice. Additionally, metformin therapy increased circulating and splenic inflammatory monocytes (CD11b+Ly-6Chigh), but not neutrophils (CD11b+Ly-6G+), with no effect on respective bone marrow cell populations.
Conclusions: Metformin treatment suppresses existing experimental AAA progression in part via AMPK agonist activity, limiting interferon-γ-producing T cell differentiation while enhancing circulating and splenic inflammatory monocyte retention.

Keywords:  5′ AMP-activated protein kinase; Abdominal aortic aneurysm; Cytokine; Inflammatory monocytes; Metformin

DOI:  https://doi.org/10.1016/j.jvssci.2023.100102
Clin Exp Hypertens. 2023 Dec 31. 45(1): 2208774

Ghrelin improves endothelial function and reduces blood pressure in Ang II-induced hypertensive mice: Role of AMPK.

Juan Deng, Yuan Hu, Yindi Zhang, Fadong Yu.

   BACKGROUND: Endothelial dysfunction is a major pathophysiology observed in hypertension. Ghrelin, a key regulator of metabolism, has been shown to play protective roles in cardiovascular system. However, whether it has the effect of improving endothelial function and lowering blood pressure in Ang II-induced hypertensive mice remains unclear.
METHODS: In this study, hypertension was induced by continuous infusion of Ang II with a subcutaneous osmotic pumps and ghrelin (30 μg/kg/day) was intraperitoneal injection for 4 weeks. Acetylcholine-induced endothelium-dependent relaxation in aortae was measured on wire myograph and superoxide production in mouse aortae was assessed by ﬂuorescence imaging.
RESULTS: We found that ghrelin had protective effects on Ang II-induced hypertension by inhibiting oxidative stress, increasing NO production, improving endothelial function, and lowering blood pressure. Furthermore, ghrelin activated AMPK signaling in Ang II-induced hypertension, leading to inhibition of oxidative stress. Compound C, a specific inhibitor of AMPK, reversed the protective effects of ghrelin on the reduction of oxidative stress, the improvement of endothelial function and the reduction of blood pressure.
CONCLUSIONS: our findings indicated that ghrelin protected against Ang II-induced hypertension by improving endothelial function and lowering blood pressure partly through activating AMPK signaling. Thus, ghrelin may be a valuable therapeutic strategy for hypertension.

Keywords:  AMPK; Ghrelin; endothelial function; hypertension; oxidative stress

DOI:  https://doi.org/10.1080/10641963.2023.2208774
Exp Ther Med. 2023 Jun;25(6): 259

Diosgenin alleviates the inflammatory damage and insulin resistance in high glucose‑induced podocyte cells via the AMPK/SIRT1/NF‑κB signaling pathway.

Haoyu Yuan, Huacheng Sui, Saimei Li.

  Diabetic nephropathy (DN) is the predominant cause of end-stage renal disease globally. Diosgenin (DSG) has been reported to play a protective role in podocyte injury in DN. The present study aimed to explore the role of DSG in DN, as well as its mechanism of action in a high glucose (HG)-induced in vitro model of DN in podocytes. Cell viability, apoptosis, inflammatory response and insulin-stimulated glucose uptake were evaluated using Cell Counting Kit-8, TUNEL, ELISA and 2-deoxy-D-glucose assay, respectively. In addition, the expression of AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1)/NF-κB signaling-related proteins in podocyte cells was measured using western blotting. The results indicated that DSG enhanced the viability of podocytes after HG exposure, but inhibited inflammatory damage and attenuated insulin resistance. Moreover, DSG induced the activation of the AMPK/SIRT1/NF-κB signaling pathway. Furthermore, treatment with compound C, an inhibitor of AMPK, counteracted the protective effects of DSG on HG-induced podocyte cells. Therefore, DSG may be a potential therapeutic compound for the treatment of diabetic nephropathy.

Keywords:  AMP-activated protein kinase/sirtuin 1/NF-κB; diabetic nephropathy; diosgenin; inflammatory damage; insulin resistance

DOI:  https://doi.org/10.3892/etm.2023.11958
Life Sci. 2023 May 09. pii: S0024-3205(23)00399-5. [Epub ahead of print] 121765

d-Glucosamine induces circadian phase delay by promoting BMAL1 degradation through AMPK/mTOR pathway.

Zeqi Li, Bo Fu, Aili Wei, Yanchen Wu, Ming Huang, Enhao Zhang, Bo Cui, Bo Wang, Hui Peng.

  Circadian rhythms are closely linked to the metabolic network through circadian feedback regulation. The hexosamine biosynthetic pathway (HBP) is a branch of glucose metabolism that affects circadian rhythms through the O-linked N-acetylglucosamine modification (O-GlcNAcylation) of clock proteins. Here, we found out that, among the downstream metabolites regulated by d-glucosamine (GlcN) in HBP salvage pathway, only GlcN is able to induce circadian phase delay both in vitro and in vivo. Mechanistic studies indicated that the phase-shift induced by GlcN is independent of O-GlcNAcylation. Instead, GlcN selectively up-regulates p-AMPK activity, leading to the inhibition of mTOR signaling pathway, and thus down-regulation of p-BMAL1 both in human cell line and mouse tissues. Moreover, GlcN promoted BMAL1 degradation via proteasome pathway. These findings reveal a novel molecular mechanism of GlcN in regulating clock phase and suggest the therapeutic potential of GlcN as new use for an old drug in the future treatment of shift work and circadian misalignment.

Keywords:  AMPK/mTOR signaling; BMAL1; Circadian phase; Glucosamine; O-GlcNAcylation

DOI:  https://doi.org/10.1016/j.lfs.2023.121765
FEBS J. 2023 May 12.

Metformin exerts antileukemic effects by modulating lactate metabolism and overcomes imatinib resistance in chronic myeloid leukemia.

Meher Bolisetti Gayatri, Rama Krishna Kancha, Dorababu Patchva, Nagaraju Velugonda, Sadasivudu Gundeti, Aramati Bm Reddy.

  Imatinib is the frontline treatment option in treating chronic myeloid leukemia (CML). Hitherto, some patients relapse following treatment. Biochemical analysis of a panel of clonally derived imatinib-resistant cells revealed enhanced glucose uptake and ATP production, suggesting increased rates of glycolysis. Interestingly, increased lactate export was also observed in imatinib-resistant cell lines. Here, we show that metformin inhibits the growth of imatinib-resistant cell lines as well as PBMCs isolated from patients who relapsed following imatinib treatment. Metformin exerted these antiproliferative effects by inhibiting MCT1 and MCT4, leading to the inhibition of lactate export. Furthermore, glucose uptake and ATP production were also inhibited following metformin treatment due to the inhibition of GLUT1 and HK-II in an AMPK-dependent manner. Our results also confirmed that metformin-mediated inhibition of lactate export and glucose uptake occurs through the regulation of mTORC1 and HIF-1α. These results delineate the molecular mechanisms underlying metabolic reprogramming leading to secondary imatinib resistance and the potential of metformin as a therapeutic option in CML.

Keywords:  GLUT1; HIF1-α and lactate; MCT1; MCT4; Metformin

DOI:  https://doi.org/10.1111/febs.16818
Am J Physiol Endocrinol Metab. 2023 May 11.

Obesity wars: may the smell be with you.

Miguel López, José Manuel Fernández-Real, Stanislav I Tomarev.

  Classically, the regulation of energy balance has been based on central and peripheral mechanisms sensing energy, nutrients, metabolites, and hormonal cues. Several cellular mechanisms at central level, such as hypothalamic AMP-activated protein kinase (AMPK), integrate this information to elicit counterregulatory responses that control feeding, energy expenditure and glucose homeostasis, among other processes. Recent data have added more complexity to the homeostatic regulation of metabolism by introducing, for example, the key role of "traditional" senses and sensorial information in this complicated network. In this regard, current evidence is showing that olfaction plays a key and bidirectional role in energy homeostasis. While nutritional status dynamically and profoundly impacts olfactory sensitivity, the sense of smell is involved in food appreciation and selection, as well as in brown adipose tissue (BAT) thermogenesis and substrate utilization, with some newly described actors, such as olfactomedin 2 (OLFM2), likely playing a major role. Thus, olfactory inputs are contributing to the regulation of both sides of the energy balance equation, namely feeding and energy expenditure (EE), as well as whole-body metabolism. Here, we will review the current knowledge and advances about the role of olfaction in the regulation of energy homeostasis.

Keywords:  food intake; hypothalamus; obesity; olfaction; thermogenesis

DOI:  https://doi.org/10.1152/ajpendo.00040.2023