Elsevier

Cellular Signalling

Volume 78, February 2021, 109866
Cellular Signalling

Adiponectin enhances the bioenergetics of cardiac myocytes via an AMPK- and succinate dehydrogenase-dependent mechanism

https://doi.org/10.1016/j.cellsig.2020.109866Get rights and content

Highlights

  • Adiponectin acutely enhances cellular bioenergetics via an AMPK-dependent mechanism

  • The effects of Adiponectin require succinate dehydrogenase complex assembly

  • Adiponectin restores basal OCR after hypoxia via promoting the assembly of succinate dehydrogenase complex

  • The effects of Adiponectin on cellular bioenergetic also require the mitochondrial sirtuin 3

Abstract

Adiponectin is one of the most abundant circulating hormones, which through adenosine monophosphate-activated protein kinase (AMPK), enhances fatty acid and glucose oxidation, and exerts a cardioprotective effect. However, its effects on cellular bioenergetics have not been explored. We have previously reported that 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR, an AMPK activator) enhances mitochondrial respiration through a succinate dehydrogenase (SDH or complex II)-dependent mechanism in cardiac myocytes, leading us to predict that Adiponectin would exert a similar effect via activating AMPK. Our results show that Adiponectin enhances basal mitochondrial oxygen consumption rate (OCR), ATP production, and spare respiratory capacity (SRC), which were all abolished by the knockdown of AMPKγ1, inhibition of SDH complex assembly, via the knockdown of the SDH assembly factor 1 (Sdhaf1), or inhibition of SDH activity. Additionally, Adiponectin alleviated hypoxia-induced reductions in OCR and ATP production, in a Sdhaf1-dependent manner, whereas overexpression of Sdhaf1 confirmed its sufficiency for mediating these effects. Importantly, the levels of holoenzyme SDH under the various conditions correlated with OCR. We also show that the effects of Adiponectin, AMPK, Sdhaf1, as well as, SDH complex assembly all required sirtuin 3 (Sirt3). In conclusion, Adiponectin potentiates mitochondrial bioenergetics via promoting SDH complex assembly in an AMPK-, Sdhaf1-, and Sirt3-dependent fashion in cardiac myocytes.

Introduction

The cell's ATP production is linked to its energy requirements, which is monitored by metabolic sensors, including adenosine monophosphate-activated protein kinase (AMPK) [1]. AMPK senses the levels of AMP in the cells and its activity is accordingly adjusted, triggered by allosteric modulation and phosphorylation [2]. An increase in AMP, as a consequence of energy deprivation, results in activation of AMPK, which, thereby, enhances catabolism in muscle and reduces anabolism in the liver, in an effort to increase ATP production and reduce the synthesis and storage of metabolic substrates. It is known to exert its effects through inhibitory phosphorylation of acetyl-CoA carboxylases and glycogen synthases, thereby inhibiting lipid synthesis and glycogen storage, respectively [3,4]. Alternatively, AMPK is also regulated by hormones that maintain energy homeostasis, such as the adipocytokine Adiponectin [5].

Adiponectin was first discovered as a circulating hormone that enhances the cells' sensitivity to insulin, while a decrease in its level is associated with insulin resistance and type 2 diabetes [[6], [7], [8]]. It was soon realized though, that it also functions in maintaining systemic energy homeostasis via elevating fatty acid oxidation in skeletal muscle [9]. Moreover, transgenic mice overexpressing Adiponectin exhibit reduced body fat and longevity after a high fat diet [10]. Its effects are thought to be largely mediated by APPL1 (adaptor protein containing pleckstrin homology domain, phosphotyrosine binding (PTB) domain and leucine zipper motif) [11], as well as, AMPK [12,13].

Adiponectin has also been linked to cardioprotection, as cardiac hypertrophy and mortality increase in Adiponectin-deficient mice and are associated with reduced AMPK activity [14]. The antihypertrophic effects of this hormone on cardiac myocytes are indeed mediated by AMPK. Consistently, Adiponectin deficiency increases infarct size after ischemia-reperfusion in the mouse heart via inhibition of AMPK [15,16]. In both cases, the phenotype is rescued by supplementing the mice with exogenous Adiponectin. Some of the mechanisms underlying its function include stimulation of AMPK-mediated angiogenesis [17], APPL1-AMPK-mediated fatty acid uptake and oxidation [18], and AMPK-PGC-1α-enhanced mitochondrial biogenesis [19]. Additionally, it has been reported to reduce fibrosis by upregulating matrix metallopeptidase 9 [20], protect against inflammation by inhibiting toll-like receptor 4 signaling [21], and reduce oxidative/nitrative stress via activation of protein kinase A and inhibition of NFκB [22]. Finally, a meta-analysis study shows that high levels of Adiponectin correlate with lower risk of cardiovascular disease [23].

We have previously reported that AICAR – an AMPK activator - enhances the cell's basal and maximum oxygen consumption rates (OCR) and spare respiratory capacity (SRC), and that these effects were completely abolished by the succinate dehydrogenase (SDH) inhibitor, 3-nitroproprionic acid (3NP) [24]. Conversely, the loss of the metabolic sensor, AMPK, has been shown to be associated with lower basal, maximum, and SRC in fibroblasts from patients with X-linked adrenoleukodystrophy [25]. These results reveal a direct effect of AMPK on OCR, through regulating SDH activity. SDH, also known as complex II (cII), oxidizes succinate into fumarate while reducing FAD in the tricarboxylic acid (TCA) cycle [26]. Subsequently, electrons are transferred from FADH2, via the iron‑sulfur clusters in SDH, to CoQ/ubiquinol in the electron transport chain (ETC), but unlike the complexes I, III, and IV, CII/SDH does not pump protons across the mitochondrial inner membrane [27]. Accordingly, it does not play vital role in sustaining electron flow and ATP production. However, it is the only enzyme that is common to both the TCA cycle and the ETC and is, thus, well-positioned to boost the cell's bioenergetics through enhancing production of FADH2 and the transfer of its electrons to the ETC.

Thus, we hypothesized that Adiponectin, through AMPK, enhances mitochondrial bioenergetics via promoting the assembly of SDH. Our results confirm this hypothesis and further show that this is mediated in a Sdhaf1- and sirtuin 3 (Sirt3)-dependent manner, during normoxia and hypoxia.

Section snippets

Neonatal rat cardiac myocyte culture and treatments

Cardiac myocytes were prepared as we previously described [28]. Hearts from 1 to 2-day old Sprague-Dawley rats were isolated, chopped, and digested by collagenase to dissociate the cells. The dissociated cells were sorted by centrifugation on a Percoll gradient, followed by differential preplating for 30 min, which enriches for cardiac myocytes and depletes non-myocytes. The purified myocytes were plated in Dulbecco's modified essential medium/Ham F12 (DMEM-F12) with 10% fetal bovine serum

Adiponectin increases cellular bioenergetics via an AMPK-dependent mechanism

We have previously shown that AICAR – an AMPK activator - augments the cells‘bioenergetics via an SDH-dependent mechanism [24], which is regulated by the assembly of its holoenzyme [30]. Thus, we hypothesized that Adiponectin, a regulator of AMPK, would enhance aerobic respiration through an AMPK-SDH-dependent mechanism. To address this, we first knocked down the Prkag1 (AMPKγ1) subunit of AMPK, which binds AMP/ADP/ATP [31], using short hairpin interfering RNA targeting its mRNA (si-Prkag1)

Discussion

The circulating levels of Adiponectin is known to reciprocally correlate with caloric intake, thus, regulating energy homeostasis by increasing the appetite, boosting substrate storage, and decreasing energy expenditure [39]. Accordingly, it has been characterized as a starvation hormone. However, it should be noted that its effects are tissue-dependent. For example, in adipocytes, Adiponectin inhibits lipolysis [40,41], whereas, in skeletal muscle, it increases fatty acid oxidation, mainly

Credit author statement

Yong Heui Jeon: Investigation, Minzhen He: Investigation, Julianne Austin: Investigation, Hyewon Shin: Investigation, Jessica Pfleger: Investigation, and Maha Abdellatif: Conceptualization, Data curation, Formal analysis, Writing -review & editing, Funding acquisition.

Disclaimer

The authors declare that they have no conflicts of interest with the contents of this article.

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Declaration of Competing Interest

None.

Acknowlegment

We thank Dr. Junichi Sadoshima, Chairman of the Department of Cell Biology and Molecular Medicine, Rutgers University, for his support. This work was supported by National Institute of Health funding [1R01HL119726 to M.A.]

References (65)

  • S. Grimm

    Respiratory chain complex II as general sensor for apoptosis

    Biochim. Biophys. Acta

    (2013)
  • M.D. Hirschey et al.

    SIRT3 deficiency and mitochondrial protein hyperacetylation accelerate the development of the metabolic syndrome

    Mol. Cell

    (2011)
  • L. Wu et al.

    AMP-activated protein kinase (AMPK) regulates energy metabolism through modulating thermogenesis in adipose tissue

    Front. Physiol.

    (2018)
  • R. Shibata et al.

    Adiponectin protects against the development of systolic dysfunction following myocardial infarction

    J. Mol. Cell. Cardiol.

    (2007)
  • S. Maruyama et al.

    Adiponectin ameliorates doxorubicin-induced cardiotoxicity through Akt protein-dependent mechanism

    J. Biol. Chem.

    (2011)
  • K.P. Nickens et al.

    A bioenergetic profile of non-transformed fibroblasts uncovers a link between death-resistance and enhanced spare respiratory capacity

    Mitochondrion

    (2013)
  • G.J. van der Windt et al.

    Mitochondrial respiratory capacity is a critical regulator of CD8+ T cell memory development

    Immunity

    (2012)
  • A. Siddiqui et al.

    Mitochondrial DNA damage is associated with reduced mitochondrial bioenergetics in Huntington’s disease

    Free Radic. Biol. Med.

    (2012)
  • J.M. Flynn et al.

    Impaired spare respiratory capacity in cortical synaptosomes from Sod2 null mice

    Free Radic. Biol. Med.

    (2011)
  • T. Albayrak et al.

    A high-throughput screen for single gene activities: isolation of apoptosis inducers

    Biochem. Biophys. Res. Commun.

    (2003)
  • C.L. Quinlan et al.

    Mitochondrial complex II can generate reactive oxygen species at high rates in both the forward and reverse reactions

    J. Biol. Chem.

    (2012)
  • B.P. Dranka et al.

    Assessing bioenergetic function in response to oxidative stress by metabolic profiling

    Free Radic. Biol. Med.

    (2011)
  • S. Herzig et al.

    AMPK: guardian of metabolism and mitochondrial homeostasis

    Nat. Rev. Mol. Cell Biol.

    (2018)
  • A. McBride et al.

    AMP-activated protein kinase—a sensor of glycogen as well as AMP and ATP?

    Acta Physiol. (Oxford)

    (2009)
  • T. Yamauchi et al.

    Adiponectin stimulates glucose utilization and fatty-acid oxidation by activating AMP-activated protein kinase

    Nat. Med.

    (2002)
  • K. Hotta et al.

    Circulating concentrations of the adipocyte protein adiponectin are decreased in parallel with reduced insulin sensitivity during the progression to type 2 diabetes in rhesus monkeys

    Diabetes

    (2001)
  • T. Yamauchi et al.

    The fat-derived hormone adiponectin reverses insulin resistance associated with both lipoatrophy and obesity

    Nat. Med.

    (2001)
  • N. Maeda et al.

    Diet-induced insulin resistance in mice lacking adiponectin/ACRP30

    Nat. Med.

    (2002)
  • B. Lee et al.

    Adiponectin and energy homeostasis

    Rev. Endocr. Metab. Disord.

    (2014)
  • S. Otabe et al.

    Overexpression of human adiponectin in transgenic mice results in suppression of fat accumulation and prevention of premature death by high-calorie diet

    Am. J. Physiol. Endocrinol. Metab.

    (2007)
  • X. Mao et al.

    APPL1 binds to adiponectin receptors and mediates adiponectin signalling and function

    Nat. Cell Biol.

    (2006)
  • Y. Liao et al.

    Exacerbation of heart failure in adiponectin-deficient mice due to impaired regulation of AMPK and glucose metabolism

    Cardiovasc. Res.

    (2005)
  • Cited by (6)

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    Present address: Jeju-si, Jeju-do, 63236, South Korea.

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