bims-mimcad Biomed News
on Mitochondrial metabolism and cardiometabolic diseases
Issue of 2024‒02‒11
twelve papers selected by
Henver Brunetta, University of Guelph

  1. Sci Adv. 2024 Feb 09. 10(6): eadj2752
      Exercise-induced activation of adenosine monophosphate-activated protein kinase (AMPK) and substrate phosphorylation modulate the metabolic capacity of mitochondria in skeletal muscle. However, the key effector(s) of AMPK and the regulatory mechanisms remain unclear. Here, we showed that AMPK phosphorylation of the folliculin interacting protein 1 (FNIP1) serine-220 (S220) controls mitochondrial function and muscle fuel utilization during exercise. Loss of FNIP1 in skeletal muscle resulted in increased mitochondrial content and augmented metabolic capacity, leading to enhanced exercise endurance in mice. Using skeletal muscle-specific nonphosphorylatable FNIP1 (S220A) and phosphomimic (S220D) transgenic mouse models as well as biochemical analysis in primary skeletal muscle cells, we demonstrated that exercise-induced FNIP1 (S220) phosphorylation by AMPK in muscle regulates mitochondrial electron transfer chain complex assembly, fuel utilization, and exercise performance without affecting mechanistic target of rapamycin complex 1-transcription factor EB signaling. Therefore, FNIP1 is a multifunctional AMPK effector for mitochondrial adaptation to exercise, implicating a mechanism for exercise tolerance in health and disease.
  2. J Mol Cell Cardiol. 2024 Feb;pii: S0022-2828(23)00197-9. [Epub ahead of print]187 101-117
      AIMS: The sympathetic nervous system regulates numerous critical aspects of mitochondrial function in the heart through activation of adrenergic receptors (ARs) on cardiomyocytes. Mounting evidence suggests that α1-ARs, particularly the α1A subtype, are cardioprotective and may mitigate the deleterious effects of chronic β-AR activation by shared ligands. The mechanisms underlying these adaptive effects remain unclear. Here, we tested the hypothesis that α1A-ARs adaptively regulate cardiomyocyte oxidative metabolism in both the uninjured and infarcted heart.METHODS: We used high resolution respirometry, fatty acid oxidation (FAO) enzyme assays, substrate-specific electron transport chain (ETC) enzyme assays, transmission electron microscopy (TEM) and proteomics to characterize mitochondrial function comprehensively in the uninjured hearts of wild type and α1A-AR knockout mice and defined the effects of chronic β-AR activation and myocardial infarction on selected mitochondrial functions.
    RESULTS: We found that isolated cardiac mitochondria from α1A-KO mice had deficits in fatty acid-dependent respiration, FAO, and ETC enzyme activity. TEM revealed abnormalities of mitochondrial morphology characteristic of these functional deficits. The selective α1A-AR agonist A61603 enhanced fatty-acid dependent respiration, fatty acid oxidation, and ETC enzyme activity in isolated cardiac mitochondria. The β-AR agonist isoproterenol enhanced oxidative stress in vitro and this adverse effect was mitigated by A61603. A61603 enhanced ETC Complex I activity and protected contractile function following myocardial infarction.
    CONCLUSIONS: Collectively, these novel findings position α1A-ARs as critical regulators of cardiomyocyte metabolism in the basal state and suggest that metabolic mechanisms may underlie the protective effects of α1A-AR activation in the failing heart.
    Keywords:  Adrenergic; Alpha; Basal metabolism; Heart; Lipid metabolism; Mitochondria; Oxidative phosphorylation; Receptors
  3. Cell Metab. 2024 Feb 06. pii: S1550-4131(24)00007-X. [Epub ahead of print]36(2): 422-437.e8
      Time-restricted feeding (TRF) has gained attention as a dietary regimen that promotes metabolic health. This study questioned if the health benefits of an intermittent TRF (iTRF) schedule require ketone flux specifically in skeletal and cardiac muscles. Notably, we found that the ketolytic enzyme beta-hydroxybutyrate dehydrogenase 1 (BDH1) is uniquely enriched in isolated mitochondria derived from heart and red/oxidative skeletal muscles, which also have high capacity for fatty acid oxidation (FAO). Using mice with BDH1 deficiency in striated muscles, we discover that this enzyme optimizes FAO efficiency and exercise tolerance during acute fasting. Additionally, iTRF leads to robust molecular remodeling of muscle tissues, and muscle BDH1 flux does indeed play an essential role in conferring the full adaptive benefits of this regimen, including increased lean mass, mitochondrial hormesis, and metabolic rerouting of pyruvate. In sum, ketone flux enhances mitochondrial bioenergetics and supports iTRF-induced remodeling of skeletal muscle and heart.
    Keywords:  acylcarnitines; beta-oxidation; fiber type; intermittent fasting; ketones; metabolic flux; mitochondria; proteomics; striated muscles; time-restricted feeding
  4. Am J Physiol Heart Circ Physiol. 2024 Feb 09.
      Prior animal and cell studies have demonstrated a direct role of high-density lipoprotein (HDL) and Apolipoprotein A-I (Apo A-I) in enhancing skeletal muscle mitochondrial function and exercise capacity. However, the relevance of these animal and cell investigations in humans remains unknown. Therefore, a cross-sectional study was conducted in 48 adults (67% female, 8% Black participants, age 39 ± 15.4 years) to characterize the associations between HDL measures, Apo A-I, and muscle mitochondrial function. Forearm muscle oxygen recovery time (tau) from post-exercise recovery kinetics was used to assess skeletal muscle mitochondrial function. Lipoprotein measures were assessed by nuclear magnetic resonance. HDL efflux capacity was assessed using J774 macrophages, radiolabeled cholesterol, and Apolipoprotein B-depleted plasma both with and without added cyclic adenosine monophosphate. In univariate analyses, faster skeletal muscle oxygen recovery time (lower tau) was significantly associated with higher levels of HDL cholesterol (HDL-C), ApoA-I, and larger mean HDL size, but not HDL cholesterol efflux capacity. Slower recovery time (higher tau) was positively associated with body mass index (BMI) and fasting plasma glucose (FPG). In multivariable linear regression analyses, higher levels of HDL-C and Apo A-I, as well as larger HDL size, were independently associated with faster skeletal muscle oxygen recovery times that persisted after adjusting for BMI and FPG (all p <0.05). In conclusion, higher levels of HDL-C, Apo A-I, and larger mean HDL size were independently associated with enhanced skeletal muscle mitochondrial function in healthy humans.
    Keywords:  Apolipoprotein A-I; High-density lipoprotein; Mitochondrial Function; Skeletal Muscle
  5. Biochem Pharmacol. 2024 Feb 05. pii: S0006-2952(24)00025-X. [Epub ahead of print] 116042
      Fibroblast growth factor 21 (FGF21) reduces body weight, which was attributed to induced energy expenditure (EE). Conflicting data have been published on the role of uncoupling protein 1 (UCP1) in this effect. Therefore, we aimed to revisit the thermoregulatory effects of FGF21 and their implications for body weight regulation. We found that an 8-day treatment with FGF21 lowers body weight to similar extent in both wild-type (WT) and UCP1-deficient (KO) mice fed high-fat diet. In WT mice, this effect is solely due to increased EE, which is associated with a strong activation of UCP1, so excess heat must be dissipated through the tail. This thermogenesis takes place in the interscapular region and can be attenuated by a β-adrenergic inhibitor propranolol. In KO mice, FGF21-induced weight loss correlates with a modest increase in EE, which is independent of adrenergic signaling, and a reduced energy intake. Interestingly, the gene expression profile of interscapular brown adipose tissue (but not subcutaneous white adipose tissue) of KO mice is massively affected by FGF21, as shown by increased expression of genes encoding triacylglycerol/free fatty acid cycle enzymes. Thus, FGF21 elicits central thermogenic and pyretic effects followed by a concomitant increase in EE and body temperature, respectively. The associated weight loss is strongly dependent on UCP1-based thermogenesis. However, in the absence of UCP1, alternative mechanisms of energy dissipation may contribute, possibly based on futile triacylglycerol/free fatty acid cycling in brown adipose tissue and reduced food intake.
    Keywords:  Brown adipose tissue; Energy expenditure; Fibroblast growth factor 21; Futile fatty acid cycle; UCP1; Weight loss
  6. Am J Physiol Endocrinol Metab. 2024 Feb 07.
      Background. Resveratrol (RSV), a natural polyphenol compound contained in numerous plants, has been proposed as a treatment for obesity-related disease processes such as insulin resistance. However, in humans there are conflicting results concerning the efficacy of RSV in improving insulin action; the purpose of the present study was to determine if obesity status (lean, severely obese) affects the response to RSV in human skeletal muscle. Methods. Primary skeletal muscle cells were derived from biopsies obtained from age-matched lean and insulin-resistant women with severe obesity and incubated with RSV (1µM) for 24-hours. Insulin-stimulated glucose oxidation and incorporation in glycogen, insulin signal transduction, and energy-sensitive protein targets (AMPK, Sirt1, and PGC1α) were analyzed. Results. RSV increased insulin-stimulated glycogen synthesis, glucose oxidation, and AMPK phosphorylation in both groups but did not enhance insulin signaling or SIRT1 and citrate synthase content in women with severe obesity. Conclusions. AMPK phosphorylation may play an indispensable role in improving glucose metabolism following resveratrol treatment and may be able to overcome intrinsic deficits in the insulin signaling cascade in myotubes from individuals with severe obesity.
    Keywords:  glucose metabolism; human skeletal muscle; insulin signaling; obesity; resveratrol
  7. Clin Sci (Lond). 2024 Feb 05. pii: CS20231016. [Epub ahead of print]
      Semaglutide is an anti-diabetes and weight loss drug that decreases food intake, slows gastric emptying, and increases insulin secretion. Patients begin treatment with low-dose semaglutide and increase dosage over time as efficacy plateaus. With increasing dosage, there is also greater incidence of gastrointestinal side effects. One reason for the plateau in semaglutide efficacy despite continued low food intake is due to compensatory actions whereby the body becomes more metabolically efficient to defend against further weight loss. Mitochondrial uncoupler drugs decrease metabolic efficiency, therefore we sought to investigate the combination therapy of semaglutide with the mitochondrial uncoupler BAM15 in diet-induced obese mice. Mice were fed high-fat western diet (WD) and stratified into 6 treatment groups including WD control, BAM15, low-dose semaglutide without or with BAM15, and high-dose semaglutide without or with BAM15. Combining BAM15 with either semaglutide dose decreased body fat and liver triglycerides, which was not achieved by any monotherapy, while high-dose semaglutide with BAM15 had the greatest effect on glucose homeostasis. This study demonstrates a novel approach to improve weight loss without loss of lean mass and improve glucose control by simultaneously targeting energy intake and energy efficiency. Such a combination may decrease the need for semaglutide dose escalation and hence minimise potential gastrointestinal side effects.
    Keywords:  drug effects; glucose homeostasis; mouse models
  8. Acta Physiol (Oxf). 2024 Feb 05. e14111
      AIM: This study aimed to investigate the effects of caffeine on pathways associated with mitochondrial quality control and mitochondrial capacity during skeletal muscle regeneration, focusing on the role of Parkin, a key protein involved in mitophagy.METHODS: We used in vitro C2C12 myoblast during differentiation with and without caffeine in the medium, and we evaluated several markers of mitochondrial quality control pathways and myotube growth. In vivo experiments, we used C57BL/6J (WT) and Parkintm 1Shn lineage (Parkin-/- ) mice and injured tibial anterior muscle. The mice regenerated TA muscle for 3, 10, and 21 days with or without caffeine ingestion. TA muscle was used to analyze the protein content of several markers of mitochondrial quality pathways, muscle satellite cell differentiation, and protein synthesis. Furthermore, it analyzed mtDNA, mitochondrial respiration, and myofiber growth.
    RESULTS: C2C12 differentiation experiments showed that caffeine decreased Parkin content, potentially leading to increased DRP1 and PGC-1α content and altered mitochondrial population, thereby enhancing growth capacity. Using Parkin-/- mice, we found that caffeine intake during the regenerative process induces an increase in AMPKα phosphorylation and PGC-1α and TFAM content, changes that were partly Parkin-dependent. In addition, the absence of Parkin potentiates the ergogenic effect of caffeine by increasing mitochondrial capacity and myotube growth. Those effects are related to increased ATF4 content and activation of protein synthesis pathways, such as increased 4E-BP1 phosphorylation.
    CONCLUSION: These findings demonstrate that caffeine ingestion changes mitochondrial quality control during skeletal muscle regeneration, and Parkin is a central player in those mechanisms.
    Keywords:  AMPK; caffeine; mitochondrial respiration; muscle recovery
  9. Circ Res. 2024 Feb 07.
      BACKGROUND: Mitochondrial dysfunction is a primary driver of cardiac contractile failure; yet, the cross talk between mitochondrial energetics and signaling regulation remains obscure. Ponatinib, a tyrosine kinase inhibitor used to treat chronic myeloid leukemia, is among the most cardiotoxic tyrosine kinase inhibitors and causes mitochondrial dysfunction. Whether ponatinib-induced mitochondrial dysfunction triggers the integrated stress response (ISR) to induce ponatinib-induced cardiotoxicity remains to be determined.METHODS: Using human-induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs) and a recently developed mouse model of ponatinib-induced cardiotoxicity, we performed proteomic analysis, molecular and biochemical assays to investigate the relationship between ponatinib-induced mitochondrial stress and ISR and their role in promoting ponatinib-induced cardiotoxicity.
    RESULTS: Proteomic analysis revealed that ponatinib activated the ISR in cardiac cells. We identified GCN2 (general control nonderepressible 2) as the eIF2α (eukaryotic translation initiation factor) kinase responsible for relaying mitochondrial stress signals to trigger the primary ISR effector-ATF4 (activating transcription factor 4), upon ponatinib exposure. Mechanistically, ponatinib treatment exerted inhibitory effects on ATP synthase activity and reduced its expression levels resulting in ATP deficits. Perturbed mitochondrial function resulting in ATP deficits then acts as a trigger of GCN2-mediated ISR activation, effects that were negated by nicotinamide mononucleotide, an NAD+ precursor, supplementation. Genetic inhibition of ATP synthase also activated GCN2. Interestingly, we showed that the decreased abundance of ATP also facilitated direct binding of ponatinib to GCN2, unexpectedly causing its activation most likely because of a conformational change in its structure. Importantly, administering an ISR inhibition, ISRIB, protected human-induced pluripotent stem cell-derived cardiomyocytes against ponatinib. Ponatinib-treated mice also exhibited reduced cardiac function, effects that were attenuated upon systemic ISRIB administration. Importantly, ISRIB does not affect the antitumor effects of ponatinib in vitro.
    CONCLUSIONS: Neutralizing ISR hyperactivation could prevent or reverse ponatinib-induced cardiotoxicity. The findings that compromised ATP production potentiates GCN2-mediated ISR activation have broad implications across various cardiac diseases. Our results also highlight an unanticipated role of ponatinib in causing direct activation of a kinase target despite its role as an ATP-competitive kinase inhibitor.
    Keywords:  cardiotoxicity; mice; mitochondria; ponatinib; proteomics
  10. J Appl Physiol (1985). 2024 Feb 08.
      Optimal skeletal muscle oxidative function (microvascular reactivity and mitochondrial capacity) is an integral part of healthy aging and is related to physical function and quality of life. We aimed to extend upon the understanding of skeletal muscle oxidative function with healthy aging in males and females across the adult lifespan. Younger (N = 22; 11 males), middle-aged (N = 19; 10 males), and older (N = 21; 10 males) adults completed this study. Time spent in moderate and vigorous physical activity was self-reported and similar among groups. Near-infrared spectroscopy was used to investigate skeletal muscle microvascular reperfusion (O2Hb+Mb half time to peak hyperemia; T 1/2), mitochondrial capacity (mVO2 recovery rate constant), and walking tissue oxygen saturation (StO2) of the tibialis anterior (TA) muscle at 7 incremental walking speeds. Mitochondrial capacity was not significantly different across groups (p = 0.07). Younger adults exhibited significantly slower T 1/2 compared with older adults (p = 0.006) and middle-aged adults (p = 0.025). There were no observed sex differences for mitochondrial capacity (p = 0.442) or T 1/2 (p = 0.402). Older adults exhibited significantly lower StO2 across all walking speeds compared with younger adults (p = 0.003). Mitochondrial capacity and microvascular reperfusion are maintained in middle- and older age with no sex differences in either outcome. However, in older adults, whole-body functional movement, such as walking, may place an additional demand on the TA as a compensatory response to lower functional reserve not evident in distinct measures of mitochondrial capacity and microvascular reperfusion.
    Keywords:  aging; microvascular reperfusion; mitochondrial capacity; sex differences; skeletal muscle
  11. Cardiovasc Res. 2024 Feb 03. pii: cvae026. [Epub ahead of print]
      AIMS: Virus infection triggers inflammation and, may impose nutrient shortage to the heart. Supported by type I interferon (IFN) signaling, cardiomyocytes counteract infection by various effector processes, with the IFN-stimulated gene of 15 kDa (ISG15) system being intensively regulated and protein modification with ISG15 protecting mice Coxsackievirus B3 (CVB3) infection. The underlying molecular aspects how the ISG15 system affects the functional properties of respective protein substrates in the heart are unknown.METHODS AND RESULTS: Based on the protective properties due to protein ISGylation, we set out a study investigating CVB3-infected mice in depth and found cardiac atrophy with lower cardiac output in ISG15-/- mice. By mass spectrometry, we identified the protein targets of the ISG15 conjugation machinery in heart tissue and explored how ISGylation affects their function. The cardiac ISGylome showed a strong enrichment of ISGylation substrates within glycolytic metabolic processes. Two control enzymes of the glycolytic pathway, hexokinase 2 (HK2) and phosphofructokinase muscle form (PFK1), were identified as bona fide ISGylation targets during infection. In an integrative approach complemented with enzymatic functional testing and structural modeling, we demonstrate that protein ISGylation obstructs the activity of HK2 and PFK1. Seahorse-based investigation of glycolysis in cardiomyocytes revealed that, by conjugating proteins, the ISG15 system prevents the infection-/IFN-induced upregulation of glycolysis. We complemented our analysis with proteomics-based advanced computational modeling of cardiac energy metabolism. Our calculations revealed an ISG15-dependent preservation of the metabolic capacity in cardiac tissue during CVB3 infection. Functional profiling of mitochondrial respiration in cardiomyocytes and mouse heart tissue by Seahorse technology showed an enhanced oxidative activity in cells with a competent ISG15 system.
    CONCLUSIONS: Our study demonstrates that ISG15 controls critical nodes in cardiac metabolism. ISG15 reduces the glucose demand, supports higher ATP production capacity in the heart, despite nutrient shortage in infection, and counteracts cardiac atrophy and dysfunction.
    Keywords:  ISG15; ISGylation; glycolysis; metabolism; mitochondrial function; virus infection
  12. iScience. 2024 Feb 16. 27(2): 108927
      Obesity and its co-morbidities including type 2 diabetes are increasing at epidemic rates in the U.S. and worldwide. Brown adipose tissue (BAT) is a potential therapeutic to combat obesity and type 2 diabetes. Increasing BAT mass by transplantation improves metabolic health in rodents, but its clinical translation remains a challenge. Here, we investigated if transplantation of 2-4 million differentiated brown pre-adipocytes from mouse BAT stromal fraction (SVF) or human pluripotent stem cells (hPSCs) could improve metabolic health. Transplantation of differentiated brown pre-adipocytes, termed "committed pre-adipocytes" from BAT SVF from mice or derived from hPSCs improves glucose homeostasis and insulin sensitivity in recipient mice under conditions of diet-induced obesity, and this improvement is mediated through the collaborative actions of the liver transcriptome, tissue AKT signaling, and FGF21. These data demonstrate that transplantation of a small number of brown adipocytes has significant long-term translational and therapeutic potential to improve glucose metabolism.
    Keywords:  Biological sciences; Endocrinology; Health sciences; Natural sciences; Physiology