bims-lypmec 2022-08-28 papers

bims-lypmec

Biomed News

on Lysosomal positioning and metabolism in cardiomyocytes

Issue of 2022–08–28
eight papers selected by
Satoru Kobayashi, New York Institute of Technology

In-Depth Characterization of Endo-Lysosomal Aβ in Intact Neurons.
Intermittent Hypoxia-Induced Cardiomyocyte Death Is Mediated by HIF-1 Dependent MAM Disruption.
Fatty acid translocase: a culprit of lipid metabolism dysfunction in disease.
Tunicamycin-Induced Endoplasmic Reticulum Stress Damages Complex I in Cardiac Mitochondria.
Peroxisomal regulation of energy homeostasis: Effect on obesity and related metabolic disorders.
AMPKβ isoform expression patterns in various adipocyte models and in relation to body mass index.
Targeting AMPK Signaling in the Liver: Implications for Obesity and Type 2 Diabetes Mellitus.
Impaired fatty acid metabolism perpetuates lipotoxicity along the transition to chronic kidney injury.

Biosensors (Basel). 2022 Aug 20. pii: 663. [Epub ahead of print]12(8):

In-Depth Characterization of Endo-Lysosomal Aβ in Intact Neurons.

Alec K McKendell, Mei C Q Houser, Shane P C Mitchell, Michael S Wolfe, Oksana Berezovska, Masato Maesako.

  Amyloid-beta (Aβ) peptides are produced within neurons. Some peptides are released into the brain parenchyma, while others are retained inside the neurons. However, the detection of intracellular Aβ remains a challenge since antibodies against Aβ capture Aβ and its precursor proteins (i.e., APP and C99). To overcome this drawback, we recently developed 1) the C99 720-670 biosensor for recording γ-secretase activity and 2) a unique multiplexed immunostaining platform that enables the selective detection of intracellular Aβ with subcellular resolution. Using these new assays, we showed that C99 is predominantly processed by γ-secretase in late endosomes and lysosomes, and intracellular Aβ is enriched in the same subcellular loci in intact neurons. However, the detailed properties of Aβ in the acidic compartments remain unclear. Here, we report using fluorescent lifetime imaging microscopy (FLIM) that intracellular Aβ includes both long Aβ intermediates bound to γ-secretase and short peptides dissociated from the protease complex. Surprisingly, our results also suggest that the dissociated Aβ is bound to the glycoproteins on the inner membrane of lysosomes. Furthermore, we show striking cell-to-cell heterogeneity in intracellular Aβ levels in primary neurons and APP transgenic mouse brains. These findings provide a basis for the further investigation of the role(s) of intracellular Aβ and its relevance to Alzheimer's disease (AD).

Keywords:  Alzheimer’s disease; fluorescence resonance energy transfer (FRET); glycoconjugates; intracellular amyloid-beta (Aβ); lysosomes; γ-secretase

DOI:  https://doi.org/10.3390/bios12080663
Antioxidants (Basel). 2022 Jul 27. pii: 1462. [Epub ahead of print]11(8):

Intermittent Hypoxia-Induced Cardiomyocyte Death Is Mediated by HIF-1 Dependent MAM Disruption.

Sophie Moulin, Amandine Thomas, Stefan Wagner, Michael Arzt, Hervé Dubouchaud, Frédéric Lamarche, Sophie Bouyon, Guillaume Vial, Diane Godin-Ribuot, Jean-Louis Pépin, Claire Arnaud, Elise Belaidi.

   RATIONALE: Intermittent hypoxia (IH) is one of the main features of sleep-disordered breathing (SDB). Recent findings indicate that hypoxia inducible factor-1 (HIF-1) promotes cardiomyocytes apoptosis during chronic IH, but the mechanisms involved remain to be elucidated. Here, we hypothesize that IH-induced ER stress is associated with mitochondria-associated ER membrane (MAM) alteration and mitochondrial dysfunction, through HIF-1 activation.
METHODS: Right atrial appendage biopsies from patients with and without SDB were used to determine HIF-1α, Grp78 and CHOP expressions. Wild-type and HIF-1α+/- mice were exposed to normoxia (N) or IH (21-5% O2, 60 cycles/h, 8 h/day) for 21 days. Expressions of HIF-1α, Grp78 and CHOP, and apoptosis, were measured by Western blot and immunochemistry. In isolated cardiomyocytes, we examined structural integrity of MAM by proximity ligation assay and their function by measuring ER-to-mitochondria Ca2+ transfer by confocal microscopy. Finally, we measured mitochondrial respiration using oxygraphy and calcium retention capacity (CRC) by spectrofluorometry. MAM structure was also investigated in H9C2 cells incubated with 1 mM CoCl2, a potent HIF-1α inducer.
RESULTS: In human atrial biopsies and mice, IH induced HIF-1 activation, ER stress and apoptosis. IH disrupted MAM, altered Ca2+ homeostasis, mitochondrial respiration and CRC. Importantly, IH had no effect in HIF-1α+/- mice. Similar to what observed under IH, HIF-1α overexpression was associated with MAM alteration in H9C2.
CONCLUSION: IH-induced ER stress, MAM alterations and mitochondrial dysfunction were mediated by HIF-1; all these intermediate mechanisms ultimately inducing cardiomyocyte apoptosis. This suggests that HIF-1 modulation might limit the deleterious cardiac effects of SDB.

Keywords:  cardiomyocyte death; hypoxia inducible factor-1; intermittent hypoxia; mitochondria associated-ER membrane; sleep disordered breathing

DOI:  https://doi.org/10.3390/antiox11081462
Immunometabolism (Cobham). 2022 Jul;4(3): e00001

Fatty acid translocase: a culprit of lipid metabolism dysfunction in disease.

Joseph E Rupert, Mikhail G Kolonin.

  Dysregulation of lipid deposition into and mobilization from white adipose tissue (WAT) underlies various diseases. Long-chain fatty acids (LCFA) and cholesterol trafficking in and out of adipocytes is a process relying on transporters shuttling lipids from the plasma membrane (PM) to lipid droplets (LD). CD36 is the fatty acid translocase (FAT) that transports LCFA and cholesterol across the PM. Interactions of CD36 with proteins PHB1, ANX2, and CAV1 mediate intercellular lipid transport between adipocytes, hematopoietic, epithelial, and endothelial cells. Intracellularly, the FAT complex has been found to regulate LCFA trafficking between the PM and LD. This process is regulated by CD36 glycosylation and S-acylation, as well as by post-translational modifications of PHB1 and ANX2, which determine both protein-protein interactions and the cellular localization of the complex. Changes in extracellular and intracellular LCFA levels have been found to induce the post-translational modifications and the function of the FAT complex in lipid uptake and mobilization. The role of the CD36/PHB1/ANX2 complex may span beyond lipid trafficking. The requirement of PHB1 for mitochondrial oxidative metabolism in brown adipocytes has been revealed. Cancer cells which take advantage of lipids mobilized by adipocytes and oxidized in leukocytes are indirectly affected by the function of FAT complex in other tissues. The direct importance of CD36 interaction with PHB1/and ANX2 in cancer cells remains to be established. This review highlights the multifaceted roles of the FAT complex in systemic lipid trafficking and discuss it as a potential target in metabolic disease and cancer.

Keywords:  fatty acid translocase; lipid metabolism

DOI:  https://doi.org/10.1097/IN9.0000000000000001
Life (Basel). 2022 Aug 09. pii: 1209. [Epub ahead of print]12(8):

Tunicamycin-Induced Endoplasmic Reticulum Stress Damages Complex I in Cardiac Mitochondria.

Qun Chen, Jeremy Thompson, Ying Hu, Edward J Lesnefsky.

   BACKGROUND: Induction of acute ER (endoplasmic reticulum) stress using thapsigargin contributes to complex I damage in mouse hearts. Thapsigargin impairs complex I by increasing mitochondrial calcium through inhibition of Ca2+-ATPase in the ER. Tunicamycin (TUNI) is used to induce ER stress by inhibiting protein folding. We asked if TUNI-induced ER stress led to complex I damage.
METHODS: TUNI (0.4 mg/kg) was used to induce ER stress in C57BL/6 mice. Cardiac mitochondria were isolated after 24 or 72 h following TUNI treatment for mitochondrial functional analysis.
RESULTS: ER stress was only increased in mice following 72 h of TUNI treatment. TUNI treatment decreased oxidative phosphorylation with complex I substrates compared to vehicle with a decrease in complex I activity. The contents of complex I subunits including NBUPL and NDUFS7 were decreased in TUNI-treated mice. TUNI treatment activated both cytosolic and mitochondrial calpain 1. Our results indicate that TUNI-induced ER stress damages complex I through degradation of its subunits including NDUFS7.
CONCLUSION: Induction of the ER stress using TUNI contributes to complex I damage by activating calpain 1.

Keywords:  NBUPL; NDUFS7; calpain; oxidative phosphorylation

DOI:  https://doi.org/10.3390/life12081209
Mol Metab. 2022 Aug 19. pii: S2212-8778(22)00146-6. [Epub ahead of print] 101577

Peroxisomal regulation of energy homeostasis: Effect on obesity and related metabolic disorders.

Brian Kleiboeker, Irfan J Lodhi.

   BACKGROUND: Peroxisomes are single membrane-bound organelles named for their role in hydrogen peroxide production and catabolism. However, their cellular functions extend well beyond reactive oxygen species (ROS) metabolism and include fatty acid oxidation of unique substrates that cannot be catabolized in mitochondria, and synthesis of ether lipids and bile acids. Metabolic functions of peroxisomes involve crosstalk with other organelles, including mitochondria, endoplasmic reticulum, lipid droplets and lysosomes. Emerging studies suggest that peroxisomes are important regulators of energy homeostasis and that disruption of peroxisomal functions influences the risk for obesity and the associated metabolic disorders, including type 2 diabetes and hepatic steatosis.
SCOPE OF REVIEW: Here, we focus on the role of peroxisomes in ether lipid synthesis, β-oxidation and ROS metabolism, given that these functions have been most widely studied and have physiologically relevant implications in systemic metabolism and obesity. Efforts are made to mechanistically link these cellular and systemic processes.
MAJOR CONCLUSIONS: Circulating plasmalogens, a form of ether lipids, have been identified as inversely correlated biomarkers of obesity. Ether lipids influence metabolic homeostasis through multiple mechanisms, including regulation of mitochondrial morphology and respiration affecting brown fat-mediated thermogenesis, and through regulation of adipose tissue development. Peroxisomal β-oxidation also affects metabolic homeostasis through generation of signaling molecules, such as acetyl-CoA and ROS that inhibit hydrolysis of stored lipids, contributing to development of hepatic steatosis. Oxidative stress resulting from increased peroxisomal β-oxidation-generated ROS in the context of obesity mediates β-cell lipotoxicity. A better understanding of the roles peroxisomes play in regulating and responding to obesity and its complications will provide new opportunities for their treatment.

Keywords:  Diabetes; Fatty liver; Lipid metabolism; Obesity; Peroxisomes; Plasmalogen

DOI:  https://doi.org/10.1016/j.molmet.2022.101577
Front Physiol. 2022 ;13 928964

AMPKβ isoform expression patterns in various adipocyte models and in relation to body mass index.

Franziska Kopietz, Eva Degerman, Olga Göransson.

  AMP-activated protein kinase (AMPK) activation is considered a useful strategy for the treatment of type 2 diabetes (T2D). It is unclear whether the expression and/or activity of AMPK in adipocytes is dysregulated in obesity. Also, the expression/activity pattern of AMPKβ isoforms, which are targets for AMPK activators, in adipocytes remains elusive. In this study we show that the two AMPKβ isoforms make roughly equal contributions to AMPK activity in primary human and mouse adipocytes, whereas in cultured 3T3-L1 adipocytes of mouse origin and in primary rat adipocytes, β1-associated activity clearly dominates. Additionally, we found that obesity is not associated with changes in AMPK subunit expression or kinase activity in adipocytes isolated from subcutaneous adipose tissue from individuals with various BMI.

Keywords:  AMPKβ; adipocytes; expression; human; kinase activity; obesity

DOI:  https://doi.org/10.3389/fphys.2022.928964
Curr Drug Targets. 2022 ;23(11): 1057-1071

Targeting AMPK Signaling in the Liver: Implications for Obesity and Type 2 Diabetes Mellitus.

Doudou Wang, Lin Yang, Ying Liu.

  Obesity and type 2 diabetes mellitus (T2DM), as common metabolic diseases, are pathologically characterized by overnutrition and insulin resistance (IR), which subsequently lead to glucose and lipid metabolism disorders. The liver, a major metabolic organ of the body, integrates hormone and metabolic signals to regulate the synthesis of lipids and glucose as well as their transport to peripheral tissues, hence playing an essential role in the development of obesity and T2DM. Adenosine 5'-monophosphate-activated protein kinase (AMPK) is a central regulator involved in cellular and organismal metabolism in eukaryotes, which activates processes that produce ATP and diminishes its consumption. In addition, AMPK also regulates mitochondrial homeostasis and promotes autophagy, both of which are associated with the pathogenesis of IR. Therefore, increasing AMPK activity is considered a promising therapeutic strategy to prevent obesity and T2DM. In this review, we summarize the role of hepatic AMPK in obesity and T2DM and the potential of using AMPK activators as therapeutics for metabolic disorders.

Keywords:  AMPK; AMPK activators; hyperglycemia; liver; obesity; type 2 diabetes mellitus

DOI:  https://doi.org/10.2174/1389450123666220429082702
JCI Insight. 2022 Aug 23. pii: e161783. [Epub ahead of print]

Impaired fatty acid metabolism perpetuates lipotoxicity along the transition to chronic kidney injury.

Anna Rinaldi, Hélène Lazareth, Virginie Poindessous, Ivan Nemazanyy, Julio L Sampaio, Daniele Malpetti, Yohan Bignon, Maarten Naesens, Marion Rabant, Dany Anglicheau, Pietro E Cippà, Nicolas Pallet.

  Energy metabolism failure in proximal tubule cells (PTC) is a hallmark of chronic kidney injury. We combined transcriptomic, metabolomic and lipidomic approaches in experimental models and patient cohorts to investigate the molecular bases of the progression to chronic kidney allograft injury initiated by ischemia-reperfusion injury (IRI). The urinary metabolome of kidney transplant recipients with chronic allograft injury and who experienced severe IRI was significantly enriched with long chain fatty acids (FA). We identified a renal FA-related gene signature with low levels of Cpt2 and Acsm5 and high levels of Acsl4 and Acsm5 associated with IRI, transition to chronic injury, and established CKD in mouse models and kidney transplant recipients. The findings were consistent with the presence of Cpt2-, Acsl4+, Acsl5+, Acsm5- PTC failing to recover from IRI as identified by snRNAseq. In vitro experiments indicated that endoplasmic reticulum (ER) stress contributes to CPT2 repression, which, in turn, promotes lipids accumulation, drives profibrogenic epithelial phenotypic changes, and activates the unfolded protein response. ER stress through CPT2 inhibition and lipid accumulation, engages an auto-amplification loop leading to lipotoxicity and self-sustained cellular stress. Thus, IRI imprints a persistent FA metabolism disturbance in the proximal tubule sustaining the progression to chronic kidney allograft injury.

Keywords:  Bioenergetics; Nephrology; Transplantation

DOI:  https://doi.org/10.1172/jci.insight.161783