scholarly journals Mitochondrial pyruvate and fatty acid flux modulate MICU1-dependent control of MCU activity

2020 ◽  
Vol 13 (628) ◽  
pp. eaaz6206 ◽  
Author(s):  
Neeharika Nemani ◽  
Zhiwei Dong ◽  
Cassidy C. Daw ◽  
Travis R. Madaris ◽  
Karthik Ramachandran ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Tca Cycle ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Mitochondrial Morphology ◽  
Autophagic Flux ◽  
Fatty Acid Transport ◽  
Mitochondrial Matrix ◽  
Genetic Ablation ◽  
Mitochondrial Fatty Acid

The tricarboxylic acid (TCA) cycle converts the end products of glycolysis and fatty acid β-oxidation into the reducing equivalents NADH and FADH2. Although mitochondrial matrix uptake of Ca2+ enhances ATP production, it remains unclear whether deprivation of mitochondrial TCA substrates alters mitochondrial Ca2+ flux. We investigated the effect of TCA cycle substrates on MCU-mediated mitochondrial matrix uptake of Ca2+, mitochondrial bioenergetics, and autophagic flux. Inhibition of glycolysis, mitochondrial pyruvate transport, or mitochondrial fatty acid transport triggered expression of the MCU gatekeeper MICU1 but not the MCU core subunit. Knockdown of mitochondrial pyruvate carrier (MPC) isoforms or expression of the dominant negative mutant MPC1R97W resulted in increased MICU1 protein abundance and inhibition of MCU-mediated mitochondrial matrix uptake of Ca2+. We also found that genetic ablation of MPC1 in hepatocytes and mouse embryonic fibroblasts resulted in reduced resting matrix Ca2+, likely because of increased MICU1 expression, but resulted in changes in mitochondrial morphology. TCA cycle substrate–dependent MICU1 expression was mediated by the transcription factor early growth response 1 (EGR1). Blocking mitochondrial pyruvate or fatty acid flux was linked to increased autophagy marker abundance. These studies reveal a mechanism that controls the MCU-mediated Ca2+ flux machinery and that depends on TCA cycle substrate availability. This mechanism generates a metabolic homeostatic circuit that protects cells from bioenergetic crisis and mitochondrial Ca2+ overload during periods of nutrient stress.

scholarly journals Mitochondrial Fission Governed by Drp1 Regulates Exogenous Fatty Acid Usage and Storage in Hela Cells

Metabolites ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 322
Author(s):  
Jae-Eun Song ◽  
Tiago C. Alves ◽  
Bernardo Stutz ◽  
Matija Šestan-Peša ◽  
Nicole Kilian ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Lipid Droplets ◽  
Mitochondrial Fission ◽  
Acid Oxidation ◽  
Mitochondrial Morphology ◽  
Mitochondrial Fatty Acid Oxidation ◽  
Mitochondrial Fatty Acid ◽  
And Storage

In the presence of high abundance of exogenous fatty acids, cells either store fatty acids in lipid droplets or oxidize them in mitochondria. In this study, we aimed to explore a novel and direct role of mitochondrial fission in lipid homeostasis in HeLa cells. We observed the association between mitochondrial morphology and lipid droplet accumulation in response to high exogenous fatty acids. We inhibited mitochondrial fission by silencing dynamin-related protein 1(DRP1) and observed the shift in fatty acid storage-usage balance. Inhibition of mitochondrial fission resulted in an increase in fatty acid content of lipid droplets and a decrease in mitochondrial fatty acid oxidation. Next, we overexpressed carnitine palmitoyltransferase-1 (CPT1), a key mitochondrial protein in fatty acid oxidation, to further examine the relationship between mitochondrial fatty acid usage and mitochondrial morphology. Mitochondrial fission plays a role in distributing exogenous fatty acids. CPT1A controlled the respiratory rate of mitochondrial fatty acid oxidation but did not cause a shift in the distribution of fatty acids between mitochondria and lipid droplets. Our data reveals a novel function for mitochondrial fission in balancing exogenous fatty acids between usage and storage, assigning a role for mitochondrial dynamics in control of intracellular fuel utilization and partitioning.

scholarly journals Adiponectin improves insulin sensitivity via activation of autophagic flux

2017 ◽  
Vol 59 (4) ◽  
pp. 339-350 ◽  
Author(s):  
Penny Ahlstrom ◽  
Esther Rai ◽  
Suharto Chakma ◽  
Hee Ho Cho ◽  
Palanivel Rengasamy ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Er Stress ◽  
Western Blotting ◽  
Muscle Cells ◽  
Dominant Negative ◽  
Skeletal Muscle Cells ◽  
Dominant Negative Mutant ◽  
Autophagic Flux

Skeletal muscle insulin resistance is known to play an important role in the pathogenesis of diabetes, and one potential causative cellular mechanism is endoplasmic reticulum (ER) stress. Adiponectin mediates anti-diabetic effects via direct metabolic actions and by improving insulin sensitivity, and we recently demonstrated an important role in stimulation of autophagy by adiponectin. However, there is limited knowledge on crosstalk between autophagy and ER stress in skeletal muscle and in particular how they are regulated by adiponectin. Here, we utilized the model of high insulin/glucose (HIHG)-induced insulin resistance, determined by measuring Akt phosphorylation (T308 and S473) and glucose uptake in L6 skeletal muscle cells. HIHG reduced autophagic flux measured by LC3 and p62 Western blotting and tandem fluorescent RFP/GFP-LC3 immunofluorescence (IF). HIHG also induced ER stress assessed by thioflavin T/KDEL IF, pIRE1, pPERK, peIF2α and ATF6 Western blotting and induction of a GRP78-mCherry reporter. Induction of autophagy by adiponectin or rapamycin attenuated HIHG-induced ER stress and improved insulin sensitivity. The functional significance of enhanced autophagy was validated by demonstrating a lack of improved insulin sensitivity in response to adiponectin in autophagy-deficient cells generated by overexpression of dominant negative mutant of Atg5. In summary, adiponectin-induced autophagy in skeletal muscle cells alleviated HIHG-induced ER stress and insulin resistance.

In obese rat muscle transport of palmitate is increased and is channeled to triacylglycerol storage despite an increase in mitochondrial palmitate oxidation

2009 ◽  
Vol 296 (4) ◽  
pp. E738-E747 ◽  
Author(s):  
Graham P. Holloway ◽  
Carley R. Benton ◽  
Kerry L. Mullen ◽  
Yuko Yoshida ◽  
Laelie A. Snook ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Zucker Rats ◽  
Acid Oxidation ◽  
Fatty Acid Transport ◽  
Acid Transport ◽  
Mitochondrial Fatty Acid Oxidation ◽  
Palmitate Oxidation ◽  
Mitochondrial Fatty Acid ◽  
Obese Zucker Rats

Intramuscular triacylglycerol (IMTG) accumulation in obesity has been attributed to increased fatty acid transport and/or to alterations in mitochondrial fatty acid oxidation. Alternatively, an imbalance in these two processes may channel fatty acids into storage. Therefore, in red and white muscles of lean and obese Zucker rats, we examined whether the increase in IMTG accumulation was attributable to an increased rate of fatty acid transport rather than alterations in subsarcolemmal (SS) or intermyofibrillar (IMF) mitochondrial fatty acid oxidation. In obese animals selected parameters were upregulated, including palmitate transport (red: +100%; white: +51%), plasmalemmal FAT/CD36 (red: +116%; white: +115%; not plasmalemmal FABPpm, FATP1, or FATP4), IMTG concentrations (red: ∼2-fold; white: ∼4-fold), and mitochondrial content (red +30%). Selected mitochondrial parameters were also greater in obese animals, namely, palmitate oxidation (SS red: +91%; SS white: +26%; not IMF mitochondria), FAT/CD36 (SS: +65%; IMF: +65%), citrate synthase (SS: +19%), and β-hydroxyacyl-CoA dehydrogenase activities (SS: +20%); carnitine palmitoyltransferase-I activity did not differ. A comparison of lean and obese rat muscles revealed that the rate of change in IMTG concentration was eightfold greater than that of fatty acid oxidation (SS mitochondria), when both parameters were expressed relative to fatty transport. Thus fatty acid transport, esterification, and oxidation (SS mitochondria) are upregulated in muscles of obese Zucker rats, with these effects being most pronounced in red muscle. The additional fatty acid taken up is channeled primarily to esterification, suggesting that upregulation in fatty acid transport as opposed to altered fatty acid oxidation is the major determinant of intramuscular lipid accumulation.

Mitochondrial function and dysfunction in exercise and insulin resistanceThis paper article is one of a selection of papers published in this Special Issue, entitled 14th International Biochemistry of Exercise Conference – Muscles as Molecular and Metabolic Machines, and has undergone the Journal’s usual peer review process.

2009 ◽  
Vol 34 (3) ◽  
pp. 440-446 ◽  
Author(s):  
Graham P. Holloway
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Peer Review Process ◽  
Acid Oxidation ◽  
Fatty Acid Transport ◽  
Acid Transport ◽  
Mitochondrial Content ◽  
Mitochondrial Fatty Acid

Fatty acid translocase (FAT/CD36) represents a novel flexible regulatory system, influencing rates of mitochondrial fatty acid metabolism in both human and rodent skeletal muscle. During exercise, the subcellular redistribution of FAT/CD36 provides a mechanism to increase not only plasma membrane fatty acid transport, but also mitochondrial fatty acid oxidation. This FAT/CD36-mediated coordination of long chain fatty acid (LCFA) transport and oxidation is an intriguing model in the context of insulin resistance. It was believed for almost a decade that reductions in fatty acid oxidation increased intramuscular lipids, thereby contributing to insulin resistance. A reduction in mitochondrial content may reduce the capacity of skeletal muscle LCFA oxidation; however, work from my laboratory has shown that, in some insulin-resistant muscles, mitochondrial content and fatty acid oxidation are both increased, yet these muscles accumulate lipids because of a considerably greater increase in fatty acid transport. Therefore, an alternative model is being considered, in which the balance between LCFA uptake and oxidation is a determining factor in the development of insulin resistance. A permanent redistribution of the LCFA transport protein FAT/CD36 to the sarcolemmal has been consistently found, which results in an increased rate of LCFA transport. This work suggests that the accumulation of skeletal muscle lipids, regardless of changes in mitochondria, is attributable to an increased rate of LCFA transport that exceeds the capacity for oxidation.

FAT/CD36-null mice reveal that mitochondrial FAT/CD36 is required to upregulate mitochondrial fatty acid oxidation in contracting muscle

2009 ◽  
Vol 297 (4) ◽  
pp. R960-R967 ◽  
Author(s):  
Graham P. Holloway ◽  
Swati S. Jain ◽  
Veronic Bezaire ◽  
Xiao Xia Han ◽  
Jan F. C. Glatz ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Fatty Acid ◽  
Muscle Contraction ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
Fatty Acid Transport ◽  
Mitochondrial Fatty Acid Oxidation ◽  
Palmitate Oxidation ◽  
Oxidation Rates ◽  
Mitochondrial Fatty Acid

The plasma membrane fatty acid transport protein FAT/CD36 is also present at the mitochondria, where it may contribute to the regulation of fatty acid oxidation, although this has been challenged. Therefore, we have compared enzyme activities and rates of mitochondrial palmitate oxidation in muscles of wild-type (WT) and FAT/CD36 knockout (KO) mice, at rest and after muscle contraction. In WT and KO mice, carnitine palmitoyltransferase-I, citrate synthase, and β-hydroxyacyl-CoA dehydrogenase activities did not differ in subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria of WT and FAT/CD36 KO mice. Basal palmitate oxidation rates were lower ( P < 0.05) in KO mice (SS −18%; IMF −13%). Muscle contraction increased fatty acid oxidation (+18%) and mitochondrial FAT/CD36 protein (+16%) in WT IMF but not in WT SS, or in either mitochondrial subpopulation in KO mice. This revealed that the difference in IMF mitochondrial fatty acid oxidation between WT and KO mice can be increased ∼2.5-fold from 13% under basal conditions to 35% during muscle contraction. The FAT/CD36 inhibitor sulfo- N-succinimidyl oleate (SSO), inhibited palmitate transport across the plasma membrane in WT, but not in KO mice. In contrast, SSO bound to mitochondrial membranes and reduced palmitate oxidation rates to a similar extent in both WT and KO mitochondria (∼80%; P < 0.05). In addition, SSO reduced state III respiration with succinate as a substrate, without altering mitochondrial coupling (P/O ratios). Thus, while SSO inhibits FAT/CD36-mediated palmitate transport at the plasma membrane, SSO has undefined effects on mitochondria. Nevertheless, the KO animals reveal that FAT/CD36 contributes to the regulation of mitochondrial fatty acid oxidation, which is especially important for meeting the increased metabolic demands during muscle contraction.

Abstract P028: Activation Of The Renin-angiotensin System Drives Renal Metabolic Abnormalities In Diabetic Nephropathy

Hypertension ◽  
2020 ◽  
Vol 76 (Suppl_1) ◽  
Author(s):  
Kengo Azushima ◽  
Jean Paul Kovalik ◽  
Jianhong Ching ◽  
Susan B Gurley ◽  
Thomas M Coffman
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Metabolism ◽  
Acid Metabolism ◽  
Renin Angiotensin System ◽  
Tca Cycle ◽  
High Grade ◽  
Wild Type ◽  
Angiotensin System ◽  
Renin Angiotensin ◽  
Mitochondrial Fatty Acid

Activation of the renin-angiotensin system (RAS) is a major contributor to the pathogenesis of diabetic nephroathy (DN). However, the precise mechanisms of renoprotection associated with RAS blockade in DN are not entirely clear. The aim of this study is to examine whether metabolic effects of RAS blockade might contribute to renoprotection. We utilized a mouse model of DN combining severe type I diabetes (the Akita mutation) with a single-copy renin transgene (ReninTG) driven by the albumin promoter. Akita-ReninTG mice on a 129/Sv background (DN-susceptible mice) develop clinical features of human DN including high-grade albuminuria, renal interstitial inflammation and glomerulosclerosis, while Akita-ReninTG mice on a C57BL/6 background (DN-resistant mice) do not develop significant kidney disease. These two experimental groups were treated with the angiotensin receptor blocker (ARB) losartan 10 mg/kg/day for 12 weeks, and metabolic profiles in kidney tissues were examined using a targeted metabolomics assay. The DN-susceptible mice exhibited high-grade albuminuria that was significantly attenuated by ARB (Vehicle vs ARB: 1480±562 vs 193±42 μg/day, p =0.045), while DN-resistant mice had minimal albuminuria that was not affected by ARB (Vehicle vs ARB: 80±14 vs 75±14 μg/day, p =0.801). The metabolomics profiles of the DN-resistant mice were similar to C57BL/6 wild-type controls. By contrast, DN-susceptible mice exhibited broad reductions in even-chain acyl-carnitines and an abnormal profile of TCA cycle intermediates compared to 129/Sv wild-type controls, suggesting substantial impairments of renal mitochondrial fuel oxidation including altered fatty acid metabolism. RAS blockade had broad effects to correct this profile by increasing acetyl-carnitines generated from acetyl-CoA and concomitantly normalizing expression of genes associated with mitochondrial fatty acid metabolism including PPAR-α, PGC-1α, CPT1 and CPT2. ARB treatment restored TCA cycle activity to normal. These findings suggest that effects of RAS blockade re-establish normal fuel metabolism and mitochondrial fatty acid oxidation in kidney and may contribute to renoprotection.

FAT/CD36 is located on the outer mitochondrial membrane, upstream of long-chain acyl-CoA synthetase, and regulates palmitate oxidation

2011 ◽  
Vol 437 (1) ◽  
pp. 125-134 ◽  
Author(s):  
Brennan K. Smith ◽  
Swati S. Jain ◽  
Stéphanie Rimbaud ◽  
Aaron Dam ◽  
Joe Quadrilatero ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Mitochondrial Membrane ◽  
Functional Role ◽  
Muscle Fibres ◽  
Fatty Acid Transport ◽  
Outer Mitochondrial Membrane ◽  
Acid Transport ◽  
Mitochondrial Fatty Acid ◽  
Chain Acyl ◽  
Long Chain

FAT/CD36 (fatty acid translocase/Cluster of Differentiation 36), a plasma membrane fatty-acid transport protein, has been found on mitochondrial membranes; however, it remains unclear where FAT/CD36 resides on this organelle or its functional role within mitochondria. In the present study, we demonstrate, using several different approaches, that in skeletal muscle FAT/CD36 resides on the OMM (outer mitochondrial membrane). To determine the functional role of mitochondrial FAT/CD36 in this tissue, we determined oxygen consumption rates in permeabilized muscle fibres in WT (wild-type) and FAT/CD36-KO (knockout) mice using a variety of substrates. Despite comparable muscle mitochondrial content, as assessed by unaltered mtDNA (mitochondrial DNA), citrate synthase, β-hydroxyacyl-CoA dehydrogenase, cytochrome c oxidase complex IV and respiratory capacities [maximal OXPHOS (oxidative phosphorylation) respiration] in WT and KO mice, palmitate-supported respiration was 34% lower in KO animals. In contrast, palmitoyl-CoA-supported respiration was unchanged. These results indicate that FAT/CD36 is key for palmitate-supported respiration. Therefore we propose a working model of mitochondrial fatty-acid transport, in which FAT/CD36 is positioned on the OMM, upstream of long-chain acyl-CoA synthetase, thereby contributing to the regulation of mitochondrial fatty-acid transport. We further support this model by providing evidence that FAT/CD36 is not located in mitochondrial contact sites, and therefore does not directly interact with carnitine palmitoyltransferase-I as original proposed.

scholarly journals Oocyte developmental failure in response to elevated nonesterified fatty acid concentrations: mechanistic insights

Reproduction ◽  
2013 ◽  
Vol 145 (1) ◽  
pp. 33-44 ◽  
Author(s):  
V Van Hoeck ◽  
J L M R Leroy ◽  
M Arias Alvarez ◽  
D Rizos ◽  
A Gutierrez-Adan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Fatty Acid ◽  
Energy Metabolism ◽  
Ovarian Follicle ◽  
Developmental Competence ◽  
Nonesterified Fatty Acid ◽  
Mitochondrial Morphology ◽  
Functional Perspective ◽  
Expression Of Genes ◽  
Mitochondrial Fatty Acid

Elevated plasma nonesterified fatty acid (NEFA) concentrations are associated with negative energy balance and metabolic disorders such as obesity and type II diabetes. Such increased plasma NEFA concentrations induce changes in the microenvironment of the ovarian follicle, which can compromise oocyte competence. Exposing oocytes to elevated NEFA concentrations during maturation affects the gene expression and phenotype of the subsequent embryo, notably prompting a disrupted oxidative metabolism. We hypothesized that these changes in the embryo are a consequence of modified energy metabolism in the oocyte. To investigate this, bovine cumulus oocyte complexes were matured under elevated NEFA conditions, and energy metabolism-related gene expression, mitochondrial function, and ultrastructure evaluated. It was found that expression of genes related to REDOX maintenance was modified in NEFA-exposed oocytes, cumulus cells, and resultant blastocysts. Moreover, the expression of genes related to fatty acid synthesis in embryos that developed from NEFA-exposed oocytes was upregulated. From a functional perspective, inhibition of fatty acid β-oxidation in maturing oocytes exposed to elevated NEFA concentrations restored developmental competence. There were no clear differences in mitochondrial morphology or oxygen consumption between treatments, although there was a trend for a higher mitochondrial membrane potential in zygotes derived from NEFA-exposed oocytes. These data show that the degree of mitochondrial fatty acid β-oxidation has a decisive impact on the development of NEFA-exposed oocytes. Furthermore, the gene expression data suggest that the resulting embryos adapt through altered metabolic strategies, which might explain the aberrant energy metabolism previously observed in these embryos originating from NEFA-exposed maturing oocytes.

scholarly journals Loss of the Mitochondrial Fission GTPase Drp1 Contributes to Neurodegeneration in a Drosophila Model of Hereditary Spastic Paraplegia

2020 ◽  
Vol 10 (9) ◽  
pp. 646
Author(s):  
Philippa C. Fowler ◽  
Dwayne J. Byrne ◽  
Craig Blackstone ◽  
Niamh C. O'Sullivan
Keyword(s):  
Hereditary Spastic Paraplegia ◽  
Neurodegenerative Disorder ◽  
Mitochondrial Fission ◽  
Dominant Negative ◽  
In Vivo Model ◽  
Mitochondrial Morphology ◽  
Autophagic Flux ◽  
Spastic Paraplegia ◽  
Drosophila Model

Mitochondrial morphology, distribution and function are maintained by the opposing forces of mitochondrial fission and fusion, the perturbation of which gives rise to several neurodegenerative disorders. The large guanosine triphosphate (GTP)ase dynamin-related protein 1 (Drp1) is a critical regulator of mitochondrial fission by mediating membrane scission, often at points of mitochondrial constriction at endoplasmic reticulum (ER)-mitochondrial contacts. Hereditary spastic paraplegia (HSP) subtype SPG61 is a rare neurodegenerative disorder caused by mutations in the ER-shaping protein Arl6IP1. We have previously reported defects in both the ER and mitochondrial networks in a Drosophila model of SPG61. In this study, we report that knockdown of Arl6IP1 lowers Drp1 protein levels, resulting in reduced ER–mitochondrial contacts and impaired mitochondrial load at the distal ends of long motor neurons. Increasing mitochondrial fission, by overexpression of wild-type Drp1 but not a dominant negative Drp1, increases ER–mitochondrial contacts, restores mitochondrial load within axons and partially rescues locomotor deficits. Arl6IP1 knockdown Drosophila also demonstrate impaired autophagic flux and an accumulation of ubiquitinated proteins, which occur independent of Drp1-mediated mitochondrial fission defects. Together, these findings provide evidence that impaired mitochondrial fission contributes to neurodegeneration in this in vivo model of HSP.

Protein-mediated fatty acid uptake: regulation by contraction, AMP-activated protein kinase, and endocrine signals

2007 ◽  
Vol 32 (5) ◽  
pp. 865-873 ◽  
Author(s):  
James G. Nickerson ◽  
Iman Momken ◽  
Carley R. Benton ◽  
James Lally ◽  
Graham P. Holloway ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Fatty Acid ◽  
Protein Kinase ◽  
Acid Oxidation ◽  
Fatty Acid Transport ◽  
Acid Uptake ◽  
Acid Transport ◽  
Fatty Acid Binding ◽  
Mitochondrial Fatty Acid ◽  
Amp Activated Protein Kinase

Fatty acid transport into heart and skeletal muscle occurs largely through a highly regulated protein-mediated mechanism involving a number of fatty acid transporters. Chronically altered muscle activity (chronic muscle stimulation, denervation) alters fatty acid transport by altering the expression of fatty acid transporters and (or) their subcellular location. Chronic exposure to leptin downregulates while insulin upregulates fatty acid transport by altering concomitantly the expression of fatty acid transporters. Fatty acid transport can also be regulated within minutes, by muscle contraction, AMP-activated protein kinase activation, leptin, and insulin, through induction of the translocation of fatty acid translocase (FAT)/CD36 from its intracellular depot to the plasma membrane. In insulin-resistant muscle, a permanent relocation of FAT/CD36 to the sarcolemma appears to account for the excess accretion of intracellular lipids that interfere with insulin signaling. Recent work has also shown that FAT/ CD36, but not plasma membrane associated fatty acid binding protein, is involved, along with carnitine palmitoyltransferase, in regulating mitochondrial fatty acid oxidation. Finally, studies in FAT/CD36 null mice indicate that this transporter has a key role in regulating fatty acid metabolism in muscle.

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