Mitochondrial dysfunction caused by saturated fatty acid loading induces myocardial insulin-resistance in differentiated H9c2 myocytes: A novel ex vivo myocardial insulin-resistance model

Background: Insulin resistance (IR), considered a hallmark of diabetes at the cellular level, is implicated in pre-diabetes, results in type 2 diabetes, and negatively affects mitochondrial function. Diabetes is increasingly associated with enhanced risk of developing Parkinson’s disease (PD); however, the underlying mechanism remains unclear. This study investigated the probable culpability of IR in the pathogenesis of PD. Methods: Using MitoPark mice in vivo models, diabetes was induced by a high-fat diet in the in vivo models, and IR was induced by protracted pulse-stimulation with 100 nM insulin treatment of neuronal cells, in vitro to determine the molecular mechanism(s) underlying altered cellular functions in PD, including mitochondrial dysfunction and α-synuclein (SNCA) aberrant expression. Findings: We observed increased SNCA expression in the dopaminergic (DA) neurons of both the wild-type and diabetic MitoPark mice, coupled with enhanced degeneration of DA neurons in the diabetic MitoPark mice. Ex vivo, in differentiated human DA neurons, IR was associated with increased SNCA and reactive oxygen species (ROS) levels, as well as mitochondrial depolarization. Moreover, we demonstrated concomitant hyperactivation of polo-like kinase-2 (PLK2), and upregulated p-SNCA (Ser129) and proteinase K-resistant SNCA proteins level in IR SH-SY5Y cells, however the inhibition of PLK2 reversed IR-related increases in phosphorylated and total SNCA. Similarly, the overexpression of peroxisome proliferator-activated receptor-γ coactivator 1-alpha (PGC)-1α suppressed ROS production, repressed PLK2 hyperactivity, and resulted in downregulation of total and Ser129-phosphorylated SNCA in the IR SH-SY5Y cells. Conclusions: These findings demonstrate that IR-associated diabetes promotes the development and progression of PD through PLK2-mediated mitochondrial dysfunction, upregulated ROS production, and enhanced SNCA signaling, suggesting the therapeutic targetability of PLK2 and/or SNCA as potential novel disease-modifying strategies in patients with PD.

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Cultured hypothalamic neurons are resistant to inflammation and insulin resistance induced by saturated fatty acids

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00006.2010 ◽

2010 ◽

Vol 298 (6) ◽

pp. E1122-E1130 ◽

Cited By ~ 51

Author(s):

Sun Ju Choi ◽

Francis Kim ◽

Michael W. Schwartz ◽

Brent E. Wisse

Keyword(s):

Insulin Resistance ◽

Fatty Acids ◽

Fatty Acid ◽

Saturated Fatty Acid ◽

Cell Lines ◽

Saturated Fatty Acids ◽

Neuronal Cell ◽

Acid Exposure ◽

Inflammatory Signaling ◽

Hypothalamic Neurons

Hypothalamic inflammation induced by high-fat feeding causes insulin and leptin resistance and contributes to the pathogenesis of obesity. Since in vitro exposure to saturated fatty acids causes inflammation and insulin resistance in many cultured cell types, we determined how cultured hypothalamic neurons respond to this stimulus. Two murine hypothalamic neuronal cell cultures, N43/5 and GT1–7, were exposed to escalating concentrations of saturated fatty acids for up to 24 h. Harvested cells were evaluated for activation of inflammation by gene expression and protein content. Insulin-treated cells were evaluated for induction of markers of insulin receptor signaling (p-IRS, p-Akt). In both hypothalamic cell lines, inflammation was induced by prototypical inflammatory mediators LPS and TNFα, as judged by induction of IκBα (3- to 5-fold) and IL-6 (3- to 7-fold) mRNA and p-IκBα protein, and TNFα pretreatment reduced insulin-mediated p-Akt activation by 30% ( P < 0.05). By comparison, neither mixed saturated fatty acid (100, 250, or 500 μM for ≤6 h) nor palmitate exposure alone (200 μM for ≤24 h) caused inflammatory activation or insulin resistance in cultured hypothalamic neurons, whereas they did in control muscle and endothelial cell lines. Despite the lack of evidence of inflammatory signaling, saturated fatty acid exposure in cultured hypothalamic neurons causes endoplasmic reticulum stress, induces mitogen-activated protein kinase, and causes apoptotic cell death with prolonged exposure. We conclude that saturated fatty acid exposure does not induce inflammatory signaling or insulin resistance in cultured hypothalamic neurons. Therefore, hypothalamic neuronal inflammation in the setting of DIO may involve an indirect mechanism mediated by saturated fatty acids on nonneuronal cells.

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Mitochondrial dysfunction in insulin resistance: differential contributions of chronic insulin and saturated fatty acid exposure in muscle cells

Bioscience Reports ◽

10.1042/bsr20120034 ◽

2012 ◽

Vol 32 (5) ◽

pp. 465-478 ◽

Cited By ~ 28

Author(s):

Chenjing Yang ◽

Cho Cho Aye ◽

Xiaoxin Li ◽

Angels Diaz Ramos ◽

Antonio Zorzano ◽

...

Keyword(s):

Insulin Resistance ◽

Oxygen Consumption ◽

Fatty Acid ◽

Membrane Potential ◽

Mitochondrial Membrane Potential ◽

Saturated Fatty Acid ◽

Mitochondrial Function ◽

Mitochondrial Membrane ◽

Acid Exposure ◽

High Insulin

Mitochondrial dysfunction has been associated with insulin resistance, obesity and diabetes. Hyperinsulinaemia and hyperlipidaemia are hallmarks of the insulin-resistant state. We sought to determine the contributions of high insulin and saturated fatty acid exposure to mitochondrial function and biogenesis in cultured myocytes. Differentiated C2C12 myotubes were left untreated or exposed to chronic high insulin or high palmitate. Mitochondrial function was determined assessing: oxygen consumption, mitochondrial membrane potential, ATP content and ROS (reactive oxygen species) production. We also determined the expression of several mitochondrial genes. Chronic insulin treatment of myotubes caused insulin resistance with reduced PI3K (phosphoinositide 3-kinase) and ERK (extracellular-signal-regulated kinase) signalling. Insulin treatment increased oxygen consumption but reduced mitochondrial membrane potential and ROS production. ATP cellular levels were maintained through an increased glycolytic rate. The expression of mitochondrial OXPHOS (oxidative phosphorylation) subunits or Mfn-2 (mitofusin 2) were not significantly altered in comparison with untreated cells, whereas expression of PGC-1α (peroxisome-proliferator-activated receptor γ co-activator-1α) and UCPs (uncoupling proteins) were reduced. In contrast, saturated fatty acid exposure caused insulin resistance, reducing PI3K (phosphoinositide 3-kinase) and ERK (extracellular-signal-regulated kinase) activation while increasing activation of stress kinases JNK (c-Jun N-terminal kinase) and p38. Fatty acids reduced oxygen consumption and mitochondrial membrane potential while up-regulating the expression of mitochondrial ETC (electron chain complex) protein subunits and UCP proteins. Mfn-2 expression was not modified by palmitate. Palmitate-treated cells also showed a reduced glycolytic rate. Taken together, our findings indicate that chronic insulin and fatty acid-induced insulin resistance differentially affect mitochondrial function. In both conditions, cells were able to maintain ATP levels despite the loss of membrane potential; however, different protein expression suggests different adaptation mechanisms.

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Hepatic saturated fatty acid fraction is associated with de novo lipogenesis and hepatic insulin resistance

Nature Communications ◽

10.1038/s41467-020-15684-0 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 5

Author(s):

Kay H. M. Roumans ◽

Lucas Lindeboom ◽

Pandichelvam Veeraiah ◽

Carlijn M. E. Remie ◽

Esther Phielix ◽

...

Keyword(s):

Insulin Resistance ◽

Fatty Acid ◽

Saturated Fatty Acid ◽

De Novo ◽

Fatty Acid Fraction ◽

De Novo Lipogenesis ◽

Hepatic Insulin Resistance ◽

Acid Fraction

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Palmitate Induced Mitochondrial Deoxyribonucleic Acid Damage and Apoptosis in L6 Rat Skeletal Muscle Cells

Endocrinology ◽

10.1210/en.2006-0998 ◽

2007 ◽

Vol 148 (1) ◽

pp. 293-299 ◽

Cited By ~ 93

Author(s):

L. I. Rachek ◽

S. I. Musiyenko ◽

S. P. LeDoux ◽

G. L. Wilson

Keyword(s):

Insulin Resistance ◽

Reactive Oxygen Species ◽

Skeletal Muscle ◽

Fatty Acid ◽

Free Fatty Acid ◽

Mitochondrial Dysfunction ◽

No Synthase ◽

Oxygen Species ◽

Mtdna Damage ◽

L6 Myotubes

A major characteristic of type 2 diabetes mellitus (T2DM) is insulin resistance in skeletal muscle. A growing body of evidence indicates that oxidative stress that results from increased production of reactive oxygen species and/or reactive nitrogen species leads to insulin resistance, tissue damage, and other complications observed in T2DM. It has been suggested that muscular free fatty acid accumulation might be responsible for the mitochondrial dysfunction and insulin resistance seen in T2DM, although the mechanisms by which increased levels of free fatty acid lead to insulin resistance are not well understood. To help resolve this situation, we report that saturated fatty acid palmitate stimulated the expression of inducible nitric oxide (NO) synthase and the production of reactive oxygen species and NO in L6 myotubes. Additionally, palmitate caused a significant dose-dependent increase in mitochondrial DNA (mtDNA) damage and a subsequent decrease in L6 myotube viability and ATP levels at concentrations as low as 0.5 mm. Furthermore, palmitate induced apoptosis, which was detected by DNA fragmentation, caspase-3 cleavage, and cytochrome c release. N-acetyl cysteine, a precursor compound for glutathione formation, aminoguanidine, an inducible NO synthase inhibitor, and 5,10,15,20-tetrakis(4-sulphonatophenyl) porphyrinato iron (III), a peroxynitrite inhibitor, all prevented palmitate-induced mtDNA damage and diminished palmitate-induced cytotoxicity. We conclude that exposure of L6 myotubes to palmitate induced mtDNA damage and triggered mitochondrial dysfunction, which caused apoptosis. Additionally, our findings indicate that palmitate-induced mtDNA damage and cytotoxicity in skeletal muscle cells were caused by overproduction of peroxynitrite.

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SELENON (SEPN1) protects skeletal muscle from saturated fatty acid-induced ER stress and insulin resistance

Redox Biology ◽

10.1016/j.redox.2019.101176 ◽

2019 ◽

Vol 24 ◽

pp. 101176 ◽

Cited By ~ 10

Author(s):

Ersilia Varone ◽

Diego Pozzer ◽

Simona Di Modica ◽

Alexander Chernorudskiy ◽

Leonardo Nogara ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Fatty Acid ◽

Er Stress ◽

Saturated Fatty Acid

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Calpain-10 interacts with plasma saturated fatty acid concentrations to influence insulin resistance in individuals with the metabolic syndrome

American Journal of Clinical Nutrition ◽

10.3945/ajcn.110.010512 ◽

2011 ◽

Vol 93 (5) ◽

pp. 1136-1141 ◽

Cited By ~ 18

Author(s):

Pablo Perez-Martinez ◽

Javier Delgado-Lista ◽

Antonio Garcia-Rios ◽

Jane F Ferguson ◽

Hanne L Gulseth ◽

...

Keyword(s):

Insulin Resistance ◽

Metabolic Syndrome ◽

Fatty Acid ◽

Saturated Fatty Acid ◽

The Metabolic Syndrome ◽

Calpain 10

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LRH-1 NUTRIGENOMICS: The Provision of Lauric Acid Results in the Endogenous Production of the Liver Receptor Homolog-1 Ligand, Dilauroylphosphatidylcholine, and LRH-1 Transactivation

10.1101/2021.02.01.429240 ◽

2021 ◽

Author(s):

KC Klatt ◽

S. Zhang ◽

OV Malysheva ◽

Z. Sun ◽

B. Dong ◽

...

Keyword(s):

Fatty Acid ◽

Saturated Fatty Acid ◽

Transcriptional Activation ◽

Lauric Acid ◽

Culture Media ◽

Ex Vivo ◽

Coconut Oil ◽

Endogenous Production ◽

Human Participants ◽

The Impact

ABSTRACTBackgroundThe unusual phosphatidylcholine species, dilauroylphosphatidylcholine (DLPC), has been reported to bind and activate the orphan nuclear receptor, liver receptor homolog-1 (LRH-1). To date, DLPC has not been reported endogenously in metabolomic databases.ObjectiveHerein, we test the hypothesis that the provision of the acyl constituent of DLPC, lauric acid (C12:0), a saturated fatty acid rich in tropical oils such as coconut oil, will 1) result in endogenous DLPC production and 2) enhance LRH-1 transcriptional activity.MethodsWe measured DLPC following provision of C12:0 to HepG2 cells, C57/BL6J mice, and to healthy human participants in an acute, randomized, controlled cross-over trial. LRH-1fl/fl and LRH-1fl/fl Albumin-Cre mice were used in ex vivo and in vivo approaches. to assess the impact of C12:0 on LRH-1 target gene expression. 1-13C-lauric acid and methyl-d9-choline were used to assess DLPC production dynamics.ResultsDLPC was not observed in any C12:0-free approach. Provision of C12:0 in the culture media or to C57/BL6J mice resulted in the rapid production of DLPC, including DLPC’s presence in multiple LRH-1 expressing tissues. Coconut oil-fed human participants exhibited DLPC in postprandial serum samples. Ex vivo and in vivo C12:0 provision resulted in increased mRNA expression of LRH-1 target genes, an effect that was not observed in hepatic knockout mice. Methyl-d9-choline administration revealed a complex reliance on CDP-choline-derived DLPC.ConclusionC12:0 provision results in endogenous production of the LRH-1 ligand, DLPC, and LRH-1 transcriptional activation phenotypes. Our findings highlight pleiotropic effects of lauric acid, a common hypercholesterolemic dietary saturated fatty acid, secondary to LRH-1 agonism.

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