Fatty acid type–specific regulation of SIRT1 does not affect insulin sensitivity in human skeletal muscle

In rodent skeletal muscle, acyl-coenzyme A (CoA) synthetase 5 (ACSL-5) is suggested to localize to the mitochondria but its precise function in human skeletal muscle is unknown. The purpose of these studies was to define the role of ACSL-5 in mitochondrial fatty acid metabolism and the potential effects on insulin action in human skeletal muscle cells (HSKMC). Primary myoblasts isolated from vastus lateralis (obese women (body mass index (BMI) = 34.7 ± 3.1 kg/m2)) were transfected with ACSL-5 plasmid DNA or green fluorescent protein (GFP) vector (control), differentiated into myotubes, and harvested (7 days). HSKMC were assayed for complete and incomplete fatty acid oxidation ([1-14C] palmitate) or permeabilized to determine mitochondrial respiratory capacity (basal (non-ADP stimulated state 4), maximal uncoupled (carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone (FCCP)-linked) respiration, and free radical (superoxide) emitting potential). Protein levels of ACSL-5 were 2-fold higher in ACSL-5 overexpressed HSKMC. Both complete and incomplete fatty acid oxidation increased by 2-fold (p < 0.05). In permeabilized HSKMC, ACSL-5 overexpression significantly increased basal and maximal uncoupled respiration (p < 0.05). Unexpectedly, however, elevated ACSL-5 expression increased mitochondrial superoxide production (+30%), which was associated with a significant reduction (p < 0.05) in insulin-stimulated p-Akt and p-AS160 protein levels. We concluded that ACSL-5 in human skeletal muscle functions to increase mitochondrial fatty acid oxidation, but contrary to conventional wisdom, is associated with increased free radical production and reduced insulin signaling.

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Promoter-specific regulation of PPARGC1A gene expression in human skeletal muscle

Journal of Molecular Endocrinology ◽

10.1530/jme-15-0150 ◽

2015 ◽

Vol 55 (2) ◽

pp. 159-168 ◽

Cited By ~ 12

Author(s):

Daniil V Popov ◽

Evgeny A Lysenko ◽

Tatiana F Vepkhvadze ◽

Nadia S Kurochkina ◽

Pavel A Maknovskii ◽

...

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Human Skeletal Muscle ◽

Stop Codon ◽

Constitutive Expression ◽

Alternative Promoter ◽

Specific Expression ◽

Post Exercise ◽

Specific Regulation ◽

Intensity Of Exercise

The goal of this study was to identify unknown transcription start sites of thePPARGC1A(PGC-1α) gene in human skeletal muscle and investigate the promoter-specific regulation ofPGC-1αgene expression in human skeletal muscle. Ten amateur endurance-trained athletes performed high- and low-intensity exercise sessions (70 min, 70% or 50%o2max). High-throughput RNA sequencing and exon–exon junction mapping were applied to analyse muscle samples obtained at rest and after exercise.PGC-1αpromoter-specific expression and activation of regulators of PGC-1α gene expression (AMPK, p38 MAPK, CaMKII, PKA and CREB1) after exercise were evaluated using qPCR and western blot. Our study has demonstrated that during post-exercise recovery, human skeletal muscle expresses thePGC-1αgene via two promoters only. As previously described, the additional exon 7a that contains a stop codon was found in all samples. Importantly, only minor levels of other splice site variants were found (and not in all samples). Constitutive expressionPGC-1αgene occurs via the canonical promoter, independent of exercise intensity and exercise-induced increase of AMPKThr172phosphorylation level. Expression ofPGC-1αgene via the alternative promoter is increased of two orders after exercise. This post-exercise expression is highly dependent on the intensity of exercise. There is an apparent association between expression via the alternative promoter and activation of CREB1.

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65 Fatty acid oxidation in human skeletal muscle mitochondria determined by oxidative phosphorylation as a function of age

Mitochondrion ◽

10.1016/j.mito.2007.08.069 ◽

2007 ◽

Vol 7 (6) ◽

pp. 422-423

Author(s):

George Kypriotakis ◽

Bruce H. Cohen ◽

Sumit Parikh ◽

Douglas S. Kerr ◽

Charles L. Hoppel ◽

...

Keyword(s):

Skeletal Muscle ◽

Fatty Acid ◽

Oxidative Phosphorylation ◽

Fatty Acid Oxidation ◽

Human Skeletal Muscle ◽

Acid Oxidation ◽

Muscle Mitochondria ◽

Skeletal Muscle Mitochondria

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The membrane-associated 40 KD fatty acid binding protein (Berk's protein), a putative fatty acid transporter is present in human skeletal muscle

Life Sciences ◽

10.1016/0024-3205(95)02251-1 ◽

1995 ◽

Vol 58 (1) ◽

pp. 19-28 ◽

Cited By ~ 30

Author(s):

Jorge Calles-Escandon ◽

Leigh Sweet ◽

Olle Ljungqvist ◽

Michael F. Hirshman

Keyword(s):

Skeletal Muscle ◽

Fatty Acid ◽

Human Skeletal Muscle ◽

Fatty Acid Binding Protein ◽

Binding Protein ◽

Protein A ◽

Fatty Acid Binding ◽

Acid Binding Protein ◽

Fatty Acid Transporter ◽

Acid Transporter

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Differential epigenetic and transcriptional response of the skeletal muscle carnitine palmitoyltransferase 1B (CPT1B) gene to lipid exposure with obesity

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00505.2014 ◽

2015 ◽

Vol 309 (4) ◽

pp. E345-E356 ◽

Cited By ~ 15

Author(s):

Jill M. Maples ◽

Jeffrey J. Brault ◽

Carol A. Witczak ◽

Sanghee Park ◽

Monica J. Hubal ◽

...

Keyword(s):

Skeletal Muscle ◽

Dna Methylation ◽

Transcription Factor ◽

Fatty Acid ◽

Histone Acetylation ◽

Human Skeletal Muscle ◽

Epigenetic Modifications ◽

Carnitine Palmitoyltransferase ◽

Severely Obese ◽

Metabolic Inflexibility

The ability to increase fatty acid oxidation (FAO) in response to dietary lipid is impaired in the skeletal muscle of obese individuals, which is associated with a failure to coordinately upregulate genes involved with FAO. While the molecular mechanisms contributing to this metabolic inflexibility are not evident, a possible candidate is carnitine palmitoyltransferase-1B (CPT1B), which is a rate-limiting step in FAO. The present study was undertaken to determine if the differential response of skeletal muscle CPT1B gene transcription to lipid between lean and severely obese subjects is linked to epigenetic modifications (DNA methylation and histone acetylation) that impact transcriptional activation. In primary human skeletal muscle cultures the expression of CPT1B was blunted in severely obese women compared with their lean counterparts in response to lipid, which was accompanied by changes in CpG methylation, H3/H4 histone acetylation, and peroxisome proliferator-activated receptor-δ and hepatocyte nuclear factor 4α transcription factor occupancy at the CPT1B promoter. Methylation of specific CpG sites in the CPT1B promoter that correlated with CPT1B transcript level blocked the binding of the transcription factor upstream stimulatory factor, suggesting a potential causal mechanism. These findings indicate that epigenetic modifications may play important roles in the regulation of CPT1B in response to a physiologically relevant lipid mixture in human skeletal muscle, a major site of fatty acid catabolism, and that differential DNA methylation may underlie the depressed expression of CPT1B in response to lipid, contributing to the metabolic inflexibility associated with severe obesity.

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Human skeletal muscle malonyl-CoA at rest and during prolonged submaximal exercise

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1996.270.3.e541 ◽

1996 ◽

Vol 270 (3) ◽

pp. E541-E544 ◽

Cited By ~ 33

Author(s):

L. M. Odland ◽

G. J. Heigenhauser ◽

G. D. Lopaschuk ◽

L. L. Spriet

Keyword(s):

Skeletal Muscle ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

High Performance ◽

Human Skeletal Muscle ◽

Vastus Lateralis ◽

Submaximal Exercise ◽

Acid Oxidation ◽

Vastus Lateralis Muscle ◽

Malonyl Coa

Previous literature has indicated that contraction-induced decreases in malonyl-CoA are instrumental in the regulation of fatty acid oxidation during prolonged submaximal exercise. This study was designed to measure malonyl-CoA in human vastus lateralis muscle at rest and during submaximal exercise. Eight males and one female cycled for 70 min (10 min at 40% and 60 min at 65% maximal O2 uptake). Needle biopsies were obtained at rest and at 10 min, 20 min, and 70 min of exercise. Malonyl-CoA content in preexercise biopsy samples determined by high-performance liquid chromatography (HPLC) was 1.53 +/- 0.18 micromol/kg dry mass (dm). Malonyl-CoA content did not change significantly during exercise (1.39 +/- 0.21 at 10 min, 1.46 +/- 0.14 at 20 min, and 1.22 +/- 0.15 micromol/kg dm at 70 min). In contrast, malonyl-CoA content determined by HPLC in perfused rat red gastrocnemius muscle decreased significantly during 20 min of stimulation at 0.7 Hz [3.44 +/- 0.54 to 1.64 +/- 0.23 nmol/g dm, (n=9)]. We conclude that human skeletal muscle malonyl-CoA content 1) is less than reported in rat skeletal muscle at rest, 2) does not decrease with prolonged submaximal exercise, and 3) is not predictive of increased fatty acid oxidation during exercise.

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Leptin, skeletal muscle lipids, and lipid-induced insulin resistance

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00133.2007 ◽

2007 ◽

Vol 293 (2) ◽

pp. R642-R650 ◽

Cited By ~ 34

Author(s):

John J. Dube ◽

Bankim A. Bhatt ◽

Nikolas Dedousis ◽

Arend Bonen ◽

Robert M. O'Doherty

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Fatty Acid ◽

Lipid Metabolism ◽

Insulin Sensitivity ◽

Insulin Action ◽

Glycogen Synthase ◽

Acid Oxidation ◽

Fatty Acid Binding ◽

Lipid Metabolites

Leptin-induced increases in insulin sensitivity are well established and may be related to the effects of leptin on lipid metabolism. However, the effects of leptin on the levels of lipid metabolites implicated in pathogenesis of insulin resistance and the effects of leptin on lipid-induced insulin resistance are unknown. The current study addressed in rats the effects of hyperleptinemia (HL) on insulin action and markers of skeletal muscle (SkM) lipid metabolism in the absence or presence of acute hyperlipidemia induced by an infusion of a lipid emulsion. Compared with controls (CONT), HL increased insulin sensitivity, as assessed by hyperinsulinemic-euglycemic clamp (∼15%), and increased SkM Akt (∼30%) and glycogen synthase kinase 3α (∼52%) phosphorylation. These improvements in insulin action were associated with decreased SkM triglycerides (TG; ∼61%), elevated ceramides (∼50%), and similar diacylglycerol (DAG) levels in HL compared with CONT. Acute hyperlipidemia in CONT decreased insulin sensitivity (∼25%) and increased SkM DAG (∼33%) and ceramide (∼60%) levels. However, hyperlipidemia did not induce insulin resistance or SkM DAG and ceramide accumulation in HL. SkM total fatty acid transporter CD36, plasma membrane fatty acid binding protein, acetyl Co-A carboxylase phosphorylation, and fatty acid oxidation were similar in HL compared with CONT. However, HL decreased SkM protein kinase Cθ (PKCθ), a kinase implicated in mediating the detrimental effects of lipids on insulin action. We conclude that increases in insulin sensitivity induced by HL are associated with decreased levels of SkM TG and PKCθ and increased SkM insulin signaling, but not with decreases in other lipid metabolites implicated in altering SkM insulin sensitivity (DAG and ceramide). Furthermore, insulin resistance induced by an acute lipid infusion is prevented by HL.

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