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Scientific Reports Sep 2021This study investigated whether oxidative and glycolytic rat skeletal muscles respond differently to a high-fat (HF) sucrose-enriched diet with respect to diacylglycerol...
This study investigated whether oxidative and glycolytic rat skeletal muscles respond differently to a high-fat (HF) sucrose-enriched diet with respect to diacylglycerol (DAG) and ceramides accumulation, protein kinase C (PKC) activation, glucose metabolism, and the expression of inflammatory genes. HF diet (8 weeks) suppressed insulin-stimulated glycogen synthesis and glucose oxidation in soleus (Sol), extensor digitorum longus (EDL) and epitrochlearis (Epit) muscles. However, DAG and ceramides levels increased in Sol and EDL, but not in Epit muscles of HF-fed rats. Additionally, membrane-bound PKC-delta and PKC-theta increased in Sol and EDL, whereas in Epit muscles both PKC isoforms were reduced by HF diet. In Epit muscles, HF diet also increased the expression of tumor necrosis factor-α (TNF-α) receptors (CD40 and FAS), toll-like receptor 4 (TLR4), and nuclear factor kappa light polypeptide gene enhancer in B cells (NF-kB), whereas in Sol and EDL muscles the expression of these inflammatory genes remained unchanged upon HF feeding. In conclusion, HF diet caused DAG and ceramides accumulation, PKC activation, and the induction of inflammatory pathways in a fiber type-specific manner. These findings help explain why oxidative and glycolytic muscles similarly develop insulin resistance, despite major differences in their metabolic characteristics and responsiveness to dietary lipid abundance.
Topics: Animals; Ceramides; Diet, High-Fat; Dietary Sucrose; Diglycerides; Disease Models, Animal; Glycolysis; Humans; Inflammation; Insulin; Insulin Resistance; Male; Muscle, Skeletal; Obesity; Oxidative Stress; Rats
PubMed: 34580412
DOI: 10.1038/s41598-021-98819-7 -
Nutrients May 2020The majority of the epidemiological evidence over the past few decades has linked high intake of fats, especially saturated fats, to increased risk of diabetes and... (Review)
Review
The majority of the epidemiological evidence over the past few decades has linked high intake of fats, especially saturated fats, to increased risk of diabetes and cardiovascular disease. However, findings of some recent studies (e.g., the PURE study) have contested this association. High saturated fat diets (HFD) have been widely used in rodent research to study the mechanism of insulin resistance and metabolic syndrome. Two separate but somewhat overlapping models-the diacylglycerol (DAG) model and the ceramide model-have emerged to explain the development of insulin resistance. Studies have shown that lipid deposition in tissues such as muscle and liver inhibit insulin signaling via the toxic molecules DAG and ceramide. DAGs activate protein kinase C that inhibit insulin-PI3K-Akt signaling by phosphorylating serine residues on insulin receptor substrate (IRS). Ceramides are sphingolipids with variable acyl group chain length and activate protein phosphatase 2A that dephosphorylates Akt to block insulin signaling. In adipose tissue, obesity leads to infiltration of macrophages that secrete pro-inflammatory cytokines that inhibit insulin signaling by phosphorylating serine residues of IRS proteins. For cardiovascular disease, studies in humans in the 1950s and 1960s linked high saturated fat intake with atherosclerosis and coronary artery disease. More recently, trials involving Mediterranean diet (e.g., PREDIMED study) have indicated that healthy monounsaturated fats are more effective in preventing cardiovascular mortality and coronary artery disease than are low-fat, low-cholesterol diets. Antioxidant and anti-inflammatory effects of Mediterranean diets are potential mediators of these benefits.
Topics: Adipose Tissue; Animals; Cardiovascular Diseases; Ceramides; Cytokines; Diabetes Mellitus; Diet, Fat-Restricted; Diet, High-Fat; Diglycerides; Fatty Acids; Humans; Insulin; Insulin Resistance; Metabolic Syndrome; Obesity; Phosphatidylinositol 3-Kinases
PubMed: 32455838
DOI: 10.3390/nu12051505 -
Proceedings of the National Academy of... May 2020
Topics: Diglycerides; Lipid Metabolism; Lipidomics; Lipids
PubMed: 32398365
DOI: 10.1073/pnas.2004764117 -
Diabetologia Feb 2022Energy-dense nutrition generally induces insulin resistance, but dietary composition may differently affect glucose metabolism. This study investigated initial effects... (Comparative Study)
Comparative Study Randomized Controlled Trial
AIMS/HYPOTHESIS
Energy-dense nutrition generally induces insulin resistance, but dietary composition may differently affect glucose metabolism. This study investigated initial effects of monounsaturated vs saturated lipid meals on basal and insulin-stimulated myocellular glucose metabolism and insulin signalling.
METHODS
In a randomised crossover study, 16 lean metabolically healthy volunteers received single meals containing safflower oil (SAF), palm oil (PAL) or vehicle (VCL). Whole-body glucose metabolism was assessed from glucose disposal (R) before and during hyperinsulinaemic-euglycaemic clamps with D-[6,6-H]glucose. In serial skeletal muscle biopsies, subcellular lipid metabolites and insulin signalling were measured before and after meals.
RESULTS
SAF and PAL raised plasma oleate, but only PAL significantly increased plasma palmitate concentrations. SAF and PAL increased myocellular diacylglycerol and activated protein kinase C (PKC) isoform θ (p < 0.05) but only PAL activated PKCɛ. Moreover, PAL led to increased myocellular ceramides along with stimulated PKCζ translocation (p < 0.05 vs SAF). During clamp, SAF and PAL both decreased insulin-stimulated R (p < 0.05 vs VCL), but non-oxidative glucose disposal was lower after PAL compared with SAF (p < 0.05). Muscle serine-phosphorylation of IRS-1 was increased upon SAF and PAL consumption (p < 0.05), whereas PAL decreased serine-phosphorylation of Akt more than SAF (p < 0.05).
CONCLUSIONS/INTERPRETATION
Lipid-induced myocellular insulin resistance is likely more pronounced with palmitate than with oleate and is associated with PKC isoforms activation and inhibitory insulin signalling.
TRIAL REGISTRATION
ClinicalTrials.gov .NCT01736202.
FUNDING
German Federal Ministry of Health, Ministry of Culture and Science of the State North Rhine-Westphalia, German Federal Ministry of Education and Research, European Regional Development Fund, German Research Foundation, German Center for Diabetes Research.
Topics: Adult; Blood Glucose; Calorimetry; Cross-Over Studies; Dietary Fats; Diglycerides; Fatty Acids; Female; Glucose Clamp Technique; Healthy Volunteers; Humans; Insulin Resistance; Male; Muscle, Skeletal; Oleic Acid; Palm Oil; Palmitates; Protein Kinase C; Safflower Oil; Young Adult
PubMed: 34704121
DOI: 10.1007/s00125-021-05596-z -
Frontiers in Physiology 2022Diacylglycerol (DG) is unique in lipid metabolism because it serves not only as an intermediate product for triglyceride synthesis, but also as a signaling molecule that... (Review)
Review
Diacylglycerol (DG) is unique in lipid metabolism because it serves not only as an intermediate product for triglyceride synthesis, but also as a signaling molecule that activates proteins containing DG-responsive elements, such as protein kinase C. Consequently, DG acts as a hub between energy metabolism and intracellular signaling. Of DG metabolizing pathways, DG kinase (DGK) phosphorylates DG to produce phosphatidic acid, which also serves as a second messenger. Several lines of evidence suggest that DGK is deeply involved in metabolic diseases such as obesity and insulin resistance. Of DGK isozymes, DGKε is simplest in terms of structure, but it is characterized by substrate specificity toward arachidonoyl-DG. Recently, we have reported that DGKε deficiency promotes adipose tissue remodeling in mice during the course of high fat diet (HFD) feeding regimen including obesity, insulin resistance, and beige adipogenesis. DGKε ablation engenders altered expression of other lipid metabolizing enzymes, including adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), and diacylglycerol acyltransferase (DGAT). Subcellular localization of DGKε in the endoplasmic reticulum suggests involvement of this isozyme in lipid energy homeostasis. This review presents current findings of DGKε in lipid-orchestrated pathophysiology, especially unique phenotypes of DGKε-knockout mice in the early and late stages of obesogenic conditions.
PubMed: 35153836
DOI: 10.3389/fphys.2022.815085 -
International Journal of Molecular... Sep 2022Phospholipids (PLs) are a class of lipids with many proven biological functions. They are commonly used in lipid replacement therapy to enrich cell membranes damaged in...
Phospholipids (PLs) are a class of lipids with many proven biological functions. They are commonly used in lipid replacement therapy to enrich cell membranes damaged in chronic neurodegenerative diseases, cancer, or aging processes. Due to their amphipathic nature, PLs have been widely used in food, cosmetic, and pharmaceutical products as natural emulsifiers and components of liposomes. In , PLs are synthesized through a similar pathway like in higher eukaryotes. However, PL biosynthesis in this yeast is still poorly understood. The key intermediate in this pathway is phosphatidic acid, which in is mostly directed to the production of triacylglycerols and, in a lower amount, to PL. This study aimed to deliver a strain with improved PL production, with a particular emphasis on increased biosynthesis of phosphatidylcholine (PC). Several genetic modifications were performed: overexpression of genes from PL biosynthesis pathways as well as the deletion of genes responsible for PL degradation. The best performing strain (overexpressing CDP-diacylglycerol synthase () and phospholipid methyltransferase ()) reached 360% of PL improvement compared to the wild-type strain in glucose-based medium. With the substitution of glucose by glycerol, a preferred carbon source by , an almost 280% improvement of PL was obtained by transformant overexpressing , , diacylglycerol kinase (), and glycerol kinase () in comparison to the wild-type strain. To further increase the amount of PL, the optimization of culture conditions, followed by the upscaling to a 2 L bioreactor, were performed. Crude glycerol, being a cheap and renewable substrate, was used to reduce the costs of PL production. In this process 653.7 mg/L of PL, including 352.6 mg/L of PC, was obtained. This study proved that is an excellent potential producer of phospholipids, especially from waste substrates.
Topics: Carbon; Diacylglycerol Cholinephosphotransferase; Diacylglycerol Kinase; Glucose; Glycerol; Glycerol Kinase; Liposomes; Phosphatidic Acids; Phosphatidyl-N-Methylethanolamine N-Methyltransferase; Phosphatidylcholines; Triglycerides; Yarrowia
PubMed: 36142650
DOI: 10.3390/ijms231810737 -
American Journal of Physiology.... Dec 2021Physical inactivity impairs muscle insulin sensitivity. However, its mechanism is unclear. To model physical inactivity, we applied 24-h hind-limb cast immobilization...
Physical inactivity impairs muscle insulin sensitivity. However, its mechanism is unclear. To model physical inactivity, we applied 24-h hind-limb cast immobilization (HCI) to mice with normal or high-fat diet (HFD) and evaluated intramyocellular lipids and the insulin signaling pathway in the soleus muscle. Although 2-wk HFD alone did not alter intramyocellular diacylglycerol (IMDG) accumulation, HCI alone increased it by 1.9-fold and HCI after HFD further increased it by 3.3-fold. Parallel to this, we found increased protein kinase C ε (PKCε) activity, reduced insulin-induced 2-deoxyglucose (2-DOG) uptake, and reduced phosphorylation of insulin receptor β (IRβ) and Akt, key molecules for insulin signaling pathway. Lipin1, which converts phosphatidic acid to diacylglycerol, showed increase of its activity by HCI, and dominant-negative lipin1 expression in muscle prevented HCI-induced IMDG accumulation and impaired insulin-induced 2-DOG uptake. Furthermore, 24-h leg cast immobilization in human increased lipin1 expression. Thus, even short-term immobilization increases IMDG and impairs insulin sensitivity in muscle via enhanced lipin1 activity. Physical inactivity impairs muscle insulin sensitivity. However, its mechanism is unclear. To model physical inactivity, we applied 24-h hind-limb cast immobilization to mice with normal or high-fat diet and evaluated intramyocellular lipids and the insulin signaling pathway in the soleus muscle. We found that even short-term immobilization increases intramyocellular diacylglycerol and impairs insulin sensitivity in muscle via enhanced lipin1 activity.
Topics: Adult; Animals; Casts, Surgical; Diglycerides; Hindlimb Suspension; Humans; Insulin; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Muscle, Skeletal; Phosphatidate Phosphatase; Sedentary Behavior; Signal Transduction; Time Factors; Young Adult
PubMed: 34719943
DOI: 10.1152/ajpendo.00254.2020 -
Plant Physiology Oct 2020Seed triacylglycerol (TAG) biosynthesis involves a metabolic network containing multiple different diacylglycerol (DAG) and acyl donor substrate pools. This network of...
Seed triacylglycerol (TAG) biosynthesis involves a metabolic network containing multiple different diacylglycerol (DAG) and acyl donor substrate pools. This network of pathways overlaps with those for essential membrane lipid synthesis and utilizes multiple different classes of TAG biosynthetic enzymes. Acyl flux through this network ultimately dictates the final oil fatty acid composition. Most strategies to alter seed oil composition involve the overexpression of lipid biosynthetic enzymes, but how these enzymes are assembled into metabolons and which substrate pools are used by each is still not well understood. To understand the roles of different classes of TAG biosynthetic acyltransferases in seed oil biosynthesis, we utilized the Arabidopsis () diacylglycerol acyltransferase mutant (in which phosphatidylcholine:diacylglycerol acyltransferase (AtPDAT1) is the major TAG biosynthetic enzyme), and enhanced TAG biosynthesis by expression of Arabidopsis acyltransferases AtDGAT1 and AtDGAT2, as well as the DGAT2 enzymes from soybean (), and castor (), followed by isotopic tracing of glycerol flux through the lipid metabolic network in developing seeds. The results indicate each acyltransferase has a unique effect on seed oil composition. AtDGAT1 produces TAG from a rapidly produced phosphatidylcholine-derived DAG pool. However, AtPDAT1 and plant DGAT2 enzymes utilize a different and larger bulk phosphatidylcholine-derived DAG pool that is more slowly turned over for TAG biosynthesis. Based on metabolic fluxes and protein:protein interactions, our model of TAG synthesis suggests that substrate channeling to select enzymes and spatial separation of different acyltransferases into separate metabolons affect efficient TAG production and oil fatty acid composition.
Topics: Acyltransferases; Arabidopsis; Arabidopsis Proteins; Diacylglycerol O-Acyltransferase; Seeds; Triglycerides
PubMed: 32732347
DOI: 10.1104/pp.20.00461 -
Journal of Exposure Science &... May 2022Phthalates have been reported to alter circulating lipid concentrations in animals, and investigation of these associations in humans will provide greater understanding...
BACKGROUND
Phthalates have been reported to alter circulating lipid concentrations in animals, and investigation of these associations in humans will provide greater understanding of potential mechanisms for health outcomes.
OBJECTIVE
To explore associations between phthalate metabolite biomarkers and lipidomic profiles among pregnant women (n = 99) in the Puerto Rico PROTECT cohort.
METHODS
We measured 19 urinary phthalate metabolites during 24-28 weeks of pregnancy. Lipidomic profiles were identified from plasma samples by liquid chromatography-mass spectrometry-based shotgun lipidomics. Relationships between phthalate metabolites and lipid profiles were estimated using compound-by-compound comparisons in multiple linear regression and dimension reduction techniques. We derived sums for each lipid class and sub-class (saturated, mono-unsaturated, polyunsaturated) which were then regressed on phthalate metabolites. Associations were adjusted for false discovery.
RESULTS
After controlling for multiple comparisons, 33 phthalate-lipid associations were identified (False discovery rate adjusted p value < 0.05), and diacylglycerol 40:7 and plasmenyl-phosphatidylcholine 35:1 were the most strongly associated with multiple phthalate metabolites. Metabolites of di-2-ethylhexyl phthalate, bis(2-ethylhexyl) phthalate, dibutyl phthalates, and diisobutyl phthalate were associated with increased ceramides, lysophosphatidylcholines, lysophosphatidylethanolamines, and triacylglycerols, particularly those containing saturated and mono-unsaturated fatty acid chains.
SIGNIFICANCE
Characterization of associations between lipidomic markers and phthalate metabolites during pregnancy will yield mechanistic insight for maternal and child health outcomes.
IMPACT
This study leverages emerging technology to evaluate lipidome-wide signatures of phthalate exposure during pregnancy. The greatest lipid signatures of phthalate exposure were observed for diacylglycerol 40:7 and plasmenyl-phosphatidylcholine 35:1. Polymerized glycerides are important for energy production and regulated through hormone signaling, while plasmenyl-phosphatidylcholines have been implicated in membrane dynamics and important for cell-to-cell signaling. Characterization of these mechanisms are relevant for informing the etiology of maternal and children's health outcomes.
Topics: Biomarkers; Diglycerides; Environmental Pollutants; Female; Humans; Lipidomics; Phosphatidylcholines; Phthalic Acids; Pregnancy; Pregnant Women; Puerto Rico
PubMed: 35075242
DOI: 10.1038/s41370-022-00410-3 -
Proceedings of the National Academy of... Mar 2021Possible segregation of plasma membrane (PM) phosphoinositide metabolism in membrane lipid domains is not fully understood. We exploited two differently lipidated...
Possible segregation of plasma membrane (PM) phosphoinositide metabolism in membrane lipid domains is not fully understood. We exploited two differently lipidated peptide sequences, L10 and S15, to mark liquid-ordered, cholesterol-rich (L) and liquid-disordered, cholesterol-poor (L) domains of the PM, often called raft and nonraft domains, respectively. Imaging of the fluorescent labels verified that L10 segregated into cholesterol-rich L phases of cooled giant plasma-membrane vesicles (GPMVs), whereas S15 and the dye FAST DiI cosegregated into cholesterol-poor L phases. The fluorescent protein markers were used as Förster resonance energy transfer (FRET) pairs in intact cells. An increase of homologous FRET between L10 probes showed that depleting membrane cholesterol shrank L domains and enlarged L domains, whereas a decrease of L10 FRET showed that adding more cholesterol enlarged L and shrank L Heterologous FRET signals between the lipid domain probes and phosphoinositide marker proteins suggested that phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)] and phosphatidylinositol 4-phosphate (PtdIns4) are present in both L and L domains. In kinetic analysis, muscarinic-receptor-activated phospholipase C (PLC) depleted PtdIns(4,5) and PtdIns4 more rapidly and produced diacylglycerol (DAG) more rapidly in L than in L Further, PtdIns(4,5) was restored more rapidly in L than in L Thus destruction and restoration of PtdIns(4,5) are faster in L than in L This suggests that L is enriched with both the receptor G protein/PLC pathway and the PtdIns/PI4-kinase/PtdIns4 pathway. The significant kinetic differences of lipid depletion and restoration also mean that exchange of lipids between these domains is much slower than free diffusion predicts.
Topics: Bacterial Proteins; Cell Line, Transformed; Cholesterol; Diffusion; Diglycerides; Fluorescence Resonance Energy Transfer; Gene Expression; Genes, Reporter; Green Fluorescent Proteins; HEK293 Cells; Humans; Kinetics; Lipoylation; Luminescent Proteins; Membrane Lipids; Membrane Microdomains; Peptides; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositol Phosphates; Protein Processing, Post-Translational; Receptors, Muscarinic; Type C Phospholipases; Unilamellar Liposomes
PubMed: 33619111
DOI: 10.1073/pnas.2025343118