Diacylglyceride Research Articles

Lipidomic signature of stroke recurrence after transient ischemic attack

While TIA patients have transient symptoms, they should not be underestimated, as they could have an underlying pathology that may lead to a subsequent stroke: stroke recurrence (SR). Previously, it has been described the involvement of lipids in different vascular diseases. The aim of the current study was to perform a lipidomic analysis to identify differences in the lipidomic profile between patients with SR and patients without. Untargeted lipidomic analysis was performed in plasma samples of 460 consecutive TIA patients recruited < 24 h after the onset of symptoms. 37 (8%) patients suffered SR at 90 days. Lipidomic profiling disclosed 7 lipid species differentially expressed between groups: 5 triacylglycerides (TG), 1 diacylglyceride (DG), and 1 alkenyl-PE (plasmalogen) [specifically, TG(56:1), TG(63:0), TG(58:2), TG(50:5), TG(53:7, DG(38:5)) and PE(P-18:0/18:2)]. 6 of these 7 lipid species belonged to the glycerolipid family and a plasmalogen, pointing to bioenergetics pathways, as well as oxidative stress response. In this context, it was proposed the PE(P-18:0/18:2) as potential biomarker of SR condition.The observed changes in lipid patterns suggest pathophysiological mechanisms associated with lipid droplets metabolism and antioxidant protection that is translated to plasma level as consequence of a more intensive or high-risk ischemic condition related to SR.

Utilization of biodiesel and glycerol for the synthesis of epoxidized acyl glycerides and its application as a plasticizer

AbstractIn many regions, even if waste vegetable oil is used as raw material, the profits of biodiesel (fatty acid methyl ester, FAME) enterprises still remain restricted, and they are facing environmental problems caused by the by‐product glycerol. Hence, value‐added utilization of FAME and glycerol is a promising alternative to improve the competitiveness of biodiesel enterprises in the economy and environmental protection. In this paper, FAME and glycerol were utilized to prepare epoxidized acyl glycerides by transesterification and epoxidation. In the transesterification, acyl glycerides were prepared by reacting FAME and glycerol catalyzed by K2CO3. The contents of monoacyl glyceride, diacyl glyceride, and triacyl glyceride in the acyl glycerides were about 50%, 40%, and 10%, and the optimal conditions were a temperature of 200°C and the molar ratio of FAME to glycerol of 1:1. In the epoxidation, selectivity of epoxides was significantly affected by monoacyl glyceride content, and a treatment method was developed to control the monoacyl glyceride content &lt;5%. In addition, the plasticity of epoxidized acyl glycerides to partially substitute dioctyl phthalate in polyvinyl chloride was studied, the overall mechanical properties, thermal stability, and extraction resistance were improved. In this work, FAME and glycerol were utilized to prepare epoxidized acyl glycerides with higher value‐added, which provide a potential solution for improving the market competitiveness of biodiesel enterprises.

Targeted Lipidomics Analysis of Adipose and Skeletal Muscle Tissues by Multiple Reaction Monitoring Profiling.

Lipid homeostasis is critical for maintaining normal cellular functions including membrane structural integrity, cell metabolism, and signal transduction. Adipose tissue and skeletal muscle are two major tissues involved in lipid metabolism. Adipose tissue can store excessive lipids in the form of triacylglyceride(TG), which can be hydrolyzed to release free fatty acids (FFAs)under insufficient nutrition states. In the highly energy-demanding skeletal muscle, lipids serve as oxidative substrates for energy production but can cause muscle dysfunction when overloaded. Lipids undergo fascinating cycles of biogenesis and degradation depending on physiological demands, while dysregulation of lipid metabolism has been increasingly recognized as a hallmark of diseases such as obesity and insulin resistance. Thus, it is important to understand the diversity and dynamics of lipid composition in adipose tissue and skeletal muscle. Here, we describe the use of multiple reaction monitoring profiling, based on lipid class and fatty acyl chain specific fragmentation, to explore various classes of lipids in skeletal muscle and adipose tissues. We provide a detailed method for exploratory analysis of acylcarnitine (AC), ceramide (Cer), cholesteryl ester (CE), diacylglyceride (DG), FFA, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylserine (PS), sphingomyelin (SM), and TG. Characterization of lipid composition within adipose tissue and skeletal muscle under different physiological situations will provide biomarkers and therapeutic targets for obesity-related diseases.

Lipidomic Determination of Serum Lipids by Ultra-High Performance Liquid Chromatography – Mass Spectrometry (UPLC-MS) for the Characterization of Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is highly prevalent with identifiable risk factors including obesity, hyperlipidemia and diabetes. A lipidomic approach was taken to quantify the major lipid classes in human serum. Comprehensive characterization of serum lipids determined by ultraperformance liquid chromatography (UPLC)-mass spectrometry (MS) was performed in NAFLD patients and healthy controls. Nine lipid subgroups including lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), phosphatidylcholine (PC), phosphatidylethanolamine (PE), cholesterol ester (ChE), diacylglyceride (DG), triglyceride (TG), sphingomyelin (SM), and ceramide (Cer) were determined in the positive ionization mode. The current study further corroborates existing evidence that increased TG and DG accumulation is the hallmark. The results showed that compared with healthy controls, the abundance of PC in the sera of NAFLD patients decreased, and the phosphatidylethanolamine (PE) level increased, resulting in a reduced PC/PE ratio in NAFLD patients. In NAFLD samples, Cer(18:0/16:0), Cer(18:1/24:0), and Cer(18:1/24:1) were present at significantly higher levels than in controls, while the Cer(18:0/14:0) and Cer(18:0/20:0) levels were lower. In addition, the determination of sphingolipids showed that the abundances of long-chain ceramides were significantly increased in NAFLD patients. These results demonstrate the identification of NAFLD using UPLC-MS lipidomics and provide insights into changes in lipids associated with this disease.

Identification of lipidomic profiles associated with drug-resistant prostate cancer cells

BackgroundThe association of circulating lipids with clinical outcomes of drug-resistant castration-resistant prostate cancer (DR-CRPC) is not fully understood. While it is known that increases in select lipids correlate to decreased survival, neither the mechanisms mediating these alterations nor the correlation of resistance to drug treatments is well characterized.MethodsThis gap-in-knowledge was addressed using in vitro models of non-cancerous, hormone-sensitive, CRPC and drug-resistant cell lines combined with quantitative LC-ESI-Orbitrap-MS (LC-ESI-MS/MS) lipidomic analysis and subsequent analysis such as Metaboanalyst and Lipid Pathway Enrichment Analysis (LIPEA).ResultsSeveral lipid regulatory pathways were identified that are associated with Docetaxel resistance in prostate cancer (PCa). These included those controlling glycerophospholipid metabolism, sphingolipid signaling and ferroptosis. In total, 7460 features were identified as being dysregulated between the cell lines studied, and 21 lipid species were significantly altered in drug-resistant cell lines as compared to nonresistant cell lines. Docetaxel resistance cells (PC3-Rx and DU145-DR) had higher levels of phosphatidylcholine (PC), oxidized lipid species, phosphatidylethanolamine (PE), and sphingomyelin (SM) as compared to parent control cells (PC-3 and DU-145). Alterations were also identified in the levels of phosphatidic acid (PA) and diacylglyceride (DAG), whose levels are regulated by Lipin (LPIN), a phosphatidic acid phosphatase that converts PA to DAG. Data derived from cBioPortal demonstrated a population of PCa patients expressing mutations aligning with amplification of LPIN1, LPIN2 and LPIN3 genes. Lipin amplification in these genes correlated to decreased survival in these patients. Lipin-1 mRNA expression also showed a similar trend in PCa patient data. Lipin-1, but not Lipin-2 or − 3, was detected in several prostate cancer cells, and was increased in 22RV1 and PC-3 cell lines. The increased expression of Lipin-1 in these cells correlated with the level of PA.ConclusionThese data identify lipids whose levels may correlate to Docetaxel sensitivity and progression of PCa. The data also suggest a correlation between the expression of Lipin-1 in cells and patients with regards to prostate cancer cell aggressiveness and patient survivability. Ultimately, these data may be useful for identifying markers of lethal and/or metastatic prostate cancer.

Molecular Reaction Mechanism for the Formation of 3-Chloropropanediol Esters in Oils and Fats.

3-Chloro-1,2-propanediol fatty acid esters (3-MCPD esters) are a group of process-induced contaminants that form during the refining and heating of fats and oils. In this study, a combined method of simulated deodorization and computational simulation was used to explore the precursor substance and the generation path of 3-MCPD esters. From the results, 3-MCPD esters reached a content level of 2.268 mg/kg when the diacylglyceride (DAG) content was 4% and temperature was 220 °C. A good correlation was observed between DAG and 3-MCPD ester contents ( y = 0.0612 x2 - 1.6376 x + 10.558 [ R2 = 0.958]). There were three pathways for the formation of 3-MCPD esters: (A) a direct nucleophilic substitution reaction, (B) an indirect nucleophilic substitution reaction, and (C) a mechanism of an intermediate (glycidyl ester) from the calculation of Gaussian software at the B3LYP/6-31+g** level. The data showed that the ester-based direct nucleophilic substitution reaction was the most likely reaction pathway. The energy barriers for the formation of the 3-MCPD esters dipalmitin, diolein, and dilinolein were 74.261, 66.017, and 59.856 kJ/mol, respectively, indicating that the formation process of 3-MCPD esters is a high-temperature endothermic process. Therefore, by controlling the introduction of precursor (DAG) and reducing the temperature, 3-MCPD ester formation was prevented.

Glycerides isolated from the aerial parts of Malva verticillata cause immunomodulation effects via splenocyte function and NK anti-tumor activity.

A preliminary study revealed that a 10µg/mL n-BuOH fraction of Malva verticillata aerial parts significantly enhanced splenocyte proliferation and induced significant enhancement of natural-killer (NK) cell activity against tumor cells (YAC-1). This study was initiated to identify the principal components that exhibited these activities, and four glycerides were isolated through repeated SiO2 and ODS column chromatography. Structures of compounds 1-4 were determined to be (2S)-1-O-palmitoyl glyceride, (2S)-1-O-stearoyl glyceride, (2S)-1-O-linolenoyl glyceride, and (2S)-1,2-di-O-linoleoyl glyceride, respectively. Compounds 1-3 showed potential immune-enhancing activity in murine splenocyte and natural-killer (NK) cells at 10µM. In contrast, compound 4 showed weak activity, indicating the monoacyl glycerides (1-3) are more effective than diacyl glyceride (4). Also, the longer the carbon number of the fatty acid in monoacyl glyceride, the better the activity, and the monoacyl glyceride including an unsaturated fatty acid (3) is more effective than the glycerides including the saturated fatty acids (1-2).

Impact of alogliptin and pioglitazone on lipid metabolism in islets of prediabetic and diabetic Zucker Diabetic Fatty rats

Prolonged exposure of pancreatic beta (β) cells to elevated glucose and free fatty acids (FFA) as occurs in type 2 diabetes results in loss of β cell function and survival. In Zucker Diabetic Fatty (ZDF) rats, β cell failure is associated with increased triacylglyceride (TAG) synthesis and disruption of the glycerolipid/FFA (GL/FFA) cycle, a critical arm of glucose-stimulated insulin secretion (GSIS). The aim of this study was to determine the impact of activation of PPARγ and increased incretin action via dipeptidyl-peptidase inhibition using pioglitazone and/or alogliptin, respectively, on islet lipid metabolism in prediabetic and diabetic ZDF rats. Transition of control prediabetic ZDF rats to diabetes was associated with reduced plasma insulin levels, reduced islet insulin content and GSIS, reduced stearoyl-CoA desaturase 2 (SCD 2) expression, and increased islet TAG, diacylglyceride (DAG) and ceramides species containing saturated FA. Treatment of prediabetic ZDF rats with a combination of pioglitazone and alogliptin, but not individually, prevented the transition to diabetes and was associated with marked lowering of islet TAG and DAG levels. Pioglitazone and alogliptin, however, did not restore SCD2 expression, the degree of FA saturation in TAG, DAG or ceramides, islet insulin content, or lower ceramide levels. These findings are consistent with activation of PPARγ and increased incretin action working in concert to restore GL/FFA cycle in β cells of ZDF rats. Restoration of the GL/FFA cycle without correcting islet FA desaturation, production of islet ceramides, and/or insulin sensitivity, however, may place these islets at risk for β cell failure.

Short term fat feeding rapidly increases plasma insulin but does not result in dyslipidaemia.

Although the association between obesity and hypertension is well-known, the underlying mechanism remains elusive. Previously, we have shown that 3 week fat feeding in rabbits produces greater visceral adiposity, hypertension, tachycardia and elevated renal sympathetic nerve activity (RSNA) compared to rabbits on a normal diet. Because hyperinsulinaemia, hyperleptinemia, and dyslipidaemia are independent cardiovascular risk factors associated with hypertension we compared plasma insulin, leptin, and lipid profiles in male New Zealand White rabbits fed a normal fat diet (NFD 4.3% fat, n = 11) or high fat diet (HFD 13.4% fat, n = 13) at days 1, 2, 3 and weeks 1, 2, 3 of the diet. Plasma concentrations of diacylglyceride (DG), triacylglyceride (TG), ceramide and cholesteryl esters (CE) were obtained after analysis by liquid chromatography mass spectrometry. Plasma insulin and glucose increased within the first 3 days of the diet in HFD rabbits (P < 0.05) and remained elevated at week 1 (P < 0.05). Blood pressure and heart rate (HR) followed a similar pattern. By contrast, in both groups, plasma leptin levels remained unchanged during the first few days (P > 0.05), increasing by week 3 in fat fed animals alone (P < 0.05). Concentrations of total DG, TG, CE, and Ceramide at week 3 did not differ between groups (P > 0.05). Our data show plasma insulin increases rapidly following consumption of a HFD and suggests that it may play a role in the rapid rise of blood pressure. Dyslipidaemia does not appear to contribute to the hypertension in this animal model.

VALIDASI MODIFIKASI METODE WEIßHAAR UNTUK ANALISIS 3-MCPD ESTER DALAM MINYAK GORENG SAWIT [Validation of Modified Weißhaar’s Method for 3-MCPD Esters Analysis in Palm Oil

The 3-monochloropropane-1,2-diol (3-MCPD) and 3-MCPD esters were found in any type of refined vegetable oil - mostly produced during the refining process - and recognized as emerging food contaminants . Several analytical methods have been developed and one of which was a Weishaar's method. The study aims to validate the modified Weishaar's method for analysis of 3-MCPD and 3-MCPD esters in refined palm oil. Ion fragments were used for identification and quantification of 3-MCPD and 3-MCPD-d 5 . 3-MCPD was determined by GC-MS after released from its ester by transesterification with sodium methoxide and derivatized with phenylboronic acid. The validation showed that liniarity response (r=0.994) was observed from a linear regression by using external standard and internal standard at a concentration range of 0.008 and 0.377 µg mL -1 . The LOD of the validated method was 0.06 µg g -1 while its LOQ was 0.20 µg g -1 , precision (relative standard deviation, RSD) was 6.16%, and accuracy (as percentage of recovery) was in the range of 95.83-113.27 %. This results indicated that the modified method was valuable and sensitive for detection of 3-MCPD and 3-MCPD esters. Using the validated method , 3-MCPD esters content of a commercial palm oil sample was determined and calculated as the difference between total 3-MCPD and free 3-MCPD, which was 13.24 µg g -1 . Total 3-MCPD content of several palm oils were at a concentration range of 13.94-34.52 µg g -1 . These results also showed that there was a correlation between 3-MCPD with diacylglyceride (DAG). Samples with DAG content gave a high test results of 3-MCPD with a coefficient of correlation of r=0.752.

Altered Lipid Metabolism in Residual White Adipose Tissues of Bscl2 Deficient Mice

Mutations in BSCL2 underlie human congenital generalized lipodystrophy type 2 disease. We previously reported that Bscl2 −/− mice develop lipodystrophy of white adipose tissue (WAT) due to unbridled lipolysis. The residual epididymal WAT (EWAT) displays a browning phenotype with much smaller lipid droplets (LD) and higher expression of brown adipose tissue marker proteins. Here we used targeted lipidomics and gene expression profiling to analyze lipid profiles as well as genes involved in lipid metabolism in WAT of wild-type and Bscl2−/− mice. Analysis of total saponified fatty acids revealed that the residual EWAT of Bscl2−/− mice contained a much higher proportion of oleic18:1n9 acid concomitant with a lower proportion of palmitic16:0 acid, as well as increased n3- polyunsaturated fatty acids (PUFA) remodeling. The acyl chains in major species of triacylglyceride (TG) and diacylglyceride (DG) in the residual EWAT of Bscl2−/− mice were also enriched with dietary fatty acids. These changes could be reflected by upregulation of several fatty acid elongases and desaturases. Meanwhile, Bscl2−/− adipocytes from EWAT had increased gene expression in lipid uptake and TG synthesis but not de novo lipogenesis. Both mitochondria and peroxisomal β-oxidation genes were also markedly increased in Bscl2−/− adipocytes, highlighting that these machineries were accelerated to shunt the lipolysis liberated fatty acids through uncoupling to dissipate energy. The residual subcutaneous white adipose tissue (ScWAT) was not browning but displays similar changes in lipid metabolism. Overall, our data emphasize that, other than being essential for adipocyte differentiation, Bscl2 is also important in fatty acid remodeling and energy homeostasis.

Overexpression of lipogenic genes in the heart distinguishes physiologic from pathologic left ventricle hypertrophy

Molecular remodeling in the heart caused by hypertrophy differs between physiological and pathological stimuli. The main goal of this study was to determine how cardiac hypertrophy that is induced by pressure overload or endurance training influences lipid metabolism in the myocardium. The expression of lipogenic genes was upregulated in exercise‐induced hypertrophy and was accompanied by the activation of fatty acid (FA) oxidation pathways regulated by AMPK and RRARα. Intracellular diacylglyceride (DAG), triglyceride (TG) and free FA were not changed in trained compared with untrained hearts. In contrast, in the heart with abdominal aortic banding (AAB)‐induced hypertrophy, we found an increased accumulation of TG and DAG, although the expression of lipogenic genes and the level of FA transport proteins were not augmented. Cardiac steatosis in AAB‐induced hypertrophy was associated with decreased lipolysis, as evidenced by increased hormone‐sensitive lipase phosphorylation at Ser565 and decreased DAG lipase‐α and ‐β protein levels. Obtained results show that cardiac lipid metabolism is differentially regulated in response to physiological and pathological hypertrophic stimuli and suggest that activation of lipogenesis might be involved in the regulatory mechanisms of heart adaptation to stress. Support: NCN UMO‐2011/01/D/NZ3/04777, NCBR LIDER/19/2/L‐2/10/NCBiR/2011.

Rice Os9BGlu31 Is a Transglucosidase with the Capacity to Equilibrate Phenylpropanoid, Flavonoid, and Phytohormone Glycoconjugates

Glycosylation is an important mechanism of controlling the reactivities and bioactivities of plant secondary metabolites and phytohormones. Rice (Oryza sativa) Os9BGlu31 is a glycoside hydrolase family GH1 transglycosidase that acts to transfer glucose between phenolic acids, phytohormones, and flavonoids. The highest activity was observed with the donors feruloyl-glucose, 4-coumaroyl-glucose, and sinapoyl-glucose, which are known to serve as donors in acyl and glucosyl transfer reactions in the vacuole, where Os9BGlu31 is localized. The free acids of these compounds also served as the best acceptors, suggesting that Os9BGlu31 may equilibrate the levels of phenolic acids and carboxylated phytohormones and their glucoconjugates. The Os9BGlu31 gene is most highly expressed in senescing flag leaf and developing seed and is induced in rice seedlings in response to drought stress and treatment with phytohormones, including abscisic acid, ethephon, methyljasmonate, 2,4-dichlorophenoxyacetic acid, and kinetin. Although site-directed mutagenesis of Os9BGlu31 indicated a function for the putative catalytic acid/base (Glu(169)), catalytic nucleophile residues (Glu(387)), and His(386), the wild type enzyme displays an unusual lack of inhibition by mechanism-based inhibitors of GH1 β-glucosidases that utilize a double displacement retaining mechanism.

Testosterone suppresses phospholipase D, causing sex differences in leukotriene biosynthesis in human monocytes

Sex disparities in inflammation have been reported, but the cellular and molecular basis for these discrepancies is unknown. Monocytes are central effector cells in immunity and possess high capacities to produce proinflammatory leukotrienes (LTs). Here, we investigated sex differences in the activation of 5-lipoxygenase (5-LO), the key enzyme in LT biosynthesis, in human peripheral monocytes. In cells from females, 5-LO product formation was 1.8-fold higher than in cells from males, as evaluated by HPLC. When female monocytes were resuspended in plasma from males, 5-LO products were significantly lower than in female plasma. Interestingly, 5α-dihydrotestosterone (5α-DHT, 10 nM) repressed LT synthesis in female cells down to the levels observed in males, while estradiol (100 nM) was without effect, and progesterone (100 nM) caused only a slight inhibition. 5α-DHT (10 nM) caused ERK phosphorylation and inhibition of phospholipase D (PLD), as evaluated by Western blot and measurement of PLD activity via radioenzymatic diacylglyceride (DAG) and nonradioactive choline assays. Accordingly, PLD activity and DAG formation were 1.4- to 1.8-fold lower in male vs. female monocytes connected to increased ERK phosphorylation. Our data indicate that ERK activation by androgens in monocytes represses PLD activity, resulting in impaired 5-LO product formation due to lack of activating DAGs.

Human Lysophosphatidylcholine Acyltransferases 1 and 2 Are Located in Lipid Droplets Where They Catalyze the Formation of Phosphatidylcholine

Phosphatidylcholine (PC) is synthesized by two different pathways, the Lands cycle and the Kennedy pathway. The recently identified key enzymes of the Lands cycle, lysophosphatidylcholine acyltransferase 1 and 2 (LPCAT1 and -2), were reported to localize to the endoplasmic reticulum and to function in lung surfactant production and in inflammation response. Here, we show in various mammalian cell lines that both enzymes additionally localize to lipid droplets (LDs), which consist of a core of neutral lipids surrounded by a monolayer of phospholipid, mainly PC. This dual localization is enabled by the monotopic topology of these enzymes demonstrated in this study. Furthermore, we show that LDs have the ability to locally synthesize PC and that this activity correlates with the LPCAT1 and -2 expression level. This suggests that LPCAT1 and -2 have, in addition to their known function in specialized cells, a ubiquitous role in LD-associated lipid metabolism.

Instantaneous characterization of vegetable oils via TAG and FFA profiles by easy ambient sonic-spray ionization mass spectrometry

A fast and reliable method is presented for the analysis of vegetable oils. Easy ambient sonic-spray ionization mass spectrometry (EASI-MS) is shown to efficiently desorb and ionize the main oil constituents from an inert surface under ambient conditions and to provide comprehensive triacylglyceride (TAG) and free fatty acid (FFA) profiles detected mainly as either [TAG + Na](+) or [FFA-H](-) ions. EASI(+/-)-MS analysis is simple, easily implemented, requires just a tiny droplet of the oil and is performed without any pre-separation or chemical manipulation. It also causes no fragmentation of TAG ions hence diacylglyceride (DAG) and monoacylglyceride (MAG) profiles and contents can also be measured. The EASI(+/-)-MS profiles of TAG and FFA permit authentication and quality control and can be used, for instance, to access levels of adulteration, acidity, oxidation or hydrolysis of vegetable oils in general.

Blood Lipid-Lowering and Antioxidant Effects of a Structured Lipid Containing Monoacylglyceride Enriched with Monounsaturated Fatty Acids in C57BL/6 Mice

We recently reported that a synthetic edible oil-containing monoacylglyceride (MAG) and diacylglyceride (DAG) exerted anti-atherosclerotic effects. In order to further investigate the activities and individual effects of MAG and DAG on the atherosclerotic process, we prepared a structured oil with various MAG and DAG contents and tested them both in vitro and in vivo, using C57BL/6 mice. The structured oil to be tested was mixed (final concentration 5%, wt/wt) with a high-cholesterol high-fat diet (1.2% cholesterol/15% fat/0.5% sodium cholate) and provided to the mice for 7 weeks. After administration, the mice consuming MAG97%-oil and DAG50%/MAG10%-oil evidenced 17% and 24% decreases in plasma total cholesterol (TC) level, respectively, as compared to a group of mice fed on lard. The experimental mice also had reduced plasma triglyceride concentrations and elevated high-density lipoprotein-cholesterol to TC ratios, by up to 31% in the case of the DAG50%/MAG10%-oil fed mice. The mice fed on MAG97%-oil exhibited elevated plasma antioxidant activity and lecithin:cholesterol acyltransferase activity. Histological assessments of the livers of the mice showed that the consumption of MAG-containing oil attenuated the adhesion of inflammatory cells and also ameliorated fatty liver changes, as compared to what was observed in the case of DAG85%-oil consumption. In conclusion, the MAG-containing oil exhibited anti-inflammatory and antioxidant activities in vivo, as well as in vitro inhibitory activity against human cholesteryl ester transfer protein. These results provide us with new insights into MAG-containing oil in terms of hypocholesterolemic effects and antioxidant activities.

Elevated Insulin Secretion from Liver X Receptor-Activated Pancreatic β-Cells Involves Increased de Novo Lipid Synthesis and Triacylglyceride Turnover

Increased basal and loss of glucose-stimulated insulin secretion (GSIS) are hallmarks of beta-cell dysfunction associated with type 2 diabetes. It has been proposed that elevated glucose promotes insulin secretory defects by activating sterol regulatory element binding protein (SREBP)-1c, lipogenic gene expression, and neutral lipid storage. Activation of liver X receptors (LXRs) also activates SREBP-1c and increases lipogenic gene expression and neutral lipid storage but increases basal and GSIS. This study was designed to characterize the changes in de novo fatty acid and triacylglyceride (TAG) synthesis in LXR-activated beta-cells and determine how these changes contribute to elevated basal and GSIS. Treatment of INS-1 beta-cells with LXR agonist T0901317 and elevated glucose led to markedly increased nuclear localization of SREBP-1, lipogenic gene expression, de novo synthesis of monounsaturated fatty acids and TAG, and basal and GSIS. LXR-activated cells had increased fatty acid oxidation and expression of genes involved in mitochondrial beta-oxidation, particularly carnitine palmitoyltransferase-1. Increased basal insulin release from LXR-activated cells coincided with rapid turnover of newly synthesized TAG and required acyl-coenzyme A synthesis and mitochondrial beta-oxidation. GSIS from LXR-activated INS-1 cells required influx of extracellular calcium and lipolysis, suggesting production of lipid-signaling molecules from TAG. Inhibition of diacylglyceride (DAG)-binding proteins, but not classic isoforms of protein kinase C, attenuated GSIS from LXR-activated INS-1 cells. In conclusion, LXR activation in beta-cells exposed to elevated glucose concentrations increases de novo TAG synthesis; subsequent lipolysis produces free fatty acids and DAG, which are oxidized to increase basal insulin release and activate DAG-binding proteins to enhance GSIS, respectively.

Translocation of PKC theta by fatty acids causes hypothalamic insulin resistance.

Diets high in saturated fats (HFS) promote obesity and attenuate insulin-induced glucose uptake in peripheral tissues. Several potential mechanisms for this disruption have been proposed including altered intracellular signaling, gene expression and protein trafficking. Numerous recent studies have demonstrated that protein-kinase-C isoforms theta, delta and epsilon attenuate insulin and metabolic signaling in peripheral tissues. Because the product of fatty acid metabolism, diacylglyceride (DAG) can directly induce translocation of PKCs and thereby activate them, DAG and activated PKCs may represent a mechanism by which dietary fatty acids induce insulin resistance. Importantly, here we report that obesity and high-fat diets attenuate insulin signaling in the brain. Here we assessed the hypothesis that CNS PKC isoforms mediated the deleterious effects of HFS on CNS function. We found that consumption of HFS increased membrane localization of PKC theta and delta in rat hypothalamus. This was associated with impaired hypothalamic insulin signaling, including a reduction in activation of intracellular insulin signaling cascades, increased food intake, and the development of obesity. This effect was recapitulated both in vivo and in vitro by the addition of the phorbol-ester PMA, which induces PKC membrane-translocation. Collectively, these results suggest that saturated-fats can attenuate CNS insulin signaling, similar to peripheral insulin resistance, by directly influencing the trafficking of hypothalamic PKC isoforms. Therefore, PKC may represent a novel unifying mechanism by which diets high in saturated fats promote both peripheral and central metabolic disease.

Apolipoprotein A-I induces translocation of protein kinase Cα to a cytosolic lipid-protein particle in astrocytes

Apolipoprotein A-I (apoA-I) induces the translocation of newly synthesized cholesterol as well as caveolin-1 to the cytosolic lipid-protein particle (CLPP) fraction in astrocytes before its appearance in high density lipoprotein generated in the medium (Ito, J., Y. Nagayasu, K. Kato, R. Sato, and S. Yokoyama. 2002. Apolipoprotein A-I induces translocation of cholesterol, phospholipid, and caveolin-1 to cytosol in rat astrocytes. J. Biol. Chem. 277: 7929-7935). We here report the association of signal-related molecules with CLPP. ApoA-I induces rapid translocation of protein kinase Calpha to the CLPP fraction and its phosphorylation in astrocytes. ApoA-I also induces the translocation of phospholipase Cgamma to CLPP. Diacylglyceride (DG) production is increased by apoA-I in the cells, with a maximum at 5 min after the stimulation, and the increase takes place also in the CLPP fraction. An inhibitor of receptor-coupled phospholipase C, U73122, inhibited all the apoA-I-induced events, such as DG production, cholesterol translocation to the cytosol, release of cholesterol, and translocation of protein kinase Calpha into the CLPP fraction. CLPP may thus be involved in the apoA-I-initiated signal transduction in astrocytes that is related to intracellular cholesterol trafficking for the generation of high density lipoprotein in the brain.