Triglyceride Fatty Acid Research Articles

Isothermal Curing Kinetics of Epoxidized Fatty Acid Methyl Esters and Triacylglycerols

AbstractPlant oil triacylglycerols are attractive renewable resources for biobased epoxy resins. We investigated the curing kinetics of three model epoxidized fatty acid methyl esters and representative epoxidized triacylglycerols with varied epoxide functionalities and distributions in the presence of a latent cationic initiator. Isothermal differential scanning calorimetry (DSC) was used to analyze the curing kinetics of the epoxy systems, and kinetic parameters (i.e., rate constants, reaction orders) were determined. Both epoxidized fatty esters and triacylglycerols followed the autocatalytic curing mechanism, and the DSC data were analyzed according to the Kamal autocatalytic model. Epoxidized methyl linoleate (EMLO) had the highest maximum curing rate, followed by epoxidized methyl linolenate (EMLON), and epoxidized methyl oleate (EMO) had the lowest maximum curing rate. We conclude that EMLO with two epoxide groups has the highest reactivity in this curing system, while the EMO with one epoxide group has the lowest reactivity. For epoxidized triacylglycerols, epoxidized camelina oil had the highest curing reactivity at higher temperatures, followed by epoxidized linseed oil and soybean oil.

Analysis of the Correlations of the Content of Clinically Important Fatty Acids in Diet and Blood with the Absorption Spectrum in the Near-Infrared Range

Fatty acid triglycerides are essential components of the human diet, while possessing unique biological activity. Their content in biological media is traditionally determined by gas and liquid chromatography. They are not readily available for mass analysis of food products and blood serum due to the complexity of these methods. The aim of our work is to study the correlation of the absorption spectra of near-infrared radiation with the characteristic oscillations of functional groups of clinically important fatty acids, such as palmitic saturated ones and oleic and linoleic unsaturated ones, as well as their trans-isomers, as well as to develop techniques and test equipment for rapid assessment of their content in fat products and blood serum. As a result, evidence of the applicability of the Fourier spectrometer in the wavelength range of 1.0–2.4 μm for the operational analysis of clinically important fatty acids in butter, spreads and serum, as well as the correlation of the absorption spectra of serum with the content of total triglycerides and cholesterol were revealed. In addition, using a portable spectrometer in the wavelength range of 1.0–1.65 μm suitable for mass analysis of fat-and-oil products quality, the content of these fatty acids was determined, and the selectivity of their determination was studied.

Adipokine zinc-α2-glycoprotein alleviates lipopolysaccharide-induced inflammatory responses through the β3-AR/PKA/CREB pathway

Humans and animals frequently experience dysmetabolism induced by inflammation. Zinc-α2-glycoprotein (ZAG), a newly identified adipokine, is potentially involved in lipid metabolism. Our previous study revealed that the ZAG content increased after lipopolysaccharide (LPS) treatment. To clarify ZAG’s possible effects on inflammatory responses and lipid metabolism, we used gene overexpression and knockout mice as models to investigate the function of ZAG during inflammation. The results showed that LPS increased plasma triglyceride, non-esterified fatty acid and hepatic triglyceride, while ZAG overexpression decreased these effects. Furthermore, ZAG overexpression weakened inflammatory responses, suppressed lipogenesis, and improved mitochondrial function during inflammation. ZAG overexpression also increased β3-adrenoreceptor, protein kinase A, and phosphorylated cyclic adenosine monophosphate-response element binding protein (CREB), promoted the combination of CREB and CREB-binding protein (CBP), and competitively inhibited the combination of nuclear factor-κB and CBP. After ZAG knockout, LPS-induced the hyperlipidemia worsened. ZAG knockout aggravated inflammatory responses, promoted lipogenesis, and weakened mitochondrial function during inflammation. ZAG knockout also decreased β3-adrenoreceptor and protein kinase A. The present study demonstrated that ZAG alleviated lipid metabolism disorders by weakening inflammatory responses. The β3-adrenoreceptor/protein kinase A/CREB pathway mediated the effects of ZAG on inflammation. These results will provide new insight for research on anti-inflammation.

Soybean (Glycine max L.) triacylglycerol lipase GmSDP1 regulates the quality and quantity of seed oil

Seeds of soybean (Glycine max L.) are a major source of plant-derived oils. In the past, improvements have been made in the quantity and quality of seed oil. Triacylglycerols (TAGs) are the principal components of soybean seed oil, and understanding the metabolic regulation of TAGs in soybean seeds is essential. Here, we identified four soybean genes encoding TAG lipases, designated as SUGAR DEPENDENT1-1 (GmSDP1-1), GmSDP1-2, GmSDP1-3 and GmSDP1-4; these are homologous to Arabidopsis thaliana SDP1 (AtSDP1). To characterize the function of these genes during grain filling, transgenic lines of soybean were generated via RNA interference to knockdown the expression of all four GmSDP1 genes. The seed oil content of the transgenic soybean lines was significantly increased compared with the wild type (WT). Additionally, fatty acid profiles of the WT and transgenic soybean lines were altered; the content of linoleic acid, a major fatty acid in soybean seeds, was significantly reduced, whereas that of oleic acid was increased in transgenic soybean seeds compared with the WT. Substrate specificity experiments showed that TAG lipase preferentially cleaved oleic acid than linoleic acid in the oil body membrane in WT soybean. This study demonstrates that the GmSDP1 proteins regulate both the TAG content and fatty acid composition of soybean seeds during grain filling. These results provide a novel strategy for improving both the quantity and quality of soybean seed oil.

Regulatory carbon metabolism underlying seawater-based promotion of triacylglycerol accumulation in Chlorella kessleri

Chlorella kessleri accumulates triacylglycerol usable for biodiesel-fuel production to >20% dry cell weight in three days when cultured in three-fold diluted seawater, which imposes the combinatory stress of hyperosmosis and nutrients limitation. The quantitative behavior of major C-compounds, and related-gene expression patterns were investigated in Chlorella cells stressed with hyperosmosis, nutrients limitation, or their combination, to elucidate the C-metabolism for economical seawater-based triacylglycerol accumulation. Combinatory-stress cells showed repressed protein synthesis with initially accumulated starch being degraded later, the C-metabolic flow thereby being diverted to fatty acid and subsequent triacylglycerol accumulation. This C-flow diversion was induced by cooperative actions of nutrients-limitation and hyperosmosis. Semi-quantitative PCR analysis implied positive rewiring of the diverted C-flow into triacylglycerol in combinatory-stress cells through upregulation of gene expression concerning fatty acid and triacylglycerol synthesis, and starch synthesis and degradation. The information of regulatory C-metabolism will help reinforce the seawater-based triacylglycerol accumulation ability in algae including Chlorella.

Evaluation model for cocoa butter equivalents based on fatty acid compositions and triacylglycerol patterns.

An effective evaluation model was established to digitize the quality of cocoa butter equivalents (CBEs) based on determinations of total and sn-2 fatty acid compositions and triacylglycerol (TAG) profiles and the "deducting score" principle. Similarity scores for selected fats and oils calculated from the model revealed differences between them and parallel cocoa butter compositions. For CBE1 and CBE2, total similarity scores were 90.6 and 90.0, whereas those of mango (76.3), dhupa (84.1), sal fat (84.7), kokum (78.3), palm mid fractions (PMF, 77.9), shea butter (64.0), illipe butter (89.7) and Pentadesma butyracea butter (67.2), respectively. Similarity scores were found to agree with physical properties, including polymorphism, crystal morphology, crystallization or melting behaviors, and solid fat content. The present study provides an accurate means of assessing CBE quality and hopefully will contribute to the development of commercial CBEs.

A Randomized Crossover Trial on the Effects of Whole Apple Consumption on Postprandial Response to an Oral Fat Tolerance Test in Overweight and Obese Individuals (P08-109-19)

ObjectivesPostprandial lipemia (PPL) is a possible target for dietary strategies seeking to reduce cardiovascular disease (CVD) risk, including in overweight and obese individuals. Apples contain pectin and polyphenols that have shown potential to modulate PPL in in vitro and animal studies. However, whole apples, as a complex food matrix, have not been investigated in terms of their impact on PPL in humans. Therefore, this study used an oral fat tolerance test (OFTT) with the aim of exploring the influence of co-ingesting whole apples with a high fat dairy beverage on PPL and possible mediators, including chylomicron metabolism, glycemia, insulinemia and gastric emptying in generally healthy, but overweight and obese adults. MethodsSix overweight and 20 obese participants (17 women and 9 men, mean ± SEM age of 45.5 ± 3.1 years, BMI of 34.1 ± 0.2 kg/m2, and fasting triacylglycerol (TAG) of 1.38 ± 0.08 mmol/L) completed this randomized, crossover acute meal study. After fasted participants consumed the OFTT (1 g fat/kg body weight, containing 1500 mg acetaminophen per meal for estimating gastric emptying rate) with and without 3 apples (∼200 g), plasma TAG, ApoB48, glucose, insulin, acetaminophen, and chylomicron-rich fraction (CMRF) particle size and fatty acid composition were analyzed over 6 hours. Differences in postprandial response (i.e., mean concentration, peak concentration (Cmax), time to peak (Tmax) and incremental area under the curve) between treatments were assessed by analysis of covariance. ResultsConsuming whole apples with the OFTT did not modify postprandial TAG, CMRF properties, glucose or gastric emptying rate (P > 0.05), but led to a higher Apo48 peak concentration (P < 0.01) and higher insulin concentrations between 20–180 min (P < 0.05). ConclusionsConsumption of apples, as a complex food matrix containing pectin and polyphenols, did not alter overall PPL following a high fat meal, but did lead to initially higher postprandial insulin. These results have relevance for using apples as a dietary strategy to manage CVD risk associated with high fat consumption in overweight and obese individuals. Funding SourcesOntario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and Ontario Apple Growers, Canada.

Gentiopicroside isolated from Gentiana scabra Bge. inhibits adipogenesis in 3T3-L1 cells and reduces body weight in diet-induced obese mice.

Gentiopicroside is a major active component of the Gentiana scabra Bge., which is commonly used as herbal medicine for the treatment of inflammation in Asia. Gentiopicroside significantly down-regulated expression of key adipogenic transcription factors (PPARγ, C/EBPα, SREBP-1c) and dose-dependently inhibited the lipid uptake-related gene (LPL), fatty acid transport-related gene (FABP4) and triglyceride (TG) synthesis-related gene (DGAT2), as well as fatty acid synthesis-related genes (FAS, SCD1), which resulted in reduced intracellular lipid droplet accumulation and TG content in 3T3-L1 cells. Gentiopicroside also down-regulated expression of inflammatory cytokine genes (NFκB1, TNFα, IL6) compared with vehicle. Oral administration of gentiopicroside (50 mg/kg) in mice fed with high-fat diet for 12 weeks resulted in reduced body weight and visceral fat mass compared with the control group. Overall, the results of this study showed that gentiopicroside had positive anti-obesity effects by regulating the expression of adipogenesis/lipogenesis-related genes and inflammatory genes in 3T3-L1, and that it effectively reduced body weight and visceral fat mass in vivo.

RETRACTED ARTICLE: FABP4 contributes to renal interstitial fibrosis via mediating inflammation and lipid metabolism

Fatty acid binding protein 4 (FABP4), a subtype of fatty acid-binding protein family, shows critical roles in metabolism and inflammation. However, its roles on regulating renal interstitial fibrosis (RIF) remain unclear. In this work, LPS-stimulated in vitro models on NRK-52E and NRK-49F cells, and in vivo UUO models in rats and mice were established. The results showed that comparing with control groups or sham groups, the expression levels of α-SMA, COL1A, COL3A, IL-1β, IL-6, and TNF-α in LPS-stimulated cells or UUO animals were significantly increased. Meanwhile, the levels of TC, TG, and free fatty acid were also significantly increased as well as the obvious lipid droplets, and the serum levels of BUN, Cr were significantly increased with large amounts of collagen deposition in renal tissues. Further investigation showed that compared with control groups or sham groups, the expression levels of FABP4 in LPS-stimulated cells and UUO animals were significantly increased, resulting in down- regulating the expression levels of PPARγ, upregulating the levels of p65 and ICAM-1, and decreasing the expression levels of ACADM, ACADL, SCP-2, CPT1, EHHADH, and ACOX1. To deeply explore the mechanism of FABP4 in RIF, FABP4 siRNA and inhibitor interfered cell models, and UUO model on FABP4 knockout (KO) mice were used. The results showed that the expression levels of α-SMA, COL1A, and COL3A were significantly decreased, the deposition of lipid droplets decreased, and the contents of TC, TG, and free fatty acids were significantly decreased after gene silencing. Meanwhile, the expression levels of PPAR-γ, ACADM, ACADL, SCP-2, CPT1, EHHADH, and ACOX1 were upregulated, the levels of p65 and ICAM-1 were downregulated, and the mRNA levels of IL-1β, IL-6, and TNF-α were decreased. Our results supported that FABP4 contributed to RIF via promoting inflammation and lipid metabolism, which should be considered as one new drug target to treat RIF.

Composition and thermal characteristics of seed oil obtained from Chinese amaranth

Amaranthus tricolor and Amaranthus dubius are the most prevalent vegetable amaranths in China. The fatty acid composition, triacylglycerol (TAG) profile, vitamin E and sterol content, and thermal properties of seed oils extracted from these two vegetable amaranths were investigated in this work. The results reveal that the seed contains ∼8% oil. The main fatty acids in the oils are linoleic (51.5–53.5%), oleic (14.8–18.4%), palmitic (15.7–17.1%) and stearic (3.6–4.1%). PLL (∼22%), LLL (∼20%), LLO (∼17%) and POL (∼11%) are the dominant TAGs in the oils. The amaranth seed oils exhibit a distinct melting and crystallization profile that consists of 5 endothermic peaks and 2 exothermic peaks. The oils are rich in vitamin E (705–829 mg/kg) with δ-tocopherol as the major component. The two oils have similar total sterol contents (2488.7 and 2762.1 mg/100 g) but different individual sterol percentages. The higher contents of oil, linoleic acid, vitamin E, and sterols make the amaranth seed oil desirable in terms of nutrition.

Dysregulation of Lipid Metabolism during Gram-Negative Sepsis in Mkp-1 Deficient Mice

Abstract Mitogen-activated protein kinase phosphatase (Mkp)-1 exerts its anti-inflammatory activities during Gramnegative sepsis by deactivating p38 and JNK. We have previously shown that Mkp-1+/+ mice, but not Mkp-1−/− mice, exhibit hypertriglyceridemia and hepatic glycogen depletion during severe sepsis. However, the regulation of hepatic lipid stores and the underlying mechanism of lipid dysregulation during sepsis remains an enigma. To understand the molecular mechanism underlying the sepsis-associated metabolic changes and the role of Mkp-1 in the process, we infected Mkp-1+/+ and Mkp-1−/− mice with Escherichia coli i.v., and assessed the effects of Mkp-1 deficiency on tissue lipid contents. We also examined global gene expression profile by RNA-seq in the livers. We found that in the absence of E. coli infection, Mkp-1 deficiency decreased liver triglyceride levels. Upon E. coli infection, Mkp-1+/+ mice, but not Mkp-1−/− mice, developed hepatocyte ballooning and increased lipid deposition in the livers. E. coli infection caused profound changes in gene expression profile of a large number of proteins that regulate lipid metabolism in wildtype mice, while these changes were substantially disrupted in Mkp-1−/− mice. Interestingly, in Mkp-1+/+ mice E. coli infection resulted in down-regulation of genes that facilitate fatty acid synthesis but upregulation of CD36 and Dgat2, whose protein products mediate fatty acid uptake and triglyceride synthesis, respectively. Taken together, our studies indicate that sepsis leads to a profound change in metabolic gene expression programs and Mkp-1 plays an important role in this process.

Reengineering lipid biosynthetic pathways of Aspergillus oryzae for enhanced production of γ-linolenic acid and dihomo-γ-linolenic acid

Biological significance of 18-carbon polyunsaturated fatty acids, γ-linolenic acid (GLA; C18:3 n-6) and dihomo-γ-linolenic acid (DGLA; C20:3 n-6) has gained much attention in the systematic development of optimized strains for industrial applications. In this work, a n-6 PUFAs-producing strain of Aspergillus oryzae was generated by manipulating metabolic reactions in fatty acid modification and triacylglycerol biosynthesis. The codon-optimized genes coding for Δ6-desaturase and Δ6-elongase of Pythium sp., and diacylglycerol acyltransferase 2 (mMaDGAT2) of Mortierella alpina were co-transformed in a single vector into A. oryzae BCC14614, yielding strain TD6E6-DGAT2. Comparative phenotypic analysis showed that a 70% increase of lipid titer was found in the engineered strain, which was a result of a significant increase in triacylglycerol (TAG) content (52.0 ± 1.8% of total lipids), and corresponded to the increased size of lipid particles observed in the fungal cells. Interestingly, the proportions of GLA and DGLA in neutral lipids of the engineered strain were similar, with the highest titers obtained in the high C:N culture (29:0; 6% glucose) during the lipid-accumulating stage of growth. Time-course expression analysis of the engineered strain revealed transcriptional control of TAG biosynthesis through a co-operation between the native DGAT2 of A. oryzae and the transformed mMaDGAT2.

Pterostilbene Reduces Liver Steatosis and Modifies Hepatic Fatty Acid Profile in Obese Rats.

Excessive fat accumulation within the liver is known as “simple hepatic steatosis”, which is the most benign form of non-alcoholic fatty liver disease (NAFLD). The aim of the present study was to determine whether pterostilbene improves this hepatic alteration in Zucker (fa/fa) rats. Animals were distributed in two experimental groups (n = 10) and fed a standard laboratory diet. Rats in the pterostilbene group were given a dose of 30 mg/kg body weight/d for six weeks. After sacrifice, serum glucose, transaminase, and insulin concentrations were quantified and the liver triacylglycerol content and fatty acid profile was analyzed. Different pathways of triacylglycerol metabolism in liver were studied, including fatty acid synthesis and oxidation, triglyceride assembly, fatty acid uptake, and glucose uptake. With pterostilbene administration, a reduction in insulin concentrations (consequently in the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR)) and hepatic triacylglycerol content were observed. No effects were observed in pterostilbene-treated rats in the activity of de novo lipogenesis enzymes. An improvement in the fatty acid profile was observed in pterostilbene-treated rats. In conclusion, pterostilbene is a useful molecule to reduce liver steatosis. Its delipidating effect is due, at least in part, to reduced fatty acid availability and triacylglycerol synthesis, as well as to an increased very low-density lipoprotein assembly and fatty acid oxidation.

Production of biodiesel from dairy waste scum using eggshell waste

An effluent from the dairy industry, waste scum oil containing triglycerides of fatty acids from C4- C18 was selected as a potential feedstock for biodiesel production in the presence of nano calcium oxide obtained from modified eggshell. The eggshell waste was calcined at 800 °C to facile synthesize nano calcium oxide and was characterized by X-ray diffractometer (XRD), Fourier Transform Infrared spectrometer (FTIR) and Scanning Electron Microscope (SEM). The calcined eggshell contains mainly nano calcium oxide (CaO) in calcite form with the crystallite size ranging from 16 to 22 nm. The transesterification reaction was carried out in a batch reactor and the operating parameters like catalyst loading, the molar ratio of methanol: oil, reaction temperature and time were optimized. Maximum biodiesel yield of 96% was obtained at the molar ratio of methanol: oil of 6:1, catalyst amount of 2.4 wt% and the reaction temperature of 65 °C for 3 h. The quality of biodiesel produced by transesterification of dairy waste scum was tested on variable four-stroke compressible diesel engine and found to be comparable with conventional diesel in brake thermal efficiency and specific fuel consumption. The biodiesel produced possessed high cetane number and low NOx, than conventional diesel. The results proved that nano CaO obtained from eggshell can be effectively reused and recycled as a heterogeneous catalyst for biodiesel production.

Prolonged monitoring of postprandial lipid metabolism after a western meal rich in linoleic acid and carbohydrates.

Today, awareness has been raised regarding high consumption of n-6 polyunsaturated fatty acids (PUFA) in western diets. A comprehensive analysis of total and individual postprandial fatty acids profiles would provide insights into metabolic turnover and related health effects. After an overnight fast, 9 healthy adults consumed a mixed meal comprising 97 g carbohydrate and 45 g fat, of which 26.4 g was linoleic acid (LA). Nonesterified fatty acids (NEFA), phospholipid fatty acids (PL-FA) and triacylglycerol fatty acids (TG-FA) were monitored in plasma samples, at baseline and hourly over a 7-h postprandial period. Total TG-FA concentration peaked at 2 h after the meal and steadily decreased thereafter. LA from TG18:2n-6 and behenic acid from TG22:0 showed the highest response among TG-FA, with a biphasic response detected for the former. PL-FA exhibited no change. Total NEFA initially decreased to nadir at 1 h, then increased to peak at 7 h. The individual NEFA showed the same response curve except LA and some very-long-chain saturated fatty acids (VLCSFA, ≥20 carbon chain length) that markedly increased shortly after the meal intake. The similarities and dissimilarities in lipid profiles between study subjects at different time points were visualized using nonmetric multi-dimensional scaling. Overall, the results indicate that postprandial levels of LA and VLCSFA, either as NEFA or TG, were most affected by the test meal, which might provide an explanation for the health effects of this dietary lifestyle characterized by high intake of mixed meals rich in n-6 PUFA.

Molecular Composition of and Potential Health Benefits Offered by Natural East African Virgin Sunflower Oil Products: A 400 MHz 1H NMR Analysis Study

Objectives: Sunflower oil (SFO) is regularly employed for cosmetic, emollient and food frying purposes, the latter representing its foremost use globally. Therefore, full investigations of the molecular composition and quality of SFO products are a major requirement. In this study high-field 1H NMR analysis was employed to explore the molecular composition and authenticities of East African virgin (EAV) SFO products, particularly their acylglycerol fatty acid contents, together with those of selected minor constituents. Results acquired were statistically compared to those obtained on commercially-available, EU-approved refined SFO products via NMR-linked multivariate chemometrics strategies. Methodology: High-field 1H NMR spectra of EAV and refined SFOs (n = 55 and 4 respectively) were acquired at an operating frequency of 400 MHz. Their triacylglycerol fatty acid, triacylglycerol hydrolysis product, and sterol and stanol contents were determined via intelligent frequency bucketing and electronic integration of selected resonances. Univariate analysis-of-variance, and multivariate ROC curve evaluations were conducted to determine the magnitude and statistical significance of analyte concentration differences between these two sample classifications. Further multivariate NMR-linked chemometrics analyses such as principal component, random forest and support vector machine classification analyses were also utilised for this purpose. Key Results: Multicomponent 1H NMR analysis demonstrated that EAV SFOs had significantly higher and lower contents of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs), respectively, than those of refined SFOs. Furthermore, significantly higher concentrations of ‘health-friendly’, cholesterol-blocking sterols and stanols were also found in these virgin SFO products. Major Conclusions: 1H NMR analysis provides much valuable molecular information regarding the composition and virginal status of SFOs.The high [MUFA]:[PUFA] content ratio of unrefined EAV SFO products renders them more suitable and safer for commercial or domestic deep-frying episodes than refined SFOs (MUFAs are much more resistant to thermally-induced peroxidation than PUFAs). These products also potentially offer valuable health benefits in view of their high natural sterol and stanol contents.

Characterization of the Chemical Composition of Chinese Moringa oleifera Seed Oil

AbstractThis work focused on physicochemical property assaying, fatty acid composition, triacylglycerol (TAG) profiles, and unsaponifiable matter composition of the Chinese Moringa oleifera seed oil. The results indicated that there was no significant difference in approximate nutritional components between M. oleifera seeds from China and India, while variations in the mineral element contents are significant. Both the Soxhlet extraction method and the aqueous enzymatic extraction method were adopted to extract oil from Chinese M. oleifera seeds. Oil yield obtained using the Soxhlet extraction method was higher than that obtained using the aqueous enzymatic extraction method. While both the iodine value and unsaponifiable matter content of the aqueous enzymatic extracted oil were a little higher than that of the Soxhlet extracted oil. Both oils possess a very low acid value and peroxide value, suggesting their good quality as edible oil. Fatty acid composition results indicated that this oil was especially high in oleic acid. Characterization of the TAG composition was achieved by a two‐dimensional high‐performance liquid chromatography (HPLC) coupling of nonaqueous reverse‐phase and silver ion HPLC with the atmospheric pressure chemical ionization mass spectrometry method. A total of 22 TAG including 16 regioisomers were determined. Composition results of unsaponifiable matters revealed that this oil possesses a number of phytosterols, in which β‐sitosterol and stigmasterol are most predominant.

Fetuin-A modulates lipid mobilization in bovine adipose tissue by enhancing lipogenic activity of adipocytes

Fetuin-A (FetA) is an adipokine and free fatty acid (FFA) carrier linked to adipose tissue (AT) function in monogastrics and ruminants. In dairy cows, plasma and AT FetA decrease after parturition, coinciding with reduced lipogenesis and increased lipolysis. In monogastrics, FetA enhances lipogenesis, but its role on lipid mobilization of ruminants is unclear. We hypothesized that FetA modulates lipid mobilization in bovine AT by enhancing the lipogenic activity of adipocytes. Our objective was to determine the effects of FetA on lipogenesis and lipolysis in cultured primary adipocytes from dairy cows. Preadipocytes from the tailhead subcutaneous AT depot were induced to differentiate in a 7-d coculture in vitro model. The effects of FetA on lipolytic responses of adipocytes were evaluated after a 2-h β-adrenergic stimulation with 1 µM isoproterenol (ISO) alone or combined with 0.1 mg/mL of FetA (FetA+ISO), and in cells treated with medium alone (CON) or with 0.1 mg/mL of FetA (FetA). Lipogenic responses of adipocytes treated with CON or FetA from d 5 to 7 of differentiation were assessed by fatty acid (FA) uptake quantification and triacylglycerol (TAG) accumulation, and the gene and protein expression of lipogenic markers. Bovine adipocytes abundantly expressed FetA gene and protein and secreted 48 ± 3.5 ng/DNA relative fluorescence units (RFU). Adrenergic stimulation with ISO increased lipolysis compared with CON, as reflected in the release of glycerol (0.12 ± 0.04 vs. 0.04 ± 0.02 nM/DNA RFU) and FFA (15 ± 13 vs. 6.2 ± 2.4 nM/DNA RFU). Lipolysis induced by ISO was attenuated by the addition of FetA (FetA+ISO) as reflected by lower glycerol (0.06 ± 0.04 nM/DNA RFU) and FFA (5.7 ± 2.7 nM/DNA RFU) release compared with ISO alone. Compared with CON, FetA enhanced lipogenic responses as demonstrated by higher FA uptake and increased accumulation of TAG. Exposure to FetA upregulated 1-acylglycerol-3-phosphate acyltransferase-2 (AGPAT2) gene expression and protein content, as well as its activity. Adipocytes exposed to FetA increased the secretion of the metabolite of AGPAT2, phosphatidic acid. In conclusion, FetA attenuates lipolytic responses and enhances lipogenesis in bovine adipocytes. The upregulation of the rate-limiting lipogenic enzyme AGPAT2 by FetA suggests a potential pathway by which this adipokine promotes TAG synthesis in adipocytes. These findings suggest that FetA is a potential target for lipid mobilization modulation in AT of dairy cows.

It takes a village: channeling fatty acid metabolism and triacylglycerol formation via protein interactomes

Diet, hormones, gene transcription, and posttranslational modifications control the hepatic metabolism of FAs; metabolic dysregulation causes chronic diseases, including cardiovascular disease, and warrants exploration into the mechanisms directing FA and triacylglycerol (TAG) synthesis and degradation. Long-chain FA metabolism begins by formation of an acyl-CoA by a member of the acyl-CoA synthetase (ACSL) family. Subsequently, TAG synthesis begins with acyl-CoA esterification to glycerol-3-phosphate by a member of the glycerol-3-phosphate acyltransferase (GPAT) family. Our studies of the isoforms ACSL1 and GPAT1 strongly suggest that these proteins are members of larger protein assemblies (interactomes). ACSL1 targeted to the ER interacts with peroxisomal, lipid droplet, and tethering proteins, uncovering a dynamic role for ACSL1 in organelle and lipid droplet interactions. On the outer mitochondrial membrane (OMM), PPARα upregulates ACSL1, which interacts with proteins believed to tether lipid droplets to the OMM. In contrast, GPAT1 is upregulated nutritionally by carbohydrate and insulin in a coordinated sequence of enzyme reactions, from saturated FA formation via de novo lipogenesis to FA esterification by GPAT1 and entry into the TAG biosynthesis pathway. We propose that involved enzymes form a dynamic protein interactome that facilitates esterification and that other lipid-metabolizing pathways will exist in similar physiologically regulated interactomes.

18F]BODIPY-triglyceride-containing chylomicron-like particles as an imaging agent for brown adipose tissue in vivo

Brown adipose tissue (BAT) is present in human adults and the current gold standard to visualize and quantify BAT is [18F]FDG PET-CT. However, this method fails to detect BAT under insulin-resistant conditions associated with ageing and weight gain, such as type 2 diabetes. The aim of this study was to develop a novel triglyceride-based tracer for BAT. For this purpose we designed a dual-modal fluorescent/PET fatty acid tracer based on commercially available BODIPY-FL-C16, which can be esterified to its correspondent triglyceride, radiolabeled and incorporated into pre-synthesized chylomicron-like particles. BODIPY-FL-C16 was coupled to 1,2-diolein with a subsequent radiolabeling step resulting in [18F]BODIPY-C16-triglyceride that was incorporated into chylomicron-like particles. Various quality control steps using fluorescent and radioactive methods were conducted before BAT visualization was tested in mice. Triglyceride synthesis, radiolabeling and subsequent incorporation into chylomicron-like particles was carried out in decent yields. This radiotracer appeared able to visualize BAT in vivo, and the uptake of the radiotracer was stimulated by cold exposure. The here reported method can be used to incorporate radiolabeled triglycerides into pre-synthesized chylomicron-like particles. Our approach is feasible to visualize and quantify the uptake of triglyceride-derived fatty acids by BAT.