Biodegradation of waste grease by Penicillium chrysogenum for production of fatty acid

The aim of present work was to effectively remediate grease waste by Penicillium chrysogenum. For efficient degradation, grease waste was pre-treated using various lipases, among them lipolase was the best. The pretreated grease was used as a substrate by P. chrysogenum resulting into the production of fatty acids. Process was optimized by response surface methodology (RSM) using four variables viz; FeCl₂ (mM), spore concentration (spores/ml), time period (days) and amount of grease (g). The optimized conditions viz; FeCl₂ 1.25mM, culture amount 5×10¹¹spores/ml and time period 16days led to the production of 6.6mg/g fatty acid from 10.0g of pre-treated grease mixed with 5.0g wheat bran in 10.0ml czapek-dox medium under solid state fermentation. The fermented media was extracted with hexane and subjected to GCMS analysis, which showed the presence of higher amount of palmitic acid. It was purified by crystallization method and 2.8g of palmitic acid was recovered from 1.0kg grease waste in tray fermentation.

Profile of bioactive compounds in Nymphaea alba L. leaves growing in Egypt: hepatoprotective, antioxidant and anti-inflammatory activity

Background

Nymphaea alba L. represents an interesting field of study. Flowers have antioxidant and hepatoprotective effects, rhizomes constituents showed cytotoxic activity against liver cell carcinoma, while several Nymphaea species have been reported for their hepatoprotective effects. Leaves of N. alba have not been studied before. Therefore, in this study, in-depth characterization of the leaf phytoconstituents as well as its antioxidant and hepatoprotective activities have been performed where N. alba leaf extract was evaluated as a possible therapeutic alternative in hepatic disorders.

Methods

The aqueous ethanolic extract (AEE, 70%) was investigated for its polyphenolic content identified by high-resolution electrospray ionisation mass spectrometry (HRESI-MS/MS), while the petroleum ether fraction was saponified, and the lipid profile was analysed using gas liquid chromatography (GLC) analysis and compared with reference standards. The hepatoprotective activity of two doses of the extract (100 and 200 mg/kg; P.O.) for 5 days was evaluated against CCl₄-induced hepatotoxicity in male Wistar albino rats, in comparison with silymarin. Liver function tests; aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma glutamyl transpeptidase (GGT) and total bilirubin were performed. Oxidative stress parameters; malondialdehyde (MDA), reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), total antioxidant capacity (TAC) as well as inflammatory mediator; tumour necrosis factor (TNF)-α were detected in the liver homogenate. Histopathological examination of the liver and immunohistochemical staining of caspase-3 were performed

Results

Fifty-three compounds were tentatively identified for the first time in N.alba leaf extract, where ellagitannins represent the main identified constituents. Nine hydrocarbons, two sterols and eleven fatty acids were identified in the petroleum ether extract where, palmitic acid and linolenic acids represented the major saturated and unsaturated fatty acid respectively. N.alba AEE significantly improved the liver function, oxidative stress parameters as well as TNF-α in addition to the amelioration of histopathological features of the liver and a profound decrease in caspase-3 expression.

Conclusion

These results shed light on the hepatoprotective effect of N. alba that is comparable with that of silymarin. The antioxidant activities of N. alba extract in addition to the inhibition of crucial inflammatory mediator, as TNF-α, might be the possible hepatoprotective mechanisms.

Cyanidin-3-O-glucoside ameliorates palmitate-induced insulin resistance by modulating IRS-1 phosphorylation and release of endothelial derived vasoactive factors

Increased plasma levels of free fatty acids, including palmitic acid (PA), cause insulin resistance in endothelium characterized by a decreased synthesis of insulin-mediated vasodilator nitric oxide (NO), and by an increased production of the vasoconstrictor protein, endothelin-1. Several in vitro and in vivo studies suggest that anthocyanins, natural phenols commonly present in food and vegetables from Mediterranean Diet, exert significant cardiovascular health-promoting activities. These effects are possibly mediated by a positive regulation of the transcription factor Nrf2 and activation of cellular antioxidant and cytoprotective genes. The present study examined, at a molecular level, the effects of cyanidin-3-O-glucoside (C3G), a widely distributed anthocyanin, on PA-induced endothelial dysfunction and insulin resistance in human umbilical vein endothelial cells (HUVECs). Our results indicate that C3G pretreatment effectively reverses the effects of PA on PI3K/Akt axis, and restores eNOS expression and NO release, altered by PA. We observed that these effects were exerted by changes on the phosphorylation of IRS-1 on specific serine and tyrosine residues modulated by PA through the modulation of JNK and IKK activity. Furthermore, silencing Nrf2 transcripts demonstrated that the protective effects of C3G are directly related to the activation of Nrf2.

Dietary saturated fat and monounsaturated fat have reversible effects on brain function and the secretion of pro-inflammatory cytokines in young women

BACKGROUND

Previous literature suggests that a higher ratio of palmitic acid (PA)/oleic acid (OA) in the diet induces inflammation, which may result in deficient brain insulin signaling, and, secondarily, impaired physical activity, sleep efficiency, and cognitive functioning.

OBJECTIVE

We hypothesized that lowering the typical dietary PA/OA would affect the activation of relevant brain networks during a working memory task and would also lower secretion of pro-inflammatory cytokines.

DESIGN

In 12 female subjects participating in a randomized, cross-over trial comparing 3-week high PA diet (HPA) and low PA and a high OA diet (HOA), we evaluated functional magnetic resonance imaging (fMRI) using an N-back test of working memory, cytokine secretion by lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMC), and plasma cytokine concentrations.

RESULTS

Brain activation during the HPA diet compared to the HOA diet was increased in regions of the basal ganglia including the caudate and putamen (p<0.005). In addition, compared to the HOA diet, during the HPA diet, the plasma concentrations of IL-6 (p=0.04) and IL-1β (p=0.05) were higher, and there was a higher secretion of IL-18 (p=0.015) and a trend for higher IL-1β secretion (p=0.066) from LPS-stimulated PBMCs.

CONCLUSIONS

The HPA diet resulted in increased brain activation in the basal ganglia compared to the HOA diet as well as increased secretion of pro-inflammatory cytokines. These data provide evidence that short-term (2week) diet interventions impact brain network activation during a working memory task and that these effects are reversible since the order of the study diets was randomized. These data are consistent with the hypothesis that lowering the dietary PA content via substitution with OA also could affect cognition.

Protective effects of bezafibrate against elaidic acid-induced accumulation of lipid droplets in monocytic cells

Some factors related to diet, such as trans fatty acids (TFA), are known to be involved in the progression of atherosclerosis in humans. Thus, the aim of our study was (i) to evaluate the effects of three dietary free fatty acids (FFA) (elaidic (EA), oleic (OA) and palmitic acid (PA)) on U937 human monocytes, and (ii) to study the eventual benefits of bezafibrate (BZF), a pan-agonist for PPAR isoforms (α, γ and δ) in U937 cells treated with FFA. Morphologic and functional changes were investigated by microscopic and flow cytometric methods. Cellular lipid content, lipid droplets and FA composition were identified and studied. All analyses were also realized in association with or without BZF. Contrary to OA and PA, EA slightly induced both propidium iodide-positive cells and mitochondrial depolarization. In addition, in contrast to OA and PA, EA induced only a slight increase in superoxide anion production. However, EA and OA promoted cytoplasmic lipid droplets accumulation. Only EA and OA significantly increased CD36 expression. It is noteworthy that BZF had a more or less pronounced protective effect against EA-, OA- and PA-induced side effects: BZF attenuated the impaired cell viability and inflammatory response, decreased superoxide anion production and prevented the accumulation of neutral and polar lipids. The effects were less pronounced with OA and PA than with EA. Altogether, our data revealed a benefit of BZF on the side effects induced especially with EA. It may thus be of interest in preventing the early stages of atherosclerotic plaque formation.

Palmitate-induced Endoplasmic Reticulum stress and subsequent C/EBPα Homologous Protein activation attenuates leptin and Insulin-like growth factor 1 expression in the brain

The peptide hormones Insulin-like growth factor-1 (IGF1) and leptin mediate a myriad of biological effects - both in the peripheral and central nervous systems. The transcription of these two hormones is regulated by the transcription factor C/EBPα, which in turn is negatively regulated by the transcription factor C/EBP Homologous Protein (CHOP), a specific marker of endoplasmic reticulum (ER) stress. In the peripheral system, disturbances in leptin and IGF-1 levels are implicated in a variety of metabolic diseases including obesity, diabetes, atherosclerosis and cardiovascular diseases. Current research suggests a positive correlation between consumption of diets rich in saturated free fatty acids (sFFA) and metabolic diseases. Induction of ER stress and subsequent dysregulation in the expression levels of leptin and IGF-1 have been shown to mediate sFFA-induced metabolic diseases in the peripheral system. Palmitic acid (palmitate), the most commonly consumed sFFA, has been shown to be up-taken by the brain, where it may promote neurodegeneration. However, the extent to which palmitate induces ER stress in the brain and attenuates leptin and IGF1 expression has not been determined. We fed C57BL/6J mice a palmitate-enriched diet and determined effects on the expression levels of leptin and IGF1 in the hippocampus and cortex. We further determined the extent to which ER stress and subsequent CHOP activation mediate the palmitate effects on the transcription of leptin and IGF1. We demonstrate that palmitate induces ER stress and decreases leptin and IGF1 expression by inducing the expression of CHOP. The molecular chaperone 4-phenylbutyric acid (4-PBA), an inhibitor of ER stress, precludes the palmitate-evoked down-regulation of leptin and IGF1 expression. Furthermore, the activation of CHOP in response to ER stress is pivotal in the attenuation of leptin and IGF1 expression as knocking-down CHOP in mice or in SH-SY5Y and Neuro-2a (N2a) cells rescues the palmitate-induced mitigation in leptin and IGF1 expression. Our study implicates for the first time ER stress-induced CHOP activation in the brain as a mechanistic link in the palmitate-induced negative regulation of leptin and IGF1, two neurotrophic cytokines that play an indispensable role in the mammalian brain.

Energetic and conformational features linked to the monomeric and dimeric states of bovine BLG

Bovine β-lactoglobulin (BLG) belong to the lipocalin family. This is a group of proteins involved in the binding and transporting of hydrophobic molecules. Experimental and theoretical reports have stated its complex structural behavior in solution, with coupled effects between homodimerization and ligand recognition. Nonetheless, structural evidence at the atomic level about the cause of this coupled effect has not been reported to date. To address this issue microsecond molecular dynamics (MD) simulations were combined with the molecular mechanics generalized Born surface area (MM/GBSA) approach, clustering analysis and principal component analysis (PCA), to explore the conformational complexity of BLG protein-protein self-association and palmitic acid (PLM) or dodecyl sulfate (SDS) ligand recognition in the monomeric and dimeric state. MD simulations, coupled to the MM/GBSA method, revealed that dimerization exerts contrasting effects on the ligand-binding capacity of BLG. Protein dimerization decreases PLM affinity, promoting dimer association. For SDS the dimeric state increases affinity, enhancing dimer dissociation. MD simulations based on PCA revealed that while few differences in the conformational subspace are observed between the free and bound monomer and dimer coupling for PLM, substantial changes are observed between the free and bound monomer and dimer coupling for SDS.

Orexin A attenuates palmitic acid-induced hypothalamic cell death

Palmitic acid (PA), an abundant dietary saturated fatty acid, contributes to obesity and hypothalamic dysregulation in part through increase in oxidative stress, insulin resistance, and neuroinflammation. Increased production of reactive oxygen species (ROS) as a result of PA exposure contributes to the onset of neuronal apoptosis. Additionally, high fat diets lead to changes in hypothalamic gene expression profiles including suppression of the anti-apoptotic protein B cell lymphoma 2 (Bcl-2) and upregulation of the pro-apoptotic protein B cell lymphoma 2 associated X protein (Bax). Orexin A (OXA), a hypothalamic peptide important in obesity resistance, also contributes to neuroprotection. Prior studies have demonstrated that OXA attenuates oxidative stress induced cell death. We hypothesized that OXA would be neuroprotective against PA induced cell death. To test this, we treated an immortalized hypothalamic cell line (designated mHypoA-1/2) with OXA and PA. We demonstrate that OXA attenuates PA-induced hypothalamic cell death via reduced caspase-3/7 apoptosis, stabilization of Bcl-2 gene expression, and reduced Bax/Bcl-2 gene expression ratio. We also found that OXA inhibits ROS production after PA exposure. Finally, we show that PA exposure in mHypoA-1/2 cells significantly reduces basal respiration, maximum respiration, ATP production, and reserve capacity. However, OXA treatment reverses PA-induced changes in intracellular metabolism, increasing basal respiration, maximum respiration, ATP production, and reserve capacity. Collectively, these results support that OXA protects against PA-induced hypothalamic dysregulation, and may represent one mechanism through which OXA can ameliorate effects of obesogenic diet on brain health.

Astrocyte arachidonate and palmitate uptake and metabolism is differentially modulated by dibutyryl-cAMP treatment

Astrocytes play a vital role in brain lipid metabolism; however the impact of the phenotypic shift in astrocytes to a reactive state on arachidonic acid metabolism is unknown. Therefore, we determined the impact of dibutyryl-cAMP (dBcAMP) treatment on radiolabeled arachidonic acid ([1-(14)C]20:4n-6) and palmitic acid ([1-(14)C]16:0) uptake and metabolism in primary cultured murine cortical astrocytes. In dBcAMP treated astrocytes, total [1-(14)C]20:4n-6 uptake was increased 1.9-fold compared to control, while total [1-(14)C]16:0 uptake was unaffected. Gene expression of long-chain acyl-CoA synthetases (Acsl), acyl-CoA hydrolase (Acot7), fatty acid binding protein(s) (Fabp) and alpha-synuclein (Snca) were determined using qRT-PCR. dBcAMP treatment increased expression of Acsl3 (4.8-fold) and Acsl4 (1.3-fold), which preferentially use [1-(14)C]20:4n-6 and are highly expressed in astrocytes, consistent with the increase in [1-(14)C]20:4n-6 uptake. However, expression of Fabp5 and Fabp7 were significantly reduced by 25% and 45%, respectively. Acot7 (20%) was also reduced, suggesting dBcAMP treatment favors acyl-CoA formation. dBcAMP treatment enhanced [1-(14)C]20:4n-6 (2.2-fold) and [1-(14)C]16:0 (1.6-fold) esterification into total phospholipids, but the greater esterification of [1-(14)C]20:4n-6 is consistent with the observed uptake through increased Acsl, but not Fabp expression. Although total [1-(14)C]16:0 uptake was not affected, there was a dramatic decrease in [1-(14)C]16:0 in the free fatty acid pool as esterification into the phospholipid pool was increased, which is consistent with the increase in Acsl3 and Acsl4 expression. In summary, our data demonstrates that dBcAMP treatment increases [1-(14)C]20:4n-6 uptake in astrocytes and this increase appears to be due to increased expression of Acsl3 and Acsl4 coupled with a reduction in Acot7 expression.

Sexually dimorphic brain fatty acid composition in low and high fat diet-fed mice

OBJECTIVE

In this study, we analyzed the fatty acid profile of brains and plasma from male and female mice fed chow or a western-style high fat diet (WD) for 16 weeks to determine if males and females process fatty acids differently. Based on the differences in fatty acids observed in vivo, we performed in vitro experiments on N43 hypothalamic neuronal cells to begin to elucidate how the fatty acid milieu may impact brain inflammation.

METHODS

Using a comprehensive mass spectrometry fatty acid analysis, which includes a profile for 52 different fatty acid isomers, we assayed the plasma and brain fatty acid composition of age-matched male and female mice maintained on chow or a WD. Additionally, using the same techniques, we determined the fatty acid composition of N43 hypothalamic cells following exposure to palmitic and linoleic acid, alone or in combination.

RESULTS

Our data demonstrate there is a sexual dimorphism in brain fatty acid content both following the consumption of the chow diet, as well as the WD, with males having an increased percentage of saturated fatty acids and reductions in ω6-polyunsaturated fatty acids when compared to females. Interestingly, we did not observe a sexual dimorphism in fatty acid content in the plasma of the same mice. Furthermore, exposure of N43 cells to the ω6-PUFA linoleic acid, which is higher in female brains when compared to males, reduces palmitic acid-induced inflammation.

CONCLUSIONS

Our data suggest male and female brains, and not plasma, differ in their fatty acid profile. This is the first time, to our knowledge, lipidomic analyses has been used to directly test the hypothesis there is a sexual dimorphism in brain and plasma fatty acid composition following consumption of the chow diet, as well as following exposure to the WD.

Palmitic acid induces interleukin-1β secretion via NLRP3 inflammasomes and inflammatory responses through ROS production in human placental cells

Maternal obesity, a major risk factor for adverse pregnancy complications, results in inflammatory cytokine release in the placenta. Levels of free fatty acids are elevated in the plasma of obese human. These fatty acids include obesity-related palmitic acids, which is a major saturated fatty acid, that promotes inflammatory responses. Increasing evidence indicates that nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasomes mediate inflammatory responses induced by endogenous danger signals. We hypothesized that inflammatory responses associated with gestational obesity cause inflammation. To test this hypothesis, we investigated the effect of palmitic acid on the activation of NLRP3 inflammasomes and inflammatory responses in a human Sw.71 trophoblast cell line. Palmitic acid stimulated caspase-1 activation and markedly increased interleukin (IL)-1β secretion in Sw.71 cells. Treatment with a caspase-1 inhibitor diminished palmitic acid-induced IL-1β release. In addition, NLRP3 and caspase-1 genome editing using a CRISPR/Cas9 system in Sw.71 cells suppressed IL-1β secretion, which was stimulated by palmitic acid. Moreover, palmitic acid stimulated caspase-3 activation and inflammatory cytokine secretion (e.g., IL-6 and IL-8). Palmitic acid-induced cytokine secretion were dependent on caspase-3 activation. In addition, palmitic acid-induced IL-1β, IL-6, and IL-8 secretion was depended on reactive oxygen species (ROS) generation. In conclusion, palmitic acid caused activation of NLRP3 inflammasomes and inflammatory responses, inducing IL-1β, IL-6, and IL-8 secretion, which is associated with ROS generation, in human Sw.71 placental cells. We suggest that obesity-related palmitic acid induces placental inflammation, resulting in association with pregnancy complications.

Effect of esterified oligosaccharides on the formation and stability of oil-in-water emulsions

Hydrophobically modified oligosaccharides were prepared by an enzyme-catalyzed reaction of maltodextrin/xylo-oligosaccharide and palmitic acid. Maltodextrin with dextrose equivalent (DE) of 16 palmitate (DE16_P) and 9 palmitate (DE9_P), as well as xylo-oligosaccharide palmitate (Xylo_P), were used. The effect of the concentration (10-50% (w/w)) and type of esterified oligosaccharides on the Sauter mean diameter and droplet-size distribution, the rate of coalescence (Kc), and the creaming properties of O/W emulsions were investigated. Esterified oligosaccharides (EO) adsorbed to the surface of the oil droplets. EO formed polydisperse O/W emulsions with particle sizes between 12 and 70 μm, depended on concentration of EO. The Sauter mean diameter, Kc, and the creaming index decreased markedly, with increasing concentration of EO. The type of ester minimally affected the Sauter mean diameter at each ester concentration. DE9_P inhibited coalescence and creaming more efficiently than other EO, mainly due to the higher viscosity of the continuous phase.

Palmitic Acid Reduces Circulating Bone Formation Markers in Obese Animals and Impairs Osteoblast Activity via C16-Ceramide Accumulation

Obesity and impaired lipid metabolism increase circulating and local fatty acid (FA) levels. Our previous studies showed that a high high-saturated -fat diet induced greater bone loss in mice than a high high-unsaturated-fat diet due to increased osteoclast numbers and activity. The impact of elevated FA levels on osteoblasts is not yet clear. We induced obesity in 4 week old male mice using a palmitic acid (PA)- or oleic acid (OA)-enriched high fat high-fat diet (HFD) (20 % of calories from FA), and compared them to mice on a normal (R) caloric diet (10 % of calories from FA). We collected serum to determine FA and bone metabolism marker levels. Primary osteoblasts were isolated; cultured in PA, OA, or control (C) medium; and assessed for mineralization activity, gene expression, and ceramide levels. Obese animals in the PA and OA groups had significantly lower serum levels of bone formation markers P1NP and OC compared to normal weight animals (*p < 0.001), with the lowest marker levels in animals on an PA-enriched HFD (*p < 0.001). Accordingly, elevated levels of PA significantly reduced osteoblast mineralization activity in vitro (*p < 0.05). Elevated PA intake significantly increased C16 ceramide accumulation. This accumulation was preventable through inhibition of SPT2 (serine palmitoyl transferase 2) using myriocin. Elevated levels of PA reduce osteoblast function in vitro and bone formation markers in vivo. Our findings suggest that saturated PA can compromise bone health by affecting osteoblasts, and identify a potential mechanism through which obesity promotes bone loss.

Mouse Strain Impacts Fatty Acid Uptake and Trafficking in Liver, Heart, and Brain: A Comparison of C57BL/6 and Swiss Webster Mice

C57BL/6 and Swiss Webster mice are used to study lipid metabolism, although differences in fatty acid uptake between these strains have not been reported. Using a steady state kinetic model, [1-(14)C]16:0, [1-(14)C]20:4n-6, or [1-(14)C]22:6n-3 was infused into awake, adult male mice and uptake into liver, heart, and brain determined. The integrated area of [1-(14)C]20:4n-6 in plasma was significantly increased in C57BL/6 mice, but [1-(14)C]16:0 and [1-(14)C]22:6n-3 were not different between groups. In heart, uptake of [1-(14)C]20:4n-6 was increased 1.7-fold in C57BL/6 mice. However, trafficking of [1-(14)C]22:6n-3 into the organic fraction of heart was significantly decreased 33 % in C57BL/6 mice. Although there were limited differences in fatty acid tracer trafficking in liver or brain, [1-(14)C]16:0 incorporation into liver neutral lipids was decreased 18 % in C57BL/6 mice. In heart, the amount of [1-(14)C]16:0 and [1-(14)C]22:6n-3 incorporated into total phospholipids were decreased 45 and 49 %, respectively, in C57BL/6 mice. This was accounted for by a 53 and 37 % decrease in [1-(14)C]16:0 and 44 and 52 % decrease in [1-(14)C]22:6n-3 entering ethanolamine glycerophospholipids and choline glycerophospholipids, respectively. In contrast, there was a significant increase in [1-(14)C]20:4n-6 esterification into all heart phospholipids of C57BL/6 mice. Although changes in uptake were limited to heart, several significant differences were found in fatty acid trafficking into heart, liver, and brain phospholipids. In summary, our data demonstrates differences in tissue fatty acid uptake and trafficking between mouse strains is an important consideration when carrying out fatty acid metabolic studies.

Improved oral delivery of resveratrol from N-trimethyl chitosan-g-palmitic acid surface-modified solid lipid nanoparticles

Despite the therapeutic effects of resveratrol, its clinical application is restricted by its poor oral bioavailability, low water solubility, and instability. Solid lipid nanoparticles (SLNs)-based drug delivery systems have been shown to provide excellent support for the delivery of hydrophobic drugs. The poor stability and burst release behavior in stomach acidic pH conditions of SLNs result in increased aggregation of the particles in the gastrointestinal environment, limiting the success of these particles as an oral delivery system for hydrophobic drugs. N-trimethyl chitosan (TMC) graft palmitic acid (PA) (TMC-g-PA) mucoadhesive copolymer was hypothesized to be a promising candidate for the surface modification of PA-decorated resveratrol-loaded SLNs to stabilize SLNs and circumvent all the above mentioned obstacles. TMC and TMC-g-PA copolymers were therefore synthesized and characterized by (1)H-nuclear magnetic resonance ((1)H NMR) and Fourier-transformed infra-red (FT-IR) spectroscopy. Resveratrol-loaded SLNs (SLRNs) that comprised Precirol ATO 5, PA, Gelucire 50/13, Tween 80, and resveratrol as well as TMC-g-PA SLRNs were formulated and characterized in terms of physicochemical properties, stability, cytotoxicity, and in vitro and in vivo effects. The in vitro release studies of TMC-g-PA SLRNs demonstrated negligible release of resveratrol in simulated gastric and sustained release in simulated intestinal conditions and the relative bioavailability of resveratrol was furthermore found to be 3.8-fold higher from TMC-g-PA SLRNs than that from resveratrol suspension. Overall, the findings reported here indicate that TMC-g-PA SLRNs represent a potential oral drug delivery system for resveratrol.

Palmitic acid (16:0) competes with omega-6 linoleic and omega-3 ɑ-linolenic acids for FADS2 mediated Δ6-desaturation

Sapienic acid, 16:1n-10 is the most abundant unsaturated fatty acid on human skin where its synthesis is mediated by FADS2 in the sebaceous glands. The FADS2 product introduces a double bond at the Δ6, Δ4 and Δ8 positions by acting on at least ten substrates, including 16:0, 18:2n-6, and 18:3n-3. Our aim was to characterize the competition for accessing FADS2 mediated Δ6 desaturation between 16:0 and the most abundant polyunsaturated fatty acids (PUFA) in the human diet, 18:2n-6 and 18:3n-3, to evaluate whether competition may be relevant in other tissues and thus linked to metabolic abnormalities associated with FADS2 or fatty acid levels. MCF7 cells stably transformed with FADS2 biosynthesize 16:1n-10 from exogenous 16:0 in preference to 16:1n-7, the immediate product of SCD highly expressed in cancer cell lines, and 16:1n-9 via partial β-oxidation of 18:1n-9. Increasing availability of 18:2n-6 or 18:3n-3 resulted in decreased bioconversion of 16:0 to 16:1n-10, simultaneously increasing the levels of highly unsaturated products. FADS2 cells accumulate the desaturation-elongation products 20:3n-6 and 20:4n-3 in preference to the immediate desaturation products 18:3n-6 and 18:4n-3 implying prompt/coupled elongation of the nascent desaturation products. MCF7 cells incorporate newly synthesized 16:1n-10 into phospholipids. These data suggest that excess 16:0 due to, for instance, de novo lipogenesis from high carbohydrate or alcohol consumption, inhibits synthesis of highly unsaturated fatty acids, and may in part explain why supplemental preformed EPA and DHA in some studies improves insulin resistance and other factors related to diabetes and metabolic syndrome aggravated by excess calorie consumption.

Palmitic acid but not palmitoleic acid induces insulin resistance in a human endothelial cell line by decreasing SERCA pump expression

Palmitic acid is a negative regulator of insulin activity. At the molecular level, palmitic acid reduces insulin stimulated Akt Ser473 phosphorylation. Interestingly, we have found that incubation with palmitic acid of human umbilical vein endothelial cells induced a biphasic effect, an initial transient elevation followed by a sustained reduction of SERCA pump protein levels. However, palmitic acid produced a sustained inhibition of SERCA pump ATPase activity. Insulin resistance state appeared before there was a significant reduction of SERCA2 expression. The mechanism by which palmitic acid impairs insulin signaling may involve endoplasmic reticulum stress, because this fatty acid induced activation of both PERK, an ER stress marker, and JNK, a kinase associated with insulin resistance. None of these effects were observed by incubating HUVEC-CS cells with palmitoleic acid. Importantly, SERCA2 overexpression decreased the palmitic acid-induced insulin resistance state. All these results suggest that SERCA pump might be the target of palmitic acid to induce the insulin resistance state in a human vascular endothelial cell line. Importantly, these data suggest that HUVEC-CS cells respond to palmitic acid-exposure with a compensatory overexpression of SERCA pump within the first hour, which eventually fades out and insulin resistance prevails.

Fetuin A promotes lipotoxicity in β cells through the TLR4 signaling pathway and the role of pioglitazone in anti-lipotoxicity

OBJECTIVE

Fetuin A (FetA), a secreted glycoprotein, is known to affect inflammation and insulin resistance (IR) in obese humans and animals. Lipotoxicity from chronic hyperlipidemia damages pancreatic β cells, hastening the onset of diabetes. We sought to determine whether FetA promotes lipotoxicity through modulation of the toll-like receptor 4 (TLR4) inflammatory signaling pathway as well as the protective effect of pioglitazone(PIO) on lipotoxicity.

METHODS

βTC6, a glucose-sensitive mouse pancreatic β cell line, and Sprague-Dawley rats with diet-induced obesity, were used to investigate FetA-mediated lipotoxicity. Protein expression/activation were measured by Western blotting. Small interfering (si)RNAs for TLR4 were used. Cell apoptosis was quantified by TUNEL analysis or flow cytometry, respectively. Insulin release was assessed with an insulin ELISA.

RESULTS

FetA dose-dependently aggravated palmitic acid (PA)-induced βTC6 cell apoptosis, insulin secretion impairment, and inhibition of the expression of G-protein-coupled receptor 40 (GPR40) and pancreatic duodenal homeobox-1(PDX-1). Combined FetA + PA induced TLR4 expression, and subsequent inhibition of TLR4 signaling or expression was shown to prevent the strengthening effect of FetA on PA-induced lipotoxicity in βTC6 cells. FetA + PA induced p-JNK and nuclear factor-κB (NF-κB) subunit P65 expression, and inhibition of this activity reduced PA+ FetA lipotoxicity in βTC6 cells. PIO could ameliorate PA+ FetA-induced damage to βTC6 cells. Similarly, PIO improved insulin secretion disorder, reduced apoptosis, decreased FetA, TLR4, p-JNK, NF-κB subunit P65 and cleaved caspase 3 expression, and increased GPR40 and PDX-1 expression in islet β cells of diet-induced obese rats. The correlative bivariate analysis showed that increases in Fetuin A were directly proportional to the development of β cell injury.

CONCLUSIONS

FetA can promote lipotoxicity in β cells through the TLR4-JNK-NF-κB signaling pathway. The protective effects of PIO on lipotoxicity in β cells may involve the inhibition of the activation of the FetA and TLR4 signaling pathway.

Role of orexin A signaling in dietary palmitic acid-activated microglial cells

Excess dietary saturated fatty acids such as palmitic acid (PA) induce peripheral and hypothalamic inflammation. Hypothalamic inflammation, mediated in part by microglial activation, contributes to metabolic dysregulation. In rodents, high fat diet-induced microglial activation results in nuclear translocation of nuclear factor-kappa B (NFκB), and increased central pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6). The hypothalamic neuropeptide orexin A (OXA, hypocretin 1) is neuroprotective in brain. In cortex, OXA can also reduce inflammation and neurodegeneration through a microglial-mediated pathway. Whether hypothalamic orexin neuroprotection mechanisms depend upon microglia is unknown. To address this issue, we evaluated effects of OXA and PA on inflammatory response in immortalized murine microglial and hypothalamic neuronal cell lines. We demonstrate for the first time in microglial cells that exposure to PA increases gene expression of orexin-1 receptor but not orexin-2 receptor. Pro-inflammatory markers IL-6, TNF-α, and inducible nitric oxide synthase in microglial cells are increased following PA exposure, but are reduced by pretreatment with OXA. The anti-inflammatory marker arginase-1 is increased by OXA. Finally, we show hypothalamic neurons exposed to conditioned media from PA-challenged microglia have increased cell survival only when microglia were pretreated with OXA. These data support the concept that OXA may act as an immunomodulatory regulator of microglia, reducing pro-inflammatory cytokines and increasing anti-inflammatory factors to promote a favorable neuronal microenvironment.

Lipidomic evidence that lowering the typical dietary palmitate to oleate ratio in humans decreases the leukocyte production of proinflammatory cytokines and muscle expression of redox-sensitive genes

We recently reported that lowering the high, habitual palmitic acid (PA) intake in ovulating women improved insulin sensitivity and both inflammatory and oxidative stress. In vitro studies indicate that PA can activate both cell membrane toll-like receptor-4 and the intracellular nucleotide oligomerization domain-like receptor protein (NLRP3). To gain further insight into the relevance to human metabolic disease of dietary PA, we studied healthy, lean and obese adults enrolled in a randomized, crossover trial comparing 3-week, high-PA (HPA) and low-PA/high-oleic-acid (HOA) diets. After each diet, both hepatic and peripheral insulin sensitivities were measured, and we assessed cytokine concentrations in plasma and in supernatants derived from lipopolysaccharide-stimulated peripheral blood mononuclear cells (PBMCs) as well as proinflammatory gene expression in skeletal muscle. Insulin sensitivity was unaffected by diet. Plasma concentration of tumor necrosis factor-α was higher during the HPA diet. Lowering the habitually high PA intake by feeding the HOA diet resulted in lower secretion of interleukin (IL)-1β, IL-18, IL-10, and tumor necrosis factor-α by PBMCs, as well as lower relative mRNA expression of cJun and NLRP3 in muscle. Principal components analysis of 156 total variables coupled to analysis of covariance indicated that the mechanistic pathway for the differential dietary effects on PBMCs involved changes in the PA/OA ratio of tissue lipids. Our results indicate that lowering the dietary and tissue lipid PA/OA ratio resulted in lower leukocyte production of proinflammatory cytokines and muscle expression of redox-sensitive genes, but the relevance to diabetes risk is uncertain.

Essential role of Nrf2 in the protective effect of lipoic acid against lipoapoptosis in hepatocytes

Excess of saturated free fatty acids, such as palmitic acid (PA), in hepatocytes has been implicated in nonalcoholic fatty liver disease. α-Lipoic acid (LA) is an antioxidant that protects against oxidative stress conditions. We have investigated the effects of LA in the early activation of oxidative and endoplasmic reticulum stress, lipid accumulation, and Nrf2-mediated antioxidant defenses in hepatocytes treated with PA or in rats fed a high-fat diet. In primary human hepatocytes, a lipotoxic concentration of PA triggered endoplasmic reticulum stress, induced the apoptotic transcription factor CHOP, and increased the percentage of apoptotic cells. Cotreatment with LA prevented these effects. Similar results were found in mouse hepatocytes in which LA attenuated PA-mediated activation of caspase 3 and reduced lipid accumulation by decreasing PA uptake and increasing fatty acid oxidation and lipophagy, thereby preventing lipoapoptosis. Moreover, LA augmented the proliferation capacity of hepatocytes after PA challenge. Antioxidant effects of LA ameliorated reactive oxygen species production and endoplasmic reticulum stress and protected against mitochondrial apoptosis in hepatocytes treated with PA. Cotreatment with PA and LA induced an early nuclear translocation of Nrf2 and activated antioxidant enzymes, whereas reduction of Nrf2 by siRNA abolished the benefit of LA on PA-induced lipoapoptosis. Importantly, posttreatment with LA reversed the established damage induced by PA in hepatocytes, as well as preventing obesity-induced oxidative stress and lipoapoptosis in rat liver. In conclusion, our work has revealed that in hepatocytes, Nrf2 is an essential early player in the rescue of oxidative stress by LA leading to protection against PA-mediated lipoapoptosis.

Effect of fatty acids on self-assembly of soybean lecithin systems

With the increasing interest in natural formulations for drug administration and functional foods, it is desirable a good knowledge of the phase behavior of lecithin/fatty acid formulations. Phase structure and properties of ternary lecithin/fatty acids/water systems are studied at 37°C, making emphasis in regions with relatively low water and fatty acid content. The effect of fatty acid saturation degree on the phase microstructure is studied by comparing a fully saturated (palmitic acid, C16:0), monounsaturated (oleic acid, C18:1), and diunsaturated (linoleic acid, C18:2) fatty acids. Phase determinations are based on a combination of polarized light microscopy and small-angle X-ray scattering measurements. Interestingly, unsaturated (oleic acid and linoleic acid) fatty acid destabilizes the lamellar bilayer. Slight differences are observed between the phase diagrams produced by the unsaturated ones: small lamellar, medium cubic and large hexagonal regions. A narrow isotropic fluid region also appears on the lecithin-fatty acid axis, up to 8wt% water. In contrast, a marked difference in phase microsctructure was observed between unsaturated and saturated systems in which the cubic and isotropic fluid phases are not formed. These differences are, probably, a consequence of the high Krafft point of the C16 saturated chains that imply rather rigid chains. However, unsaturated fatty acids result in more flexible tails. The frequent presence of, at least, one unsaturated chain in phospholipids makes it very likely a better mixing situation than in the case of more rigid chains. This swelling potential favors the formation of reverse hexagonal, cubic, and micellar phases. Both unsaturated fatty acid systems evolve by aging, with a reduction of the extension of reverse hexagonal phase and migration of the cubic phase to lower fatty acid and water contents. The kinetic stability of the systems seems to be controlled by the unsaturation of fatty acids.

Fatty acids composition of Spanish black (Morus nigra L.) and white (Morus alba L.) mulberries

This research has determined qualitatively and quantitatively the fatty acids composition of white (Morus alba) and black (Morus nigra) fruits grown in Spain, in 2013 and 2014. Four clones of each species were studied. Fourteen fatty acids were identified and quantified in mulberry fruits. The most abundant fatty acids were linoleic (C18:2), palmitic (C16:0), oleic (C18:1), and stearic (C18:0) acids in both species. The main fatty acid in all clones was linoleic (C18:2), that ranged from 69.66% (MN2) to 78.02% (MA1) of the total fatty acid content; consequently Spanish mulberry fruits were found to be rich in linoleic acid, which is an essential fatty acid. The fatty acid composition of mulberries highlights the nutritional and health benefits of their consumption.

Exendin-4 Inhibits the Expression of SEPP1 and Fetuin-A via Improvement of Palmitic Acid-Induced Endoplasmic Reticulum Stress by AMPK

BACKGROUND

Selenoprotein P (SEPP1) and fetuin-A, both circulating liver-derived glycoproteins, are novel biomarkers for insulin resistance and nonalcoholic fatty liver disease. However, the effect of exendin-4 (Ex-4), a glucagon-like peptide-1 receptor agonist, on the expression of hepatokines, SEPP1, and fetuin-A, is unknown.

METHODS

The human hepatoma cell line HepG2 was treated with palmitic acid (PA; 0.4 mM) and tunicamycin (tuni; 2ug/ml) with or without exendin-4 (100 nM) for 24 hours. The change in expression of PA-induced SEPP1, fetuin-A, and endoplasmic reticulum (ER) stress markers by exendin-4 treatment were evaluated using quantitative real-time reverse transcription polymerase chain reaction and Western blotting. Transfection of cells with AMP-activated protein kinase (AMPK) small interfering RNA (siRNA) was performed to establish the effect of exendin-4-mediated AMPK in the regulation of SEPP1 and fetuin-A expression.

RESULTS

Exendin-4 reduced the expression of SEPP1, fetuin-A, and ER stress markers including PKR-like ER kinase, inositol-requiring kinase 1α, activating transcription factor 6, and C/EBP homologous protein in HepG2 cells. Exendin-4 also reduced the expression of SEPP1 and fetuin-A in cells treated with tunicamycin, an ER stress inducer. In cells treated with the AMPK activator 5-aminoidazole-4-carboxamide ribonucleotide (AICAR), the expression of hepatic SEPP1 and fetuin-A were negatively related by AMPK, which is the target of exendin-4. In addition, exendin-4 treatment did not decrease SEPP1 and fetuin-A expression in cells transfected with AMPK siRNA.

CONCLUSION

These data suggest that exendin-4 can attenuate the expression of hepatic SEPP1 and fetuin-A via improvement of PA-induced ER stress by AMPK.

Sab (Sh3bp5) dependence of JNK mediated inhibition of mitochondrial respiration in palmitic acid induced hepatocyte lipotoxicity

BACKGROUND & AIMS

Sustained c-Jun N-terminal kinase (JNK) activation by saturated fatty acids plays a role in lipotoxicity and the pathogenesis of non-alcoholic steatohepatitis (NASH). We have reported that the interaction of JNK with mitochondrial Sab leads to inhibition of respiration, increased reactive oxygen species (ROS), cell death and hepatotoxicity. We tested whether this pathway underlies palmitic acid (PA)-induced lipotoxicity in hepatocytes.

METHODS

Primary mouse hepatocytes (PMH) from adeno-shlacZ or adeno-shSab treated mice and HuH7 cells were used.

RESULTS

In PMH, PA dose-dependently up to 1mM stimulated oxygen consumption rate (OCR) due to mitochondrial β-oxidation. At ⩾1.5mM, PA gradually reduced OCR, followed by cell death. Inhibition of JNK, caspases or treatment with antioxidant butylated hydroxyanisole (BHA) protected PMH against cell death. Sab knockdown or a membrane permeable Sab blocking peptide prevented PA-induced mitochondrial impairment, but inhibited only the late phase of both JNK activation (beyond 4h) and cell death. In PMH, PA increased p-PERK and its downstream target CHOP, but failed to activate the IRE-1α arm of the UPR. However, Sab silencing did not affect PA-induced PERK activation. Conversely, specific inhibition of PERK prevented JNK activation and cell death, indicating a major role upstream of JNK activation.

CONCLUSIONS

The effect of p-JNK on mitochondria plays a key role in PA-mediated lipotoxicity. The interplay of p-JNK with mitochondrial Sab leads to impaired respiration, ROS production, sustained JNK activation, and apoptosis.

Palm oil and the heart: A review

Palm oil consumption and its effects on serum lipid levels and cardiovascular disease in humans is still a subject of debate. Advocacy groups with varying agenda fuel the controversy. This update intends to identify evidence-based evaluations of the influence of palm oil on serum lipid profile and cardiovascular disease. Furthermore, it suggests a direction for future research. The sources of information were based on a PubMed, Google Scholar, African Journal online and Medline search using key words including: palm oil, palmitic acid, saturated fatty acids and heart disease. Published animal and human experiments on the association of palm oil and its constituents on the serum lipid profile and cardiovascular disease were also explored for relevant information. These papers are reviewed and the available evidence is discussed. Most of the information in mainstream literature is targeted at consumers and food companies with a view to discourage the consumption of palm oil. The main argument against the use of palm oil as an edible oil is the fact that it contains palmitic acid, which is a saturated fatty acid and by extrapolation should give rise to elevated total cholesterol and low-density lipoprotein cholesterol levels. However, there are many scientific studies, both in animals and humans that clearly show that palm oil consumption does not give rise to elevated serum cholesterol levels and that palm oil is not atherogenic. Apart from palmitic acid, palm oil consists of oleic and linoleic acids which are monounsaturated and polyunsaturated respectively. Palm oil also consists of vitamins A and E, which are powerful antioxidants. Palm oil has been scientifically shown to protect the heart and blood vessels from plaques and ischemic injuries. Palm oil consumed as a dietary fat as a part of a healthy balanced diet does not have incremental risk for cardiovascular disease. Little or no additional benefit will be obtained by replacing it with other oils rich in mono or polyunsaturated fatty acids.

GPR40/FFA1 and neutral sphingomyelinase are involved in palmitate-boosted inflammatory response of microvascular endothelial cells to LPS

OBJECTIVES

Increased levels of both saturated fatty acids (SFAs) and lipopolysaccharide (LPS) are associated with type 2 diabetes. However, it remains largely unknown how SFAs interact with LPS to regulate inflammatory responses in microvascular endothelial cells (MIC ECs) that are critically involved in atherosclerosis as a diabetic complication. In this study, we compared the effects of LPS, palmitic acid (PA), the most abundant saturated fatty acid, or the combination of LPS and PA on interleukin (IL)-6 expression by MIC ECs and explored the underlying mechanisms.

METHODS

Human cardiac MIC ECs were treated with LPS, PA and LPS plus PA and the regulatory pathways including receptors, signal transduction, transcription and post-transcription, and sphingolipid metabolism for IL-6 expression were investigated.

RESULTS

G protein-coupled receptor (GPR)40 or free fatty acid receptor 1 (FFA1), but not toll-like receptor 4, was involved in PA-stimulated IL-6 expression. PA not only stimulated IL-6 expression by itself, but also remarkably enhanced LPS-stimulated IL-6 expression via a cooperative stimulation on mitogen-activated protein kinase and nuclear factor kappa B signaling pathways, and both transcriptional and post-transcriptional activation. Furthermore, PA induced a robust neutral sphingomyelinase (nSMase)-mediated sphingomyelin hydrolysis that was involved in PA-augmented IL-6 upregulation.

CONCLUSION

PA boosted inflammatory response of microvascular endothelial cells to LPS via GPR40 and nSMase.

Palmitic acid induces central leptin resistance and impairs hepatic glucose and lipid metabolism in male mice

The consumption of diets rich in saturated fat largely contributes to the development of obesity in modern societies. A diet high in saturated fats can induce inflammation and impair leptin signaling in the hypothalamus. However, the role of saturated fatty acids on hypothalamic leptin signaling, and hepatic glucose and lipid metabolism remains largely undiscovered. In this study, we investigated the effects of intracerebroventricular (icv) administration of a saturated fatty acid, palmitic acid (PA, C16:0), on central leptin sensitivity, hypothalamic leptin signaling, inflammatory molecules and hepatic energy metabolism in C57BL/6J male mice. We found that the icv administration of PA led to central leptin resistance, evidenced by the inhibition of central leptin's suppression of food intake. Central leptin resistance was concomitant with impaired hypothalamic leptin signaling (JAK2-STAT3, PKB/Akt-FOXO1) and a pro-inflammatory response (TNF-α, IL1-β, IL-6 and pIκBa) in the mediobasal hypothalamus and paraventricular hypothalamic nuclei. Furthermore, the pre-administration of icv PA blunted the effect of leptin-induced decreases in mRNA expression related to gluconeogenesis (G6Pase and PEPCK), glucose transportation (GLUT2) and lipogenesis (FAS and SCD1) in the liver of mice. Therefore, elevated central PA concentrations can induce pro-inflammatory responses and leptin resistance, which are associated with disorders of energy homeostasis in the liver as a result of diet-induced obesity.

Lipid metabolism in response to individual short chain fatty acids during mixotrophic mode of microalgal cultivation: Influence on biodiesel saturation and protein profile

Critical influence of different short chain fatty acids as organic carbon source, during growth (GP) and nutrient stress lipogenic phase (NSLP) was investigated on biomass and lipid productivity, in mixotrophic fed-batch microalgae cultivation. Nutrient deprivation induced physiological stress stimulated highest lipid productivity with acetate (total/neutral lipids, 35/17) with saturation index of 80.53% by the end of NSLP followed by butyrate (12/7%; 78%). Biomass growth followed the order of acetate (2.23 g/l) >butyrate (0.99 g/l) >propionate (0.77 g/l). VFA removal (as COD) was maximum with acetate (87%) followed by butyrate (55.09%) and propionate (10.60%). Palmitic acid was the most dominant fatty acid found in the fatty acid composition of all variants and butyrate fed system yielded a maximum of 44% palmitic acid. Protein profiling illustrated prominence of acetyl CoA-synthetase activity in acetate system. Thus, fatty acids provide a promising alternative feedstock for biodiesel production with integrated microalgae-biorefinery.

Glucagon-like peptide-1 suppresses palmitic acid induced L02 cell apoptosis through JNK pathway

AIM: To investigate the potential effects of glucagon-like peptide-1 (GLP-1) on palmitic acid (PA) induced apoptosis of hepatic L02 cells and the underlying mechanism.

METHODS: L02 cells were stimulated with different levels (0.125, 0.250 and 0.500 mmol/L) of PA for different durations (12, 24 and 48 h) in the presence or absence of GLP-1. Cell Counting Kit-8 (CCK-8) assay was used to analyze the inhibitory effects on growth of L02 cells, and terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) assay was used to observe the apoptotic rate of the cells. The expression of c-Jun N-terminal kinase (JNK), c-Jun, p-JNK and p-c-Jun proteins was detected by Western blot assay.

RESULTS: The growth of the L02 cells was significantly inhibited by PA in vitro, and PA induced the expression of p-JNK and p-c-Jun. GLP-1 suppressed the activation of JNK and c-Jun induced by PA.

CONCLUSION: PA can inhibit the proliferation of L02 cells and induce cell apoptosis. The JNK signaling pathway is probably involved in the mechanism of PA induced apoptosis.

5-Fluorouracil-lipid conjugate: potential candidate for drug delivery through encapsulation in hydrophobic polyester-based nanoparticles

The encapsulation of 5-fluorouracil (5-FU) in hydrophobic polymeric materials is made feasible by a lipid-based prodrug approach. A lipid-5-FU conjugate of 5-FU with palmitic acid was synthesized in two-step process. A synthesized dipalmitoyl derivative (5-FUDIPAL) was characterized using Fourier transform infrared spectroscopy and (1)H-nuclear magnetic resonance. The 5-FUDIPAL was encapsulated in polyester-based polymers by the double emulsion-solvent evaporation method. The nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy and dynamic light scattering. The thermal stability was assessed by differential scanning calorimetry data. In vitro release kinetics measurements of the drug from nanoparticles showed the controlled release pattern over a period of time. Cytotoxicity measurements by MTT assay confirmed that dipalmitoyl derivative in nano formulation successfully inhibited the cell growth. Thus the combined physical and biological evaluation of the different polyester-based nanoparticle containing the modified drug showed a facile approach to delivering 5-FU to the tumour site with enhanced efficacy.

The saturated fatty acid, palmitic acid, induces anxiety-like behavior in mice

OBJECTIVES

Excess fat in the diet can impact neuropsychiatric functions by negatively affecting cognition, mood and anxiety. We sought to show that the free fatty acid (FFA), palmitic acid, can cause adverse biobehaviors in mice that last beyond an acute elevation in plasma FFAs.

METHODS

Mice were administered palmitic acid or vehicle as a single intraperitoneal (IP) injection. Biobehaviors were profiled 2 and 24 h after palmitic acid treatment. Quantification of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and their major metabolites was performed in cortex, hippocampus and amygdala. FFA concentration was determined in plasma. Relative fold change in mRNA expression of unfolded protein response (UPR)-associated genes was determined in brain regions.

RESULTS

In a dose-dependent fashion, palmitic acid rapidly reduced mouse locomotor activity by a mechanism that did not rely on TLR4, MyD88, IL-1, IL-6 or TNFα but was dependent on fatty acid chain length. Twenty-four hours after palmitic acid administration mice exhibited anxiety-like behavior without impairment in locomotion, food intake, depressive-like behavior or spatial memory. Additionally, the serotonin metabolite 5-HIAA was increased by 33% in the amygdala 24h after palmitic acid treatment.

CONCLUSIONS

Palmitic acid induces anxiety-like behavior in mice while increasing amygdala-based serotonin metabolism. These effects occur at a time point when plasma FFA levels are no longer elevated.

Interaction of palmitic Acid with metoprolol succinate at the binding sites of bovine serum albumin

PURPOSE

The aim of this study was to characterize the binding profile as well as to notify the interaction of palmitic acid with metoprolol succinate at its binding site on albumin.

METHODS

The binding of metoprolol succinate to bovine serum albumin (BSA) was studied by equilibrium dialysis method (ED) at 27°C and pH 7.4, in order to have an insight in the binding chemistry of the drug to BSA in presence and absence of palmitic acid. The study was carried out using ranitidine as site-1 and diazepam as site-2 specific probe.

RESULTS

Different analysis of binding of metoprolol succinate to bovine serum albumin suggested two sets of association constants: high affinity association constant (k1 = 11.0 x 10(5) M(-1)) with low capacity (n1 = 2) and low affinity association (k2 = 4.0×10(5) M(-1)) constant with high capacity (n2 = 8) at pH 7.4 and 27°C. During concurrent administration of palmitic acid and metoprolol succinate in presence or absence of ranitidine or diazepam, it was found that palmitic acid displaced metoprolol succinate from its binding site on BSA resulting reduced binding of metoprolol succinate to BSA. The increment in free fraction of metoprolol succinate was from 26.27% to 55.08% upon the addition of increased concentration of palmitic acid at a concentration of 0×10(-5) M to 16×10(-5) M. In presence of ranitidine and diazepam, palmitic acid further increases the free fraction of metoprolol succinate from 33.05% to 66.95% and 40.68% to 72.88%, respectively.

CONCLUSION

This data provided the evidence of interaction at higher concentration of palmitic acid at the binding sites on BSA, which might change the pharmacokinetic properties of metoprolol succinate.

Palmitic acid-induced lipotoxicity and protection by (+)-catechin in rat cortical astrocytes

BACKGROUND

Astrocytes do not only maintain homeostasis of the extracellular milieu of the neurons, but also play an active role in modulating synaptic transmission. Palmitic acid (PA) is a saturated fatty acid which, when being excessive, is a significant risk factor for lipotoxicity. Activation of astrocytes by PA has been shown to cause neuronal inflammation and demyelination. However, direct damage by PA to astrocytes is relatively unexplored. The aim of this study was to identify the mechanism(s) of PA-induced cytotoxicity in rat cortical astrocytes and possible protection by (+)-catechin.

METHODS

Cytotoxicity and endoplasmic reticulum (ER) markers were assessed by MTT assay and Western blotting, respectively. Cytosolic Ca(2+) and mitochondrial membrane potential (MMP) were measured microfluorimetrically using fura-2 and rhodamine 123, respectively. Intracellular reactive oxygen species (ROS) production was assayed by the indicator 2'-7'-dichlorodihydrofluorescein diacetate.

RESULTS

Exposure of astrocytes to 100μM PA for 24h resulted in apoptotic cell death. Whilst PA-induced cell death appeared to be unrelated to ER stress and perturbation in cytosolic Ca(2+) signaling, it was likely a result of ROS production and subsequent MMP collapse, since ascorbic acid (anti-oxidant, 100μM) prevented PA-induced MMP collapse and cell death. Co-treatment of astrocytes with (+)-catechin (300μM), an anti-oxidant found abundantly in green tea, significantly prevented PA-induced ROS production, MMP collapse and cell death.

CONCLUSION

Our results suggest that PA-induced cytotoxicity in astrocytes may involve ROS generation and MMP collapse, which can be prevented by (+)-catechin.

GC/MS-based metabolomics approach to identify biomarkers differentiating survivals from death in crucian carps infected by Edwardsiella tarda

Microbial disease problems constitute the largest single cause of economic losses in aquaculture. An understanding of immune system in aquaculture animals how to function in defense against bacterial infections is especially important to control these diseases and improve food quality and safety. In the present study, we use a crucian carp model to explore which pathways and metabolites are crucial for the defense against infection caused by Edwardsiella tarda EIB202. We establish the metabolic profile of crucian carps and then compare the metabolic difference between survivals and dead fish by self-control. We identify elevating unsaturated fatty acid biosynthesis and decreasing fructose and mannose metabolism as the most key pathways and increasing palmitic acid and decreasing d-mannose as the most crucial metabolites differentiating survivals from death in these fish infected by E. tarda. Our findings highlight the importance of metabolic strategy against bacterial infections.

Erythrocyte saturated fatty acids and systemic inflammation in adults

OBJECTIVE

The role of saturated fatty acids (SFAs) in chronic disease remains controversial; inflammation is one pathway by which SFAs influence the risk for chronic disease. The aim of this study was to investigate the associations between red blood cell (RBC) phospholipid SFAs and systemic inflammation.

METHODS

As part of a randomized controlled trial, we measured RBC phospholipid FA composition in 55 generally healthy adults twice at 3-mo intervals. We estimated associations of RBC total SFAs and two major SFA subtypes, palmitic and stearic acids, with C-reactive protein (CRP), interleukin (IL)-6, white blood count (WBC), and a composite inflammation measure using generalized estimating equations in multivariable FA substitution models.

RESULTS

Mean (±SD) SFA level across both visits was 45% ± 3% of the total RBC FAs, mainly palmitic (21% ± 1%) and stearic (17% ± 3%) acids. In models adjusted for age, sex, race, smoking, body mass index, statin use, aspirin use, transunsaturated FAs, and ω-3 FAs, SFAs were significantly associated with IL-6 (20% increase per 1 SD increment; 95% confidence interval [CI], 0.03%-43%; P = 0.05) and the composite inflammation measure (P = 0.05) and marginally associated with CRP (34% increase; 95% CI, -1% to 81%; P = 0.06), but not associated with WBC. Stearic acid was positively associated with CRP (35% increase; 95% CI, 2%-79%; P = 0.04). Palmitic acid was marginally associated with the composite inflammation measure (P = 0.06) and, upon additional ω-6 FA adjustment, significantly associated with IL-6 (15% increase; 95% CI, 0.4%-27%; P = 0.006).

CONCLUSIONS

RBC SFAs, which represent longer-term dietary intake, are positively associated with inflammation. In particular, palmitic acid was associated with IL-6, and stearic acid was associated with CRP after multivariable adjustment.

Impact of interfacial cholesterol-anchored polyethylene glycol on sterol-rich non-phospholipid liposomes

HYPOTHESIS

Liposomes made of single-chain amphiphiles and a large amount of sterols display several advantages including a limited permeability. In the present paper, we examine the possibility to prepare such non-phospholipid liposomes with interfacial polyethylene glycol (PEG) in order to improve their circulation in the blood stream. Cholesterol (Chol) was chosen as the PEG anchor.

EXPERIMENTS

The phase behavior of mixtures of palmitic acid (PA) and cholesterol including various proportions of PEGylated cholesterol (PEG-Chol) was characterized. In conditions leading to the formation of fluid bilayers, properties of the resulting liposomes were assessed.

FINDINGS

Up to 20 mol% of PEGylated cholesterol could be introduced without significant perturbations in fluid bilayers made of PA and cholesterol. With 10 mol% PEG-Chol, PA/Chol/PEG-Chol liposomes showed a very limited permeability to calcein and doxorubicin. Doxorubicin could be actively loaded in PA/Chol/PEG-Chol liposomes with a high drug loading efficiency and a high drug to lipid ratio. Pharmaco-kinetic experiments in rats indicated that interfacial PEG reduced the clearance of PA/Chol liposomes compared to the naked ones. However the lifetime of these non-phospholipid liposomes in the blood circulation was considerably shorter than that observed for control PEGylated phospholipid liposomes, a phenomenon associated with the negative interfacial charge of the PA/Chol/PEG-Chol liposomes.

Palmitic acid suppresses apolipoprotein M gene expression via the pathway of PPARβ/δ in HepG2 cells

It has been demonstrated that apolipoprotein M (APOM) is a vasculoprotective constituent of high density lipoprotein (HDL), which could be related to the anti-atherosclerotic property of HDL. Investigation of regulation of APOM expression is of important for further exploring its pathophysiological function in vivo. Our previous studies indicated that expression of APOM could be regulated by platelet activating factor (PAF), transforming growth factors (TGF), insulin-like growth factor (IGF), leptin, hyperglycemia and etc., in vivo and/or in vitro. In the present study, we demonstrated that palmitic acid could significantly inhibit APOM gene expression in HepG2 cells. Further study indicated neither PI-3 kinase (PI3K) inhibitor LY294002 nor protein kinase C (PKC) inhibitor GFX could abolish palmitic acid induced down-regulation of APOM expression. In contrast, the peroxisome proliferator-activated receptor beta/delta (PPARβ/δ) antagonist GSK3787 could totally reverse the palmitic acid-induced down-regulation of APOM expression, which clearly demonstrates that down-regulation of APOM expression induced by palmitic acid is mediated via the PPARβ/δ pathway.

Multiple pathways are involved in palmitic acid-induced toxicity

In this study, we identified the toxic mechanism following the accumulation of palmitic acid (PA), a saturated fatty acid, in human Chang liver cells. After PA exposure for 24 h, the mitochondria and the endoplasmic reticulum (ER) became dilated, and lipid droplets and organelles were observed within autophagosomes. Cell viability decreased with an ATP reduction and the G2/M phase arrest. The expression of SOD-2, but not of SOD-1, markedly increased after PA exposure, which also elevated the number of cells generating ROS. PA enhanced the levels of proteins related to apoptosis, necroptosis, autophagy, and ER stress. Moreover, the inhibition of caspases, p53, necroptosis, or ER stress substantially rescued PA-induced cytotoxicity and, similarly, the inhibition of caspases and ER stress counteracted PA-induced changes in the cell cycle. Conversely, the inhibition of necroptosis and p53 signaling accelerated the changes in the cell cycle triggered by PA exposure. Blocking autophagy exacerbated PA-induced cytotoxicity and alterations in the cell cycle and caused disappearance of cellular components. These results suggest that PA induces apoptosis accompanied by autophagy through mitochondrial dysfunction and ER stress, which are triggered by oxidative stress in Chang liver cells and that blocking autophagy accelerates cell damage following PA exposure.

Lipotoxicity of palmitic Acid on neural progenitor cells and hippocampal neurogenesis

Lipotoxicity involves pathological alterations to cells and tissues in response to elevated fat levels in blood. Furthermore, this process can disturb both cellular homeostasis and viability. In the current study, the authors show that neural progenitor cells (NPCs) are vulnerable to high levels of palmitic acid (PA) a saturated fatty acid. PA was found to cause cell death associated with elevated reactive oxygen species (ROS) levels, and to reduce NPCs proliferation. To evaluate the lipotoxicity of PA in adult NPCs in the hippocampus, male C57BL/6 mice were divided into two groups and maintained on either a normal diet (ND) or PA-rich high fat diet (HFD) for 2 weeks. Interestingly, short-term PA-rich HFD feeding reduced the survival of newly generated cells in the hippocampal dentate gyrus and hippocampal brain-derived neurotrophic factor levels. These findings suggest PA has a potent lipotoxicity in NPCs and that a PA-rich HFD disrupts hippocampal neurogenesis.

Partitioning of lysolipids, fatty acids and their mixtures in aqueous lipid bilayers: solute concentration/composition effects

Distributions of lysopalmitoylphosphatidylcholine (LPPC), palmitic acid (PA) and their 1:1 mixtures between water and dipalmitoylphosphatidylcholine (DPPC) bilayer were determined using a fluorescence probe that selectively detects only the solutes in water. Water solute concentrations were obtained at each of several lipid concentrations. Dynamic Light Scattering experiments confirmed that the lipid/solute aggregates were vesicles in the concentration range investigated. Lipid concentration dependence of the solute component in water was fit to a thermodynamic model of solute distribution between two coexisting solvents. Water/bilayer partition coefficient and the free energy of transfer, for each of these solutes were determined from the fit. Main findings are: (1) Water/bilayer partition coefficient of solute is greater for 2 to 10% solute mole fraction than for 0 to 2%, signaling solute induced bilayer perturbation that increases bilayer solubility, beginning at 2% solute mole fraction. (2) Partition coefficients are in the order LPPC<PA<LPPC+PA at 37°C and LPPC+PA≤LPPC<PA at 50°C. This signifies synergism toward increased solute solubility in the bilayer-gel phase and lack of it in the bilayer-liquid phase when LPPC and PA are present together. Implications of the solute concentration/composition and bilayer phase dependences of the partition coefficients to the reported solute induced enhancements in transmembrane permeability are discussed.

Plasma phospholipid saturated fatty acids and heart failure risk in the Physicians' Health Study

BACKGROUND & AIMS

Previous studies have suggested that some plasma phospholipid saturated fatty acids (SFA) are associated with an increased risk of coronary heart disease and hypertension, major risk factors for heart failure (HF). However, little is known about the association between SFA and HF. This study examines associations of individual plasma phospholipid SFA with HF risk in US male physicians.

METHODS

The current ancillary study used a prospective nested matched case-control design to select 788 cases of incident HF and 788 controls. Plasma phospholipid SFAs were measured using gas chromatography. HF was self-reported on follow-up questionnaires and validated by review of medical records in a subsample. We used conditional logistic regression to estimate relative risks.

RESULTS

Mean age was 58.7 ± 8.0 years. One standard deviation higher plasma phospholipid 16:0 was associated with an odds ratio (95% CI) of 1.20 (1.04, 1.38) controlling for established HF risk factors and other SFAs (p = 0.042). However, this association was not significant after Bonferroni correction (p > 0.008). We did not observe associations between other SFAs (14:0, 15:0, 18:0, 20:0, or 22:0) and HF risk (all p for trend > 0.05).

CONCLUSIONS

Our data suggested no association between plasma phospholipid SFAs and HF in US male physicians.

Protective Effects of Oleic Acid Against Palmitic Acid-Induced Apoptosis in Pancreatic AR42J Cells and Its Mechanisms

Palmitic acid (PAM), one of the most common saturated fatty acid (SFA) in animals and plants, has been shown to induce apoptosis in exocrine pancreatic AR42J cells. In this study, we investigated cellular mechanisms underlying protective effects of oleic acid (OLA) against the lipotoxic actions of PAM in AR42J cells. Exposure of cells to long-chain SFA induced apoptotic cell death determined by MTT cell viability assay and Hoechst staining. Co-treatment of OLA with PAM markedly protected cells against PAM-induced apoptosis. OLA significantly attenuated the PAM-induced increase in the levels of pro-apoptotic Bak protein, cleaved forms of apoptotic proteins (caspase-3, PARP). On the contrary, OLA restored the decreased levels of anti-apoptotic Bcl-2 family proteins (Bcl-2, Bcl-xL, and Mcl-1) in PAM-treated cells. OLA also induced up-regulation of the mRNA expression of Dgat2 and Cpt1 genes which are involved in triacylglycerol (TAG) synthesis and mitochondrial β-oxidation, respectively. Intracellular TAG accumulation was increased by OLA supplementation in accordance with enhanced expression of Dgat2 gene. These results indicate that restoration of anti-apoptotic/pro-apoptotic protein balance from apoptosis toward cell survival is involved in the cytoprotective effects of OLA against PAM-induced apoptosis in pancreatic AR42J cells. In addition, OLA-induced increase in TAG accumulation and up-regulation of Dgat2 and Cpt1 gene expressions may be possibly associated in part with the ability of OLA to protect cells from deleterious actions of PAM.

Comparative analysis of volatile metabolomics signals from melanoma and benign skin: a pilot study

The analysis of volatile organic compounds (VOC) as biomarkers of cancer is both promising and challenging. In this pilot study, we used an untargeted approach to compare volatile metabolomic signatures of melanoma and matched control non-neoplastic skin from the same patient. VOC from fresh (non-fixed) biopsied tissue were collected using the headspace solid phase micro extraction method (HS SPME) and analyzed by gas chromatography and mass spectrometry (GCMS). We applied the XCMS analysis platform and MetaboAnalyst software to reveal many differentially expressed metabolic features. Our analysis revealed increased levels of lauric acid (C12:0) and palmitic acid (C16:0) in melanoma. The identity of these compounds was confirmed by comparison with chemical standards. Increased levels of these fatty acids are likely to be a consequence of up-regulated de novo lipid synthesis, a known characteristic of cancer. Increased oxidative stress is likely to cause an additional increase in lauric acid. Implementation of this study design on larger number of cases will be necessary for the future metabolomics biomarker discovery applications.

Effect of palmitic acid on ethanol-induced fatty degeneration in hepatic cells in vitro

AIM: To determine the effect of different concentrations of palmitic acid on alcohol-induced lipogenesis in L-02 liver cells and to explore mechanisms involved.

METHODS: Cultured L-02 liver cells were divided into three groups: blank control group, alcohol induction group, and palmitic acid intervention group, which were cultured in RPMI 1640 medium containing 10% serum, RPMI 1640 medium containing 10% serum and 6% ethanol, and RPMI 1640 medium containing 10% serum, 6% ethanol and different concentrations of palmitic acid (2.5, 5, 10, 20, 30, and 40 µmol/L), respectively. Cell proliferation was measured by MTT assay. The accumulation of lipid droplets was observed by light inverted microscopy after red oil-O staining. Intracellular triglyceride (TG) level was determined using commercial kits. Western blot was used to detect the levels of nuclear SREBP-1c protein in hepatocytes of each group.

RESULTS: A model of alcohol-induced steatosis was successfully induced in L-02 liver cells by incubation with 0.6% ethanol for 72 h. Compared to the alcohol induction group, palmitic acid at concentrations of 2.5, 5, and 10 µmol/L could not only significantly promote cell proliferation (all P < 0.05) but also significantly reduce the accumulation of lipid droplets and the levels of intracellular TG and nuclear SREBP-1c protein (all P < 0.05), showing concentration-dependent protective effects. However, palmitic acid at concentrations of 20, 30 and 40 µmol/L significantly inhibited cell proliferation (all P < 0.05) and increased the accumulation of lipid droplets and the levels of intracellular TG and nuclear SREBP-1c protein (all P < 0.05), showing harmful effect on alcohol-induced steatosis in L-02 liver cells.

CONCLUSION: Palmitic acid at concentrations <10 µmol/L has protective effects and palmitic acid at concentrations >10 µmol/L has harmful effects on alcohol-induced steatosis in L-02 liver cells. Palmitic acid exerts effects on alcohol-induced steatosis in L-02 liver cells via mechanisms associated with regulating the expression of nuclear SREBP-1c protein in hepatocytes.

Construction of efficient and effective transformation vectors for palmitoyl-acyl carrier protein thioesterase gene silencing in oil palm

Palm oil obtained from E. guineensis Jacq. Tenera is known to have about 44% of palmitic acid (C16:0). Palmitoyl-Acyl Carrier Protein Thioesterase (PATE) is one of the key enzymes involved in plastidial fatty acid biosynthesis; and it determines the level of the C16:0 assimilation in oilseeds. This enzyme's activity in oil palm is responsible for high (> 44 % in E. guineensis Jacq. Tenera and 25 % in E. oleifera) content of C16:0 in its oil. By post-transcriptional PATE gene silencing, C16:0 content can be minimized for nutritional value improvement of the palm oil. The objective of this study was the construction of novel transformation vectors for PATE gene silencing. Six different transformation vectors targeted against PATE gene were constructed using 619 bp long PATE gene (5' region) fragment (from GenBank AF507115). In one set of three transformation vectors, PATE gene fragment was fused with CaMV 35S promoter in antisense, intron-spliced inverted repeat (ISIR), and inverted repeat (IR) orientations to generate antisense mRNA and hair-pin RNAs (hpRNA). In another set of three transformation vectors with same design, CaMV 35S was replaced with Oil palm mesocarp tissue-specific promoter (MSP). The expression cassette of antisense, ISIR, and IR of PATE gene fragments were constructed in primary cloning vector, pHANNIBAL or its derivative/s. Finally, all 6 expression cassettes were sub-cloned into pCAMBIA 1301 which contains the Hygromycinr and the GUS reporter genes for transformant selection and transformation detection respectively. The results of the RE analyses of the constructs and sequence analyses of PATE and MSP shows and confirms the orientation, size and locations of all the components from constructs. We hypothesize that 4 (pISIRPATE-PC, pIRPATE-PC, pMISIRPATE-PC and pMIRPATE-PC) out of 6 transformation vectors constructed in this study will be efficient and effective in palmitoyl-ACP thioesterase gene silencing in oil palm.

ABBREVIATIONS

antiPATE - Antisense Palmitoyl-acyl carrier protein thioesterase, BCV - Binary cloning vector, cDNA - Complementary deoxyribonucleic acid, hpRNA - hair-pin RNA, ihpRNA - intron containing hair-pin RNA, IR - inverted repeat, ISIR - intron-spliced inverted repeat, MCS - Multiple cloning site, MSP - Oil palm mesocarp tissue-specific promoter, nt - Nucleotide/s, PATE - Palmitoyl-acyl carrier protein thioesterase, PCR - Polymerase chain reaction, PCV - Primary cloning vector, pDNA - Plasmid deoxyribonucleic acid, PTGS - Post-transcriptional gene silencing, RE - Restriction enzyme.