Oxidation Of Oleic Acid Research Articles

Krill oil supplementation in vivo promotes increased fuel metabolism and protein synthesis in cultured human skeletal muscle cells.

Krill oil is a dietary supplement derived from Antarctic krill; a small crustacean found in the ocean. Krill oil is a rich source of omega-3 fatty acids, specifically eicosapentaenoic acid and docosahexaenoic acid, as well as the antioxidant astaxanthin. The aim of this study was to investigate the effects of krill oil supplementation, compared to placebo oil (high oleic sunflower oil added astaxanthin), in vivo on energy metabolism and substrate turnover in human skeletal muscle cells. Skeletal muscle cells (myotubes) were obtained before and after a 7-week krill oil or placebo oil intervention, and glucose and oleic acid metabolism and leucine accumulation, as well as effects of different stimuli in vitro, were studied in the myotubes. The functional data were combined with proteomic and transcriptomic analyses. In vivo intervention with krill oil increased oleic acid oxidation and leucine accumulation in skeletal muscle cells, however no effects were observed on glucose metabolism. The krill oil-intervention-induced increase in oleic acid oxidation correlated negatively with changes in serum low-density lipoprotein (LDL) concentration. In addition, myotubes were also exposed to krill oil in vitro. The in vitro study revealed that 24 h of krill oil treatment increased both glucose and oleic acid metabolism in myotubes, enhancing energy substrate utilization. Transcriptomic analysis comparing myotubes obtained before and after krill oil supplementation identified differentially expressed genes associated with e.g., glycolysis/gluconeogenesis, metabolic pathways and calcium signaling pathway, while proteomic analysis demonstrated upregulation of e.g., LDL-receptor in myotubes obtained after the krill oil intervention. These findings suggest that krill oil intervention promotes increased fuel metabolism and protein synthesis in human skeletal muscle cells, with potential implications for metabolic health.

Diflunisal activates AMP-activated protein kinase and stimulates glucose uptake, glycolysis and oxidation of glucose and oleic acid in skeletal muscle cells

Diflunisal activates AMP-activated protein kinase and stimulates glucose uptake, glycolysis and oxidation of glucose and oleic acid in skeletal muscle cells

Time-dependent reduction in oxidative capacity among cultured myotubes from spinal cord injured individuals.

Skeletal muscle adapts in reaction to contractile activity to efficiently utilize energy substrates, primarily glucose and free fatty acids (FA). Inactivity leads to atrophy and a change in energy utilization in individuals with spinal cord injury (SCI). The present study aimed to characterize possible inactivity-related differences in the energy metabolism between skeletal muscle cells cultured from satellite cells isolated 1- and 12-months post-SCI. To characterize inactivity-related disturbances in spinal cord injury, we studied skeletal muscle cells isolated from SCI subjects. Cell cultures were established from biopsy samples from musculus vastus lateralis from subjects with SCI 1 and 12 months after the injury. The myoblasts were proliferated and differentiated into myotubes before fatty acid and glucose metabolism were assessed and gene and protein expressions were measured. The results showed that glucose uptake was increased, while oleic acid oxidation was reduced at 12 months compared to 1 month. mRNA expressions of PPARGC1α, the master regulator of mitochondrial biogenesis, and MYH2, a determinant of muscle fiber type, were significantly reduced at 12 months. Proteomic analysis showed reduced expression of several mitochondrial proteins. In conclusion, skeletal muscle cells isolated from immobilized subjects 12 months compared to 1 month after SCI showed reduced fatty acid metabolism and reduced expression of mitochondrial proteins, indicating an increased loss of oxidative capacity with time after injury.

A novel fullerene composite material for directional oil control and antioxidant.

There are very few cosmetic ingredients that can target oil control and extend the wear time. Fullerenes have been reported to have excellent antioxidant capacity and a variety of biological activities, such as quenching free radicals, inhibiting lipid peroxidation, and promoting lipid flocculation. The purpose of applying foundation makeup on the face is to make the skin color even, but the secretion and oxidation of skin oil will make the makeup mottled and dull. In order to solve this problem, a fullerene composite material that can directionally absorb oil and resist oil oxidation has been developed. Fullerenes and hydroxyapatite composite was prepared by high pressure homogenization under alkaline condition. The indicated morphology and structure were characterized by SEM, UV-Vis, Raman, and XRD. The oil absorption capacity was determined by adding the C60-hydroxyapatite composite to a mixed solution of hexane and oil, shaking for 1 h, filtering, analyzed by GC-MS, and calculating the oil absorption by external standard method. Artificial sebum was prepared by adding different mass of water and oleic acid to screen the optimum ratio. C60-hydroxyapatite mixture and C60-hydroxyapatite composite were added to the artificial sebum to test the oil-absorbing capacity of the materials. The hydroxyl radical scavenging ability of C60-hydroxyapatite composite containing different fullerene contents was measured by X-band ESR spectroscopy, and the long-term radical scavenging ability of the composites was tested in comparison with VC. Antioxidant experiment is adding C60-hydroxyapatite composite material, and hydroxyapatite to oleic acid, then the UV light irradiation is aimed to accelerate the oxidation of oleic acid. Oleic acid act as a control group, and make the detection of oleic acid peroxide value after 7 days. The safety of the materials was tested by using culture media to soak the C60-hydroxyapatite composite for 24 h and then used to culture cells. The characterization of SEM, UV-Vis, Raman, and XRD showed that fullerene clusters were dispersed on the surface of hydroxyapatite stably, and they formed a stable composite. The adsorption rates of C60-hydroxyapatite composites for oleic acid, phenyl trimethicone, caprylic capric glyceride, isooctyl palmitate, mineral oil, olive oil, and dimethicone were 60.5%, 9.3%, 9.15%, 5.24%, 2.94%, 1.01%, and 0%, respectively. The flocculation amount of artificial sebum was 5.9 g per gram of C60-hydroxyapatite mixture and 24.2 g per gram of C60-hydroxyapatite composite. C60-hydroxyapatite composites have excellent quenching ability for hydroxyl radicals. When the fullerene content is 1, 2, 3, and 4 mg/kg, the quenching rates are 25.02%, 39.57%, 49.75%, and 62.24%, respectively. The quenching effect was enhanced with the increase of fullerene content, and it had strong long-term antioxidant properties. It can also be proved that C60-hydroxyapatite composites have strong antioxidant capacity through antioxidant experiments. The peroxide value of oleic acid on Day 0 was 2.8, and after 7 days of UV irradiation, the peroxide values of blank control, hydroxyapatite group, C60-hydroxyapatite composite containing 0.5% and 1% fullerenes four groups of materials were 8.02 meq O2/kg, 7.98 meq O2/kg, 7.11 meq O2/kg, and 6.87 meq O2/kg, respectively. The cell activity was 20.94% and 99.2% after the cells were cultured for 24 h using C60-hydroxyapatite composite and hydroxyapatite extracts, respectively, and the addition of fullerene was able to significantly increase the cell activity. Fullerene hydroxyapatite complex has excellent directional oil absorption characteristics, which can effectively remove free radicals and reduce skin oil oxidation.

Density functional theory studies on the oleic acid thermal oxidation into volatile compounds.

Oleic acid oxidation is one of the main sources of food flavor compounds. Volatile profiling was investigated using thermal desorption cryo-trapping combined with gas chromatography-mass spectrometry to analyze the volatile composition of oleic acid oxidation. A total of 43 volatile compounds, including aldehydes (11), ketones (2), alcohols (5), furans (2), acids (8), ester (12) and alkane (3) were identified from oleic acid during heating. Then, density functional theory (DFT) was applied to analyze the oxidative mechanism of oleic acid during heating. A total of 30 reactions were obtained and grouped into the peroxide (ROOH), alkoxy radical (RO•), and peroxide radical (ROO•) pathways. The structures of intermediates, transition states (TS), and products in each reaction were also determined. Results show that the branch chemical reactions were the key reactions in different reaction pathway. Moreover, the reaction priority of the thermal oxidation reaction of oleic acid was the peroxide radical mechanism>the peroxide mechanism>the alkoxy radical mechanism.

Unsaturated Fatty Acids Enhance Aqueous Atmospheric Oxidation Ability by Producing Oxygen‐Containing Radicals in Fog Droplets

AbstractThe surface of atmospheric aqueous aerosol is covered with an organic film. However, there have been limited studies about the photochemical process between the organic coating and aqueous samples such as fogwater, which contains light absorbing brown carbon (BrC). Here, the interactional aging process between unsaturated fatty acids and aqueous samples was performed by laboratory studies and field observations. On the one hand, glycine and alanine were selected as organic nitrogen‐containing compounds to form BrC with carbonyl compounds like glyoxal or methylglyoxal. Oleic acid was induced to form organic peroxy radicals through H‐abstraction by the excited triplet BrC or hydroxyl radical (OH). On the other hand, one type of aqueous formation pathway of Criegee intermediates (CIs) was proposed through the oxidation of oleic acid. CIs may be formed by OH addition to C=C bonds and scavenged by interfacial reactions. Results from ultra‐high resolution Fourier transform ion cyclotron resonance mass spectrometry show that the synergistic effect of oleic acid and OH may have a higher oxidative capacity than OH. Furthermore, our study demonstrates that oleic acid can improve the aqueous oxidation ability by producing oxygen‐containing radicals. These findings highlight that the formation of free radicals is greatly influenced by photochemical reactions, which further reveal the complexities of fog organic chemistry.

Formation of Lipid-Derived Flavors in Dry-Cured Mackerel (Scomberomorus niphonius) via Simulation of Autoxidation and Lipoxygenase-Induced Fatty Acid Oxidation.

In this study, lipoxygenase (LOX) extracted from dry-cured mackerel was purified, resulting in a 4.1-fold purification factor with a specific activity of 493.60 U/min·g. LOX enzymatic properties were assessed, referring to its optimal storage time (1-2 days), temperature (30 °C), and pH value (7.0). The autoxidation and LOX-induced oxidation of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:2n9c), linoleic acid (C18:2n6c), arachidonic acid (C20:4), EPA (C20:5), and DHA (C22:6n3) were simulated to explore the main metabolic pathways of key flavors in dry-cured mackerel. The results showed that the highest LOX activity was observed when arachidonic acid was used as a substrate. Aldehydes obtained from LOX-treated C18:1n9c and C18:2n6c oxidation, which are important precursors of flavors, were the most abundant. The key flavors in dry-cured mackerel were found in the oxidative products of C16:0, C18:0, C18:1n9c, C18:2n6c, and C20:4. Heptanaldehyde could be produced from autoxidation or LOX-induced oxidation of C18:0 and C18:1n9c, while nonal could be produced from C18:1n9c and C18:2n6c oxidation. Metabolic pathway analysis revealed that C18:1n9c, C18:2n6c, EPA, and DHA made great contributions to the overall flavor of dry-cured mackerel. This study may provide a relevant theoretical basis for the scientific control of the overall taste and flavor of dry-cured mackerel and further standardize its production.

Introduction of chlorogenic acid into thermal processed starch- oleic acid system controls the ordered structure and inhibits oleic acid oxidation through molecular interactions

In this study, the effects of starch- oleic acid (OA)- chlorogenic acid (CA) molecular interaction on OA oxidation during thermal processing were investigated based on structural analysis, oxidation characteristics and quantum calculations. The results showed that in the ternary system, on the one hand, OA could enter the spiral cavity of starch through hydrophobic forces and form V-type crystalline structure, which delayed its oxidation. On the other hand, CA could further inhibit the oxidation of OA through free radical reaction and did not affect the molecular interactions between OA and starch due to the steric hindrance and hydrophily. Notably, starch-OA-CA interactions could effectively decrease total oxidation value (19.07), prolong the induction time of oxidation (114.6 min) and reduce the abundance of oxidation products through hydrogen atom transfer reactions with active phenolic hydroxyl to protect the α-methylene groups at C=C. Overall, these results provided insights into functional property regulation by the interaction of starch-based multi-component systems.

Energetics and fuel use vary with migration strategy across populations of Common Blackbirds

Abstract Seasonal migration is a physiologically demanding endeavour that animals prepare for by finding and storing energy. Species and populations vary in their tendencies to migrate and the energetic demands of migration likely determine the degree and type of preparation that different animals undergo. Birds fuel their migratory flight using stored fat. Previous work has suggested that in addition to being energetically dense, certain lipids like polyunsaturated fatty acids (PUFAs) may be particularly efficient fuels that are preferentially mobilized for flight or serve may additional functions, such as modulating membrane fluidity or stimulating gene expression as ligands, during long‐distance migratory flight. Using a series of behavioural and metabolic experiments in a partial transplant aviary setting of Common Blackbirds (Turdus merula) populations that range from being fully migratory to partially migratory to sedentary, we asked how migratory restlessness (Zugunruhe), weight gain and oxidation of stearic acid (18:0), oleic acid (18:1n‐9), linoleic acid (18:2n‐6) and alpha linolenic acid (18:3n‐3; ALA) varied with migratory mode and season. We found no population‐level differences in the timing of Zugunruhe. However, before migration, a greater proportion of individuals from fully migratory populations exhibited weight gain and migratory restlessness, as well as increased oxidation of PUFAs. After Zugunruhe, only individuals from migratory populations showed reduced PUFA oxidation. All populations showed increased oxidation of saturated fat after Zugunruhe. Our results demonstrate that certain migratory traits, like the timing of Zugunruhe are expressed similarly across populations in response to local environmental conditions, while other traits, like lipid oxidation, can vary among populations. Read the free Plain Language Summary for this article on the Journal blog.

Volatile compounds comparison and mechanism exploration of non-smoked traditional Chinese bacon in Southwestern China and Eastern China

Non-smoked traditional Chinese bacon is popular in China. However, the aromas of the non-smoked bacon from Eastern China (EC bacon) and Southwestern China (SW bacon) differed significantly. This study investigated these differences and the key volatile compound formation mechanisms. A total of 175 volatile compounds were detected in the bacon samples, while 32 key aroma compounds were screened based on odor activity values (OAVs). Multivariate statistical analysis showed that ten odorants could be considered discriminative compounds, including hexanal, octanal, and 1-octen-3-ol, etc. The fatty aroma of EC bacon was mainly attributed to a higher aldehydes content, which is due to more oxidation of fatty acids. Meanwhile, the SW bacon smelled sweeter since there was more ester in the sample. The correlation analysis between the fatty acid profiles and key aroma compounds indicated that the discriminative aldehyde formation in the EC bacon was primarily attributed to oleic and linoleic acid oxidation, which were both potential biomarkers.

SENP2 knockdown in human adipocytes reduces glucose metabolism and lipid accumulation, while increases lipid oxidation

Adipose tissue is one of the main regulative sites for energy metabolism. Excess lipid storage and expansion of white adipose tissue (WAT) is the primary contributor to obesity, a strong predisposing factor for development of insulin resistance. Sentrin-specific protease (SENP) 2 has been shown to play a role in metabolism in murine fat and skeletal muscle cells, and we have previously demonstrated its role in energy metabolism of human skeletal muscle cells. In the present work, we have investigated the impact of SENP2 on fatty acid and glucose metabolism in primary human fat cells by using cultured primary human adipocytes to knock down the SENP2 gene. Glucose uptake and oxidation, as well as accumulation and distribution of oleic acid into complex lipids were decreased, while oleic acid oxidation was increased in SENP2-knockdown cells compared to control adipocytes. Furthermore, lipogenesis was reduced by SENP2-knockdown in adipocytes. Although TAG accumulation relative to total uptake was unchanged, there was increased mRNA expression of metabolically relevant genes such as UCP1 and PPARGC1A and mRNA and proteomic data revealed increased levels of mRNA and proteins related to mitochondrial function by SENP2-knockdown. In conclusion, SENP2 is an important regulator of energy metabolism in primary human adipocytes and its knockdown reduce glucose metabolism and lipid accumulation, while increasing lipid oxidation in human adipocytes.

L-Arginine supplementation regulates energy-substrate metabolism in skeletal muscle and adipose tissue of diet-induced obese rats.

Dietary supplementation with l-arginine has been reported to reduce white fat mass in diet-induced obese rats and in obese humans. This study was conducted to test the hypothesis that the arginine treatment regulates glucose and fatty acid metabolism in insulin-sensitive tissues. Male Sprague-Dawley rats (4-week-old) were fed either low- or high-fat diets for 15 weeks (n = 16/diet). Thereafter, lean or obese rats were fed their respective diets and received drinking water containing either 1.51% l-arginine-HCl or 2.55% alanine (isonitrogenous control) (n = 8/treatment group). After 12 weeks of treatment, rats were euthanized and tissue samples were collected for biochemical assays. High-fat feeding increased the size of adipocytes isolated from retroperitoneal (RP) adipose tissue, while arginine treatment reduced their size. The total number of adipocytes in the adipose tissue did not differ among the four groups of rats. Glucose oxidation in extensor digitorum longus (EDL) muscle, soleus muscle, and RP adipose tissue were reduced in response to high-fat feeding. On the contrary, oleic acid oxidation in RP adipose tissue was enhanced in rats fed the high-fat diet. Arginine treatment stimulated both glucose and oleic acid oxidation in EDL and soleus muscles, while having no effect on glucose oxidation, oleic acid oxidation, or basal lipolysis per 106 adipocytes in RP adipose tissue. Collectively, these results indicate that oral supplementation with arginine to diet-induced obese rats promoted the oxidation of energy substrates in skeletal muscle, thereby reducing white fat in the body.

Microglia with fatty acid‐binding protein 5 deficiency exhibit proinflammatory phenotype contributing to neuroinflammation

AbstractBackgroundMicroglia are the resident immune cells in the brain, which show a broad spectrum of phenotypes ranging from the pro‐inflammatory, potentially cytotoxic to the anti‐inflammatory, scavenging, and regenerative. Fatty‐acid binding protein 5, an intracellular protein that are important for cellular metabolism, have been identified in human and mouse microglia; however, its role in microglia is yet to be defined. Studies from our laboratory and others have shown that FABP5 is downregulated in the brain of Alzheimer’s disease patients and APP/PS1 mice. This study is to explore the impact of FABP5‐deficiency on microglia phenotype.MethodTotal protein from FABP5‐knockout mouse brains (4‐5 months old) was extracted to assess cytokine levels (TNFα, IL‐1ß). Microglia abundance in the hippocampus of FABP5‐knockout mice and their wildtype control mice was quantified immunohistochemically. FABP5 in the immortalized mouse microglia BV2 was downregulated using siRNA, and the metabolism of the treated microglia was assessed via [3H]‐2‐deoxy‐D‐glucose (2dg) uptake and oleic acid oxidation assay.ResultA significant increased levels of TNFα (1.4‐fold) and IL‐1ß (1.25‐fold) was detected in the brain homogenates of FABP5‐knockout mice (vs wildtype control mice). Interestingly, a higher abundance (8%) of microglia was observed in the hippocampus of the FABP5‐knockout mice. The downregulated FABP5 in BV2 using siRNA and achieved a 76.4% reduction in FABP5 protein expression. We subsequently observed a 1.5‐fold elevation of 3H‐2dg uptake in FABP5‐downregulated BV2 cells, suggesting a possible increase in glycolysis. This shift was in agreement with the metabolism requirement of the proinflammatory microglia.ConclusionFurther studies need to be performed to confirm the role of FABP5 in microglia. Our data supports that FABP5 deficiency possibly leads to microglia proinflammatory activation and contribute to neuroinflammation in mice.

Energy metabolism in skeletal muscle cells from donors with different body mass index.

Obesity and physical inactivity have a profound impact on skeletal muscle metabolism. In the present work, we have investigated differences in protein expression and energy metabolism in primary human skeletal muscle cells established from lean donors (BMI<25kg/m2) and individuals with obesity (BMI>30kg/m2). Furthermore, we have studied the effect of fatty acid pretreatment on energy metabolism in myotubes from these donor groups. Alterations in protein expression were investigated using proteomic analysis, and energy metabolism was studied using radiolabeled substrates. Gene Ontology enrichment analysis showed that glycolytic, apoptotic, and hypoxia pathways were upregulated, whereas the pentose phosphate pathway was downregulated in myotubes from donors with obesity compared to myotubes from lean donors. Moreover, fatty acid, glucose, and amino acid uptake were increased in myotubes from individuals with obesity. However, fatty acid oxidation was reduced, glucose oxidation was increased in myotubes from subjects with obesity compared to cells from lean. Pretreatment of myotubes with palmitic acid (PA) or eicosapentaenoic acid (EPA) for 24h increased glucose oxidation and oleic acid uptake. EPA pretreatment increased the glucose and fatty acid uptake and reduced leucine fractional oxidation in myotubes from donors with obesity. In conclusion, these results suggest that myotubes from individuals with obesity showed increased fatty acid, glucose, and amino acid uptake compared to cells from lean donors. Furthermore, myotubes from individuals with obesity had reduced fatty acid oxidative capacity, increased glucose oxidation, and a higher glycolytic reserve capacity compared to cells from lean donors. Fatty acid pretreatment enhances glucose metabolism, and EPA reduces oleic acid and leucine fractional oxidation in myotubes from donor with obesity, suggesting increased metabolic flexibility after EPA treatment.

Elucidation of Olive Oil Oxidation Mechanisms by Analysis of Triacylglycerol Hydroperoxide Isomers Using LC-MS/MS.

Despite the importance of the insight about the oxidation mechanisms (i.e., radical and singlet oxygen (1O2) oxidation) in extra virgin olive oil (EVOO), the elucidation has been difficult due to its various triacylglycerol molecular species and complex matrix. This study tried to evaluate the mechanisms responsible for EVOO oxidation in our daily use by quantitative determination of triacylglycerol hydroperoxide (TGOOH) isomers using LC-MS/MS. The standards of dioleoyl-(hydroperoxy octadecadienoyl)-triacylglycerol and dioleoyl-(hydroperoxy octadecamonoenoyl)-triacylglycerol, which are the predominant TGOOHs contained in EVOO, were prepared. Subsequently, fresh, thermal-, and photo-oxidized EVOO were analyzed. The obtained results mostly agreed with the previously reported characteristics of the radical and 1O2 oxidation of linoleic acid and oleic acid. This suggests that the methods described in this paper should be valuable in understanding how different factors that determine the quality of EVOO (e.g., olive species, cultivation area, cultivation timing, and extraction methods) contribute to its oxidative stability.

L-Arginine increases AMPK phosphorylation and the oxidation of energy substrates in hepatocytes, skeletal muscle cells, and adipocytes.

Previous work has shown that dietary L-arginine (Arg) supplementation reduced white fat mass in obese rats. The present study was conducted with cell models to define direct effects of Arg on energy-substrate oxidation in hepatocytes, skeletal muscle cells, and adipocytes. BNL CL.2 mouse hepatocytes, C2C12 mouse myotubes, and 3T3-L1 mouse adipocytes were treated with different extracellular concentrations of Arg (0, 15, 50, 100 and 400µM) or 400µM Arg + 0.5mM NG-nitro-L-arginine methyl ester (L-NAME; an NOS inhibitor) for 48h. Increasing Arg concentrations in culture medium dose-dependently enhanced (P < 0.05) the oxidation of glucose and oleic acid to CO2 in all three cell types, lactate release from C2C12 cells, and the incorporation of oleic acid into esterified lipids in BNL CL.2 and 3T3-L1 cells. Arg at 400µM also stimulated (P < 0.05) the phosphorylation of AMP-activated protein kinase (AMPK) in all three cell types and increased (P < 0.05) NO production in C2C12 and BNL CL.2 cells. The inhibition of NOS by L-NAME moderately reduced (P < 0.05) glucose and oleic acid oxidation, lactate release, and the phosphorylation of AMPK and acetyl-CoA carboxylase (ACC) in BNL CL.2 cells, but had no effect (P > 0.05) on these variables inC2C12 or 3T3-L1 cells. Collectively, these results indicate that Arg increased AMPK activity and energy-substrate oxidation in BNL CL.2, C2C12, and 3T3-L1 cells through both NO-dependent and NO-independent mechanisms.

Nonanoic acid esterification with 2-ethylhexanol: From batch to continuous operation

Nonanoic acid is considered a feedstock of growing interest due to the promising applicability of its derivatives. It can be obtained from vegetable oils, one of the products of oleic acid oxidation. Recently, a very interesting application of the ester obtained from nonanoic acid esterification with 2-ethylhexanol was found. In fact, it showed excellent properties as solvent for varnishes. The aim of this work was the kinetic investigation of the nonanoic acid esterification with 2-ethylhexanol in batch and continuous reactors, promoted by Amberlyst-15 and Amberlite IR120 resins, and to demonstrate the technical feasibility of the mentioned technology in flow systems. A mathematical model was developed to simulate the collected experimental data taking into account all the phenomena appearing in the system: intrinsic kinetics, mass transfer and flow pattern. Experiments were also conducted in the continuous packed bed reactor to compare the catalyst performances and validate the results obtained in the batch reactor. The best nonanoic acid conversion (85%) was obtained fixing T = 363 K, Q = 4.17·10−9 m3/s with an alcohol:acid molar ratio of 5:1 using Amberlyst-15 as heterogeneous catalyst.

Knockdown of sarcolipin (SLN) impairs substrate utilization in human skeletal muscle cells

BackgroundRecent studies have highlighted that uncoupling of sarco-/endoplasmic reticulum Ca2+-ATPase (SERCA) by sarcolipin (SLN) increases ATP consumption and contributes to heat liberation. Exploiting this thermogenic mechanism in skeletal muscle may provide an attractive strategy to counteract obesity and associated metabolic disorders. In the present study, we have investigated the role of SLN on substrate metabolism in human skeletal muscle cells.Methods and resultsAfter generation of skeletal muscle cells with stable SLN knockdown (SLN-KD), cell viability, glucose and oleic acid (OA) metabolism, mitochondrial function, as well as gene expressions were determined. Depletion of SLN did not influence cell viability. However, glucose and OA oxidation were diminished in SLN-KD cells compared to control myotubes. Basal respiration measured by respirometry was also observed to be reduced in cells with SLN-KD. The metabolic perturbation in SLN-KD cells was reflected by reduced gene expression levels of peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) and forkhead box O1 (FOXO1). Furthermore, accumulation of OA was increased in cells with SLN-KD compared to control cells. These effects were accompanied by increased lipid formation and incorporation of OA into complex lipids. Additionally, formation of complex lipids and free fatty acid from de novo lipogenesis with acetate as substrate was enhanced in SLN-KD cells. Detection of lipid droplets using Oil red O staining also showed increased lipid accumulation in SLN-KD cells.ConclusionsOverall, our study sheds light on the importance of SLN in maintaining metabolic homeostasis in human skeletal muscle. Findings from the current study suggest that therapeutic strategies involving SLN-mediated futile cycling of SERCA might have significant implications in the treatment of obesity and associated metabolic disorders.Graphical abstract

The effect of toll-like receptor ligands on energy metabolism and myokine expression and secretion in cultured human skeletal muscle cells

Skeletal muscle plays an important role in glycaemic control and metabolic homeostasis, making it a tissue of interest with respect to type 2 diabetes mellitus. The aim of the present study was to determine if ligands of Toll-like receptors (TLRs) could have an impact on energy metabolism and myokine expression and secretion in cultured human skeletal muscle cells. The myotubes expressed mRNA for TLRs 1–6. TLR3, TLR4, TLR5 and TLR6 ligands (TLRLs) increased glucose metabolism. Furthermore, TLR4L and TLR5L increased oleic acid metabolism. The metabolic effects of TLRLs were not evident until after at least 24 h pre-incubation of the cells and here the metabolic effects were more evident for the metabolism of glucose than oleic acid, with a shift towards effects on oleic acid metabolism after chronic exposure (168 h). However, the stimulatory effect of TLRLs on myokine expression and secretion was detected after only 6 h, where TLR3-6L stimulated secretion of interleukin-6 (IL-6). TLR5L also increased secretion of interleukin-8 (IL-8), while TLR6L also increased secretion of granulocyte–macrophage colony stimulating factor (GM-CSF). Pre-incubation of the myotubes with IL-6 for 24 h increased oleic acid oxidation but had no effect on glucose metabolism. Thus IL-6 did not mimic all the metabolic effects of the TLRLs, implying metabolic effects beyond the actions of this myokine.

Novel polyhydroxy anionic surfactants with excellent water-solid interfacial wettability control capability for enhanced oil recovery

Surfactant flooding has received considerable attention as a proven chemically enhanced oil recovery method. Traditional surfactants are mainly focused on water-oil interfacial tension reduction. However, a large amount of oil film remains on rock surfaces after surfactant flooding. Therefore, developing novel surfactants with excellent water-solid interfacial wettability control capability would significantly enhance oil recovery. In this study, novel polyhydroxy anionic surfactants, 9,10-dihydroxyl sodium stearate (SDHS) and 9,10,12,13-tetrahydroxyl sodium stearate, were synthesized by oxidation and hydrolysis of oleic acid and linoleic acid, respectively, followed by a neutralisation reaction. The polyhydroxy structure on the long hydrophobic carbon chains facilitated the adsorption of surfactants on the rock surface. Atomic force microscopy results showed that the SDHS layer had a uniform sheet structure. The exposed anions led to the accumulation of negative charges, significantly improving the hydrophilicity of the rock surface, with the underwater oil contact angle of the rock surface changing substantially from 18.1° to 152°. The surface (super)hydrophilicity and electrostatic repulsive force between the rock surface and the oil film synergistically contributed to the superior oil-film-peeling performance of SDHS. After SDHS treatment, the area reduction of the oil film surpassed 92.5%, which was significantly higher than that with other traditional surfactants. Furthermore, an increase of 10.15% in oil recovery was achieved by SDHS flooding. The novel surfactants with excellent water-solid interfacial wettability control capability exhibited superior performance in recovering residual oil adhered to oil-wet rocks. This is significant for efficient oilfield development.