Lipid metabolism in sickness and in health: Emerging regulators of lipotoxicity.

Lipids play crucial roles in signal transduction, contribute to the structural integrity of cellular membranes, and regulate energy metabolism. Questions remain as to which lipid species maintain metabolic homeostasis and which disrupt essential cellular functions, leading to metabolic disorders. Here, we discuss recent advances in understanding lipid metabolism with a focus on catabolism, synthesis, and signaling. Technical advances, including functional genomics, metabolomics, lipidomics, lipid-protein interaction maps, and advances in mass spectrometry, have uncovered new ways to prioritize molecular mechanisms mediating lipid function. By reviewing what is known about the distinct effects of specific lipid species in physiological pathways, we provide a framework for understanding newly identified targets regulating lipid homeostasis with implications for ameliorating metabolic diseases.

Engineering Yarrowia lipolytica for sustainable ricinoleic acid production: A pathway to free fatty acid synthesis.

Ricinoleic acid (C18:1-OH, RA) is a valuable hydroxy fatty acid with versatile applications. The current industrial source of RA relies on the hydrolysis of castor bean oil. However, the coexistence of the toxic compound ricin and the unstable supply of this plant have led to an exploration of promising alternatives: generating RA in heterologous plants or microorganisms. In this study, we engineered the oleaginous yeast Yarrowia lipolytica to produce RA in the form of free fatty acids (FFA). First, we overexpressed fungal Δ12 oleate hydroxylase gene (CpFAH12) from Claviceps purpurea while deleting genes related to fatty acid degradation (MEF1 and PEX10) and oleic acid desaturation (FAD2). Since Δ12 oleate hydroxylase converts oleic acid (C18:1) located at the sn-2 position of phosphatidylcholine (PC), we next focused on increasing the PC pool containing oleic acid. This objective was achieved thorough implementing metabolic engineering strategies designed to enhance the biosynthesis of PC and C18 fatty acids. To increase the PC pool, we redirected the flux towards phospholipid biosynthesis by deleting phosphatidic acid phosphatase genes (PAH1 and APP1) and diacylglycerol acyltransferase gene (DGA1), involved in the production of diacylglycerol and triacylglycerol, respectively. Furthermore, the PC biosynthesis via the CDP-DAG pathway was enhanced through the overexpression of CDS1, PSD1, CHO2, and OPI3 genes. Subsequently, to increase the oleic acid content within PC, we overexpressed the heterologous fatty acid elongase gene (MaC16E) involved in the conversion of C16 to C18 fatty acids. As RA production titer escalated, the produced RA was mainly found in the FFA form, leading to cell growth inhibition. The growth inhibition was mitigated by inducing RA secretion via Triton X-100 treatment, a process that simultaneously amplified RA production by redirecting flux towards RA synthesis. The final engineered strain JHYL-R146 produced 2.061 g/L of free RA in a medium treated with 5% Triton X-100, constituting 74% of the total FFAs produced. Generating free RA offers the added benefit of bypassing the hydrolysis stage required when employing castor bean oil as an RA source. This achievement represents the highest level of RA synthesis from glucose reported thus far, underscoring the potential of Y. lipolytica as a host for sustainable RA production.

High-Light-Induced Stress Activates Lipid Deacylation at the Sn-2 Position in the Cyanobacterium Synechocystis Sp. PCC 6803.

Cyanobacterial mutants defective in acyl-acyl carrier protein synthetase (Aas) produce free fatty acids (FFAs) because the FFAs generated by deacylation of membrane lipids cannot be recycled. An engineered Aas-deficient mutant of Synechocystis sp. PCC 6803 grew normally under low-light (LL) conditions (50 µmol photons m-2 s-1) but was unable to sustain growth under high-light (HL) conditions (400 µmol photons m-2 s-1), revealing a crucial role of Aas in survival under the HL conditions. Several-times larger amounts of FFAs were produced by HL-exposed cultures than LL-grown cultures. Palmitic acid accounted for ∼85% of total FFAs in HL-exposed cultures, while C18 fatty acids (FAs) constituted ∼80% of the FFAs in LL-grown cultures. Since C16 FAs are esterified to the sn-2 position of lipids in the Synechocystis species, it was deduced that HL irradiation activated deacylation of lipids at the sn-2 position. Heterologous expression of FarB, the FFA exporter protein of Neisseria lactamica, prevented intracellular FFA accumulation and rescued the growth defect of the mutant under HL, indicating that intracellular FFA was the cause of growth inhibition. FarB expression also decreased the 'per-cell' yield of FFA under HL by 90% and decreased the proportion of palmitic acid to ∼15% of total FFA. These results indicated that the HL-induced lipid deacylation is triggered not by strong light per se but by HL-induced damage to the cells. It was deduced that there is a positive feedback loop between HL-induced damage and lipid deacylation, which is lethal unless FFA accumulation is prevented by Aas.

Integrated LC-MS metabolomics with dual derivatization for quantification of FFAs in fecal samples of hepatocellular carcinoma patients.

FFAs display pleiotropic functions in human diseases. Short-chain FAs (SCFAs), medium-chain FAs, and long-chain FAs are derived from different origins, and precise quantification of these FFAs is critical for revealing their roles in biological processes. However, accessing stable isotope-labeled internal standards is difficult, and different chain lengths of FFAs challenge the chromatographic coverage. Here, we developed a metabolomics strategy to analyze FFAs based on isotope-free LC-MS-multiple reaction monitoring integrated with dual derivatization. Samples and dual derivatization internal standards were synthesized using 2-dimethylaminoethylamine or dansyl hydrazine as a "light" label and N,N-diethyl ethylene diamine or N,N-diethyldansulfonyl hydrazide as a "heavy" label under mild and efficient reaction conditions. General multiple reaction monitoring parameters were designed to analyze these FFAs. The limit of detection of SCFAs varied from 0.5 to 3 nM. Furthermore, we show that this approach exhibits good linearity (R2 = 0.99374-0.99929), there is no serious substrate interference, and no quench steps are required, confirming the feasibility and reliability of the method. Using this method, we successfully quantified 15 types of SCFAs in fecal samples from hepatocellular carcinoma patients and healthy individuals; among these, propionate, butyrate, isobutyrate, and 2-methylbutyrate were significantly decreased in the hepatocellular carcinoma group compared with the healthy control group. These results indicate that the integrated LC-MS metabolomics with isotope-free and dual derivatization is an efficient approach for quantifying FFAs, which may be useful for identifying lipid biomarkers of cancer.

Impact of curcumin on fatty acid metabolism.

Free fatty acids (FFAs) and fatty acid synthesis (FAS) activity have significantly contributed to disease states such as insulin resistance, obesity, type 2 diabetes, myocardial infarction, blood pressure, and several types of cancer. Currently, several treatment options are available for patients with these conditions. Due to safety concerns, adverse effects, limited efficacy, and low tolerability associated with many medications, the identification of novel agents with less toxicity and a more favorable outcome is warranted. Curcumin is a phenolic compound derived from the turmeric plant with various biological activities, including anticarcinogenic, antioxidant, antiinflammatory, and hypolipidemic properties. PubMed, Scopus, and Web of Science were searched up to February 2020 for studies that demonstrated the efficacy and mechanisms of curcumin action on FFAs, FAS, and ß-oxidation activity, as well as the desaturation system. Most of the evidence is in-vivo and in-vitro studies that demonstrate that curcumin possesses regulatory properties on FFAs levels through its effects on FAS and ß-oxidation activity as well as desaturation system, which could improve insulin resistance, obesity, and other FFAs-related disorders. The present study provides a review of the existing in-vitro, in-vivo, and clinical evidence on the effect of curcumin on FFAs and FAS activity, ß-oxidation, and desaturation system.

Applications of an electronic nose in the prediction of oxidative stability of stored biodiesel derived from soybean and waste cooking oil.

Waste cooking oil (WCO) is a valuable feedstock for the synthesis of biodiesel but the product exhibits poor oxidative stability. Techniques available for assessing this parameter are generally expensive and time-consuming, hence the purpose of this study was to develop and validate a rapid and reliable predictive system based on signals from the sensors of a commercial hand-held e-nose instrument. Biodiesels were synthesized from soybean oil and six samples of WCO, and their physicochemical characteristics and oxidative stabilities determined before and after storage in different types of containers for 30 or 60 days at room temperature or 43 °C. Linear regression models were constructed based on principal component analysis of the signals generated by all 32 e-nose sensors and stochastic modeling of signal profiles from individual sensors. The regression model with principal components as predictors was unable to explain the oxidative stability of biodiesels, while the regression model with stochastic parameters (combining signals from 11 sensors) as predictors showed an excellent goodness of fit (R2 = 0.91) with a 45-sample training set and a good quality of prediction (R2 = 0.84) with a 18-sample validation set. The proposed e-nose system was shown to be accurate and efficient and could be used to advantage by producers/distributors of biodiesel in the assessment fuel quality.

Serum FFAs profile analysis of Normal weight and obesity individuals of Han and Uygur nationalities in China.

BACKGROUND: Han and Uygur are the two main nationalities living in Xinjiang, China. There are significant differences in the incidence of metabolic diseases for two nationalities, but the specific reasons are not clear. Obesity is an important risk factor for the development of metabolic syndrome, which may be closely related to the increase of serum free fatty acids (FFAs) content. This study aims to use metabolomics to compare the changes of serum FFAs profiles between normal weight (NW) and obese (OB) individuals of two nationalities, screening out the differential FFAs, predicting and evaluating their relationship with diseases. METHODS: Thirty-four kinds of FFAs in serum were detected by ultra-high-pressure liquid chromatography-mass spectrometry (UHPLC-MS) and distinctions in FFAs profiles were evaluated using a metabolomics method while Receiver operating characteristics (ROC) and logistic regression models were used to explore FFAs significant for diagnosing obesity and obesity-associated comorbidities. RESULTS: In the Han nationality, ten kinds of FFAs (C7:0, C8:0, C9:0, C10:0, C11:0, C14:0, C18:2, C20:3, C20:4 and C22:6) showed significant differences between NW and OB individuals. These differential FFAs may be related to hypertension and gestational diabetes mellitus. In the Uygur nationality, C20:3 and C20:5 showed significant differences between NW and OB individuals. C9:0 and C19:0, which were screened out among the female subjects, showed a good ability to predict obesity status in Uygur females (AUC = 0.950). CONCLUSION: In both the Han and Uygur nationalities, the FFAs profiles of NW individuals differed from those of OB individuals. The significantly differential FFAs are closely related to obesity and may be important risk factors for obesity and related metabolic diseases.

Intracellular and extracellular miRNome deregulation in cellular models of NAFLD or NASH: Clinical implications.

BACKGROUND & AIMS: Nonalcoholic fatty liver disease (NAFLD) represents the most common chronic liver disease in industrialized countries. NAFLD has the potential to progress through the inflammatory phase of nonalcoholic steatohepatitis (NASH) to fibrosis, cirrhosis, and hepatocellular carcinoma. Identifying patients at risk for this transition is a relevant clinical challenge. The complexity of these phenotypes in vivo made necessary the development of in vitro models in order to dissect the molecular signalling affected in NAFLD and NASH, but also to identify potential circulating biomarkers. METHODS AND RESULTS: We profiled the expression of 754 cellular and medium-secreted human miRNAs in HepG2 cells after lipotoxic (Palmitate, model of NASH) or not-lipotoxic stimuli (Oleate-Palmitate, model of NAFLD). Results were validated through Single TaqMan assays. We performed computational analysis of miRNA targets and pathways. Oleate-palmitate treatment induced a variation of 2.8% and 10% of total miRNAs in cells and medium, respectively; palmitate treatment caused 10% and 19% intracellular and extracellular miRNA deregulation, respectively. We validated miR-126, miR-150, miR-223, miR-483-3p, miR-1226*, and miR-1290 deregulation. Through computational analysis, we observed that targets of both intracellular and extracellular DE miRNAs were involved in processes associated with the onset and progression of NAFLD and NASH, such as fatty acid metabolism, apoptosis and inflammation. CONCLUSIONS: These data would be useful to elucidate the role of miRNAs in the pathogenesis and progression of the NAFLD spectrum, but they also allow the identification of novel potential biomarkers for differential diagnosis to be tested in vivo.

A simple method for isolation and construction of markerless cyanobacterial mutants defective in acyl-acyl carrier protein synthetase.

Cyanobacterial mutants defective in acyl-acyl carrier protein synthetase (Aas) secrete free fatty acids (FFAs) into the external medium and hence have been used for the studies aimed at photosynthetic production of biofuels. While the wild-type strain of Synechocystis sp. PCC 6803 is highly sensitive to exogenously added linolenic acid, mutants defective in the aas gene are known to be resistant to the externally provided fatty acid. In this study, the wild-type Synechocystis cells were shown to be sensitive to lauric, oleic, and linoleic acids as well, and the resistance to these fatty acids was shown to be enhanced by inactivation of the aas gene. On the basis of these observations, we developed an efficient method to isolate aas-deficient mutants from cultures of Synechocystis cells by counter selection using linoleic acid or linolenic acid as the selective agent. A variety of aas mutations were found in about 70 % of the FFA-resistant mutants thus selected. Various aas mutants were isolated also from Synechococcus sp. PCC 7002, using lauric acid as a selective agent. Selection using FFAs was useful also for construction of markerless aas knockout mutants from Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002. Thus, genetic engineering of FFA-producing cyanobacterial strains would be greatly facilitated by the use of the FFAs for counter selection.

Camel milk ameliorates hyperglycaemia and oxidative damage in type-1 diabetic experimental rats.

This study was designed to assess anti-diabetic potential of goat, camel, cow and buffalo milk in streptozotocin (STZ) induced type 1 diabetic albino wistar rats. A total of 48 rats were taken for the study where one group was kept as non-diabetic control group (8 rats) while others (40 rats) were made diabetic by STZ (50 mg/kg of body weight) injection. Among diabetic rats, a control group (8 rats) was kept and referred as diabetic control whereas other four groups (8 rats each) of diabetic rats were fed on 50 ml of goat or camel or cow or buffalo milk for 4 weeks. All the rats (non-diabetic and diabetic) were maintained on standard diet for four weeks. STZ administration resulted in enhancement of glucose, total cholesterol, triglyceride, low density lipoprotein, HbA1c and reduction in high density lipoprotein in plasma and lowering of antioxidative enzymes (catalase, glutathione peroxidase and superoxide dismutase) activities in pancreas, kidney, liver and RBCs, coupled with enhanced levels of TBARS and protein carbonyls in pancreas, kidney, liver and plasma. OGTT carried out at the end of 4 week milk feeding indicated that all milks helped in early maintenance of glucose level. All milks reduced atherogenic index. In camel milk fed diabetic group, insulin concentration enhanced to level noted for non-diabetic control while goat, cow and buffalo milk failed to restore insulin level. HbA1c level was also restored only in camel milk fed diabetic group. The level of antioxidative enzymes (catalase, GPx and SOD) in pancreas enhanced in all milk fed groups. Camel milk and to a reasonable extent goat milk reduced formation of TBARS and PCs in tissues and blood. It can be concluded that camel milk ameliorates hyperglycaemia and oxidative damage in type-1 diabetic experimental rats. Further, only camel milk completely ameliorated oxidative damage in pancreas and normalised insulin level.

tert-Butylhydroquinone (tBHQ) protects hepatocytes against lipotoxicity via inducing autophagy independently of Nrf2 activation.

Saturated fatty acids (SFAs) induce hepatocyte cell death, wherein oxidative stress is mechanistically involved. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a master transcriptional regulator of cellular antioxidant defense enzymes. Therefore, Nrf2 activation is regarded as an effective strategy against oxidative stress-triggered cellular damage. In this study, tert-butylhydroquinone (tBHQ), a widely used Nrf2 activator, was initially employed to investigate the potential protective role of Nrf2 activation in SFA-induced hepatoxicity. As expected, SFA-induced hepatocyte cell death was prevented by tBHQ in both AML-12 mouse hepatocytes and HepG2 human hepatoma cells. However, the protective effect of tBHQ is Nrf2-independent, because the siRNA-mediated Nrf2 silencing did not abrogate tBHQ-conferred protection. Alternatively, our results revealed that autophagy activation was critically involved in the protective effect of tBHQ on lipotoxicity. tBHQ induced autophagy activation and autophagy inhibitors abolished tBHQ's protection. The induction of autophagy by tBHQ exposure was demonstrated by the increased accumulation of LC3 puncta, LC3-II conversion, and autophagic flux (LC3-II conversion in the presence of proteolysis inhibitors). Subsequent mechanistic investigation discovered that tBHQ exposure activated AMP-activated protein kinase (AMPK) and siRNA-mediated AMPK gene silencing abolished tBHQ-induced autophagy activation, indicating that AMPK is critically involved in tBHQ-triggered autophagy induction. Furthermore, our study provided evidence that tBHQ-induced autophagy activation is required for its Nrf2-activating property. Collectively, our data uncover a novel mechanism for tBHQ in protecting hepatocytes against SFA-induced lipotoxicity. tBHQ-triggered autophagy induction contributes not only to its hepatoprotective effect, but also to its Nrf2-activating property.

MicroRNA 375 mediates palmitate-induced enteric neuronal damage and high-fat diet-induced delayed intestinal transit in mice.

BACKGROUND & AIMS: A high-fat diet (HFD) can cause serious health problems, including alteration of gastrointestinal transit, the exact mechanism of which is not clear. Several microRNAs (miRNAs) are involved in energy homeostasis, lipid metabolism, and HFD-induced weight gain. We investigated the role of miRNAs in HFD-induced damage to the enteric nervous system. METHODS: Male mice were fed a HFD (60% calories from fat) or regular diets (18% calories from fat) for 11 weeks. Mice on regular diets and HFDs were given intraperitoneal injections of Mir375 inhibitor or a negative control. Body weights, food intake, stool indices, and gastrointestinal transit (following Evans blue gavage) were measured. An enteric neuronal cell line (immorto-fetal enteric neuronal) and primary enteric neurons were used for in vitro studies. RESULTS: HFD delayed intestinal transit, which was associated with increased apoptosis and loss of colonic myenteric neurons. Mice fed a low-palmitate HFD did not develop a similar phenotype. Palmitate caused apoptosis of enteric neuronal cells associated with mitochondrial dysfunction and endoplasmic reticulum stress. Palmitate significantly increased the expression of Mir375 in vitro; transfection of cells with a Mir375 inhibitor prevented the palmitate-induced enteric neuronal cell apoptosis. Mir375 expression was increased in myenteric ganglia of mice fed HFD and associated with decreased levels of Mir375 target messenger RNAs, including Pdk1. Systemic injection of a Mir375 inhibitor for 5 weeks prevented HFD-induced delay in intestinal transit and morphologic changes. CONCLUSIONS: HFDs delay colonic transit, partly by inducing apoptosis in enteric neuronal cells. This effect is mediated by Mir375 and is associated with reduced levels of Pdk1. Mir375 might be targeted to increase survival of enteric neurons and gastrointestinal motility.

Methyl Cinnamate (MC) Alleviates Free Fatty Acids (FFAs) Induced Lipid Accumulation Through the AMPK Pathway in HepG2 Cells.

Background: AMP-activated protein kinase (AMPK) plays a critical role in energy metabolism. Its activation leads to the phosphorylation of downstream proteins such as acetyl-CoA carboxylase (ACC) and sterol regulatory element-binding protein-1 (SREBP1), subsequently inhibiting de novo fatty acid synthesis, thereby reducing intracellular triglyceride accumulation. MC is a compound found in extracts from Zanthoxylum armatum DC plants. Research has shown that MC can inhibit the differentiation of 3T3-L1 adipocytes through the CAMKK2-AMPK pathway. However, the biological effect of MC in HepG2 cells remains unknown. Methods: In this study, we utilized HepG2 cells to establish a model of MAFLD through FFAs stimulation. We investigated the biological effects of MC on HepG2 cells and studied its impact on lipid metabolism. Small interfering RNA was employed to explore the mechanism by which MC activates AMPK. Finally, molecular docking was conducted, establishing a model of the interaction between AMPK and MC. Results: We observed that MC can alleviate triglyceride accumulation in HepG2 cells. We observed the elevated p-AMPK/AMPK, P-ACC/ ACC, and elevated CPT1a after treatment of MC in HepG2 cells. The interference of CAMKK2 mRNA did not impact the ability of MC to phosphorylate AMPK. Compound C attenuates the ability of MC to increase p-AMPK. Molecular docking results led us to hypothesize that MC directly interacts with AMPK, resulting in AMPK phosphorylation and improved lipid accumulation in HepG2 cells.

The role of hepassocin in the development of non-alcoholic fatty liver disease.

BACKGROUND & AIMS: While non-alcoholic fatty liver disease (NAFLD) is the most common risk factor of chronic liver disease, the mechanisms that initiate its development are obscure. Hepassocin (HPS) is a hepatokine that has been reported to be involved in liver regeneration. In addition to the mitogenic activity of HPS, HPS expression is decreased in patients with hepatoma. However, the role of HPS in NAFLD is still unknown. METHODS: A total of 393 subjects with (n=194) or without (n=199) NAFLD were enrolled to evaluate the serum HPS concentration. In order to clarify the causal inference between HPS and NAFLD, we used experimental animal and cell models. Hepatic overexpression or silencing of HPS was achieved by lentiviral vector delivery in mice and lipofectamine transfection in HepG2 cells. Lipogenesis related proteins were detected by Western blots. The expression of inflammatory factors was determined by real-time polymerase chain reaction. RESULTS: Subjects with NAFLD had a higher serum HPS concentration than those without it. Overexpression of HPS increased hepatic lipid accumulation and NAFLD activity scores (NAS), whereas deletion of HPS improved high fat diet-induced hepatic steatosis and decreased NAS in mice. Additionally, oleic acid, a steatogenic reagent, increased HPS expression in hepatocytes. Furthermore, overexpression of HPS in HepG2 cells induced lipid accumulation through an extracellular signal-regulated kinase 1/2 (ERK1/2)-dependent pathway, whereas deletion of HPS decreased oleic acid-induced lipid accumulation. CONCLUSIONS: The present study provides evidence that HPS plays an important role in NAFLD and induces hepatic lipid accumulation through an ERK1/2-dependent pathway.

Multi-Omics Analysis of Genes Encoding Proteins Involved in Alpha-Linolenic Acid Metabolism in Chicken.

Alpha-linolenic acid (ALA, ω-3) is an antioxidant that reduces triglyceride (TG) levels in blood, a component of cell membranes and a precursor compound of eicosapentaenoic acid (EPA, ω-3) and eicosatrienoic acid (DHA, ω-3). Fatty acid content is a quantitative trait regulated by multiple genes, and the key genes regulating fatty acid metabolism have not been systematically identified. This study aims at investigating the protein-encoding genes regulating ω-3 polyunsaturated fatty acid (PUFA) content in chicken meat. We integrated genomics, transcriptomics and lipidomics data of Jingxing yellow chicken (JXY) to explore the interactions and associations among multiple genes involved in the regulation of fatty acid metabolism. Several key genes and pathways regulating ω-3 fatty acid metabolism in chickens were identified. The upregulation of GRB10 inhibited the mTOR signaling pathway, thereby improving the content of EPA and DHA. The downregulation of FGFR3 facilitated the conversion of ALA to EPA. Additionally, we analyzed the effects of ALA supplementation dose on glycerol esters (GLs), phospholipid (PL) and fatty acyl (FA) contents, as well as the regulatory mechanisms of nutritional responses in FFA metabolism. This study provides a basis for identifying genes and pathways that regulate the content of FFAs, and offers a reference for nutritional regulation systems in production.

Rapid and sensitive determination of free fatty acids based on in-source microdroplet-driven derivatization coupled with high-resolution mass spectrometry.

Accurate and sensitive measurements of free fatty acids (FFAs) in biological samples are valuable for diagnosing and prognosing diseases. In this study, an in-source microdroplet derivation strategy combined with high-resolution mass spectrometry was developed to analyze FFAs in lipid extracts of biological samples directly. FFAs were rapidly derivated with 2-picolylamine (PA) in the microdroplet which is derived by electrospray. With the proposed method, twelve typical FFAs were determined reliably with high sensitivity and acceptable linearities (R2 ≥ 0.94). The LODs and LOQs for the twelve FFAs were 9-76 pg mL-1 and 30-253 pg mL-1, respectively. The developed method was applied to analyze the alteration of FFAs in liver and kidney samples of rats induced by perfluorooctane sulfonate (PFOS) exposure. The good results demonstrate that the established analysis technique is dependable and has promising applications in detecting FFAs associated with complex biological samples.

Adipocytes in obesity: A perfect reservoir for SARS-CoV-2?

Research evidence suggests that adipocytes in obesity might facilitate SARS-CoV-2 replication, for it was only found in adipose tissue of individuals with overweight or obesity but not lean individuals who died from COVID-19. As lipid metabolism is key to adipocyte function, and viruses are capable of exploiting and manipulating lipid metabolism of host cells for their own benefit of infection, we hypothesize that adipocytes could not only impair host immune defense against viral infection, but also facilitate SARS-CoV-2 entry, replication and assembly as a reservoir to boost the viral infection in obesity. The latter of which could mainly be mediated by SARS-CoV-2 hijacking the abnormal lipid metabolism in the adipocytes. If these were to be confirmed, an approach to combat COVID-19 in people with obesity by taking advantage of the abnormal lipid metabolism in adipocytes might be considered, as well as modifying lipid metabolism of other host cells as a potential adjunctive treatment for COVID-19.

Encapsulation of resveratrol-loaded Pickering emulsions in alginate/pectin hydrogel beads: Improved stability and modification of digestive behavior in the gastrointestinal tract.

In this study, alginate/pectin hydrogel beads were prepared with different mixing ratios (9:1, 8:2, 7:3, 6:4, and 5:5) to encapsulate resveratrol-loaded Pickering emulsions using Ca2+ crosslinking. The system with a suitable ratio of pectin and alginate can enhance the encapsulation efficiency and loading capacity. Scanning electron microscopy (SEM) study confirmed that the hydrogel beads were spherical, in which Pickering emulsion was distributed evenly within the polymer network. Fourier Transform Infrared Spectroscopy (FTIR) study indicated that the hydrogel beads were formed by physical cross-linking. X-ray diffraction (XRD) study demonstrated that resveratrol existed in hydrogel beads with an amorphous or dissolved form. Besides, the stability and antioxidant capacity suggested that hydrogel beads could offer protection to resveratrol by preventing degradation through environmental stresses, while maintaining its antioxidant capacity. Importantly, hydrogels significantly reduced the release of free fatty acids and resveratrol during in vitro digestion compared to emulsions, especially with the appropriate ratio of sodium alginate and pectin. Overall, Pickering emulsions-loaded alginate/pectin hydrogel beads could offer a novel option for the preparation of low-calorie foods and a potential substitute model for controlling the release of free fatty acids contributing to the transportation of resveratrol.

Potential low-calorie model that inhibits free fatty acid release and helps curcumin deliver in vitro: Ca2+-induced emulsion gels from low methyl-esterified pectin with the presence of erythritol.

Our previous study showed that pectin de-esterified by high hydrostatic pressure assisted enzymatic method (HHP-pectin) had better Ca2+-induced gel performance and more stable emulsion than those from conventional enzymatic and alkaline methods. In this study, Ca2+-induced emulsion gels were further prepared by HHP-pectin in the presence of erythritol, and their texture properties, moisture distribution, the release of free fatty acids (FFAs) and curcumin were investigated. Results showed that gel strength, gel elasticity, and water cut-off capacity of the prepared emulsion gels significantly increased with Ca2+ concentration increasing. Compared with emulsions, HHP-pectin emulsion gels can significantly decrease FFAs and curcumin release in vitro digestion, especially for samples with better texture properties (higher Ca2+ concentration). This study indicated that Ca2+-induced HHP-pectin emulsion gels prepared with erythritol may provide a new choice for low-calorie foods preparing, and may become a potential alternative model that inhibiting FFAs release and helping fat-soluble nutrients (curcumin) deliver.

RNA-seq Based Transcriptome Analysis Reveals The Cross-Talk of Macrophage and Adipocyte of Chicken Subcutaneous Adipose Tissue during The Embryonic and Post-Hatch Period.

With high fecundity and short production cycle, poultry is one of the important sources of meat. During the embryonic and post-hatch period, the higher death rate caused huge economic losses in poultry production. Our previous study showed that chick subcutaneous adipose tissue is an important energy supply tissue besides yolk. Therefore, the metabolic mechanism of subcutaneous adipose tissue in chicks could provide a new perspective of brooding. The objectives of the current study were to evaluate the differences between chick subcutaneous adipose tissue and abdominal adipose tissue before and after hatching and reveal the cross-talk of different cells within the chick subcutaneous adipose tissue. The results of RNA-seq and weighted gene co-expression network analysis (WGCNA) of chick subcutaneous and abdominal adipose tissues showed that the function of chick subcutaneous tissue was related to immunoreaction, and macrophage could be the major immune infiltration cell type in chicken subcutaneous adipose tissue, which were also verified by qPCR, HE stain, and IHC. The results of free fatty acids (FFAs)-induced the cross-talk between macrophages and adipocytes showed that FFAs-Ccl2 (chicken CCL26) axis could have an important role in lipid transportation in adipose tissue. The results of Oil Red O and Nile red stain demonstrated that macrophages have the ability to absorb FFAs quickly. Interestingly, according to the genomic organization of CCL family with representative vertebrate species, we found that chicken CCL26 could be the major chemokine in chicken adipocyte as the status of CCL2 in mammal adipocyte. In conclusion, we demonstrate that FFA-induced Ccl2 (chicken CCL26) secretion is crucial in determining fat depot-selective adipose tissue macrophage (ATM) infiltration, which could be an important medium of lipid transportation in chicken subcutaneous adipose tissue. These findings may have multiple important implications for understanding macrophage biology with chick subcutaneous adipose tissue and provide theoretical basis for lipid metabolism in poultry brooding.