The life cycle of neutral lipids: synthesis, storage and degradation

Membranes that make fat: roles of membrane lipids as acyl donors for triglyceride synthesis and organelle function

Triglycerides constitute an inert storage form for fatty acids deposited in lipid droplets and are mobilized to provide metabolic energy or membrane building blocks. The biosynthesis of triglycerides is highly conserved within eukaryotes and normally involves the sequential esterification of activated fatty acids with a glycerol backbone. Some eukaryotes, however, can also use cellular membrane lipids as direct fatty acid donors for triglyceride synthesis. The biological significance of a pathway that generates triglycerides at the expense of organelle membranes has remained elusive. Here we review current knowledge on how cells use membrane lipids as fatty acid donors for triglyceride synthesis and discuss the hypothesis that a primary function of this pathway is to regulate membrane lipid remodeling and organelle function.

Accumulation of neutral lipids in dystrophic neurites surrounding amyloid plaques in Alzheimer's disease

Alzheimer's disease (AD) is characterized by the formation β-amyloid (Aβ) deposited neuritic plaques. Recent evidence suggests that abnormal lipid metabolism and accumulation could serve as biomarkers for neurodegenerative diseases, including AD. Tubular endoplasmic reticulum protein, reticulon 3 (RTN3), plays a crucial role in the development of neuritic plaque and lipid metabolism in AD brains. In present study, we sought to investigate a potential association between neutral lipid accumulation and AD pathology. BODIPY 500/510 dye was used to label neutral lipid surrounding Aβ plaques in APPNL-G-F mouse and AD postmortem brains samples. Immunofluorescent images were captured using confocal microscope and co-localization between lipid metabolism proteins and neutral lipids were evaluated. Lipid accumulation in Aβ plaque surrounding dystrophic neurites (DNs) was observed in the cortical region of AD mouse models and human AD brain samples. The neutral lipid staining was not co-localized with IBA1-labeled microglia or GFAP-labeled astrocytes, but it was co-labeled with VAMP2 and neurofilament. We further showed that neutral lipids were accumulated in RTN3 immunoreactive DNs. Both the neutral lipids accumulation and RIDNs formation showed age-dependent patterns in surrounding amyloid plaques. Mechanistic studies revealed that RTN3 likely contributes to the enrichment of neutral lipids near plaques by interacting with heat shock cognate protein 70 (HSC70) and diminishing its function in chaperone-mediated lipophagy. Our study provides immunohistochemical evidence of neutral lipids being enriched in DNs near amyloid plaques. Our findings shed light on RTN3-mediaed lipid accumulation in AD neuropathology and provide fresh insights into the role of RTN3 in neurodegenerative diseases.

Exploring the oxidative rancidity mechanism and changes in volatile flavors of watermelon seed kernels based on lipidomics

Watermelon seed kernels (WSK) are prone to oxidative rancidity, while their evaluation biomarkers and changes in volatile flavor are still unknown. The research tracked the changes in volatile compounds and lipid components before and after rancidity using HS-SPME-GC-O-MS and lipidomic techniques. The results showed the flavor of watermelon seed kernels changed significantly before and after rancidity, from mild aroma to rancidity. A total of 42 volatile compounds were detected via GC-O-MS, and a total of 220 lipid molecules were detected via lipidomic technology. 55 lipids with significant differences were screened via multivariate statistical analysis. Combining the above analysis, it found that glycerol phospholipid and glyceride pathways were the most important metabolic pathways and 1-Pentanol and styrene could be used as potential biomarkers to judge the rancidity process of watermelon seed kernels. The research could provide powerful technical support for the storage, transportation and freshness preservation of watermelon seed kernels.

Allele-dependent expression and functionality of lipid enzyme phospholipid:diacylglycerol acyltransferase affect diatom carbon storage and growth

In the acyl-CoA-independent pathway of triacylglycerol (TAG) synthesis unique to plants, fungi, and algae, TAG formation is catalyzed by the enzyme phospholipid:diacylglycerol acyltransferase (PDAT). The unique PDAT gene of the model diatom Phaeodactylum tricornutum strain CCMP2561 boasts 47 single nucleotide variants within protein coding regions of the alleles. To deepen our understanding of TAG synthesis, we observed the allele-specific expression of PDAT by the analysis of 87 published RNA-sequencing (RNA-seq) data and experimental validation. The transcription of one of the two PDAT alleles, Allele 2, could be specifically induced by decreasing nitrogen concentrations. Overexpression of Allele 2 in P. tricornutum substantially enhanced the accumulation of TAG by 44% to 74% under nutrient stress; however, overexpression of Allele 1 resulted in little increase of TAG accumulation. Interestingly, a more serious growth inhibition was observed in the PDAT Allele 1 overexpression strains compared with Allele 2 counterparts. Heterologous expression in yeast (Saccharomyces cerevisiae) showed that enzymes encoded by PDAT Allele 2 but not Allele 1 had TAG biosynthetic activity, and 7 N-terminal and 3 C-terminal amino acid variants between the 2 allele-encoded proteins substantially affected enzymatic activity. P. tricornutum PDAT, localized in the innermost chloroplast membrane, used monogalactosyldiacylglycerol and phosphatidylcholine as acyl donors as demonstrated by the increase of the 2 lipids in PDAT knockout lines, which indicated a common origin in evolution with green algal PDATs. Our study reveals unequal roles among allele-encoded PDATs in mediating carbon storage and growth in response to nitrogen stress and suggests an unsuspected strategy toward lipid and biomass improvement for biotechnological purposes.

Coarse-graining of perplexity for the spatial distribution of molecules

Biological tissue consists of various molecules. Instead of focusing on a particular molecule, we consider the Shannon entropy which is calculated from the abundance of different molecules at each spot in the tissue. The spatial distribution of the Shannon entropy is of interest. In this paper, we first obtain the heat map of perplexity, whose logarithm is the entropy. To characterize the spatial variety of molecules, we propose a scalar k that is concerned with the coarse-graining of the perplexity heat map. To verify the usefulness of the number, experiments with mass spectrometry imaging were performed for mouse kidneys. We found that k has large values in the renal pelvis area, cortex area, veins, and arteries in the mouse kidney, whereas fractal dimensions fail to distinguish those regions.

Faecal metabolome responses to an altered dietary protein:carbohydrate ratio in adult dogs

High-protein diets may aid weight loss and weight maintenance programs in both humans and dogs, although the effect of dietary protein levels on gut metabolism and functionality has not been studied in depth. The current study aimed to investigate the effect of an altered dietary protein:carbohydrate ratio on gut function in adult dogs by means of faecal metabolomic fingerprinting. More specifically, functional metabolic differences in dogs fed a high-protein/low-carbohydrate (HPLC) vs. low-protein/high-carbohydrate (LPHC) diet were studied by equally allocating twelve clinically healthy (6 lean and 6 obese) Beagles into two groups in a cross-over design, with each group receiving two isocaloric diets for four weeks. The faecal metabolome revealed that different protein:carbohydrate ratio can influence host and/or gut microbiome metabolism and function, while no effect was observed on the body condition. Targeted analysis demonstrated that the HPLC diet significantly increased the concentration of indole, spermidine, and pipecolinic acid and decreased the concentration of azelaic acid, D-fructose, mannose, and galactose (p < 0.05). Multivariate modelling (OPLS-DA) of the untargeted faecal metabolome revealed distinctly different metabolomic profiles following the HPLC vs. LPHC diet, with 18 altered pathways. The HPLC diet influenced amino acid and lipid metabolism, potentially promoting weight loss and immune function, whereas the LPHC diet affected carbohydrate fermentation and may promote anti-oxidative function.

Lipidomic features of honey bee and colony health during limited supplementary feeding

Honey bee nutritional health depends on nectar and pollen, which provide the main source of carbohydrates, proteins and lipids to individual bees. During malnutrition, insect metabolism accesses fat body reserves. However, this process in bees and its repercussions at the colony level are poorly understood. Using untargeted lipidomics and gene expression analysis, we examined the effects of different feeding treatments (starvation, sugar feeding and sugar + pollen feeding) on bees and correlated them with colony health indicators. We found that nutritional stress led to an increase in unsaturated triacylglycerols and diacylglycerols, as well as a decrease in free fatty acids in the bee fat body. Here, we hypothesise that stored lipids are made available through a process where unsaturations change lipid's structure. Increased gene expression of three lipid desaturases in response to malnutrition supports this hypothesis, as these desaturases may be involved in releasing fatty acyl chains for lipolysis. Although nutritional stress was evident in starving and sugar-fed bees at the colony and physiological level, only starved colonies presented long-term effects in honey production.

TRPV4 enhances the synthesis of fatty acids to drive the progression of ovarian cancer through the calcium-mTORC1/SREBP1 signaling pathway

Transient receptor potential vanilloid 4 (TRPV4) is a nonselective cation channel activated by various stimuli, such as heat. A recent study reported that high expression of TRPV4 predicted a poor prognosis in ovarian cancer patients. This study demonstrated that TRPV4 was highly expressed in ovarian cancer and had the ability to promote proliferation and migration. Through RNA-seq and related experiments, we confirmed that the oncogenic pathway of TRPV4 in ovarian cancer may be related to the fatty acid synthesis. By correlation analysis and RNA-seq, we demonstrated that SREBP1 and mTORC1 were inseparably related to that. Therefore, we used inhibitors to perform experiments. Calcium fluorescent probe experiments suggest that the change of calcium content in ovarian cancer cells was related to the downstream mTORC1 signaling pathway and fatty acid synthesis. These results confirmed that TRPV4 affected the fatty acid synthesis through the calcium-mTOR/SREBP1 signaling pathway, thereby promoting ovarian cancer progression.

The transcription factor CREB3-2 regulated neutral lipase gene expression in ovary of Nilaparvata lugens

The cyclic AMP-responsive element-binding protein 3 (CREB3) members have unique regulatory roles in cellular lipid metabolism as transcription factors. Two CREB3 proteins in Nilaparvata lugens were identified and analyzed. In ovary, when silencing NlCREB3-2, triacylglycerol (TAG) content dramatically increased but glycerol and free fatty acid (FFA) significantly decreased, which implicated that NlCREB3-2 was involved in the lipase-related TAG metabolism. In N. lugens, five neutral lipases with complete features for TAG hydrolytic activity and high expression in ovary were focused. Among them, the expression levels of three neutral lipase genes were significantly down-regulated by NlCREB3-2 RNAi. The direct regulation of NlCREB3-2 towards the three neutral lipase genes was evidenced by the dual-luciferase reporter assay. After jointly silencing three neutral lipase genes, TAG and glycerol contents displayed similar changes as NlCREB3-2 RNAi. The study proved that NlCREB3-2 participated in TAG metabolism in ovary via the direct activation towards the ovary-specific neutral lipase genes.

Transcriptome and Metabolome Analyses of Thitarodes xiaojinensis in Response to Ophiocordyceps sinensis Infection

Ophiocordyceps sinensis exhibits more than 5 months of vegetative growth in Thitarodes xiaojinensis hemocoel. The peculiar development process of O. sinensis has been elucidated through morphological observation and omics technology; however, little information has been reported regarding the changes that occur in the host T. xiaojinensis. The RNA sequencing data showed that when O. sinensis blastospores were in the proliferative stage, the greatest change in the infected larval fat body was the selectively upregulated immune recognition and antimicrobial peptide genes. When O. sinensis blastospores were in the stationary stage, the immune pathways of T. xiaojinensis reverted to normal levels, which coincides with the successful settlement of O. sinensis. Pathway enrichment analysis showed a higher expression of genes involved in energy metabolism pathway in this stage. Metabolomic analyses revealed a reduction of amino acids and lipids in hemolymph, but an upregulation of lipids in the fat body of the host larvae after O. sinensis infection. We present the first transcriptome integrated with the metabolome study of T. xiaojinensis infected by O. sinensis. It will improve our understanding of the interaction mechanisms between the host and entomopathogenic fungi, and facilitate future functional studies of genes and pathways involved in these interactions.

Development of a high polarity-sensitive fluorescent probe for visualizing the lipid droplets and endoplasmic reticulum with dual colors in living cells

Lipid droplets (LDs) are unique organelles that control the lipid metabolism in cells. It has been identified that the generations of LDs derive from endoplasmic reticulum (ER) and they have closely related with amount of cellular activities for maintaining homeostasis. To further explore the detail interactions between LDs and ER, we have developed a novel polarity-sensitive fluorescent probe LP with distinct D-π-A-π-D framework and applied it to imaging LDs and ER with dual colors at the same time. Probe LP showed well red-shifted emissions with the increase fraction of water in the 1,4- dioxane due to ICT process. In biological imaging, probe LP could visualize LDs and ER with green and red fluorescence separately. Besides, the dynamic behaviors of LDs and ER were achieved using LP during the oleic acids and starvation stimulations. Therefore, probe LP is a valuable molecular tool for investigating the relationships of LDs and ER in various cellular activities.

Characterization of neutral lipases revealed the tissue-specific triacylglycerol hydrolytic activity in Nilaparvata lugens

The lipid metabolism plays an essential role in the development and reproduction of insects, and lipases are important enzymes in lipid metabolism. In Nilaparvata lugens, an important insect pest on rice, triacylglycerol hydrolytic activities were different among tissues, with high activity in integument, ovary, and fat body, but low activity in intestine. To figure out the tissue-specific triacylglycerol hydrolytic activity, we identified 43 lipases in N. lugens. Of these 43 lipases, 23 belonged to neutral lipases, so this group was selected to perform further experiments on triacylglycerol hydrolysis. The complete motifs of catalytic triads, β9 loop, and lid motif, are required for the triacylglycerol hydrolytic activity in neutral lipases, which were found in some neutral lipases with high gene expression levels in integument and ovary, but not in intestine. The recombinant proteins of 3 neutral lipases with or without 3 complete motifs were obtained, and the activity determination confirmed the importance of 3 motifs. Silencing XM_022331066.1, which is highly expressed in ovary and with 3 complete motifs, significantly decreased the egg production and hatchability of N. lugens, partially through decline of the lipid metabolism. In summary, at least one-third of important motifs were incomplete in all neutral lipases with high gene expression in intestine, which could partially explain why the lipase activity in intestine was much lower than that in other tissues. The low activity to hydrolyze triacylglycerol in N. lugens intestine might be associated with its food resource and nutrient components, and the ovary-specific neutral lipases were important for N. lugens reproduction.

A Plasmodium falciparum lysophospholipase regulates host fatty acid flux via parasite lipid storage to enable controlled asexual schizogony

Phospholipid metabolism is crucial for membrane biogenesis and homeostasis of Plasmodium falciparum. To generate such phospholipids, the parasite extensively scavenges, recycles, and reassembles host lipids. P. falciparum possesses an unusually large number of lysophospholipases, whose roles and importance remain to be elucidated. Here, we functionally characterize one P. falciparum lysophospholipase, PfLPL3, to reveal its key role in parasite propagation during asexual blood stages. PfLPL3 displays a dynamic localization throughout asexual stages, mainly localizing in the host-parasite interface. Inducible knockdown of PfLPL3 disrupts parasite development from trophozoites to schizont, inducing a drastic reduction in merozoite progenies. Detailed lipidomic analyses show that PfLPL3 generates fatty acids from scavenged host lipids to generate neutral lipids. These are then timely mobilized to allow schizogony and merozoite formation. We then identify inhibitors of PfLPL3 from Medicine for Malaria Venture (MMV) with potent antimalarial activity, which could also serve as pertinent chemical tools to study parasite lipid synthesis.

Lipidomic Analysis of Liver Lipid Droplets after Chronic Alcohol Consumption with and without Betaine Supplementation

The earliest manifestation of alcohol-associated liver disease is hepatic steatosis, which is characterized by fat accumulation in specialized organelles called lipid droplets (LDs). Our previous studies reported that alcohol consumption elevates the numbers and sizes of LDs in hepatocytes, which is attenuated by simultaneous treatment with the methyl group donor, betaine. Here, we examined changes in the hepatic lipidome with respect to LD size and dynamics in male Wistar rats fed for 6 weeks with control or ethanol-containing liquid diets that were supplemented with or without 10 mg betaine/mL. At the time of sacrifice, three hepatic LD fractions, LD1 (large droplets), LD2 (medium-sized droplets), and LD3 (small droplets) were isolated from each rat. Untargeted lipidomic analyses revealed that each LD fraction of ethanol-fed rats had higher phospholipids, cholesteryl esters, diacylglycerols, ceramides, and hexosylceramides compared with the corresponding fractions of pair-fed controls. Interestingly, the ratio of phosphatidylcholine to phosphatidylethanolamine (the two most abundant phospholipids on the LD surface) was lower in LD1 fraction compared with LD3 fraction, irrespective of treatment; however, this ratio was significantly lower in ethanol LD fractions compared with their respective control fractions. Betaine supplementation significantly attenuated the ethanol-induced lipidomic changes. These were mainly associated with the regulation of LD surface phospholipids, ceramides, and glycerolipid metabolism in different-sized LD fractions. In conclusion, our results show that ethanol-induced changes in the hepatic LD lipidome likely stabilizes larger-sized LDs during steatosis development. Furthermore, betaine supplementation could effectively reduce the size and dynamics of LDs to attenuate alcohol-associated hepatic steatosis.

Anti-inflammatory properties of neutral lipids, glycolipids, and phospholipids isolated from Ammodytes personatus eggs in LPS-stimulated RAW264.7 cells

In the present study, total lipids were extracted from Ammodytes personatus eggs and separated into neutral lipids, glycolipids, and phospholipids. The anti-inflammatory activity of the neutral lipids, glycolipids, and phospholipids was investigated in macrophages, as well as the fatty acid profiles of the lipids. Palmitic acid, oleic acid, docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) were the primary fatty acids in the three fractionated lipids. Among the lipids, the phospholipids contained the highest concentration of polyunsaturated fatty acids (PUFAs), particularly DHA and EPA (31.89 and 16.93% of the total fatty acids, respectively). The anti-inflammatory effects of the three lipids isolated from A. personatus eggs were analyzed in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The three lipids significantly reduced nitric oxide (NO) production and the mRNA expression of immune-associated genes in a dose-dependent manner. All lipids down-regulated the protein expression of phosphorylated NF-κB-p65 and MAPK (p38, JNK, and ERK1/2) signaling pathways, suggesting that they could inhibit cell signaling pathways by activating NF-κB and MAPK. The expression of CD40 and CD86 in LPS-stimulated RAW264.7 cells was also significantly decreased by A. personatus lipids. Consequently, the neutral lipids, glycolipids, and phospholipids from A. personatus eggs could serve as anti-inflammatory agents.

Neuronal calcium sensor 2 is key to moulting and oocyte development in the brown planthopper, Nilaparvata lugens

Intracellular calcium (Ca²⁺ ) is vital for signal transduction in many cellular events. Several Ca²⁺ -binding proteins mediate the transduction of intracellular calcium signals. The EF-hand motifs containing neuronal calcium sensor (NCS) proteins are mainly expressed in the nervous system, where they have important roles in the regulation of a variety of neuronal functions. NCS1 has four EF-hand motifs and well-defined neuronal development functions in a variety of eukaryotes. However, NCS2 has only been identified in invertebrates such as insects and nematodes thus far. The functions of NCS2 remain largely unknown. Here, we identified an orthologous NCS2 in the hemipteran Nilaparvata lugens. Based on qRT-PCR, this gene was found to be primarily expressed in the brain. Knockdown of NCS2 in each nymphal instar by RNA interference led to lethality and caused aggradation and disordered arrangement of lipid droplets in the ovaries and testes of adults, which were associated with the absence of mature oocytes in female ovaries and reduction of spermiation in male adults. Our findings revealed a novel function for NCS2 as a regulator in development and reproduction and suggested that this protein had an important role in modulating lipid droplet remodelling in ovary and testis of N. lugens adults.

Role of Lipids in Phosphine Resistant Stored-Grain Insect Pests Tribolium castaneum and Rhyzopertha dominica

Insects rely on lipids as an energy source to perform various activities, such as growth, flight, diapause, and metamorphosis. This study evaluated the role of lipids in phosphine resistance by stored-grain insects. Phosphine resistant and susceptible strains of the two main stored-grain insects, Tribolium castaneum and Rhyzopertha dominica, were analyzed using liquid chromatography-mass spectroscopy (LC-MS) to determine their lipid contents. Phosphine resistant strains of both species had a higher amount of lipids than susceptible stains. Significant variance ratios between the resistant and susceptible strains of T. castaneum were observed for glycerolipids (1.13- to 53.10-fold) and phospholipids (1.05- to 20.00-fold). Significant variance ratios between the resistant and susceptible strains of R. dominica for glycerolipids were 1.04- to 31.50-fold and for phospholipids were 1.04- to 10.10-fold. Glycerolipids are reservoirs to face the long-term energy shortage. Phospholipids act as a barrier to isolate the cells from the surrounding environment and allow each cell to perform its specific function. Thus, lipids offer a consistent energy source for the resistant insect to survive under the stress of phosphine fumigation and provide a suitable environment to protect the mitochondria from phosphine. Hence, it was proposed through this study that the lipid content of phosphine-resistant and phosphine-susceptible strains of T. castaneum and R. dominica could play an important role in the resistance of phosphine.

Interplay between Lipid Metabolism, Lipid Droplets, and DNA Virus Infections

Lipid droplets (LDs) are cellular organelles rich in neutral lipids such as triglycerides and cholesterol esters that are coated by a phospholipid monolayer and associated proteins. LDs are known to play important roles in the storage and availability of lipids in the cell and to serve as a source of energy reserve for the cell. However, these structures have also been related to oxidative stress, reticular stress responses, and reduced antigen presentation to T cells. Importantly, LDs are also known to modulate viral infection by participating in virus replication and assembly. Here, we review and discuss the interplay between neutral lipid metabolism and LDs in the replication cycle of different DNA viruses, identifying potentially new molecular targets for the treatment of viral infections.

Exposure to polystyrene nanoplastics impairs lipid metabolism in human and murine macrophages in vitro

The use of polystyrene micro and nanoplastics in cosmetics and personal care products continues to grow every day. The harmful effects of their biological accumulation in organisms of all trophic levels including humans have been reported by several studies. While we have accumulating evidence on the impact of nanoplastics on different organ systems in humans, only a handful of reports on the impact of polystyrene nanoplastics upon direct contact with the immune system at the cellular level are avialable. The present study offers significant evidence on the cell-specific harmful impact of sulfate-modified nanoplastics (S-NPs) on human macrophages. Here we report that exposure of human macrophages to S-NPs (100 µg/mL) stimulated the accumulation of lipids droplets (LDs) in the cytoplasm resulting in the differentiation of macrophages into foam cells. The observed effect was specific for human and murine macrophages but not for other cell types, especially human keratinocytes, liver, and lung cell models. Furthermore, we found that S-NPs mediated LDs accumulation in human macrophages was accompanied by acute mitochondrial oxidative stress. The accumulated LDs were further delivered and accumulated into lysosomes leading to impaired lysosomal clearance. In conclusion, our study reveals that exposure to polystyrene nanoplastics stabilized with anionic surfactants can be a potent stimulus for dysregulation of lipid metabolism and macrophage foam cell formation, a characteristic feature observed during atherosclerosis posing a serious threat to human health.

ATPase subunits of the 26S proteasome are important for oocyte maturation in the brown planthopper

The 26S proteasome is the major engine of protein degradation in all eukaryotic cells. Adenosine triphosphatase (ATPase) regulatory subunits (Rpts) are constituents of the proteasome that are involved in the unfolding and translocation of substrate proteins into the core particle. In this study, by using the brown planthopper Nilaparvata lugens as a model insect, we report the biological importance of Rpts in female reproduction. We identified six homologous Rpt genes (Rpt1-6) in N. lugens. These genes were detected at high transcript levels in eggs and ovaries of females but at low transcript levels in males. RNA interference-mediated knockdown of N. lugens Rpt genes significantly decreased the proteolytic activity of the proteasome and impeded the transcription of triacylglycerol lipase and vitellogenin genes in the fat bodies and ovaries of adult females and reduced the triglyceride content in the ovaries. The decrease in the proteolytic activity of the proteasome via knockdown of Rpts also downregulated the transcription of the CYP307A2 gene encoding an important rate-limiting enzyme in the 20-hydroxyecdysone biosynthetic pathway in the ovaries, reduced 20E production in adult females and impaired ovarian development and oocyte maturation, leading to the failure of egg production and egg-laying. These novel findings indicate that Rpts are required for the proteolytic activity of the proteasome, which is important for female reproductive success in N. lugens.

Comprehensive lipidomics analysis of the lipids in hazelnut oil during storage

Although hazelnut oil is is nutritious, it is easily oxidized during storage. Thus far, changes in lipids during storage have not been comprehensively analyzed. Here, we used ultra-high liquid chromatography tandem quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) to dynamically monitor the lipid composition of hazelnut oil during accelerated storage for 24 d. A total of 10 subclasses of 103 lipids were identified. After 24 d, the content of triacylglycerol, diacylglycerol, phosphatidic acid, phosphatidylethanolamine, phosphatidylethanol, ceramide, and total lipids decreased significantly (P < 0.05). A total of 51 significantly different lipids were screened (Variable Importance in Projection > 1, P < 0.05), and these lipids could be used as biomarkers to distinguish fresh and oxidized hazelnut oil. We also detected seven most important pathways by bioinformatics analysis to explore the mechanism underlying changes. Our results provide useful information for future applications of hazelnut oil and provide new insight into edible oil oxidation.

Transcriptomic Analysis of the Pistacia vera (L.) Fruits Enable the Identification of Genes and Hormone-Related Gene Linked to Inflorescence Bud Abscission

Pistacia vera (L.) is an alternate bearing species. The tree produces axillary inflorescence buds every year. Still, they abscise in “ON” overloaded shoots, causing a limited production in the following “OFF” year, causing a significant and unfavorable production fluctuation. In this work, we carried out de novo discovery and transcriptomic analysis in fruits of “ON” and “OFF” shoots of the cultivar Bianca. We also investigated whether the fruit signaling pathway and hormone biosynthesis directly or indirectly linked to the premature fall of the inflorescence buds causing alternate bearing. We identified 1536 differentially expressed genes (DEGs) in fruits of “ON” vs. “OFF” shoots, which are involved primarily in sugar metabolism, plant hormone pathways and transcription factors. The premature bud abscission linked to the phenomenon is attributable to a lack of nutrients (primarily sugar) and the possible competition between the same branches’ sinks (fruits vs. inflorescence buds). Hormone pathways are involved as a response to signals degradation and remobilization of carbon and nutrients due to the strengthening of the developing embryos. Genes of the secondary metabolism and transcription factors are also involved in tailoring the individual branches response to the nutritional stress and sink competition. Crosstalk among sugar and various hormone-related genes, e.g., ethylene, auxin, ABA and cytokinin, were determined. The discovery of putative biomarkers like callose synthase 5, trehalose-6-phosphate synthase, NAD(P)-linked oxidoreductase and MIOX2, Jasmonate, and salicylic acid-related genes can help to design precision farming practices to mitigate the alternate bearing phenomenon to increase farming profitability. The aim of the analysis is to provide insight into the gene expression profiling of the fate of “ON” and “OFF” fruits associated with the alternate bearing in the pistachio.

An MD-2-related lipid-recognition protein is required for insect reproduction and integument development

The myeloid differentiation factor 2 (MD-2)-related lipid-recognition protein is involved in immune responses through recognizing bacteria lipopolysaccharide in mammals, arthropods and plants. However, the physiological roles of MD-2 in other biological processes are largely unknown. Here, we identified three homologue MD-2 genes (NlML1, NlML2 and NlML3) by searching the genome and transcriptome databases of the brown planthopper Nilaparvata lugens, a hemipteran insect species. Temporospatial analysis showed that the NlML1 gene was highly expressed in the fat body but much less so in the other tissues, while the NlML2 and NlML3 genes were highly expressed in the testis or digestive tract. RNA interference-mediated depletion of the NlML1 gene significantly downregulated the transcription of numerous integument protein genes. The NlML1 knockdown led to moulting failure and mortality at the nymph-adult transition phase, impaired egg laying and hatching, and reduced 20-hydroxyecdysone (20E) production in the nymphs. 20E could rescue the deficient moulting phenotypes derived from dsNlML1 RNAi. These novel findings indicate that NlML1 is required for nymphal moulting and female reproductive success as it plays an important role in regulating 20E synthesis, lipid and chitin metabolisms in N. lugens, thus contributing to our understanding of developmental and reproductive mechanisms in insects.

Lipid Metabolism, Disorders and Therapeutic Drugs - Review

Different lifestyles have an impact on useful metabolic functions, causing disorders. Different lipids are involved in the metabolic functions that play various vital roles in the body, such as structural components, storage of energy, in signaling, as biomarkers, in energy metabolism, and as hormones. Inter-related disorders are caused when these functions are affected, like diabetes, cancer, infections, and inflammatory and neurodegenerative conditions in humans. During the Covid-19 period, there has been a lot of focus on the effects of metabolic disorders all over the world. Hence, this review collectively reports on research concerning metabolic disorders, mainly cardiovascular and diabetes mellitus. In addition, drug research in lipid metabolism disorders have also been considered. This review explores lipids, metabolism, lipid metabolism disorders, and drugs used for these disorders.

Functions of elements in soil microorganisms

The soil microbial community fulfils various functions, such as nutrient cycling and carbon (C) sequestration, therefore contributing to maintenance of soil fertility and mitigation of global warming. In this context, a major focus of research has been on C, nitrogen (N) and phosphorus (P) cycling. However, from aquatic and other environments, it is well known that other elements beyond C, N, and P are essential for microbial functioning. Nonetheless, for soil microorganisms this knowledge has not yet been synthesised. To gain a better mechanistic understanding of microbial processes in soil systems, we aimed at summarising the current knowledge on the function of a range of essential or beneficial elements, which may affect the efficiency of microbial processes in soil. This knowledge is discussed in the context of microbial driven nutrient and C cycling. Our findings may support future investigations and data evaluation, where other elements than C, N, and P affect microbial processes.

An essential vesicular-trafficking phospholipase mediates neutral lipid synthesis and contributes to hemozoin formation in Plasmodium falciparum

Background

Plasmodium falciparum is the pathogen responsible for the most devastating form of human malaria. As it replicates asexually in the erythrocytes of its human host, the parasite feeds on haemoglobin uptaken from these cells. Heme, a toxic by-product of haemoglobin utilization by the parasite, is neutralized into inert hemozoin in the food vacuole of the parasite. Lipid homeostasis and phospholipid metabolism are crucial for this process, as well as for the parasite’s survival and propagation within the host. P. falciparum harbours a uniquely large family of phospholipases, which are suggested to play key roles in lipid metabolism and utilization.

Results

Here, we show that one of the parasite phospholipase (P. falciparum lysophospholipase, PfLPL1) plays an essential role in lipid homeostasis linked with the haemoglobin degradation and heme conversion pathway. Fluorescence tagging showed that the PfLPL1 in infected blood cells localizes to dynamic vesicular structures that traffic from the host-parasite interface at the parasite periphery, through the cytosol, to get incorporated into a large vesicular lipid rich body next to the food-vacuole. PfLPL1 is shown to harbour enzymatic activity to catabolize phospholipids, and its transient downregulation in the parasite caused a significant reduction of neutral lipids in the food vacuole-associated lipid bodies. This hindered the conversion of heme, originating from host haemoglobin, into the hemozoin, and disrupted the parasite development cycle and parasite growth. Detailed lipidomic analyses of inducible knock-down parasites deciphered the functional role of PfLPL1 in generation of neutral lipid through recycling of phospholipids. Further, exogenous fatty-acids were able to complement downregulation of PfLPL1 to rescue the parasite growth as well as restore hemozoin levels.

Conclusions

We found that the transient downregulation of PfLPL1 in the parasite disrupted lipid homeostasis and caused a reduction in neutral lipids essentially required for heme to hemozoin conversion. Our study suggests a crucial link between phospholipid catabolism and generation of neutral lipids (TAGs) with the host haemoglobin degradation pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01042-z.

Adipokine and fat body in flies: Connecting organs

Under conditions of nutritional and environmental stress, organismal homeostasis is preserved through inter-communication between multiple organs. To do so, higher organisms have developed a system of interorgan communication through which one tissue can affect the metabolism, activity or fate of remote organs, tissues or cells. In this review, we discuss the latest findings emphasizing Drosophila melanogaster as a powerful model organism to study these interactions and may constitute one of the best documented examples depicting the long-distance communication between organs. In flies, the adipose tissue appears to be one of the main organizing centers for the regulation of insect development and behavior: it senses nutritional and hormonal signals and in turn, orchestrates the release of appropriate adipokines. We discuss the nature and the role of recently uncovered adipokines, their regulations by external cues, their secretory routes and their modes of action to adjust developmental growth and timing accordingly. These findings have the potential for identification of candidate factors and signaling pathways that mediate conserved interorgan crosstalk.

Segmentation of the subcuticular fat body in Apis mellifera females with different reproductive potentials

Evolution has created different castes of females in eusocial haplodiploids. The difference between them lies in their functions and vulnerability but above all in their reproductive potentials. Honeybee queens are highly fertile. On the other hand, the workers are facultatively sterile. However, rebel workers, i.e. workers that develop in a queenless colony, reproduce more often than normal workers. As a result, the fat body of these bees, which apart from acting as the energy reserve, is also the site of numerous metabolic processes, had to specialize in different functions perfected over millions of years of eusocial evolution. Assuming that the variety of functions manifests itself in the pleomorphic structure of the fat body cells, we predicted that also different parts of the fat body, e.g. from different segments of the abdomen, contain different sets of cells. Such differences could be expected between queens, rebels and normal workers, i.e. females with dramatically different reproductive potentials. We confirmed all these expectations. Although all bees had the same types of cells, their proportion and segmental character corresponded with the caste reproductive potential and physiological characteristics shaped in the evolutionary process. The females with an increased reproductive potential were characterized by the presence of oenocytes in the third tergite and high concentrations of compounds responsible for energy reserves, like glucose, glycogen and triglycerides. Queens had very large trophocytes, especially in the third tergite. Only in workers did we observe intercellular spaces in all the segments of the fat body, as well as high protein concentrations-especially in the sternite. As expected, the rebels combined many features of the queens and normal workers, what with other findings can help understand the ways that led to the origin of different castes in females of eusocial Hymenoptera.

Fat Body-Multifunctional Insect Tissue

Simple Summary

Efficient and proper functioning of processes within living organisms play key roles in times of climate change and strong human pressure. In insects, the most abundant group of organisms, many important changes occur within their tissues, including the fat body, which plays a key role in the development of insects. Fat body cells undergo numerous metabolic changes in basic energy compounds (i.e., lipids, carbohydrates, and proteins), enabling them to move and nourish themselves. In addition to metabolism, the fat body is involved in the development of insects by determining the time an individual becomes an adult, and creates humoral immunity via the synthesis of bactericidal proteins and polypeptides. As an important tissue that integrates all signals from the body, the processes taking place in the fat body have an impact on the functioning of the entire body.

Abstract

The biodiversity of useful organisms, e.g., insects, decreases due to many environmental factors and increasing anthropopressure. Multifunctional tissues, such as the fat body, are key elements in the proper functioning of invertebrate organisms and resistance factors. The fat body is the center of metabolism, integrating signals, controlling molting and metamorphosis, and synthesizing hormones that control the functioning of the whole body and the synthesis of immune system proteins. In fat body cells, lipids, carbohydrates and proteins are the substrates and products of many pathways that can be used for energy production, accumulate as reserves, and mobilize at the appropriate stage of life (diapause, metamorphosis, flight), determining the survival of an individual. The fat body is the main tissue responsible for innate and acquired humoral immunity. The tissue produces bactericidal proteins and polypeptides, i.e., lysozyme. The fat body is also important in the early stages of an insect’s life due to the production of vitellogenin, the yolk protein needed for the development of oocytes. Although a lot of information is available on its structure and biochemistry, the fat body is an interesting research topic on which much is still to be discovered.

Role of arachidonic cascade in COVID-19 infection: A review

The World Health Organization has described the 2019 Coronavirus disease caused by an influenza-like virus called SARS-CoV-2 as a pandemic. Millions of people worldwide are already infected by this virus, and severe infection causes hyper inflammation, thus disrupting lung function, exacerbating breath difficulties, and death. Various inflammatory mediators bio-synthesized through the arachidonic acid pathway play roles in developing cytokine storms, injuring virus-infected cells. Since pro-inflammatory eicosanoids, including prostaglandins, and leukotrienes, are key brokers for physiological processes such as inflammation, fever, allergy, and pain but, their function in COVID-19 is not well defined. This study addresses eicosanoid's crucial role through the arachidonic pathway in inflammatory cascading and recommends using bioactive lipids, NSAIDs, steroids, cell phospholipase A2 (cPLA2) inhibitors, and specialized pro-resolving mediators (SPMs) to treat COVID-19 disease. The role of soluble epoxide hydrolase inhibitors (SEHIs) in promoting the activity of epoxyeicosatrienoic acids (EETs) and 17-hydroxide-docosahexaenoic acid (17-HDHA) is also discussed. Additional research that assesses the eicosanoid profile in COVID-19 patients or preclinical models generates novel insights into coronavirus-host interaction and inflammation regulation.

Vitamin E Derivative with Modified Side Chain Induced Apoptosis by Modulating the Cellular Lipids and Membrane Dynamics in MCF7 Cells

The vitamin E derivative with side chain modification (TC6OAc) has been shown to possess anticancer activity in our earlier in vivo studies. It was hypothesized that, as Vitamin E (VE) and VE derivative are fat soluble lipophilic molecules, they exert their function by modulating the lipid metabolism and related pathways. This study aimed to evaluate the cellular impact of this VE derivative (2,5,7,8-Tetramethyl-2-(4'-Methyl-3'-Pentenyl)-6-Acetoxy Chromane-TC6OH), using α-tocopherol as a reference compound throughout the experiments. Their effects on the cellular metabolism, the biophysical properties of cellular lipids and the functional characteristics of cells were monitored in human estrogen receptor (ER) positive breast cancer cells. It has been documented that TC6OH treatment induces tumor cell apoptosis by dissipating the mitochondrial membrane potential, modulating the lipid, transportation and degradation as well as downregulating certain anti-apoptotic and growth factor related proteins. Due to resistance of ER positive cells to the established therapies, the findings of this study are of translational value.

Significance of two intracellular triacylglycerol lipases of Aspergillus oryzae in lipid mobilization: A perspective in industrial implication for microbial lipid production

Microbial lipid production of oleaginous strains involves in a complex cellular metabolism controlling lipid biosynthesis, accumulation and degradation. Particular storage lipid, triacylglycerol (TAG), contributes to dynamic traits of intracellular lipids and cell growth. To explore a basis of TAG degradation in the oleaginous strain of Aspergillus oryzae, the functional role of two intracellular triacylglycerol lipases, AoTgla and AoTglb, were investigated by targeted gene disruption using CRISPR/Cas9 system. Comparative lipid profiling of different cultivation stages between the control, single and double disruptant strains (ΔAotgla, ΔAotglb and ΔAotglaΔAotglb strains) showed that the inactivation of either AoTgla or AoTglb led to the increase of total lipid contents, particularly in the TAG fraction. Moreover, the prolonged lipid-accumulating stage of all disruptant strains was obtained as indicated by a reduction in specific rate of lipid turnover, in which a holding capacity in maximal lipid and TAG levels was achieved. The involvement of AoTgls in spore production of A. oryzae was also discovered. In addition to the significance in lipid physiology of the oleaginous fungi, this study provides an impact on industrial practice by overcoming the limitation in short lipid-accumulating stage of the fungal strain, which facilitate the cell harvesting step at the maximum lipid production yield.

Anopheles coluzzii stearoyl-CoA desaturase is essential for adult female survival and reproduction upon blood feeding

Vitellogenesis and oocyte maturation require anautogenous female Anopheles mosquitoes to obtain a bloodmeal from a vertebrate host. The bloodmeal is rich in proteins that are readily broken down into amino acids in the midgut lumen and absorbed by the midgut epithelial cells where they are converted into lipids and then transported to other tissues including ovaries. The stearoyl-CoA desaturase (SCD) plays a pivotal role in this process by converting saturated (SFAs) to unsaturated (UFAs) fatty acids; the latter being essential for maintaining cell membrane fluidity amongst other housekeeping functions. Here, we report the functional and phenotypic characterization of SCD1 in the malaria vector mosquito Anopheles coluzzii. We show that RNA interference (RNAi) silencing of SCD1 and administration of sterculic acid (SA), a small molecule inhibitor of SCD1, significantly impact on the survival and reproduction of female mosquitoes following blood feeding. Microscopic observations reveal that the mosquito thorax is quickly filled with blood, a phenomenon likely caused by the collapse of midgut epithelial cell membranes, and that epithelial cells are depleted of lipid droplets and oocytes fail to mature. Transcriptional profiling shows that genes involved in protein, lipid and carbohydrate metabolism and immunity-related genes are the most affected by SCD1 knock down (KD) in blood-fed mosquitoes. Metabolic profiling reveals that these mosquitoes exhibit increased amounts of saturated fatty acids and TCA cycle intermediates, highlighting the biochemical framework by which the SCD1 KD phenotype manifests as a result of a detrimental metabolic syndrome. Accumulation of SFAs is also the likely cause of the potent immune response observed in the absence of infection, which resembles an auto-inflammatory condition. These data provide insights into mosquito bloodmeal metabolism and lipid homeostasis and could inform efforts to develop novel interventions against mosquito-borne diseases.

Female mosquitoes can become infected with malaria parasites upon ingestion of blood from an infected person and can transmit the disease when they bite another person some days later. The bloodmeal is rich in proteins which female mosquitoes use to develop their eggs after converting them first to saturated and then to unsaturated fatty acids inside their gut cells. Here, we present the characterization of the enzyme that mosquitoes use to convert saturated to unsaturated fatty acids and show that when this enzyme is eliminated or inhibited mosquitoes cannot produce eggs and die soon after they feed on blood. The mosquito death appears to be primarily associated with the collapse of their gut epithelial barrier due to the loss of cell membrane integrity, leading to their inner body cavity being filled with the ingested blood. These mosquitoes also suffer from an acute and detrimental auto-inflammatory condition due to mounting of a potent immune response in the absence of any infection. We conclude that this enzyme and the mechanism of converting blood-derived proteins to unsaturated fatty acids as a whole can be a good target of interventions aiming at limiting the mosquito abundance and blocking malaria transmission.

Comparison of neutral lipid fatty acid composition in organisms from different trophic levels

The profiles of total fatty acids (TFAs) and the neutral lipid fatty acids (NLFAs) were compared for the bacterium Rhodopirellula rubra and the alga Raphidocelis subcapitata (conventional food source for Daphnia magna). D. magna NLFAs were assessed when this crustacean was fed with bacterium and alga, individually or in combination. After NLFA extraction, the profiles of the various organisms were characterized by gas chromatography. Results evidenced the relevance of the different composition of the fatty acid (FAs) fractions in the different organisms, R. rubra and R. subcapitata. In these species, the NFLA analyses revealed high amounts of long chain FAs (C₁₉). The FA profile of D. magna was influenced by the different diets provided although the preferred diet was the alga. D. magna showed the capacity to adapt to the available food resources as it defines its FA profile according to its needs, namely for the long chain FAs (C₁₉).

Proteolytic activity of the proteasome is required for female insect reproduction

Non-ATPase regulatory subunits (Rpns) are components of the 26S proteasome involved in polyubiquitinated substrate recognition and deubiquitination in eukaryotes. Here, we identified 15 homologues sequences of Rpn and associated genes by searching the genome and transcriptome databases of the brown planthopper, Nilaparvata lugens, a hemipteran rice pest. Temporospatial analysis showed that NlRpn genes were significantly highly expressed in eggs and ovaries but were less-highly expressed in males. RNA interference-mediated depletion of NlRpn genes decreased the proteolytic activity of proteasome and impeded the transcription of lipase and vitellogenin genes in the fat bodies and ovaries in adult females, and reduced the triglyceride content in the ovaries. Decrease of the proteolytic activity of the proteasome via knockdown of NlRpns also inhibited the transcription of halloween genes, including NlCYP307A2, NlCYP306A2 and NlCYP314A1, in the 20-hydroxyecdysone (20E) biosynthetic pathway in the ovaries, reduced 20E production in adult females, and impaired ovarian development and oocyte maturation, resulting in reduced fecundity. These novel findings indicate that the proteolytic activity of the proteasome is required for female reproductive processes in N. lugens, thus furthering our understanding of the reproductive and developmental strategies in insects.

Oestrogen replacement fails to fully revert ovariectomy-induced changes in adipose tissue monoglycerides, diglycerides and cholesteryl esters of rats fed a lard-enriched diet

Menopause may be accompanied by abdominal obesity and inflammation, conditions accentuated by high-fat intake, especially of saturated fat (SFA)-rich diets. We investigated the consequences of high-SFA intake on the fatty acid (FA) profile of monoglycerides, diglycerides and cholesteryl esters from retroperitoneal white adipose tissue (RET) of rats with ovariectomy-induced menopause, and the effect of oestradiol replacement. Wistar rats were either ovariectomized (Ovx) or sham operated (Sham) and fed either standard chow (C) or lard-enriched diet (L) for 12 weeks. Half of the Ovx rats received 17β-oestradiol replacement (Ovx + E2). Body weight and food intake were measured weekly. RET neutral lipids were chromatographically separated and FAs analysed by gas chromatography. Ovariectomy alone increased body weight, feed efficiency, RET mass, leptin and insulin levels, leptin/adiponectin ratio, HOMA-IR and HOMA-β indexes. OvxC + E2 showed attenuation in nearly all blood markers. HOMA-β index was restored in OvxL + E2. OvxC showed significantly disturbed SFA and polyunsaturated FA (PUFA) profile in RET cholesteryl esters (CE). OvxC also showed increased monounsaturated FA (MUFA) in the monoglyceride diglyceride (Mono-Di) fraction. Similar changes were not observed in OvxL, although increased SFA and decreased PUFA was observed in Mono-Di. Overall, HRT was only partially able to revert changes induced by ovariectomy. There appears to be increased mobilization of essential FA in Ovx via CE, which is a dynamic lipid species. The same results were not found in Mono-Di, which are more inert. HRT may be helpful to preserve FA profile in visceral fat, but possibly not wholly sufficient in reverting the metabolic effects induced by menopause.

Functional characterization of an novel acyl-CoA:diacylglycerol acyltransferase 3-3 (CsDGAT3-3) gene from Camelina sativa

Diacylglycerol acyltransferases (DGAT) catalyze the final committed step of de novo biosynthesis of triacylglycerol (TAG) in plant seeds. This study was to functionally characterize DGAT3 genes in Camelina sativa, an important oil crops accumulating high levels of unsaturated fatty acids (UFAs) in seeds. Three camelina DGAT3 genes (CsDGAT3-1, CsDGAT3-2 and CsDGAT3-3) were identified, and the encoded proteins were predicted to be cytosolic-soluble proteins present as a homodimer containing the 2Fe-2S domain. They had divergent expression patterns in various tissues, suggesting that they may function in tissue-specific manner with CsDGAT3-1 in roots, CsDGAT3-2 in flowers and young seedlings, and CsDGAT3-3 in developing seeds. Functional complementation assay in yeast demonstrated that CsDGAT3-3 restored TAG synthesis. TAG content and UFAs, particularly eicosenoic acid (EA, 20:1n-9) were largely increased by adding exogenous UFAs in the yeast medium. Further heterogeneously transient expression in N. benthamiana leaves and seed-specific expression in tobacco seeds indicated that CsDGAT3-3 significantly enhanced oil and UFA accumulation with much higher level of EA. Overall, CsDGAT3-3 exhibited a strong abilty catalyzing TAG synthesis and high substrate preference for UFAs, especially for 20:1n-9. The present data provide new insights for further understanding oil biosynthesis mechanism in camelina seeds, indicating that CsDGAT3-3 may have practical applications for increasing both oil yield and quality.

UV-Induced Reduction of ACVR1C Decreases SREBP1 and ACC Expression by the Suppression of SMAD2 Phosphorylation in Normal Human Epidermal Keratinocytes

Activin A receptor type 1C (ACVR1C), a type I transforming growth factor-β (TGF-β) receptor, has been implicated in sensitive skin and psoriasis and is involved in the regulation of metabolic homeostasis as well as cell proliferation and differentiation. In this study, we identified a novel role of ACVR1C in the ultraviolet (UV)-irradiation-induced reduction of epidermal lipogenesis in human skin. UV irradiation decreased ACVR1C expression and epidermal triglyceride (TG) synthesis in human skin in vivo and in primary normal human epidermal keratinocytes (NHEK) in vitro. Lipogenic genes, including genes encoding acetyl-CoA carboxylase (ACC) and sterol regulatory element binding protein-1 (SREBP1), were significantly downregulated in UV-irradiated NHEK. ACVR1C knockdown by shRNA resulted in greater decreases in SREBP1 and ACC in response to UV irradiation. Conversely, the overexpression of ACVR1C attenuated the UV-induced decreases in SREBP1 and ACC. Further mechanistic study revealed that SMAD2 phosphorylation mediated the ACVR1C-induced lipogenic gene modulation. Taken together, a decrease in ACVR1C may cause UV-induced reductions in SREBP1 and ACC as well as epidermal TG synthesis via the suppression of SMAD2 phosphorylation. ACVR1C may be a target for preventing or treating UV-induced disruptions in lipid metabolism and associated skin disorders.

The Diapause Lipidomes of Three Closely Related Beetle Species Reveal Mechanisms for Tolerating Energetic and Cold Stress in High-Latitude Seasonal Environments

During winter insects face energetic stress driven by lack of food, and thermal stress due to sub-optimal and even lethal temperatures. To survive, most insects living in seasonal environments such as high latitudes, enter diapause, a deep resting stage characterized by a cessation of development, metabolic suppression and increased stress tolerance. The current study explores physiological adaptations related to diapause in three beetle species at high latitudes in Europe. From an ecological perspective, the comparison is interesting since one species (Leptinotarsa decemlineata) is an invasive pest that has recently expanded its range into northern Europe, where a retardation in range expansion is seen. By comparing its physiological toolkit to that of two closely related native beetles (Agelastica alni and Chrysolina polita) with similar overwintering ecology and collected from similar latitude, we can study if harsh winters might be constraining further expansion. Our results suggest all species suppress metabolism during diapause and build large lipid stores before diapause, which then are used sparingly. In all species diapause is associated with temporal shifts in storage and membrane lipid profiles, mostly in accordance with the homeoviscous adaptation hypothesis, stating that low temperatures necessitate acclimation responses that increase fluidity of storage lipids, allowing their enzymatic hydrolysis, and ensure integral protein functions. Overall, the two native species had similar lipidomic profiles when compared to the invasive species, but all species showed specific shifts in their lipid profiles after entering diapause. Taken together, all three species show adaptations that improve energy saving and storage and membrane lipid fluidity during overwintering diapause. While the three species differed in the specific strategies used to increase lipid viscosity, the two native beetle species showed a more canalized lipidomic response, than the recent invader. Since close relatives with similar winter ecology can have different winter ecophysiology, extrapolations among species should be done with care. Still, range expansion of the recent invader into high latitude habitats might indeed be retarded by lack of physiological tools to manage especially thermal stress during winter, but conversely species adapted to long cold winters may face these stressors as a consequence of ongoing climate warming.

Dengue virus dominates lipid metabolism modulations in Wolbachia-coinfected Aedes aegypti

Competition between viruses and Wolbachia for host lipids is a proposed mechanism of Wolbachia-mediated virus blocking in insects. Yet, the metabolomic interaction between virus and symbiont within the mosquito has not been clearly defined. We compare the lipid profiles of Aedes aegypti mosquitoes bearing mono- or dual-infections of the Wolbachia wMel strain and dengue virus serotype 3 (DENV3). We found metabolic signatures of infection-induced intracellular events but little evidence to support direct competition between Wolbachia and virus for host lipids. Lipid profiles of dual-infected mosquitoes resemble those of DENV3 mono-infected mosquitoes, suggesting virus-driven modulation dominates over that of Wolbachia. Interestingly, knockdown of key metabolic enzymes suggests cardiolipins are host factors for DENV3 and Wolbachia replication. These findings define the Wolbachia-DENV3 metabolic interaction as indirectly antagonistic, rather than directly competitive, and reveal new research avenues with respect to mosquito × virus interactions at the molecular level.

Koh, Islam, Ye et al. describe lipid profiles of Aedes aegypti mosquitoes bearing mono- or dual-infections of Wolbachia (wMel) and dengue virus serotype 3 (DENV3), finding that virus modulation dominates the dual-infection lipid profile and that cardiolipins support DENV3 and Wolbachia replication. This study suggests that direct competition for lipids do not underlie Wolbachia-mediated virus blocking.

Inhibiting diacylglycerol acyltransferase-1 reduces lipid biosynthesis in bovine blastocysts produced in vitro

Diacylglycerol acyltransferase-1 (DGAT1) is one of the DGAT enzymes that catalyzes the final step in the synthesis of triacylglycerol, which is a major component of the lipid droplets in embryos. Intracellular lipids accumulated in embryos produced in vitro have been associated with reduced cryotolerance and quality. The objective of the present study was to investigate the influence of DGAT1 inhibition on embryo development, quality, and post-vitrification survival, in addition to expression profiles of selected lipid metabolism-regulating and oxidative stress genes. Bovine cumulus-oocyte complexes were matured and fertilized in vitro and were cultured in synthetic oviduct fluid (SOF) supplemented with 5% fetal calf serum (FCS) alone (Control) or with 1, 5, 10 or 50 μM DGAT1 inhibitor (A922500®; D1, D5, D10, and D50, respectively) or 0.1% dimethyl sulfoxide (CDMSO: vehicle for DGAT1 inhibitor dilution) from 54 h post-insemination until Day 8 post insemination. No differences were found in blastocyst yield on days 7 and 8 in Control, CDMSO, D10, and D50 groups. Embryos cultured with 10 or 50 μM DGAT1 inhibitor had greater mitochondrial activity (P < 0.01), and increased number of cells (P < 0.05), while the cytoplasmic lipid content was reduced (P < 0.01), the latter associated with altered expression profiles of selected genes regulating lipid metabolism or genes related with oxidative stress (transcript abundance increased for SLC2A1 and SLC2A5 and decreased for DGAT1 and GPX1). Importantly, the survival rate of blastocysts produced with 10 μM DGAT1 was higher than that of Control, CDMSO and D50 groups at 72 h after vitrification and warming (73.8 vs 57.1, 55.9 and 56.1%, respectively, P < 0.001). In conclusion, inhibition of DGAT1 synthesis in bovine embryos produced in vitro abrogates the negative effect of FCS by decreasing their lipid content, increasing mitochondria activity and improving embryo cryotolerance, as well as favoring the expression of lipid metabolism regulating and oxidative stress-related transcripts.

Green-lipped mussel (Perna canaliculus) hemocytes: A flow cytometric study of sampling effects, sub-populations and immune-related functions

Green-lipped mussels (Perna canaliculus) are a commercially and culturally important bivalve species in New Zealand (NZ). As the highest value export aquaculture product in NZ, understanding and safeguarding the health of this species is imperative. The identification and characterization of hemocytes can provide useful information regarding the health of this species. Using flow cytometry (FCM), the present study assessed for the first time the use of different antiaggregant solutions and storage times on the immune-related parameters of hemocytes from cultured adult P. canaliculus. In addition, characterization of the immune-related functions of hemocyte sub-populations within the hemolymph were assessed. The two antiaggregant solutions tested (Modified Alserver's, MAS, A and B) maintained similar numbers of hemocytes in circulation over a 60 min period but, reduced the viability (MAS A) and increased the ROS production (MAS B) of the hemocytes compared to hemocytes diluted in cold filtered seawater (FSW). Hemocytes diluted in FSW and kept on ice showed significant aggregation after 2 h and a reduction in viability from 4 h. Three different hemocyte sub-populations were identified, discernible by their relative size and internal complexity: blast-like cells, hyalinocytes and granulocytes, which accounted for approximately 4, 67 and 29% of the total hemolymph population respectively. Granulocytes showed significantly higher reactive oxygen species production, phagocytic capabilities and neutral lipid content compared to hyalinocytes and blast-like cells. Results indicate that maintaining extracted hemolymph in cold FSW, completing analysis of fresh samples within 2 h of extraction and FCM assay incubation times of no longer than 30 min are best to obtain accurate results. Formalin fixation can also be used for future determination of hemocyte sub-populations and internal structures. Results from this study will allow effective future study of the effects of various stressors on P. canaliculus health and lead to improved management and production strategies in this species.

Physicochemical Properties and Liposomal Formulations of Hydrolysate Fractions of Four Sea Cucumbers (Holothuroidea: Echinodermata) from the Northwestern Algerian Coast

To promote the nutritional and pharmacological values of four sea cucumber species (Holothuria poli, H. tubulosa, H. arguinensis, and H. sanctori), harvested from the Algerian coast, we aimed to study their proximate composition, fatty acid profile and angiotensin-converting enzyme (ACE) inhibitory activity. Their phospholipids were also used to elaborate nanoliposomes and to encapsulate peptides obtained from the same source. After the physico-chemical characterization of nanoliposomes and peptides, in vitro analyses were realized. The four holothurian species showed a high amount of protein (49.26-69.34%), and an impressive lipid profile of 27 fatty acids, mainly composed of polar fatty acids (91.16-93.85%), with a high polyunsaturated fatty acids (PUFA) content (50.90-71.80%), particularly eicosapentaenoic acid (EPA) (5.07-8.76%) and docosahexaenoic acid (DHA) (4.86-7.25%). A high phospholipids amount was also found (55.20-69.85%), mainly composed of phosphatidylcholine (PC) (51.48-58.56%). Their peptide fractions exhibited a high ACE inhibitory activity (IC50 0.30 to 0.51 mg/mL). The results also showed that the nanoliposomes do not induce cytotoxicity and cell death in human MSCs and no perturbation of proliferation for all the times and the tested concentrations, as well as the combined nanoliposomes and hydrolysates (HTS) at a concentration of 0.1 mg/mL. All four sea cucumbers show potential as a new source for omega-3, omega-6, and bioactive peptides.

The Fifth WS/DGAT Enzyme of the Bacterium Marinobacter aquaeolei VT8

Wax esters (WE) belong to the class of neutral lipids. They are formed by an esterification of a fatty alcohol and an activated fatty acid. Dependent on the chain length and desaturation degree of the fatty acid and the fatty alcohol moiety, WE can have diverse physicochemical properties. WE derived from monounsaturated long-chain acyl moieties are of industrial interest due to their very good lubrication properties. Whereas WE were obtained in the past from spermaceti organs of the sperm whale, industrial WE are nowadays mostly produced chemically from fossil fuels. In order to produce WE more sustainably, attempts to produce industrial WE in transgenic plants are steadily increasing. To achieve this, different combinations of WE producing enzymes are expressed in developing Arabidopsis thaliana or Camelina sativa seeds. Here we report the identification and characterization of a fifth wax synthase from the organism Marinobacter aquaeolei VT8, MaWSD5. It belongs to the class of bifunctional wax synthase/acyl-CoA:diacylglycerol O-acyltransferases (WSD). The protein was purified to homogeneity. In vivo and in vitro substrate analyses revealed that MaWSD5 is able to synthesize WE but no triacylglycerols. The protein produces WE from saturated and monounsaturated mid- and long-chain substrates. Arabidopsis thaliana seeds expressing a fatty acid reductase from Marinobacter aquaeolei VT8 and MaWSD5 produce WE. Main WE synthesized are 20:1/18:1 and 20:1/20:1. This makes MaWSD5 a suitable candidate for industrial WE production in planta.

Dynamic miRNA-mRNA interactions coordinate gene expression in adult Anopheles gambiae

microRNAs (miRNAs) are increasingly recognized as important regulators of many biological processes in mosquitoes, vectors of numerous devastating infectious diseases. Identification of bona fide targets remains the bottleneck for functional studies of miRNAs. In this study, we used CLEAR-CLIP assays to systematically analyze miRNA-mRNA interactions in adult female Anopheles gambiae mosquitoes. Thousands of miRNA-target pairs were captured after direct ligation of the miRNA and its cognate target transcript in endogenous Argonaute–miRNA–mRNA complexes. Using two interactions detected in this manner, miR-309-SIX4 and let-7-kr-h1, we demonstrated the reliability of this experimental approach in identifying in vivo gene regulation by miRNAs. The miRNA-mRNA interaction dataset provided an invaluable opportunity to decipher targeting rules of mosquito miRNAs. Enriched motifs in the diverse targets of each miRNA indicated that the majority of mosquito miRNAs rely on seed-based canonical target recognition, while noncanonical miRNA binding sites are widespread and often contain motifs complementary to the central or 3’ ends of miRNAs. The time-lapse study of miRNA-target interactomes in adult female mosquitoes revealed dynamic miRNA regulation of gene expression in response to varying nutritional sources and physiological demands. Interestingly, some miRNAs exhibited flexibility to use distinct sequences at different stages for target recognition. Furthermore, many miRNA-mRNA interactions displayed stage-specific patterns, especially for those genes involved in metabolism, suggesting that miRNAs play critical roles in precise control of gene expression to cope with enormous physiological demands associated with egg production. The global mapping of miRNA-target interactions contributes to our understanding of miRNA targeting specificity in non-model organisms. It also provides a roadmap for additional studies focused on regulatory functions of miRNAs in Anopheles gambiae.

Metazoan miRNAs typically bind to partially complementary sites in their target mRNAs. The interactions between miRNAs and target RNAs are generally stage-specific and context-dependent. Thus, identification of authentic miRNA targets remains a big challenge. Target identification is even more difficult in mosquitoes where miRNA-mRNA pairing rules are poorly characterized. Using an experimental approach, this study captures thousands of endogenous miRNA-target interactions in female mosquitoes at several critical stages during adult reproduction. Analyses of the target sequences reveal how individual miRNAs accomplish their target recognition in mosquitoes. Interestingly, many mosquito miRNAs exhibit flexibility to use distinct sequences at different stages to pair with their targets, greatly altering target selectivity and expanding target repertoire of miRNAs. Drastic changes in mRNA abundance have been previously reported when adult female mosquitoes attend to varying nutritional sources and physiological demands. The temporal patterns of miRNA-target interactions obtained in this study provide new insights into the roles of miRNAs in tightly controlled gene expression associated with blood-feeding and mosquito oogenesis.