Genetic architecture of seed glycerolipids in Asian cultivated rice.

Glycerolipids are essential for rice development and grain quality but its genetic regulation remains unknown. Here we report its genetic base using metabolite-based genome-wide association study and metabolite-based quantitative traits locus (QTL) analyses based on lipidomic profiles of seeds from 587 Asian cultivated rice accessions and 103 chromosomal segment substitution lines, respectively. We found that two genes encoding phosphatidylcholine (PC):diacylglycerol cholinephosphotransferase (OsLP1) and granule-bound starch synthase I (Waxy) contribute to variations in saturated triacylglycerol (TAG) and lyso-PC contents, respectively. We demonstrated that allelic variation in OsLP1 sequence between indica and japonica results in different enzymatic preference for substrate PC-16:0/16:0 and different saturated TAG levels. Further evidence demonstrated that OsLP1 also affects heading date, and that co-selection of OsLP1 and a flooding-tolerant QTL in Aus results in the abundance of saturated TAGs associated with flooding tolerance. Moreover, we revealed that the sequence polymorphisms in Waxy has pleiotropic effects on lyso-PC and amylose content. We proposed that rice seed glycerolipids have been unintentionally shaped during natural and artificial selection for adaptive or import seed quality traits. Collectively, our findings provide valuable genetic resources for rice improvement and evolutionary insights into seed glycerolipid variations in rice.

Gemfibrozil-Induced Intracellular Triglyceride Increase in SH-SY5Y, HEK and Calu-3 Cells.

Gemfibrozil is a drug that has been used for over 40 years to lower triglycerides in blood. As a ligand for peroxisome proliferative-activated receptor-alpha (PPARα), which is expressed in many tissues, it induces the transcription of numerous genes for carbohydrate and lipid-metabolism. However, nothing is known about how intracellular lipid-homeostasis and, in particular, triglycerides are affected. As triglycerides are stored in lipid-droplets, which are known to be associated with many diseases, such as Alzheimer's disease, cancer, fatty liver disease and type-2 diabetes, treatment with gemfibrozil could adversely affect these diseases. To address the question whether gemfibrozil also affects intracellular lipid-levels, SH-SY5Y, HEK and Calu-3 cells, representing three different metabolically active organs (brain, lung and kidney), were incubated with gemfibrozil and subsequently analyzed semi-quantitatively by mass-spectrometry. Importantly, all cells showed a strong increase in intracellular triglycerides (SH-SY5Y: 170.3%; HEK: 272.1%; Calu-3: 448.1%), suggesting that the decreased triglyceride-levels might be due to an enhanced cellular uptake. Besides the common intracellular triglyceride increase, a cell-line specific alteration in acylcarnitines are found, suggesting that especially in neuronal cell lines gemfibrozil increases the transport of fatty acids to mitochondria and therefore increases the turnover of fatty acids for the benefit of additional energy supply, which could be important in diseases, such as Alzheimer's disease.

Specific triacylglycerol, diacylglycerol, and lyso-phosphatidylcholine species for the prediction of type 2 diabetes: a ~ 16-year prospective study in Chinese.

BACKGROUND: Bioactive lipids play an important role in insulin secretion and sensitivity, contributing to the pathophysiology of type 2 diabetes (T2D). This study aimed to identify novel lipid species associated with incident T2D in a nested case-control study within a long-term prospective Chinese community-based cohort with a median follow-up of ~ 16 years. METHODS: Plasma samples from 196 incident T2D cases and 196 age- and sex-matched non-T2D controls recruited from the Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS) were first analyzed using untargeted lipidomics. Potential predictive lipid species selected by the Boruta analysis were then verified by targeted lipidomics. The associations between these lipid species and incident T2D were assessed. Effects of novel lipid species on insulin secretion in mouse islets were investigated. RESULTS: Boruta analysis identified 16 potential lipid species. After adjustment for body mass index (BMI), triacylglycerol/high-density lipoprotein (TG/HDL) ratio and the presence of prediabetes, triacylglycerol (TG) 12:0_18:2_22:6, TG 16:0_11:1_18:2, TG 49:0, TG 51:1 and diacylglycerol (DG) 18:2_22:6 were independently associated with increased T2D risk, whereas lyso-phosphatidylcholine (LPC) O-16:0, LPC P-16:0, LPC O-18:0 and LPC 18:1 were independently associated with decreased T2D risk. Addition of the identified lipid species to the clinical prediction model, comprised of BMI, TG/HDL ratio and the presence of prediabetes, achieved a 3.8% improvement in the area under the receiver operating characteristics curve (AUROC) (p = 0.0026). Further functional study revealed that, LPC O-16:0 and LPC O-18:0 significantly potentiated glucose induced insulin secretion (GSIS) in a dose-dependent manner, whereas neither DG 18:2_22:6 nor TG 12:0_18:2_22:6 had any effect on GSIS. CONCLUSIONS: Addition of the lipid species substantially improved the prediction of T2D beyond the model based on clinical risk factors. Decreased levels of LPC O-16:0 and LPC O-18:0 may contribute to the development of T2D via reduced insulin secretion.

The Influence of Acitretin on Brain Lipidomics in Adolescent Mice-Implications for Pediatric and Adolescent Dermatological Therapy.

Administration of systemic retinoids such as acitretin has not been approved yet for pediatric patients. An adverse event of retinoid-therapy that occurs with lower prevalence in children than in adults is hyperlipidemia. This might be based on the lack of comorbidities in young patients, but must not be neglected. Especially for the development of the human brain up to young adulthood, dysbalance of lipids might be deleterious. Here, we provide for the first time an in-depth analysis of the influence of subchronic acitretin-administration on lipid composition of brain parenchyma of young wild type mice. For comparison and to evaluate the systemic effect of the treatment, liver lipids were analogously investigated. As expected, triglycerides increased in liver as well as in brain and a non-significant increase in cholesterol was observed. However, specifically brain showed an increase in lyso-phosphatidylcholine and carnitine as well as in sphingomyelin. Group analysis of lipid classes revealed no statistical effects, while single species were tissue-dependently changed: effects in brain were in general more subtly as compared to those in liver regarding the mere number of changed lipid species. Thus, while the overall impact of acitretin seems comparably small regarding brain, the change in individual species and their role in brain development and maturation has to be considered.

Shiga toxin glycosphingolipid receptors and their lipid membrane ensemble in primary human blood-brain barrier endothelial cells.

Shiga toxin (Stx)-mediated injury to microvascular endothelial cells in the brain significantly contributes to the pathogenesis of the hemolytic-uremic syndrome caused by enterohemorrhagic Escherichia coli (EHEC). Stxs are AB5 toxins and the B-pentamers of the two major Stx subtypes Stx1a and Stx2a preferentially bind to the glycosphingolipid (GSL) globotriaosylceramide (Gb3Cer) expressed by human endothelial cells. Here we report on comprehensive structural analysis of the different lipoforms of Gb3Cer (Galα4Galß4Glcß1Cer) and globotetraosylceramide (Gb4Cer, GalNAcß3Galα4Galß4Glcß1Cer, the less effective Stx receptor) of primary human brain microvascular endothelial cells and their association with lipid rafts. Detergent-resistant membranes (DRMs), obtained by sucrose density gradient ultracentrifugation, were used as lipid raft-analogous microdomains of the liquid-ordered phase and nonDRM fractions were employed as equivalents for the liquid-disordered phase of cell membranes. Structures of the prevalent lipoforms of Gb3Cer and Gb4Cer were those with Cer (d18:1, C16:0), Cer (d18:1, C22:0) and Cer (d18:1, C24:1/C24:0) determined by electrospray ionization mass spectrometry that was combined with thin-layer chromatography immunodetection using anti-Gb3Cer and anti-Gb4Cer antibodies as well as Stx1a and Stx2a subtypes. Association of Stx receptor GSLs was determined by co-localization with lipid raft-specific membrane protein flotillin-2 and canonical lipid raft marker sphingomyelin with Cer (d18:1, C16:0) and Cer (d18:1, C24:1/C24:0) in the liquid-ordered phase, whereas lyso-phosphatidylcholine was detectable exclusively in the liquid-disordered phase. Defining the precise microdomain structures of primary endothelial cells may help to unravel the initial mechanisms by which Stxs interact with their target cells and will help to develop novel preventive and therapeutic measures for EHEC-mediated diseases.

DHA supplementation during pregnancy as phospholipids or TAG produces different placental uptake but similar fetal brain accretion in neonatal piglets.

The great variety of n-3 long-chain PUFA sources raises the question of the most adequate for using as a DHA supplement during pregnancy. Placental and fetal availability of different DHA sources remains unclear. We investigated DHA availability in maternal lipoproteins, placenta and fetal tissues in pregnant sows fed DHA as phospholipid (PL) or TAG to identify the best DHA source during this period. Pregnant Iberian sows were fed diets containing 0·8 % DHA of total fatty acids as PL from egg yolk or TAG from algae oil during the last third of gestation (40 d). Maternal tissues, placentas and fetal tissues were obtained at delivery and DHA quantified by GC. Major Facilitator Superfamily Domain Containing 2a (MFSD2a) carrier expression was analysed in both placenta and fetal brain by Western blotting. Sows fed the DHA-PL diet showed higher DHA incorporation in plasma LDL but not in plasma total lipids. No differences were found in DHA content between groups in maternal liver, adipose tissue or brain. Placental tissue incorporated more DHA in both total lipids and PL fraction in sows fed DHA-PL. However, this did not lead to an enhanced DHA accretion either in fetal plasma, fetal liver or fetal brain. MFSD2a expression was similar between both experimental groups. Maternal DHA supplementation during pregnancy in sow either as PL or TAG produces similar DHA accretion in fetal tissues but not in placenta. Both fat sources are equally available for fetal brain.

Dietary and biliary phosphatidylcholine activates PKCζ in rat intestine.

Chylomicron output by the intestine is proportional to intestinal phosphatidylcholine (PC) delivery. Using five different variations of PC delivery to the intestine, we found that lyso-phosphatidylcholine (lyso-PC), the absorbed form of PC, concentrations in the cytosol (0 to 0.45 nM) were proportional to the input rate. The activity of protein kinase C (PKC)ζ, which controls prechylomicron output rate by the endoplasmic reticulum (ER), correlated with the lyso-PC concentration suggesting that it may be a PKCζ activator. Using recombinant PKCζ, the Km for lyso-PC activation was 1.49 nM and the Vmax 1.12 nM, more than the maximal lyso-PC concentration in cytosol, 0.45 nM. Among the phospholipids and their lyso derivatives, lyso-PC was the most potent activator of PKCζ and the only one whose cytosolic concentration suggested that it could be a physiological activator because other phospholipid concentrations were negligible. PKCζ was on the surface of the dietary fatty acid transport vesicle, the caveolin-1-containing endocytic vesicle. Once activated, PKCζ, eluted off the vesicle. A conformational change in PKCζ on activation was suggested by limited proteolysis. We conclude that PKCζ on activation changes its conformation resulting in elution from its vesicle. The downstream effect of dietary PC is to activate PKCζ, resulting in greater chylomicron output by the ER.

Lyso-phosphatidylcholine as an interfacial stabilizer for parenteral monoclonal antibody formulations.

Therapeutic proteins suffer from physical and chemical instability in aqueous solution. Polysorbates and poloxamers are often added for protection against interfacial stress to prevent protein aggregation and particle formation. Previous studies have revealed that the hydrolysis and oxidation of polysorbates in parenteral formulations can lead to the formation of free fatty acid particles, insufficient long-term stabilization, and protein oxidation. Poloxamers, on the other hand, are considered to be less effective against protein aggregation. Here we investigated two lyso-phosphatidylcholines (LPCs) as potential alternative surfactants for protein formulations, focusing on their physicochemical behavior and their ability to protect against the formation of monoclonal antibody particles during mechanical stress. The hemolytic activity of LPC was tested in varying ratios of plasma and buffer mixtures. LPC effectively stabilized mAb formulations when shaken at concentrations several orders of magnitude below the onset of hemolysis, indicating that the potential for erythrocyte damage by LPC is non-critical. LPC formulations subjected to mechanical stress through peristaltic pumping exhibited comparable protein particle formation to those containing polysorbate 80 or poloxamer 188. Profile analysis tensiometry and dilatational rheology indicated that the stabilizing effect likely arises from the formation of a viscoelastic film at approximately the CMC. Data gathered from concentration-gradient multi-angle light scattering and isothermal titration calorimetry support this finding. Surfactant desorption was evaluated through sub-phase exchange experiments. While LPCs readily desorbed from the interface, resorption occurred rapidly enough in the bulk solution to prevent protein adsorption. Overall, LPCs behave similarly to polysorbate with respect to interfacial stabilization and show promise as a potential substitute for polysorbate in parenteral protein formulations.

Changes in plasma phospholipids and sphingomyelins with aging in men and women: A comprehensive systematic review of longitudinal cohort studies.

BACKGROUND: Aging affects the serum levels of various metabolites which may be involved in the pathogenesis of chronic diseases. The aim of this review article is to summarize the relationship between aging and alterations in the plasma phospholipids and sphingomyelins. METHODS: PRISMA guidelines were employed during all steps. MEDLINE (PubMed), Scopus, Embase and Web of Sciences databases and Google Scholar were searched up to October 2020. Cohort studies investigating the relationship between aging and within-person changes in sphingomyelin (SM), phosphatidyl choline (PC), lyso PC (LPC) and phosphatidyl ethanolamine (PE) were included. Newcastle-Ottawa scale was used to assess the quality of included studies. RESULTS: A total of 1425 studies were identified. After removing 610 duplicates and 723 irrelevant studies, full texts of 92 articles were evaluated. Of these 92, 6 studies (including data from 7 independent cohorts) met the inclusion criteria and are included in this review. All study populations were healthy and included both men and women. Results by sex were reported in 3 cohorts for PC, 5 cohorts for LPC, 3 cohorts for SM, and only 1 cohort for PE. In men, PC, SM, PE and LPC decreased with aging, although results for LPC were inconsistent. In women, LPC, SM, and PE increased age, whereas changes in PC were inconsistent. CONCLUSION: Within-person serum levels of phospholipids and sphingomyelins, decrease during aging in men and increase in women. Notably, however, there were some inconsistencies across studies of LPC in men and of PC in women.

Impact of Vitamin D3 Deficiency on Phosphatidylcholine-/Ethanolamine, Plasmalogen-, Lyso-Phosphatidylcholine-/Ethanolamine, Carnitine- and Triacyl Glyceride-Homeostasis in Neuroblastoma Cells and Murine Brain.

Vitamin D3 hypovitaminosis is associated with several neurological diseases such as Alzheimer's disease, Parkinson's disease or multiple sclerosis but also with other diseases such as cancer, diabetes or diseases linked to inflammatory processes. Importantly, in all of these diseases lipids have at least a disease modifying effect. Besides its well-known property to modulate gene-expression via the VDR-receptor, less is known if vitamin D hypovitaminosis influences lipid homeostasis and if these potential changes contribute to the pathology of the diseases themselves. Therefore, we analyzed mouse brain with a mild vitamin D hypovitaminosis via a targeted shotgun lipidomic approach, including phosphatidylcholine, plasmalogens, lyso-phosphatidylcholine, (acyl-/acetyl-) carnitines and triglycerides. Alterations were compared with neuroblastoma cells cultivated in the presence and with decreased levels of vitamin D. Both in cell culture and in vivo, decreased vitamin D level resulted in changed lipid levels. While triglycerides were decreased, carnitines were increased under vitamin D hypovitaminosis suggesting an impact of vitamin D on energy metabolism. Additionally, lyso-phosphatidylcholines in particular saturated phosphatidylcholine (e.g., PC aa 48:0) and plasmalogen species (e.g., PC ae 42:0) tended to be increased. Our results suggest that vitamin D hypovitaminosis not only may affect gene expression but also may directly influence cellular lipid homeostasis and affect lipid turnover in disease states that are known for vitamin D hypovitaminosis.

Impact of maternal smoking associated lyso-phosphatidylcholine 20:3 on offspring brain development.

Maternal smoking during pregnancy affects fetal neurological development. Metabolomic studies in the general population suggest that smoking is associated with characteristic metabolic alterations. We investigated the association between the maternal smoking status, the fetal metabolome and head circumference at birth, as a surrogate parameter of brain development. 320 mother/newborn pairs of the Berlin Birth Cohort were investigated. Anthropometric parameters, including head circumference, of newborns of smoking mothers, former smoking mothers, and never smoking mothers were compared to assess the impact of maternal smoking behavior. Associations between maternal smoking behavior and 163 cord blood metabolites and associations between newborn head circumference and concentrations of smoking behavior related metabolites were analysed. Male newborns of smoking mothers had a reduced head circumference when compared with newborns from former smoking and never smoking mothers (p < 0.05). Using linear regression models corrected for established confounding factors, maternal smoking during pregnancy showed an independent association with head circumference (95% CI: -0.75～-0.41 cm, p = 2.45×10-11). In a stepwise linear regression model corrected for known confounding factors of brain growth lyso-phosphatidylcholine 20:3 (95% CI: 6.68～39.88 cm, p = 4.62×10-4) was associated with head circumference in male offspring only. None of the metabolites were associated with head circumference of female newborns. In conclusion, maternal smoking during pregnancy impacted on male offspring's development including brain development. The smoking related metabolite lyso-phosphatidylcholine 20:3 was associated with head circumference of male offspring.

A comprehensive strategy for studying protein-metabolite interactions by metabolomics and native mass spectrometry.

Protein-metabolite interactions play important roles in many cellular and physiological processes in biological systems. However, the lack of effective research approaches impedes the understanding of the protein-metabolite interactions. In this study, a novel comprehensive strategy by combining metabolomics platform with native mass spectrometry was developed for investigating the protein-metabolite interactions. Peroxisome proliferator-activated receptors gamma (PPARγ) is a lipid-binding nuclear receptors that plays a key role in regulating fatty-acid oxidation and lipid metabolism, which was selected as the model protein. Seven metabolites including lyso-phosphatidylcholine (LPC) 16:0, LPC18:0, LPC18:1, arachidonic acid, oleic acid, linoleic acid and palmitoleic acid (p < 0.05) were found to have the possible interactions with the PPARγ, these LPCs were discovered as candidate ligands for the first time by using untargeted metabolomics method. Native mass spectrometry based on 15 T Fourier transform ion cyclotron resonance mass spectrometer was employed to directly detect the PPARγ-LPCs complexes to obtain their stoichiometry and kinetic constants. Isothermal titration calorimetry, circular dichroism spectrum and molecular modeling were further utilized to investigate the thermodynamics, conformation and binding mechanism of the interaction between PPARγ and LPCs. It was found that the PPARγ-LPC interaction was an endothermic process, and these LPCs have similar binding constants with stoichiometric number of 1:1. The novel strategy can provide a very useful approach for mapping and identifying unknown protein-metabolite interactions in biological systems.

Lipidomic profiles disturbed by the internet gaming disorder in young Korean males.

Internet Gaming Disorder (IGD) is characterized by uncontrollable and persistent playing of internet games despite the occurrence of negative consequences. Although there is a worldwide treatment demand, IGD still doesn't have an explicit biomarker. The primary goal of the study is to characterize lipidomic profiles specific to internet gaming disorder (IGD) based on liquid-chromatography Orbitrap mass-spectrometry (LC Orbitrap MS). Primarily, a total of 19 lipids were significantly dys-regulated in the IGD group compared to healthy controls. The lipidomic feature was mainly characterized by various types of phosphatidylcholines (PCs) and lyso-phosphatidylcholines (LysoPCs). Subsequent multivariate statistical model and linear regression model prioritized two LysoPCs (C16:0 and C18:0) for potential biomarker. Receiver operating characteristic (ROC) analysis demonstrated excellent performance of the combined lipid set for discriminating the IGD group from healthy controls (AUC: 0.981, 95% confidence interval: 0.958-1.000). Additional evaluation with potential confounders and clinical parameters suggested robustness and potential applicability of the outcome as biomarkers which may aid diagnosis.

A dynamic in vitro permeation study on solid mono- and diacyl-phospholipid dispersions of celecoxib.

The current study documents enhanced apparent solubility of the BCS class II drug celecoxib (CXB) when formulated as solid phospholipid dispersion (SPD) with either mono- or diacyl-phospholipids by freeze drying from hydro-alcoholic solvent. The enhanced solubility upon dispersion in buffer or fasted state simulated intestinal fluid (FaSSIF) is interpreted to be due to two effects: (1) amorphization of CXB, inducing supersaturation, which is also observed when CXB is freeze dried in the absence of phospholipids and (2) association of CXB with spontaneously forming colloidal structures, such as vesicles and/or micelles, promoting solubilization. The latter effect depended on the CXB-to-phospholipid ratio, where monoacyl-phospholipid was a more efficient solubilizer than diacyl-phospholipid. In the case of diacyl-phospholipid, solubilization also depended strongly on the dispersion medium, where FaSSIF induced a more pronounced solubilization effect than buffer. In contrast, a significantly enhanced in-vitro permeability of CXB across a biomimetic barrier (Permeapad®) was found only with low lipid contents up to a CXB to phospholipid mass-ratio of 1:10 or in the absence of phospholipid; above this critical ratio, permeability was not enhanced, i.e. comparable to that observed with a suspension of non-processed (crystalline) drug. This non-linear dissolution-/permeation-behavior was observed independently of (1) the type of phospholipid (monoacyl- or diacyl-) employed and (2) the dispersion medium (buffer or FaSSIF), despite the fact that different patterns of co-existing colloidal states were observed from mono-/diacyl-phospholipid formulations in buffer/FaSSIF (small bile salt micelles, intermediate size mixed micelles and large vesicular structures), assessed by asymmetric flow field-flow fractionation/multi angle laser light scattering. A uniform mechanistic hypothesis is presented to describe the impact of phospholipids on CXB permeation behavior: Obviously, the critical drug-to-phospholipid ratio represents a compromise between optimal stabilization of the amorphous state-induced supersaturation and reduced thermodynamic activity of CXB due to association with colloidal states, where the type of colloidal state (vesicle or micelle) appears to be of minor importance.

Phospholipase A2: Potential roles in native membrane fusion.

Membrane fusion is a fundamental molecular mechanism by which two apposed membrane bilayers coalesce in rapid, transient steps that enable the successive merging of the outer and inner leaflets allowing lipid intermixing and subsequent mixing of the two previously separate compartments. The actual membrane merger mechanism - fusion, by definition - is conceptualized to be protein- or lipid-centric. According to the widely vetted stalk-pore hypothesis, membrane fusion proceeds via high curvature lipid intermediates. By cleaving membrane phospholipids at the sn-2 position, Phospholipase A2 generates metabolites that exert spontaneous curvature stress (both negative and positive) on the membrane, thus influencing local membrane bending by altering the packing and conformation of lipids and proteins, respectively. Such changes could potentially modulate priming and attachment/docking steps that precede fusion, as well as the membrane merger steps per se.

Efficient Docosahexaenoic Acid Uptake by the Brain from a Structured Phospholipid.

Docosahexaenoic acid (DHA) is the main essential omega-3 fatty acid in brain tissues required for normal brain development and function. An alteration of brain DHA in neurodegenerative diseases such as Alzheimer's and Parkinson's is observed. Targeted intake of DHA to the brain could compensate for these deficiencies. Blood DHA is transported across the blood-brain barrier more efficiently when esterified at the sn-2 position of lyso-phosphatidylcholine. We used a structured phosphatidylcholine to mimic 2-docosahexaenoyl-lysoPC (lysoPC-DHA), named AceDoPC (1-acetyl,2-docosahexaenoyl-glycerophosphocholine), that may be considered as a stabilized form of the physiological lysoPC-DHA and that is neuroprotective in experimental ischemic stroke. The aim of the present study was to investigate whether AceDoPC is a relevant delivery form of DHA to the brain in comparison with other forms of the fatty acid. By combining in vitro and in vivo experiments, our findings report for the first time that AceDoPC is a privileged and specific carrier of DHA to the brain, when compared with DHA-containing PC and non-esterified DHA. We also show that AceDoPC was hydrolyzed, in part, into lysoPC-DHA. Ex vivo autoradiography of rat brain reveals that DHA from AceDoPC was localized in specific brain regions playing key roles in memory, thoughts, and cognitive functions. Finally, using molecular modeling approaches, we demonstrate that electrostatic and lipophilic potentials are distributed very similarly at the surfaces of AceDoPC and lysoPC-DHA. Our findings identify AceDoPC as an efficient way to specifically target DHA to the brain, which would allow potential preventive and therapeutic approaches for neurological diseases.

Ca2+ signaling in taste bud cells and spontaneous preference for fat: unresolved roles of CD36 and GPR120.

Recent compelling evidences from rodent and human studies raise the possibility for an additional sixth taste modality devoted to oro-gustatory perception of dietary lipids. Understanding the mechanisms underlying oro-gustatory detection of dietary fat is critical for the prevention and treatment of obesity. A number of studies have suggested that lingual CD36, a glycoprotein, highly expressed by circumvallate papillae of the tongue, is implicated in the perception of dietary fat taste. G protein-coupled receptors (GPCRs) are important signaling molecules for many aspects of cellular functions. It has been shown that these receptors, particularly GPR120, are also involved in lipid taste perception. We have shown that dietary long-chain fatty acids (LCFAs), in CD36-positive taste bud cells (TBC), induce increases in free intracellular Ca(2+) concentrations, [Ca(2+)]i, by recruiting Ca(2+) from endoplasmic reticulum (ER) pool via inositol 1,4,5-triphosphate production, followed by Ca(2+) influx via opening of store-operated Ca(2+) (SOC) channels. GPR120 is also coupled to increases in [Ca(2+)]i by dietary fatty acids. We observed that stromal interaction molecule 1 (STIM1), a sensor of Ca(2+) depletion in the ER, mediated fatty acid-induced Ca(2+) signaling and spontaneous preference for fat in the mouse. In this review article, we discuss the recent advances and unresolved roles of CD36 and GPR120 in lipid taste signaling in taste bud cells.

Characterization of choline uptake in Trypanosoma brucei procyclic and bloodstream forms.

Choline is an essential nutrient for eukaryotic cells, where it is used as precursor for the synthesis of choline-containing phospholipids, such as phosphatidylcholine (PC). According to published data, Trypanosoma brucei parasites are unable to take up choline from the environment but instead use lyso-phosphatidylcholine as precursor for choline lipid synthesis. We now show that T. brucei procyclic forms in culture readily incorporate [(3)H]-labeled choline into PC, indicating that trypanosomes express a transporter for choline at the plasma membrane. Characterization of the transport system in T. brucei procyclic and bloodstream forms shows that uptake of choline is independent of sodium and potassium ions and occurs with a Km in the low micromolar range. In addition, we demonstrate that choline uptake can be blocked by the known choline transport inhibitor, hemicholinium-3, and by synthetic choline analogs that have been established as anti-malarials. Together, our results show that T. brucei parasites express an uptake system for choline and that exogenous choline is used for PC synthesis.

Seasonal changes in minor membrane phospholipid classes, sterols and tocopherols in overwintering insect, Pyrrhocoris apterus.

Ectotherm animals including insects are known to undergo seasonal restructuring of the cell membranes in order to keep their functionality and/or protect their structural integrity at low body temperatures. Studies on insects so far focused either on fatty acids or on composition of molecular species in major phospholipid classes. Here we extend the scope of analysis and bring results on seasonal changes in minor phospholipid classes, lysophospholipids (LPLs), free fatty acids, phytosterols and tocopherols in heteropteran insect, Pyrrhocoris apterus. We found that muscle tissue contains unusually high amounts of LPLs. Muscle and fat body tissues also contain high amounts of ß-sitosterol and campesterol, two phytosterols derived from plant food, while only small amounts of cholesterol are present. In addition, two isomers (γ and δ) of tocopherol (vitamin E) are present in quantities comparable to, or even higher than phytosterols in both tissues. Distinct seasonal patterns of sterol and tocopherol concentrations were observed showing a minimum in reproductively active bugs in summer and a maximum in diapausing, cold-acclimated bugs in winter. Possible adaptive meanings of such changes are discussed including: preventing the unregulated transition of membrane lipids from functional liquid crystalline phase to non-functional gel phase; decreasing the rates of ion/solute leakage; silencing the activities of membrane bound enzymes and receptors; and counteracting the higher risk of oxidative damage to PUFA in winter membranes.