Membrane Polyunsaturated Fatty Acids Research Articles

52 Ferroptosis Suppressor Protein 1 is a Potent and Targetable Inhibitor of Ferroptosis in Chromophobe Renal Cell

Abstract Background There are currently no proven therapies for metastatic or unresectable Chromophobe renal cell carcinoma (ChRCC). Ferroptosis is an iron-dependent form of cell death characterized by the peroxidation of membrane polyunsaturated fatty acids, leading to membrane damage and cell death. Glutathione, a potent cellular antioxidant, counters lipid peroxidation to prevent ferroptosis. Both reduced and oxidized glutathione are markedly elevated in ChRCC (PNAS, 2018). We have previously discovered that ChRCC is hypersensitive to ferroptotic cell death induced by the pharmacologic disruption of glutathione homeostasis via the cysteine transporter SLC7A11 or glutathione peroxidase (GPX4) inhibition (PNAS, 2022). Ferroptosis suppressor protein (FSP1) is a glutathione-independent suppressor of ferroptosis. FSP1’s role in ChRCC is unexplored. Methods Transcriptional data from DepMap (484 cell lines) and Cancer Therapeutics Response Portal (CTRP) (860 cell lines) were used to study genetic or pharmacologic inhibition of GPX4 and SLC7A11. Statistical analysis was performed in PRISM 10 using Mann-Whitney U and ANOVA tests. Statistical significance was defined as p < 0.05. Results DepMap data revealed that FSP1 is the top upregulated gene in cells resistant to RNAi inhibition of GPX4 (Achilles, DEMETER2) (Panel A). In CTRP data, FSP1 was the top upregulated gene in cells resistant to the GPX4 inhibitor RSL3 and the 19th most upregulated gene in cells resistant to the SCL7A11 inhibitor, Erastin (Panel B). In The Cancer Genomic Atlas (TCGA) KICH (ChRCC) dataset, FSP1 was 2-fold higher in ChRCC compared to normal kidney (mean RSEM = 818.9 vs 445.9, p-value <0.0001) (Panel C). In vitro studies of two ChRCC cell lines, UOK276 and RCJ-T2, revealed that while siRNA-mediated inhibition of GPX4 or FSP1 individually did not induce substantial cell death, their combination was synergistic and resulted in almost complete cell death (UOK276 mean viability 8% of siCTRL, p<0.0001; RCJ-T2 mean viability 13% of siCTRL, p<0.0001). Cell viability was completely rescued by the ferroptosis inhibitor ferrostatin-1 but not by the necroptosis inhibitor necrostatin-1 or the apoptosis inhibitor Z-Vad-FMK (Panel D). siRNA-mediated GPX4 knockdown combined with FSP1 pharmacologic inhibition (icFSP1 or FSEN1) induced extensive cell death (mean viability of siGPX4 + icFSP1 group = 21% of siCTRL + DMSO group, p<0.0001; mean viability of siGPX4 + FSEN1 group = 29% of siCTRL + DMSO group, p<0.0001) (Panel E). Combining RSL3 with FSEN1, or IKE with icFSP1, also demonstrated synergy, with the ChRCC cell lines showing increased overall sensitivity to these drug combinations compared to 786-0 cells (ccRCC-derived) and HeLa cells (Panel F). Snapshots from these experiments taken at [IKE] = 177nM and/or [icFSP1] = 20 mM for UOK276, and [RSL3] = 39.4 nM and/or [FSEN1] = 20 mM for RCJ-T2, show almost complete cell death when pharmacologic inhibitors of glutathione-dependent and -independent ferroptosis suppressors are combined, but no substantial cell death when each is used individually (7% and 10% viability in combination group compared to DMSO group for UOK276 and RCJ-T2 respectively, p<0.0001) (Panel G). Conclusions We show that in vitro genetic or pharmacologic inhibition of FSP1, a glutathione-independent inhibitor of ferroptosis, leads to ferroptosis in ChRCC-derived cells when combined with genetic or pharmacologic inhibition of the glutathione-dependent suppressors of ferroptosis GPX4 or SLC7A11.

Erythrocyte membrane fatty acid concentrations and myelin integrity in young people at ultra-high risk of psychosis

Decreased white matter (WM) integrity and disturbance in fatty acid composition have been reported in individuals at ultra-high risk of psychosis (UHR). The current study is the first to investigate both WM integrity and erythrocyte membrane polyunsaturated fatty acid (PUFA) levels as potential risk biomarkers for persistent UHR status, and global functioning in UHR individuals. Forty UHR individuals were analysed at baseline for erythrocyte membrane PUFA concentrates. Tract-based spatial statistics (TBSS) was used to analyse fractional anisotropy (FA) and diffusivity measures. Measures of global functioning and psychiatric symptoms were evaluated at baseline and at 12-months. Fatty acids and WM indices did not predict functional outcomes at baseline or 12-months. Significant differences were found in FA between UHR remitters and non-remitters (individuals who no longer met UHR criteria versus those who continued to meet criteria at 12-months). Docosahexaenoic acid (DHA) was found to be a significant predictor of UHR status at 12-months, as was the interaction between the sum of ώ-3 and whole brain FA, and the interaction between the right anterior limb of the internal capsule and the sum of ώ-3. The results confirm that certain fatty acids have a unique relationship with WM integrity in UHR individuals.

Development and Validation of an LC-MS/MS Method for the Determination of Plasma and Red Blood Cell Omega Fatty Acids: A Useful Diagnostic Tool

Development and Validation of an LC-MS/MS Method for the Determination of Plasma and Red Blood Cell Omega Fatty Acids: A Useful Diagnostic Tool

High linoleic acid levels in red blood cells predict a poor response to neoadjuvant chemotherapy in human epidermal growth factor receptor type 2-positive breast cancer patients

ObjectivePolyunsaturated fatty acids are categorized as ω-3 or ⍵-6. Previous studies demonstrate that breast cancers display a high expression of fatty acid synthase and high fatty acid levels. Our study sought to determine if changes in plasma or red blood cell membrane fatty acid levels were associated with the response to preoperative (neoadjuvant) chemotherapy in non-metastatic breast cancer patients. MethodsOur prospective study assessed fatty acid levels in plasma and red blood cell membrane. Response to neoadjuvant chemotherapy was evaluated by the presence or absence of pathologic complete response and/or residual cancer burden. ResultsA total of 28 patients were included. First, patients who achieved pathologic complete response had significantly higher neutrophil-to-lymphocyte ratio versus no pathologic complete response (P = 0.003). Second, total red blood cell membrane polyunsaturated fatty acids were higher in the absence of pathologic complete response (P = 0.0028). Third, total red blood cell membrane ⍵-6 polyunsaturated fatty acids were also higher in no pathologic complete response (P < 0.01). Among ⍵-6 polyunsaturated fatty acids, red blood cell membrane linoleic acid was higher in the absence of pathologic complete response (P < 0.01). Notably, plasma polyunsaturated fatty acid, ⍵-6, and linoleic acid levels did not have significant differences. A multivariate analysis confirmed red blood cell membrane linoleic acid was associated with no pathologic complete response; this was further confirmed by receiver operating characteristic analysis (specificity = 92.3%, sensitivity = 76.9%, and area under the curve = 0.855). ConclusionsPending further validation, red blood cell membrane linoleic acid might serve as a predictor biomarker of poorer response to neoadjuvant chemotherapy in non-metastatic human epidermal growth factor receptor type 2–positive breast cancer. Measuring fatty acids in red blood cell membrane could offer a convenient, minimally invasive strategy to identifying patients more likely to respond or those with chemoresistance.

Abstract C051: Alteration of protein translation by eIF4A1 inhibition exquisitely primes lymphoma cells to induction of ferroptosis

Abstract Background: Ferroptosis induction as a cancer therapy faces challenges establishing clinical therapeutic windows. Cells employ diverse mechanisms to prevent iron-mediated oxidation of membrane polyunsaturated fatty acids that causes ferroptosis, but populations with low rates of protein synthesis such as hematopoietic stem cells are more susceptible. Therefore, we hypothesized protein synthesis inhibitors might enhance therapeutic ferroptosis induction. Rocaglates, inhibitors targeting eIF4A1, have entered clinical trials with promising potential against diffuse large B-cell lymphoma (DLBCL), which also exhibits pre-clinical susceptibility to ferroptosis induction. Up to 40% of patients with DLBCL, the most common lymphoma type, have poor outcomes requiring new approaches to address these persistent unmet clinical needs. Our results reveal striking synergy of rocaglates, including the clinical compound zotatifin (eFT226), with ferroptosis inducers. TMT-pSILAC and RNA-seq analyses revealed profound deregulation of ferroptotic protection resulting from rocalate effects on protein synthesis. Methods: We used RNA-seq and TMT-pSILAC followed by mass spectrometry to analyze transcriptome and protein output in SU-DHL-10 DLBCL cells treated with zotatifin or DMSO for 24h. Enrichment analyses (Enrichr platform, ChIP-X Enrichment Analysis 3, GSEA) identified differentially expressed genes, proteins and transcription factors. We explored synergy between zotatifin and ferroptosis modulators in DLBCL cell lines and measured a wide variety of associated cellular endpoints including lipid peroxidation, glutathione levels, and glutathione peroxidase 4 (GPX4) expression. Results: TMT-pSILAC translatome assessment during rocaglate exposure revealed expression alteration(log2FC ≥ 1.5) of numerous key proteins involved in oxidative stress (i.e. SDHB, SDHA, TRAP1, SCO1, UQCRH, ETFA, COX7C) and enrichment of factors indicating induction of an antioxidant response (CD98HC, NRF1, ATF2, SP2, and NFE2L). These changes led to high synergy of zotatifin in combination with a wide variety of ferroptosis inducers (Bliss δ synergy score &amp;gt; 10) and antagonism with ferroptosis inhibitors (Bliss δ synergy score &amp;lt; - 10). These results were consistent across multiple DLBCL mouse and human experimental systems, and preliminarily appear present also in models of T-cell lymphomas. Lipid peroxidation levels were significantly enhanced when zotatifin was combined with erastin (p-value &amp;lt; 0.0005). Moreover, zotatifin treatment resulted in elevated levels of reduced glutathione (GSH), an effect overcome by addition of ferroptosis inducers (p-value &amp;lt; 0.005). Consistently, GPX4 expression was also impaired. Conclusions: Rocaglates induce novel alterations in oxidative stress factors and associated response pathways, sensitizing B and T lymphomas to therapeutic ferroptosis induction. These findings provide valuable insights for using rocaglates in combination with ferroptosis induction to overcome heterogeneous resistance pathways in high-risk lymphoma patients. Citation Format: Paola Manara, Alexa Marie Barroso, Abdessamad Youssfi Alaoui, Olivia Barbara Lightfuss, Tyler Andrew Cunningham, Kyle Hoffman, Caroline Alice Coughlin, Jonathan Harry Schatz. Alteration of protein translation by eIF4A1 inhibition exquisitely primes lymphoma cells to induction of ferroptosis [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C051.

The associations of erythrocyte membrane polyunsaturated fatty acids with skeletal muscle loss: A prospective cohort study

Polyunsaturated fatty acids (PUFAs) may play a vital role in maintaining skeletal muscle mass in the aged population. This study investigated the longitudinal relationship between the concentrations of erythrocyte membrane PUFAs and age-related changes in skeletal muscle mass over an average 6.5 years of follow-up in a Chinese middle-aged and older adult population. A total of 1494 participants aged 57.4±4.7 years were included in this study. Skeletal muscle mass was determined using dual-energy X-ray absorptiometry. Per year percent changes in the skeletal muscle index (Δ% SMI), appendicular skeletal muscle index (Δ% ASMI), and total body lean mass index (Δ% TBLMI) from baseline were calculated. Concentrations of total and individual cis-n-3 and cis-n-6 PUFAs of the erythrocyte membrane were determined using gas-liquid chromatography. Fully adjusted linear regression models showed that per unit increases in the concentrations of C18:2 n-6, C20:4 n-6, C22:4 n-6, and total n-6 PUFAs resulted in increases of 0.022%-0.155% in the Δ% SMI (P for linearity: <0.001-0.006). Restricted cubic spline analysis revealed an inverted U-shaped relationship between the concentrations of C20:2 n-6, C22:5 n-3, C22:6 n-3, and total n-3 PUFAs and the Δ% SMI (P for non-linearity: <0.001-0.036). In addition, an inverted U-shaped curve was also detected for the relationships of the linoleic acid/α-linolenic acid ratio (P for non-linearity=0.010) and n-6/n-3 PUFA ratio (P for non-linearity=0.013) with the Δ% SMI, with the Δ% SMI peaking at respective ratios of 124.96 and 3.69. Similar associations were revealed by the Bayesian kernel machine regression model. No interaction effect was detected between the individual PUFAs for the Δ% SMI in the bivariate exposure-response analysis. Overall, similar results were observed for the Δ% ASMI and Δ% TBLMI. The associations between different individual PUFAs and age-related muscle loss in middle-aged and older adults may be different. Our results suggest that high concentrations of erythrocyte membrane n-6 PUFAs may be correlated with less skeletal muscle mass loss, whereas extremely high concentrations of n-3 PUFAs may be correlated with more muscle loss.

The role of HIF-1α/HO-1 pathway in hippocampal neuronal ferroptosis in epilepsy

Epilepsy, a common central nervous system disorder, remains an enigma in pathogenesis. Emerging consensus designates hippocampal neuronal injury as a cornerstone for epileptogenic foci, pivotal in epileptic genesis and progression. Ferroptosis, a regulated cell death modality hinging on iron, catalyzes lipid reactive oxygen species formation through iron and membrane polyunsaturated fatty acid interplay, culminating in oxidative cell death. This research investigates the role of hypoxia-inducible factor (HIF)-1α/heme oxygenase (HO)-1 in hippocampal neuron ferroptosis during epilepsy. Untargeted metabolomics exposes metabolite discrepancies between epilepsy patients and healthy individuals, unveiling escalated oxidative stress, heightened bilirubin, and augmented iron metabolism in epileptic blood. Enrichment analyses unveil active HIF-1 pathway in epileptic pathogenesis, reinforced by HIF-1α signaling perturbations in DisGeNET database. PTZ-kindled mice model confirms increased ferroptotic markers, oxidative stress, HIF-1α, and HO-1 in epilepsy. Study implicates HIF-1α/HO-1 potentially regulates hippocampal neuronal ferroptosis, iron metabolism, and oxidative stress, thereby promoting the propagation of epilepsy.

A randomized, double-blind, placebo-controlled, phase 2 study to assess safety, tolerability and efficacy of RT001 in patients with amyotrophic lateral sclerosis.

RT001 is a deuterated synthetic homologue of linoleic acid, which makes membrane polyunsaturated fatty acids resistant to lipid peroxidation, a process involved in motor neuron degeneration in amyotrophic lateral sclerosis (ALS). We conducted a randomized, multicenter, placebo-controlled clinical trial. Patients with ALS were randomly allocated to receive either RT001 or placebo for 24 weeks. After the double-blind period, all patients received RT001 during an open-label phase for 24 weeks. The primary outcome measures were safety and tolerability. Key efficacy outcomes included the ALS functional rating scale (ALSFRS-R), %predicted slow vital capacity, and plasma neurofilament light chain concentration. In total, 43 patients (RT001=21; placebo=22) were randomized. RT001 was well tolerated; one patient required dose reduction due to adverse events (AEs). Numerically, there were more adverse events in the RT001 group compared to the placebo group (71% versus 55%, p = 0.35), with gastrointestinal symptoms being the most common (43% in RT001, 27% in placebo, p = 0.35). Two patients in the RT001 group experienced a serious AE, though unrelated to treatment. The least-squares mean difference in ALSFRS-R total score at week 24 of treatment was 1.90 (95% CI: -1.39, 5.19) in favor of RT001, p = 0.25. The directions of other efficacy outcomes favored RT001 compared to placebo, although no inferential statistics were performed. Initial data indicate that RT001 is safe and well-tolerated. Given the exploratory nature of the study, a larger clinical trial is required to evaluate its efficacy.

P27-038-23 The Impact of Membrane Polyunsaturated Fatty Acid Composition on Neuronal Cell Development

P27-038-23 The Impact of Membrane Polyunsaturated Fatty Acid Composition on Neuronal Cell Development

Differential Behavior of Eicosapentaenoic and Docosahexaenoic Acids on the Organization, Dynamics, and Fusion of Homogeneous and Heterogeneous Membranes.

Membrane fusion is a common course in innumerable biological processes that helps in the survival of eukaryotes. Enveloped viruses utilize this process to enter the host cells. Generally, the membrane lipid compositions play an important role in membrane fusion by modulating the membrane's physical properties and the behavior of membrane proteins in the cellular milieu. In this work, we have demonstrated the role of polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, on the organization, dynamics, and fusion of homogeneous and heterogeneous membranes. We have exploited arrays of steady-state and time-resolved fluorescence spectroscopic methods and polyethylene glycol-induced membrane fusion assay to elucidate the behavior of EPA and DHA on dioleoyl phosphatidylcholine (DOPC)/cholesterol (CH) homogeneous and DOPC/sphingomyelin/CH heterogeneous membranes. Our results suggest that EPA and DHA display differential effects on two different membranes. The effects of PUFAs in homogeneous membranes are majorly attributed to their flexible chain dynamics, whereas the ability of PUFA-induced cholesterol transfer from the lo to the ld phase rules their behavior in heterogeneous membranes. Overall, our results provide detailed information on the effect of PUFAs on homogeneous and heterogeneous membranes.

Lipid peroxidation in avian semen.

The main cause of sperm chromatin damage is oxidative stress related to embryo development failure and adult infertility in mammals and also avian. Oxidative stress results in lipid peroxidation (LPO) causing cell damage. Lipid peroxidation is the oxidation of polyunsaturated fatty acids (PUFAs) in biological systems and causes changes in the physical structure and characteristics of the cell membrane. Due to the high amounts of PUFAs in the avian sperm membrane, its sperm seem susceptible to pe-roxidative damage and is a substantial factor in the fertilization capacity of sperm. The most commonly used methods for measuring LPO or its by-products, such as malondialdehyde (MDA) and 4-hydroksy-2-nonenal (4-HNE), in bird semen are based on the colorimetric method TBARS (thiobarbituric acid reactive substances) and on the use of a fluorescence probe (CC 11-BODIPY 581/591) as a marker to evaluate membrane lipid peroxidation. This review aims first to introduce LPO in avian semen and its effects on avian sperm and second to summarize the commonly applied methods of evaluating LPO and its damage in fresh and stored avian semen.

The role of Hippo pathway in ferroptosis.

The role of Hippo pathway in ferroptosis The Hippo pathway is mainly composed of mammalian serine/threonine (Ste20)like kinases 1/2 (MST1/2), large tumor suppressor 1/2 (LATS1/2), and transcriptional coactivator Yes-associated protein (YAP), and is closely related to cell growth, survival, proliferation, and migration; tissue and organ size control; and tumorigenesis and development. Ferroptosis is a regulated form of cell death characterized by the accumulation of iron-dependent reactive oxygen species (ROS) and the depletion of plasma membrane polyunsaturated fatty acids (PUFAs), which is caused by the imbalance of oxidation and the antioxidant system. This article elaborates the role of Hippo pathway in ferroptosis, providing ideas for the regulation of cell fate and the treatment of tumors.

A prospective analysis of red blood cell membrane polyunsaturated fatty acid levels and risk of non-Hodgkin lymphoma

Published studies report inconsistent associations of polyunsaturated fatty acid (PUFA) intake with non-Hodgkin lymphoma (NHL) risk. We conducted a nested case-control study in Nurses’ Health Study and Health Professionals Follow-Up Study participants to evaluate a hypothesis of inverse association of pre-diagnosis red blood cell (RBC) membrane PUFA levels with risk of NHL endpoints. We confirmed 583 NHL cases and matched 583 controls by cohort/sex, age, race and blood draw date/time. We estimated odds ratios (OR) and 95% confidence intervals (CI) for risk of NHL endpoints using logistic regression. RBC PUFA levels were not associated with all NHL risk; cis 20:2n-6 was associated with follicular lymphoma risk (OR [95% CI] per one standard deviation increase: 1.35 [1.03–1.77]), and the omega-6/omega-3 PUFA ratio was associated with diffuse large B-cell lymphoma risk (2.33 [1.23–4.43]). Overall, PUFA did not demonstrate a role in NHL etiology; the two unexpected positive associations lack clear biologic explanations.

Niacin skin flush and membrane polyunsaturated fatty acids in schizophrenia from the acute state to partial remission: a dynamic relationship

Despite the consistent finding of an attenuated niacin-induced flush response in schizophrenia, its long-term stability and relationship to the membrane polyunsaturated fatty acid (PUFA) levels remain unknown. We conducted niacin skin tests and measured the membrane PUFAs using gas chromatography among 46 schizophrenia inpatients and 37 healthy controls at the baseline and the 2-month follow-up. Attenuated flush responses were persistently observed in schizophrenia patients in both acute and partial remission states, whereas an increased flush response was found in the controls. A persistent decrease in both dihomo-gamma-linolenic acid and docosahexaenoic acid and an increased turnover of arachidonic acid (ARA) via endogenous biosynthesis were found in schizophrenia patients. A composite niacin flush score by combining those with a control-to-case ratio of >1.4 (i.e., scores at 5 min of 0.1 M, 0.01 M, and 0.001 M + 10 min of 0.01 M and 0.001 M + 15 min of 0.001 M) at the baseline was correlated positively with ARA levels among controls but not among schizophrenia patients, whereas the flush score at the 2-month follow-up was correlated positively with ARA levels among patients. The 2-month persistence of attenuated niacin-induced flush response in schizophrenia patients implies that the niacin skin test might tap a long-term vulnerability to schizophrenia beyond acute exacerbation.

Reduced erythrocyte membrane polyunsaturated fatty acid levels indicate diminished treatment response in patients with multi- versus first-episode schizophrenia

Antipsychotic effects seem to decrease in relapsed schizophrenia patients and the underlying mechanisms remain to be elucidated. Based on the essential role of polyunsaturated fatty acids in brain function and the treatment of schizophrenia, we hypothesize that disordered fatty acid metabolism may contribute to treatment resistance in multi-episode patients. We analyzed the erythrocyte membrane fatty acids in 327 schizophrenia patients under various episodes (numbers of patients: first-episode drug naïve 89; 2–3 episodes 110; 4–6 episodes 80; over 6 episodes 48) and 159 age- and gender-matched healthy controls. Membrane fatty acid levels and PANSS scales were assessed at baseline of antipsychotic-free period and one-month of follow-up after treatment. Totally, both saturated and unsaturated fatty acids were reduced at baseline when compared to healthy controls. Subgroup analyses among different episodes indicated that in response to atypical antipsychotic treatment, the membrane fatty acids were only increased in patients within 3 episodes, and this therapeutic effects on omega-3 index were merely present in the first episode. Results of fatty acid ratios suggested that dysregulations of enzymes such as D6 desaturase, D5 desaturase, and elongases for polyunsaturated fatty acids in patients with multi-episode schizophrenia could account for the differences. Additionally, certain fatty acid level/ratio changes were positively correlated with symptom improvement. The alterations of C22:5n3 and omega-3 index, gender, and the number of episodes were significant risk factors correlated with treatment responsiveness. Using targeted metabolomic approach, we revealed the potential mechanisms underlying abnormal fatty acid metabolism responsible for reduced treatment response in patients with multi-episode schizophrenia.

Evaluation of erythrocyte membrane fatty-acid compositions in association with interleukin-6 levels in patients with COVID-19

ObjectiveThe cytokine storm presented in the hyperimmune response is related to poor prognosis in people with COVID-19. Interleukin-6 (IL-6) is one of the most prominent cytokines, especially on mucosal surfaces during infection, causing the cytokine storm. Polyunsaturated fatty acids (PUFAs) are the precursors of eicosanoids, which play critical roles in immune regulation and inflammation. The balance between ω-3 and ω-6 levels in the cell membrane has a critical role in regulating the equilibrium between proinflammatory and antiinflammatory processes and inducing IL-6 production. The present study focused on inflammatory and antiinflammatory mechanisms in COVID-19 over PUFAs and on relating their levels with disease prognosis and severity. MethodsA total of 106 participants were included in the study. They were divided into three groups according to IL-6 level— 1: <35 pg/mL, 2: between 35 and 300 pg/mL, and 3: >300 pg/mL. Erythrocyte membrane PUFA compositions were analyzed by group. ResultsLevels of γ-linolenic acid and ω-6/ω-3 ratios were significantly increased in all comparison groups (P < 0.05). Total ω-6 and the ratio of arachidonic acid to eicosopentaenoic acid showed a statistically significant difference only between groups 1 and 3 (P < 0.05). There was a moderately negative correlation between total ω-3 and IL-6 and procalcitonin. There were positive correlations with ω-6/ω-3 ratio inflammatory markers, and the total ω-6 index also showed a moderately positive correlation with IL-6, procalcitonin, and D-dimer levels. ConclusionsThe ratio of arachidonic acid to eicosopentaenoic acid, and ω-3 PUFAs, can be systemic signs of poor prognosis, increased lung damage, and high mortality in COVID-19, together with IL-6.

The Association of Nε-Carboxymethyllysine With Polyunsaturated and Saturated Fatty Acids in Healthy Individuals.

Red blood cell (RBC) fatty acid status is used as a biomarker of dietary intake of fats; however, there is still a paucity of evidence regarding individual fatty acids and modulation of endogenous advanced glycation end product (AGE) levels. Due to membrane polyunsaturated fatty acid (PUFA) being a well-known target for peroxidation, we hypothesized that cellular PUFAs are positively associated with circulatory Nε-carboxymethyllysine (CML) that is also influenced by glyoxal levels in healthy cohorts. To test this, we investigated the association between RBC fatty acids and circulatory AGE biomarkers in healthy individuals. The results showed a negative association between saturated fatty acids (SFA) and CML, and stepwise multivariate regression analysis indicated that stearic acid was negatively associated with CML levels (β = -0.200, p = .008) after adjusting for age, body mass index (BMI), and gender. In addition, stearic acid:palmitic acid ratio was also negatively correlated with plasma concentrations of CML (rp = -.191, p = .012) and glucose (rp = -.288, p = .0001). PUFAs showed a positive association with CML levels, particularly docosapentaenoic acid, γ-linolenic acid, arachidonic acid, and docosadienoic acid. However, these associations were not evident after the multiple regression analysis adjusted for age, BMI, and gender. A strong negative correlation (rp = -.98, p < .0001) between total PUFA and total SFA was observed. Furthermore, the SFA:PUFA ratio was inversely correlated with CML (rp = -.227, p < .003). Overall, this study indicates that different fats and their combinations may influence the formation of AGEs and that carefully controlled interventions are required to further test this hypothesis.

Regulation of membrane phospholipids during the adult life of worker honey bee

Two female castes that are genetically identical are found in honey bees: workers and queens. Adult female honey bees differ in their morphology and behaviors, but the most intriguing difference between the castes is the difference in their longevity. Queens live for years while workers live generally for weeks. The mechanisms that mediate this extraordinary difference in lifespan remain mostly unknown. Both castes share similar developmental stages and are fed liquid food (i.e. a jelly) during development. However, after emergence, workers begin to feed on pollen while queens are fed the same larval food for their entire life. Pollen has a high content of polyunsaturated fatty acids (PUFA) while royal jelly has negligible amounts. The difference in food during adult life leads to drastic changes in membrane phospholipids of female honey bees, and those changes have been proposed as mechanisms that could explain the difference in lifespan. To provide further details on those mechanisms, we characterized the membrane phospholipids of adult workers at seven different ages covering all life-history stages. Our results suggest that the majority of changes in worker membranes occur in the first four days of adult life. Shortly after emergence, workers increase their level of total phospholipids by producing phospholipids that contained saturated (SFA) and monounsaturated fatty acids (MUFA). From the second day, workers start replacing fatty acid chains from those pre-synthesized molecules with PUFA acquired from pollen. After four days, worker membranes are set and appear to be maintained for the rest of adult life, suggesting that damaged PUFA are replaced effectively. Plasmalogen phospholipids increase continuously throughout worker adult life, suggesting that plasmalogen might help to reduce lipid peroxidation in worker membranes. We postulate that the diet-induced increase in PUFA in worker membranes makes them far more prone to lipid-based oxidative damage compared to queens.

4-Hydroxy-2-nonenal antimicrobial toxicity is neutralized by an intracellular pathogen

Pathogens encounter numerous antimicrobial responses during infection, including the reactive oxygen species (ROS) burst. ROS-mediated oxidation of host membrane poly-unsaturated fatty acids (PUFAs) generates the toxic alpha-beta carbonyl 4-hydroxy-2-nonenal (4-HNE). Although studied extensively in the context of sterile inflammation, research into 4-HNE's role during infection remains limited. Here, we found that 4-HNE is generated during bacterial infection, that it impacts growth and survival in a range of bacteria, and that the intracellular pathogen Listeria monocytogenes induces many genes in response to 4-HNE exposure. A component of the L. monocytogenes 4-HNE response is the expression of the genes lmo0103 and lmo0613, deemed rha1 and rha2 (reductase of host alkenals), respectively, which code for two NADPH-dependent oxidoreductases that convert 4-HNE to the product 4-hydroxynonanal (4-HNA). Loss of these genes had no impact on L. monocytogenes bacterial burdens during murine or tissue culture infection. However, heterologous expression of rha1/2 in Bacillus subtilis significantly increased bacterial resistance to 4-HNE in vitro and promoted bacterial survival following phagocytosis by murine macrophages in an ROS-dependent manner. Thus, Rha1 and Rha2 are not necessary for 4-HNE resistance in L. monocytogenes but are sufficient to confer resistance to an otherwise sensitive organism in vitro and in host cells. Our work demonstrates that 4-HNE is a previously unappreciated component of ROS-mediated toxicity encountered by bacteria within eukaryotic hosts.

Perspective: What Should I Eat to Maintain Membrane Lipid Rafts and Avoid Metabolic Disease?

Discerning meaningful patterns in lipidomic studies of metabolic diseases is daunting. Consideration of changes in dietary lipids over the last 150 years and the effects of this variance on membrane raft formation provides a tool to better understand lipidomic data. In vitro, mixtures of low and high melting point lipids and cholesterol spontaneously form bilayers with heterologous areas of differing order, composition, and physical properties. Through dozens of studies, the general behavior of different lipid mixtures in phase separation has been mapped and displayed as ternary lipid mixture phase diagrams; areas that show both liquid order (Lo) and liquid disorder (Ld) allow raft formation (Figure 1). In vivo, ordered membrane areas composed of sterols, sphingolipids and proteins provide platforms necessary for a complex network of cellular signaling. Although there is controversy regarding the primacy of lipids versus proteins in organizing these signaling rafts, this perspective focuses on the role that variations in dietary lipids might play in raft formation. Comparison of dietary lipids in humans living before the agricultural revolution to those living in 21st century developed areas reveals major differences. Modern diets have: increased polyunsaturated fatty acids (PUFA) from vegetable oils, an increased ratio of omega 6:3 PUFA, increased trans fatty acids (TFA), and decreased cholesterol. Plotting these variations in dietary lipids on a ternary graph provides a framework to understand the theoretical effect of dietary lipid variance on phase separation and membrane behavior. For example, how might increased dietary TFA, a widely recognized risk factor in cardiovascular disease, disrupt raft formation? Substitution of TFA for PUFA at sn-2 in low melting point phospholipids would raise the melting point; substitution at sn-1 on sphingolipids would lower the melting point. Because disparity in the order of membrane domains is critical in the maintenance of phase separation, convergence of melting points of these compounds would thus impede raft formation (Figure 2). To compensate, incorporation of highly unsaturated PUFA to lower the melting point of non raft phospholipids, or incorporation of longer chain saturated fatty acids to raise the melting point of raft associated lipids would restore order differential and allow raft formation, but would require other changes to maintain optimal membrane viscosity. Elevated membrane PUFA increases oxidative damage and an elevated omega 6:3 ratio increases thrombosis and inflammation. Compared to cis forms, TFA phospholipids require eight times more cholesterol to be incorporated into a membrane; with reduced cholesterol diets, accommodation of TFAs into membranes would require stimulation of endogenous cholesterol synthesis. Increased membrane cholesterol also decreases permeability to oxygen. Because most fatty acids are incorporated into cell membranes unmodified from the form in which they were absorbed from the GI tract, changes in dietary lipids critically impact cell membrane composition. This example illustrates the theoretical impact of dietary lipids on raft formation and behavior as a means to understand lipidomic data and the pathophysiologic elements of dyslipidemia, oxidative stress, inflammation and cellular hypoxia.