Uptake Of Long-chain Fatty Acids Research Articles

UCP1-dependent brown adipose activation accelerates cardiac metabolic remodeling and reduces initial hypertrophic and fibrotic responses to pathological stress.

Brown adipose tissue (BAT) is correlated to cardiovascular health in rodents and humans, but the physiological role of BAT in the initial cardiac remodeling at the onset of stress is unknown. Activation of BAT via 48 h cold (16°C) in mice following transverse aortic constriction (TAC) reduced cardiac gene expression for LCFA uptake and oxidation in male mice and accelerated the onset of cardiac metabolic remodeling, with an early isoform shift of carnitine palmitoyltransferase 1 (CPT1) toward increased CPT1a, reduced entry of long chain fatty acid (LCFA) into oxidative metabolism (0.59 ± 0.02 vs. 0.72 ± 0.02 in RT TAC hearts, p < .05) and increased carbohydrate oxidation with altered glucose transporter content. BAT activation with TAC reduced early hypertrophic expression of β-MHC by 61% versus RT-TAC and reduced pro-fibrotic TGF-β1 and COL3α1 expression. While cardiac natriuretic peptide expression was yet to increase at only 3 days TAC, Nppa and Nppb expression were elevated in Cold TAC versus RT TAC hearts 2.7- and 2.4-fold, respectively. Eliminating BAT thermogenic activation with UCP1 KO mice eliminated differences between Cold TAC and RT TAC hearts, confirming effects of BAT activation rather than autonomous cardiac responses to cold. Female responses to BAT activation were blunted, with limited UCP1 changes with cold, partly due to already activated BAT in females at RT compared to thermoneutrality. These data reveal a previously unknown physiological mechanism of UCP1-dependent BAT activation in attenuating early cardiac hypertrophic and profibrotic signaling and accelerating remodeled metabolic activity in the heart at the onset of cardiac stress.

Obesity induces an increase in fatty acid uptake in endothelium of visceral adipose arteries without altering CD36 expression

Obesity is a prevalent metabolic condition and major contributor to the development of cardiovascular disease. Arteries of visceral adipose present with significant endothelial dysfunction whereas subcutaneous adipose arteries remain functional in obese humans and diet-induced obese mice. Obesity is also associated with elevated plasma long chain fatty acids (LCFAs), well-established contributors to endothelial dysfunction, which require a receptor to facilitate their uptake. CD36, a scavenger receptor, facilitates LCFA uptake, which when in excess would contribute to endothelial dysfunction. Therefore, we aimed to determine the role of CD36 in arteries ex vivo in both mouse and human subcutaneous and visceral adipose arteries as well as examine the difference in uptake of LCFAs in arteries from both depots. First, to determine if CD36 contributes to obesity-induced endothelial dysfunction in visceral adipose arteries, mesenteric (visceral) and subcutaneous adipose arteries isolated from lean and diet-induced obese WT and CD36 knockout were mounted for pressure myography. As expected, visceral adipose arteries of obese mice exhibited a blunted response to endothelium-dependent stimuli, whereas subcutaneous adipose arteries remained functional. CD36 ablation restored endothelium-dependent vasodilation in visceral arteries of obese mice, suggesting a critical role for CD36 in obesity-induced endothelial dysfunction. We next aimed to determine if obesity alters endothelial CD36 expression using two distinct approaches: flow cytometry and immunofluorescence staining of en face preparations in isolated mouse and/or human arteries. For flow cytometry, arteries were digested and sorted to identify the endothelial cell population (i.e., CD45-CD31+ cells). En face preparations were stained for VE-cadherin to locate the endothelial cell layer via confocal microscopy. In both experiments, an antibody that detects an extracellular epitope to CD36 was used to detect membrane expression. Obesity did not alter the expression of CD36 expression in visceral adipose arteries relative to lean counterpart controls or subcutaneous arteries from obese mice or humans. We next aimed to determine if LCFA uptake was altered by obesity. Arteries were exposed to a fluorescent fatty acid, and internalized endothelial LCFA uptake was assessed at different time points via confocal microscopy. Visceral arteries from obese mice and humans had elevated LCFA uptake relative to respective controls which may be an underlying mediator for the dichotomy in endothelial dysfunction observed in obesity. Ongoing work in our lab is focused on determining if this is indeed the case and, if so, if this process is mediated by endothelial CD36. National Institutes of Health (NIH) Grant P20GM113125-6564 (IF). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 198: Selective targeting of endothelial mTORC1 reduces transendothelial fatty acid delivery to improve anti-tumor immunity and suppress metastatic outgrowth

Abstract Tumor metastasis requires sufficient nutrients to support outgrowth of disseminated tumor cells. Cancer cells utilize fatty acids as a key source of energy and biomass, but these nutrients impair the cytotoxic activities of T cells, serving to support metastatic progression. Blood is a rich source of fatty acids, but the vascular endothelium serves as a barrier to limit access to the surrounding tumor tissue. However, it is unclear how long-chain fatty acid delivery to early metastatic tumors is regulated. Here, we report that endothelial mTORC1 promotes transport of fatty acids into developing metastatic tumors, leading to reduced anti-tumor immune responses and improved outgrowth. Using a murine model of metastatic outgrowth in the lung, tumor burden was significantly reduced upon targeted deletion of Raptor, an essential component of the mTORC1 complex, in endothelial cells (RptorECKO). We employed a multifaceted approach using metabolomics, transcriptomics, and molecular assays to identify a Raptor/mTORC1-mediated mechanism of transendothelial fatty acid transport via RAB and CLSTN1 cargo trafficking. In vivo uptake of a fluorescent palmitic acid analog in tumor cells and T cells was reduced in RptorECKO lung metastatic tumors, which correlated with improved markers of cytotoxicity. Combination of low-dose RAD001/everolimus, which selectively inhibits mTORC1 in endothelial cells, with anti-PD1 reduces metastatic disease and impairs long-chain fatty acid uptake in T cells, corresponding to improved anti-tumor immunity. These findings describe a novel mechanism of transendothelial fatty acid transportation during metastatic outgrowth, supporting future development of therapeutic strategies to target endothelial mTORC1 activity. Citation Format: Deanna N. Edwards, Shan Wang, Wenqiang Song, Laura C. Kim, Yoonha Hwang, Jin Chen. Selective targeting of endothelial mTORC1 reduces transendothelial fatty acid delivery to improve anti-tumor immunity and suppress metastatic outgrowth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 198.

Research Progress on the Mechanism of Milk Fat Synthesis in Cows and the Effect of Conjugated Linoleic Acid on Milk Fat Metabolism and Its Underlying Mechanism: A Review.

Milk fat synthesis in cows mainly includes the synthesis of short- and medium-chain fatty acids, the uptake, transport, and activation of long-chain fatty acids (LCFAs), the synthesis of triglycerides, and the synthesis of the genes, transcription factors, and signaling pathways involved. Although the various stages of milk fat synthesis have been outlined in previous research, only partial processes have been revealed. CLA consists of an aggregation of positional and geometric isomers of linoleic fatty acid, and the accumulated evidence suggests that the two isomers of the active forms of CLA (cis-9, trans-11 conjugated linoleic acid and trans-10, cis-12 conjugated linoleic acid, abbreviated as c9, t11-CLA and t10, c12-CLA) can reduce the fat content in milk by regulating lipogenesis, fatty acid (FA) uptake, oxidation, and fat synthesis. However, the mechanism through which CLA inhibits milk fat synthesis is unique, with most studies focusing only on the effects of CLA on one of the genes, transcription factors, or signaling pathways involved. In this study, we summarized the structure and function of classic genes and pathways (mTOR, SREBP, AMPK, and PPARG) and new genes or pathways (THRSP, METTL3, ELOVL, and LPIN1) involved in each stage of milk fat synthesis and demonstrated the interactions between genes and pathways. We also examined the effects of other substances (melanin, nicotinic acid, SA, etc.). Furthermore, we evaluated the influence of β-sitosterol, sodium butyrate, Met arginine, and Camellia oleifera Abel on milk fat synthesis to improve the mechanism of milk fat synthesis in cows and provide a mechanistic reference for the use of CLA in inhibiting milk fat biosynthesis.

Elevated glycosylation of CD36 in platelets is a risk factor for oxLDL-mediated platelet activation in type 2 diabetes.

Platelet activation and related cardiovascular complications are the hallmarks of type 2 diabetes (T2D). We investigated the mechanism of platelet activation in T2D using MS-based identification of differentially expressed platelet proteins with a focus on glycosylated forms. Glycosylation is considered one of the common post-translational modifications in T2D, and N/O-linked glycosylation of glycoproteins (GPs)/integrins is known to play crucial roles in platelet activation. Our platelet proteome data revealed elevated levels of GPs GPIbα, GPIIbIIIa, GPIV (CD36), GPV and integrins in T2D patients. T2D platelets had elevated N-linked glycosylation of CD36 at asparagine (Asn)408,417 . Enrichment analysis revealed a close association of glycosylated CD36 with thrombospondin-1, fibrinogen and SERPINA1 in T2D platelets. The glycosylation of CD36 has previously been reported to increase cellular uptake of long-chain fatty acids. Our in silico molecular docking data also showed a favorable binding of cholesterol with glycosylated Asn417 CD36 compared to the non-glycosylated form. We further investigated the CD36:LDL cholesterol axis in T2D. Elevated levels of oxidized-low density lipoprotein (oxLDL) were found to cause significant platelet activation via CD36-mediated stimulation of Lyn-JNK signaling. Sulfo-N-succinimidyl oleate, an inhibitor of CD36, effectively inhibited oxLDL-mediated platelet activation and adhesion in vitro. Our study suggests increased glycosylation of CD36 in T2D platelets as a potential route for oxLDL-mediated platelet activation. The oxLDL:CD36 axis may thus be exploited as a prospective target to develop therapeutics against thrombosis in T2D.

CD36 as a gatekeeper of myocardial lipid metabolism and therapeutic target for metabolic disease.

The multifunctional membrane glycoprotein CD36 is expressed in different types of cells and plays a key regulatory role in cellular lipid metabolism, especially in cardiac muscle. CD36 facilitates the cellular uptake of long-chain fatty acids, mediates lipid signaling, and regulates storage and oxidation of lipids in various tissues with active lipid metabolism. CD36 deficiency leads to marked impairments in peripheral lipid metabolism, which consequently impact on the cellular utilization of multiple different fuels because of the integrated nature of metabolism. The functional presence of CD36 at the plasma membrane is regulated by its reversible subcellular recycling from and to endosomes and is under the control of mechanical, hormonal, and nutritional factors. Aberrations in this dynamic role of CD36 are causally associated with various metabolic diseases, in particular insulin resistance, diabetic cardiomyopathy, and cardiac hypertrophy. Recent research in cardiac muscle has disclosed the endosomal proton pump vacuolar-type H+-ATPase (v-ATPase) as a key enzyme regulating subcellular CD36 recycling and being the site of interaction between various substrates to determine cellular substrate preference. In addition, evidence is accumulating that interventions targeting CD36 directly or modulating its subcellular recycling are effective for the treatment of metabolic diseases. In conclusion, subcellular CD36 localization is the major adaptive regulator of cellular uptake and metabolism of long-chain fatty acids and appears a suitable target for metabolic modulation therapy to mend failing hearts.

Deletion of PGAM5 Downregulates FABP1 and Attenuates Long-Chain Fatty Acid Uptake in Hepatocellular Carcinoma.

Phosphoglycerate mutase 5 (PGAM5) is a Ser/His/Thr phosphatase responsible for regulating mitochondrial homeostasis. Overexpression of PGAM5 is correlated with a poor prognosis in hepatocellular carcinoma, colon cancer, and melanoma. In hepatocellular carcinoma, silencing of PGAM5 reduces growth, which has been attributed to decreased mitophagy and enhanced apoptosis. Yet in colon cancer, PGAM5's pro-tumor survival effect is correlated to lipid metabolism. We sought to identify whether deletion of PGAM5 modulated lipid droplet accrual in hepatocellular carcinoma. HepG2 and Huh7 PGAM5 knockout cell lines generated using CRISPR/Cas9 technology were used to measure cell growth, cellular ATP, and long-chain fatty acid uptake. Expression of hepatocellular fatty acid transporters, cluster of differentiation 36 (CD36), solute carrier family 27 member 2 (SLC27A2), solute carrier family 27 member 5 (SLC27A5), and fatty acid binding protein 1 (FABP1) was measured by quantitative PCR and Western blot. We found that deletion of PGAM5 attenuates hepatocellular carcinoma cell growth and ATP production. Further, PGAM5 knockout ameliorates palmitate-induced steatosis and reduces expression of FABP1 in HepG2 and Huh7 cell lines. PGAM5's role in hepatocellular carcinoma includes regulation of fatty acid metabolism, which may be related to expression of the fatty acid transporter, FABP1.

Voltage-dependent anion channel 1 (VDAC1) overexpression alleviates cardiac fibroblast activation in cardiac fibrosis via regulating fatty acid metabolism

Cardiac fibrosis is characterized by the excessive deposition of extracellular matrix in the myocardium with cardiac fibroblast activation, leading to chronic cardiac remodeling and dysfunction. However, little is known about metabolic alterations in fibroblasts during cardiac fibrosis, and there is a lack of pharmaceutical treatments that target metabolic dysregulation. Here, we provided evidence that fatty acid β-oxidation (FAO) dysregulation contributes to fibroblast activation and cardiac fibrosis. With transcriptome, metabolome, and functional assays, we demonstrated that FAO was downregulated during fibroblast activation and cardiac fibrosis, and that perturbation of FAO reversely affected the fibroblast-to-myofibroblast transition. The decrease in FAO may be attributed to reduced long-chain fatty acid (LCFA) uptake. Voltage-dependent anion channel 1 (VDAC1), the main gatekeeper of the outer mitochondrial membrane (OMM), serves as the transporter of LCFA into the mitochondria for further utilization and has been shown to be decreased in myofibroblasts. In vitro, the addition of exogenous VDAC1 was shown to ameliorate cardiac fibroblast activation initiated by transforming growth factor beta 1 (TGF-β1) stimuli, and silencing of VDAC1 displayed the opposite effect. A mechanistic study revealed that VDAC1 exerts a protective effect by regulating LCFA uptake into the mitochondria, which is impaired by an inhibitor of carnitine palmitoyltransferase 1A. In vivo, AAV9-mediated overexpression of VDAC1 in myofibroblasts significantly alleviated transverse aortic constriction (TAC)-induced cardiac fibrosis and rescued cardiac function in mice. Finally, we treated mice with the VDAC1-derived R-Tf-D-LP4 peptide, and the results showed that R-Tf-D-LP4 prevented TAC-induced cardiac fibrosis and dysfunction in mice. In conclusion, this study provides evidence that VDAC1 maintains FAO metabolism in cardiac fibroblasts to repress fibroblast activation and cardiac fibrosis and suggests that the VDAC1 peptide is a promising drug for rescuing fibroblast metabolism and repressing cardiac fibrosis.

The role of candidate transport proteins in β-cell long-chain fatty acid uptake: Where are we now?

Type 2 diabetes (T2D) in humans is typically preceded by elevated levels of circulatory long-chain free fatty acids (LC-FFA). These excess LC-FFA are widely thought to be taken up by pancreatic β-cells, contributing to their dysfunction and death during the development of T2D; a process that has been termed lipotoxicity. Depending on their degree of saturation and carbon chain length, LC-FFA can exert different effects on pancreatic β-cells viability and function in vitro. Long-chain saturated fatty acids (LC-SFA) are thought to be toxic, whereas monounsaturated fatty acids are not and may even offer protection against the toxic effects of LC-SFAs. However, the mechanism of LC-FFA uptake into pancreatic β-cells is poorly understood, partly because it has been an understudied area of research. Determining how LC-FFA are taken up into β-cells is crucial for later formulation of therapies to prevent potential cellular overload of LC-FFA, thereby slowing the onset of T2D. In this work, we detail more than 40 years of literature investigating the role of membrane-associated transport proteins in LC-FFA uptake. By focussing on what is known in other cell types, we highlight where we can extrapolate our current understanding of protein-mediated transport to β-cells and uncover where further understanding is required.

RabGAP AS160/TBC1D4 deficiency increases long-chain fatty acid transport but has little additional effect on obesity and metabolic syndrome in ADMSCs-derived adipocytes of morbidly obese women.

The Akt substrate of 160kDa (AS160), also known as TBC1 domain family member 4 (TBC1D4), represents a crucial regulator of insulin-stimulated glucose uptake in skeletal muscle and adipose tissue. Recent evidence suggests that AS160/TBC1D4 may also control the cellular entry of long-chain fatty acids (LCFAs), resulting in changes to the lipid profile of muscles and fat cells in lean subjects. However, there are virtually no data on AS160/TBC1D4 expression and its modulatory role in lipid metabolism in the adipocytes from morbidly obese individuals of different metabolic status. In this study, we evaluated the effect of the three main factors, i.e., AS160 silencing, obesity, and metabolic syndrome on lipid uptake and profile in fully differentiated adipocytes derived from mesenchymal stem cells (ADMSCs) of lean and obese (with/without metabolic syndrome) postmenopausal women. Additionally, we tested possible interactions between the explanatory variables. In general, obesity translated into a greater content of fatty acid transporters (especially CD36/SR-B2 and SLC27A4/FATP4) and boosted accumulation of all the examined lipid fractions, i.e., triacylglycerols (TAGs), diacylglycerols (DAGs), and free fatty acids (FFAs). The aforementioned were further enhanced by metabolic syndrome. Moreover, AS160 deficiency also increased the abundance of SLC27A4/FATP4 and CD36/SR-B2, especially on the cell surface of the adipocytes derived from ADMSCs of subcutaneous deposit. This was further accompanied by increased LCFA (palmitic acid) uptake. Despite the aforementioned, AS160 silencing seemed unable to significantly affect the phenotype of the adipocytes stemming from obese patients with respect to their cellular lipid profile as we observed virtually no changes in TAG, DAG, and FFA contents when compared to cells with the reference level of proteins. Nevertheless, knockdown of AS160 stimulated fatty acid oxidation, which may indicate that adaptive mechanisms counteract excessive lipid accumulation. At the same time, adipocytes of visceral origin were rather insensitive to the applied intervention.

Uptake of long-chain fatty acids from the bone marrow suppresses CD8+ T-cell metabolism and function in multiple myeloma

AbstractT cells demonstrate impaired function in multiple myeloma (MM) but suppressive mechanisms in the bone marrow microenvironment remain poorly defined. We observe that bone marrow CD8+ T-cell function is decreased in MM compared with controls, and is also consistently lower within bone marrow samples than in matched peripheral blood samples. These changes are accompanied by decreased mitochondrial mass and markedly elevated long-chain fatty acid uptake. In vitro modeling confirmed that uptake of bone marrow lipids suppresses CD8+ T function, which is impaired in autologous bone marrow plasma but rescued by lipid removal. Analysis of single-cell RNA-sequencing data identified expression of fatty acid transport protein 1 (FATP1) in bone marrow CD8+ T cells in MM, and FATP1 blockade also rescued CD8+ T-cell function, thereby identifying this as a novel target to augment T-cell activity in MM. Finally, analysis of samples from cohorts of patients who had received treatment identified that CD8+ T-cell metabolic dysfunction resolves in patients with MM who are responsive to treatment but not in patients with relapsed MM, and is associated with substantial T-cell functional restoration.

Retained Metabolic Flexibility of the Failing Human Heart.

The failing heart is traditionally described as metabolically inflexible and oxygen starved, causing energetic deficit and contractile dysfunction. Current metabolic modulator therapies aim to increase glucose oxidation to increase oxygen efficiency of adenosine triphosphate production, with mixed results. To investigate metabolic flexibility and oxygen delivery in the failing heart, 20 patients with nonischemic heart failure with reduced ejection fraction (left ventricular ejection fraction 34.9±9.1) underwent separate infusions of insulin+glucose infusion (I+G) or Intralipid infusion. We used cardiovascular magnetic resonance to assess cardiac function and measured energetics using phosphorus-31 magnetic resonance spectroscopy. To investigate the effects of these infusions on cardiac substrate use, function, and myocardial oxygen uptake (MVo2), invasive arteriovenous sampling and pressure-volume loops were performed (n=9). At rest, we found that the heart had considerable metabolic flexibility. During I+G, cardiac glucose uptake and oxidation were predominant (70±14% total energy substrate for adenosine triphosphate production versus 17±16% for Intralipid; P=0.002); however, no change in cardiac function was seen relative to basal conditions. In contrast, during Intralipid infusion, cardiac long-chain fatty acid (LCFA) delivery, uptake, LCFA acylcarnitine production, and fatty acid oxidation were all increased (LCFA 73±17% of total substrate versus 19±26% total during I+G; P=0.009). Myocardial energetics were better with Intralipid compared with I+G (phosphocreatine/adenosine triphosphate 1.86±0.25 versus 2.01±0.33; P=0.02), and systolic and diastolic function were improved (LVEF 34.9±9.1 baseline, 33.7±8.2 I+G, 39.9±9.3 Intralipid; P<0.001). During increased cardiac workload, LCFA uptake and oxidation were again increased during both infusions. There was no evidence of systolic dysfunction or lactate efflux at 65% maximal heart rate, suggesting that a metabolic switch to fat did not cause clinically meaningful ischemic metabolism. Our findings show that even in nonischemic heart failure with reduced ejection fraction with severely impaired systolic function, significant cardiac metabolic flexibility is retained, including the ability to alter substrate use to match both arterial supply and changes in workload. Increasing LCFA uptake and oxidation is associated with improved myocardial energetics and contractility. Together, these findings challenge aspects of the rationale underlying existing metabolic therapies for heart failure and suggest that strategies promoting fatty acid oxidation may form the basis for future therapies.

Cyclic AMP is a critical mediator of intrinsic drug resistance and fatty acid metabolism in M. tuberculosis.

Cyclic AMP (cAMP) is a ubiquitous second messenger that transduces signals from cellular receptors to downstream effectors. Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis, devotes a considerable amount of coding capacity to produce, sense, and degrade cAMP. Despite this fact, our understanding of how cAMP regulates Mtb physiology remains limited. Here, we took a genetic approach to investigate the function of the sole essential adenylate cyclase in Mtb H37Rv, Rv3645. We found that a lack of rv3645 resulted in increased sensitivity to numerous antibiotics by a mechanism independent of substantial increases in envelope permeability. We made the unexpected observation that rv3645 is conditionally essential for Mtb growth only in the presence of long-chain fatty acids, a host-relevant carbon source. A suppressor screen further identified mutations in the atypical cAMP phosphodiesterase rv1339 that suppress both fatty acid and drug sensitivity phenotypes in strains lacking rv3645. Using mass spectrometry, we found that Rv3645 is the dominant source of cAMP under standard laboratory growth conditions, that cAMP production is the essential function of Rv3645 in the presence of long-chain fatty acids, and that reduced cAMP levels result in increased long-chain fatty acid uptake and metabolism and increased antibiotic susceptibility. Our work defines rv3645 and cAMP as central mediators of intrinsic multidrug resistance and fatty acid metabolism in Mtb and highlights the potential utility of small molecule modulators of cAMP signaling.

Targeting first trimester trophoblast cell metabolism modulates its susceptibility to Zika virus infection.

In the last 15 years Zika virus (ZIKV) caused several outbreaks of increasing scale in Micronesia, South Pacific islands, and more recently in the Caribbean and South America. The severity of the clinical presentation in neonates from pregnant women infected with ZIKV during the last outbreak supports the relevance of unraveling the mechanism of infection and viral persistence in the placenta with local viral isolates. Here, we investigated the relevance of trophoblast metabolic rewiring for viral multiplication and the role of the vasoactive intestinal peptide (VIP) as an endogenous factor associated with placental restriction to ZIKV infection at early pregnancy. Our in vitro model demonstrated that ZIKV triggers metabolic rewiring in first trimester cytotrophoblast-derived cells by increasing glucose utilization as fuel to sustain its replication, decreasing long-chain polyunsaturated fatty acid uptake, and promoting lipid droplets accumulation to favor its multiplication. Of note, variations in nutrient availability modulated viral spread in trophoblast cultures. The presence of VIP during trophoblast infection impaired ZIKV infective particle production and viral replication, restoring cell migration and metabolism. Moreover, the blockade of endogenous VIP signaling increased viral particle production and the viral entry receptor AXL expression. These results highlight the potential role of VIP as an endogenous antiviral factor related to trophoblast cell permissiveness to ZIKV infection at early pregnancy.

Cellular Uptake, Metabolism and Sensing of Long-Chain Fatty Acids.

Fatty acids (FAs) are critical nutrients that regulate an organism's health and development in mammal. Long-chain fatty acids (LCFAs) can be divided into saturated and unsaturated fatty acids, depending on whether the carbon chain contains at least 1 double bond. The fatty acids that are required for humans and animals are obtained primarily from dietary sources, and LCFAs are absorbed from outside of cells in mammals. LCFAs enter cells through several mechanisms, including passive diffusion and protein-mediated translocation across the plasma membrane, the latter in which FA translocase (FAT/CD36), plasma membrane FA-binding protein (FABPpm), FA transport protein (FATP), and caveolin-1 are believed to have important functions. The LCFAs that are taken up by cells bind to FA-binding proteins (FABPs) and are transported to the specific organelles, where they are activated into acyl-CoA to target specific metabolic pathways. LCFA-CoAs can be esterified to phospholipids, triacylglycerol, cholesteryl ester, and other specialized lipids. Non-esterified free fatty acids are preferentially stored as triacylglycerol molecules. The main pathway by which fatty acids are catabolized is β-oxidation, which occurs in mitochondria and peroxisomes. stearoyl-CoA desaturase (SCD)-dependent and Fatty acid desaturases (FADS)-dependent fatty acid desaturation pathways coexist in cells and provide metabolic plasticity. The process of fatty acid elongation occurs by cycling through condensation, reduction, dehydration, and reduction. Extracellular LCFA can be mediated by membrane protein G protein-coupled receptor 40 (GPR40) or G protein-coupled receptor 120 (GPR120) to activate mammalian target of rapamycin complex 1 (mTORC1) signaling, and intracellular LCFA's sensor remains to be determined. The crystal structures of a phosphatidic acid phosphatase and a membrane-bound fatty acid elongase-condensing enzyme and other LCFA-related proteins provide important insights into the mechanism of utilization, increasing our understanding of the cellular uptake, metabolism and sensing of LCFAs.

In Vivo Imaging of Bone Marrow Long-Chain Fatty Acid Uptake.

In vivo imaging enables the detection and visualization of many different processes occurring within the body. Fatty acid uptake is a fundamental cellular process which is essential for the use of free fatty acids (FFAs) as a fuel source for metabolism. Detection and visualization of in vivo FFA uptake in the bone marrow has been relatively unknown. Here, we describe the process of non-invasive bioluminescent imaging of in vivo FFA uptake within the bone marrow.

Fatty Acid Transfer from Blood to Milk Is Disrupted in Mothers with Low Milk Production, Obesity, and Inflammation

Obesity is associated with chronic inflammation and is a risk factor for insufficient milk production. Inflammation-mediated suppression of LPL could inhibit mammary uptake of long-chain fatty acids (LCFAs; >16 carbons). In an ancillary case-control analysis, we investigated whether women with low milk production despite regular breast emptying have elevated inflammation and disrupted transfer of LCFAs from plasma into milk. Data and specimens from a low milk supply study and an exclusively breastfeeding control group were analyzed, with milk production measured by 24-h test-weighing at 2-10 wk postpartum. Low milk supply groups were defined as very low (VL; <300mL/d; n=23) or moderate (MOD; ≥300mL/d; n=20) milk production, and compared with controls (≥699mL/d; n=18). Serum and milk fatty acids (weight% of total) were measured by GC, serum and milk TNF-α by ELISA, and serum high-sensitivity C-reactive protein (hsCRP) by clinical analyzer. Group differences were assessed by linear regression models, chi-square exact tests, and Kruskal-Wallis nonparametric tests. VL cases, as compared with MOD cases and controls, had higher prevalence of elevated serum hsCRP (>5mg/L; 57%, 15%, and 22%, respectively; P=0.004), detectable milk TNF-α (67%, 32%, and 33%, respectively; P=0.04), and obesity (78%, 40%, and 22%, respectively; P=0.003). VL cases had lower mean±SD LCFAs in milk (60%±3%) than MOD cases (65%±4%) and controls (66%±5%) (P<0.001). Milk and serum LCFAs were strongly correlated in controls (r=0.82, P<0.001), but not in the MOD (r=0.25, P=0.30) or VL (r=0.20, P=0.41) groups (Pint<0.001). Mothers with very low milk production have significantly higher obesity and inflammatory biomarkers, lower LCFAs in milk, and disrupted association between plasma and milk LCFAs. These data support the hypothesis that inflammation disrupts normal mammary gland fatty acid uptake. Further research should address impacts of inflammation and obesity on mammary fatty acid uptake for milk production.

Dysfunction of T Cells from Chronic Lymphocytic Leukemia (CLL) Patients Is Linked to Disturbed Lipid and Fatty Acid Homeostasis

Background: Successful T cell-based anti-cancer therapies require proliferation and longevity of effector cells, features that highly depend on metabolic processes. A key feature of chronic lymphocytic leukemia (CLL) is acquired T cell dysfunction, resulting in impaired proliferative capacity (van Bruggen, et al Blood Adv 2022). T cell lipid metabolism has only recently come into focus as an important source of energy production and at the same time as essential component for the formation of new membranes upon proliferation. Fatty acid (FA) and lipid uptake in T cells requires several membrane proteins, among which the scavenger FA transporter CD36 and the low-density lipoprotein receptor (LDL-R). Specifically CD36-mediated FA transport has been identified to modulate (intratumoral) Treg and cytotoxic CD8+ T cells (Kolonin, et al, 2021 Immunometab). Whether T cell lipid and FA metabolism are affected in CLL is currently unknown. Methods: Peripheral blood mononuclear cells (PBMCs) of untreated CLL patients and, as control, age-matched healthy donors (HD) were studied. T cells were analyzed by transcriptomics, lipidomics and flow cytometry, either directly after thawing or after a 2-day culture with or without αCD3/αCD28 antibodies. Results: Unbiased transcriptomic analyses of patient-derived T cells following αCD3/αCD28 activation showed reduced expression of the master regulators of FA and cholesterol biosynthesis SREBF1 and SREBF2 in the presence of autologous CLL cells. This was associated with significantly reduced protein abundance of downstream targets of the SREBP pathway, including the key enzymes in FA synthesis and saturation FASN and SCD. In accordance with these data, lipidomic analyses highlighted an altered lipid profile in T cells from CLL patients that clearly demarcated them from HD T cells. In short, unbiased analyses revealed disturbed lipid homeostasis in CLL T cells at multiple levels, which led us to investigate lipid and FA metabolic pathways and their related functional consequences. Studying lipid and FA uptake capacity revealed lower expression of the FA transporter CD36 on CLL T cells. Stimulation of HD T cells resulted in upregulation of CD36 and the main receptor for cholesterol uptake LDL-R, accompanied by increased uptake of long chain fatty acids (LCFA) and increased FA-oxidation, concomitantly with induced expression of the activation marker CD25. In contrast, CLL-derived T cells did not increase CD36 or LDL-R expression, LCFA uptake or oxidation (Fig 1 and 2). Because of a recently suggested role for CD36 in T cell function, we next specifically analyzed CD36-expressing T cells (CD36+), and found these to have higher ability for LCFA and glucose uptake, and higher expression of the glucose transporter GLUT-1 than CD36 negative T cells from the same HD. Accordingly, CD36+ cells were also more likely to increase their CD25 expression and mitochondrial mass upon a 48h stimulation. This CD36+ T cell subpopulation, with potential metabolic and functional advantage, was virtually absent in CLL PBMCs. Impact of FA and lipid metabolism on proliferation was further established by the observation that culturing of HD T cells in absence of exogenous lipids resulted in nearly absent proliferative capacity. However, despite decreased expression of lipid and FA transporters, we observed marked accumulation of lipid droplets (LD) in T cells from CLL patients, suggesting an impaired ability to mobilize lipids towards oxidation pathways or as building blocks for membranes. In line with this, we found that in contrast to HD T cells that increased the expression of the rate-limiting enzyme for lipolysis ATGL, CLL T cells failed to do so. Conclusions: We provide the first data showing a disturbed lipid and FA metabolism of CLL T cells that contributes to T cell dysfunction. This includes decreased expression of FA synthesis enzymes as well as FA and cholesterol transporters. CD36+ T cells are metabolically distinct and are largely absent in CLL. We are investigating strategies to increase FA and lipid metabolism in order to rebalance lipid homeostasis. This could ameliorate CLL T cell dysfunction and specifically proliferation defects in CLL. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Characterisation of the mechanism of long-chain fatty acid uptake in human-derived pancreatic beta cells

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Overexpression of ATGL impairs lipid droplet accumulation by accelerating lipolysis in goat mammary epithelial cells

Adipose triglyceride lipase (ATGL) is the key enzyme for the degradation of triacylglycerols (TAGs). It functions in concert with other enzymes to mobilize TAG and supply fatty acids (FAs) for energy production. Dysregulated lipolysis leads to excess concentrations of circulating FAs, which may lead to destructive and lipotoxic effects to the organism. To understand the role of ATGL in mammary lipid metabolism, ATGL was overexpressed in goat mammary epithelial cells (GMECs) by using a recombinant adenovirus system. ATGL overexpression decreased lipid droplet (LD) accumulation and cellular TG content (p < 0.05) along with a decrease in the expression of the key enzyme that catalyzes the final step of TG synthesis (DGAT). Significant increases were observed in the expression of genes related to lipolysis (hormone-sensitive lipase [HSL]) and FA desaturation (SCD) by ATGL overexpression. Genes responsible for FA oxidation (PPARα), LD formation and secretion (ADRP and BTN1A1), and long-chain FA uptake (CD36) were all decreased by ATGL overexpression (p < 0.05). The primary products of TAG lipolysis, free FAs (FFAs), were notably increased in the ATGL-overexpressing cells. Taken together, our results demonstrated that ATGL activation impairs lipid formation partially through accelerating lipolysis in GMECs.