Utilization Of Long-chain Fatty Acids Research Articles

Smoking Primes the Metabolomic Response in Trauma.

Smoking is a public health threat due to its well described link to increased oxidative stress-related diseases including peripheral vascular disease and coronary artery disease. Tobacco use has been linked to risk of inpatient trauma morbidity including acute respiratory distress syndrome, however its mechanistic effect on comprehensive metabolic heterogeneity has yet to be examined. Plasma was obtained on arrival from injured patients at a Level 1 Trauma Center and analyzed with modern mass spectrometry-based metabolomics. Patients were stratified by non-smoker, passive smoker and active smoker by lower, inter-quartile and upper quartile ranges of cotinine intensity peaks. Patients were sub-stratified by High Injury/High Shock (Injury Severity Score ≥ 15, Base Excess<-6) and compared to healthy controls. P-value <0.05 following FDR correction of t-test was considered significant. 48 patients with High Injury/High Shock (7 (15%) non-smokers, 25 (52%) passive smokers and 16 (33%) active smokers) and 95 healthy patients who served as controls (30 (32%) non-smokers, 43 (45%) passive smokers and 22 (23%) active smokers) were included. Elevated metabolites in our controls who were active smokers include enrichment in chronic inflammatory and oxidative processes. Elevated metabolites in active smokers in high injury/high shock include enrichment in the malate-aspartate shuttle, tyrosine metabolism, carnitine synthesis, and oxidation of very long-chain fatty acids. Smoking promotes a state of oxidative stress leading to mitochondrial dysfunction which is additive to the inflammatory milieu of trauma. Smoking is associated with impaired mitochondrial substrate utilization of long-chain fatty acids, aspartate and tyrosine all of which accentuate oxidative stress following injury. This altered expression represents an ideal target for therapies to reduce oxidative damage toward the goal of personalized treatment of trauma patients. Level III, Prognostic/Epidemiological.

The MoLfa1 Protein Regulates Fungal Development and Septin Ring Formation in Magnaporthe oryzae.

Septins play a key regulatory role in cell division, cytokinesis, and cell polar growth of the rice blast fungus (Magnaporthe oryzae). We found that the organization of the septin ring, which is essential for appressorium-mediated infection in M. oryzae, requires long-chain fatty acids (LCFAs), which act as mediators of septin organization at membrane interfaces. However, it is unclear how septin ring formation and LCFAs regulate the pathogenicity of the rice blast fungus. In this study, a novel protein was named MoLfa1 because of its role in LCFAs utilization. MoLfa1 affects the utilization of LCFAs, lipid metabolism, and the formation of the septin ring by binding with phosphatidylinositol phosphates (PIPs), thereby participating in the construction of penetration pegs of M. oryzae. In addition, MoLfa1 is localized in the endoplasmic reticulum (ER) and interacts with the ER-related protein MoMip11 to affect the phosphorylation level of Mps1. (Mps1 is the core protein in the MPS1-MAPK pathway.) In conclusion, MoLfa1 affects conidia morphology, appressorium formation, lipid metabolism, LCFAs utilization, septin ring formation, and the Mps1-MAPK pathway of M. oryzae, influencing pathogenicity.

Peroxin MoPex22 Regulates the Import of Peroxisomal Matrix Proteins and Appressorium-Mediated Plant Infection in Magnaporthe oryzae.

Magnaporthe oryzae, the pathogen responsible for rice blast disease, utilizes specialized infection structures known as appressoria to breach the leaf cuticle and establish intracellular, infectious hyphae. Our study demonstrates that the peroxin MoPex22 is crucial for appressorium function, specifically for the development of primary penetration hyphae. The ∆Mopex22 mutant exhibited slow growth, reduced aerial hyphae, and almost complete loss of virulence. Specifically, despite the mutant's capability to form appressoria, it showed abnormalities during appressorium development, including reduced turgor, increased permeability of the appressorium wall, failure to form septin rings, and significantly decreased ability to penetrate host cells. Additionally, there was a delay in the degradation of lipid droplets during conidial germination and appressorium development. Consistent with these findings, the ΔMopex22 mutant showed an inefficient utilization of long-chain fatty acids and defects in cell wall integrity. Moreover, our findings indicate that MoPex22 acts as an anchor for MoPex4, facilitating the localization of MoPex4 to peroxisomes. Together with MoPex4, it affects the function of MoPex5, thus regulating the import of peroxisomal matrix proteins. Overall, these results highlight the essential role of MoPex22 in regulating the transport of peroxisomal matrix proteins, which affect fatty acid metabolism, glycerol accumulation, cell wall integrity, growth, appressorium development, and the pathogenicity of M. oryzae. This study provides valuable insights into the significance of peroxin functions in fungal biology and appressorium-mediated plant infection.

A novel role of FoxO3a in the migration and invasion of trophoblast cells: from metabolic remodeling to transcriptional reprogramming

BackgroundThe forkhead box O3a protein (FoxO3a) has been reported to be involved in the migration and invasion of trophoblast, but its underlying mechanisms unknown. In this study, we aim to explore the transcriptional and metabolic regulations of FoxO3a on the migration and invasion of early placental development.MethodsLentiviral vectors were used to knock down the expression of FoxO3a of the HTR8/SVneo cells. Western blot, matrigel invasion assay, wound healing assay, seahorse, gas-chromatography-mass spectrometry (GC–MS) based metabolomics, fluxomics, and RNA-seq transcriptomics were performed.ResultsWe found that FoxO3a depletion restrained the migration and invasion of HTR8/SVneo cells. Metabolomics, fluxomics, and seahorse demonstrated that FoxO3a knockdown resulted in a switch from aerobic to anaerobic respiration and increased utilization of aromatic amino acids and long-chain fatty acids from extracellular nutrients. Furthermore, our RNA-seq also demonstrated that the expression of COX-2 and MMP9 decreased after FoxO3a knockdown, and these two genes were closely associated with the migration/invasion progress of trophoblast cells.ConclusionsOur results suggested novel biological roles of FoxO3a in early placental development. FoxO3a exerts an essential effect on trophoblast migration and invasion owing to the regulations of COX2, MMP9, aromatic amino acids, energy metabolism, and oxidative stress.

Characterization of the fatty acid binding protein 3 (FABP3) promoter and its transcriptional regulation by cAMP response element binding protein 1 (CREB1) in goat mammary epithelial cells

Fatty acid binding protein 3 (FABP3) is involved in signal transduction pathways, and in the uptake and utilization of long-chain fatty acids. However, the transcriptional regulation of FABP3 in goat is unclear. In this study, the FABP3 5′ flanking region was amplified from goat (Capra hircus) genomic DNA. Luciferase reporter vectors containing promoter fragments of five different lengths were constructed and transfected into dairy goat mammary epithelial cells. The region of the promoter located between −1801 and −166 bp upstream of the transcription start site (TSS) exhibited the highest luciferase activity, and contained two cAMP response elements (CREs) located at −1632 bp and −189 bp. Interference with CREB1 significantly downregulated FABP3 promoter activity. In addition, FABP3 promoter activity was significantly reduced after mutation of the CRE1 (−1632 bp) and CRE2 (−189 bp) sites. Further analysis indicated that the CRE2 site was essential for the transcriptional activity induced by CREB1. These results demonstrated that CREB1 is involved in the transcriptional regulation of FABP3 expression in the goat mammary gland via a direct mechanism, thus revealing a novel signaling pathway involved in fatty acid metabolism in goat.

Dual-stage pulse-feed operation enhanced methanation of lipidic waste during co-digestion using acclimatized consortia

Methanation was improved during the dual-stage pulse-feed anaerobic co-digestion of extracted lipid (EL) from food waste leachate using acclimatized consortia by gradually increasing the organic loading rates (OLRs) in the subsequent phases. The utilization of major saturated and unsaturated long chain fatty acids (LCFAs) reached 78% and 98% in the acidogenic fermenters with consecutive organic loading, respectively. The acclimatized consortium induced the LCFA degradation and interconversion of short-medium chain fatty acids (SCFA–MCFAs) in the fermenters, even under highest OLR values. The highest methane yield (0.46 g g−1 VSinitial) was achieved in the third phase (61% EL loading of total injected volatile solid) with the complete utilization of LCFAs and SCFA–MCFAs in the digester. The assessment of the microbial community revealed that acidogenic Intestinimonas and Megasphaera, and acetogenic Levilinea were predominant in the fermenters due to their preeminent activities. The predominance of acetogenic Syntrophomonas (26%) indicated that it played a major role in β-oxidation, and its syntrophy with mixotrophic methanogens, such as Methanosarcina (93%), facilitated methanation through the complete degradation of EL in the digesters. The use of pulse-feed operation in dual-stage anaerobic co-digestion improved the methanation through complete utilization of EL under varied OLRs mediated by the acclimatized consortia.

Revisiting long-chain fatty acid metabolism in Escherichia coli: integration with stress responses.

Long-chain fatty acids (LCFAs) are a tremendous source of metabolic energy, an essential component of membranes, and important effector molecules that regulate a myriad of cellular processes. As an energy-rich nutrient source, the role of LCFAs in promoting bacterial survival and infectivity is well appreciated. LCFA degradation generates a large number of reduced cofactors that may confer redox stress; therefore, it is imperative to understand how bacteria deal with this paradoxical situation. Although the LCFA utilization pathway has been studied in great detail, especially in Escherichia coli, where the earliest studies date back to the 1960s, the interconnection of LCFA degradation with bacterial stress responses remained largely unexplored. Recent work in E. coli shows that LCFA degradation induces oxidative stress and also impedes oxidative protein folding. Importantly, both issues arise due to the insufficiency of ubiquinone, a lipid-soluble electron carrier in the electron transport chain. However, to maintain redox homeostasis, bacteria induce sophisticated cellular responses. Here, we review these findings in light of our current knowledge of the LCFA metabolic pathway, metabolism-induced oxidative stress, the process of oxidative protein folding, and stress combat mechanisms. We discuss probable mechanisms for the activation of defense players during LCFA metabolism and the likely feedback imparted by them. We suggest that besides defending against intrinsic stresses, LCFA-mediated upregulation of stress response pathways primes bacteria to adapt to harsh external environments. Collectively, the interplay between LCFA metabolism and stress responses is likely an important factor that underlies the success of LCFA-utilizing bacteria in the host.

L-カルニチンの食餌性給与は歩行運動を付加したラットの エネルギー合成に対する長鎖脂肪酸の均等利用を誘起する

L-カルニチンの食餌性給与は歩行運動を付加したラットの エネルギー合成に対する長鎖脂肪酸の均等利用を誘起する

Human embryonic stem cell-derived cardiomyocytes as an in vitro model to study cardiac insulin resistance

Patients with type 2 diabetes (T2D) and/or insulin resistance (IR) have an increased risk for the development of heart failure (HF). Evidence indicates that this increased risk is linked to an altered cardiac substrate preference of the insulin resistant heart, which shifts from a balanced utilization of glucose and long-chain fatty acids (FAs) towards an almost complete reliance on FAs as main fuel source. This shift leads to a loss of endosomal proton pump activity and increased cardiac fat accumulation, which eventually triggers cardiac dysfunction. In this review, we describe the advantages and disadvantages of currently used in vitro models to study the underlying mechanism of IR-induced HF and provide insight into a human in vitro model: human embryonic stem cell-derived cardiomyocytes (hESC-CMs). Using functional metabolic assays we demonstrate that, similar to rodent studies, hESC-CMs subjected to 16h of high palmitate (HP) treatment develop the main features of IR, i.e., decreased insulin-stimulated glucose and FA uptake, as well as loss of endosomal acidification and insulin signaling. Taken together, these data propose that HP-treated hESC-CMs are a promising in vitro model of lipid overload-induced IR for further research into the underlying mechanism of cardiac IR and for identifying new pharmacological agents and therapeutic strategies. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

Maternal adipose tissue becomes a source of fatty acids for the fetus in fasted pregnant rats given diets with different fatty acid compositions.

The utilization of long-chain polyunsaturated fatty acids (LCPUFA) by the fetus may exceed its capacity to synthesize them from essential fatty acids, so they have to come from the mother. Since adipose tissue lipolytic activity is greatly accelerated under fasting conditions during late pregnancy, the aim was to determine how 24h fasting in late pregnant rats given diets with different fatty acid compositions affects maternal and fetal tissue fatty acid profiles. Pregnant Sprague-Dawley rats were given isoenergetic diets containing 10% palm-, sunflower-, olive- or fish-oil. Half the rats were fasted from day 19 of pregnancy and all were studied on day 20. Triacylglycerols (TAG), glycerol and non-esterified fatty acids (NEFA) were analyzed by enzymatic methods and fatty acid profiles were analyzed by gas chromatography. Fasting caused increments in maternal plasma NEFA, glycerol and TAG, indicating increased adipose tissue lipolytic activity. Maternal adipose fatty acid profiles paralleled the respective diets and, with the exception of animals on the olive oil diet, maternal fasting increased the plasma concentration of most fatty acids. This maintains the availability of LCPUFA to the fetus during brain development. The results show the major role played by maternal adipose tissue in the storage of dietary fatty acids during pregnancy, thus ensuring adequate availability of LCPUFA to the fetus during late pregnancy, even when food supply is restricted.

Expression of long-chain polyunsaturated fatty acids (LC-PUFA) biosynthesis genes and utilization of fatty acids during early development in rabbitfish Siganus canaliculatus

Rabbitfish S. canaliculatus is the first marine fish reported to possess long-chain polyunsaturated fatty acids (LC-PUFA) biosynthetic ability, but the initiation of the LC-PUFA biosynthesis in this species is still unknown. In this study, the gene expression of Δ5/Δ6 fatty acid desaturase (Fad), Δ4 Fad and two fatty acid elongases, four key enzymes for LC-PUFA biosynthesis, were measured during the embryonic and unfed larval development of rabbitfish. Correspondingly, the fatty acid composition of rabbitfish embryos was determined. The results showed that DHA was the primary fatty acid utilized at the zygotic stages. The mRNA expression of the four key genes was detected from 8hpf (hours post-fertilization) onwards, with a low level of elovl5 mRNA contrary to the high expression of Δ4 fad mRNA. Subsequently, the elevated expression of Δ5/Δ6 fad and two elongase genes was observed after hatching, and then a great increment in the expression of all four key genes was detected at 3–4dph (days post-hatching). These results indicate the production of DHA from EPA via the “Δ4 Fad” pathway as well as the alternative “Sprecher” pathway at the yolk-sac larval stages. Furthermore, the entire LC-PUFA biosynthetic pathway of converting C18 PUFA precursors to DHA is activated just after the onset of first-feeding. This study provides information on LC-PUFA biosynthesis during early development in rabbitfish, and offers an approach to determine the nutritional requirements of first-feeding larvae for rabbitfish and other marine fish.

Uncoupling EPA and DHA in Fish Nutrition: Dietary Demand is Limited in Atlantic Salmon and Effectively Met by DHA Alone.

Due to the scarcity of marine fish oil resources, the aquaculture industry is developing more efficient strategies for the utilization of dietary omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). A better understanding of how fish utilize EPA and DHA, typically provided by fish oil, is needed. However, EPA and DHA have different physiological functions, may be metabolized and incorporated into tissues differently, and may vary in terms of their importance in meeting the fatty acid requirements of fish. To address these questions, Atlantic salmon were fed experimental diets containing, as the sole added dietary lipid source, fish oil (positive control), tallow (negative control), or tallow supplemented with EPA, DHA, or both fatty acids to ~50 or 100% of their respective levels in the positive control diet. Following 14 weeks of feeding, the negative control diet yielded optimum growth performance. Though surprising, these results support the notion that Atlantic salmon requirements for n-3 LC-PUFA are quite low. EPA was largely β-oxidized and inefficiently deposited in tissues, and increasing dietary levels were associated with potential negative effects on growth. Conversely, DHA was completely spared from catabolism and very efficiently deposited into flesh. EPA bioconversion to DHA was largely influenced by substrate availability, with the presence of preformed DHA having little inhibitory effect. These results clearly indicate EPA and DHA are metabolized differently by Atlantic salmon, and suggest that the n-3 LC-PUFA dietary requirements of Atlantic salmon may be lower than reported and different, if originating primarily from EPA or DHA.

Dietary Supplementation with L-Carnitine Induces Equal Utilization of Long-Chain Fatty Acids for Energy Production in Rats Trained with Walking

Dietary Supplementation with LCarnitine Induces Equal Utilization of Long-Chain Fatty Acids for Energy Production in Rats Trained with Walking The present experiment was conducted to evaluate the effects of L-carnitine supplementation on the fatty acid composition of epididymal adipose tissue and femoral muscle in rats trained with walking. The rats were assigned to four groups receiving dietary treatments to evaluate the effects of supplementation with 0 ppm L-carnitine or 50 ppm L-carnitine in combination with two types of exercise: free moving and walking (4 h/day at a speed of 840 m/h). L-carnitine supplementation significantly increased its level in the blood plasma. There was a main effect of L-carnitine supplementation on body weight gain and blood plasma triglyceride level, with both parameters reduced by L-carnitine supplementation. The results of the fatty acid composition analysis revealed that walking reduced the C16:0 level, resulting in a low total saturated fatty acid (SFA) proportion. Dietary L-carnitine suppressed the decrease in the C16:0 proportion observed in the walking group and accelerated the use of fatty acids for energy production so that it was the same as in the control condition. There was no specific relation between L-carnitine and fatty acid type. In conclusion, the current results suggest that dietary supplementation with L-carnitine reversed the unbalanced fatty acid degradation caused by walking without L-carnitine supplementation.

Biomass Production and Fatty Acids Long Chain Polyunsaturated Omega 3 (LC-PUFAs) Chilean Strain Using &lt;i&gt;Thraustochytrids&lt;/i&gt;

Global utilization of long-chain polyunsaturated fatty acids (LC-PUFAs) has increased steadily in the last decade which has imposed a huge demand for fish oil as it is currently the only source capable of sustaining the enormous commercial requirements this input worldwide. They are currently using various microorganisms to produce single cells oil (SCO) high in LC-PUFAs, within which highlights the thraustochytrids (TH). The TH is a group of marine protists (pseudofungi) with capacity to produce LC-PUFAs such as eicosapentaenoic acid (EPA), docosapentaenoic (DPA) and docosahexaenoic acid (DHA). In this study the chilean VAL-B1 strain was grown in glucose, starch and glycerol being obtained biomass production and LC-PUFAs. Biomass values ​​obtained were 1.02 ± 0.32 g/L, 1.25 ± 0.44 g/L and 1.44 ± 0.27 g/L of glucose, glycerol and starch respectively. The profile of LC-PUFAs showed a percentage of omega-3 fatty acids on glucose of 59.34%, 61.50% in starch and glycerol of 47.86%. The greater this value was to omega-3 DHA when starch was used, with 68.16 mg/g being greater than 45.77 mg/g glycerol and 63.89 mg/g in glucose. Therefore, we conclude that VAL-B1 produces more biomass has greater value of omega-3 LC-PUFAs and greater concentration of DHA when starch is used as a source of substrate for cultures.

Novel regulatory mechanisms in muscle metabolism during exercise.

Novel regulatory mechanisms in muscle metabolism during exercise.

Mechanisms of subcellular remodeling in heart failure due to diabetes

Diabetic cardiomyopathy is not only associated with heart failure but there also occurs a loss of the positive inotropic effect of different agents. It is now becoming clear that cardiac dysfunction in chronic diabetes is intimately involved with Ca(2+)-handling abnormalities, metabolic defects and impaired sensitivity of myofibrils to Ca(2+) in cardiomyocytes. On the other hand, loss of the inotropic effect in diabetic myocardium is elicited by changes in signal transduction mechanisms involving hormone receptors and depressions in phosphorylation of various membrane proteins. Ca(2+)-handling abnormalities in the diabetic heart occur mainly due to defects in sarcolemmal Na(+)-K(+) ATPase, Na(+)-Ca(2+) exchange, Na(+)-H(+) exchange, Ca(2+)-channels and Ca(2+)-pump activities as well as changes in sarcoplasmic reticular Ca(2+)-uptake and Ca(2+)-release processes; these alterations may lead to the occurrence of intracellular Ca(2+) overload. Metabolic defects due to insulin deficiency or ineffectiveness as well as hormone imbalance in diabetes are primarily associated with a shift in substrate utilization and changes in the oxidation of fatty acids in cardiomyocytes. Mitochondria initially seem to play an adaptive role in serving as a Ca(2+) sink, but the excessive utilization of long-chain fatty acids for a prolonged period results in the generation of oxidative stress and impairment of their function in the diabetic heart. In view of the activation of sympathetic nervous system and renin-angiotensin system as well as platelet aggregation, endothelial dysfunction and generation of oxidative stress in diabetes and blockade of their effects have been shown to attenuate subcellular remodeling, metabolic derangements and signal transduction abnormalities in the diabetic heart. On the basis of these observations, it is suggested that oxidative stress and subcellular remodeling due to hormonal imbalance and metabolic defects play a critical role in the genesis of heart failure during the development of diabetic cardiomyopathy.

Stearoyl-CoA Desaturase-1 (SCD1) Augments Saturated Fatty Acid-Induced Lipid Accumulation and Inhibits Apoptosis in Cardiac Myocytes

Mismatch between the uptake and utilization of long-chain fatty acids in the myocardium leads to abnormally high intracellular fatty acid concentration, which ultimately induces myocardial dysfunction. Stearoyl-Coenzyme A desaturase-1 (SCD1) is a rate-limiting enzyme that converts saturated fatty acids (SFAs) to monounsaturated fatty acids. Previous studies have shown that SCD1-deficinent mice are protected from insulin resistance and diet-induced obesity; however, the role of SCD1 in the heart remains to be determined. We examined the expression of SCD1 in obese rat hearts induced by a sucrose-rich diet for 3 months. We also examined the effect of SCD1 on myocardial energy metabolism and apoptotic cell death in neonatal rat cardiac myocytes in the presence of SFAs. Here we showed that the expression of SCD1 increases 3.6-fold without measurable change in the expression of lipogenic genes in the heart of rats fed a high-sucrose diet. Forced SCD1 expression augmented palmitic acid-induced lipid accumulation, but attenuated excess fatty acid oxidation and restored reduced glucose oxidation. Of importance, SCD1 substantially inhibited SFA-induced caspase 3 activation, ceramide synthesis, diacylglycerol synthesis, apoptotic cell death, and mitochondrial reactive oxygen species (ROS) generation. Experiments using SCD1 siRNA confirmed these observations. Furthermore, we showed that exposure of cardiac myocytes to glucose and insulin induced SCD1 expression. Our results indicate that SCD1 is highly regulated by a metabolic syndrome component in the heart, and such induction of SCD1 serves to alleviate SFA-induced adverse fatty acid catabolism, and eventually to prevent SFAs-induced apoptosis.

Post-translational modifications, a key process in CD36 function: Lessons from the spontaneously hypertensive rat heart

CD36, a multifunctional protein, is involved in cardiac long chain fatty acid (LCFA) metabolism and in the etiology of heart diseases, yet the functional impact of Cd36 gene variants remains unclear. In 7-week-old spontaneously hypertensive rats (SHR), which, like humans, carry numerous mutations in Cd36, we tested the hypothesis that their restricted cardiac LCFA utilization occurs prior to hypertrophy due to defective CD36 post-translational modifications (PTM), as assessed by ex vivo perfusion of 13C-labeled substrates and biochemical techniques. Compared to their controls, SHR hearts displayed a lower (i) contribution of LCFA to β-oxidation (− 40%) and triglycerides (+ 2.8 folds), which was not explained by transcriptional changes or malonyl-CoA level, a recognized β-oxidation inhibitor, and (ii) membrane-associated CD36 protein level, but unchanged distribution. Other results demonstrate alterations in CD36 PTM in SHR hearts, specifically by N-glycosylation, and the importance of O-linked-β-N-acetylglucosamine for its membrane recruitment and role in LCFA use in the heart.

Endothelin‐1 Suppresses Long‐Chain Fatty Acid Uptake and Glucose Uptake Via Distinct Mechanisms in 3T3‐L1 Adipocytes

Endothelin-1 (ET-1) has been demonstrated to induce insulin resistance (IR) and lipolysis, raising the possibility that ET-1 may also contribute to the elevated fatty acid levels in IR-associated comorbidities. We attempted to evaluate whether ET-1 also affects the long-chain fatty acid (LCFA) utilization in 3T3-L1 adipocytes. The effects of chronic ET-1 exposure on basal and insulin-stimulated LCFA uptake, and LCFA uptake kinetics were examined in 3T3-L1 adipocytes. Chronic exposure to ET-1 induced IR and suppressed basal and insulin-stimulated LCFA uptake. Given that insulin acutely stimulates LCFA uptake, there was dramatically similar trend of dose-response curves for ET-1-suppressed LCFA uptake, and also similar corresponding IC₅₀ values, between basal and insulin-stimulated states, reflecting that ET-1 predominantly suppresses basal LCFA uptake. Results of LCFA kinetics, western blots, and CD36 inhibition using sulfosuccinimidyl oleate (SSO) revealed that suppression of LCFA uptake by ET-1 is associated with downregulation of CD36. ET type A receptor (ET(A)R) antagonist BQ-610 reversed the IR induction and the ET-1-suppressed LCFA uptake. Exogenous replenishment of phosphatidylinositol (PI) 4, 5-bisphosphate (PIP₂) prevented IR induction, but not the suppression of LCFA uptake by ET-1. Pharmacological inhibition of the activation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) completely blocked the ET-1-suppressed LCFA uptake. Serving as an inducer of IR, ET-1 also chronically suppresses LCFA uptake via PIP₂-independent and ERK-dependent pathway. The interplay between impaired glucose disposal and diminished LCFA utilization, induced by ET-1, could worsen the dysregulation of adipose metabolism and energy homeostasis in insulin-resistant states.

254 The spontaneously hypertensive rat heart displays a reduced capacity to use long chain fatty acids for energy production prior to hypertrophy: role of Cd36

The spontaneously hypertensive rat (SHR) is a model of hypertension with a Cd36 gene defect, which develops left ventricular hypertrophy (LVH) between 9 and 12 weeks. At 15 weeks, perfused SHR hearts display a reduced capacity to use long chain fatty acids (LCFAs) but not carbohydrates (CHOs) for energy production. In this study, we have further examined LCFA metabolism and its potential (dys) regulation in SHR hearts prior to LVH. SHR and control Wistar rat hearts (7 weeks) have been used for: i) functional and metabolic phenotyping using ex vivo perfusion with 13 C-labeled substrates, ii) metabolic gene expression profiling using qPCR, iii) studies of mechanisms regulating-oxydation (malonyl-CoA, AMPK) and of the functional impact of the gene mutation in the LCFA transporter Cd36 (western blot, confocal microscopy, qPCR, gene analysis). Compared to controls, 7-week-old SHR hearts display a lower contribution of LCFA (i.e. oleate) to oxidation (40%) and triglyceride (2.8-fold) formation, which is associated with a compensatory increase in CHO oxidation. These alterations cannot be explained by changes in metabolic gene expression or common mechanisms regulating-oxidation. Western analyses demonstrate that compared to controls, cardiac CD36 protein level is lower in the SHR, while data from confocal microscopy indicate a similar intracellular localization. Sequence alignment of Cd36 cDNA indicates non-synonymous mutations in the SHR that do not impact on the molecular weight of the native protein, but may affect its post-translational modification (PTM). This notion is supported by additional data, which suggest an alteration in O -linked-N-acetylglucosamination. Our results emphasize the role of the SHR Cd36 gene defect as the factor underlying its cardiac restricted LCFA utilization. The functional impact of this gene defect includes alterations in CD36 protein level and susceptibility to PTM.