Palmitoleic Acid Ameliorates Metabolic Disorders and Inflammation by Modulating Gut Microbiota and Serum Metabolites

SCOPE

Palmitoleic acid (POA) is an omega-7 monounsaturated fatty acid that has been suggested to improve metabolic disorders. However, it remains unclear whether gut microbiota plays a role in the amelioration of metabolic disorders by POA. This study aims to investigate the regulation of POA on metabolism, as well as systemic inflammation in HFD-fed mice from the perspective of serum metabolome and gut microbiome.

METHODS AND RESULTS

Thirty-six C57BL/6 male mice are randomly assigned to either a normal chow diet containing 1.9% w/w lard or an HFD containing 20.68% w/w lard or 20.68% w/w sea buckthorn pulp oil for 16 weeks. The study finds that POA significantly attenuated hyperlipidemia, insulin resistance, and inflammation in HFD-fed mice. POA supplementation significantly alters the composition of serum metabolites, particularly lipid metabolites in the glycerophospholipid metabolism pathway. POA obviously increases the abundance of Bifidobacterium and decreases the abundance of Allobaculum. Importantly, the study finds that glycerophosphocholine mediates the effect of Bifidobacterium on LDL-C, sphingomyelin mediates the effect of Bifidobacterium on IL-6, and maslinic acid mediates the effect of Allobaculum on IL-6.

CONCLUSION

The results suggest that exogenous POA can improve metabolic disorders and inflammation in HFD-fed mice, potentially by modulating the serum metabolome and gut microbiome.

Lysophosphatidylcholines Enriched with cis and trans Palmitoleic Acid Regulate Insulin Secretion via GPR119 Receptor

Among lipids, lysophosphatidylcholines (LPCs) with various fatty acyl chains have been identified as potential agonists of G protein-coupled receptors (GPCRs). Recently, targeting GPCRs has been switched to diabetes and obesity. Concomitantly, our last findings indicate the insulin secretagogue properties of cis and trans palmitoleic acid (16:1, n-7) resulting from GPCR activation, however, associated with different signaling pathways. We here report the synthesis of LPCs bearing two geometrical isomers of palmitoleic acids and investigation of their impact on human pancreatic β cells viability, insulin secretion, and activation of four GPCRs previously demonstrated to be targeted by free fatty acids and LPCs. Moreover, molecular modeling was exploited to investigate the probable binding sites of tested ligands and calculate their affinity toward GPR40, GPR55, GPR119, and GPR120 receptors.

Protocol for a randomized placebo-controlled clinical trial using pure palmitoleic acid to ameliorate insulin resistance and lipogenesis in overweight and obese subjects with prediabetes

Palmitoleic acid (POA), a nonessential, monounsaturated omega-7 fatty acid (C16:1n7), is a lipid hormone secreted from adipose tissue and has beneficial effects on distant organs, such as the liver and muscle. Interestingly, POA decreases lipogenesis in toxic storage sites such as the liver and muscle, and paradoxically increases lipogenesis in safe storage sites, such as adipose tissue. Furthermore, higher POA levels in humans are correlated with better insulin sensitivity, an improved lipid profile, and a lower incidence of type-2 diabetes and cardiovascular pathologies, such as myocardial infarction. In preclinical animal models, POA improves glucose intolerance, dyslipidemia, and steatosis of the muscle and liver, while improving insulin sensitivity and secretion. This double-blind placebo-controlled clinical trial tests the hypothesis that POA increases insulin sensitivity and decreases hepatic lipogenesis in overweight and obese adult subjects with pre-diabetes. Important to note, that this is the first study ever to use pure (>90%) POA with < 0.3% palmitic acid (PA), which masks the beneficial effects of POA. The possible positive findings may offer a therapeutic and/or preventative pathway against diabetes and related immunometabolic diseases.

Tuning Fatty Acid Profile and Yield in Pichia pastoris

Fatty acids have been supplied for diverse non-food, industrial applications from plant oils and animal fats for many decades. Due to the massively increasing world population demanding a nutritious diet and the thrive to provide feedstocks for industrial production lines in a sustainable way, i.e., independent from food supply chains, alternative fatty acid sources have massively gained in importance. Carbohydrate-rich side-streams of agricultural production, e.g., molasses, lignocellulosic waste, glycerol from biodiesel production, and even CO2, are considered and employed as carbon sources for the fermentative accumulation of fatty acids in selected microbial hosts. While certain fatty acid species are readily accumulated in native microbial metabolic routes, other fatty acid species are scarce, and host strains need to be metabolically engineered for their high-level production. We report the metabolic engineering of Pichia pastoris to produce palmitoleic acid from glucose and discuss the beneficial and detrimental engineering steps in detail. Fatty acid secretion was achieved through the deletion of fatty acyl-CoA synthetases and overexpression of the truncated E. coli thioesterase 'TesA. The best strains secreted >1 g/L free fatty acids into the culture medium. Additionally, the introduction of C16-specific ∆9-desaturases and fatty acid synthases, coupled with improved cultivation conditions, increased the palmitoleic acid content from 5.5% to 22%.

Exploring the Potential of Sago Caterpillars as Cooking Oils: Extraction, Purifying and Characterization

<b>Background and Objective:</b> The dual demand for palm oil, both as a cooking oil and as a raw material for biodiesel, gives rise to concerns regarding potential shortages. Hence, it is crucial to explore alternative sources of cooking oil, with one such alternative being the oil extracted from sago caterpillars. This study aims to extract and determine the characteristics of sago caterpillar oil and its potential as cooking oil. <b>Materials and Methods:</b> Sago caterpillar oil extraction was done using pressing, Soxhlet extraction and Folch's lipid extraction. The yield of sago caterpillar oil obtained by pressing, Soxhlet and Folch's lipid extraction were 20, 16 and 2.2%, respectively. Oil purifying was done using degumming, neutralization and bleaching. Furthermore, the resulting sago caterpillar oil was characterized physically, chemically and organoleptic. <b>Results:</b> The sago caterpillar oil met the requirements as cooking oil based on the Indonesian National Standard for cooking oil and other chemical parameters. The results of the analysis of sago caterpillar oil with gas chromatography-mass spectrometer showed that the sago caterpillar oil contained 0.15% lauric acid, 2.06% myristic acid, 5.92% palmitoleic acid, 55.05% palmitic acid, 0.84% linoleic acid, 34.00% oleic acid and 1.43% stearic acid. The main peak positions from the fourier transform infrared spectrophotometer are at 725, 1118, 1165, 1234, 1373, 1458, 1743, 2854 and 2924 cm¹. The results of the analysis of sago caterpillar oil showed that the lipid profile of sago caterpillar oil was similar to commercial palm oil. <b>Conclusion:</b> Based on the results of extraction, purifying and characterization, it was concluded that sago caterpillar oil has the potential to be used as cooking oil.

Positional and compositional analysis of saturated, monounsaturated, and polyunsaturated fatty acids in human adipose tissue triglyceride by 13 C nuclear magnetic resonance

The synthesis and turnover of triglyceride in adipose tissue involves enzymes with preferences for specific fatty acid classes and/or regioselectivity regarding the fatty acid position within the glycerol moiety. The focus of the current study was to characterize both the composition of fatty acids and their positional distribution in triglycerides of biopsied human subcutaneous adipose tissue, from subjects with wide ranges of body mass index (BMI) and insulin sensitivity, using ¹³ C nuclear magnetic resonance (NMR) spectroscopy. The triglyceride sn2 position was significantly more enriched with monounsaturated fatty acids compared with that of sn1,3, while the abundance of saturated fatty acids was significantly lower in the sn2 position compared with that of sn1,3. Furthermore, the analysis revealed significant positive correlations between the total fraction of palmitoleic acid with both BMI and insulin sensitivity scores (homeostatic model assessment of insulin resistance index). Additionally, we established that ¹³ C NMR chemical shifts for ω-3 signals, centered at 31.9 ppm, provided superior resolution of the most abundant fatty acid species, including palmitoleate, compared with the ω-2 signals that were used previously. ¹³ C NMR spectroscopy reveals for the first time a highly nonhomogenous distribution of fatty acids in the glycerol sites of human adipose tissue triglyceride, and that these distributions are correlated with different phenotypes, such as BMI and insulin sensitivity.

Treatment of Resistant Acne Vulgaris in Adolescents Using Dietary Supplementation with Magnesium, Phosphate and Fatty Acids (Omega 6 and 7): Comparison with 13-Cis-Retinoic Acid

The burden of disease associated with acne vulgaris has continued to increase over time in the world population. This continued growth suggests that there is an unmet dermatologic need for this condition worldwide. Potential sequelae of acne, such as scarring, depigmentation, and marked emotional and psychological problems (e.g., low self-esteem), can lead to significant morbidity. The purpose of this study was to investigate whether dietary supplementation with magnesium, phosphate, omega 6 (linoleic acid calcium salt - C18:2 fatty acid Ca salt), and omega 7 (palmitoleic acid calcium salt - C16:1 fatty acid Ca salt) would help patients with acne vulgaris, and to compare with isotretinoin (13-cis retinoic acid). Magnesium has anti-inflammatory properties. Linoleic and palmitoleic acids have bactericidal activity against Staphylococcus aureus and Cutibacterium acnes (formerly known as Propionibacterium acnes). A single-blind randomized study was conducted in which 257 patients were treated with the above dietary supplementation (group A) and 275 patients with isotretinoin (group B) for 6 months. All patients in group A (100%) reported complete regression of symptoms after 6 months of treatment. On the other hand, 187 subjects (68%) in group B reported complete resolution of symptoms during the same period. The difference between the groups (p < 0.05) was statistically significant. The study was approved by the CEP/CONEP. This natural formulation promotes regression and/or cure of acne vulgaris symptoms and has better results than drugs (such as isotretinoin), without significant side effects.

Producing high value unsaturated fatty acid by whole-cell catalysis using microalga: A case study with Tribonema minus

High value unsaturated fatty acids can be produced by de novo synthesis in microalgal cells, especially via heterotrophic cultivation. Unfortunately, the lipid accumulation of heterotrophic microalgae cannot be improved efficiently in conventional ways. Here we reported heterotrophic Tribonema minus, a promising resource for the production of palmitoleic acid which has increasing demands in health service for patients with metabolic syndrome, as whole-cell biocatalyst to develop a novel way of shifting low value exogenous saturated fatty acids to high value ones. Results showed that myristic acid is the best precursor for whole-cell catalysis; it elevated the lipid content of T. minus to 42.2%, the highest among the tried precursors. The influences of cultivation condition on the utilization of extrinsic myristic acid and lipid accumulation were also determined. Under the optimized condition, the lipid content reached as high as 48.9%. In addition, our findings showed that ~13.0% of C16:1 in T. minus is derived from extrinsic myristic acid, and 30.1% of metabolized precursor is converted into heterologous fatty acids. Thus, a feasible approach for both increasing the value of low value saturated fatty acid by bioconversion and enhancing the lipid accumulation in microalgae is proposed by supplementing extrinsic myristic acid.

Elevated stearoyl-CoA desaturase 1 activity is associated with alcohol-associated liver disease

Chronic binge drinking induces hepatic lipid accumulation, but only certain individuals develop alcohol-associated liver disease (ALD). Specific patterns of lipid accumulation are thought to be associated with ALD, but this has not been comprehensively investigated to date. We analyzed plasma fatty acid levels, quantified by gas chromatography-mass spectrometry, in a sample of patients with alcohol use disorder (AUD). Given that elevation in serum alanine transaminase (ALT) levels are strongly associated with ALD, patients were stratified into two groups based on ALT levels: an ALD group (ALT >40 IU/L) and a non-ALD group (ALT ≤40 IU/L). There was a shift toward greater concentrations of monounsaturated fatty acids in the ALD group compared to the non-ALD group. Stearoyl-CoA desaturase (SCD1) activity in the ALD group was then estimated as the ratio of palmitoleic acid (16:1) to palmitic acid (16:0). SCD1 activity was greater in the ALD than the non-ALD group. A series of linear regression models demonstrated that SCD1 activity mediated the association between binge drinking and ALD. These findings provide initial evidence that SCD1 activity may be associated with ALD. If validated prospectively, elevated SCD1 activity could potentially be used as a biomarker to identify individuals at high risk for developing ALD.

CD8+ T cells and fatty acids orchestrate tumor ferroptosis and immunity via ACSL4

Tumor cell intrinsic ferroptosis-initiating mechanisms are unknown. Here, we discover that T cell-derived interferon (IFN)γ in combination with arachidonic acid (AA) induces immunogenic tumor ferroptosis, serving as a mode of action for CD8+ T cell (CTL)-mediated tumor killing. Mechanistically, IFNγ stimulates ACSL4 and alters tumor cell lipid pattern, thereby increasing incorporations of AA into C16 and C18 acyl chain-containing phospholipids. Palmitoleic acid and oleic acid, two common C16 and C18 fatty acids in blood, promote ACSL4-dependent tumor ferroptosis induced by IFNγ plus AA. Moreover, tumor ACSL4 deficiency accelerates tumor progression. Low-dose AA enhances tumor ferroptosis and elevates spontaneous and immune checkpoint blockade (ICB)-induced anti-tumor immunity. Clinically, tumor ACSL4 correlates with T cell signatures and improved survival in ICB-treated cancer patients. Thus, IFNγ signaling paired with selective fatty acids is a natural tumor ferroptosis-promoting mechanism and a mode of action of CTLs. Targeting the ACSL4 pathway is a potential anti-cancer approach.

INTERESTERIFIED FAT MATERNAL CONSUMPTION BEFORE CONCEPTION PROGRAMMS MEMORY AND LEARNING OF ADULTHOOD OFFSPRING: how big is this deleterious repercussion?

In recent years, interesterified fat (IF) has largely replaced trans fat in industrialized food. Studies of our research group showed that IF consumption may not be safe for central nervous system (CNS) functions. Our current aim was to evaluate IF maternal consumption before conception on cognitive performance of adult rat offspring. Female Wistar rats were fed with standard chow plus 20% soybean and fish oil mix (control group) or plus 20% IF from weaning until adulthood (before mating), when the diets were replaced by standard chow only. Following the gestation and pups' development, locomotion and memory performance followed by neurotrophin immunocontent and fatty acids (FA) profile in the hippocampus of the adulthood male offspring were quantified. Maternal IF consumption before conception decreased hippocampal palmitoleic acid incorporation, proBDNF and BDNF levels, decreasing both exploratory activity and memory performance in adult offspring. Considering that, the adult male offspring did not consume IF directly, further studies are needed to understand the molecular mechanisms and if the IF maternal preconception consumption could induce the epigenetic changes observed here. Our outcomes reinforce an immediate necessity to monitor and / or question the replacement of trans fat by IF with further studies involving CNS functions.

An Enantiodefined Conformationally Constrained Fatty Acid Mimetic and Potent Inhibitor of ToxT

The chiral conformation that palmitoleic acid takes when it is bound to ToxT, the master regulator of virulence genes in the bacterial pathogen Vibrio cholerae, was used as inspiration to design a novel class of fatty acid mimetics. The best mimetic, based on a chiral hydrindane, was found to be a potent inhibitor of this target. The synthetic chemistry that enabled these studies was based on the sequential use of a stereoselective annulative cross-coupling reaction and dissolving metal reduction to establish the C13 and C9 stereocenters, respectively.

Serum Non-Esterified Fatty Acids, Carotid Artery Intima-Media Thickness and Flow-Mediated Dilation in Older Adults: The Cardiovascular Health Study (CHS)

Backgrounds and aims: Elevated common carotid artery intima-media thickness (carotid IMT) and diminished flow-mediated dilation (FMD) are early subclinical indicators of atherosclerosis. Serum total non-esterified fatty acid (NEFA) concentrations have been positively associated with subclinical atherosclerosis. The relations between individual NEFA, carotid IMT and FMD have as yet to be assessed. Methods: We investigated the associations between fasting serum individual NEFA, carotid IMT and FMD among Cardiovascular Health Study (CHS) participants with (n = 255 for carotid IMT, 301 for FMD) or without (n = 1314 for carotid IMT, 1462 for FMD) known atherosclerotic cardiovascular disease (ASCVD). Using archived samples (fasting) collected from 1996-1997 (baseline), 35 individual NEFAs were measured using gas chromatography. Carotid IMT and estimated plaque thickness (mean of maximum internal carotid IMT) were determined in 1998-1999. FMD was measured in 1997-1998. Linear regression adjusted by the Holm-Bonferroni method was used to assess relations between individual NEFA, carotid IMT and FMD. Results: In multivariable adjusted linear regression models per SD increment, the non-esterified trans fatty acid conjugated linoleic acid (trans-18:2 CLA) was positively associated with carotid IMT [β (95% CI): 44.8 (19.2, 70.4), p = 0.025] among participants with, but not without, ASCVD [2.16 (-6.74, 11.5), p = 1.000]. Non-esterified cis-palmitoleic acid (16:1n-7c) was positively associated with FMD [19.7 (8.34, 31.0), p = 0.024] among participants without, but not with ASCVD. No significant associations between NEFAs and estimated plaque thickness were observed. Conclusions: In older adults, serum non-esterified CLA and palmitoleic acid were positively associated with carotid IMT and FMD, respectively, suggesting potential modifiable biomarkers for arteriopathy.

Omega-7 Mixed Fatty Acid Supplementation Fails to Reduce Serum Inflammatory Biomarkers: A Placebo-Controlled, Double-Blind Randomized Crossover Trial

We report the effects of mixed omega-7 fatty acid supplementation on changes in serum hsCRP, TNFα, and IL-6 levels and self-reported outcomes in people with non-specific chronic musculoskeletal discomfort. Design: A double-blind, placebo-controlled, 1:1 randomized single crossover trial composed of 688 mg/day palmiteolate for the verum and an equivalent amount of medium-chain triglycerides for the placebo. Method: Data were analyzed in two independent groups and as a crossover group. Results: From 211 screened participants in 2017–2019, 56 were randomized. Six participants dropped out and fifty completers contributed to the statistical analyses. At baseline, none of the investigated biomarkers were significantly correlated to subjectively assessed musculoskeletal discomfort levels. For the two-group analysis (n = 26 and n = 24), none of the serum biomarkers reached statistical significance; however, a statistically significant placebo effect was found in the subjective outcomes. Conclusion: For the crossover analysis (n = 50), three weeks of supplementation with n7FA containing 688 mg per day of palmiteolate did not reduce serum inflammatory biomarkers nor did it improve subjectively measured quality of life (QoL) compared to placebo. Future studies should explore appropriate biomarkers, sufficient power, length of dosing, inclusion criteria for volunteers with higher BMI, and the verification of cis-palmiteolate versus trans-palmiteolate.

Palmitoleoylethanolamide Is an Efficient Anti-Obesity Endogenous Compound: Comparison with Oleylethanolamide in Diet-Induced Obesity

Obesity is currently a major epidemic in the developed world. However, we lack a wide range of effective pharmacological treatments and therapies against obesity, and those approved are not devoid of adverse effects. Dietary components such as palmitoleic acid have been proposed to improve metabolic disbalance in obesity, although the mechanisms involved are not well understood. Both palmitoleic acid (POA) and oleic acid (OA) can be transformed in N-acylethanolamines (NAEs), mediating the effects of dietary POA and OA. To test this hypothesis, here, we study the effects on food intake and body weight gain of palmitoleylethanolamide (POEA) and the OA-derived NAE analogue, oleoylethanolamide (OEA), in Sprague-Dawley rats with a hypercaloric cafeteria diet (HFD). Plasma biochemical metabolites, inflammatory mediators, and lipogenesis-associated liver protein expression were also measured. The results indicate that POEA is able to improve health status in diet-induced obesity, decreasing weight, liver steatosis, inflammation, and dyslipemia. The action of POEA was found to be almost identical to that of OEA, which is an activator of the nuclear peroxisome proliferator receptor alpha (PPARα), and it is structurally related to POEA. These results suggest that the dietary administration of either POA or POEA might be considered as nutritional intervention as complementary treatment for complicated obesity in humans.

Using an erythrocyte fatty acid fingerprint to predict risk of all-cause mortality: the Framingham Offspring Cohort

BACKGROUND

RBC long-chain omega-3 (n-3) fatty acid (FA) percentages (of total fatty acids) are associated with lower risk for total mortality, but it is unknown if a suite of FAs could improve risk prediction.

OBJECTIVES

The objective of this study was to compare a combination of RBC FA levels with standard risk factors for cardiovascular disease (CVD) in predicting risk of all-cause mortality.

METHODS

Framingham Offspring Cohort participants without prevalent CVD having RBC FA measurements and relevant baseline clinical covariates (n = 2240) were evaluated during 11 y of follow-up. A forward, stepwise approach was used to systematically evaluate the association of 8 standard risk factors (age, sex, total cholesterol, HDL cholesterol, hypertension treatment, systolic blood pressure, smoking status, and prevalent diabetes) and 28 FA metrics with all-cause mortality. A 10-fold cross-validation process was used to build and validate models adjusted for age and sex.

RESULTS

Four of 28 FA metrics [14:0, 16:1n-7, 22:0, and omega-3 index (O3I; 20:5n-3 + 22:6n-3)] appeared in ≥5 of the discovery models as significant predictors of all-cause mortality. In age- and sex-adjusted models, a model with 4 FA metrics was at least as good at predicting all-cause mortality as a model including the remaining 6 standard risk factors (C-statistic: 0.778; 95% CI: 0.759, 0.797; compared with C-statistic: 0.777; 95% CI: 0.753, 0.802). A model with 4 FA metrics plus smoking and diabetes (FA + Sm + D) had a higher C-statistic (0.790; 95% CI: 0.770, 0.811) compared with the FA (P < 0.01) or Sm + D models alone (C-statistic: 0.766; 95% CI: 0.739, 0.794; P < 0.001). A variety of other highly correlated FAs could be substituted for 14:0, 16:1n-7, 22:0, or O3I with similar predicted outcomes.

CONCLUSIONS

In this community-based population in their mid-60s, RBC FA patterns were as predictive of risk for death during the next 11 y as standard risk factors. Replication is needed in other cohorts to validate this FA fingerprint as a predictor of all-cause mortality.

Lycopene Inhibits Oxidative Stress-Mediated Inflammatory Responses in Ethanol/Palmitoleic Acid-Stimulated Pancreatic Acinar AR42J Cells

High alcohol intake results in the accumulation of non-oxidative ethanol metabolites such as fatty acid ethyl esters (FAEEs) in the pancreas. High FAEE concentrations mediate pancreatic acinar cell injury and are associated with alcoholic pancreatitis. Treatment with ethanol and the fatty acid palmitoleic acid (EtOH/POA) increased the levels of palmitoleic acid ethyl ester and induced zymogen activation and cytokine expression in pancreatic acinar cells. EtOH/POA induces nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mediated reactive oxygen species (ROS) production and pancreatic acinar cell injury. Lycopene, a bright-red carotenoid, is a potent antioxidant due to its high number of conjugated double bands. This study aimed to investigate whether lycopene inhibits the EtOH/POA-induced increase in ROS production, zymogen activation, and expression of the inflammatory cytokine IL-6 in EtOH/POA-stimulated pancreatic acinar AR42J cells. EtOH/POA increased the ROS levels, NADPH oxidase and NF-κB activities, zymogen activation, IL-6 expression, and mitochondrial dysfunction, which were inhibited by lycopene. The antioxidant N-acetylcysteine and NADPH oxidase 1 inhibitor ML171 suppressed the EtOH/POA-induced increases in ROS production, NF-κB activation, zymogen activation, and IL-6 expression. Therefore, lycopene inhibits EtOH/POA-induced mitochondrial dysfunction, zymogen activation, and IL-6 expression by suppressing NADPH oxidase-mediated ROS production in pancreatic acinar cells.

Palmitoleic and Dihomo-γ-Linolenic Acids Are Positively Associated With Abdominal Obesity and Increased Metabolic Risk in Children

Background: The impact of abdominal obesity (AO) on plasma fatty acid changes and cardiometabolic risk in children who are obese and overweight has rarely been investigated. This study determined whether plasma fatty acid composition differed between children with AO and those without AO and its relationship with metabolic risk, particularly in the obese and overweight groups. Methods: A total of 181 schoolchildren (aged 7-18 years) were included. Anthropometric and biochemical data and plasma fatty acid profiles were analyzed, and the indices of desaturase activity were estimated. Children were categorized based on their body weight and AO status. A continuous metabolic risk score was calculated using the sum of the z-scores of metabolic variables. A one-way analysis of variance test was used to compare the composition ratio of fatty acids between children with and without AO in the obese and overweight groups and normal-weight controls. Pearson analysis was also used to explore significant fatty acid and desaturase indicators associated with metabolic abnormalities. Results: Children who were obese and overweight (N = 126) displayed higher dihomo-γ-linolenic acid (20:3n-6) and γ-linolenic acid (18:3n-6) proportions than normal-weight controls (N = 55), but lower heptadecanoic acid (17:0) proportion, regardless of the AO status of each individual. Obese and overweight children with AO (N = 89), but not their non-AO counterparts (N = 37), exhibited a significantly higher proportion of palmitoleic acid (16:1n-7) than the remaining study groups. Pearson analysis showed that high proportions of palmitoleic acid and dihomo-γ-linolenic acid, as well as increased stearoyl-coenzyme A desaturase-1(16) and delta-6 desaturase and decreased delta-5 desaturase activities, are strongly correlated with weight-height ratio, homeostasis model of assessment values for insulin resistance, hypertriglyceridemia, and continuous metabolic risk scores. Conclusion: Higher palmitoleic acid and dihomo-γ-linolenic acid proportions, as well as increased stearoyl-coenzyme A desaturase-1(16) and delta-6 desaturase and decreased delta-5 desaturase activities are associated with AO and increased metabolic risk in children who are obese and overweight.

Enrichment of Palmitoleic Acid by a Combination of Two-step Solvent Crystallization and Molecular Distillation

Palmitoleic acid shows a variety of beneficial properties to human health. In this study, enrichment of palmitoleic acid from sea buckthorn pulp oil by two-step solvent crystallization and molecular distillation was investigated. Sea buckthorn pulp oil was first converted to its corresponding mixed fatty acids (SPOMFs) containing 27.17% palmitoleic acid. Subsequently, the effects of various factors on crystallization (i.e., crystallization temperature, type of solvent, ratio of SPOMFs to solvent (w/v), crystallization time) and molecular distillation (distillation temperature) were assessed on a 5-g scale. It was found that optimal primary crystallization conditions were a 1:15 ratio of SPOMFs to methanol (w/v), -20°C and 12 h. Secondary crystallization conditions were set to a 1:4 ratio of methanol to palmitoleic acid product obtained from the first step crystallization to methanol (w/v), -40°C and 6 h. For further purification of palmitoleic acid by molecular distillation, the optimal distillation temperature was determined to be 100°C. After purification by crystallization and molecular distillation under the optimal conditions, the final product consisted of 54.18% palmitoleic acid with an overall yield of 56.31%. This method has great potential for adoption by the food and medical industries for the preparation of palmitoleic acid concentrate for nutritional studies.

Structure and immune recognition of the porcine epidemic diarrhea virus spike protein

Porcine epidemic diarrhea virus (PEDV) is an alphacoronavirus responsible for significant morbidity and mortality in pigs. A key determinant of viral tropism and entry, the PEDV spike protein is a key target for the host antibody response and a good candidate for a protein-based vaccine immunogen. We used electron microscopy to evaluate the PEDV spike structure, as well as pig polyclonal antibody responses to viral infection. The structure of the PEDV spike reveals a configuration similar to that of HuCoV-NL63. Several PEDV protein-protein interfaces are mediated by non-protein components, including a glycan at Asn264 and two bound palmitoleic acid molecules. The polyclonal antibody response to PEDV infection shows a dominance of epitopes in the S1 region. This structural and immune characterization provides insights into coronavirus spike stability determinants and explores the immune landscape of viral spike proteins.

Characterization of a Novel Acyl-ACP Δ9 Desaturase Gene Responsible for Palmitoleic Acid Accumulation in a Diatom Phaeodactylum tricornutum

Palmitoleic acid (16:1Δ⁹) possesses a double bond at the seventh carbon atom from methyl end of the acyl chain and belongs to unusual ω-7 monounsaturated fatty acids with broad applications in food, pharmaceuticals, cosmetics, biofuel, and other industries. This high-value fatty acid accumulates up to >40% of total lipid in the marine diatom Phaeodactylum tricornutum. The present study was conducted to determine the key gene responsible for 16:1Δ⁹ biosynthesis in this unicellular alga. A new full-length cDNA and genomic DNA encoding acyl-ACP Δ⁹ desaturase (PtAAD) were isolated from P. tricornutum cells. Expression levels of PtAAD gene under normal and stress culture conditions were both positively correlated with 16:1Δ⁹ accumulation, implying its potential role for fatty acid determination. Functional complementation assay of a yeast mutant strain BY4839 evidenced that PtAAD could restore the synthesis of unsaturated fatty acid, especially generating high levels of 16:1Δ⁹. Further transient expression of PtAAD gene in Nicotiana benthamiana leaves was accompanied by the accumulation of 16:1Δ⁹, which was absent from control groups. Three-dimensional structure modeling studies showed that functional domain of PtAAD contained three variant amino acids (F160, A223, and L156), which may narrow the space shape of substrate-binding cavity to ensure the entry of 16:0-ACP. Consistent with this prediction, the mutated version of PtAAD gene (F160L, A223T, and L156M) in N. benthamiana systems failed to accumulate 16:1Δ⁹, but increased levels of 18:1Δ⁹. Taken together, PtAAD exhibits a strong enzymatic activity and substrate preference for 16:0-ACP, acting as the key player for high biosynthesis and accumulation of 16:1Δ⁹ in this alga. These findings provide new insights for better understanding the palmitoleic acid and oil biosynthetic mechanism in P. tricornutum, indicating that PtAAD gene may have practical applications for enriching palmitoleic acid and oil yield in other commercial oleaginous algae and crops.

The effect of trans-palmitoleic acid on cell viability and sirtuin 1 gene expression in hepatocytes and the activity of peroxisome-proliferator-activated receptor-alpha

Background:

Accumulation of fatty acids in liver causes lipotoxicity which is followed by nonalcoholic fatty liver disease. The association between intakes of trans-fatty acids with metabolic diseases is still controversial. Accordingly, the objective of this study was to investigate the in vitro effects of trans-palmitoleic acid (tPA) and palmitic acid (PA) on lipid accumulation in hepatocytes, focusing on the gene expression of sirtuin 1 (SIRT1) as well as the transcriptional activity of peroxisome proliferator-activated receptor alpha (PPARα).

Materials and Methods:

In this experimental study, hepatocellular carcinoma (HepG2) cells were cultured and treated with various concentrations of tPA and PA (C16:0). The accumulation of triglyceride in the cells was measured by enzymatic method. Gene expression was evaluated by real-time polymerase chain reaction. The activity of PPARα was assessed by luciferase reporter assay after transfection of human embryonic kidney 293T cells by a vector containing the PPAR response element.

Results:

While concentration >1 mM for PA and cis-PA (cPA) reduced the viability of hepatocytes, tPA revealed an opposite effect and increased cell survival. Lipid accumulation in HepG2 cells after treatment with tPA was significantly lower than that in cells treated with PA. In addition, tPA at physiological concentration had no effect on the expression of SIRT1 while at high concentration significantly augmented its expression. There was a modest increase in PPARα activity at low concentration of tPA.

Conclusion:

tPA causes less lipid accumulation in hepatocytes with no detrimental effect on cell viability and might be beneficial for liver cells by the activation of SIRT1 and induction of PPARα activity.

[Effects of substrate on growth and lipid accumulation of Tribonema sp. FACHB-1786]

Filamentous microalga Tribonema sp. has the advantages of highly resistance to zooplankton-predation, easy harvesting, and high cellular lipid content, in particular large amounts of palmitoleic acid (PA) and eicosapentaenoic acid (EPA). Therefore, Tribonema sp. is considered as a promising biomass feedstock to produce biodiesel and high-value products. In this work, we studied the effect of different concentrations of nitrogen (NaNO₃: 255-3 060 mg/L), phosphorus (K₂HPO₄: 4-240 mg/L), iron ((NH₄)₃FeC₁₂H₁₀O₁₄: 0.6-12 mg/L) and magnesium (MgSO₄: 7.5-450 mg/L) on the biomass, lipid content, and fatty acid composition of Tribonema sp. FACHB-1786, aiming at enhancing cell lipid productivity. The growth of Tribonema sp. had a positive correlation with the concentration of magnesium, and the maximum biomass of Tribonema sp. (under the condition of 450 mg/L MgSO₄) was 8.09 g/L, much greater than those reported in previous studies using the same and other Tribonema species under autotrophic conditions. Different nitrogen concentrations exerted no significant effect on algal growth (P > 0.05), but a higher nitrogen concentration resulted in a greater amount of lipid in the cells. The maximum volumetric productivities of total lipids (319. 6 mg/(L·d)), palmitoleic acid (135.7 mg/(L·d)), and eicosapentaenoic acid (24.2 mg/(L·d)) of Tribonema sp. were obtained when the concentrations of NaNO₃, K₂HPO₄, (NH₄)₃FeC₁₂H₁₀O₁₄, and MgSO₄ were 765 mg/L, 80 mg/L, 6 mg/L, and 75 mg/L, respectively. This study will provide a reference for substrate optimization for Tribonema sp. growth and lipid production.

Release of Anti-Inflammatory Palmitoleic Acid and Its Positional Isomers by Mouse Peritoneal Macrophages

Positional isomers of hexadecenoic acid are considered as fatty acids with anti-inflammatory properties. The best known of them, palmitoleic acid (cis-9-hexadecenoic acid, 16:1n-7), has been identified as a lipokine with important beneficial actions in metabolic diseases. Hypogeic acid (cis-7-hexadecenoic acid, 16:1n-9) has been regarded as a possible biomarker of foamy cell formation during atherosclerosis. Notwithstanding the importance of these isomers as possible regulators of inflammatory responses, very little is known about the regulation of their levels and distribution and mobilization among the different lipid pools within the cell. In this work, we describe that the bulk of hexadecenoic fatty acids found in mouse peritoneal macrophages is esterified in a unique phosphatidylcholine species, which contains palmitic acid at the sn-1 position, and hexadecenoic acid at the sn-2 position. This species markedly decreases when the macrophages are activated with inflammatory stimuli, in parallel with net mobilization of free hexadecenoic acid. Using pharmacological inhibitors and specific gene-silencing approaches, we demonstrate that hexadecenoic acids are selectively released by calcium-independent group VIA phospholipase A₂ under activation conditions. While most of the released hexadecenoic acid accumulates in free fatty acid form, a significant part is also transferred to other phospholipids to form hexadecenoate-containing inositol phospholipids, which are known to possess growth-factor-like-properties, and are also used to form fatty acid esters of hydroxy fatty acids, compounds with known anti-diabetic and anti-inflammatory properties. Collectively, these data unveil new pathways and mechanisms for the utilization of palmitoleic acid and its isomers during inflammatory conditions, and raise the intriguing possibility that part of the anti-inflammatory activity of these fatty acids may be due to conversion to other lipid mediators.

Fatty Acid Profile and Desaturase Activities in 7-10-Year-Old Children Attending Primary School in Verona South District: Association between Palmitoleic Acid, SCD-16, Indices of Adiposity, and Blood Pressure

In previous studies, dietary and circulating fatty acids (FA) and desaturases activity (delta-5 desaturase [D5D], delta-6 desaturase [D6D], and stearoyl-CoA desaturase [SCD-16]) involved in their metabolism were associated with metabolic and cardiovascular disorders. The aim of the study was to assess the association between different FAs and desaturases activity (estimated as product:precursor ratios) with individual cardiovascular risk factors (in particular, anthropometric measurements and blood pressure [BP]) in children. The FA profile was determined on a whole-blood drop in 243 children (age: 8.6 ± 0.72 years) participating in a school-based cross-sectional study. Docosahexaenoic acid (DHA) inversely correlated with indices of adiposity, glucose, and triglycerides. Palmitoleic acid and SCD-16 were directly associated with markers of adiposity and BP, even after adjustment for main confounders. D6D correlated directly with the waist/height ratio. Children with excess weight (>85th percentile; that is overweight plus obese ones) showed higher palmitic acid, palmitoleic acid, and higher SCD-16 activity as compared to normal-weight children. Most of the associations were confirmed in the excess-weight group. Omega-3 FAs, particularly DHA, but not omega-6 FA, showed a potentially beneficial association with metabolic parameters, whereas palmitoleic acid and SCD-16 showed a potentially harmful association with indices of adiposity and BP, especially in obese children.

Serum C16:1n7/C16:0 ratio as a diagnostic marker for non-alcoholic steatohepatitis

BACKGROUND AND AIMS

Accurate diagnosis of non-alcoholic steatohepatitis (NASH) from non-alcoholic fatty liver disease (NAFLD) is clinically important. Therefore, there is a need for easier ways of diagnosing NASH. In this study, we investigated the serum fatty acid composition and evaluated the possibility of using the serum fatty acid composition as a diagnostic marker of NASH.

METHODS

The subjects were 78 NAFLD patients (non-alcoholic fatty liver [NAFL]: 30, NASH: 48) and 24 healthy individuals. Fatty acids extracted from the liver tissue and serum were identified and quantified by gas chromatography. In addition, we evaluated the relationship between serum and liver tissue fatty acid composition, patient background, and liver histology. The diagnostic performance of NASH was evaluated by calculating the area under the receiver operating characteristic (AUROC).

RESULTS

The results of the fatty acid analysis showed the C16:1n7/C16:0 ratio to have the strongest correlation between serum and liver tissue (r = 0.865, P < 0.0001). The serum C16:1n7/C16:0 ratio in the NASH group was higher compared with that in the NAFL group (P = 0.0007). Evaluation of the association of the serum C16:1n7/C16:0 ratio with liver histology revealed significant correlation with lobular inflammation score, ballooning score, and fibrosis score. The AUROC for predicting NASH in all NAFLD patients was 0.7097. The AUROC was nearly equivalent even when the study subjects were restricted to patients with a fibrosis score ≤ 2 only (AUROC 0.6917).

CONCLUSION

Measuring the serum C16:1n7/C16:0 ratio may be an effective non-invasive method for diagnosing NASH, particularly in its early stages.

Comparison of Lipid and Palmitoleic Acid Induction of Tribonema minus under Heterotrophic and Phototrophic Regimes by Using High-Density Fermented Seeds

Palmitoleic acid, one scarce omega-7 monounsaturated fatty acid, has important applications in the fields of medicine and health products. Tribonema has been considered as a promising candidate for the production of palmitoleic acid due to its high lipid and palmitoleic acid content and remarkable heterotrophic ability. The high-density heterotrophic cultivation of Tribonema minus was conducted in this work, and the highest biomass of 42.9 g L⁻¹ and a relatively low lipid content of 28.7% were observed. To further enhance the lipid and palmitoleic acid accumulation, induction strategies under two regimes of phototrophy and heterotrophy with different conditions were investigated and compared. Results demonstrated encouraging promotions both by heterotrophic and phototrophic ways, and the final lipid contents reached 41.9% and 49.0%, respectively. In consideration of the time cost, however, the induction under heterotrophic conditions was much more advantageous, by which the highest lipid and palmitoleic acid productivities of 1.77 g L⁻¹ d⁻¹ and 924 mg L⁻¹ d⁻¹ were obtained respectively, with the lipid yield on glucose of 0.26 g g⁻¹.

Fasting hepatic de novo lipogenesis is not reliably assessed using circulating fatty acid markers

Background

Observational studies often infer hepatic de novo lipogenesis (DNL) by measuring circulating fatty acid (FA) markers; however, it remains to be elucidated whether these markers accurately reflect hepatic DNL.

Objectives

We investigated associations between fasting hepatic DNL and proposed FA markers of DNL in subjects consuming their habitual diet.

Methods

Fasting hepatic DNL was assessed using 2H2O (deuterated water) in 149 nondiabetic men and women and measuring the synthesis of very low-density lipoprotein triglyceride (VLDL-TG) palmitate. FA markers of blood lipid fractions were determined by gas chromatography.

Results

Neither the lipogenic index (16:0/18:2n-6) nor the SCD index (16:1n-7/16:0) in VLDL-TG was associated with isotopically assessed DNL (r = 0.13, P = 0.1 and r = -0.08, P = 0.35, respectively). The relative abundances (mol%) of 14:0, 16:0, and 18:0 in VLDL-TG were weakly (r ≤ 0.35) associated with DNL, whereas the abundances of 16:1n-7, 18:1n-7, and 18:1n-9 were not associated. When the cohort was split by median DNL, only the abundances of 14:0 and 18:0 in VLDL-TG could discriminate between subjects having high (11.5%) and low (3.8%) fasting hepatic DNL. Based on a subgroup, FA markers in total plasma TG, plasma cholesteryl esters, plasma phospholipids, and red blood cell phospholipids were generally not associated with DNL.

Conclusions

The usefulness of circulating FAs as markers of hepatic DNL in healthy individuals consuming their habitual diet is limited due to their inability to discriminate clearly between individuals with low and high fasting hepatic DNL.

Stearoyl-ACP Δ9 Desaturase 6 and 8 (GhA-SAD6 and GhD-SAD8) Are Responsible for Biosynthesis of Palmitoleic Acid Specifically in Developing Endosperm of Upland Cotton Seeds

Palmitoleic acid (16:1Δ⁹) is one kind of ω-7 fatty acids (ω-7 FAs) widely used in food, nutraceutical and industry. However, such high-valued ω-7 FA only has a trace level in mature seeds of cotton and other common oil crops. We found that palmitoleic acid (>10.58 Mol%) was specially enriched in developing cotton endosperm which is disappeared in its mature seed. The present study was conducted to investigate the mechanism underlying high accumulation of palmitoleic acid in developing endosperm but not in embryo of upland cotton (Gossypium hirsutum L.) seed. Of 17 stearoyl-ACP Δ⁹ desaturases (SAD) gene family members identified in upland cotton, six GhSADs may specifically work in the desaturation of palmitic acid (16:0-ACP) to produce palmitoleic acid (16:1Δ⁹-ACP), which were revealed by examining the key amino acids in the catalytic center and their cis-elements. Gene expression analysis showed that spatial patterns of these GhSADs were different in developing ovules, with GhA-SAD6 and GhD-SAD8 preferentially expressed in developing endosperms. Functional analysis by transient expression in Nicotiana benthamiana leaves and genetic complementary assay using yeast mutant BY4389 strain unable to synthesize unsaturated fatty acids demonstrated that GhA-SAD6 and GhD-SAD8 have strong substrate specificity for 16:0-ACP. In contrast, GhA-SAD5 and GhA-SAD7 exhibited high specific activity on 18:0-ACP. Taken together, these data evidence that GhA-SAD6 and GhD-SAD8 are responsible for making palmitoleic acid in developing cotton endosperms, and provide endogenous gene targets for genetic modification to enrich ω-7 FAs in cotton seed oil required for sustainable production of functionality-valued products.

Detoxification and Immune Transcriptomic Response of the Gill Tissue of Bay Scallop (Argopecten irradians) Following Exposure to the Algicide Palmitoleic Acid

Palmitoleic acid (PA) is an effective algicide against Alexandrium tamarense. However, the toxicological mechanism of PA exposure is unclear. The transcript abundance and differentially expressed genes (DEGs) in gills of bay scallop were investigated following 80 mg/L PA exposure up to 48 h using the Illumina HiSeq 4000 deep-sequencing platform with the recommended read length of 100 bp. De novo assembly of paired-end reads yielded 62,099 unigenes; 5414 genes were identified as being significantly increased, and 4452 were decreased. Based on gene ontology classification and enrichment analysis, the ‘cellular process’, ‘metabolic process’, ‘response to stimulus’, and ‘catalytic process’ with particularly high functional enrichment were revealed. The DEGs, which are related to detoxification and immune responses, revealed that acid phosphatase, fibrinogen C domain-containing protein, cyclic AMP-responsive element-binding protein, glutathione reductase, ATP-binding cassette, nuclear factor erythroid 2-related factor, NADPH2:quinone reductase, and cytochrome P450 4F22, 4B1, and 2C8-related gene expression decreased. In contrast, some genes related to glutathione S-transferase, C-type lectin, superoxide dismutase, toll-like receptors, and cytochrome P450 2C14, 2U1, 3A24 and 4A2 increased. The results of current research will be a valuable resource for the investigation of gene expression stimulated by PA, and will help understanding of the molecular mechanisms underlying the scallops’ response to PA exposure.

Palmitoleic Acid has Stronger Anti-Inflammatory Potential in Human Endothelial Cells Compared to Oleic and Palmitic Acids

SCOPE

Fatty acids (FAs) may affect endothelial cell (EC) function, influencing atherogenesis and inflammatory processes. Palmitoleic acid (POA) has been described as an anti-inflammatory FA. However, its effects on ECs are underexplored. This study compares the effects of POA with those of palmitic acid (PA) and oleic acid (OA) on EC inflammatory responses.

METHODS AND RESULTS

EAHy926 cells (EC lineage) are exposed to PA, OA, or POA, and stimulated with tumor necrosis factor (TNF)-α. Associated with the FA's own incorporation, PA induces a twofold increase in arachidonic acid, while POA increases the amount of cis-vaccenic acid. PA, but not OA, enhances the production of IL-6 and IL-8 in response to TNF-α. In contrast, POA decreases production of monocyte chemotactic protein (MCP)-1, IL-6, and IL-8 compared to PA. TNF-α increases surface intercellular adhesion molecule-1 expression previously decreased by POA. TNF-α stimulation increases the expression of NFκB, cyclooxygenase (COX)-2, MCP-1, and IL-6 genes and reduces the expression of peroxisome proliferator-activated receptor (PPAR)-α gene. PA enhances the expression of MCP-1, IL-6, and COX-2 genes, while POA downregulates these genes, decreases expression of NFκB, and upregulates PPAR-α gene expression.

CONCLUSION

POA has anti-inflammatory effects on ECs stimulated with TNF-α and may counter endothelial dysfunction.

Implications of Palmitoleic Acid (Palmitoleate) On Glucose Homeostasis, Insulin Resistance and Diabetes

Obesity is a metabolic, multifactorial disease that is underpinned by factors such as genetics, epigenetics, as well as high-energy food intake and sedentarism. Obesity is often associated with, and exacerbated by, other metabolic disorders such as type 2 diabetes mellitus (T2DM). A hallmark of T2DM is failure of insulin secretion from pancreatic β-cell to regulate blood glucose disposal into peripheral tissues, such as skeletal muscle, termed insulin resistance, as well as deregulation of pancreatic α-cell function. It has been proposed that insulin resistance is, in part, a consequence of impaired signal transduction of insulin caused by several molecules released from adipose tissue that include (adipo)cytokines and fatty acids. However, not all fatty acids exert a negative impact on insulin sensitivity. In fact, it has been suggested that palmitoleic acid (16:1n-7) has hormone-like properties and improves some metabolic parameters that are impaired in obesity and T2DM. Moreover, in vitro approaches reveal that cis-16:1n-7 can influence pancreatic β-cell survival, insulin secretion, and skeletal muscle insulin response and adipocyte metabolism. In vivo experiments using animal models show that the ingestion of cis-16:1n-7 or sources of it (e.g., macadamia oil) can partially prevent the metabolic alterations caused by high-fat/carbohydrate diets. In general, studies in humans found positive associations between higher trans-16:1n-7 proportion in plasma phospholipids and improved insulin sensitivity or decreased the onset of T2DM. However, plasma cis-16:1n-7 data are still controversial. In this brief review, we discuss the main studies on 16:1n-7 effects on obesity and T2DM and their potential for clinical application.

Unsaturated Fatty Acids Affect Quorum Sensing Communication System and Inhibit Motility and Biofilm Formation of Acinetobacter baumannii

The increasing threat of Acinetobacter baumannii as a nosocomial pathogen is mainly due to the occurrence of multidrug-resistant strains that are associated with the real problem of its eradication from hospital wards. The particular ability of this pathogen to form biofilms contributes to its persistence, increases antibiotic resistance, and promotes persistent/device-related infections. We previously demonstrated that virstatin, which is a small organic compound known to decrease virulence of Vibrio cholera via an inhibition of T4-pili expression, displayed very promising activity to prevent A. baumannii biofilm development. Here, we examined the antibiofilm activity of mono-unsaturated chain fatty acids, palmitoleic (PoA), and myristoleic (MoA) acids, presenting similar action on V. cholerae virulence. We demonstrated that PoA and MoA (at 0.02 mg/mL) were able to decrease A. baumannii ATCC 17978 biofilm formation up to 38% and 24%, respectively, presented a biofilm dispersing effect and drastically reduced motility. We highlighted that these fatty acids decreased the expression of the regulator abaR from the LuxIR-type quorum sensing (QS) communication system AbaIR and consequently reduced the N-acyl-homoserine lactone production (AHL). This effect can be countered by addition of exogenous AHLs. Besides, fatty acids may have additional non-targeted effects, independent from QS. Atomic force microscopy experiments probed indeed that PoA and MoA could also act on the initial adhesion process in modifying the material interface properties. Evaluation of fatty acids effect on 22 clinical isolates showed a strain-dependent antibiofilm activity, which was not correlated to hydrophobicity or pellicle formation ability of the tested strains, and suggested a real diversity in cell-to-cell communication systems involved in A. baumannii biofilm formation.

Is Palmitoleic Acid a Plausible Nonpharmacological Strategy to Prevent or Control Chronic Metabolic and Inflammatory Disorders?

Although dietary fatty acids can modulate metabolic and immune responses, the effects of palmitoleic acid (16:1n-7) remain unclear. Since this monounsaturated fatty acid is described as a lipokine, studies with cell culture and rodent models have suggested it enhances whole body insulin sensitivity, stimulates insulin secretion by β cells, increases hepatic fatty acid oxidation, improves the blood lipid profile, and alters macrophage differentiation. However, human studies report elevated blood levels of palmitoleic acid in people with obesity and metabolic syndrome. These findings might be reflection of the level or activity of stearoyl-CoA desaturase-1, which synthesizes palmitoleate and is enhanced in liver and adipose tissue of obese patients. The aim of this review is to describe the immune-metabolic effects of palmitoleic acid observed in cell culture, animal models, and humans to answer the question of whether palmitoleic acid is a plausible nonpharmacological strategy to prevent, control, or ameliorate chronic metabolic and inflammatory disorders. Despite the beneficial effects observed in cell culture and in animal studies, there are insufficient human intervention studies to fully understand the physiological effects of palmitoleic acid. Therefore, more human-based research is needed to identify whether palmitoleic acid meets the promising therapeutic potential suggested by the preclinical research.

Palmitoleic Acid Inhibits RANKL-Induced Osteoclastogenesis and Bone Resorption by Suppressing NF-κB and MAPK Signalling Pathways

Osteoclasts are large, multinucleated cells that are responsible for the breakdown or resorption of bone during bone remodelling. Studies have shown that certain fatty acids (FAs) can increase bone formation, reduce bone loss, and influence total bone mass. Palmitoleic acid (PLA) is a 16-carbon, monounsaturated FA that has shown anti-inflammatory properties similar to other FAs. The effects of PLA in bone remain unexplored. Here we investigated the effects of PLA on receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL)-induced osteoclast formation and bone resorption in RAW264.7 murine macrophages. PLA decreased the number of large, multinucleated tartrate resistant acid phosphatase (TRAP) positive osteoclasts and furthermore, suppressed the osteolytic capability of these osteoclasts. This was accompanied by a decrease in expression of resorption markers (Trap, matrix metalloproteinase 9 (Mmp9), cathepsin K (Ctsk)). PLA further decreased the expression of genes involved in the formation and function of osteoclasts. Additionally, PLA inhibited NF-κB activity and the activation of mitogen activated protein kinases (MAPK), c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK). Moreover, PLA induced apoptosis in mature osteoclasts. This study reveals that PLA inhibits RANKL-induced osteoclast formation in RAW264.7 murine macrophages through suppression of NF-κB and MAPK signalling pathways. This may indicate that PLA has potential as a therapeutic for bone diseases characterized by excessive osteoclast formation.

Fatty Acids in Membranes as Homeostatic, Metabolic and Nutritional Biomarkers: Recent Advancements in Analytics and Diagnostics. Diagnostics (Basel). 2016;7. [PMID: 28025506 PMCID: PMC5373010 DOI: 10.3390/diagnostics7010001]

Fatty acids, as structural components of membranes and inflammation/anti-inflammatory mediators, have well-known protective and regulatory effects. They are studied as biomarkers of pathological conditions, as well as saturated and unsaturated hydrophobic moieties in membrane phospholipids that contribute to homeostasis and physiological functions. Lifestyle, nutrition, metabolism and stress—with an excess of radical and oxidative processes—cause fatty acid changes that are examined in the human body using blood lipids. Fatty acid-based membrane lipidomics represents a powerful diagnostic tool for assessing the quantity and quality of fatty acid constituents and also for the follow-up of the membrane fatty acid remodeling that is associated with different physiological and pathological conditions. This review focuses on fatty acid biomarkers with two examples of recent lipidomic research and health applications: (i) monounsaturated fatty acids and the analytical challenge offered by hexadecenoic fatty acids (C16:1); and (ii) the cohort of 10 fatty acids in phospholipids of red blood cell membranes and its connections to metabolic and nutritional status in healthy and diseased subjects.

1.65 Å resolution structure of the AraC-family transcriptional activator ToxT from Vibrio cholerae

A crystal structure of ToxT at 1.65 Å resolution with a similar overall structure to the previously determined structure is reported. A region that extends from Asp101 to Glu110, which can influence ToxT activity but was disordered in the previous structure, can be traced entirely in the current structure.

ToxT is an AraC-family transcriptional activator protein that controls the expression of key virulence factors in Vibrio cholerae, the causative agent of cholera. ToxT directly activates the expression of the genes that encode the toxin-coregulated pilus and cholera toxin, and also positively auto-regulates its own expression from the tcp promoter. The crystal structure of ToxT has previously been solved at 1.9 Å resolution (PDB entry 3gbg). In this study, a crystal structure of ToxT at 1.65 Å resolution with a similar overall structure to the previously determined structure is reported. However, there are distinct differences between the two structures, particularly in the region that extends from Asp101 to Glu110. This region, which can influence ToxT activity but was disordered in the previous structure, can be traced entirely in the current structure.

Effect of the Algaecide Palmitoleic Acid on the Immune Function of the Bay Scallop Argopecten irradians

Palmitoleic acid (PA), an algicidal compound, is used against the toxin producing dinofagelate Alexandrium tamarense, however, its impact on the edible bay scallop (Argopecten irradians) is still unclear. Therefore, we investigated the impacts of effective algicidal concentrations (20, 40, and 80 mg/L) of PA on immune responses in A. irradians. Various immune parameters including acid phosphatase (ACP) activity, superoxide dismutase (SOD), lysozyme, phagocytic activity, total protein, malondialdehyde (MDA) level, and reactive oxygen species (ROS) production and the expression of immune-related genes (PrxV, CLT-6, MT, and BD) were measured at 3, 6, 12, 24, and 48 h post-exposure (hpe) to PA. Lysozyme activity was lower in scallops at 12-48 hpe to 80 mg/L. SOD, ACP activity, ROS production, the total protein, and MDA level was higher at 12 to 48 hpe with different concentrations of PA. Phagocytic activity increased at 6-12 hpe to 40-80 mg/L of PA, but decreased at 24-48 hpe. The expressions of genes PrxV, CLT-6, MT and BD down-regulated at 3 hpe were observed, while differential expressions from 6-48 hpe with different concentrations of PA. The present study demonstrated that immersing A. irradians in PA at effective concentrations could result in differential effects on non-specific immune responses and expressions of immune-related genes.

Defense Priming and Jasmonates: A Role for Free Fatty Acids in Insect Elicitor-Induced Long Distance Signaling

Green leaf volatiles (GLV) prime plants against insect herbivore attack resulting in stronger and faster signaling by jasmonic acid (JA). In maize this response is specifically linked to insect elicitor (IE)-induced signaling processes, which cause JA accumulation not only around the damage site, but also in distant tissues, presumably through the activation of electrical signals. Here, we present additional data further characterizing these distal signaling events in maize. Also, we describe how exposure to GLV increases free fatty acid (fFA) levels in maize seedlings, but also in other plants, and how increased fFA levels affect IE-induced JA accumulation. Increased fFA, in particular α-linolenic acid (LnA), caused a significant increase in JA accumulation after IE treatment, while JA induced by mechanical wounding (MW) alone was not affected. We also identified treatments that significantly decreased certain fFA level including simulated wind and rain. In such treated plants, IE-induced JA accumulation was significantly reduced when compared to un-moved control plants, while MW-induced JA accumulation was not significantly affected. Since only IE-induced JA accumulation was altered by changes in the fFA composition, we conclude that changing levels of fFA affect primarily IE-induced signaling processes rather than serving as a substrate for JA.

Altered Levels of Fatty Acids and Inflammatory and Metabolic Mediators in Epicardial Adipose Tissue in Patients With Systolic Heart Failure

BACKGROUND

Adipose tissue has endocrine properties, secreting a wide range of mediators into the circulation, including factors involved in cardiovascular disease. However, little is known about the potential role of adipose tissue in heart failure (HF), and the aim of this study was to investigate epicardial (EAT) and subcutaneous (SAT) adipose tissue in HF patients.

METHODS AND RESULTS

Thirty patients with systolic HF and 30 patients with normal systolic function undergoing thoracic surgery were included in the study. Plasma was sampled and examined with the use of enzyme-linked immunosorbent assays, whereas SAT and EAT biopsies were collected and examined by means of reverse-transcription polymerase chain reaction and gas chromatography. Significantly higher expressions of mRNA encoding interleukin-6, adrenomedullin, peroxisome proliferator-activated receptor α, and fatty acid (FA)-binding protein 3, as well as higher levels of monounsaturated FA and palmitoleic acid, were seen in the EAT of HF patients, whereas the levels of docosahexaenoic acid were lower. Palmitoleic acid levels in EAT were correlated with 2 parameters of cardiac remodeling: increasing left ventricular end-diastolic diameter and N-terminal pro-B-type natriuretic peptide.

CONCLUSIONS

Our results demonstrate adipose tissue depot-specific alterations of synthesis of FA and inflammatory and metabolic mediators in systolic HF patients. EAT may be a source of increased circulatory and myocardial levels of these mediators through endocrine actions.

Effect of PEGylated lipid and Lecinol S-10 on physico-chemical properties and encapsulation efficiency of palmitoleate-palmitoleic acid vesicles

A vesicle is a microscopic particle composed of a lipid bilayer membrane that separates the inner aqueous compartment from the outer aqueous environment. Palmitoleate-palmitoleic acid vesicles were prepared and their physico-chemical properties were investigated. Moreover, mixed vesicles composed of palmitoleic acid and PEGylated lipid and/or a mixture of phospholipids were also prepared. The stabilizing effects of these double-chain lipids on the formation of palmitoleate-palmitoleic acid vesicles were studied. Stability of the vesicle suspension was examined using particle size and zeta potential at 30 °C. The magnitude of the zeta potential was relatively lower in the vesicle suspension with the presence of phospholipid. Although some of the mixed vesicles that were formed were not very stable, they displayed potential for encapsulating the active ingredient calcein and the encapsulation efficiencies of calcein were encouraging. The palmitoleate-palmitoleic acid-DPPE-PEG2000 vesicle showed the most promising stability and encapsulation efficiency.

Ethanol contributes to neurogenic pancreatitis by activation of TRPV1

Alcohol abuse is a major cause of pancreatitis in people, but the mechanism is unknown. It has been recently demonstrated that transient receptor potential vanilloid 1 (TRPV1) activation causes neurogenic inflammation and plays an important role in acute pancreatitis. Moreover, TRPV1 is activated by ethanol. We examined the direct effects of ethanol on acute pancreatitis. Acute inflammation of the pancreas was produced by injection of ethanol and palmitoleic acid (POA), a nonoxidative metabolite of ethanol, in wild-type C57BL/6J mice and Trpv1-knockout C57BL/6J mice. Inflammatory indexes were analyzed 24 h later. Injection of ethanol + POA produced acute pancreatitis indicated by significant increases in histopathological damage, serum amylase levels, and pancreatic MPO concentrations (P<0.05-0.001). All parameters of pancreatitis were blocked by pretreatment with the TRPV1 antagonist drug AMG9810. In addition, ethanol + POA administration to Trpv1knockout mice did not produce pancreatic inflammation. Treatment with vehicle, ethanol alone, or POA alone had no inflammatory effects. TRPV1 partially mediates inflammation induced by ethanol + POA in the mouse pancreas, consistent with the ability of ethanol to activate TRPV1. We propose that ethanol may contribute to alcohol-induced pancreatitis by a neurogenic mechanism.

Plasma fatty acid composition, estimated desaturase activities, and their relation with the metabolic syndrome in a population at high risk of cardiovascular disease

BACKGROUND & AIMS

The metabolic syndrome (MetS) is a clustering of various metabolic abnormalities which is associated with increased risk of cardiovascular disease (CVD) and type 2 diabetes mellitus. Due to its increasing prevalence, it has become an important public health concern. Altered fatty acid (FA) composition and desaturase activities have been associated with several metabolic diseases, including MetS. The aim of the present study was to evaluate the relationship of the plasma FA profile and desaturase activities with the MetS in a Mediterranean population at high risk of CVD.

METHODS

Baseline data from 427 participants aged 55-80 years who took part in the interventional PREDIMED study were obtained. Individual FA was determined in plasma and desaturase activities were estimated from product/precursor ratios. Odds ratios (OR) and partial correlation coefficients were used to examine these relations with MetS and its components, respectively.

RESULTS

We found higher levels of C14:0, C16:0, C16:1n-7, estimated Δ(9)- or stearoyl-CoA desaturase (SCD), and estimated Δ(6) desaturase (D6D), and lower levels of C18:2n-6 in people with MetS compared to those without it. After adjustment for several confounders, only higher quartiles of C14:0, C16:0, C16:1n-7, and D6D were found to be associated with an increasing prevalence of MetS, while higher quartiles of C18:2n-6 were inversely associated with MetS. High proportions of C14:0, C16:0, C16:1n-7, C20:3n-6, SCD, and D6D, and decreased proportions of C18:2n-6 and estimated Δ(5)-desaturase (D5D) were associated with adverse profiles of several metabolic risk factors. Women showed more unhealthy FA pattern and lipid profiles than men, but only among those with MetS.

CONCLUSION

A FA composition and estimated desaturase activities consisting in high levels of SFA, SCD and D6D, and low levels of PUFA and D5D are associated with increased MetS probability and are characteristic of people presenting MetS, especially women. These findings support those observed in non-Mediterranean populations in which an altered FA profile and estimated desaturase activities are associated with MetS.

Modulation of cellular insulin signaling and PTP1B effects by lipid metabolites in skeletal muscle cells

Normal glucose regulation is achieved by having adequate insulin secretion and effective glucose uptake/disposal. Excess lipids in peripheral tissues - skeletal muscle, liver and adipose tissue - may attenuate insulin signaling through the protein kinase B (AKt) pathway and up-regulate protein tyrosine phosphatase 1B (PTP1B), a negative regulator of insulin signaling. We studied accumulation of lipid metabolites [triglycerides (TAGs), diglycerides (DAGs)] and ceramides in relation to insulin signaling and expression and phosphorylation of PTP1B by preincubating rat skeletal muscle cells (L6 myotubes) with three saturated and three unsaturated free fatty acids (FFAs) (200 μM). Cells were also evaluated in the presence of wortmannin, an inhibitor of phosphatidylinositol 3-kinases and thus AKt (0-100 nM). Unsaturated FFAs increased DAGs, TAGs and PTP1B expression significantly, but cells remained insulin sensitive as assessed by robust AKt and PTP1B phosphorylation at serine (Ser) 50, Ser 398 and tyrosine 152. Saturated palmitic and stearic acids increased ceramides, up-regulated PTP1B, and had AKt and PTP1B phosphorylation at Ser 50 impaired. We show a significant correlation between phosphorylation levels of AKt and of PTP1B at Ser 50 (R(2)=0.84, P<.05). The same was observed with increasing wortmannin dose (R(2)=0.73, P<.05). Only FFAs that increased ceramides caused impairment of AKt and PTP1B phosphorylation at Ser 50. PTP1B overexpression in the presence of excess lipids may not directly cause insulin resistance unless it is accompanied by decreased PTP1B phosphorylation. A clear relationship between PTP1B phosphorylation levels at Ser 50 and its negative effect on insulin signaling is shown.

Effects of the gap junction uncoupler palmitoleic acid on the activation and repolarization wavefronts in isolated rabbit hearts

1. The heart normally acts as an electrical syncytium coupled via gap junctional channels. Since closure of these channels has been considered arrhythmogenic, we wanted to elucidate, how activation and repolarization wavefronts are altered during progressive pharmacological gap junctional uncoupling. 2. We used the well known gap junction uncoupler palmitoleic acid (PA). The specificity of PA was tested in rabbit papillary muscles, which exhibited slowed conduction without affecting action potential morphology. We submitted isolated rabbit hearts (Langendorff-technique) to increasing concentrations of palmitoleic acid (0.2, 1, 2, 5, 10, 20 microM), while 256 channel epicardial potential mapping was carried out. 3. In presence of PA activation recovery intervals (ARI) at the 256 electrodes became highly inhomogeneous with a dramatic increase in the dispersion of activation recovery intervals (from 6 to 35 ms, P>0.01; EC50=7 microM), while the mean ARI-duration at 256 sites remained stable. PA led to marked alterations of the activation pattern, expressed as percentage of unchanged activation vectors (reduction from 32 to 10%, P<0.01, EC50=3.3 microM), to prolongation of atrioventricular conduction time (from 58 to 107 ms, P<0.01; EC50=8 microM) of total activation time (from 7 to 14 ms, P<0.05, EC50=11 microM) and of QRS-complex-duration. 4. In additional experiments the ventricle was paced via a bipolar electrode during the mapping procedure. From the isochrones longitudinal and transversal velocities were assessed showing that PA reduced transversal conduction velocity more distinctly than longitudinal. 5. With regard to maximum effects and EC50 values we conclude that gap junction uncoupling by PA mainly affects atrioventricular conduction, ARI-dispersion and ventricular activation pattern. As important arrhythmogenic effects of uncoupling enhancement of dispersion with concomitant disturbation of the normal activation pattern and slowing of conduction might be considered.