Dietary myristic acid at physiologically relevant levels increases the tissue content of C20:5 n-3 and C20:3 n-6 in the rat

Association between maternal obesity, essential fatty acids and biomarkers of fetal liver function

Maternal obesity and the imbalance in linoleic acid (C18:2 n-6, LA) and alpha-linolenic acid (C18:3 n-3, ALA) levels are related with hepatic disturbances in the offspring. However, whether these alterations are present during fetal life is not well understood. Obese and normal weight pregnant women were recruited to determine fatty acids (FAs) consumption, FAs profile (in maternal erythrocytes, placenta and neonatal very low-density lipoproteins VLDL) and biomarkers of fetal liver function, such as gamma-glutamyl transferase (GGT), alpha-fetoprotein (AFP) and albumin, in umbilical cord blood. Stearic acid (C18:0, ST) was lower, and total n-3 FAs tended to be lower in umbilical cord VLDLs of obese women compared to controls. Independently of maternal obesity, GGT levels in umbilical cord blood was positively correlated with the LA content and negatively correlated with the ALA content in maternal erythrocytes. We conclude that maternal obesity and its imbalance of LA and ALA are associated with changes in biomarkers of fetal liver function.

Short-Term High-Fat Diet Fuels Colitis Progression in Mice Associated With Changes in Blood Metabolome and Intestinal Gene Expression

Clinical cases and animal experiments show that high-fat (HF) diet is involved in inflammatory bowel disease (IBD), but the specific mechanism is not fully clear. A close association between long-term HF-induced obesity and IBD has been well-documented. However, there has been limited evaluation of the impact of short-term HF feeding on the risk of intestinal inflammation, particularly on the risk of disrupted metabolic homeostasis. In this study, we analyzed the metabolic profile and tested the vulnerability of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis after short-term HF feeding in mice. The results showed that compared with the control diet (CD), the fatty acid (FA), amino acid (AA), and bile acid (BA) metabolisms of mice in the HF group were significantly changed. HF-fed mice showed an increase in the content of saturated and unsaturated FAs and a decrease in the content of tryptophan (Trp). Furthermore, the disturbed spatial distribution of taurocholic acid (TCA) in the ileum and colon was identified in the HF group using matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI). After HF priming, mice on TNBS induction were subjected to more severe colonic ulceration and histological damage compared with their CD counterparts. In addition, TNBS enema induced higher gene expressions of mucosal pro-inflammatory cytokines under HF priming conditions. Overall, our results show that HF may promote colitis by disturbing lipid, AA, and BA metabolic homeostasis and inflammatory gene expressions.

Ginsenoside Rb1 Improves Metabolic Disorder in High-Fat Diet-Induced Obese Mice Associated With Modulation of Gut Microbiota

Gut microbiota plays an important role in metabolic homeostasis. Previous studies demonstrated that ginsenoside Rb1 might improve obesity-induced metabolic disorders through regulating glucose and lipid metabolism in the liver and adipose tissues. Due to low bioavailability and enrichment in the intestinal tract of Rb1, we hypothesized that modulation of the gut microbiota might account for its pharmacological effects as well. Here, we show that oral administration of Rb1 significantly decreased serum LDL-c, TG, insulin, and insulin resistance index (HOMA-IR) in mice with a high-fat diet (HFD). Dynamic profiling of the gut microbiota showed that this metabolic improvement was accompanied by restoring of relative abundance of some key bacterial genera. In addition, the free fatty acids profiles in feces were significantly different between the HFD-fed mice with or without Rb1. The content of eight long-chain fatty acids (LCFAs) was significantly increased in mice with Rb1, which was positively correlated with the increase of Akkermansia and Parasuttereller, and negatively correlated with the decrease of Oscillibacter and Intestinimonas. Among these eight increased LCFAs, eicosapentaenoic acid (EPA), octadecenoic acids, and myristic acid were positively correlated with metabolic improvement. Furthermore, the colonic expression of the free fatty acid receptors 4 (Ffar4) gene was significantly upregulated after Rb1 treatment, in response to a notable increase of LCFA in feces. These findings suggested that Rb1 likely modulated the gut microbiota and intestinal free fatty acids profiles, which should be beneficial for the improvement of metabolic disorders in HFD-fed mice. This study provides a novel mechanism of Rb1 for the treatment of metabolic disorders induced by obesity, which may provide a therapeutic avenue for the development of new nutraceutical-based remedies for treating metabolic diseases, such as hyperlipidemia, insulin resistance, and type 2 diabetes.

The relationship between hair metabolites, air pollution exposure and gestational diabetes mellitus: A longitudinal study from pre-conception to third trimester

BACKGROUND

Gestational diabetes mellitus (GDM) is a metabolic condition defined as glucose intolerance with first presentation during pregnancy. Many studies suggest that environmental exposures, including air pollution, contribute to the pathogenesis of GDM. Although hair metabolite profiles have been shown to reflect pollution exposure, few studies have examined the link between environmental exposures, the maternal hair metabolome and GDM. The aim of this study was to investigate the longitudinal relationship (from pre-conception through to the third trimester) between air pollution exposure, the hair metabolome and GDM in a Chinese cohort.

METHODS

A total of 1020 women enrolled in the Complex Lipids in Mothers and Babies (CLIMB) birth cohort were included in our study. Metabolites from maternal hair segments collected pre-conception, and in the first, second, and third trimesters were analysed using gas chromatography-mass spectrometry (GC-MS). Maternal exposure to air pollution was estimated by two methods, namely proximal and land use regression (LUR) models, using air quality data from the air quality monitoring station nearest to the participant's home. Logistic regression and mixed models were applied to investigate associations between the air pollution exposure data and the GDM associated metabolites.

RESULTS

Of the 276 hair metabolites identified, the concentrations of fourteen were significantly different between GDM cases and non-GDM controls, including some amino acids and their derivatives, fatty acids, organic acids, and exogenous compounds. Three of the metabolites found in significantly lower concentrations in the hair of women with GDM (2-hydroxybutyric acid, citramalic acid, and myristic acid) were also negatively associated with daily average concentrations of PM_2.5, PM₁₀, SO₂, NO₂, CO and the exposure estimates of PM_2.5 and NO_2, and positively associated with O₃.

CONCLUSIONS

This study demonstrated that the maternal hair metabolome reflects the longitudinal metabolic changes that occur in response to environmental exposures and the development of GDM.

Serum lysophospholipidome of dietary origin as a suitable susceptibility/risk biomarker of human hypercholesterolemia: A cross-sectional study

BACKGROUND & AIMS

Whether bioactive lysophospholipids (lyso-PLs) and trimethylamine-N-oxide (TMAO) serve as non-invasive biomarkers in early human hypercholesterolemia (HC) is unknown. This study aimed to assess whether serum lyso-PLs and plasma TMAO may be suitable susceptibility/risk biomarkers of HC in humans. Secondarily, we aimed to evaluate the relationships between targeted metabolites, diet composition and circulating liver transaminases, and verify these results in hamsters.

METHODS

A targeted metabolomics and lipidomics approach determined plasma TMAO and serum lysophosphatidylcholines (lyso-PCs) and lysophosphatidylethanolamines (lyso-PEs) in low (L-LDL-c) and moderate to high (MH-LDL-c) LDL-cholesterol subjects. Additionally, the relationships between targeted metabolites, liver transaminases and diet, particularly fatty acid intake, were tested. In parallel, plasma and liver lyso-PL profiles were studied in 16 hamsters fed a moderate high-fat (HFD) or low-fat (LFD) diet for 30 days.

RESULTS

Predictive models identified lyso-PC15:0 and lyso-PE18:2 as the most discriminant lyso-PLs among groups. In MH-LDL-c (n = 48), LDL-cholesterol and saturated FAs were positively associated with lyso-PC15:0, whereas in L-LDL-c (n = 70), LDL-cholesterol and polyunsaturated fatty acids (PUFAs) were negatively and positively related to lyso-PE18:2, respectively. Interestingly, in MH-LDL-c, the lower lyso-PE 18:2 concentrations were indicative of higher LDL-cholesterol levels. Intrahepatic accumulation of lyso-PLs-containing essential n-6 PUFAs, including lyso-PE18:2, were higher in HFD-fed hamsters than LFD-fed hamsters.

CONCLUSIONS

Overall, results revealed a possible hepatic adaptive mechanism to counteract diet-induced steatosis in animal and hypercholesterolemia progression in humans. In particular, low serum lyso-PE18:2 suggests a suitable susceptibility/risk biomarker of HC 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.

Productive parameters, cecal microflora, nutrient digestibility, antioxidant status, and thigh muscle fatty acid profile in broiler chickens fed with Eucalyptus globulus essential oil

This study was conducted to evaluate the effects of different dietary inclusion of eucalyptus essential oil (EEO) on growth performance, relative organ weight, cecal microflora, nutrient digestibility, serum biochemical parameters, and thigh muscle fatty acid profile in broiler chickens. A total of six hundred 1-day-old male broiler chickens were randomly allocated into 5 treatment groups with 8 replicate pens, and each pen contained 15 birds. The experiment lasted for 42 d. Dietary treatments included corn–soybean meal-based diet supplemented with 0, 250, 500, 750, and 1,000 mg/kg EEO. The results indicated that dietary treatments had no effect on growth performance parameters in the 1 to 10 d period. From day 11 to 24, dietary supplementation of EEO showed a linear decrease in feed conversion ratio (FCR, P < 0.05). From day 25 to 42 and the overall period (1–42 d), broilers fed with different levels of EEO showed a linear increase in body weight gain (BWG) and reduction in feed conversion ratio (linear, P < 0.05). The relative organ weight were unaffected by any of the dietary treatments. With increasing levels of EEO, the cecal Escherichia coli (linear, P = 0.085) count showed a trend in reduction, and the cecal lactic acid bacteria population tended to increase (linear, P = 0.063). The apparent ileal digestibility of ether extract and organic matter were linearly and quadratically increased in response to increasing dietary EEO supplementation (P < 0.05). A trend of linear decrease in total cholesterol in the serum of birds fed with different levels of EEO was recorded (P = 0.074). Eucalyptus essential oil's inclusion increased serum superoxide dismutase linearly but reduced serum malondialdehyde linearly (P < 0.05). Dietary supplementation of EEO affected the fatty acid profile of thigh muscle so that increased the concentrations of total polyunsaturated fatty acids (linear, P < 0.05) and reduced total saturated fatty acid contents (linear, P < 0.05). Taken together, the inclusion of EEO increased BWG and decreased FCR during day 25 to 42 and day 1 to 42, and partially improved cecal microflora balance, nutrient digestibility, antioxidant activity, and thigh muscle fatty acid profile in broiler chickens.

The Protective Effect of Myristica fragrans Houtt. Extracts Against Obesity and Inflammation by Regulating Free Fatty Acids Metabolism in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a disorder characterized by the excess accumulation of fat in the hepatocytes. It is commonly associated with severe obesity and inflammation. Free fatty acids (FFAs) are the key to regulate lipid metabolism and immune response in hepatocyte cells. This study examined the effects of AEN (alcohol extract of nutmeg, the seed of Myristica fragrans Houtt.) on the inhibition of lipid synthesis and inflammation in vitro and in vivo and on high-fat diet-induced obesity in NAFLD mice. Our results showed that AEN treatment could downregulate the expression of lipid synthesis-related genes fatty acid synthase (FASN) and sterol regulatory element-binding protein 1c (SREBP-1c) and lower the lipid content of cells. AEN also inhibited FFAs-mediated inflammation-related cytokines interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) expression in cells. In a mouse model, AEN reduced the bodyweight of obese mice and improved NAFLD without affecting food intake. Further analysis revealed that AEN significantly reduced inflammation level, cholesterol and lipid accumulation, blood glucose, and other liver function indexes in mice fed with a high-fat diet. In conclusion, AEN inhibited the aggravation of obesity and inflammation by downregulating lipid-gene expression in the liver to ameliorate NAFLD.

Fatty acids of human milk - a review

The composition of human milk is the result of the evolution of mammals over millions of years. Among the most important components of milk are fatty acids. Approximately 85% are saturated and monounsaturated fatty acids - the rest are polyunsaturated one. Their role is to provide energy and immunity and to serve as buildings blocks, as well as assisting the hormonal system and the metabolism of fats, carbohydrates and proteins. The structural differences between fatty acids determine their biodiversity and give them particular physiological importance. Correct development of the nervous system, retina and other structures depend on an adequate supply of both these fatty acids during intrauterine development and in the newborn and infant stages. The fats present in milk form milk fat globules - structures that do not appear in milk formula prepared using vegetable oils. Apart from the mother's diet, other sources of fatty acids are endogenous biosynthesis in the mammary gland and the fat deposits from which the fatty acids are released. Evolution of the mother's body has also created adaptive mechanisms that adjust the amount of fatty acids in milk to the state of health and needs of the child. These mechanisms go some way to creating a buffer with regard to dietary shortages experienced by pregnant/breastfeeding women, and optimalise the composition of milk fatty acids depending on the age of the pregnant woman, the birth weight of the infant and the efficiency of the placenta during pregnancy.

Meat quality, fatty acid profile, and sensory attributes of spent laying hens fed expeller press canola meal or a conventional diet

This study evaluated the effects of feeding an expeller press canola meal (EPCM) supplement (20%) on the carcass, meat, and sensory quality characteristics of spent laying hens. Thirty EPCM-based and thirty conventionally (soybean based) fed Lohmann Brown-Elite spent laying hens were obtained from a commercial egg farm. Carcass, portions, physical quality, proximate composition, fatty acids, and sensory quality were determined. EPCM-fed hens had higher (P ≤ 0.05) drum yield, breast bone weights and percentages, but lower (P ≤ 0.05) thigh and breast meat yields. Conventionally fed hens had higher (P ≤ 0.05) thaw losses, skin yellowness (b*), Chroma values and breast fat content with lower (P ≤ 0.05) cooking losses, skin redness (a*) and hue angle values, as well as breast Warner-Bratzler shear force values (N) (15.43 ± 0.600 vs. 12.37 ± 0.411). Palmitic acid, stearic acid, heneicosanoic acid, palmitoleic acid, saturated fatty acids (SFA) (34.0 ± 0.56 vs. 38.7 ± 0.71), n-6:n-3 polyunsaturated fatty acids (PUFA) ratio (5.5 ± 0.13 vs. 7.2 ± 0.28), atherogenic index, thrombogenic index, delta-5 desaturase, elongase index, and thiosterase index were lower (P ≤ 0.05) for EPCM-fed hen breast meat. Myristic acid, lignoceric acid, nervonic acid, alpha-linolenic acid, docosahexaenoic acid (DHA), PUFA:SFA ratio (0.7 ± 0.05 vs. 0.9 ± 0.02), n-3 PUFA (3.4 ± 0.31 vs. 5.1 ± 0.17), hypocholesterolemic:Hypercholesterolaemic, stearoyl-CoA desaturase 16, and stearoyl-CoA desaturase 18 were higher (P ≤ 0.05) for EPCM-fed hen breast meat. Metallic flavor was decreased (P ≤ 0.05) for EPCM-fed hen breast meat. Generally, effects of EPCM supplementation were observed to have an effect on the carcass, physical quality, proximate composition, fatty acids, and health indices. The sensory profiles did not differ between EPCM and conventionally fed spent laying hen breast meat (except for metallic flavor). The EPCM improved the nutritional profile of spent laying hen meat with low intramuscular fat, low n-6:n-3 PUFA ratio, and favorable lipid health indices.

Interactive effects of maternal and weaning high linoleic acid intake on hepatic lipid metabolism, oxylipins profile and hepatic steatosis in offspring

Non-alcoholic fatty liver disease (NAFLD) has been described as a hepatic manifestation of the metabolic syndrome. When several studies correlated maternal linoleic acid (LA) intake with the development of obesity, only few links have been made between n-6 fatty acid (FA) and NAFLD. Herein, we investigated the influence of both maternal and weaning high LA intake on lipid metabolism and susceptibility to develop later metabolic diseases in offspring. Pregnant rats were fed a control-diet (2% LA) or a LA-rich diet (12% LA) during gestation and lactation. At weaning, offspring was assigned to one of the two diets, i.e., either maintained on the same maternal diet or fed the other diet for 6 months. Physiological, biochemical parameters and hepatic FA metabolism were analyzed. We demonstrated that the interaction between the maternal and weaning LA intake altered metabolism in offspring and could lead to hepatic steatosis. This phenotype was associated with altered hepatic FA content and lipid metabolism. Interaction between maternal and weaning LA intake led to a specific pattern of n-6 and n-3 oxylipins that could participate to the development of hepatic steatosis in offspring. Our findings highlight the significant interaction between maternal and weaning high LA intake to predispose offspring to later metabolic disease and support the predictive adaptive response hypothesis.

Dairy Fat Consumption and the Risk of Metabolic Syndrome: An Examination of the Saturated Fatty Acids in Dairy

Lifestyle is a key modifiable risk factor involved in the manifestation of metabolic syndrome and, in particular, diet plays a pivotal role in its prevention and development. Current dietary guidelines discourage the consumption of saturated fat and dietary sources rich in saturated fat, such as dairy products, despite data suggesting that full-fat dairy consumption is protective against metabolic syndrome. This narrative review assessed the recent epidemiological and clinical research that examined the consumption of dairy-derived saturated fatty acids (SFA) on metabolic syndrome risk. In addition, this review evaluated studies of individual SFA to gain insight into the potential mechanisms at play with intake of a diet enriched with these dairy-derived fatty acids. This work underscores that SFA are a heterogenous class of fatty acids that can differ considerably in their biological activity within the body depending on their length and specific chemical structure. In summary, previous work on the impact of dairy-derived SFA consumption on disease risk suggests that there is currently insufficient evidence to support current dietary guidelines which consolidate all dietary SFA into a single group of nutrients whose consumption should be reduced, regardless of dietary source, food matrix, and composition.

Alyssum homolocarpum seed oil (AHSO), containing natural alpha linolenic acid, stearic acid, myristic acid and β-sitosterol, increases proliferation and differentiation of neural stem cells in vitro

Background

Embryonic neural stem cells (eNSCs) are immature precursors of the central nervous system (CNS), with self-renewal and multipotential differentiation capacities. These are regulated by endogenous and exogenous factors such as alpha-linolenic acid (ALA), a plant-based essential omega-3 polyunsaturated fatty acid.

Methods

In this study, we investigated the effects of various concentrations of Alyssum homolocarpum seed oil (AHSO), containing natural ALA, stearic acid (SA), myristic acid (MA), and β-sitosterol, on proliferation and differentiation of eNSCs, in comparison to controls and to synthetic pure ALA.

Results

Treatment with natural AHSO (25 to 75 μM), similar to synthetic ALA, caused a significant ~ 2-fold increase in eNCSs viability, in comparison to controls. To confirm this proliferative activity, treatment of NSCs with 50 or 75 μM AHSO resulted in a significant increase in mRNA levels of notch1, hes-1 and Ki-67and NICD protein expression, in comparison to controls. Moreover, AHSO administration significantly increased the differentiation of eNSCs toward astrocytes (GFAP+) and oligodendrocytes (MBP+) in a dose dependent manner and was more potent than ALA, at similar concentrations, in comparison to controls. Indeed, only high concentrations of 100 μM AHSO, but not ALA, caused a significant increase in the frequency of neurons (β-III Tubulin+).

Conclusion

Our data demonstrated that AHSO, a rich source of ALA containing also other beneficial fatty acids, increased the proliferation and stimulated the differentiation of eNSCs. We suggest that AHSO’s effects are caused by β-sitosterol, SA and MA, present within this oil. AHSO could be used in diet to prevent neurodevelopmental syndromes, cognitive decline during aging, and various psychiatric disorders.

Moderate chronic ethanol consumption exerts beneficial effects on nonalcoholic fatty liver in mice fed a high-fat diet: possible role of higher formation of triglycerides enriched in monounsaturated fatty acids

PURPOSE

Several clinical studies suggested that light-to-moderate alcohol intake could alleviate nonalcoholic fatty liver disease (NAFLD), but the underlying mechanism is still poorly understood.

METHODS

Mice fed a high-fat diet (HFD) were submitted or not to moderate ethanol intake for 3 months (ca. 10 g/kg/day) via drinking water. Biochemical, analytical and transcriptomic analyses were performed in serum and liver.

RESULTS

Serum ethanol concentrations in ethanol-treated HFD mice comprised between 0.5 and 0.7 g/l throughout the experiment. NAFLD improvement was observed in ethanol-treated HFD mice as assessed by reduced serum transaminase activity. This was associated with less microvesicular and more macrovacuolar steatosis, the absence of apoptotic hepatocytes and a trend towards less fibrosis. Liver lipid analysis showed increased amounts of fatty acids incorporated in triglycerides and phospholipids, reduced proportion of palmitic acid in total lipids and higher desaturation index, thus suggesting enhanced stearoyl-coenzyme A desaturase activity. mRNA expression of several glycolytic and lipogenic enzymes was upregulated. Genome-wide expression profiling and gene set enrichment analysis revealed an overall downregulation of the expression of genes involved in collagen fibril organization and leukocyte chemotaxis and an overall upregulation of the expression of genes involved in oxidative phosphorylation and mitochondrial respiratory chain complex assembly. In addition, mRNA expression of several proteasome subunits was upregulated in ethanol-treated HFD mice.

CONCLUSIONS

Moderate chronic ethanol consumption may alleviate NAFLD by several mechanisms including the generation of non-toxic lipid species, reduced expression of profibrotic and proinflammatory genes, restoration of mitochondrial function and possible stimulation of proteasome activity.

Comparative effects of dietary n-3 docosapentaenoic acid (DPA), DHA and EPA on plasma lipid parameters, oxidative status and fatty acid tissue composition

The specific and shared physiologic and metabolic effects of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and even more of n-3 docosapentaenoic acid (DPA) are poorly known. We investigated the physiological effects and the overall fatty acid tissue composition of a nutritional supplementation of DPA compared both to EPA and DHA in healthy adult rats. Rats (n=32) were fed with semisynthetic diets supplemented or not with 1% of total lipids as EPA, DPA or DHA in ethyl esters form from weaning for 6 weeks. Fatty acid tissue composition was determined by gas chromatography-mass spectrometry, and blood assays were performed. The DPA supplementation was the only one that led to a decrease in plasma triglycerides, total cholesterol, non-high-density lipoprotein (HDL)-cholesterol, cholesterol esters and total cholesterol/HDL-cholesterol ratio compared to the nonsupplemented control group. The three supplemented groups had increased plasma total antioxidant status and superoxide dismutase activity. In all supplemented groups, the n-3 polyunsaturated fatty acid level increased in all studied tissues (liver, heart, lung, spleen, kidney, red blood cells, splenocytes, peripheral mononucleated cells) except in the brain. We showed that the DPA supplementation affected the overall fatty acid composition and increased DPA, EPA and DHA tissue contents in a similar way than with EPA. However, liver and heart DHA contents increased in DPA-fed rats at the same levels than in DHA-fed rats. Moreover, a large part of DPA seemed to be retroconverted into EPA in the liver (38.5%) and in the kidney (68.6%). In addition, the digestibility of DPA was lower than that of DHA and EPA.

Production of Structured Phosphatidylcholine with High Content of Myristic Acid by Lipase-Catalyzed Acidolysis and Interesterification

Synthesis of structured phosphatidylcholine (PC) enriched with myristic acid (MA) was conducted by acidolysis and interesterification reactions using immobilized lipases as catalysts and two acyl donors: trimyristin (TMA) isolated from ground nutmeg, and myristic acid obtained by saponification of TMA. Screening experiments indicated that the most effective biocatalyst for interesterification was Rhizomucor miehei lipase (RML), whereas for acidolysis, the most active were Thermomyces lanuginosus lipase (TLL) and RML. The effect of the molar ratio of substrates (egg-yolk PC/acyl donor), enzyme loading, and different solvent on the incorporation of MA into PC and on PC recovery was studied. The maximal incorporation of MA (44 wt%) was achieved after 48 h of RML-catalyzed interesterification in hexane using substrates molar ratio (PC/trimyristin) 1/5 and 30% enzyme load. Comparable results were obtained in toluene with 1/3 substrates molar ratio. Interesterification of PC with trimyristin resulted in significantly higher MA incorporation than acidolysis with myristic acid, particularly in the reactions catalyzed by RML.

Incorporation of Dairy Lipids in the Diet Increased Long-Chain Omega-3 Fatty Acids Status in Post-weaning Rats

In human nutrition, optimized the status of n-3 long-chain polyunsaturated fatty acids (LCPUFA) and especially docosahexaenoic acid (DHA) during growth appears to be one of the most important goal. We investigated the potential impact of a partial incorporation of dairy lipids (DL) in the diet to increase the n-3 LCPUFA content in tissues, compared to a mixture of vegetable oils. Rats were fed with vegetable oil diet or DL diet, supplemented or not supplemented with DHA, from weaning for 6 weeks. All diets provided the same quantity of 2.3% of total fatty acids of precursor α-linolenic acid. LCPUFA levels in brain, retina, liver, heart, red blood cells and epididymal adipose tissue, Δ-6 desaturase activity and mRNA expression in liver, and plasma cholesterol were measured. Rats fed a DL diet increased their DHA content in brain and retina compared with rats fed a vegetable oil diet and reached the same level than rats directly supplemented with DHA. The status of n-3 docosapentaenoic acid increased with DL diet in heart, red blood cells and liver. The n-3 docosapentaenoic acid specifically discriminated DL diets in the heart. DL diet increased α-linolenic acid content in liver and epididymal adipose tissue, provided specific fatty acids as short- and medium-chain fatty acids and myristic acid, and increased plasma cholesterol. We hypothesized that dairy lipids may increase the n-3 LCPUFA enrichment in tissues by preserving precursor α-linolenic acid from β-mitochondrial oxidation, associated with the presence of short- and medium-chain fatty acids in DL diets. In conclusion, a partial incorporation of dairy lipids in the diet with an adequate α-linolenic acid content improved the n-3 LCPUFA status, especially DHA in brain and retina.

Amino Acid and Fatty Acid Levels Affect Hepatic Phosphorus Metabolite Content in Metabolically Healthy Humans

OBJECTIVE

Hepatic energy metabolism negatively relates to insulin resistance and liver fat content in patients with type 2 diabetes, but its role in metabolically healthy humans is unclear. We hypothesized that intrahepatocellular γ-adenosine triphosphate (γATP) and inorganic phosphate (Pi) concentrations exhibit similar associations with insulin sensitivity in nondiabetic, nonobese volunteers.

DESIGN

A total of 76 participants underwent a four-point sampling, 75-g oral glucose tolerance test (OGTT), as well as in vivo31P/1H magnetic resonance spectroscopy. In 62 of them, targeted plasma metabolomic profiling was performed. Pearson correlation analyses were performed for the dependent variables γATP and Pi.

RESULTS

Adjusted for age, sex, and body mass index (BMI), hepatic γATP and Pi related to 2-hour OGTT glucose (r = 0.25 and r = 0.27, both P < 0.05), and Pi further associated with nonesterified fatty acids (NEFAs; r = 0.28, P < 0.05). However, neither γATP nor Pi correlated with several measures of insulin sensitivity. Hepatic γATP correlated with circulating leucine (r = 0.42, P < 0.001) and Pi with C16:1 fatty acids palmitoleic acid and C16:1w5 (r = 0.28 and 0.30, respectively, P < 0.01), as well as with δ-9-desaturase index (r = 0.33, P < 0.05). Only the association of γATP with leucine remained important after correction for multiple testing. Leucine and palmitoleic acid, together with age, sex, and BMI, accounted for 26% and for 15% of the variabilities in γATP and Pi, respectively.

CONCLUSIONS

Specific circulating amino acids and NEFAs, but not measures of insulin sensitivity, partly affect hepatic phosphorus metabolites, suggesting mutual interaction between hepatic energy metabolism and circulating metabolites in nondiabetic humans.

Impact of Lactobacillus fermentum and dairy lipids in the maternal diet on the fatty acid composition of pups' brain and peripheral tissues

The aim of the study was to determine the effect of maternal diets administered since day 1 of gestation and containing dairy lipids or vegetable oils differing in the supply of n-3 polyunsaturated fatty acids (n-3 PUFAs) (equilibrated or deficient) and of Lactobacillus fermentum (L. fermentum) on the docosahexaenoic acid (DHA) accretion in the pups at postnatal day 14 in the prefrontal cortex (PFC) and hippocampus (HC) for brain structures and in the liver and adipose tissue for peripheral tissues. Maternal milk fatty acid composition was also assessed by analyzing the fatty acid composition of the gastric content of the pups. DHA was higher in mice supplemented with L. fermentum than in mice in the deficient group in HC and PFC and also in liver and adipose tissue. This increase could be linked to the slight but significant increase in C18:3n-3 in the maternal milk. This proportion was comparable in the dairy lipid group for which the brain DHA level was the highest. L. fermentum may have a key role in the protection of the brain during the perinatal period via the neuronal accretion of n-3 PUFAs, especially during n-3 PUFA deficiency.

Myristic acid potentiates palmitic acid-induced lipotoxicity and steatohepatitis associated with lipodystrophy by sustaning de novo ceramide synthesis

Palmitic acid (PA) induces hepatocyte apoptosis and fuels de novo ceramide synthesis in the endoplasmic reticulum (ER). Myristic acid (MA), a free fatty acid highly abundant in copra/palmist oils, is a predictor of nonalcoholic steatohepatitis (NASH) and stimulates ceramide synthesis. Here we investigated the synergism between MA and PA in ceramide synthesis, ER stress, lipotoxicity and NASH. Unlike PA, MA is not lipotoxic but potentiated PA-mediated lipoapoptosis, ER stress, caspase-3 activation and cytochrome c release in primary mouse hepatocytes (PMH). Moreover, MA kinetically sustained PA-induced total ceramide content by stimulating dehydroceramide desaturase and switched the ceramide profile from decreased to increased ceramide 14:0/ceramide16:0, without changing medium and long-chain ceramide species. PMH were more sensitive to equimolar ceramide14:0/ceramide16:0 exposure, which mimics the outcome of PA plus MA treatment on ceramide homeostasis, than to either ceramide alone. Treatment with myriocin to inhibit ceramide synthesis and tauroursodeoxycholic acid to prevent ER stress ameliorated PA plus MA induced apoptosis, similar to the protection afforded by the antioxidant BHA, the pan-caspase inhibitor z-VAD-Fmk and JNK inhibition. Moreover, ruthenium red protected PMH against PA and MA-induced cell death. Recapitulating in vitro findings, mice fed a diet enriched in PA plus MA exhibited lipodystrophy, hepatosplenomegaly, increased liver ceramide content and cholesterol levels, ER stress, liver damage, inflammation and fibrosis compared to mice fed diets enriched in PA or MA alone. The deleterious effects of PA plus MA-enriched diet were largely prevented by in vivo myriocin treatment. These findings indicate a causal link between ceramide synthesis and ER stress in lipotoxicity, and imply that the consumption of diets enriched in MA and PA can cause NASH associated with lipodystrophy.

Dairy fat blend improves brain DHA and neuroplasticity and regulates corticosterone in mice

Mimicking the breast milk lipid composition appears to be necessary for infant formula to cover the brain's needs in n-3 PUFA. In this study, we evaluated the impact of partial replacement of vegetable oil (VL) in infant formula by dairy fat (DL) on docosahexaenoic acid (DHA) brain level, neuroplasticity and corticosterone in mice. Mice were fed with balanced VL or balanced DL diets enriched or not in DHA and arachidonic acid (ARA) from the first day of gestation. Brain DHA level, microglia number, neurogenesis, corticosterone and glucocorticoid receptor expression were measured in the offsprings. DL diet increased DHA and neuroplasticity in the brain of mice at postnatal day (PND) 14 and at adulthood compared to VL. At PND14, ARA and DHA supplementation increased DHA in VL but not in DL mice brain. Importantly, DHA and ARA supplementation further improved neurogenesis and decreased corticosterone level in DL mice at adulthood. In conclusion, dairy lipids improve brain DHA level and neuroplasticity.

Excessive dietary linoleic acid induces proinflammatory markers in rats

Following the historical dietary recommendations, the substitution of polyunsaturated fatty acids (PUFAs) for saturated fatty acids (SFAs) resulted in a dramatic increase of linoleic acid (LA) in the Western diet. While proatherogenic properties of SFAs have been described, the involvement of LA on the inflammatory process remains controversial. Herein, we evaluated the effects of an excessive LA intake on the cytokine-induced expression of endothelial adhesion molecules vascular cell adhesion molecule-1 (VCAM-1) and intercellular cell adhesion molecule-1 (ICAM-1), through the nuclear factor (NF)-κB pathway, in comparison with a control diet and regarding a "positive" SFA diet. Wistar rats were fed experimental diets - a control diet or diets enriched with LA or SFA - for 11 weeks. Plasma lipid parameters and proinflammatory cytokine production such as interleukin-1β and tumor necrosis factor (TNF)-α were analyzed. Expression of endothelial adhesion molecules and NF-κB was determined by immunohistochemical analysis. No difference was observed in body weight. The enriched diets did not affect triglyceride and total cholesterol levels in plasma. Our results demonstrated that excessive dietary LA intake increased TNF-α levels (P<.05) in plasma. Rats fed the LA-enriched diet showed a significantly higher expression of VCAM-1, ICAM-1 and NF-κB in aortas. In addition, our results demonstrated that an excess of LA is more efficient to activate endothelial molecular process than an excess of SFA. The present study provides further support for the proinflammatory properties of LA and suggests an LA-derivatives pathway involved in the inflammatory process.

Dietary Caprylic Acid (C8:0) Does Not Increase Plasma Acylated Ghrelin but Decreases Plasma Unacylated Ghrelin in the Rat

Focusing on the caprylic acid (C8:0), this study aimed at investigating the discrepancy between the formerly described beneficial effects of dietary medium chain fatty acids on body weight loss and the C8:0 newly reported effect on food intake via ghrelin octanoylation. During 6 weeks, Sprague-Dawley male rats were fed with three dietary C8:0 levels (0, 8 and 21% of fatty acids) in three experimental conditions (moderate fat, caloric restriction and high fat). A specific dose-response enrichment of the stomach tissue C8:0 was observed as a function of dietary C8:0, supporting the hypothesis of an early preduodenal hydrolysis of medium chain triglycerides and a direct absorption at the gastric level. However, the octanoylated ghrelin concentration in the plasma was unchanged in spite of the increased C8:0 availability. A reproducible decrease in the plasma concentration of unacylated ghrelin was observed, which was consistent with a decrease in the stomach preproghrelin mRNA and stomach ghrelin expression. The concomitant decrease of the plasma unacylated ghrelin and the stability of its acylated form resulted in a significant increase in the acylated/total ghrelin ratio which had no effect on body weight gain or total dietary consumption. This enhanced ratio measured in rats consuming C8:0 was however suspected to increase (i) growth hormone (GH) secretion as an increase in the GH-dependent mRNA expression of the insulin like growth Factor 1 (IGF-1) was measured (ii) adipocyte diameters in subcutaneous adipose tissue without an increase in the fat pad mass. Altogether, these results show that daily feeding with diets containing C8:0 increased the C8:0 level in the stomach more than all the other tissues, affecting the acylated/total ghrelin plasma ratio by decreasing the concentration of circulating unacylated ghrelin. However, these modifications were not associated with increased body weight or food consumption.

Lipid Quality in Infant Nutrition: Current Knowledge and Future Opportunities

Dietary lipids are key for infants to not only meet their high energy needs but also fulfill numerous metabolic and physiological functions critical to their growth, development, and health. The lipid composition of breast milk varies during lactation and according to the mother's diet, whereas the lipid composition of infant formulae varies according to the blend of different fat sources. This report compares the compositions of lipids in breast milk and infant formulae, and highlights the roles of dietary lipids in term and preterm infants and their potential biological and health effects. The major differences between breast milk and formulae lie in a variety of saturated fatty acids (such as palmitic acid, including its structural position) and unsaturated fatty acids (including arachidonic acid and docosahexaenoic acid), cholesterol, and complex lipids. The functional outcomes of these differences during infancy and for later child and adult life are still largely unknown, and some of them are discussed, but there is consensus that opportunities exist for improvements in the qualitative lipid supply to infants through the mother's diet or infant formulae. Furthermore, research is required in several areas, including the needs of term and preterm infants for long-chain polyunsaturated fatty acids, the sites of action and clinical effects of lipid mediators on immunity and inflammation, the role of lipids on metabolic, neurological, and immunological outcomes, and the mechanisms by which lipids act on short- and long-term health.

A dairy fat matrix providing alpha-linolenic acid (ALA) is better than a vegetable fat mixture to increase brain DHA accretion in young rats

Achieving an appropriate DHA status in the neonatal brain is an important goal of neonatal nutrition. We evaluated how alpha-linolenic acid (ALA), provided for six weeks after weaning by different dietary fat matrix, improved brain DHA content of young male rats born from deficient-dams. The level of ALA achieved was based on the fat composition of usual infant vegetable formula. A palm oil-blend diet thus providing 1.5%ALA was compared to dairy fat-blend-based diets that provided either 1.5%ALA or 2.3%ALA, or a rapeseed oil diet providing 8.3%ALA (n-6/n-3 ratio were, respectively 10,10,5,2.5). The 1.5%ALA-dairy-fat-blend was superior to 1.5%ALA-palm-oil-blend to restore values of brain DHA, while the 2.3%ALA-dairy-fat-blend exhibited a further increase and reached the values obtained with pure rapeseed diet (8.3%ALA). Dairy-fat-blends enriched with ALA appear to be an interesting strategy for achieving optimal DHA levels in the brain of post-weaning rats. Providing dairy fat as well as a reduction of the LA/ALA ratio should be reconsidered to design infant formula.

Supplemental intravenous n-3 fatty acids and n-3 fatty acid status and outcome in critically ill elderly patients in the ICU receiving enteral nutrition

BACKGROUND & AIMS

N-3 fatty acids (FA) may have benefits in ICU patients. The aims were to identify whether FA status is altered in critical illness and to evaluate the effect of supplemental intravenous n-3 FA on plasma FA status and clinical outcome in ICU patients receiving enteral nutrition.

METHODS

Enterally fed patients (n = 49; 60-80 years) were recruited in the first 48 h of ICU admission. Fifteen patients received n-3 FA emulsion (0.2 g/kg) over 6 h for 3 consecutive days, and 34 patients did not (control). Samples were collected before supplementation, and 24 and 72 h after the third infusion. Nineteen healthy elderly subjects were also studied; they gave a single blood sample. FA were measured in plasma phosphatidylcholine (PC).

RESULTS

Critically ill patients had altered plasma PC FA compared with healthy elderly subjects. Surviving ICU patients had higher levels of docosahexaenoic acid and total n-3 FA and a lower ratio of n-6:n-3 FA in plasma PC than non-survivors. Infusion of n-3 FA increased eicosapentaenoic, docosahexaenoic and total n-3 FA, and decreased arachidonic and total n-6 FA and n-6:n-3 FA and arachidonic:eicosapentaenoic acid ratios. Gas exchange was enhanced 72 h after the third n-3 FA infusion (p = 0.001).

CONCLUSIONS

Critically ill patients may have altered plasma FA profiles. A higher total n-3 FA and docosahexaenoic acid content in plasma PC is associated with survival and improved gas exchange.

In rat hepatocytes, myristic acid occurs through lipogenesis, palmitic acid shortening and lauric acid elongation

The origin of myristic acid in mammalian cells and the regulation of its endogenous cellular low concentration are not known. Another intriguing question is the potential metabolic properties of endogenous myristic acid as compared with exogenous myristic acid. In the present paper, we hypothesised and demonstrated that, in liver cells, in addition to the usual fatty acid synthase (FAS) pathway that produces predominantly palmitic acid and minor amounts of myristic acid, part of endogenous cellular myristic acid also comes from a shortening of palmitic acid, likely by peroxisomal β-oxidation and from lauric acid by elongation. From a nutritional point of view, C16:0 is universally found in natural fats and its shortening to myristic acid could contribute to a non-negligible source of this fatty acid (FA) in the organism. Then, we measured the distribution of endogenously synthesised myristic acid in lipid species and compared it with that of exogenous myristic acid. Our results do not support the hypothesis of different metabolic fates of endogenous and exogenous myristic acid and suggest that whatever the origin of myristic acid, its cellular concentration and lipid distribution are highly regulated.

Plasma free myristic acid proportion is a predictor of nonalcoholic steatohepatitis

BACKGROUND/AIMS

Serum free fatty acid (FFA) composition and abnormal fatty acid metabolism have been implicated in the pathogenesis of nonalcoholic steatohepatitis (NASH). Therefore, we determined if the serum FFA composition can provide accurate diagnosis of NASH.

METHODS

We compared fasting serum FFA compositions in 20 patients with simple steatosis to those in 77 patients with NASH, including 65 patients with early-stage NASH.

RESULTS

By univariate analysis, the proportions of serum free myristic acid (P = 0.002) and palmitoleic acid (P = 0.033) and the stearoyl CoA desaturase (SCD)-1 index (P = 0.047) were significantly elevated in NASH patients in comparison to patients with simple steatosis. Only the serum free myristic acid proportion was significantly elevated in the early-stage NASH group in comparison to the simple steatosis group (P = 0.003). Multiple logistic regression analysis demonstrated that the serum free myristic acid proportion was significantly elevated in all patients with NASH (P = 0.011) and the subset of patients with early-stage NASH (P = 0.012) in comparison to those with simple steatosis. The area under the curve (AUC) for the serum free myristic acid proportion was 0.734 to detect NASH and 0.719 to detect early-stage NASH in comparison to simple steatosis.

CONCLUSIONS

Serum free myristic acid proportion could be a useful independent predictor to differentiate NASH from simple steatosis.

The role of fatty acids in anti-inflammatory effects of low-intensity extremely high-frequency electromagnetic radiation

The effects of low-intensity extremely high-frequency electromagnetic radiation (EHF EMR; 42.2 GHz, 0.1 mW/cm(2) , exposure duration 20 min) on the fatty acid (FA) composition of thymic cells and blood plasma in normal mice and in mice with peritoneal inflammation were studied. It was found that the exposure of normal mice to EHF EMR increased the content of polyunsaturated FAs (PUFAs) (eicosapentaenoic and docosapentaenoic) in thymic cells. Using a model of zymosan-induced peritoneal inflammation, it was shown that the exposure of mice to EHF EMR significantly increased the content of PUFAs (dihomo-γ-linolenic, arachidonic, eicosapentaenoic, docosapentaenoic, and docosahexaenoic) and reduced the content of monounsaturated FAs (MUFAs) (palmitoleic and oleic) in thymic cells. Changes in the FA composition in the blood plasma were less pronounced and manifested themselves as an increase in the level of saturated FAs during the inflammation. The data obtained support the notion that MUFAs are replaced by PUFAs that can enter into the thymic cells from the external media. Taking into account the fact that the metabolites of PUFAs are lipid messengers actively involved in inflammatory and immune reactions, we assume that the increase in the content of n-3 and n-6 PUFAs in phospholipids of cellular membranes facilitates the realization of anti-inflammatory effects of EHF EMR.

Short chain saturated fatty acids decrease circulating cholesterol and increase tissue PUFA content in the rat

This study investigates the effect of various dietary saturated fatty acid (SFA) profiles on plasma lipid parameters and tissue fatty acid composition in rats. The experiment was designed to monitor polyunsaturated fatty acids (PUFA) levels, while examining different amounts and types of SFA. Four isocaloric diets were prepared, containing 10-11 mol% of fatty acids (FA) as linoleic acid (LNA) and 2.5 mol% as α-linolenic acid (ALA), leading to an identical and well-balanced LNA/ALA ratio. The initial rapeseed oil/corn oil mixture providing ALA and LNA was enriched with olive oil to prepare the olive oil diet. The butterfat diet was supplemented with butterfat, containing short-chain SFA (C4:0-C10:0, 17 mol% of FA), lauric acid (C12:0, 3.2 mol%), myristic acid (C14:0, 10.5 mol%) and palmitic acid (C16:0, 14.5 mol%). The saturates diet was supplemented with trilaurin, trimyristin and tripalmitin to obtain the same level of lauric, myristic and palmitic acids as the butterfat diet, without the short-chain SFA. The trimyristin diet was enriched with trimyristin only. The results showed that the butterfat diet contributed to specific effects, compared to the olive oil diet and the saturates and trimyristin diets: a decrease in plasma total, LDL- and HDL-cholesterol, higher tissue storage of ALA and LNA, and a higher level of (n-3) highly unsaturated fatty acids in some tissues. This study supports the hypothesis that in diets with identical well-balanced LNA/ALA ratios, short chain SFA may decrease circulating cholesterol and increase tissue polyunsaturated fatty acid content in the rat.

The complex and important cellular and metabolic functions of saturated fatty acids

This review summarizes recent findings on the metabolism and biological functions of saturated fatty acids (SFA). Some of these findings show that SFA may have important and specific roles in the cells. Elucidated biochemical mechanisms like protein acylation (N-myristoylation, S-palmitoylation) and regulation of gene transcription are presented. In terms of physiology, SFA are involved for instance in lipogenesis, fat deposition, polyunsaturated fatty acids bioavailability and apoptosis. The variety of their functions demonstrates that SFA should no longer be considered as a single group.

Regulation of mammalian desaturases by myristic acid: N-terminal myristoylation and other modulations

Myristic acid, the 14-carbon saturated fatty acid (C14:0), usually accounts for small amounts (0.5%-1% weight of total fatty acids) in animal tissues. Since it is a relatively rare molecule in the cells, the specific properties and functional roles of myristic acid have not been fully studied and described. Like other dietary saturated fatty acids (palmitic acid, lauric acid), this fatty acid is usually associated with negative consequences for human health. Indeed, in industrialized countries, its excessive consumption correlates with an increase in plasma cholesterol and mortality due to cardiovascular diseases. Nevertheless, one feature of myristoyl-CoA is its ability to be covalently linked to the N-terminal glycine residue of eukaryotic and viral proteins. This reaction is called N-terminal myristoylation. Through the myristoylation of hundreds of substrate proteins, myristic acid can activate many physiological pathways. This review deals with these potentially activated pathways. It focuses on the following emerging findings on the biological ability of myristic acid to regulate the activity of mammalian desaturases: (i) recent findings have described it as a regulator of the Δ4-desaturation of dihydroceramide to ceramide; (ii) studies have demonstrated that it is an activator of the Δ6-desaturation of polyunsaturated fatty acids; and (iii) myristic acid itself is a substrate of some fatty acid desaturases. This article discusses several topics, such as the myristoylation of the dihydroceramide Δ4-desaturase, the myristoylation of the NADH-cytochrome b5 reductase which is part of the whole desaturase complex, and other putative mechanisms.

Oleic acid inhibits stearic acid-induced inhibition of cell growth and pro-inflammatory responses in human aortic endothelial cells

Saturated fatty acids (SFAs), significant components of both enteral/parenteral nutritional formulations (including diet), are linked to cardiovascular disease complications, such as atherosclerosis. We investigated whether oleic acid (C18:1n-9) reduces the growth inhibitory and pro-inflammatory effects of the stearic acid (C18:0) in human aortic endothelial cells (HAEC). Stearic acid induced growth inhibition at concentrations less than 50 μM, whereas higher concentrations invoked cytotoxicity. Stearic acid-induced growth inhibition and cytotoxic effects were eradicated upon cosupplementation with oleic acid (25 μM). Oleic acid (as low as 5 μM) also inhibited the stearic acid-induced increase in intercellular adhesion molecule-1 (ICAM-1) expression. Stearic acid-induced phosphorylation of nuclear factor-kappa B (NF-κB), a transcriptional regulator of ICAM-1, was also reduced by oleic acid. HAECs supplemented with either stearic or oleic acid resulted in cellular incorporation of C18:0 and C18:1n-9, respectively. Stearic acid primarily incorporated into phospholipids without increasing the total fatty acid content in HAECs. In contrast, oleic acid, with or without stearic acid, incorporated into both phospholipids and triglycerides, with a significant increase in total fatty acid amounts in triglycerides. Our data suggest that oleic acid has the ability to reduce the inflammatory effects of long-chain SFAs in HAECs through reducing cellular stearic acid incorporation and NF-κB activation.

Long-chain saturated fatty acids induce pro-inflammatory responses and impact endothelial cell growth

BACKGROUND & AIMS

Saturated fatty acids (SFAs), significant components of enteral and parenteral formulations, have been linked to cardiovascular complications. However, the effect of SFAs upon vascular inflammation is less clear. Endothelial cells (EC) play an important role in the acute inflammatory responses. We, therefore, evaluated the acute effects of different chain-length SFAs upon EC functions.

METHODS

Endothelial cells were cultured with various SFAs. Growth and cytotoxicity were determined by WST-1 assay. Apoptosis and pro-inflammatory adhesion molecule (ICAM-1) expression was assayed using flow cytometry. Activation of NF-kappaB was analyzed using western blot analysis.

RESULTS

Long-chain SFAs (C14:0-C20:0) inhibited EC growth in a chain-length dependent manner. Medium-chain SFAs (C6:0-C12:0) did not significantly affect EC growth. In contrast, the short-chain SFA (C4:0) stimulated cellular growth. Stearic acid induced significantly more EC apoptosis and necrosis than palmitic acid or myristic acids. Stearic acid (>10muM) treatment also significantly increased ICAM-1 expression. Stearic acid's pro-inflammatory response was confirmed by phosphorylation of IkappaB-alpha and NF-kappaB in a dose dependent manner.

CONCLUSIONS

Long-chain SFAs can induce pro-inflammatory responses and significantly impact growth and viability of EC. Our data suggest that the presence of long-chain SFAs in parenteral formulations may have harmful effects on the vascular system.

N-Myristoylation targets dihydroceramide Delta4-desaturase 1 to mitochondria: partial involvement in the apoptotic effect of myristic acid

This study was designed to analyze the effect of myristic acid on ceramide synthesis and its related lipoapoptosis pathway. It was previously observed that myristic acid binds dihydroceramide Delta4-desaturase 1 (DES1) through N-myristoylation and activates this enzyme involved in the final de novo ceramide biosynthesis step. In the present study, we show first by immunofluorescence microscopy and subcellular fractionation that DES1 myristoylation targets part of the recombinant protein to the mitochondria in COS-7 cells. In addition, native dihydroceramide Delta4-desaturase activity was found in both the endoplasmic reticulum and mitochondria in rat hepatocytes. Dihydroceramide conversion to ceramide was increased in COS-7 cells expressing DES1 and incubated with myristic acid. The expression of the wild-type myristoylable DES1-Gly alone, but not the expression of the unmyristoylable mutant DES1-Ala, induced apoptosis of COS-7 cells. Finally, myristic acid alone also increased the production of cellular ceramide and had an apoptotic effect. This effect was potentiated on caspase activity when the myristoylable form of DES1 was expressed. Therefore, these results suggest that the myristoylation of DES1 can target the enzyme to the mitochondria leading to an increase in ceramide levels which in turn contributes to partially explain the apoptosis effect of myristic acid in COS-7 cells.

[New regulatory and signal functions for myristic acid]

Myristic acid is a 14 carbon saturated fatty acid, which is mostly found in milk fat. In industrialized countries, its excessive consumption is correlated with an increase in plasma cholesterol and mortality due to cardiovascular diseases. Nevertheless, one feature of this fatty acid is its ability to acylate proteins, a reaction which is called N-terminal myristoylation. This article describes various examples of important cellular regulations where the intervention of myristic acid is proven. Modulations of the cellular concentration of this fatty acid and its associated myristoylation function might be used as regulators of these metabolic pathways.

Fatty acids metabolic profile in high fat diet-induced non-alcoholic fatty liver disease in rats

AIM: To analyze fatty acid metabolic profile changes of fatty livers induced by a high fat diet and to determine it's role in non-alcoholic steatohepatitis (NASH).

METHODS: Sprague-Dawley rats were randomly divided into two groups: the control group (treated with normal diet, n = 7) and the model group (treated with high fat diet, n = 7). The rats were all killed at wk 16 to detect pathological changes in liver tissues. The metabolic profile changes of fatty acid in NASH and normal liver tissue samples were detected by ECF derivatization for GC/MS technology. Data were analyzed using SPSS 11.0 software package.

RESULTS: After a high fat diet for 16 wk, severe fatty livers (+++) were present in the high fat diet group with remarkable inflammation. A significant morphological difference was detected between the two groups. Total ion current (TIC) and principal component analysis (PCA) indicated that there were significantly different metabolic patterns in liver tissues between the two groups. Compared with the control group, all fatty acids were raised significantly except a 56% decrease in dodecanoic acid (P < 0.05). Octadecanoic acid, tetradecanoic acid, hexadecanoic acid, eicosanoic acid, 9-octadecenoic acid, 9, 12, 15-octadecatrienoic acid, 5, 8, 11, 14-eicosatetraenoic acid and 9, 12-octadecadienoic acid were raised 5.42, 4.10, 11.56, 5.86, 1.82 and 8.00, 2.44-folds, respectively. Moreover, ω-6/ω-3 polyunsaturated fatty acids (PUFAs) ratio was raised.

CONCLUSION: Our results suggest that there are significant fatty acids metabolic profile changes in NASH. Excessive fatty acids accumulation in hepatic cells, ω-6/ω-3 ratio imbalance and dudecanoic acid decrease may pay a crucial role in steatohepatitis and hepatic injury.

Myristic acid increases the activity of dihydroceramide Delta4-desaturase 1 through its N-terminal myristoylation

Dihydroceramide Delta4-desaturase (DES) catalyzes the desaturation of dihydroceramide into ceramide. In mammals, two gene isoforms named DES1 and DES2 have recently been identified. The regulation of these enzymes is still poorly understood. This study was designed to examine the possible N-myristoylation of DES1 and DES2 and the effect of this co-translational modification on dihydroceramide Delta4-desaturase activity. N-MyristoylTransferases (NMT) catalyze indeed the formation of a covalent linkage between myristoyl-CoA and the N-terminal glycine of candidate proteins, as found in the sequence of DES proteins. The expression of both rat DES in COS-7 cells evidenced first that DES1 but not DES2 was associated with an increased dihydroceramide Delta4-desaturase activity. Then, we showed that recombinant DES1 was myristoylated in vivo when expressed in COS-7 cells. In addition, in vitro myristoylation assay with a peptide substrate corresponding to the N-terminal sequence of the protein confirmed that NMT1 has a high affinity for DES1 myristoylation motif (apparent K(m)=3.92 microM). Compared to an unmyristoylable mutant form of DES1 (Gly replaced by an Ala), the dihydroceramide Delta4-desaturase activity of the myristoylable DES1-Gly was reproducibly and significantly higher. Finally, the activity of wild-type DES1 was also linearly increased in the presence of increased concentrations of myristic acid incubated with the cells. These results demonstrate that DES1 is a newly discovered myristoylated protein. This N-terminal modification has a great impact on dihydroceramide Delta4-desaturase activity. These results suggest therefore that myristic acid may play an important role in the biosynthesis of ceramide and in sphingolipid metabolism.

Saturated fatty acids: simple molecular structures with complex cellular functions

PURPOSE OF REVIEW

This review summarizes recent findings on the biological functions of saturated fatty acids. Some of these findings suggest that saturated fatty acids may have important and specific regulatory roles in the cells. Until now these roles have largely been outweighed by the negative impact of dietary saturated fatty acids on atherosclerosis biomarkers. Elucidated biochemical mechanisms like protein acylation (N-myristoylation, S-palmitoylation) and putative physiological roles are described.

RECENT FINDINGS

The review will focus on the following topics: new aspects on the metabolism of saturated fatty acids; recent reports on the biochemical functions of saturated fatty acids; current investigations on the physiological roles (elucidated and putative) of saturated fatty acids; and a discussion of the nutritional dietary recommendations (amounts and types) of saturated fatty acids.

SUMMARY

Dietary saturated fatty acids are usually associated with negative consequences for human health. Experimental results on the relationship between doses, physiological effects, specificities and functions of individual saturated fatty acids are, however, conflicting. In this context, this review describes emerging recent evidence that some saturated fatty acids have important and specific biological roles. Such data are needed to allow a balanced view in terms of potential nutritional benefits of saturated fatty acids, and, if necessary, reassessment of the current nutritional dietary recommendations.