Low intake of ruminant trans fatty acids ameliorates the disordered lipid metabolism in C57BL/6J mice fed a high-fat diet

Currently, the health benefits of ruminant trans fatty acids (R-TFA) are still controversial. Our previous investigations indicated that R-TFA at higher dosages (1.3% and 4% E) caused disordered lipid metabolism in mice; however, through collecting R-TFA intake data in 9 provinces of China, it was suggested that, in 2021, the range of R-TFA intake for Chinese residents was about 0.053-0.307 g d-1. Based on the 2022 Nutritional Dietary Guidelines for Chinese Residents, the recommended daily energy supply from R-TFA was about 0.11%-0.15% E. However, the health effects of R-TFA at a lower dosage are still unknown; therefore, our current research aims to further explore the effects of R-TFA on health. Through in vivo experiments, it was shown that R-TFA (0.15% E) decreased body weight gain and serum cholesterol levels in C57BL/6J mice fed a high-fat diet, while it had no significant effect on mice fed a low-fat diet. Besides, hepatic histopathology analysis suggested that R-TFA (0.15% E) ameliorated the degree of hepatic steatosis and reduced intrahepatocyte lipid droplet accumulation in C57BL/6J mice fed a high-fat diet. Through lipidomics analysis, we further screened 8 potential lipid metabolites that participate in regulating the dysregulation of lipid metabolism. Finally, it was suggested that R-TFA (0.15% E) down-regulated the expression of genes related to inflammation and cholesterol synthesis while up-regulated the expression of genes related to cholesterol clearance, which might partially explain the salutary effect of R-TFA (0.15% E) in ameliorating the hepatic steatosis and improving disordered lipid metabolism in mice fed a high-fat diet. Our current research will provide a reference for the intake of R-TFA and, furthermore, give some insights into understanding the health effects of R-TFA.

Interesterified fat consumption since gestation decreases striatal dopaminergic targets levels and gdnf impairing locomotion of adult offspring

Interesterified fat (IF) currently substitutes the hydrogenated vegetable fat (HVF) in processed foods. However, the IF consumption impact on the central nervous system (CNS) has been poorly studied. The current study investigated connections between IF chronic consumption and locomotor impairments in early life period and adulthood of rats and access brain molecular targets related to behavior changes in adulthood offspring. During pregnancy and lactation, female rats received soybean oil (SO) or IF and their male pups received the same maternal supplementation from weaning until adulthood. Pups' motor ability and locomotor activity in adulthood were evaluated. In the adult offspring striatum, dopaminergic targets, glial cell line-derived neurotrophic factor (GDFN) and lipid profile were quantified. Pups from IF supplementation group presented impaired learning concerning complex motor skill and sensorimotor behavior. The same animals showed decreased locomotion in adulthood. Moreover, IF group showed decreased immunoreactivity of all dopaminergic targets evaluated and GDNF, along with important changes in FA composition in striatum. This study shows that the brain modifications induce by IF consumption resulted in impaired motor control in pups and decreased locomotion in adult animals. Other studies about health damages induced by IF consumption may have a contribution from our current outcomes.

Cis-2 and trans-2-eisocenoic fatty acids are novel inhibitors for Mycobacterium tuberculosis Protein tyrosine phosphatase A

Small protein tyrosine phosphatase (PtpA) of Mycobacterium tuberculosis is attributed to the development of latent tuberculosis infection, and hence bocomes an interesting target for drug development. In this communication, inhibition of PtpA by naturally occurring fatty acids cis-2 and trans-2-eicosenoic acid is investigated. Mtb PtpA was heterologously expressed in Escherichia coli, and the activity of PtpA was inhibited by cis-2 and trans-2 eicosenoic fatty acids. Both compunds showed strong inhibition of PtpA activity with IC50 at low micromolar concentration. As comparison, trans-11-eicosenoic acid only slightly inhibit PtpA. In silico analysis confirmed the inhibition of PtpB by cis-2-eicosenoic acid by formation of several hydrogen bonds. These findings show that cis-2 and trans-2 eicosenoic fatty acids are potential candidates for latent tuberculosis inhibitors.

Comprehensive genetic study of fatty acids helps explain the role of noncoding inflammatory bowel disease associated SNPs and fatty acid metabolism in disease pathogenesis

Fatty acids and their derivatives play an important role in inflammation. Diet and genetics influence fatty acid profiles. Abnormalities of fatty acid profiles have been observed in inflammatory bowel diseases (IBD), a group of complex diseases defined by chronic gastrointestinal inflammation. IBD associated fatty acid profile abnormalities were observed independently of nutritional status or disease activity, suggesting a common genetic background. However, no study so far has attempted to look for overlap between IBD loci and fatty acid associated loci or investigate the genetics of fatty acid profiles in IBD. To this end, we conducted a comprehensive genetic study of fatty acid profiles in IBD using iCHIP, a custom microarray platform designed for deep sequencing of immune-mediated disease associated loci. This study identifies 10 loci associated with fatty acid profiles in IBD. The most significant associations were a locus near CBS (p = 7.62 × 10^-8) and a locus in LRRK2 (p = 1.4 × 10^-7). Of note, this study replicates the FADS gene cluster locus, previously associated with both fatty acid profiles and IBD pathogenesis. Furthermore, we identify 18 carbon chain trans-fatty acids (p = 1.12 × 10^-3), total trans-fatty acids (p = 4.49 × 10^-3), palmitic acid (p = 5.85 × 10^-3) and arachidonic acid (p = 8.58 × 10^-3) as significantly associated with IBD pathogenesis.

New data on harmful effects of trans-fatty acids

Various margarines containing trans-fatty acids were marketed as being healthier because of the absence of cholesterol, suggesting to use margarine instead of butter. Fifteen years ago, research documented the grave health risk of trans-fats (T-fat). US FDA in 2015 finalized its decision that T-fat is not safe and set a three-year time limit for complete removal of T-fat from all foods. The greatest danger from T-fat lies in its capacity to distort the cell membranes. The primary health risk identified for T-fat consumption is an elevated risk of coronary heart disease. T-fats have an adverse effect on the brain and nervous system. T-fat from the diet is incorporated into brain cell membranes and alter the ability of neurons to communicate. This can diminish mental performance. Relationship between T-fat intake and depression risk was observed. There is growing evidence for a possible role of T-fat in the development of Alzheimer´s disease and cognitive decline with age.

Current Evidence Supporting the Link Between Dietary Fatty Acids and Cardiovascular Disease

Lack of consensus exists pertaining to the scientific evidence regarding effects of various dietary fatty acids on cardiovascular disease (CVD) risk. The objective of this article is to review current evidence concerning cardiovascular health effects of the main dietary fatty acid types; namely, trans (TFA), saturated (SFA), polyunsaturated (PUFA; n-3 PUFA and n-6 PUFA), and monounsaturated fatty acids (MUFA). Accumulating evidence shows negative health impacts of TFA and SFA; both may increase CVD risk. Policies have been proposed to reduce TFA and SFA consumption to less than 1 and 7 % of energy intake, respectively. Cardiovascular health might be promoted by replacing SFA and TFA with n-6 PUFA, n-3 PUFA, or MUFA; however, the optimal amount of PUFA or MUFA that can be used to replace SFA and TFA has not been defined yet. Evidence suggests of the potential importance of restricting n-6 PUFA up to 10 % of energy and obtaining an n-6/n-3 ratio as close as possible to unity, along with a particular emphasis on consuming adequate amounts of essential fatty acids. The latest evidence shows cardioprotective effects of MUFA-rich diets, especially when MUFA are supplemented with essential fatty acids; namely, docosahexaenoic acid. MUFA has been newly suggested to be involved in regulating fat oxidation, energy metabolism, appetite sensations, weight maintenance, and cholesterol metabolism. These favorable effects might implicate MUFA as the preferable choice to substitute for other fatty acids, especially given the declaration of its safety for up to 20 % of total energy.

Trans Fatty Acid Levels in Foods and Intakes among Population Aged 3 Years and above in Beijing and Guangzhou Cities, China

OBJECTIVE

To understand the dietary intake levels of trans fatty acids (TFA) in a Chinese population and establish a basis for health risk assessment of trans fatty acids.

METHODS

The TFA contents data of 2613 food items and food consumption data of 10,533 people aged 3 years and above in two large cities in China were matched and a simple assessment method was used to estimate the distribution of dietary TFA intake.

RESULTS

The mean content of TFA was highest in margarine (1.68 ± 0.83 g/100g), followed by chocolate and candy (0.89 ± 2.68 g/100g), edible vegetable oils (0.86 ± 0.82 g/100g), milk (0.83 ± 1.56 g/100g), and bakery foods (0.41 ± 0.91 g/100g). TFA intake accounted for 0.34%, 0.30%, 0.32%, and 0.29% of the total energy intake in the 3-6, 7-12, 13-17, and ⋝18 year age groups, respectively. Of the populations studied, 0.42% demonstrated TFA intakes (as percentage of energy intake) greater than 1%. The main sources of dietary TFA intake were edible vegetable oils, milk, mutton, and beef, and baked foods, which accounted for 49.8%, 16.56%, 12.21%, and 8.87%, respectively.

CONCLUSION

The current intake of TFA among people in two cities did not appear to be of major health concern regarding the threshold of TFA intake as the percentage of total energy recommended by the World Health Organization. Because most TFA were derived from industrially processed foods, the government should reinforce nutrition labeling and regulate food producers to further reduce TFA in food and to provide scientific instruction for consumers to make sound choices.

Plasma elaidic acid level as biomarker of industrial trans fatty acids and risk of weight change: report from the EPIC study

BACKGROUND

Few epidemiological studies have examined the association between dietary trans fatty acids and weight gain, and the evidence remains inconsistent. The main objective of the study was to investigate the prospective association between biomarker of industrial trans fatty acids and change in weight within the large study European Prospective Investigation into Cancer and Nutrition (EPIC) cohort.

METHODS

Baseline plasma fatty acid concentrations were determined in a representative EPIC sample from the 23 participating EPIC centers. A total of 1,945 individuals were followed for a median of 4.9 years to monitor weight change. The association between elaidic acid level and percent change of weight was investigated using a multinomial logistic regression model, adjusted by length of follow-up, age, energy, alcohol, smoking status, physical activity, and region.

RESULTS

In women, doubling elaidic acid was associated with a decreased risk of weight loss (odds ratio (OR) = 0.69, 95% confidence interval (CI) = 0.55-0.88, p = 0.002) and a trend was observed with an increased risk of weight gain during the 5-year follow-up (OR = 1.23, 95% CI = 0.97-1.56, p = 0.082) (p-trend<.0001). In men, a trend was observed for doubling elaidic acid level and risk of weight loss (OR = 0.82, 95% CI = 0.66-1.01, p = 0.062) while no significant association was found with risk of weight gain during the 5-year follow-up (OR = 1.08, 95% CI = 0.88-1.33, p = 0.454). No association was found for saturated and cis-monounsaturated fatty acids.

CONCLUSIONS

These data suggest that a high intake of industrial trans fatty acids may decrease the risk of weight loss, particularly in women. Prevention of obesity should consider limiting the consumption of highly processed foods, the main source of industrially-produced trans fatty acids.

Trans fatty acids consumption in type 1 diabetic patients: evaluation by dietary records and measurement in serum phospholipids

The consumption of foods containing trans fatty acids (TFA), especially those produced by food industries, induces pleiotropic negative effects on health. Therefore, it is important to assess the amount of TFA consumed, especially in age groups more exposed to the consumption of TFA-containing foods. The present pilot study evaluates TFA intake in 54 young people with and without type 1 diabetes (29 young subjects with type 1 diabetes and 25 healthy subjects) through both dietary records (7-day food record) and the measurement of TFA levels in serum phospholipids, a possibly more objective marker of TFA intake. The comparison between the two groups was made by the student t test for independent samples. The intake of synthetic TFA was low in both groups (type 1 diabetic patients: 0.25 ± 0.25 g/day; healthy subjects 0.48 ± 0.37 g/day), but significantly lower in diabetic patients vs controls (P < 0.05); TFA levels in serum phospholipids also confirmed a low intake of these fatty acids. These data indicate that the intake of trans fatty acids is relatively low in our population, i.e.,<1% of total calories in the diet, in line with what recommended by the World Health Organization.

Erythrocyte trans-fatty acids, type 2 diabetes and cardiovascular risk factors in middle-aged and older Chinese individuals

AIMS/HYPOTHESIS

Few data are available about intakes and food sources of trans-fatty acids (TFAs) or their associations with cardiometabolic outcomes in Asian people who consume a prudent diet but are experiencing rapid nutritional transitions. We aimed to investigate the relationships between TFA biomarkers and type 2 diabetes and cardiovascular risk factors in Chinese individuals.

METHODS

Erythrocyte fatty acids were measured by gas chromatography among 3,107 men and women (50-70 years) recruited from urban and rural areas in Beijing and Shanghai, China.

RESULTS

Total trans-18:1 and two trans-18:2 isomers were detected and accounted for 0.37% of the total fatty acids in the erythrocytes. Concentrations of TFAs were higher in women than men, and in urban than rural residents. Of the TFAs, trans-18:1, but not trans-18:2, showed a modest association with dairy consumption (β = 0.27), but not with other foods. After adjustment for BMI, social-demographic, lifestyle and dietary factors and other TFAs, erythrocyte trans-18:1 was shown to be associated with a lower risk of type 2 diabetes (OR comparing extreme [first and fourth] quartiles 0.68, 95% CI 0.48, 0.97, p(trend) = 0.02), as well as 20-50% lower odds of central obesity, dyslipidaemia, hyperglycaemia, insulin resistance and chronic inflammation. In contrast, trans-18:2 fatty acids were positively associated with high triacylglycerol (p(trend) < 0.001) and LDL-cholesterol (p(trend) = 0.03) levels, but not with diabetes and other cardiometabolic risk factors.

CONCLUSIONS/INTERPRETATION

Among middle-aged and older Chinese individuals with overall low erythrocyte TFAs levels, trans-18:1 might serve as a marker of dairy intake. Higher trans-18:1 levels were associated with a lower risk of type 2 diabetes, whereas higher trans-18:2 levels were associated with dyslipidaemia.

Effects of Different Dietary Fat Types on Postprandial Appetite and Energy Expenditure

OBJECTIVE

Observational studies suggest that monounsaturated (MUFA) and trans fatty acids (TRANS) are more fattening than polyunsaturated fatty acids (PUFA). Therefore, the aim of this study was to investigate the acute effect of intake of PUFA, MUFA, or TRANS on appetite and energy expenditure (EE).

RESEARCH METHODS AND PROCEDURES

Three test meals were randomly given in a cross-over design to 19 overweight (BMI: 26.8 +/- 0.4 kg/m2), young (25.2 +/- 0.7 years) men. The fat-rich breakfasts (0.8 g fat/kg body weight, 60% energy from fat) varied only in the source of C:18-fat. EE was measured continuously in a respiration chamber, and appetite sensations were rated by visual analog scales before and every 30 minutes, for 5 hours, after the meal. After 5 hours, an ad libitum meal was served, and energy intake was registered. Sensory evaluations of all meals were given using visual analog scales. Data were analyzed by two-way ANOVA.

RESULTS

There were no differences in basal or postprandial values of appetite ratings and EE, in subsequent ad libitum energy intake, or in the sensory evaluation of the test meals among the 3 test days.

DISCUSSION

Giving acutely large amounts of MUFA, PUFA, or TRANS did not impose any differences in appetite and EE in overweight humans. However, studies with extended protocols and other subject groups are warranted to investigate the long-term effect of dietary fat quality on the regulation of energy balance and body weight.

Dietary influence on the m. longissimus dorsi fatty acid composition of lambs in relation to protein source

Dietary lipid effect, as a consequence of protein supplement, on lamb m. longissimus dorsi fatty acid composition was investigated, with emphasis on biohydrogenation intermediates. Crossbred lambs (White Swedish Landrace × Texel) were fed a barley-based diet without (CON) or with protein supplements including peas (PEA), rapeseed cake (RC) or hempseed cake (HC). The HC diet resulted in the highest muscle 22:6n-3 proportion, with the RC diet being similar (P<0.05). Protein supplement did not affect the c9,t11 conjugated linoleic acid (CLA) proportion, however the HC diet increased some minor CLA isomers, including t10,c12 CLA (P<0.05). The t10-18:1 and total trans-18:1 were lowest for the RC diet (P<0.05), likely relating to rumen conditions and precursor availability. The saturated, monounsaturated and branched-chain fatty acids were largely unaffected by protein supplement. In conclusion, feeding the RC diet lowered the t10-18:1 and total trans-18:1 in meat, and modestly increased 22:6n-3 content. The direction of these changes would be beneficial, making the RC diet the preferred protein supplement; however the magnitude of the changes in the present experiment may not be sufficient to have an impact on human health.

Trans fatty acids: induction of a pro-inflammatory phenotype in endothelial cells

Epidemiological data have shown an association of the intake of industrial produced trans fatty acids (TFA) and sudden cardiac death. The present study examines the impact of elaidic acid (t18:1n-9) and linoelaidic acid (t18:2n-6) on the human aortic endothelial cell functional response. Trans fatty acids predominately incorporated into the phospholipid component while only a minute fraction of the total fatty acids (FA) incorporated into triacylglycerol. Trans fatty acids incorporated into the plasma membranes at the expense of the saturated-FA, stearic, palmitic, and to a lesser extent, myristic acid. Both t18:1n-9 and t18:2n-6 induced a pro-inflammatory response by elevating surface expression of intercellular adhesion molecule-1 (ICAM-1). Neither oleic nor linoleic evoked a pro-inflammatory phenotype under the maximal 50 µM treatments. Both TFA and stearic acid increased phosphorylation of the ICAM-1 transcriptional regulator, nuclear factor-κβ (NF-κβ), while oleic and linoleic acids did not appear to alter the phosphorylation status. Elaidic acid minimally affected endothelial cell growth, whereas linoelaidic acid completely inhibited growth at 100 µM and imparted limited cytotoxicity up to 300 µM. Stearic acid induced cytotoxicity at concentrations above 75 µM, while oleic and linoleic acids evoked gradual dose-dependent growth inhibition with cytotoxicity occurring only at linoleic acid concentrations greater than 200 µM. In conclusion, t18:1n-9 and t18:2n-6 fatty acids effectively incorporated into the phospholipid component of endothelial cells and subsequently induce a pro-inflammatory phenotype.

Could dietary trans fatty acids induce movement disorders? Effects of exercise and its influence on Na⁺K⁺-ATPase and catalase activity in rat striatum

The influence of trans fatty acids (FA) on development of orofacial dyskinesia (OD) and locomotor activity was evaluated. Rats were fed with diets enriched with 20% soybean oil (SO; n-6 FA), lard (L; saturated FA) or hydrogenated vegetable fat (HVF; trans FA) for 60 weeks. In the last 12 weeks each group was subdivided into sedentary and exercised (swimming). Brains of HVF and L-fed rats incorporated 0.33% and 0.20% of trans FA, respectively, while SO-fed group showed no incorporation of trans FA. HVF increased OD, while exercise exacerbated this in L and HVF-fed rats. HVF and L reduced locomotor activity, and exercise did not modify. Striatal catalase activity was reduced by L and HVF, but exercise increased its activity in the HVF-fed group. Na(+)K(+)-ATPase activity was not modified by dietary FA, however it was increased by exercise in striatum of SO and L-fed rats. We hypothesized that movement disorders elicited by HVF and less by L could be related to increased dopamine levels in striatum, which have been related to chronic trans FA intake. Exercise increased OD possibly by increase of brain dopamine levels, which generates pro-oxidant metabolites. Thus, a long-term intake of trans FA caused a small but significant brain incorporation of trans FA, which favored development of movement disorders. Exercise worsened behavioral outcomes of HVF and L-fed rats and increased Na(+)K(+)-ATPase activity of L and SO-fed rats, indicating its benefits. HVF blunted beneficial effects of exercise, indicating a critical role of trans FA in brain neurochemistry.

Camelina sativa cake improved unsaturated fatty acids in ewe's milk

BACKGROUND

Camelina sativa cake (CSC), a rich source of unsaturated fatty acids, in the case of ruminants, may improve the energy value of a diet and also increase the unsaturated fatty acid content in milk. Effects of basal diet (control), basal diet plus 30 g kg(-1) of CSC in dietary dry matter (DM), basal diet plus 60 g kg(-1) of CSC in dietary dry matter on milk production and the fatty acid composition of ewe's milk with particular emphasis on the monoenes and conjugated isomers of linoleic acid content were examined.

RESULTS

Elevated concentration of total monounsaturated fatty acids, the effect of an increase in monounsaturated fatty acids in the trans configuration, as well as the increased content of total polyunsaturated fatty acids, resulted from CSC supplementation. Total saturated fatty acid concentration was decreased.

CONCLUSION

Milk from CSC-supplemented ewes was characterized by increased levels of beneficial nutritional factors, including mono- and n-3 polyunsaturated fatty acids, and was also by lower atherogenic and thrombogenic indices. Taking into consideration all the obtained results and recommended fat concentrations in a daily ruminant ration, we recommend supplementing a dairy ewe's diet with 30 g kg(-1) DM of CSC cake in practice.

Effects of ruminant trans fatty acids on cardiovascular disease and cancer: a comprehensive review of epidemiological, clinical, and mechanistic studies

There are 2 predominant sources of dietary trans fatty acids (TFA) in the food supply, those formed during the industrial partial hydrogenation of vegetable oils (iTFA) and those formed by biohydrogenation in ruminants (rTFA), including vaccenic acid (VA) and the naturally occurring isomer of conjugated linoleic acid, cis-9, trans-11 CLA (c9,t11-CLA). The objective of this review is to evaluate the evidence base from epidemiological and clinical studies to determine whether intake of rTFA isomers, specifically VA and c9,t11-CLA, differentially affects risk of cardiovascular disease (CVD) and cancer compared with iTFA. In addition, animal and cell culture studies are reviewed to explore potential pro- and antiatherogenic mechanisms of VA and c9,t11-CLA. Some epidemiological studies suggest that a positive association with coronary heart disease risk exists between only iTFA isomers and not rTFA isomers. Small clinical studies have been conducted to establish cause-and-effect relationships between these different sources of TFA and biomarkers or risk factors of CVD with inconclusive results. The lack of detection of treatment effects reported in some studies may be due to insufficient statistical power. Many studies have used doses of rTFA that are not realistically attainable via diet; thus, further clinical studies are warranted. Associations between iTFA intake and cancer have been inconsistent, and associations between rTFA intake and cancer have not been well studied. Clinical studies have not been conducted investigating the cause-and-effect relationship between iTFA and rTFA intake and risk for cancers. Further research is needed to determine the health effects of VA and c9,t11-CLA in humans.

Trans fatty acids induce a proinflammatory response in endothelial cells through ROS-dependent nuclear factor-κB activation

It has been shown that increased intake of trans fatty acids (TFAs) is associated with a higher risk of cardiovascular disease. In this study, we have investigated the effects of linoelaidic (LA) and elaidic (EA) acids on the proinflammatory response in endothelial cells, a key step in vascular disease. Human aortic endothelial cells (HAECs) were treated with different concentrations (100 μmol/l in most experiments) of LA or EA for different periods of time. The surface protein and mRNA expression of ICAM-1 and VCAM-1 were determined by flow cytometry and real time RT-PCR, respectively. Adhesion of leukocytes to TFA-treated HAECs was evaluated by an adhesion assay. Activation of nuclear factor-κB (NF-κB) was evaluated by measuring NF-κB p65 phosphorylation using flow cytometry. ROS production was determined by the reduction of fluorescent 2',7'-dichlorofluorescein diacetate (DCFH-DA). LA treatment significantly increased protein and mRNA levels of ICAM-1 and VCAM-1, leukocyte adhesion to HAECs, phosphorylation of NF-κB and ROS generation. Similar effects were achieved for cells incubated with EA. Experiments with HAECs pretreated with pyrrolidine dithiocarbamate, an inhibitor of NF-κB, revealed that both LA and EA-mediated induction of ICAM-1 and VCAM-1 is mainly regulated by NF-κB. The ROS production induced by both of the studied acids was inhibited in the presence of diphenyleneiodonium (DPI), a NADPH oxidase inhibitor, suggesting ROS production through the activation of NADPH oxidase. Furthermore, LA or EA-induced ICAM-1 and VCAM-1 expression, activation of NF-κB and adhesion of leukocytes to HAECs were abolished in the presence of DPI.

CONCLUSION

TFAs present in our diet have a direct proinflammatory effect, which promotes leukocyte adhesion to the endothelium through ROS-dependent NF-κB activation.

trans-fatty acid isomers in adipose tissue have divergent associations with adiposity in humans

The aim of this study was to evaluate the association between adipose tissue trans-fatty acid isomers and adiposity. This cross-sectional study included 1,785 subjects from Costa Rica. Fatty acid concentrations (as a percentage of the total fatty acids) in subcutaneous adipose tissue were assessed by gas–liquid chromatography. Dietary intakes were assessed with a food frequency questionnaire. Multivariate linear regression models were used to relate adipose tissue trans-fatty acid content to BMI, waist circumference, and skinfold thickness while adjusting for age, sex, and area of residence. To account for variations in lifestyle, we adjusted for smoking, physical activity, income, self-reported history of diabetes and hypertension, and for adipose tissue alpha-linolenic acid and energy intake in a third model. After adjustments, positive associations were found between 18:2t-fatty acids (primarily from partially hydrogenated oils) and BMI, waist circumference, and skinfold thickness (P for each association <0.01). Rumenic acid was positively associated with skinfold thickness (P < 0.0001), but not with BMI or waist circumference (P > 0.05). Inverse associations were found between 16:1n-7t-fatty acids and skinfold thickness and between 18:1t-fatty acids and BMI and waist circumference (P < 0.0001). This study suggests that individual trans-fatty acid isomers may have divergent effects on adiposity. 18:2t-fatty acids show consistent positive associations with measures of adiposity. These isomer-specific associations are an interesting new finding. Other prospective and intervention studies are necessary to examine these relationships further.

[Dietary trans fatty acids and its metabolic implications]

Fats are important nutrients in our diet, they have wide chemical properties that drive diverse metabolic effects. The trans fatty acids (TFA) are common compounds found in industrialized food, and recent research has shown they should be avoided due to their increased risk of cardiovascular disease (CVD). Some of the mechanisms involved include: reduction of c-HDL concentration, increase of low density lipoprotein, Lp (a), triglycerides; disturbance in prostaglandin balance and they may also promote insulin resistance. Obese subjects are prone to increased CVD risk associated with a state of chronic inflammation that can be worsened by TFA intake. The US population consumes approximately 5.3 g TFA per day (2.6% of their total energy intake and 7.4% of their fat energy). Recently, WHO recommendations suggest the intake of TFA should be lower than 1% of energy per day. Current fast food industry products have to decrease the amount of TFA content, and the experience from different countries shows that the elimination of trans fatty acids is a cost effective and feasible public health intervention.

Effect of animal and industrial trans fatty acids on HDL and LDL cholesterol levels in humans--a quantitative review

BACKGROUND

Trans fatty acids are produced either by industrial hydrogenation or by biohydrogenation in the rumens of cows and sheep. Industrial trans fatty acids lower HDL cholesterol, raise LDL cholesterol, and increase the risk of coronary heart disease. The effects of conjugated linoleic acid and trans fatty acids from ruminant animals are less clear. We reviewed the literature, estimated the effects trans fatty acids from ruminant sources and of conjugated trans linoleic acid (CLA) on blood lipoproteins, and compared these with industrial trans fatty acids.

METHODOLOGY/PRINCIPAL FINDINGS

We searched Medline and scanned reference lists for intervention trials that reported effects of industrial trans fatty acids, ruminant trans fatty acids or conjugated linoleic acid on LDL and HDL cholesterol in humans. The 39 studies that met our criteria provided results of 29 treatments with industrial trans fatty acids, 6 with ruminant trans fatty acids and 17 with CLA. Control treatments differed between studies; to enable comparison between studies we recalculated for each study what the effect of trans fatty acids on lipoprotein would be if they isocalorically replaced cis mono unsaturated fatty acids. In linear regression analysis the plasma LDL to HDL cholesterol ratio increased by 0.055 (95%CI 0.044-0.066) for each % of dietary energy from industrial trans fatty acids replacing cis monounsaturated fatty acids The increase in the LDL to HDL ratio for each % of energy was 0.038 (95%CI 0.012-0.065) for ruminant trans fatty acids, and 0.043 (95% CI 0.012-0.074) for conjugated linoleic acid (p = 0.99 for difference between CLA and industrial trans fatty acids; p = 0.37 for ruminant versus industrial trans fatty acids).

CONCLUSIONS/SIGNIFICANCE

Published data suggest that all fatty acids with a double bond in the trans configuration raise the ratio of plasma LDL to HDL cholesterol.

[Effects of dietary trans fatty acids in pregnancy and lactation]

Unsaturated fatty acids with the trans configuration (TFA) are recognized as the most harmful type of fatty acids. The main human source of TFA are foods containing hardened plant oils. Evidence is aplenty that TFA are responsible for increased risk of cardiovascular diseases, tumors, type 2 diabetes, and inflammatory conditions. Due to the harmful action of TFA it is of particular importance to determine the exact effects of TFA on pregnancy and fetal development which will in consequence affect the health of adults. It is believed that the inhibited synthesis of polyunsaturated fatty acids in the presence of TFA is among factors that determine birthweight, duration of pregnancy, and development of the nervous system during intrauterine life and after birth. Pregnant women consuming significant amounts of TFA are at risk of pregnancy-induced hypertension, preeclampsia, and insulin resistance. Reports on the harmful action of TFA on humans persuasively reveal the need to limit their intake, particularly during pregnancy and lactation.

Trans fatty acids: current contents in Canadian foods and estimated intake levels for the Canadian population

Research conducted in the mid-1990s indicated that the levels of trans fats in Canadian diets were among the highest in the world. The consumption of trans fats raises blood levels of low-density lipoprotein (LDL)-cholesterol, while reducing levels of high-density lipoprotein (HDL)-cholesterol. In June 2007, Health Canada called on the food industry to voluntarily reduce levels of trans fats in vegetable oils and soft (tub)-margarines to < 2% of total fat, and in all other foods, to < 5%. Industry must show satisfactory progress by June 2009, or Health Canada might have to introduce legislation to ensure that recommended limits are achieved. Since 2005, Health Canada has been performing a national assessment of prepackaged and restaurant foods that likely contain trans fats. From 2005 to 2009, 1120 samples were analyzed, of which 852 or approximately 76% met the recommended trans fat limits. As a result of reformulation, most of the products had decreased trans + saturated fat content. The estimated average intake of trans fatty acids (TFA) in Canada significantly dropped from the high value of 8.4 g/day in the mid-1990s to 3.4 g/day (or 1.4% food energy) in 2008. However, this TFA intake of 1.4% of energy is still above the World Health Organization recommended limit of TFA intake of < 1% of energy, which suggests that the Canadian food industry needs to put more effort into reducing the TFA content in its products, especially in tub-margarines, donuts, and bakery products.

Trans fat labeling and levels in U.S. foods: assessment of gas chromatographic and infrared spectroscopic techniques for regulatory compliance

Trans fatty acids are found in a variety of foods like dairy and meat products, but the major dietary sources are products that contain commercially hydrogenated fats. There has been a renewed need for accurate analytical methods for the quantitation of total trans fat since mandatory requirements to declare the amount of trans fat present in food products and dietary supplements were issued in many countries. Official capillary GC and IR methodologies are the two most common validated methods used to identify and quantify trans fatty acids for regulatory compliance. The present article provides a comprehensive discussion of the GC and IR techniques, including the latest attenuated total reflection (ATR)-FTIR methodology called the negative second derivative ATR-FTIR procedure, which is currently being validated in an international collaborative study. The identification and quantitation of trans fatty acid isomers by GC is reviewed and an alternative GC method is proposed using two temperature programs and combining their results; this proposed method deals more effectively with the resolution of large numbers of geometric and positional monoene, diene, and triene fatty acid isomers present in ruminant fats. In addition, the different methylation procedures that affect quantitative conversion to fatty acid methyl esters are reviewed. There is also a lack of commercial chromatographic standards for many trans fatty acid isomers. This review points to potential sources of interferences in the FTIR determination that may lead to inaccurate results, particularly at low trans levels. The presence of high levels of saturated fats may lead to interferences in the FTIR spectra observed for trans triacylglycerols (TAGs). TAGs require no derivatization, but have to be melted prior to IR measurement. While GC is currently the method of choice, ATR-FTIR spectroscopy is a viable, rapid alternative, and a complementary method to GC for a more rapid determination of total trans fats for food labeling purposes.

Consumption and health effects of trans fatty acids: a review

Consumption of industrially produced trans fatty acids (TFA) remains high in many populations, particularly in developing nations where partially hydrogenated vegetable oils are frequently used for home cooking and among individuals in developed countries having high intakes of bakery or processed foods. Well-controlled observational studies and randomized trials indicate that TFA consumption adversely affects multiple risk factors for chronic diseases, including numerous blood lipids and lipoproteins, systemic inflammation, endothelial dysfunction, and possibly insulin resistance, diabetes, and adiposity. Growing evidence for the latter effects is particularly concerning given the worldwide obesity pandemic and high contents of industrially produced TFA in many foods marketed toward children. Consistent evidence from prospective observational studies of habitual TFA consumption and retrospective observational studies using TFA biomarkers indicates that TFA consumption increases risk of clinical coronary heart disease (CHD). Based on the adverse effects of risk factors and consistent relationships with clinical endpoints, the evidence that TFA consumption increases CHD risk is convincing. Some evidence suggests that TFA consumption may also increase other disease outcomes, but further investigation is needed to confirm the presence and magnitude of such effects. More research is also needed to understand how specific TFA isomers of varying chain length and double bond location may affect different biologic pathways of disease. Both individual- and policy-level initiatives to decrease TFA consumption should continue, particularly in population subgroups and in developing nations with high consumption of partially hydrogenated vegetable oils.

Levels of trans fats in diets consumed in developing economies

Cardiovascular complications are a leading cause of mortality worldwide, and dietary patterns and lifestyle are key factors responsible for their progression. Sedentary lifestyle and transient changes in nutrition have led to drastic increases in such maladies during the last few decades, and dietary changes are significant, as they are coupled with high fat intake, especially trans fats. In developed countries, legislations and monitoring systems have resulted in reduced consumption of these metabolites. The developing world, especially South Asia, is also facing the menace of trans fats; lack of governmental interest and ignorance among consumers are the main reasons. In these regions, the use of hydrogenated vegetable oil (ghee) and shortening in deep-fat frying of culinary items, such as samosa, paratha, bhatura, poori, and tikkies, results in increased consumption of trans fats. Research investigations and cohort studies showed a positive correlation between consumption of trans fats and cardiovascular disorders. In this article, trans fats intake and its level in different products available in developing countries, particularly in South Asia, were reviewed along with information regarding processes involved in the production and possible reduction of trans fats.

Trans fatty acids (tFA): sources and intake levels, biological effects and content in commercial Spanish food

Recent studies of dietary habits in children and adolescents performed in Spain show that a high percentage of the daily energy intake corresponds to fat (42.0-43.0%). These findings show an excessive contribution of saturated fatty acids and also a considerable supply of trans fatty acids. These compounds are formed generally during partial hydrogenation of vegetable oils, a process that converts vegetable oils into semisolid fats. Also, in some cases naturally occurring trans fatty acids in smaller amounts in meat and dairy products from ruminants (cows, sheep), these trans fatty acids are produced by the action of bacteria in the ruminant stomach by reactions of biohydrogenation. On the other hand, metabolic studies have clearly shown that trans fatty acids increase LDL cholesterol and reduce HDL cholesterol. Our results show that major sources of trans fatty acids in commercial Spanish foods are fast-food (hamburger, French fries), snacks, bakery products (cakes, donuts, biscuits), margarines and dehydrated soups.

Metabolic implications of dietary trans-fatty acids

Dietary trans-fatty acids are associated with increased risk of cardiovascular disease and have been implicated in the incidence of obesity and type 2 diabetes mellitus (T2DM). It is established that high-fat saturated diets, relative to low-fat diets, induce adiposity and whole-body insulin resistance. Here, we test the hypothesis that markers of an obese, prediabetic state (fatty liver, visceral fat accumulation, insulin resistance) are also worsened with provision of a low-fat diet containing elaidic acid (18:1t), the predominant trans-fatty acid isomer found in the human food supply. Male 8-week-old Sprague-Dawley rats were fed a 10% trans-fatty acid enriched (LF-trans) diet for 8 weeks. At baseline, 3 and 6 weeks, in vivo magnetic resonance spectroscopy (1H-MR) assessed intramyocellular lipid (IMCL) and intrahepatic lipid (IHL) content. Euglycemic-hyperinsulinemic clamps (week 8) determined whole-body and tissue-specific insulin sensitivity followed by high-resolution ex vivo 1H-NMR to assess tissue biochemistry. Rats fed the LF-trans diet were in positive energy balance, largely explained by increased energy intake, and showed significantly increased visceral fat and liver lipid accumulation relative to the low-fat control diet. Net glycogen synthesis was also increased in the LF-trans group. A reduction in glucose disposal, independent of IMCL accumulation was observed in rats fed the LF-trans diet, whereas in rats fed a 45% saturated fat (HF-sat) diet, impaired glucose disposal corresponded to increased IMCLTA. Neither diet induced an increase in IMCLsoleus. These findings imply that trans-fatty acids may alter nutrient handling in liver, adipose tissue, and skeletal muscle and that the mechanism by which trans-fatty acids induce insulin resistance differs from diets enriched with saturated fats.

Effect of radical stress and ageing on the occurrence of trans fatty acids in rats fed a trans-free diet

In a previous paper, we demonstrated that tissue trans fatty acids can not only derive from the diet but also be endogenously formed. The central focus of this study was to prove that the in vivo isomerization occurs via a radical process. Two different models of radical insult were used: CCl(4) and AAPH injection to rats fed a diet completely free of trans isomers. Following this acute radical stress, a significant increase in unnatural trans fatty acid content of erythrocyte, kidney, and heart, but not liver, was observed. These results can be mainly explained by the high content, particularly in the liver, of antioxidant vitamins A and E that exhibit also an "anti-isomerizing" effect. Since during ageing cellular components are exposed to increasing radical insults, the observation of a significant trans fatty acid accumulation in 30-month-old rats could confirm that the in vivo formation of unnatural isomers is due to a radical process. Trans fatty acids can influence the physical characteristics of bilayer microdomains, affecting membrane properties and functions; thus, knowledge of biological radical species responsible for cis/trans isomerization and their possible sources can provide protective systems for preserving lipid geometry.

Utilizing biotechnology in producing fats and oils with various nutritional properties

The role of dietary fat in health and wellness continues to evolve. In today's environment, trans fatty acids and obesity are issues that are impacted by dietary fat. In response to new information in these areas, changes in the amount and composition of edible fats and oils have occurred and are occurring. These compositional changes include variation in fatty acid composition and innovation in fat structure. Soybean, canola, and sunflower are examples of oilseeds with varied fatty acid composition, including mid-oleic, high-oleic, and low-linolenic traits. These trait-enhanced oils are aimed to displace partially hydrogenated vegetable oils primarily in frying applications. Examples of oils with innovation in fat structure include enzyme interesterified (EIE) fats and oils and diacylglycerol oil. EIE fats are a commercial edible fat innovation, where a lipase is used to modify the fat structure of a blend of hard fat and liquid oil. EIE fats are aimed to displace partially hydrogenated vegetable oils in baking and spread applications. Diacylglycerol and medium-chain triglyceride (MCT)-based oils are commercial edible oil innovations. Diacylglycerol and MCT-based oils are aimed for individuals looking to store less of these fats as body fat when they are used in place of traditional cooking and salad oils.

Trans Fatty Acids in Membranes: The Free Radical Path

The double bond geometry of most of the naturally occurring unsaturated fatty acid residues is cis. Due to the relevance of fatty acids as structural components of cell membranes and as biologically active molecules, the change of the cis geometry means a change of the associated functions and activities. The finding that the cis to trans isomerization is effective in phospholipids by the intervention of radical species led to the discovery that there can indeed occur an endogenous formation of trans fatty acids, whose significance in biological systems started to be addressed with in vitro and in vivo studies. Studies of liposome models simulating the formation of isomerizing species and evaluating their ability to interact with the hydrophobic part of the membrane bilayer has contributed to the gain in knowledge of the fundamental features of the lipid isomerization in membranes. Further work is in progress for the identification of the real culprits of the in vivo lipid isomerization, and recent results are shown on oleic acid micelles, where *NO2 radicals are not able to induce double bond isomerization in comparison with amphiphilic thiol, such as 2-mercaptoethanol. H2S and sulfur-containing amino acid residues are two of the possible species involved in this process at a biological level. An update of the scenario of the geometrical isomerization in membranes by free radicals is provided, together with applications and perspectives in life sciences.

Trans fatty acid-forming processes in foods: a review

There is a mounting concern about the intake of foods containing trans fatty acids (TFA) due to their deleterious effects on human health, mainly on the cardiovascular system. In this way, it is important to consider the processes that form TFA in foods, and the alternatives to minimize them. Among the processes that result in the formation of TFA, the hydrogenation of vegetable oils stands out for its impact on the diet of people living in industrialized countries. Other processes such as edible oil refining, meat irradiation, food frying, and biohydrogenation also contribute to increase the daily intake of TFA.

Effects of products made from a high-palmitic acid, trans-free semiliquid fat or a high-oleic acid, low-trans semiliquid fat on the serum lipoprotein profile and on C-reactive protein concentrations in humans

BACKGROUND

Many studies have shown that trans fatty acids have unfavorable effects on the serum lipoprotein profile. In general, however, fats were compared with different functional characteristics, which lower the practical applications of the results.

OBJECTIVE

The major aim of this study was to compare the effects of a high-palmitic acid, trans-free semiliquid fat with those of a high-oleic acid, low-trans semiliquid fat on the serum lipoprotein profile of healthy subjects.

SUBJECTS AND DESIGN

Forty-four subjects (33 women and 11 men) consumed, in random order, two experimental diets, each for 3 weeks. Diets provided 40 energy percent (En%) from fat, while 15 En% was supplied by the experimental fats. At the end of each intervention period, concentrations of serum lipoproteins, C-reactive protein, glucose and insulin were measured.

RESULTS

When subjects consumed the high-oleic acid, low-trans semiliquid fat, intakes of stearic acid (+1.3 En%), oleic acid (+2.9 En%), alpha-linolenic acid (+0.1 En%) and trans fatty acids (+0.6 En%) were higher and that of palmitic acid (-4.2 En%) lower. Serum concentration of low-density lipoprotein cholesterol decreased by 0.34+/-0.39 mmol/l (mean+/-s.d.; 95% confidence interval (CI), -0.46 to -0.23 mmol/l; P<0.001) and high-density lipoprotein (HDL) cholesterol by -0.06+/-0.17 mmol/l (95% CI, -0.11 to -0.01 mmol/l; P=0.021). Also, the total to HDL cholesterol ratio was lower (-0.15+/-0.34; 95% CI, -0.25 to -0.05; P=0.006). Other parameters did not change.

CONCLUSIONS

A high-oleic acid, low-trans semiliquid fat has a more favorable effect on the serum lipoprotein profile than a trans-free semiliquid fat with comparable functional characteristics, but high in palmitic acid.

Determinants of plasma dihydrophylloquinone in men and women

Commercial hydrogenation results in the formation of trans fatty acids. An unintended consequence of the hydrogenation process is conversion of phylloquinone (vitamin K1) to dihydrophylloquinone. Plasma dihydrophylloquinone concentrations have yet to be characterized in population-based studies. Dietary determinants of plasma dihydrophylloquinone were estimated using a semi-quantitative food frequency questionnaire in 803 men and 913 women in the Framingham Offspring Study. Geometric mean dihydrophylloquinone intake was 21·3 (95 % CI 20·4, 22·3) μg/d in men and 19·4 (95 % CI 18·5, 20·2) μg/d in women. Detectable (>0·05 nmol/l) plasma dihydrophylloquinone concentrations were measured in 41 % and 30 % of men and women, respectively. The multivariate odds ratio (OR) of detectable plasma dihydrophylloquinone from the lowest to the highest quartile category of dihydrophylloquinone intake were 1 (referent), 1·13 (95 % CI 0·83, 1·53), 1·66 (95 % CI 1·21, 2·26) and 1·84 (95 % CI 1·31, 2·58), P for trend <0·001, adjusted for sex, age, body mass index, triacylglycerols, season and energy intake. Higher trans fatty acid intake was associated with higher multivariate OR for detectable plasma dihydrophylloquinone (OR comparing extreme quartiles 2·41 (95 % CI 1·59, 3·64), P for trend <0·001). There were limitations in the use of plasma dihydrophylloquinone, evident in the high proportion of the population that had non-detectable dihydrophylloquinone concentrations. Despite this caveat, higher plasma dihydrophylloquinone was associated with higher dihydrophylloquinone intake and higher trans fatty acid intake.

Dynamic Features of the Rumen Metabolism of Linoleic Acid, Linolenic Acid and Linseed Oil Measured in Vitro

The lipid quality of ruminant products is largely determined by the extent of rumen microbial biohydrogenation (BH) of polyunsaturated fatty acids (FAs) and the substances formed thereby. In vitro batch incubations with mixed rumen bacteria were tracked over 24 h to characterize the profiles and kinetics of the BH products from three lipid sources: pure linoleic acid (c9,c12-18:2), pure linolenic acid (c9,c12,c15-18:3) and linseed oil (mainly c9,c12,c15-18:3 in triacylglycerols). After 24 h of incubation biohydrogenation was more complete for c9,c12-18:2, which gave mainly stearic acid (18:0), than for c9,c12,c15-18:3, which yielded mainly trans-18:1 FAs. This suggests inhibition of the final BH step (18:1 to 18:0). Incubations of c9,c12-18:2 resulted in high levels of carbon 10- and 12-desaturated 18:1, t10,c12- and c9,t11-CLAs. Incubations of c9,c12,c15-18:3 resulted in high levels of t11-18:1, carbon 13- and 15-desaturated 18:1 as well as t11,c15-18:2 and 11,13-CLAs. A comparative study of linolenic acid and linseed oil kinetics revealed that the BH process was not significantly slowed by the esterification of polyunsaturated FAs, but may have been limited by the isomerization step in which the cis12 double bond goes to the trans11 position. The disappearance rates of c9,c12-18:2 and c9,c12,c15-18:3 ranged from 23.6 to 44.6%/h. The wide variety of BH intermediates found here underlines the large number of possible BH pathways. These data help provide a basis for dynamic approaches to BH processes.

trans-Fatty acids and radical stress: What are the real culprits?

Free radical-catalysed cis-trans isomerization of unsaturated lipids in biomimetic models and their significance in eukaryotic cells have been explored in the last few years, an integrating hypothesis being that trans-fatty acids have their origins in both dietary sources and from isomerization of natural isomers by an endogenous radical stress. In this perspective, a summary of the achievements and a discussion of the possible biological sources of isomerizing radical species are given, indicating a need for further research on thiyl radical generation in biological systems. In this context, crucial questions remain to be answered by free radical research involving membrane lipids, thus contributing to lipidomics and embracing biology and medicine.

Effect of dietary supply of butters rich either in trans-10-18 : 1 or in trans-11-18 : 1 plus cis-9, trans-11-18 : 2 on rabbit adipose tissue and liver lipogenic activities

Experimental butters with a high content of trans-18 : 1 fatty acids and/or cis-9,trans-11-18 : 2 (rumenic acid; RA) were fed to thirty-six New Zealand White rabbits to investigate their effects on adipose tissue (AT) and liver lipogenic activities. Animals received one of three atherogenic (0.2 % cholesterol) diets containing 12 % butter with either a standard fatty acid composition (rich in saturated fatty acids), rich in trans-10-18 : 1 (T10 diet) or in trans-11-18 : 1 plus RA (T11+ RA diet) for 6 or 12 weeks. The ingestion of butters rich in trans fatty acids and/or RA for 6 weeks had little or no effect on liver and AT lipogenesis. The ingestion for 12 weeks of butter rich in T11+ RA decreased perirenal AT weight, lipogenic enzyme and lipoprotein lipase activities, without affecting liver lipid concentration or lipogenic activities except for a decrease in glycerol-3-phosphate dehydrogenase activity. Similar trends, but of a lower magnitude, were observed in rabbits fed the T10 diet for 12 weeks. Ingestion of the T10 or T11+ RA diets for 6 or 12 weeks had no significant effect on plasma metabolites and hormones except for glucose which increased at 6 weeks in the T10 group. Plasma leptin concentration was positively correlated with AT weight but did not differ between the three diets. In conclusion, the supply of butters rich in either T10 or T11+ RA in an atherogenic diet for 12 weeks decreased rabbit AT lipogenesis, with a more marked effect of the T11+RA diet, but had no effect on liver lipogenesis.

Novel soybean oils with different fatty acid profiles alter cardiovascular disease risk factors in moderately hyperlipidemic subjects

BACKGROUND

A variety of soybean oils were developed with improved oxidative stability and functional characteristics for use as alternatives to partially hydrogenated fat.

OBJECTIVE

The objective was to assess the effect of selectively bred and genetically modified soybean oils with altered fatty acid profiles, relative to common soybean and partially hydrogenated soybean oils, on cardiovascular disease risk factors.

DESIGN

Thirty subjects (16 women and 14 men) aged >50 y with LDL-cholesterol concentrations >130 mg/dL at screening consumed 5 experimental diets in random order for 35 d each. Diets contained the same foods and provided 30% of energy as fat, of which two-thirds was either soybean oil (SO), low-saturated fatty acid soybean oil (LoSFA-SO), high-oleic acid soybean oil (HiOleic-SO), low-alpha-linolenic acid soybean oil (LoALA-SO), or partially hydrogenated soybean oil (Hydrog-SO).

RESULTS

Plasma phospholipid patterns reflected the predominant fat in the diet. LDL-cholesterol concentrations were 3.66 +/- 0.67(b), 3.53 +/- 0.77(b), 3.70 +/- 0.66(b), 3.71 +/- 0.64(a,b), and 3.92 +/- 0.70(a) mol/L; HDL-cholesterol concentrations were 1.32 +/- 0.32(a,b), 1.32 +/- 0.35(b), 1.36 +/- 0.33(a), 1.32 +/- 0.33(b), and 1.32 +/- 0.32(a,b) mol/L for the SO, LoSFA-SO, HiOleic-SO, LoALA-SO, and Hydrog-SO diets, respectively (values with different superscript letters are significantly different, P < 0.05). No significant effects were observed on VLDL-cholesterol, triacylglycerol, lipoprotein(a), and C-reactive protein concentrations or on ratios of LDL cholesterol to apolipoprotein B (apo B) and HDL cholesterol to apo A-I. Total cholesterol:HDL cholesterol was lower after subjects consumed the unhydrogenated soybean oils than after they consumed the Hydrog-SO diet.

CONCLUSIONS

All varieties of soybean oils resulted in more favorable lipoprotein profiles than did the partially hydrogenated form. These soybean oils may provide a viable option for reformulation of products to reduce the content of trans fatty acids.

Trans fatty acids promote the growth of some Lactobacillus strains

Five Lactobacillus strains (2 L. gasseri, 2 L. plantarum and 1 L. reuteri) were cultured in modified MRS medium containing fatty acids (FAs) instead of Tween 80 for 24 h at 37 degrees C, to learn the effect of saturated and unsaturated FAs on the Lactobacillus growth. Free FAs included palmitic (16:0), palmitoleic (c9-16:1), stearic (18:0), oleic (c9-18:1), elaidic (t9-18:1), cis-vaccenic (c11-18:1), vaccenic (t11-18:1), linoleic (c9, c12-18:2), conjugated linoleic (c9, t11- and t10, c12-18:2), alpha-linolenic (c9, c12, c15-18:3), alpha-eleostearic (c9, t11, t13-18:3), eicosapentaenoic (20:5), and docosahexaenoic (22:6) acids. Among free FAs, oleic acid stimulated the growth of all Lactobacillus strains, whereas palmitoleic acid had almost no affect on the Lactobacillus growth. Saturated FAs such as stearic and palmitic acids inhibited or did not affect the Lactobacillus growth. Polyunsaturated FAs such as alpha-linolenic, eicosapentaenoic and docosahexaenoic acids strongly inhibited the Lactobacillus growth at 7.6 x 10(-4) m. Octadecenoic acids such as oleic, elaidic, cis-vaccenic and vaccenic acids remarkably promoted the growth of L. gasseri, regardless of the different double bond positions and configurations. When oleic or cis-vaccenic acid was incubated with L. gasseri, the FAs was transformed to cyclopropane FAs (methyleneoctadecanoic acids) after incorporation into the cells. On the other hand, trans FAs such as elaidic and vaccenic acids incorporated into the cells were not converted to another FAs. Conjugated linoleic and alpha-eleostearic acids having a trans double bond promoted the Lactobacillus growth. The growth of L. gasseri was also stimulated by trans-rich free FAs from hydrogenated canola and fish oils. These results showed that octadecenoic acid and trans FAs had strong promotion activities for the Lactobacillus growth due to their incorporation into membrane lipids.

Trans fatty acids and cardiovascular disease-epidemiological data

Prospective epidemiologic studies and case-control studies using adipose tissue analyses support a major role of trans fatty acids (TFA) in risk of coronary heart disease (CHD). The magnitude of the association with CHD is considerably stronger than for saturated fat, and is stronger than predicted by the effects of TFA on LDL and HDL cholesterol. The apparent gap between the epidemiologic findings and effects of TFA on LDL:HDL has been bridged, at least in part, by recent metabolic studies showing effects of TFA on inflammatory factors and other indicators of insulin resistance.

Trans-fatty acids and sudden cardiac death

Sudden cardiac death (SCD) is usually due to ventricular fibrillation and can occur as a first manifestation of heart disease. Prevention of ventricular fibrillation and SCD with n-3 polyunsaturated fatty acids is well documented. Trans-fatty acids (TFA) in the diet and cell membranes might affect the risk of SCD as well. We review evidence from an observational study that high levels of trans-18:2 (9 cis-, 12 trans- and 9 trans-, 12 cis-isomers of linoleic acid) in red blood cell membranes are associated with markedly higher risk of SCD. In contrast, cell membrane levels of trans-18:1 (trans-isomers of oleic acid), the major TFA in foods, do not appear associated with higher risk of SCD. While further studies are needed to investigate possible effects of trans-18:2 on arrhythmia, it would be prudent to limit dietary intake of trans-18:2.

Trans fatty acids and insulin resistance

Since trans fatty acids (TFA) might interfere with cell membrane functions, there are reasons to believe that high TFA intakes could affect insulin sensitivity and consequently diabetes risk. It is possible that low amounts of TFA consumed during long time-periods might be clinically relevant. Data from controlled intervention studies investigating the effects of TFA on insulin sensitivity are reviewed. The results show no significant effect of TFA on insulin sensitivity in lean healthy subjects. However, there is some evidence that TFA could impair insulin sensitivity compared to unsaturated fat in insulin resistant or diabetic individuals. This is especially true for conjugated TFA, i.e. conjugated linoleic acid (CLA), which clearly impairs insulin sensitivity. In fact, the effect of CLA on insulin action is the most dramatic adverse effect described for a dietary fatty acid. The inconsistent effect of TFA as a group might partly be due to methodological limitations (e.g. few studies, short duration or small sample size) and differences between studies in design, type and amount of TFA used. Large controlled trials have been required to demonstrate adverse effects of saturated fat on insulin sensitivity, and similar efforts will probably be needed to clarify the effect of TFA on insulin sensitivity.

Trans fatty acids - effects on systemic inflammation and endothelial function

Consumption of trans fatty acids (TFA) predicts higher risk of coronary heart disease, sudden death, and possibly diabetes mellitus. These associations are greater than would be predicted by effects of TFA on serum lipoproteins alone. Systemic inflammation and endothelial dysfunction may be involved in the pathogenesis of atherosclerosis, acute coronary syndromes, sudden death, insulin resistance, dyslipidemia, and heart failure. Evidence from both observational and experimental studies indicates that TFA are pro-inflammatory. Limited evidence suggests that pro-inflammatory effects may be stronger for trans isomers of linoleic acid (trans-C18:2) and oleic acid (trans-C18:1), rather than of palmitoleic acid (trans-C16:1), but further study of potential isomer-specific effects is needed. TFA also appear to induce endothelial dysfunction. The mechanisms underlying these effects are not well-established, but may involve TFA incorporation into endothelial cell, monocyte/macrophage, or adipocyte cell membranes (affecting membrane signaling pathway relating to inflammation) or ligand-dependent effects on peroxisome proliferator-activated receptor (PPAR) or retinoid X receptor (RXR) pathways. Activation of inflammatory responses and endothelial dysfunction may represent important mediating pathways between TFA consumption and risk of coronary heart disease, sudden death, and diabetes. Further study is indicated to define these effects of TFA and the implications of such effects for cardiovascular health.

Differential biohydrogenation and isomerization of [U-13C]Oleic and [1-13C]Oleic acids by mixed ruminal microbes

The additional mass associated with 13C in metabolic tracers may interfere with their metabolism. The comparative isomerization and biohydrogenation of oleic, [1-(13)C]oleic, and [U-13C]oleic acids by mixed ruminal microbes was used to evaluate this effect. The percent of stearic, cis-14 and -15, and trans-9 to -16 18:1 originating from oleic acid was decreased for [U-(13)C]oleic acid compared with [1-(13)C]oleic acid. Conversely, microbial utilization of [U-(13)C]oleic acid resulted in more of the 13C label in cis-9 18:1 compared with [1-(13)C]oleic acid (53.7 vs. 40.1%). The isomerization and biohydrogenation of oleic acid by ruminal microbes is affected by the mass of the labeled tracer.

Occurrence of trans fatty acids in rats fed a trans-free diet: a free radical-mediated formation?

Trans isomers of unsaturated fatty acids are absorbed from the diet, due to their presence in diary fat and hydrogenated vegetable oils, and health concern has risen due to their effects on lipid risk factors in cardiovascular diseases. On the basis of the efficiency of the thiyl-radical-catalyzed cis/trans isomerization in vitro and the presence of many sulfur-containing compounds in the cell, the aim of this study was to demonstrate that trans geometry of lipid double bonds can be endogenously generated within membrane phospholipids. The study reports trans fatty acids occurrence in tissue and erythrocyte phospholipids of young adult rats fed a diet completely free of trans isomers. Results show that tissues are differently prone to the endogenous isomerization and that, following a free radical attack, trans fatty acids can reach very high amounts. The effectiveness of this process is considerably inhibited in the presence of all-trans retinol, confirming previous data in model membranes. Our results suggest that geometrical isomerization of unsaturated fatty acids, which causes a structural modification of membrane lipids and may influence basic membrane properties and vital biochemical functions, can occur under radical stress conditions and could be efficiently prevented by vitamin A.

The conversion efficiency of trans-11 and trans-12 18:1 by Delta9-desaturation differs in rats

The present study evaluated and compared the efficiency of the conversion of t11 18:1 and t12 18:1 to their corresponding dienoic acids (c9,tn 18:2) and assessed whether differences due to gender existed in several tissues of rats. Three groups of 4-wk-old male and female rats were fed for 3 wk a diet supplemented with 0, 0.5, or 1% of a trans-octadecenoic acid isomer mixture (tOIM) containing t11 18:1 and t12 18:1 in equal proportion. t11 18:1 and t12 18:1 were incorporated in a tissue-specific manner, and the accrual was significant with increased dietary intake of these trans fatty acid (tFA) isomers. The t12 18:1 isomer was more readily incorporated into the rat tissues than the t11 18:1 isomer. From t11 and t12 18:1, the respective desaturase products, c9,t11 18:2 and c9,t12 18:2, were formed. The calculated conversion rates varied greatly among the tissues of the rats but they were consistently lower for t12 18:1 than for t11 18:1, suggesting that t12 18:1 is a poorer substrate than t11 18:1 for Delta9-desaturase. For both fatty acids investigated, the calculated conversion rates in decreasing order of conversion efficiency were: testes = kidneys > adipose tissue > ovaries > muscle > liver > heart. Overall, there were distinct differences in the conversion of t11 18:1 and t12 18:1, indicating that these 2 fatty acids are metabolized differently despite their structural similarities. Such metabolic differences in tFA accumulation and metabolism may have potential implication in assessing the safety of these tFA isomers because there is a positive correlation between the intake of tFA and the incidence of various diseases.