The impact of dietary mono‐ and poly‐unsaturated fatty acids on risk factors for atherosclerosis in humans

The fatty acid composition of the diet has various effects on atherosclerosis risk factors. Dietary saturated fatty acids (SFA) and trans‐unsaturated fatty acids increase the low‐density lipoprotein (LDL)‐/high‐density lipoprotein (HDL)‐cholesterol ratio in serum, while these fats do not have a significant bearing on serum triglyceride levels. By contrast, dietary monounsaturated fatty acids (MUFA), n‐6 polyunsaturated fatty acids (PUFA), and α‐linolenic acid (C18:3n‐3) similarly reduce LDL cholesterol concentrations, while their influence on serum HDL cholesterol and triglycerides is not appreciable. Dietary long‐chain n‐3 PUFA slightly increase serum LDL cholesterol concentrations, but are nevertheless considered salubrious with regard to serum lipids due to the distinct triglyceride‐lowering effects. MUFA‐rich compared to n‐6 PUFA‐rich diets strongly reduce the in vitro oxidizability of LDL. The available studies on this subject also suggest that n‐3 PUFA in the small amounts usually present in the diet are not unduly harmful. These findings are consistent with reports from observational studies: the amount of SFA is positively and the amount of MUFA and n‐6 PUFA in the diet is inversely associated with the risk of cardiovascular disease in most epidemiological studies. The available studies have had an impact on current dietary guidelines, which unanimously recommend that most of the dietary fat should be in the form of MUFA, while the amount of SFA and trans fatty acids in the diet should be as low as possible.     

The twisted tale of saturated fat

Recent research results mandate a careful re‐evaluation of the widespread belief that dietary saturated fat is harmful. Specifically, multiple recent reports find no association between dietary saturated fat intakes and cardiovascular disease (CVD). There is, however, a consistent pattern of increased risk for both CVD and type‐2 diabetes associated with increased levels of saturated fatty acids (SFA) in circulating lipids. This raises the important question as to what contributes to increased levels of saturated fat in the blood? Whereas dietary intake of saturated fats and serum levels of SFA show virtually no correlation, an increased intake of carbohydrate is associated with higher levels of circulating SFA. This leads to the paradoxical conclusion that dietary saturated fat is not the problem; rather it's the over‐consumption of carbohydrate relative to the individual's ability to metabolize glucose without resorting to de novo lipogenesis. From this perspective, insulin resistant states like metabolic syndrome and type‐2 diabetes can be viewed as carbohydrate intolerance, in which a high carbohydrate intake translates to increased serum SFA and therefore increased risk.     

An increase in dietary n-3 fatty acids decreases a marker of bone resorption in humans

Human, animal, and in vitro research indicates a beneficial effect of appropriate amounts of omega-3 (n-3) polyunsaturated fatty acids (PUFA) on bone health. This is the first controlled feeding study in humans to evaluate the effect of dietary plant-derived n-3 PUFA on bone turnover, assessed by serum concentrations of N-telopeptides (NTx) and bone-specific alkaline phosphatase (BSAP). Subjects (n = 23) consumed each diet for 6 weeks in a randomized, 3-period crossover design: 1) Average American Diet (AAD; [34% total fat, 13% saturated fatty acids (SFA), 13% monounsaturated fatty acids (MUFA), 9% PUFA (7.7% LA, 0.8% ALA)]), 2) Linoleic Acid Diet (LA; [37% total fat, 9% SFA, 12% MUFA, 16% PUFA (12.6% LA, 3.6% ALA)]), and 3) α-Linolenic Acid Diet (ALA; [38% total fat, 8% SFA, 12% MUFA, 17% PUFA (10.5% LA, 6.5% ALA)]). Walnuts and flaxseed oil were the predominant sources of ALA. NTx levels were significantly lower following the ALA diet (13.20 ± 1.21 nM BCE), relative to the AAD (15.59 ± 1.21 nM BCE) (p < 0.05). Mean NTx level following the LA diet was 13.80 ± 1.21 nM BCE. There was no change in levels of BSAP across the three diets. Concentrations of NTx were positively correlated with the pro-inflammatory cytokine TNFα for all three diets. The results indicate that plant sources of dietary n-3 PUFA may have a protective effect on bone metabolism via a decrease in bone resorption in the presence of consistent levels of bone formation.     

Bioactivity and emerging role of short and medium chain fatty acids

Cardiovascular disease (CVD) and insulin resistance are directly linked to overweight and obesity. Thus, any dietary strategy capable of causing weight reduction will lower CVD and diabetes risk. Oils rich in medium‐chain saturated fatty acids (MCFA) are among several dietary components that may have potential in the treatment of obesity. MCFA are less energy dense and highly ketogenic compared to long‐chain saturated and unsaturated fatty acids (LCFA). MCFA also differ from LCFA in their digestive and metabolic pathways, since they are easily oxidized and utilized as energy, with little tendency to deposit as body fat. The dietary intake of short (SCFA) and medium‐chain saturated fatty acids from natural food sources is approximately 2.4 g/day and accounts for about 9% of the total saturated fatty acid (SFA) intake. Although early clinical studies with high levels of MCFA resulted in increased levels of plasma triacylglycerols (TAG) and low‐density lipoprotein cholesterol (LDL‐C), and reduced levels of high‐density lipoprotein cholesterol (HDL‐C) compared to diets enriched in unsaturated LCFA, these adverse effects have not been observed in more recent studies with smaller more realistic amounts of MCFA. The lower caloric value of SCFA and MCFA and their unique metabolic features form the basis for their clinical use in enteral and parenteral nutrition and for novel reduced calorie lipids for use in conventional food products.     

Postprandial Lipid Responses do not Differ Following Consumption of Butter or Vegetable Oil when Consumed with Omega-3 Polyunsaturated Fatty Acids

Dietary saturated fat (SFA) intake has been associated with elevated blood lipid levels and increased risk for the development of chronic diseases. However, some animal studies have demonstrated that dietary SFA may not raise blood lipid levels when the diet is sufficient in omega‐3 polyunsaturated fatty acids (n‐3PUFA). Therefore, in a randomised cross‐over design, we investigated the postprandial effects of feeding meals rich in either SFA (butter) or vegetable oil rich in omega‐6 polyunsaturated fatty acids (n‐6PUFA), in conjunction with n‐3PUFA, on blood lipid profiles [total cholesterol, low density lipoprotein cholesterol (LDL‐C), high density lipoprotein cholesterol (HDL‐C) and triacylglycerol (TAG)] and n‐3PUFA incorporation into plasma lipids over a 6‐h period. The incremental area under the curve for plasma cholesterol, LDL‐C, HDL‐C, TAG and n‐3PUFA levels over 6 h was similar in the n‐6PUFA compared to SFA group. The postprandial lipemic response to saturated fat is comparable to that of n‐6PUFA when consumed with n‐3PUFA; however, sex‐differences in response to dietary fat type are worthy of further attention.     

Effects of the ratio of polyunsaturated and monounsaturated fatty acid to saturated fatty acid on rat plasma and liver lipid concentrations

The effects of dietary monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid+MUFA/saturated fatty acid (PUFA+MUFA/SFA) ratio on plasma and liver lipid concentrations were studied. In experiment I, when rats were fed with 40% fat (energy%, PUFA/SFA ratio 1.0) and 1% (w/w) cholesterol (C) diets for 21 d, a large amount of MUFA (28.1 energy%, PUFA+MUFA/SFA=5.7) in the diet was found to increase the plasma total C, triacylglycerol (TAG), and phospholipid (PL) as compared with the low-MUFA diet (7.0 energy%, PUFA+MUFA/SFA=1.4). The plasma very low density lipoprotein (VLDL)-C, VLDL-TAG, VLDL-PL, and low density lipoprotein (LDL)-C increased significantly in the high-MUFA diet group, but high density lipoprotein (HDL)-C did not change significantly. The high-MUFA diet resulted in greater accumulation of liver C but lesser accumulation of TAG. In experiment II, when dietary SFA was fixed at a certain level (13.2 energy%; PUFA+MUFA/SFA=2.0), rats given a larger amount of MUFA (23.1 energy%; PUFA/MUFA=0.2; MUFA/SFA=1.8) showed higher plasma and liver C levels than did the low-MUFA diet (7.7 energy%; PUFA/MUFA=2.5; MUFA/SFA=0.6). When PUFA was fixed at a certain level (24.4 energy%), there was not a significant difference in the plasma C level between the high-and low-MUFA dietary groups (PUFA+MUFA/SFA=4.8 and 8.4), but the higher PUFA+MUFA/SFA diet, which was high in MUFA/SFA ratio, significantly decreased the plasma HDL-C and TAG levels. However, when MUFA content was fixed at a certain level (16.4 energy%), no significant difference was observed between the two groups with different PUFA/SFA ratios of 0.2 and 4.1, but liver C level was raised in the higher PUFA/SFA diet. It appears that the PUFA/SFA ratio alone is unsuitable to predict the change of plasma C level, because a large amount of dietary MUFA may lead to an increase of plasma and liver lipids in rats. It seems that the prerequisites for keeping low plasma and liver C are (i) low MUFA/SFA ratio, (ii) high PUFA/MUFA ratio, and (iii) PUFA+MUFA/SFA ratio not to exceed 2.     

Serum β-carotene concentrations are associated with self-reported fatty acid intake in United States adults from the National Health and Examination Surveys

Bioavailability of dietary β-carotene (BC) is dependent on dose, quantity, dispersion, and presence of fat in the diet. Fats are comprised of a variety of fatty acids, which may impact the bioavailability of carotenoids. However, there is a gap in research on whether specific fatty acid classes affect serum BC concentrations in population samples. The primary objective of this study was to assess the association between reported fat and fatty acid intake and serum BC concentrations utilizing data from the National Health and Nutrition Examination Surveys (NHANES) 2003–2006. Data from 3278 NHANES participants 20–85 years old were analyzed to estimate the relationships between serum BC concentrations and reported saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acid intakes. Multiple linear regression estimated ln(serum BC) based on reported fatty acid intakes adjusted for age, sex, race/ethnicity, and reported dietary BC intakes. Mean and standard error (SE) for serum BC concentrations were 14.31 ± 0.05 μg/dl. Means and SE for total fat, SFA, MUFA, and PUFA were 85.7 ± 1.3, 26.9 ± 0.4, 31.1 ± 0.5, and 17.8 ± 0.4 g, respectively. There was a significant trend for association between serum BC and reported total fat intakes (r = −0.002, p < 0.0001), but the association was not strong. Multiple linear regression showed positive associations between serum BC concentrations and higher reported dietary PUFA consumption. PUFA alpha-linolenic acid intakes are positively associated with serum BC concentrations, while MUFA palmitoleic acid and SFA stearic acid were inversely associated with serum BC. The inverse association between MUFA and SFA suggests there may be multiple post-digestion factors affecting serum carotenoid concentrations.     

Dietary Monounsaturated Fatty Acids but not Saturated Fatty Acids Preserve the Insulin Signaling Pathway via IRS-1/PI3K in Rat Skeletal Muscle

Saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) show different effects on the development of insulin resistance. In this study, we compared the effect of dietary SFA and MUFA on the insulin signaling pathway in the skeletal muscle of a type 2 diabetic animal model. Twenty-nine-week-old male Otsuka Long-Evans Tokushima fatty (OLETF) rats were randomly divided into three groups and fed one of the following diets for 3 weeks; a normal chow diet, an SFA (lard oil) enriched or a MUFA (olive oil) enriched high-fat diet. The vastus lateralis muscle was used for analyses. Insulin tolerance test showed improved insulin sensitivity in rats fed the MUFA diet, as compared to those fed the SFA diet (p < 0.001). The SFA diet reduced IRS-1 expression and phosphorylated PI3K levels in skeletal muscle, as compared with a chow diet (p < 0.001, respectively). On the contrary, muscle IRS-2 expression and phosphorylated ERK1/2 was significantly increased in rats fed the SFA diet (p < 0.001, respectively). Membrane translocation of glucose transporter type 4 decreased in the skeletal muscle of rats fed the SFA diet, as compared to those fed a chow diet (p < 0.001). These changes in insulin signaling pathway in skeletal muscle were not observed in rats fed the MUFA diet. In conclusion, the beneficial effect of dietary MUFA on insulin sensitivity is associated with a conserved IRS-1/PI3K insulin signaling pathway which was altered by dietary SFA.     

Positional analysis of triacylglycerols from bovine adipose tissue lipids varying in degree of unsaturation

The objective of this study was to demonstrate that changing the fatty acid composition of bovine adipose tissue concurrently changed (i) proportions of triacylglycerol species, (ii) fatty acid composition of triacylglycerol species, and (iii) positional distribution of the component fatty acids of the triacylglycerol species. To achieve this, we took advantage of adipose tissue lipids, from cattle fed in Australia and Japan, that varied widely in fatty acid composition and melting points. Treatment groups produced in Australia were cattle fed: a cornbased diet (MUFA1); a grain-based diet containing whole cottonseed (SFA); a grain-based diet containing protected cottonseed oil (PUFA); and a grain-based diet that resulted in high contents of trans fatty acids (TFA). Treatment groups produced in Japan (MUFA2 and MUFA3) were diets of unknown composition fed for over 300 d. The MUFA1, MUFA2, and MUFA3 samples all were rich in monounsaturated fatty acids, varying only in the proportions of the individual monounsaturates. The SFA, PUFA, and TFA samples had relatively high concentrations of stearic acid (18:0), PUFA, and TFA, respectively. Slip points (indicative of melting points) were 45.1, 41.5, 38.5, 30.7, 28.4, and 22.8°C, for the SFA, TFA, PUFA, MUFA1, MUFA2, and MUFA3 groups, respectively (P<0.05). Triacylglycerols were separated by high-performance liquid chromatography on a silver nitrate-impregnated column into sn-1,2,3-saturated fatty acid triacylglycerol (SSS); [triacylglycerols containing two saturated acids and one trans-monounsaturated fatty acid (SSMt sn-positions unknown)]; sn-1-saturated, 2-monounsaturated, 3-saturated triacylglycerol (SMS); sn-1-saturated, 2-monounsaturated, 3-trans-monounsaturated triacylglycerol (SMMt); sn-1-saturated, 2,3-monounsaturated fatty acid triacylglycerol (SMM); sn-1-saturated, 2-polyunsaturated, 3-trans-monounsaturated triacylglycerol; sn-1,2,3-monounsaturated fatty acid triacylglycerol (MMM); and sn-1-saturated, 2-polyunsaturated, 3-monounsaturated triacylglycerol. Fatty acid methyl esters of each triacylglycerol species also were determined, and further analysis indicated sn-2, and sn-1/3 positions. As the percentage oleic acid increased in the total lipid extract, the proportions of SMM and MMM increased (e.g., from 31.4 and 2.4% in the SFA group to 55.4 and 17.8% in the MUFA3 group). The elevated 18:0 in the SFA group (26%) was reflected in increased percentages of SSS and SSM, and caused an increase in the proportion of 18:0 in all triacylglycerol species relative to the other treatment groups. The percentage of 18:0 in the sn-1/3 positions was elevated markedly in the SMS fraction of the SFA group (to 44%); this would account for the high melting point of the fat of these animals. We conclude that long-term feeding of cattle is sufficient to produce significant alterations in fatty acid composition in bovine adipose tissue. Alterations in the fatty acid composition of bovine adipose tissue changed both the distribution and the composition of the triacylglycerol species, which, in turn, accounted for marked differences in melting points among treatment groups.     

Dietary modifications of animal fats: status and future perspectives

The purpose of modifying animal fats is to produce high quality products, which meet the dietary recommendations for a reduced intake of fat in the human diet, notably that of certain saturated fatty acids and cholesterol, and an increased intake of mono- (MUFA) and polyunsaturated fatty acids (PUFA) in order to minimize the risk for obesity, cancer, cardiovascular, and other life-style diseases. The body fat of farm animals is partly synthesized from dietary carbohydrates, partly from dietary fatty acids. In monogastric animals, preruminants and poultry PUFAs are readily absorbed and deposited in the edible parts of the body and incorporated into egg yolk lipids. In ruminants, however, PUFAs are hydrogenated to mainly saturated fatty acids by the rumen microorganisms with some formation of MUFAs, trans-, odd-, branched chain, and conjugated fatty acids. The latter fatty acids are absorbed, deposited in adipose and muscle tissue and incorporated into milk lipids, unless dietary PUFAs are protected against hydrogenation. Thus, it is relatively easy to change the fatty acid composition of pork, poultry meat, lamb, and veal, whereas beef and milk can only be enriched significantly with PUFAs by manipulation. Products enriched with PUFAs are, however, prone to oxidation, and enrichment with antioxidants, notably with dietary vitamin E, is necessary in order to prevent the risk of oxidative damage.     

Fatty Acids of Microbial Origin in the Perirenal Fat of Rats (Rattus norvegicus domestica) and Guinea Pigs (Cavia porcellus) Fed Various Diets

Guinea pigs are assumed to practice caecotrophy to a higher degree than rats. Studies from leporids suggest that through the practice of caecotrophy, hindgut fermenting species could build up microbial fatty acids (FA) in body tissues. We hypothesized that microbial FA would be detectable in the body tissue of guinea pigs and rats, and this to a higher degree in guinea pigs. Twenty-four rats and guinea pigs were fed with four different pelleted diets (lucerne-, meat-, meat-bone-, insect-based) in groups of six animals for 8 weeks. Perirenal adipose tissue differed in FA composition between the species in spite of the common diets. FA typically associated with microbial activity (saturated FA (SFA; typically 18:0), monounsaturated FA (MUFA; typically trans-fatty acids TFA), and odd- and branched-chain FA (Iso-FA)), were all detected. Guinea pigs had higher SFA levels than rats except on the lucerne diet. Concentrations of 18:0 were higher for guinea pigs on the meat and bone diet. Iso-FA concentrations in guinea pigs exceeded those of rats on all diets. FA profiles with a microbial fingerprint appear—although in low proportions—in the body tissue of both species, and this seemingly to a higher extent in guinea pigs. With respect to whether consumption of rodent meat rich in microbial FA has particular effects on human health as shown for ruminant products, microbial FA concentrations are probably too low to cause any distinct effects.     

Dietary CLA Combined with Palm Oil or Ovine Fat Differentially Influences Fatty Acid Deposition in Tissues of Obese Zucker Rats

The effect of dietary conjugated linoleic acid (CLA) supplementation in combination with fat from vegetable versus animal origin on the fatty acid deposition, including that of individual 18:1 and 18:2 (conjugated and non-conjugated) isomers, in the liver and muscle of obese rats was investigated. For this purpose, 32 male Zucker rats were randomly assigned to one of four diets containing palm oil or ovine fat, supplemented or not with 1% of 1:1 cis(c)9,trans(t)11 and t10,c12 CLA isomers mixture. Total fatty acid content decreased in the liver and muscle of CLA-fed rats. In the liver, CLA increased saturated fatty acids (SFA) in 11.9% and decreased monounsaturated fatty acids (MUFA) in 6.5%. n-3 Polyunsaturated fatty acids (PUFA) relative proportions were increased in 30.6% by CLA when supplemented to the ovine fat diet. In the muscle, CLA did not affect SFA but decreased MUFA and PUFA percentages. The estimation of Δ9-indices 16 and 18 suggested that CLA inhibited the stearoyl-CoA desaturase activity in the liver (a decrease of 13–38%), in particular when supplemented to the ovine fat diet. Concerning CLA supplementation, the t10,c12 isomer percentage was 60–80% higher in the muscle than in the liver. It is of relevance that rats fed ovine fat, containing bio-formed CLA, had more c9,t11 CLA isomer deposited in both tissues than rats fed palm oil plus synthetic CLA. These results highlight the importance to further clarify the biological effects of consuming foods naturally enriched in CLA, alternatively to CLA dietary supplementation.     

The effect of fatty acid composition of rapeseed oil on plasma lipids and oxidative stability of low‐density lipoproteins in cholesterol‐fed hamsters

We studied the effect of four rapeseed oils with different fatty acid profiles on parameters implicated in the pathogenesis of atherosclerosis in humans in a model experiment with hamsters. The hamsters were divided into seven groups and fed a semi‐synthetic, cholesterol‐enriched diet (5 g/kg diet) containing 15% of the fat in question for a period of six weeks. The following rapeseed oils were used: (1) conventional rapeseed oil (6% saturated fatty acids [SFA], 64% monounsaturated fatty acids [MUFA], 18% linoleic acid [LA], 9% α‐linolenic acid [ALA]), (2) linoleic acid‐rich rapeseed oil (6% SFA, 61% MUFA, 28% LA, 2% ALA), (3) oleic acid‐rich rapeseed oil (6% SFA, 74% MUFA, 11% LA, 5% ALA), (4) myristic acid‐rich rapeseed oil (11% myristic acid, 35% SFA, 44% MUFA, 14% LA, 5% ALA). Sunflower oil, olive oil and lard were used as control fats. The concentrations of the lipids in the plasma, in the lipoprotein fractions and in the liver, the fatty acid composition of various tissues, the tocopherol status and the susceptibility of low‐density lipoproteins (LDL) to in vitro‐oxidation were determined. The concentrations of total cholesterol found in the plasma and in the LDL fraction and the ratios of LDL to HDL were similar after feeding the four different types of rapeseed oil, sunflower oil and olive oil. Lard produced the highest concentrations of cholesterol in plasma and the LDL fraction and the highest ratio of LDL to HDL. Feeding conventional, oleic acid‐ and myristic acid‐rich rapeseed oils resulted in markedly lower ratios of arachidonic to eicosapentaenoic acid in the lipids of the liver and the erythrocytes. This is considered beneficial for the formation of eicosanoids. The lag‐time before the onset of peroxidation of the LDL lipids, induced by copper ions, was not statistically significant between the seven hamster groups suggesting that the susceptibility of LDL to lipid peroxidation was similar after feeding all types of fat. Considering all parameters obtained in the used hamster model it is obvious that all four rapeseed oils are at least as favourable as olive oil or sunflower oil.     

Effect of temperature on fatty acid composition in the Nile tilapia (Oreochromis niloticus): A temperature dependent nutritive lipid profile

In this study, the effects of temperature on the fatty acids profile and the effects of temperature on the degree of unsaturation of fatty acids of Oreochromis niloticus were investigated. The analysis was performed by gas chromatography. The study showed that there were large temperature variations (10.0–32.0°C) during the study period (January–December). The highest crude fat content was found in January (3380 mg/100 g) and the lowest in June (2050 mg/100 g). The fatty acids profile showed significantly different diversity (p < 0.05). Total saturated fatty acid (∑SFA) content ranged from 409.54 to 1297.61 mg/100 g, monounsaturated fatty acid (∑MUFA) from 207.68 to 665.81 mg/100 g, and polyunsaturated fatty acid (∑PUFA) from 175.12 to 972.23 mg/100 g. The ∑MUFA and ∑PUFA concentrations were highest in January and lowest in June, and the ∑SFA concentration was lowest in January and highest in June. EPA and DHA contents were highest in January (198.96 mg/100 g) and lowest in June (48.76 mg/100 g). The contents of omega-3 (653.17 mg/100 g) and omega-6 fatty acids (252.54 mg/100 g) were highest in January and lowest in June (ω-3; 106.43 and ω-6; 60.91 mg/100 g). It concluded that the degree of unsaturation of fatty acids increases with decreasing temperature. In this study, the nutritional quality of the FAs profile was assessed using lipid quality indices. The indices indicating dietary quality of lipids by their values: Atherogenic index (0.47), thrombogenic index (0.38), hypocholesterolemic to hypercholesterolemic (3.00), meat fat quality (6.78), ω6/ω3 ratio (0.39), PUFA/SFA (2.37), MUFA/SFA (1.62), PUFA/MUFA (1.46), and PUFA + MUFA/SFA (3.99). These values are within the recommended range, indicating that the lipid profile of O. niloticus has high nutritional quality, which can be further improved by harvesting the fish during the winter season. Due to the nutritional importance of O. niloticus, the culture of this species could have significant interest to the people of Karachi, especially the coastal communities. To promote the nutritional diet in local population, the government should support the aquaculture of Nile tilapia.     

Effect of high fat corn oil,olive oil and fish oil on phospholipid fatty acid composition in male F344 rats

Epidemiological and laboratory animal model studies have provided evidence that the effect of dietary fat on colon tumorigenesis depends on the amount of fat and its composition. Because of the importance of the composition of dietary fat and of tissue membrane fatty acid composition in tumor promotion, experiments were designed to investigate the relative effects of high fat diets rich in ω3, ω6 and ω9 fatty acids and colon carcinogen on the phospholipid fatty acid composition of liver, colon, small intestine, erythrocytes and blood plasma. At 6 wk of age, groups of animals were fed diets containing 5% corn oil (LFCO), 23.5% corn oil (HFCO), 23.5% olive oil (HFOO), and 20.5% fish oil plus 3% corn oil (HFFO). Two weeks later all the animals except the vehicle-treated animals received azoxymethanes.c. once weekly for 2 wk at a dose rate of 15 mg/kg body weight. Animals were sacrificed 5 d later and liver, colon, small intestine and erythrocytes and blood plasma were analyzed for phospholipid fatty acids. The results indicate that the phospholipid fatty acid composition of liver, colon and small intestine of HFCO diet fed animals, were not significantly different from those fed the LFCO diet. The levels of palmitoleic acid and linoleic acid were increased in erythrocytes and blood plasma of the animals fed the HFCO diet compared to those fed the LFCO diet. Feeding the HFCO diet significantly increased the oleic acid content and decreased the linoleic acid and arachidonic acid levels in various organs when compared to the HFCO diet. Animals fed the HFFO diet showed a marked increase in eicosapentaenoic acid and docosahexaenoic acid and a decrease in linoleic acid and arachidonic acid levels as compared to those fed the HFCO diet. The results also indicate that carcinogen treatment had only a minimal effect on the phospholipid fatty acid composition.     

High-Fat Diet Alters Serum Fatty Acid Profiles in Obesity Prone Rats: Implications for In Vitro Studies

High‐fat diets (HFD) are commonly used in rodents to induce obesity, increase serum fatty acids and induce lipotoxicity in various organs. Invitro studies commonly utilize individual free fatty acids (FFA) to study lipid exposure in an effort to model what is occurring in vivo; however, these approaches are not physiological as tissues are exposed to multiple fatty acids in vivo. Here we characterize circulating lipids in obesity‐prone rats fed an HFD in both fasted and fed states with the goal of developing physiologically relevant fatty acid mixtures for subsequent in vitro studies. Rats were fed an HFD (60 % kcal fat) or a control diet (10 % kcal fat) for 3 weeks; liver tissue and both portal and systemic blood were collected. Fatty acid profiles and absolute concentrations of triglycerides (TAG) and FFA in the serum and TAG, diacylglycerol (DAG) and phospholipids in the liver were measured. Surprisingly, both systemic and portal serum TAG were ~40 % lower in HFD‐fed compared to controls. Overall, compared to the control diet, HFD feeding consistently induced an increase in the proportion of circulating polyunsaturated fatty acids (PUFA) with a concomitant decline in monounsaturated fatty acids (MUFA) and saturated fatty acids (SFA) in both serum TAG and FFA. The elevations of PUFA were mostly attributed to increases in n‐6 PUFA, linoleic acid and arachidonic acid. In conclusion, fatty acid mixtures enriched with linoleic and arachidonic acid in addition to SFA and MUFA should be utilized for in vitro studies attempting to model lipid exposures that occur during in vivo HFD conditions.     

Rapid FT-NIR Analysis of Edible Oils for Total SFA, MUFA, PUFA, and Trans FA with Comparison to GC

Declarations of the total content of trans fatty acids (FA) and saturated FA (SFA) are mandatory on food labels in the US and Canada. Gas chromatography (GC) has been the method of choice for the determination of FA composition. However, GC is time consuming and requires conversion of fats and oils to their FA methyl esters. In the present study, a recently published Fourier transform near-infrared (FT-NIR) spectroscopic procedure was applied to the rapid (<5 min) determination of total SFA, monounsaturated FA (MUFA), polyunsaturated FA (PUFA), and trans FA contents of 30 commercially available edible fats and oils. Good agreement was obtained between the GC and FT-NIR methods for the determination of total SFA, MUFA, and PUFA contents. Differences between the two methods were apparent for the determination of trans fat at trans fat levels <2 % of total fat. The analytical determinations of total SFA, MUFA, and PUFA contents for many of the oils examined differed from the respective values declared on the product labels. Our findings demonstrate that the FT-NIR procedure serves as a suitable alternative method for the rapid determination of total SFA, MUFA, PUFA and trans FA contents of neat vegetable oils.     

Alteration in mouse splenic phospholipid fatty acid composition and lymphoid cell populations by dietary fat

The fatty acid composition of diacyl- and alkylacylglycerophosphocholine (PC), phosphatidylinositol (PI), phosphatidylserine (PS), alkenylacyl-glycerophosphoethanolamine (aPE), and diacyl- and alkylacyl-glycerophosphoethanolamine (dPE) was assessed in isolated splenocytes from C3H/Hen mice fed one of four purified isocaloric diets for six weeks. Diets contained 20% by weight of either a high-linoleate sunflower oil (Hi 18∶2), a high-oleate sunflower oil (Hi 18∶1), a mixture of 17% menhaden fish oil and 3% high-linoleate sunflower oil (Hi n−3), or a mixture of 17% coconut oil and 3% high-linoleate sunflower oil (Hi SFA). Spleen weight and immune cell yield were significantly higher (P<0.05) in mice fed the Hi 18∶1 or the Hi n−3 diets compared with those fed the Hi 18∶2 and Hi SFA diets. Distinctive patterns of fatty acids were observed for each phospholipid in response to dietary fatty acids. Dietary fat significantly affected (P<0.05) total polyunsaturated fatty acids (PUFA) in PC and dPE, total saturated fatty acids (SFA) in PC, total monounsaturated fatty acids (MUFA), and n−3 PUFA in all phospholipid classes examined. In mice fed the Hi n−3 diet, n−3 PUFA were significantly elevated, whereas n−6 PUFA decreased in all of the phospholipids. In these mice, eicosapentaenoic acid (EPA) was the predominant n−3 PUFA in PC and PI, whereas docosahexaenoic acid (DHA) was the major n−3 PUFA in aPE and PS. Interestingly, the ratios of n−3/n−6 PUFA in the phospholipids from these mice were 3.2, 2.4, 1.8, 0.8 and 0.8 for aPE, PS, dPE, PC and PI, respectively. These data suggest a preferential incorporation of n−3 PUFA into aPE, PS and dPE over PC and PI.     

Selective improvement of porcine fat firmness by a diet enriched in medium-chain fatty acids

The effects of 4% fat either rich in medium-chain fatty acids (MCFA; saturated fat) or in polyenoic fatty acids (PUFA; unsaturated fat) isoenergetically exchanging carbohydrates of a low-fat diet (control) on performance and product quality were evaluated with 180 growing pigs. Growth, carcass and meat quality were not affected by the fat treatments. Although elevated in blood serum, cholesterol was not increased in belly meat when the MCFA-rich diet was fed. Fatty acid composition of backfat reflected dietary fat composition. The significantly lowest shelf life and melting temperatures were found with the unsaturated-fat diet. When compared with control, fat tissue PUFA contents were slightly higher in the saturated-fat diet, and fat melting temperatures were somewhat lower. In contrast, the use of this MCFA-enriched diet increased penetrometer firmness in pure 4°C temperated backfat by more than 50% as compared with control and to about the tenfold level of the firmness obtained in the unsaturated-fat diet. Impression of flavour and odor in lean and fatty meat were not systematically affected by the diets. The present results show a high potential of MCFA-enriched diets to selectively increase fat firmness in pigs without greater undesired side effects on other traits of product quality.     

Different Ratios of Corn and Coconut Oil Blends in High-Fat Diets Influence Fat Deposition without Altering Metabolic Biomarkers in Male Rats

The effects of high-fat diets with the recommended dietary linoleic acid (LA) intake levels on health outcomes have not been studied extensively. This study investigated the effects of high-fat diets containing different weight ratios of coconut and corn oil with LA levels of <1.00% of energy (very low LA), 2.80% of energy (low LA), 5.80% of energy (moderate LA), and 9.70% of energy (high LA) on fat deposition and selected metabolic biomarkers of male Sprague-Dawley rats. Their initial and terminal body weights are recorded. Blood, adipose tissue, and liver samples are obtained for analysis after an 8-week feeding intervention. Compared with the very low-LA diet, the high-LA diet resulted in higher body weight gain and epididymal fat deposition. No significant differences are observed in liver-to-body weight ratio, blood glucose, visfatin, and leptin levels between the test diets. Serum tumor necrosis factor-alpha (TNF-α), insulin, and C-peptide levels do not significantly increase with the increase in dietary LA levels. High-LA diet results in higher LA levels in the liver and adipose tissue. It is concluded that a high-fat diet containing high LA levels induced body weight gain and epididymal fat deposition in rats but has no effect on selected metabolic biomarkers. Practical applications: Linoleic acid (LA) (C18:2) plays an important role as one of the nutritional elements to meet the daily essential fatty acid requirements. However, a full understanding is perplexed by the various ways that LA can be included in the diet when there is a recommendation to substitute saturated fatty acid (SFA), trans- or n-3 fatty acids intake. The data provide additional findings on the effects of excessive dietary intake of LA (C18:2) on fat deposition when different levels of SFAs are replaced.