Trans-fat Diet Research Articles

Dietary trans-fatty acid induced NASH is normalized following loss of trans-fatty acids from hepatic lipid pools.

Previous experiments in mice showed that dietary trans-fats could play a role in non-alcoholic steatohepatitis (NASH) yet little is known about the accumulation trans-fats in hepatic lipid pools in relationship to liver injury. NASH is also associated with obesity yet improves with only modest weight loss. To distinguish the role of obesity versus sustained consumption of a trans-fat containing diet in causing NASH, mice with obesity and NASH induced by consuming a high trans-fat diet for 16weeks were subsequently fed standard chow or maintained on trans-fat chow for another 8weeks. The accumulation, partitioning and loss of trans-fats in the major hepatic lipid pools during and after trans-fat consumption were determined. Obese mice switched to standard chow remained obese but steatohepatitis improved. trans-fats were differentially incorporated into the major hepatic lipid pools and the loss of trans-fats after crossover to control chow was greatest in the cholesteryl ester pool. In summary, dietary changes can improve the biochemical and histopathological changes of NASH despite persistent obesity in mice. Analysis of hepatic lipids confirmed that dietary trans-fats accumulate in the major lipid pools and are released differentially with diet normalization. The substantial loss of trans-fats from the cholesteryl ester pool in parallel with improvement in NASH suggests that this pool of trans-fats could play a role in the pathogenesis of NASH.

P87 Vascular Adhesion Protein-1 promotes increases in liver infiltrating CD4+ T cells and NKT cells and induction of fibrogenesis in steatohepatitis

IntroductionVascular Adhesion Protein-1 (VAP-1) is an adhesion molecule and membrane-bound amine oxidase. Our group has previously demonstrated that VAP-1 is able to support lymphocyte recruitment across human hepatic sinusoidal endothelium...

Loss of function mutation in toll-like receptor-4 does not offer protection against obesity and insulin resistance induced by a diet high in trans fat in mice

BackgroundToll-like receptor-4 (TLR4) triggers inflammatory signaling in response to microbial lipoploysaccharide. It has been reported that loss of TLR4 protected against saturated fat-induced inflammation and insulin resistance. It is not known whether loss of TLR4 function offers protection against trans fat (TF) induced obesity, inflammation, and insulin resistance. We investigated whether mice with loss of function mutation in TLR4 were resistant to TF-induced pathologies such as obesity, inflammation, hyperglycemia, and hyperinsulinemia.MethodsC57BL/6j and C57BL/10 mice were cross bred to generate TLR4 mutant and wild type (WT). TLR4 mutant (n = 12) and WT (n = 12) mice were fed either low fat (LF) (13.5% fat energy) or high TF diets (60% fat energy) for 12 weeks. In vitro experiments were conducted on mouse macrophage cells (RAW 264.7 and J774A.1) to investigate whether elaidic (trans 18:1) or oleic acid (cis 18:1) would upregulate inflammatory markers.ResultsTLR4 mutant mice were ~26.4% heavier than WT mice. In both genotypes, mice that received TF diet were significantly heavier than those mice that received LF diet (P < 0.01). TLR4 mutant mice compared to WT mice had significantly higher fasting blood glucose, serum insulin, insulin resistance, serum leptin, and serum cholesterol when they received TF diet (P < 0.05). No upregulation of iNOS or COX2 in response to either elaidic or oleic acid in macrophage cells was observed.ConclusionsLoss of function mutation in TLR4 not only did not protect mice from TF-induced obesity, hyperglycemia, hyperinsulinemia, and hypercholesterolemia but also exacerbated the above pathologies suggesting that functional TLR4 is necessary in attenuating TF-induced deleterious effects. It is likely that TF induces pathologies through pathways independent of TLR4.

Trans fat diet causes decreased brood size and shortened lifespan in Caenorhabditis elegans delta‐6‐desaturase mutant fat‐3

Trans-fatty acids (TFAs) enter the diet through industrial processes and can cause adverse human health effects. The present study was aimed to examine the effects of dietary cis- and trans-fatty acids on the model organism Caenorhabditis elegans. Cis- or trans-18:1n9 triglycerides (25 μM) caused no apparent changes in the numbers of viable progeny of wild-type N2 animals. However, in fat-3 mutants lacking delta-6-desaturase, the trans-isomer caused modest decreases in lifespan and progeny after three generations. Long-chain polyunsaturated fatty acids (PUFA) profiles were significantly altered in fat-3 mutants compared to wild type but were not altered after exposure to dietary cis- or trans-18:1n9. Genome-wide expression analysis of fat-3 mutants revealed hundreds of changes. Several genes involved in fat metabolism (acs-2, fat-7, mdt-15) were significantly increased by cis- or trans-18:1n9 without discrimination between isomers. These results provide support for the hypothesis that dietary trans fats are detrimental to development and aging.

High-Fructose, Medium Chain Trans Fat Diet Induces Liver Fibrosis and Elevates Plasma Coenzyme Q9 in a Novel Murine Model of Obesity and Nonalcoholic Steatohepatitis†

Diets high in saturated fat and fructose have been implicated in the development of obesity and nonalcoholic steatohepatitis (NASH) in humans. We hypothesized that mice exposed to a similar diet would develop NASH with fibrosis associated with increased hepatic oxidative stress that would be further reflected by increased plasma levels of the respiratory chain component, oxidized coenzyme Q9 ((ox)CoQ9). Adult male C57Bl/6 mice were randomly assigned to chow, high-fat (HF), or high-fat high-carbohydrate (HFHC) diets for 16 weeks. The chow and HF mice had free access to pure water, whereas the HFHC group received water with 55% fructose and 45% sucrose (wt/vol). The HFHC and HF groups had increased body weight, body fat mass, fasting glucose, and were insulin-resistant compared with chow mice. HF and HFHC consumed similar calories. Hepatic triglyceride content, plasma alanine aminotransferase, and liver weight were significantly increased in HF and HFHC mice compared with chow mice. Plasma cholesterol (P < 0.001), histological hepatic fibrosis, liver hydroxyproline content (P = 0.006), collagen 1 messenger RNA (P = 0.003), CD11b-F4/80+Gr1+ monocytes (P < 0.0001), transforming growth factor beta1 mRNA (P = 0.04), and alpha-smooth muscle actin messenger RNA (P = 0.001) levels were significantly increased in HFHC mice. Hepatic oxidative stress, as indicated by liver superoxide expression (P = 0.002), 4-hydroxynonenal, and plasma (ox)CoQ9 (P < 0.001) levels, was highest in HFHC mice. These findings demonstrate that nongenetically modified mice maintained on an HFHC diet in addition to developing obesity have increased hepatic ROS and a NASH-like phenotype with significant fibrosis. Plasma (ox)CoQ9 correlated with fibrosis progression. The mechanism of fibrosis may involve fructose inducing increased ROS associated with CD11b+F4/80+Gr1+ hepatic macrophage aggregation, resulting in transforming growth factor beta1-signaled collagen deposition and histologically visible hepatic fibrosis.

Trans fat feeding results in higher serum alanine aminotransferase and increased insulin resistance compared with a standard murine high-fat diet

Diets high in trans fats are associated with an increased risk of cardiovascular disease and components of the metabolic syndrome. The influence of these toxic fatty acids on the development of nonalcoholic fatty liver disease has not been significantly examined. Therefore, we sought to compare the effect of a murine diet high in trans fat to a standard high-fat diet that is devoid of trans fats but high in saturated fats. Male AKR/J mice were fed a calorically identical trans fat diet or standard high-fat diet for 10 days, 4 wk, and 8 wk. Serum alanine aminotransferase (ALT), lipid, insulin, and leptin levels were determined and the quantitative insulin-sensitivity check index (QUICKI) was calculated as a measure of insulin resistance. Additionally, hepatic triglyceride content and gene expression of several proinflammatory genes were assessed. By 8 wk, trans fat-fed mice exhibited higher ALT values than standard high-fat-fed mice (126 +/- 16 vs. 71 +/- 7 U/l, P < 0.02) despite similar hepatic triglyceride content at each time point. Trans fat-fed mice also had increased insulin resistance compared with high-fat-fed mice at 4 and 8 wk with significantly higher insulin levels and lower QUICKI values. Additionally, hepatic interleukin-1beta (IL-1beta) gene expression was 3.6-fold higher at 4 wk (P < 0.05) and 5-fold higher at 8 wk (P < 0.05) in trans fat-fed mice compared with standard high-fat-fed mice. Trans fat feeding results in higher ALT values, increased insulin resistance, and elevated IL-1beta levels compared with standard high-fat feeding.

Toll‐like receptor‐4 (TLR‐4) deficiency did not offer protection against trans fat or high fat diet‐induced hyperinsulinemia and hyperglycemia in mice

Low‐grade chronic inflammation is linked to insulin resistance, type‐2 diabetes, obesity, and atherosclerosis. TLR‐4 signaling plays an important role in inflammation. It has been reported that TLR‐4 deficiency offers protection against obesity and inflammatory response induced by diets high in fat. We investigated whether natural TLR‐4 mutation (BL‐10 background) protects against trans fat (TF) and high fat (HF) induced insulin resistance, hyperglycemia, and hyperleptinemia. TLR‐4 deficient and wild‐type (WT) mice were fed either low fat control (LF; 4.5%), TF (35%), or HF (35%) diets ad libitum for 12 weeks. Both groups of mice had significantly higher serum insulin, glucose, cholesterol, and leptin in response to TF and HF diets compared to LF control (P&lt;0.05). Mice fed TF diet had hepatomegaly regardless of TLR‐4 genotype. There was no significant difference in serum insulin, glucose, and triacylglycerol between TLR‐4 deficient and WT mice fed LF, TF, or HF diets. There was a tendency toward higher serum cholesterol in TLR‐4 deficient mice compared to WT mice, in all three diet groups. Neither TLR‐4 genotype nor diet type had effect on serum adiponectin. These data suggest that lack of TLR‐4 signaling does not confer protection against TF or HF induced hyperinsulinemia and hyperglycemia in BL‐10 mice. Supported by Intramural Grant from the College of Health and Human Sciences, Georgia State University.

A rodent model of NASH with cirrhosis, oval cell proliferation and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a well recognized complication of advanced NASH (non-alcoholic steatohepatitis). We sought to produce a rat model of NASH, cirrhosis and HCC. Adult Sprague-Dawley rats, weighing 250-300g, were fed a choline-deficient, high trans-fat diet and exposed to DEN in drinking water. After 16 weeks, the animals underwent liver ultrasound (US), sacrifice and assessment by microscopy, immunohistochemistry and transmission electron microscopy (TEM). US revealed steatosis and focal lesions in 6 of 7. All had steatohepatitis defined as inflammation, advanced fibrosis and ballooning with Mallory-Denk bodies (MDB) with frank cirrhosis in 6. Areas of more severe injury were associated with anti-CK19 positive ductular reaction. HCC, present in all, were macro-trabecullar or solid with polyhedral cells with foci of steatosis and ballooned cells. CK19 was positive in single or solid nests of oval cells and in neoplastic hepatocytes. TEM showed ballooning with small droplet fat, dilated endoplasmic reticulum and MDB in non-neoplastic hepatocytes and small droplet steatosis in some cancer cells. This model replicated many features of NASH including steatohepatitis with ballooning, fibrosis, cirrhosis and hepatocellular carcinoma. Oval cell proliferation was evident and the presence anti-CK 19 positivity in the cancer suggests oval cell origin of the malignancy.

Trans Fat Diet Induces Abdominal Obesity and Changes in Insulin Sensitivity in Monkeys

There is conflicting evidence about the propensity of trans fatty acids (TFAs) to cause obesity and insulin resistance. The effect of moderately high intake of dietary monounsaturated TFAs on body composition and indices of glucose metabolism was evaluated to determine any pro-diabetic effect in the absence of weight gain. Male African green monkeys (Chlorocebus aethiops; n=42) were assigned to diets containing either cis-monounsaturated fatty acids or an equivalent diet containing the trans-isomers (approximately 8% of energy) for 6 years. Total calories were supplied to provide maintenance energy requirements and were intended to not promote weight gain. Longitudinal body weight and abdominal fat distribution by computed tomography scan analysis at 6 years of study are reported. Fasting plasma insulin, glucose, and fructosamine concentrations were measured. Postprandial insulin and glucose concentrations, and insulin-stimulated serine/threonine protein kinase (Akt), insulin receptor activation, and tumor necrosis factor-alpha concentrations in subcutaneous fat and muscle were measured in subsets of animals. TFA-fed monkeys gained significant weight with increased intra-abdominal fat deposition. Impaired glucose disposal was implied by significant postprandial hyperinsulinemia, elevated fructosamine, and trends toward higher glucose concentrations. Significant reduction in muscle Akt phosphorylation from the TFA-fed monkeys suggested a mechanism for these changes in carbohydrate metabolism. Under controlled feeding conditions, long-term TFA consumption was an independent factor in weight gain. TFAs enhanced intra-abdominal deposition of fat, even in the absence of caloric excess, and were associated with insulin resistance, with evidence that there is impaired post-insulin receptor binding signal transduction.

Trans 지방산 함유 지방이 콜레스테롤대사와 간 세포막 유동성에 미치는 영향

식생활의 변화로 인해 fast food 및 가공식품의 소비가 급속히 증가하고 있으며 이러한 식품에 많이 함유되어 있는 trans 지방산의 생리적 기능에 대한 관심이 모아지고 있다. 따라서 본 연구에서는 한국인이 즐겨 섭취하는 유지중 trans 지방산 함량을 함유하고 있는 마가린, 버터의 장기간 섭취가 횐쥐의 콜레스테롤 대사와 세포막 유동성에 미치는 영향을 옥수수유와 비교하여 trans 지방산 함유 식품의 생리기능성을 제시하고자 하였다. 이유 직후의 흰쥐(S.D. male)를 trans 지방산 함량이 다른 마가린(25%)과 버터(8.5%), 옥수수유를 포함하는 식이로 각각 8주간 섭취시켜 사육한 결과, 체중증가와 1일 식이 섭취량은 식이군간에 차이가 없었으나 trans 지방산을 함유한 식이군(마가린, 버터)의 식이효율이 감소하였다. 혈장 지질 조성에서 중성지방 농도는 차이가 없었지만, 콜레스테롤 농도는 옥수수유 식이군에 비해 trans 지방산을 함유한 식이군에서 유의적으로 낮았다. 지단백 획분 중 LDL 콜레스테롤 농도는 옥수수유 식이군에 비해 마가린 식이군에서 유의적으로 낮았으며, 버터 식이군에서 유의적으로 높았다. HDL 콜레스테롤 농도는 버터 식이군이 다른 식이군에 비해 낮았으며 그 결과 버터 식이군의 동맥경화지수가 가장 높았다. 또한 간 중성지방 함량은 마가린과 옥수수유 식이군에 비해 버터 식이군에서 낮았으며 콜레스테롤의 농도는 옥수수유 식이군에서 가장 높았다. 간 조직으로의 trans 지방산의 축적 정도는 마가린 식이군에서 가장 높았으며 간의 HMG-CoA reductase 활성은 버터와 마가린 식이군에서 다소 감소하였다. 분변으로의 콜레스테롤 배설량은 trans 지방산을 함유한 마가린과 버터 식이군에서 유의적으로 높았으며 배설되는 trans 지방산 함량은 마가린 식이군에서 가장 높았다. 세포막 유동성은 옥수수유군에 비해 마가린과 버터식이군에서 유의적으로 감소하였다. 본 연구의 결과로 미루어 볼 때 trans 지방산 함유 지방 섭취에 의한 고콜레스테롤혈증 유발효과는 확인할 수 없었으며, trans 지방산의 섭취가 분변으로의 콜레스테롤 배설을 증가시키고 HMG-CoA reductase 활성을 저하시켜 혈장 콜레스테롤을 감소시킨 것으로 사료되며 버터군에서 동맥경화지수가 가장 높게 나타난 것은 버터의 포화지방산, 특히 미리스틴산과 팔미트산의 높은 함량 때문으로 사료된다. 그러나 마가린과 버터식이군의 세포막 유동성이 현저히 감소한 것은 세포막에서 trans 지방산이 포화지방산과 유사한 거동을 보이는 때문으로 풀이된다. Although negative evidences of trans fatty acids(tFAs) are gradually increasing, the hypercholesterolemic effect of tFAs are controversial and its biological significances are still not known. The objective of this study was to examine the effect of dietary tFAs on cholesterol metabolism and membrane fluidity in rats. Animals were fed diets containing 0.5% cholesterol and 20% test fats(margarine, butter, corn oil) for 8 weeks. Each test fats(margarine, butter, corn oil) contained 25%, 8.5% and no tFAs, respectively, Plasma total triglyceride(TG) were not different among diet treatments. Feeding trans fat diets (margarine and butter) lowered plasma cholesterol. Specially, butter diet elevated LDL-cholesterol and decreased HDL-cholesterol levels, resulting in the highest atherogenic index among diet treatments. Hepatic cholesterol concentration and HMG CoA reductase activity were also decreased, whereas fecal excretion of cholesterol was increased in trans fat-fed animals. trans fat containing diets also decreased hepatic membrane fluidity. From these results, it can be concluded that hypercholesterolemic effect of tFAs can be modulated by the fatty acid composition of diets, but its spatial cofiguration may help behave like saturated fatty acid in membrane fluidity.

Effects of Dietary Trans Fatty Acids on Mutagenesis of Known Carcinogens

The metabolic activating potential of liver homogenates from animals fed a diet containing 46.6% trans fatty acids or a diet containing less than .1% trans fatty acids was compared in the Ames assay with 2-aminofluorene (AF), benzo(a)pyrene (BP), and dimethylbenz(a)anthracene (DMBA). The control fat had a similar fatty acid composition only consisting of cis fatty acid (cis fats). Since both the cis and trans fats contained moderate levels of saturated fatty acids, a comparison was made between these two fats and corn oil. All three fats were incorporated into high fat, 20%, and low fat, 5%, diets and fed to male Sprague-Dawley rats for three weeks. Although the mutagenic potentials of AF and BP increased with increasing mutagen concentration and with increasing level of dietary fat, there was no consistent difference in mutagenic potential between the cis and trans fats. DMBA was mutagenic only at the two highest concentrations with livers from corn oil-fed rats. The mutagenic activating potential of S-9 from animals fed trans fat diets generally was similar to that of animals fed cis fat diets, but did not follow the trend of animals fed corn oil diets. Thus the amount and/or type of polyunsaturated fatty acids (essential fatty acids) present in the diet may be key factors in evaluating the enhancement of mutagenic activity of DMBA by dietary fat.

Influence of dietary cis- and trans-fat on 1,2-dimethylhydrazine-induced colon tumors and fecal steroid excretion in Fischer 344 rats.

To investigate the effects of the difference in the geometry of dietary fatty acids on colon tumorigenesis, male rats were fed semipurified diets containing either partially hydrogenated corn oil (trans-monoene fat) or olive oil (cis-monoene fat) at the 10% level and received a single oral dosage of 1,2-dimethylhydrazine (DMH). The difference in the fatty acid composition of dietary fats was confined essentially to the geometrical isomerism of octadecenoate, and the linoleic acid content was made equivalent (2% of total energy). After about 15 mo of feeding, colon tumor incidence in DMH treated rats was nearly the same in both fat groups. Fecal neutral steroid excretion was higher, while the transformation of cholesterol to coprostanol was lower in rats given the trans-fat. There were no marked differences in the excretion and composition of fecal bile acids between two fat groups. Serum cholesterol and tocopherol levels of rats given trans-fat diets tended to be low. The results suggested that the trans-monoene behaves much like the cis-monoene in the incidence of DMH-induced colon tumors, although there were characteristic differences in metabolic events in the intestine.

Cholesterol dynamics in rats fed cis- and trans-octadecenoate in the form of triglyceride.

The cholesterol dynamics were compared in rats fed diets containing either camellia oil or partially hydrogenated corn oil as a source of cis- and trans-octadecenoate, respectively. The diets contained approximately the same amount of octadecenoic acid, and an equivalent amount of linoleic acid. In rats fed the trans-fat for about 30 days, liver cholesterol levels were clearly low relative to levels in rats fed the cis-fat, while the concentration of serum cholesterol and the distribution of cholesterol in serum lipoproteins were comparable. The activity of hepatic microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase and the incorporation of [I-14C]acetate into digitonin-precipitable sterols in the liver homogenate tended to increase in rats fed the trans-fat diet. Cholesterol 7 alpha-hydroxylase activity increased significantly. Cholesterol absorption measured by the dual isotope serum ratio method was markedly lower, and much more radioactivity both from orally and intravenously administered cholesterol was excreted quickly into feces in the trans-fat group, with relatively more excretion in the neutral than in the acidic steroids. Apparent absorption of dietary fat was slightly lower in the trans-fat group. Cholesterol turnover as analyzed according to the two-pool model was much faster in rats fed trans-fat and the pool A size was reduced mainly as a consequence of stimulation of the removal rate from this pool. The intestinal epithelial cells contained relatively more trans-octadecenoate compared to the serum and liver and trans-fat modified the lipid composition specifically. These observations suggest that the changes in cholesterol metabolism due to the ingestion of trans-fat, compared to cis-fat, are as a result of metabolic events in the intestine.