Thermally oxidized oil increases the expression of insulin-induced genes and inhibits activation of sterol regulatory element-binding protein-2 in rat liver

Dietary oxidized frying oil activates hepatic stellate cells and accelerates the severity of carbon tetrachloride- and thioacetamide-induced liver fibrosis in mice

Deep-frying is a common cooking practice worldwide, and after repeated heating's, the oil undergoes various chemical reactions, including hydrolysis, polymerization, lipid oxidation, and the Maillard reaction. Studies have pointed out that oxidized dietary frying oil may cause teratogenesis in mice and increase cancer and cardiovascular risks. The liver is the main organ involved in dietary nutrient catabolism, detoxification, bile production, and lipid metabolism. Nevertheless, the effects of oxidized frying oil exposure on the activation of hepatic stellate cells (HSCs) and liver fibrosis are still unclear. In this study, we showed that exposure to oxidized frying oil enhanced the sensitivity of HSCs to transforming growth factor (TGF)-β1-induced α-smooth muscle actin (α-SMA), collagen 1a2, collagen 1a1, metalloproteinase-2, and phosphorylated smad2/3 activation. In both carbon tetrachloride (CCl₄)- and thioacetamide (TAA)-induced liver fibrosis mouse models, we showed that long-term administration of a 10% fried oil-containing diet significantly upregulated fibrogenesis genes expression and deposition of hepatic collagen. Furthermore, long-term fried oil exposure not only promoted macrophage infiltration and increased inflammatory-related gene expression, but also accumulated excess cholesterol and lipid peroxidation in the liver tissues. In conclusion, our study demonstrated that feeding a fried oil-containing diet may trigger TGF-β1-induced HSCs activation and thereby promote liver damage and fibrosis progression through enhancing the inflammatory response and lipid peroxidation.

Identification of Protective Amino Acid Metabolism Events in Nursery Pigs Fed Thermally Oxidized Corn Oil

Feeding thermally oxidized lipids to pigs has been shown to compromise growth and health, reduce energy digestibility, and disrupt lipid metabolism. However, the effects of feeding oxidized lipids on amino acid metabolism in pigs have not been well defined even though amino acids are indispensable for the subsistence of energy metabolism, protein synthesis, the antioxidant system, and many other functions essential for pig growth and health. In this study, oxidized corn oil (OCO)-elicited changes in amino acid homeostasis of nursery pigs were examined by metabolomics-based biochemical analysis. The results showed that serum and hepatic free amino acids and metabolites, including tryptophan, threonine, alanine, glutamate, and glutathione, as well as associated metabolic pathways, were selectively altered by feeding OCO, and more importantly, many of these metabolic events possess protective functions. Specifically, OCO activated tryptophan-nicotinamide adenosine dinucleotide (NAD⁺) synthesis by the transcriptional upregulation of the kynurenine pathway in tryptophan catabolism and promoted adenine nucleotide biosynthesis. Feeding OCO induced oxidative stress, causing decreases in glutathione (GSH)/oxidized glutathione (GSSG) ratio, carnosine, and ascorbic acid in the liver but simultaneously promoted antioxidant responses as shown by the increases in hepatic GSH and GSSG as well as the transcriptional upregulation of GSH metabolism-related enzymes. Moreover, OCO reduced the catabolism of threonine to α-ketobutyrate in the liver by inhibiting the threonine dehydratase (TDH) route. Overall, these protective metabolic events indicate that below a certain threshold of OCO consumption, nursery pigs are capable of overcoming the oxidative stress and metabolic challenges posed by the consumption of oxidized lipids by adjusting antioxidant, nutrient, and energy metabolism, partially through the transcriptional regulation of amino acid metabolism.

Deep-frying oil induces cytotoxicity, inflammation and apoptosis on intestinal epithelial cells

BACKGROUND

Deep-frying oil has been found to cause inflammatory bowel disease (IBD). However, the molecular mechanism of the effect of deep-frying palm oil on IBD still remains undetermined.

RESULTS

In the present study, bioinformatics and cell biology were used to investigate the functions and signal pathway enrichments of differentially expressed genes. The bioinformatics analysis of three original microarray datasets (GSE73661, GSE75214 and GSE126124) in the NCBI-Gene Expression Omnibus database showed 17 down-regulated genes (logFC < 0) and 2 up-regulated genes (logFC > 0) existed in the enteritis tissue. Meanwhile, pathway enrichment and protein-protein interaction network analysis suggested that IBD is relevant to cytotoxicity, inflammation and apoptosis. Furthermore, Caco-2 cells were treated with the main oxidation products of deep-frying oil-total polar compounds (TPC) and its components (polymerized triglyceride, oxidized triglycerides and triglyceride degradation products) isolated from deep-frying oil. The flow cytometry experiment revealed that TPC and its components could induce apoptosis, especially for oxidized triglyceride. A quantitative polymerase chain reaction analysis demonstrated that TPC and its component could induce Caco-2 cell apoptosis through AQP8/CXCL1/TNIP3/IL-1.

CONCLUSION

The present study provides fundamental knowledge for understanding the effects of deep-frying oils on the cytotoxic and inflammatory of Caco-2 cells, in addition to clarifying the molecular function mechanism of deep-frying oil in IBD. © 2021 Society of Chemical Industry.

Molecular dynamics revealed the effect of epoxy group on triglyceride digestion

The digestion behavior of epoxy triglyceride, the main cytotoxic product of deep-frying oil, remains unknown, which may affect its biosafety. In this study, epoxy triglyceride (EGT) and triglyceride (GT) were used to reveal the effect of epoxy group on digestion. Digestibility rate analysis showed that the free fatty acids release rate of EGT was slower. To clarify this phenomenon, binding ability with salt ions in digestive juice and particle size were also been studied. Cluster size analysis indicated that epoxy group increased triglyceride particle size, resulting in smaller contact area between EGT and lipase. Interface behaviors displayed EGT decreased binding ability with salt ions in digestive juice. Spectroscopic analysis showed EGT caused the red shift of lipase peak, indicating that epoxy group changed lipase structure. Molecular dynamics simulation suggested EGT leads to loosen lipase structure. In conclusion, this study highlights that epoxy group could weaken the triglyceride digestion.

Limitation and Potential Effects of Different Levels of Aging Corn on Performance, Antioxidative Capacity, Intestinal Health, and Microbiota in Broiler Chickens

Simple Summary

Corn is an important ingredient and staple food in China; thus, corn storage has a certain importance to ensure domestic food resources. Normally, corn has been stored for 3 or more years under the proper storage conditions in national barns before it is used as a feed ingredient. This study aimed to investigate the effect of different levels of aging corn (AC) on performance, antioxidative capacity, intestinal health, and microbiota in broilers. In the present study, AC grains were stored for 4 years under the proper storage conditions at the national storage facility. The results indicated that a lower level of AC diet showed improved performance and overall bird health than a higher level of AC, and comparable with a normal corn diet. However, antioxidative capacity is reduced by AC diets.

Abstract

Three-hundred and sixty-day-old male broilers underwent three treatments with six replicates of 20 birds per treatment. The experimental diets included NC: normal corn diet; ACL: lower level (39.6–41.24%) of AC; and ACH: a higher level (56.99–59.12%) of AC. During phase 1 (0–21 d), broilers fed on AC showed lower (p < 0.05) body weight (BW), body weight gain (BWG), and feed conversion ratio (FCR) as compared with the NC group. During phase 2 (22–42 d), the NC group and ACL group showed better (p < 0.05) BW, BWG, and FCR than the ACH group. The footpad lesion score (p = 0.05) and litter moisture percentage (p < 0.05) were found to be higher in the ACH group. During phase 1, the ACL group showed a lower level of malondialdehyde (MDA) contents (p < 0.05) in serum; moreover, catalase (CAT) (p < 0.05) and glutathione peroxidase (GSH-Px) activities (p < 0.05) were found lower in both AC-containing groups. During phase 2, CAT activity in serum was found higher (p < 0.05) in the ACH group. During phase 1, the NC group showed higher CAT (p = 0.05), GSH-Px (p < 0.05), and superoxide dismutase (SOD) activity (p = 0.03); however, it showed lower MDA (p < 0.05) and total-antioxidative capability (T-AOC) (p < 0.05) in the liver. During phase 1, in breast muscle, CAT, SOD, and T-AOC were higher (p < 0.05) in the NC group. During phase 1, total cholesterol and high-density lipoprotein were found to be lower (p < 0.05) in the ACL group. Similarly, triglyceride and low-density lipoprotein were found to be lower (p < 0.05) in the ACL group than the ACH group. During phase 1, villus height was found to be higher (p < 0.05) in the ACH group. Moreover, the goblet cell (GC) was found to be higher (p < 0.05) in the NC group than the ACL group. During phase 2, GC was found to be higher (p < 0.05) in the ACL group. In ileal digesta, during phase 1, acetic acid, propionic acid, and butyric acid (BA) levels were found to be higher (p < 0.05) in the ACL group. In cecal digesta, BA was significantly lower (p < 0.05) in the NC group.

Consuming oxidative frying oil impairs cardiac energy production and calcium recycling, causing cardiac hypertrophy, fibrosis and diastolic dysfunction in male Sprague Dawley rats

With regards to cardiovascular health, frequent consumption of fried foods is discouraged, despite a lack of clear evidence of a direct link between eating oxidative frying oil (OFO) and cardiovascular diseases. In this study, male Sprague Dawley rats were exposed to diets containing fresh or fried soybean oil (groups C and O, respectively) from in utero to 28 weeks of age. A subset of rats in group O was supplemented with vitamin E (500 mg/kg of DL-α-tocopherol acetate; group OE) from 8 week of age onward to mitigate oxidative stress associated with OFO ingestion. Echocardiography, cardiac histology and indices associated with ATP production and calcium cycling in cardiac tissues were measured. Compared to group C, there was cardiac hypertrophy, fibrosis and diastolic dysfunction, in groups O and OE, with no differences between the latter two groups. Although cardiac mRNA levels of genes associated with mitochondrial biogenesis and function were increased, there were lower ATP concentrations and higher transcripts of uncoupling proteins in groups O and OE than in group C. In addition, decreases in phosphorylation of phospholamban and Ca²⁺/calmodulin-dependent protein kinase II activity, plus increased protein phosphatase 2A activity in groups O and OE, implied calcium cycling required for cardiac function was disrupted by OFO consumption. We concluded that long-term OFO exposure resulted in cardiac hypertrophy, fibrosis and diastolic dysfunction that was not mitigated by vitamin E supplementation. Underlying mechanisms were partly attributed to inefficient energy production via uncoupled phosphorylation and disrupted calcium cycling.

Vitamin E improves antioxidant status but not lipid metabolism in laying hens fed a aged corn-containing diet

OBJECTIVE

The objective of this study was to determine whether a dietary vitamin E (VE) supplement could alleviate any detrimental effects of aged corn on lipid metabolism and antioxidant status in laying hens.

METHODS

The experiment consisted of a 2×3 factorial design with two corn types (normal corn and aged corn (stored for 4 yr) and three concentrations of VE (0, 20, and 100 IU/kg). A total of 216 Lohmann laying hens (50 wk of age) were randomly allocated into six treatment diets for 12 wk. Each treatment had 6 replicates of 6 hens per replicate.

RESULTS

The results show that aged corn significantly decreased the content of low-density lipoprotein cholesterol (p<0.05), and reduced chemokine-like receptor 1 (CMKLR1) mRNA expression (p<0.05) in the liver compared to controls. Diet with VE did not alter the content of crude fat and cholesterol (p>0.05), or acetyl-CoA carboxylase, lipoprotein lipase, fatty acid synthase or CMKLR1 mRNA expression (p>0.05) in the liver among treatment groups. Aged corn significantly increased the content of malondialdehyde (MDA) (p<0.05) and decreased superoxide dismutase (SOD) activity (p<0.05) in the liver. The VE increased the content of MDA (p<0.05) but decreased glutathione peroxidase (GSH-Px) activity in serum (p<0.01) and in the ovaries (p<0.05). Adding VE at 20 and 100 IU/kg significantly increased GSH-Px activity (p<0.05) in liver and in serum (p<0.01), 100 IU/kg VE significantly increased SOD activity (p<0.05) in serum. Aged corn had no significant effects on GSH-Px mRNA or SOD mRNA expression (p<0.01) in the liver and ovaries. Addition of 100 IU/kg VE could significantly increase SOD mRNA expression (p<0.01) in the liver and ovary.

CONCLUSION

Aged corn affected lipid metabolism and decreased the antioxidant function of laying hens. Dietary VE supplementation was unable to counteract the negative effects of aged corn on lipid metabolism. However, addition of 100 IU/kg VE prevented aged corninduced lipid peroxidation in the organs of laying hens.

Oxidized Oils and Oxidized Proteins Induce Apoptosis in Granulosa Cells by Increasing Oxidative Stress in Ovaries of Laying Hens

The storage and preparation of corn for animal feed inevitably lead to lipid and protein peroxidation. Granulosa cells play an important role in follicular development in the ovaries, and hen laying productivity is likely to be dependent on follicle health and number. We hypothesized that oxidized oil and protein induce apoptosis via oxidative stress in laying hen granulosa cells. A sample of 360 38-week-old Lohmann commercial laying hens was used in a 2 × 2 factorial design for 8 weeks. Dietary treatments included dietary oil (fresh corn oil (FO) or oxidized corn oil (OO)) and corn gluten meal (fresh corn gluten meal (FP) or oxidized corn gluten meal (OP)). Productivity, ovarian histology, granulosa cell apoptosis, and indicators of oxidative stress were evaluated in all groups. Both dietary OO and OP decreased egg production and the average daily feed intake (ADFI) of laying hens. Flow cytometry, TUNEL, and real-time PCR revealed that both dietary OO and OP induced granulosa cell apoptosis in prehierarchical and hierarchical follicles. Furthermore, dietary OO and OP caused oxidative stress in prehierarchical and hierarchical follicles, as indicated by the downregulation of antioxidant-related-gene expression. Moreover, forkhead box O1 (FoxO1), extracellular regulated protein kinase (ERK), and c-Jun NH₂ kinase (JNK) are involved in potential apoptosis regulation pathways in the granulosa cells of laying hens fed OO and OP, as indicated by the upregulation of FoxO1 expression and downregulation of ERK/JNK expression. These results indicate that OO and OP induce granulosa cell apoptosis via oxidative stress, and the combined use of OO and OP aggravates the adverse effects of oxidative stress in laying hens.

Dietary Exposure to Oxidized Frying Oil from Fetus to Adulthood Suppresses Male Reproductive Development by Altering Testicular Cholesterol and Testosterone Homeostasis in Sprague Dawley Rats

BACKGROUND

Dietary frying oil may have endocrine-disrupting effects, as a feminization effect was observed in cohorts of C57BL/6J male mice fetuses from dams consuming oxidized frying oil (OFO) during pregnancy.

OBJECTIVE

The aim of present study was to test the hypothesis that OFO is an anti-androgen.

METHODS

In experiment 1, male progeny of Sprague Dawley female rats fed fresh oil or an OFO diet (10 g fat/100 g, from fresh or 24-h-fried soybean oil; [control diet (C) and OFO groups, respectively] from midgestation through lactation were studied. Pups were weaned at 3 wk of age and then consumed their mothers' diet until 9 wk of age. In addition, a group of dams and pups that consumed a high-fat diet (HF; 10 g fried and 20 g fresh soybean oil/100 g) was included to counteract body-weight loss associated with OFO ingestion. Indices of male reproductive development and testosterone homeostasis were measured. In experiment 2, male rats were allocated to C and OFO groups (treated as above) and indices of male fertility compared at 9-10 wk of age.

RESULTS

In experiment 1, final body weights of the HF group were lower (17%) than the C group but higher (14%) than the OFO group (P < 0.0001 for each). In addition to abnormalities in seminiferous tubules, HF and OFO groups did not differ from one another, but, compared with the C group, had delayed preputial separation (4.9 d) and reductions in serum testosterone concentrations (17-74%), anogenital distance (8-20%), weights of androgen-dependent tissues (8-30%), testicular testosterone and cholesterol concentrations (30-40%), and mRNA levels of genes involved in steroidogenesis and cholesterol homeostasis (30-70%). In experiment 2, OFO-exposed males had 20% lower sperm motility (P < 0.05); however, when mated to normal females, pregnancy rates and litter sizes did not differ between OFO and C groups.

CONCLUSIONS

The anti-androgenic effect of OFO in Sprague Dawley rats was attributed to decreased testicular concentrations of cholesterol (testosterone precursor) and not body-weight loss.

Lactic Acid Bacteria With Antioxidant Activities Alleviating Oxidized Oil Induced Hepatic Injury in Mice

In order to screening new Lactic acid bacteria (LAB) strains to alleviating liver injury induced by oxidized oil, we isolated and screened LAB from Chinese fermented foods. Lactobacillus plantarum AR113, Pediococcus pentosaceus AR243, and Lactobacillus plantarum AR501 showed higher scavenging activity of α, α-Diphenyl-β-Picrylhydrazyl (DPPH) free radical and hydrogen radical, stronger inhibition of lipid peroxidation, and better protective effect on yeast cells in vitro. In vivo, oral administration of L. plantarum AR501 improved the antioxidant status of injury mice induced by oxidized oil including decreasing lipid peroxidation, recovering activities of antioxidant enzymes. Meanwhile, the gene expression of Nuclear factor erythroid 2-related factor 2 (Nrf2) of L. plantarum AR501 group was markedly elevated, and several antioxidant genes such as glutathione S-transferase (GSTO1), heme oxygenase-1 (HO-1), Glutamate cysteine ligase (GCL), and NAD(P)H:quinone oxidoreductase-l (NQO1) were subsequently up regulated in mice liver. Therefore, L. plantarum AR501 could be considered as potential candidates for production of functional foods that can alleviate the oxidative damage induced by oxidized oil.

Administration of repeatedly heated coconut oil alters lipid levels and antioxidant status in cholesterol fed rats

BACKGROUND: Oxidation products generated during repeated heating of cooking oils can participate in the development of cardiovascular diseases. OBJECTIVE: The purpose of the study was to investigate the effects of administration of high fat diet with and without cholesterol and to compare the effects of fresh and repeatedly heated coconut oil in rats. The effects of various diets containing coconut oil on lipid levels in serum and tissues, oxidative damage and antioxidant status in tissues were studied. METHODS: Coconut oil was heated at 210 ± 10°C for fifteen hours. Male Sprague Dawley rats were divided into four groups of six animals each and were fed the experimental diet for sixty days. RESULTS: Results revealed that rats fed high fat – cholesterol enriched diet significantly influenced the lipid levels and antioxidant status in experimental animals. The results indicate that repeated heating of coconut oil increased the lipid levels and oxidative stress in cholesterol fed rats. CONCLUSIONS: Study demonstrates that thermally stressed dietary oil increases the atherosclerotic tendency in experimental animals by inducing oxidative stress in addition to those induced by dietary cholesterol.

Effects of Polar Compounds Generated from the Deep-Frying Process of Palm Oil on Lipid Metabolism and Glucose Tolerance in Kunming Mice

In the present study, effects of deep-fried palm oil, specifically polar compounds generated during the frying process, on animal health including lipid and glucose metabolism and liver functions were investigated. Kunming mice were fed a high-fat diet containing deep-fried palm oil or purified polar compounds for 12 weeks. Their effects on animal health including hepatic lipid profile, antioxidant enzyme activity, serum biochemistry, and glucose tolerance were analyzed. Our results revealed that the consumption of polar compounds was related to the change of lipid deposition in liver and adipose tissue, as well as glucose tolerance alteration in Kunming mice. Correspondingly, the transcription study of genes involved in lipid metabolism including PPARα, Acox1, and Cpt1α indicated that polar compounds probably facilitated the fatty acid oxidation on peroxisomes, whereas lipid oxidation in mitochondria was suppressed. Furthermore, glucose tolerance test (GTT) revealed that a high amount of polar compound intake impaired glucose tolerance, indicating its effect on glucose metabolism in vivo. Our results provide critical information on the effects of polar compounds generated from the deep-frying process of palm oil on animal health, particularly liver functions and lipid and glucose metabolism, which is important for the evaluation of the biosafety of frying oil.

Resistant starch attenuates impaired lipid biosynthesis induced by dietary oxidized oil via activation of insulin signaling pathways

The current study found that deep-frying process led to an increased content of oxidized triacylglycerols in canola oil, 3.5 times higher than that of fresh canola oil (not used for frying).

Treatment with PPARα Agonist Clofibrate Inhibits the Transcription and Activation of SREBPs and Reduces Triglyceride and Cholesterol Levels in Liver of Broiler Chickens

PPARα agonist clofibrate reduces cholesterol and fatty acid concentrations in rodent liver by an inhibition of SREBP-dependent gene expression. In present study we investigated the regulation mechanisms of the triglyceride- and cholesterol-lowering effect of the PPARα agonist clofibrate in broiler chickens. We observed that PPARα agonist clofibrate decreases the mRNA and protein levels of LXRα and the mRNA and both precursor and nuclear protein levels of SREBP1 and SREBP2 as well as the mRNA levels of the SREBP1 (FASN and GPAM) and SREBP2 (HMGCR and LDLR) target genes in the liver of treated broiler chickens compared to control group, whereas the mRNA level of INSIG2, which inhibits SREBP activation, was increased in the liver of treated broiler chickens compared to control group. Taken together, the effects of PPARα agonist clofibrate on lipid metabolism in liver of broiler chickens involve inhibiting transcription and activation of SREBPs and SREBP-dependent lipogenic and cholesterologenic gene expression, thereby resulting in a reduction of the triglyceride and cholesterol levels in liver of broiler chickens.

Ingestion of thermally oxidized sunflower oil decreases postprandial lipemia mainly in younger individuals

Animal studies have shown that diets rich in thermally oxidized fat increase glucose and decrease insulin and triglyceride (TG) concentrations in the blood. We hypothesized that ingestion of a potato meal rich in thermally oxidized sunflower oil (TOSO) would decrease postprandial concentrations of insulin, incretins, and TG and increase plasma glucose concentrations. Twenty healthy subjects aged 22 to 70 years consumed meals rich in TOSO or unheated sunflower oil and containing paracetamol (1.5 g) in a randomized, crossover trial. Blood samples were taken at baseline and 10, 20, 30, 60, 90, and 120 minutes after the meals and glucose, insulin, TG, nonesterified fatty acids, glucagon-like polypeptide-1, glucose-independent polypeptide, and paracetamol (as a marker of gastric emptying) were measured in plasma or serum. The incremental areas under the curve of glucose, insulin, nonesterified fatty acid, incretins, and paracetamol levels were not significantly different between the meals. Plasma TG incremental area under the curve was 44% lower after the TOSO meal at a marginal level of significance (P = .06) in the total study population and was significantly (P = .04) and 61% lower in those of median age and younger (n = 11). These data suggest that ingestion of TOSO may acutely decrease plasma TG mainly in younger individuals and does not acutely affect glucose and insulin metabolism or gastric emptying in healthy subjects.

Dietary moderately oxidized oil induces expression of fibroblast growth factor 21 in the liver of pigs

Background

Fibroblast growth factor 21 (FGF21), whose expression is induced by peroxisome proliferator-activated receptor α (PPARα), has been recently identified as a novel metabolic regulator which plays a crucial role in glucose homeostasis, lipid metabolism, insulin sensitivity and obesity. Previous studies have shown that administration of oxidized fats leads to an activation of PPARα in the liver. Therefore, the present study investigated the hypothesis that feeding of oxidized fats causes an induction of FGF21 in the liver.

Methods

Twenty four crossbred pigs were allocated to two groups of 12 pigs each and fed nutritionally adequate diets with either fresh rapeseed oil or oxidized rapeseed oil prepared by heating at a temperature of 175°C for 72 h.

Results

In pigs fed the oxidized fat mRNA abundance and protein concentrations of FGF21 in liver were significantly increased (P < 0.05), and the protein concentrations of FGF21 in plasma tended to be increased (P < 0.1) in comparison to control pigs. Moreover, pigs fed the oxidized fat had increased transcript levels of the PPARα target genes acyl-CoA oxidase, carnitine palmitoyltransferase-1 and novel organic cation transporter 2 in the liver (P < 0.05), indicative of PPARα activation.

Conclusion

The present study shows for the first time that administration of an oxidized fat induces the expression of FGF21 in the liver, probably mediated by activation of PPARα. Induction of FGF21 could be involved in several effects observed in animals administered an oxidized fat.

Acrolein-induced dyslipidemia and acute-phase response are independent of HMG-CoA reductase

SCOPE

Aldehydes are ubiquitous natural constituents of foods, water and beverages. Dietary intake represents the greatest source of exposure to acrolein and related aldehydes. Oral acrolein induces dyslipidemia acutely and chronically increases atherosclerosis in mice, yet the mechanisms are unknown. Because lipid synthesis and trafficking are largely under hepatic control, we examined hepatic genes in murine models of acute and chronic oral acrolein exposure.

METHODS AND RESULTS

Changes in hepatic gene expression were examined using a Steroltalk microarray. Acute acrolein feeding modified plasma and hepatic proteins and increased plasma triglycerides within 15  min. By 6  h, acrolein altered hepatic gene expression including Insig1, Insig2 and Hmgcr genes and stimulated an acute-phase response (APR) with up-regulation of serum amyloid A genes (Saa) and systemic hypoalbuminemia. To test if decreased HMG-CoA reductase activity could modify acrolein-induced dyslipidemia or the APR, mice were pretreated with simvastatin. Statin treatment, however, did not alter acrolein-induced dyslipidemia or hypoalbuminemia associated with an APR. Few hepatic genes were dysregulated by chronic acrolein feeding in apoE-null mice. These studies confirmed that acute acrolein exposure altered expression of hepatic genes involved with lipid synthesis and trafficking and APR, and thus, indicated a hepatic locus of acrolein-induced dyslipidemia and APR that was independent of HMG CoA-reductase.

CONCLUSION

Dietary intake of acrolein could contribute to cardiovascular disease risk by disturbing hepatic function.

Monocarboxylate transporter 1 and CD147 are up-regulated by natural and synthetic peroxisome proliferator-activated receptor alpha agonists in livers of rodents and pigs

Monocarboxylate transporter (MCT)-1 mediates the transport of ketone bodies and other monocarboxylic acids across the plasma membrane. MCT1 is up-regulated by peroxisome proliferator-activated receptor (PPAR)-alpha, a transcription factor that mediates the adaptive response to fasting by up-regulation of genes involved in fatty acid oxidation and ketogenesis. Here, we show for the first time that MCT1 is up-regulated by dietary natural PPAR-alpha agonists. Both, an oxidized fat and conjugated linoleic acids increased MCT1 mRNA concentration in the liver of rats. Also, in the liver of pigs as non-proliferating species MCT1 was up-regulated upon PPAR-alpha activation by clofibrate, oxidized fat and fasting. Concomitant with up-regulation of MCT1, mRNA level of CD147 was increased in livers of rats and pigs. CD147 is a plasma membrane glycoprotein that is required for translocation and transport activity of MCT1. CD147 mRNA increase upon PPAR-alpha activation could not be observed in mice lacking PPAR-alpha, which also fail in up-regulation of MCT1 indicating a co-regulation of MCT1 and CD147. Analysis of the 5'-flanking region of mouse MCT1 gene by reporter gene assay revealed that promoter activity of mouse MCT1 was not induced by PPAR-alpha, indicating that the 5'-flanking region is not involved in MCT1 regulation by PPAR-alpha.

Feeding a thermally oxidised fat inhibits atherosclerotic plaque formation in the aortic root of LDL receptor-deficient mice

Activators of PPARα have been demonstrated to inhibit atherosclerosis development due to lipid lowering in plasma and direct protective effects on the vasculature. Because dietary oxidised fats (OF) have strong PPARα-activating and lipid-lowering properties, we hypothesised that dietary OF has also an inhibitory influence on atherosclerosis development. To verify our hypothesis, we investigated the effect of feeding diets containing an OF (a 92 : 8 mixture of heated (170°C, 48 h) hydrogenated palm fat and fresh sunflower oil) compared with a fresh fat (fresh hydrogenated palm fat) on the development of atherosclerotic lesions in LDL receptor-deficient (LDLR- / - ) mice. We observed that a dietary OF caused a strong up-regulation of PPARα-regulated genes in the liver and a marked reduction in plasma concentrations of cholesterol and TAG (P < 0·05). Cross-sectional lesion area and the lipids and collagen levels in the aortic root were approximately 40-50 % lower in mice fed diets containing OF than in those fed diets containing fresh fat (P < 0·05). Immunohistochemical analysis of aortic root sections revealed an about 8-fold increased expression of PPARα and a markedly reduced expression of the proinflammatory vascular cell adhesion molecule-1 and smooth muscle cell (SMC)-specific marker α-actin in LDLR- / - mice fed OF (P < 0·05). We postulate that OF exert anti-atherogenic effects by activation of PPARα both in the liver, which contributes to lipid lowering in plasma, and in the vasculature, which inhibits pro-atherogenic events such as monocyte recruitment and SMC proliferation and migration.

Effect of Chinese prescription Kangen-karyu on lipid metabolism in type 2 diabetic db/db mice

AIM OF THE STUDY

Chinese prescription Kangen-karyu is clinically used as a treatment for cardiovascular diseases, and we have reported the beneficial effects on chemically induced hyperlipidemic animal models. The present study was investigated to evaluate the hypolipidemic effect of Kangen-karyu in type 2 diabetic db/db mice which has not been explored yet.

MATERIALS AND METHODS

Male db/db mice were divided into three groups, vehicle (control), Kangen-karyu 100, or 200 mg/kg body weight/day, and orally administered for 5 weeks every day. Age-matched non-diabetic m/m mice were used as a normal group.

RESULTS

Serum triglyceride (TG) and total cholesterol levels in db/db mice were increased compared with those of m/m mice. However, the administration of Kangen-karyu reduced hyperlipidemia in db/db mice through a decline in the serum levels of TG and total cholesterol. The hepatic TG and total cholesterol levels of db/db mice were markedly higher than those of m/m mice, but these elevated lipid levels were significantly reduced by 200 mg/kg Kangen-karyu administration. Also, oil red O staining showed that the increased lipid deposition level in the liver of db/db control mice was improved by Kangen-karyu administration. The expression of sterol regulatory element-binding protein-1 in the liver of db/db mice was significantly down-regulated by the administration of Kangen-karyu at a dose of 200 mg/kg body weight. Kangen-karyu caused a slight elevation in the expression of peroxisome proliferator-activated receptor alpha in the liver of db/db mice.

CONCLUSIONS

This study provides scientific evidence that Kangen-karyu improves hyperlipidemia and lipid deposition via the regulation of hepatic SREBP-1 expression in type 2 diabetic db/db mice.

A novel body weight-loss promoting oil prepared with vegetable protein

It has been reported that oil thermally processed with wheat gluten (gluten oil) exhibited safe weight-loss promoting effects in animal experiments. However, as the oil has a high color index, and its chemical properties and smell differ from those of fresh oil, it is uncertain if the oil will find market acceptance. In order to resolve the issue, frying oil was heated with soybean protein under reduced pressure (soybean protein oil), resulting in a product with an appearance, chemical properties and smell comparable to those of fresh oil. This improved oil was mixed (7 wt%) with powdered AIN93G no fat, defined standard diet and fed to 10-week-old Wistar rats ad libitum. The experimental rats grew normally, ingesting the same amount as that of the control rats; however, there was a negative correlation between body weight increases and fecal weight increases. After the 12-week feeding period, all the rats were sacrificed to obtain blood and organs. In the experimental group, liver weight, retroperitoneal fat tissue weight and serum triacylglycerol (TG) levels decreased significantly. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), and histological analysis supported the safety of the improved oil. In conclusion, it was found that soybean protein oil inhibited body weight increases without any adverse effects in animal experiments. The oil holds promise as a novel dieting oil that steadily decreases body weight at an appropriate rate.

Acrolein consumption induces systemic dyslipidemia and lipoprotein modification

Aldehydes such as acrolein are ubiquitous pollutants present in automobile exhaust, cigarette, wood, and coal smoke. Such aldehydes are also constituents of several food substances and are present in drinking water, irrigation canals, and effluents from manufacturing plants. Oral intake represents the most significant source of exposure to acrolein and related aldehydes. To study the effects of short-term oral exposure to acrolein on lipoprotein levels and metabolism, adult mice were gavage-fed 0.1 to 5 mg acrolein/kg bwt and changes in plasma lipoproteins were assessed. Changes in hepatic gene expression related to lipid metabolism and cytokines were examined by qRT-PCR analysis. Acrolein feeding did not affect body weight, blood urea nitrogen, plasma creatinine, electrolytes, cytokines or liver enzymes, but increased plasma cholesterol and triglycerides. Similar results were obtained with apoE-null mice. Plasma lipoproteins from acrolein-fed mice showed altered electrophoretic mobility on agarose gels. Chromatographic analysis revealed elevated VLDL cholesterol, phospholipids, and triglycerides levels with little change in LDL or HDL. NMR analysis indicated shifts from small to large VLDL and from large to medium-small LDL with no change in the size of HDL particles. Increased plasma VLDL was associated with a significant decrease in post-heparin plasma hepatic lipase activity and a decrease in hepatic expression of hepatic lipase. These observations suggest that oral exposure to acrolein could induce or exacerbate systemic dyslipidemia and thereby contribute to cardiovascular disease risk.

Meta-analysis of the INSIG2 association with obesity including 74,345 individuals: does heterogeneity of estimates relate to study design?

The INSIG2 rs7566605 polymorphism was identified for obesity (BMI≥30 kg/m²) in one of the first genome-wide association studies, but replications were inconsistent. We collected statistics from 34 studies (n = 74,345), including general population (GP) studies, population-based studies with subjects selected for conditions related to a better health status (‘healthy population’, HP), and obesity studies (OB). We tested five hypotheses to explore potential sources of heterogeneity. The meta-analysis of 27 studies on Caucasian adults (n = 66,213) combining the different study designs did not support overall association of the CC-genotype with obesity, yielding an odds ratio (OR) of 1.05 (p-value = 0.27). The I² measure of 41% (p-value = 0.015) indicated between-study heterogeneity. Restricting to GP studies resulted in a declined I² measure of 11% (p-value = 0.33) and an OR of 1.10 (p-value = 0.015). Regarding the five hypotheses, our data showed (a) some difference between GP and HP studies (p-value = 0.012) and (b) an association in extreme comparisons (BMI≥32.5, 35.0, 37.5, 40.0 kg/m² versus BMI<25 kg/m²) yielding ORs of 1.16, 1.18, 1.22, or 1.27 (p-values 0.001 to 0.003), which was also underscored by significantly increased CC-genotype frequencies across BMI categories (10.4% to 12.5%, p-value for trend = 0.0002). We did not find evidence for differential ORs (c) among studies with higher than average obesity prevalence compared to lower, (d) among studies with BMI assessment after the year 2000 compared to those before, or (e) among studies from older populations compared to younger. Analysis of non-Caucasian adults (n = 4889) or children (n = 3243) yielded ORs of 1.01 (p-value = 0.94) or 1.15 (p-value = 0.22), respectively. There was no evidence for overall association of the rs7566605 polymorphism with obesity. Our data suggested an association with extreme degrees of obesity, and consequently heterogeneous effects from different study designs may mask an underlying association when unaccounted for. The importance of study design might be under-recognized in gene discovery and association replication so far.

A polymorphism of the INSIG2 gene was identified as being associated with obesity in one of the first genome-wide association studies. However, this association has since then been highly debated upon inconsistent subsequent reports. We collected association information from 34 studies including a total of 74,000 participants. In a meta-analysis of the 27 studies including 66,000 Caucasian adults, we found no overall association of this polymorphism rs7566605 with obesity, comparing subjects with a body-mass-index (BMI)≥30 kg/m² with normal BMI subjects (BMI<30 kg/m²). Our data suggested an association of this polymorphism with extreme obesity (e.g., BMI≥37.5 kg/m²) compared to normal controls. Such an association with extreme obesity might induce heterogeneous effects from different study designs depending on the proportion of extreme obesity included by the design. However, further studies would be required to substantiate this finding. The importance of study design might be under-recognized in gene discovery and association replication so far.

Vitamin E dependent microRNA regulation in rat liver

Dietary vitamin E (VE) is known to regulate gene expression by altering mRNA concentrations. Recently, microRNA (miRNA) have been discovered as a means of posttranscriptional gene regulation. Since the effect of VE on miRNA regulation is unknown, we fed rats for 6 months diets deficient or sufficient in VE and determined hepatic concentrations of miRNA involved in processes previously associated with VE (lipid metabolism, miRNA-122a; cancer and inflammation, miRNA-125b). VE-deficiency resulted in reduced concentrations of miRNA-122a and miRNA-125b. The findings of the present study demonstrate that differences in dietary VE may affect hepatic miRNA concentrations in vivo.