Dietary fat saturation produces lipid modifications in peritoneal macrophages of mouse

Supplementation with linoleic acid-rich soybean oil stimulates macrophage foam cell formation via increased oxidative stress and diacylglycerol acyltransferase1-mediated triglyceride biosynthesis

During the last decades there has been a staggering rise in human consumption of soybean oil (SO) and its major polyunsaturated fatty acid linoleic acid (LA). The role of SO or LA in cardiovascular diseases is highly controversial, and their impact on macrophage foam cell formation, the hallmark of early atherogenesis, is unclear. To investigate the effects of high SO or LA intake on macrophage lipid metabolism and the related mechanisms of action, C57BL/6 mice were orally supplemented with increasing levels of SO-based emulsion or equivalent levels of purified LA for 1 month, followed by analyses of lipid accumulation and peroxidation in aortas, serum and in peritoneal macrophages (MPM) of the mice. Lipid peroxidation and triglyceride mass in aortas from SO or LA supplemented mice were dose-dependently and significantly increased. In MPM from SO or LA supplemented mice, lipid peroxides were significantly increased and a marked accumulation of cellular triglycerides was found in accordance with enhanced triglyceride biosynthesis rate and overexpression of diacylglycerol acyltransferase1 (DGAT1), the key enzyme in triglyceride biosynthesis. In cultured J774A.1 macrophages treated with SO or LA, triglyceride accumulated via increased oxidative stress and a p38 mitogen-activated protein kinase (MAPK)-mediated overexpression of DGAT1. Accordingly, anti-oxidants (pomegranate polyphenols), inhibition of p38 MAPK (by SB202190) or DGAT1 (by oleanolic acid), all significantly attenuated SO or LA-induced macrophage triglyceride accumulation. These findings reveal novel mechanisms by which supplementation with SO or LA stimulate macrophage foam cell formation, suggesting a pro-atherogenic role for overconsumption of SO or LA. © 2016 BioFactors, 43(1):100-116, 2017.

Antihyperlipidemic and antitumor effects of chickpea albumin hydrolysate

This study was undertaken to determine the effects of chickpea albumin hydrolysate (CAH) on antihyperlipidemic and antitumor functions. The antihyperlipidemic results showed that CAH exhibited a dose dependent ability to decrease the levels of serum total cholesterol, triglyceride, LDL cholesterol (LDL-C), while increasing HDL cholesterol (HDL-C). Additionally, the appearance of the hyperlipidemic livers was ameliorated significantly. The antitumor results showed that CAH administration significantly increased the tumor inhibition rate and decreased tumor volume. CAH was also able to increase the spleen index and promote spleen lymphocyte proliferation. In addition, CAH treatment led to a remarkable rise in the superoxide dismutase (SOD) activity, while dramatically decreasing malondialdehyde (MDA) in the liver. Most importantly, we found that the physical conditions, such as appetite, activity, and coat luster of the mice in the CAH test group were better than those in the tumor control (TC) and positive control (PC) groups. These results taken together indicate that CAH warrants being further investigated and developed as an adjunctive element for hepatic lipid control, as well as antitumor and hypolipidemic therapies.

Paradoxical effect of a pequi oil-rich diet on the development of atherosclerosis: balance between antioxidant and hyperlipidemic properties

Pequi is the fruit of Caryocar brasiliense and its oil has a high concentration of monounsaturated and saturated fatty acids, which are anti- and pro-atherogenic agents, respectively, and of carotenoids, which give it antioxidant properties. Our objective was to study the effect of the intake of a cholesterol-rich diet supplemented with pequi oil, compared to the same diet containing soybean oil, on atherosclerosis development, and oxidative stress in atherosclerosis-susceptible LDL receptor-deficient mice (LDLr^−/−, C57BL/6-background). Female mice were fed a cholesterol-rich diet containing 7% soybean oil (Soybean group, N = 12) or 7% pequi oil (Pequi group, N = 12) for 6 weeks. The Pequi group presented a more atherogenic lipid profile and more advanced atherosclerotic lesions in the aortic root compared to the Soybean group. However, the Pequi group presented a less advanced lesion in the aorta than the Soybean group and showed lower lipid peroxidation (Soybean group: 50.2 ± 7.1; Pequi group: 30.0 ± 4.8 µmol MDA/mg protein) and anti-oxidized LDL autoantibodies (Soybean group: 35.7 ± 9.4; Pequi group: 15.6 ± 3.7 arbitrary units). Peritoneal macrophages from the Pequi group stimulated with zymosan showed a reduction in the release of reactive oxygen species compared to the Soybean group. Our data suggest that a pequi oil-rich diet slows atherogenesis in the initial stages, possibly due to its antioxidant activity. However, the increase of serum cholesterol induces a more prominent LDL migration toward the intimae of arteries, increasing the advanced atherosclerotic plaque. In conclusion, pequi oil associated with an atherogenic diet worsens the lipid profile and accelerates the formation of advanced atherosclerotic lesions despite its antioxidant action.

Short-term adaptation of postprandial lipoprotein secretion and intestinal gene expression to a high-fat diet

Western diet is characterized by a hypercaloric and hyperlipidic intake, enriched in saturated fats, that is associated with the increased occurrence of metabolic diseases. To cope with this overload of dietary lipids, the intestine, which delivers dietary lipids to the body, has to adapt its capacity in lipid absorption and lipoprotein synthesis. We have studied the early effects of a high-fat diet (HFD) on intestinal lipid metabolism in mice. After 7 days of HFD, mice displayed normal fasting triglyceridemia but postprandial hypertriglyceridemia. HFD induced a decreased number of secreted chylomicrons with increased associated triglycerides. Secretion of larger chylomicrons was correlated with increased intestinal microsomal triglyceride transfer protein (MTP) content and activity. Seven days of HFD induced a repression of genes involved in fatty acid synthesis (FAS, ACC) and an increased expression of genes involved in lipoprotein assembly (apoB, MTP, and apoA-IV), suggesting a coordinated control of intestinal lipid metabolism to manage a high-fat loading. Of note, the mature form of the transcription factor SREBP-1c was increased and translocated to the nucleus, suggesting that it could be involved in the coordinated control of gene transcription. Activation of SREBP-1c was partly independent of LXR. Moreover, HFD induced hepatic insulin resistance whereas intestine remained insulin sensitive. Altogether, these results demonstrate that a short-term HFD is sufficient to impact intestinal lipid metabolism, which might participate in the development of dyslipidemia and metabolic diseases.

Influence of dietary fat on oxidative stress and inflammation in murine macrophages

OBJECTIVE

Many studies have shown that the nature of the lipid consumed in the diet significantly affects the development of inflammatory diseases. In this study, we compared the effect of diets supplemented with 15% by weight of fish oil (FO), refined olive oil (ROO), and pomace olive oil (POO) with that of a low-fat diet, 2% by weight of corn oil, considered as the basal diet (BD), on the ability to modify reactive oxidative species and proinflammatory mediator generation by stimulated murine macrophages.

METHODS

Mice were fed the different oil-enriched diets for 8 wk. Peritoneal macrophages were isolated from these mice and subsequently stimulated. Reactive oxygen species and proinflammatory mediators were measured in the corresponding supernatants. Data were statistically treated by one-way analysis of variance and Tukey's multiple comparison post hoc test.

RESULTS

The ROO and POO significantly reduced the hydrogen peroxide production compared with BD, whereas FO stimulated its production. Moreover, the generation of nitric oxide was significantly prevented in all the experimental oil-enriched dietary groups. The ROO and FO groups showed significantly reduced cytokine (tumor necrosis factor-alpha, interleukin-1beta, interleukin-6) and prostaglandin E(2) production.

CONCLUSION

These results confirm the prevention action on proinflammatory mediator generation exerted by FO and demonstrate the protective antioxidant properties not only of olive oil but also of POO. The consumption of these olive oils may help to prevent cellular oxidative stress and inflammation.

Anti-hyperlipidemic effect of an edible brown algae, Ecklonia stolonifera, and its constituents on poloxamer 407-induced hyperlipidemic and cholesterol-fed rats

We conducted this study to isolate novel anti-hyperlipidemic agents derived from natural marine products. To accomplish this, we investigated the effects of ethanolic (EtOH) extracts of Ecklonia stolonifera and its phlorotannin constituents, eckol and dieckol, on serum lipid levels in rats with hyperlipidemia that was induced by a high-cholesterol diet or poloxamer 407. Treatment with the EtOH extracts of E. stolonifera and its phlorotannin-rich ethyl acetate (EtOAc) and n-butanol (n-BuOH) fractions induced a significant reduction in triglycerides (TG), total cholesterol (TC), and low-density lipoprotein-cholesterol (LDL-C) levels, as well as a significant increase in the high-density lipoprotein-cholesterol (HDLC) level in hyperlipidemic rats. However, treatment with the water (H(2)O) fraction did not exert any significant effects on the serum levels of hyperlipidemic rats. In addition, eckol and dieckol isolated from the active EtOAc fraction induced a significant reduction in serum TG, TC, and LDL-C levels, as well as in the atherogenic index (A.I.). Furthermore, treatment with dieckol induced a greater decrease in the serum TG, TC, and LDL-C levels of hyperlipidemic rats than eckol or lovastatin, as well as an increase in the serum HDL-C levels. Taken together, these results suggest that phlorotannins such as eckol and dieckol have the potential for use for the prevention of hyperlipidemic atherosclerosis.

Differential regulation of cholesterol homeostasis in transgenic mice expressing human cholesterol ester transfer proteinThis paper is one of a selection of papers published in this Special Issue, entitled The Cellular and Molecular Basis of Cardiovascular Dysfunction, Dhalla 70th Birthday Tribute

We investigated whether expression of cholesterol ester transfer protein (CETP) in mice alters the regulation of cholesterol metabolism. Transgenic mice expressing human CETP (CETP-TG) and nontransgenic littermates (non-TG) were fed either a monounsaturated fatty acid (MUFA) or a saturated fatty acid (SFA)-rich diet in the presence or absence of cholesterol. Mice fed with MUFA diet had higher CETP activity compared with SFA-fed mice. Addition of cholesterol to the MUFA diet decreased CETP activity, whereas addition of cholesterol to the SFA diet had no effect. Cholesterol 7α-hydroxylase (Cyp7a) activity was higher in CETP-TG mice compared with non-TG mice when fed a MUFA diet, whereas SFA fed CETP-TG mice showed lower Cyp7a activity as compared with non-TG. Microsomal triglyceride transfer protein (MTTP) activity was higher in CETP-TG mice compared with non-TG mice when fed a MUFA diet. HMG-CoA reductase activity was lower in CETP-TG mice compared with non-TG mice when fed a MUFA or a SFA diet. These data demonstrate that the regulation of Cyp7a, HMG-CoA reductase, and MTTP is altered in CETP-TG mice as compared with non-TG mice and these alterations are further modulated by the quality of dietary fats. These findings highlight the importance of CETP in regulating cholesterol homeostasis.

Antihyperlipidemic and antioxidant effects of extracts from Pleurotus citrinopileatus

Pleurotus citrinopileatus is a popular edible mushroom which is physiologically active in both humans and animals. In the study we investigate the effects of this mushroom on hyperlipidemic hamster rats. Four dietary forms of the mushroom were created as follows. The powdered dry fruiting body, hot-water extract, and two kinds of elutes were obtained, from ethyl acetate extract and methanol extract, respectively, in different mixed proportion solvents over silica gel column chromatography (referred to as EAE and MOE, respectively). They were tested at different dosages as a supplement to a high-fat diet in hyperlipidemic rats. Serum triglycerides and total cholesterol levels were significantly lower in groups supplemented with the highest dosages of EAE and MOE (0.5 g/kg, body weight daily) as compared with the control groups that received no mushroom additive. High-density lipoprotein levels in these same two experimental groups were also significantly higher than those in the negative control group. The tested rats that were fed with EAE had the highest serum glutathione peroxidase and superoxide dismutase activity, and those with the MOE and EAE had the highest DPPH free radical scavenging activities and ferric-reducing abilities, tested in vitro. The major constituents of MOE and EAE were identified as ergosterol and nicotinic acid, respectively. P. citrinopileatus extracts may have a significant antihyperlipidemia effect. Furthermore, antioxidant activities and antihyperlipidemic effects of MOE and EAE seemed to display similar tendencies.

Effect of five cysteine-containing compounds on three lipogenic enzymes in Balb/cA mice consuming a high saturated fat diet

The in vivo effects of N-acetyl cysteine (NAC), S-allyl cysteine, S-ethyl cysteine (SEC), S-methyl cysteine (SMC), and S-propyl cysteine (SPC) against hyperlipidemia development and oxidation stress in Balb/cA mice consuming a high saturated fat diet were examined. The influence of these agents on plasma levels of glucose, insulin, uric acid, TG, cholesterol, and the activity of three lipogenic enzymes--glucose-6-phosphate dehydrogenase, malic enzyme, and FA synthase--was determined. All mice consumed the coconut oil-basd, high saturated fat diet, water, and cysteine or one of the five cysteine-containing compounds for 4 wk. The diet with 18% saturated fat significantly elevated the activity of three lipogenic enzymes and significantly increased TG and cholesterol biosynthesis in plasma and liver (P < 0.05). When compared with the water and cysteine groups, the treatments from five cysteine-containing agents significantly reduced high saturated fat diet-increased malic enzyme and FA synthase activities, and significantly lowered TG levels in plasma and liver (P< 0.05); however, only NAC, SAC, and SMC treatments significantly reduced cholesterol levels in plasma and liver (P < 0.05). The five cysteine-containing agents significantly restored high saturated fat diet-decreased glutathione peroxidase (GPX) activity in liver (P< 0.05); however, only SMC and SPC significantly restored GPX activity in heart and kidney (P< 0.05). These agents also significantly improved high saturated fat diet-related hyperglycemia, hyperuricemia, and oxidation stress (P < 0.05). These data support the hypothesis that these compounds are potential multiply-protective agents for hyperlipidemia prevention or therapy.

Dietary α-linolenic acid increases brain but not heart and liver docosahexaenoic acid levels

Fish oil-enriched diets increase n-3 FA in tissue phospholipids; however, a similar effect by plant-derived n-3 FA is poorly defined. To address this question, we determined mass changes in phospholipid FA, individual phospholipid classes, and cholesterol in the liver, heart, and brain of rats fed diets enriched in flax oil (rich in 18:3n-3), fish oil (rich in 22:6n-3 and 20:5n-3), or safflower oil (rich in 18:2n-6) for 8 wk. In the heart and liver phospholipids, 22:6n-3 levels increased only in the fish oil group, although rats fed flax oil accumulated 20:5n-3 and 22:5n-3. However, in the brain, the flax and fish oil diets increased the phospholipid 22:6n-3 mass. In all tissues, these diets decreased the 20:4n-6 mass, although the effect was more marked in the fish oil than in the flax oil group. Although these data do not provide direct evidence for 18:3n-3 elongation and desaturation by the brain, they demonstrate that 18:3n-3-enriched diets reduced tissue 20:4n-6 levels and increased cellular n-3 levels in a tissue-dependent manner. We hypothesize, based on the lack of increased 22:6n-3 but increased 18:3n-3 in the liver and heart, that the flax oil diet increased circulating 18:3n-3, thereby presenting tissue with this EFA for further elongation and desaturation.