Low omega-6/omega-3 polyunsaturated fatty acid ratios reduce hepatic C-reactive protein expression in apolipoprotein E-null mice

Impact of dietary n-6/n-3 fatty acid ratio of atherosclerosis risk: A review

Atherosclerosis is a causative factor associated with cardiovascular disease (CVD). Over the past few decades, extensive research has been carried out on the relationship between the n-6/n-3 fatty acid ratio of ingested lipids and the progression of atherosclerosis. However, there are still many uncertainties regarding the precise nature of this relationship, which has led to challenges in providing sound dietary advice to the general public. There is therefore a pressing need to review our current understanding of the relationship between the dietary n-6/n-3 fatty acid ratio and atherosclerosis, and to summarize the underlying factors contributing to the current uncertainties. Initially, this article reviews the association between the n-6/n-3 fatty acid ratio and CVDs in different countries. A summary of the current understanding of the molecular mechanisms of n-6/n-3 fatty acid ratio on atherosclerosis is then given, including inflammatory responses, lipid metabolism, low-density lipoprotein cholesterol oxidation, and vascular function. Possible reasons behind the current controversies on the relationship between the n-6/n-3 fatty acid ratio and atherosclerosis are then provided, including the precise molecular structures of the fatty acids, diet-gene interactions, the role of fat-soluble phytochemicals, and the impact of other nutritional factors. An important objective of this article is to highlight areas where further research is needed to clarify the role of n-6/n-3 fatty acid ratio on atherosclerosis.

Lowering n-6/n-3 Ratio as an Important Dietary Intervention to Prevent LPS-Inducible Dyslipidemia and Hepatic Abnormalities in ob/ob Mice

Obesity is closely associated with low-grade chronic and systemic inflammation and dyslipidemia, and the consumption of omega-3 polyunsaturated fatty acids (n-3 PUFAs) may modulate obesity-related disorders, such as inflammation and dyslipidemia. An emerging research question is to understand the dietary intervention strategy that is more important regarding n-3 PUFA consumption: (1) a lower ratio of n-6/n-3 PUFAs or (2) a higher amount of n-3 PUFAs consumption. To understand the desirable dietary intervention method of n-3 PUFAs consumption, we replaced lard from the experimental diets with either perilla oil (PO) or corn oil (CO) to have identical n-3 amounts in the experimental diets. PO had a lower n-6/n-3 ratio, whereas CO contained higher amounts of PUFAs; it inherently contained relatively lower n-3 but higher n-6 PUFAs than PO. After the 12-week dietary intervention in ob/ob mice, dyslipidemia was observed in the normal chow and CO-fed ob/ob mice; however, PO feeding increased the high density lipoprotein-cholesterol (HDL-C) level; further, not only did the HDL-C level increase, the low density lipoprotein-cholesterol (LDL-C) and triglyceride (TG) levels also decreased significantly after lipopolysaccharide (LPS) injection. Consequently, extra TG accumulated in the liver and white adipose tissue (WAT) of normal chow- or CO-fed ob/ob mice after LPS injection; however, PO consumption decreased serum TG accumulation in the liver and WAT. PUFAs replacement attenuated systemic inflammation induced by LPS injection by increasing anti-inflammatory cytokines but inhibiting pro-inflammatory cytokine production in the serum and WAT. PO further decreased hepatic inflammation and fibrosis in comparison with the ND and CO. Hepatic functional biomarkers (aspartate aminotransferase (AST) and alanine transaminase (ALT) levels) were also remarkably decreased in the PO group. In LPS-challenged ob/ob mice, PO and CO decreased adipocyte size and adipokine secretion, with a reduction in phosphorylation of MAPKs compared to the ND group. In addition, LPS-inducible endoplasmic reticulum (ER) and oxidative stress decreased with consumption of PUFAs. Taken together, PUFAs from PO and CO play a role in regulating obesity-related disorders. Moreover, PO, which possesses a lower ratio of n-6/n-3 PUFAs, remarkably alleviated metabolic dysfunction in LPS-induced ob/ob mice. Therefore, an interventional trial considering the ratio of n-6/n-3 PUFAs may be desirable for modulating metabolic complications, such as inflammatory responses and ER stress in the circulation, liver, and/or WAT.

The Effects of Fish Oil on Cardiovascular Diseases: Systematical Evaluation and Recent Advance

Fish oil is rich in unsaturated fatty acids, i.e., eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both of which are widely distributed in the body such as heart and brain. In vivo and in vitro experiments showed that unsaturated fatty acids may have effects of anti-inflammation, anti-oxidation, protecting vascular endothelial cells, thrombosis inhibition, modifying autonomic nerve function, improving left ventricular remodeling, and regulating blood lipid. Given the relevance to public health, there has been increasing interest in the research of potential cardioprotective effects of fish oil. Accumulated evidence showed that fish oil supplementation may reduce the risk of cardiovascular events, and, in specific, it may have potential benefits in improving the prognosis of patients with hypertension, coronary heart disease, cardiac arrhythmias, or heart failure; however, some studies yielded inconsistent results. In this article, we performed an updated systematical review in order to provide a contemporary understanding with regard to the effects of fish oil on cardiovascular diseases.

Combined Effects of Plant Sterols with Low Ratio of n-6/n-3 Polyunsaturated Fatty Acids against Atherosclerosis in ApoE-/- Mice

The effects of low ratio of n-6/n-3 polyunsaturated fatty acids (PUFA) have been clarified against atherosclerosis. Increasing evidence indicated that plant sterols (PS) have a significant cholesterol-lowering effect. This study explored the effects of PS combined with n-6/n-3 (2:1) PUFA on atherosclerosis and investigated the possible mechanism. In ApoE^-/- mice, the milk fat in high fat diets was replaced with n-6/n-3 (2:1) PUFA alone or supplemented with 6% PS for 16 weeks. Results demonstrated that PS combined with PUFA exerted commentary and synergistic effects on ameliorating atherosclerosis, improving lipid metabolism and lipid deposition in liver, and alleviating inflammatory response. These changes were accompanied with decreased serum TC, TG, LDL-C and increased fecal cholesterol efflux, as well as the lower inflammatory cytokine CRP, IL-6, TNF-α. It is suggested that the underlying mechanism of PS combined with n-6/n-3 (2:1) PUFA promoting the fecal cholesterol efflux may be mediated by liver X receptor α/ATP-binding cassette transporter A1 pathway.

Current Research Landscape of Marine-Derived Anti-Atherosclerotic Substances

Atherosclerosis is a chronic disease characterized by lipid accumulation and chronic inflammation of the arterial wall, which is the pathological basis for coronary heart disease, cerebrovascular disease and thromboembolic disease. Currently, there is a lack of low-cost therapeutic agents that effectively slow the progression of atherosclerosis. Therefore, the development of new drugs is urgently needed. The research and development of marine-derived drugs have gained increasing interest from researchers across the world. Many marine organisms provide a rich material basis for the development of atherosclerotic drugs. This review focuses on the latest technological advances in the structures and mechanisms of action of marine-derived anti-atherosclerotic substances and the challenges of the application of these substances including marine polysaccharides, proteins and peptides, polyunsaturated fatty acids and small molecule compounds. Here, we describe the theoretical basis of marine biological resources in the treatment of atherosclerosis.

Characterization of spontaneous hydrocephalus development in the young atherosclerosis-prone mice

Little has been reported on whether abnormal lipid metabolism affects hydrocephalus, although congenital malformations and infectious diseases are major causal factors for hydrocephalus development. In a study on the pathogenesis of atherogenesis in mice, we unexpectedly discovered that hydrocephalus occurred in partial apolipoptotein E (apoE) and low-density lipoprotein receptor (LDLR) double-knockout (apoE/LDLR) mice fed either chow or a high-fat and high-cholesterol diet between the ages of 4 and 12 weeks. In the 12-week-old high-fat and high-cholesterol group, the incidence rate was as high as 15%. Transcription levels of transforming growth factor-β1 (TGF-β1), Smad3, Smad4, and Smad7 in the cortex of the hydrocephalic cerebrum were significant downregulated in 4-week-old mice, but were increased in the 8 and 12-week-old groups compared with that of age-matched nonhydrocephalic mice. The mRNA level of tissue inhibitor of metalloproteinases 1 was significantly increased, whereas matrix metalloproteinase-9 was lower in hydrocephalic mice of all ages. The translation level of TGF-β1 increased in the hydrocephalic brains of 8 and 12-week-old mice. This study provides primary evidence for the connection between lipid metabolic disorder and hydrocephalus development. This may suggest that both hyperglyceridemia and hypercholesterolemia are harmful factors in hydrocephalus development because of adverse effects on TGF-β1/Smad signaling in the brain.

Altered Adipogenesis in Zebrafish Larvae Following High Fat Diet and Chemical Exposure Is Visualised by Stimulated Raman Scattering Microscopy

Early life stage exposure to environmental chemicals may play a role in obesity by altering adipogenesis; however, robust in vivo methods to quantify these effects are lacking. The goal of this study was to analyze the effects of developmental exposure to chemicals on adipogenesis in the zebrafish (Danio rerio). We used label-free Stimulated Raman Scattering (SRS) microscopy for the first time to image zebrafish adipogenesis at 15 days post fertilization (dpf) and compared standard feed conditions (StF) to a high fat diet (HFD) or high glucose diet (HGD). We also exposed zebrafish embryos to a non-toxic concentration of tributyltin (TBT, 1 nM) or Tris(1,3-dichloroisopropyl)phosphate (TDCiPP, 0.5 µM) from 0-6 dpf and reared larvae to 15 dpf under StF. Potential molecular mechanisms of altered adipogenesis were examined by qPCR. Diet-dependent modulation of adipogenesis was observed, with HFD resulting in a threefold increase in larvae with adipocytes, compared to StF and HGD. Developmental exposure to TBT but not TDCiPP significantly increased adipocyte differentiation. The expression of adipogenic genes such as pparda, lxr and lepa was altered in response to HFD or chemicals. This study shows that SRS microscopy can be successfully applied to zebrafish to visualize and quantify adipogenesis, and is a powerful approach for identifying obesogenic chemicals in vivo.

Comparative effects of plant oils and trans-fat on blood lipid profiles and ischemic stroke in rats

Since plant oils are believed to be better than animal fats for cerebrovascular and cardiovascular diseases, the effects of various plant oils and trans-fat on blood lipid profiles and ischemic stroke were investigated. Sprague-Dawley rats were fed a diet containing the oils or trans-fat, and then body weights, blood lipids, and effects on brain infarction and physical dysfunction induced by middle cerebral artery occlusion (MCAO) were analyzed. All the oils and trans-fat, except perilla oil, significantly increased body fats and body weight gain. Sesame oil and trans-fat specifically increased blood cholesterols and triglycerides, respectively, while perilla oil decreased both cholesterols and triglycerides. Perilla oil not only attenuated cerebral infarction, but also restored locomotor activity and rota-rod performances of MCAO rats. It is suggested that perilla oil among oils and fats could be the first choice to reduce the risk of metabolic syndrome and ischemic stroke.

Anti-atherosclerotic effects of perilla oil in rabbits fed a high-cholesterol diet

Anti-atherosclerosis effects of perilla oil were investigated, in comparison with lovastatin, in rabbits fed a high-cholesterol diet (HCD). Hypercholesterolemia was induced in rabbits by feeding the HCD containing 0.5% cholesterol and 1% corn oil, and perilla oil (0.1 or 0.3%) was added to the diet containing 0.5% cholesterol for 10 weeks. HCD greatly increased blood total cholesterol and low-density lipoproteins, and caused thick atheromatous plaques, covering 74% of the aortic wall. Hyper-cholesterolemia also induced lipid accumulation in the liver and kidneys, leading to lipid peroxidation. Perilla oil not only attenuated hypercholesterolemia and atheroma formation, but also reduced fat accumulation and lipid peroxidation in hepatic and renal tissues. The results indicate that perilla oil prevents atherosclerosis and fatty liver by controlling lipid metabolism, and that it could be the first choice oil to improve diet-induced metabolic syndrome.

Comparative effects of plant oils on the cerebral hemorrhage in stroke-prone spontaneously hypertensive rats

OBJECTIVES

Since oils and fats can induce metabolic syndrome, leading to cardiovascular and cerebrovascular diseases, the present study was performed to find out whether the plant oils affect the cerebral hemorrhage in stroke-prone spontaneously hypertensive (SHR-SP) rats.

METHODS

From 47 days of age, male SHR-SP rats were given drinking water containing 1% NaCl to induce hypertension, and simultaneously fed semi-purified diets containing 10% perilla oil, canola oil, or shortening. The onset time of convulsion following cerebral hemorrhage was recorded, and the areas of hemorrhage and infarction were analyzed in the stroke brains.

RESULTS

In comparison with 58-day survival of SHR-SP rats during feeding NaCl alone, perilla oil extended the survival time to 68.5 days, whereas canola oil shortened it to 45.7 days. Feeding perilla oil greatly reduced the total volume of cerebral hemorrhage from 17.27% in the control group to 4.53%, while shortening increased the lesions to 21.23%. In a microscopic analysis, perilla oil also markedly decreased the hemorrhagic and infarction lesions to 1/10 of those in control rats, in contrast to an exacerbating effect of shortening. In blood analyses, perilla oil reduced blood total cholesterol and low-density lipoproteins which were increased in SHR-SP, but canola oil further increased them and markedly lowered platelet counts.

DISCUSSION

Perilla oil delayed and attenuated cerebral hemorrhage by improving hyperlipidemia in hypertensive stroke animals, in contrast to the aggravating potential of canola oil and shortening. It is suggested that perilla oil should be the first choice oil for improving metabolic syndrome in hypertensive persons at risk of hemorrhagic stroke.

A protective lipidomic biosignature associated with a balanced omega-6/omega-3 ratio in fat-1 transgenic mice

A balanced omega-6/omega-3 polyunsaturated fatty acid (PUFA) ratio has been linked to health benefits and the prevention of many chronic diseases. Current dietary intervention studies with different sources of omega-3 fatty acids (omega-3) lack appropriate control diets and carry many other confounding factors derived from genetic and environmental variability. In our study, we used the fat-1 transgenic mouse model as a proxy for long-term omega-3 supplementation to determine, in a well-controlled manner, the molecular phenotype associated with a balanced omega-6/omega-3 ratio. The fat-1 mouse can convert omega-6 to omega-3 PUFAs, which protect against a wide variety of diseases including chronic inflammatory diseases and cancer. Both wild-type (WT) and fat-1 mice were subjected to an identical diet containing 10% corn oil, which has a high omega-6 content similar to that of the Western diet, for a six-month duration. We used a multi-platform lipidomic approach to compare the plasma lipidome between fat-1 and WT mice. In fat-1 mice, an unbiased profiling showed a significant increase in the levels of unesterified eicosapentaenoic acid (EPA), EPA-containing cholesteryl ester, and omega-3 lysophosphospholipids. The increase in omega-3 lipids is accompanied by a significant reduction in omega-6 unesterified docosapentaenoic acid (omega-6 DPA) and DPA-containing cholesteryl ester as well as omega-6 phospholipids and triacylglycerides. Targeted lipidomics profiling highlighted a remarkable increase in EPA-derived diols and epoxides formed via the cytochrome P450 (CYP450) pathway in the plasma of fat-1 mice compared with WT mice. Integration of the results of untargeted and targeted analyses has identified a lipidomic biosignature that may underlie the healthful phenotype associated with a balanced omega-6/omega-3 ratio, and can potentially be used as a circulating biomarker for monitoring the health status and the efficacy of omega-3 intervention in humans.

Perilla oil improves blood flow through inhibition of platelet aggregation and thrombus formation

The inhibitory effects of perilla oil on the platelet aggregation in vitro and thrombosis in vivo were investigated in comparison with aspirin, a well-known blood flow enhancer. Rabbit platelet-rich plasma was incubated with perilla oil and aggregation inducers collagen or thrombin, and the platelet aggregation rate was analyzed. Perilla oil significantly inhibited both the collagen- and thrombin-induced platelet aggregations, in which the thromboxane B₂ formation from collagen-activated platelets were reduced in a concentration-dependent manner. Rats were administered once daily by gavage with perilla oil for 1 week, carotid arterial thrombosis was induced by applying 35% FeCl₃-soaked filter paper for 10 min, and the blood flow was monitored with a laser Doppler probe. Perilla oil delayed the FeCl₃-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at 0.5 mL/kg. In addition, a high dose (2 mL/kg) of perilla oil greatly prevented the occlusion, comparable to the effect of aspirin (30 mg/kg). The results indicate that perilla oil inhibit platelet aggregation by blocking thromboxane formation, and thereby delay thrombosis following oxidative arterial wall injury. Therefore, it is proposed that perilla oil could be a good candidate without adverse effects for the improvement of blood flow.

Nutritional influences on age-related skeletal muscle loss

Age-related muscle loss impacts on whole-body metabolism and leads to frailty and sarcopenia, which are risk factors for fractures and mortality. Although nutrients are integral to muscle metabolism the relationship between nutrition and muscle loss has only been extensively investigated for protein and amino acids. The objective of the present paper is to describe other aspects of nutrition and their association with skeletal muscle mass. Mechanisms for muscle loss relate to imbalance in protein turnover with a number of anabolic pathways of which the mechanistic TOR pathway and the IGF-1–Akt–FoxO pathways are the most characterised. In terms of catabolism the ubiquitin proteasome system, apoptosis, autophagy, inflammation, oxidation and insulin resistance are among the major mechanisms proposed. The limited research associating vitamin D, alcohol, dietary acid–base load, dietary fat and anti-oxidant nutrients with age-related muscle loss is described. Vitamin D may be protective for muscle loss; a more alkalinogenic diet and diets higher in the anti-oxidant nutrients vitamin C and vitamin E may also prevent muscle loss. Although present recommendations for prevention of sarcopenia focus on protein, and to some extent on vitamin D, other aspects of the diet including fruits and vegetables should be considered. Clearly, more research into other aspects of nutrition and their role in prevention of muscle loss is required.

Atherosclerosis prevention by nutritional factors: a meta-analysis in small animal models

BACKGROUND AND AIMS

Atherosclerosis prevention in small laboratory models has been used as a preclinical stage in the development of functional foods with claimed antiatherogenic properties. However, a high heterogeneity of experimental atherosclerosis models as well as species-specific differences in lipoprotein metabolism could limit the usefulness of these developments. To solve this, we have performed a meta-analysis on the effects of nutritional complements (i.e. less than 2% of diet) with potential antiatherogenic properties in mice, rabbits and hamsters, and compared the outcomes with those obtained in humans.

METHODS AND RESULTS

A meta-analysis comprising works dealing with dietary prevention of experimental atherosclerosis (i.e. macroscopic and/or pathological evidences of atheromatosis in aorta) has been performed (n = 110 works). Quality criteria were applied resulting in selection of 16 works comprising 511 animals. Despite high heterogeneity, there is a significant effect of nutritional interventions reducing atheroma globally (mean effect 24.38% (95% CI: 13.24-35.51%) of prevention). In mouse studies (20.64% (95% CI: 8.38-32.90%)) and in rabbits (40.48% (95% CI: 6.73-74.23%)) this effect was significant, in contrast with hamster-based works (95% CI: 13.66-49.48%). Meta-regression showed that reduction of atheroma plaque formation was not linked to changes either in total circulating cholesterol or LDL cholesterol levels.

CONCLUSION

Nutritional addition of selected compounds significantly prevents experimental atheromatosis, but the reproduction of positive effects observed in humans was very limited. These analyses reinforce the need for adequate standardization of atherosclerosis studies in preclinical models and for human intervention trials.

Characterization of monocyte chemoattractant proteins and CC chemokine receptor 2 expression during atherogenesis in apolipoprotein E-null mice

AIM

We aimed to investigate the expression of monocyte chemoattractant proteins (MCPs) and their cognate receptor CC chemokine receptor 2 (CCR2) in aortas of apolipoprotein E-null (apoE(-/-)) mice during atherogenesis as well as the possible transcription pathway involved in the early induction of MCP-1 in vascular smooth muscle cells (VSMCs) in vivo.

METHODS

Atherosclerotic lesion development, aortic MCPs and CCR2 mRNA expression as well as the cellular localization of MCP-1, CCR2 and MCP-1 related transcription factors in atherosclerotic lesions were analyzed in apoE(-/-) mice fed a high fat and cholesterol diet.

RESULTS

MCP-1 and CCR2 mRNA expression was significantly induced during early atherogenesis and peaked after 10 and 12 weeks of diet, respectively, whereas MCP-2 and MCP-3 mRNA expression elevated in the late phases of lesion development. Immunostaining revealed that early MCP-1 expression was localized to VSMCs and that, in advanced lesions, both neointimal VSMCs and intimal macrophages expressed high levels of MCP-1. During the early (0 and 4 weeks of diet) induction of MCP-1 in VSMCs, the regulatory activator protein-1 (AP-1) proteins c-Jun and c-Fos were highly expressed and observed within the VSMCs nuclei, whereas nuclear factor-κB (NF-κB) protein p65 was only observed within the nuclei of VSMCs after 4 weeks of diet. CCR2 was also identified on intimal macrophages, endothelial cells and VSMCs in advanced lesions.

CONCLUSION

This study provides fundamental information on the expression kinetics of MCPs and CCR2 during atherogenesis and indicates that the earliest induction of MCP-1 in VSMCs of apoE(-/-)mice appears to correlate with AP-1 but not NF-κB regulatory pathways.