Monounsaturated fatty acids and atherosclerosis: opposing views from epidemiology and experimental animal models

Fatty acids act on vascular endothelial cells and influence the development of cardiovascular disease

Endothelial cells (ECs) maintain the health of blood vessels and prevent the development of cardiovascular disease (CVD). Free saturated fatty acids (FAs) induce EC damage and increase the risk of CVD by promoting arteriosclerosis. Conversely, polyunsaturated FAs (PUFAs), such as docosahexaenoic acid, are thought to suppress EC damage induced during the early stages of CVD. This review describes the effects of multiple dietary FAs on EC disorders involved in the development of CVD. The roles of FAs in atherosclerosis and CVD were analyzed by evaluating articles published in PubMed, Science Direct, and Web of Science. Saturated FAs were found to induce EC damage by reducing the production and action of EC-derived nitric oxide. Oxidative stress, inflammation, and the renin-angiotensin system were found to be involved in EC disorder. Furthermore, n-3 PUFAs were found to reduce EC dysfunction and prevent the development of EC disorder. These results indicate that FAs may affect EC failure induced during the early stages of CVD and reduce the risk of developing the disease.

Docosahexaenoic acid-rich fish oil alleviates hepatic steatosis in association with regulation of gut microbiome in ob/ob mice

It remains to study whether docosahexaenoic acid-rich fish oil (DHA-FO) improves hepatic lipid metabolism by leptin-independent mechanisms. We used ob/ob mice as a model to investigate the effects of DHA-FO on hepatic steatosis. DHA-FO inhibited lipid droplets (LD) formation in liver of ob/ob mice. Probably because DHA-FO consumption prevented the accumulation of oleic acid, and suppressed the synthesis of triglycerides and cholesteryl esters. These beneficial effects might be concerned with the promotion of short chain fatty acids (SCFAs) production. Furthermore, DHA-FO could reverse gut bacteria dysbiosis, including increasing the abundance of SCFAs producers (e.g. Akkermansia and unclassified_Muribaculaceae), and suppressing the proliferation of conditional pathogenic bacteria, such as unclassified_Lachnospiraceae. DHA-FO also promoted colonic microbial function ("Glycerolipid metabolism") associated with lipid metabolism. As a potential ingredient for functional food, DHA-FO reduced LD accumulation, which might be associated with modulation of obesity-linked gut microbiome in ob/ob mice.

Mediterranean and MIND Diets Containing Olive Biophenols Reduces the Prevalence of Alzheimer's Disease

The risk of Alzheimer’s disease (AD) increases with nonmodifiable conditions including age and lack of effective efficacious pharmacotherapy. During the past decades, the non-pharmacotherapy mode of treatment of dietary modification received extensive attention in AD research. In order to reduce the AD pathology and cognitive decline, various dietary patterns have been attempted including caloric restriction (CR), dietary approaches to stop hypertension (DASH), ketogenic diets (KD), Mediterranean diet (MedDi) and Mediterranean-DASH diet Intervention for Neurological Delay (MIND) diet. Higher adherence to the MedDi diet was associated with decreases in cardiovascular and neurological disorders including AD and related cognitive decline. However, another emerging healthy dietary pattern MIND diet has also been associated with slower rates of cognitive decline and significant reduction of AD rate. Olive serves as one of the building block components of MedDi and MIND diets and the exerted potential health beneficial might be suggested due to the presence of its bioactive constituents such as oleic acids and phenolic compounds (biophenols). A few trials using medical food showed an optimal result in presymptomatic or early stages of AD. The review supports the notion that MedDi and MIND diets display potential for maintaining the cognitive function as nonpharmacological agents against AD pathology and proposed preventative mechanism through the presence of olive biophenols and presents the gaps along with the future directions.

The monounsaturated fatty acid oleate is the major physiological toxic free fatty acid for human beta cells

Free fatty acids (FFAs) can cause glucose intolerance and diabetes. Lipotoxicity to the pancreatic beta cells is considered to be a major underlying cause for this phenomenon. The aim of this study was to analyse the toxicity profile of FFAs in the human EndoC-βH1 beta-cell line and to compare the results with isolated rat and human islets with special reference to the physiologically most prevalent FFAs palmitic acid (PA) and oleic acid (OA). Toxicity after a 2-day incubation with the different FFAs was analysed by the caspase-3 assay and confirmed by the propidium iodide and annexin V staining tests. The long-chain saturated PA (C16:0) and the monounsaturated OA (C18:1) were both toxic to human EndoC-βH1 beta cells and pseudoislets, as well as to rat islets, and, as confirmed in a pilot experiment, also to human islets. Furthermore, OA provided no protection against the toxicity of PA. Likewise, elaidic acid (EA, the trans isomer of OA; trans-OA) was significantly toxic, in contrast to the non-metabolisable analogues methylated PA (MePA) and methylated OA (MeOA). Fatty acids with a chain length  < C16 were not toxic in EndoC-βH1 beta cells. Caspase-3 was also activated by linoleic acid (LA)(C18:2) but not by γ-linolenic acid (γ-LNA)(C18:3). Overall, only long-chain FFAs with chain lengths  > C14, which generate hydrogen peroxide in the peroxisomal beta-oxidation, were toxic. This conclusion is also supported by the toxicity of the branched-chain FFA pristanic acid, which is exclusively metabolised in the peroxisomal beta-oxidation. The lack of a protective effect of the monounsaturated fatty acid OA has important consequences for a beta-cell protective lipid composition of a diet. A cardioprotective diet with a high OA content does not fulfil this requirement.

Anti-obesity effect of a traditional Chinese dietary habit-blending lard with vegetable oil while cooking

Obesity, which is associated with dietary habits, has become a global social problem and causes many metabolic diseases. In China, both percentages of adult obesity and overweight are far lower compared to western countries. It was designed to increase the two levels of daily intake in human, namely 3.8% and 6.5%, which are recommendatory intake (25 g/d) and Chinese citizens' practical intake (41.4 g/d), respectively. The mice were respectively fed with feeds added with soybean oil, lard or the oil blended by both for 12 weeks. In the mice fed with diet containing 3.8% of the three oils or 6.5% blended oil, their body weight, body fat rate, cross-sectional area of adipocytes, adipogenesis and lipogenesis in adipose were decreased, whereas hydrolysis of triglyserides in adipose was increased. This study demonstrated that the oil mixture containing lard and soybean oil had a remarkable anti-obesity effect. It suggests that the traditional Chinese dietary habits using oils blended with lard and soybean oil, might be one of the factors of lower percentages of overweight and obesity in China, and that the increasing of dietary oil intake and the changing of its component resulted in the increasing of obesity rate in China over the past decades.

Alteration of fatty acid profile and nucleotide-related substances in post-mortem breast meat of α-lipoic acid-fed broiler chickens

The present study was conducted to determine the effects of α-lipoic acid supplementation on post-mortem changes in the fatty acid profile and concentrations of nucleotide-related substances, especially those of a taste-active compound, inosine 5'-monophosphate, in chicken meat. Mixed-sex broiler chicks aged 14 d were divided into three groups of 16 birds each and were fed on diets supplemented with α-lipoic acid at levels of 0, 100 or 200 mg/kg for 4 weeks. Blood and breast muscle samples were taken at 42 d of age under the fed condition and then after fasting for 18 h. The breast muscle obtained from fasted chickens was subsequently refrigerated at 2°C for one and 3 d. α-Lipoic acid supplementation did not affect any plasma metabolite concentration independently of feeding condition, while a slight increase in plasma glucose concentration was shown with both administration levels of α-lipoic acid. In early post-mortem breast muscle under the fed condition, α-lipoic acid had no effect on concentrations of fatty acids or nucleotides of ATP, ADP, and AMP. In post-mortem breast tissues obtained from fasted chickens, total fatty acid concentrations were markedly increased by α-lipoic acid feeding at 200 mg/kg irrespective of length of refrigeration. This effect was dependent on stearic acid, oleic acid, linoleic acid and linolenic acid. However, among fatty acids, the only predominantly increased unsaturated fatty acid was oleic acid. Dietary supplementation with α-lipoic acid at 200 mg/kg increased the inosine 5'-monophosphate concentration in breast meat and, in contrast, reduced the subsequent catabolites, inosine and xanthine, regardless of the length of refrigeration. Therefore, the present study suggests that α-lipoic acid administration altered the fatty acid profile and improved meat quality by increasing taste-active substances in the post-mortem meat obtained from fasted chickens.

Clinical Strategies for Managing Dyslipidemias

Dyslipidemia is defined as elevated fasting blood levels of total cholesterol (TC), and its primary lipoprotein carrier—low-density lipoprotein (LDL), triglycerides (TG), or reduced high-density lipoprotein (HDL), alone, or in combination (mixed dyslipidemia). Dyslipidemia is well known to be associated with cardiovascular disease (CVD) risk. All patients with dyslipidemia should initiate therapeutic lifestyle changes to target lifestyle-related factors such as physical inactivity, dietary habits, and obesity. The combination of a proper dietary plan and regular aerobic exercise has been reported to lower TC, LDL-C, and TG by 7% to 18%, while increasing HDL-C by 2% to 18%. Numerous pharmacological therapies are available and aggressive therapy using a HMG-CoA reductase (3-hydroxy-3-methyl-glutaryl coenzyme A reductase) inhibitor (statins) should be initiated if lifestyle therapy is not enough to achieve optimal lipid levels with a primary target of lowering LDL-C levels. Aggressive treatment of dyslipidemia with maximal dosage of statin drugs have been reported to reduce LDL-C by 30% to 60%. If mixed dyslipidemia is present, a combination therapy with statin, niacin, cholestyramine, or fibrates should be initiated to reduce the risk of CVD events. These strategies have been shown to reduce CVD risk and optimize LDL-C levels in primary and secondary prevention of CVD.

Nutrition, nonalcoholic fatty liver disease and the microbiome: recent progress in the field

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide and it has overlapping pathogenesis with diabetes and cardiovascular disease. Reviewed here are recent advances in understanding the contribution of diet and selected nutrients to NAFLD.

RECENT FINDINGS

To understand the effect of diet, the microbiome must be considered because it is the interface of diet and the liver. Early studies suggest that the characteristic of the microbiota is altered in NAFLD. Fructose is a lipogenic carbohydrate that contributes to insulin resistance, hypertriglyceridemia and appears to be associated with the severity of NAFLD. Fructose absorption and malabsorption may alter the microbiota and could be mediating effects on the liver. Lipids also have potent microbiome interactions and could contribute to the benefit of diets emphasizing lipid changes. Several new studies demonstrate that the Mediterranean diet and 'lifestyle change' are effective in modestly improving NAFLD. A new study of 'lifestyle' in children showed simultaneous improvement in cardiovascular disease risk measurements and hepatic steatosis.

SUMMARY

Current data supports limiting sugar in the diet and 'lifestyle change' as a first-line treatment for NAFLD; however, the benefits from these appear to be modest. The effects of diet on the liver are mediated through the microbiome and expansion of research in this area is needed.

Predicted changes in fatty acid intakes, plasma lipids, and cardiovascular disease risk following replacement of trans fatty acid-containing soybean oil with application-appropriate alternatives

The varied functional requirements satisfied by trans fatty acid (TFA)--containing oils constrains the selection of alternative fats and oils for use as potential replacements in specific food applications. We aimed to model the effects of replacing TFA-containing partially hydrogenated soybean oil (PHSBO) with application-appropriate alternatives on population fatty acid intakes, plasma lipids, and cardiovascular disease (CVD) risk. Using the National Health and Nutrition Examination Survey 24-hour dietary recalls for 1999-2002, we selected 25 food categories, accounting for 86 % of soybean oil (SBO) and 79 % of TFA intake for replacement modeling. Before modeling, those in the middle quintile had a mean PHSBO TFA intake of 1.2 % of energy. PHSBO replacement in applications requiring thermal stability by either low-linolenic acid SBO or mid-oleic, low-linolenic acid SBO decreased TFA intake by 0.3 % of energy and predicted CVD risk by 0.7-0.8 %. PHSBO replacement in applications requiring functional properties with palm-based oils reduced TFA intake by 0.8 % of energy, increased palmitic acid intake by 1.0 % of energy, and reduced predicted CVD risk by 0.4 %, whereas replacement with fully hydrogenated interesterified SBO reduced TFA intake by 0.7 % of energy, increased stearic acid intake by 1.0 % of energy, and decreased predicted CVD risk by 1.2 %. PHSBO replacement in both thermal and functional applications reduced TFA intake by 1.0 % of energy and predicted CVD risk by 1.5 %. Based solely on changes in plasma lipids and lipoproteins, all PHSBO replacement models reduced estimated CVD risk, albeit less than previously reported using simpler replacement models.

The role of nutraceutical supplements in the treatment of dyslipidemia

The combination of a lipid-lowering diet and scientifically proven nutraceutical supplements has the ability to significantly reduce low-density lipoprotein (LDL) cholesterol, increase LDL particle size, decrease LDL particle number, lower trigylcerides and very LDL levels, and increase total and high-density lipoprotein 2b cholesterol. In addition, inflammation, oxidative stress, and immune responses are decreased. In several prospective clinical trials, coronary heart disease and cardiovascular disease have been reduced with many nutraceutical supplements. This nutritional and nutraceutical supplement treatment is a valid alternative for patients who are intolerant to statins, cannot take other drugs for the treatment of dyslipidemia, or prefer alternative treatments. This new approach to lipid management to decrease vascular disease utilizes a functional medicine approach with a broader treatment program that will address the multitude of steps involved in lipid-induced vascular damage.

Pretreatment with n-6 PUFA protects against subsequent high fat diet induced atherosclerosis--potential role of oxidative stress-induced antioxidant defense

OBJECTIVES

Recent evidence suggests that oxidative stress can promote antioxidant defense and thus be athero-protective. n-6 polyunsaturated fatty acids (n-6 PUFA) are more prone to oxidation, compared to monounsaturated fatty acids (MUFA) and yet have proven anti-atherosclerotic effects. In this study, we tested whether early exposure to a diet rich in n-6 PUFA, compared to a MUFA rich diet would reduce lesion burden, even with subsequent exposure to a high fat, high cholesterol diet (HF). Further, we tested to determine whether oxidative mechanisms are involved in such protection.

METHODS AND RESULTS

Twenty four, 4 week old, male, LDL receptor knockout (LDL-R(-/-)) mice were divided into two groups and fed either a n-6 PUFA rich or a MUFA rich diet for a period of 12 weeks. At this point, 4 mice from each group were euthanized and the remaining 8 mice from each group were fed a HF diet for four weeks. Atherosclerotic lesions, plasma lipids, autoantibodies to lipid peroxide modified proteins, isoprostanes and aortic catalase levels were measured. The n-6 PUFA diet reduced aortic lesions and plasma lipids compared to the MUFA diet and this reduction in lesions continued even after the mice were switched over to the HF diet, despite the fact that the plasma lipids were similar in both groups after the HF diet. n-6 PUFA fed mice had highest plasma isoprostane levels, indicating oxidative stress, but also had higher levels of aortic catalase. On the other hand, MUFA fed mice had comparatively lower levels of isoprostanes and their aortic catalase levels remained low. Finally, aortic lesions were negatively correlated with isoprostanes and catalase.

CONCLUSION

An initial exposure to a n-6 PUFA rich diet compared to a MUFA rich diet reduces atherosclerotic lesions and this protection probably involves oxidative stress induced by PUFA.

The role of reducing intakes of saturated fat in the prevention of cardiovascular disease: where does the evidence stand in 2010?

Current dietary recommendations advise reducing the intake of saturated fatty acids (SFAs) to reduce coronary heart disease (CHD) risk, but recent findings question the role of SFAs. This expert panel reviewed the evidence and reached the following conclusions: the evidence from epidemiologic, clinical, and mechanistic studies is consistent in finding that the risk of CHD is reduced when SFAs are replaced with polyunsaturated fatty acids (PUFAs). In populations who consume a Western diet, the replacement of 1% of energy from SFAs with PUFAs lowers LDL cholesterol and is likely to produce a reduction in CHD incidence of ≥2-3%. No clear benefit of substituting carbohydrates for SFAs has been shown, although there might be a benefit if the carbohydrate is unrefined and has a low glycemic index. Insufficient evidence exists to judge the effect on CHD risk of replacing SFAs with MUFAs. No clear association between SFA intake relative to refined carbohydrates and the risk of insulin resistance and diabetes has been shown. The effect of diet on a single biomarker is insufficient evidence to assess CHD risk. The combination of multiple biomarkers and the use of clinical endpoints could help substantiate the effects on CHD. Furthermore, the effect of particular foods on CHD cannot be predicted solely by their content of total SFAs because individual SFAs may have different cardiovascular effects and major SFA food sources contain other constituents that could influence CHD risk. Research is needed to clarify the role of SFAs compared with specific forms of carbohydrates in CHD risk and to compare specific foods with appropriate alternatives.

Dietary monounsaturated fatty acids appear not to provide cardioprotection

Dietary interventions have been consistently proposed as a part of a comprehensive strategy to lower the incidence and severity of coronary heart disease (CHD), in the process providing long-term cardioprotection. Replacement of dietary saturated fatty acids (SFA) with higher intakes of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) has been reported to be inversely associated with risk of CHD. The observed lower incidence of CHD among populations consuming a Mediterranean-type diet, mainly enriched in MUFA from olive oil, has long supported the belief that MUFA are an optimal substitution for SFA. However, both epidemiologic and interventional studies suggest that although substituting MUFA-rich foods for SFA-rich foods in the diet can potentially lower total plasma cholesterol concentrations, this substitution does not lower the extent of coronary artery atherosclerosis. In addition, although recent evidence suggests that the source of MUFA (animal fat vs vegetable oils) may differentially influence the correlation between MUFA intake and CHD mortality, animal studies suggest that neither source is cardioprotective.

Fatty acids in serum phospholipids and carotid intima-media thickness in Spanish subjects with primary dyslipidemia

BACKGROUND

Low rates of incident ischemic heart disease (IHD) and cardiac death occur in Spain despite a high prevalence of cardiovascular risk factors. High consumption of unsaturated fatty acid-rich foods, such as olive oil, nuts, and seafood, might underlie this paradox.

OBJECTIVE

We investigated whether serum phosphatidylcholine enrichment in oleic, linoleic, alpha-linolenic, and n-3 (omega-3) long-chain polyunsaturated fatty acids (as biomarkers of olive oil, seed oil, walnut, and fish intake, respectively) relate to carotid atherosclerosis in Spanish subjects at risk of IHD.

DESIGN

In a cross-sectional study, we measured fatty acid concentrations in serum phosphatidylcholine and measured carotid intima-media thickness (IMT) by using ultrasound in 451 asymptomatic subjects (261 men, 190 women; mean age: 45 y) with primary dyslipidemia. Main and secondary outcomes were mean and maximum IMT in the common carotid artery (CCA) and other carotid segments, respectively.

RESULTS

Phosphatidylcholine fatty acid composition was similar to that reported for other Spanish populations. Multiple regression analyses showed that proportions of oleic and docosahexaenoic acids were inversely related to mean CCA IMT (P < 0.02, all) after adjustment for several confounders. In similar models, alpha-linolenic acid related inversely to mean and maximum internal carotid artery IMT (P < 0.05 for all). Linoleic and eicosapentaenoic acids were unrelated to IMT.

CONCLUSIONS

Higher phospholipid proportions of oleic, alpha-linolenic, and docosahexaenoic acids showed inverse associations with IMT at specific carotid segments in subjects with primary dyslipidemia. High intakes of healthy fats might explain, in part, the Spanish paradox of low IHD rates in the face of a high burden of cardiovascular risk factors.

Dietary n-3 LCPUFA from fish oil but not alpha-linolenic acid-derived LCPUFA confers atheroprotection in mice

The atheroprotective potential of n-3 alpha-linolenic acid (ALA) has not yet been fully determined, even in murine models of atherosclerosis. We tested whether ALA-derived, n-3 long chain polyunsaturated fatty acids (LCPUFA) could offer atheroprotection in a dose-dependent manner. Apolipoprotein B (ApoB)100/100LDLr-/- mice were fed with diets containing two levels of ALA from flaxseed oil for 16 weeks. Fish oil- and cis-monounsaturated-fat-enriched diets were used as positive and negative controls, respectively. The mice fed cis-monounsaturated fat and ALA-enriched diets exhibited equivalent plasma total cholesterol (TPC) and LDL-cholesterol (LDL-c) levels; only mice fed the fish-oil diet had lower TPC and LDL-c concentrations. Plasma LDL-CE fatty acid composition analysis showed that ALA-enriched diets lowered the percentage of atherogenic cholesteryl oleate compared with cis-monounsaturated-fat diet (44% versus 55.6%) but not as efficiently as the fish-oil diet (32.4%). Although both ALA and fish-oil diets equally enriched hepatic phospholipids with eicosapentaenoic acid (EPA) and ALA-enriched diets lowered hepatic cholesteryl ester (CE) levels compared with cis-monounsaturated-fat diet, only fish oil strongly protected from atherosclerosis. These outcomes indicate that dietary n-3 LCPUFA from fish oil and n-3 LCPUFA (mostly EPA) synthesized endogenously from ALA were not equally atheroprotective in these mice.

LDL cholesteryl oleate as a predictor for atherosclerosis: evidence from human and animal studies on dietary fat

This review focuses on the relationships among dietary fat type, plasma and liver lipid, and lipoprotein metabolism and atherosclerosis. Dietary polyunsaturated fatty acids are beneficial for the prevention of coronary artery atherosclerosis. By contrast, dietary monounsaturated fatty acids appear to alter hepatic lipoprotein metabolism, promote cholesteryl oleate accumulation, and confer atherogenic properties to lipoproteins as shown in data from experimental animal studies. Polyunsaturated fat appears to provide atheroprotection, at least in part, because it limits the accumulation of cholesteryl oleate in favor of cholesteryl linoleate in plasma lipoproteins.