Acute fish oil and soy isoflavone supplementation increase postprandial serum (n-3) polyunsaturated fatty acids and isoflavones but do not affect triacylglycerols or biomarkers of oxidative stress in overweight and obese hypertriglyceridemic men

Polyphenols and atherosclerosis: A critical review of clinical effects on LDL oxidation

Atherosclerosis is a major etiology of cardiovascular disease that causes considerable mortality. Oxidized low-density lipoprotein (oxLDL) is a fundamental attributor to atherosclerosis. Therefore, there seems to be an essential place for antioxidant therapy besides the current treatment protocols for coronary heart disease. Polyphenols are a class of compounds with substantial antioxidant properties that have shown the ability to reduce LDL oxidation in preclinical studies. However, clinical evidence has not been as conclusive although offering many promising signs. This review aims to examine the trials that have evaluated how dietary intake of polyphenols in different forms might influence the oxidation of LDL. Lowering the circulating cholesterol, incorporation into LDL particles, and enhancing systemic antioxidant activity are among the main mechanisms of action for polyphenols for lowering oxLDL. On the other hand, the population under study significantly affects the impact on oxLDL, as the type of the supplement and phenolic content. To conclude, although the polyphenols might decrease inflammation and enhance endothelial function via lowering oxLDL, there are still many gaps in our knowledge that need to be filled with further high-quality studies.

Does timing of phytonutrient intake influence the suppression of postprandial oxidative stress? A systematic literature review

BACKGROUND

Postprandial oxidative stress markers in blood are generated transiently from various tissues and cells following high-fat and/or high-carbohydrate (HFHC) meals, and may be suppressed by certain phytonutrients, such as polyphenols and carotenoids. However, the transient presence of phytonutrients in circulation suggests that timing of consumption, relative to the meal, could be important. This systematic review investigates the effect of timing of phytonutrient intake on blood markers of postprandial oxidative processes.

METHOD

EMBASE, Medline, Scopus and Web of Science were searched up to December 2020. Eligible studies met the criteria: 1) healthy human adults; 2) phytonutrient(s) consumed in solid form within 24 h of a HFHC meal; 3) postprandial measurements of oxidative stress or antioxidants in blood; and 4) controlled study design. Cohen's d effect sizes were calculated to compare studies.

RESULTS

Nine studies, involving 256 participants, were included. Phytonutrients were consumed either at the same time, 1 h before, or the day (>12 h) before a HFHC meal. Significant decreases in blood markers - plasma lipid hydroperoxides, plasma malondialdehyde, serum sNox2-dp, serum 8-iso-PGF2α, platelet p47phox phosphorylation, and Keap-1 and p47phox protein levels in mononuclear cells (MNCs) - were observed where the phytonutrient was consumed together with the challenge meal (n = 4). Lack of any effect on oxidative stress markers was observed where phytonutrients were consumed with (n = 1), 1 h before (n = 1), and the day before (n = 2) the HFHC meal.

CONCLUSION

Phytonutrients consumed with a HFHC meal significantly suppressed some markers of oxidative stress in blood. Although there were only a limited number of studies, it appears that suppression appeared effective at the time of peak phytonutrient concentration in plasma. However, further studies are required to confirm the observations and systematically optimise the effect of timing.

Polyphenols and Human Health: The Role of Bioavailability

Polyphenols are a group of phytochemicals with potential health-promoting effects. They are classified as flavonoid (flavonols, flavanols, flavones, flavanones, isoflavones, and anthocyanins) and non-flavonoid molecules (phenolic acids, hydroxycinnamic acids, lignans, stilbenes, and tannins). Although an increasing number of trials have shown a correlation among polyphenol consumption and a reduction in risk factors for chronic diseases, discrepancies in explaining their positive effects have been found in terms of the bioavailability. In fact, polyphenols show a low bioavailability due to several factors: interaction with the food matrix, the metabolic processes mediated by the liver (phase I and II metabolism), intestine and microbiota. On the other hand, the biological activities of phenol compounds may be mediated by their metabolites, which are produced in vivo, and recent studies have confirmed that these molecules may have antioxidant and anti-phlogistic properties. This review discusses the studies performed in vivo, which consider the polyphenol bioavailability and their different food sources. Factors influencing the biological effects of the main classes of polyphenols are also considered.

The Antioxidant Role of Soy and Soy Foods in Human Health

Oxidative stress seems to play a role in many chronic diseases, such as cardiovascular diseases, diabetes, and some cancers. Research is always looking for effective approaches in the prevention and treatment of these pathologies with safe strategies. Given the central role of nutrition, the identification of beneficial healthy foods can be the best key to having a safe and at the same time effective approach. Soy has always aroused great scientific interest but often this attention is galvanized by the interaction with estrogen receptors and related consequences on health. However, soy, soy foods, and soy bioactive substances seem to have antioxidant properties, suggesting their role in quenching reactive oxygen species, although it was frequently mentioned but not studied in depth. The purpose of this review is to summarize the scientific evidence of the antioxidant properties of soy by identifying the human clinical trials available in the literature. A total of 58 manuscripts were individuated through the literature search for the final synthesis. Soy bioactive substances involved in redox processes appear to be multiple and their use seems promising. Other larger clinical trials with adequate standardization and adequate choice of biomarkers will fill the gap currently existing on the suggestive role of soy in antioxidant mechanisms.

Biomarkers of meat and seafood intake: an extensive literature review

Meat, including fish and shellfish, represents a valuable constituent of most balanced diets. Consumption of different types of meat and fish has been associated with both beneficial and adverse health effects. While white meats and fish are generally associated with positive health outcomes, red and especially processed meats have been associated with colorectal cancer and other diseases. The contribution of these foods to the development or prevention of chronic diseases is still not fully elucidated. One of the main problems is the difficulty in properly evaluating meat intake, as the existing self-reporting tools for dietary assessment may be imprecise and therefore affected by systematic and random errors. Dietary biomarkers measured in biological fluids have been proposed as possible objective measurements of the actual intake of specific foods and as a support for classical assessment methods. Good biomarkers for meat intake should reflect total dietary intake of meat, independent of source or processing and should be able to differentiate meat consumption from that of other protein-rich foods; alternatively, meat intake biomarkers should be specific to each of the different meat sources (e.g., red vs. white; fish, bird, or mammal) and/or cooking methods. In this paper, we present a systematic investigation of the scientific literature while providing a comprehensive overview of the possible biomarker(s) for the intake of different types of meat, including fish and shellfish, and processed and heated meats according to published guidelines for biomarker reviews (BFIrev). The most promising biomarkers are further validated for their usefulness for dietary assessment by published validation criteria.

Oxidative Stress and Non-Alcoholic Fatty Liver Disease: Effects of Omega-3 Fatty Acid Supplementation

Aging is a complex phenomenon characterized by the progressive loss of tissue and organ function. The oxidative-stress theory of aging postulates that age-associated functional losses are due to the accumulation of ROS-induced damage. Liver function impairment and non-alcoholic fatty liver disease (NAFLD) are common among the elderly. NAFLD can progress to non-alcoholic steatohepatitis (NASH) and evolve to hepatic cirrhosis or hepatic carcinoma. Oxidative stress, lipotoxicity, and inflammation play a key role in the progression of NAFLD. A growing body of evidence supports the therapeutic potential of omega-3 polyunsaturated fatty acids (n-3 PUFA), mainly docosahaexenoic (DHA) and eicosapentaenoic acid (EPA), on metabolic diseases based on their antioxidant and anti-inflammatory properties. Here, we performed a systematic review of clinical trials analyzing the efficacy of n-3 PUFA on both systemic oxidative stress and on NAFLD/NASH features in adults. As a matter of fact, it remains controversial whether n-3 PUFA are effective to counteract oxidative stress. On the other hand, data suggest that n-3 PUFA supplementation may be effective in the early stages of NAFLD, but not in patients with more severe NAFLD or NASH. Future perspectives and relevant aspects that should be considered when planning new randomized controlled trials are also discussed.

Tart Cherry Reduces Inflammation in Adipose Tissue of Zucker Fatty Rats and Cultured 3T3-L1 Adipocytes

Obesity increases adipose tissue inflammation and secretion of pro-inflammatory adipokines, which have systemic effects on the organism's health status. Our objective was to dissect mechanisms of anti-inflammatory effects of tart cherry (TC) in adipose tissue of Zucker fatty rats, and cultured 3T3-L1 adipocytes. Rats were fed either a control diet, or 4% TC powder diets for eight weeks. Body and epididymal fat pad weights were not significantly different between control and TC groups. However, rats fed the TC diet had significantly reduced adipose tissue inflammation (p < 0.05), as determined by reduced mRNA levels of pro-inflammatory markers including interleukin-6 (IL-6), tumor necrosis factor alpha (TNFα), interleukin-1beta (IL-1β), monocyte chemoattractant protein 1 (MCP-1), inducible nitric oxide synthase (iNOS), and CD-11b, and increased mRNA levels of type-1 arginase (Arg-1) anti-inflammatory marker. Consistent with these in vivo results, TC significantly decreased expression of IL-6 mRNA and protein levels in lipopolysaccharide (LPS) stimulated adipocytes compared to those stimulated with LPS, but no TC. Moreover, both in vivo (rat adipose tissue) and in vitro (3T3-L1 adipocytes), phosphorylation of p65-NF-κB subunit was significantly reduced by TC. Additionally, TC decreased mRNA expression of fatty acid synthase (FASN), and increased expression of peroxisome proliferator-activated receptor alpha (PPARα), master regulator of lipid oxidation, and anti-oxidant markers nuclear factor erythroid-derived 2-related factor (NRFs) in both models. In conclusion, our findings indicate that TC downregulates inflammation in part via the nuclear factor kappa B (NF-κB) pathway in adipose tissue. Thus, TC may serve as a potential intervention to reduce obesity-associated inflammation.

The Effects of Long-Term Dietary Therapy on Patients with Hypertriglyceridemia

Aim: This study aimed to evaluate the effect of diet on serum lipids and to assess the effectiveness of long-term dietary therapy for hypertriglyceridemia.

Methods: Seventy-nine patients (34 males and 45 females) with hypertriglyceridemia were enrolled and underwent dietary counseling for 12 months based on the following three recommendations: (1) reduce carbohydrate intake, (2) increase n-3 polyunsaturated fatty acid (PUFA) intake, and (3) limit alcohol drinking. We examined the effect of dietary therapy for 6 months on serum triglyceride (TG) levels and also compared the effectiveness of dietary and combined drug therapies on preventing arteriosclerotic disease from 7 to 12 months.

Results: We observed that serum TG levels of the patients receiving dietary counseling were decreased compared with baseline at 6 months. Body weight and serum TG levels were decreased, and serum high-density lipoprotein levels were increased in the dietary therapy alone group, whereas BW, body mass index, and abdominal circumference were decreased in the combined drug treatment group compared with baselines at 6 and 12 months. Furthermore, the dietary therapy alone group demonstrated reductions in intake of total energy, carbohydrate, and saturated fatty acids, as well as n-6/n-3 PUFA ratio compared with baselines, but only n-6/n-3 PUFA ratio was decreased in the combined drug treatment group.

Conclusion: This study demonstrated a decrease in serum TG level after 12 months of dietary therapy similar to drug therapy, which suggests that it is an effective treatment for hypertriglyceridemia, and heightened awareness should be made to encourage its use.

The clinical trial registration number: UMIN000028860.

Consumption of Soymilk Reduces Lipid Peroxidation But May Lower Micronutrient Status in Apparently Healthy Individuals

Consumption of soy products is speculated to reduce the risk and progression of some disease conditions. The underlying mechanisms mediating this effect are uncertain, but the lowering of oxidative stress has been suggested. This study was aimed at investigating the effect of soymilk on antioxidant status and lipid peroxidation in apparently healthy individuals. Five hundred milliliters of soymilk was taken daily by each of 39 apparently healthy individuals for a period of 28 days. Two sets of blood samples (baseline and after 28 days of soymilk intake) were collected and assayed for total antioxidant capacity (TAC), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione S-transferase (GST), manganese (Mn) and zinc (Zn) levels, using standard methods. Consumption of soymilk significantly increased serum TAC and reduced serum MDA when compared with baseline values (P < .001, P < .001 respectively). The decrease in MDA concentration was significantly contributed by the women (P < .001). Mean serum Mn was also significantly reduced (P = .03) when compared with baseline values. There were no changes in serum Zn concentration and the activity of SOD enzyme. The serum GST activity was significantly increased in men (P = .02) and significantly reduced in women (P < .001) in comparison with their corresponding baseline values. Daily consumption of soymilk enhanced antioxidant status and this led to reduced lipid peroxidation. It also resulted in a significant reduction of Mn. The dietary use of soymilk as an adjuvant to supplement meals seems beneficial health wise. However, soymilk should be taken with caution as it could result in micronutrient deficiency.

Validity of a food frequency questionnaire to estimate long-chain polyunsaturated fatty acid intake among Japanese women in early and late pregnancy

Background

The relative validity of food frequency questionnaires for estimating long-chain polyunsaturated fatty acid (LC-PUFA) intake among pregnant Japanese women is currently unclear. The aim of this study was to verify the external validity of a food frequency questionnaire, originally developed for non-pregnant adults, to assess the dietary intake of LC-PUFA using dietary records and serum phospholipid levels among Japanese women in early and late pregnancy.

Methods

A validation study involving 188 participants in early pregnancy and 169 participants in late pregnancy was conducted. Intake LC-PUFA was estimated using a food frequency questionnaire and evaluated using a 3-day dietary record and serum phospholipid concentrations in both early and late pregnancy.

Results

The food frequency questionnaire provided estimates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) intake with higher precision than dietary records in both early and late pregnancy. Significant correlations were observed for LC-PUFA intake estimated using dietary records in both early and late pregnancy, particularly for EPA and DHA (correlation coefficients ranged from 0.34 to 0.40, p < 0.0001). Similarly, high correlations for EPA and DHA in serum phospholipid composition were also observed in both early and late pregnancy (correlation coefficients ranged 0.27 to 0.34, p < 0.0001).

Conclusions

Our findings suggest that the food frequency questionnaire, which was originally designed for non-pregnant adults and was evaluated in this study against dietary records and biological markers, has good validity for assessing LC-PUFA intake, especially EPA and DHA intake, among Japanese women in early and late pregnancy.

Soya products and serum lipids: a meta-analysis of randomised controlled trials

Soya proteins and isoflavones have been reported to exert beneficial effects on the serum lipid profile. More recently, this claim is being challenged. The objective of this study was to comprehensively examine the effects of soya consumption on the lipid profile using published trials. A detailed literature search was conducted via MEDLINE (from 2004 through February 2014), CENTRAL (The Cochrane Controlled Clinical Trials Register) and ClinicalTrials.gov for randomised controlled trials assessing the effects of soya on the lipid profile. The primary effect measure was the difference in means of the final measurements between the intervention and control groups. In all, thirty-five studies (fifty comparisons) were included in our analyses. Treatment duration ranged from 4 weeks to 1 year. Intake of soya products resulted in a significant reduction in serum LDL-cholesterol concentration, -4.83 (95% CI -7.34, -2.31) mg/dl, TAG, -4.92 (95% CI -7.79, -2.04) mg/dl, and total cholesterol (TC) concentrations, -5.33 (95% CI -8.35, -2.30) mg/dl. There was also a significant increase in serum HDL-cholesterol concentration, 1.40 (95% CI 0.58, 2.23) mg/dl. The I² statistic ranged from 92 to 99%, indicating significant heterogeneity. LDL reductions were more marked in hypercholesterolaemic patients, -7.47 (95% CI -11.79, -3.16) mg/dl, than in healthy subjects, -2.96 (95% CI -5.28, -0.65) mg/dl. LDL reduction was stronger when whole soya products (soya milk, soyabeans and nuts) were used as the test regimen, -11.06 (95% CI -15.74, -6.37) mg/dl, as opposed to when 'processed' soya extracts, -3.17 (95% CI -5.75, -0.58) mg/dl, were used. These data are consistent with the beneficial effects of soya proteins on serum LDL, HDL, TAG and TC concentrations. The effect was stronger in hypercholesterolaemic subjects. Whole soya foods appeared to be more beneficial than soya supplementation, whereas isoflavone supplementation had no effects on the lipid profile.

Postprandial Dysmetabolism and Oxidative Stress in Type 2 Diabetes: Pathogenetic Mechanisms and Therapeutic Strategies

Postprandial dysmetabolism in type 2 diabetes (T2D) is known to impact the progression and evolution of this complex disease process. However, the underlying pathogenetic mechanisms still require full elucidation to provide guidance for disease prevention and treatment. This review focuses on the marked redox changes and inflammatory stimuli provoked by the spike in blood glucose and lipids in T2D individuals after meals. All the causes of exacerbated postprandial oxidative stress in T2D were analyzed, also considering the consequence of enhanced inflammation on vascular damage. Based on this in-depth analysis, current strategies of prevention and pharmacologic management of T2D were critically reexamined with particular emphasis on their potential redox-related rationale.

Postprandial lipid and insulin responses among healthy, overweight men to mixed meals served with baked herring, pickled herring or baked, minced beef

PURPOSE

The aim was to compare postprandial lipid, insulin and vitamin D responses after consumption of three otherwise identical meals served either with baked herring, pickled herring or with baked, minced beef.

METHODS

Seventeen healthy, overweight men (mean age 58 years, BMI 26.4-29.5 kg/m(2)) consumed standardized lunches together with baked herring, pickled herring or baked, minced beef on three occasions in a crossover design. Blood samples were taken just before and up to 7 h after the meal. The postprandial response was measured as serum concentrations of triglycerides (TG), total cholesterol and lipoproteins (LDL, HDL and VLDL), insulin, 25-OH vitamin D and plasma fatty acid composition.

RESULTS

There was no difference in postprandial lipid responses between the two herring meals, whereas a slower TG clearance was observed after the baked, minced beef meal. The 150 g servings of baked and pickled herring provided 3.3 and 2.8 g of long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA), respectively, which was reflected in a substantial postprandial increase in plasma LC n-3 PUFA levels. The pickled herring contained 22% sugar and consequently gave a higher insulin response compared with the other two meals.

CONCLUSIONS

Both pickled and baked herring are good sources of LC n-3 PUFA in the diet, but the presence of sugar in pickled herring should be taken into consideration, especially if large amounts are consumed. The faster postprandial TG clearance after a meal with baked herring compared with baked beef supports previous studies on the beneficial effects of herring on cardiovascular health.

High-fat meals rich in EPA plus DHA compared with DHA only have differential effects on postprandial lipemia and plasma 8-isoprostane F2α concentrations relative to a control high-oleic acid meal: a randomized controlled trial

BACKGROUND

Eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) supplementation has beneficial cardiovascular effects, but postprandial influences of these individual fatty acids are unclear.

OBJECTIVES

The primary objective was to determine the vascular effects of EPA + DHA compared with DHA only during postprandial lipemia relative to control high-oleic acid meals; the secondary objective was to characterize the effects of linoleic acid-enriched high-fat meals relative to the control meal.

DESIGN

We conducted a randomized, controlled, double-blind crossover trial of 4 high-fat (75-g) meals containing 1) high-oleic acid sunflower oil (HOS; control), 2) HOS + fish oil (FO; 5 g EPA and DHA), 3) HOS + algal oil (AO; 5 g DHA), and 4) high-linoleic acid sunflower oil (HLS) in 16 healthy men (aged 35-70 y) with higher than optimal fasting triacylglycerol concentrations (mean ± SD triacylglycerol, 1.9 ± 0.5 mmol/L).

RESULTS

Elevations in triacylglycerol concentration relative to baseline were slightly reduced after FO and HLS compared with the HOS control (P < 0.05). The characteristic decrease from baseline in plasma nonesterified fatty acids after a mixed meal was inhibited after AO (Δ 0-3 h, P < 0.05). HLS increased the augmentation index compared with the other test meals (P < 0.05), although the digital volume pulse-reflection index was not significantly different. Plasma 8-isoprostane F2α analysis revealed opposing effects of FO (increased) and AO (reduced) compared with the control (P < 0.05). No differences in nitric oxide metabolites were observed.

CONCLUSIONS

These data show differential postprandial 8-isoprostane F2α responses to high-fat meals containing EPA + DHA-rich fish oil compared with DHA-rich AO, but these differences were not associated with consistent effects on postprandial vascular function or lipemia. More detailed analyses of polyunsaturated fatty acid-derived lipid mediators are required to determine possible divergent functional effects of single meals rich in either DHA or EPA. This trial was registered at clinicaltrials.gov as NCT01618071.

DHA concentration of red blood cells is inversely associated with markers of lipid peroxidation in men taking DHA supplement

An increase in the proportion of fatty acids with higher numbers of double bonds is believed to increase lipid peroxidation, which augments the risk for many chronic diseases. (n-3) Polyunsaturated fatty acids provide various health benefits, but there is a concern that they might increase lipid peroxidation. We examined the effects of docosahexaenoic acid [22:6 (n-3)] supplementation on lipid peroxidation markers in plasma and red blood cells (RBC) and their associations with red blood cell and plasma fatty acids. Hypertriglyceridemic men (n = 17 per group) aged 39–66 years participated in a double-blind, randomized, placebo-controlled, parallel study. They received no supplements for the first 8 days and then received 7.5 g/day docosahexaenoic acid oil (3 g/day docosahexaenoic acid) or olive oil (placebo) for 90 days. Fasting blood samples were collected 0, 45, and 91 days after supplementation. Docosahexaenoic acid supplementation did not change plasma or RBC concentrations of lipid peroxidation markers (total hydroxyoctadecadienoic acid, total hydroxyeicosatetraenoic acid, total 8-isoprostaglandin F_2α, 7α-hydroxycholesterol, 7β-hydroxycholesterol) when pre- and post-supplement values were compared. However, the post-supplement docosahexaenoic acid (DHA) concentration was inversely associated with RBC concentrations of ZE-HODE, EE-HODE, t-HODE, and total 8-isoprostaglandin F_2α, (p<0.05). RBC concentration of hydroxycholesterol was also inversely associated with DHA but it did not attain significance (p = 0.07). Our results suggest that increased concentration of DHA in RBC lipids reduced lipid peroxidation. This may be another health benefit of DHA in addition to its many other health promoting effects.

Exercise and dietary-mediated reductions in postprandial lipemia

Postprandial hyperlipemia produces long-term derangements in lipid/lipoprotein metabolism, vascular endothelial dysfunction, hypercoagulability, and sympathetic hyperactivity which are strongly linked to atherogenesis. The purpose of this review is to (1) provide a qualitative analysis of the available literature examining the dysregulation of postprandial lipid metabolism in the presence of obesity, (2) inspect the role of adiposity distribution and sex on postprandial lipid metabolism, and (3) examine the role of energy deficit (exercise- and/or energy restriction-mediated), isoenergetic low-carbohydrate diets, and omega-3 (n-3) fatty acid supplementation on postprandial lipid metabolism. We conclude from the literature that central adiposity primarily accounts for sex-related differences in postprandial lipemia and that aerobic exercise attenuates this response in obese or lean men and women to a similar extent through potentially unique mechanisms. In contrast, energy restriction produces only mild reductions in postprandial lipemia suggesting that exercise may be superior to energy restriction alone as a strategy for lowering postprandial lipemia. However, isoenergetic very low-carbohydrate diets and n-3 fatty acid supplementation reduce postprandial lipemia indicating that macronutrient manipulations reduce postprandial lipemia in the absence of energy restriction. Therefore, interactions between exercise/energy restriction and alterations in macronutrient content remain top priorities for the field to identify optimal behavioral treatments to reduce postprandial lipemia.

Diets naturally rich in polyphenols improve fasting and postprandial dyslipidemia and reduce oxidative stress: a randomized controlled trial

BACKGROUND

The postprandial triglyceride-rich lipoprotein (TRL) concentration is a recognized independent cardiovascular disease risk factor. Diet is the natural approach for these postprandial alterations. Dietary polyphenols and long chain n-3 polyunsaturated fatty acids (LCn3s) are associated with a lower cardiovascular disease risk.

OBJECTIVE

This randomized controlled study evaluated, in persons with a high risk of cardiovascular disease, the effects of diets naturally rich in polyphenols and/or marine LCn3s on plasma TRLs and urinary 8-isoprostane concentrations, a biomarker of oxidative stress.

DESIGN

According to a 2 × 2 factorial design, 86 overweight/obese individuals with a large waist circumference and any other component of the metabolic syndrome were randomly assigned to an isoenergetic diet 1) poor in LCn3s and polyphenols, 2) rich in LCn3s, 3) rich in polyphenols, or 4) rich in LCn3s and polyphenols. The diets were similar in all other components. Before and after the 8-wk intervention, fasting and postmeal TRLs and 8-isoprostane concentrations in 24-h urine samples were measured.

RESULTS

Dietary adherence was good in all participants. Polyphenols significantly reduced fasting triglyceride concentrations (2-factor ANOVA) in plasma (P = 0.023) and large very-low-density lipoproteins (VLDLs) (P = 0.016) and postprandial triglyceride total area under the curve in plasma (P = 0.041) and large VLDLs (P = 0.004). LCn3s reduced postprandial chylomicron cholesterol and VLDL apolipoprotein B-48. The concentrations of urinary 8-isoprostane decreased significantly with the polyphenol-rich diets. Lipoprotein changes induced by the intervention significantly correlated with changes in 8-isoprostane.

CONCLUSIONS

Diets naturally rich in polyphenols positively influence fasting and postprandial TRLs and reduce oxidative stress. Marine LCn3s reduce TRLs of exogenous origin. Through their effects on postprandial lipemia and oxidative stress, polyphenols may favorably affect cardiovascular disease risk.

Interactions between prebiotics, probiotics, polyunsaturated fatty acids and polyphenols: diet or supplementation for metabolic syndrome prevention?

The metabolic syndrome can be prevented by the Mediterranean diet, characterized by fiber, omega-3 polyunsaturated fatty acids and polyphenols. However, the composition of the Mediterranean diet, which can be viewed as a natural multiple supplement, is poorly controlled, and its beneficial effects poorly predictable. The metabolic syndrome is associated with intestinal dysbiosis and the gut microbioma seems to be the main target and player in the interactions occurring between probiotics, prebiotics, omega 3 polyunsaturated fatty acids, and polyphenols. From the reviewed evidence, it is reasonable to manage growth and metabolism of gut microflora with specific prebiotics and polyphenols. Even though the healthy properties of functional foods and nutraceuticals still need to be fully elucidated, available data suggest that well-designed supplements, containing the better ratio of omega-3 polyunsaturated fatty acids and antioxidants, specific probiotic strains, and selected polyphenols and prebiotics, could be useful in metabolic syndrome prevention and treatment.

The short-term effects of soybean intake on oxidative and carbonyl stress in men and women

Beyond other beneficial effects, a soy-rich diet has been shown to reduce the risk of cardiovascular diseases and diabetic complications. Reduction of oxidative and carbonyl stress has been proposed as the underlying mechanism, but the evidence for this is lacking. The aim of our study was to evaluate the effects of short-term increased soy intake on oxidative and carbonyl stress parameters in young volunteers. Young healthy probands (omnivores) of both genders (55 women, 33 men) were given soybeans (2 g/kg bodyweight daily) for one week. Markers of oxidative and carbonyl stress were measured in plasma at the beginning and at the end of one week soybean intake and after another week of a wash-out period. Total antioxidant capacity was increased by soybean intake in both genders. This led to decreased levels of advanced oxidation protein products in women, but not in men. On the contrary, in men, soybean intake increased lipoperoxidation. No effects on carbonyl stress markers (advanced glycation end products-specific fluorescence and fructosamine) were found. Soybean intake has gender-specific effects on oxidative stress in young healthy probands potentially due to divergent action and metabolism of phytoestrogens in men and women. Effects of soybean intake on carbonyl stress should be evaluated in longer studies.

High fat intake leads to acute postprandial exposure to circulating endotoxin in type 2 diabetic subjects

OBJECTIVE

To evaluate the changes in circulating endotoxin after a high-saturated fat meal to determine whether these effects depend on metabolic disease state.

RESEARCH DESIGN AND METHODS

Subjects (n = 54) were given a high-fat meal (75 g fat, 5 g carbohydrate, 6 g protein) after an overnight fast (nonobese control [NOC]: age 39.9 ± 11.8 years [mean ± SD], BMI 24.9 ± 3.2 kg/m(2), n = 9; obese: age 43.8 ± 9.5 years, BMI 33.3 ± 2.5 kg/m(2), n = 15; impaired glucose tolerance [IGT]: age 41.7 ± 11.3 years, BMI 32.0 ± 4.5 kg/m(2), n = 12; type 2 diabetic: age 45.4 ± 10.1 years, BMI 30.3 ± 4.5 kg/m(2), n = 18). Blood was collected before (0 h) and after the meal (1-4 h) for analysis.

RESULTS

Baseline endotoxin was significantly higher in the type 2 diabetic and IGT subjects than in NOC subjects, with baseline circulating endotoxin levels 60.6% higher in type 2 diabetic subjects than in NOC subjects (P < 0.05). Ingestion of a high-fat meal led to a significant rise in endotoxin levels in type 2 diabetic, IGT, and obese subjects over the 4-h time period (P < 0.05). These findings also showed that, at 4 h after a meal, type 2 diabetic subjects had higher circulating endotoxin levels (125.4%↑) than NOC subjects (P < 0.05).

CONCLUSIONS

These studies have highlighted that exposure to a high-fat meal elevates circulating endotoxin irrespective of metabolic state, as early as 1 h after a meal. However, this increase is substantial in IGT and type 2 diabetic subjects, suggesting that metabolic endotoxinemia is exacerbated after high fat intake. In conclusion, our data suggest that, in a compromised metabolic state such as type 2 diabetes, a continual snacking routine will cumulatively promote their condition more rapidly than in other individuals because of the greater exposure to endotoxin.

n-3 PUFA prevent metabolic disturbances associated with obesity and improve endothelial function in golden Syrian hamsters fed with a high-fat diet

Glucose intolerance and dyslipidaemia are independent risk factors for endothelium dysfunction and CVD. The aim of the present study was to analyse the preventive effect of n-3 PUFA (EPA and DHA) on lipid and carbohydrate disturbances and endothelial dysfunction. Three groups of adult hamsters were studied for 20 weeks: (1) control diet (Control); (2) high-fat diet (HF); (3) high-fat diet enriched with n-3 PUFA (HFn-3) groups. The increase in body weight and fat mass in the HF compared to the Control group (P < 0.05) was not found in the HFn-3 group. Muscle TAG content was similar in the Control and HF groups, but significantly lower in the HFn-3 group (P = 0.008). Glucose tolerance was impaired in the HF compared to the Control group, but this impairment was prevented by n-3 PUFA in the HFn-3 group (P < 0.001). Plasma TAG and cholesterol were higher in the HF group compared to the Control group (P < 0.001), but lower in the HFn-3 group compared to the HF group (P < 0.001). HDL-cholesterol was lower in the HFn-3 group compared to the Control and HF groups (P < 0.0005). Hepatic secretion of TAG was lower in the HFn-3 group compared to the HF group (P < 0.005), but did not differ from the Control group. Hepatic gene expression of sterol regulatory element-binding protein-1c, diacylglycerol O-acyltransferase 2 and stearyl CoA desaturase 1 was lower in the HFn-3 group, whereas carnitine palmitoyl transferase 1 and scavenger receptor class B type 1 expression was higher (P < 0.05). In adipocytes and adipose macrophages, PPARγ and TNFα expression was higher in the HF and HFn-3 groups compared to the Control group. Endothelium relaxation was higher in the HFn-3 (P < 0.001) than in the HF and Control groups, and was correlated with glucose intolerance (P = 0.03) and cholesterol (P = 0.0003). In conclusion, n-3 PUFA prevent some metabolic disturbances induced by high-fat diet and improve endothelial function in hamsters.

Omega-3 fatty acids and metabolic syndrome: effects and emerging mechanisms of action

Epidemiological, human, animal, and cell culture studies show that n-3 fatty acids, especially α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), reduce the risk factors of cardiovascular diseases. EPA and DHA, rather than ALA, have been the focus of research on the n-3 fatty acids, probably due to the relatively inefficient conversion of ALA to EPA and DHA in rodents and humans. This review will assess our current understanding of the effects and potential mechanisms of actions of individual n-3 fatty acids on multiple risk factors of metabolic syndrome. Evidence for pharmacological responses and the mechanism of action of each of the n-3 fatty acid trio will be discussed for the major risk factors of metabolic syndrome, especially adiposity, dyslipidemia, insulin resistance and diabetes, hypertension, oxidative stress, and inflammation. Metabolism of n-3 and n-6 fatty acids as well as the interactions of n-3 fatty acids with nutrients, gene expression, and disease states will be addressed to provide a rationale for the use of n-3 fatty acids to reduce the risk factors of metabolic syndrome.

A combination of (ω-3) polyunsaturated fatty acids, polyphenols and L-carnitine reduces the plasma lipid levels and increases the expression of genes involved in fatty acid oxidation in human peripheral blood mononuclear cells and HepG2 cells

BACKGROUND

Hyperlipidemia and obesity are associated with metabolic syndrome and increased risk in developing diabetes and cardiovascular disease. Nutritional supplements, e.g. L-carnitine and polyunsaturated fatty acids (PUFAs), exert lipid-lowering effects. Hence, the hypothesis that dietetic intervention reduces plasma lipid levels and metabolic enzymes in overweight hyperlipidemic subjects was tested.

SUBJECTS AND METHODS

In a prospective placebo-controlled double-blind study in 22 moderately hyperlipidemic obese humans consuming low-fat yoghurt enriched with a combination of low-dose PUFAs, polyphenols and L-carnitine (PPC) twice a day for 12 weeks were compared to 20 matching participants ingesting low-fat yoghurt. The effects on plasma lipids and expression of enzymes involved in regulation of fatty acid oxidation in peripheral blood mononuclear cells (PBMCs) and HepG2 cells were evaluated.

RESULTS

PPC consumption led to significantly reduced plasma free fatty acid (-29%) and triglyceride (-24%) concentrations (each p < 0.05). PPC application increased significantly peroxisome proliferator-activated receptor α (PPARα) mRNA abundances and those of PPARα target genes (carnitine palmitoyltransferases-1, CPT1A and CPT1B, carnitine acetyltransferase and organic cation transporter 2; each p < 0.05) in PBMCs. In controls, plasma lipid levels and PBMC gene expression did not change. These findings were substantiated by the results of cell culture experiments in HepG2 cells.

CONCLUSION

Supplementation of PPC had marked lipid-lowering effects and PBMC gene expression profiles seemed to reflect nutrition-related metabolic changes.

Green tea catechins and their oxidative protection in the rat eye

Catechins, active constituents of green tea, are well-known antioxidative natural products. It was proposed that green tea extract (GTE) consumption could benefit the eye, and the pharmacokinetics of catechins and oxidation status in rat eye were investigated after oral administration. Sprague-Dawley rats were fed GTE and sacrificed at different time intervals. Their eyes were dissected into cornea, lens, retina, choroid-sclera, vitreous humor, and aqueous humor for analysis of catechins and 8-epi-isoprostane by HPLC-ECD and GC-NCI-MS, respectively. Catechins were differentially distributed in eye tissues. Gallocatechin was present at the highest concentration in the retina, 22729.4 +/- 4229.4 pmol/g, and epigallocatechin in aqueous humor at 602.9 +/- 116.7 nM. The corresponding area-under-curves were 207,000 pmol x h/g and 2035.0 +/- 531.7 nM x h, respectively. The time of maximum concentration of the catechins varied from 0.5 to 12.2 h. Significant reductions in 8-epi-isoprostane levels were found in the compartments except the choroid-sclera or plasma, indicating antioxidative activities of catechins in these tissues.