Postprandial effect of n-3 polyunsaturated fatty acids on apolipoprotein B-containing lipoproteins and vascular reactivity in type 2 diabetes

A single, high-fat meal adversely affects postprandial endothelial function: a systematic review and meta-analysis

BACKGROUND

Endothelial dysfunction is a predictive risk factor for the development of atherosclerosis and is assessed by flow-mediated dilation (FMD). Although it is known that NO-dependent endothelial dysfunction occurs after consuming a high-fat meal, the magnitude of the effect and the factors that affect the response are unquantified.

OBJECTIVES

We conducted a systematic review and meta-analysis exploring the quantitative effects of a single high-fat meal on endothelial function and determined the factors that modify the FMD response.

METHODS

Six databases were systematically searched for original research published up to January 2022. Eligible studies measured fasting and postprandial FMD following consumption of a high-fat meal. Meta-regression was used to analyze the effect of moderator variables.

RESULTS

There were 131 studies included, of which 90 were suitable for quantitative meta-analysis. A high-fat meal challenge transiently caused endothelial dysfunction, decreasing postprandial FMD at 2 hours [-1.02 percentage points (pp); 95% CI: -1.34 to -0.70 pp; P < 0.01; I2 = 93.3%], 3 hours [-1.04 pp; 95% CI: -1.48 to -0.59 pp; P < 0.001; I2 = 84.5%], and 4 hours [-1.19 pp; 95% CI: -1.53 to -0.84 pp; P < 0.01; I2 = 94.6%]. Younger, healthy-weight participants exhibited a greater postprandial reduction in the FMD percentage change than older, heavier, at-risk groups after a high-fat meal ( P < 0.05). The percentage of fat in the meals was inversely associated with the magnitude of postprandial changes in FMD at 3 hours (P < 0.01).

CONCLUSIONS

A single, high-fat meal adversely impacts endothelial function, with the magnitude of the impact on postprandial FMD moderated by the fasting FMD, participant age, BMI, and fat content of the meal. Recommendations are made to standardize the design of future postprandial FMD studies and optimize interpretation of results, as high-fat meals are commonly used in clinical studies as a challenge to assess endothelial function and therapeutics. This trial was registered at PROSPERO as CRD42020187244.

Effect of omega-3 polyunsaturated fatty acids in modulation of vascular tone under physiological and pathological conditions

Omega-3 polyunsaturated fatty acids (n-3 PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are mainly found in marine fish oils and commercially available fish oil supplements. Several studies have documented that n-3 PUFAs can reduce the risk of cardiovascular diseases through anti-inflammatory, anti-thrombotic, and anti-atherosclerotic properties. Notably, regulation of vascular tone is one of the most important bases of cardiovascular health and especially for maintaining blood pressure within optimal physiological ranges. Recent clinical and animal studies indicate an association between n-3 PUFAs and vascular functions. In this regard, many clinical trials and basic experimental studies have been conducted so far to investigate the influence of n-3 PUFAs on vascular tone. In this review, we have summarized the results obtained from both clinical and basic studies that evaluated the effect of n-3 PUFAs under physiological and pathological conditions. Moreover, we also focus on verifying the underlying basic molecular mechanism of n-3 PUFAs on the vascular system.

Omega-3 Fatty Acids Effects on Inflammatory Biomarkers and Lipid Profiles among Diabetic and Cardiovascular Disease Patients: A Systematic Review and Meta-Analysis

The purpose of this systematic review and meta-analysis was to investigate omega-3 fatty acids’ influence on 12 inflammatory biomarkers—LDL, HDL, total cholesterol, TG, HbA1c, Apo AI, Apo AII, Apo B, CRP, TNF-α, glucose, and fasting blood glucose among diabetic and cardiovascular disease (CVD) patients. We searched articles in six database engines, and 16 of the 696 articles reviewed met the inclusion criteria. Among these, lipid and inflammatory biomarkers investigated commonly included total cholesterol (11 studies), LDL, and TG (10 studies each). Overall, omega-3 was associated with a significant reduction in Apo AII among diabetic patients, as compared to different controls (−8.0 mg/dL 95% CI: −12.71, −3.29, p = 0.0009), triglycerides (−44.88 mg/dL 95% CI: −82.6, −7.16, p < 0.0001), HDL (−2.27 mg/dL 95% CI: −3.72, −0.83, p = 0.002), and increased fasting blood glucose (16.14 mg/dL 95% CI: 6.25, 26.04, p = 0.001). Omega-3 also was associated with increased LDL among CVD patients (2.10 mg/dL 95% CI: 1.00, 3.20, p = 0.0002). We conclude that omega-3 fatty acids may be associated with lower inflammatory biomarkers among diabetic and cardiovascular patients. Clinicians should be aware of these potential benefits; however, it is essential to recommend that patients consult with clinicians before any omega-3 intake.

In Vitro Effects of Eicosapentaenoic and Docosahexaenoic Acid on the Vascular Tone of a Human Saphenous Vein: Influence of Precontractile Agents

BACKGROUND

Cardiovascular effects of omega-3 polyunsaturated fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been widely reported. However, there are limited studies concerning their effects on human blood vessels. Therefore, the aim of this study was to investigate the direct vascular effects of EPA and DHA on the human saphenous vein (SV) precontracted with either prostaglandin F2α (PGF2α), or thromboxane A2 analogue (U46619), or norepinephrine (NE). Moreover, we aimed to investigate the protein expression of free fatty acid receptor 4 (FFAR4) in human SV.

METHODS

Pretreatment of human SV rings with EPA and DHA (100 μM, 30 min) was tested on vascular reactivity induced by PGF2α (10 nM to 5 μM), NE (10 nM to 100 μM), and U46619 (1 nM to 100 nM). In addition, direct relaxant effects of EPA/DHA (1-100 μM) were tested in human SV rings precontracted by PGF2α, NE, and U46619. Furthermore, the involvement of potassium channels on their vascular effects was investigated in the presence of the nonselective K⁺ channel inhibitor tetraethylammonium chloride.

RESULTS

Pretreatment with EPA and DHA resulted in a significant decrease in vascular reactivity induced by U46619 and PGF2α compared to NE. In the presence of TEA, the relaxant effects of EPA and DHA were significantly decreased in SV preparations precontracted by U46619 and PGF2α for DHA. Furthermore, FFAR-4 protein was expressed in tissue extracts of human SV.

CONCLUSIONS

Our study demonstrates that both EPA and DHA reduce the increased vascular tone elicited by contractile agents on the human SV and that the direct vasorelaxant effect is likely to involve potassium channels.

Anti-inflammatory effects of resolvins in diabetic nephropathy: Mechanistic pathways

The incidence of diabetes mellitus is growing rapidly. The exact pathophysiology of diabetes is unclear, but there is increasing evidence of the role of the inflammatory response in both developing diabetes as well as its complications. Resolvins are naturally occurring polyunsaturated fatty acids that are found in fish oil and sea food that have been shown to possess anti-inflammatory actions in several tissues including the kidneys. The pathways by which resolvins exert this anti-inflammatory effect are unclear. In this review we discuss the evidence showing that resolvins can suppress inflammatory responses via at least five molecular mechanisms through inhibition of the nucleotide-binding oligomerization domain protein 3 inflammasome, inhibition of nuclear factor κB molecular pathways, improvement of oxidative stress, modulation of nitric oxide synthesis/release and prevention of local and systemic leukocytosis. Complete understanding of these molecular pathways is important as this may lead to the development of new effective therapeutic strategies for diabetes and diabetic nephropathy.

Serum apolipoproteins and apolipoprotein-defined lipoprotein subclasses: a hypothesis-generating prospective study of cardiovascular events in T1D

APOB, APOC3, and APOE and apolipoprotein-defined lipoprotein subclasses (ADLSs; based on qualitative apolipoprotein complement) have been associated with dyslipidemia and CVD. Our main objective was to define associations of serum apolipoproteins and ADLSs with "any CVD" and "major atherosclerotic cardiovascular events" (MACEs) in a prospective study of T1D. Serum apolipoproteins and ADLSs (14 biomarkers in total) were measured in sera (obtained between 1997 and 2000) from a subset (n = 465) of the Epidemiology of Diabetes Interventions and Complications cohort. Prospective associations of "any CVD" (myocardial infarction, stroke, confirmed angina, silent myocardial infarction, revascularization, or congestive heart failure) and MACEs (fatal or nonfatal myocardial infarction or stroke), over 5,943 and 6,180 patient-years follow-up, respectively, were investigated using Cox proportional hazards models that were unadjusted and adjusted for risk factors. During 15 years of follow-up, 50 "any CVD" events and 24 MACEs occurred. Nominally significant positive univariate associations with "any CVD" were APOB, APOC3 and its subfractions [heparin precipitate, heparin-soluble (HS)], and ADLS-defined Lp-B. In adjusted analyses, APOC3-HS remained nominally significant. Nominally significant positive univariate associations with MACEs were APOC3 and its subfractions and Lp-B:C; those with total APOC3 and APOC3-HS persisted in adjusted analyses. However, these associations did not reach significance after adjusting for multiple testing. There were no significant associations of APOA1, APOA2, APOE, or other ADLSs with either "any CVD" or MACEs. These hypothesis-generating data suggest that total serum APOC3 and APOC3 in HDL are potentially important predictive biomarkers for any CVD and MACEs in adults with T1D.

Apolipoprotein-defined lipoprotein subclasses, serum apolipoproteins, and carotid intima-media thickness in T1D

Circulating apolipoprotein-defined lipoprotein subclasses (ADLS) and apolipoproteins predict vascular events in the general and type 2 diabetes populations, but data in T1D are limited. We examined associations of ADLS, serum apolipoproteins, and conventional lipids with carotid intima-media thickness (IMT) measured contemporaneously and 6 years later in 417 T1D participants [men: n = 269, age 42 ± 6 y (mean ± SD); women: n = 148, age 39 ± 8 y] in the Epidemiology of Diabetes Interventions and Complications study, the follow-up of the Diabetes Control and Complications Trial (DCCT). Date were analyzed by multiple linear regression stratified by sex, and adjusted for time-averaged hemoglobin A1C, diabetes duration, hypertension, BMI, albuminuria, DCCT randomization, smoking, statin treatment, and ultrasound devices. In cross-sectional analyses, lipoprotein B (Lp-B), Lp-B:C, Lp-B:E+Lp-B:C:E, Apo-A-II, Apo-B, Apo-C-III-HP (heparin precipitate; i.e., Apo-C-III in Apo-B-containing lipoproteins), and Apo-E were positively associated with common and/or internal carotid IMT in men, but only Apo-C-III (total) was (positively) associated with internal carotid IMT in women. In prospective analyses, Lp-B, Apo-B, and Apo-C-III-HP were positively associated with common and/or internal carotid IMT in men, while Lp-A1:AII and Apo-A1 were inversely associated with internal carotid IMT in women. The only significant prospective association between conventional lipids and IMT was between triacylglycerols and internal carotid IMT in men. ADLS and apolipoprotein concentrations may provide sex-specific biomarkers and suggest mechanisms for IMT in people with T1D.

Effects of Torcetrapib and Statin Treatment on ApoC-III and Apoprotein-Defined Lipoprotein Subclasses (from the ILLUMINATE Trial)

In the ILLUMINATE Trial, treatment with the cholesteryl ester transfer protein inhibitor torcetrapib resulted in a significant increase in both atherosclerotic cardiovascular disease events and total mortality which was not explained by changes in the routinely measured plasma lipids. To determine whether alterations in lipoproteins defined by their apoprotein content that are not estimated with conventional laboratory methods contributed to these unexpected events, we measured the apoB- and apoA-containing subclasses in a subgroup of ILLUMINATE participants. We find that torcetrapib treatment significantly increased the high-density lipoprotein subclasses LpA-I and LpA-I:A-II equally (p <0.0001) and the apoC-III content of high-density lipoprotein (p <0.001) without altering the apoB-containing subclasses. In conclusion, these findings provide further evidence that the untoward effects of torcetrapib were attributable to off-target effects and not related to disturbances in lipoprotein transport.

Dose-response effects of marine omega-3 fatty acids on apolipoproteins, apolipoprotein-defined lipoprotein subclasses, and Lp-PLA2 in individuals with moderate hypertriglyceridemia

BACKGROUND

Apolipoprotein (apo) distribution and lipoprotein (Lp)-associated markers of inflammation, such as lipoprotein-associated phospholipase A2 (Lp-PLA2), influence the atherogenicity of circulating lipids and lipoproteins. Little evidence exists regarding the dose-response effects of the marine omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on apos, apo-defined Lps, and Lp-PLA2.

OBJECTIVE

The purpose of this study was to compare the effects of 0, 0.85, and 3.4 g/d of EPA + DHA on Lp-PLA2 mass and activity in individuals with moderate hypertriglyceridemia. We also measured effects on concentrations of apoAI, apoAII, apoB, apoC, apoD, and apoE-defined Lp subclasses.

METHODS

The study was a randomized, doubleblind, crossover design with 8-week treatment periods and 6-week washout periods. During the 3 treatment periods, subjects (n = 25) received 0 g/d EPA + DHA, 0.85 g/d EPA + DHA (low dose), and 3.4 g/d EPA + DHA (high dose) in random order.

RESULTS

apoB and apoC-III were significantly decreased by the high dose relative to placebo and low dose (P < .01), as was very low-density lipoprotein cholesterol (P < .005). The low dose had no effect on Lp outcomes compared with placebo. The high- and low-dose effects differed significantly for heparin-precipitated apoC-III, LpB, LpA-I, and apoB/apoA-I ratio (P < .05). There was a trend for a decreased Lp-PLA2 mass with the high dose (P = .1).

CONCLUSION

The effects of 3.4 g/d EPA + DHA on apoB and apoC-III may reduce atherosclerotic plaque progression in individuals with elevated triglycerides.

Apolipoprotein-defined lipoproteins and apolipoproteins: associations with abnormal albuminuria in type 1 diabetes in the diabetes control and complications trial/epidemiology of diabetes interventions and complications cohort

AIMS

Dyslipoproteinemia has been associated with nephropathy in diabetes, with stronger correlations in men than in women. We aimed to characterize and compare plasma lipoprotein profiles associated with normal and increased albuminuria in men and women using apolipoprotein-defined lipoprotein subclasses and simple apolipoprotein measures.

METHODS

This is a cross-sectional study in a subset (154 women and 282 men) of the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) cohort, using samples obtained in 1997-9. Immunochemical methods were used to quantify plasma apolipoprotein-based lipoprotein subclasses and individual apolipoprotein levels.

RESULTS

In adjusted analyses, elevated Lipoprotein-B (Lp-B) was significantly associated with macroalbuminuria in men [odds ratios (OR) and 95% confidence interval (CI): 2.13 (1.15-3.97)] and women [3.01 (1.11-8.12)], while association with Lp-B:C was observed only in men [1.84 (1.19-2.86)]. For individual apolipoproteins the following significant associations with macroalbuminuria were observed in men only: Apolipoprotein B (ApoB) [1.97 (1.20-3.25)], Apo-AII [0.52 (0.29-0.93)], ApoC-III [1.95 (1.16-3.30)], "ApoC-III in VLDL" (heparin-manganese precipitate) [1.88 (1.16-3.04)], and "ApoCIII in HDL" (heparin-manganese supernatant) [2.03 (1.27-3.26)], all P<0.05).

CONCLUSIONS

Atherogenic apolipoprotein-based profiles are associated with nephropathy in Type 1 diabetic men and to a lesser extent in women. The difference could result from the greater prevalence and severity of dyslipoproteinemia, and from the greater prevalence of renal dysfunction, in men vs women.

Endothelial dysfunction in diabetes: pathogenesis, significance, and treatment

Type 2 diabetes (T2D) markedly increases the risk of cardiovascular disease. Endothelial dysfunction (ED), an early indicator of diabetic vascular disease, is common in T2D and independently predicts cardiovascular risk. Although the precise pathogenic mechanisms for ED in T2D remain unclear, at inception they probably involve uncoupling of both endothelial nitric oxide synthase activity and mitochondrial oxidative phosphorylation, as well as the activation of vascular nicotinamide adenine dinucleotide phosphate oxidase. The major contributing factors include dyslipoproteinemia, oxidative stress, and inflammation. Therapeutic interventions are designed to target these pathophysiological factors that underlie ED. Therapeutic interventions, including lifestyle changes, antiglycemic agents and lipid-regulating therapies, aim to correct hyperglycemia and atherogenic dyslipidemia and to improve ED. However, high residual cardiovascular risk is seen in both research and clinical practice settings. Well-designed studies of endothelial function in appropriately selected volunteers afford a good opportunity to test new therapeutic interventions, paving the way for clinical trials and utilization in the care of the diabetic patient. However, based on the results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled low-density lipoprotein cholesterol.

Apolipoprotein B-containing lipoprotein subclasses as risk factors for cardiovascular disease in patients with rheumatoid arthritis

OBJECTIVE

The purpose of this study was to explore whether nontraditional risk factors, such as apolipoprotein C-III (Apo C-III) and its corresponding Apo B lipoprotein (Lp) subclasses, contribute to the risk of cardiovascular disease in rheumatoid arthritis (RA) patients.

METHODS

Apolipoprotein and lipoproteins were measured in 152 RA patients by immunoturbidimetric procedures, electroimmunoassay, and immunoprecipitation. Patients had a coronary artery calcium (CAC) score assessed at baseline and at year 3. Differences in the CAC scores between baseline and year 3 were calculated and dichotomized at 0, where patients with a difference score >0 were denoted as progressors and the rest were denoted as nonprogressors. Differences between means were tested with a 2-sided independent Student's t-test with Satterthwaite's adjustment. Proportion differences were tested with a chi-square test. Multiple logistic regression was performed to assess the relationship between apolipoprotein and lipoprotein levels and the dichotomized CAC score.

RESULTS

Progressors accounted for almost 60% of the cohort. Progressors had significantly higher levels of triglycerides, very low-density lipoprotein (VLDL) cholesterol, total cholesterol/high-density lipoprotein (HDL), triglycerides/HDL, Apo B, LpA-II:B:C:D:E, LpB:C, Apo B/Apo A-I, Apo C-III, and Apo C-III-heparin precipitate than the nonprogressors. After adjusting for age, sex, statin use (yes/no), and hypertension (yes/no), significant risk factors of progressors were total cholesterol, triglycerides, VLDL cholesterol, LDL cholesterol, Apo B, LpB:C, Apo C-III, and Apo B/Apo A-I.

CONCLUSION

Apo C-III-containing Apo B lipoprotein subclasses were found to be significantly elevated in progressors compared to nonprogressors. Many of these same lipoproteins were found to be associated with an increase in CAC scores among progressors. These lipoproteins may be considered new risk factors for progression of atherosclerosis in RA patients.

Natural polypill Xuezhikang: its clinical benefit and potential multicomponent synergistic mechanisms of action in cardiovascular disease and other chronic conditions

Polypill has been a hot issue since it was first advanced in 2003. This new concept immediately spurred a worldwide discussion. Xuezhikang is a partially purified extract of fermented red yeast rice (Monascus purpureus). It is composed of 13 kinds of natural statins, unsaturated fatty acids, ergosterol, amino acids, flavonoids, alkaloid, trace element, and other substances, and thus could be regarded as a natural lipid-lowering polypill. Interestingly, Xuezhikang in the China Coronary Secondary Prevention Study trial lowered lipid levels less as compared with provastatin in the Cholesterol and Recurrent Events trial, but seemed to gain more benefit in reducing the cardiovascular events and the risk of death from cancer. In recent years, Xuezhikang has been further demonstrated to have additional health benefits and thus raised great interest. This article reviews the clinical benefits of Xuezhikang and the potential multicomponent synergetic mechanism. The authors hold that polypill is anticipated to be a more effective and feasible way to treat complicated diseases.

Impact of n-3 fatty acids on endothelial function: results from human interventions studies

PURPOSE OF REVIEW

Dysfunction of the endothelium plays an integral role in atherogenesis. This review summarizes recent findings on the effects of marine [eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)] and plant [alpha-linolenic acids (ALA)] n-3 polyunsaturated fatty acids (PUFAs) on endothelial function in healthy individuals and in patients with cardiovascular disease (CVD) risk factors or manifest CVD.

RECENT FINDINGS

We identified 33 intervention trials investigating the effects of n-3 PUFA on fasting and/or postprandial endothelial function. In healthy individuals regular supplementation of EPA/DHA or ALA shows inconsistent results on endothelial function, whereas markers of endothelial function seem to be improved in overweight dyslipidaemic patients and type 2 diabetics. Conflicting results are observed in CVD patients. Reasons for discrepancies between the study results include the health status and age of participants, duration of supplementation, dose and fatty acid composition of the administered n-3 PUFAs as well as methods used to assess endothelial function.

SUMMARY

In individuals with CVD risk factors including overweight, dyslipidemia and type 2 diabetes n-3 PUFAs may improve endothelial function. However, the evidence for a clinical efficacy is not strong enough to make final recommendations with respect to a specific dose and the duration of supplementation.

Cod liver oil supplementation improves cardiovascular and metabolic abnormalities in streptozotocin diabetic rats

Abnormalities in the metabolism of essential fatty acids and the results of increased oxidative stress have been implicated in cardiovascular disorders observed in diabetes mellitus. This study, therefore, aimed to investigate the effects of cod liver oil (CLO, Lysi Ltd, Iceland), which comprises mainly an antioxidant vitamin A, n:3 polyunsaturated fatty acids (n:3 PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on cardiovascular abnormalities in streptozotocin (STZ)-diabetic rats. Two days after single STZ (55 mg kg−1, i.p.) or vehicle injection, diabetes was verified by increased blood glucose, and non-diabetic and diabetic rats were left untreated or treated with CLO (0.5 mL kg−1 daily, by intragastric probing) for 12 weeks. Plasma glucose, triacylglycerol and cholesterol concentrations were significantly elevated in 12-week untreated-diabetic rats; CLO provided better weight gain, entirely prevented the plasma lipid abnormalities, but partially controlled the glycaemia in diabetic rats. In isolated aorta rings, diabetes resulted in increased phenylephrine-induced vasoconstriction and isoprenaline-induced vasorelaxation, impaired endothelium-dependent vasodilatation and unchanged responsiveness to sodium nitroprusside. CLO treatment completely prevented endothelial deficiency, partly corrected the phenylephrine-induced vasoconstriction and did not affect the responses to isoprenaline and sodium nitroprusside in diabetic aorta. Diabetes also produced a marked decrease in the rate of spontaneously beating right atria and a significant increase in basal contractile force of left ventricular papillary muscle. The responsiveness of right atria to the positive chronotropic effect of isoprenaline was significantly decreased in diabetic rats, and was increased in CLO-treated diabetic rats. The positive chronotropic effect of noradrenaline was markedly increased in diabetic atria, but prevented by CLO treatment. Diabetes also resulted in an increased positive inotropic response of papillary muscle to both noradrenaline and isoprenaline, which were prevented by CLO treatment. CLO treatment also resulted in lower tissue sensitivity (pD2) to these agonists in diabetic papillary muscle. Ventricular hydroxy-proline content was found to be unchanged among the experimental groups. The ultrastructure of diabetic myocardium displayed various degenerations (i.e. intracellular oedema, myofibrillar fragmentation, condensed pleomorphic mitochondria, thick capillary irregular basement membrane, swollen endothelial cells), which were partially prevented by CLO treatment. We conclude that the supplementation with CLO is effective in preventing cardiovascular disorders observed in experimental diabetes.

Predicting postprandial lipemia in healthy adults and in at-risk individuals with components of the cardiometabolic syndrome

To determine whether a single-point triglyceride (TG) concentration could estimate the 8-hour postprandial lipemic (PPL) response, men and women performed baseline PPL (n=188) and postexercise PPL (n=92) trials. Correlations were generated between TG concentrations at baseline and at various time points after a high-fat meal vs 8-hour area under the TG curve (TG-AUC) and peak TG level. Stepwise multiple regression and bootstrap simulations using TG level and additional predictor variables of sex, age, percentage of body fat, training status, and maximal oxygen consumption indicated that the 4-hour TG concentrations accounted for >90% of the variance in TG-AUC and peak TG responses during the PPL trials. Equations were confirmed by cross-validation in healthy as well as at-risk individuals with components of the cardiometabolic syndrome. Our data suggest that the 4-hour TG value is highly related to the total 8-hour PPL response and can be used for accurate estimation of PPL in a clinical or research setting.

Distribution of immunochemically defined apoB-containing lipoprotein subclasses in T1D

OBJECTIVE

Young women with T1D develop CHD without any apparent lipid related risk factor. To determine whether abnormalities in the five immunochemically defined apoB-containing lipoprotein subclasses might influence this risk, we have measured these subclasses in T1D subjects.

RESEARCH DESIGN AND METHODS

ApoA- and B-containing lipoprotein subclasses were isolated immunochemically and quantitated in 37 young (mean age 31.8+/-12.7 years) otherwise healthy subjects (16 males; 21 females) with T1D (HbA1c=8.2+/-1.7%) treated conventionally with subcutaneous insulin.

RESULTS

T1D women had significantly more cholesterol-rich Lp-B particles (T1D: 55.9+/-4.5 vs. control 46.8+/-11.1mg apoB/dL; p<.01) which were over-represented in the apolipoprotein B particle pool (apoB/Lp-B: T1D: 1.49+/-.19 vs. control: 1.67+/-.22; p<.01). HbA1c correlated with Lp-B (r=0.60; p<.001) and the mass of apoB subclasses containing apoC-III (r=0.69; p<.001).

CONCLUSIONS

Women with T1D have a disturbance in the transport of Lp-B particles manifested by both an absolute and relative increase in their number that may result from portal hypoinsulinemia and reduced LDL B,E receptor activity. This pathway may enhance CHD risk in T1D women when of LDL and apoB levels are normal.

Dietary saturated and unsaturated fats as determinants of blood pressure and vascular function

The amount and type of dietary fat have long been associated with the risk of CVD. Arterial stiffness and endothelial dysfunction are important risk factors in the aetiology of CHD. A range of methods exists to assess vascular function that may be used in nutritional science, including clinic and ambulatory blood pressure monitoring, pulse wave analysis, pulse wave velocity, flow-mediated dilatation and venous occlusion plethysmography. The present review focuses on the quantity and type of dietary fat and effects on blood pressure, arterial compliance and endothelial function. Concerning fat quantity, the amount of dietary fat consumed habitually appears to have little influence on vascular function independent of fatty acid composition, although single high-fat meals postprandially impair endothelial function compared with low-fat meals. The mechanism is related to increased circulating lipoproteins and NEFA which may induce pro-inflammatory pathways and increase oxidative stress. Regarding the type of fat, cross-sectional data suggest that saturated fat adversely affects vascular function whereas polyunsaturated fat (mainly linoleic acid (18 : 2n-6) and n-3 PUFA) are beneficial. EPA (20 : 5n-3) and DHA (22 : 6n-3) can reduce blood pressure, improve arterial compliance in type 2 diabetics and dyslipidaemics, and augment endothelium-dependent vasodilation. The mechanisms for this vascular protection, and the nature of the separate physiological effects induced by EPA and DHA, are priorities for future research. Since good-quality observational or interventional data on dietary fatty acid composition and vascular function are scarce, no further recommendations can be suggested in addition to current guidelines at the present time.

Potential impact of omega-3 treatment on cardiovascular disease in type 2 diabetes

PURPOSE OF REVIEW

Hypothesis-generating systematic review of the impact of marine-derived omega-3 polyunsaturated fatty acids (PUFAs) on lipid, glycemic and hematological risk factors in type 2 diabetes using pooled data from randomized controlled trials searched up to 20 September 2008.

RECENT FINDINGS

Seven new trials in 2007 and 2008 were identified from 206 abstracts to give a total of 24 trials between 1966 and 2008 involving 1533 participants that could be pooled. The mean omega-3 PUFAs dose and duration of treatment in the new trials was 2.4 g/day and 24 weeks, respectively. Compared with placebo, omega-3 PUFAs supplementation decreased triglycerides by 7% (mean -0.17 mmol/l, 24 trials, 1530 participants), fibrinogen by 10% (mean -0.96 micromol/l, three trials, 159 participants), ADP platelet aggregation to ADP by 22% (mean -10.30%, two trials, 64 participants) and to collagen by 21% (mean -10.55%, two trials, 64 participants), with an LDL-cholesterol increase of 3% (mean 0.08 mmol/l, 21 trials, 1104 participants). None of the following risk factors appeared to be beneficially influenced: HDL-cholesterol, LDL particle size, glycemia, insulinemia, inflammatory biomarkers, blood pressure. However for some of these risk factors (such as inflammatory biomarkers) the number of trial patients was small Higher doses of omega-3 PUFAs (>or=2 g/day) may have greater triglyceride lowering effects.

SUMMARY

This systematic review and meta-analysis confirms the triglyceride lowering effects of omega-3 PUFAs, demonstrates potential dose-response effects and shows improvements in thrombogenesis. Omega-3 PUFAs raise LDL levels without concomitant changes in lipid particle size. Changes seen in conventional risk factors are insufficient to explain the cardiovascular disease risk reductions suggested to occur with omega-3 PUFAs.

Apolipoprotein-B subclasses as acceptors of cholesteryl esters transferred by CETP

BACKGROUND

Five apolipoprotein (apo)-defined apoB-containing lipoprotein (Lp) subclasses designated LpB, LpB:C, LpB:E, LpB:C:E and LpA-II:B:C:D:E are present in human plasma. This study was to determine whether these subclasses functioned equally as acceptors of cholesteryl esters (CE) transferred from high-density lipoproteins (HDL) by CE transfer protein in healthy subjects with normal and mildly increased plasma triglyceride (TG) levels.

MATERIALS AND METHODS

After 4 h incubation of plasma from 14 subjects at 37 degrees C, apoB-containing lipoproteins were separated from HDL by heparin-Mn++ precipitation and fractionated by immunochemical methods into these five subclasses. The neutral lipid (NL) composition for each subclass was measured by gas chromatography (GC) and compared between 0 h and 4 h. A subclass was considered to be a CE acceptor if its CE content increased more than 5% at 4 h and a non-acceptor if no change was observed.

RESULTS

Employing the above definition, TG-rich LpB:C and LpB:E + LpB:C:E functioned as CE acceptors and TG-poor LpB and LpA-II:B:C:D:E as non-acceptors. Both LpB:C and LpB:E + LpB:C:E could only actively accept CE as long as they retained their TG-rich character and displayed neutral lipid profiles similar to those of very low-density lipoproteins (VLDL) and intermediate density lipoproteins (IDL). When, as a result of lipolysis their TG content dropped below 25%, they ceased to function as CE acceptors. In subjects with elevated plasma TG, LpB:C was the dominant CE acceptor, a condition that may have pro-atherogenic consequences.

CONCLUSIONS

Among the apoB-containing particles, LpB:C and LpB:C:E + LpB:E functioned as CE acceptors while LpB and LpA-II:B:C:D:E did not.

Effects of pistachios on cardiovascular disease risk factors and potential mechanisms of action: a dose-response study

BACKGROUND

Nut consumption lowers cardiovascular disease (CVD) risk. Studies are lacking about the effects of pistachios, a nutrient-dense nut, on CVD risk factors, dose-response relations, and lipid-lowering mechanisms.

OBJECTIVE

We evaluated the effects of 2 doses of pistachios, added to a lower-fat diet, on lipids and lipoproteins, apolipoprotein (apo)-defined lipoprotein subclasses, and plasma fatty acids. To investigate the mechanisms of action, we measured cholesteryl ester transfer protein and indexes of plasma stearoyl-CoA desaturase activity (SCD).

DESIGN

In a randomized crossover controlled-feeding study, 28 individuals with LDL cholesterol > or = 2.86 mmol/L consumed 3 isoenergetic diets for 4 wk each. Baseline measures were assessed after 2 wk of a typical Western diet. The experimental diets included a lower-fat control diet with no pistachios [25% total fat; 8% saturated fatty acids (SFAs), 9% monounsaturated fatty acids (MUFAs), and 5% polyunsaturated fatty acids (PUFAs)], 1 serving/d of a pistachio diet (1 PD; 10% of energy from pistachios; 30% total fat; 8% SFAs, 12% MUFAs, and 6% PUFAs), and 2 servings/d of a pistachio diet (2 PD; 20% of energy from pistachios; 34% total fat; 8% SFAs, 15% MUFAs, and 8% PUFAs).

RESULTS

The 2 PD decreased (P < 0.05 compared with the control diet) total cholesterol (-8%), LDL cholesterol (-11.6%), non-HDL cholesterol (-11%), apo B (-4%), apo B/apo A-I (-4%), and plasma SCD activity (-1%). The 1 PD and 2 PD, respectively, elicited a dose-dependent lowering (P < 0.05) of total cholesterol/HDL cholesterol (-1% and -8%), LDL cholesterol/HDL cholesterol (-3% and -11%), and non-HDL cholesterol/HDL cholesterol (-2% and -10%).

CONCLUSIONS

Inclusion of pistachios in a healthy diet beneficially affects CVD risk factors in a dose-dependent manner, which may reflect effects on SCD.

Fish oil in the treatment of dyslipidemia

PURPOSE OF REVIEW

The recent availability of a concentrated prescription omega-3 fatty acid preparation provides physicians with an additional anti-dyslipidemic agent at a time when limitations of statin therapy in dyslipidemic high-risk patients are recognized. This review examines the evidence supporting the use of omega-3 fatty acid treatment in dyslipidemic states.

RECENT FINDINGS

There is now considerable evidence that omega-3 fatty acid treatment at the prescription strength of 4 g/day effectively and safely lowers triglyceride levels and increases low-density lipoprotein size, as well as affecting high-density lipoprotein metabolism. Similar effects have been noted in patients treated with statins, and add-on prescription omega-3 fatty acid therapy significantly increases the proportion of statin-treated dyslipidemic patients reaching their non-high-density lipoprotein cholesterol goals. In addition to past studies showing a cardioprotective effect of low-dose omega-3 fatty acid treatment against sudden death, a recent controlled clinical trial showed that 1.8 g of omega-3 fatty acid in statin-treated patients reduced major coronary events by 19% compared with statin plus placebo treatment.

SUMMARY

Omega-3 fatty acid treatment should be considered in patients with severe hypertriglyceridemia as well as in high-risk patients with an atherogenic lipoprotein phenotype.

Teaching children with diabetes about adequate dietary choices

Recent recommendations by the American Diabetes Association suggest that children with type 1 diabetes should follow the recommendations for age, sex and body size of the general population. In the case of being overweight or obese, weight-control strategies should be applied. Adherence to recommendations should be pursued by continuous nutritional education that should start at the onset of diabetes and maintained by means of nutritional counselling to the family. The second main target of nutritional intervention is to encourage a reproducible daily meal plan that can be maintained by acquiring good habits when making nutritional choices. Finally, children and parents should be taught how to count carbohydrates, which would help them manage exceptions in their daily meal plan. Specifically, nutritional recommendations for children with diabetes focus on limiting the intake of foods of animal origin (red meat, cheese, cold cuts), moderating fat intake and promoting the intake of foods that naturally contain fibre (mainly vegetables, legumes, fruit). There are two at-risk periods in the lives of children when nutritional education procedures as well as diabetes care in general are less likely to be effective: early years of life and adolescence. In the case of very young children, new behavioural-based intervention strategies to help parents improve mealtimes could be useful in teaching diabetic children to learn to follow a structured eating schedule, which is desirable for long-lasting efficacy in diabetes care. In adolescents, eating disorders and insulin misuse for weight control purposes are concrete and difficult problems to deal with. A good balance between eating for pleasure and maintaining one's health is a challenge for anyone. Appropriate nutritional education helps children with diabetes to find this balance and enjoy a better quality of life.

Therapeutic regulation of endothelial dysfunction in type 2 diabetes mellitus

Endothelial dysfunction is universal in diabetes, being intimately involved with the development of cardiovascular disease. The pathogenesis of endothelial dysfunction in diabetes is complex. It is initially related to the effects of fatty acids and insulin resistance on 'uncoupling' of both endothelial nitric oxide synthase activity and mitochondrial function. Oxidative stress activates protein kinase C (PKC), polyol, hexosamine and nuclear factor kappa B pathways, thereby aggravating endothelial dysfunction. Improvements in endothelial function in the peripheral circulation in diabetes have been demonstrated with monotherapies, including statins, fibrates, angiotensin-converting enzyme (ACE) inhibitors, metformin and fish oils. These observations are supported by large clinical end point trials. Other studies show benefits with certain antioxidants, L-arginine, folate, PKC-inhibitors, peroxisome proliferator activated receptor (PPAR)-alpha and -gamma agonists and phosphodiesterase (PDE-5) inhibitors. However, the benefits of these agents remain to be shown in clinical end point trials. Combination treatments, for example, statins plus ACE inhibitors and statins plus fibrates, have also been demonstrated to have additive benefits on endothelial function in diabetes, but there are no clinical outcome data to date. Measurement of endothelial dysfunction in cardiovascular research can provide fresh opportunities for exploring the mechanism of benefit of new therapeutic regimens and for planning and designing large clinical trials.