Differences in postprandial concentrations of very-low-density lipoprotein and chylomicron remnants between normotriglyceridemic and hypertriglyceridemic men with and without coronary heart disease

Characterisation of Fasting and Postprandial NMR Metabolites: Insights from the ZOE PREDICT 1 Study

BACKGROUND

Postprandial metabolomic profiles and their inter-individual variability are not well characterised. Here, we describe postprandial metabolite changes, their correlations with fasting values and their inter- and intra-individual variability, following a standardised meal in the ZOE PREDICT 1 cohort.

METHODS

In the ZOE PREDICT 1 study (n = 1002 (NCT03479866)), 250 metabolites, mainly lipids, were measured by a Nightingale NMR panel in fasting and postprandial (4 and 6 h after a 3.7 MJ mixed nutrient meal, with a second 2.2 MJ mixed nutrient meal at 4 h) serum samples. For each metabolite, inter- and intra-individual variability over time was evaluated using linear mixed modelling and intraclass correlation coefficients (ICC) were calculated.

RESULTS

Postprandially, 85% (of 250 metabolites) significantly changed from fasting at 6 h (47% increased, 53% decreased; Kruskal-Wallis), with 37 measures increasing by >25% and 14 increasing by >50%. The largest changes were observed in very large lipoprotein particles and ketone bodies. Seventy-one percent of circulating metabolites were strongly correlated (Spearman's rho >0.80) between fasting and postprandial timepoints, and 5% were weakly correlated (rho <0.50). The median ICC of the 250 metabolites was 0.91 (range 0.08-0.99). The lowest ICCs (ICC <0.40, 4% of measures) were found for glucose, pyruvate, ketone bodies (β-hydroxybutyrate, acetoacetate, acetate) and lactate.

CONCLUSIONS

In this large-scale postprandial metabolomic study, circulating metabolites were highly variable between individuals following sequential mixed meals. Findings suggest that a meal challenge may yield postprandial responses divergent from fasting measures, specifically for glycolysis, essential amino acid, ketone body and lipoprotein size metabolites.

Body composition, but not insulin resistance, influences postprandial lipemia in patients with Turner's syndrome

OBJECTIVE

The aim of the present study was to examine the influence of body composition and insulin resistance on the magnitude of postprandial lipemia in patients with Turner's syndrome receiving oral versus transdermal estrogen replacement.

METHODS

Twenty-five patients with Turner's syndrome receiving oral or transdermal estrogen replacement were evaluated for body mass index, waist-to-hip and waist-to-height ratios, fasting glycemia, insulin, body composition (dual-energy X-ray absorptiometry), and postprandial lipid metabolism. For statistical analysis, we used parametric tests to compare numeric variables between the two subgroups.

RESULTS

We observed no difference in postprandial triglyceride levels between patients receiving oral versus transdermal hormone replacement therapy. The postprandial triglycerides increment correlated positively with the percentage of total fat mass (p=0.02) and android fat mass (p=0.02) in the transdermal group. In the oral estrogen group, a positive correlation was observed between the increment in postprandial triglycerides and waist-to-hip (p=0.15) and waist-to-height (p=0.009) ratios. No association was observed between the estrogen replacement route and insulin resistance evaluated by the homeostatic model assessment-insulin resistance (HOMA-IR) index (p=0.19 and p=0.65 for the oral and transdermal groups, respectively).

CONCLUSION

We concluded that body composition and anthropometric characteristics possibly affect the extent of postprandial lipemia independently from the route of estrogen replacement.

Comparison of calculated remnant lipoprotein cholesterol levels with levels directly measured by nuclear magnetic resonance

BACKGROUND

Remnant cholesterol (RC) can partly explain the residual risk in atherosclerotic cardiovascular disease (ASCVD). A consensus method of measuring RC levels has not been established yet. In clinical practice, RC levels are usually calculated from the standard lipid profile, which are not true RC. Nuclear magnetic resonance (NMR) can measure RC levels directly. This study aimed to characterize RC at fasting and non-fasting states in more details and establish the performance of calculated RC and NMR-measured RC.

METHODS

Blood samples at fasting state and at 2 h and 4 h postprandial states were collected in 98 subjects. Lipid parameters including total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), subfractions 3, 4, and 5 of very low-density lipoprotein cholesterol (VLDL3-C, VLDL4-C, and VLDL5-C, respectively), and intermediate-density lipoprotein cholesterol (IDL-C) were measured by enzymatic method and NMR. RC levels calculated from the standard lipid profile or measured by NMR were referred here as RCe or RCn.

RESULTS

The RCe and RCn levels were different, but both of them increased after a meal (P < 0.05), especially at 4 h postprandial state. Low correlations were found between RCe and RCn in the 1st, 2nd, and 3rd quartiles of TG, but RCn showed great correlation with RCe in the highest quartile regardless of the fasting or non-fasting state (R = 0.611, 0.536, and 0.535 for 0 h, 2 h, and 4 h, respectively). However, across the 2nd and 3rd quartiles, RCe levels were nearly close to RCn levels. RCe levels tended to overestimate RCn levels in the 1st quartile of TGe levels with median differences of 0.23(- 0.13, 0.63) and underestimate RCn levels with median differences of - 0.23(- 0.33, 0.07) in the highest quartile of TGe levels.

CONCLUSIONS

RC calculated from the standard lipid profile as TC minus LDL-C minus HDL-C is different from the NMR-measured RC. According to different TG levels, RC could overestimate or underestimate the actual RC level. Developing a consensus clinical method to measure RC levels is necessary, so that results from different studies and platforms can be more directly compared.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR1900020873. Registered in 21 January 2019 - Retrospectively registered.

Lipoprotein removal mechanisms and aging: implications for the cardiovascular health of the elderly

PURPOSE OF REVIEW

The speed of removal from the plasma of apolipoprotein B-containing lipoproteins, for example, chylomicrons, VLDL and LDL is determinant of the plasma concentration of these lipoproteins, is influenced by genetic features and ambient factors, and has implications in atherogenesis. As aging increases the clinical complications of atherosclerosis, it is important to appraise the status of the removal mechanisms in elderly individuals.

RECENT FINDINGS

Removal of triglyceride-rich lipoproteins remnants is delayed but the triglyceride breakdown is unchanged in elderly individuals. The discovery of PCSK9, enzyme that degrades LDL receptors, and the recent observation that PCSK9 is elevated in the elderly raises another hypothesis to account for the increased LDL-cholesterol levels in the elderly. The removal of cholesterol from cells by HDL, the first step of cholesterol reverse transport is also less efficient in the elderly, which may compromise the body cholesterol homeostasis.

SUMMARY

Aging determines reduction of the efficiency of lipoprotein plasma removal mechanisms, which is implicated in increased incidence of cardia complications. Moreover, aging is frequently accompanied by physical activity reduction, weight gain, and metabolic disturbances that can further decrease the efficacy of the removal mechanisms. This knowledge is important for promoting cardiovascular health in the elderly and prolonging survival.

Comparison of nonfasting and fasting lipoprotein subfractions and size in 15,397 apparently healthy individuals: An analysis from the VITamin D and OmegA-3 TriaL

BACKGROUND

Elevated postprandial triglycerides reflect a proatherogenic milieu, but underlying mechanisms are unclear.

OBJECTIVE

We examined differences between fasting and nonfasting profiles of directly measured lipoprotein size and subfractions to assess if postprandial triglycerides reflected increases in very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL) and remnants, or small dense lipid depleted LDL (sdLDL) particles.

METHODS

We conducted a cross-sectional analysis of 15,397 participants (10,135 fasting; 5262 nonfasting [<8 hours since last meal]) from the VITamin D and OmegA-3 TriaL. Baseline cholesterol subfractions were measured by the vertical auto profile method and particle subfractions by ion mobility. We performed multivariable linear regression adjusting for cardiovascular and lipoprotein-modifying risk factors.

RESULTS

Mean age (SD) was 68.0 years (±7.0), with 50.9% women. Adjusted mean triglyceride concentrations were higher nonfasting by 17.8 ± 1.3%, with higher nonfasting levels of directly measured VLDL cholesterol (by 3.5 ± 0.6%) and total VLDL particles (by 2.0 ± 0.7%), specifically large VLDL (by 12.3 ± 1.3%) and medium VLDL particles (by 5.3 ± 0.8%), all P < .001. By contrast, lower concentrations of low density lipoprotein (LDL) and IDL cholesterol and particles were noted for nonfasting participants. sdLDL cholesterol levels and particle concentrations showed no statistically significant difference by fasting status (-1.3 ± 2.1% and 0.07 ± 0.6%, respectively, P > .05).

CONCLUSIONS

Directly measured particle and cholesterol concentrations of VLDL, not sdLDL, were higher nonfasting and may partly contribute to the proatherogenicity of postprandial hypertriglyceridemia. These differences, although statistically significant, were small and may not fully explain the increased risk of postprandial hypertriglyceridemia.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY GUIDELINES FOR MANAGEMENT OF DYSLIPIDEMIA AND PREVENTION OF CARDIOVASCULAR DISEASE

OBJECTIVE

The development of these guidelines is mandated by the American Association of Clinical Endocrinologists (AACE) Board of Directors and American College of Endocrinology (ACE) Board of Trustees and adheres with published AACE protocols for the standardized production of clinical practice guidelines (CPGs).

METHODS

Recommendations are based on diligent reviews of the clinical evidence with transparent incorporation of subjective factors, according to established AACE/ACE guidelines for guidelines protocols.

RESULTS

The Executive Summary of this document contains 87 recommendations of which 45 are Grade A (51.7%), 18 are Grade B (20.7%), 15 are Grade C (17.2%), and 9 (10.3%) are Grade D. These detailed, evidence-based recommendations allow for nuance-based clinical decision-making that addresses multiple aspects of real-world medical care. The evidence base presented in the subsequent Appendix provides relevant supporting information for Executive Summary Recommendations. This update contains 695 citations of which 203 (29.2 %) are EL 1 (strong), 137 (19.7%) are EL 2 (intermediate), 119 (17.1%) are EL 3 (weak), and 236 (34.0%) are EL 4 (no clinical evidence).

CONCLUSION

This CPG is a practical tool that endocrinologists, other health care professionals, health-related organizations, and regulatory bodies can use to reduce the risks and consequences of dyslipidemia. It provides guidance on screening, risk assessment, and treatment recommendations for a range of individuals with various lipid disorders. The recommendations emphasize the importance of treating low-density lipoprotein cholesterol (LDL-C) in some individuals to lower goals than previously endorsed and support the measurement of coronary artery calcium scores and inflammatory markers to help stratify risk. Special consideration is given to individuals with diabetes, familial hypercholesterolemia, women, and youth with dyslipidemia. Both clinical and cost-effectiveness data are provided to support treatment decisions.

ABBREVIATIONS

4S = Scandinavian Simvastatin Survival Study A1C = glycated hemoglobin AACE = American Association of Clinical Endocrinologists AAP = American Academy of Pediatrics ACC = American College of Cardiology ACE = American College of Endocrinology ACS = acute coronary syndrome ADMIT = Arterial Disease Multiple Intervention Trial ADVENT = Assessment of Diabetes Control and Evaluation of the Efficacy of Niaspan Trial AFCAPS/TexCAPS = Air Force/Texas Coronary Atherosclerosis Prevention Study AHA = American Heart Association AHRQ = Agency for Healthcare Research and Quality AIM-HIGH = Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides trial ASCVD = atherosclerotic cardiovascular disease ATP = Adult Treatment Panel apo = apolipoprotein BEL = best evidence level BIP = Bezafibrate Infarction Prevention trial BMI = body mass index CABG = coronary artery bypass graft CAC = coronary artery calcification CARDS = Collaborative Atorvastatin Diabetes Study CDP = Coronary Drug Project trial CI = confidence interval CIMT = carotid intimal media thickness CKD = chronic kidney disease CPG(s) = clinical practice guideline(s) CRP = C-reactive protein CTT = Cholesterol Treatment Trialists CV = cerebrovascular CVA = cerebrovascular accident EL = evidence level FH = familial hypercholesterolemia FIELD = Secondary Endpoints from the Fenofibrate Intervention and Event Lowering in Diabetes trial FOURIER = Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects With Elevated Risk trial HATS = HDL-Atherosclerosis Treatment Study HDL-C = high-density lipoprotein cholesterol HeFH = heterozygous familial hypercholesterolemia HHS = Helsinki Heart Study HIV = human immunodeficiency virus HoFH = homozygous familial hypercholesterolemia HPS = Heart Protection Study HPS2-THRIVE = Treatment of HDL to Reduce the Incidence of Vascular Events trial HR = hazard ratio HRT = hormone replacement therapy hsCRP = high-sensitivity CRP IMPROVE-IT = Improved Reduction of Outcomes: Vytorin Efficacy International Trial IRAS = Insulin Resistance Atherosclerosis Study JUPITER = Justification for the Use of Statins in Primary Prevention: An Intervention Trial Evaluating Rosuvastatin LDL-C = low-density lipoprotein cholesterol Lp-PLA2 = lipoprotein-associated phospholipase A2 MACE = major cardiovascular events MESA = Multi-Ethnic Study of Atherosclerosis MetS = metabolic syndrome MI = myocardial infarction MRFIT = Multiple Risk Factor Intervention Trial NCEP = National Cholesterol Education Program NHLBI = National Heart, Lung, and Blood Institute PCOS = polycystic ovary syndrome PCSK9 = proprotein convertase subtilisin/kexin type 9 Post CABG = Post Coronary Artery Bypass Graft trial PROSPER = Prospective Study of Pravastatin in the Elderly at Risk trial QALY = quality-adjusted life-year ROC = receiver-operator characteristic SOC = standard of care SHARP = Study of Heart and Renal Protection T1DM = type 1 diabetes mellitus T2DM = type 2 diabetes mellitus TG = triglycerides TNT = Treating to New Targets trial VA-HIT = Veterans Affairs High-Density Lipoprotein Cholesterol Intervention Trial VLDL-C = very low-density lipoprotein cholesterol WHI = Women's Health Initiative.

Removal of Chylomicron Remnants from the Bloodstream is Delayed in Aged Subjects

Dietary fats absorbed in the intestine are transported in the circulation as chylomicrons and remnants that have atherogenic potential. Although postprandial lipidemia is increased in older subjects, the specific chylomicron metabolism has not been explored in older subjects nor compared to young subjects, which is the focus of this study. After a 12 h fast, artificially-made emulsions similar to lymph chylomicrons and doubly labeled with radioactive cholesteryl esters and triglycerides were intravenously injected in 23 older (66±4 years) and 20 young (24±3 years) subjects. Sequential blood samples were collected to determine fractional clearance rates (FCR, in min^-1) by compartmental analysis. Older subjects had higher LDL-cholesterol (p<0.001) and triglycerides (p<0.0001) than young subjects; HDL-cholesterol presented no difference. The emulsion cholesteryl-ester FCR was lower in older subjects compared to the young (p=0.0001). The emulsion triglyceride FCR did not differ in the two groups. Tested in vitro, however, the lipolysis of the emulsion triglycerides was less intense in the older than in the young subjects. As delayed removal of remnants, indicated by the pronouncedly smaller cholesteryl ester FCR, is related to the presence of cardiovascular diseases, this can be a risk factor which could accelerate atherogenic complications occurring in aged subjects

Different Patterns of Walking and Postprandial Triglycerides in Older Women

Purpose

Although a single bout of continuous exercise (≥30 min) reduces postprandial triglyceride (TG), little evidence is available regarding the effect of multiple short (≤10 min) bouts of exercise on postprandial TG in individuals at increased risk for cardiovascular diseases. This study compared the effects of different patterns of walking on postprandial TG in postmenopausal, older women with hypertriglyceridemia.

Methods

Twelve inactive women (mean age ± SD, 71 ± 5 yr) with hypertriglyceridemia (fasting TG ≥1.70 mmol·L⁻¹) completed three, 1-d laboratory-based trials in a random order: 1) control, 2) continuous walking, and 3) multiple short bouts of walking. On the control trial, participants sat in a chair for 8 h. For the walking trials, participants walked briskly in either one 30-min bout in the morning (0900–0930 h) or twenty 90-s bouts over 8 h. Except for walking, both exercise trials mimicked the control trial. In each trial, participants consumed a standardized breakfast (0800 h) and lunch (1100 h). Venous blood samples were collected in the fasted state and at 2, 4, 6, and 8 h after breakfast.

Results

The serum TG incremental area under the curve was 35% and 33% lower on the continuous and multiple short bouts of walking trials than that on the control trial (8.2 ± 3.1 vs 8.5 ± 5.4 vs 12.7 ± 5.8 mmol per 8 h·L⁻¹, respectively; main effect of trial: effect size = 0.459, P = 0.001).

Conclusions

Accumulating walking in short bouts limits postprandial TG in at-risk, inactive older women with fasting hypertriglyceridemia.

Influence of Apolipoprotein E on the Lipid Profile and Postprandial Triglyceride Levels in Brazilian Postmenopausal Women With Artery Disease

This study confirms the association of risk factors for coronary artery disease (CAD) and the apoE polymorphisms, specifically related to the APOE*4 allele, with coronary disease in postmenopausal women. Significantly altered values of the lipid profile were found in patients when compared with controls, independent of the presence of the APOE*4 allele. However, the controls showed higher high-density lipoprotein cholesterol (HDL-C) levels and reduced triglyceride (TG) levels, differing significantly from patients. In this case, the study of subgroups, considering the APOE*3/3 and APOE*3/4 genotypes, suggests that the APOE*4 allele is not implicated in the variations of the lipid profile of patients and determined an increase in the production levels of HDL-C and a reduction in TG highly benefiting the control group compared with APOE*3/3 genotype. The metabolic kinetics of TG, although with the same pattern between groups, and the presence of the APOE*4 allele are suggested to be associated with accelerated clearance compared with APOE*3 allele in non-CAD group.

The effect of exercise intensity and excess postexercise oxygen consumption on postprandial blood lipids in physically inactive men

Reductions in postprandial lipemia have been observed following aerobic exercise of sufficient energy expenditure. Increased excess postexercise oxygen consumption (EPOC) has been documented when comparing high- versus low-intensity exercise. The contribution of EPOC energy expenditure to alterations in postprandial lipemia has not been determined. The purpose of this study was to evaluate the effects of low- and high-intensity exercise on postprandial lipemia in healthy, sedentary, overweight and obese men (age, 43 ± 10 years; peak oxygen consumption, 31.1 ± 7.5 mL·kg^-1·min^-1; body mass index, 31.8 ± 4.5 kg/m²) and to determine the contribution of EPOC to reductions in postprandial lipemia. Participants completed 4 conditions: nonexercise control, low-intensity exercise at 40%-50% oxygen uptake reserve (LI), high-intensity exercise at 70%-80% oxygen uptake reserve (HI), and HI plus EPOC re-feeding (HI+EERM), where the difference in EPOC energy expenditure between LI and HI was re-fed in the form of a sports nutrition bar (Premier Nutrition Corp., Emeryville, Calif., USA). Two hours following exercise participants ingested a high-fat (1010 kcals, 99 g sat fat) test meal. Blood samples were obtained before exercise, before the test meal, and at 2, 4, and 6 h postprandially. Triglyceride incremental area under the curve was significantly reduced following LI, HI, and HI+EERM when compared with nonexercise control (p < 0.05) with no differences between the exercise conditions (p > 0.05). In conclusions, prior LI and HI exercise equally attenuated postprandial triglyceride responses to the test meal. The extra energy expended during EPOC does not contribute significantly to exercise energy expenditure or to reductions in postprandial lipemia in overweight men.

Dietary fat and physiological determinants of plasma chylomicron remnant homoeostasis in normolipidaemic subjects: insight into atherogenic risk

TAG depleted remnants of postprandial chylomicrons are a risk factor for atherosclerosis. Recent studies have demonstrated that in the fasted state, the majority of chylomicrons are small enough for transcytosis to arterial subendothelial space and accelerate atherogenesis. However, the size distribution of chylomicrons in the absorptive state is unclear. This study explored in normolipidaemic subjects the postprandial distribution of the chylomicron marker, apoB-48, in a TAG-rich lipoprotein plasma fraction (Svedberg flotation rate (Sf>400), in partially hydrolysed remnants (Sf 20-400) and in a TAG-deplete fraction (Sf<20), following ingestion of isoenergetic meals with either palm oil (PO), rice bran or coconut oil. Results from this study show that the majority of fasting chylomicrons are within the potentially pro-atherogenic Sf<20 fraction (70-75 %). Following the ingestion of test meals, chylomicronaemia was also principally distributed within the Sf<20 fraction. However, approximately 40 % of subjects demonstrated exaggerated postprandial lipaemia specifically in response to the SFA-rich PO meal, with a transient shift to more buoyant chylomicron fractions. The latter demonstrates that heterogeneity in the magnitude and duration of hyper-remnantaemia is dependent on both the nature of the meal fatty acids ingested and possible metabolic determinants that influence chylomicron metabolism. The study findings reiterate that fasting plasma TAG is a poor indicator of atherogenic chylomicron remnant homoeostasis and emphasises the merits of considering specifically, chylomicron remnant abundance and kinetics in the context of atherogenic risk. Few studies address the latter, despite the majority of life being spent in the postprandial and absorptive state.

Postprandial Hyperlipidemia and Remnant Lipoproteins

Fasting hypertriglyceridemia is positively associated with the morbidity of coronary heart disease (CHD), and postprandial (non-fasting) hypertriglyceridemia is also correlated with the risk status for CHD, which is related to the increase in chylomicron (CM) remnant lipoproteins produced from the intestine. CM remnant particles, as well as oxidized low density lipoprotein (LDL) or very low density lipoprotein (VLDL) remnants, are highly atherogenic and act by enhancing systemic inflammation, platelet activation, coagulation, thrombus formation, and macrophage foam cell formation. The cholesterol levels of remnant lipoproteins significantly correlate with small, dense LDL; impaired glucose tolerance (IGT) and CHD prevalence. We have developed an assay of apolipoprotein (apo)B-48 levels to evaluate the accumulation of CM remnants. Fasting apoB-48 levels correlate with the morbidity of postprandial hypertriglyceridemia, obesity, type III hyperlipoproteinemia, the metabolic syndrome, hypothyroidism, chronic kidney disease, and IGT. Fasting apoB-48 levels also correlate with carotid intima-media thickening and CHD prevalence, and a high apoB-48 level is a significant predictor of CHD risk, independent of the fasting TG level. Diet interventions, such as dietary fibers, polyphenols, medium-chain fatty acids, diacylglycerol, and long-chain n-3 polyunsaturated fatty acids (PUFA), ameliorate postprandial hypertriglyceridemia, moreover, drugs for dyslipidemia (n-3 PUFA, statins, fibrates or ezetimibe) and diabetes concerning incretins (dipeptidyl-peptidase IV inhibitor or glucagon like peptide-1 analogue) may improve postprandial hypertriglyceridemia. Since the accumulation of CM remnants correlates to impaired lipid and glucose metabolism and atherosclerotic cardiovascular events, further studies are required to investigate the characteristics, physiological activities, and functions of CM remnants for the development of new interventions to reduce atherogenicity.

Investigation into the acute effects of total and partial energy restriction on postprandial metabolism among overweight/obese participants

The intermittent energy restriction (IER) approach to weight loss involves short periods of substantial (75-100 %) energy restriction (ER) interspersed with normal eating. This study aimed to characterise the early metabolic response to these varying degrees of ER, which occurs acutely and prior to weight loss. Ten (three female) healthy, overweight/obese participants (36 (SEM 5) years; 29·0 (sem 1·1) kg/m2) took part in this acute three-way cross-over study. Participants completed three 1-d dietary interventions in a randomised order with a 1-week washout period: isoenergetic intake, partial 75 % ER and total 100 % ER. Fasting and postprandial (6-h) metabolic responses to a liquid test meal were assessed the following morning via serial blood sampling and indirect calorimetry. Food intake was also recorded for two subsequent days of ad libitum intake. Relative to the isoenergetic control, postprandial glucose responses were increased following total ER (+142 %; P=0·015) and to a lesser extent after partial ER (+76 %; P=0·051). There was also a delay in the glucose time to peak after total ER only (P=0·024). Both total and partial ER interventions produced comparable reductions in postprandial TAG responses (-75 and -59 %, respectively; both P<0·05) and 3-d energy intake deficits of approximately 30 % (both P=0·015). Resting and meal-induced thermogenesis were not significantly affected by either ER intervention. In conclusion, our data demonstrate the ability of substantial ER to acutely alter postprandial glucose-lipid metabolism (with partial ER producing the more favourable overall response), as well as incomplete energy-intake compensation amongst overweight/obese participants. Further investigations are required to establish how metabolism adapts over time to the repeated perturbations experienced during IER, as well as the implications for long-term health.

Effect of sleeve gastrectomy on postprandial lipoprotein metabolism in morbidly obese patients

BACKGROUND

Obesity is associated with abnormal fasting and postprandial lipids, which may link obesity with atherosclerosis. We explored fasting and postprandial lipids in morbidly obese patients treated with sleeve gastrectomy and in control subjects.

METHODS

After fasting for 12 h 15 morbidly obese patients (BMI 51.4±6.5 kg/m2, 43.7±12.6 years) received a standardized oral fat load before and 3 months after bariatric surgery (sleeve gastrectomy). Controls (n=9, BMI 23.1±1.4 kg/m²) were studied once. Plasma was obtained fasting and then postprandially every 2 h for 8 h. Triglycerides (TG), chylomicron-TG (CM-TG), VLDL/chylomicron-remnant (VLDL/CR)-TG, cholesterol, LDL-cholesterol, VLDL/CR-cholesterol and HDL-cholesterol were isolated by ultracentrifugation at each time point. Postprandial values were expressed as area under the curve (AUC) and incremental area under the curve (iAUC). In addition, fasting glucose and insulin values and HOMA-IR-Index was measured (n=14).

RESULTS

Compared to controls morbidly obese patients had elevated TG and slightly altered postprandial lipids. Following surgery (weight loss 23.4 kg±6.2 kg; p<0.001) fasting TG (-19.1%; p=0.04), VLDL/CR-TG (-20.0%; p=0.05) decreased significantly, while fasting cholesterol, VLDL-, HDL- and LDL-cholesterol did not change. AUC and iAUC decreased significantly for VLDL/CR-TG (-20.4%, p=0.04 and -38.5%, p=0.04, respectively). Neither fasting nor postprandial changes correlated with the change in weight. In patients with preoperatively elevated TG (>150 mg/dl) a similar pattern was observed. Fasting insulin and HOMA were reduced significantly (-51.9%; p=0.004 and -47.9%; p=0.011).

CONCLUSIONS

Three months after sleeve gastrectomy fasting and postprandial lipoprotein metabolism and glucose metabolism is improved in morbidly obese patients. The potential mechanisms may relate to decreased caloric intake but also to hormonal changes.

Effect of Spirulina maxima on postprandial lipemia in young runners: a preliminary report

Trained people exhibit low plasma concentrations of triacylglcyerols in both fasting and postprandial states. Exercise practice is commonly believed to improve postprandial lipemia. In addition, elevated postprandial lipemia is an indicator of poor lipid clearance, and it has been associated with atherosclerosis, insulin resistance, and obesity. Spirulina maxima is an edible microorganism with a high nutritional value. When it is consumed, beneficial properties to health have been demonstrated, such as hypolipemic and antihypertensive properties in human beings. This work evaluates the effects of orally administrated S. maxima on postprandial lipemia in a young Mexican sporting population after 15 days of consumption, as a possible alternative treatment to improve their lipid clearance. Forty-one runners (10-26 years old; 21 men and 20 women) volunteered to participate in the study. All of them were physically active for at least 1 year before the study and were not undergoing training during the study. The subjects consumed 5 g of Spirulina during 15 days. Before and after the treatment with Spirulina, they consumed (12 h fasting) a standardized meal with high fat content (53.2% total calories). Postprandial lipemia was measured at 1.5, 3, and 4.5 h after the fatty meal. Fasting plasma triacylglycerol (TAG) concentrations were lower after Spirulina treatment than before treatment. In addition, the postprandial area under the curve of TAG concentrations was lower after the treatment with Spirulina. Sixty-two percent of the youngest runners (10-16 years) studied exhibited the best response to the treatment. Orally administered S. maxima decreased postprandial lipemia in sporting teenagers. The youngest people were the most responsive to the beneficial effects of Spirulina on postprandial lipemia.

Postprandial lipoprotein metabolism: VLDL vs chylomicrons

Since Zilversmit first proposed postprandial lipemia as the most common risk of cardiovascular disease, chylomicrons (CM) and CM remnants have been thought to be the major lipoproteins which are increased in the postprandial hyperlipidemia. However, it has been shown over the last two decades that the major increase in the postprandial lipoproteins after food intake occurs in the very low density lipoprotein (VLDL) remnants (apoB-100 particles), not CM or CM remnants (apoB-48 particles). This finding was obtained using the following three analytical methods; isolation of remnant-like lipoprotein particles (RLP) with specific antibodies, separation and detection of lipoprotein subclasses by gel permeation HPLC and determination of apoB-48 in fractionated lipoproteins by a specific ELISA. The amount of the apoB-48 particles in the postprandial RLP is significantly less than the apoB-100 particles, and the particle sizes of apoB-48 and apoB-100 in RLP are very similar when analyzed by HPLC. Moreover, CM or CM remnants having a large amount of TG were not found in the postprandial RLP. Therefore, the major portion of the TG which is increased in the postprandial state is composed of VLDL remnants, which have been recognized as a significant risk for cardiovascular disease.

Dietary fats, cerebrovasculature integrity and Alzheimer's disease risk

An emerging body of evidence is consistent with the hypothesis that dietary fats influence Alzheimer's disease (AD) risk, but less clear is the mechanisms by which this occurs. Alzheimer's is an inflammatory disorder, many consider in response to fibrillar formation and extracellular deposition of amyloid-beta (Abeta). Alternatively, amyloidosis could notionally be a secondary phenomenon to inflammation, because some studies suggest that cerebrovascular disturbances precede amyloid plaque formation. Hence, dietary fats may influence AD risk by either modulating Abeta metabolism, or via Abeta independent pathways. This review explores these two possibilities taking into consideration; (i) the substantial affinity of Abeta for lipids and its ordinary metabolism as an apolipoprotein; (ii) evidence that Abeta has potent vasoactive properties and (iii) studies which show that dietary fats modulate Abeta biogenesis and secretion. We discuss accumulating evidence that dietary fats significantly influence cerebrovascular integrity and as a consequence altered Abeta kinetics across the blood-brain barrier (BBB). Specifically, chronic ingestion of saturated fats or cholesterol appears to results in BBB dysfunction and exaggerated delivery from blood-to-brain of peripheral Abeta associated with lipoproteins of intestinal and hepatic origin. Interestingly, the pattern of saturated fat/cholesterol induced cerebrovascular disturbances in otherwise normal wild-type animal strains is analogous to established models of AD genetically modified to overproduce Abeta, consistent with a causal association. Saturated fats and cholesterol may exacerbate Abeta induced cerebrovascular disturbances by enhancing exposure of vessels of circulating Abeta. However, presently there is no evidence to support this contention. Rather, SFA and cholesterol appear to more broadly compromise BBB integrity with the consequence of plasma protein leakage into brain, including lipoprotein associated Abeta. The latter findings are consistent with the concept that AD is a dietary-fat induced phenotype of vascular dementia, reflecting the extraordinary entrapment of peripherally derived lipoproteins endogenously enriched in Abeta. Rather than being the initiating trigger for inflammation in AD, accumulation of extracellular lipoprotein-Abeta may be a secondary amplifier of dietary induced inflammation, or possibly, simply be consequential. Clearly, delineating the mechanisms by which dietary fats increase AD risk may be informative in developing new strategies for prevention and treatment of AD.

Remnant lipoproteins as strong key particles to atherogenesis

Recent epidemiologic studies have revealed that hypertriglyceridemia is associated with atherosclerosis independent of other coronary risk factors. However, it is difficult to select patients at high risk for coronary artery disease using only serum triglyceride levels compared with low-density lipoprotein cholesterol levels since multiple factors are associated with elevating triglycerides. Atherosclerotic diseases with high triglyceride levels can be found in patients with familial combined hyperlipidemia, diabetes mellitus, and metabolic syndrome, in which remnant lipoproteins accumulate in the circulating blood. Recent researches have paid attention to remnant lipoproteins as atherogenic particles with the development of methods for measuring remnant cholesterol levels and apolipoprotein B-48 levels directly from human serum. Measurement of these parameters in addition to serum triglycerides may help to distinguish high-risk patients and enable us to prevent or suppress the progression of atherosclerotic diseases in those patients. However, questions remain to be answered to evaluate the significance of remnant lipoproteins. Here, we focus on three issues: the underlying problems in measuring remnant lipoprotein cholesterol, the assessment of postprandial hyperlipidemia as an atherogenic condition, and finally a review of our experimental and clinical findings about the mechanisms by which remnant lipoproteins induce atherosclerosis.

Postprandial triacylglycerol metabolism is modified by the presence of genetic variation at the perilipin (PLIN) locus in 2 white populations

BACKGROUND

Several perilipin (PLIN) polymorphic sites have been studied for their potential use as markers for obesity and the metabolic syndrome.

OBJECTIVE

We aimed to examine whether the presence of polymorphisms at the perilipin (PLIN) locus (PLIN1, 6209T-->C; PLIN4, 11482G-->A; PLIN5, 13041A-->G; and PLIN6, 14995A-->T) influence postprandial lipoprotein metabolism in 2 white populations.

DESIGN

Eighty-eight healthy Spanish men and 271 healthy US subjects (men and women) underwent an oral-fat-load test in 2 independent studies. Blood samples were taken in the fasting state and during the postprandial phase at regular intervals. Total cholesterol and triacylglycerol and triacylglycerol in triacylglycerol-rich lipoproteins (TRL, large and small) were measured.

RESULTS

Carriers of the minor C allele at the PLIN1 variant displayed lower postprandial concentrations of large-TRL triacylglycerol (Spanish subjects: P = 0.024; US subjects: P = 0.005) than did subjects carrying the T/T genotype. The same pattern was observed in the Spanish population at the PLIN4 locus (P = 0.015), and both SNPs were in strong linkage disequilibrium. In both populations, subjects carrying the minor C and A alleles at PLIN1 and PLIN4, respectively, had significantly lower postprandial concentrations of plasma triacylglycerol (P < 0.05) and lower concentrations of small-TRL triacylglycerol than did those who were homozygous for the major alleles at PLIN1 and PLIN4 (Spanish subjects: P = 0.020 and 0.008, respectively; US subjects: P = 0.021 and 0.035, respectively).

CONCLUSION

These 2 studies suggest that the presence of the minor C and A alleles at PLIN1 and PLIN4, respectively, are associated with a lower postprandial response that may result in lower atherogenic risk for these persons.

Influence of aging and menopause on postprandial lipoprotein responses in healthy adult women

AIM

To analyze the influence of menopause and age on postprandial lipoprotein responses in healthy adult women.

METHOD

Twenty-seven healthy young and middle-aged pre- and postmenopausal female volunteers aged 21-53 y were enrolled. They ingested OFTT cream(Jomo, Takasaki, Japan). Fasting and postprandial blood samples were obtained for up to 6 h, and serum concentrations of lipoproteins were analyzed.

RESULTS

In the postprandial phase, serum triglycerides(TG), remnant-like particle(RLP)-TG(RLP-TG), RLP-cholesterol(RLP-C), and TG-rich lipoprotein-TG(TRL-TG)concentrations in all groups peaked after 2 h. After 4 h, the TG, RLP-C, RLP-TG and TRL-TG concentrations in the young women returned to the fasting concentrations. However, at 6 h, these parameters in the pre- and postmenopausal women had barely returned to the fasting concentrations.

CONCLUSION

The present results suggest that:(1)the magnitude of postprandial TG concentrations is dependent on age, but not on menopause;(2)clearance of remnant lipoproteins is delayed with age in pre- and postmenopausal women compared to young women, and(3)menopause is associated with an increase of RLP-C, but may not influence LDL particle size.

Prior exercise does not affect chylomicron particle number following a mixed meal of moderate fat content

Background

A single session of exercise has been reported to reduce fasting and postprandial triacylglycerol concentrations on the subsequent day. It is possible that exercise also reduces chylomicron particle number, which may underlie the observed reduction in postprandial triacylglycerol concentration. In the present study we aimed to determine whether a single session of exercise reduces fasting and postprandial chylomicron particle number on the subsequent day. In a randomised crossover design eight lean and healthy male and female subjects attended two postprandial testing days. On the previous day the subjects either performed 90 minutes of moderate intensity exercise or did not perform any exercise. Fasting blood samples were then collected prior to ingestion of a moderate fat mixed meal (0.44 g fat, 0.94 g carbohydrate, 0.27 g protein/kg body weight), blood was then collected after 1 h, 2 h, 4 h, 6 h, and 8 h.

Results

The fasting and postprandial apolipoprotein B48 concentration (marker of chylomicron particle number) was not affected by prior exercise. However exercise reduced fasting triacylglycerol concentration by 16% (P < 0.05) and there was a trend towards a reduction in the total area under the postprandial triacylglycerol curve (23%; P = 0.053). However when corrected for baseline concentration postprandial triacylglycerol concentration was not affected by prior exercise.

Conclusion

A single session of exercise of moderate intensity and 90 minutes duration reduces fasting triacylglycerol levels, however fasting and postprandial chylomicron particle number was unaffected. Furthermore it appears that previously observed reductions in postprandial triacylglycerol levels following exercise are only mediated following consumption of high, non-physiologically relevant doses of fat.

Postprandial lipemia is modified by the presence of the APOB-516C/T polymorphism in a healthy Caucasian population

Apolipoprotein (apoB) plays a fundamental role in the transport and metabolism of plasma triacylglycerols (TAGs) and cholesterol. Several apoB polymorphic sites have been studied for their potential use as markers for coronary heart disease in the population. In view of the importance of apoB in postprandial metabolism, our objective was to determine whether the presence of the -516C/T polymorphism in the APOB gene promoter could influence postprandial lipoprotein metabolism in healthy subjects. Forty-seven volunteers who were homozygous for the E3 allele at the APOE gene were selected (30 homozygous for the common genotype (C/C) and 17 heterozygotes for the -516T allele (C/T). They were given a fat-rich meal containing 1 g fat and 7 mg cholesterol per kg body weight and vitamin A 60,000 IU/m(2) body surface. Fat accounted for 60% of calories, and protein and carbohydrates for 15 and 25% of energy, respectively. Blood samples were taken at time 0, every 1 h until 6 h, and every 2.5 h until 11 h. Total cholesterol and TAGs in plasma, and cholesterol, TAGs and retinyl palmitate in triacylglycerol-rich lipoproteins (large and small triacylglycerol-rich lipoproteins) were determined by ultracentrifugation. Individuals carrying the C/T genotype presented greater postprandial concentrations of TAGs in small triacylglycerol-rich lipoproteins than did carriers of the C/C genotype (P = 0.022). Moreover, C/T individuals presented higher concentrations of plasma TAGs during the postprandial period than did C/C subjects (P = 0.039). No other statistically significant genotype-related differences for other parameters were observed. These results suggest that the presence of the genotype C/T is associated with a higher postprandial response. Thus, the allele variability in the -516C/T polymorphism in the APOB gene promoter may partly explain the interindividual differences in postprandial lipemic response in healthy subjects.

Effect of weight loss on the postprandial response to high-fat and high-carbohydrate meals in obese women

OBJECTIVE

To assess the effect of weight loss on the plasma lipid and remnant-like lipoprotein cholesterol (RLPc) response to a high-fat or a high-carbohydrate meal in a population of obese women.

DESIGN

Nutritional intervention study.

SUBJECTS

Sixteen obese women (mean body mass index (BMI): 37.6+/-5 kg/m(2)).

METHODS

Subjects were asked to follow an energy-restricted diet (800 kcal/day) for 7 weeks, followed by a 1-week maintenance diet. Before and after weight loss, each participant was given (in random order) two iso-energetic meals containing either 80% fat and 20% protein (the high-fat meal) or 80% carbohydrate and 20% protein (the high-carbohydrate meal). Blood samples were collected over the following 10-h period. A two-way analysis of variance with repeated measures was used to assess the effect of the meal and postprandial time on biological variables and postprandial responses (notably RLPc levels).

RESULTS

Weight loss was associated with a significant decrease in fasting triglyceride (P=0.0102), cholesterol (P<0.0001), low-density lipoprotein cholesterol (P=0.0003), high-density lipoprotein-cholesterol (P=0.0009) and RLPc (P=0.0015) levels. The triglyceride response to the high-fat meal was less intense after weight reduction than before (interaction P<0.002). This effect persisted after adjustment on baseline triglyceride levels. The triglyceride response to the high-carbohydrate meal was biphasic (i.e. with two peaks, 1 and 6 h after carbohydrate intake). After adjustment on baseline values, weight reduction was associated with a trend towards a reduction in the magnitude of the second triglyceride peak (interaction P<0.054). In contrast, there was no difference in postprandial RLPc responses before and after weight loss, again after adjustment on baseline levels.

CONCLUSION

Our data suggest that weight loss preferentially affects postprandial triglyceride metabolism.

Circadian rhythm of serum concentration of small dense low-density lipoprotein cholesterol

BACKGROUND

The atherogenicity of small dense low-density lipoprotein (sdLDL) has been reported and recently a new easy-handling method for measuring serum concentration of sdLDL cholesterol (sdLDLC) has been developed. Using this method, we observed the circadian rhythm of sdLDLC to determine the adequacy of fasting measurement of it and to seek the modulator of the atherogenic lipoprotein.

METHODS

Study population was consisted of 20 healthy volunteers (10 women and 10 men, mean age 28 y). They had 3 meals per day and blood samples were taken before and 2 h after every meal and next morning. Serum concentrations of sdLDLC and other valuables including triglyceride (TG) and remnant-like particles cholesterol (RLPC) were determined.

RESULTS

Serum concentration of sdLDLC had a unique circadian rhythm that was highest before breakfast (fasting status), decreased after each meal, hit the bottom after dinner and then increased during at night. Fasting sdLDLC was highly correlated with TG levels. The sum of the 6 TG values during a day (i.e., average TG level) had higher correlation coefficient with sdLDLC than fasting TG or fasting RLPC.

CONCLUSIONS

From the observation of the unique circadian rhythm, measuring sdLDLC at fasting status is exactly reasonable because it never underestimate the risk of atherosclerotic diseases. Measuring sdLDLC can also be used as a marker for average TG levels regardless of the existence of postprandial hyperlipidemia.

The elevation of ingested lipids within plasma chylomicrons is prolonged in men compared with women

The lipemic response to a high-fat meal is greater in men than in women. However, sex-related differences in the metabolic fate of ingested fat are not well understood. The purpose of this study was to measure the recovery of ingested fat in plasma fractions of chylomicrons (CHYLO), VLDL, and plasma fatty acids, as well as in expired breath (i.e., oxidation) in men and women. Nonobese subjects (n = 10; 5 men, 5 women) consumed 0.7 g fat/kg body weight containing 7 mg/kg of [1,1,1-13C]-trioleate the morning after an overnight fast. Plasma total triglyceride (TG) concentration and 13C recovery in the CHYLO, VLDL, and plasma fatty acid fractions, as well as expired breath samples, were measured over the 11-h period after the meal. Plasma total TG excursion was greater (P < 0.05) in men than in women during the 11-h period after the meal. Similarly, the recovery of the ingested tracer-labeled fat in the CHYLO fraction was greater in men than in women (main effect for sex; P < 0.05). Recovery of ingested tracer-labeled fat in VLDL, the plasma fatty acid fraction, and expired breath did not differ in men and women. Therefore, the elevated postprandial lipemia found in men compared with women was due to a prolonged availability of the lipid in chylomicrons, but was not related to differences in oxidation rates or incorporation of the ingested lipid into VLDL by the liver.

Metabolism of apoB lipoproteins of intestinal and hepatic origin during constant feeding of small amounts of fat

We aimed to identify mechanisms by which apolipoprotein B-48 (apoB-48) could have an atherogenic role by simultaneously studying the metabolism of postprandial apoB-48 and apoB-100 lipoproteins. The kinetics of apoB-48 and apoB-100, each in four density subfractions of VLDL and intermediate density lipoprotein (IDL), were studied by stable isotope labeling in a constantly fed state with half-hourly administration of almond oil in five postmenopausal women. A non-steady-state, multicompartmental model was used. Despite a much lower production rate, VLDL and IDL apoB-48 shared a similar secretion pattern with apoB-100: both were directly secreted into all fractions with similar percentage mass distributions. Fractional catabolic rates (FCRs) of apoB-48 and apoB-100 were similar in VLDL and IDL. We identified a fast turnover compartment of light VLDL that had a residence time of <30 min for apoB-48 and apoB-100. Finally, a high secretion rate of apoB-48 was associated with a slow FCR of VLDL and IDL apoB-100. In conclusion, the intestine secretes a spectrum of apoB lipoproteins, similar to what the liver secretes, albeit with a much lower secretion rate. Once in plasma, intestinal and hepatic triglyceride-rich lipoproteins have similar rates of clearance and participate interactively in similar metabolic pathways, with high apoB-48 production inhibiting the clearance of apoB-100.

Prescribing Aerobic Exercise for the Regulation of Postprandial Lipid Metabolism

Prolonged presence of elevated plasma triglycerides (TGs) during the postprandial period has been suggested to increase the risk for coronary artery disease. Aerobic exercise attenuates postprandial lipaemia and this has generally been described as a short-term effect of the exercise. Effects of exercise on postprandial lipaemia have mostly been investigated, and documented, with large exercise-induced energy expenditures (i.e. 1000 kcal). The exact mechanisms involved in the attenuation of postprandial lipaemia with exercise are not completely understood, but it appears that at least two mechanisms are involved: a decrease in TG secretion by the liver and an increase in plasma TG clearance by the muscle. Changes in the metabolism of other lipids, such as those in high-density lipoprotein cholesterol, have been documented only when the exercise is performed some hours before the fat meal. Although factors such as the physical fitness and percentage body fat of an individual are likely to also be involved, the most important factors determining the magnitude of the attenuation in postprandial lipaemia appear to be the magnitude of the exercise-induced energy expenditure and the intensity of exercise. To date, the evidence suggests that healthy individuals can generally induce favourable changes in postprandial lipaemia with aerobic exercise that: (i) is completed during the period extending from 16 hours before a meal through 1.5 hours after a meal; (ii) is of moderate intensity; and (iii) results in an energy expenditure of approximately 500 kcal (or more).

Association between postprandial remnant-like particle triglyceride (RLP-TG) levels and carotid intima-media thickness (IMT) in Japanese patients with type 2 diabetes: assessment by meal tolerance tests (MTT)

Our study evaluated the relationship between the pathologic changes associated with atherosclerosis, as primarily represented by postprandial remnant-like lipoproteins and carotid intima-media thickness (IMT), in type 2 diabetic patients. Meal tolerance tests (MTT) were performed in 68 patients with type 2 diabetes. The subjects were divided by pre-meal and 2-h postprandial triglyceride (TG) levels into the normotriglyceridemia (NTG) group; the postprandial hypertriglyceridemia (PHTG) group; and the fasting hypertriglyceridemia (FHTG) group. HOMA-R values were significantly higher in the FHTG group than in the NTG group, with the plasma pre-heparin LPL mass and serum adiponectin levels in the FHTG and PHTG groups significantly lower than in the NTG group. One- and two hour postprandial RLP-TG levels were significantly higher in the PHTG group than in the NTG group, while there was no significant difference in postprandial glucose levels between the two groups. The IMT values were significantly higher in both the FHTG and PHTG groups than in the NTG group. Logistics regression analysis of the 1- and 2-h RLP-TG values using IMT as an induced variable showed the odds ratio for high IMT values to be 5.17 (p < 0.05) for the 1-h RLP-TG values and 3.01 (p = 0.105) for the 2-h RLP-TG values. Our study results suggest that delayed TG metabolism leading to the retention of remnants in type 2 diabetic patients appears to be closely associated with atherosclerosis, and that postprandial hyperlipidemia is an independent risk factor for the early onset of atherosclerosis.

Association between small dense low-density lipoprotein and postprandial accumulation of triglyceride-rich remnant-like particles in normotriglyceridemic patients with myocardial infarction

BACKGROUND

Although the small dense low-density lipoprotein (sd-LDL) is associated with hypertriglyceridemia, more than 60% of myocardial infarction (MI) patients are normotriglyceridemic in the fasting state. This study was aimed to investigate the relationship between the low-density lipoprotein (LDL) phenotype and postprandial hyperlipemia (PPL) in MI patients.

METHODS AND RESULTS

Oral fat tolerance tests were performed in 71 patients with acute MI and fasting triglyceride concentrations below 200 mg/dl. Postprandial changes in the LDL particle diameter (LDL-PD) and lipids over a 6-h period after a meal were compared among 4 groups of patients classified according to fasting triglyceride levels (A, B as <150, and C, D as > or =150) and postprandial triglyceride levels (A, C as <230 and B, D as > or =230). Although fasting concentrations of triglyceride and remnant-like particle (RLP)-triglyceride were significantly higher in group C than in group B, the areas under the curves of the RLPs were significantly higher in group B. The triglyceride-to-cholesterol ratio in the RLPs was significantly higher in the PPL group than in the nonPPL group postprandially. The prevalence of sd-LDL (LDL-PD < or =25.5 nm) was significantly higher in group D but similar between groups B and C (23%, 42%, 50% and 83% in groups A, B, C and D, respectively).

CONCLUSION

These results suggest that postprandial accumulation of triglyceride-rich lipoproteins is strongly associated with sd-LDL in MI patients without hypertriglyceridemia.

Diurnal and acute patterns of postprandial apolipoprotein B-48 in VLDL, IDL, and LDL from normolipidemic humans

Smaller size particles of intestinal origin may be more relevant to atherosclerosis than larger particles because of easier transendothelial transport. We examined the diurnal pattern in response to low-fat high-carbohydrate meals and the effect of a single high-fat milkshake on apoB-48 in very light Sf degrees >400, light Sf degrees 60-400, and dense Sf degrees 20-60 VLDL, IDL, and LDL in 24 subjects (12 in each study). After the high-fat meal, apoB-48 concentrations peaked at 3 h for very light VLDL, 4 h for light VLDL, and 5 h for dense VLDL and IDL, suggesting a delipidation cascade. The diurnal pattern was characterized by a sharp increase in light and dense VLDL apoB-48 after breakfast, reaching the highest concentration 4-8h after breakfast. Less response was observed after lunch, dinner or snack, despite 75% of energy supplied by these meals. The proportion of apoB-48 in LDL in the fasting state ranged between 48 and 54%. LDL apoB-48 concentration decreased by 35% after the high-fat meal, and slowly recovered to near fasting concentrations after 10-12 h. In contrast, in the diurnal study, LDL apoB-48 concentration steady increased peaking 13 h after breakfast, followed by a sharp decrease. In sum, most intestinally synthesized apoB lipoproteins circulate in LDL, and are likely formed in the late postprandial period from larger VLDL-size particles. Although small apoB-48 lipoproteins may be atherogenic remnant particles, their very low concentration may diminish their clinical significance.

8302A/C and (TTA)n polymorphisms in the HMG-CoA reductase gene may be associated with some plasma lipid metabolic phenotypes in patients with coronary heart disease

HMG-CoA reductase (HMGCR) is a rate-limiting enzyme that participates in cholesterol metabolism. Here we analyzed the 8302A/C and the (TTA)n polymorphisms in the HMGCR gene in 169 Chinese patients with coronary heart disease (CHD) and 161 age-matched controls. Results indicated that the levels of plasma VLDL and TG in patients with the AA genotype of the 8302A/C locus were significantly higher than in patients with other genotypes (P < 0.05). In addition, the frequency of allele A4 of the (TTA)n locus was higher (P < 0.05) and the frequency of allele A5 was lower (P = 0.002) in CHD patients than in the controls. This suggests that both polymorphisms in the HMGCR gene may be associated with lipid and lipoprotein abnormalities in CHD in the Chinese.

Postprandial lipoprotein changes in patients taking antiretroviral therapy for HIV infection

OBJECTIVE

Dyslipidemia is common among patients receiving antiretroviral therapy for HIV infection. The purpose of this study was to determine whether postprandial lipemia contributes to the dyslipidemia observed in HIV-positive patients taking antiretroviral therapy.

METHODS AND RESULTS

A standardized fat load was administered to 65 subjects (group 1 35 HIV-positive subjects receiving protease inhibitors [PIs]; group 2 20 HIV-positive subjects not receiving PIs; group 3 10 HIV-negative controls). Serum triglycerides, retinyl palmitate, and lipoproteins were measured using enzymatic and nuclear magnetic resonance spectroscopic techniques. Compared with HIV-negative controls, peak postprandial retinyl palmitate and large very low-density lipoprotein (VLDL) levels occurred later in both HIV-positive groups, and a delayed decrease in serum triglycerides was observed. However, postprandial areas under the curve (AUCs) for triglycerides, retinyl palmitate, chylomicrons, and large VLDL were similar. Postprandial AUCs for intermediate-density lipoproteins (IDLs) and low-density lipoproteins (LDLs) were higher in group 1 than groups 2 and 3 (all P<0.035).

CONCLUSIONS

Postprandial clearance of triglyceride-rich lipoproteins is delayed in HIV-positive individuals receiving antiretroviral therapy. Compared with HIV-positive individuals not on PIs, those taking PIs do not have increased postprandial triglyceride-rich lipoproteins but do have increased postprandial IDLs and LDLs. An oral fat load was administered to 55 HIV-positive and 10 HIV-negative individuals. Postprandial clearance of triglyceride-rich lipoproteins was delayed in HIV-positive individuals. Compared with HIV-positive subjects not on PIs, those taking PIs do not have increased postprandial triglyceride-rich lipoproteins but do have increased postprandial intermediate-density and low-density lipoproteins.

Triacylglycerol-rich lipoprotein margination: a potential surrogate for whole-body lipoprotein lipase activity and effects of eicosapentaenoic and docosahexaenoic acids

BACKGROUND

Margination occurs when blood borne particles attach to the vessel wall. Triacylglycerol-rich lipoprotein (TRL) particles marginate when they bind to endothelial lipoprotein lipase (LpL).

OBJECTIVE

This study was undertaken to determine whether TRL margination reflects in vivo LpL activity and whether n-3 fatty acids affect fasting and fed TRL margination.

DESIGN

Healthy subjects (n = 33) began with a 4-wk, placebo (olive oil; 4 g/d) run-in period and were then randomly assigned to 4 wk of treatment with 4 g/d of ethyl esters of either safflower oil (SAF; control), eicosapentaenoic acid (EPA), or docosahexaenoic acid (DHA). Margination volume (MV) was calculated by subtracting true from apparent plasma volume.

RESULTS

MVs were 3 times as great during the fasting state as during the fed state (P < 0.0001). In both the fasting and the fed states, MV was significantly correlated with plasma triacylglycerol and TRL half-lives. In the fed state, MV was also correlated with preheparin LpL, whereas in the fasting state it was not. There was no significant correlation between preheparin LpL and postheparin LpL in the fasting state. Relative to SAF, EPA and DHA supplementation resulted in higher MVs by 64% and 53% (both P < 0.001), respectively, in the fasting state, without significantly reducing fasting triacylglycerol concentrations. In the fed state, DHA doubled the MV (P < 0.05), whereas EPA had no significant effect.

CONCLUSIONS

The correlations between MV and TRL half-lives and preheparin LpL suggest that MV could be a reflection of whole-body LpL binding capacity. The increases in MVs with EPA and DHA supplementation suggest that these fatty acids may increase the amount of endothelial-bound LpL or its affinity for TRL.

The intracellular transport of chylomicrons requires the small GTPase, Sar1b

PURPOSE OF REVIEW

The transport of lipoproteins through the secretory pathways of enterocytes and hepatocytes is pivotal for whole-body lipid homeostasis. This review focuses on the assembly and structural evolution of COPII (coat protein) transport carriers that are essential for the transport of chylomicrons from the endoplasmic reticulum to the Golgi apparatus.

RECENT FINDINGS

The assembly of endoplasmic reticulum to Golgi transport carriers commences with the coating of specific areas of the endoplasmic reticulum membrane with Sar1-GTP and the Sec23/24 heterodimer. An important advance has been the crystallographic analysis of the Sar1-Sec23/24 complex. The proteins form a bow-tie shaped structure, with a concave face that seems to match the curvature of transport carriers. Mammalian cells produce two isoforms of Sar1, designated Sar1a and Sar1b, both of which are expressed in enterocytes. Sar1b is defective in chylomicron retention disease and Anderson disease, two rare recessive disorders characterized by severe fat malabsorption and a failure to thrive in infancy. Patients with chylomicron retention disease and Anderson disease selectively retain chylomicron-like particles within membrane-bound compartments. By analogy with procollagen, chylomicrons may drive the formation of endoplasmic reticulum to Golgi transport carriers from endoplasmic reticulum sites close to, but separate from, domains of the endoplasmic reticulum coated with Sar1-Sec23/24. The COPII machinery also mediates the transport of VLDL to the Golgi.

SUMMARY

New insights into the role of the COPII machinery in the intracellular transport of cargo, including chylomicrons and VLDL, may suggest new drug targets for ameliorating the lipid abnormalities of the metabolic syndrome.

Clinical Significance of Small Dense Low-Density Lipoprotein Cholesterol Levels Determined by the Simple Precipitation Method

OBJECTIVE

Recently, we established a simple method for the quantification of small dense LDL cholesterol (C) using heparin-magnesium precipitation. The small dense LDL-C level was identical to cholesterol in the denser LDL fraction with a density of 1.044 to 1.063 g/mL. The aim of this study was to examine clinical significance of this precipitation method for small dense LDL-C.

METHODS AND RESULTS

Small dense LDL-C was measured by a direct homogenous LDL-C assay in the supernatant that remained after heparin-magnesium precipitation with density <1.044 lipoproteins. In 313 normolipidemic subjects, the mean value of small dense LDL-C was 31+/-13 mg/dL. In 462 healthy subjects, small dense LDL-C levels were positively correlated with serum triglyceride and LDL-C and were inversely correlated with high-density lipoprotein cholesterol (HDL-C). Combined hyperlipidemia showed the highest small dense LDL-C level among the various types of hyperlipidemia. Patients with type 2 diabetes had an increased small dense LDL-C level (55+/-17). Patients with coronary heart disease also had increased small dense LDL-C levels (53+/-30) irrespective of the presence of diabetes, whereas their LDL-C levels were comparable to those of normolipidemic controls (111+/-31 versus 104+/-22).

CONCLUSIONS

These results suggest that measurement of small dense LDL-C by the present precipitation method is useful to evaluate atherogenic risk and may be applicable to routine clinical examination.

Effects of low and moderate exercise intensity on postprandial lipemia and postheparin plasma lipoprotein lipase activity in physically active men

This study was designed to assess differences in the intensity of exercise to attenuate postprandial lipemia (PPL). Thirteen healthy men (age 23.8 +/- 0.9 yr) participated in three random-ordered trials: in low-(25% peak oxygen consumption; Low) and moderate-intensity (65% peak oxygen consumption; Mod) exercise trials, which were completed 1 h before a high-fat meal (1.3 g fat/kg body mass), and a control (Con), fat meal only, trial. Venous blood samples were obtained before the fat meal, and at 2, 4, 6, 8, and 20 h after the fat meal. PPL in the Mod trial (267 +/- 50 mg.dl-1.8 h) was lower compared with that in either Con (439 +/- 81 mg.dl-1.8 h) or Low (403 +/- 91 mg.dl-1.8 h) trials (P < 0.05), whereas there was no difference in PPL between Con and Low trials (P > 0.05). High-density lipoprotein cholesterol (HDL-C) and HDL subtype 2 cholesterol were not different between or within trials (P > 0.05). Postprandial insulinemia was lower in the Mod trial (20.5 +/- 5.7 microIU.ml-1.8 h; P < 0.05), but not in the Low trial (31.4 +/- 4.7 microIU.ml-1.8 h), compared with that in the Con trial (34.9 +/- 5.0 microIU.ml-1.8 h). Postheparin lipoprotein lipase activity at 8 h was higher in the Low trial compared with that in either Con or Mod trials, whereas there were no differences between trials at 20 h. These results suggest that, when exercise is performed 1 h before a fat meal, only exercise of moderate but not of low intensity attenuates PPL and that this effect is not associated with changes in postheparin lipoprotein lipase activity.

Contribution of visceral adiposity to the exaggerated postprandial lipemia of men with impaired glucose tolerance

OBJECTIVE

Impaired glucose tolerance (IGT) has been associated with alterations in numerous coronary heart disease risk factors, including postprandial hyperlipidemia. An excess visceral adipose tissue accumulation is also predictive of IGT and of an exaggerated postprandial lipemia. The objective of the present study was therefore to compare the respective contributions of visceral adipose tissue accumulation versus IGT with the variation in postprandial lipemia.

RESEARCH DESIGN AND METHODS

Potential differences in postprandial triglyceride (TG)-rich lipoprotein (TRL) levels following a standardized breakfast with a high fat content were examined among men characterized by normal glucose tolerance (NGT) or IGT. Sixty-seven men were classified according to their glucose tolerance status (<7.8 mmol/l [NGT] or between 7.8 and 11.1 mmol/l [IGT] 2 h after a 75-g oral glucose test).

RESULTS

Men with IGT showed the highest TRL-TG concentrations (P < 0.05) at the 4-, 6-, and 8-h time points compared with men with NGT. These higher postprandial TRL-TG levels among men with IGT were also accompanied by a greater postprandial TG total area under the incremental curve in all TRL fractions (large, medium, and small) (P < 0.05). Furthermore, subjects characterized by IGT had also the highest visceral adipose tissue accumulation (P < 0.009). When subgroups of IGT and NGT men were individually matched (n = 11) for similar visceral adipose tissue accumulation, no significant difference was found in postprandial responses of all TRL-TG fractions between the two groups.

CONCLUSIONS

These results provide evidence that visceral adipose tissue accumulation is an important factor involved in the deterioration of postprandial lipemia noted among men with IGT.

Effects of treatment with Sandostatin LAR on small dense LDL and remnant-like lipoproteins in patients with acromegaly

OBJECTIVE

Acromegalic patients have been shown to have an increase in the concentrations of small dense low-density lipoprotein (LDL) and remnant-like lipoprotein particles (RLP). These lipoproteins are atherogenic and may contribute to the cardiovascular risk of these patients. The aim of this study was to determine whether treatment of acromegaly using Sandostatin LAR could lower these atherogenic lipoproteins.

METHODS

Fourteen patients with active acromegaly were recruited and Sandostatin LAR, a long-acting somatostatin analogue, was given every 4 weeks by intramuscular injection for 6 months. Fasting lipids, lipoproteins, lipolytic enzymes were determined at baseline, 12 and 24 weeks after treatment. Small dense LDL was measured using density gradient ultracentrifugation and RLP-cholesterol (RLP-C) by an immunoseparation assay.

RESULTS

There was already a marked reduction in GH and IGF-1 by week 8 and, in all subjects, IGF-1 levels within their respective age-specific normal range were achieved. At week 12, plasma triglyceride significantly decreased (P < 0.01) and both HDL2 (P < 0.01) and HDL3 (P < 0.01) subfractions increased. A reduction was seen in small dense LDL concentration (P < 0.05) and RLP-C (P < 0.05). Lipoprotein lipase (LPL) activity increased (P < 0.01) and the magnitude of the increase in LPL activity correlated with the increase in HDL at 3 months (r = 0.55, P < 0.05) but not with the changes in plasma triglyceride, small dense LDL or RLP-C. The improvement in plasma lipids and lipoproteins persisted until the end of the study.

CONCLUSION

Sandostatin LAR is effective in the treatment of acromegaly and is associated with favourable changes in plasma lipids and a reduction in small dense LDL and RLP-C.

Experimental model of postprandial hypertriglyceridemia in sucrose-fed rats and the effectiveness of atorvastatin in the model

Although postprandial hypertriglyceridemia has drawn attention as an independent risk factor of cardiovascular disease, there is no established animal model that shows a physiological transitory change in lipoprotein metabolism after ingestion of a fatty meal. We developed an animal model of postprandial hypertriglyceridemia using sucrose-fed rats, and used this model to evaluate the effect of atorvastatin on this condition. Compared with normal rats, sucrose-fed rats orally loaded with olive oil showed a high and prolonged increase in plasma triglyceride (TG) concentration accompanied by both an increase in TG secretion and decrease in TG clearance. Atorvastatin (30 mg/kg orally) for 2 weeks reduced not only fasting plasma TG concentration, but also the postprandial TG concentration. Atorvastatin also suppressed rates of TG secretion in both chylomicron (CM)-rich (d < 0.96 g/mL) and very-low-density lipoprotein (VLDL) (d = 0.96 to 1.006 g/mL) fractions after oral fat loading. Further, atorvastatin improved the elimination time of exogenous TG emulsion only in the nonfasted, namely, high plasma TG condition. These results indicate that this animal model satisfactorily replicates the postprandial hypertriglyceridemia observed in humans and may therefore be useful in evaluation of lipid-lowering agents. Furthermore, atorvastatin not only improves fasting but also postprandial lipoprotein metabolism, presumably by reducing TG secretion from the liver or intestine or both, and by secondarily increasing TG-rich lipoprotein clearance by eliminating saturation.

Lipoprotein subclass measurements by nuclear magnetic resonance spectroscopy improve the prediction of coronary artery disease in Type 1 diabetes. A prospective report from the Pittsburgh Epidemiology of Diabetes Complications Study

AIM/HYPOTHESIS

To examine whether nuclear magnetic resonance lipoprotein spectroscopy improves the prediction of coronary artery disease in patients with Type 1 diabetes, independently of conventional lipid and other risk factors.

METHODS

A prospective nested case-control design of subjects with childhood onset Type 1 diabetes from the Pittsburgh Epidemiology of Diabetes Complications Study was used. 59 controls were age-, sex- and duration-matched to 59 incident cases of coronary artery disease (fatal or non-fatal myocardial infarction, angina, coronary stenosis >50%) occurring during 10 years of follow-up. Lipid mass and particle concentrations of VLDL, LDL, and HDL subclasses, grouped into three size categories (large, medium, and small), were assessed prior to event with nuclear magnetic resonance spectroscopy.

RESULTS

Univariate analyses showed that both lipid mass and particle concentrations of all three VLDL subclasses, small LDL, medium LDL, and medium HDL were increased in CAD cases compared to controls, while large HDL was decreased. Mean LDL and HDL particle sizes were lower in cases. In multivariate models using conventional lipid and non-lipid risk factors, triglycerides and overt nephropathy were the strongest predictors of CAD. Nuclear magnetic resonance measures further improved the prediction, i.e. large HDL particle concentration (OR=0.43, p=0.030), medium HDL mass (OR=3.79, p=0.026) and total VLDL particle concentration (OR=2.33, p=0.033).

CONCLUSION/INTERPRETATION

While these results underscore the importance of triglycerides and overt nephropathy in CAD risk in Type 1 diabetic patients, they also suggest that nuclear magnetic resonance lipoprotein spectroscopy could further refine its prediction and show novel findings concerning HDL subclasses.

Chylomicron remnant concentrations in patients with coronary artery disease

Persisting chylomicron remnants have been linked to premature atherosclerosis. The analysis of chylomicron remnant concentrations by an oral triglyceride tolerance test, however, is time-consuming for the study subjects and requires large resources in the laboratory. Therefore, only small numbers of subjects have been studied in the past. The aim of this study was to elucidate the prevalence of elevated chylomicron remnants, to identify effectors of chylomicron remnant clearance and to compare chylomicron remnants in the prediction of coronary artery disease with other risk factors. We applied a novel oral triglyceride tolerance test to 423 patients (368 males, 55 females) with a confirmed diagnosis of coronary artery disease (CAD) and to 390 control subjects (295 males, 95 females) in a case-control setting. This study revealed that elevated chylomicron remnant concentrations (retinyl esters > 1.5 micromol/l) are present in 20% of all subjects. Male gender, the apolipoprotein E2 isoform, and higher body mass index were associated with increased chylomicron remnant concentrations. However, chylomicron remnants were lower and plasma triglycerides higher in patients with CAD. We conclude that screening for a delayed clearance of chylomicron remnants is of little clinical value in CAD.

Omega-3 fatty acid supplementation accelerates chylomicron triglyceride clearance

Omega-3 fatty acids (FAs) reduce postprandial triacylglycerol (TG) concentrations. This study was undertaken to determine whether this effect was due to reduced production or increased clearance of chylomicrons. Healthy subjects (n = 33) began with a 4-week, olive oil placebo (4 g/d) run-in period. After a 4-week wash-out period, subjects were randomized to supplementation with 4 g/d of ethyl esters of either safflower oil (SAF), eicosapentaenoic acid (EPA), or docosahexaenoic acid (DHA) for 4 weeks. Results for EPA and DHA were similar, and therefore the data were combined into one omega-3 FA group. Omega-3 FA supplementation reduced the postprandial TG and apolipoprotein B (apo B)-48 and apoB-100 concentrations by 16% (P = 0.08), 28% (P < 0.001), and 24% (P < 0.01), respectively. Chylomicron TG half-lives in the fed state were reduced after omega-3 FA treatment (6.0 +/- 0.5 vs. 5.1 +/- 0.4 min; P < 0.05), but not after SAF (6.9 +/- 0.7 vs. 7.1 +/- 0.7 min). Omega-3 FA supplementation decreased chylomicron particle sizes (mean diameter; 293 +/- 44 vs. 175 +/- 25 nm; P < 0.01) and increased preheparin lipoprotein lipase (LPL; 0.6 +/- 0.1 vs. 0.9 +/- 0.1 micromol/h/ml; P < 0.05) activity during the fed state, but had no effect on postheparin LPL or hepatic lipase activities. The results suggest that omega-3 FA supplementation accelerates chylomicron TG clearance by increasing LPL activity, and that EPA and DHA are equally effective.

Clinical Utility and Approach to Estimate Postprandial Hypertriglycemia by A Newly Designed Oral Fat-loading Test

The objective of this study was to estimate postprandial hypertriglycemia by a newly designed oral fat-loading test. Twenty-three healthy normolipidemic volunteers were orally administered a test meal consisting of a mixture of Telmeal 2.0 and 20 g of salt-free butter after fasting for 12 h. To measure the levels of total cholesterol (T-Cho), triglycerides (TG), high-density lipoprotein-cholesterol (HDL-C), remnant-like particle-cholesterol (RLP-C), lipoprotein (a) [Lp (a)], free fatty acid, apolipoproteins (Apos), plasma glucose (PG), immunoreactive insulin (IRI), and high-sensitivity C-reactive protein (hs-CRP), venous blood samples were collected before the meal and at each hour until 9 h after fat-loading. The levels of both TG and RLP-C were drastically elevated at 2 h after fat-loading and these levels remained high until 4 h (p < 0.01). A significant correlation between TG and RLP-C was also observed at 2, 3 and 4 h, and the values of the correlation coefficients (r) were 0.837, 0.838, and 0.908, respectively. In contrast, the levels of T-Cho, HDL-C, Lp (a), Apos, PG, and hs-CRP did not change. Furthermore, there were no gastrointestinal symptoms during or after the study. These results strongly suggested that this newly designed fat-loading test was very useful for evaluating postprandial hypertriglycemia, including remnant concentrations.

Significance of small dense low-density lipoproteins and other risk factors in patients with various types of coronary heart disease

BACKGROUND

It remains unclear how closely the small dense low-density lipoprotein (LDL) (diameter < or =25.5 nm) is associated with various types of coronary heart disease (CHD) in Japanese patients, an ethnic group with lower serum cholesterol levels and less massive obesity compared with Western populations.

METHODS AND RESULTS

We measured mean LDL particle diameter by gradient gel electrophoresis in 571 patients with CHD and in 263 healthy subjects who served as control patients. Patients with CHD were classified into acute coronary syndrome (ACS), stable CHD and vasospastic angina. High-density lipoprotein cholesterol and apolipoprotein-A1 and -B were significantly different between patients with CHD and controls. LDL size in patients with CHD was markedly smaller than that in controls in both men and women (25.5 +/- 0.7 vs 25.9 +/- 0.4 and 25.7 +/- 0.7 vs 26.0 +/- 0.5 nm, respectively). LDL cholesterol was significantly higher in patients with ACS than in other groups. Plasma levels of high-density lipoprotein cholesterol decreased as the number of diseased vessels or angiographic coronary severity evaluated by Gensini score increased, but the LDL size was comparable irrespective of the type of CHD and the extent and severity of the lesions. Multiple logistic regression analysis revealed that small dense LDL was independently associated with the incidence of CHD in both sexes (odds ratio [OR] 3.5, 95% CI 2.1-5.7, and OR 2.9, 95% CI 1.5-5.6, P <.005).

CONCLUSION

Our study suggests that the small dense LDL is strongly associated with various types of CHD, independent of traditional and nontraditional coronary risk factors, but is not related to the severity and extent of the coronary lesions.