Postprandial changes in LDL phenotypes in patients with myocardial infarction

Cardiovascular events and atherosclerosis in patients with type 2 diabetes and impaired glucose tolerance -What are the medical treatments to prevent cardiovascular events in such patients?

Type 2 diabetes mellitus (T2DM) and impaired glucose tolerance (IGT) significantly induce advanced coronary artery disease and systemic atherosclerosis. Thus, T2DM and IGT are traditional risk factors of cardiovascular disease (CVD). On the other hand, acute coronary syndrome is frequently caused by the rupture of coronary atherosclerotic plaques, which reduces patients' quality of life and may result in death. To date, many trials have sought to identify ways to determine the coronary plaque volume and its vulnerability, and many studies have demonstrated that some specific antihyperglycemic agents may prevent coronary or carotid plaque progression, decrease plaque volume, induce plaque stability, and improve clinical outcomes in patients with T2DM and IGT. This article reviews i) the association between coronary or carotid plaques and abnormal glucose tolerance, including T2DM; and ii) the effects of oral antihyperglycemic drugs to improve clinical outcomes and stabilize atherosclerotic plaques in patients with T2DM and IGT.

Small Dense Low-Density Lipoprotein Cholesterol: A Residual Risk for Rapid Progression of Non-Culprit Coronary Lesion in Patients with Acute Coronary Syndrome

Aim: This study investigated whether the small dense low-density lipoprotein cholesterol (sd-LDL-c) level is associated with the rapid progression (RP) of non-culprit coronary artery lesions and cardiovascular events (CE) after acute coronary syndrome (ACS).

Methods: In 142 consecutive patients with ACS who underwent primary percutaneous coronary intervention for the culprit lesion, the sd-LDL-c level was measured using a direct homogeneous assay on admission for ACS and at the 10-month follow-up coronary angiography. RP was defined as a progression of any pre-existing coronary stenosis and/or stenosis development in the initially normal coronary artery. CEs were defined as cardiac death, myocardial infarction, stroke, or coronary revascularization.

Results: Patients were divided into two groups based on the presence ( n =29) or absence ( n =113) of RP after 10 months. The LDL-c and sd-LDL-c levels at baseline were equivalent in both the groups. However, the sd-LDL-c, triglyceride, remnant lipoprotein cholesterol (RL-c), and apoC3 levels at follow-up were significantly higher in the RP group than in the non-RP group. The optimal threshold values of sd-LDL-c, triglyceride, RL-c, and apoC3 for predicting RP according to receiver operating characteristics analysis were 20.9, 113, 5.5, and 9.7 mg/dL, respectively. Only the sd-LDL-c level (≥ 20.9 mg/dL) was significantly associated with incident CEs at 31±17 months (log-rank: 4.123, p =0.043).

Conclusions: The sd-LDL-c level on treatment was significantly associated with RP of non-culprit lesions, resulting in CEs in ACS patients. On-treatment sd-LDL-c is a residual risk and aggressive reduction of sd-LDL-c might be needed to prevent CEs.

Elevated small dense low-density lipoprotein cholesterol as a predictor for future cardiovascular events in patients with stable coronary artery disease

AIM

The aim of the present study was to investigate how small dense low-density lipoprotein cholesterol (sdLDL-C) compared with LDL-C affect the long-term prognosis in patients with stable coronary artery disease (CAD).

METHODS

sdLDL-C measured by heparin magnesium precipitation and LDL particle size measured by non-denatured gradient-gel electrophoresis were compared in 190 consecutive CAD patients who underwent coronary arteriography between 2003 and 2004 who did or did not develop cardiovascular events during a seven-year follow-up period. Cardiovascular events were death caused by cardiovascular diseases(CVDs), onset of acute coronary syndrome, need for coronary and peripheral arterial revascularization, hospitalization for heart failure, surgical procedure for any CVDs, and/or hospitalization for stroke.

RESULTS

First-time cardiovascular events were observed in 72 patients. Those who experienced cardiovascular events were older and had higher prevalence rates of hypertension and diabetes; significantly higher Gensini coronary atherosclerotic scores; significantly higher levels of sdLDL-C, sdLDL-C/LDL-C, and LDL-C/high-density lipoprotein cholesterol (HDL-C) ratios; and greater glycated hemoglobin(Hb)A1c and brain natriuretic peptide (BNP) levels. They also had significantly smaller LDL particle sizes, HDL-C, apolipoprotein A-1, and estimated glomerular filtration rate (GFR) compared with patients without cardiovascular events. Conversely, LDL-C, non-HDL-C, apolipoprotein B, remnantlike particle cholesterol, and high-sensitivity C-reactive protein (hs-CRP) levels were similar between the two groups. A Kaplan-Meyer event-free survival curve demonstrated that patients with sdLDL-C≥35 mg/dL (median level) had significantly poorer prognosis compared with those with lower sdLDL-C levels, while patients with LDL-C ≥100 mg/dL had a non-significantly lower survival rate.

CONCLUSION

These results confirm that sdLDL-C is a very promising biomarker to predict future cardiovascular events in the secondary prevention of stable CAD.

Postprandial changes of lipoprotein profile: effect of abdominal obesity

Background

Majority of studies that focused on the influence of abdominal obesity on lipoprotein profile, were conducted in the fasting conditions. The effects of visceral fat accumulation on postprandial lipoprotein concentrations have not yet been studied in details. We therefore focused on the postprandial lipoprotein profile in otherwise healthy men and women with abdominal obesity and their comparison with the control group of volunteers with normal waist circumference. The concentration of lipoprotein classes and subclasses was measured before and 4 hours after a standard meal by linear polyacrylamide gel electrophoresis.

Results

A statistically significant postprandial rise in triacylglycerol concentration occurred in all subjects. VLDL increased 4 hours after meal in all subjects except the women with normal waist circumference. The concentration of large IDL particles increased in both non-obese men and women. In women with abdominal obesity, however, it decreased, while in obese men there was no statistically significant change. The concentration of small and medium-sized IDL particles decreased in all volunteers. Analyzing subclasses changes of large, medium-sized and small LDL particles we saw no significant shift in their concentrations except the subclass of large LDL particles, which decreased in men. Concentrations of medium and small HDL particles decreased postprandially in all volunteers with normal waist circumference. However, they remained unchanged in subjects with abdominal obesity.

Conclusions

We observed significant postprandial changes of the lipoprotein profile, but the nature and extent of these changes depended on gender and presence of abdominal obesity.

Effect of three consecutive meals on the physicochemical properties of HDL and LDL in individuals with the metabolic syndrome and patients with type 2 diabetes

BACKGROUND/OBJECTIVES

Postprandial hyperlipidemia, which is exaggerated and prolonged in insulin-resistant individuals, has been associated with cardiovascular disease. The objective of this study was to investigate whether and how the composition, size and function of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles are affected in the postprandial state among males with the metabolic syndrome (MetS) or type 2 diabetes (T2DM), compared with controls.

SUBJECTS/METHODS

A total of 14 males with T2DM, 14 with the MetS and 14 age-matched controls were given three standardized high-fat mixed meals (900 kcal; 50-g fat, 75-g carbohydrate and 35-g protein) as breakfast, lunch and dinner. Blood sampling was performed just before each meal, and 4 and 8 h after the last meal. HDL and LDL were isolated by ultracentrifugation and analyzed for their composition, particle diameter and functional properties.

RESULTS

Postprandial triglycerides levels in plasma, HDL and LDL particles increased significantly in all groups (P<0.01). Compared with the control subjects, patients with T2DM had smaller LDL particles, and in agreement, a lower cholesterol-to-protein content in both fasting and postprandial samples. A prolonged increase in susceptibility of LDL to oxidation was found in all subjects, but was most evident in T2DM. The postprandial effect on LDL oxidation was associated with an increase in LDL triglyceride (r=0.29, P<0.05). In T2DM the anti-oxidative capacity of HDL trended to impairment after the third meal.

CONCLUSIONS

Postprandial increases in triglycerides, especially in T2DM, are accompanied by pro-atherosclerotic functional changes in HDL and LDL particles.

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.

Sustained postprandial decrease in plasma levels of LDL cholesterol in patients with type-2 diabetes mellitus

OBJECTIVE

Low density lipoprotein cholesterol (LDL-C) is an independent and modifiable risk factor for development of cardiovascular disease (CVD). Postprandial lipid metabolism has been linked to CVD, but little is known about the postprandial LDL-C profile in patients with type-2 diabetes (T2DM). We aimed to study the postprandial levels of LDL-C in T2DM patients.

MATERIAL AND METHODS

After an overnight fast, 74 T2DM patients, mean age approximately 60 years, were served a standard fat-rich meal of 3515 kJ containing 54% fat, 13 % protein and 33 % carbohydrates. Only drinking water was allowed postprandially. Blood samples were drawn at times 0 (fasting), 1.5, 3.0, 4.5 and 6.0 h (postprandial). In all samples, LDL-C was measured with modified beta quantification (separation by ultracentrifugation followed by measurement of infranate high density lipoprotein cholesterol (HLD-C) using a homogeneous assay).

RESULTS

At all postprandial times, levels of LDL-C showed highly significant (p < 0.005) decreases compared to time 0 (mean [95% CI] maximum change in LDL-C levels at 3.0 h: -0.16 mmol/L [-0.12; -0.20]; p < 0.001). Independently of fasting LDL-C levels and ongoing statin therapy, LDL-C decreased significantly more in female compared to male patients postprandially (mean [95% CI] maximum unadjusted change versus time 0 in LDL-C for men [n=56] at 3.0 h: -0.14 mmol/L [-0.19; -0.10], p < 0.001; for women [n=18] at 4.5 h: -0.26 mmol/L [-0.35; -0.18], p < 0.001; -0.14 mmol/L [-0.24; -0.05], p = 0.005 between genders for the mean [95% CI] fasting adjusted difference at 4.5 h in the change versus time 0 in LDL-C; gender by time interaction: p = 0.007 (repeated measures mixed model)).

CONCLUSIONS

In T2DM patients served a fat-rich meal, levels of LDL-C decreased significantly more in women compared to men postprandially, irrespective of fasting levels or ongoing statin therapy. This might have implications in the atherosclerotic process and on any difference in the risk of CVD between genders.

Clinical importance and therapeutic modulation of small dense low-density lipoprotein particles

The National Cholesterol Education Programme Adult Treatment Panel III accepted the predominance of small dense low-density lipoprotein (sdLDL) as an emerging cardiovascular disease (CVD) risk factor. Most studies suggest that measuring low-density lipoprotein (LDL) particle size, sdLDL cholesterol content and LDL particle number provides additional assessment of CVD risk. Therapeutic modulation of small LDL size, number and distribution may decrease CVD risk; however, no definitive causal relationship is established, probably due to the close association between sdLDL and triglycerides and other risk factors (e.g., high-density lipoprotein, insulin resistance and diabetes). This review addresses the formation and measurement of sdLDL, as well as the relationship between sdLDL particles and CVD. The effect of hypolipidaemic (statins, fibrates and ezetimibe) and hypoglycaemic (glitazones) agents on LDL size and distribution is also discussed.

Impact of postprandial lipaemia on low-density lipoprotein (LDL) size and oxidized LDL in patients with coronary artery disease

BACKGROUND

Remnant lipoprotein particles (RLPs) and oxidative stress are components of postprandial state. We investigated the concentrations of triglyceride-rich lipoproteins (TRLs), RLPs, low-density lipoprotein (LDL) size, and oxidized LDL (oxLDL) during alimentary lipaemia, and evaluated whether changes among these variables could be associated with the severity and extent of coronary artery disease (CAD).

MATERIALS AND METHODS

Eighty men and 27 women with clinically suspected CAD underwent quantitative coronary angiography (QCA). TRLs were isolated by density gradient ultracentrifugation before and 6 h after an oral fat load. RLPs were measured by an immunoseparation method, oxLDL by ELISA, and LDL size by gradient gel electrophoresis.

RESULTS

Triglycerides, apolipoprotein (apo) B-48, and apoB-100 concentration in Swedberg flotation units (Sf) > 400 and in Sf 12-400 fractions were markedly increased at 6 h. Postprandial cholesterol content of RLPs (RLP-C) correlated with respective triglycerides in Sf > 400 (r = 0.737) and Sf 12-400 (r = 0.857), apoB-48 in Sf > 400 (r = 0.710) and Sf 12-400 (r = 0.664), apoB-100 in Sf > 400 (r = 0.812) and Sf 12-400 (r = 0.533). RLP-C correlated with oxLDL both in fasting and in fed state (r = 0.482 and r = 0.543, respectively) and inversely with LDL size (r = -0.459 and r = -0.442, respectively). (P < 0.001 for all). OxLDL was elevated postprandially (P < 0.001). In multivariate analysis, oxLDL was a determinant of severity and extent of CAD.

CONCLUSION

Postprandial state is associated with oxidative stress. The magnitude of oxLDL increases during alimentary lipaemia and is associated with coronary atherosclerosis.

Intensive insulin therapy reduces small dense low-density lipoprotein particles in patients with type 2 diabetes mellitus: relationship to triglyceride-rich lipoprotein subspecies

It remains unclear whether insulin improves dyslipidemia in patients with type 2 diabetes mellitus. Small dense low-density lipoprotein (sd-LDL) particles are recognized as a powerful risk factor for coronary heart disease and are often elevated in type 2 diabetes mellitus. We examined the effect of intensive insulin therapy on sd-LDL particles and triglyceride (TG)-rich lipoprotein subspecies. Intensive insulin therapy (insulin aspart [NovoRapid, Tokyo, Japan] before each meal and isophane insulin suspension at bedtime) was given to poorly controlled type 2 diabetic patients (n = 46) who were on high doses of sulfonylureas. Fasting serum samples were collected before and 14 days after the commencement of insulin therapy. Low-density lipoprotein size was measured by gradient gel electrophoresis, and the small dense LDL cholesterol (sd-LDL-C) concentration was measured by a new precipitation method. Chylomicrons (Svedberg flotation unit >400), very low-density lipoprotein 1 (VLDL1) (Sf, 60-400), and VLDL2 (Sf, 20-60) were separated by ultracentrifugation. Serum apolipoprotein B-48 and lipoprotein lipase levels were measured by the enzyme immunoassay method. Serum glucose and glycoalbumin levels were substantially decreased by insulin treatment. The LDL size increased (25.8-26.0 nm, P < .05) and the sd-LDL-C level was significantly reduced (44-34 mg/dL, P < .005). Apolipoproteins B-48 and C-III were decreased, whereas lipoprotein lipase was increased. Triglyceride levels in chylomicrons, VLDL1, and VLDL2 all showed a decrease. Changes of sd-LDL-C or LDL size were associated with changes of the TG levels in the major TG-rich lipoprotein subspecies. These results suggest that intensive insulin therapy decreases atherogenic sd-LDL particles by reducing TG in TG-rich lipoproteins. We did not find any specific relationship between VLDL1 and sd-LDL during insulin treatment.

Postprandial lipoprotein metabolism, genes and risk of cardiovascular disease

PURPOSE OF REVIEW

Several lines of evidence suggest that postprandial lipemia increases the risk of atherogenesis, and in each of the systems involved in postprandial metabolism the roles of many genes have been explored in order to establish the possible implications of their variability in coronary heart disease risk.

RECENT FINDINGS

This report focuses on recent results pertaining to postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and coronary heart disease. The postprandial lipid response was modified by polymorphisms within the genes for apolipoprotein AI, apolipoprotein E, apolipoprotein B, apolipoprotein CI, apolipoprotein CIII, apolipoprotein AIV, apolipoprotein AV, lipoprotein lipase, hepatic lipase, fatty acid-binding protein-2, the fatty acid transport proteins, microsomal triglyceride transfer protein and scavenger receptor class B type I. We also discuss recent advances in the effects of gene regulation using knockdown animal models on postprandial lipoprotein metabolism.

SUMMARY

The review discusses several of these factors as well as the potential impact of gene polymorphism on the variability of postprandial lipoprotein metabolism as intermediate phenotypes for coronary heart disease. The variability in postprandial lipid response is highly complex. Future studies will need to be large if they are to assess the effects of multiple polymorphisms.

Predominance of Small Dense Low-Density Lipoproteins and Abnormal Glucose Regulation in Patients With Acute Coronary Syndrome

BACKGROUND

Although small dense low-density lipoprotein (sd-LDL) has an established association with diabetic dyslipidemia, previous studies have failed to show an association between sd-LDL and diabetes among coronary heart disease patients. This study investigated the prevalence of sd-LDL and abnormal glucose regulation in acute coronary syndrome (ACS).

METHODS AND RESULTS

LDL size at the onset of ACS was measured by nondenatured gradient gel electrophoresis in 314 of 429 consecutive patients. Sd-LDL was prevalent in 54% of the patients, irrespective of the presence of previously known diabetes (50% vs 60% in nondiabetes and diabetes, respectively). Diabetes was present in 122 (28%) of the patients, and 110 patients without diabetes underwent an oral glucose tolerance test. Impaired glucose tolerance (IGT) and newly detected diabetes were found in as many as 44% and 22% of the patients tested, even though their hemoglobinA1c levels were in the normal range (5.3+/-0.5%). The prevalence of sd-LDL was significantly higher in patients with glucose intolerance than in those with normal glucose tolerance (61% vs 42%).

CONCLUSION

IGT and diabetes were far more common than normal glucose regulation in ACS patients, and the abnormal glycometabolism was closely associated with highly atherogenic sd-LDL.