Predictive value of remnant-like particle cholesterol as an indicator of coronary artery stenosis in patients with normal serum triglyceride levels

Significance of Circulating Remnant Lipoprotein Cholesterol Levels Measured by Homogeneous Assay in Patients with Type 2 Diabetes

Remnant lipoproteins (RLs), which are typically present at high concentrations in patients with type 2 diabetes mellitus (T2DM), are associated with cardiovascular disease (CVD). Although an RL cholesterol homogeneous assay (RemL-C) is available for the measurement of RL concentrations, there have been no studies of the relationship between RemL-C and clinical parameters in T2DM. Therefore, we evaluated the relationships between RemL-C and CVD-related parameters in patients with T2DM. We performed a cross-sectional study of 169 patients with T2DM who were hospitalized at Kumamoto University Hospital. Compared with those with low RemL-C, those with higher RemL-C had higher fasting plasma glucose, homeostasis model assessment for insulin resistance (HOMA-R), total cholesterol, triglyceride, small dense low-density lipoprotein cholesterol (sdLDL-C), and urinary albumin-creatinine ratio; and lower high-density lipoprotein cholesterol, adiponectin, and ankle brachial pressure index (ABI). Multivariate logistic regression analysis showed that sdLDL-C and ABI were significantly and independently associated with high RemL-C. Although LDL-C was lower in participants with CVD, there was no difference in RemL-C between participants with or without CVD. Thus, RemL-C may represent a useful index of lipid and glucose metabolism, and that may be a marker of peripheral atherosclerotic disease (PAD) in male patients with T2DM.

The relationship of remnant cholesterol and abdominal obesity in children: A cross-sectional study

Background

Previous studies found that remnant cholesterol (RC) is a risk factor for cardiovascular diseases and childhood obesity is associated with cardiometabolic diseases. This study aimed to explore the relationship between RC and abdominal obesity in children.

Methods

A total of 5,959 children, aged 6−12 years old, were selected from a cross-sectional study in urban-rural areas of Chongqing, China. RC was calculated by total cholesterol (TC)—high-density lipoprotein (HDL-C) cholesterol—low-density lipoprotein (LDL-C) cholesterol and was divided into four groups by quartiles (Q1–Q4).

Results

Compared to children with the lowest RC (Q1), children with higher RC had significantly higher odds of abdominal obesity (Q2: OR = 1.450, 95% CI: 1.131−1.859, p < 0.05; Q3: OR = 2.127, 95% CI: 1.632−2.772, p < 0.001; Q4: OR = 2.386, 95% CI: 1.819−3.130, p < 0.001). In the stratified analyses by urban-rural areas, the odds ratios were greater in rural areas (Q2: OR = 2.228, 95% CI: 1.572−3.160, p < 0.001; Q3: OR = 3.668, 95% CI: 2.191−6.140, p < 0.001; Q4: OR = 6.490, 95% CI: 2.271−18.551, p < 0.001) than in urban areas (Q2: OR = 1.644, 95% CI: 1.192−2.266, p < 0.05; Q3: OR = 2.266, 95% CI: 1.667−3.082, p < 0.001; Q4: OR = 2.711, 95% CI: 2.005−3.665, p < 0.001).

Conclusions

Our study found that RC was positively correlated with abdominal obesity in children, and this association was higher for children living in rural areas.

Antidiabetic drugs and oxidized low-density lipoprotein: A review of anti-atherosclerotic mechanisms

Cardiovascular disease is one of the leading causes of mortality globally. Atherosclerosis is an important step towards different types of cardiovascular disease. The role of oxidized low-density lipoprotein (oxLDL) in the initiation and progression of atherosclerosis has been thoroughly investigated in recent years. Moreover, clinical trials have established that diabetic patients are at a greater risk of developing atherosclerotic plaques. Hence, we aimed to review the clinical and experimental impacts of various classes of antidiabetic drugs on the circulating levels of oxLDL. Metformin, pioglitazone, and dipeptidyl peptidase-4 inhibitors were clinically associated with a suppressive effect on oxLDL in patients with impaired glucose tolerance. However, there is an insufficient number of studies that have clinically evaluated the relationship between oxLDL and newer agents such as agonists of glucagon-like peptide 1 receptor or inhibitors of sodium-glucose transport protein 2. Next, we attempted to explore the multitude of mechanisms that antidiabetic agents exert to counter the undesirable effects of oxLDL in macrophages, endothelial cells, and vascular smooth muscle cells. In general, antidiabetic drugs decrease the uptake of oxLDL by vascular cells and reduce subsequent inflammatory signaling, which prevents macrophage adhesion and infiltration. Moreover, these agents suppress the oxLDL-induced transformation of macrophages into foam cells by either inhibiting oxLDL entrance, or by facilitating its efflux. Thus, the anti-inflammatory, anti-oxidant, and anti-apoptotic properties of antidiabetic agents abrogate changes induced by oxLDL, which can be extremely beneficial in controlling atherosclerosis in diabetic patients.

Effect of ezetimibe on low- and high-density lipoprotein subclasses in sitosterolemia

BACKGROUND AND AIMS

Sitosterolemia displays high plasma total sterols [high plant sterols (PS) + normal to high total cholesterol (TC)] with normal to moderately elevated low-density lipoprotein (LDL) levels. High LDL, intermediate-density lipoprotein (IDL) and very low-density lipoprotein (VLDL) particles, low high-density lipoprotein (HDL), and increased non-HDL and the ratios of TC and triglycerides (TG) to HDL can increase the risk for atherosclerosis. Ezetimibe (EZE) can reduce plasma PS and TC levels in sitosterolemia, but its effect on lipoprotein subclasses has not been previously reported.

METHODS

Sitosterolemia patients (n = 8) were taken off EZE for 14 weeks (OFF EZE) and placed on EZE (10 mg/d) for 14 weeks (ON EZE). Serum lipids were measured enzymatically and lipoprotein subclasses were assessed by polyacrylamide gel electrophoresis.

RESULTS

EZE reduced (p < 0.05) total sterols (-12.5 ± 4.1%) and LDL-sterol (-22.7 ± 5.7%) and its sterol mass of large VLDL (-24.4 ± 4.5%), VLDL remnants (-21.1 ± 7.9%) and large IDL (-22.4 ± 7.2%) compared to OFF EZE. EZE did not affect large LDL subclasses or mean LDL particle size (273.8 ± 0.6 vs. 274.6 ± 0.3 Å). EZE increased HDL-sterol (25.5 ± 8.0%, p = 0.008) including intermediate (34 ± 14%, p = 0.02) and large (33 ± 16%, p = 0.06) HDL. EZE reduced non-HDL-sterol (-21.8± 5.0%), total sterols/HDL (-28.2 ± 5.5%) and TG/HDL (-27.4 ± 6.5%, all p < 0.01).

CONCLUSIONS

EZE improves VLDL and HDL subfraction distribution, thereby reducing the atherogenic lipid profile, thus providing potential clinical benefit in sitosterolemia beyond TC and PS reduction.

Remnant cholesterol predicts periprocedural myocardial injury following percutaneous coronary intervention in poorly-controlled type 2 diabetes

BACKGROUND

Remnant cholesterol (RC) is receiving increasing attention regarding its relation to cardiovascular risk. Whether RC is associated with periprocedural myocardial injury (PMI) following percutaneous coronary intervention (PCI) in type 2 diabetes (T2D) is currently unknown.

METHODS

We prospectively enrolled 1182 consecutive T2D patients who were scheduled for PCI but with baseline normal preprocedural cardiac troponin I (cTnI). Patients were divided according to their glycemic control status: group A [glycated hemoglobin (HbA1c)<7%, n=563] and group B (HbA1c≥7%, n=619). PMI was evaluated by cTnI analysis within 24h. The associations of preprocedural RC and the RC to high-density lipoprotein cholesterol ratio (RC/HDL-C) with PMI were investigated.

RESULTS

The associations of RC and RC/HDL-C with PMI were observed in group B (both p<0.05) but not in group A (both p>0.05). Patients in group B, a 1-SD increase of RC produced 30% and 32% increased risk for postprocedural cTnI>3× upper limit of normal (ULN) and >5×ULN, respectively. The odds ratios for RC/HDL-C were the highest compared with any cholesterol fractions including total cholesterol (TC)/HDL-C, low density lipoprotein cholesterol (LDL-C)/HDL-C, nonHDL-C/HDL-C, and triglyceride/HDL-C with 1.43 [95% confidence interval (CI): 1.10-1.88] for >3× ULN and 1.49 (95% CI: 1.13-1.97) for >5× ULN. However, no such associations were found in group A. Furthermore, patients with RC >27.46mg/dL (third tertile) [RC≤14.15mg/dL (first tertile) as reference] were associated with a 1.57-fold and 2-fold increased risk for >3× ULN and >5× ULN in group B, respectively.

CONCLUSIONS

RC and RC/HDL-C might be valuable, independent predictors for PMI in poorly-controlled diabetic patients undergoing PCI.

Effect of Ezetimibe on LDL-C Lowering and Atherogenic Lipoprotein Profiles in Type 2 Diabetic Patients Poorly Controlled by Statins

Background

There exists a subpopulation of T2DM in whom first-line doses of statin are insufficient for optimally reducing LDL-C, representing a major risk of CVD. The RESEARCH study focuses on LDL-C reduction in this population along with modifications of the lipid profiles leading to residual risks.

Methods

Lipid changes were assessed in a randomized, multicenter, 12-week, open-label study comparing a high-potency statin (10mg of atorvastatin or 1mg of pitavastatin) plus ezetimibe (EAT: n = 53) with a double dose of statin (20mg of atorvastatin or 2mg of pitavastatin) (DST: n = 56) in DM subjects who had failed to achieve the optimal LDL-C targets. Lipid variables were compared with a primary focus on LDL-C and with secondary focuses on the percentage of patients who reached the LDL-C targets and changes in the levels of RLP-C (remnant like particle cholesterol) and sd-LDL-C, two characteristic atherogenic risks of DM.

Results

The reduction of LDL-C (%), the primary endpoint, differed significantly between the two groups (-24.6 in EAT vs. -10.9 in DST). In the analyses of the secondary endpoints, EAT treatment brought about significantly larger reductions in sd-LDL-C (-20.5 vs. -3.7) and RLP-C (-19.7 vs. +5.5). In total, 89.4% of the patients receiving EAT reached the optimized treatment goal compared to 51.0% of the patients receiving DST. The changes in TC (-16.3 vs. -6.3) and non-HDL-C (-20.7 vs. -8.3) differed significantly between the two groups.

Conclusion

Ezetimibe added to high-potency statin (10 mg of atorvastatin or 1 mg of pitavastatin) was more effective than the intensified-dose statin (20 mg of atorvastatin or 2 mg of pitavastatin) treatment not only in helping T2DM patients attain more LDL-C reduction, but also in improving their atherogenic lipid profiles, including their levels of sd-LDL-C and RLP-C.

We thus recommend the addition of ezetimibe to high-potency statin as a first line strategy for T2DM patients with insufficient statin response.

Trial Registration

The UMIN Clinical Trials Registry UMIN000002593

Estimation of lipoprotein profile in patients with type II diabetes and its relevance to remnant lipoprotein cholesterol levels

BACKGROUND

Remnant lipoprotein (RLP), associated with atherosclerosis progression, is often elevated in diabetes mellitus. The RLP level is estimated by immune-separation method and agarose-gel electrophoresis (AGE).

METHODS

The patients were grouped into three groups according to tertile of RLP-cholesterol (RLP-C) levels. The lipoprotein profiles of type II diabetic patients (T2DM) (n=194) were measured by an anion-exchange liquid chromatography (AEX-HPLC) and an AGE with lipid-staining or cholesterol-staining.

RESULTS

IDL- and VLDL-cholesterol by the AEX-HPLC, and VLDL-levels by the AGE with lipid-staining and with cholesterol-staining were significantly different in the three groups. In all the subjects, IDL-cholesterol (r=0.531) and VLDL-cholesterol (r=0.880) by the AEX-HPLC method were strongly correlated with RLP-C, but only VLDL levels were correlated with RLP-C in AGE, respectively.

CONCLUSION

These results suggest that the AEX-HPLC, which can provide cholesterol levels of not only VLDL but also IDL, is helpful for estimation of lipid profiles in T2DM with high RLP-C.

Effects of statin on small dense low-density lipoprotein cholesterol and remnant-like particle cholesterol in heterozygous familial hypercholesterolemia

AIM

The effects of statin on small dense low-density lipoprotein cholesterol (sd-LDL-C) and remnant-like particle cholesterol (RLP-C) levels in heterozygous familial hypercholesterolemia (FH) have not been examined. This study aimed to clarify the effects of statin on sd-LDL-C and RLP-C levels in heterozygous FH.

METHODS

Seventeen patients with heterozygous FH were randomly assigned to 2 mg/day pitavastatin or 10 mg/day atorvastatin. At baseline and 12 weeks after treatment with statin, we measured sd-LDL-C and RLP-C levels.

RESULTS

Sd-LDL-C levels significantly decreased from 43 +/- 24 to 16 +/- 10 mg/dL (-63%, p=0.001) in the pitavastatin group, and from 44 +/- 17 to 19 +/- 10 mg/dL (-55%, p<0.001) in the atorvastatin group. RLP-C levels decreased from 8.4 +/- 2.8 to 6.6 +/- 2.7 mg/dL (-16%, p=0.156) in the pitava-statin group, and from 9.8 +/- 4.7 to 5.9 +/- 5.4 mg/dL (-45%, p=0.044) in the atorvastatin group. There were no significant differences in percent changes of sd-LDL-C (p=0.370) and RLP-C levels (p=0.097) between the two groups.

CONCLUSIONS

Sd-LDL-C measured by the heparin-magnesium precipitation method and RLP-C levels in heterozygous FH were decreased by 12 weeks of statin therapy. Statin might have additional anti-atherogenic effects by reducing not only LDL-C but also sd-LDL-C and RLP-C.

Lectin-like oxidized LDL receptor-1 (LOX-1) acts as a receptor for remnant-like lipoprotein particles (RLPs) and mediates RLP-induced migration of vascular smooth muscle cells

OBJECTIVE

Remnant-like lipoprotein particles (RLPs) have been implicated in atherogenesis especially by diabetic dyslipidemia; however, their receptor(s) and effects on vascular smooth muscle cells (VSMCs) remain unclear. In this study, we examined if lectin-like oxidized LDL receptor-1 (LOX-1) acts as a receptor for RLPs and its biological effects in VSMCs.

METHODS AND RESULTS

RLPs were isolated from human plasma by immunoaffinity gel containing anti-apolipoprotein A-I and anti-apolipoprotein B-100 monoclonal antibodies. DiI-labeled RLPs were taken up by CHO-K1 cells stably expressing LOX-1 but not by wild-type CHO-K1 cells. RLPs induced LOX-1 expression and cell migration in bovine VSMCs (BVSMCs), which were significantly suppressed by transfection with LOX-1 specific siRNAs. Inhibitors of metalloproteinases, epidermal growth factor (EGF) receptor tyrosine kinase, heparin-binding EGF-like growth factor (HB-EGF), p38 mitogen-activated protein kinase (p38 MAPK), MAPK kinase (MEK1) and phosphoinositide 3-kinase (PI3K) significantly blocked RLP-induced LOX-1 expression and cell migration of BVSMCs.

CONCLUSIONS

The present study provides direct evidence that LOX-1 is a novel receptor for RLPs in VSMCs. LOX-1-mediated uptake of RLPs may thus play important roles in atherogenesis by inducing LOX-1 expression and VSMC migration especially in the settings of postprandial hyperlipidemia, diabetes and metabolic syndrome.

Increased remnant lipoprotein in patients with coronary artery disease--evaluation utilizing a newly developed remnant assay, remnant lipoproteins cholesterol homogenous assay (RemL-C)

AIM

Remnant lipoprotein is an emerging risk factor for coronary artery disease (CAD); however, the development of a specific remnant lipoprotein assay has struggled due to its heterogeneous nature. This study aimed to evaluate the clinical importance of a newly developed assay for remnant lipoprotein, RemL-C, in patients with CAD.

METHODS

This assay utilizes surfactant and phospholipase-D to selectively degrade and solubilize remnant lipoprotein. One hundred and sixty consecutive CAD patients who underwent coronary catheterization were recruited.

RESULTS

Remnant liporotein, RemL-C, was significantly higher in CAD patients (p< 0.001). Additionally, TG, hs-CRP, ICAM-1, VCAM-1, and homocysteine were significantly higher, but HDL-C and adiponectin were lower with LDL-C unchanged. Since RemL-C levels correlated with plasma TG levels, two subgroups, normotriglycedemic and normolipidemic CAD groups, were extracted. In both groups, RemL-C was still significantly higher than controls. HDL-C, but not RemL-C, was associated with the severity of CAD. RemL-C significantly correlated with TG-rich lipoproteins, in particular VLDL and IDL, when limited to normolipidemic CAD patients.

CONCLUSION

Remnant lipoprotein, measured by RemL-C, was increased in CAD patients independent of TG levels, indicating impaired remnant lipoprotein metabolism in these patients. CAD severity was associated with HDL-C, but not with remnant lipoprotein, indicating differential roles of lipoproteins in the development of coronary atherosclerosis. This study therefore provides clinical significance to assess coronary risk by measuring RemL-C, particularly among patients with normal TG levels.

Remnant lipoprotein density profiling by CsBiEDTA density gradient ultracentrifugation

Remnant lipoproteins (RLPs) are now considered a strong marker of the triglyceride-rich lipoprotein (TRL) class for cardiovascular heart disease. The purpose of this research is to demonstrate the efficacy of a novel method that combines an established immunoseparation assay used to measure the RLP class in human serum with ultracentrifugal density gradient separation. These two methods are combined to obtain an RLP density profile. The immunoseparation effectively removes the non-RLP lipoproteins from serum. The RLPs obtained from the immunoseparation are separated into two density-distinct fractions by ultracentrifugal density gradient separation in CsBiEDTA. It is now clear that IDL is distinct in density and immunoreactivity from the two RLP classes isolated by the immunoseparation and ultracentrifugation. This methodology defines the RLP by density and measures their relative prevalence in the TRL class. When applied to clinical samples, variations in the RLP subclasses in different patients are examined. The differences in the RLP density profile are also examined in fasting and postprandial samples. The RLP density profile significantly increases in the postprandial state versus the fasting state. However, the overall quantity of TRL does not appreciably increase in the postprandial state. This work demonstrates the feasibility of measuring the postprandial state in clinical samples to provide insight into the clearance of RLP by the liver as well as the general atherogenicity of these particles. The major outcome of this research is a novel analytical method that couples immunoseparation and density gradient ultracentrifugation to separate and differentially profile the RLP subclass against its nascent counterparts in the TRL class.

The oxidative modification hypothesis of atherosclerosis: The comparison of atherogenic effects on oxidized LDL and remnant lipoproteins in plasma

A tremendous number of articles on oxidized LDL (Ox-LDL) and scavenger receptor in macrophage have been published since Steinberg proposed Ox-LDL hypothesis as the major cause of atherosclerosis. This hypothesis has provided strong support for the efficacy of LDL lowering drugs, indicating that lowering LDL means lowering Ox-LDL in vivo. This manuscript proposed a new oxidative modification hypothesis that remnant lipoproteins determined as remnant-like lipoprotein particles (RLP), not LDL are the major oxidized lipoproteins in plasma, resulting from the plasma concentration of these oxidized lipoproteins. Remnant lipoproteins may play a pivotal role for the initiation of atherosclerosis via lectin-like oxidized LDL receptor-1 (LOX-1) in endothelial cells. Isolated remnant lipoproteins were found to be oxidized or susceptible to be oxidized in plasma, not necessary to be further oxidized in vitro as Ox-LDL. High similarity of proatherogenic and proinflammatory properties of isolated Ox-LDL and remnant lipoporteins have been reported and predicted the presence of similar oxidized phospholipids in both lipoproteins as bioactive components. These results suggest the possibility that reducing plasma remnant lipoproteins rather than LDL should be the target for hyperlipidemic therapy especially in patients with metabolic syndrome for the prevention of endothelial dysfunction in the initiation of atherosclerosis.

Remnant lipoproteins and atherosclerosis

A recently developed assay for quantification of remnant-like particle cholesterol has provided considerable evidence that reinforces the concept that elevated levels of plasma remnants are associated with increased cardiovascular disease in different populations and distinct patient groups. In this review, we provide a brief summary of the most recently published studies, emphasizing the clinical relevance of remnant analysis. We discuss recent evidence that sheds light on the mechanisms that may underlie the atherogenicity of remnant lipoproteins. Taken together, these data provide new insight into the significance of remnant lipoproteins in the onset and development of premature atherosclerosis.

Elevated remnant-like particles in heterozygous familial hypercholesterolemia and response to statin therapy

BACKGROUND

Remnant lipoproteins (RLP-C) are considered important in atherogenesis. Hence, this study was designed to assess RLP-C levels and the effect of statin therapy in patients with familial hypercholesterolemia (FH). Elevated RLP-C levels have been associated with the presence and progression of atherosclerotic disease, and their presence in FH patients has been proposed but never established in a large cohort, nor has their response to statin therapy been confirmed.

METHODS AND RESULTS

FH patients were recruited from 36 lipid clinics. After a washout period of 6 weeks, all patients were started on monotherapy with 80 mg of simvastatin for 2 years. RLP-C levels were assessed by an immune-separation assay. In 327 FH patients, RLP-C measurements could be performed before and after treatment. Mean total cholesterol (10.55+/-2.17 mmol/L), mean LDL cholesterol (8.40+/-2.13 mmol/L), and median RLP-C (0.47 mmol/L) levels were all severely elevated at baseline. After treatment, RLP-C levels were reduced by 49% (0.24 mmol/L; P<0.0001). Even patients with normal triglyceride levels had elevated RLP-C levels at baseline, and those with high RLP-C levels were generally characterized by a very atherogenic lipoprotein profile.

CONCLUSIONS

Baseline RLP-C levels are severely elevated in FH patients and are reduced by simvastatin but do not return to normal. These elevated RLP-C levels could be the consequence of impaired function of the LDL receptor in FH. RLP-C levels in FH contribute to an atherogenic lipoprotein profile and could identify patients who require additional treatment.

Markers of Triglyceride-rich Lipoprotein Remnant Metabolism in Visceral Obesity

Background: Triglyceride-rich lipoprotein remnants are atherogenic, and this may be particularly important in visceral obesity. We investigated remnant metabolism in obese men by measuring remnant-like particle-cholesterol (RLP-C), apolipoprotein (apo) B-48, apoC-III, and the clearance of a labeled remnant-like emulsion.

Methods: Fasting RLP-C, apoB-48, and apoC-III concentrations were measured in 48 viscerally obese men and 10 lean controls. RLP-C was determined by immunoseparation assay, apoB-48 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and enhanced chemiluminescence, and apoC-III by immunoturbidimetric assay. The catabolism of chylomicron remnants was measured by intravenous injection of a remnant-like emulsion containing cholesteryl [13C]oleate, with isotopic enrichment of 13CO2 in breath determined by isotope-ratio mass spectrometry and a multicompartmental model to estimate fractional catabolic rate (FCR) of the emulsion.

Results: Compared with controls, obese men had significantly increased plasma concentrations of RLP-C, apoB-48, and apoC-III (P &lt;0.001 for all). Plasma total apoB-100, non-HDL-cholesterol, LDL-cholesterol, triglycerides, and insulin resistance (HOMA score) were also significantly higher in the obese group (P &lt;0.001 for all). Obese men had a significantly lower FCR of the remnant-like emulsion compared with controls (P = 0.020).

Conclusions: Viscerally obese individuals have insulin resistance and increased plasma concentrations of triglyceride-rich lipoprotein remnants, which may be attributable to decreased catabolism of these particles.