Small dense LDL-cholesterol determined by a simple precipitation assay for screening familial combined hyperlipidemia

The Relationship Between Small Dense Low-Density Lipoprotein Cholesterol and Metabolic Syndrome

Background

Prior research has established an association between small dense low-density lipoprotein cholesterol (sdLDL-C) and dyslipidemia, serving as a significant marker for predicting cardiovascular diseases. Nevertheless, the connection between sdLDL-C and metabolic syndrome (MetS) remains unclear.

Methods

This study retrospectively analyzed 23,187 individuals who underwent health checkups at Taizhou Hospital's health management center. Here, we investigated the relationship between sdLDL-C and MetS, along with its components, utilizing Spearman correlation analysis, receiver operating characteristic (ROC) curve analysis, logistic regression, and mediation analysis.

Results

The MetS group exhibited significantly higher level of sdLDL-C compared to the non-MetS group (P<0.001). We observed a strong correlation between sdLDL-C and several key factors: TG (r = 0.711), TC (r = 0.672), LDL-C (r = 0.781), GGT (r = 0.420), and HDL-C (r = -0.417). After adjusting for age and gender, the odds ratio (OR) (95% confidence interval [CI]) for MetS incidence in the second, third, and fourth quartiles versus the first quartile of sdLDL-C concentration were 2.264 (95% CI: 1.851, 2.770), 4.053 (95% CI: 3.350, 4.903), and 9.034 (95% CI: 7.531, 10.837). The optimal cut-off value for diagnosing MetS using sdLDL-C was determined to be 0.98 mmol/L, with an area under the ROC curve (AUC) of 0.716 (95% CI: 0.705, 0.726). Additionally, mediation analysis revealed that sdLDL-C mediated a 12.8% correlation between GGT and TG concentration.

Conclusion

The sdLDL-C is correlated with MetS and it can successfully mediate the relationship between GGT and TG. Our data suggests that sdLDL-c and GGT are suitable parameters for preventing and monitoring MetS.

Atherosclerotic Cardiovascular Risk in Japan

Increased global mortality is associated with atherosclerosis, which appears to be independent of race. Cardiovascular disease is one of the leading causes of mortality and morbidity in Japan. Atherosclerosis, an inflammatory disease characterized by abnormal lipid accumulation and inflammation in the arterial wall, is the main underlying cause of cardiovascular disease. Numerous cardiovascular risk scores have been developed and are used to prioritize patients' treatment needs. The predictive performance of risk scores established in Western nations needs to be examined in Japanese populations. For secondary prevention, it is imperative to control hypertension, hyperlipidemia, diabetes mellitus, smoking, and local interventions. In this review, we present a historical overview of atherosclerotic risk research and the risk factors for atherosclerosis in Japan and compare the situation in Japan with that in Western nations. In addition, we discuss relevant cardiovascular risk assessment tools in the context of clinical practice in Japan.

Method for estimating high sdLDL-C by measuring triglyceride and apolipoprotein B levels

Background

We previously developed an assay to directly measure small dense (sd) low-density lipoprotein cholesterol (LDL-C) levels, which is not widely used in general clinical practice. Therefore, we propose a simpler method, “LDL window,” that uses conventional methods for estimating high sdLDL-C levels.

Methods

We analyzed our previous studies (2006–2008) on healthy subjects and patients with type 2 diabetes and coronary artery disease (CAD). The sdLDL-C level was measured using the precipitation method, and LDL size was determined using gradient gel electrophoresis. The “LDL window” comprises the estimation of LDL particle number and size. We adopted apolipoprotein B (apoB) for the estimation of the LDL particle number and used 110 mg/dL as the cutoff value for hyper-apoB. Triglycerides (TGs) are a powerful inverse determinant of LDL particle size. Therefore, we adopted TG for the estimation of the LDL particle size and used 150 mg/dL as the cutoff value for hyper-TG. Subjects were stratified into the following four subgroups: normal, hyper-TG, hyper-apoB, and hyper-TG/-apoB. Non-high-density lipoprotein cholesterol (non-HDL-C) is a surrogate marker for apoB; therefore, the “alternative LDL window” comprised non-HDL-C (cutoff, 170 mg/dL) and TG.

Results

The top quartile (Q4) of sdLDL-C (>31 mg/dL) doubled in patients with diabetes and CAD. The hyper-TG/-apoB group in the “LDL window” represented >90% Q4 and <4% Q1 and Q2, irrespective of the subjects. The sdLDL-C levels in the hyper-TG/-apoB group were 50% higher in patients with diabetes and CAD than those in controls. Similar results were obtained using the “alternative LDL window.”

Conclusions

Our proposed “LDL window” may help identify patients at high risk of CAD independent of LDL-C.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-017-0417-6) contains supplementary material, which is available to authorized users.

Estimation of the Presence of Small Dense Lipoprotein Cholesterol in Acute Ischemic Stroke

Small dense low-density lipoprotein (sdLDL) is an established risk factor in ischemic heart disease. However, its clinical significance in acute ischemic stroke (AIS) is uncertain. This study evaluates the prognostic value of the presence of sdLDL in patients with AIS by determining whether it contributes to clinical outcome or not. We studied 530 consecutive patients admitted within the first 48 hours after onset of ischemic stroke and 50 corresponding controls. Serum lipid parameters were measured on admission by standard laboratory methods. The percentage of AIS patients with sdLDL was significantly higher than the one of matched controls with sdLDL. Concerning comparisons between AIS patients with or without sdLDL, the percentages of males and patients with histories of smoking, hypertension, and cardiovascular disease were significantly higher in AIS patients with sdLDL. Concerning the grade of severity, modified Rankin Scale (mRS) on discharge was significantly higher in AIS patients with sdLDL. On logistic regression analysis, age (OR=2.29, P<0.001), male gender (OR=0.49, P<0.01), history of atrial fibrillation (OR=3.46, P<0.001), and the presence of sdLDL (OR=1.59, P<0.05) were significantly associated with poor prognosis (mRS on discharge >3). Our study showed that the presence of sdLDL might be independently associated with a poor prognosis after AIS.

Small dense LDL cholesterol measured by homogeneous assay in Japanese healthy controls, metabolic syndrome and diabetes patients with or without a fatty liver

BACKGROUND

Serum small dense LDL-cholesterol (sdLDL-C) levels in healthy controls and the cases with diabetes (T2DM) and metabolic syndrome (MetS) with or without a fatty liver in a large, typical Japanese population was determined.

METHODS

The plasma lipids and lipoproteins, including sdLDL-C by homogeneous assay, were determined in controls, MetS and T2DM patients (n=5255). The cases with MetS and preliminary MetS (pre-MetS) as well as T2DM and preliminary T2DM (pre-DM) were selected based on the Japanese criteria for MetS and T2DM. Fatty liver was diagnosed using the ultrasonography.

RESULTS

The 75th percentile values for sdLDL-C were 27.5mg/dl for men and 23.3mg/dl for women and increased with age. The concentrations of sdLDL-C and sdLDL-C/LDL-C were significantly higher in pre-MetS and pre-T2DM patients than healthy controls as well as in MetS and T2DM patients. Significantly higher sdLDL-C was found in cases with a fatty liver than without a fatty liver in all five groups.

CONCLUSIONS

Significantly elevated sdLDL-C levels were found in pre-MetS, MetS and pre-T2DM, T2DM patients compared to the healthy controls. Fatty liver significantly enhanced serum sdLDL-C levels and the multiple regression analyses ascertained that fatty liver was an independent determinant for sdLDL-C.

Small dense LDL cholesterol is a robust therapeutic marker of statin treatment in patients with acute coronary syndrome and metabolic syndrome

BACKGROUND

Small dense low-density lipoprotein (sd-LDL) is an atherogenic LDL subfraction and often increased in metabolic syndrome (MetS). This study aimed to determine whether sd-LDL cholesterol (sd-LDL-C) is a therapeutic marker of statin treatment in patients with acute coronary syndrome (ACS) and MetS.

METHODS

We examined 71 patients with ACS and 50 non-ACS subjects with normal coronary arteries (controls). The patients with ACS were treated with life-style modifications (n=36) or those plus 20mg atorvastatin daily (n=35) for 6 months. We measured sd-LDL-C by a novel detergent-based homogenous assay and calculated buoyant LDL-C (b-LDL-C).

RESULTS

The patients with ACS had higher sd-LDL-C than did the controls (30±14 vs. 22±8 mg/dl, p<0.001). Furthermore, sd-LDL-C was higher in the patients with ACS and MetS (n=31) than in those without MetS (n=40) (35±17 vs. 27±11 mg/dl, p<0.05). Atorvastatin reduced LDL-C and sd-LDL-C by 31% (102±23 to 70±28 mg/dl, p<0.0001) and 24% (29±15 to 22±13 mg/dl, p<0.01). The reduction in sd-LDL-C by atorvastatin was 5.5-fold greater in the patients with ACS and MetS than in those without MetS (p<0.001). Contrary, that in b-LDL-C was similar between the groups.

CONCLUSIONS

sd-LDL-C is a superior therapeutic marker of statin treatment in patients with ACS and MetS.

Development of a homogeneous assay for measurement of small dense LDL cholesterol

BACKGROUND

Plasma concentrations of small dense (sd)-LDL are associated with the prevalence of cardiovascular events. However, the special equipment and long assay times required for sd-LDL measurement have hindered its clinical application. Herein, we report development of a simple homogeneous assay for sd-LDL-cholesterol (C) adaptable to autoanalyzers.

MATERIALS AND METHODS

We identified suitable surfactants and phospholipases by screening for those selective for the sd-LDL fraction (d 1.044-1.063 kg/L) and for the dissociation of other lipoproteins, including large buoyant LDL (lb-LDL). Principal characteristics of this assay were compared with ultracentrifugal isolation of LDL subfractions and with our previous heparin-magnesium precipitation assay for sd-LDL. We measured sd-LDL-C concentrations in 460 healthy, normolipidemic individuals.

RESULTS

We used a polyoxyethylene benzylphenyl ether derivative to dissociate triglyceride-rich lipoproteins and HDLs, whereas sphingomyelinase proved most effective for dissociation of lb-LDL from LDL owing to the higher sphingomyelin content in the lb-LDL subfractions. A polyoxyethylene styrenephenyl ether derivative protected sd-LDL against the dissociative actions of sphingomyelinase and cholesterol oxidase/esterase during an initial incubation step. Next, polyoxyethylene alkyl ether dissociated sd-LDL-C and the cholesterol released from sd-LDL were subsequently measured by using cholesterol oxidase/esterase. The homogeneous method correlated excellently with ultracentrifugation for sd-LDL-C (y = 0.99x-0.09, R(2) = 0.91, n = 60) and exhibited within-run precision CVs <1.1%. The distribution of sd-LDL-C was skewed, and the central 95% of sd-LDL-C concentrations ranged from 0.24 to 0.88 mmol/L (9.4-34.0 mg/dL).

CONCLUSIONS

The homogeneous assay allows reproducible measurement of sd-LDL-C within 10 min and appears promising in further investigations of the clinical significance of sd-LDL-C.