Analysis and correlation of small dense low-density lipoprotein-cholesterol (sdLDL-C) with various lipoproteins and cardiac markers in acute coronary syndrome patients associated with normal Low-density lipoprotein-cholesterol (LDL-C) level: A cross sectional study.

 

Greeshma B. Kotian1, Mahalaxmi S. Petimani2, Prabhakar Adake3, Rahul Ramanujam4*,

Afrah B. Kunjibettu5

1Associate Professor of Biochemistry, AJ Institute of Medical Sciences and Research Centre,

Mangalore, Karnataka, India.

2Associate Professor of Biochemistry, KAHER’s JGMM Medical College, Hubballi, Karnataka, India.

3Professor and Head, Department of Pharmacology,

KAHER’s JGMM Medical College, Hubballi, Karnataka, India.

4Registrar, Department of Cardiology, Yenepoya Medical College,

Yenepoya (Deemed to be University), Mangalore, Karnataka, India.

5Final year medical scholar, Yenepoya Medical College,

Yenepoya (Deemed to be University), Mangalore, Karnataka, India.

*Corresponding Author E-mail: rahul_suvarna@hotmail.com

 

ABSTRACT:

Title of the article: Analysis and correlation of small dense low-density lipoprotein-cholesterol (sdLDL-C) with various lipoproteins and cardiac markers in acute coronary syndrome patients associated with normal Low-density lipoprotein-cholesterol (LDL-C) level: A cross-sectional study. Aim: To analyze the levels of sdLDL cholesterol in acute coronary syndrome patients (ACS) with normal LDL cholesterol (LDL-C) and correlate with various lipoproteins and cardiac markers. Methodology: The present study included 100 patients diagnosed with ACS with normal LDL-C. Demographic details and cardiac markers were correlated with sdLDL levels. A detailed history was elicited from the patients and the details of clinical examination and laboratory findings such as cardiac Troponin, C- reactive protein, and CK-MB were obtained from patient case files. Results: The results are expressed in mean±sd. The mean age of study participants was 39.5±10.5yrs. The majority of the participants were men (69%) between the age group of 31-40 years.  Mean values of total cholesterol, VLDL, sdLDL, Trop-I, CRP, and CKMB are at higher levels in men when compared to women. Whereas, mean values of triglycerides, LDL, and HDL are higher in women when compared to men. The majority of participants were having unstable angina (42%) followed by STEMI (33%) and NSTEMI (25%). Correlation between sdLDL and other parameters was carried out using Mann–Whitney–Wilcoxon test. The result showed a statistically significant correlation between sdLDL and VLDL, Trop-I, and CRP with p <0.05. Patients with sdLDL of > 25mg/dl had a higher incidence of unstable angina and STEMI. Conclusion: Our study result suggests that ACS with normolipidemic patients has a positive correlation with sdLDL levels and sdLDL can be a new diagnostic marker along with cardiac troponins in ACS.

 

KEYWORDS: Acute coronary syndrome, sd LDL, Cardiac markers, Unstable angina, STEMI, NSTEMI.

 

 


 

 

INTRODUCTION:

Acute Coronary Syndrome (ACS) is the main cause of death worldwide and is expected to continue for the next 20 years.1-3 Around 3.8 million men and 3.4 million women die from ACS each year.4 The Registrar General of India reported that ACS led to 17% of total deaths and 26% of adult deaths in 2001-2003, which increased to 23% of total and 32% of adult deaths in 2010-2013.5

 

Coronary artery disease in India is more complicated at present and it has different dyslipidemic patterns compared to the western population.6 Low-density lipoprotein-cholesterol (LDL-C) levels have been identified as one of the important risk factors for coronary artery disease (CAD) since long.7-9

 

Different subclasses of LDL-C can be distinguished by advanced techniques, depending on the size, chemical composition, and density. Two particle-based LDL phenotypes have been identified–pattern A with a diameter of LDL> 25.5nm (large buoyant LDL or lbLDL) and pattern B with a diameter of LDL up to 25.5 nm (small, dense LDL or sdLDL).10

 

The smaller the particle of LDL, the more toxic is the effect due to the high chance of oxidation, increased endothelial permeability, low LDL receptor affinity, and increased interaction with matrix components, hence small dense LDL particles (sdLDL) are considered to be more atherogenic.11,12

 

At present, the lipid profile is the diagnostic tool to assess the risk of coronary artery disease. Cardiac risk, however, does not necessarily have to do with lipid levels, but it is more complex. Many people have normal levels of lipids but are still suffering from coronary artery disease. The lack of robust CAD risk indicators increases the difficulty in timely identification of people at risk and reduces the efficacy of treatment and disease management.13

 

National cholesterol education program adult panel III has identified a predominance of sdLDL particles as a potential risk factor for CAD and significant clinical studies have demonstrated the association of sdLDL particles with cardiovascular diseases. sdLDL proves to be a better marker for early detection and intervention in premature CAD.14 The contribution of sdLDL to atherogenicity in Indians is less studied. Further studies are needed to establish recommendations for the evaluation and correlation of sdLDL in clinical practice.15 So the present study was carried out to determine and correlate the levels of small dense LDL with other lipoproteins and cardiac markers in acute coronary syndrome patients with normal LDL-C levels.

 

MATERIALS AND METHODS:

Study setting and design:

Present cross-sectional study was carried out from August 2019 to October 2019. The study was initiated after the approval of the Scientific Review Board and Institutional Ethics committee (YEC-1/286). The sample size was calculated using the statistical software, G* power with a level of significance α as 5% and Power B as 80%with 95% level of the confidence interval and effect size d as 0.45. A minimum sample size of 100 patients with clinical signs and symptoms of ACS with normal lipid profiles were included. So the total sample size of 100 is included in the present study.

 

Inclusion criteria:

Normolipidemic patients of either gender and age group between 20-50 years, diagnosed with the acute coronary syndrome (ACS) which includes-Unstable Angina (UA), ST-Elevation Myocardial Infarction (STEMI), and Non-ST Elevation Myocardial Infarction (NSTEMI) in our institution.

 

Exclusion criteria:

Patients diagnosed with chronic kidney disease (CKD), sepsis, recent infection or fever, chronic inflammatory systemic disorders such as rheumatoid arthritis, systemic lupus erythematosus, angina of secondary etiology, recent surgery, thyroid disorders, aortic valve disease, obstructive hypertrophic cardiomyopathy and patients who are already on hypolipidemic agents, steroids, oral contraceptive pills were excluded.

 

Methodology:

A total number of 100 (n=100) ACS patients having normal lipid levels were included in our study by consecutive sampling method. Written informed consent was obtained from all the participants before starting the study. A detailed history was elicited from the patients and the details of clinical examination and laboratory findings such as cardiac Troponin, C- reactive protein, and CK-MB were obtained from patient case files.

 

Estimation of serum lipids:

Under aseptic precaution, 5ml of venous blood was drawn from these patients and collected in plain vacutainers (without anticoagulant) for serum lipids estimation (total cholesterol, triglycerides, high-density lipoprotein cholesterol) and small dense LDL (sdLDL-C). Serum lipids were estimated by the CHOL-Micro slide method using VITROS 5600 Integrated Chemistry Systems in our institutional central laboratory.

 

Sd LDL-C was quantified by the modified method described by Tsutomu Hirano et al.15 In this method lipoproteins of density <1.044 g/ml containing very-low-density lipoprotein (VLDL), Intermediate density lipoprotein (IDL) and large buoyant low-density lipoprotein (lbLDL) was precipitated first by manganese chloride (MnCl2) and heparin sodium salt. The total cholesterol content in the supernatant was assayed from which the value of HDL-C was deducted to obtain the value of sd-LDL-C.16

 

Statistical analysis:

To analyze the data both descriptive and inferential statistical methods were used. Descriptive methods such as frequency and percentage were calculated for categorical data. Mean and standard deviation were calculated to summarize all laboratory parameters. An inferential method such as an independent‘t’ test and Mann Whitney test were used to compare the various laboratory parameters with respect to sdLDL levels. Analysis was performed using SPSS –version 23 was used, level of significance was 5%.

 

RESULTS:

Table 1: Demographic details of study participants.

Variables

Frequency and percentage

Total

Gender

Male: 69                Female: 31

 

 

100

 

Age

(in years)

<30

 8

31-40

49

41-50

43


 

Table 2: Laboratory findings of study participants.

Laboratory parameters

Values in Men (Mean ±SD)

Values in Women (Mean ±SD)

Reference value

Total Cholesterol (TC)

168±29.5

156±40.5

<200mg/dl

Triglyceride

121±27

122±28

<150 mg/dl

Low density lipoprotein (LDL)

77.5 ± 21.5

78±22

<100 mg/dl

High density lipoprotein (HDL)

43.5 ±3.5

48.5±8.5

> 30 mg/dl

Very low density lipoprotein (VLDL)

21 ±7

19.5±7.5

< 32 mg/dl

Small dense low density lipoprotein (sdLDL)

32 ±10

31±9

< 25mg/dl

Troponin-I (Trop-I)

10.05 ± 10.02

10.056±10.04

0.04-0.39 ng/ml

C-reactive protein (CRP)

6.045 ±3.155

5.82±3.06

0 to 5 mg/L

Creatine Kinase-MB (CKMB)

21.54 ±17.91

16.025±12.39

< 5 ng/ml

 

Table 3: Correlation of various laboratory parameters with small dense LDL-C.

Laboratory parameter

sdLDL level with frequency

Value (Mean±SD)

p value

Total Cholesterol (TC)

> 25(79)

166.76±15.47

0.35

≤ 25(21)

163.24±13.73

Triglyceride (TG)

> 25(79)

124.92±16.33

0.80

≤ 25(21)

125.90±15.21

Low density lipoprotein (LDL)

> 25(79)

83.86±12.59

0.06

≤ 25(21)

89.29±6.21

High density lipoprotein (HDL)

> 25(79)

42.57±3.29

0.64

≤ 25(21)

42.19±3.34

Very low density lipoprotein (VLDL)

> 25(79)

21.06±3.74

0.04*

≤ 25(21)

19.33±2.01

Troponin-I (Trop-I)

> 25(79)

1.79±2.03

0.03*

≤ 25(21)

2.61±2.29

C-reactive protein (CRP)

> 25(79)

5.10±2.05

0.01*

≤ 25(21)

3.86±0.84

Creatine Kinase-MB (CKMB)

> 25(79)

23.75±12.20

0.69

≤ 25(21)

24.93±11.90

n=100; * p<0.05.

 

 

 

Figure 1: Pie chart showing the distributions of ACS among the participants.

Figure 2: Bar diagram showing the ACS severity compared with sdLDL-C level.

 


The mean age of study participants was 39.5±10.5yrs. The majority of the participants were men (69%) between the age group of 31-40 years (Table 1). Our study result has shown that mean values of total cholesterol, VLDL, sdLDL, Trop-I, CRP, and CKMB were at higher levels in men when compared to women. Whereas, mean values of triglycerides, LDL, and HDL were higher in women when compared to men (Table 2). With respect to the type of ACS, the majority of participants were having unstable angina (42%) followed by STEMI (33%) and NSTEMI (25%) (Figure 1). Patients with sdLDL of >25mg/dl had a higher incidence of unstable angina and STEMI (Figure 2). A correlation between serum sdLDL and other laboratory parameters was carried out using Mann–Whitney–Wilcoxon test. The result shows a statistically significant correlation between sdLDL and VLDL, Trop-I, and CRP with p <0.05 (Table 3).

 

DISCUSSION:

A very substantial proportion of all the acute medical hospitalizations are the patients with chest pain.17,18 ACS can be unstable angina pectoris or myocardial infarction.19 Diagnosis of ACS with no specific symptoms or features of ECG is really challenging.20

 

Lipoprotein particle heterogeneity, particularly LDL, plays an important role in modifying an individual's susceptibility to CAD.21 Patients with normolipidemic ACS are of major concern. The main goal of this study was to establish the role of sdLDL particles in patients with normolipidemic ACS. In the present study, ACS patients are labeled normolipidemic due to the normal range of their lipid and lipoprotein cholesterol levels as per ATP III guidelines.

 

Although there was no significant difference among LDL-C in three ACS classes such as UA, STEMI, and NSTEMI, it has been documented that Indians have typical dyslipidemia characterized by high triglycerides and low HDL levels with almost average LDL cholesterol levels compared to Western populations with high sdLDL.22,23

 

In our study, men had higher levels of sdLDL than women and higher levels of HDL-C were noted in women. These findings are similar to the study conducted by Abhishek Singh et al.24

 

Another study by Masakazu Hori et al. studied the association between triglyceride levels and small dense LDL-C. The study concluded that patients with high body mass index and triglyceride levels had high levels of sd-LDL. However, in our study, we didn’t find a correlation between sd-LDL and triglyceride levels.25

 

Many studies investigated factors related to sdLDL. Gender has been reported to be a determinant of LDL volume. Reduced hepatic lipase activity in women is the possible reason for women having a larger LDL diameter compared to men.26,27

 

Our study demonstrated a positive correlation between sdLDL and VLDL, Trop-I, and CRP (p<0.05). There is also a significant association between the severity of ACS and the sdLDL levels. High-level sdLDL was noted for unstable angina and STEMI, these finding is very similar to the previous study conducted by Jiawei Zhang and Lingjie He.28

 

CONCLUSION:

Our study results suggest that there is a strong association between sdLDL and ACS in normolipidemic patients. sdLDL can be a new diagnostic tool marker in ACS along with cardiac troponins.

 

LIMITATIONS:

Our study did not include lipoprotein A which is also a predictor of ACS. A comparison between Lipoprotein A and sdLDL could have been done.

 

CONFLICT OF INTEREST:

NIL

 

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Received on 30.11.2021             Modified on 09.04.2022

Accepted on 20.06.2022           © RJPT All right reserved

Research J. Pharm. and Tech 2023; 16(3):1214-1218.

DOI: 10.52711/0974-360X.2023.00201