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ORIGINAL ARTICLE
Year : 2021  |  Volume : 24  |  Issue : 3  |  Page : 99-103

Apolipoprotein B/A1 ratio as a potential marker of cardiovascular risk in women


1 Department of Chemical Pathology, University College Hospital, Ibadan, Oyo, Nigeria
2 Department of Chemical Pathology, University of Uyo, Uyo, Akwa Ibom, Nigeria

Date of Submission01-Jun-2020
Date of Decision03-Aug-2020
Date of Acceptance17-Sep-2020
Date of Web Publication29-Oct-2021

Correspondence Address:
Dr. Olufisayo Gabriel Ayoade
Department of Chemical Pathology, University College Hospital, Ibadan, Oyo
Nigeria
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DOI: 10.4103/smj.smj_62_20

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  Abstract 


Background: There has been a significant steady rise in the prevalence of cardiovascular disease (CVD) among Nigerian women within the last decade. The balance between pro-atherogenic particles and antiatherogenic particles has been markedly reflected in the apolipoprotein B/A1 ratio (Apo B/A1), and this ratio has been shown to be the strongest single lipoprotein-related cardiovascular risk factor. The cutoff value for the apo B/A1 ratio that defines high cardiovascular risk has been proposed to be 0.8 for women. This study is to determine the apo B/A1 ratio in apparently healthy Nigerian women and to evaluate the relationship of this ratio with other lipid indices. Methods: A total of 161 apparently healthy female adults between the ages of 30 and 66 years were selected for this study over a period of 6 months. Plasma total cholesterols (TC), triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C) were measured using the enzymatic methods, whereas low-density lipoprotein cholesterol (LDL-C) was calculated using the Friedewald formula. Apolipoprotein A1 and B were determined using immunoturbidimetry methods. Results: The mean of plasma apo B/A-I ratio in the studied participants was 0.68, with values ranging from 0.27 to 1.46. The percentage of participants with the apoB/apoA-I ratio exceeding 0.8 (the cutoff value for CVD risk) was 24.2%. The participants with apoB/apoA-I >0.8 were characterized by higher mean TC (216 mg/dl vs. 171 mg/dl; P < 0.001), TG (80 mg/dl vs. 66 mg/dl; P = 0.007), LDL-C (163 mg/dl vs. 120 mg/dl; P < 0.001), and lower HDL-C (36 mg/dl vs. 43 mg/dl; P < 0.001) compared with women with apoB/apoA-I < 0.8. Conclusion: This study has demonstrated that the women with apo B/A1 >0.8 have worse atherogenic lipid profile (high plasma TC, TG, low-density lipoprotein cholesterol, and low high-density cholesterol). It has also shown that only the apoB/A-I ratio correlates with other lipid markers; it should be considered as a potential useful tool in cardiovascular risk assessment in women. Its potential use in the national guideline for assessment and management of dyslipidemia will be invaluable.

Keywords: Apolipoprotein B/A1 ratio, cardiovascular disease, dyslipidemia


How to cite this article:
Ayoade OG, Essien SI, Sonuga O. Apolipoprotein B/A1 ratio as a potential marker of cardiovascular risk in women. Sahel Med J 2021;24:99-103

How to cite this URL:
Ayoade OG, Essien SI, Sonuga O. Apolipoprotein B/A1 ratio as a potential marker of cardiovascular risk in women. Sahel Med J [serial online] 2021 [cited 2021 Dec 8];24:99-103. Available from: https://www.smjonline.org/text.asp?2021/24/3/99/329520




  Introduction Top


Cardiovascular disease (CVD) is a major cause of morbidity and mortality in developed nations and has recently emerged as one of the most prominent health challenges facing the developing countries.[1],[2] According to the recent reports from the World Health Organization, CVD is the number one cause of death globally and over 75% of these deaths occur in low- and middle-income countries.[3] This has been attributed to a lack of health-care programs for early detection and treatment of people with risk factors for CVD. There has been a significant steady rise in the prevalence of CVD among Nigerian women within the last decade.[4]

Dyslipidemia is a major independent risk factor for CVD also has been on the rise among Nigerians especially women which might be due to dietary habits and more sedentary lifestyle in the population.[5] Although the atherogenesis which underlies the pathogenetic mechanism of CVD is a multifactorial process, the main factor in its development is the abnormalities in lipid metabolism with approximately 50% population attributable risk.[6]

The risk of developing CVD is directly proportional to the number of circulating atherogenic particles which apo B correctly estimates. Apo B and apo A1 are carriers of lipids into and out of the arterial wall.[7] Most recent studies have shown that conventional lipid indices are not adequate in its assessment. Lipoprotein-related risk of vascular disease is primarily determined by the balance between pro-atherogenic particles (apo B) and antiatherogenic particles.[8],[9],[10]

Apo B/A1 ratio has been shown to be the strongest single lipoprotein-related atherosclerotic risk factor.[11] Multiple clinical and epidemiologic studies have confirmed that apo B/A1 is a superior marker of CVD compared with lipids, lipoproteins, or their ratio.[12],[13],[14],[15],[16] These studies further demonstrate that it can discriminate patients with the disease from those without the disease. The cutoff value for the apolipoprotein B/A1 ratio that defines high cardiovascular risk has been proposed to be 0.8 for women and 0.9 for men.[15],[17] There are a dearth of data regarding apolipoproteins B, A1, and B/A1 ratio in Nigerian women despite the rising prevalence of CVD among them. The aim of this study is to determine the apo B/A1 ratio in apparently healthy Nigerian women and to evaluate the relationship of this ratio with other lipid indices.


  Methods Top


Study design

This study is a descriptive cross-sectional survey which determines the apolipoprotein B/A1 ratio and its association with other lipid indices over a period of 6 months (June 2016 to December 2016) done of University College Hospital (UCH), Ibadan.

Study area

The study center was the Chemical Pathology Department at the UCH, Ibadan. The ethical approval was granted by the UI/UCH Health Research Ethics Committee with assigned number: UI/EC/15/0049. Samples were collected at the Metabolic Research Ward of the UCH, Ibadan.

Study population

The participants for the study were recruited from apparently healthy female health-care workers of the UCH, Ibadan. The health-care female workers were specifically recruited for this study because they are more likely to be aware of their medical history. The inclusion criteria for selecting the participants were women between the age of 30 and 66 years, were nonpregnant, nondiabetic, or nonhypertensive, and apparently healthy individuals who were willing to participate in the study. Persons with a history of chronic diseases or who are ill and on any drugs such as antihypertensives, antidiabetics, or lipid-lowering drugs are excluded from the study. The sample size calculated from the standard formula is 145, with the 10% attrition making the total sample size to 159. A total number of 161 apparently healthy female adults between the ages of 30 and 66 years were recruited over a period of 6 months.

Sample collection and storage

After informed consent was taken, 5 ml of blood was drawn from each participant after overnight fast of 8–10 h. It was collected in a plain tube, allowed to clot, and separated through centrifugation. It was then stored at − 20°C until assays were run. The assays were run in 3 batches; the duration storage of each batch of samples is between 6 and 8 weeks.

Biochemical analysis

The lipid profile (total cholesterol [TC], triglycerides [TG], and high-density lipoprotein cholesterol [HDL-C]) was analyzed using the enzymatic method (CHOD-PAP) on Landwind C100 Plus automated chemistry analyzer. Low-density lipoprotein cholesterol (LDL-C) was calculated using the Friedewald formula.[15] Serum apolipoprotein B and Al concentrations were determined using immunoturbidimetry methods on Landwind C100 plus automated chemistry analyzer (Shenzhen Landwind Industry Co. China).

Data analysis

The statistical analysis was done using IBM Statistical Package for the Social Science (SPSS) version 20 software (IBM Corp., Armonk, NY, USA). All tests of statistical significance were 2 sized with 95% confidence interval. Continuous data are presented as mean (standard deviation), whereas proportions are presented as numbers (percent). Comparisons of means were performed using the Student's t-test, whereas proportions were compared using the Chi-square test. Correlations between contrary variables were assessed using Pearson's correlation coefficient. P < 0.05 was accepted as statistically significant.

Quality control

The QC samples were run with the samples in duplicates in each batch. The test results were accepted only if the QC results of the analytical run were in control. The intra-assay CV was determined, and it is 3.2% for TC, 5.4% for HDL, 4.9% for TG, and 6.3% for apo B and 5.8% for apo A1.


  Results Top


The demographic characteristics of the 161 participants are shown in [Table 1]. The age ranges from 30 to 66 years with an average of 47 years. The mean body mass index and waist circumference are 26.3 kg/m2 and 90.5 cm, respectively. The mean apo B/A1 ratio is 0.68 with minimum and maximum values of 0.27 and 1.46, respectively.
Table 1: Baseline characteristics of study participants

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[Table 2] compares the study participants with apo B/A1 <0.8 with those with apo B/A1 ≥0.8. The group of the participants with apo B/AI ≥0.8 was characterized by lower HDL-C levels (P < 0.001) compared to the group of the men with apoB/AI <0.8. The TC, TG, LDL-C, non-HDL-C levels and TC/HDL-C ratio are statistically significantly higher in the group with apo B/A1 ≥0.8, all with P < 0.001. Therefore, the participants with the high apoB/apoA-I ratio have more atherogenic lipid profile than the group within the apo B/A1 cut-point. A significant decrease of the LDL-C/apo B ratio in the participants with apo B/A1 ≥0.8 (compared with those with apo B/A1 <0.8) reflected the presence of small, dense low-density lipoprotein particles.
Table 2: The plasma lipids and apolipoproteins in the groups with apolipoprotein B/A1<0.8 (n=121) and apoB/A1≥0.8(n=39)

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Apo B/A1 ratio is significantly correlated with all other lipid markers (TC, TG, LDL-C, and non-HDL-C.). It performs better than either apoB or apoA1 alone in association with as shown in [Table 3].
Table 3: Pearson's correlation apolipoprotein A1, apolipoprotein B, apolipoprotein B/A1, and other lipid parameters

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  Discussion Top


In the present study, the apoB/AI ratio was related to a direct measurement of lipids and lipoprotein. The mean apoB/A1 ratio was 0.68, which is similar to the study on African-Americans by Metcalf et al.,[18] which is lower than in Caucasians. This is consistent with studies on ethnic variations in the lipids with African-american having lower value than Caucasian and Hispanics.[18],[19] The atherogenic lipid profile is an important risk factor for CVD. This profile is characterized by elevated levels of TC, LDL-C, and TG and lowered levels of HDL-C. However, these conventional lipid risk factors are not always adequate indicators of cardiovascular risk.[20] The epidemiological studies have shown that the diagnostic accuracy of the apo B/A1 ratio is significantly greater than that of any lipid parameters. A higher apoB/apoA-I ratio indicates a higher cardiovascular risk, such that the cutoff value of 0.8 for women and 0.9 for men has been proposed to define the risk of developing CVD.[17] Thus, consistent with these, the women with apoB/A1 ratio >0.8 have shown worse atherogenic lipids characterized significant hypercholesterolemia, hypertriglyceridemia, and low HDL-C. Similar data have been reported by other authors.[21],[22] The results of these clinical cross-sectional and prospective studies have shown that the apoB/apoA-I ratio was the only lipid-related variable that correlates with other lipid markers of cardiovascular risk. It is a valid cardiovascular risk index and that means it reflects the level of CV risk for virtually all patients with different lipid phenotypes. The higher the value of the apo B/A1 ratio, the higher is the risk of adverse cardiovascular events.

The Korean study by Kim et al.,[22] a cross-sectional study in a low-risk Korean population, reported that only the apo B/A1 ratio was associated with coronary artery disease (CAD) in both men and women. They concluded that the apo-ratio is the only variable that differentiates the patients with CAD from those without it. Agoston-Coldea et al.[23] also in their study of 208 patients demonstrated that the apo-ratio had a stronger correlation with MI than the TC/HDL-C ratio. They also reported after multivariate analysis that apo-ratio and Lp (a) are significant independent CV risk factors and therefore, recommend that the apo-ratio and should be included in clinical practice for management of patients withdyslipidemia.


  Conclusion Top


Our findings suggest that increased cardiovascular risk in women can be identified by an increased Apo-B/A1 ratio despite participants being apparently healthy. The women with apoB/apoA-I >0.8 had more atherogenic lipid profile. Thus, the apoB/apoA-I ratio may be useful to identify cardiovascular risk in Nigerian women, and these apolipoproteins can be suited to clinical practice as early screening for dyslipidemia in adults.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3]



 

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