This was a case control study conducted in the Department of Biochemistry, in collaboration with Department of Medicine SCB Medical College and Hospital Cuttack from March 2014 to September 2015. The study has undergone institutional ethical clearance. Written, informed consent was obtained from all subjects for collection of the blood samples as well as data required for the study.

The study group comprised of 55 essential hypertension patients-39 males and 16 females within age group 30-50 years, attending OPD and indoors in the Department of Medicine, SCB. Medical College and Hospital, Cuttack and 55 healthy volunteers-30 males and 25 females between 30-50 years of age with no symptoms and signs suggestive of hypertension and no family history of the hypertensive disease as controls. The lipid profile of most of the patients of the control group was within the reference range.

The selection of the essential hypertension cases was made on the basis of their history, physical examination, biochemical investigations according to the JNC 7 (Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure) Criteria for the diagnosis of hypertension [12].

A 3ml of venous blood was collected after overnight fasting of 8 hours from all enrolled patients and healthy controls for the assessment of Apolipoprotein A1 and Apolipoprotein B100 levels and other biochemical parameters like fasting plasma glucose, serum urea, creatinine, lipid profile. Detailed history and physical examination which includes systolic and diastolic blood pressures, Waist- Hip Ratio (WHR), weight were recorded. Patient with diabetes mellitus, renal disease, endocrinopathy, pregnancy induced hypertension, immunosupression and history of illicit drug use were excluded from the study. In the control group, subjects with family history of hypertension, renal diseases and chronic metabolic diseases were also excluded. All the case records were collected in a specified proforma.

The blood pressure measurement was taken while the subject was in the sitting position. Manual blood pressure measuring instrument sphygmomanometer was used. Two readings were taken at a single visit and the average was calculated. The routine biochemical parameters were carried out by the standard methods using Toshiba 120 FR autoanalyser. The novel markers Apo A1 and Apo B 100 were assayed by immunoturbidimetric methods in the Biolis 24i autoanalyser. Anti – Apo A1 and Anti – apo B100 antibodies when mixed with samples containing Apo A and Apo B, form insoluble complexes causing an absorbance change, depending upon the apoA and apo B concentration of the patient sample. The ApoA and ApoB levels in the patients samples be quantified can be comparison with calibrators of known Apo A and Apo B concentration.

All statistical analyses were performed using SPSS version 16.0 software and Microsoft Office Excel 2007. Data were expressed as mean ± SD. Student’s t-test and Anova test were used to compare mean values and calculate significance. Data were considered statistically significant if p-values were < 0.05. Pearson’s coefficient of correlation was used to assess linear correlation between serum apolipoprotein A1, B100 and other variables.

[Table/Fig-1] reveals majority of the hypertensive patients were smokers, belonged to the good socioeconomic status and had higher WHR in comparison to the control group. [Table/Fig-2] revealed that the hypertensive patients had raised values for Fasting Blood Sugar (FBS), renal function and all fractions of lipid profile in comparison to the control group. Comparision of data was done by one-way ANOVA and post-hoc Tukey HSD. [Table/Fig-3] reveals significant positive association of different fractions lipid profile with systolic, diastolic blood pressure.

In [Table/Fig-4] revealed a significant rise in apoB100 and nonsignificant fall in the apo A1 in both stages of hypertensive patients as compared to the control group.

[Table/Fig-5a&b] revealed a positive association of apo B100 with Systolic Blood Pressure (SBP) and a and a negative association of apo A with SBP. [Table/Fig-6] reveals a more positive association of ApoB100/ApoA1 with both systolic and diastolic blood pressure than the LDL/HDL ratio.

[Table/Fig-5a,b]:

Correlation of Apo A & Apo B 100 with Systolic Blood Pressure.

X Axis- Systolic Blood Pressure (mm Hg)

Y Axis- apoA(mg/dl)

X Axis - Systolic Blood Pressure (mm Hg)

Y Axis – apoB (mg/dl)

The present study aims to identify the association of conventional lipid parameters LDL and HDL and new parameters such as Apo A1 and Apo B 100 in essential hypertensive patients. The mean Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP) were significantly higher in stage 1 and stage II hypertensive patients than the controls. The stage II hypertensive patients had significantly raised SBP in comparison to the stage 1 patients [Table/Fig-1]. The blood pressure has a continuous and consistent relationship with the risk of cardiovascular events, the higher the BP, the higher the chance of cardiovascular disease [13]. The hypertensive patients belonged to the older age group and had higher WHR in comparison to the controls which was significant statistically [Table/Fig-1]. 90% of the hypertensive patients were from the good socio economic status and adopted a sedentary life style [Table/Fig-1]. This is in accordance with the study conducted by James and Welborn who observed that WHR can be used as an indicator of risk in the ethically diverse population [14,15]. With ageing there is a rise in the systolic blood pressure which may be due to an increase in vascular stiffness of the arteries in combination which atherosclerotic change in the vessel wall. Several epidemiological studies have highlighted the association of arterial stiffness in hypertensive patients and other cardiovascular diseases in aged as compared to the younger age group. The prevalence of arterial stiffness and hypertension increases with age [16,17].

A rising trend for serum cholesterol TG, LDL, and VLDL along with a fall in HDL was found with the severity of hypertension [Table/Fig-2]. Significant positive correlation between serum lipid profile and both systolic and diastolic blood pressure was observed with increasing severity [Table/Fig-3]. Hypertension and dyslipidemia are well established and partially overlapping risk factors for cardiovascular disease [18,19]. Dyslipidemia plays a role in endothelial dysfunction which is central in the pathogenesis of atherosclerosis, thrombosis, insulin resistance as well hypertension. Triglyceride rich lipoproteins and LDL cholesterol have been shown to be toxic to endothelial cells, where as HDL cholesterol may be protective [20]. High levels of serum cholesterol are known to increase the risk of developing macrovascular complications such as Coronary Heart Disease (CHD) and stroke [21]. The increased risk of CHD when the cholesterol level exceeds 5.0 mmol [22] as seen in several epidemiological studies prompted Lewis [23] to suggest that serum TC in the range 5.0–6.5mmol/L may be considered undesirable.

Various studies [24–27] have revealed the role of apolipoproteins- Apo A1 & Apo B100, the two major apolipoprotein for lipid transport in the processes involving atherosclerosis and its complications. In the present study, we found a non-significant fall in the value of serum Apo A1 in the hypertensive patients when compared to controls (110±7.63 and 109±5.29 vs 117±7.06) [Table/Fig-4]. Estimation of serum Apo B100 revealed a significant increasing trend from the control group to Stage I and Stage II hypertensive patients reflecting its contributing role as cardiovascular risk marker (61.0±18.2 vs 101±14.2 and 99.4±10.9) [Table/Fig-4]. There was no significant change in the apolipoprotein levels in both stages of hypertension. These results simulate the study in a group of men at Harvard Medical School who found out the plasma concentration of atherogenic lipoprotein patients i.e., Apo B100 worked better in predicting coronary artery disease [28]. Haidari et al., showed that the severity of atherosclerosis correlated significantly with the serum Apo B which is in the normolipidemic subgroup [29]. Sabino et al., found out that after adjusting the role of gender, age, smoking and hypertension, Apo B level and Apo B/A1 ratio correlated independently with peripheral atherosclerosis and brain stroke [30].

Apo B100 /Apo A1 ratio is an indicator of the balance between the atherogenic and antiatherogenic cholesterol particles. In the present study, this ratio increased with the severity of hypertension. As hypertension is associated with increased risk of cardiovascular disease, Apo B/A1 ratio may serve as a potential predictive marker for future cardiovascular disease. Our observation corroborates with the study of Waldius et al., and Sniderman et al., [31,32]. In their study, ApoB100/Apo A1 was the best variable in comparison to other lipid ratios such as total cholesterol/HDL, LDL/HDL, Non HDL/HDL in quantifying cardiovascular diseases.

The ratio of Apo B100/A1 revealed a significant positive correlation with hypertension in the study group. LDL/HDL also revealed similar significant positive association with hypertension, but the former ratio showed a more positive correlation as compared to the latter ratio [Table/Fig-6]. A total of 36 out of 55 patients had a Apo B/A1 ratio above the cut-off value (0.9 in males and 0.8 in females).

Similar observation was also studied in large population based studies such as the “INTER HEART” study [25], MONICA/KORA study [26], and AMORIS STUDY [27]. The INTERHEART study is the largest case control study comprising of 15,152 patients with myocardial infarction compared to 14,820 subjects from 52 countries worldwide. The aim of the study was to find out the most common of the identified risk factors of MI. The strongest and most prevalent of the risk factor was apo ratio both in men and women in each of the 52 countries worldwide.

In the AMORIS study, the relationship between different types of stroke and lipid fractions, Apo B100, Apo A1, their ratio were examined in large group of, men and women and followed for a mean period of 10.3 years. The risk of stroke was seen in patients with high apo B and low apo A1 values. In multivariate risk analysis, the apo ratio was a stronger risk predictor than total cholesterol/HDL-C and LDL-C/HDL-C ratios.

The German MONICA/Kora study showed that in 1414 men and 1436 women without prior median follow-up of 13 years the TC/HDL C ratio predicted MI risk. In addition, the apo ratio was significantly related to increased risk of MI adjusted for age, smoking, alcohol, BMI, diabetes and hypertension.

Apolipoprotein measurement also present with some methodological advantages when compared to LDL [33]. LDL is quantified by Friedwald equation and cannot be extended in samples presenting with higher TG levels. On the other hand apolipoprotein may be measured directly in the plasma through accurate and precise internationally standardized methods [34,35] by using common reference material for Apo A1 and Apo B 100. Plasma apolipoprotein levels are less influenced by biological variables in contrast to plasma lipid levels which fluctuate during different metabolic alterations [36]. Therefore preanalytical variables have less influence in the measurements of apolipoproteins A-I and B [29,37].

The limitation of the study includes smaller sample size and association of Apo B100, Apo A1and their ratio with other risk factors associated with CHD.

Apo B/Apo A1 ratio has emerged as an important complementary parameter for the evaluation of risk for future cardiovascular disease especially in essential hypertensive patients. However this study can be strengthened by taking a larger sample size and correlating the Apo B100/ Apo A1 ratio with angiographic studies, intimal thickness or other associated laboratory markers.