Study of the levels of lipid profile and MDA levels and their correlation in hypertensive chronic smokers

 

Pushpa S Rajan¹, Sunita M Aghade^2*

 

¹Assistant Professor, Department of Biochemistry, SRTR Medical College, Ambajogai, Maharashtra, INDIA.

²Assistant Professor, Department of Biochemistry, JIIU’s Indian Institute of Medical Science and Research, Badnapur, Jalna, Maharashtra, INDIA.

Email: drpushpad@gmail.com, aghadesunita@gmail.com

 

Abstract               Background: Atherosclerosis is the underlying process involved in coronary heart disease, peripheral vascular disease and stroke. Elevated plasma low-density lipoprotein cholesterol levels, lowered high-density lipoprotein cholesterol levels, and elevated blood pressure are associated with more extensive and more severe atherosclerosis and also associated with greater risk of clinical disease¹. Chronic exposure to a biologically active agent such as cigarette smoke could influence atherogenesis by many possible mechanisms². There is a positive association between smoking and advanced coronary atherosclerosis^3,4. Aims and Objectives: 1) To study lipid profile and serum MDA (malondialdehyde) levels in chronic smokers and hypertensives. 2) To find out the correlation between lipid profile, MDA level, smoking and hypertension. Methods: We studied lipid profile and serum MDA in four groups, consisting of control, chronic smokers, chronic hypertensives and individuals who were chronic smokers +hypertensives. Lipid profile included serum total cholesterol (TC), triglycerides(TG), high density lipoprotein(HDL), low density lipoprotein(LDL),andVLDL. Serum MDA level was estimated as measure of lipid peroxidation Results: Serum TC was 250.19±15.36 in chronic smokers, 238.19±91.6 in chronic hypertensives and266.56±43.18 in individuals who were chronic smokers + hypertensive (p<0.001). Serum TG was 236.89±71 in chronic smokers, 226±76.23 in chronic hypertensives and242.14±23.48 in individuals who were chronic smokers + hypertensive (p<0.001), HDL level of chronic smokers were 32.18±46.02, 33.14±12.03 in chronic hypertensives and33.18±19.08 in individuals who were chronic smokers and had hypertension (p<0.001),serum LDL was 158.38±62.46 in chronic smokers, 137.16±42.15 in chronic hypertensives and152.75±36.74 in individuals who were chronic smokers + hypertensive (p<0.001), serum MDA levels of chronic smokers were 2.29±0.04, 2.16±0.05 in chronic hypertensives and2.32±0.18 in individuals who were chronic smokers + hypertensive (p<0.001). Conclusion: Findings suggest that smoking induces Oxidative stress, depleted antioxidant activities and subsequent alteration in circulating lipids in hypertension. Thus hypertensive smokers are more likely to develop severe form of hypertension and cardiovascular disease.

Key Words: Malondialdehyde (MDA), Total Cholesterol, Triglyceride, High density cholesterol, Oxidative stress.

 

 

 

 

INTRODUCTION

Atherosclerosis is the underlying process involved in coronary heart disease, peripheral vascular disease and stroke. Elevated plasma low-density lipoprotein cholesterol levels, lowered high-density lipoprotein cholesterol levels, and elevated blood pressure are associated with more extensive and more severe atherosclerosis and also associated with greater risk of clinical disease1.Chronic exposure to a biologically active agent such as cigarette smoke could influence atherogenesis by many possible mechanisms². There is a positive association between smoking and advanced coronary atherosclerosis^3,4. Smoking in different forms brings about changes in lipid profile, which increases the risk of atherosclerosis and coronary heart disease⁵. Cigarette smoking is believed to cause harmful cardiovascular and atherogenic effects resulting from changes in lipid metabolism6.Smoking alters the lipid profile adversely causing dyslipidemia and the changes becomes more marked with the number of cigarettes smoked7. Smoking leads to increase in the concentration of serum TC, LDL, TG, VLDL, and fall in the levels of anti-atherogenic HDL-cholesterol^8,14. There is a direct dose relationship between smoking and serum TG, LDL, VLDL and TC9. A high level of LDL, VLDL, and TG are strongly associated with the development of coronary artery disease, while a low level of HDL-C remains a significant independent predictor of coronary artery disease. The modification of HDL by MDA which is a product of lipid peroxidation, leads to impairement of its atheroprotective effect i.e., HDL becomes dysfunctional under certain conditions¹⁰. Hypertension is one of the major risk factors for coronary artery disease and stroke. Hypertension is an independent risk factor for atherosclerosis. It is well known fact that hypertension is associated with abnormal changes in lipid profile (dyslipidemia) which is a cause for atherosclerosis. Smoking is negatively associated with blood pressure. Smoking increases blood pressure transiently probably by causing sympathetic stimulation but the net result of chronic smoking on blood pressure is negatively associated¹¹. Cigarette smoking and hypertension individually potentiates lipid abnormalities but the combined effect has to be studied. Both cigarette smoking and hypertension are proven independent risk factors for atherosclerosis, both are associated with abnormalities in lipid profile and also show high values of serum MDA indicating increased rate of lipid peroxidation which suggest involvement of high rate of oxidative stress. As oxidative stress is potential mechanism for initiating cardiovascular dysfunction this study was designed to compare effect of smoking on lipid peroxidation product and lipid profile in hypertensive smokers compared to age matched controls.

MATERIAL AND METHODS

The present study was undertaken in Government Medical College, Aurangabad and patients were taken from their outpatient departments. Patients were devided under four groups

GROUP I: Constitutes 25consecutive normal healthy men aged between 30 to 50 years.

GROUP II: Constitutes 25 individuals aged between 30 to 50 years. who are chronic smokers but healthy without hypertension.

GROUP III: Constitutes 25 individuals aged between 30 to 50 years who havehypertension but are not smokers.

GROUP IV: Constitutes 25 individuals aged between 30 to 50 years who arechronic smokers and also have hypertension. These entire subjects venous blood sample was collected in fasting state (overnight 12 hours fasting). Precautions were taken so that the blood did not haemolyze. The blood samples were allowed to stand to form clot. Serum was then separated and analyzed for lipid profile and MDA levels.

ESTIMATION OF SERUM LIPIDS: Serum total cholesterol (TC), triglycerides (TG) and HDL-C levels were determined using commercially available kits. The LDL-cholesterol (LDL-C) levels were calculated using Friedewald formula.¹²

Estimation of by-product of lipid peroxidation, malondialdehyde (MDA): This assay is based upon the action of thiobarbituric acid (TBA) with MDA, one of the aldehyde products of lipidperoxidation. Basically the sample is heated with TBA under acidic conditions and the intensity of the pink chromogen of MDA-TBA adduct is measured at 530 nm in spectrophotometer.

 

RESULTS                    

The results of the present study were statistically analyzed and tabulated as following

 

Table 1: Mean pattern of Lipid profile and MDA

 

 

 

Table 2: Comparison of Effect size of each group from control group

DISCUSSION

Hypertension and cigarette smoking are the major precipitating factors for cardiovascular events, though exact mechanism is unknown. Various studies suggest the coexistence of hypertension and smoking increases inflammation, thrombosis, oxidative stress and depletion of antioxidant .In the present study we studied 25 consecutive normal nonsmoker healthy individuals aged between 30-50 years. Studies have shown that cigarette smoking increases serum TC, LDL, and TG levels, and it decreases anti-atherogenic HDL^13,14,16,17. The results of our study are hereby discussed individually under separate headings for each variable.

Total Cholesterol Levels: In the present study we found that the serum TC levels of cases i.e. group-II, group-III, and group-IV is more than that of the control group i.e. group-I normal nonsmoker non-hypertensive individuals. When compared between smokers and hypertensives it appears that the serum TC levels is more in chronic smokers than hypertensive individuals. The serum total TC of group IV individuals who have both the risk factors i.e. smoking and hypertension is even more than that of smokers and hypertensives.

Serum Triglyceride Levels: From the results of present study it is clear that that the serum TG levels of cases i.e. group-II, group-III, and group-IV is more than that of the control group i.e. group-I normal nonsmoker non-hypertensive individuals. When compared between smokers and hypertensives it appears that the serum TG levels is more in chronic smokers than hypertensive individuals. The serum Triglyceride levels of group IV individuals who have both the risk factors i.e. smoking and hypertension is even more than that of smokers and hypertensives.

Serum HDL-Cholesterol Levels: In this study we observed that the serum HDL levels of cases i.e. group-II, group-III, and group-IV is decreased than that of the control group i.e. group-I normal nonsmoker non hypertensive individuals. When compared between smokers and hypertensives it appears that the serum HDL levels are more decreased in chronic smokers than hypertensive individuals. The serum HDL of group IV individuals who have both the risk factors i.e. smoking and hypertension is decreased more than that of hypertensive individuals but not decreased significantly when compared to chronic smoker individuals.

Serum LDL Cholesterol Levels: From the above observations of this study we found that the serum LDL levels of cases i.e. group-II, group-III, and group-IV is increased than that of the control group i.e. group-I normal nonsmoker non-hypertensive individuals. When compared between smokers and hypertensives it appears that the serum LDL levels are more increased in chronic smokers than hypertensive individuals. The serum LDL of group IV individuals who have both the risk factors i.e. smoking and hypertension is increased more than that of hypertensive individuals but not increased significantly when compared to chronic smoker individuals.

Serum MDA Levels: Studies have shown that there is increased oxidative stress in cigarette smokers and hypertension individuals resulting in increased lipid peroxidation and increased serum MDA levels^18,19,20,21. Similar results were found in the present study that is the serum MDA levels of cases i.e. group-II, group-III, and group-IV is increased than that of the control group i.e. group-I normal non-smoker non-hypertensive individuals. When compared between smokers and hypertensives it appears that the serum MDA levels are more increased in chronic smokers than hypertensive individuals. The serum MDA of group IV individuals who have both the risk factors i.e. smoking and hypertension is increased more than that of chronic smokers and hypertensives.

 

CONCLUSION

From the present study we concluded that there is cumulative effect of cigarette smoking and hypertension on lipid profile and lipid peroxidation along with the higher rate of lipid peroxidation indicated by higher level of serum MDA and that there is more dyslipidemia indicated by higher values of total cholesterol, triglycerides, LDL, VLDL, and lower value of cardio protective HDL. We also concluded that there is more risk of progression of atherosclerosis in individuals who have both the risk factors i.e. smoking and hypertension.

 

 

 

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