Journal of Medical Sciences and Health
DOI: 10.46347/jmsh.2015.v01i02.003
Year: 2015, Volume: 1, Issue: 2, Pages: 14-18
Original Article
D Namitha1, Aliya Nusrath2, A Rajeshwari3, N Asha Rani4
1Post-graduate, Department of Biochemistry, Adichunchanagiri Institute of Medical Sciences, BG Nagara, Mandya,Karnataka, India,
2Professor and Head, Department of Biochemistry, Adichunchanagiri Institute of Medical Sciences, BG Nagara, Mandya, Karnataka, India,
3Associate Professor, Department of Biochemistry, Adichunchanagiri Institute of Medical Sciences, BG Nagara, Mandya, Karnataka, India,
4Assistant Professor, Department of Biochemistry, Adichunchanagiri Institute of Medical Sciences, BG Nagara, Mandya, Karnataka, India
Address for correspondence:
Aliya Nusrath, Professor and Head, Department of Biochemistry, Adichunchanagiri Institute of Medical Sciences, BG Nagara,
Mandya, Karnataka, India. Phone: +91-9448168236, E-mail: [email protected]
Background and Objectives: Diabetes, a lifelong progressive disease, with metabolic dysregulation, is associated with increased risk of cardiovascular complications. Paraoxonase (PON), an enzyme associated with high-density lipoprotein (HDL) is known to modulate the antioxidant and anti-inflammatory role of HDL and may have a protective role in the prevention of these complications. The present study was undertaken to evaluate serum PON, thiobarbituric acid reacting substances (TBARS) and serum lipid profile in Type 2 diabetes mellitus (DM).
Materials and Methods: The study group consisted of 60 cases of clinically diagnosed Type 2 DM and 60 age and sex-matched controls. Lipid profile was estimated by enzymatic methods using EM-200 auto- analyzer, TBARS by thiobarbituric acid assay and serum PON by spectrophotometric method.
Results: Type 2 DM patients showed significant increase in total cholesterol (P < 0.05), triacylglycerol (P < 0.0001), very low density lipoproteins (P < 0.0001), TBARS (P < 0.0001) levels, and significant decrease in HDL (P < 0.05) compared to controls. A significant decrease was observed in both basal (P < 0.0001) and salt stimulated PON activity in cases (P < 0.0001). Salt stimulated PON activity showed a positive correlation with HDL levels (P < 0.05) in cases, whereas basal PON activity showed negative correlation with TBARS in controls (P < 0.005).
Conclusion: Type 2 DM patients have significantly lower levels of PON activity along with dyslipidemia with a direct correlation of PON with HDL levels. This may reduce the protective role of HDL and increases the susceptibility of cardiovascular complications.
KEY WORDS:Dyslipidemia, thiobarbituric acid reacting substances, paraoxonase, Type 2 diabetes mellitus
Diabetes mellitus (DM), a chronic progressive metabolic disorder, occurring due to body’s inability to secrete or use insulin to its full potential is characterized by hyperglycemia. The sustained hyperglycemia attacks both microvessels and macro vessels in the body.[1]
Type 2 DM is a disease of metabolic dysregulation, involving derangements in glucose and lipid metabolism resulting in accumulation of altered lipid species in the circulation and in the tissues, and alteration in metabolic signaling pathways that regulate insulin secretion from the pancreatic beta- cells.[2]
Paraoxonase (PON) (EC 3.1.8.1), a human serum arylesterase is a polymorphic enzyme consisting of PON1, PON2, and PON3 that catalyzes the hydrolysis of organophosphates such as paraoxon and aromatic carboxylic acid esters of fatty acid. It is a glycoprotein containing 337 amino acid residues with a molecular weight of approximately 43kDa and a serum concentration of about 50 mg/L.[3] It is produced by the liver and is associated with high-density lipoprotein (HDL) particles and is known to modulate the antioxidant and anti-inflammatory role of HDL.[4,5]
It hydrolyzes proinflammatory oxidized lipids, which are present in oxidized low-density lipoprotein and ruins their atherogenic characteristics, and it also decreases the accumulation of lipid peroxidation products.[3,5] The enzyme plays a role in decreasing oxidative stress. PON1 is an important endogenous free radical scavenging system in the human body.[5]
Homocysteine thiolactone hydrolase, a calciumdependent protein of 45kDa is a component of HDL and is identical with serum PON.[6] Homocysteine thiolactones, a metabolite of homocysteine causes endothelial dysfunction and vascular damage. PON1 plays a vital role in cardioprotection, as it is required for detoxification of homocysteine thiolactone.[3] Study by Suvarna et al. reported that Type 2 DM patients with complications have significantly decreased HDL-C and PON1 activity, leading to decreased functioning of HDL-C in these patients.[2] Study done by Ferretti et al. reported significantly lower PON1 activity in Type 1 DM.[4] Another study by Abbott et al. reported that PON activity was lower in both Type 1 and Type 2 diabetes patients.[7] However, Beer et al. found no significant difference in PON 1 activity and concentration in the diabetic group when compared to impaired fasting glucose and control although postprandial hyperlipidemia was associated with changes in serum PON1 in diabetic subjects.[8] Reduced PON activity increases the oxidative stress in the patients. Hence, the present study was undertaken to evaluate serum PON levels and serum lipid profile in Type 2 DM. Monitoring the trends in cardiovascular complications via PON 1 is of critical importance in managing patients with Type 2 DM
Materials and Methods Clinically diagnosed 60 DM cases attending Medicine outpatient department at Adichunchanagiri Hospital and Research Centre, B G Nagar, Mandya were included in the study. Age and sex matched 60 healthy individuals were taken as a control group. Informed consent was taken and the study was approved by the ethical committee of the institution. Patients suffering from acute and chronic inflammatory conditions, other metabolic conditions like ketoacidosis, cerebrovascular accidents, preeclamptic patients, pre-existing chronic kidney disease, chronic renal failure, nephrotic syndrome, and primary hypertensives were excluded from the study. 5 ml of fasting blood sample was drawn from all subjects under the aseptic precaution and 2 ml of blood was drawn in postprandial period. Fasting samples were analyzed for routine blood parameters, fasting plasma glucose (FPG), serum lipid profile, TBARS levels, and PON levels. Postprandial sample was analyzed for postprandial plasma glucose (PPPG). Plasma Glucose was measured by glucose oxidase - peroxidase method (Trinder’s method), serum total cholesterol (TC) by CHOD-PAP method, HDL by modified polyvinyl sulfonic acid and polyethylene glycol methyl ether coupled classic precipitation method and triacylglycerol (TG) by glycerol phosphate oxidase Trinder method using standard kits from ERBA diagnostics on EM-200 auto-analyzer. Very low-density lipoprotein (VLDL) was calculated by dividing TG with five (TG/5). LDL level were calculated using Friedwald’s formula, LDL= TC - (HDL+TG/5). Serum PON was measured by spectrophotometric method using p-nitrophenyl acetate as a substrate, in which PON catalyzes the cleavage of p-nitrophenyl acetate resulting in the formation of phenol. The rate of formation of phenol is measured by monitoring the increase in the absorbance at 412 nm.[9,10] Serum TBARS, a marker of lipid peroxidation and hence oxidative stress was measured by thiobarbituric acid method.[11]
Statistical analysis Results are represented as mean ± standard deviation. Statistical analysis was done using Student’s t-test, and statistical significance was compared between the cases and the controls. Pearson correlation between the study variables was performed to establish the relationship. Probability value (P) of < 0.05 was considered as statistically significant. Statistical analysis was done using the Statistical Software: SPSS-16.
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