It has long been recognized that atherosclerosis, the main cause of CAD, is an inflammatory disease in which immune mechanisms interact with metabolic risk factors to initiate, propagate and activate lesions in the arterial tree. The prevalence of CAD is rising rapidly in developing countries due to increased exposure to CAD risk factors, which may lead to an expanding epidemic. CAD is believed to be caused by multiple genetic factors, environmental factors and interactions among these factors. Identification of these genetic and environmental factors will provide valuable information for prevention and control of CAD. Significant advances have been made in identifying disease-causing genes and susceptibility genes for CAD.
The sirtuin, a family of enzymes, has been identified as the pivotal regulator of lifespan and health. SIRT1 is the best-known member of the sirtuin family of nicotinamide adenine dinucleotide (NAD+) - dependent protein deacetylases, whose activation appears beneficial for aging associated metabolic, inflammatory and cardiac diseases. Several studies have demonstrated the protective roles of SIRT1 in vascular biology and atherosclerosis. SIRT1 activation is associated with improved endothelial function, enhanced lipid metabolism and inhibition of atherogenesis. Conversely, SIRT1 inhibition is associated with vascular dysfunction and arterial thrombosis.
Polymorphisms related to SIRT1 gene have been reported to be associated with a higher incidence of type 2 diabetes, cholesterol metabolism, coronary artery calcification and increase risk of obesity, etc. In addition, the mRNA expression of the SIRT1 gene was suggested to be related to SIRT1 SNPs.
The current work aimed to investigate the association of SIRT1 promoter SNP rs3758391 T/C with coronary atherosclerosis and to explore the impact of this polymorphism on SIRT1 gene expression. Moreover, the present study aimed to investigate the association of SIRT1 mRNA expression with coronary atherosclerosis and to evaluate the correlation between SIRT1 expression and coronary atherosclerosis severity, validated by angiographic Gensini score.
The present study was conducted in Cardiology Catheter Unit at Benha University Hospitals. Data were collected from 200 patients undergoing elective coronary angiography because of complaining of chest pain. Patients were divided according to coronary angiography into two groups:
CAD group: 100 patients with significant coronary artery atherosclerosis detected by coronary angiography.
Control group: 100 patients with normal coronary arteries proved by coronary angiography.
• Those with acute or chronic infections.
• Systemic inflammatory diseases and autoimmune diseases.
• Blood diseases and hematologic disorders.
• Patients suffering from DM.
• Severe liver or renal diseases.
• Those with malignant tumors.
• Previous history of PCI or CABG.
All cases included in this study were subjected to the following:
1) Full history taking with emphasis on risk factors of CAD.
2) Full clinical examination.
3) Diagnostic coronary angiography:
Severity of coronary artery atherosclerosis was assessed by Gensini score which is based on the degree of luminal narrowing and its regional importance
4) Laboratory investigations:
A peripheral venous blood sample was obtained from each subject after obtaining consent under complete aseptic conditions and was used for:
a) Biochemical laboratory investigations: CBC, liver function tests, kidney function test, ESR, fasting blood glucose and lipid profile (total cholesterol, LDLc, HDLc and TG).
b) Molecular laboratory investigations:
1. Genotyping and SNP rs3758391 T/C analysis of SIRT1 gene by RT-PCR.
2. Relative quantification of SIRT1 mRNA expression by RT-PCR.
According to the current study:
• HDLc levels were significantly lower in CAD group compared to control group.
• Gensini scores were significantly higher in males and in smoker patients. In addition, Gensini scores correlated negatively with HDLc levels.
• There was a statistically significant association between SIRT1 SNP rs3758391 T/C and coronary atherosclerosis; the frequency of CC genotype increased significantly in CAD group.
• Gensini scores were significantly higher in CC genotype compared to CT and TT genotypes.
• SIRT1 gene expression levels reduced significantly in CAD group compared to control group. Furthermore, SIRT1 gene expression levels reduced significantly in CC genotype compared to CT and TT genotypes.
• SIRT1 gene expression levels showed significant positive correlation with HDLc levels.
• At a cut off value of 0.665 for the relative quantification of SIRT1 gene expression, the sensitivity and specificity to diagnose coronary atherosclerosis were 76 % & 65% respectively as shown by ROC curve analysis.