Subclinical Atherosclerosis And Polymorphisms Of CD36, SRB1 In Type 2 Diabetes Mellitus

Background Subclinical atherosclerosis specifies the early stage of atherosclerosis (AS),when the presence of intima-medial thickness (IMT≥1.0mm) of common carotid artery (CCA),femoral artery (FA) or common iliac artery (CIA) and/or atherosclerotic plaque was found by color ultrasound in the absence of clinical symptoms. One of the primary purposes of multi-approach intervention on Type 2 Diabetes (T2DM) is to block the progression of subclinical atherosclerosis among these patients. Scavenger receptor class B (Scarb,SR-B) is a group of important receptor protein family, including CD36 and scavenger receptor class B type I (Scarbl,SRBl). CD36 antigen is a cellular membrane glucoprotein, binding to many ligands such as oxidized and acetylizad low density lipoprotein-cholesterol (ox-LDL-c and Ac-LDL-c), participating various physiology and pathology processes, such as lipid metabolism and AS. SRB1 is one member of CD36 protein family, sharing 30% homologisation with the CD36 sequence. SRB1 is the only lipoprotein receptor on membrane that mediates the cellular binding to high density lipoprotein( HDL). Objective To investigate the progress of subclinical atherosclerosis in type 2 diabetes patients under multi-approach intervention and its association with polymorphisms of Scavenger receptor class B genes. Four-year multi-approach intervention was carried out in a group of newly diagnosed type 2 diabetes (T2DM) patients. The metabolic status and incidence of subclinical atherosclerosis were monitored periodically. Together with genotyping of CD36 (CD36-rs1984112 and CD36-T620C) and SRBl-rs5888 polymorphisms and phenotyping of CD36 expression by flow cytometry in peripheral blood monouclear cells (PBMC),the associations among CD36/SRB1 gene polymorphisms, metabolic status and the progression of subclinical atherosclerosis were analized. PartⅠThe progress of subclinical atherosclerosis in newly diagnosed type 2 diabetes patients under multi-approach intervention - a prospective clinical observationObjective To investigate the metabolic status and the incidence/progression of subclinical atherosclerosis (AS) in newly diagnosed type 2 diabetes (T2DM) patients under multi-approach intervention.Methods In this prospective case-controlled study, one hundred and seventy newly diagnosed type 2 diabetes patients without AS (35～70 years-old, duration≤1 year) were recruited and allocated into 4 groups (random digits table): group A (intensified control of blood glucose and blood pressure levels), group B (intensified control of blood glucose, blood pressure and blood lipid levels), group C (vitamin E was prescribed on the base of Group-B regimen), group D (Compound Danshen Pill was prescribed on the base of Group-B regimen). All patients were followed-up once a month in a 4-year period. Fasting blood sugar (FBS), postprandial blood sugar (PBS), HbA1c (Glycosylated hemoglobin), lipid profile, SBP (systolic blood pressure), DBP (diastolic blood pressure), BMI (body mass index), WHR (waist-to-hip ratio) and the intima-media thickness (IMT) or AS plaques of common carotid artery (CCA) and femoral artery (FA) were evaluated regularly. Results 149 of the 170 cases complied the intervention protocol in the four-year follow up (the losed rate is 12.4%), thus were taken into the final analysis. The levels of HbA1c, TG, TC, LDL-c, SBP and DBP at the end of intervention were significantly lower than the baseline (p<0.01). Also, the normalization rate of WHR, HbA1c, TG, TC, LDL-c, SBP and DBP was 29.5%,54.4%,74.5%,71.1%,73.8%,98.0% and 98.7% respectively, which was significantly higher than that at the beginning of intervention (p<0.01). Subclinical AS was found in 88 patients (59.1 %) by the end of the fourth year. The levels of CCA-IMT and FA-IMT were significantly higher than the baseline levels in group A, B, C and D (p<0.01). The incidence rate of subclinical AS was 69.4%, 53.8%, 62.2% and 51.4% in the four group, respectively (p>0.05). In group B, C and D, serum LDL-c and TC levels were significantly lower than those in group A(p<0.01,p<0.05).Conclusions Multi-approach intervention significantly improved the metabolic status of T2DM patients in terms of both levels and normalization-rate of WHR,HbA1c,TG,TC,LDL-c,SBP and DBP. However, the present intervention protocol did not stop the progression of subclinical AS in the 4-year observation. Part II The association between polymorphisms of Scavenger receptor class B genes and progress of Subclinical Atherosclerosis in Type 2 Diabetic patientsObjective To investigate the role of polymorphisms of Scavenger receptor class B genes (CD36 and SRB1 gene) in affecting the progress of Subclinical Atherosclerosis (AS) in newly diagnosed type 2 diabetics under multi-approach intervention.Methods 470 cases of T2DM and 220 non diabetic controls from Hunan, southern China were typed for CD36 (CD36-rs1984112, CD36-T620C) and SRBl-rs5888 polymorphisms using PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) method. The genotypes and allele frequencies were compared between cases and controls. Logistic regression model was used to analysis the risk factors contributing to the progress of subclinical atherosclerosis (AS) in newly diagnosed type 2 diabetics under multi-approach intervention.Results The genotypes and allele frequencies of CD36-rsl984112 in T2DM were not significantly different between cases and controls (p>0.05), either did CD36-T620C (p>0.05). Yet the genotype and allele frequencies of SRBl-rs5888 were found significantly different between T2DM and controls (p<0.01): the frequency of SRB1-rs5888C/C genotype in T2DM was lower than that in controls (46.6% vs. 63.2%, p<0.01), the frequency of SRBl-rs5888C/T genotype in T2DM was higher than that in controls (43.4% vs. 30.5%, p<0.01), SRB1-rs5888 T allele frequency in T2DM was higher than that in controls (31.7% vs. 24.5%, p<0.01). When haplotypes carrying CD36-rs1984112 A/A and /or SRB1-rs5888T/T were combined to haplotype A, and other haplotypes were classified into haplotype B, the incidence of subclinical AS was 65.4% for haplotype A and 52.1% for haplotype B respectively (p=0.133). Logistic regression analysis revealed that the risk factors contributing to subclinical AS were age (OR = 1.103), LDL-c(OR = 2.552) and smoke (OR =2.242), while the genotypes of CD36, SRB1, and the interaction term of both were not significant factors.Conclusions SRB1-rs5888 T allele might increase risk of T2DM in Han population in southern China. Age, low-density lipoprotein cholesterol and cigarette smoking were the major determinants of the onset of subclinical AS in T2DM patients. Part III The study of CD36 expression of monocyte surface in T2DM and effecting factor of CD36 expressionObjective To investigate associated factors affecting the expression of CD36 on the surface of peripheral blood monouclear cells (PBMC) in T2DM, and the association between CD36 expression and progress of subclinical atherosclerosis.Methods 102 cases of T2DM and 8 non diabetes controls from Hunan, southern China were recruited in this study. The fluorescence intensity of CD36 on the surface of PBMC was analyzed by flow cytometry.CD36-rsl984112 and SRBl-rs5888 polymorphisms were typed by PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) method. Multiple linear regression was used to evaluate the relevant factors contributing to CD36 expression. Logistic regression model was used to analysis the relationship between CD36 expression and subclinical atherosclerosis in type 2 diabetics under multifactorial intervention.Results The mean florescence intensity (MFI) of CD36 in T2DM with subclinical atherosclerosis was higher than that in the T2DM without atherosclerosis (1382.23±658.69 vs. 1173.02±339.71, p=0.047). SBP (systolic blood pressure) was significantly lower in subjects with high-level of CD36 expression than that in the low-expression subjects (p=0.020). Linear regression analysis showed that factor affecting the CD36 expression were: age (p=0.005), gender (p=0.021), SBP (p=0.027), standardized coefficients Beta was 0.28, 0.31 and -0.21, respectively. In man, age contributes to the CD36 expression levels in males (p=0.002), while in females DBP contributes to the CD36 expression levels (p=0.001). Logistic regression analysis revealed that age (p=0.004) and LDL-c (p=0.095) were remained in the equation while CD36-MFI wasn't contributed to the onset of AS.Conclusions CD36 expression level was higher in T2DM with subclinical atherosclerosis in contrast with T2DM without atherosclerosis. Age, gender and SBP affect CD36 expression: CD36 expression on PBMC surface is higher in aging males with lower SBP; Age and DBP are factors affecting the CD36 expression levels in males and female, respectively. CD36 expression is not associated with the progress of subclinical atherosclerosis.