Impact of the interaction between the polymorphisms and hypermethylation of the CD36 gene on a new biomarker of type 2 diabetes mellitus: circulating soluble CD36 (sCD36) in Senegalese females.

BACKGROUND: Several predisposing factors for diabetes mellitus have been identified, including cluster determinant 36 (CD36) receptor expression. We aimed to determine the effects of CD36 gene polymorphisms and hypermethylation on the plasma CD36 protein levels in type 2 diabetes. MATERIALS AND METHODS: We conducted a cross-sectional study involving 100 females (lean healthy control subjects and subjects with type 2 diabetes). This study was conducted at the Human Physiology Laboratory at the Dakar Faculty of Medicine in Senegal. Circulating sCD36 levels and DNA methyltransferase 3a levels were determined by enzyme-linked immunosorbent assay. The other biological parameters were evaluated in a biochemical laboratory. CD36 gene polymorphisms and methylation were explored by real-time polymerase chain reaction and methylation-specific polymerase chain reaction, respectively. RESULTS: sCD36 was negatively correlated with HDL-cholesterol levels (r = - 0.52 p = 0.0001) and triglyceride levels (r = - 0.36 p = 0.01) in control subjects. However, in the type 2 diabetes group, sCD36 levels were positively correlated with total cholesterol levels (r = 0.28 p = 0.04). For rs3211867, control subjects harboring the CC genotypes had significantly higher sCD36 levels than control subjects harboring the AA/AC genotype (p = 0.02); in the type 2 diabetes group, the sCD36 level was not significantly lower in subjects harboring the AA/AC genotype than in subjects harboring the CC genotype (p = 0.27). CD36 gene methylation reduced the sCD36 level in the control subjects compared to control subjects without CD36 gene methylation (p = 0.03). This difference was not significant in the type 2 diabetes group comparing subjects with diabetes with CD36 gene methylation to subjects with diabetes without CD36 gene methylation (p = 0.09). We noted a nonsignificant increase in sCD36 levels in subjects with diabetes with CD36 gene methylation compared to control subjects with CD36 gene methylation (p = 0.27). A combination of the CD36 polymorphism effect and the CD36 methylation effect did not significantly reduce sCD36 levels in subjects with type 2 diabetes. CONCLUSION: CD36 gene polymorphisms and CD36 gene methylation separately reduce sCD36 levels. Their impacts are compensated for in subjects with type 2 diabetes by an increase in sCD36 levels, the mechanism of which needs to be elucidated.

Association between polymorphisms and hypermethylation of CD36 gene in obese and obese diabetic Senegalese females.

BACKGROUND: Obesity and related metabolic disorders are associated with genetic and epigenetic alterations. In this study, we have examined the association between polymorphisms and hypermethylation of the CD36 gene promoter with obesity in Senegalese females with or without type 2 diabetes mellitus to identify novel molecular markers of these pathologies (obesity and type 2 diabetes mellitus). MATERIALS AND METHODS: The study was conducted in Senegal with healthy lean control, obese, and obese diabetic (age; 49.98 years ± 7.52 vs 50.50 years ± 8.76 vs 51.06 ± 5.78, and body mass index (BMI); 24.19 kg/m2 ± 2.74 vs 34.30 kg/m2 ± 4.41 vs 33.09 kg/m2 ± 4.30). We determined three genetic polymorphisms of CD36 i.e., rs1761667, rs1527483, and rs3211867 by real-time polymerase chain reaction, and methylation of CPG islands of CD36 was assessed by methylation-specific polymerase chain reaction (MS-PCR) in DNA isolated from peripheral blood of each participant. Plasma sCD36 levels and DNA methyltransferase 3a (DNMT3a) levels were determined by enzyme-linked immunosorbent assay (ELISA). According to the standard laboratory protocol, all biochemical parameters were analyzed from fasting serum or plasma. RESULTS: For rs1761667, obese and obese diabetic subjects had statistically significant different parameters depending on the genotypic distribution. These were waist size for obese and HDL cholesterol for obese diabetic, they were significantly higher in subjects harboring GG genotype of rs1761667 (respectively p = 0.04 and p = 0.04). For rs3211867, obese subjects harboring the AA/AC genotype had significantly higher BMI (p = 0.02) and total cholesterol (p = 0.03) than obese subjects harboring the CC genotype. At the same time, the obese diabetic subjects harboring the AA/AC genotype had total cholesterol levels significantly higher than the obese diabetic subjects harboring the CC genotype (p = 0.03). For rs1527483, only the control subjects had statistically significant different parameters depending on the genotypic distribution. The control subjects harboring the GG genotype had a significantly higher BMI than the control subjects harboring the AA/AG genotype (p = 0.003). The CD36 gene methylation was significantly 1.36 times more frequent in obese and obese diabetic compared to lean control (RR = 1.36; p = 0.04). DNMT3a levels were higher in subjects with CD36 gene methylation than in subjects without CD36 gene methylation in each group. Obese diabetic subjects with CD36 gene methylation had significantly fewer plasmas sCD36 (p = 0.03) and more LDL-cholesterol (p = 0.01) than obese diabetic subjects without CD36 gene methylation. In the control group, an increase in sCD36 levels would be associated with a decrease in total cholesterol and triglyceride levels (coef = -7647.56 p = 0.01 and coef = -2528.50 p = 0.048, respectively) would be associated with an increase in LDL cholesterol levels. For the obese group, an increase in sCD36 levels would be associated with an increase in fasting insulin levels (coef = 490.99 p = 0.02) and a decrease in glycated hemoglobin levels (coef = -1196.26 p = 0.03). An increase in the sCD36 levels would be associated with an increase in the triglyceride levels in the obese diabetic group (coef = 9937.41 p = 0.02). The AA/AC genotype of SNP rs3211867 polymorphism was significantly associated with CD36 gene methylation in the control and obese diabetic groups (respectively p = 0.05, p = 0.002; 95% CI). CONCLUSION: These observations suggest that polymorphisms and epigenetic changes in CD36 gene promoters may be implicated in the onset of obesity and its related complication type 2 diabetes mellitus.

Frequencies and Distribution of APOE Gene Polymorphisms and Its Association With Lipid Parameters in the Senegalese Population.

Background Apolipoprotein E is a multifunctional protein that plays an important role in lipid metabolism. It is encoded by the APOE gene. However, APOE gene polymorphism has not been very well studied in the Senegalese population. Therefore, we studied allele frequencies, genotype distributions, and the relationship between APOE gene polymorphisms and lipid parameters in the Senegalese women population. Methodology This study included 110 healthy women aged 35-72 years. The mean age was 49.8 ± 8.1 years. For all subjects, lipid parameters were analyzed from fasting serum, and APOE genotypes were identified by PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) based analysis. Results Variations in the frequencies and distribution of the APOE alleles and genotypes were observed (ε3: 47.3%; ε2: 43.2%; ε4: 9.6%; and ε2/ε3: 70%; ε2/ε4: 16.4%; ε3/ε3: 10.9%; ε2/ε4: 2.7%). Compared to the ε3ε3 genotype carriers, carriers of the ε3ε4 genotype had a significantly higher rate of total cholesterol (p=0.03) and no high-density lipoprotein-cholesterol (p=0.02). Univariate analysis showed that the APOE ε4 allele increases the low-density lipoprotein-cholesterol rate (OR=3.06; 95% CI: 1.16-8.22; p=0.02). Conclusion Our study has shown a difference in APOE allele frequencies and genotype distributions with a total absence of ε2ε2 and ε4ε4 genotypes in a sample of Senegalese women. We also found that APOE gene polymorphism might play a role in plasma lipid levels.