Apolipoprotein E gene polymorphism: effects on plasma lipids and risk of type 2 diabetes and coronary artery disease.

BACKGROUND: The most common apolipoprotein E (apoE) gene polymorphism has been found to influence plasma lipid concentration and its correlation with coronary artery disease (CAD) has been extensively investigated in the last decade. It is, however, unclear whether apoE gene polymorphism is also associated with increased risk of type 2 diabetes mellitus (T2DM). The knowledge of this study may provide the primary prevention for T2DM and CAD development before its initiation and progression. Therefore, this study was carried out to determine the association between apoE gene polymorphism and T2DM with and without CAD and its role in lipid metabolism. METHODS: The case-control study was carried out on a total of 451 samples including 149 normal control subjects, 155 subjects with T2DM, and 147 subjects with T2DM complicated with CAD. The apoE gene polymorphism was tested by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Univariable and multivariable logistic regression analyses were used to identify the possible risks of T2DM and CAD. RESULTS: A significantly increased frequency of E3/E4 genotype was observed only in T2DM with CAD group (p = 0.0004), whereas the ε4 allele was significantly higher in both T2DM (p = 0.047) and T2DM with CAD (p = 0.009) as compared with controls. E3/E4 genotype was also the independent risk in developing CAD after adjusting with established risk factors with adjusted odds ratio (OR) 2.52 (95%CI 1.28-4.97, p = 0.008). The independent predictor of individuals carrying ε4 allele still remained significantly associated with both CAD (adjusted OR 2.32, 95%CI 1.17-4.61, p = 0.016) and T2DM (adjusted OR 2.04, 95%CI 1.07-3.86, p = 0.029). After simultaneously examining the joint association of E3/E4 genotype combined with either obesity or smoking the risk increased to approximately 5-fold in T2DM (adjusted OR 4.93, 95%CI 1.74-13.98, p = 0.003) and 10-fold in CAD (adjusted OR 10.48, 95%CI 3.56-30.79, p < 0.0001). The association between apoE genotypes on plasma lipid levels was compared between E3/E3 as a reference and E4-bearing genotypes. E4-bearing genotypes showed lower HDL-C and higher VLDL-C and TG, whereas other values of plasma lipid concentrations showed no significant difference. CONCLUSIONS: These results indicate that ε4 allele has influence on lipid profiles and is associated with the development of both T2DM with and without CAD, and furthermore, it increased the risk among the subjects with obesity and/or smoking, the conditions associated with high oxidative stress.

Paraoxonase 1 polymorphisms as the risk factor of coronary heart disease in a Thai population.

OBJECTIVE: Two common polymorphisms of the paraoxonase (PON1) gene, L55M and Q192R, were proven to mitigate atherosclerosis pathogenesis by protecting lipoproteins against peroxidation. This study was to evaluate the associations between both PON1 gene polymorphisms in Thai hyperlipidaemia with and without coronary heart disease (CHD). METHODS: Both PON1 genotypes were determined using PCR-RFLP in 103 healthy control subjects, 103 primary hyperlipidaemia without history of such diseases and 106 angiographically documented CHD patients. RESULTS: The frequencies of PON1 192R allele and 192RR genotype were significantly higher in CHD patients than in normal control subjects (P = 0.009 and 0.037, respectively). The significantly higher frequencies of 55M allele and 55LM genotype were also observed in CHD patients (P = 0.037 and P = 0.034, respectively). The frequencies of both PON1 polymorphisms were not different in primary hyperlipidaemia as compared to the normal control subjects. The odds ratio (OR) of 192RR genotype and 192R allele for CHD were 2.84 (1.17-6.99, P = 0.011) and 1.70 (1.11-2.61, P = 0.009), respectively. The age-adjusted OR for CHD was 2.72 (1.25-5.94, P = 0.012). These frequencies of both PON1 alleles were similar to those seen in other Asian populations. CONCLUSIONS: The association between PON1 polymorphisms and CHD risk was demonstrated in aThai population. These new data underscore the essence of ethnic variations in the interpretation of CHD associated with PON1 polymorphism.

Lipid peroxidation and antioxidant enzyme activities in erythrocytes of type 2 diabetic patients.

BACKGROUND AND OBJECTIVE: Although diabetes mellitus (DM) patients are claimed to be under oxidative stress because of prolonged exposure to hyperglycemia, the influence of glycemic control and cardiovascular complication in diabetes on oxidative stress parameters has not been fully studied. The present study aimed to investigate lipid peroxidation end product (malondialdehyde, MDA) and antioxidant enzymes in fairly controlled type 2 DM (fasting plasma glucose [FPG] < or = 180 mg/dl) or type 2 DM complicated with coronary heart disease (CHD) and poorly controlled type 2 DM (FPG > 180 mg/dl) in comparison to a normal healthy group (FPG < 110 mg/dl). MATERIAL AND METHOD: MDA and antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) were determined in the red cell of 19 subjects with poorly controlled type 2 DM, 26 subjects with fairly controlled type 2 DM and 20 subjects with type 2 DM complicated with CHD who were matched for age and gender. Twenty healthy subjects with normal plasma glucose level and matched for age and gender were served as a control group. In all groups of DM these oxidative stress parameters were compared to a control group by one-way ANOVA test. Pearson rank correlation coefficient was used to compare the relationship between FPG and oxidative stress status in type 2 DM and normal controls. RESULTS: The red cell MDA levels were significantly higher in all types of diabetes compared to age-matched normal controls. The mean of red cell MDA level was highest in type 2 DM complicated with CHD. Red cell antioxidant enzyme activities were also significantly increased except for SOD and GPx activities in fairly controlled type 2 DM. The significant positive correlation between oxidative stress status (as MDA and CAT) and FPG was found in poorly controlled type 2 DM and type 2 DM complicated with CHD whereas in fairly controlled type 2 DM the significant positive correlation between CAT and FPG was only observed. CONCLUSION: These findings strongly confirmed the evidence that diabetic patients were susceptible to oxidative stress and higher blood glucose level had an association with free radical-mediated lipid peroxidation. The highest level of MDA in type 2 DM complicated with CHD suggested that oxidative stress played an important role in the pathogenesis of cardiovascular complication. The results also showed the increase in antioxidant enzymes. These could probably be due to adaptive response to pro-oxidant in diabetic state. Hence, there seems to be imbalance between oxidant and antioxidant systems in type 2 diabetic patients.

Glutathione and glutathione peroxidase in type 1 diabetic patients.

OBJECTIVE: Diabetic (DM) patients are claimed to be under oxidative stress because of hyperglycemia. The influence of free radical production by this hyperglycemic induction may involve cardiovascular complications in diabetes. The present study aimed to compare the glutathione (GSH) level and glutathione peroxidase (GPx) activity in type 1 DM and a normal healthy group. MATERIAL AND METHOD: GSH level and GPx activity were determined in red cells of 20 subjects of type 1 DM containing fasting plasma glucose (FPG) > or = 140 mg/dL. Twenty healthy normal subjects with normal plasma glucose level (FPG < or = 110 mg/dL) and matched for gender and age served as the control group. These oxidative stress parameters of type 1 DM were compared to a control group by unpaired student's t-test. The association of these parameters with FPG was performed by Pearson product moment correlation. RESULTS: The level of red cell GSH was significantly lower in type 1 DM (p = 0.011) but red cell GPx activity was significantly increased (p = 0.003) when compared to age-matched normal control. The decrement of red cell GSH may be due to the higher rate of consumption of GSH, increasing GPx activity or a reduction of pentose phosphate pathway, stimulated by insulin, resulting in lowered GSH recycle. The correlation between FPG and GSH in type I diabetic patients compared with healthy normal subjects was also observed and it was found that there was a negative correlation, but not found between FPG and GPx activity. CONCLUSION: The present finding suggested that type 1 DM patients were susceptible to oxidative stress and higher blood glucose level had an association with free-radical-mediated lipid peroxidation. Therefore, any means that can reduce oxidative stress may be beneficial for slow progression of cardiovascular complication in type 1 diabetic patients.

Antioxidant status and lipid peroxidation end products in patients of type 1 diabetes mellitus.

BACKGROUND AND OBJECTIVE: In Type 1 diabetes mellitus (DM), hyperglycemia is considered a primary cause of diabetic vascular complications and is associated with oxidative stress. The role of antioxidants, particularly alpha tocopherol, in Type 1 DM and its contribution in the development of vascular complications is not clear. Therefore, the present study aims to investigate the relationship between antioxidant status (alpha tocopherol) and lipid peroxidation end products (malondialdehyde; MDA) in the plasma of 20 Type 1 DM and 20 nondiabetic healthy control subjects. MATERIAL AND METHOD: Lipid levels in all subjects were analyzed spectrophotometrically by enzymatic reagent kits. Plasma MDA was assessed by spectrofluorometry, whereas plasma alpha tocopherol was estimated by high performance liquid chromatography in Type 1 DM as well as in the control subjects of matched sex and ages. The results of Type 1 DM were compared with a control group using unpaired Student's t-test. The correlations between fasting plasma glucose and other laboratory parameters were assessed by Pearson rank correlation coefficient. RESULTS: The plasma MDA concentration was significantly higher in Type 1 diabetic patients as compared to controls, (p < 0.01). A significantly reduced plasma antioxidant status of Type 1 DM patients was found only in alpha tocopherol / total lipid as compared to controls (p < 0.05). However, no significant difference was observed in plasma a tocopherol and a tocopherol / total cholesterol (p > 0.05) as compared to the control subjects. The positive correlation between MDA and FPG was demonstrated in Type 1 diabetic compared with normal subjects. CONCLUSION: We conclude that antioxidant supplementation may be necessary for treatment to reduce oxidative stress for diabetic complication protection in Type 1 DM.

Plasma lipid peroxidation and antioxidiant nutrients in type 2 diabetic patients.

BACKGROUND AND OBJECTIVE: Observation shows diabetic patients to be more prone to oxidative stress because of hyperglycemia. The elevation of free radical production by this hyperglycemic production may exacerbate cardiovascular complication in diabetes. This study aims to investigate the oxidative stress related parameters in type 2 DM. Since the effects of glycemic control and cardiovascular complications in DM on these parameters has been not fully determined, the comparison between plasma MDA (malondialdehyde) and antioxidant nutrients with their age-matched normal healthy group may be used to determine the susceptibility of oxidative stress in this type of DM. MATERIAL AND METHOD: MDA and antioxidant nutrients (vitamin A, C, E and beta-carotene) were analyzed in plasma of 19 subjects with poorly controlled type 2 DM (fasting plasma glucose [FPG] > 180 mg/dl), 26 subjects with fairly controlled type 2 DM (FPG < or = 180 mg/dl), and 20 subjects with type 2 DM complicated coronary heart disease (CHD) who were matched for age and gender. Twenty healthy subjects with normal plasma glucose level (FPG < 110 mg/dl) and matched for age and gender served as a control group. In all groups of DM these oxidative stress parameters were compared to a normal group. RESULTS: The plasma MDA levels were significantly higher in all types of DM compared to age-matched normal control. Plasma antioxidant vitamin C and E significantly lower only in poorly controlled and CHD complicated type 2 DM, respectively. The mean of plasma vitamin E level was lowest in type 2 DM complicated with CHD. No significant differences in both plasma vitamin A and beta-carotene were noted between any types of DM and age-matched normal healthy group. The positive correlation between MDA and FPG was demonstrated in most group of patients with their normal subjects except in fairly controlled type 2 DM and negative correlation between vitamin E and FPG was also demonstrated in type 2 DM with CHD. CONCLUSION: These findings suggested that diabetic patients were susceptible to oxidative stress and higher plasma glucose level had an association with free radical-mediated lipid peroxidation. The lowest level of vitamin E in type 2 DM complicated with CHD indicated that oxidative stress played an important role in cardiovascular complication and vitamin E supplementation may be necessary for treatment and prevention in this group of diabetics.

Effects of cytochrome P450 2C19 and paraoxonase 1 polymorphisms on antiplatelet response to clopidogrel therapy in patients with coronary artery disease.

Clopidogrel is an antiplatelet prodrug that is recommended to reduce the risk of recurrent thrombosis in coronary artery disease (CAD) patients. Paraoxonase 1 (PON1) is suggested to be a rate-limiting enzyme in the conversion of 2-oxo-clopidogrel to active thiol metabolite with inconsistent results. Here, we sought to determine the associations of CYP2C19 and PON1 gene polymorphisms with clopidogrel response and their role in ADP-induced platelet aggregation. Clopidogrel response and platelet aggregation were determined using Multiplate aggregometer in 211 patients with established CAD who received 75 mg clopidogrel and 75-325 mg aspirin daily for at least 14 days. Polymorphisms in CYP2C19 and PON1 were genotyped and tested for association with clopidogrel resistance. Linkage disequilibrium (LD) and their epistatic interaction effects on ADP-induced platelet aggregation were analysed. The prevalence of clopidogrel resistance in this population was approximately 33.2% (n = 70). The frequencies of CYP2C19*2 and *3 were significantly higher in non-responder than those in responders. After adjusting for established risk factors, CYP2C19*2 and *3 alleles independently increased the risk of clopidogrel resistance with adjusted ORs 2.94 (95%CI, 1.65-5.26; p<0.001) and 11.26 (95%CI, 2.47-51.41; p = 0.002, respectively). Patients with *2 or *3 allele and combined with smoking, diabetes and increased platelet count had markedly increased risk of clopidogrel resistance. No association was observed between PON1 Q192R and clopidogrel resistance (adjusted OR = 1.13, 95%CI, 0.70-1.82; p = 0.622). Significantly higher platelet aggregation values were found in CYP2C19*2 and *3 patients when compared with *1/*1 allele carriers (p = 1.98 × 10(-6)). For PON1 Q192R genotypes, aggregation values were similar across all genotype groups (p = 0.359). There was no evidence of gene-gene interaction or LD between CYP2C19 and PON1 polymorphisms on ADP-induced platelet aggregation. Our findings indicated that only CYP2C19*2 and *3 alleles had an influence on clopidogrel resistance. The risk of clopidogrel resistance increased further with smoking, diabetes, and increased platelet count.

Glutathione and glutathione peroxidase in type 1 diabetic patients.

OBJECTIVE: Diabetic (DM) patients are claimed to be under oxidative stress because of hyperglycemia. The influence of free radical production by this hyperglycemic induction may involve cardiovascular complications in diabetes. The present study aimed to compare the glutathione (GSH) level and glutathione peroxidase (GPx) activity in type 1 DM and a normal healthy group. MATERIAL AND METHOD: GSH level and GPx activity were determined in red cells of 20 subjects of type 1 DM containing fasting plasma glucose (FPG) > or = 140 mg/dL. Twenty healthy normal subjects with normal plasma glucose level (FPG < or = 110 mg/dL) and matched for gender and age served as the control group. These oxidative stress parameters of type 1 DM were compared to a control group by unpaired student's t-test. The association of these parameters with FPG was performed by Pearson product moment correlation. RESULTS: The level of red cell GSH was significantly lower in type 1 DM (p = 0.011) but red cell GPx activity was significantly increased (p = 0.003) when compared to age-matched normal control. The decrement of red cell GSH may be due to the higher rate of consumption of GSH, increasing GPx activity or a reduction of pentose phosphate pathway, stimulated by insulin, resulting in lowered GSH recycle. The correlation between FPG and GSH in type I diabetic patients compared with healthy normal subjects was also observed and it was found that there was a negative correlation, but not found between FPG and GPx activity. CONCLUSION: The present finding suggested that type 1 DM patients were susceptible to oxidative stress and higher blood glucose level had an association with free-radical-mediated lipid peroxidation. Therefore, any means that can reduce oxidative stress may be beneficial for slow progression of cardiovascular complication in type 1 diabetic patients.

Antioxidant status and lipid peroxidation end products in patients of type 1 diabetes mellitus.

BACKGROUND AND OBJECTIVE: In Type 1 diabetes mellitus (DM), hyperglycemia is considered a primary cause of diabetic vascular complications and is associated with oxidative stress. The role of antioxidants, particularly alpha tocopherol, in Type 1 DM and its contribution in the development of vascular complications is not clear. Therefore, the present study aims to investigate the relationship between antioxidant status (alpha tocopherol) and lipid peroxidation end products (malondialdehyde; MDA) in the plasma of 20 Type 1 DM and 20 nondiabetic healthy control subjects. MATERIAL AND METHOD: Lipid levels in all subjects were analyzed spectrophotometrically by enzymatic reagent kits. Plasma MDA was assessed by spectrofluorometry, whereas plasma alpha tocopherol was estimated by high performance liquid chromatography in Type 1 DM as well as in the control subjects of matched sex and ages. The results of Type 1 DM were compared with a control group using unpaired Student's t-test. The correlations between fasting plasma glucose and other laboratory parameters were assessed by Pearson rank correlation coefficient. RESULTS: The plasma MDA concentration was significantly higher in Type 1 diabetic patients as compared to controls, (p < 0.01). A significantly reduced plasma antioxidant status of Type 1 DM patients was found only in alpha tocopherol / total lipid as compared to controls (p < 0.05). However, no significant difference was observed in plasma a tocopherol and a tocopherol / total cholesterol (p > 0.05) as compared to the control subjects. The positive correlation between MDA and FPG was demonstrated in Type 1 diabetic compared with normal subjects. CONCLUSION: We conclude that antioxidant supplementation may be necessary for treatment to reduce oxidative stress for diabetic complication protection in Type 1 DM.

Plasma lipid peroxidation and antioxidiant nutrients in type 2 diabetic patients.

BACKGROUND AND OBJECTIVE: Observation shows diabetic patients to be more prone to oxidative stress because of hyperglycemia. The elevation of free radical production by this hyperglycemic production may exacerbate cardiovascular complication in diabetes. This study aims to investigate the oxidative stress related parameters in type 2 DM. Since the effects of glycemic control and cardiovascular complications in DM on these parameters has been not fully determined, the comparison between plasma MDA (malondialdehyde) and antioxidant nutrients with their age-matched normal healthy group may be used to determine the susceptibility of oxidative stress in this type of DM. MATERIAL AND METHOD: MDA and antioxidant nutrients (vitamin A, C, E and beta-carotene) were analyzed in plasma of 19 subjects with poorly controlled type 2 DM (fasting plasma glucose [FPG] > 180 mg/dl), 26 subjects with fairly controlled type 2 DM (FPG < or = 180 mg/dl), and 20 subjects with type 2 DM complicated coronary heart disease (CHD) who were matched for age and gender. Twenty healthy subjects with normal plasma glucose level (FPG < 110 mg/dl) and matched for age and gender served as a control group. In all groups of DM these oxidative stress parameters were compared to a normal group. RESULTS: The plasma MDA levels were significantly higher in all types of DM compared to age-matched normal control. Plasma antioxidant vitamin C and E significantly lower only in poorly controlled and CHD complicated type 2 DM, respectively. The mean of plasma vitamin E level was lowest in type 2 DM complicated with CHD. No significant differences in both plasma vitamin A and beta-carotene were noted between any types of DM and age-matched normal healthy group. The positive correlation between MDA and FPG was demonstrated in most group of patients with their normal subjects except in fairly controlled type 2 DM and negative correlation between vitamin E and FPG was also demonstrated in type 2 DM with CHD. CONCLUSION: These findings suggested that diabetic patients were susceptible to oxidative stress and higher plasma glucose level had an association with free radical-mediated lipid peroxidation. The lowest level of vitamin E in type 2 DM complicated with CHD indicated that oxidative stress played an important role in cardiovascular complication and vitamin E supplementation may be necessary for treatment and prevention in this group of diabetics.