Coronary heart disease, echo-Doppler evidence of peripheral arterial disease and polymorphism of apolipoprotein B gene and Apo AI/CIII cluster

Association of serum apolipoprotein C III levels and apolipoprotein C III gene Sst I polymorphism with carotid intima-media thickness in Chinese type 2 diabetic patients

Apolipoprotein C III (apo C III) plays a central role in regulating plasma metabolism of triglyceride-rich lipoprotein (TRL). The G3238C allele (Sst I) in the 3'-untranslated region has been found to be associated with raised apo C III levels and hypertriglyceridemia (HTG). Some studies suggest that apo C III and the S(2) allele of apo C III gene are independent risk factors for atherosclerotic diseases. To study the potential association between these factors we analyzed the clinical data and their correlations with serum apo C III levels, apo C III gene Sst I polymorphism, and carotid intima-media thickness (IMT) in 78 unrelated Chinese patients with type 2 diabetes. Apo C III gene Sst I polymorphism was examined using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Carotid IMT was measured by color doppler ultrasound examination. Serum apo C III levels were found to be positively associated with plasma TG ( r = 0.527, P < 0.001), TC (r = 0.424, P < 0.001), LDL-C (r = 0.308, P < 0.01) concentrations, and carotid IMT (r =0.359, P < 0.01 ). Multivariate analysis (backward) showed that diastolic blood pressure, apo C III, and fasting insulin levels were independent risk factors of carotid IMT. However, the results did not show the association between S(2) allele and carotid IMT in our diabetic patients. Thus, our study suggested that apo C III is an independent risk factor for atherosclerotic diseases in Chinese type 2 diabetes.

Influence of polymorphism (RFLP-sstI) at the apolipoprotein C-III gene locus on the lipoprotein metabolism and insulin resistance in essential hypertensive patients. Interaction between gender and genetic polymorphism

BACKGROUND AND AIM

With respect to the general population, hypertensive patients show an increase in plasma total cholesterol and triglycerides, a decrease in HDL-cholesterol (HDLc) and a higher degree of insulin resistance. Apolipoprotein C-III (apo C-III) plays a regulatory role in the catabolism of triacylglycerol-rich lipoproteins. The S2 allele has been associated with elevated plasma triglycerides concentration, blood pressure and increased risk of myocardial infarction, all of which are characteristic of an insulin resistant state. The aim of this study was to investigate the SstI polymorphism of the apo C-III gene locus on the lipoprotein metabolism, apolipoproteins and basal glucose and insulin levels in essential hypertensive patients. We also examined the influence of the S1S2 allele on blood pressure and the interaction of the mutation at the apo C-III gene and the gender.

METHODS AND RESULTS

We studied 104 essential hypertensive patients (59 males and 45 females) determining the carriers of the S2 allele of the genetic polymorphism in the apo C-III gene by polymerase chain reaction, lipoprotein metabolism by standard laboratory methods and ultracentrifugation, apolipoproteins A-I and B by immunoturbidimetry and basal glucose and insulin levels by enzymatic method and radioimmunoassay, respectively. The frequency for the carriers of the SstI minor allele S2 (S1S2 genotype) was 0.17. Patients with the rare S2 allele compared with those with S1S1 allele showed higher plasma triglycerides, total cholesterol and apo B (255.9 +/- 114.6 vs 135.8 +/- 89.1; 250.6 +/- 56.6 vs 214.8 +/- 47.9 and 128.7 +/- 34.8 vs 103.1 +/- 28.6 respectively). Furthermore, basal glucose, insulin levels in S2 allele, and the rate Tg-VLDL/HDLc were increased in the same group. Subgroup analysis revealed that the association between these polymorphism and lipoprotein metabolism, apolipoprotein and basal glucose and insulin levels occurred predominantly in females. A study on the effect of the interaction between this mutation with gender revealed an additive effect on changes in total triglycerides levels. However age, blood pressure and body mass index were similar in both groups of patients (S1S1 and S1S2 genotypes).

CONCLUSIONS

These results provide evidence of interaction between gender and the Sst1 polymorphism of the apo C-III on lipoprotein metabolism and insulin resistance in essential hypertensive patients. However, the studied mutation does not contribute to blood pressure levels in essential hypertensive patients (crossover study).

Allele-specific Differences in Apolipoprotein C-III mRNA Expression in Human Liver

Background: Sequence variations at the apolipoprotein (apo)C-III gene locus have been associated with increased plasma triglycerides. In particular, the S2 allele of an SstI polymorphism in the 3′ untranslated region has been associated with hypertriglyceridemia in many populations. The aim of this study was to determine whether the variant S2 allele is related to increased mRNA expression in vivo.

Methods: We measured allele-specific apoC-III expression in liver biopsies of five obese subjects, using restriction isotyping and a primer extension method, both based on the SstI polymorphism.

Results: The expression of mRNA by the S1 and S2 alleles was similar in two patients, whereas the mRNA encoded by the S2 allele was 14%, 26%, and 29% more abundant than the wild-type mRNA in the remaining three patients. Because other polymorphisms at the apoC-III gene locus have been implicated in the S2-associated hypertriglyceridemia, we determined apoC-III haplotypes comprising promoter polymorphisms at −935, −641, −630, −625, −482, −455, as well as the SstI sites and a BbvI site, both located in the 3′ untranslated region. None of these polymorphisms nor any haplotype exhibited a perfect association with allele-specific expression, but variation at the T-482C site correlated in four of five subjects with the relative allele abundance.

Conclusion: These data provide preliminary evidence for allele-specific differences in apoC-III mRNA expression in vivo and suggest that such differences may contribute to associations of apoC-III gene polymorphisms with hypertriglyceridemia.