The effect of sterol regulatory element-binding protein 2 polymorphism on the serum lipid in northern Chinese subjects

A Genome-Wide Analysis of a Sudden Cardiac Death Cohort: Identifying Novel Target Variants in the Era of Molecular Autopsy

Sudden cardiac death (SCD) is an unexpected natural death due to cardiac causes, usually happening within one hour of symptom manifestation or in individuals in good health up to 24 h before the event. Genomic screening has been increasingly applied as a useful approach to detecting the genetic variants that potentially contribute to SCD and helping the evaluation of SCD cases in the post-mortem setting. Our aim was to identify the genetic markers associated with SCD, which might enable its target screening and prevention. In this scope, a case-control analysis through the post-mortem genome-wide screening of 30 autopsy cases was performed. We identified a high number of novel genetic variants associated with SCD, of which 25 polymorphisms were consistent with a previous link to cardiovascular diseases. We ascertained that many genes have been already linked to cardiovascular system functioning and diseases and that the metabolisms most implicated in SCD are the lipid, cholesterol, arachidonic acid, and drug metabolisms, suggesting their roles as potential risk factors. Overall, the genetic variants pinpointed herein might be useful markers of SCD, but the novelty of these results requires further investigations.

Effect of genetic polymorphisms in SREBF-SCAP pathway on therapeutic response to rosuvastatin in Saudi metabolic syndrome patients

AIM

Genetic variants contribute to statins' therapeutic variability. SREBF-SCAP pathway is a key player in lipid homeostasis. Hence, effect of SREBF-SCAP polymorphisms on therapeutic response was studied.

PATIENTS & METHODS

Metabolic syndrome patients of either sex were prescribed rosuvastatin 10 mg for 24 weeks. Clinical, anthropometric and lipid measurements were done before and after treatment. Genotyping was done by pyrosequencing.

RESULTS & CONCLUSION

No associations of SCAP and SREBF-1a genotypes with baseline lipids but significant associations with lipid reductions were observed. Significant effect of SCAP (GG; B = -8.16, p = 0.001); SREBF-1a (GG; B = -7.47, p = 0.001) and SREBF-1a (-delG; B = -7.42, p = 0.001) was observed on total cholesterol reduction. Additive trend was found between SCAP genotypes and lipid reductions. A total of 88% responders have SCAP 'G' allele (p = 0.001). Patients carrying SCAP (GG) and SREBF-1a (GG and -delG) have 9.5-, 8.6- and 14.6-times more likelihood of being responders (p < 0.05). 'G' allele in SCAP and SREBF-1a is significant predictor of rosuvastatin response.

Association of genetic variations in the lipid regulatory pathway genes FBXW7 and SREBPs with coronary artery disease among Han Chinese and Uygur Chinese populations in Xinjiang, China

Background

Hyperlipidemia is a major risk factor for coronary artery disease (CAD). The current study was designed to explore the possible correlation between single nucleotide polymorphisms (SNPs) in the lipid homeostasis regulatory genes F-box and WD repeat domain-containing 7 (FBXW7) and sterol regulatory element-binding proteins (SREBPs) with CAD among Han Chinese and Uygur Chinese populations in Xinjiang, China.

Results

In the Uygur Chinese population, rs9902941 in SREBP-1 and rs10033601 in FBXW7 were found to be associated with CAD in a recessive model (TT vs. CT + CC, P = 0.032; GG vs. AG + AA, P = 0.010, respectively), and rs7288536 in SREBP-2 was found to be associated with CAD in an additive model (CT vs. CC + TT, P = 0.045). The difference was statistically significant in the Uygur Chinese population after multivariate adjustments [Odds ratio (OR) = 1.803, 95% confidence interval (CI): 1.036~3.137, P = 0.037; OR = 1.628, 95% CI: 1.080~2.454, P = 0.020; OR = 1.368; and 95% CI: 1.018~1.837, P = 0.037, respectively]. There were also significant interactions between the above-mentioned models in the Uygur Chinese population. However, these relationships were not observed before or after multivariate adjustment in the Han Chinese population.

Materials and Methods

A total of 1,312 Han Chinese (650 CAD patients and 662 controls) and 834 Uygur Chinese (414 CAD patients and 420 controls) were enrolled in this case-control study. Three SNPs (rs9902941 in SREBP-1, rs7288536 in SREBP-2 and rs10033601 in FBXW7) were selected and genotyped using the improved multiplex ligase detection reaction (iMLDR) method.

Conclusions

The results of this study indicate that variations in the lipid regulatory pathway genes FBXW7 and SREBPs (rs9902941 in SREBP-1, rs7288536 in SREBP-2 and rs10033601 in FBXW7) are associated with CAD in the Uygur Chinese population in Xinjiang, China.

Expression of Sterol Regulatory Element-Binding Proteins in epicardial adipose tissue in patients with coronary artery disease and diabetes mellitus: preliminary study

Objectives: Sterol regulatory element-binding proteins (SREBP) genes are crucial in lipid biosynthesis and cardiovascular homeostasis. Their expression in epicardial adipose tissue (EAT) and their influence in the development of coronary artery disease (CAD) and type-2 diabetes mellitus remain to be determined. The aim of our study was to evaluate the expression of SREBP genes in EAT in patients with CAD according to diabetes status and its association with clinical and biochemical data. Methods: SREBP-1 and SREBP-2 mRNA expression levels were measured in EAT from 49 patients with CAD (26 with diabetes) and 23 controls without CAD or diabetes. Results: Both SREBPs mRNA expression were significantly higher in patients with CAD and diabetes (p<0.001) and were identified as independent cardiovascular risk factor for coronary artery disease in patients with type-2 diabetes (SREBP-1: OR 1.7, 95%CI 1.1-2.5, p=0.02; SREBP-2: OR 1.6, 95%CI 1.2-3, p=0.02) and were independently associated with the presence of multivessel CAD, left main and anterior descending artery stenosis, and higher total and LDL cholesterol levels, and lower HDL cholesterol levels, in patients with CAD and diabetes. Conclusions: SREBP genes are expressed in EAT and were higher in CAD patients with diabetes than those patients without CAD or diabetes. SREBP expression was associated as cardiovascular risk factor for the severity of CAD and the poor lipid control. In this preliminary study we suggest the importance of EAT in the lipid metabolism and cardiovascular homeostasis for coronary atherosclerosis of patients with diabetes and highlight a future novel therapeutic target.

A spontaneous mutation in Srebf2 leads to cataracts and persistent skin wounds in the lens opacity 13 (lop13) mouse

Lens opacity 13 (lop13) is a spontaneous, autosomal recessive mouse mutant that exhibits nuclear cataracts. Histological analysis revealed swollen lens fiber cells and the presence of bladder cells within the lens cortex, as well as morgagnian globules and liquefied material at the lens posterior. At 3 months of age, in addition to cataracts, lop13 mice also develop persistent skin wounds. Linkage analysis assigned the lop13 locus to a 1.1-Mb region on mouse Chr 15, encompassing 19 candidate genes. Sequence analysis identified a C3112T mutation in exon 18 of Sterol Regulatory Element Binding-Transcription Factor 2 (Srebf2) resulting in the R1038C substitution of a highly conserved arginine within the Srebf2 regulatory domain. Srebf2 belongs to a family of membrane-bound basic helix-loop-helix leucine zipper transcription factors that control the expression of genes involved in the biosynthesis and uptake of cholesterol and fatty acids. The lack of complementation observed in Srebf2 ( lop13/GT ) compound heterozygotes carrying the Srebf2 gene trapped allele (Srebf2 ( GT )) provides genetic evidence that the identified C3112T substitution in Srebf2 is responsible for the lop13 phenotype. Gas chromatography analysis identified lower levels of cholesterol in the lop13 brain, liver, and lens when compared to wild-type mice. These findings suggest that lop13 is a hypomorphic mutation in Srebf2. As such, the lop13 mouse presents an invaluable in vivo model for studying the contribution of Srebf2 and cholesterol to maintaining the homeostasis of the lens and skin.

Sterol regulatory element-binding transcription factor (SREBF)-2, SREBF cleavage-activating protein (SCAP), and premature coronary artery disease in a Chinese population

Cellular cholesterol homeostasis is controlled by the sterol-regulatory element binding transcription factors (SREBFs) that are activated by an SREBF cleavage-activating protein (SCAP). SREBF-2 1784G > C single nucleotide polymorphism (SNP, rs2228314) and SCAP 2386A > G variant (rs12487736) are associated with early onset myocardial infarction (MI) and sudden cardiac death in middle-aged men. We investigated whether these two SNPs are determinants of premature coronary artery disease (CAD) in a Chinese population. We studied 431 consecutive patients, including 197 with coronary stenosis ≥50% or previous MI and 234 controls without documented CAD (males <55 years and females <65 years). All subjects were genotyped for two SNPs by using the ligase detection reaction method. The three genotypes GG, GC, and CC were present in rs2228314 and two genotypes AA and AG in rs12487736. No gender-specific differences were found in genotype distribution and allele frequencies of these two SNPs between patients with and without CAD. The biochemical and clinical risk factors among participants were not influenced by variants at rs2228314. Logistic regression did not detect the association of these two SNPs with premature CAD, nor did there exist any association of these two SNPs among groups of patients with 0, 1, 2, and 3-vessel disease (all P > 0.05). We could not identify any association between these two SNPs and premature CAD or extent of coronary lesions in a Chinese population.

Interactions among genetic variants from SREBP2 activating-related pathway on risk of coronary heart disease in Chinese Han population

Sterol regulatory element binding proteins (SREBPs), as a family of membrane-bound transcription factors, control the metabolism of cholesterol and fatty acids. We conducted a case-control study to investigate whether the common variants of genes from the SREBP2 activating-related pathway, involving SREBP2, SCAP, INSIG1 and INSIG2 genes, were associated with coronary heart disease (CHD) of Chinese Han population individually or interactively. Three, four and two single nucleotide polymorphisms (SNPs) from the INSIG1, INSIG2 and SCAP genes were chosen as haplotype-tagging SNPs (htSNPs), respectively, and one nonsynonymous coding SNP was selected from SREBP2. All of the SNPs were genotyped in 853 CHD cases and 948 unrelated control subjects. The interactions among SNPs of the four genes were evaluated with multifactor-dimensionality reduction (MDR) and logistic regression models (LRM). The results from MDR indicated that there existed the SNP-SNP interactive effect of INSIG1 gene on CHD (best prediction accuracy=56.09%, p=0.002 on 1000 permutations). The results from LRM also identified the 2-locus interaction model (adjusted p< or =0.001 for interaction) as well as the 3-locus gene-gene interaction (adjusted p=0.026 for interaction). Single polymorphism analysis showed that the rs4822063 of SREBP2 was associated with LDL-C in the controls. The genotype CC carriers had higher LDL-C than the major allele G carriers (3.44+/-0.90 mmol/L versus 3.17+/-0.84 mmol/L, adjusted p=0.038). Our results suggested that the INSIG1 gene was associated with CHD; there might be potential interactive effect on CHD among genes from SREBP2 activating-related pathway; and the SREBP2 gene might be associated with plasma lipid level.

Novel serum paraoxonase activity assays are associated with coronary artery disease

BACKGROUND

Serum paraoxonase (PON1) exerts antiatherogenic effects. Novel PON1 enzymatic tests have been recently developed: 5-thiobutyl butyrolactone (TBBL) estimates PON1 lactonase activity, whereas 7-O-diethylphosphoryl-3-cyano-4-methyl-7-hydroxycoumarin (DEPCyMC) is considered a surrogate marker of PON1 concentration. The TBBL to DEPCyMC ratio provides the normalized lactonase activity (NLA), which may reflect the degree of PON1 lactonase catalytic stimulation. The aim of this study was to evaluate for the first time TBBLase and DEPCyMCase activity in patients with coronary artery disease (CAD).

METHODS

An angiography-based case-control study was conducted, including 300 sex- and age-matched subjects [100 CAD-free, 100 CAD without myocardial infarction (MI) and 100 CAD with MI].

RESULTS

A low DEPCyMCase activity (lowest vs. highest tertile: OR 2.96, 95% CI 1.18-7.43) and a high NLA (highest vs. lowest tertile: OR 3.25, 95% CI 1.28-8.26) were both associated with CAD, independent of classical atherosclerosis risk factors, lipid-lowering therapy and PON1 genotype. Total TBBLase activity was, however, not different in CAD compared to CAD-free subjects.

CONCLUSIONS

Novel PON1 activity assays may be associated with CAD. In this study, CAD patients had low DEPCyMCase activity, a possible marker of low PON1 concentration, but showed a high stimulation of PON1 lactonase activity.

Polymorphism of the sterol regulatory element-binding protein-2 gene and its association with serum lipid levels in the Guangxi Hei Yi Zhuang and Han populations

BACKGROUND

Information about the association of sterol regulatory element-binding protein-2 (SREBP-2) gene polymorphism at the 1784G>C locus and serum lipid parameters is limited and contradictory. The present study was undertaken to compare the difference in the SREBP-2 gene polymorphism and its association with serum lipid levels between the Guangxi Hei Yi Zhuang and Han populations.

METHODS

Genotyping of the SREBP-2 gene in 768 subjects of Hei Yi Zhuang and 798 participants of Han Chinese aged 15 to 89 was performed by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

The frequency of G allele was 88.9% in Hei Yi Zhuang and 84.7% in Han (P < 0.001). The frequencies of GG, GC, and CC genotypes were 78.9%, 20.1%, and 1.0% in Hei Yi Zhuang, and 70.4%, 28.6%, and 1.0% in Han (P < 0.001), respectively. The frequencies of G allele and GG genotype in Han, but not in Hei Yi Zhuang, were higher in males than in females, or in high total cholesterol (TC >5.18 mmol/L) subgroup than in normal TC subgroup (P < 0.01 for all). In high TC subgroup, TC, triglycerides, low-density lipoprotein cholesterol, and apolipoprotein B levels in Han were lower in GG genotype than in GC/CC genotype (P < 0.05-0.01).

CONCLUSIONS

There were significant differences in the genotypic and allelic frequencies of the SREBP-2 gene polymorphism at the 1784G>C locus between the Hei Yi Zhuang and Han populations. The individuals carrying the G allele have more favorable lipid profiles than those carrying the C allele in Han but not in Hei Yi Zhuang.

Expression of sterol regulatory element-binding transcription factor (SREBF) 2 and SREBF cleavage-activating protein (SCAP) in human atheroma and the association of their allelic variants with sudden cardiac death

Background

Disturbed cellular cholesterol homeostasis may lead to accumulation of cholesterol in human atheroma plaques. Cellular cholesterol homeostasis is controlled by the sterol regulatory element-binding transcription factor 2 (SREBF-2) and the SREBF cleavage-activating protein (SCAP). We investigated whole genome expression in a series of human atherosclerotic samples from different vascular territories and studied whether the non-synonymous coding variants in the interacting domains of two genes, SREBF-2 1784G>C (rs2228314) and SCAP 2386A>G, are related to the progression of coronary atherosclerosis and the risk of pre-hospital sudden cardiac death (SCD).

Methods

Whole genome expression profiling was completed in twenty vascular samples from carotid, aortic and femoral atherosclerotic plaques and six control samples from internal mammary arteries. Three hundred sudden pre-hospital deaths of middle-aged (33–69 years) Caucasian Finnish men were subjected to detailed autopsy in the Helsinki Sudden Death Study. Coronary narrowing and areas of coronary wall covered with fatty streaks or fibrotic, calcified or complicated lesions were measured and related to the SREBF-2 and SCAP genotypes.

Results

Whole genome expression profiling showed a significant (p = 0.02) down-regulation of SREBF-2 in atherosclerotic carotid plaques (types IV-V), but not in the aorta or femoral arteries (p = NS for both), as compared with the histologically confirmed non-atherosclerotic tissues. In logistic regression analysis, a significant interaction between the SREBF-2 1784G>C and the SCAP 2386A>G genotype was observed on the risk of SCD (p = 0.046). Men with the SREBF-2 C allele and the SCAP G allele had a significantly increased risk of SCD (OR 2.68, 95% CI 1.07–6.71), compared to SCAP AA homologous subjects carrying the SREBF-2 C allele. Furthermore, similar trends for having complicated lesions and for the occurrence of thrombosis were found, although the results were not statistically significant.

Conclusion

The results suggest that the allelic variants (SREBF-2 1784G>C and SCAP 2386A>G) in the cholesterol homeostasis regulating SREBF-SCAP pathway may contribute to SCD in early middle-aged men.

Analysis of the SREBF2 gene as a genetic risk factor for vascular dementia

A case-control study was performed to examine the association between vascular dementia and the polymorphisms of the human gene encoding sterol regulatory element binding protein-2 (SREBF2) that regulates cholesterol metabolism. The 16 genetic variants of SREBF2 were identified in 24 Koreans, and 5 out of 16 variants were genotyped in 207 vascular dementia patients and 207 control subjects. Significant association with vascular dementia was shown in 34995G/T with the GT genotype (odds ratio [OR] = 1.57; 95% CI = 1.04-2.37; P < 0.05) and the GG genotype (OR = 0.65; 95% CI = 0.44-0.96; P < 0.05). The CGC, the most common haplotype combined with three SNPs, 24489C/T, 34995G/T, and 68891C/T, was associated with the disease (OR = 0.72; 95% CI = 0.53-0.97; P < 0.05), and the individuals with the CGC might be less susceptible to vascular dementia than those carrying any haplotype including at least one minor allele. This study implied that the variants of SREBF2 might be genetic factors involved in the pathogenesis of vascular dementia.

The correlation of paraoxonase (PON1) activity with lipid and lipoprotein levels differs with vascular disease status

Paraoxonase (PON1) is an HDL-associated enzyme. Low PON1 activity predicts vascular disease status and is a more reliable predictor of vascular disease than are functional PON1 genotypes. There is evidence that the relationship of PON1 to vascular disease is, in part, due to its antioxidant activity. However, the physical relationship of PON1 with HDL and the existence of cholesterol pathway regulatory elements at the PON1 locus suggest a further relationship of PON1 with lipoproteins, which may contribute to its role in vascular disease. We investigated the relationship of PON1 activity and genotype to lipid-related traits in 91 Caucasian men with severe carotid artery disease and 184 without vascular disease who were not on lipid-lowering medications. Prior studies of PON1 relationship to lipids have not stratified by disease status.. We found that PON1 activity was correlated with HDL traits in controls and with LDL- and VLDL-related traits in cases. We hypothesize differences in the joint regulation of PON1 and lipoproteins in cases and controls.

Genetic variant of the SREBF-1 gene is significantly related to cholesterol synthesis in man

Sterol regulatory element binding proteins-1 and -2 (SREBPs) are transcription factors controlling lipid homeostasis in human cells. The G-allele carriers of the SREBF-1 gene C-G polymorphism in exon 18c and coding for glycine at the protein level (G952G) have shown to associate more frequently with obesity and type 2 diabetes than the C-allele carriers. However, the C-allele has suggested to be linked to dyslipidemia. Thus, our aim was to study effect of the SREBF-1 gene polymorphism (G952G) on sterol metabolism in man. Ninety-five subjects with moderate hypercholesterolemia participated in this study and 14 homozygous CC carriers of the SREBF-1 (G952G) gene were found. Plasma lathosterol concentration and lathosterol-to-cholesterol ratio, markers of endogenous cholesterol synthesis, were significantly higher in CC homozygous subject compared to others. Similarly muscle cholesterol (p=0.045) and lathosterol (p=0.054) concentrations were elevated in the CC homozygotes supporting the view that endogenous cholesterol synthesis rate is SREBF-1 genotype-dependent.