Low-density lipoprotein and high-density lipoprotein cholesterol levels in relation to genetic polymorphisms and menopausal status: the Atherosclerosis Risk in Communities (ARIC) Study

Racial Differences in Blood Lipids Lead to Underestimation of Cardiovascular Risk in Black Women in a Nested observational Study

Background:

During screening for enrollment in a clinical trial, we noticed potential racial disparities in metabolic syndrome variables in women who responded to our study advertisement. We designed a nested observational study to investigate whether metabolic syndrome variables differed between non-Hispanic blacks and non-Hispanic whites.

Methods:

The cohort comprised of women who have met the preliminary clinical trial criteria (body mass index [BMI] 25-45, age 20-75 years, and no use of lipid-lowering medications or supplements). These women, including 116 blacks and 138 whites, provided fasting blood samples for analysis of serum lipid profile.

Results:

Blacks had lower mean triglycerides (81.1 ± 3.3 mg/dL vs 140.6 ± 5.9 mg/dL; P < .0001), total cholesterol (176.1 ± 3.6 mg/dL vs 201.6 ± 3.3 mg/dL; P < .0001), and low-density lipoprotein (111.7 ± 3.3 mg/dL vs 128.2 ± 2.9 mg/dL; P < .001) and higher mean BMI (37.2 ± 0.5 vs 35.2 ± 0.5; P < .01) and diastolic blood pressure (82.4 ± 0.8 mmHg vs 79.4 ± 0.7 mmHg; P < .01) than whites. Only 7% of blacks, compared with 41% of whites, had triglycerides ≥150 mg/dL; as a result, fewer black women met metabolic syndrome criteria than white women. Additionally, in women with waist circumference ≥88 cm (N = 215), high-density lipoprotein was higher in blacks than in whites (48.3 ± 1.5 mg/dL vs 44.2 ±1.3 mg/dL; P < .05).

Conclusions:

Due to racial differences in blood lipids, current metabolic syndrome criteria may result in underestimation of cardiovascular risk in blacks.

Cardiometabolic risk profiles in pre- versus postmenopausal women with spinal cord injury:: preliminary findings

OBJECTIVE

To compare the cardiometabolic risk (CMR) profile of premenopausal and postmenopausal women with spinal cord injury (SCI).

METHOD

Post hoc analysis of a multicenter cross-sectional study assessing CMR. Seventeen women with ASIA Impairment Scale (AIS) A or B SCI between C5 and T12 were stratified into 2 groups according to menopausal status (11 premenopausal vs 6 postmenopausal women). Data collected included demographic, social, medical, menopausal, hormone use, and menstrual histories. Assessments included physical, anthropometric, and blood pressure measures; fasting serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), and hemoglobin A1C (Hb1Ac); calculated low-density lipoprotein (LDL-C); and an oral glucose tolerance test.

RESULTS

The premenopausal group had a mean age of 32.4 years compared with 56.0 years in the postmenopausal group. Similar group findings included body mass index (BMI) (22.4 vs 22.2), HDL-C (52.5 vs 53 mg/dL), HbA1c (4.9 vs 5.1%), fasting blood glucose (FBG) (79.3 vs 84.8 mg/dL), and systolic blood pressure (SBP) (104.6 vs 111.8 mm Hg). TG, TC and LDL-C were significantly higher in postmenopausal group (55.7 vs 101.8 mg/dL, P = .01; 158.3 vs 191.6 mg/dL, P = .04; 94.7 vs 118.2 mg/dL, P = .04).

CONCLUSIONS

The findings from this study suggest that postmenopausal women with SCI have CMR trends similar to those observed in nondisabled women, characterized by increases in TG, TC, and LDL-C despite favorable BMIs and glycemic indices. Even though the present study includes significant limitations, future evidence may also suggest that heightened surveillance and guideline-driven interventions are indicated for perimenopausal and postmenopausal women with SCI.

Association of LIPC and advanced age-related macular degeneration

PURPOSE

To determine whether there is an association between hepatic lipase (LIPC) and age-related macular degeneration (AMD) in two independent Caucasian cohorts.

METHODS

A discovery cohort of 1626 patients with advanced AMD and 859 normal controls and a replication cohort of 2159 cases and 1150 controls were genotyped for two single-nucleotide polymorphisms (SNPs) in the promoter region of LIPC. The associations between the SNPs and AMD were examined by χ(2) tests.

RESULTS

In the discovery cohort, rs493258 and rs10468017 were both associated with advanced AMD (P=9.63E-3 and P=0.048, respectively). The association was corroborated in the replication cohort (P=4.48E-03 for rs493258 and P=0.015 for rs10468017). Combined analysis resulted in even more significant associations (P=1.21E-04 for rs493258 and P=1.67E-03 for rs10468017).

CONCLUSION

The LIPC promoter variants rs493258 and rs10468017 were associated with advanced AMD in two independent Caucasian populations, confirming that LIPC polymorphisms may be a genetic risk factor for AMD in the Caucasian population.

Association studies of several cholesterol-related genes (ABCA1, CETP and LIPC) with serum lipids and risk of Alzheimer's disease

Objectives

Accumulating evidence suggested that dysregulation of cholesterol homeostasis might be a major etiologic factor in initiating and promoting neurodegeneration in Alzheimer’s disease (AD). ATP-binding cassette transporter A1 (ABCA1), hepatic lipase (HL, coding genes named LIPC) and cholesteryl ester transfer protein (CETP) are important components of high-density lipoprotein (HDL) metabolism and reverse cholesterol transport (RCT) implicated in atherosclerosis and neurodegenerative diseases. In the present study, we will investigate the possible association of several common polymorphisms (ABCA1R219K, CETPTaqIB and LIPC-250 G/A) with susceptibility to AD and plasma lipid levels.

Methods

Case–control study of 208 Han Chinese (104 AD patients and 104 non-demented controls) from Changsha area in Hunan Province was performed using the PCR-RFLP analysis. Cognitive decline was assessed using Mini Mental State Examination (MMSE) as a standardized method. Additionally, fasting lipid profile and the cognitive testing scores including Wechsler Memory Scale (WMS) and Wisconsin Card Sorting Test (WCST) were recorded.

Results and conclusions

We found significant differences among the genotype distributions of these three genes in AD patients when compared with controls. But after adjusting other factors, multivariate logistic regression analysis showed only ABCA1R219K (B = −0.903, P = 0.005, OR = 0.405, 95%CI:0.217-0.758) and LIPC-250 G/A variants(B = −0.905, P = 0.018, OR = 0.405, 95%CI:0.191-0.858) were associated with decreased AD risk. There were significantly higher levels of high-density lipoprotein cholesterol (HDL-C) and apolipoproteinA-I in the carriers of KK genotype and K allele (P < 0.05), and B2B2 genotype of CETP Taq1B showed significant association with higher HDL-C levels than other genotypes (F = 5.598, P = 0.004), while -250 G/A polymorphisms had no significant effect on HDL-C. In total population, subjects carrying ABCA1219K allele or LIPC-250A allele obtained higher MMSE or WMS scores than non-carriers, however, no significant association was observed in AD group or controls. Therefore, this preliminary study showed that the gene variants of ABCA1R219K and LIPC-250 G/A might influence AD susceptibility in South Chinese Han population, but the polymorphism of CETPTaq1B didn't show any association in despite of being a significant determinant of HDL-C.

P wave indices, obesity, and the metabolic syndrome: the atherosclerosis risk in communities study

Atrial fibrillation and obesity are increasing in prevalence and are interrelated epidemics. There has been limited assessment of how obesity and the metabolic syndrome impact P wave indices, established electrocardiographic predictors of atrial fibrillation. We conducted a cross-sectional analysis to determine the association of obesity and the components of the metabolic syndrome with P wave indices in the population-based Atherosclerosis Risk in Communities (ARIC) study. Analyses were adjusted for demographic, anthropometric and clinical variables, and cardiovascular diseases and risk factors. Following relevant exclusions, 14,433 subjects were included (55% women and 24.7% black). In multivariable analyses, we identified significant, progressive increases in PR interval, P wave maximum duration, and P wave terminal force with BMI 25-30 kg/m(2) and BMI ≥30 kg/m(2) compared to the reference group <25 kg/m(2) (P < 0.0001 for trend for all P wave indices). These effects were present in both blacks and whites. Presence of metabolic syndrome was also associated with longer P wave indices. When components of the metabolic syndrome were examined separately, hypertension resulted in significant (P < 0.001) augmentation of the three P wave indices. Similarly, waist circumference was associated with greater P wave maximum duration in both races (P < 0.001). We concluded that P wave indices are significantly associated with obesity and particularly with hypertension and waist circumference. P wave indices may comprise intermediate markers, independent of age and cardiovascular risk, of the pathway linking obesity and with the risk of atrial fibrillation (AF).

Positive association of the hepatic lipase gene polymorphism c.514C > T with estrogen replacement therapy response

Background

Hepatic lipase (HL), an enzyme present in the hepatic sinusoids, is responsible for the lipolysis of lipoproteins. Human HL contains four polymorphic sites: G-250A, T-710C, A-763G, and C-514T single-nucleotide polymorphism (SNPs). The last polymorphism is the focus of the current study. The genotypes associated with the C-514T polymorphism are CC (normal homozygous - W), CT (heterozygous - H), and TT (minor-allele homozygous - M). HL activity is significantly impaired in individuals of the TT and CT genotypes. A total of 58 post-menopausal women were studied. The subjects were hysterectomized women receiving hormone replacement therapy consisting of 0.625 mg of conjugated equine estrogen once a day. The inclusion criteria were menopause of up to three years and normal blood tests, radiographs, cervical-vaginal cytology, and densitometry. DNA was extracted from the buccal and blood cells of all 58 patients using a commercially available kit (GFX^® - Amersham-Pharmacia, USA).

Results

Statistically significant reductions in triglycerides (t = 2.16; n = 58; p = 0.03) but not in total cholesterol (t = 0.14; n = 58; p = 0.89) were found after treatment. This group of good responders were carriers of the T allele; the CT and TT genotypes were present significantly more frequently than in the group of non-responders (p = 0.02 or p = 0.07, respectively). However, no significant difference in HDL-C (t = 0.94; n = 58; p = 0.35) or LDL-C (t = -0.83; n = 58; p = 0.41) was found in these patients.

Conclusions

The variation in lipid profile associated with the C-514T polymorphism is significant, and the T allele is associated with the best response to ERT.

Immobilization of heparin on polysulfone surface for selective adsorption of low-density lipoprotein (LDL)

A versatile method was developed to immobilize heparin covalently on polysulfone sheets (PSu) to achieve selective adsorption of low-density lipoprotein (LDL). This was achieved by activation of PSu with successive treatments of chlorodimethyl ether and ethylenediamine, and subsequent chemical binding of heparin with bifunctional linker molecules. A heparin density up to 0.86 microg cm(-2) on a dense PSu film was achieved. The modified PSu films were characterized by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The hydrophilicity of the PSu film was improved greatly by covalent immobilization of heparin. The water contact angle of PSu film was decreased from 86.6 + or - 3.7 degrees to 50.5 + or - 3.2 degrees after binding of 0.36 microg cm(-2) heparin. An enzyme-linked immunosorbent assay was used to measure the binding of LDL on plain and modified PSu films. It was found that the heparin-modified PSu film could selectively recognize LDL from binary protein solutions. Furthermore, it was possible to desorb LDL from heparinized PSu, but not from plain PSu, with heparin, sodium chloride or urea solution, which indicates a selective but reversible binding of LDL to heparin. The results suggest that heparin-modified PSu membranes are promising for application in simultaneous hemodialysis and LDL apheresis therapy.

Impact of age and menopausal status on the postprandial triacylglycerol response in healthy women

OBJECTIVE

To examine the impact of age and the natural menopause on the postprandial triacylglycerol (TAG) response in healthy women.

METHODS AND RESULTS

Thirty-seven premenopausal and sixty-one postmenopausal women underwent a sequential meal postprandial investigation, in which blood samples were taken at regular intervals after a test breakfast and lunch given at 0 and 330 min respectively. Lipids and glucose were measured in the fasting sample, with TAG analysed in the postprandial samples. Postmenopausal women were shown to have higher fasting total cholesterol, low density lipoprotein cholesterol (LDL-C) and glucose (P<0.02). Marked differences in the postprandial TAG response were evident between the groups, with a greater incremental area under the curve (IAUC) and maximum TAG concentration in the postmenopausal women (P<0.04). Multivariate regression analysis revealed both age and fasting TAG to be independently associated with the summary measures of the postprandial TAG response in the premenopausal women only. Interestingly, sub-division of the women into both younger and older pre- and postmenopausal subgroups, showed the most marked difference in TAG-IAUC to be between the younger and the older premenopausal women, whereas differences in fasting LDL-C were most evident between the older premenopausal and the younger postmenopausal women.

CONCLUSIONS

Our results suggest a divergence in the relationship of age and menopausal status with fasting LDL-C and postprandial TAG which may reflect differences in the metabolic effects of age and the menopause on these lipid risk markers or a greater impact of early oestrogen decline on pathways of TAG rather than LDL metabolism.

Association of blood lipids with common DNA sequence variants at 19 genetic loci in the multiethnic United States National Health and Nutrition Examination Survey III

BACKGROUND

Using the genome-wide association approach in individuals of European ancestry, we and others recently identified single-nucleotide polymorphisms (SNPs) at 19 loci as associated with blood lipids; 8 of these loci were novel. Whether these same SNPs associate with lipids in a broader range of ethnicities is unknown.

METHODS AND RESULTS

We genotyped index SNPs at 19 loci in the Third United States National Health and Nutrition Examination Survey (n=7159), a population-based probability sample of the United States comprised primarily of non-Hispanic blacks, Mexican Americans, and non-Hispanic whites. We constructed ethnic-specific residual blood lipid levels after adjusting for age and gender. Ethnic-specific linear regression was used to test the association of genotype with blood lipids. To summarize the statistical evidence across 3 racial groups, we conducted a fixed-effects variance-weighted meta-analysis. After exclusions, there were 1627 non-Hispanic blacks, 1659 Mexican Americans, and 2230 non-Hispanic whites. At 5 loci (1p13 near CELSR2/PSRC1/SORT1, HMGCR, CETP, LPL, and APOA5), the index SNP was associated with low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, or triglycerides in all 3 ethnic groups. At the remaining loci, there was mixed evidence by ethnic group. In meta-analysis, we found that, at 14 of the 19 loci, SNPs exceeded a nominal P<0.05.

CONCLUSIONS

At 5 loci including the recently discovered region on 1p13 near CELSR2/PSRC1/SORT1, the same SNP discovered in whites associates with blood lipids in non-Hispanic blacks and Mexican Americans. For the remaining loci, fine mapping and resequencing will be required to definitively evaluate the relevance of each locus in individuals of African and Hispanic ancestries.

Human SA gene polymorphisms are associated with non-high-density lipoprotein cholesterol in postmenopausal women: a pilot study

OBJECTIVE

The purpose of the study is to evaluate the associations between polymorphisms of the human SA (SAH) gene, an acyl-CoA synthetase gene, with dyslipidemia and phenotypes of the insulin resistance syndrome in postmenopausal women.

METHODS

One hundred and forty-two postmenopausal women were recruited for the study. Each subject received anthropometric and blood pressure measurements, fasting sampling for lipids, and a 75-g oral glucose tolerance test for insulin resistance. Genotypes of two polymorphisms in the promoter region (c.-962ins/del, c.-451G>A), one missense variant (c.1077G>C, p.K359N) in exon 8, and one in intron 12 (A>G) of the SAH gene, were determined.

RESULTS

There were significant differences in genetic distribution of the SAH gene promoter I/D polymorphism between the two groups of subjects by non-high-density lipoprotein cholesterol (non-HDL-C) levels (p=0.004). The subjects with the DD genotype was associated with high levels of non-HDL-C (>160 mg/dL) as compared with the ID or II genotypes (p=0.002). Furthermore, three haplotypes were constructed based on the promoter I/D and the exon 8 G/C polymorphisms. Homozygosity for SAH haplotype 3 was associated with increased adiposity, insulin resistance, and elevated levels of non-HDL-C in the post menopausal women. The subjects with haplotype 3 had double the risk to have higher non-HDL-C levels than those with haplotype 1.

CONCLUSION

Our results suggest that the polymorphisms of the SAH gene are associated with non-HDL-C levels in postmenopausal women. Further studies with larger sample sizes or different populations are warranted to confirm our preliminary findings.