Irina Movsesyan

A Polymorphism in the Protease-Like Domain of Apolipoprotein(a) Is Associated With Severe Coronary Artery Disease

Objectives—The purpose of this study was to identify genetic variants associated with severe coronary artery disease (CAD). Methods and Results—We used 3 case-control studies of white subjects whose severity of CAD was assessed by angiography. The first 2 studies were used to generate hypotheses that were then tested in the third study. We tested 12 077 putative functional single nucleotide polymorphisms (SNPs) in Study 1 (781 cases, 603 controls) and identified 302 SNPs nominally associated with severe CAD. Testing these 302 SNPs in Study 2 (471 cases, 298 controls), we found 5 (in LPA, CALM1, HAP1, AP3B1, and ABCG2) were nominally associated with severe CAD and had the same risk alleles in both studies. We then tested these 5 SNPs in Study 3 (554 cases, 373 controls). We found 1 SNP that was associated with severe CAD: LPA I4399M (rs3798220). LPA encodes apolipoprotein(a), a component of lipoprotein(a). I4399M is located in the protease-like domain of apolipoprotein(a). Compared with noncarriers, carriers of the 4399M risk allele (2.7% of controls) had an adjusted odds ratio for severe CAD of 3.14 (confidence interval 1.51 to 6.56), and had 5-fold higher median plasma lipoprotein(a) levels (P=0.003). Conclusions—The LPA I4399M SNP is associated with severe CAD and plasma lipoprotein(a) levels.

An internal promoter underlies the difference in disease severity between N- and C-terminal truncation mutations of Titin in zebrafish

Truncating mutations in the giant sarcomeric protein Titin result in dilated cardiomyopathy and skeletal myopathy. The most severely affected dilated cardiomyopathy patients harbor Titin truncations in the C-terminal two-thirds of the protein, suggesting that mutation position might influence disease mechanism. Using CRISPR/Cas9 technology, we generated six zebrafish lines with Titin truncations in the N-terminal and C-terminal regions. Although all exons were constitutive, C-terminal mutations caused severe myopathy whereas N-terminal mutations demonstrated mild phenotypes. Surprisingly, neither mutation type acted as a dominant negative. Instead, we found a conserved internal promoter at the precise position where divergence in disease severity occurs, with the resulting protein product partially rescuing N-terminal truncations. In addition to its clinical implications, our work may shed light on a long-standing mystery regarding the architecture of the sarcomere. DOI: http://dx.doi.org/10.7554/eLife.09406.001

Effects of the absence of apolipoprotein e on lipoproteins, neurocognitive function, and retinal function.

IMPORTANCE The identification of a patient with a rare form of severe dysbetalipoproteinemia allowed the study of the consequences of total absence of apolipoprotein E (apoE). OBJECTIVES To discover the molecular basis of this rare disorder and to determine the effects of complete absence of apoE on neurocognitive and visual function and on lipoprotein metabolism. DESIGN, SETTING, AND PARTICIPANTS Whole-exome sequencing was performed on the patients DNA. He underwent detailed neurological and visual function testing and lipoprotein analysis. Lipoprotein analysis was also performed in the Cardiovascular Research Institute, University of California, San Francisco, on blood samples from the probands mother, wife, 2 daughters, and normolipidemic control participants. MAIN OUTCOME MEASURES Whole-exome sequencing, lipoprotein analysis, and neurocognitive function. RESULTS The patient was homozygous for an ablative APOE frameshift mutation (c.291del, p.E97fs). No other mutations likely to contribute to the phenotype were discovered, with the possible exception of two, in ABCC2 (p.I670T) and LIPC (p.G137R). Despite complete absence of apoE, he had normal vision, exhibited normal cognitive, neurological, and retinal function, had normal findings on brain magnetic resonance imaging, and had normal cerebrospinal fluid levels of β-amyloid and tau proteins. He had no significant symptoms of cardiovascular disease except a suggestion of myocardial ischemia on treadmill testing and mild atherosclerosis noted on carotid ultrasonography. He had exceptionally high cholesterol content (760 mg/dL; to convert to millimoles per liter, multiply by 0.0259) and a high cholesterol to triglycerides ratio (1.52) in very low-density lipoproteins with elevated levels of small-diameter high-density lipoproteins, including high levels of prebeta-1 high-density lipoprotein. Intermediate-density lipoproteins, low-density lipoproteins, and very low-density lipoproteins contained elevated apoA-I and apoA-IV levels. The patients apoC-III and apoC-IV levels were decreased in very low-density lipoproteins. Electron microscopy revealed large lamellar particles having electron-opaque cores attached to electron-lucent zones in intermediate-density and low-density lipoproteins. Low-density lipoprotein particle diameters were distributed bimodally. CONCLUSIONS AND RELEVANCE Despite a profound effect on lipoprotein metabolism, detailed neurocognitive and retinal studies failed to demonstrate any defects. This suggests that functions of apoE in the brain and eye are not essential or that redundant mechanisms exist whereby its role can be fulfilled. Targeted knockdown of apoE in the central nervous system might be a therapeutic modality in neurodegenerative disorders.

Metabolic Abnormalities and Coronary Heart Disease Risk in Human Immunodeficiency Virus–Infected Adults

BACKGROUND Metabolic syndrome is a combination of risk factors for cardiovascular disease and diabetes, It has been reported to be increased in human immunodeficiency virus (HIV)-infected individuals. METHODS In a cohort of HIV-infected adults we examined parameters that contribute to defining the metabolic syndrome and to estimating the 10-year risk of coronary heart disease (CHD). The study group consisted of 296 participants (217 men and 79 women) of mixed ethnicity with a mean age of 45.3 years. RESULTS There was an appreciable prevalence of metabolic syndrome (30.0%), with the frequency increasing to 42.5% in those over 50 years of age. Those with the metabolic syndrome had a lower viral load. More women had abdominal obesity (59.5%) than men (20.7%, P < 0.001). The frequency of elevated plasma glucose was higher in females (37.2%) compared to males (16.9%, P = 0.004). High frequencies of decreased high-density lipoprotein cholesterol (HDL-C) and elevated blood pressure were seen in both sexes. Hypertriglyceridemia was less prevalent in African Americans. In those under 50 years of age, the 10-year CHD risk score for men was double that for women (6.2% vs 2.7%, P < 0.001). In older participants, the risk was similar between the sexes, with a third having scores over 10%. CONCLUSIONS The prevalence of metabolic syndrome was higher than in most other HIV cohorts. Those with the syndrome had significantly lower viral loads. Mean 10-year Framingham Cardiovascular Risk (FCR) scores were nearly doubled for those with metabolic syndrome. Both researchers and clinicians should consider age as well as sex when assessing patients with HIV infection for risks associated with metabolic syndrome.

Lipoprotein (a), LPA Ile4399Met, and Fibrin Clot Properties

INTRODUCTION Elevated lipoprotein(a) (Lp(a)) levels were reported to be associated with dense fibrin clots. The apo(a) component of Lp(a) is encoded by LPA, and the Met allele of the LPA Ile4399Met polymorphism is associated with elevated Lp(a) levels and cardiovascular disease risk. We investigated whether Ile4399Met was associated with fibrin clot properties. MATERIALS AND METHODS We determined plasma Lp(a) levels, fibrin clot permeability and lysis time for 64 LPA 4399Met carriers and 128 noncarriers matched for age, sex, ethnicity, and enrollment site. RESULTS Elevated Lp(a) levels were associated with reduced clot permeability and prolonged lysis time (P<0.0001). Carriers of 4399Met had higher Lp(a) levels compared with noncarriers (P=0.0003). However, this association differed by ethnicity (P=0.003 for interaction between genotype and ethnicity): compared with noncarriers, 4399Met carriers had 2.89 fold higher Lp(a) levels among Caucasians while no difference was observed among non-Caucasians (primarily East Asians and Hispanics). Among all subjects, no association was observed between Ile4399Met and clot properties, but this relationship also differed by ethnicity: among non-Caucasians, 4399Met carriers had increased clot permeability and shorter lysis time; whereas among Caucasians, the trend was for decreased permeability and longer lysis time (P<0.01 for interactions between genotype and ethnicity). CONCLUSIONS We confirmed that elevated Lp(a) levels are associated with dense fibrin clots, and found that the association of LPA 4399Met carriers and clot permeability as well as lysis time differ by ethnicity.

Genetic Variants of the ENPP1/PC-1 Gene Are Associated With Hypertriglyceridemia in Male Subjects

BACKGROUND Hypertriglyceridemia is associated with insulin resistance, type 2 diabetes, and the metabolic syndrome. Membrane glycoprotein PC-1 (also termed ENPP1) is a direct insulin receptor inhibitor, and certain polymorphisms of the ENPP1/PC-1 gene have been associated with insulin resistance, type 2 diabetes, obesity, and diabetic complications. METHODS We examined the effect of 3 ENPP1/PC-1 variants (K121Q, rs1044498, and IVS20delT-11, rs1799774, and A-->G+1044TGA, rs7754561) on plasma triglyceride levels in 1112 subjects of non-Hispanic American white European ancestry. RESULTS Two of the ENPP1/PC-1 variants--A-->G+1044TGA (odds ratio [OR] 1.48, 95% confidence interval [CI], 1.54-1.82, P = 0.002) and IVS20delT-11 (OR 1.41, 95% CI, 1.08-1.84, P = 0.012)--were significantly associated with hypertriglyceridemia. Haplotype analyses also revealed an association with hypertriglyceridemia. In the variant analyses and in the haplotype analysis, the associations with hypertriglyceridemia were observed in male but not female subjects. Interestingly, the more widely studied K121Q ENPP1/PC-1 variant was not associated with hypertriglyceridemia in any group or subgroup analysis. CONCLUSION In the present study, we find that genetic variants of the ENPP1/PC-1 gene are associated with hypertriglyceridemia in male subjects, and may contribute to the development of the insulin resistance/metabolic syndrome in this population.

Advanced Lipid Testing Uncovers Hidden Cardiovascular Disease Risk: A Case Control Analysis

Lead Author’s Financial Disclosures: None Study Funding: This study was funded by Boston Heart Diagnostics on a contract and approved protocol with the Cardiovascular Research Institute, University of California, San Francisco, CA. All analyses were run in a blinded fashion. Background/Synopsis: Recommended standard lipid testing includes total cholesterol (TC), triglycerides (TG), high density lipoprotein cholesterol (HDL-C), and calculated low density lipoprotein cholesterol (LDL-C), which many healthcare providers view as providing insufficient information about cardiovascular disease (CVD) risk. Objective/Purpose: To compare standard lipid profile testing with advanced lipid and inflammatory marker analysis in a CVD case-control study. Methods: In addition to standard methods, we measured serum direct LDL-C, small dense LDL-C (sdLDL-C), very low density lipoprotein cholesterol (VLDL-C), apolipoprotein (apo) B, apoA-I, lipoprotein(a) or Lp(a), HDL particles by gel electrophoresis and apoA-I immunoblotting, high sensitivity C reactive protein (hsCRP), and serum amyloid A (SAA) in 298 documented CVD cases (mean age 68.4 years, 54% male, 46% female) and 609 age and gender matched controls. All subjects were off lipid altering medications. All cases were sampled more than 4 weeks after any CVD event. All subjects had blood drawn after an overnight fast. Results: In male and female cases, median TC levels were 1% and 3% higher, TG levels 19% and 29% higher, direct LDL-C 2% and 17% higher, sdLDL-C 46% and 46% higher, VLDL-C 22% and 4% higher, apoB 6% and 17% higher, and Lp(a) 26% and 70% higher, respectively, than in matched controls. In male and female cases, median HDL-C levels were 25% and 26% lower, apoA-I 9% and 7% lower, while apoA-I values in HDL particles were 30% and 26% lower in very large a-1 HDL, 9% and 11% lower in large a-2 HDL, 4% and 4% lower in medium a-3 HDL, 13% and 6% lower in small a-4 HDL, and 16% and 15% higher in very small preb-1 HDL as compared to matched controls. In male and female cases, median hsCRP levels were 113% and 178% higher, and SAA levels were 41% and 43% higher than in matched controls. Values for sdLDL-C, Lp(a), apoA-I in preb-1 HDL and a-1 HDL, hsCRP, and SAA were all significantly different (p,0.001) in male and female cases versus controls. Conclusions: Our results indicate that advanced lipid and inflammatory marker testing provides significantly more information distinguishing CVD cases from controls than does standard lipid testing. Our data supports the use of advanced testing in CVD prevention, especially in CVD patients being considered for proprotein convertase subtilisin/kexin type 9 inhibitor therapy.

STATIN TREATMENT REDUCES PEBETA-1 HDL LEVELS IN DYSLIPIDEMIC PATIENTS

Prebeta-1 HDL is a small molecular species of high-density lipoprotein (HDL) that is the principal acceptor of cholesterol effluxed from macrophages. High prebeta-1 HDL levels are associated with increased risk of structural coronary artery disease (CAD) and myocardial infarction. Prebeta-1 HDL