Genome-wide analysis of blood lipid metabolites in over 5000 South Asians reveals biological insights at cardiometabolic disease loci.

BACKGROUND: Genetic, lifestyle, and environmental factors can lead to perturbations in circulating lipid levels and increase the risk of cardiovascular and metabolic diseases. However, how changes in individual lipid species contribute to disease risk is often unclear. Moreover, little is known about the role of lipids on cardiovascular disease in Pakistan, a population historically underrepresented in cardiovascular studies. METHODS: We characterised the genetic architecture of the human blood lipidome in 5662 hospital controls from the Pakistan Risk of Myocardial Infarction Study (PROMIS) and 13,814 healthy British blood donors from the INTERVAL study. We applied a candidate causal gene prioritisation tool to link the genetic variants associated with each lipid to the most likely causal genes, and Gaussian Graphical Modelling network analysis to identify and illustrate relationships between lipids and genetic loci. RESULTS: We identified 253 genetic associations with 181 lipids measured using direct infusion high-resolution mass spectrometry in PROMIS, and 502 genetic associations with 244 lipids in INTERVAL. Our analyses revealed new biological insights at genetic loci associated with cardiometabolic diseases, including novel lipid associations at the LPL, MBOAT7, LIPC, APOE-C1-C2-C4, SGPP1, and SPTLC3 loci. CONCLUSIONS: Our findings, generated using a distinctive lipidomics platform in an understudied South Asian population, strengthen and expand the knowledge base of the genetic determinants of lipids and their association with cardiometabolic disease-related loci.

Single step PCR for the identification of Low Density Lipoprotein Receptor (LDL-R) gene mutations.

BACKGROUND AND OBJECTIVE: This study was conducted to determine the common mutation of low density lipoprotein receptor in patients with familial hypercholesterolemia (FH) in our population and identify the different point mutation in the LDL-receptor gene. The main aim of this study was to reduce the cost of PCR without extracting DNA and do the diagnosis at single step. METHODS: This study was carried out in the period of one year, from 2009- 2011. All the patients selected for this study were from Dr. Ziauddin Hospital, National Institute of Cardiovascular Diseases, and Dr. Rubina Ghani's Pathological & Molecular Laboratories. While collecting the blood sample, the patients were in overnight fasting condition. The clinical and biochemical analysis was performed on hyperlipidemic patients (n=120) to determine the frequency of familial hypercholesterolemia in our population. After lipid profile the patients were selected and direct multiplex PCR (Polymerase chain reaction) was performed from whole blood collected in a single tube using forward and reverse primers of exons 3, 4, 9 and 14 of without extracting DNA. RESULTS: Genomic DNA was extracted from blood samples as well as direct whole ETDA blood of healthy control group and hypercholesterolemia patients to detect mutations in exons 3, 4, 9, and 14 of the LDLR gene, with modification in the technique by using type-specific primers. These results for exon 4 mutation were confirmed by DNA sequencing. CONCLUSION: Screening method based on PCR by using Kappa direct PCR could be a faster and cheaper method with least contamination for screening a large number of FH patients for mutation of LDLR gene.

Determination of site-specific carotid-intima media thickness: common -carotid artery and carotid bifurcation in hypercholesterolemia patients.

OBJECTIVE: To determine site specific carotid intima-media thickness: common-carotid artery and carotid bifurcation in hypercholesterolemia patients as a marker for atherosclerosis. METHODS: Fifty patients with hypercholesterolemia and twenty controls were selected after getting informed consent regarding the investigation of carotid- intima media thickness by B-mode ultrasound. All the patients of hypercholesterolemia with LDL-C > 160mg/dL had family history of coronary artery diseases. This procedure was carried out in the Radiology Department of Dr. Ziauddin Hospitals. Measurement of carotid -intima media thickness, B-mode ultrasonography of common carotid artery, carotid bifurcation and internal carotid artery (left and right carotid arteries) was performed with Toshiba (M# SSA-580A/E2) ultrasound scanner with linear probe. The posterior or far wall of the carotid artery is, the distance between the leading edge first bright line (lumen -intima interface) and the leading edge of the second bright line (media-adventitia interface) of far wall was recorded as intima -media thickness. The average mean of six segments of intima-media thickness was taken as mean CIMT of right and left common carotid, bifurcation and internal carotid arteries. RESULTS: Maximal CIMT was significantly increased at sites common carotid, carotid bifurcation and internal carotid arteries in fifty patients with hypercholesterolemia as compared to controls. At carotid bifurcation mean of maximal CIMT was (0.9+ 0.3mm). Range of maximum CIMT in hypercholesterolemia patients was (0.8- 3.3mm) and in controls (0.4- 0.8 mm). The thickness was more frequently increased at site of bifurcation. CONCLUSIONS: Carotid intima- media thickness in hypercholesterolemia patients was increased and carotid bifurcation was site that has shown greater increase in intima-media thickness and plaques in these patients predict high risk for atherosclerosis.

Carotid intima-media thickness correlation with lipid profile in patients with familial hypercholesterolemia versus controls.

OBJECTIVE: To determine the variations in carotid intima-media thickness (CIMT) in familial hypercholesterolemia (FH) patients and its use as predictive marker for premature cardiovascular diseases. STUDY DESIGN: Comparative study. PLACE AND DURATION OF STUDY: National Institute of Cardiovascular Diseases and Dr. Ziauddin Hospital, Karachi, from June 2008 to October 2009. METHODOLOGY: Familial hypercholesterolemia was clinically diagnosed by premature coronary diseases, xanthomas, arcus cornealis and family history of premature coronary heart diseases. Controls were age matched normal individuals without hypercholesterolemia. Their lipid profile was tested after overnight fasting. CIMT was measured in mm using B-mode ultrasonography using linear probe. Student t-test was applied to compare mean CIMT of cases and the control. The mean CIMT values of the FH cases were correlated with LDL using Pearson's correlation test. RESULTS: Forty cases with hypercholesterolemia gave consent to participate in the study. These patients had total cholesterol ≥200 mg/dL and LDL ≥160 mg/dL as compared to twenty controls of similar age with total cholesterol ≤200 mg/dL and LDL ≤130 mg/dL. Mean CIMT for the cases was 0.77 ± 0.18 mm while mean CIMT for control was 0.59 ± 0.08 mm. The mean CIMT for the cases ranged from 0.7-1.83 mm and 0.48-0.73 mm for controls. Among the FH cases, 25% (n=11) had arterial plaques. Mean CIMT was significantly correlated to LDL-cholesterol (r = 0.725**, p < 0.001). CONCLUSION: In this study, CIMT was found to be significantly increased in familial hypercholesterolemia and it correlated with raised LDL-cholesterol. Both are predictive of premature cardiovascular diseases.