Apolipoprotein C3 SstI polymorphism and triglyceride levels in Asian Indians

BACKGROUND: A close association between Sst I polymorphism in the 3' untranslated region of the apolipoproteinC3 (APOC3) gene and levels of plasma triglycerides (TG) had been reported by different investigators. Hypertriglyceridemia(HTG) is a known risk factor for coronary artery disease (CAD) in the context of Asian Indians. We conducted a study on the relationship between APOC3 SstI polymorphism (S1S1, S1S2 and S2S2 genotypes) and plasma TG levels in a group of 139 male healthy volunteers from Northern India. METHODS: DNA samples were analyzed by polymerase chain reaction (PCR) followed by SstI digestion. Digested PCR products were run on 3% agarose gel and visualized by ethidium bromide staining. RESULTS: Rare S2 allele was highly prevalent in our study population (0.313) as compared to the Caucasians (0.00–0.11). The genotypic distribution was in agreement with Hardy-Weinberg equilibrium. S2 allele was almost two times more prevalent in the HTG group (N = 34) as compared to NTG group (N = 105) (p = 0.001). Multiple logistic regression revealed S1S2 individuals had age-adjusted odds ratio of 2.43 (95%CI = 0.99–6.01, p = 0.054) and S2S2 had 9.9 (95%CI = 2.66–37.29, p = 0.0006) for developing HTG in comparison to S1S1 genotype. CONCLUSIONS: Our study shows a significant association between rare S2 allele and HTG in Asian Indians

Association of serum lipids and coronary artery disease with polymorphisms in the Apolipoprotein AI-CIII-AIV gene cluster

Genetic variants are considered as one of the main determinants of the concentration of serum lipids and coronary artery disease (CAD). Polymorphisms in the Apolipoprotein (Apo) AI-CIII-AIV gene cluster has been known to affect the concentrations of various lipid sub-fractions and the risk of CAD. The present study assessed associations between polymorphisms of the Apo AI-CIII-AIV gene cluster, [ApoA-I,-75G > A, (rs1799837); ApoC-III 3238C > G, (SstI), (rs5128) and ApoA-IV, Thr347Ser(347A > T), (rs675)] with serum lipids and their contributions to CAD in North Indian population. We recruited age, sex matched, 200 CAD patients and 200 healthy controls and tested them for fasting levels of serum lipids. We genotyped selected polymorphisms using polymerase chain reaction-restriction fragment length polymorphism. There were no statistically significant association of selected polymorphisms (or their combinations) with CAD even after employing additive, dominant and recessive models. However there was significant association of selected polymorphisms with various lipid traits amongst the control cohort (p < 0.05). Mean levels of high density lipoprotein cholesterol and triglycerides were found to be significantly higher among controls carrying at least one mutant allele at ApoA1- 75G > A (p = 0.019) and ApoCIII SstI (p < 0.001) polymorphism respectively. Our study observed that the selected polymorphisms in the ApoAI-CIII-AIV gene cluster although significantly affect various lipid traits but this affect does not seem to translate into association with CAD, at least among North Indian population

Lipoprotein Genotype and Conserved Pathway for Exceptional Longevity in Humans

Alteration of single genes involved in nutrient and lipoprotein metabolism increases longevity in several animal models. Because exceptional longevity in humans is familial, it is likely that polymorphisms in genes favorably influence certain phenotypes and increase the likelihood of exceptional longevity. A group of Ashkenazi Jewish centenarians ( n = 213), their offspring ( n = 216), and an age-matched Ashkenazi control group ( n = 258) were genotyped for 66 polymorphisms in 36 candidate genes related to cardiovascular disease (CVD). These genes were tested for association with serum lipoprotein levels and particle sizes, apolipoprotein A1, B, and C-3 levels and with outcomes of hypertension, insulin resistance, and mortality. The prevalence of homozygosity for the −641C allele in the APOC3 promoter (rs2542052) was higher in centenarians (25%) and their offspring (20%) than in controls (10%) ( p = 0.0001 and p = 0.001, respectively). This genotype was associated with significantly lower serum levels of APOC3 and a favorable pattern of lipoprotein levels and sizes. We found a lower prevalence of hypertension and greater insulin sensitivity in the −641C homozygotes, suggesting a protective effect against CVD and the metabolic syndrome. Finally, in a prospectively studied cohort, a significant survival advantage was demonstrated in those with the favorable −641C homozygote ( p < 0.0001). Homozygosity for the APOC3 −641C allele is associated with a favorable lipoprotein profile, cardiovascular health, insulin sensitivity, and longevity. Because modulation of lipoproteins is also seen in genetically altered longevity models, it may be a common pathway influencing lifespan from nematodes to humans

Factors affecting high-density lipoprotein cholesterol in HIV-infected patients on nevirapine-based antiretroviral therapy.

BACKGROUND & OBJECTIVES Cardiovascular disease (CVD) risk with low high-density lipoprotein cholesterol (HDL-C) and high triglycerides is common in the general population in India. As nevirapine (NVP)-based antiretroviral therapy (ART) tends to increase HDL-C, gene polymorphisms associated with HDL-C metabolism in HIV-infected adults on stable NVP-based ART were studied. METHODS A cross-sectional study was conducted between January 2013 and July 2014 among adults receiving NVP-based ART for 12-15 months. Blood lipids were estimated and gene polymorphisms in apolipoprotein C3 (APOC3), cholesteryl ester transfer protein (CETP) and lipoprotein lipase (LPL) genes were analyzed by real-time polymerase chain reaction. Framingham's 10-yr CVD risk score was estimated. Logistic regression was done to show factors related to low HDL-C levels. RESULTS Of the 300 patients included (mean age: 38.6±8.7 yr; mean CD4 count 449±210 cell/μl), total cholesterol (TC) >200 mg/dl was observed in 116 (39%) patients. Thirty nine per cent males and 47 per cent females had HDL-C levels below normal while 32 per cent males and 37 per cent females had TC/HDL ratio of 4.5 and 4.0, respectively. Body mass index [adjusted odds ratio (aOR)=1.70, 95% confidence interval (CI) 1.01-2.84, P=0.04] and viral load (aOR=3.39, 95% CI: 1.52-7.52, P=0.003) were negatively associated with serum HDL-C levels. The 10-yr risk score of developing CVD was 11-20 per cent in 3 per cent patients. Allelic variants of APOC3 showed a trend towards low HDL-C. INTERPRETATION & CONCLUSIONS High-risk lipid profiles for atherosclerosis and cardiovascular disease were common among HIV-infected individuals, even after 12 months of NVP-based ART. Targeted interventions to address these factors should be recommended in the national ART programmes

Expression and structure-functional studies of human apolipoproteinciii

Apolipoprotein (Apo) CIII plays a key role in triglyceride (TG)-rich lipoprotein metabolism and is a risk factor for coronary heart disease (CHD). The study involved in this thesis is the first in vitro structure-functional study using recombinant apoCIII proteins. The physicochemical properties of recombinant wild type and A23T, a naturally occurring mutation that is associated with apoCIII deficiency and lower plasma TG levels, as well as three site-directed mutants of apoCIII, designed by molecular modelling and implicated in lipid binding (L9T/T20L, F64A/W65A) or lipoprotein lipase (LPL) inhibition (K21A), were compared. Relative lipid binding efficiencies of each apoCIII variants to 1.2-dimyristoyl-sn-glycero-3- phosphatidylcholine (DMPC) were: L9T/T20L>WT>K21A>A23T>F64A/W65A with an inverse correlation with size of the discoidal complexes formed. Physicochemical analysis (Trp fluorescence, circular dichroism (CD) and GdnHC1 denaturation) suggested that the stability of the resulting apoCIII:DMPC complexes were dependent on their lipid binding properties. The displacement of apoE by apoCIII variants were tested by gel filtration of apoE:dipalmitoylphosphatidylcholine (DPPC) discoidal complexes mixed with the various apoCIII variants. All apoCIII proteins bound to the apoE:DPPC complexes and the capacity to displace apoE from the complex was dependent on their lipid binding affinity. All the recombinant apoCIII proteins inhibited LPL in the presence or in the absence of apoCII, with F64A/W65A displaying the most inhibition, suggesting that apoCIII inhibition of LPL is independent of lipid binding and therefore due to the protein:protein interaction with apoCII and/or LPL. Taken together, our data suggest that the hydrophobic residues F64 and W65 are crucial for the lipid binding properties of apoCIII and the redistribution of the N- terminal helix of apoCIII (L9T/T20L permutation) can enhance the lipid binding properties of the protein. Additionally, the reduced lipid binding capacity of the naturally occurring mutation A23T could lead to reduced plasma apoCIII and lower plasma TG levels in carriers

Genetic disposition and response of blood lipids to diet : studies on gene-diet interaction in humans

Even though a cholesterol-lowering diet is effective for most people, it is not for all. Identification of genetic determinants of the serum lipid response to diet may be of help in the identification of subjects who will not benefit from a cholesterol-lowering diet. It may also clarify the role of certain proteins in cholesterol metabolism. The objective of our research was to determine whether genetic polymorphisms affect the response of serum lipids to diet in humans.We first assessed sex differences in the response of serum lipids to changes in the diet. Men had larger responses of total and low-density lipoprotein cholesterol to saturated fat and cafestol than women. There were no sex differences in the responses to trans fat and dietary cholesterol. We also used these data to study the effect of 11 genetic polymorphisms on responses of serum lipids to the various dietary treatments. Apoprotein E, A4 347 and 360, and cholesteryl-ester transfer protein TaqIb polymorphisms affected the lipid response to diet slightly.We further studied the effect of the apoprotein A4 360-1/2 polymorphism on response of serum lipids to dietary cholesterol in a controlled trial specially designed for this purpose. The apoprotein A4 360-1/2 polymorphism did not affect the response of serum lipids to a change in the intake of cholesterol in a group of healthy Dutch subjects who consumed a background diet high in saturated fat.Although it is not directly related to genetic polymorphisms and lipid response, we finally reviewed the effect of dietary cholesterol on the ratio of total to high-density lipoprotein cholesterol, which is a more specific predictor of coronary heart disease than either lipid value alone. Dietary cholesterol raised the ratio of total to high-density lipoprotein cholesterol.In conclusion, the effect of genetic polymorphisms on serum lipid response to diet is small. It is therefore not possible to identify individuals who will not benefit from a cholesterol-lowering diet on the basis of a specific genetic polymorphism.</p

Mutationssuche in regulatorischen Sequenzen der Gene der Apolipoproteine AI, AIV und CIII mithilfe der denaturierenden Gradientengelelektrophorese

Adipositas und hohe Triglyzeridkonzentrationen sind neben erhöhten LDL-, Cholesterin- und Lipoprotein(a)- sowie niedrigen HDL-Spiegeln, Diabetes mellitus, Nikotinkonsum, arterieller Hypertonie, hohem Alter und familiärer Prädisposition anerkannte Risikofaktoren für die Entwicklung einer koronaren Herzkrankheit (KHK). Im Allgemeinen führt eine Adipositas zu einer verstärkten Freisetzung von freien Fettsäuren und darüber zu einer Hypertriglyzeridämie. Es gibt jedoch noch eine Vielzahl anderer Ursachen für eine Hypertriglyzeridämie, und einige Patienten entwickeln eine Hypertriglyzeridämie auch bei relativ gering ausgeprägter Adipositas. Die Apolipoproteine AI, AIV und CIII spielen sowohl im Cholesterin- als auch im Triglyzeridstoffwechsel Schlüsselrollen. Ihre regulatorischen Genabschnitte, die Promoter und Enhancer, sind unerlässlich für ihre Expression. Die vorliegende Arbeit sollte untersuchen, ob Mutationen im ApoAI, ApoAIV oder ApoCIII Promoter, sowie dem ApoCIII Enhancer eine Erklärung für einen niedrigen BMI bei gleichzeitig erhöhtem Triglyzeridspiegel bieten können. Zu diesem Zweck wurde zunächst eine Fall-Kontroll-Studie entworfen, um einen Zusammenhang zwischen eventuellen häufigen Mutationen und der BMI-Triglyzerid-Konstellation belegen zu können. Die Zielabschnitte der DNA der gesamten Studienpopulation wurden dann auf Mutationen gescreent. Dazu wurden 264 EDTA-Blut-Proben von Patienten der Marburger Präventionsallianz in eine Fallgruppe (BMI unter 25kg/m2 und Triglyzeridplasmaspiegel über 150mg/dl, 134 Proben) und eine Kontrollgruppe (BMI unter 25kg/m2 und Triglyzeridplasmaspiegel unter 150mg/dl, 130 Proben) eingeteilt. Die DNA der Probanden wurde isoliert und mittels Polymerasekettenreaktion amplifiziert. Die Amplifikate wurden mithilfe der denaturierenden Gradientengelelektrophorese (DGGE) auf Auffälligkeiten im Laufverhalten untersucht. Die DGGE wurde vielfach als das zurzeit effektivste Screeningverfahren zur Mutationssuche mit einer Sensitivität von etwa 95% und der Möglichkeit, relativ viele Proben zeitgleich zu untersuchen, beschrieben. In der DGGE detektierte auffällige Proben wurden sequenziert. Die untersuchten Abschnitte sind in einem gemeinsamen Gencluster auf dem langen Arm des Chromosoms 11 organisiert. Die hier untersuchte Sequenz des ApoAI Promoters umfasste 229bp zwischen den Nukleotiden 116708439 bis 116708667 (-329 bis -101 in Bezug auf den Transkriptionsstart). Die untersuchte ApoAIV Promotersequenz umfasste 437bp zwischen den Nukleotiden 116693995 bis 11669444231 (-439 bis -3). Die ApoCIII Promotersequenz umfasste 226bp zwischen den Nukleotiden 116700604 bis 116700351 (-251 bis -26). In allen Bereichen gibt es vereinzelte bekannte Mutationen, deren Bedeutung jeweils noch nicht geklärt ist. Lediglich im ApoCIII Enhancergen (hier untersucht: 340bp zwischen den Nukleotiden 116700210 bis 116699819, -800 bis -471) gibt es mehrere Polymorphismen, deren Auswirkungen in Studien belegt werden konnten. Im Rahmen dieser Arbeit konnten wir eine Mutation (-63C-->G) im ApoAIV Promotergen nachweisen. Diese wurde mittlerweile unter anderem durch das 1000Genome-Projekt validiert und als rs5090 veröffentlicht. Die in anderen Arbeiten beobachtete, durchweg sehr hohe Sensitivität der DGGE ließ sich in dieser Arbeit nicht bestätigen. Trotz einer beschriebenen C-Allelfrequenz des rs5090-SNP von 4 bis 6%, fand sich in 264 Proben lediglich eine Mutation. Weder bei den Kontrollpersonen noch bei den Patienten mit Hypertriglyzeridämie fanden sich weitere Mutationen. Weitere Studien sollten folgen, um zum Beispiel in einem Expressionsmodell die Relevanz der gefundenen Mutation zu überprüfen

Γονιδιακή μελέτη του παράγοντα φλεγμονής και του παράγοντα ομοιόστασης της ενέργειας του μεταβολικού συνδρόμου στον ελληνικό πληθυσμό

Το Μεταβολικό σύνδρομο χαρακτηρίζεται ως ένα συνάθροισμα παραγόντων κινδύνου (δυσλιπιδαιμία, αυξημένη αρτηριακή πίεση, διαταραγμένος μεταβολισμός γλυκόζης, κεντρική παχυσαρκία) για πρώιμη ανάπτυξη καρδιοαγγειακών νοσημάτων καθώς και σακχαρώδη διαβήτη. Ο ολοένα αυξανόμενος επιπολασμός του Μεταβολικού συνδρόμου παρουσιάζει τις επιδεμικές, πλέον, διαστάσεις του προβλήματος. Ως προς την αιτιολογία του, το Μεταβολικό σύνδρομο κατατάσσεται, πλέον, στα πολυπαραγοντικά νοσήματα αφού η εμφάνιση του εξαρτάται από επιρρεπές γενετικό υπόβαθρο του ατόμου σε συνδυασμό με περιβαλλοντικές επιδράσεις. Η πιθανή επίδραση συγκεκριμένων γενετικών δεικτών στην ανάπτυξη του συνδρόμου και η μελλοντική χρήση τους ως βιοδείκτες για την έγκαιρη πρόληψη σε γενετικά επιρρεπή άτομα είναι ο σκοπός της παρούσας εργασίας. Δείγμα 90 ατόμων συλλέχθηκε και τα κριτήρια του NCEP ATP III χρησιμοποιήθηκαν για την κατάταξή τους σε δύο ομάδες (με ή χωρίς Μεταβολικό σύνδρομο). Η τεχνική PCR-RFLP χρησιμοποιήθηκε για την ανάλυση των πολυμορφισμών IL 6 G634C, IL 6 G174C, TNF G308A, APOC3 3175G και MTHFR C677T. Τα αποτελέσματα για τους τέσσερις πολυμορφισμούς IL6 G634C, IL6 G174C, TNF G308A, APOC3 3175G έδειξαν μη σημαντικές διαφορές στη συχνότητα των πολυμορφισμών μεταξύ ατόμων με και χωρίς μεταβολικό σύνδρομο. Αντίθετα, φάνηκε θετική συσχέτιση του πολυμορφισμού MTHFR C677T με την εμφάνιση Μεταβολικού συνδρόμου ενισχύοντας την υπόθεση του σημαντικού ρόλου του γονιδίου MTHFR στη διαταραχή της μεταβολικής ομοιόστασης της ενέργειας του οργανισμού και τη συμμετοχή του παράγοντα αυτού στον παθογενετικό μηχανισμό ανάπτυξης του Μεταβολικού συνδρόμου στον ελληνικό πληθυσμό

Genetic susceptibility to the metabolic syndrome

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2004-2005Le syndrome métabolique est caractérisé par un regroupement de facteurs de risque présents chez un même individu et augmentant ainsi ses chances de développer le diabète de type 2 et les maladies cardiovasculaires. Il est donc important de comprendre l’étiologie génétique de ce trait. Dans cette thèse, une multitude d’approches génétiques ont été utilisées afin d’apporter un brin de connaissance sur l’architecture génétique du syndrome métabolique et de ses composantes individuelles. Trois gènes candidats ont été testés incluant le récepteur activé par les proliférateurs de péroxisomes (PPAR) α et PPARγ ainsi que la protéine de transfert des phospholipides (PLTP). Les gènes PPARα et PLTP ont tous deux été associés significativement avec plusieurs variables d’adiposité. Des effets significatifs d’interaction entre les gènes PPARα et PPARγ ont été obtenus pour les paramètres de glucose et d’insuline. Il a aussi été démontré que le polymorphisme PPARα L162V influence les changements de cholestérol-HDL2 suite à un traitement au gemfibrozil. Par la suite, des criblages génomiques ont été effectués sur les concentrations de lipides et de lipoprotéines plasmatiques. Plusieurs régions chromosomiques ont été identifiées incluant 1q43, 11q13 q24, 15q26.1, et 19q13.32 pour le cholestérol-LDL, 12q14.1 pour le cholestérol-HDL, 2p14, 11p13, et 11q24.1 pour les triglycérides, 18q21.32 pour l’apolipoprotéine (apo) B-LDL, et 3p25.2 pour l’apoAI. La contribution génétique à la variation du diamètre principal des particules LDL (DP-LDL) a aussi été étudiée. Les résultats démontrent une forte ressemblance familiale avec des coefficients d’héritabilité de plus de 50%, la présence d’un gène à effet majeur, et une forte évidence de liaison sur le chromosome 17q. Le gène de l’apoH, localisé à cet endroit, a par la suite été significativement associé au DP-LDL, suggérant que ce gène est responsable du signal de liaison observé sur le chromosome 17. Finalement, une variable quantitative du syndrome métabolique a été construite à l’aide d’une analyse factorielle. Un criblage génomique effectué sur cette variable a démontré une évidence de liaison sur le chromosome 15q, suggérant la présence d’un gène à cet endroit contribuant au regroupement des facteurs de risques caractérisant le syndrome métabolique. Plusieurs de ces résultats devront être répliqués, alors que d’autres méritent d’être suivis.The metabolic syndrome is a cluster of interrelated cardiovascular risk factors co-occurring in the same individual. People with this syndrome are at increased risk for developing diabetes mellitus and cardiovascular diseases. Accordingly, it is important to elucidate the genetic aetiology governing this trait in order to better comprehend its pathogenesis. In the present thesis, heritability and complex segregation analyses as well as candidate gene and genome-wide scan approaches have been applied to shed some lights on the genetic architecture of the metabolic syndrome and its individual components. A total of three candidate genes have been investigated including peroxisome proliferator-activated receptor (PPAR) α and PPARγ as well as phospholipid transfer protein (PLTP). It has been shown that polymorphisms in both PPARα and PLTP genes are significantly associated with several indices of adiposity. In addition, significant gene-gene interactions have been observed between PPARα and PPARγ on glucose/insulin parameters. It has also been shown that the HDL2-cholesterol response to gemfibrozil therapy is modulated by the PPARα L162V polymorphism. Genome-wide linkage scans have been performed on lipid and lipoprotein concentrations. Many chromosome regions harbouring lipoprotein/lipid genes have been identified including 1q43, 11q13 q24, 15q26.1, and 19q13.32 for LDL-cholesterol, 12q14.1 for HDL-cholesterol, 2p14, 11p13, and 11q24.1 for triglycerides, 18q21.32 for LDL-apolipoprotein (apo) B, and 3p25.2 for apoAI. The genetic contribution of the variation in LDL peak particle diameter (LDL-PPD) has been also investigated. Overall, the results indicate: 1) that LDL-PPD strongly aggregates within families with heritability estimate above 50%; 2) the existence of a major gene effect affecting the phenotype; and 3) the presence of a major quantitative trait locus located on chromosome 17q. The apo H gene, a positional candidate gene, was then significantly associated with LDL-PPD, suggesting that this gene is responsible for the linkage signal observed on 17q. Finally, factor analyses have been used to construct a quantitative metabolic syndrome variable and a genome-wide linkage scan has been conducted to identify the genomic regions underlying this trait. A major quantitative trait locus has been observed on chromosome 15q suggesting a gene within this region contributing to the clustering of the metabolic syndrome-related phenotypes. Many of these findings must go through independent replication, while others produced new leads that deserve follow-up