Identifying Genetic and Biological Determinants of Race-Ethnic Disparities in Stroke in the United States.

In the United States, causes of racial differences in stroke and its risk factors remain only partly understood, and there is a long-standing disparity in stroke incidence and mortality impacting Black Americans. Only half of the excess risk of stroke in the United States Black population is explained by traditional risk factors, suggesting potential effects of other factors including genetic and biological characteristics. Here, we nonsystematically reviewed candidate laboratory biomarkers for stroke and their relationships to racial disparities in stroke. Current evidence indicates that IL-6 (interleukin-6), a proinflammatory cytokine, mediates racial disparities in stroke through its association with traditional risk factors. Only one reviewed biomarker, Lp(a) (lipoprotein[a]), is a race-specific risk factor for stroke. Lp(a) is highly genetically determined and levels are substantially higher in Black than White people; clinical and pharmaceutical ramifications for stroke prevention remain uncertain. Other studied stroke risk biomarkers did not explain racial differences in stroke. More research on Lp(a) and other biological and genetic risk factors is needed to understand and mitigate racial disparities in stroke.

Oral Contraceptives and Venous Thromboembolism: Focus on Testing that May Enable Prediction and Assessment of the Risk.

Combined oral contraceptives (COCs) induce several changes in the levels of coagulation factors. The levels of procoagulant factors are often increased, while levels of anticoagulant factors are decreased. Fibrinolysis is also affected, even if the effect seems to be more counterbalanced by opposite regulation of profibrinolytic and antifibrinolytic factors. These effects on hemostasis are more pronounced with third- or fourth-generation COC compared with second-generation COC. Venous thromboembolism (VTE) risk increases when multiple risk factors, including genetic and environmental, are present simultaneously. COC use causes changes in coagulation that modify the prothrombotic state induced by preexisting hemostatic alterations in a supra-additive manner. Therefore, testing appears to be of importance not only before implementing COC but also to monitor any potential thrombogenicity induced by COC therapy. Inherited genetic factors, such as factor V Leiden, G20210A prothrombin mutation, antithrombin, protein C or protein S deficiencies, non-O blood group, as well as CYP2C9*2 and the rs4379368 mutations, have all been identified as genetic predictive risk factors of VTE in women. Nevertheless, the screening of these genetic biomarkers is not capable of assessing the phenotypic expression of the risk. This review will focus on the different options for screening the thrombogenic status in this population. Specific attention will be given to the endogenous thrombin potential-based activated protein C resistance, a test aiming at assessing the thrombogenicity induced by hormonal therapies and inherited or acquired thrombophilia.

Thrombophilia in childhood: to test or not to test.

Inherited thrombophilia is defined as a genetically determined tendency to develop venous thromboembolism. In children, inherited thrombophilia contributes to the development of pediatric thromboembolic disease. As a consequence, pediatric hematologists are increasingly requested to test thrombophilia in pediatric patients with thrombosis or asymptomatic children from thrombophilic families. This article reviews the benefits and limitations of testing for thrombophilic disorders, for example, factor V Leiden, prothrombin mutation, and deficiencies of antithrombin, protein C, or protein S in childhood.

Protein C and protein S assessment in hospital laboratories: which strategy and what role for DNA sequencing?

This paper presents a critical assessment of protein C (PC) and protein S (PS) functional and immunological approaches with regard to DNA sequencing in a large hospital recruitment for thrombosis exploration in more than 1700 consecutive patients. After examination of clinical status and PC and PS phenotype, a genotypic study was implemented for 17 PC-deficient and 28 PS-deficient patients (activity < 70%). Sixty-five percent of the genotyped PC-deficient patients were found to have heterozygous mutations. Among the < 70% values, decreases in PC activity without gene mutation were always slight (mean value 64 +/- 7%) while patients presenting a PC gene mutation had a mean 50 +/- 17% activity (P < 0.05). Among the eight PC mutations found, only one has previously been described. A novel mutation in the promoter region (-1522), located in the HNF-1 site and associated with the Y226H heterozygous mutation, was found in a 9-month-old girl with 4% PC activity. Determination of PS functional activity was considerably improved by contemporaneous measurement of calibration and samples in a single step. Only 50% of the genotyped PS-deficient patients demonstrated heterozygous alterations of the gene. The benefit of sequencing to identify putative causal mutations was only 39% in PS-deficient women, while it was 90% in men. Among the nine PS mutations found, six have not yet been published. In the present paper, we explain our methodological choices and diagnostic strategy.

[Public health economic evaluation of screening for APC resistance (Leiden mutation) in new oral contraceptive users]. / Gesundheitsökonomische Evaluation des Screenings auf APC-Resistenz (Mutation Leiden) bei Neuanwenderinnen von Ovulationshemmern

BACKGROUND: Thromboembolic events in users of oral contraceptives rank among the most important complications with potential economic consequences. It is well known that a large part of thromboembolic complications correlates with hereditary thrombophilias. The relative high prevalence of the newly described resistance of activated protein C and an easy test for it rise up the question if general screening of new users of oral contraceptives is sensible of health economic view. METHOD: We conducted a cost-effectiveness analysis using decision analytic techniques, analysing the costs and outcomes in a hypothetical cohort of 10,000 women. RESULT AND CONCLUSION: From a third party payer perspective we estimate that screening for APC resistance by new users of oral contraceptives is more cost-effective than many other primary preventive methods. The cost per life-year gained of testing for APC resistance were in the order of DM 1544,--including direct medical cost only. From perspective of sickness insurance fund as cost unit we estimate that screening for APC resistance by new users of oral contraceptives is more cost-effective than many other primary preventive methods.

Structure-function assessment of the role of the helical stack domain in the properties of human recombinant protein C and activated protein C.

The role of the helical stack (HS) in defining the properties of human recombinant (r) protein C (PC) and activated protein C (APC) was assessed. To do so, several mutations were made in this region of the molecule and their effects on the proteins examined. Substitution of the entire HS of PC (residues 38-46) by that of human coagulation factor (f) IX (residues 39-47), yielding r-[HSIX]PC, did not result in any substantial changes in the gamma-carboxyglutamic acid domain (GD)-related Ca(2+)-dependent properties of PC or APC, suggesting that the conformation of the HS may play a more dominant role in these Ca(2+)-dependent properties than do the specific amino acids that differ between these two HS regions. On the other hand, the catalytic efficiency of activation of r-[HSIX]PC by the thrombin/thrombomodulin complex was reduced to approximately one-third of that of wtr-PC, a result that demonstrates a specific role for the HS of PC in this activation process. Another mutation, [Ser42-->Pro], was generated in the HS region of r-PC, providing r-[S42P]PC, a change that according to the empirical algorithm based on the Chou-Fasman secondary structure rules, would disrupt the alpha-helical conformation of the HS. The anticoagulant activity of the corresponding r-[S42P]APC was found to be approximately 35% of that of wtr-APC. Because of the lack of any notable effects of this mutation on other GD-related Ca(2+)-dependent properties of r-PC and r-APC, the basis of this anticoagulant activity loss may be due to its nonmaximal alignment with substrate on the PL surface. The results of this study indicate that the role of the HS of r-PC and r-APC is to provide a region of the protein that is needed to assure optimal alignment on the PL or cell surface of the active site of the enzyme with that of the cleavage sites of the substrates, perhaps by functioning as a scaffold for separation of the active site of APC from the PL surface.

Nuclear transfer in the bovine using microinjected donor embryos: assessment of development and deoxyribonucleic acid detection frequency.

Bovine embryos that had been microinjected with DNA were examined for their potential use as donor embryos in nuclear transfer. Donor embryos were obtained from oocytes collected by transvaginal oocyte aspiration, matured and fertilized in vitro, microinjected with a murine whey acidic protein-human protein C genomic DNA construct, and cultured in vitro on liver cells of buffalo rat (Rattus norvegicus). Blastomeres from these embryos were transferred into enucleated bovine oocytes received from an abattoir by electrofusion at 40 h postmaturation. Following 7 d of culture, the developmental stage was recorded, and resulting embryos were prepared for analysis by polymerase chain reaction. Embryos that were derived from microinjected donor embryos did not differ from control donor embryos (11 vs. 8.6%) in development to the morula and blastocyst stage. Of the biopsies from 20 microinjected donor embryos, 19 were positive for the injected DNA. Of 37 embryos developing normally, only 12 (32.4%) were positive for the injected DNA. These results indicate that microinjected embryos can be successfully used in a nuclear transfer program to produce additional viable embryos and that these embryos may be reliably screened for the transgene for transfer to recipients.