A Genome-Wide Methylation Study on Essential Hypertension in Young African American Males

Objective

There is emerging evidence from animal studies suggesting a key role for methylation in the pathogenesis of essential hypertension. However, to date, very few studies have investigated the role of methylation in the development of human hypertension, and none has taken a genome-wide approach. Based on the recent studies that highlight the involvement of inflammation in the development of hypertension, we hypothesize that changes in DNA methylation of leukocytes are involved in the pathogenesis of hypertension.

Method & Results

We conducted a genome-wide methylation analysis on 8 hypertensive cases and 8 normotensive age-matched controls aged 14–23 years and performed validation of the most significant CpG sites in 2 genes in an independent sample of 36 hypertensive cases and 60 normotensive controls aged 14–30 years. Validation of the CpG sites in the SULF1 gene was further conducted in a second replication sample of 36 hypertensive cases and 34 controls aged 15.8–40 years. A CpG site in the SULF1 gene showed higher methylation levels in cases than in healthy controls in the genome-wide step (p = 6.2×10⁻⁵), which was confirmed in the validation step (p = 0.011) for subjects ≤30 years old but was not significant for subjects of all ages combined (p = 0.095).

Conclusion

The identification of a difference in a blood leukocyte DNA methylation site between hypertensive cases and normotensive controls suggests that changes in DNA methylation may play an important role in the pathogenesis of hypertension. The age dependency of the effect further suggests complexity of epigenetic regulation in this age-related disease.     

Replication in hydroxyurea: it's a matter of time

Hydroxyurea (HU) is a DNA replication inhibitor that negatively affects both the elongation and initiation phases of replication and triggers the "intra-S phase checkpoint." Previous work with budding yeast has shown that, during a short exposure to HU, MEC1/RAD53 prevent initiation at some late S phase origins. In this study, we have performed microarray experiments to follow the fate of all origins over an extended exposure to HU. We show that the genome-wide progression of DNA synthesis, including origin activation, follows the same pattern in the presence of HU as in its absence, although the time frames are very different. We find no evidence for a specific effect that excludes initiation from late origins. Rather, HU causes S phase to proceed in slow motion; all temporal classes of origins are affected, but the order in which they become active is maintained. We propose a revised model for the checkpoint response to HU that accounts for the continued but slowed pace of the temporal program of origin activation.     

Technical note: Artificial Resynthesis Technology for the experimental formation of dental microwear textures

Dental microwear formation on the posterior dentition is largely attributed to an organism's diet. However, some have suggested that dietary and environmental abrasives contribute more to the formation process than food, calling into question the applicability of dental microwear to the reconstruction of diet in the fossil record. Creating microwear under controlled conditions would benefit this debate, but requires accurately replicating the oral environment. This study tests the applicability of Artificial Resynthesis Technology (ART 5) to create microwear textures while mitigating the challenges of past research. ART 5 is a simulator that replicates the chewing cycle, responds to changes in food texture, and simulates the actions of the oral cavity. Surgically extracted, occluding pairs of third molars (n = 2 pairs) were used in two chewing experiments: one with dried beef and another with sand added to the dried beef. High-resolution molds were taken at 0, 50, 100, 2500, and 5000 simulated chewing cycles, which equates to approximately 1 week of chewing. Preliminary results show that ART 5 produces microwear textures. Meat alone may produce enamel prism rod exposure at 5000 cycles, although attrition cannot be ruled out. Meat with sand accelerates the wear formation process, with enamel prism rods quickly obliterated and “pit-and-scratch” microwear forming at approximately 2500 cycles. Future work with ART 5 will incorporate a more thorough experimental protocol with improved controls, pH of the simulated oral environment, and grit measurements; however, these results indicate the potential of ART 5 in untangling the complex variables of dental microwear formation.     

Maternal provisioning in Ophionereis fasciata and O. schayeri: brittle stars with contrasting modes of development

Evolutionary change from planktotrophic to lecithotrophic development in echinoderms is closely tied to an increase in maternal provisioning. We provide the first data on the major energetic constituents in the eggs of two ophiuroids, the planktotroph Ophionereis fasciata (egg diameter 103 microm) and the lecithotroph O. schayeri (egg diameter 248 microm), to document changes in maternal investment associated with the switch to lecithotrophy in O. schayeri. Lipid classes in the eggs of the two species did not differ except for the presence of small amounts of wax esters in the eggs of O. schayeri. Production of a large egg in O. schayeri is mostly due to enhanced deposition of one energy-storage lipid, triglyceride. The eggs of O. schayeri are not simply scaled-up versions of the ancestral-type eggs of O. fasciata. The relationship between lipid and protein content and egg volume conformed to the relationship previously established for echinoderm eggs. Surprisingly, total lipid and protein data for the eggs of O. schayeri grouped with data for the eggs of planktotrophic echinoderms. The eggs of O. schayeri are small compared with those of other echinoderms with lecithotrophic development, and their energetic contents may approach the minimum provisions necessary to permit development without feeding.     

Metabolomic analysis of the effects of polychlorinated biphenyls in nonalcoholic fatty liver disease

Polychlorinated biphenyls (PCBs) are persistent organic pollutants and have been associated with abnormal liver enzymes and suspected nonalcoholic fatty liver disease (NAFLD), obesity, and the metabolic syndrome in epidemiological studies. In epidemiological surveys of human PCB exposure, PCB 153 has the highest serum levels among PCB congeners. To determine the hepatic effects of PCB 153 in mice, C57BL/6J mice were fed either a control diet (CD) or a high fat diet (HFD) for 12 weeks, with or without PCB 153 coexposure. The metabolite extracts from mouse livers were analyzed using linear trap quadrupole-Fourier transform ion cyclotron resonance mass spectrometer (LTQ-FTICR MS) via direct infusion nanoelectrospray ionization (DI-nESI) mass spectrometry. The metabolomics analysis indicated no difference in the metabolic profile between mice fed the control diet with PCB 153 exposure (CD+PCB 153) and mice fed the control diet (CD) without PCB 153 exposure. However, compared with CD group, levels of 10 metabolites were increased and 15 metabolites were reduced in mice fed HFD. Moreover, compared to CD+PCB 153 group, the abundances of 6 metabolites were increased and 18 metabolites were decreased in the mice fed high fat diet with PCB 153 exposure (HFD+PCB 153). Compared with HFD group, the abundances of 2 metabolites were increased and of 12 metabolites were reduced in HFD+PCB 153 group. These observations agree with the histological results and indicate that the metabolic effects of PCB 153 were highly dependent on macronutrient interactions with HFD. Antioxidant depletion is likely to be an important consequence of this interaction, as this metabolic disturbance has previously been implicated in obesity and NAFLD.     

A gas chromatographic/mass spectrometric assay for flutroline, a gamma-carboline antipsychotic agent, with direct derivatization on a moving needle injector

A method has been developed for the determination of flutroline in plasma using capillary gas chromatography and selected ion monitoring detection of the TMS derivative. The method is linear over the concentration range of 3-60 ng ml-1 and was used to define the drug pharmacokinetics and bioavailability in animals and man. A novel method for direct derivatization on the tip of a moving needle injector is described.     

The genetic-determination of ossification sequence polymorphism

Serial hand-wrist x-rays of 81 pairs of twins were examined to investigate the genetics of ossification sequence polymorphism. Discordance in ossification sequence was 3.5 times more common between like-sex dizygotic twins than between monozygotic twins, with the difference being significant at the 0.01 level of confidence. These findings support the contention that the major part of variation in ossification sequence is genetically determined.