Genetic Variation in the Epidermal Transglutaminase Genes Is Not Associated with Atopic Dermatitis

Background

Atopic dermatitis (AD) is a common chronic inflammatory skin disorder where epidermal barrier dysfunction is a major factor in the pathogenesis. The identification of AD susceptibility genes related to barrier dysfunction is therefore of importance. The epidermal transglutaminases (TGM1, TGM3 and TGM5) encodes essential cross-linking enzymes in the epidermis.

Objective

To determine whether genetic variability in the epidermal transglutaminases contributes to AD susceptibility.

Methods

Forty-seven single nucleotide polymorphisms (SNPs) in the TGM1, TGM3 and TGM5 gene region were tested for genetic association with AD, independently and in relation to FLG genotype, using a pedigree disequilibrium test (PDT) in a Swedish material consisting of 1753 individuals from 539 families. In addition, a German case-control material, consisting of 533 AD cases and 1996 controls, was used for in silico analysis of the epidermal TGM regions. Gene expression of the TGM1, TGM3 and TGM5 gene was investigated by relative quantification with Real Time PCR (qRT-PCR). Immunohistochemical (IHC) analysis was performed to detect TG1, TG3 and TG5 protein expression in the skin of patients and healthy controls.

Results

PDT analysis identified a significant association between the TGM1 SNP rs941505 and AD with allergen-specific IgE in the Swedish AD family material. However, the association was not replicated in the German case-control material. No significant association was detected for analyzed SNPs in relation to FLG genotype. TG1, TG3 and TG5 protein expression was detected in AD skin and a significantly increased TGM3 mRNA expression was observed in lesional skin by qRT-PCR.

Conclusion

Although TGM1 and TGM3 may be differentially expressed in AD skin, the results from the genetic analysis suggest that genetic variation in the epidermal transglutaminases is not an important factor in AD susceptibility.     

Genetic Variation of ITGB3 Is Associated with Asthma in Chinese Han Children

Previous studies have demonstrated that integrins are involved in the aetiology of asthma. Several single-nucleotide polymorphisms (SNPs) in the integrin β3 (ITGB3) gene are significantly associated with asthma in Western populations. Given the important roles of environmental exposures in the development of asthma, we evaluated the associations between six SNPs in ITGB3 and asthma in Chinese Han children. A total of 321 unrelated Chinese children with asthma and 315 healthy children were recruited for the study. SNP genotyping was performed by high-resolution melting analysis (HRM). The selected SNPs were well genotyped by HRM, and SNP rs3809865 in the 3′ untranslated region (3′UTR) of ITGB3 was found to be strongly associated with asthma (adjusted p = 0.004). The minor allele of rs3809865 showed a protective effect against asthma (OR: 0.59; 95% CI: 0.43–0.8). The seed regions of two miRNAs (hsa-mir-124 and hsa-mir-506) were predicted to bind to the sequence containing rs3809865 by TargetScan and PITA. Luciferase reporter assays demonstrated that the T allele of rs3809865 was more efficiently targeted by hsa-mir-124 than was the A allele, which suggested that rs3809865 could affect the binding of hsa-mir-124 to ITGB3. Furthermore, the transfection of A549 cells with hsa-mir-124 resulted in the downregulation of ITGB3 expression. Our results revealed that rs3809865 was significantly associated with asthma due to its effect on the binding of hsa-mir-124 to ITGB3.     

Natural Genetic Variation in Selected Populations of Arabidopsis thaliana Is Associated with Ionomic Differences

Controlling elemental composition is critical for plant growth and development as well as the nutrition of humans who utilize plants for food. Uncovering the genetic architecture underlying mineral ion homeostasis in plants is a critical first step towards understanding the biochemical networks that regulate a plant''s elemental composition (ionome). Natural accessions of Arabidopsis thaliana provide a rich source of genetic diversity that leads to phenotypic differences. We analyzed the concentrations of 17 different elements in 12 A. thaliana accessions and three recombinant inbred line (RIL) populations grown in several different environments using high-throughput inductively coupled plasma- mass spectroscopy (ICP-MS). Significant differences were detected between the accessions for most elements and we identified over a hundred QTLs for elemental accumulation in the RIL populations. Altering the environment the plants were grown in had a strong effect on the correlations between different elements and the QTLs controlling elemental accumulation. All ionomic data presented is publicly available at www.ionomicshub.org.     

Genetic Variation in the NOC Gene Is Associated with Body Mass Index in Chinese Subjects

Circadian clock genes are critical regulators of energy homeostasis and metabolism. However, whether variation in the circadian genes is associated with metabolic phenotypes in humans remains to be explored. In this study, we systemically genotyped 20 tag single nucleotide polymorphisms (SNPs) in 8 candidate genes involved in circadian clock, including CLOCK, BMAL1(ARNTL), PER1, PER2, CRY1, CRY2, CSNK1E,, and NOC(CCRN4L) in 1,510 non-diabetic Chinese subjects in Taipei and Yunlin populations in Taiwan. Their associations with metabolic phenotypes were analyzed. We found that genetic variation in the NOC gene, rs9684900 was associated with body mass index (BMI) (P = 0.0016, Bonferroni corrected P = 0.032). Another variant, rs135764 in the CSNK1E gene was associated with fasting glucose (P = 0.0023, Bonferroni corrected P = 0.046). These associations were consistent in both Taipei and Yunlin populations. Significant epistatic and joint effects between SNPs on BMI and related phenotypes were observed. Furthermore, NOC mRNA levels in human abdominal adipose tissue were significantly increased in obese subjects compared to non-obese controls.

Conclusion

Genetic variation in the NOC gene is associated with BMI in Chinese subjects.     

Learned Vocal Variation Is Associated with Abrupt Cryptic Genetic Change in a Parrot Species Complex

Contact zones between subspecies or closely related species offer valuable insights into speciation processes. A typical feature of such zones is the presence of clinal variation in multiple traits. The nature of these traits and the concordance among clines are expected to influence whether and how quickly speciation will proceed. Learned signals, such as vocalizations in species having vocal learning (e.g. humans, many birds, bats and cetaceans), can exhibit rapid change and may accelerate reproductive isolation between populations. Therefore, particularly strong concordance among clines in learned signals and population genetic structure may be expected, even among continuous populations in the early stages of speciation. However, empirical evidence for this pattern is often limited because differences in vocalisations between populations are driven by habitat differences or have evolved in allopatry. We tested for this pattern in a unique system where we may be able to separate effects of habitat and evolutionary history. We studied geographic variation in the vocalizations of the crimson rosella (Platycercus elegans) parrot species complex. Parrots are well known for their life-long vocal learning and cognitive abilities. We analysed contact calls across a ca 1300 km transect encompassing populations that differed in neutral genetic markers and plumage colour. We found steep clinal changes in two acoustic variables (fundamental frequency and peak frequency position). The positions of the two clines in vocal traits were concordant with a steep cline in microsatellite-based genetic variation, but were discordant with the steep clines in mtDNA, plumage and habitat. Our study provides new evidence that vocal variation, in a species with vocal learning, can coincide with areas of restricted gene flow across geographically continuous populations. Our results suggest that traits that evolve culturally can be strongly associated with reduced gene flow between populations, and therefore may promote speciation, even in the absence of other barriers.     

Genetic Variation in the TNF Gene Is Associated with Susceptibility to Severe Sepsis,but Not with Mortality

Background

Tumor necrosis factor (TNF) and TNF receptor superfamily (TNFR)-mediated immune response play an essential role in the pathogenesis of severe sepsis. Studies examining associations of TNF and lymphotoxin-α (LTA) single nucleotide polymorphisms (SNPs) with severe sepsis have produced conflicting results. The objective of this study was to investigate whether genetic variation in TNF, LTA, TNFRSF1A and TNFRSF1B was associated with susceptibility to or death from severe sepsis in Chinese Han population.

Methodology/Principal Findings

Ten SNPs in TNF, LTA, TNFRSF1A and TNFRSF1B were genotyped in samples of patients with severe sepsis (n = 432), sepsis (n = 384) and healthy controls (n = 624). Our results showed that rs1800629, a SNP in the promoter region of TNF, was significantly associated with risk for severe sepsis. The minor allele frequency of rs1800629 was significantly higher in severe sepsis patients than that in both healthy controls (P_adj = 0.00046, odds ratio (OR)_adj = 1.92) and sepsis patients (P_adj = 0.002, OR_adj = 1.56). Further, we investigated the correlation between rs1800629 genotypes and TNF-α concentrations in peripheral blood mononuclear cells (PBMCs) of healthy volunteers exposed to lipopolysaccharides (LPS) ex vivo, and the association between rs1800629 and TNF-α serum levels in severe sepsis patients. After exposure to LPS, the TNF-α concentration in culture supernatants of PBMCs was significantly higher in the subjects with AA+AG genotypes than that with GG genotype (P = 0.007). Moreover, in patients with severe sepsis, individuals with AA+AG genotypes had significantly higher TNF-α serum concentrations than those with GG genotype (P_adj = 0.02). However, there were no significant associations between SNPs in the four candidate genes and 30 day mortality for patients with severe sepsis.

Conclusions/Significance

Our findings suggested that the functional TNF gene SNP rs1800629 was strongly associated with susceptibility to severe sepsis, but not with lethality in Chinese Han population.     

Polymorphic Variation in TIRAP Is Not Associated with Susceptibility to Childhood TB but May Determine Susceptibility to TBM in Some Ethnic Groups

Host recognition of mycobacterial surface molecules occurs through toll like receptors (TLR) 2 and 6. The adaptor protein TIRAP mediates down stream signalling of TLR2 and 4, and polymorphisms in the TIRAP gene (TIRAP) have been associated with susceptibility and resistance to tuberculosis (TB) in adults. In order to investigate the role of polymorphic variation in TIRAP in childhood TB in South Africa, which has one of the highest TB incidence rates in the world, we screened the entire open reading frame of TIRAP for sequence variation in two cohorts of childhood TB from different ethnic groups (Xhosa and mixed ancestry). We identified 13 SNPs, including seven previously unreported, in the two cohorts, and found significant differences in frequency of the variants between the two ethnic groups. No differences in frequency between individual SNPs or combinations were found between TB cases and controls in either cohort. However the 558C→T SNP previously associated with TB meningitis (TBM) in a Vietnamese population was found to be associated with TBM in the mixed ancestry group. Polymorphisms in TIRAP do not appear to be involved in childhood TB susceptibility in South Africa, but may play a role in determining occurrence of TBM.     

Illicit Stimulant Use Is Associated with Abnormal Substantia Nigra Morphology in Humans

Use of illicit stimulants such as methamphetamine, cocaine, and ecstasy is an increasing health problem. Chronic use can cause neurotoxicity in animals and humans but the long-term consequences are not well understood. The aim of the current study was to investigate the long-term effect of stimulant use on the morphology of the human substantia nigra. We hypothesised that history of illicit stimulant use is associated with an abnormally bright and enlarged substantia nigra (termed ‘hyperechogenicity’) when viewed with transcranial sonography. Substantia nigra morphology was assessed in abstinent stimulant users (n = 36; 31±9 yrs) and in two groups of control subjects: non-drug users (n = 29; 24±5 yrs) and cannabis users (n = 12; 25±7 yrs). Substantia nigra morphology was viewed with transcranial sonography and the area of echogenicity at the anatomical site of the substantia nigra was measured at its greatest extent. The area of substantia nigra echogenicity was significantly larger in the stimulant group (0.273±0.078 cm²) than in the control (0.201±0.054 cm²; P<0.001) and cannabis (0.202±0.045 cm²; P<0.007) groups. 53% of stimulant users exhibited echogenicity that exceeded the 90^th percentile for the control group. The results of the current study suggest that individuals with a history of illicit stimulant use exhibit abnormal substantia nigra morphology. Substantia nigra hyperechogenicity is a strong risk factor for developing Parkinson''s disease later in life and further research is required to determine if the observed abnormality in stimulant users is associated with a functional deficit of the nigro-striatal system.     

Muscle Carnosine Is Associated with Cardiometabolic Risk Factors in Humans

BackgroundCarnosine is a naturally present dipeptide abundant in skeletal muscle and an over-the counter food additive. Animal data suggest a role of carnosine supplementation in the prevention and treatment of obesity, insulin resistance, type 2 diabetes and cardiovascular disease but only limited human data exists.ConclusionOur data shows that higher carnosine content in human skeletal muscle is positively associated with insulin resistance and fasting metabolic preference for glucose. Moreover, it is negatively associated with HDL-cholesterol and basal energy expenditure. Intervention studies targeting insulin resistance, metabolic and cardiovascular disease risk factors are necessary to evaluate its putative role in the prevention and management of type 2 diabetes and cardiovascular disease.     

Evidence That Breast Tissue Stiffness Is Associated with Risk of Breast Cancer

Background

Evidence from animal models shows that tissue stiffness increases the invasion and progression of cancers, including mammary cancer. We here use measurements of the volume and the projected area of the compressed breast during mammography to derive estimates of breast tissue stiffness and examine the relationship of stiffness to risk of breast cancer.

Methods

Mammograms were used to measure the volume and projected areas of total and radiologically dense breast tissue in the unaffected breasts of 362 women with newly diagnosed breast cancer (cases) and 656 women of the same age who did not have breast cancer (controls). Measures of breast tissue volume and the projected area of the compressed breast during mammography were used to calculate the deformation of the breast during compression and, with the recorded compression force, to estimate the stiffness of breast tissue. Stiffness was compared in cases and controls, and associations with breast cancer risk examined after adjustment for other risk factors.

Results

After adjustment for percent mammographic density by area measurements, and other risk factors, our estimate of breast tissue stiffness was significantly associated with breast cancer (odds ratio = 1.21, 95% confidence interval = 1.03, 1.43, p = 0.02) and improved breast cancer risk prediction in models with percent mammographic density, by both area and volume measurements.

Conclusion

An estimate of breast tissue stiffness was associated with breast cancer risk and improved risk prediction based on mammographic measures and other risk factors. Stiffness may provide an additional mechanism by which breast tissue composition is associated with risk of breast cancer and merits examination using more direct methods of measurement.     

Variation in Streptococcus pyogenes NAD+ Glycohydrolase Is Associated with Tissue Tropism

Streptococcus pyogenes is an important pathogen that causes a variety of diseases. The most common infections involve the throat (pharyngitis) or skin (impetigo); however, the factors that determine tissue tropism and severity are incompletely understood. The S. pyogenes NAD⁺ glycohydrolase (SPN) is a virulence factor that has been implicated in contributing to the pathogenesis of severe infections. However, the role of SPN in determining the bacterium''s tissue tropism has not been evaluated. In this report, we examine the sequences of spn and its endogenous inhibitor ifs from a worldwide collection of S. pyogenes strains. Analysis of average pairwise nucleotide diversity, average number of nucleotide differences, and ratio of nonsynonymous to synonymous substitutions revealed significant diversity in spn and ifs. Application of established models of molecular evolution shows that SPN is evolving under positive selection and diverging into NAD⁺ glycohydrolase (NADase)-active and -inactive subtypes. Additionally, the NADase-inactive SPN subtypes maintain the characteristics of a functional gene while ifs becomes a pseudogene. Thus, NADase-inactive SPN continues to evolve under functional constraint. Furthermore, NADase activity did not correlate with invasive disease in our collection but was associated with tissue tropism. The ability to cause infection at both the pharynx and the skin (“generalist” strains) is correlated with NADase-active SPN, while the preference for causing infection at either the throat or the skin (“specialist” strains) is associated with NADase-inactive SPN. These findings suggest that SPN has a NADase-independent function and prompt a reevaluation of the role of SPN in streptococcal pathogenesis.Many bacterial pathogens that are capable of causing infection at multiple tissue sites have considerable underlying genetic diversity that is reflected by the presence or absence of different subsets of virulence genes or by the presence of alternative alleles of specific virulence genes (37, 44, 48). For the latter genes, variation in sequence may arise under pressure to avoid the immune response or reflect proteins whose functions are diverging. Horizontal gene transfer (HGT) events can initially increase diversity through the reassortment of these variant virulence genes and may result in altered pathogenicity or the ability to more efficiently exploit a given ecological niche (37). Continued selection of fitter variants adapted for infection of a specific niche can then lead to a subsequent purging of genetic diversity and a reduction in the types of clinical syndromes a particular lineage can cause (8). As a consequence, genetically discrete subpopulations with strong tropisms for different tissues emerge within the existing species, and this process may represent a key step in the formation of new species (6). Understanding the changes that occur during niche specialization can provide important insights into pathogenic mechanisms required for infection of a specific tissue.Analysis of tissue-specific adaptation is emerging as an important approach for understanding the pathogenesis of the numerous diseases caused by Streptococcus pyogenes (group A streptococcus [GAS]). This Gram-positive bacterium has a worldwide distribution and is a pathogen of humans exclusively, causing important diseases, which include those that are destructive of tissue and life-threatening (cellulitis, necrotizing fasciitis) and those associated with deregulation of immunity (glomerulonephritis, rheumatic fever) (6, 12). However, most cases of S. pyogenes disease are more superficial and self-limiting and occur at either the throat (pharyngitis) or the skin (impetigo). These two tissue sites also represent the primary reservoirs responsible for dissemination of the organism to new hosts. A large body of epidemiological evidence that suggests that there are distinct subpopulations of strains more adapted for infection of either the throat or the skin has accumulated, suggesting that specific adaptations to these two tissues are driving the evolution of its pan-genome (6). However, the specific adaptations responsible for niche specialization are not well understood.A frequently used approach for uncovering a common molecular basis behind bacterial phenotype has been to group strains based on sequence variation in housekeeping genes (18). In the case of niche specialization, continued selection for variants more highly adapted to a particular tissue will purge neutral gene diversity in the adapted population relative to the population as a whole. However, a complication in deciphering trends associated with tissue adaptation in S. pyogenes has been that despite some niche separation, there are high rates of recombination relative to mutation within the species as a whole, on par with that of Streptococcus pneumoniae, a species considered to be highly recombinogenic (6, 22, 57). Frequent recombination has resulted in a random segregation of neutral housekeeping haplotypes between S. pyogenes strains from ecologically distinct subpopulations (6). Thus, standard approaches to establishing relationships between strains have been of only limited utility for understanding niche adaptation for S. pyogenes.A more productive approach for S. pyogenes has been to look for genetic variation outside neutral housekeeping genes that is strongly associated with ecological niche. In this regard, genotypes based on the gene encoding the M protein (emm) provide a significant correlation with tissue tropism (6). The M protein is a fibrillar surface molecule that plays multiple roles in promoting virulence, and serological typing based on M protein diversity has been the traditional method for classifying S. pyogenes strains (35). It is well established that strains with certain M types have a strong preference for infection at either the throat or the skin (9, 40). There are more than 200 known M types (50), which can be divided into 4 major subfamilies based on the sequence of the peptidoglycan-spanning domain at the 3′ end of emm (25). Furthermore, the emm locus can encode one gene or a combination of subfamily genes in a tandem arrangement (7). Analyses of large strain collections have revealed that in ∼99% of strains, the organization of emm genes in the locus can be assigned to one of five patterns (designated A to E) (6). Although strains with each emm pattern may colonize the same tissue types, there is a strong correlation between emm pattern and the ability of the organism to cause disease at specific tissue sites. Strains with emm patterns A to C generally cause pharyngitis; emm pattern D strains are typically the cause of skin diseases, such as impetigo; and emm pattern E strains are “generalists,” which can cause symptomatic infection at either tissue site at approximately equal fractions of the total (6). Since emm pattern is strongly associated with tissue tropism, it is likely that characteristics consistently coinherited with the emm pattern also play a role in determining the tissue tropism of the organism (6, 29).The S. pyogenes NAD⁺ glycohydrolase (SPN, also known as Nga) is a virulence factor with characteristics that merit evaluation for a possible role in tissue tropism. This secreted toxin has an enzymatic activity (NADase) that cleaves the glycosidic bond of β-NAD⁺ to produce nicotinamide and ADP-ribose. All S. pyogenes strains examined to date possess the gene that encodes SPN (spn), but some strains produce a SPN that lacks detectable NADase activity (1, 30, 36, 42). Since there is evidence that SPN′s robust NADase activity contributes to virulence (4, 43, 52, 56), the existence of NADase-deficient SPN has yet to be explained. Epidemiological studies conducted on several limited strain collections have not been informative, as these studies have both found (1, 52) and failed to find (15) an association between NADase activity and whether a lineage has the capacity to cause invasive disease. Whether or not SPN is associated with tissue tropism is not known.SPN also has multiple complex interactions with other proteins that suggest it has an important, yet incompletely understood role in disease pathogenesis. These interactions also imply that SPN is under considerable coevolutionary pressure with its partners (47). For example, the ability of S. pyogenes to produce NADase-active SPN is absolutely dependent on the presence of an endogenous inhibitor protein, immunity factor for SPN (IFS) (31, 42). IFS is a competitive inhibitor of SPN′s β-NAD⁺ substrate and apparently acts to inhibit self-toxicity resulting from any presecretory SPN molecules that adventitiously fold prior to their export from the streptococcal cell. In the absence of IFS, SPN is lethal for S. pyogenes. Interestingly, strains that produce NADase-inactive SPN also have a truncated form of IFS (42). Once secreted, both NADase-active SPN and NADase-inactive SPN are injected into the host cell cytoplasm by a process known as cytolysin-mediated translocation (CMT), which requires interaction between multiple domains of SPN and the pore-forming cytolysin streptolysin O (SLO) (11, 20, 39, 41). When in the cytoplasmic compartment, NADase-active SPN can trigger rapid cell death, which is associated with depletion of β-NAD⁺ pools (10, 11, 39). The genes for SPN (spn), IFS (ifs), and SLO (slo) are encoded in the same operon (31, 42), as is typical of coevolving virulence factor/inhibitor pairs (47). Thus, SPN has multiple complex interactions and is suspected of being important in pathogenesis; however, there is a considerable amount of genetic and functional variation that has yet to be fully defined.In the present study, we sought to clarify the role of SPN in the infectious process through analysis of the genetic diversity in spn and ifs and the relationship this diversity has with disease severity and ecologic niche. By examining a diverse, worldwide collection of S. pyogenes strains, we identify the SPN domains evolving under positive (diversifying) and negative (purifying) selection, correlate these sites with NADase activity, and demonstrate that NADase activity is associated with tissue tropism but not invasiveness of disease.     

Genetic Variation in the 3'-Untranslated Region of NBN Gene Is Associated with Gastric Cancer Risk in a Chinese Population

NBN plays a crucial role in carcinogenesis as a core component for both homologous recombination (HR) and non-homologous end-joining (NHEJ) DNA double-strand breaks (DSBs) repair pathways. Genetic variants in the NBN gene have been associated with multiple cancers risk, suggesting pleiotropic effect on cancer. We hypothesized that genetic variants in the NBN gene may modify the risk of gastric cancer. To test this hypothesis, we evaluated the association between four potentially functional single nucleotide polymorphisms in NBN and gastric cancer risk in a case–control study of 1,140 gastric cancer cases and 1,547 controls in a Chinese population. We found that the A allele of rs10464867 (G>A) was significantly associated with a decreased risk of gastric cancer (odds ratio [OR] = 0.81, 95% confidence interval [95% CI] = 0.71–0.94; P = 4.71×10⁻³). Furthermore, the association between A allele of rs10464867 and decreased risk of gastric cancer was more significantly in elder individuals (per-allele OR = 0.72[0.59–0.88], P = 1.07×10⁻³), and male individuals (per-allele OR = 0.73[0.62–0.87], P = 3.68×10⁻⁴). We further conducted a haplotype analysis and identified that the NBN A_rs10464867G_rs14448G_rs1063053 haplotype conferred stronger protective effect on gastric cancer (OR = 0.76[0.65–0.89], P = 6.39×10⁻⁴). In summary, these findings indicate that genetic variants at NBN gene may contribute to gastric cancer susceptibility and may further advance our understanding of NBN gene in cancer development.     

Genetic Variation in SULF2 Is Associated with Postprandial Clearance of Triglyceride-Rich Remnant Particles and Triglyceride Levels in Healthy Subjects

Context

Nonfasting (postprandial) triglyceride concentrations have emerged as a clinically significant cardiovascular disease risk factor that results from accumulation of remnant triglyceride-rich lipoproteins (TRLs) in the circulation. The remnant TRLs are cleared from the circulation by hepatic uptake, but the specific mechanisms involved are unclear. The syndecan-1 heparan sulfate proteoglycan (HSPG) pathway is important for the hepatic clearance of remnant TRLs in mice, but its relevance in humans is unclear.

Objective

We sought to determine whether polymorphisms of the genes responsible for HSPG assembly and disassembly contribute to atherogenic dyslipoproteinemias in humans.

Patients And Design

We performed an oral fat load in 68 healthy subjects. Lipoproteins (chylomicrons and very low density lipoproteins 1 and 2) were isolated from blood, and the area under curve and incremental area under curve for postprandial variables were calculated. Single nucleotide polymorphisms in genes encoding syndecan-1 and enzymes involved in the synthesis or degradation of HSPG were genotyped in the study subjects.

Results

Our results indicate that the genetic variation rs2281279 in SULF2 associates with postprandial clearance of remnant TRLs and triglyceride levels in healthy subjects. Furthermore, the SNP rs2281279 in SULF2 associates with hepatic SULF2 mRNA levels.

Conclusions

In humans, mild but clinically relevant postprandial hyperlipidemia due to reduced hepatic clearance of remnant TRLs may result from genetic polymorphisms that affect hepatic HSPG.     

Factors That Influence Microbial Contamination of Fluids Associated with Hemodialysis Machines

Studies were conducted on the microbiological quality of fluids associated with different types of dialysis systems located in six dialysis centers and 14 homes. Included were (i) single-pass systems employing either parallel flow (Kiil or Gambro) or capillary cartridge dialyzers and (ii) recirculating single-pass and batch recirculating systems using coil dialyzers. Microbiological assays were performed on the water used to prepare dialysis fluid, the concentrated dialysate, and either pre- and postdialyzer dialysate (single-pass systems) or the dialysate contained in storage reservoirs and recirculating cannisters (recirculating systems). The levels of microbial contamination consisting of gram-negative bacteria were directly related to the type of dialysis system, method of water treatment, distribution system, and in some instances, the type of dialyzer. Recirculating single-pass and batch recirculating systems consistently contained significantly higher levels of contamination than single-pass systems. These results were directly related to the design of recirculating systems which permits carbon- and nitrogen-containing waste products dialyzed from the patient to accumulate, be used as nutrients by microorganisms, and subsequently allow for 2- to 4-log increases in contamination levels during a dialysis treatment. In contrast, levels of contamination in single-pass machines were related more to the quality of the water used to prepare dialysis fluid and the adequacy of cleaning and disinfection procedures than to the design of the system.     

Analysis of Factors That Determine Weight Gain during Smoking Cessation Therapy

Cigarette smokers are generally known to gain weight after quitting smoking, and such weight gain is thought to contribute to the worsening of glucose tolerance. While smoking cessation therapy such as nicotine replacement is useful to minimize post-cessation weight gain, substantial gain occurs even during the therapy. The purpose of the present study was to identify factors associated with weight gain during smoking cessation therapy. We evaluated 186 patients(132 males and 54 females)who visited our outpatient clinic for smoking cessation, and successfully achieved smoking abstinence. We performed gender-adjusted regression analysis for the rate of BMI increase from the beginning of cessation to 3 months after initiation. Furthermore, we performed multivariate analysis to investigate factors that determine the BMI increase after smoking cessation. The mean BMI significantly (p<0.0001) increased from 23.5±3.6 kg/m² at the initial consultation to 23.9±3.8 kg/m² at 3 months after the start of therapy. There was no significant difference in the extent of BMI increase between nicotine patch and varenicline therapy groups. Factors significantly correlated with the %BMI increase at 3 months after the start of therapy were triglyceride (p = 0.0006, βa = 0.260), high-density lipoprotein cholesterol (p = 0.0386, βa = −0.168), daily cigarette consumption (p = 0.0385, βa = 0.154), and the Fagerström Test for Nicotine Dependence (FTND) score (p = 0.0060, βa = 0.203). Stepwise multivariate analysis demonstrated that triglyceride and the FTND score were the factors determining the post-cessation BMI increase and that the FTND score was the strongest one. The present study demonstrated that smokers with a high FTND score are more likely to gain weight during smoking cessation therapy. Thus, smokers with a high nicotine dependency may require intervention against weight gain in the cessation clinic.     

Extracellular Tau Levels Are Influenced by Variability in Tau That Is Associated with Tauopathies

Tauopathies are a class of neurodegenerative diseases marked by intracellular aggregates of hyperphosphorylated Tau. These diseases may occur by sporadic mechanisms in which genetic variants represent risk factors for disease, as is the case in Alzheimer disease (AD). In AD, cerebrospinal fluid (CSF) levels of soluble Tau/pTau-181 are higher in cases compared with controls. A subset of frontotemporal dementia (FTD) cases occur by a familial mechanism in which MAPT, the gene that encodes Tau, mutations are dominantly inherited. In symptomatic FTD patients expressing a MAPT mutation, CSF Tau levels are slightly elevated but are significantly lower than in AD patients. We sought to model CSF Tau changes by measuring extracellular Tau in cultured cells. Full-length, monomeric extracellular total Tau and pTau-181 were detectable in human neuroblastoma cells expressing endogenous Tau, in human non-neuronal cells overexpressing wild-type Tau, and in mouse cortical neurons. Tau isoforms influence the rate of Tau release, whereby the N terminus (exons 2/3) and microtubule binding repeat length contribute to Tau release from the cell. Compared with cells overexpressing wild-type Tau, cells overexpressing FTD-associated MAPT mutations produce significantly less extracellular total Tau without altering intracellular total Tau levels. This study demonstrates that cells actively release Tau in the absence of disease or toxicity, and Tau release is modified by changes in the Tau protein that are associated with tauopathies.     

Common Genetic Variation Near the Phospholamban Gene Is Associated with Cardiac Repolarisation: Meta-Analysis of Three Genome-Wide Association Studies

To identify loci affecting the electrocardiographic QT interval, a measure of cardiac repolarisation associated with risk of ventricular arrhythmias and sudden cardiac death, we conducted a meta-analysis of three genome-wide association studies (GWAS) including 3,558 subjects from the TwinsUK and BRIGHT cohorts in the UK and the DCCT/EDIC cohort from North America. Five loci were significantly associated with QT interval at P<1×10⁻⁶. To validate these findings we performed an in silico comparison with data from two QT consortia: QTSCD (n = 15,842) and QTGEN (n = 13,685). Analysis confirmed the association between common variants near NOS1AP (P = 1.4×10⁻⁸³) and the phospholamban (PLN) gene (P = 1.9×10⁻²⁹). The most associated SNP near NOS1AP (rs12143842) explains 0.82% variance; the SNP near PLN (rs11153730) explains 0.74% variance of QT interval duration. We found no evidence for interaction between these two SNPs (P = 0.99). PLN is a key regulator of cardiac diastolic function and is involved in regulating intracellular calcium cycling, it has only recently been identified as a susceptibility locus for QT interval. These data offer further mechanistic insights into genetic influence on the QT interval which may predispose to life threatening arrhythmias and sudden cardiac death.