A Decreased Level of Serum Soluble Klotho Is an Independent Biomarker Associated with Arterial Stiffness in Patients with Chronic Kidney Disease

Background

Klotho was originally identified in a mutant mouse strain unable to express the gene that consequently showed shortened life spans. In humans, low serum Klotho levels are related to the prevalence of cardiovascular diseases in community-dwelling adults. However, it is unclear whether the serum Klotho levels are associated with signs of vascular dysfunction such as arterial stiffness, a major determinant of prognosis, in human subjects with chronic kidney disease (CKD).

Methods

We determined the levels of serum soluble Klotho in 114 patients with CKD using ELISA and investigated the relationship between the level of Klotho and markers of CKD-mineral and bone disorder (CKD-MBD) and various types of vascular dysfunction, including flow-mediated dilatation, a marker of endothelial dysfunction, ankle-brachial pulse wave velocity (baPWV), a marker of arterial stiffness, intima-media thickness (IMT), a marker of atherosclerosis, and the aortic calcification index (ACI), a marker of vascular calcification.

Results

The serum Klotho level significantly correlated with the 1,25-dihydroxyvitamin D level and inversely correlated with the parathyroid hormone level and the fractional excretion of phosphate. There were significant decreases in serum Klotho in patients with arterial stiffness defined as baPWV≥1400 cm/sec, atherosclerosis defined as maximum IMT≥1.1 mm and vascular calcification scores of ACI>0%. The serum Klotho level was a significant determinant of arterial stiffness, but not endothelial dysfunction, atherosclerosis or vascular calcification, in the multivariate analysis in either metabolic model, the CKD model or the CKD-MBD model. The adjusted odds ratio of serum Klotho for the baPWV was 0.60 (p = 0.0075).

Conclusions

Decreases in the serum soluble Klotho levels are independently associated with signs of vascular dysfunction such as arterial stiffness in patients with CKD. Further research exploring whether therapeutic approaches to maintain or elevate the Klotho level could improve arterial stiffness in CKD patients is warranted.     

Comparison of Barium and Arsenic Concentrations in Well Drinking Water and in Human Body Samples and a Novel Remediation System for These Elements in Well Drinking Water

Health risk for well drinking water is a worldwide problem. Our recent studies showed increased toxicity by exposure to barium alone (≤700 µg/L) and coexposure to barium (137 µg/L) and arsenic (225 µg/L). The present edition of WHO health-based guidelines for drinking water revised in 2011 has maintained the values of arsenic (10 µg/L) and barium (700 µg/L), but not elements such as manganese, iron and zinc. Nevertheless, there have been very few studies on barium in drinking water and human samples. This study showed significant correlations between levels of arsenic and barium, but not its homologous elements (magnesium, calcium and strontium), in urine, toenail and hair samples obtained from residents of Jessore, Bangladesh. Significant correlation between levels of arsenic and barium in well drinking water and levels in human urine, toenail and hair samples were also observed. Based on these results, a high-performance and low-cost adsorbent composed of a hydrotalcite-like compound for barium and arsenic was developed. The adsorbent reduced levels of barium and arsenic from well water in Bangladesh and Vietnam to <7 µg/L within 1 min. Thus, we have showed levels of arsenic and barium in humans and propose a novel remediation system.     

An In Vitro ES Cell-Based Clock Recapitulation Assay Model Identifies CK2α as an Endogenous Clock Regulator

We previously reported emergence and disappearance of circadian molecular oscillations during differentiation of mouse embryonic stem (ES) cells and reprogramming of differentiated cells, respectively. Here we present a robust and stringent in vitro circadian clock formation assay that recapitulates in vivo circadian phenotypes. This assay system first confirmed that a mutant ES cell line lacking Casein Kinase I delta (CKIδ) induced ∼3 hours longer period-length of circadian rhythm than the wild type, which was compatible with recently reported results using CKIδ null mice. In addition, this assay system also revealed that a Casein Kinase 2 alpha subunit (CK2α) homozygous mutant ES cell line developed significantly longer (about 2.5 hours) periods of circadian clock oscillations after in vitro or in vivo differentiation. Moreover, revertant ES cell lines in which mutagenic vector sequences were deleted showed nearly wild type periods after differentiation, indicating that the abnormal circadian period of the mutant ES cell line originated from the mutation in the CK2α gene. Since CK2α deficient mice are embryonic lethal, this in vitro assay system represents the genetic evidence showing an essential role of CK2α in the mammalian circadian clock. This assay was successfully applied for the phenotype analysis of homozygous mutant ES cells, demonstrating that an ES cell-based in vitro assay is available for circadian genetic screening.     

Detection of Spiroplasma from the mite Macrocheles sp. (Acari; Macrochelidae) ectoparasitic to the fly Drosophila hydei (Diptera; Drosophilidae): a possible route of horizontal transmission?

Some members of the genus Spiroplasma are vertically transmitted endosymbionts of insects. Among them, Spiroplasma sp. Dhd, a member of the Spiroplasma poulsonii clade, is highly prevalent among worldwide populations of Drosophila hydei. Here we found that 53 out of 3,763 wild-caught D. hydei (1.4 %) were ectoparasitized by the mite that belong to the genus Macrocheles. Many of the ectoparasitized flies (79 %) had a single mite, but some flies had up to five mites. Among 59 mites subjected to Spiroplasma-specific PCR, 15 individuals were found to be positive. Infection status of Spiroplasma in flies and the associated mites were incongruent. Partial nucleotide sequences of the Spiroplasma P58 gene suggest that some of the mites are infected with a Spiroplasma, which is identical or closely related to Spiroplasma sp. Dhd. This finding provides a potential route of horizontal Spiroplasma transmission between D. hydei individuals in natural populations. In addition, a Spiroplasma strain that does not form a monophyletic group with S. poulsonii was also found from a mite individual.     

Molecular dynamics simulation of diffusion of hydrogen in binary hydrogen–tetrahydrofuran hydrate

The binary structure II hydrogen–tetrahydrofuran (THF) hydrate was studied with molecular dynamics simulation. The simulations were carried out at 300, 310 K and 10.1 MPa, and with various contents of hydrogen and THF. The migrations of hydrogen molecules from cage to cage were observed. The migration process of hydrogen was also analysed, and the diffusion coefficients of hydrogen in the hydrate were calculated. The calculated diffusion coefficients qualitatively agreed with the experimental data. Double and quintet occupancies of hydrogen molecules were observed in the small and large cages, respectively, without changing the hydrate structure.     

Emergence of gp120 V3 Variants Confers Neutralization Resistance in an R5 Simian-Human Immunodeficiency Virus-Infected Macaque Elite Neutralizer That Targets the N332 Glycan of the Human Immunodeficiency Virus Type 1 Envelope Glycoprotein

Neutralization-resistant simian-human immunodeficiency virus AD8 (SHIV_AD8) variants that emerged in an infected macaque elite neutralizer targeting the human immunodeficiency virus type 1 (HIV-1) gp120 N332 glycan acquired substitutions of critical amino acids in the V3 region rather than losing the N332 glycosylation site. One of these resistant variants, carrying the full complement of gp120 V3 changes, was also resistant to the potent anti-HIV-1 monoclonal neutralizing antibodies PGT121 and 10-1074, both of which are also dependent on the presence of the gp120 N332 glycan.     

Structural Basis for the Different Stability and Activity between the Cdk5 Complexes with p35 and p39 Activators

Cyclin-dependent kinase 5 (Cdk5) is a brain-specific membrane-bound protein kinase that is activated by binding to the p35 or p39 activator. Previous studies have focused on p35-Cdk5, and little is known regarding p39-Cdk5. The lack of functional understanding of p39-Cdk5 is due, in part, to the labile property of p39-Cdk5, which dissociates and loses kinase activity in nonionic detergent conditions. Here we investigated the structural basis for the instability of p39-Cdk5. p39 and p35 contain N-terminal p10 regions and C-terminal Cdk5 activation domains (AD). Although p35 and p39 show higher homology in the C-terminal AD than the N-terminal region, the difference in stability is derived from the C-terminal AD. Based on the crystal structures of the p25 (p35 C-terminal region including AD)-Cdk5 complex, we simulated the three-dimensional structure of the p39 AD-Cdk5 complex and found differences in the hydrogen bond network between Cdk5 and its activators. Three amino acids of p35, Asp-259, Asn-266, and Ser-270, which are involved in hydrogen bond formation with Cdk5, are changed to Gln, Gln, and Pro in p39. Because these three amino acids in p39 do not participate in hydrogen bond formation, we predicted that the number of hydrogen bonds between p39 and Cdk5 was reduced compared with p35 and Cdk5. Using substitution mutants, we experimentally validated that the difference in the hydrogen bond network contributes to the different properties between Cdk5 and its activators.