Publications

Ceramic components for microelectromechanical (MEMS) systems, for example the micrometer-sized gear made from SiBNC shown in the Figure, offer the opportunity to extend MEMS technology towards high-temperature and oxidizing-environment applications, such as microturbines and high-temperature sensors and actuators. Preceramic polymers are used in conjunction with soft lithography and subsequent pyrolysis to produce the high aspect ratio structures.

We have used an atomic-force microscope tip to mechanically buckle single-walled carbon nanotubes. The resistance of the induced defects ranged from 10 to 100 kΩ and varied with the local Fermi level, as determined by scanned-gate microscopy. By forming two closely spaced defects on metallic nanotubes, we defined quantum dots less than 100 nm in length. These devices exhibited single-electron charging behavior at temperatures up to ∼165 K.

Substantial progress has been made in identification of type 2 diabetes (T2D) risk loci in the past few years, but our understanding of the genetic basis of T2D in ethnically diverse populations remains limited. We performed a genome-wide association study and a replication study in Chinese Hans comprising 8,569 T2D case subjects and 8,923 control subjects in total, from which 10 single nucleotide polymorphisms were selected for further follow-up in a de novo replication sample of 3,410 T2D case and 3,412 control subjects and an in silico replication sample of 6,952 T2D case and 11,865 control subjects. Besides confirming seven established T2D loci (CDKAL1, CDKN2A/B, KCNQ1, CDC123, GLIS3, HNF1B, and DUSP9) at genome-wide significance, we identified two novel T2D loci, including G-protein–coupled receptor kinase 5 (GRK5) (rs10886471: P = 7.1 × 10−9) and RASGRP1 (rs7403531: P = 3.9 × 10−9), of which the association signal at GRK5 seems to be specific to East Asians. In nondiabetic individuals, the T2D risk-increasing allele of RASGRP1-rs7403531 was also associated with higher HbA1c and lower homeostasis model assessment of β-cell function (P = 0.03 and 0.0209, respectively), whereas the T2D risk-increasing allele of GRK5-rs10886471 was also associated with higher fasting insulin (P = 0.0169) but not with fasting glucose. Our findings not only provide new insights into the pathophysiology of T2D, but may also shed light on the ethnic differences in T2D susceptibility.

Introduction The aim of the study was to determine the association of body mass index (BMI), self-reported symptoms or diagnosis of polycystic ovary syndrome (PCOS), and hyperandrogenemia with the occurrence of gestational diabetes mellitus (GDM) through reproductive life. Material and methods A cohort of women born in 1966 were investigated at ages 14, 31 and 46. Women with self-reported PCOS symptoms (presence of both oligo-amenorrhea and hirsutism) at age 31 or with formally diagnosed polycystic ovaries (PCO)/PCOS by age 46 formed the group of self-reported PCOS (srPCOS, n = 222) and were compared with women without self-reported PCOS symptoms or diagnosis (n = 1357). We investigated also the association of hyperandrogenism (hirsutism or biochemical hyperandrogenism) at age 31 with the occurrence of GDM throughout reproductive life. Results Self-reported PCOS alone was not a risk factor for GDM, but combined with overweight at age 31 (odds ratio [OR] 2.43, 95% confidence interval [CI] 1.22-4.86) or 46 (OR 3.04, 95% CI 1.58-5.83) srPCOS was associated with GDM when compared with normal weight controls. The association disappeared when comparing overweight srPCOS women with overweight controls. However, hyperandrogenemia at age 31, but not hirsutism, was associated with GDM even after adjustment for BMI. Conclusions The increased risk of GDM in women with srPCOS was mostly attributed to overweight or obesity. Importantly, normal weight women with srPCOS did not seem to be at increased risk for developing GDM. However, hyperandrogenemia was associated with GDM even after adjustment for BMI. These findings strengthen the importance of weight management in reproductive-age women and suggest a noteworthy role of hyperandrogenemia in the pathophysiology of GDM.

Abstract Background Urinary metabolomics has demonstrated considerable potential to assess kidney function and its metabolic corollaries in health and disease. However, applications in epidemiology remain sparse due to technical challenges. Methods We added 17 metabolites to an open-access urinary nuclear magnetic resonance metabolomics platform, extending the panel to 61 metabolites (n = 994). We also introduced automated quantification for 11 metabolites, extending the panel to 12 metabolites (+creatinine). Epidemiological associations between these 12 metabolites and 49 clinical measures were studied in three independent cohorts (up to 5989 participants). Detailed regression analyses with various confounding factors are presented for body mass index (BMI) and smoking. Results Sex-specific population reference concentrations and distributions are provided for 61 urinary metabolites (419 men and 575 women), together with methodological intra-assay metabolite variations as well as the biological intra-individual and epidemiological population variations. For the 12 metabolites, 362 associations were found. These are mostly novel and reflect potential molecular proxies to estimate kidney function, as the associations cannot be simply explained by estimated glomerular filtration rate. Unspecific renal excretion results in leakage of amino acids (and glucose) to urine in all individuals. Seven urinary metabolites associated with smoking, providing questionnaire-independent proxy measures of smoking status in epidemiological studies. Common confounders did not affect metabolite associations with smoking, but insulin had a clear effect on most associations with BMI, including strong effects on 2-hydroxyisobutyrate, valine, alanine, trigonelline and hippurate. Conclusions Urinary metabolomics provides new insight on kidney function and related biomarkers on the renal-cardiometabolic system, supporting large-scale applications in epidemiology.

Genome-wide association studies (GWAS) have revealed 74 single nucleotide polymorphisms (SNPs) associated with high-density lipoprotein cholesterol (HDL) blood levels. This study is, to our knowledge, the first genome-wide interaction study (GWIS) to identify SNP×SNP interactions associated with HDL levels. We performed a GWIS in the Rotterdam Study (RS) cohort I (RS-I) using the GLIDE tool which leverages the massively parallel computing power of Graphics Processing Units (GPUs) to perform linear regression on all genome-wide pairs of SNPs. By performing a meta-analysis together with Rotterdam Study cohorts II and III (RS-II and RS-III), we were able to filter 181 interaction terms with a p-value<1 · 10−8 that replicated in the two independent cohorts. We were not able to replicate any of these interaction term in the AGES, ARIC, CHS, ERF, FHS and NFBC-66 cohorts (Ntotal = 30,011) when adjusting for multiple testing. Our GWIS resulted in the consistent finding of a possible interaction between rs774801 in ARMC8 (ENSG00000114098) and rs12442098 in SPATA8 (ENSG00000185594) being associated with HDL levels. However, p-values do not reach the preset Bonferroni correction of the p-values. Our study suggest that even for highly genetically determined traits such as HDL the sample sizes needed to detect SNP×SNP interactions are large and the 2-step filtering approaches do not yield a solution. Here we present our analysis plan and our reservations concerning GWIS.

To dissect the genetic architecture of blood pressure and assess effects on target-organ damage, we analyzed 128,272 SNPs from targeted and genome-wide arrays in 201,529 individuals of European ancestry and genotypes from an additional 140,886 individuals were used for validation. We identified 66 blood pressure loci, of which 17 were novel and 15 harbored multiple distinct association signals. The 66 index SNPs were enriched for cis-regulatory elements, particularly in vascular endothelial cells, consistent with a primary role in blood pressure control through modulation of vascular tone across multiple tissues. The 66 index SNPs combined in a risk score showed comparable effects in 64,421 individuals of non-European descent. The 66-SNP blood pressure risk score was significantly associated with target-organ damage in multiple tissues, with minor effects in the kidney. Our findings expand current knowledge of blood pressure pathways and highlight tissues beyond the classic renal system in blood pressure regulation.

A convenient experimental system is described, with which electron transport through structurally well-defined, 2-5 nm-thick, organic films can be examined. Two types of junction J have been studied in which self-assembled monolayers (SAMs, for example, SAM(1) formed on Ag from aliphatic and aromatic thiols, and SAM(2), formed on Hg from hexadecanethiol) are in contact through either van der Waals interactions or through covalent, hydrogen, or ionic bonds.