Spin-resolved mapping of spin contribution to exchange-correlation holes

By means of spin-polarized electron coincidence spectroscopy we explore the fundamental issue of spin-resolved contributions to the exchange-correlation hole in many-electron systems. We present a joint experimental and theoretical study of correlated electron pair emission from a ferromagnetic Fe(001) surface induced by spin-polarized low-energy electrons. We demonstrate that the contribution to the exchange-correlation hole due to exchange is more extended than the contribution due to the screened Coulomb interaction.

Early infant diet in children at high risk for type 1 diabetes

Infant diet affects health and development. The aim of our study was to investigate WHO infant feeding compliance in children who have a first degree family history of type 1 diabetes (T1D). One hundred and fifty children who were first degree relatives of patients with T1D were intensively followed from birth in the BABYDIET intervention study. Infant feeding, infections, and medication were recorded daily by participating families. Weight and length of children were obtained from paediatric records. Only 5% of the families followed the WHO recommendations for infant feeding that include full breastfeeding for at least 6 months (18.8% of children) and introduction of complementary foods under continued breastfeeding thereafter (22.2% of children). Maternal age in the first quartile (<29 years; p<0.0001), and maternal smoking (p<0.0001) were associated with an earlier introduction of solid food and reduced breastfeeding. Full breastfeeding > or =6 months was associated with reduced frequency of gastrointestinal infections (12 vs. 38%, p=0.02) and antibiotic treatment (24 vs. 48%, p=0.04). Our findings indicate that WHO infant feeding recommendations were poorly followed by families with a family history of T1D. Action to improve levels of infant feeding behaviour is essential, especially among young mothers with T1D.

Is islet autoimmunity related to insulin sensitivity or body weight in children of parents with type 1 diabetes?

AIMS/HYPOTHESIS

It has been suggested that metabolic demand and insulin resistance play a role in the development of type 1 diabetes, including the onset of autoimmunity. The aim of the present study was to determine whether insulin demand is increased in children with islet autoantibodies.

METHODS

BMI standard deviation score (BMI-SDS) was measured from 2 years of age in 1,650 prospectively followed children of mothers or fathers with type 1 diabetes, including 135 who developed persistent islet autoantibodies. HOMA of insulin resistance (HOMA-IR) was determined using fasting samples from 777 of the children starting from age 5 years.

RESULTS

An increased HOMA-IR was associated with female sex (p = 0.0004), older age (p < 0.0001) and increased BMI-SDS (p < 0.0001). Children with islet autoantibodies did not have an increased HOMA-IR compared with age-matched islet autoantibody-negative children (age 8 years: mean 0.61 vs mean 0.72, respectively, p = 0.21; age 11 years: mean 0.96 vs mean 1.21, respectively, p = 0.07). Furthermore, after correction for age and sex, autoantibody positivity was associated with decreased HOMA-IR values (p = 0.01). BMI-SDS was similar between islet autoantibody-positive and -negative children at age 2 (mean 0.07 vs mean 0.16, respectively), 5 (mean 0.06 vs 0.08, respectively), 8 (mean - 0.09 vs mean 0.02, respectively), and 11 years (mean 0.22 vs mean 0.16, respectively) and similar to that of national reference values.

CONCLUSIONS/INTERPRETATION

Islet autoantibody-positive children in the BABYDIAB cohort are not insulin resistant and do not have an increased BMI around and early after islet autoantibody seroconversion. These findings are inconsistent with the notion that insulin resistance is a risk factor for islet autoimmunity.

Electron pair emission from a W(001) surface: photon versus electron excitation

The electron pair emission from a W(001) surface was studied using a coincidence time-of-flight spectrometer. The aim of this study was to compare the pair emission upon electron impact and upon photon absorption. The energy distributions are markedly different for these two experiments. From this we conclude that the photon-stimulated pair emission carries a significant contribution from a double photoemission process, while the process of first creating a photoelectron, which in a subsequent collision leads to pair emission, is of less importance.

Autoantibodies to zinc transporter 8 and SLC30A8 genotype stratify type 1 diabetes risk

AIMS/HYPOTHESIS

Our aim was to determine the relationships between autoantibodies to zinc transporter 8 (ZnT8), genotypes of the ZnT8-encoding gene SLC30A8 and type 1 diabetes risk.

METHODS

ZnT8 autoantibodies (ZnT8A) were measured in sera of 1,633 children with a first-degree family history of type 1 diabetes and who were prospectively followed from birth. Antibodies were measured by Protein A-based radiobinding assays and COOH-terminal (R325, W325 or Q325 variants) or NH(2)-terminal constructs of human ZnT8. SLC30A8 genotyping at single-nucleotide polymorphism (SNP) rs13266634 was performed on 1,170 children.

RESULTS

Antibodies against COOH-terminal ZnT8 constructs (ZnT8A-COOH) developed in 58 children as early as 9 months of age (median 3 years). They were detected in 55 of 128 (43%) children with autoantibodies to insulin, GAD and/or insulinoma-associated protein 2 and 34 of 42 (81%) who progressed to diabetes. The additional presence of ZnT8A-COOH stratified diabetes risk in islet autoantibody-positive children (p < 0.0001). SLC30A8 genotype strongly influenced ZnT8A type and diabetes risk in ZnT8A-COOH-positive children. Antibody binding against the ZnT8 R325 variant was strictly correlated with the number of the corresponding SLC30A8 R325-encoding alleles, whereas binding against the W325 variant was highest in children who had SLC30A8 W325-encoding alleles (p = 0.001). Moreover, ZnT8A-COOH-positive children who carried homozygous SLC30A8 SNP rs13266634 genotypes progressed faster to diabetes than those who were heterozygous (59% [95% CI 42.3-75.7%] vs 22% [95% CI 0-44.3%] within 5 years; p = 0.01).

CONCLUSIONS/INTERPRETATION

Autoimmunity against the COOH-terminal region of ZnT8 is a highly relevant prognostic feature in childhood type 1 diabetes. Risk stratification in ZnT8A-COOH-positive children is further improved by SLC30A8 genotyping.

Quality of life and immune activation in patients with HIV-infection

Depression and impaired quality of life (QoL) are frequently observed in patients suffering from HIV-infection. As an enhanced degradation of the serotonin precursor tryptophan is well documented in HIV-infected patients, disturbances in tryptophan metabolism may be causally linked to HIV-related depression. In this study, the relationship between QoL, depression, various laboratory parameters and tryptophan metabolism was investigated. To estimate QoL and mood, 152 HIV-infected patients (classified according to CDC-criteria) were requested to complete the following psychological questionnaires: BDI and MQoL-HIV. Disease progression was monitored by determination of viral load (VL), CD4(+) cell counts, haemoglobin and urinary/plasma neopterin, tryptophan and kynurenine concentrations. Increasing VL, decreasing CD4(+) cell counts, and enhanced tryptophan degradation reflected disease progression. Forty-one patients presented with mild, 22 with moderate and 14 with severe depression. BDI and MQoL scores were associated strongly with each other (rs=-0.838; p<0.001). Patients without depression had significantly lower plasma neopterin concentrations, higher CD4(+) cell counts and haemoglobin concentrations and better QoL scores (all p<0.01) than depressive patients. Furthermore, they showed lower rates of tryptophan degradation (p<0.05). Significant associations were observed between tryptophan degradation and immune activation. Haemoglobin and viral load were predictive for impaired QoL, while high urinary neopterin concentrations and low haemoglobin were the best predictors for depression. In HIV-infected patients, depressive mood and impaired QoL appear to be related to clinical parameters like immune activation, haemoglobin values and viral load.

Exposure to environmental factors in drinking water: risk of islet autoimmunity and type 1 diabetes--the BABYDIAB study

Type 1 diabetes (T1D) is characterized by autoimmunity against pancreatic islets, and autoantibodies may be present for years before diagnosis. Environmental factors during early life, including drinking water, may play a role in pathogenesis of T1D. The German BABYDIAB study is a prospective observational study that followed newborn offspring of mothers or fathers with T1D from birth to 17 years of age. The present study was a nested case-control analysis, where subjects with islet autoimmunity were defined as cases (n=95), those without as controls (n=139). Drinking water quality was obtained from the German Water Supply Authorities for the participating families for the first year of the child's life. There was no significant association between water acidity or drinking water quality (concentration of minerals and elements) and islet autoimmunity risk. Increased progression to diabetes in islet autoantibody-positive children was associated with exposure to water with lower pH values (less than cohort median, 7.62; odds ratio [OR]: 2.5; 95% confidence interval [CI]: 1.1-5.7; p=0.03) but was not significant after correction for multiple comparisons. Concentrations of nitrate, nitrite, iron, aluminum, and manganese were not associated with risk of T1D progression. This is the first prospective study with water quality measured before the onset of islet autoimmunity and T1D. Consistent with a previous cross-sectional case-control study, we found an association between drinking water pH and the rate of T1D development in at-risk children. The association is marginal and requires validation in other prospective cohorts.

Maternal type 1 diabetes reduces the risk of islet autoantibodies: relationships with birthweight and maternal HbA(1c)

AIMS/HYPOTHESIS

The risk of type 1 diabetes is reduced in the children of mothers with type 1 diabetes compared with children of fathers with type 1 diabetes. We asked whether children of mothers with type 1 diabetes also have a decreased risk of developing islet autoantibodies, and which factors associated with maternal diabetes contribute to a reduced islet autoantibody risk in offspring.

METHODS

Singleton offspring of a mother (n = 1,008) or father with type 1 diabetes (n = 578) from the BABYDIAB study were included. Children were followed from birth for the development of islet autoantibodies defined as two or more autoantibodies to insulin, glutamic acid decarboxylase or insulinoma antigen 2 in two or more blood samples.

RESULTS

Islet autoantibody risk was lower in children of mothers with type 1 diabetes (5 year risk, 3.2% vs 5.7% in children of fathers with type 1 diabetes; p = 0.04). Among factors that differed between pregnancies from mothers with and without type 1 diabetes, birthweight was associated with islet autoantibody risk. Risk was reduced in children with birthweights in the lower (adjusted HR 0.33; 95% CI 0.14-0.75; p = 0.009) and upper (HR 0.45; 95% CI 0.21-0.97; p = 0.04) tertiles compared with the middle tertile. A sub-analysis of maternal HbA(1c) suggested that moderately elevated third trimester maternal HbA(1c) was also associated with a reduced islet autoantibody risk in children of mothers with type 1 diabetes (5.7-7%; HR 0.38; 95% CI 0.15-0.96; p = 0.04 vs children of mothers with HbA(1c) < 5.7%).

CONCLUSIONS/INTERPRETATION

The risk of islet autoimmunity is modified by maternally influenced events such as birthweight.