Klaus Strassburger

Traffic-Related Air Pollution and Incident Type 2 Diabetes: Results from the SALIA Cohort Study

Background Cross-sectional and ecological studies indicate that air pollution may be a risk factor for type 2 diabetes, but prospective data are lacking. Objective We examined the association between traffic-related air pollution and incident type 2 diabetes. Design Between 1985 and 1994, cross-sectional surveys were performed in the highly industrialized Ruhr district (West Germany); a follow-up investigation was conducted in 2006 using data from the Study on the Influence of Air Pollution on Lung, Inflammation and Aging (SALIA) cohort. Participants 1,775 nondiabetic women who were 54–55 years old at baseline participated in both baseline and follow-up investigations and had complete information available. Materials and Methods Using questionnaires, we assessed 16-year incidence (1990–2006) of type 2 diabetes and information about covariates. Complement factor C3c as marker for subclinical inflammation was measured at baseline. Individual exposure to traffic-related particulate matter (PM) and nitrogen dioxide was determined at different spatial scales. Results Between 1990 and 2006, 87 (10.5%) new cases of diabetes were reported among the SALIA cohort members. The hazards for diabetes were increased by 15–42% per interquartile range of PM or traffic-related exposure. The associations persisted when different spatial scales were used to assess exposure and remained robust after adjusting for age, body mass index, socioeconomic status, and exposure to several non–traffic-related sources of air pollution. C3c was associated with PM pollution at baseline and was a strong independent predictor of incident diabetes. Exploratory analyses indicated that women with high C3c blood levels were more susceptible for PM-related excess risk of diabetes than were women with low C3c levels. Conclusions Traffic-related air pollution is associated with incident type 2 diabetes among elderly women. Subclinical inflammation may be a mechanism linking air pollution with type 2 diabetes. Relevance to clinical practice Our study identifies traffic-related air pollution as a novel and potentially modifiable risk factor of type 2 diabetes.

Incidence of Type 2 diabetes in the elderly German population and the effect of clinical and lifestyle risk factors: KORA S4/F4 cohort study

Aims  To determine the incidence of Type 2 diabetes in an elderly population in Germany and its association with clinical and lifestyle factors.

Elevated Levels of the Anti-Inflammatory Interleukin-1 Receptor Antagonist Precede the Onset of Type 2 Diabetes: The Whitehall II Study

OBJECTIVE—Interleukin-1 receptor antagonist (IL-1Ra), a natural inhibitor of interleukin-1β, has been shown to improve β-cell function and glycemic control in patients with type 2 diabetes. The aim of this study was to investigate whether baseline systemic levels of IL-1Ra are associated with incident type 2 diabetes during more than 10 years of follow-up. RESEARCH DESIGN AND METHODS—We measured serum IL-1Ra concentrations in a nested case-control study (181 case and 376 age-, sex-, and BMI-matched normoglycemic control subjects) within the Whitehall II cohort (U.K.). RESULTS—IL-1Ra concentrations were higher in case subjects (P = 0.0006) and associated with incident type 2 diabetes (odds ratio for a 1-SD increase of IL-1Ra 1.48 [95% CI 1.21–1.80]). This association remained significant after adjustment for multiple potential confounders but was attenuated by adjusting for 2-h glucose. CONCLUSIONS—Our findings indicate that individuals who will develop type 2 diabetes are characterized by a complex immune activation that also includes upregulation of the anti-inflammatory cytokine IL-1Ra.

Compatible simultaneous lower confidence bounds for the Holm procedure and other Bonferroni-based closed tests.

We consider the problem of simultaneously testing multiple one-sided null hypotheses. Single-step procedures, such as the Bonferroni test, are characterized by the fact that the rejection or non-rejection of a null hypothesis does not take the decision for any other hypothesis into account. For stepwise test procedures, such as the Holm procedure, the rejection or non-rejection of a null hypothesis may depend on the decision of other hypotheses. It is well known that stepwise test procedures are by construction more powerful than their single-step counterparts. This power advantage, however, comes only at the cost of increased difficulties in constructing compatible simultaneous confidence intervals for the parameters of interest. For example, such simultaneous confidence intervals are easily obtained for the Bonferroni method, but surprisingly hard to derive for the Holm procedure. In this paper, we discuss the inherent problems and show that ad hoc solutions used in practice typically do not control the pre-specified simultaneous confidence level. Instead, we derive simultaneous confidence intervals that are compatible with a certain class of closed test procedures using weighted Bonferroni tests for each intersection hypothesis. The class of multiple test procedures covered in this paper includes gatekeeping procedures based on Bonferroni adjustments, fixed sequence procedures, the simple weighted or unweighted Bonferroni procedure by Holm and the fallback procedure. We illustrate the results with a numerical example.

APOA5 variants and metabolic syndrome in Caucasians

Apolipoprotein A5 (APOA5) gene variants were reported to be associated with two components of metabolic syndrome (MetS): higher TG levels and lower HDL levels. Moreover, a recent Japanese case-control study found variant −1131T>C associated with MetS itself. Thus, our study systematically analyzed the APOA5 gene for association with lipid parameters, any other features of MetS, including waist circumference, glucose-related parameters, blood pressure, uric acid, and MetS itself in Caucasians. Ten polymorphisms were analyzed in a large fasting sample of the population-based Cooperative Health Research in the Region of Augsburg (KORA) survey S4 (n = 1,354; southern Germany) and in a second fasting sample, the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR) study (n = 1,770; Austria). Minor alleles of variants −1131T>C, −3A>G, c.56C>G, 476G>A, and 1259T>C were significantly associated with higher TG levels in single polymorphism (P < 0.001) and haplotype (P ⩽ 6.6 × 10−6) analysis. Besides associations with lower HDL levels in SAPHIR (P ⩽ 0.001), there were no significant findings with any other features of MetS. Variant c.56C>G was associated with higher risk for MetS [odds ratio (95% confidence interval) = 1.43 (1.04, 1.99), P = 0.03 for KORA and 1.48 (1.10, 1.99), P = 0.009 for SAPHIR). Our study confirms the association of the APOA5 locus with TG and HDL levels in humans. Furthermore, the data suggest a different mechanism of APOA5 impact on MetS in Caucasians, as variant c.56C>G (not analyzed in the Japanese study) and not −1131T>C, as in the Japanese subjects, was associated with MetS.

Prevalence of undiagnosed diabetes and impaired glucose regulation in 35-59-year-old individuals in Southern Germany: the KORA F4 Study.

Diabet. Med. 27, 360–362 (2010)

Prediction models for incident type 2 diabetes mellitus in the older population: KORA S4/F4 cohort study.

Diabet. Med. 27, 1116–1123 (2010)

Altered chemokine levels in individuals at risk of Type 1 diabetes mellitus

Aims  The hypothesis was tested in an exploratory study that individuals at high risk of developing Type 1 diabetes mellitus have altered systemic levels of cytokines and chemokines.

Intake of Lactobacillus reuteri Improves Incretin and Insulin Secretion in Glucose Tolerant Humans: A Proof of Concept

OBJECTIVE Ingestion of probiotics can modify gut microbiota and alter insulin resistance and diabetes development in rodents. We hypothesized that daily intake of Lactobacillus reuteri increases insulin sensitivity by changing cytokine release and insulin secretion via modulation of the release of glucagon-like peptides (GLP)-1 and -2. RESEARCH DESIGN AND METHODS A prospective, double-blind, randomized trial was performed in 21 glucose-tolerant humans (11 lean: age 49 ± 7 years, BMI 23.6 ± 1.7 kg/m2; 10 obese: age 51 ± 7 years, BMI 35.5 ± 4.9 kg/m2). Participants ingested 1010 b.i.d. L. reuteri SD5865 or placebo over 4 weeks. Oral glucose tolerance and isoglycemic glucose infusion tests were used to assess incretin effect and GLP-1 and GLP-2 secretion, and euglycemic-hyperinsulinemic clamps with [6,6-2H2]glucose were used to measure peripheral insulin sensitivity and endogenous glucose production. Muscle and hepatic lipid contents were assessed by 1H-magnetic resonance spectroscopy, and immune status, cytokines, and endotoxin were measured with specific assays. RESULTS In glucose-tolerant volunteers, daily administration of L. reuteri SD5865 increased glucose-stimulated GLP-1 and GLP-2 release by 76% (P < 0.01) and 43% (P < 0.01), respectively, compared with placebo, along with 49% higher insulin (P < 0.05) and 55% higher C-peptide secretion (P < 0.05). However, the intervention did not alter peripheral and hepatic insulin sensitivity, body mass, ectopic fat content, or circulating cytokines. CONCLUSIONS Enrichment of gut microbiota with L. reuteri increases insulin secretion, possibly due to augmented incretin release, but does not directly affect insulin sensitivity or body fat distribution. This suggests that oral ingestion of one specific strain may serve as a novel therapeutic approach to improve glucose-dependent insulin release.

Vaspin (SERPINA12) genotypes and risk of type 2 diabetes: Results from the MONICA/KORA studies.

Vaspin has recently been identified as novel adipokine with high expression in adipose tissue of obese and type 2 diabetic subjects and with potentially insulin-sensitising properties. However, the impact of vaspin gene variants on the risk of type 2 diabetes mellitus (T2DM) has not been determined yet. Therefore, the aim of our study was to investigate the association of vaspin single nucleotide polymorphisms (SNPs) with T2DM and obesity. We analysed the association between 25 vaspin SNPs and T2DM in initially healthy 35-84 year-old individuals of the population-based, cross-sectional German KORA F3 study and assessed the association with measures of obesity. Genotyping was carried out with matrix-assisted laser desorption/ionisation-time of flight mass spectrometry of allele-dependent primer extension products and associations with T2DM and obesity were analysed by logistic regression analysis. Our results demonstrate a significant association of vaspin SNP rs2236242 with T2DM in the KORA F3 study with the AA genotype bearing an increased risk (adjusted OR 2.35 [1.59; 3.46] versus AT/TT). This association appears to be independent of obesity. Our finding corroborates previous studies that suggested a link between the novel adipokine vaspin and glucose metabolism.