A Method to Combine Neurofilament Light Measurements From Blood Serum and Plasma in Clinical and Population-Based Studies

Introduction

Neurofilament light (NfL) can be detected in blood of healthy individuals and at elevated levels in those with different neurological diseases. We investigated if the choice of biological matrix can affect results when using NfL as biomarker in epidemiological studies.

Method

We obtained paired serum and EDTA-plasma samples of 299 individuals aged 37–67 years (BiDirect study) and serum samples of 373 individuals aged 65–83 years (MEMO study). In BiDirect, Passing–Bablok analyses were performed to assess proportional and systematic differences between biological matrices. Associations between serum or EDTA-plasma NfL and renal function (serum creatinine, serum cystatin C, glomerular filtration rate, and kidney disease) were investigated using linear or logistic regression, respectively. All regression coefficients were estimated (1) per one ng/L increase and (2) per one standard deviation increase (standardization using z-scores). In MEMO, regression coefficients were estimated (1) per one ng/L increase of serum or calculated EDTA-plasma NfL and (2) per one standard deviation increase providing a comparison to the results from BiDirect.

Results

We found proportional and systematic differences between paired NfL measurements in BiDirect, i.e., serum NfL [ng/L] = −0.33 [ng/L] + 1.11 × EDTA-plasma NfL [ng/L]. Linear regression coefficients for the associations between NfL and renal function did not vary between the different NfL measurements. In MEMO, one standard deviation increase in serum NfL was associated with greater changes in the outcomes than in BiDirect.

Conclusion

Although there are differences between serum and EDTA-plasma NfL, results can be used interchangeably if standardized values are used.

Differential and shared genetic effects on kidney function between diabetic and non-diabetic individuals

Reduced glomerular filtration rate (GFR) can progress to kidney failure. Risk factors include genetics and diabetes mellitus (DM), but little is known about their interaction. We conducted genome-wide association meta-analyses for estimated GFR based on serum creatinine (eGFR), separately for individuals with or without DM (nDM = 178,691, nnoDM = 1,296,113). Our genome-wide searches identified (i) seven eGFR loci with significant DM/noDM-difference, (ii) four additional novel loci with suggestive difference and (iii) 28 further novel loci (including CUBN) by allowing for potential difference. GWAS on eGFR among DM individuals identified 2 known and 27 potentially responsible loci for diabetic kidney disease. Gene prioritization highlighted 18 genes that may inform reno-protective drug development. We highlight the existence of DM-only and noDM-only effects, which can inform about the target group, if respective genes are advanced as drug targets. Largely shared effects suggest that most drug interventions to alter eGFR should be effective in DM and noDM.

Association between hepatic iron overload assessed by magnetic resonance imaging and glucose intolerance states in the general population

BACKGROUND AND AIM

While there is evidence that iron overload disorders are associated with type 2 diabetes, the relationship between hepatic iron overload and prediabetes remains unclear. We aimed to investigate the association between hepatic iron overload, as assessed by magnetic resonance imaging (MRI), and different glucose intolerance states in the population-based Study.

METHODS AND RESULTS

We included data from 1622 individuals with MRI data, who did not have known type 2 diabetes (T2DM). Using an oral glucose tolerance testing, participants were classified as having isolated impaired fasting glucose (i-IFG), isolated impaired glucose tolerance (i-IGT), combined IFG and IGT (IFG + IGT) or previously unknown T2DM. Hepatic iron and fat contents were assessed through quantitative MRI. We undertook linear and multinomial logistic regression models adjusted for potential confounders and MRI-assessed hepatic fat content to examine the association of hepatic iron overload with different glucose intolerance states or continuous markers of glucose metabolism. MRI-assessed hepatic iron overload was positively associated only with both 2-h plasma glucose (β = 0.32; 95%CI 0.04-0.60) and the combined IFG + IGT category (relative risk ratio = 1.87; 95%CI 1.15-3.06). No significant associations were found between hepatic iron overload and other glucose intolerance states or biomarkers of glucose metabolism, independently of potential confounders.

CONCLUSIONS

MRI-assessed hepatic iron overload was associated with higher 2-h glucose concentrations and the combined IFG + IGT category, but not with other glucose intolerance states. Our findings suggest a weak adverse impact of hepatic iron overload on glucose metabolism, but further studies are needed to confirm these findings.

Evaluation of a pneumatic tube system carrier prototype with fixing mechanism allowing for automated unloading

OBJECTIVES

A carrier prototype by Aerocom^® (Schwäbisch Gmünd, Germany) for pneumatic tube systems (PTS) is able to transport 9 blood tubes which are automatically fixed by closing the lid. In this study, we examined the influence of the transport on blood sample quality using the carrier prototype comparing to courier transport and a conventional carrier (AD160, Aerocom^®).

METHODS

Triplicate blood samples sets (1 lithium heparin, 1 EDTA, 1 sodium citrate) of 35 probands were split among the transportation methods: 1. courier, 2. conventional carrier, and 3. carrier prototype. After transport 51 measurands from clinical chemistry, hematology and coagulation were measured and compared.

RESULTS

Overall, 49 of the investigated 51 measurands showed a good concordance among the three transport types, especially between the conventional carrier and the carrier prototype. Focusing on well-known hemolysis sensitive measurands, potassium showed no statistically significant differences. However, between courier and both carrier types lactate dehydrogenase (LDH) and free hemoglobin (fHb) showed statistically significant shifts, whereas the clinical impact of the identified differences was neglectable. The median concentration of fHb, for example, was 0.29 g/L (18 µmol/L), 0.31 g/L (19 µmol/L) and 0.32 g/L (20 µmol/L) for courier transport, conventional carrier and carrier prototype, respectively. These differences cannot be resolved analytically since the minimal difference (MD) for fHb is 0.052 g/L (3.23 µmol/L), at this concentration.

CONCLUSIONS

The carrier prototype by Aerocom^® is suitable for transportation of diagnostic blood samples. The overall workflow is improved by decreasing hands-on-time on the ward and laboratory while minimizing the risk of incorrectly packed carriers.

Plasma circulating micro-RNAs associated with alexithymia reflect a high overlap on neuropsychiatric outcomes

BACKGROUND

Alexithymia ("no word for feelings") is a personality feature that is common in patients with psychiatric disorders. However, little is known about biological causes and mechanism behind. Research so far focusses on genetic risk variants primary associated with depression, but analyses on epigenetic mechanisms are still missing.

METHODS

In a sample of n = 813 subjects from the "Study of Health in Pomerania" we analyzed the association between alexithymia and plasma circulating micro RNAs (miRNA). Significant miRNAs were compared to associations regarding depression and pathway analyses were performed.

RESULTS

Two miRNAs were significantly associated with at least one of the alexithymia scores (hsa-miR-324-3p, hsa-miR-33a-5p) and three miRNAs additionally revealed a strong association pattern to alexithymia (hsa-miR-106b-5p, hsa-miR-484, hsa-miR-25-3p). None of these miRNAs was significantly associated with depressive symptoms in our sample. Literature research showed that all of the miRNAs have been found in association with several neuropsychiatric phenotypes.

LIMITATIONS

Main limitations are the lack of a replication sample as well as the limited number of miRNAs analyzed.

CONCLUSIONS

This is the first analysis investigating the association between miRNAs and alexithymia. Results indicate that miRNAs are not specific for one psychiatric disorder but may influence biological mechanisms that are involved in various psychiatric conditions which might be relevant for future treatment options and improve the biological understanding of psychiatric conditions.

Association of osteopontin with kidney function and kidney failure in chronic kidney disease patients: the GCKD study

BACKGROUND

Osteopontin (OPN), synthesized in the thick ascending limb of Henle's loop and in the distal tubule, is involved in the pathogenesis of kidney fibrosis, a hallmark of kidney failure (KF). In a cohort of chronic kidney disease (CKD) patients, we evaluated OPN's association with kidney markers and KF.

METHODS

OPN was measured from baseline serum samples of German Chronic Kidney Disease study participants. Cross-sectional regression models for estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR) as well as Cox regression models for all-cause mortality and KF were evaluated to estimate the OPN effect. Additionally, predictive ability, of OPN and time-dependent population-attributable fraction were evaluated.

RESULTS

Over a median follow-up of 6.5 years, 471 KF events and 629 deaths occurred among 4,950 CKD patients. One-unit higher log(OPN) was associated with 5.5 mL/min/1.73m2 lower eGFR (95%CI: [-6.4,-4.6]) and 1% change in OPN with 0.7% higher UACR (estimated effect 0.7, 95%CI: [0.6,0.8]). Moreover, higher OPN levels were associated with a higher risk of KF (hazard ratio [HR] 1.4, 95%CI: [1.2,1.7]) and all-cause mortality (HR 1.5, 95%CI: [1.3,1.8]). After 6 years, 31% of the KF events could be attributed to higher OPN levels (95%CI: [3%,56%]).

CONCLUSIONS

In this study, higher OPN levels were associated with kidney function markers worsening, and a higher risk for adverse outcomes. A larger proportion of KF could be attributed to higher OPN levels warranting further research on OPN with regards to its role in CKD progression and possible treatment options.

Course of disease and risk factors for hospitalization in outpatients with a SARS-CoV-2 infection

We analyzed symptoms and comorbidities as predictors of hospitalization in 710 outpatients in North-East Germany with PCR-confirmed SARS-CoV-2 infection. During the first 3 days of infection, commonly reported symptoms were fatigue (71.8%), arthralgia/myalgia (56.8%), headache (55.1%), and dry cough (51.8%). Loss of smell (anosmia), loss of taste (ageusia), dyspnea, and productive cough were reported with an onset of 4 days. Anosmia or ageusia were reported by only 18% of the participants at day one, but up to 49% between days 7 and 9. Not all participants who reported ageusia also reported anosmia. Individuals suffering from ageusia without anosmia were at highest risk of hospitalization (OR 6.8, 95% CI 2.5–18.1). They also experienced more commonly dyspnea and nausea (OR of 3.0, 2.9, respectively) suggesting pathophysiological connections between these symptoms. Other symptoms significantly associated with increased risk of hospitalization were dyspnea, vomiting, and fever. Among basic parameters and comorbidities, age > 60 years, COPD, prior stroke, diabetes, kidney and cardiac diseases were also associated with increased risk of hospitalization. In conclusion, due to the delayed onset, ageusia and anosmia may be of limited use in differential diagnosis of SARS-CoV-2. However, differentiation between ageusia and anosmia may be useful for evaluating risk for hospitalization.

DNA methylation signature of chronic low-grade inflammation and its role in cardio-respiratory diseases

We performed a multi-ethnic Epigenome Wide Association study on 22,774 individuals to describe the DNA methylation signature of chronic low-grade inflammation as measured by C-Reactive protein (CRP). We find 1,511 independent differentially methylated loci associated with CRP. These CpG sites show correlation structures across chromosomes, and are primarily situated in euchromatin, depleted in CpG islands. These genomic loci are predominantly situated in transcription factor binding sites and genomic enhancer regions. Mendelian randomization analysis suggests altered CpG methylation is a consequence of increased blood CRP levels. Mediation analysis reveals obesity and smoking as important underlying driving factors for changed CpG methylation. Finally, we find that an activated CpG signature significantly increases the risk for cardiometabolic diseases and COPD.

Genetics of osteopontin in patients with chronic kidney disease: The German Chronic Kidney Disease study

Osteopontin (OPN), encoded by SPP1, is a phosphorylated glycoprotein predominantly synthesized in kidney tissue. Increased OPN mRNA and protein expression correlates with proteinuria, reduced creatinine clearance, and kidney fibrosis in animal models of kidney disease. But its genetic underpinnings are incompletely understood. We therefore conducted a genome-wide association study (GWAS) of OPN in a European chronic kidney disease (CKD) population. Using data from participants of the German Chronic Kidney Disease (GCKD) study (N = 4,897), a GWAS (minor allele frequency [MAF]≥1%) and aggregated variant testing (AVT, MAF<1%) of ELISA-quantified serum OPN, adjusted for age, sex, estimated glomerular filtration rate (eGFR), and urinary albumin-to-creatinine ratio (UACR) was conducted. In the project, GCKD participants had a mean age of 60 years (SD 12), median eGFR of 46 mL/min/1.73m2 (p25: 37, p75: 57) and median UACR of 50 mg/g (p25: 9, p75: 383). GWAS revealed 3 loci (p<5.0E-08), two of which replicated in the population-based Young Finns Study (YFS) cohort (p<1.67E-03): rs10011284, upstream of SPP1 encoding the OPN protein and related to OPN production, and rs4253311, mapping into KLKB1 encoding prekallikrein (PK), which is processed to kallikrein (KAL) implicated through the kinin-kallikrein system (KKS) in blood pressure control, inflammation, blood coagulation, cancer, and cardiovascular disease. The SPP1 gene was also identified by AVT (p = 2.5E-8), comprising 7 splice-site and missense variants. Among others, downstream analyses revealed colocalization of the OPN association signal at SPP1 with expression in pancreas tissue, and at KLKB1 with various plasma proteins in trans, and with phenotypes (bone disorder, deep venous thrombosis) in human tissue. In summary, this GWAS of OPN levels revealed two replicated associations. The KLKB1 locus connects the function of OPN with PK, suggestive of possible further post-translation processing of OPN. Further studies are needed to elucidate the complex role of OPN within human (patho)physiology.

Circulating Metabolome and White Matter Hyperintensities in Women and Men

BACKGROUND

White matter hyperintensities (WMH), identified on T2-weighted magnetic resonance images of the human brain as areas of enhanced brightness, are a major risk factor of stroke, dementia, and death. There are no large-scale studies testing associations between WMH and circulating metabolites.

METHODS

We studied up to 9290 individuals (50.7% female, average age 61 years) from 15 populations of 8 community-based cohorts. WMH volume was quantified from T2-weighted or fluid-attenuated inversion recovery images or as hypointensities on T1-weighted images. Circulating metabolomic measures were assessed with mass spectrometry and nuclear magnetic resonance spectroscopy. Associations between WMH and metabolomic measures were tested by fitting linear regression models in the pooled sample and in sex-stratified and statin treatment-stratified subsamples. Our basic models were adjusted for age, sex, age×sex, and technical covariates, and our fully adjusted models were also adjusted for statin treatment, hypertension, type 2 diabetes, smoking, body mass index, and estimated glomerular filtration rate. Population-specific results were meta-analyzed using the fixed-effect inverse variance-weighted method. Associations with false discovery rate (FDR)-adjusted P values (PFDR)<0.05 were considered significant.

RESULTS

In the meta-analysis of results from the basic models, we identified 30 metabolomic measures associated with WMH (PFDR<0.05), 7 of which remained significant in the fully adjusted models. The most significant association was with higher level of hydroxyphenylpyruvate in men (PFDR.full.adj=1.40×10-7) and in both the pooled sample (PFDR.full.adj=1.66×10-4) and statin-untreated (PFDR.full.adj=1.65×10-6) subsample. In men, hydroxyphenylpyruvate explained 3% to 14% of variance in WMH. In men and the pooled sample, WMH were also associated with lower levels of lysophosphatidylcholines and hydroxysphingomyelins and a larger diameter of low-density lipoprotein particles, likely arising from higher triglyceride to total lipids and lower cholesteryl ester to total lipids ratios within these particles. In women, the only significant association was with higher level of glucuronate (PFDR=0.047).

CONCLUSIONS

Circulating metabolomic measures, including multiple lipid measures (eg, lysophosphatidylcholines, hydroxysphingomyelins, low-density lipoprotein size and composition) and nonlipid metabolites (eg, hydroxyphenylpyruvate, glucuronate), associate with WMH in a general population of middle-aged and older adults. Some metabolomic measures show marked sex specificities and explain a sizable proportion of WMH variance.

Identifying the Common Genetic Basis of Antidepressant Response

Background

Antidepressants are a first-line treatment for depression. However, only a third of individuals experience remission after the first treatment. Common genetic variation, in part, likely regulates antidepressant response, yet the success of previous genome-wide association studies has been limited by sample size. This study performs the largest genetic analysis of prospectively assessed antidepressant response in major depressive disorder to gain insight into the underlying biology and enable out-of-sample prediction.

Methods

Genome-wide analysis of remission (n remit = 1852, n nonremit = 3299) and percentage improvement (n = 5218) was performed. Single nucleotide polymorphism-based heritability was estimated using genome-wide complex trait analysis. Genetic covariance with eight mental health phenotypes was estimated using polygenic scores/AVENGEME. Out-of-sample prediction of antidepressant response polygenic scores was assessed. Gene-level association analysis was performed using MAGMA and transcriptome-wide association study. Tissue, pathway, and drug binding enrichment were estimated using MAGMA.

Results

Neither genome-wide association study identified genome-wide significant associations. Single nucleotide polymorphism-based heritability was significantly different from zero for remission (h 2 = 0.132, SE = 0.056) but not for percentage improvement (h 2 = -0.018, SE = 0.032). Better antidepressant response was negatively associated with genetic risk for schizophrenia and positively associated with genetic propensity for educational attainment. Leave-one-out validation of antidepressant response polygenic scores demonstrated significant evidence of out-of-sample prediction, though results varied in external cohorts. Gene-based analyses identified ETV4 and DHX8 as significantly associated with antidepressant response.

Conclusions

This study demonstrates that antidepressant response is influenced by common genetic variation, has a genetic overlap schizophrenia and educational attainment, and provides a useful resource for future research. Larger sample sizes are required to attain the potential of genetics for understanding and predicting antidepressant response.

NMR Metabolomics Reveal Urine Markers of Microbiome Diversity and Identify Benzoate Metabolism as a Mediator between High Microbial Alpha Diversity and Metabolic Health

Microbial metabolites measured using NMR may serve as markers for physiological or pathological host–microbe interactions and possibly mediate the beneficial effects of microbiome diversity. Yet, comprehensive analyses of gut microbiome data and the urine NMR metabolome from large general population cohorts are missing. Here, we report the associations between gut microbiota abundances or metrics of alpha diversity, quantified from stool samples using 16S rRNA gene sequencing, with targeted urine NMR metabolites measures from 951 participants of the Study of Health in Pomerania (SHIP). We detected significant genus–metabolite associations for hippurate, succinate, indoxyl sulfate, and formate. Moreover, while replicating the previously reported association between hippurate and measures of alpha diversity, we identified formate and 4-hydroxyphenylacetate as novel markers of gut microbiome alpha diversity. Next, we predicted the urinary concentrations of each metabolite using genus abundances via an elastic net regression methodology. We found profound associations of the microbiome-based hippurate prediction score with markers of liver injury, inflammation, and metabolic health. Moreover, the microbiome-based prediction score for hippurate completely mediated the clinical association pattern of microbial diversity, hinting at a role of benzoate metabolism underlying the positive associations between high alpha diversity and healthy states. In conclusion, large-scale NMR urine metabolomics delivered novel insights into metabolic host–microbiome interactions, identifying pathways of benzoate metabolism as relevant candidates mediating the beneficial health effects of high microbial alpha diversity.

[Analytical Quality of Glucose Measurements in Germany]

The measurement quality of systems used for determination of glucose concentrations has to be sufficiently high to obtain measurement results that are reliable in a clinical context regarding the intended use (e. g., diabetes diagnosis and monitoring). The "Richtlinie der Bundesärztekammer zur Qualitätssicherung laboratoriumsmedizinischer Untersuchungen" (guideline of the German Medical Association on quality assurance in medical laboratory examinations) includes specifications on the internal and external quality assurance that are legally binding for glucose measurements in healthcare. In the opinion of the authors, however, there is room for improvement, and examples are provided. Systems for self-monitoring of blood glucose by patients do not fall under any legally binding requirements for quality assurance. With systems for continuous glucose monitoring, there are currently no technological means to regularly check measurement quality. Additionally, repeated manufacturer-independent evaluations, which could lead to improved measurement quality, are not available.

Effects of Apolipoprotein E polymorphism on carotid intima-media thickness, incident myocardial infarction and incident stroke

The Apolipoprotein E (APOE) gene polymorphism (rs429358 and rs7412) shows a well-established association with lipid profiles, but its effect on cardiovascular disease is still conflicting. Therefore, we examined the association of different APOE alleles with common carotid artery intima-media thickness (CCA-IMT), carotid plaques, incident myocardial infarction (MI) and stroke. We analyzed data from 3327 participants aged 20-79 years of the population-based Study of Health in Pomerania (SHIP) from Northeast Germany with a median follow-up time of 14.5 years. Linear, logistic, and Cox-regression models were used to assess the associations of the APOE polymorphism with CCA-IMT, carotid plaques, incident MI and stroke, respectively. In our study, the APOE E2 allele was associated with lower CCA-IMT at baseline compared to E3 homozygotes (β: - 0.02 [95% CI - 0.04, - 0.004]). Over the follow-up, 244 MI events and 218 stroke events were observed. APOE E2 and E4 allele were not associated with incident MI (E2 HR: 1.06 [95% CI 0.68, 1.66]; E4 HR: 1.03 [95% CI 0.73, 1.45]) and incident stroke (E2 HR: 0.79 [95% CI 0.48, 1.30]; E4 HR: 0.96 [95% CI 0.66, 1.38]) in any of the models adjusting for potential confounders. However, the positive association between CCA-IMT and incident MI was more pronounced in E2 carriers than E3 homozygotes. Thus, our study suggests that while APOE E2 allele may predispose individuals to lower CCA-IMT, E2 carriers may be more prone to MI than E3 homozygotes as the CCA-IMT increases. APOE E4 allele had no effect on CCA-IMT, plaques, MI or stroke.

Longitudinal association of Apolipoprotein E polymorphism with lipid profile, type 2 diabetes and metabolic syndrome: Results from a 15 year follow-up study

AIMS

To examine the association of different APOE alleles with type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS) as well as the influence of high-sensitive C-reactive protein (hs-CRP) on these associations.

METHODS

We analyzed data from 3917 participants aged 20-81 years of the population-based Study of Health in Pomerania (SHIP) from Northeast Germany with a median follow-up time of 10.8 years. Linear and logistic mixed models were performed to test the association of APOE alleles with T2DM and MetS.

RESULTS

We observed 393 T2DM and 1411 MetS events at baseline, and 576 T2DM and 1342 MetS events over the follow-up. The E4 carriers had a lower odds of developing T2DM (OR: 0.47 [0.24, 0.94]) than E3 homozygotes even after adjustment for potential confounders. The E2 carriers showed no associations. The inverse association between E4 alleles and T2DM moderately attenuated after adjustment for hs-CRP levels. The lower odds of developing T2DM in E4 carriers was more pronounced in participants without obesity, hypertension or MetS. However, both E2 and E4 carriers had higher odds of developing MetS (E2 OR: 1.45 [1.03, 2.03]; E4 OR: 1.56 [1.17, 2.09]) than E3 homozygotes.

CONCLUSIONS

While the presence of APOE E4 allele might increase the chance of MetS through its major action on lipids, E4 allele might offer a protection towards T2DM through its influence on inflammation.

Associations of liver volume and other markers of hepatic steatosis with all-cause mortality in the general population

AIMS

We examined the associations between liver volume and other quantitative and qualitative markers of hepatic steatosis with all-cause mortality in the general population.

METHODS

We included 2769 German middle-aged individuals with a median follow-up of 8.9 years (23,898 person-years). Quantitative markers used were serum liver enzymes and FIB-4 score, while qualitative markers of hepatic steatosis included magnetic resonance imaging (MRI) measurements of liver fat content and total liver volume. Cox proportional hazards models, adjusted for confounding factors, were undertaken to investigate the associations of liver volume and other markers of hepatic steatosis with all-cause mortality.

RESULTS

A larger MRI-assessed liver volume was associated with a nearly three-fold increased risk of all-cause mortality (Hazard Ratio = 3.16; 95% confidence interval 1.88; 5.30), independent of age, sex, body mass index, food frequency score, alcohol consumption and education level. This association was consistent in all subgroups considered (men vs. women; presence or absence of overweight/obesity, metabolic syndrome or diabetes). Higher serum liver enzyme levels and FIB-4 score were also significantly associated with higher all-cause mortality in the total population and in all subgroups. No independent associations were found between other quantitative and qualitative markers of hepatic steatosis and the risk of all-cause mortality.

CONCLUSIONS

We showed for the first time that larger liver volume was associated with a three-fold increase in long-term risk of all-cause mortality. This association remained significant after adjustment for age, sex, alcohol consumption, obesity and other coexisting metabolic disorders.

Association of thyroid function with insulin resistance: data from two population-based studies

OBJECTIVE

Thyroid dysfunction is associated with relevant disturbances in glucose metabolism. Moreover, thyroid function undergoes important changes with ageing. The objective of this study was to investigate the association of thyroid function with insulin resistance with particular consideration of possible age-related effect modifications.

DESIGN

A sample of 4193 participants from two independent epidemiological studies, the Study of Health in Pomerania-TREND-0 and the Berlin Aging Study II, was included in this cross-sectional analysis.

METHODS

Insulin resistance was estimated by homeostasis model of insulin resistance (HOMA-IR) and the insulin sensitivity index (ISI). Associations of thyroid biomarkers (thyroid-stimulating hormone, free thyroxine, and free triiodothyronine (fT3)) with parameters of glucose metabolism were analysed by regression models adjusted for age, sex, smoking status, and study site.

RESULTS

A higher fT3 was significantly associated with higher fasting glucose and higher fasting and 2-h postload insulin levels, a higher HOMA-IR, and lower ISI. A higher fT3 was also associated with a higher risk for impaired fasting glucose (RR 1.09, 95 CI 1.02; 1.18; P = 0.017). Many of these associations between thyroid markers and parameters of glucose metabolism were significant in young and middle-aged participants but not in older individuals.

CONCLUSIONS

The main finding of this study was a consistent association of fT3 with almost all markers of insulin resistance. However, this effect seems to be wearing off in higher age highlighting a potential age-related modification of the interaction between thyroid function and glucose metabolism. Further studies are needed to clarify causal relationships.

Auto-Antikörper-Diagnostik in der Diabetologie – Aktueller Stand der Analytik und klinische Anwendung in Deutschland

Die Messung von spezifischen Autoantikörpern gegen beta-Zellproteine (beta-AAK) hat in den letzten Jahren das diagnostische Repertoire in der Diabetologie erweitert. Das Vorliegen von beta-AAK kann als erstes Stadium in der Entwicklung eines Typ-1-Diabetes mellitus (DM) gewertet werden, ohne dass Symptome bzw. metabolische Veränderungen vorliegen. Da sich diese oft Jahre vor der klinischen Manifestation in Personen mit hohem Erkrankungsrisiko nachweisen lassen, stellen sie wichtige prädiktive und frühdiagnostische Marker dar. Weiterhin kann die Bestimmung von beta-AAK zur Unterscheidung von Patienten mit einem Typ-1-DM auf der einen und Typ-2-DM und Maturity-Onset Diabetes of the Young (MODY) auf der anderen Seite indiziert sein. Auch für die Differenzialdiagnostik von Patienten mit Insulinmangel aufgrund einer autoimmunen Betazelldestruktion und von Patienten mit klinisch sehr ähnlichem „severe-insulin-deficient“-Diabetes, die aber beide eine unterschiedliche Prognose haben, ist die Antikörperdiagnostik zielführend. Die Abschätzung des Risikos für die Entwicklung eines Typ-1-DM bei Patienten, die an autoimmunen Endokrinopathien leiden, stellt einen weiteren Einsatzbereich für beta-AAK dar.

Analytisch sind die beta-AAK mit recht unterschiedlichen Methoden messbar; häufig aber weichen die erhaltenen Messergebnisse bei verschiedenen Testmethoden beträchtlich voneinander ab. Es müssen daher eigene Cut-off Werte vom beauftragten Labor definiert werden, um die erhaltenen Ergebnisse klinisch interpretieren zu können. Zur besseren Vergleichbarkeit der Messergebnisse gibt es derzeit international abgestimmte Harmonisierungsbestrebungen. Für teilnehmende Laboratorien angebotene Ringversuche für die Bestimmungen der Autoantikörper gegen Insulin (IAA), Insulinoma-Antigen 2 (IA-2), Zink Transporter-8 (ZnT8) und Glutamatdecarboxylase (GAD65) können die analytische Qualität ebenfalls verbessern.

Association between thyroid function and assessment of hepatic fat and iron contents by magnetic resonance imaging

The associations of thyroid function parameters with non-alcoholic fatty liver disease (NAFLD) and hepatic iron overload are not entirely clear. We have cross-sectionally investigated these associations among 2734 participants of two population-based cross-sectional studies of the Study of Health in Pomerania. Serum levels of thyroid-stimulating hormone (TSH), free tri-iodothyronine (fT3), and free thyroxine (fT4) levels were measured. Liver fat content (by proton-density fat fraction) as well as hepatic iron content (by transverse relaxation rate; R2*) were assessed by quantitative MRI. Thyroid function parameters were associated with hepatic fat and iron contents by median and logistic regression models adjusted for confounding. There were no associations between serum TSH levels and liver fat content, NAFLD, or hepatic iron overload. Serum fT4 levels were inversely associated with liver fat content, NAFLD, hepatic iron contents, and hepatic iron overload. Serum fT3 levels as well as the fT3 to fT4 ratio were positively associated with hepatic fat, NAFLD, hepatic iron contents, but not with hepatic iron overload. Associations between fT3 levels and liver fat content were strongest in obese individuals, in which we also observed an inverse association between TSH levels and NAFLD. These findings might be the result of a higher conversion of fT4 to the biologically active form fT3. Our results suggest that a subclinical hyperthyroid state may be associated with NAFLD, particularly in obese individuals. Furthermore, thyroid hormone levels seem to be more strongly associated with increased liver fat content compared to hepatic iron content.

Association of Cardiopulmonary Exercise Capacity and Adipokines in the General Population

Adipokines and cardiorespiratory fitness (CRF) are associated with the (patho)physiology of cardiometabolic diseases. Whether CRF and adipokines are related is unclear. We investigated associations of CRF with leptin, adiponectin, chemerin, resistin and vaspin. Data from the population-based Study of Health in Pomerania was used (n=1,479; median age 49 years; 51% women). Cardiopulmonary exercise testing was used to measure CRF. Circulating adipokine concentrations were measured by enzyme-linked immunosorbent assay. The association between CRF and adipokines was assessed using multivariable sex-specific quantile regression models. Higher maximum oxygen uptake was significantly associated with lower leptin (men:-0.11 ng/ml; 95%-confidence interval [CI]:-0.18 to-0.03 ng/ml; p<0.005; women:-0.17 ng/ml; 95%-CI:-0.33 to-0.02 ng/ml; p<0.05) and chemerin (men:-0.26 ng/ml; 95%-CI:-0.52 to-0.01 ng/ml; p<0.05; women:-0.41 ng/ml; 95%-CI:-0.82 to-0.01 ng/ml; p<0.05) as well as higher adiponectin concentrations (men: 0.06 µg/ml; 95%-CI: 0.02 to 0.11 µg/ml; p<0.05; women: 0.03 µg/ml; 95%-CI:-0.05 to 0.10 µg/ml; p=0.48). We found that CRF was inversely associated with leptin and chemerin in both sexes and positively associated with adiponectin only in men.

Disregarded Measurement Uncertainty Contributions and Their Magnitude in Measuring Plasma Glucose

BACKGROUND

Each measurement is subject to measurement uncertainty (MU). Consequently, each measurement of plasma glucose concentration used for diagnosis and monitoring of diabetes mellitus (DM) is affected. Although concepts and methods of MU are well established in many fields of science and technology, they are presently only incompletely implemented by medical laboratories, neglecting MU of target values of internal quality control (IQC) materials.

METHODS

An empirical and practical approach for the estimation of MU based on the analysis of routine IQC using control samples with assigned target values is presented. Its feasibility is demonstrated exemplarily by analyzing IQC data from one year obtained for glucose employing the hexokinase method with IQC of two different concentrations.

RESULTS

Combined relative extended (k = 2) MU comprising bias, coefficient of variation (CV), and MU of the target values assigned to control materials were about 9% with a lower (~ 56 mg/dL; ~3.1 mmol/L) and 8% with a higher (~ 346 mg/dL; ~19.2 mmol/L) concentration sample, analyzing IQC of one year from three different devices.

CONCLUSIONS

Estimation of MU in this study is quite reliable due to the large number of IQC data from one year. The MU of the target values of the commercial control material in this study was considerably larger than other MU contributions, ie, standard deviation and bias. In the future, the contribution of MU of commercial IQC should be addressed more carefully and technologies to measure glucose should be geared toward smaller MU possible, as needed, especially for glucose concentration measurements in diagnosis and management of DM.

The interplay between genetic variation and gene expression of the glucocorticoid receptor gene NR3C1 and blood cortisol levels on verbal memory and hippocampal volumes

The hypothalamus-pituitary-adrenal axis is the main physiological stress response system and regulating the release of cortisol. The two corticoid receptors encoded by the genes NR3C1 and NR3C2 are the main players in regulating the physiological response to cortisol. This biological system has been linked to neurocognitive processes and memory, yet the mechanisms remain largely unclear. In two independent general population studies (SHIP, total sample size > 5500), we aim to diseantangle the effects of genetic variation, gene expression and cortisol on verbal memory and memory associated brain volume. Especially for NR3C1 results exhibited a consistent pattern of direct an interactive effects. All three biological layers, genetic variation (rs56149945), gene expression for NR3C1 and cortisol levels, were directly associated with verbal memory. Interactions between these components showed significant effects on verbal memory as well as hippocampal volume. For NR3C2 such a complex association pattern could not be observed. Our analyses revealed that different components of the stress response system are acting together on different aspects of cognition. Complex phenotypes, such as cognition and memory function are regulated by a complex interplay between different genetic and epigenetic features. We promote the glucocorticoid receptor NR3C1 as a main target to focus in the context of verbal memory and provided a mechanistic concept of the interaction between various biological layers spanning NR3C1 function and its effects on memory. Especially the NR3C1 transcript seemed to be a key element in this complex system.

Insulin-Like Growth Factor, Inflammation, and MRI Markers of Alzheimer's Disease in Predominantly Middle-Aged Adults

BACKGROUND

Insulin-like growth factor 1 (IGF-1) signaling has been implicated in Alzheimer's disease pathogenesis, and further evidence suggests inflammation can be a moderator of this association. However, most research to date has been conducted on older adults.

OBJECTIVE

To investigate the association of serum IGF-1 and IGF binding protein 3 (IGFBP-3) concentrations with MRI markers of Alzheimer's disease in predominantly middle-aged adults, and further assess moderation by chronic inflammation.

METHODS

We included participants from the Framingham Heart Study (n = 1,852, mean age 46±8, 46% men) and the Study of Health in Pomerania (n = 674, mean age 50±13, 42% men) with available serum IGF-1, IFGBP-3, as well as brain MRI. IGF-1 and IFGBP-3 were related to MRI outcomes (i.e., total brain, cortical gray matter, white matter, white matter hyperintensities (WMH), and hippocampal volumes) using multivariable regression models adjusting for potential confounders. Subgroup analyses by C-reactive protein (CRP) concentrations were also performed. Cohort-specific summary statistics were meta-analyzed using random-effects models and corrected for multiple comparisons.

RESULTS

Meta-analysis results revealed that higher IGF-1 concentrations were associated with lower WMH (estimate [β] [95% CI], -0.05 [-0.09, -0.02], p = 0.006) and larger hippocampal volumes (0.07 [0.02, 0.12], p = 0.01), independent of vascular risk factors. These associations occurred predominantly in individuals with CRP concentrations < 75th percentile. We did not observe associations between IGFBP-3 and MRI outcomes.

CONCLUSION

Our findings suggest that IGF-1-related signaling may be implicated in brain health as early as midlife.

SHIP-MR and Radiology: 12 Years of Whole-Body Magnetic Resonance Imaging in a Single Center

The Study of Health in Pomerania (SHIP), a population-based study from a rural state in northeastern Germany with a relatively poor life expectancy, supplemented its comprehensive examination program in 2008 with whole-body MR imaging at 1.5 T (SHIP-MR). We reviewed more than 100 publications that used the SHIP-MR data and analyzed which sequences already produced fruitful scientific outputs and which manuscripts have been referenced frequently. Upon reviewing the publications about imaging sequences, those that used T1-weighted structured imaging of the brain and a gradient-echo sequence for R2* mapping obtained the highest scientific output; regarding specific body parts examined, most scientific publications focused on MR sequences involving the brain and the (upper) abdomen. We conclude that population-based MR imaging in cohort studies should define more precise goals when allocating imaging time. In addition, quality control measures might include recording the number and impact of published work, preferably on a bi-annual basis and starting 2 years after initiation of the study. Structured teaching courses may enhance the desired output in areas that appear underrepresented.