Karsten Müssig

Genetic variants affecting incretin sensitivity and incretin secretion

Recent genome-wide association studies identified several novel risk genes for type 2 diabetes. The majority of these type 2 diabetes risk variants confer impaired pancreatic beta cell function. Though the molecular mechanisms by which common genetic variation within these loci affects beta cell function are not completely understood, risk variants may alter glucose-stimulated insulin secretion, proinsulin conversion, and incretin signals. In humans, the incretin effect is mediated by the secretion and insulinotropic action of two peptide hormones, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1. This review article aims to give an overview of the type 2 diabetes risk loci that were found to associate with incretin secretion or incretin action, paying special attention to the potential underlying mechanisms.

Cognitive and affective dysfunctions in autoimmune thyroiditis

Hashimotos thyroiditis (HT) is the most frequent cause of hypothyroidism in areas with sufficient iodine intake. While the impact of thyroid function on mood and cognition is well known, only in the recent years, an increasing number of studies report on the association of HT with cognitive and affective disturbances also in the euthyroid state. Recent imaging studies have shown that these impairments are accompanied by altered brain perfusion, in particular, in the frontal lobe and a reduced gray matter density in the left inferior gyrus frontalis. Brain function abnormalities in euthyroid patients with HT may be subtle and only detected by specific testing or even severe as it is the case in the rare neuropsychiatric disorder Hashimotos encephalopathy (HE). The good response to glucocorticoids in patients with HE indicates an autoimmune origin. In line with this, the cognitive deficits and the high psycho-social burden in euthyroid HT patients without apparent signs of encephalopathy appear to be associated with anti-thyroid peroxidase auto-antibody (TPO Abs) levels. Though in vitro studies showing binding of TPO Abs to human cerebellar astrocytes point to a potential direct role of TPO Abs in the pathogenesis of brain abnormalities in HT patients, TPO Abs may function only as a marker of an autoimmune disorder of the central nervous system. In line with this, anti-central nervous system auto-antibodies (CNS Abs) which are markedly increased in patients with HT disturb myelinogenesis in vitro and, therefore, may impair myelin sheath integrity. In addition, in HT patients, production of monocyte- and T-lymphocyte-derived cytokines is also markedly increased which may negatively affect multiple neurotransmitters and, consequently, diverse brain neurocircuits.

Inflammatory markers are associated with cardiac autonomic dysfunction in recent-onset type 2 diabetes

Objective Cardiovascular autonomic neuropathy is a common but underestimated diabetes-related disorder. Associations between cardiovascular autonomic dysfunction and subclinical inflammation, both risk factors of diabetic comorbidities and mortality, have been proposed in non-diabetic populations, while data for type 1 and type 2 diabetes are conflicting. Our aim was to investigate associations between inflammation-related biomarkers and cardiac autonomic dysfunction in patients with diabetes. Methods We characterised the associations between seven biomarkers of subclinical inflammation and cardiac autonomic dysfunction based on heart rate variability and cardiovascular autonomic reflex tests (CARTs) in 161 individuals with type 1 and 352 individuals with type 2 diabetes (time since diagnosis of diabetes <1 year). Analyses were adjusted for age, sex, anthropometric, metabolic and lifestyle factors, medication and cardiovascular comorbidities. Results In individuals with type 2 diabetes, higher serum interleukin (IL)-18 was associated with lower vagal activity (p≤0.015 for association with CARTs), whereas higher levels of total and high-molecular-weight adiponectin showed associations with very low frequency power, an indicator of reduced sympathetic activity (p≤0.014). Higher levels of soluble intercellular adhesion molecule-1 were associated with indicators of both lower vagal (p=0.025) and sympathetic (p=0.008) tone, soluble E-selectin with one indicator of lower vagal activity (p=0.047). Serum C-reactive protein and IL-6 were also related to cardiac autonomic dysfunction, but these associations were explained by confounding factors. No consistent associations were found in individuals with type 1 diabetes. Conclusions Biomarkers of inflammation were differentially associated with diminished cardiac autonomic dysfunction in recent-onset type 2 diabetes.

The Role of Markers of Low-Grade Inflammation for the Early Time Course of Glycemic Control, Glucose Disappearance Rate, and β-Cell Function in Recently Diagnosed Type 1 and Type 2 Diabetes.

OBJECTIVE Inflammatory processes are involved in the progression of insulin resistance and β-cell dysfunction in individuals with prediabetes and contribute to the development of diabetes. We hypothesized that higher levels of biomarkers of low-grade inflammation are associated with the early progression of recently diagnosed diabetes. RESEARCH DESIGN AND METHODS Within the prospective German Diabetes Study, patients with recently diagnosed type 1 (n = 42) and type 2 (n = 94) diabetes underwent detailed metabolic characterization within the first year after diagnosis and 2 years thereafter. Associations between changes in markers of low-grade inflammation with changes in glycemic control, β-cell function, and glucose disappearance rate were assessed using multivariable linear regression analysis. Associations were adjusted for age, sex, BMI, smoking status, and 2-year changes in BMI, smoking status, and glucose-lowering medication. RESULTS Patients with type 1 and type 2 diabetes exhibited good glucometabolic control at baseline (mean HbA1c 7.08 ± 1.58% [54 ± 17 mmol/mol] and 6.43 ± 0.98% [47 ± 11 mmol/mol], respectively) and 2 years thereafter (mean HbA1c 7.03 ± 1.20% [53 ± 13 mmol/mol] and 6.62 ± 1.14% [49 ± 13], respectively). Two-year increases of high-sensitivity C-reactive protein, soluble E-selectin (sE-selectin), and soluble intercellular adhesion molecule-1 in type 2 diabetes and of IL-18 in type 1 diabetes were associated with 2-year increases of HbA1c. Additionally, 2-year increases of sE-selectin were associated with 2-year decreases of prehepatic β-cell function in type 2 diabetes (all P < 0.05). CONCLUSIONS These data indicate that with the clinical onset of diabetes, low-grade inflammation relates to worsening of glycemia and that endothelial activation may contribute to decreasing β-cell function.

AHSG gene variation is not associated with regional body fat distribution--a magnetic resonance study.

Obesity-resistance in AHSG-knockout mice indicate an important role of alpha2-Heremans-Schmid glycoprotein/fetuin-A (AHSG) in the development of obesity. We studied whether genetic variation within AHSG affects whole-body adiposity and regional fat distribution in humans. We genotyped 321 subjects at increased risk for type 2 diabetes for five single nucleotide polymorphisms (SNP) rs2248690, rs4831, rs2070635, rs4917, and rs1071592. Body fat distribution and ectopic hepatic and intramyocellular lipids were assessed by magnetic resonance techniques. AHSG levels were determined by immunoturbidimetry. The five chosen SNPs covered 100% of common genetic variation (minor allele frequency >/=0.05) within AHSG (r (2)>/=0.8). All SNPs were significantly associated with AHSG levels (p<0.0001), except for rs4831 (p=0.9) after adjustment for gender, age, and body mass index (BMI). AHSG levels were associated with liver fat content (p=0.0160) and BMI (p=0.0247) after adjustment for gender and age. While rs2248690 was nominally associated with BMI in the dominant model (p=0.0432), none of the SNPs was associated with regional fat distribution. Common genetic variation within AHSG does not appear to influence regional body fat distribution, but may affect whole-body adiposity in humans.

Specific Metabolic Profiles and Their Relationship to Insulin Resistance in Recent-Onset Type 1 and Type 2 Diabetes

CONTEXT Insulin resistance reflects the inadequate insulin-mediated use of metabolites and predicts type 2 diabetes (T2D) but is also frequently seen in long-standing type 1 diabetes (T1D) and represents a major cardiovascular risk factor. OBJECTIVE We hypothesized that plasma metabolome profiles allow the identification of unique and common early biomarkers of insulin resistance in both diabetes types. DESIGN, SETTING, AND PATIENTS Two hundred ninety-five plasma metabolites were analyzed by mass spectrometry from patients of the prospective observational German Diabetes Study with T2D (n = 244) or T1D (n = 127) and known diabetes duration of less than 1 year and glucose-tolerant persons (CON; n = 129). Abundance of metabolites was tested for association with insulin sensitivity as assessed by hyperinsulinemic-euglycemic clamps and related metabolic phenotypes. MAIN OUTCOMES MEASURES Sixty-two metabolites with phenotype-specific patterns were identified using age, sex, and body mass index as covariates. RESULTS Compared with CON, the metabolome of T2D and T1D showed similar alterations in various phosphatidylcholine species and amino acids. Only T2D exhibited differences in free fatty acids compared with CON. Pairwise comparison of metabolites revealed alterations of 28 and 49 metabolites in T1D and T2D, respectively, when compared with CON. Eleven metabolites allowed differentiation between both diabetes types and alanine, α-amino-adipic acid, isoleucin, and stearic acid showed an inverse association with insulin sensitivity in both T2D and T1D combined. CONCLUSION Metabolome analyses from recent-onset T2D and T1D patients enables identification of defined diabetes type-specific differences and detection of biomarkers of insulin sensitivity. These analyses may help to identify novel clinical subphenotypes diabetes.

Influence of Acute and Chronic Exercise on Glucose Uptake

Insulin resistance plays a key role in the development of type 2 diabetes. It arises from a combination of genetic predisposition and environmental and lifestyle factors including lack of physical exercise and poor nutrition habits. The increased risk of type 2 diabetes is molecularly based on defects in insulin signaling, insulin secretion, and inflammation. The present review aims to give an overview on the molecular mechanisms underlying the uptake of glucose and related signaling pathways after acute and chronic exercise. Physical exercise, as crucial part in the prevention and treatment of diabetes, has marked acute and chronic effects on glucose disposal and related inflammatory signaling pathways. Exercise can stimulate molecular signaling pathways leading to glucose transport into the cell. Furthermore, physical exercise has the potential to modulate inflammatory processes by affecting specific inflammatory signaling pathways which can interfere with signaling pathways of the glucose uptake. The intensity of physical training appears to be the primary determinant of the degree of metabolic improvement modulating the molecular signaling pathways in a dose-response pattern, whereas training modality seems to have a secondary role.

Adiponectin, markers of subclinical inflammation and nerve conduction in individuals with recently diagnosed type 1 and type 2 diabetes

OBJECTIVE Subclinical inflammation has been implicated in the development of diabetic sensorimotor polyneuropathy (DSPN), but studies using electrophysiological assessment as outcomes are scarce. Therefore, we aimed to investigate associations of biomarkers reflecting different aspects of subclinical inflammation with motor and sensory nerve conduction velocity (NCV) in individuals with diabetes. DESIGN AND METHODS Motor and sensory NCV was assessed in individuals with recently diagnosed type 2 (n=352) or type 1 diabetes (n=161) from the baseline cohort of the observational German Diabetes Study. NCV sum scores were calculated for median, ulnar and peroneal motor as well as median, ulnar and sural sensory nerves. Associations between inflammation-related biomarkers, DSPN and NCV sum scores were estimated using multiple regression models. RESULTS In type 2 diabetes, high serum interleukin (IL)-6 was associated with the presence of DSPN and reduced motor NCV. Moreover, higher levels of high-molecular weight (HMW) adiponectin, total adiponectin and their ratio were associated with prevalent DSPN and both diminished motor and sensory NCV, whereas no consistent associations were observed for C-reactive protein, IL18, soluble intercellular adhesion molecule-1 and E-selectin. In type 1 diabetes, only HMW and total adiponectin showed positive associations with motor NCV. CONCLUSIONS Our results point to a link between IL6 and both DSPN and slowed motor NCV in recently diagnosed type 2 diabetes. The reverse associations between adiponectin and NCV in type 1 and type 2 diabetes are intriguing, and further studies should explore whether they may reflect differences in the pathogenesis of DSPN in both diabetes types.

Effectiveness of chronic care models for the management of type 2 diabetes mellitus in Europe: a systematic review and meta-analysis

Objectives We evaluated the effectiveness of European chronic care programmes for type 2 diabetes mellitus (characterised by integrative care and a multicomponent framework for enhancing healthcare delivery), compared with usual diabetes care. Design Systematic review and meta-analysis. Data sources MEDLINE, Embase, CENTRAL and CINAHL from January 2000 to July 2015. Eligibility criteria Randomised controlled trials focussing on (1) adults with type 2 diabetes, (2) multifaceted diabetes care interventions specifically designed for type 2 diabetes and delivered in primary or secondary care, targeting patient, physician and healthcare organisation and (3) usual diabetes care as the control intervention. Data extraction Study characteristics, characteristics of the intervention, data on baseline demographics and changes in patient outcomes. Data analysis Weighted mean differences in change in HbA1c and total cholesterol levels between intervention and control patients (95% CI) were estimated using a random-effects model. Results Eight cluster randomised controlled trials were identified for inclusion (9529 patients). One year of multifaceted care improved HbA1c levels in patients with screen-detected and newly diagnosed diabetes, but not in patients with prevalent diabetes, compared to usual diabetes care. Across all seven included trials, the weighted mean difference in HbA1c change was −0.07% (95% CI −0.10 to −0.04) (−0.8 mmol/mol (95% CI −1.1 to −0.4)); I2=21%. The findings for total cholesterol, LDL-cholesterol and blood pressure were similar to HbA1c, albeit statistical heterogeneity between studies was considerably larger. Compared to usual care, multifaceted care did not significantly change quality of life of the diabetes patient. Finally, measured for screen-detected diabetes only, the risk of macrovascular and mircovascular complications at follow-up was not significantly different between intervention and control patients. Conclusions Effects of European multifaceted diabetes care patient outcomes are only small. Improvements are somewhat larger for screen-detected and newly diagnosed diabetes patients than for patients with prevalent diabetes.

Low performance in attention testing is associated with reduced grey matter density of the left inferior frontal gyrus in euthyroid patients with Hashimoto's thyroiditis

Hashimotos thyroiditis (HT) can casually co-occur with an encephalopathy associated with autoimmune thyroid disease. Recently we found an increased occurrence of weaknesses in sustained attention and response inhibition in a subgroup of euthyroid patients with HT as obtained by the d2 attention test. Previous studies in healthy subjects and patients with brain lesions demonstrated a pivotal role for the left inferior frontal gyrus (LIFG) in these skills. Therefore, we studied the association between the performance in the d2 test and grey matter (GM) density of the LIFG in 13 euthyroid patients with HT compared to a control group of 12 euthyroid patients with other thyroid diseases. A significant correlation between GM density and d2 test total score was detected for the opercular part of the LIFG in patients with HT (p<0.001), but not in the control group (p=0.94). Regression in patients with HT was significantly stronger than in the control group (p=0.02). Moreover, GM density was significantly reduced when comparing HT patients with control patients that scored in the lower third during d2 attention testing (p<0.05). It can be concluded that in HT performance in the d2 test correlated with GM density of the LIFG. Particularly low achievement was associated with reduced GM density of this brain region suggesting an influence of autoimmune processes on the frontal cortex in this disease. This could be due to not yet known antibodies affecting brain morphology or an influence of thyroid antibodies themselves.