Andreas Oberbach

Antioxidants prevent health-promoting effects of physical exercise in humans

Exercise promotes longevity and ameliorates type 2 diabetes mellitus and insulin resistance. However, exercise also increases mitochondrial formation of presumably harmful reactive oxygen species (ROS). Antioxidants are widely used as supplements but whether they affect the health-promoting effects of exercise is unknown. We evaluated the effects of a combination of vitamin C (1000 mg/day) and vitamin E (400 IU/day) on insulin sensitivity as measured by glucose infusion rates (GIR) during a hyperinsulinemic, euglycemic clamp in previously untrained (n = 19) and pretrained (n = 20) healthy young men. Before and after a 4 week intervention of physical exercise, GIR was determined, and muscle biopsies for gene expression analyses as well as plasma samples were obtained to compare changes over baseline and potential influences of vitamins on exercise effects. Exercise increased parameters of insulin sensitivity (GIR and plasma adiponectin) only in the absence of antioxidants in both previously untrained (P < 0.001) and pretrained (P < 0.001) individuals. This was paralleled by increased expression of ROS-sensitive transcriptional regulators of insulin sensitivity and ROS defense capacity, peroxisome-proliferator-activated receptor gamma (PPARγ), and PPARγ coactivators PGC1α and PGC1β only in the absence of antioxidants (P < 0.001 for all). Molecular mediators of endogenous ROS defense (superoxide dismutases 1 and 2; glutathione peroxidase) were also induced by exercise, and this effect too was blocked by antioxidant supplementation. Consistent with the concept of mitohormesis, exercise-induced oxidative stress ameliorates insulin resistance and causes an adaptive response promoting endogenous antioxidant defense capacity. Supplementation with antioxidants may preclude these health-promoting effects of exercise in humans.

Serum Vaspin Concentrations in Human Obesity and Type 2 Diabetes

OBJECTIVE— Vaspin was identified as an adipokine with insulin-sensitizing effects, which is predominantly secreted from visceral adipose tissue in a rat model of type 2 diabetes. We have recently shown that vaspin mRNA expression in adipose tissue is related to parameters of obesity and glucose metabolism. However, the regulation of vaspin serum concentrations in human obesity and type 2 diabetes is unknown. RESEARCH DESIGN AND METHODS— For the measurement of vaspin serum concentrations, we developed an enzyme-linked immunosorbent assay (ELISA). Using this ELISA, we assessed circulating vaspin in a cross-sectional study of 187 subjects with a wide range of obesity, body fat distribution, insulin sensitivity, and glucose tolerance and in 60 individuals with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), or type 2 diabetes before and after a 4-week physical training program. RESULTS— Vaspin serum concentrations were significantly higher in female compared with male subjects. There was no difference in circulating vaspin between individuals with NGT and type 2 diabetes. In the normal glucose-tolerant group, circulating vaspin significantly correlated with BMI and insulin sensitivity. Moreover, physical training for 4 weeks resulted in significantly increased circulating vaspin levels. CONCLUSIONS— We found a sexual dimorphism in circulating vaspin. Elevated vaspin serum concentrations are associated with obesity and impaired insulin sensitivity, whereas type 2 diabetes seems to abrogate the correlation between increased circulating vaspin, higher body weight, and decreased insulin sensitivity. Low circulating vaspin correlates with a high fitness level, whereas physical training in untrained individuals causes increased vaspin serum concentrations.

Combined Proteomic and Metabolomic Profiling of Serum Reveals Association of the Complement System with Obesity and Identifies Novel Markers of Body Fat Mass Changes

Obesity is associated with multiple adverse health effects and a high risk of developing metabolic and cardiovascular diseases. Therefore, there is a great need to identify circulating parameters that link changes in body fat mass with obesity. This study combines proteomic and metabolomic approaches to identify circulating molecules that discriminate healthy lean from healthy obese individuals in an exploratory study design. To correct for variations in physical activity, study participants performed a one hour exercise bout to exhaustion. Subsequently, circulating factors differing between lean and obese individuals, independent of physical activity, were identified. The DIGE approach yielded 126 differentially abundant spots representing 39 unique proteins. Differential abundance of proteins was confirmed by ELISA for antithrombin-III, clusterin, complement C3 and complement C3b, pigment epithelium-derived factor (PEDF), retinol binding protein 4 (RBP4), serum amyloid P (SAP), and vitamin-D binding protein (VDBP). Targeted serum metabolomics of 163 metabolites identified 12 metabolites significantly related to obesity. Among those, glycine (GLY), glutamine (GLN), and glycero-phosphatidylcholine 42:0 (PCaa 42:0) serum concentrations were higher, whereas PCaa 32:0, PCaa 32:1, and PCaa 40:5 were decreased in obese compared to lean individuals. The integrated bioinformatic evaluation of proteome and metabolome data yielded an improved group separation score of 2.65 in contrast to 2.02 and 2.16 for the single-type use of proteomic or metabolomics data, respectively. The identified circulating parameters were further investigated in an extended set of 30 volunteers and in the context of two intervention studies. Those included 14 obese patients who had undergone sleeve gastrectomy and 12 patients on a hypocaloric diet. For determining the long-term adaptation process the samples were taken six months after the treatment. In multivariate regression analyses, SAP, CLU, RBP4, PEDF, GLN, and C18:2 showed the strongest correlation to changes in body fat mass. The combined serum proteomic and metabolomic profiling reveals a link between the complement system and obesity and identifies both novel (C3b, CLU, VDBP, and all metabolites) and confirms previously discovered markers (PEDF, RBP4, C3, ATIII, and SAP) of body fat mass changes.

Effects of weight loss and exercise on chemerin serum concentrations and adipose tissue expression in human obesity

Chemerin is a chemoattractant adipokine that regulates adipogenesis and may induce insulin resistance. Chemerin serum concentrations are elevated in obese, insulin-resistant, and inflammatory states in vivo. Here we investigate the role of omental (OM) and subcutaneous (SC) adipose tissue chemerin and CMKLR1 messenger RNA (mRNA) expression in human obesity. In addition, we test the hypothesis that changes in chemerin serum concentrations are primarily associated with reduced body fat mass in the context of 3 weight loss intervention studies. Chemerin serum concentration was measured in 740 individuals in a cross-sectional (n = 629) study including a subgroup (n = 161) for which OM and SC chemerin mRNA expression has been analyzed as well as in 3 interventions including 12 weeks of exercise (n = 60), 6 months of calorie-restricted diet (n = 19) studies, and 12 months after bariatric surgery (n = 32). Chemerin mRNA is significantly higher expressed in adipose tissue of patients with type 2 diabetes mellitus and correlates with circulating chemerin, body mass index (BMI), percentage body fat, C-reactive protein, homeostasis model assessment of insulin resistance, and glucose infusion rate in euglycemic-hyperinsulinemic clamps. CMKLR1 mRNA expression was not significantly different between the 2 fat depots. Obesity surgery-induced weight loss causes a significant reduction on both OM and SC chemerin expression. All interventions led to significantly reduced chemerin serum concentrations. Decreased chemerin serum concentrations significantly correlate with improved glucose infusion rate and reduced C-reactive protein levels independently of changes in BMI. Insulin resistance and inflammation are BMI-independent predictors of elevated chemerin serum concentrations. Reduced chemerin expression and serum concentration may contribute to improved insulin sensitivity and subclinical inflammation beyond significant weight loss.

Pro‐Inflammatory macrophages increase in skeletal muscle of high fat‐Fed mice and correlate with metabolic risk markers in humans

In obesity, immune cells infiltrate adipose tissue. Skeletal muscle is the major tissue of insulin‐dependent glucose disposal, and indices of muscle inflammation arise during obesity, but whether and which immune cells increase in muscle remain unclear.

Gene expression of PPARγ and PGC-1α in human omental and subcutaneous adipose tissues is related to insulin resistance markers and mediates beneficial effects of physical training

OBJECTIVE Obesity and type 2 diabetes (T2D) are reaching epidemic proportions in Western societies, and they contribute to substantial morbidity and mortality. The peroxisome proliferator-activated receptor gamma (PPARgamma) and PPARgamma coactivator-1alpha (PGC-1alpha) system plays an important role in the regulation of efficient energy utilization and oxidative phosphorylation, both of which are decreased in obesity and insulin resistance. DESIGN AND METHODS We measured the metabolic parameters and the expression of PPARgamma and PGC-1alpha mRNA using quantitative real-time PCR in omental and subcutaneous (SC) adipose tissues in an observational study of 153 individuals as well as in SC fat and skeletal muscle in an interventional study of 60 subjects (20 each with normal glucose tolerance, impaired glucose tolerance, and T2D) before and after intensive physical training for 4 weeks. RESULTS PPARgamma and PGC-1alpha mRNA expression in both fat depots as well as in skeletal muscle is associated with markers of insulin resistance and cardiovascular risk. PGC-1alpha mRNA expression is significantly higher in SC fat than in omental fat, whereas PPARgamma mRNA expression is not significantly different between these fat depots. Skeletal muscle and SC fat PPARgamma and PGC-1alpha mRNA expression increased significantly in response to physical training. CONCLUSIONS Gene expression of PPARgamma and PGC-1alpha in human adipose tissue is related to markers of insulin resistance and cardiovascular risk. Increased muscle and adipose tissue PPARgamma and PGC-1alpha expression in response to physical training may mediate the beneficial effects of exercise on insulin sensitivity.

Expression of anti-inflammatory macrophage genes within skeletal muscle correlates with insulin sensitivity in human obesity and type 2 diabetes

Aims/hypothesisLow-grade systemic inflammation and adipose tissue inflammatory macrophages are frequently detected in patients with obesity and type 2 diabetes. Whether inflammatory macrophages also increase in skeletal muscle of individuals with metabolic disorders remains controversial. Here, we assess whether macrophage polarisation markers in skeletal muscle of humans correlate with insulin sensitivity in obesity and type 2 diabetes.MethodsSkeletal muscle biopsies were obtained from individuals of normal weight and with normal glucose tolerance (NGT), and overweight/obese individuals with or without type 2 diabetes. Insulin sensitivity was determined by euglycaemic–hyperinsulinaemic clamps. Expression of macrophage genes was analysed by quantitative RT-PCR.ResultsGene expression of the inflammatory macrophage phenotype marker cluster of differentiation (CD)11c was higher in muscle of type 2 diabetes patients (p = 0.0069), and correlated with HbA1c (p = 0.0139, ρ = 0.48) and fasting plasma glucose (p = 0.0284, ρ = 0.43), but not after correction for age. Expression of TGFB1, encoding the anti-inflammatory marker TGF-β1, correlated inversely with HbA1c (p = 0.0095, ρ = −0.50; p = 0.0484, ρ = −0.50) and fasting plasma glucose (p = 0.0471, ρ = −0.39; p = 0.0374, ρ = −0.52) in two cohorts, as did HbA1c with gene expression of macrophage galactose-binding lectin (MGL) (p = 0.0425, ρ = −0.51). TGFB1 expression was higher in NGT individuals than in individuals with type 2 diabetes (p = 0.0303), and correlated with low fasting plasma insulin (p = 0.0310, ρ = −0.42). In exercised overweight/obese individuals, expression of genes for three anti-inflammatory macrophage markers, MGL (p = 0.0031, ρ = 0.71), CD163 (p = 0.0268, ρ = 0.57) and mannose receptor (p = 0.0125, ρ = 0.63), correlated with high glucose-disposal rate.Conclusions/interpretationMuscle expression of macrophage genes reveals a link between inflammatory macrophage markers, age and high glycaemia, whereas anti-inflammatory markers correlate with low glycaemia and high glucose-disposal rate.

Metaproteome Analysis and Molecular Genetics of Rat Intestinal Microbiota Reveals Section and Localization Resolved Species Distribution and Enzymatic Functionalities

The digestion of food ingredients depends on the action of the gut microbiota and has a significant influence on the health, especially in the case of metabolic diseases, of the host organism. Despite the relevance of the structure and functionalities in the microbiota for the metabolism of the host, the spatial resolution of microbial consortia and the functionalities in the different gut sections of the rat are mostly unknown. Since there are suitable rat models for human metabolic diseases, the microbiota of the rat is of special interest. Samples along the intestinal tract of rats were investigated using metaproteomics and 16S rRNA gene pyrosequencing. The procedures for harvesting bacteria from the mucus and the content of the gut sections and feces were optimized leading to 2802 nonredundant bacterial protein groups in total that were assigned to spectra measured by liquid chromatography-tandem mass spectrometry. The majority of 16S rRNA genes and protein groups belonged to members of Firmicutes, Bacteroidetes and Proteobacteria. The functionalities in the enzyme repertoire were compared between the mucus and the content of the large intestine sections and the feces samples. This spatial resolution allowed pinpointing changes in the community to specific metabolic capacities like carbohydrate transport and energy conservation. The results showed that the mere analysis of feces samples reflects the functions of the gut microbiota only to a minor extent and sheds light on the metabolic interchange between the microbiota and the host organism.

Long-term exercise training decreases interleukin-6 (IL-6) serum levels in subjects with impaired glucose tolerance: effect of the −174G/C variant in IL-6 gene

OBJECTIVE Exercise training has been shown to have anti-inflammatory effects in patients with type 2 diabetes. Changes in interleukin-6 (IL-6) serum concentrations in response to training could contribute to these beneficial effects. However, there are heterogeneous data on whether circulating IL-6 is altered by exercise training. We therefore hypothesize that genetic factors modify the individual changes in IL-6 levels after long-term training. RESEARCH DESIGN AND METHODS The -174G/C variant in the IL-6 gene was genotyped in 60 subjects with impaired glucose tolerance. For a 12-month interventional study, patients were randomized into three groups: a control group (n=16) was compared with one group, which underwent a standardized training program (n=24) and another group, which was treated with 4 mg rosiglitazone once daily (n=20). At baseline, after 1, 6, and 12 months, we measured anthropometric parameters and serum concentration of IL-6 and, at baseline and after 12 months, we determined glucose tolerance and fitness level. RESULTS Only in subjects carrying the SNP -174C allele did long-term exercise training result in significantly reduced IL-6 serum concentrations. Multivariate linear regression analysis identified the IL-6 genotype as a significant predictor of changes in IL-6 serum concentrations independent of age, gender and improvement in body mass index, hemoglobin (Hb)A(1c), and fitness level in response to training. CONCLUSIONS Genetic variants in the IL-6 gene significantly modify changes in IL-6 serum concentrations in response to long-term exercise training programs. Our data suggest that genetic factors are important determinants for the individual response to anti-inflammatory effects of exercise training.

Exercise Training in Patients with Chronic Heart Failure Promotes Restoration of High-Density Lipoprotein Functional Properties

Rationale: High-density lipoprotein (HDL) exerts endothelial-protective effects via stimulation of endothelial cell (EC) nitric oxide (NO) production. This function is impaired in patients with cardiovascular disease. Protective effects of exercise training (ET) on endothelial function have been demonstrated. Objective: This study was performed to evaluate the impact of ET on HDL-mediated protective effects and the respective molecular pathways in patients with chronic heart failure (CHF). Methods and Results: HDL was isolated from 16 healthy controls (HDLhealthy) and 16 patients with CHF-NYHA-III (HDLNYHA-IIIb) before and after ET, as well as from 8 patients with CHF-NYHA-II (HDLNYHA-II). ECs were incubated with HDL, and phosphorylation of eNOS-Ser1177, eNOS-Thr495, PKC-&bgr;II-Ser660, and p70S6K-Ser411 was evaluated. HDL-bound malondialdehyde and HDL-induced NO production by EC were quantified. Endothelial function was assessed by flow-mediated dilatation. The proteome of HDL particles was profiled by shotgun LC-MS/MS. Incubation of EC with HDLNYHA-IIIb triggered a lower stimulation of phosphorylation at eNOS-Ser1177 and a higher phosphorylation at eNOS-Thr495 when compared with HDLhealthy. This was associated with lower NO production of EC. In addition, an elevated activation of p70S6K, PKC-&bgr;II by HDLNYHA-IIIb, and a higher amount of malondialdehyde bound to HDLNYHA-IIIb compared with HDLhealthy was measured. In healthy individuals, ET had no effect on HDL function, whereas ET of CHF-NYHA-IIIb significantly improved HDL function. A correlation between changes in HDL-induced NO production and flow-mediated dilatation improvement by ET was evident. Conclusions: These results demonstrate that HDL function is impaired in CHF and that ET improved the HDL-mediated vascular effects. This may be one mechanism how ET exerts beneficial effects in CHF.