Impaired HDL function in obese adolescents: impact of lifestyle intervention and bariatric surgery

OBJECTIVE

HDL regulates endothelial function via stimulation of nitric oxide production. It is documented that endothelial function is impaired in obese adolescents, and improved by lifestyle interventions (LI).

DESIGN AND METHODS

HDL function in obese adolescents and the impact of LI or Roux-en-Y gastric bypass surgery (RYGB) was assessed. HDL was isolated from 14 adolescents with normal body mass index (HDLcontrol ), 10 obese (HDLobese ) before and after 6 month LI, and five severe obese adolescents before and one year after RYGB. HDL-mediated phosphorylation of endothelial nitric oxide synthase (eNOS)-Ser(1177) , eNOS-Thr(495) , and PKC-ßII was evaluated. In addition the HDL proteome was analyzed.

RESULTS

HDLobese -mediated eNOS-Ser(1177) phosphorylation was reduced, whereas eNOS-Thr(495) phosphorylation increased significantly when compared to HDLcontrol . No impact of obesity was observed on PKC-ßII phosphorylation. LI and RYGB had no impact on HDL-mediated phosphorylation of eNOS and PKC-ßII. A principle component plot analysis of the HDL particle separated controls and severe obese, whereas the interventions did not trigger sufficient differences to the HDL proteome to permit distinction.

CONCLUSION

These results demonstrated that HDL-function is impaired in obese adolescents, and that LI or RYGB did not correct this dysfunction. This might be an argument for developing earlier prevention strategies in obese adolescents to avoid HDL dysfunction.

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 (HDL(healthy)) and 16 patients with CHF-NYHA-III (HDL(NYHA-IIIb)) before and after ET, as well as from 8 patients with CHF-NYHA-II (HDL(NYHA-II)). ECs were incubated with HDL, and phosphorylation of eNOS-Ser(1177), eNOS-Thr(495), PKC-βII-Ser(660), and p70S6K-Ser(411) 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 HDL(NYHA-IIIb) triggered a lower stimulation of phosphorylation at eNOS-Ser(1177) and a higher phosphorylation at eNOS-Thr(495) when compared with HDL(healthy). This was associated with lower NO production of EC. In addition, an elevated activation of p70S6K, PKC-βII by HDL(NYHA-IIIb), and a higher amount of malondialdehyde bound to HDL(NYHA-IIIb) compared with HDL(healthy) 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.

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

AIMS/HYPOTHESIS

Low-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.

METHODS

Skeletal 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.

RESULTS

Gene 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/INTERPRETATION

Muscle 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.

Molecular fingerprint of high fat diet induced urinary bladder metabolic dysfunction in a rat model

AIMS/HYPOTHESIS

Diabetic voiding dysfunction has been reported in epidemiological dimension of individuals with diabetes mellitus. Animal models might provide new insights into the molecular mechanisms of this dysfunction to facilitate early diagnosis and to identify new drug targets for therapeutic interventions.

METHODS

Thirty male Sprague-Dawley rats received either chow or high-fat diet for eleven weeks. Proteomic alterations were comparatively monitored in both groups to discover a molecular fingerprinting of the urinary bladder remodelling/dysfunction. Results were validated by ELISA, Western blotting and immunohistology.

RESULTS

In the proteome analysis 383 proteins were identified and canonical pathway analysis revealed a significant up-regulation of acute phase reaction, hypoxia, glycolysis, β-oxidation, and proteins related to mitochondrial dysfunction in high-fat diet rats. In contrast, calcium signalling, cytoskeletal proteins, calpain, 14-3-3η and eNOS signalling were down-regulated in this group. Interestingly, we found increased ubiquitin proteasome activity in the high-fat diet group that might explain the significant down-regulation of eNOS, 14-3-3η and calpain.

CONCLUSIONS/INTERPRETATION

Thus, high-fat diet is sufficient to induce significant remodelling of the urinary bladder and alterations of the molecular fingerprint. Our findings give new insights into obesity related bladder dysfunction and identified proteins that may indicate novel pathophysiological mechanisms and therefore constitute new drug targets.

Correlation between endothelial function measured by finger plethysmography in children and HDL-mediated eNOS activation -- a preliminary study

BACKGROUND

The noninvasive measurement of endothelial function is a very powerful tool to assess cardiovascular disease. Especially in children this is not an easy task, and therefore an easy method like the Endo-Pat device is helpful. Due to the still existing uncertainties of the validity of endothelial measurement by the Endo-PAT device in children, we thought to analyze the correlation between endothelial functional measurement by Endo-PAT, and the capability of HDL to modify nitric oxide (NO) production by phosphorylation of endothelial nitric oxide synthase at the stimulatory site (Ser(1177)) and the inhibitory site (Thr(495)).

METHODS

The reactive hyperemic index (RHI) was measured in 11 school children by the Endo-PAT device. HDL was isolated by ultracentrifugation, and the capability to stimulate eNOS phosphorylation was assessed in cell culture.

RESULTS

A close correlation between the RHI and the eNOS-Ser(1177) phosphorylation (r=0.66, p=0.02) and the eNOS-Thr(495) phosphorylation (r=-0.60, p=0.04) was detected.

CONCLUSION

The results obtained in our limited study performed in healthy children supports the validity of endothelial function measurement in children using the Endo-PAT device. Nevertheless, studies measuring FMD and the RHI index need to confirm the strength of the Endo-Pat device also in children.

Nitric oxide synthase in skeletal muscle fibers of patients with type 2 diabetes

There is increasing interest in the role of nitric oxide (NO) in common metabolic disorders such as type 2 diabetes (T2D) however, fiber-type specific changes in NO synthase (NOS) expression in skeletal muscle of T2D patients remain to be elucidated. Here we investigated fiber-type related NOS expression in the Vastus lateralis muscle of T2D patients compared with healthy individuals with normal glucose tolerance (NGT). Cytophotometrical assay did not reveal any quantitative differences between NOS expression in muscles from NGT and T2D subjects. Positive NOS immunoreactivity in the V. lateralis of T2D patients was found to be associated with fast-oxidative glycolytic (FOG) muscle phenotype. This indicates that NOS expression in T2D patients correlates both with skeletal muscle fiber type distribution and the activity of oxidative and glycolytic enzymes.

Exercise training prevents TNF-α induced loss of force in the diaphragm of mice

Rationale

Inflammatory cytokines like tumor necrosis factor alpha (TNF-α) are elevated in congestive heart failure and are known to induce the production of reactive oxygen species as well as to deteriorate respiratory muscle function.

Objectives

Given the antioxidative effects of exercise training, the aim of the present study was to investigate if exercise training is capable of preventing a TNF-α induced loss of diaphragmatic force in mice and, if so, to elucidate the potential underlying mechanisms.

Methods

Prior to intraperitoneal injection of TNF-α or saline, C57Bl6 mice were assigned to four weeks of exercise training or sedentary behavior. Diaphragmatic force and power generation were determined in vitro. Expression/activity of radical scavenger enzymes, enzymes producing reactive oxygen species and marker of oxidative stress were measured in the diaphragm.

Main Results

In sedentary animals, TNF-α reduced specific force development by 42% concomitant with a 2.6-fold increase in the amount of carbonylated α-actin and creatine kinase. Furthermore, TNF-α led to an increased NAD(P)H oxidase activity in both sedentary and exercised mice whereas xanthine oxidase activity and intramitochondrial ROS production was only enhanced in sedentary animals by TNF-α. Exercise training prevented the TNF-α induced force reduction and led to an enhanced mRNA expression and activity of glutathione peroxidase. Carbonylation of proteins, in particular of α-actin and creatine kinase, was diminished by exercise training.

Conclusion

TNF-α reduces the force development in the diaphragm of mice. This effect is almost abolished by exercise training. This may be a result of reduced carbonylation of proteins due to the antioxidative properties of exercise training.

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

OBJECTIVE

Apelin is an adipokine which plays a role in the regulation of glucose homeostasis and may contribute to the link between increased adipose tissue mass and obesity related metabolic diseases. Here we investigate the role of omental and subcutaneous (SC) adipose tissue apelin and its receptor APJ mRNA expression in human obesity and test the hypothesis that changes in circulating apelin are associated with reduced fat mass in three weight loss intervention studies.

METHODS

Apelin serum concentration was measured in 740 individuals in a cross-sectional (n = 629) study including a subgroup (n = 161) for which omental and SC apelin mRNA expression has been analyzed and in three interventions: 12 weeks exercise (n = 60), 6 months calorie-restricted diet (n = 19), 12 months after bariatric surgery (n = 32).

RESULTS

Apelin mRNA is significantly higher expressed in adipose tissue of patients with type 2 diabetes and correlates with circulating apelin, BMI, body fat, C-reactive protein, and insulin sensitivity. Obesity surgery-induced weight loss causes a significant reduction in omental and SC apelin expression. All interventions led to significantly reduced apelin serum concentrations which significantly correlate with improved insulin sensitivity, independently of changes in BMI.

CONCLUSIONS

Reduced apelin expression and serum concentration may contribute to improved insulin sensitivity beyond significant weight loss.

Microbiota from the distal guts of lean and obese adolescents exhibit partial functional redundancy besides clear differences in community structure

Recent research has disclosed a tight connection between obesity, metabolic gut microbial activities and host health. Obtaining a complete understanding of this relationship remains a major goal. Here, we conducted a comparative metagenomic and metaproteomic investigation of gut microbial communities in faecal samples taken from an obese and a lean adolescent. By analysing the diversity of 16S rDNA amplicons (10% operational phylogenetic units being common), 22 Mbp of consensus metagenome sequences (~70% common) and the expression profiles of 613 distinct proteins (82% common), we found that in the obese gut, the total microbiota was more abundant on the phylum Firmicutes (94.6%) as compared with Bacteroidetes (3.2%), although the metabolically active microbiota clearly behaves in a more homogeneous manner with both contributing equally. The lean gut showed a remarkable shift towards Bacteroidetes (18.9% total 16S rDNA), which become the most active fraction (81% proteins). Although the two gut communities maintained largely similar gene repertoires and functional profiles, improved pili- and flagella-mediated host colonization and improved capacity for both complementary aerobic and anaerobic de novo B(12) synthesis, 1,2-propanediol catabolism (most likely participating in de novo B(12) synthesis) and butyrate production were observed in the obese gut, whereas bacteria from lean gut seem to be more engaged in vitamin B(6) synthesis. Furthermore, this study provides functional evidence that variable combinations of species from different phyla could 'presumptively' fulfil overlapping and/or complementary functional roles required by the host, a scenario where minor bacterial taxa seem to be significant active contributors.

Free fatty acid palmitate impairs the vitality and function of cultured human bladder smooth muscle cells

Background

Incidence of urinary tract infections is elevated in patients with diabetes mellitus. Those patients show increased levels of the saturated free fatty acid palmitate. As recently shown metabolic alterations induced by palmitate include production and secretion of the pro-inflammatory cytokine interleukine-6 (IL-6) in cultured human bladder smooth muscle cells (hBSMC). Here we studied the influence of palmitate on vital cell properties, for example, regulation of cell proliferation, mitochondrial enzyme activity and antioxidant capacity in hBSMC, and analyzed the involvement of major cytokine signaling pathways.

Methodology/Principal Findings

HBSMC cultures were set up from bladder tissue of patients undergoing cystectomy and stimulated with palmitate. We analyzed cell proliferation, mitochondrial enzyme activity, and antioxidant capacity by ELISA and confocal immunofluorescence. In signal transduction inhibition experiments we evaluated the involvement of NF-κB, JAK/STAT, MEK1, PI3K, and JNK in major cytokine signaling pathway regulation. We found: (i) palmitate decreased cell proliferation, increased mitochondrial enzyme activity and antioxidant capacity; (ii) direct inhibition of cytokine receptor by AG490 even more strongly suppressed cell proliferation in palmitate-stimulated cells, while counteracting palmitate-induced increase of antioxidant capacity; (iii) in contrast knockdown of the STAT3 inhibitor SOCS3 increased cell proliferation and antioxidant capacity; (iv) further downstream JAK/STAT3 signaling cascade the inhibition of PI3K or JNK enhanced palmitate induced suppression of cell proliferation; (v) increase of mitochondrial enzyme activity by palmitate was enhanced by inhibition of PI3K but counteracted by inhibition of MEK1.

Conclusions/Significance

Saturated free fatty acids (e.g., palmitate) cause massive alterations in vital cell functions of cultured hBSMC involving distinct major cytokine signaling pathways. Thereby, certain cytokines might counteract the palmitate-induced downregulation of cell proliferation and vitality. This could be an important link to clinical findings of increased risk of metabolic related bladder diseases such as overactive bladder (OAB) and bladder pain syndrome/interstitial cystitis (BPS/IC).

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.

Combined serum proteomic and metabonomic profiling after laparoscopic sleeve gastrectomy in children and adolescents

AIM

The consequences of bariatric surgery on important metabolic and signaling pathways are still poorly understood. The aim of our study was to unravel the network of metabolic changes and obesity-related protein biomarkers in morbidly obese children and adolescents undergoing laparoscopic sleeve gastrectomy (LSG).

METHODS

In a prospective study, 6 children with morbid obesity who had failed a well-established conservative weight loss therapy underwent LSG. Pre- and 6 months postoperatively, a metabonomic profiling of 163 metabolites by mass spectrometry and protein profiling by ELISA (clusterin [CLU], pigment epithelium-derived factor [PEDF], retinol binding protein 4 [RBP4], paraoxonase 1 [PON1]) was performed to identify biomarkers of important pathways.

RESULTS

At referral for surgery, the mean age was 14.5 years (range 8-17), mean body mass index (BMI in kg/m(2)) was 48.13 (range 41.1-56.3). All patients showed various metabolic comorbidities. LSG was uneventful in all of them. At 6 months postsurgery, the mean BMI has dropped to 37.1 (range 28.4-40.6). Targeted serum metabonomics resulted in 7 metabolites, which were significantly affected by LSG. Among those, the amino acid phenylalanine was increased, and methionine decreased. The glycero-phospatidylcholine PCaaC38:5 were upregulated, and PCaaC40:2 and PCaaC42:1 were down regulated after 6 months compared with baseline. Further, sphingomyoline (SM) C26:0 and SM C26:1 were decreased after 6 months. The obesity-related biomarkers CLU, PEDF, and RBP4 were decreased, whereas PON1 levels were increased.

CONCLUSION

LSG leads to changes in amino acids and in lipid metabolism indicated by glycerol-phosphatidylcholines and SM. The pattern of protein biomarkers and metabolites might provide measures for the induced physiological changes and for therapy monitoring.

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.

Cytokine effects on gap junction communication and connexin expression in human bladder smooth muscle cells and suburothelial myofibroblasts

BACKGROUND

The last decade identified cytokines as one group of major local cell signaling molecules related to bladder dysfunction like interstitial cystitis (IC) and overactive bladder syndrome (OAB). Gap junctional intercellular communication (GJIC) is essential for the coordination of normal bladder function and has been found to be altered in bladder dysfunction. Connexin (Cx) 43 and Cx45 are the most important gap junction proteins in bladder smooth muscle cells (hBSMC) and suburothelial myofibroblasts (hsMF). Modulation of connexin expression by cytokines has been demonstrated in various tissues. Therefore, we investigate the effect of interleukin (IL) 4, IL6, IL10, tumor necrosis factor-alpha (TNFα) and transforming growth factor-beta1 (TGFβ1) on GJIC, and Cx43 and Cx45 expression in cultured human bladder smooth muscle cells (hBSMC) and human suburothelial myofibroblasts (hsMF).

METHODOLOGY/PRINCIPAL FINDINGS

HBSMC and hsMF cultures were set up from bladder tissue of patients undergoing cystectomy. In cytokine stimulated cultured hBSMC and hsMF GJIC was analyzed via Fluorescence Recovery after Photo-bleaching (FRAP). Cx43 and Cx45 expression was assessed by quantitative PCR and confocal immunofluorescence. Membrane protein fraction of Cx43 and Cx45 was quantified by Dot Blot. Upregulation of cell-cell-communication was found after IL6 stimulation in both cell types. In hBSMC IL4 and TGFβ1 decreased both, GJIC and Cx43 protein expression, while TNFα did not alter communication in FRAP-experiments but increased Cx43 expression. GJ plaques size correlated with coupling efficacy measured, while Cx45 expression did not correlate with modulation of GJIC.

CONCLUSIONS/SIGNIFICANCE

Our finding of specific cytokine effects on GJIC support the notion that cytokines play a pivotal role for pathophysiology of OAB and IC. Interestingly, the effects were independent from the classical definition of pro- and antiinflammatory cytokines. We conclude, that connexin regulation involves genomic and/or post-translational events, and that GJIC in hBSMC and hsMF depend of Cx43 rather than on Cx45.

Serum vaspin concentrations are decreased after exercise-induced oxidative stress

Elevated visceral adipose tissue-derived serpin (vaspin) serum concentrations are associated with impaired insulin sensitivity, but increase unexpectedly after long-term physical training. We therefore investigated the effect of an acute exercise bout and the effects of vitamin supplementation on chronic exercise effect and on serum vaspin concentrations. We measured serum vaspin and thiobarbituric acid-reactive substances (TBARS) concentrations in 80 individuals before and after a 1-hour acute exercise bout and independently in 40 healthy young men who were randomly assigned to either antioxidant (vitamin C (1,000 mg/day) and vitamin E (400 IU/day)) or to no supplementation after a standardized 4-week physical training program as a post hoc analysis. Serum vaspin concentrations significantly decreased after acute physical exercise as well as after 4 weeks of training in individuals without antioxidants. Changes in vaspin serum concentration correlate with increased TBARS serum concentrations both in response to a 1-hour exercise bout (r = -0.42, p < 0.01) and to the 4-week training (r = -0.31, p < 0.05). Interestingly, supplementation with antioxidants rather increased circulating vaspin levels in response to 4 weeks of exercise. In conclusion, vaspin serum concentrations are decreased by exercise-induced oxidative stress, but not by exercise-associated improvement in insulin sensitivity.

Gene expression of PPARgamma and PGC-1alpha 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.

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.

Metabolic profile and nitric oxide synthase expression of skeletal muscle fibers are altered in patients with type 1 diabetes

We investigate muscle fiber composition, fiber-specific glycolytic and oxidative enzyme capacity and nitric oxide synthase (NOS) expression in skeletal muscle of patients with type 1 diabetes (T1D) compared to individuals with normal glucose tolerance (NGT). Vastus lateralis muscle was obtained by percutaneous biopsy from 7 T1D patients and 10 healthy controls with similar characteristics. Using cytophotometry, muscle fiber composition and fiber type-specific glycolytic and oxidative enzyme activities were measured in slow oxidative (SO), fast oxidative glycolytic (FOG) and fast glycolytic (FG) fibers. In addition, NOS 1-3 protein expression was mea-sured. The glycolytic fiber fraction was 1.4 fold higher, whereas FOG and SO fiber fractions were significantly reduced by 13.5% and 6.2% in skeletal muscle from T1D patients. Glycolytic enzyme activities and fiber-specific ratio of glycolytic relative to oxidative enzyme activity were significantly higher in all fiber types of T1D patients and correlated with HbA (1c). Expression of NOS1-3 isoforms was reduced in skeletal muscle of T1D subjects. Increased glycolytic enzyme activity in muscle of T1D patients is most likely due to both a higher number of fast glycolytic fibers and a shift towards increased glycolytic metabolism in all fiber types. Alterations in muscle fiber distribution and enzyme activities seem to be due to impaired long-term glycemic control.

[Lipopolysaccharide-mediated regulation of interleukin-6 in cultured human detrusor smooth muscle cells]

BACKGROUND

Interleukin-6 (IL-6) is a pleiotropic cytokine which shows elevated plasma and urine levels in cancer and inflammatory diseases of the urinary tract. The aim of the study is to define IL-6 target gene regulation in cultivated human detrusor smooth muscle cells.

PATIENTS AND METHODS

The expression of IL-6 and IL-6R (gp80, gp130) was studied by confocal immunofluorescence, rtPCR and Western blotting. Lipopolysaccharide (LPS) stimulation experiments were conducted in smooth muscle cell cultures derived from bladder biopsies of four male tumor patients.

RESULTS

IL-6 and IL-6R expression was found in urothelium, lamina propria and detrusor cells. LPS stimulation evoked a time-dependent synthesis and/or release of IL-6, IL-6R and STAT3.

CONCLUSIONS

Our results favor the notion that IL-6 can stimulate various cells of the human urinary bladder. Both detrusor cells and urothelium can serve as a source of elevated IL-6 levels. Finding genes regulated by IL-6 could be of great value for new therapeutical approaches in cancer and chronic inflammation of the lower urinary tract.

[Structure and function of suburothelial myofibroblasts in the human urinary bladder under normal and pathological conditions]

BACKGROUND

Myofibroblasts play a pivotal role in numerous pathological alterations. Clarification of the structure and function and of the cellular plasticity of this cell type in the bladder may lead to new insights into the pathogenesis of lower urinary tract disorders.

PATIENTS AND METHODS

Bladder biopsies from patients with bladder carcinoma and interstitial cystitis were used to analyse the morphology and receptor expression using confocal immunofluorescence and electron microscopy. Cytokine effects and coupling behavior were tested in cultured myofibroblasts and detrusor smooth muscle cells.

RESULTS

Myofibroblasts are in close contact with the suburothelial capillary network. They express Cx43 and form functional syncytia. The expression of muscarinic and purinergic receptors is highly variable. Dye coupling experiments showed differences to detrusor myocytes.

CONCLUSIONS

Upregulation of smooth muscle cell alpha-actin and/or transdifferentiation into smooth muscle cells may contribute to the etiology of urge incontinence. A multi-step model is presented as a working hypothesis.

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.

Gene expression of adiponectin receptors in human visceral and subcutaneous adipose tissue is related to insulin resistance and metabolic parameters and is altered in response to physical training

OBJECTIVE

Adiponectin receptors 1 and 2 (AdipoR1 and AdipoR2, respectively) mediate the effects of adiponectin on glucose and lipid metabolism in vivo. We examined whether AdipoR1 and/or AdipoR2 mRNA expression in human adipose tissue is fat-depot specific. We also studied whether their expression in visceral and subcutaneous fat depots is associated with metabolic parameters and whether their expression is regulated by intensive physical exercise.

RESEARCH DESIGN AND METHODS

We determined metabolic parameters and assessed AdipoR1 and AdipoR2 mRNA expression using quantitative real-time PCR in adipose tissue in an observational study of 153 subjects and an interventional study of 60 subjects (20 each with normal glucose tolerance, impaired glucose tolerance, and type 2 diabetes) before and after intensive physical training for 4 weeks.

RESULTS

AdipoR1 and AdipoR2 mRNA expression is not significantly different between omental and subcutaneous fat, but their expression is several-fold lower in adipose tissue than in muscle. AdipoR2 mRNA expression in visceral fat is highly correlated with its expression in subcutaneous fat. AdipoR2 mRNA expression in both visceral and subcutaneous fat is positively associated with circulating adiponectin and HDL levels but negatively associated with obesity as well as parameters of insulin resistance, glycemia, and other lipid levels before and after adjustment for fat mass. Physical training for 4 weeks resulted in increased AdipoR1 and AdipoR2 mRNA expression in subcutaneous fat.

CONCLUSIONS

AdipoR2 mRNA expression in fat is negatively associated with insulin resistance and metabolic parameters independently of obesity and may mediate the improvement of insulin resistance in response to exercise.

Retinol-binding protein 4 and insulin resistance in lean, obese, and diabetic subjects

BACKGROUND

Insulin resistance has a causal role in type 2 diabetes. Serum levels of retinol-binding protein 4 (RBP4), a protein secreted by adipocytes, are increased in insulin-resistant states. Experiments in mice suggest that elevated RBP4 levels cause insulin resistance. We sought to determine whether serum RBP4 levels correlate with insulin resistance and change after an intervention that improves insulin sensitivity. We also determined whether elevated serum RBP4 levels are associated with reduced expression of glucose transporter 4 (GLUT4) in adipocytes, an early pathological feature of insulin resistance.

METHODS

We measured serum RBP4, insulin resistance, and components of the metabolic syndrome in three groups of subjects. Measurements were repeated after exercise training in one group. GLUT4 protein was measured in isolated adipocytes.

RESULTS

Serum RBP4 levels correlated with the magnitude of insulin resistance in subjects with obesity, impaired glucose tolerance, or type 2 diabetes and in nonobese, nondiabetic subjects with a strong family history of type 2 diabetes. Elevated serum RBP4 was associated with components of the metabolic syndrome, including increased body-mass index, waist-to-hip ratio, serum triglyceride levels, and systolic blood pressure and decreased high-density lipoprotein cholesterol levels. Exercise training was associated with a reduction in serum RBP4 levels only in subjects in whom insulin resistance improved. Adipocyte GLUT4 protein and serum RBP4 levels were inversely correlated.

CONCLUSIONS

RBP4 is an adipocyte-secreted molecule that is elevated in the serum before the development of frank diabetes and appears to identify insulin resistance and associated cardiovascular risk factors in subjects with varied clinical presentations. These findings provide a rationale for antidiabetic therapies aimed at lowering serum RBP4 levels.

Cultured smooth muscle cells of the human vesical sphincter are more sensitive to histamine than are detrusor smooth muscle cells

OBJECTIVES

To compare histamine receptor expression in cultured smooth muscle cells from the human detrusor and internal sphincter using receptor-specific agonists.

METHODS

Smooth muscle cells from the bladder dome and internal sphincter were cultured from 5 male patients undergoing cystectomy for bladder cancer therapy. Calcium transients in cells stimulated with carbachol, histamine, histamine receptor 1 (H1R)-specific heptanecarboxamide (HTMT), dimaprit (H2R), and R-(alpha)-methylhistamine (H3R) were measured by calcium imaging. Histamine receptor proteins were detected by Western blot analysis and immunocytochemistry.

RESULTS

H1R, H2R, and H3R expression was found in tissue and cultured cells. Carbachol stimulated equal numbers of detrusor and sphincter cells (60% and 51%, respectively). Histamine stimulated significantly more cells than carbachol in detrusor (100%) and sphincter (99.34%) cells. Calcium responses to carbachol in detrusor and sphincter cells were comparable and did not differ from those to histamine in detrusor cells. However, histamine and specific agonists stimulated more sphincter cells than did carbachol (P <0.001), and the calcium increase was greater in sphincter cells than in detrusor cells. Single cell analysis revealed comparable H2R responses in detrusor and sphincter cells, but H1R and H3R-mediated calcium reactions were significantly greater in sphincter cells.

CONCLUSIONS

Histamine very effectively induces calcium release in smooth muscle cells. In sphincter cells, histamine is even more effective than carbachol regarding the number of reacting cells and the intracellular calcium increase. Some of the variability in the outcome of antihistaminic interstitial cystitis therapies might be caused by the ineffectiveness of the chosen antihistaminic or unintentional weakening of sphincteric function.

Effect of a 4 week physical training program on plasma concentrations of inflammatory markers in patients with abnormal glucose tolerance

OBJECTIVE

Subclinical chronic inflammation could be a unifying factor linking type 2 diabetes (T2D) and atherosclerosis. The beneficial effects of physical activity on a reduced risk of coronary heart disease could at least in part be mediated by improved markers of inflammation.

RESEARCH DESIGN AND METHODS

The aim of this study was to determine the effect of 4 weeks of physical training on plasma concentrations of interleukin (IL)-6, C-reactive protein (CRP), adiponectin and IL-10 in 60 individuals with normal glucose tolerance, impaired glucose tolerance (IGT) or T2D.

RESULTS

In patients with IGT and T2D, significant improvement in body fat, fitness level, glucose metabolism and insulin sensitivity after 4 weeks of physical training was associated with significantly improved plasma concentrations of adiponectin and CRP, but not IL-6. Regression analysis demonstrated only for the anti-inflammatory parameters adiponectin and IL-10 a significant relationship with the decrease in fasting plasma glucose, whereas changes in IL-6 and CRP were not significantly related to changes in fasting plasma glucose, body fat, maximal oxygen uptake, or insulin sensitivity. In a multivariate linear regression analysis, only changes in circulating adiponectin, fasting plasma glucose and percentage body fat were determinants of changes in insulin sensitivity.

CONCLUSIONS

Physical training was associated with a near normalization of adiponectin and CRP plasma concentrations in subjects with IGT and T2D. Increased insulin sensitivity after training was most strongly related to changes in adiponectin plasma concentrations, in fasting plasma glucose and percentage body fat, whereas changes in IL-6, IL-10 and CRP plasma concentrations did not significantly contribute to improved insulin sensitivity.

Altered fiber distribution and fiber-specific glycolytic and oxidative enzyme activity in skeletal muscle of patients with type 2 diabetes

OBJECTIVE

We investigated whether alterations of glycolytic and oxidative enzyme capacity in skeletal muscle of patients with type 2 diabetes pertain to specific muscle fibers and are associated with changes in muscle fiber composition.

RESEARCH DESIGN AND METHODS

Vastus lateralis muscle was obtained by percutaneous biopsy from 10 patients with type 2 diabetes and 15 age- and BMI-matched healthy volunteers. Using cytophotometry, muscle fiber composition and fiber type-specific glycolytic and oxidative enzyme activities were measured in slow oxidative, fast oxidative glycolytic, and fast glycolytic fibers.

RESULTS

In the whole muscle, oxidative activity was decreased in patients with type 2 diabetes. The slow oxidative fiber fraction was reduced by 16%, whereas the fast glycolytic fiber fraction was increased by 49% in skeletal muscle from the diabetic patients. Both oxidative and glycolytic enzyme activities were significantly increased in fast glycolytic and fast oxidative glycolytic fibers of type 2 diabetic patients. However, the fiber-specific ratio of glycolytic enzyme activity relative to oxidative activity was not different between type 2 diabetic patients and the control subjects. The myofibrillic ATP activity was significantly lower in all fiber types of patients with type 2 diabetes and correlates with glucose infusion rate during the steady state of a euglycemic-hyperinsulinemic clamp and maximal aerobic capacity and negatively with HbA(1c) values.

CONCLUSIONS

Reduced oxidative enzyme activity in muscle of type 2 diabetic patients is most likely due to a reduction in slow oxidative fibers. Increased glycolytic and oxidative enzyme activities in individual muscle fibers are closely related to measures of long-term glycemic control and whole-body insulin sensitivity and could therefore represent a compensatory mechanism of the muscle in function of the altered glucose metabolism.