MiR-205 is up-regulated in islets of diabetes-susceptible mice and targets the diabetes gene Tcf7l2

AIM

MicroRNAs play an important role in the maintenance of cellular functions by fine-tuning gene expression levels. The aim of the current study was to identify genetically caused changes in microRNA expression which associate with islet dysfunction in diabetic mice.

METHODS

To identify novel microRNAs involved in islet dysfunction, transcriptome and miRNome analyses were performed in islets of obese, diabetes-susceptible NZO and diabetes-resistant B6-ob/ob mice and results combined with quantitative trait loci (QTL) and functional in vitro analysis.

RESULTS

In islets of NZO and B6-ob/ob mice, 94 differentially expressed microRNAs were detected, of which 11 are located in diabetes QTL. Focusing on conserved microRNAs exhibiting the strongest expression difference and which have not been linked to islet function, miR-205-5p was selected for further analysis. According to transcriptome data and target prediction analyses, miR-205-5p affects genes involved in Wnt and calcium signalling as well as insulin secretion. Over-expression of miR-205-5p in the insulinoma cell line INS-1 increased insulin expression, left-shifted the glucose-dependence of insulin secretion and supressed the expression of the diabetes gene TCF7L2. The interaction between miR-205-5p and TCF7L2 was confirmed by luciferase reporter assay.

CONCLUSION

MiR-205-5p was identified as relevant microRNA involved in islet dysfunction by interacting with TCF7L2.

Polymorphisms in miRNA binding sites involved in metabolic diseases in mice and humans

Type 2 diabetes and obesity are well-studied metabolic diseases, which are based on genetic and epigenetic alterations in combination with an obesogenic lifestyle. The aim of this study was to test whether SNPs in miRNA-mRNA binding sites that potentially disrupt binding, elevate the expression of miRNA targets, which participate in the development of metabolic diseases. A computational approach was developed that integrates transcriptomics, linkage analysis, miRNA-target prediction data, and sequence information of a mouse model of obesity and diabetes. A statistical analysis demonstrated a significant enrichment of 566 genes for a location in obesity- and diabetes-related QTL. They are expressed at higher levels in metabolically relevant tissues presumably due to altered miRNA-mRNA binding sites. Of these, 51 genes harbor conserved and impaired miRNA-mRNA-interactions in human. Among these, 38 genes have been associated to metabolic diseases according to the phenotypes of corresponding knockout mice or other results described in the literature. The remaining 13 genes (e.g. Jrk, Megf9, Slfn8 and Tmem132e) could be interesting candidates and will be investigated in the future.

Visceral Adiposity Index as an Independent Marker of Subclinical Atherosclerosis in Individuals Prone to Diabetes Mellitus

Aims: The visceral adiposity index (VAI) has been proposed as an estimate of visceral adipose tissue (VAT) mass and as an indicator of VAT dysfunction. Both parameters are associated with cardiometabolic risk, including insulin resistance. In this study, we investigated whether VAI is associated with subclinical atherosclerosis in subjects who were free of cardiovascular disease but were at risk of developing diabetes mellitus.

Methods: A total of 731 adults with a median age of 47 years old without diabetes mellitus were included in this cross-sectional study. The anthropometric data, blood pressure, and lipid profiles of 398 women and 333 men were measured. All subjects underwent an oral glucose tolerance test, and carotid intima–media thickness (cIMT) was evaluated by ultrasound. Insulin resistance was estimated using the homeostatic model assessment of insulin resistance (HOMA-IR).

Results: VAI and HOMA-IR (β_st = 0.44, p < 0.0001), VAI and cIMT (β_st = 0.17, p < 0.0001), and HOMA-IR and cIMT (β_st = 0.09, p = 0.0127) were correlated with each other. After adjusting for cofounding variables, VAI is still correlated with HOMA-IR (β_st = 0.42, p < 0.0001). Furthermore, VAI (β_st = 0.07, p = 0.0392) but not HOMA-IR (β_st = 0.03, p = 0.37) was correlated with cIMT independently of other established cardiovascular risk factors.

Conclusion: The calculation of VAI may provide a better estimation of subclinical atherosclerosis than the calculation of HOMA-IR.

Periaortic Adipose Tissue Compared With Peribrachial Adipose Tissue Mass as Markers and Possible Modulators of Cardiometabolic Risk

Increased perivascular fat mass contributes to cardiometabolic risk (CMR). High peribrachial adipose tissue (PBAT) associates with insulin resistance independently of established CMR parameters. It is unknown to what extent periaortic adipose tissue (PAAT) may have a similar impact. In 95 participants, precise quantification of total adipose tissue, PBAT, PAAT, visceral adipose tissue (VAT), and liver fat (LF) content was performed by whole-body magnetic resonance imaging. Insulin sensitivity was determined by oral glucose tolerance test and carotid intima-media thickness (cIMT) by high-resolution ultrasound. In univariate analyses, PAAT correlated with PBAT (β = .65, P < .0001). A negative correlation of PAAT (β = -.35, P = .0002) and PBAT (β = -.43, P < .0001) with insulin sensitivity was observed. While in a stepwise forward regression analysis the relationship of PAAT with insulin sensitivity was no longer significant after adjustment for VAT, LF content, and other CMR factors ( P = 0.42), PBAT still correlated with insulin sensitivity ( r² = .35, P = .01). The association between PAAT and cIMT (β = .49, P < .0001) remained significant after adjustment for these variables ( r² = .42, P = .0001). Although PAAT and PBAT strongly correlate, PAAT is not associated with insulin resistance, but with cIMT. Therefore, PAAT and PBAT may act differently as possible modulators of insulin resistance and subclinical atherosclerosis.

Normal values for intima-media thickness of the common carotid artery - an update following a novel risk factor profiling

Abstract. Background: There is a widely approved influence of novel risk factors like the body fat distribution and the associated metabolic syndrome, subclinical inflammation, insulin resistance and prediabetic disturbances in glucose metabolism on the progression of atherosclerosis. Former studies examining normal values for intima-media thickness (IMT) did not consider all of these new study results in detail. We therefore aimed to assess an update on age- and gender-specific normal values for IMT accounting for these novel risk factors. Patients and methods: We evaluated IMT by high-resolution ultrasound (13 MHz) on the far wall of the common carotid artery in 801 subjects without cardiovascular disease (428 women aged 46.2±12.9 years; 373 men aged 47.3±13.3 years). After precise evaluation and exclusion of 14 cardiovascular risk factors, 90% limits of IMT were determined by parametric statistics. Results: The reference limits of IMT according to the age classes 18-29, 30-39, 40-49 and 50-59 years were estimated as 0.47, 0.59, 0.67 and 0.70 mm in women and 0.47, 0.62, 0.72 and 0.80 mm in men. Conclusions: Age and gender-specific normal values for IMT are lower than reported in former studies after additionally accounting for novel cardiovascular risk factors. The still widely regarded upper IMT limit of 1 mm must be strictly regarded as obsolete.

[Rare cause of an abdominal emergency--case 6/2014]

HISTORY AND ADMISSION FINDINGS

We report on a 58-year-old male patient with abdominal and right-sided flank pain, who presented with the picture of an acute abdominal emergency.

INVESTIGATIONS

Laboratory tests revealed evidence of an inflammation and a hematuria. In the Doppler duplex ultrasound and computed tomography, chronic idiopathic periaortitis was diagnosed. The inflammatory-fibrosing disease resulted in urine retention and rupture of the fornix of the right kidney.

DIAGNOSIS, TREATMENT AND COURSE

After surgical implementation of an ureteral stent and initiation of immunosuppressive therapy, it came to an improvement of the symptoms.

CONCLUSIONS

In the differential diagnosis of an acute abdominal emergency, diseases of the aorta should be taken into account. Especially in male patients with anatomical complications it is important to exclude an inflammatory-fibrosing disease.

Fetuin-A influences vascular cell growth and production of proinflammatory and angiogenic proteins by human perivascular fat cells

AIMS/HYPOTHESIS

Fetuin-A (alpha2-Heremans-Schmid glycoprotein), a liver-derived circulating glycoprotein, contributes to lipid disorders, diabetes and cardiovascular diseases. In a previous study we found that perivascular fat cells (PVFCs) have a higher angiogenic potential than other fat cell types. The aim was to examine whether fetuin-A influences PVFC and vascular cell growth and the expression and secretion of proinflammatory and angiogenic proteins, and whether TLR4-independent pathways are involved.

METHODS

Mono- and co-cultures of human PVFCs and endothelial cells were treated with fetuin-A and/or palmitate for 6-72 h. Proteins were quantified by ELISA and Luminex, mRNA expression by real-time PCR, and cell growth by BrDU-ELISA. Some PVFCs were preincubated with a nuclear factor κB NFκBp65 inhibitor, or the toll-like receptor 4 (TLR4) inhibitor CLI-095, or phosphoinositide 3-kinase (PI3K)/Akt inhibitors and/or stimulated with insulin. Intracellular forkhead box protein O1 (FoxO1), NFκBp65 and inhibitor of κB kinase β (IKKβ) localisation was visualised by immunostaining.

RESULTS

PVFCs expressed and secreted IL-6, IL-8, plasminogen activator inhibitor 1 (PAI-1), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF)-BB, monocyte chemotactic protein-1 (MCP-1), vascular endothelial growth factor (VEGF), placental growth factor (PLGF) and hepatocyte growth factor (HGF). Fetuin-A upregulated IL-6 and IL-8, and this was potentiated by palmitate and blocked by CLI-095. Immunostaining and electrophoretic mobility shift assay (EMSA) showed partial NFκBp65 activation. MCP-1 was upregulated and blocked by CLI-095, but not by palmitate. However, HGF was downregulated, which was slightly potentiated by palmitate. This effect persisted after TLR4 pathway blockade. Stimulation of insulin-PI3K-Akt signalling by insulin resulted in nuclear FoxO1 extrusion and HGF upregulation. Fetuin-A counteracted these insulin effects.

CONCLUSIONS/INTERPRETATION

Fetuin-A and/or palmitate influence the expression of proinflammatory and angiogenic proteins only partially via TLR4 signalling. HGF downregulation seems to be mediated by interference with the insulin-dependent receptor tyrosine kinase pathway. Fetuin-A may also influence angiogenic and proinflammatory proteins involved in atherosclerosis.

Exercise-induced albuminuria is associated with perivascular renal sinus fat in individuals at increased risk of type 2 diabetes

AIMS/HYPOTHESIS

Microalbuminuria represents an established surrogate marker of early diabetic nephropathy and glomerular microangiopathy. Increasing evidence is emerging of a role of perivascular adipose tissue (PVAT) as an important link between obesity, insulin resistance and both macro- and microangiopathy. It is not known whether perivascular renal sinus fat (RSF) has an impact on microalbuminuria in the prediabetic stage. We investigated whether RSF quantified by MRI is associated with microalbuminuria before or after exercise.

METHODS

Non-diabetic individuals at increased risk of type 2 diabetes were recruited into the Tübingen Lifestyle Intervention Program (TULIP); 146 participants took part in the analysis. RSF was measured in axial MRI sections at the level of the renal artery. Urine was collected before and after exercise stress testing.

RESULTS

Participants (age 47 ± 12 years; mean ± SD) reached a mean exercise load of 176 ± 49 W, with a mean arterial peak pressure (MAPP) of 112 ± 14 mmHg. After adjusting for sex, age, visceral adipose tissue (VAT) and MAPP during exercise, RSF was significantly associated with postexercise albumin/creatinine ratio (ACR; p = 0.006). No association between RSF and baseline BP could be observed after adjusting for confounders (p = 0.26), and there was no association between RSF and baseline ACR either (p = 0.2).

CONCLUSIONS

RSF is associated with exercise-induced albuminuria independently of sex, age, VAT and MAPP in a non-diabetic cohort at diabetic risk. We conclude that PVAT in the renal sinus may play a role in the pathogenesis of microalbuminuria.

The secretion pattern of perivascular fat cells is different from that of subcutaneous and visceral fat cells

AIMS/HYPOTHESIS

We have previously found that the mass of perivascular adipose tissue (PVAT) correlates negatively with insulin sensitivity and post-ischaemic increase in blood flow. To understand how PVAT communicates with vascular vessels, interactions between perivascular, subcutaneous and visceral fat cells with endothelial cells (ECs) were examined with regard to inflammatory, metabolic and angiogenic proteins. To test for possible in vivo relevance of these findings, circulating levels of the predominant secretion product, hepatocyte growth factor (HGF), was measured in individuals carefully phenotyped for fat distribution patterns.

METHODS

Mono- and co-cultures of human primary fat cells with ECs were performed. mRNA expression and protein production were studied using Luminex, cytokine array, RealTime Ready and ELISA systems. Effects of HGF on vascular cells were determined by WST assays. In patients, HGF levels were measured by ELISA, and the mass of different fat compartments was determined by whole-body MRI.

RESULTS

In contrast with other fat cell types, PVAT cells released higher amounts of angiogenic factors, e.g. HGF, acidic fibroblast growth factor, thrombospondin-1, serpin-E1, monocyte chemotactic protein-1 and insulin-like growth factor-binding protein -3. Cocultures showed different expression profiles from monocultures, and mature adipocytes differed from pre-adipocytes. HGF was preferentially released by PVAT cells and stimulated EC growth and smooth muscle cell cytokine release. Finally, in 95 patients, only PVAT, not visceral or subcutaneous mass, correlated independently with serum HGF levels (p = 0.03; r = 0.225).

CONCLUSIONS

Perivascular (pre-)adipocytes differ substantially from other fat cells with regard to mRNA expression and protein production of angiogenic factors. This may contribute to fat tissue growth and atherosclerotic plaque complications. Higher levels of angiogenic factors, such as HGF, in patients with increased perivascular fat mass may have pathological relevance.

4-1BB ligand modulates direct and Rituximab-induced NK-cell reactivity in chronic lymphocytic leukemia

NK cells play an important role in tumor immunosurveillance and largely contribute to the therapeutic success of anti-tumor antibodies like Rituximab. Here, we studied the role of the TNF family member 4-1BB ligand (4-1BBL) during the interaction of NK cells with chronic lymphocytic leukemia (CLL) cells. 4-1BBL was highly expressed on patient B-CLL cells in all 56 investigated cases. Signaling via 4-1BBL following interaction with 4-1BB, which was detected on NK cells of CLL patients but not healthy individuals, led to the release of immunoregulatory cytokines including TNF by CLL cells. CLL patient sera contained elevated levels of TNF and induced 4-1BB upregulation on NK cells, which in turn impaired direct and Rituximab-induced NK-cell reactivity against 4-1BBL-expressing targets. NK-cell reactivity was not only enhanced by blocking the interaction of NK cell-expressed 4-1BB with 4-1BBL expressed by CLL cells, but also by preventing 4-1BB upregulation on NK cells via neutralization of TNF in patient serum with Infliximab. Our data indicate that 4-1BBL mediates NK-cell immunosubversion in CLL, and thus might contribute to the reportedly compromised efficacy of Rituximab to induce NK-cell reactivity in the disease, and that TNF neutralization may serve to enhance the efficacy of Rituximab treatment in CLL.

Effects of a lifestyle intervention in metabolically benign and malign obesity

AIMS/HYPOTHESIS

We and others recently characterised metabolically benign or healthy obesity (MHO). In the present study we investigated whether a lifestyle intervention is sufficient to place obese insulin-resistant (OIR) individuals in a position where the possible metabolic consequences are similar to those for MHO individuals.

METHODS

A total of 262 non-diabetic individuals participated in a 9 month lifestyle intervention programme. Obese individuals (BMI ≥ 30.0 kg/m(2)) were stratified, based on their insulin sensitivity (IS) estimated from an OGTT, into MHO (IS in the upper quartile, n = 26) and OIR (IS in the lower three quartiles, n = 77). Total body and visceral fat were measured by magnetic resonance (MR) tomography and liver fat by (1)H-MR spectroscopy.

RESULTS

During the intervention, visceral fat decreased significantly in both groups (both p ≤ 0.009), whereas total body and liver fat decreased only in the OIR group (p < 0.0001; MHO p = 0.12 for total body fat and p = 0.47 for liver fat). IS improved in the OIR group (p < 0.0001), but remained essentially unchanged in the MHO group (p = 0.30). However, despite the significant increase in the OIR group, IS at follow-up barely exceeded 50% of the IS of the MHO group (OIR 9.30 ± 0.53 arbitrary units [AU]; MHO 16.41 ± 1.05 AU; p < 0.0001).

CONCLUSIONS/INTERPRETATION

IS improves during the lifestyle intervention in OIR individuals. However, it does not reach a level where adequate protection from type 2 diabetes and cardiovascular disease is expected. Thus, stratification of obese individuals based on their metabolic phenotype is important to identify those who are likely to need early pharmacological treatment in addition to the lifestyle intervention.

Apelin serum levels are not associated with early atherosclerosis or fat distribution in young subjects with increased risk for type 2 diabetes

Apelin is proposed to possess protective cardiovascular properties and may furthermore promote favorable effects on glucose metabolism. First data in humans seem to support this hypothesis. Therefore we aimed to assess the meaning of apelin as an early risk indicator in young subjects prone to atherosclerosis and type 2 diabetes. Furthermore we examined the association of apelin serum levels with insulin sensitivity/resistance and body fat distribution as probably dependent cardiovascular risk factors. We examined 344 individuals (f/m=216/128, mean age 46±1 years) with an increased risk for type 2 diabetes. Apelin-36 serum levels were measured via ELISA. Endothelial dysfunction and intima media thickness (IMT) were assessed using high resolution ultrasound. Visceral adipose tissue (VAT) was measured with an axial T1-weighted fast spin echo technique with a 1.5 T whole-body imager. According to the study population's age, FMD (6.4±0.2%) and IMT (0.56±0.01 mm) were within the expected ranges. Gender or age had no influence on serum apelin levels. When looked at early stages of atherosclerosis, we could not detect a significant correlation between apelin serum levels and FMD or IMT. Blood pressure as well was unaffected by serum apelin levels. Furthermore, neither parameters of insulin sensitivity like insulin sensitivity index (ISI), nor fat distribution like BMI, grade of adiposity, total adipose tissue or VAT were associated with apelin serum levels. We conclude that apelin serum levels do not add further information on the cardiovascular-, or diabetes risk pattern in a diabetes prone population.

Metabonomic fingerprints of fasting plasma and spot urine reveal human pre-diabetic metabolic traits

Impaired glucose tolerance (IGT) which precedes overt type 2 diabetes (T2DM) for decades is associated with multiple metabolic alterations in insulin sensitive tissues. In an UPLC-qTOF-mass spectrometry-driven non-targeted metabonomics approach we investigated plasma as well as spot urine of 51 non-diabetic, overnight fasted individuals aiming to separate subjects with IGT from controls thereby identify pathways affected by the pre-diabetic metabolic state. We could clearly demonstrate that normal glucose tolerant (NGT) and IGT subjects clustered in two distinct groups independent of the investigated metabonome. These findings reflect considerable differences in individual metabolite fingerprints, both in plasma and urine. Pre-diabetes associated alterations in fatty acid-, tryptophan-, uric acid-, bile acid-, and lysophosphatidylcholine-metabolism, as well as the TCA cycle were identified. Of note, individuals with IGT also showed decreased levels of gut flora-associated metabolites namely hippuric acid, methylxanthine, methyluric acid, and 3-hydroxyhippuric acid. The findings of our non-targeted UPLC-qTOF-MS metabonomics analysis in plasma and spot urine of individuals with IGT vs NGT offers novel insights into the metabolic alterations occurring in the long, asymptomatic period preceding the manifestation of T2DM thereby giving prospects for new intervention targets. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11306-010-0203-1) contains supplementary material, which is available to authorized users.

Rapid effect of single-dose rosiglitazone treatment on endothelial function in healthy men with normal glucose tolerance: data from a randomised, placebo-controlled, double-blind study

Antidiabetic thiazolidinediones (TZDs) improve endothelial function in patients with or without type 2 diabetes. The present randomised, placebo-controlled, double-blind study examined the time course of a single dose of rosiglitazone on flow-mediated endothelium-dependent vasodilation (FMD), metabolic parameters, and its effect on inflammatory markers in non-diabetic men. Forty non-obese, healthy men with normal glucose tolerance were randomised to a single dose of rosiglitazone (8 mg) or placebo, and FMD was assessed at baseline as well as after 6 h and 24 h. Rosiglitazone did not significantly affect blood glucose and insulin levels or lipid parameters after 6 and 24 h compared with placebo. Treatment with rosiglitazone significantly increased FMD after 6 h from 4.3% (3.3; 4.9) to 7.6% (5.6; 9.2) (p<0.0001 vs. baseline) resulting in a highly significant effect compared with placebo (p<0.0001 for difference between groups). After 24 h FMD was still significantly higher in the rosiglitazone group compared with baseline (p=0.001), but the effect was no longer statistically significant versus placebo (p=0.171). Our study shows a very rapid effect of single dose rosiglitazone treatment on endothelial function in non-diabetic healthy men, underscoring the hypothesis that TZDs may exhibit direct effect in the vasculature independent of their metabolic action.

Determination of unknown high-grade atherosclerotic lesions by whole-body cardiovascular imaging: assessment of patients with symptomatic atherosclerotic disease of peripheral arteries

RATIONALE AND OBJECTIVES

The long-term prospects for patients with peripheral-arterial-occlusive disease (PAOD) must be considered in the context of coexistent generalized atherosclerosis. We sought to determine the added clinical information of noninvasive magnetic resonance imaging (MRI) for detecting asymptomatic atherosclerotic disease in patients already at high risk.

MATERIALS AND METHODS

Eighty-four patients (64 men, mean age 66.2 + or - 10.0 years, range 34-84 years) with suspected or known PAOD were examined using a comprehensive cardiovascular MRI protocol. Two experienced observers reviewed all MRIs for the presence of "relevant findings," which were defined as pathology requiring immediate therapy or mid-term follow-up.

RESULTS

Assessment of cardiac structures and function in 84 study patients yielded new pathology in 40 (48%) patients, whereas cerebral imaging revealed new findings in 45 (54%) patients. Previously unsuspected vascular findings were evident in 46 (55%) patients. Using the information from the MRIs, in 54 (64%) of patients mid-term follow-up was required, whereas in 7 (8%) patients a change of therapy or immediate treatment was necessary.

CONCLUSION

Whole-body cardiovascular MRI is able to detect symptomatic and unsuspected findings in patients with PAOD. This technique was able to detect several vascular abnormalities that necessitated immediate medical attention and intervention in patients already identified as high-risk patients and, therefore, may show an increasing impact to determine individual therapeutic and follow-up concepts.

Comparison between a linear versus a macrocyclic contrast agent for whole body MR angiography in a clinical routine setting

BACKGROUND

Previous experiences of whole body MR angiography are predominantly available in linear 0.5 M gadolinium-containing contrast agents. The aim of this study was to compare image quality on a four-point scale (range 1-4) and diagnostic accuracy of a 1.0 M macrocyclic contrast agent (gadobutrol, n = 80 patients) with a 0.5 M linear contrast agent (gadopentetate dimeglumine, n = 85 patients) on a 1.5 T whole body MR system. Digital subtraction angiography served as standard of reference.

RESULTS

All examinations yielded diagnostic image quality. There was no significant difference in image quality (3.76 +/- 0.3 versus 3.78 +/- 0.3, p = n.s.) and diagnostic accuracy observed. Sensitivity and specificity of the detection of hemodynamically relevant stenoses was 93%/95% in the gadopentetate dimeglumine group and 94%/94% in the gadobutrol group, respectively.

CONCLUSION

The high diagnostic accuracy of gadobutrol in the clinical routine setting is of high interest as medical authorities (e.g. the European Agency for the Evaluation of Medicinal Products) recommend macrocyclic contrast agents especially to be used in patients with renal failure or dialysis.

Perivascular fatty tissue at the brachial artery is linked to insulin resistance but not to local endothelial dysfunction

AIMS/HYPOTHESIS

Different ectopic fat depots, such as visceral or hepatic fat, are known to affect whole body insulin sensitivity. It has recently been hypothesised that differences in perivascular adipose tissue (PVAT) mass around resistance vessels may also contribute to insulin resistance, possibly via direct vascular effects leading to reduced capillary cross-sectional area in the muscle, which in turn affects muscular blood flow and glucose uptake. Based on this, the aim of the present study was to test whether PVAT around conduit arteries (i.e. the brachial artery) influences NO bioavailability, expressed as flow-mediated dilation (FMD), or insulin sensitivity in humans in vivo.

METHODS

Insulin sensitivity was measured by OGTT in all 95 participants (59 women, 36 men; median age 47 years, range 19-66 years) and by the gold standard, a euglycaemic-hyperinsulinaemic clamp, in a randomly selected subgroup of 33 participants. Quantification of the different fat compartments, including PVAT around the brachial artery, was achieved by high-resolution magnetic resonance imaging (1.5 T). Blood flow and FMD were measured at the brachial artery using high-resolution (13 MHz) ultrasound, after 5 min of forearm occlusion.

RESULTS

PVAT was negatively correlated with insulin sensitivity and the post-ischaemic increase in blood flow. The association between PVAT and insulin sensitivity (r = -0.54, beta = -0.37, p = 0.009) was independent of age, sex, visceral adipose tissue, liver fat, BMI and further cardiovascular risk factors. No correlation could be detected between PVAT and local endothelial function. However, we observed an independent association between PVAT and post-ischaemic increase in blood flow (r = -0.241; beta = -1.69; p = 0.02).

CONCLUSIONS/INTERPRETATION

PVAT seems to play an independent role in the pathogenesis of insulin resistance. This may be due to direct vascular effects influencing muscular blood flow.

Identification and characterization of metabolically benign obesity in humans

BACKGROUND

Obesity represents a risk factor for insulin resistance, type 2 diabetes mellitus, and atherosclerosis. In addition, for any given amount of total body fat, an excess of visceral fat or fat accumulation in the liver and skeletal muscle augments the risk. Conversely, even in obesity, a metabolically benign fat distribution phenotype may exist.

METHODS

In 314 subjects, we measured total body, visceral, and subcutaneous fat with magnetic resonance (MR) tomography and fat in the liver and skeletal muscle with proton MR spectroscopy. Insulin sensitivity was estimated from oral glucose tolerance test results. Subjects were divided into 4 groups: normal weight (body mass index [BMI] [calculated as weight in kilograms divided by height in meters squared], < 25.0), overweight (BMI, 25.0-29.9), obese-insulin sensitive (IS) (BMI, > or = 30.0 and placement in the upper quartile of insulin sensitivity), and obese-insulin resistant (IR) (BMI, > or = 30.0 and placement in the lower 3 quartiles of insulin sensitivity).

RESULTS

Total body and visceral fat were higher in the overweight and obese groups compared with the normal-weight group (P < .05); however, no differences were observed between the obese groups. In contrast, ectopic fat in skeletal muscle (P < .001) and particularly the liver (4.3% +/- 0.6% vs 9.5% +/- 0.8%) and the intima-media thickness of the common carotid artery (0.54 +/- 0.02 vs 0.59 +/- 0.01 mm) were lower and insulin sensitivity was higher (17.4 +/- 0.9 vs 7.3 +/- 0.3 arbitrary units) in the obese-IS vs the obese-IR group (P < .05). Unexpectedly, the obese-IS group had almost identical insulin sensitivity and the intima-media thickness was not statistically different compared with the normal-weight group (18.2 +/- 0.9 AU and 0.51 +/- 0.02 mm, respectively).

CONCLUSIONS

A metabolically benign obesity that is not accompanied by insulin resistance and early atherosclerosis exists in humans. Furthermore, ectopic fat in the liver may be more important than visceral fat in the determination of such a beneficial phenotype in obesity.

Identification and characterization of metabolically benign obesity in humans

BACKGROUND

Obesity represents a risk factor for insulin resistance, type 2 diabetes mellitus, and atherosclerosis. In addition, for any given amount of total body fat, an excess of visceral fat or fat accumulation in the liver and skeletal muscle augments the risk. Conversely, even in obesity, a metabolically benign fat distribution phenotype may exist.

METHODS

In 314 subjects, we measured total body, visceral, and subcutaneous fat with magnetic resonance (MR) tomography and fat in the liver and skeletal muscle with proton MR spectroscopy. Insulin sensitivity was estimated from oral glucose tolerance test results. Subjects were divided into 4 groups: normal weight (body mass index [BMI] [calculated as weight in kilograms divided by height in meters squared], < 25.0), overweight (BMI, 25.0-29.9), obese-insulin sensitive (IS) (BMI, > or = 30.0 and placement in the upper quartile of insulin sensitivity), and obese-insulin resistant (IR) (BMI, > or = 30.0 and placement in the lower 3 quartiles of insulin sensitivity).

RESULTS

Total body and visceral fat were higher in the overweight and obese groups compared with the normal-weight group (P < .05); however, no differences were observed between the obese groups. In contrast, ectopic fat in skeletal muscle (P < .001) and particularly the liver (4.3% +/- 0.6% vs 9.5% +/- 0.8%) and the intima-media thickness of the common carotid artery (0.54 +/- 0.02 vs 0.59 +/- 0.01 mm) were lower and insulin sensitivity was higher (17.4 +/- 0.9 vs 7.3 +/- 0.3 arbitrary units) in the obese-IS vs the obese-IR group (P < .05). Unexpectedly, the obese-IS group had almost identical insulin sensitivity and the intima-media thickness was not statistically different compared with the normal-weight group (18.2 +/- 0.9 AU and 0.51 +/- 0.02 mm, respectively).

CONCLUSIONS

A metabolically benign obesity that is not accompanied by insulin resistance and early atherosclerosis exists in humans. Furthermore, ectopic fat in the liver may be more important than visceral fat in the determination of such a beneficial phenotype in obesity.

Induction of stearoyl-CoA desaturase protects human arterial endothelial cells against lipotoxicity

Endothelial lipotoxicity has been implicated in the pathogenesis of multiple stages of cardiovascular disease from early endothelial dysfunction to manifest atherosclerosis and its complications. Saturated free fatty acids are the major inducers of endothelial cell apoptosis and inflammatory cytokines. In humans, the enzyme human stearoyl-CoA desaturase-1 (hSCD-1) is the limiting step of the desaturation of saturated to monounsaturated fatty acids. Since we could demonstrate the expression of SCD-1 in primary human arterial endothelial cells (HAECs), we aimed to prove a beneficial role of upregulated hSCD-1 expression. In contrast to other cells that are less susceptible to lipotoxicity, hSCD-1 was not upregulated in HAECs upon palmitate treatment. Following that, we could show that upregulation of hSCD-1 using the LXR activator TO-901317 in HAECs protects the cells against palmitate-induced lipotoxicity, cell apoptosis, and expression of inflammatory cytokines IL-6 and IL-8. Increased hSCD-1 activity was determined as increased C16:1/16:0 ratio and enhanced triglyceride storage in palmitate treated cells. The beneficial effect was clearly attributed to enhanced hSCD-1 activity. Overexpression of hSCD-1 blocked palmitate-induced cytotoxicity, and knockdown of hSCD-1 using siRNA abolished the protective effect of TO-901317 in HEK-293 cells. Additionally, inhibition of hSCD-1 with 10/12 CLA blocked the effect of TO-901317 on palmitate-induced lipotoxicity, cell apoptosis, and inflammatory cytokine induction in HAECs. We conclude that upregulation of hSCD-1 leads to a desaturation of saturated fatty acids and facilitates their esterification and storage, thereby preventing downstream effects of lipotoxicity in HAECs. These findings add a novel aspect to the atheroprotective actions of LXR activators in cardiovascular disease.

A practical approach for bridging anticoagulation after mechanical heart valve replacement

BACKGROUND AND AIM OF THE STUDY

Following mechanical heart valve replacement, patients may require a form of 'bridging' anticoagulation to prevent valve-associated thromboembolism until oral vitamin K antagonists take effect. In 2000, the present authors changed their bridging protocol to a fixed dose of 40 mg enoxaparin twice daily (b.i.d., subcutaneous), regardless of the patient's body weight and renal function. The study aim was to evaluate the feasibility of this protocol with regards to thromboembolism, hemorrhage and other valve-associated adverse effects.

METHODS

Between April 2000 and December 2004, a total of 256 consecutive patients who had undergone mechanical heart valve replacement were enrolled into this retrospective study. All patients received 40 mg enoxaparin b.i.d., subcutaneously, as bridging anticoagulation for a mean of 6.7 days, commencing at a mean of 3.8 days (range: 2-42 days) after surgery. This was approximately 55% (range: 32-95%) of the recommended dose considered to be safe in this setting.

RESULTS

A total of 18 (7%) minor bleeding events and two (0.7%) arterial thromboses were seen to arise from previously existing high-grade (>90%) stenosis of the affected vessels. At discharge, all prosthetic valves showed regular, echocardiographically confirmed, function. The mean follow up was 38.6 days (range: 8-106 days). Mitral valve replacement (p = 0.005) was shown to be a significant risk factor for minor bleeding, but not for thromboembolism. None of the other risk factors reached significance when testing for minor bleeding or major thromboembolic events.

CONCLUSION

Within the special setting of postoperative cardiac surgery, this modified anticoagulation protocol appears feasible and safe, with efficacy equivalent to that of full-dose protocols reported elsewhere using either low-molecular-weight or unfractionated heparin. By using this protocol, the effort required to bridge patients to effective oral anticoagulation was greatly reduced as there was no requirement for repeated laboratory measurements and dose adjustments. A prospective multi-center study should be conducted to confirm the hypothesis that the first bridging period after prosthetic heart valve replacement with extracorporeal circulation is different, and permits the use of a bridging protocol with a lower anticoagulation dose.

Endothelial NO-synthase intron 4 polymorphism is associated with disturbed in vivo nitric oxide production in individuals prone to type 2 diabetes

Insulin resistance, as well as vascular disease, both share a relevant genetic background taking the influence of a positive family history of these disorders. On the other hand, insulin resistance is associated with a proatherosclerotic disturbance in nitric oxide dependent vasodilation, probably contributing to the link between these two disorders. We examined the association between nitric oxide dependent vasodilation (measured with high resolution ultrasound at 13 MHz) and three relevant NO-synthase (eNOS)-polymorphisms in 200 insulin resistant subjects participating in the Tuebinger Lifestyle Intervention Program (TULIP). This study revealed that carriers of the eNOS intron 4 polymorphism (aa 2.16%; ab 24.2%; bb 73.2%) show significantly worse endothelial, and thereby eNOS dependent vasodilation (p=0.03, multivariate ANOVA), as compared to wildtype carriers. The 5' UTR T-786C and the G894 T polymorphism did not show any influence on eNOS-activity. In subjects at increased risk to develop type 2 diabetes, the eNOS intron 4 polymorphism is independently associated with endothelial function as indicated by disturbed endothelial NO production. Due to the high prevalence and the relatively strong effect, this polymorphism might help to identify subjects at increased risk for atherosclerosis associated with overweight and insulin resistance.

The CCR2 promoter polymorphism T-960A, but not the serum MCP-1 level, is associated with endothelial function in prediabetic individuals

Monocyte-chemoattractant-protein (MCP)-1 and its receptor CCR2 have been shown to play a pivotal role in vascular inflammation and atherosclerotic plaque formation. However, it is currently unclear whether MCP-1/CCR2 triggered inflammation affects nitric oxide (NO)-bioavailability, hence influencing vascular function, a sign of early atherosclerosis. Therefore, we sought to investigate the association between serum levels of MCP-1 and NO-bioavailability, expressed as flow mediated dilation (FMD) in vivo, and the impact of CCR2 gene variations on FMD. We studied a German population of 242 prediabetic individuals (144 women, 98 men; mean age 45+/-0.8 years) via FMD by high-resolution ultrasound (13MHz). In order to replicate our findings, a second, independent population (n=115; 44 women, 77 men; mean age 48+/-1.0 years) (total=357 individuals) from Italy was studied. Vascular function in the Italian population was studied via intra-arterial application of acetylcholine. MCP-1 serum-levels were assessed by ELISA and CCR2 polymorphisms were determined by sequencing. MCP-1 serum levels showed no association with FMD (p=0.90), whereas the CCR2 promoter polymorphism was associated with elevated FMD (T/T: 5.6+/-0.3%; T/A: 6.7+/-0.4%; A/A: 8.3+/-0.8%; p=0.01) after adjusting for possible confounders. These results were confirmed in the independent Italian population (A/A: 97.1+/-20.3 vs. T/T: 60.5+/-5.6% forearm blood-flow increase; p<0.05). When testing for the functional relevance of the T-960A (rs3918359) polymorphism, we found that the A/A-genotype was associated with moderately increased protein binding in EMSA, increased promoter activity in luciferase assays and reduced transendothelial monocyte migration. In conclusion, MCP-1 serum levels do not reflect endothelial function in vivo in prediabetic individuals. However, the functionally relevant CCR2 promoter polymorphism T-960A (rs3918359) is associated with elevated vascular function. This might be due to reduced subendothelial inflammation, mediated by reduced transendothelial monocyte-migration ability.

Peripheral Embolism due to Bone Entrapment of the Popliteal Artery after Valgus Osteotomy: A Case Report

The authors report on a case of arterial embolism caused by bone entrapment of the popliteal artery due to a protrusion of a hydroxyl-apatite wedge. The wedge had been placed 4 years earlier during the course of a valgus osteotomy procedure. Thrombolytic therapy was performed, and the wedge was removed. Because causes for arterial embolism vary, the knowledge of its underlying mechanism is necessary to avoid recurring events. Bone entrapment after knee surgery is a differential diagnosis that should be taken into account, even years after surgery.