Low hepatic stearoyl-CoA desaturase 1 activity is associated with fatty liver and insulin resistance in obese humans

AIMS/HYPOTHESIS

Stearoyl-CoA desaturase 1 (SCD1) is the rate-limiting enzyme in monounsaturated fatty acid synthesis. It is imperative for the assembly of VLDL particles, which transport triacylglycerol (TG) from liver to adipose tissue and other sites. We aimed to determine the role of hepatic SCD1 activity in human glucose and lipid metabolism.

METHODS

We studied 54 people participating in a lifestyle intervention programme with diet modification and increased physical activity. Insulin sensitivity was determined during a euglycaemic-hyperinsulinaemic clamp and estimated from an OGTT. Liver fat was quantified by (1)H-magnetic resonance spectroscopy at baseline and after 9 months of intervention. The pattern of fatty acids in serum VLDL-TGs was determined by ultracentrifugation followed by thin layer and gas chromatography, with the 18:1 n-9: 18:0 ratio providing an index of hepatic SCD1 activity.

RESULTS

The hepatic SCD1 activity index correlated negatively with liver fat (r= -0.29, p=0.04) and positively with insulin sensitivity, both OGTT-derived (r=0.42, p=0.003) and clamp-derived (r=0.27, p=0.07). These correlations depended on overall adiposity. They were absent in leaner participants (n=27, liver fat: p=0.34, insulin sensitivity [OGTT]: p=0.75, insulin sensitivity [clamp]: p=0.24), but were strong in obese individuals (n=27, p=0.004, p=0.0002 and p=0.006, respectively). Furthermore, during intervention a high SCD1 activity index at baseline predicted a decrease in liver fat only in obese participants (r= -0.46, p=0.02).

CONCLUSIONS/INTERPRETATION

Our data suggest that high hepatic SCD1 activity may regulate fat accumulation in the liver and possibly protects from insulin resistance in obesity.

Oxidative stress, AGE, and atherosclerosis

Numerous reports on the molecular mechanism of atherogenesis indicate an increase in oxidative stress, formation of advanced glycoxidation end products (AGEs), chronic inflammation, and activated cellular response particularly in diabetic patients. To elucidate the initiating and early accelerating events this review will focus on the molecular causes of the induction of these stress factors, their interactions, and their contribution to atherogenesis. Metabolic factors such as elevated free fatty acids, high glucose levels or AGEs induce reactive oxygen species (ROS) in vascular cells leading to ongoing AGE formation and to gene induction of proinflammatory cytokines. Vice versa, numerous cytokines found elevated in obesity and diabetes may also induce oxidative stress thus a circulus vitious may be initiated and accelerated. Increased production of ROS, mainly from mitochondria and NAD(P)H oxidase, stimulates signaling cascades including protein kinase C and mitogen-activated protein kinase pathway leading to nuclear translocation of transcription factors such as nuclear factor-kappaB (NF-kappaB), activator protein 1, and specificity protein 1. Subsequently, the expression of numerous genes including cytokines is rapidly induced, which, in turn, may act on vascular cells promoting the deleterious effects. From animal models of accelerated atherosclerosis a causal role of NAD(P)H oxidase and the AGE/RAGE/NF-kappaB axis to atherogenesis is suggested. Because all factors involved form a highly interwoven network of interactions, the blockade of ROS or AGE formation at different sites may interrupt the vicious cycle. Promising candidate agents are, currently on trial. Most important to clinical practice, a number of drugs commonly used in the treatment of diabetes, hypertension, or cardiovascular disease, such as angiotensin-converting enzyme inhibitors, AT(1) receptor blockers, 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors (statins), and thiazolidindiones have shown promising 'preventive' intracellular antioxidant activity in addition to their primary pharmacological actions.

High resolution gamma ray tomography scanner for flow measurement and non-destructive testing applications

We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662 keV gamma photon energy and achieves a spatial image resolution of 0.2 line pairs/ mm at 10% modulation transfer function for noncollimated detectors. It is primarily intended for the scientific study of flow regimes and phase fraction distributions in fuel element assemblies, chemical reactors, pipelines, and hydrodynamic machines. Furthermore, it is applicable to nondestructive testing of larger radiologically dense objects. The radiation detector is based on advanced avalanche photodiode technology in conjunction with lutetium yttrium orthosilicate scintillation crystals. The detector arc comprises 320 single detector elements which are operated in pulse counting mode. For measurements at fixed vessels or plant components, we built a computed tomography scanner gantry that comprises rotational and translational stages, power supply via slip rings, and data communication to the measurement personal computer via wireless local area network.

[Bilateral nasal remission spectroscopy allows the side separated continuous measurement of changes in swelling of the nasal mucosa]

INTRODUCTION

In earlier studies optical transmission spectroscopy showed that continuous monitoring of changes in the swelling of the nasal mucosa is possible. However, independent measurement in both sides of the nose cannot be achieved by this method. With the aim of achieving real-time monitoring of endonasal swelling separately for both nostrils we developed the new method of bilateral nasal remission spectroscopy for this pilot study.

MATERIALS AND METHODS

In nasal remission spectroscopy, light at a wavelength of 790 nm (close to the isobestic point of hemoglobin) is beamed into each side of the nose, and the light that is backscattered by the internal nasal tissue is measured continuously on the same nasal side. To evaluate the principle of this new method a pilot study was conducted in five healthy probands subjected to a one-sided (unilateral) nasal histamine provocation test (0.14 ml, 2 mg/ml).

RESULTS

In each proband single-sided nasal histamine provocation led to an increase in light extinction on the provoked side by an average of 0.18 optical densities (OD). In four of the five probands a slight increase (0.04 OD) in light extinction was observed on the other side of the nose.

CONCLUSION

Nasal remission spectroscopy seems to allow single-side, continuous monitoring on both sides of the nose. Therefore, the method could also be suitable for use in studies of the nasal cycle, as well as for objectivisation of nasal allergen provocation tests.

Postprandial Mononuclear NF-κB Activation is Independent of the AGE-content of a Single Meal

OBJECTIVE

Dietary uptake of Advanced Glycation Endproducts (AGE) is supposed to potentially contribute to inflammatory reactions linked to vascular dysfunction and late diabetic complications. One mechanism by which dietary AGE might exert these effects is by activation of the proinflammatory transcription factor NF-kappa-B. The aim of this study was to analyze the postprandial effects of a casein meal with low or high AGE content on postprandial NF-kappaB activation in peripheral blood mononuclear cells (pBMC) of healthy volunteers.

RESEARCH DESIGN AND METHODS

Casein was heated for 40 h at 50 degrees C in the presence of sorbitol or glucose, resulting in either minimal (Sorbitol [S]-casein) or large (glucose [G]-casein) amounts of AGE-modified casein. Nine healthy volunteers ate 250 g of both types of casein, whereas both meals were separated at least by 2 weeks. Plasma and pBMC were taken before and 2 h after each meal. Thereafter, the defined AGE carboxymethyllysine (CML) was determined by ELISA and Western blot. NF-kappaB activation in pBMC was assayed using Electrophoretic Mobility Shift Assays (EMSA) and Western blot analysis.

RESULTS

S-casein contained only minor amounts of CML and no pentosidine, while G-casein contained large amounts of both. 2 h after ingestion, the S-casein or the G-casein-meal, both, resulted in a non-significant increase in plasma CML and in the intracellular CML-content of pBMC. This was paralleled by a highly significant increase in postprandial mononuclear NF-kappaB-binding activity. Remarkably, neither the extent of NF-kappaB induction (178% for S-casein, 188% for G-casein), nor composition of the NF-kappaB heterodimer (mainly consisting of NF-kappaB p50/p65) were significantly different after intake of S-casein or G-casein. Consistently, Western blots confirmed an increased NF-kappaBp65 nuclear translocation and a decrease of NF-kappaBp65 in the cytoplasm, while no difference in postprandial NF-kappaB nuclear translocation was observed following intake of S-casein or G-casein.

CONCLUSION

Postprandial mononuclear NF-kappaB activation after a single meal is independent of the AGE-content of the ingested protein.

[Endonasal measurement of mucociliary clearance at various locations in the nose: a new diagnostic tool for nasal function?]

INTRODUCTION

Mucociliary clearance is one of the major functions of the nasal epithelium. Limited information on the physiology or malfunction could up to now only be obtained by experimental investigations in vitro with cytological measurements of ciliary beat frequency or with extensive, time-consuming in-vivo-tests.

METHODS

We developed a new technique, which measures the transport capacity at various locations at the mucosa in the nose of a sitting patient with a short (30 sec) video-endoscopic examination. The velocity of a 500 microm TiO2-microsphere as inert marker, which is placed on the mucosa region of interest, is measured by a vector-analytic calculation in mm/min.

RESULTS

: We validated this technique in 20 subjects with measurements on the floor of the nose. The inter-individual variance and variable transport speed at different locations as known from the literature could be confirmed.

CONCLUSIONS

This technique allows for the first time to measure the mucociliary clearance at various locations inside the nose of a patient in a short and easy to perform procedure, which up to now necessitated extensive or experimental set-ups. Besides the establishment of a register of mucociliary clearance at various anatomical localisations inside the nose (olfactory epithelium, conchae, surrounding of the ostiae etc.), we intend to verify if this technique can be used as a new diagnostic tool to obtain a deeper insight into some pathologic alterations or uncharacteristic symptoms ("post-nasal-drip") or drug-effects in the nose and in the tracheo-bronchial system.

The AGE/RAGE/NF-κB Pathway May Contribute to the Pathogenesis of Polyneuropathy in Impaired Glucose Tolerance (IGT)

Binding of ligands to the receptor for advanced glycation end products (RAGE) results in activation of the transcription factor nuclear factor kappa B (NF-(kappa)B) and subsequent expression of NF-(kappa)B-regulated cytokines. This has been shown to be a relevant pathomechanism in diabetic polyneuropathies (PNP). To determine whether this pathway may contribute to the pathogenesis of PNP due to impaired glucose tolerance (IGT) we performed a pilot study to demonstrate the presence of the RAGE ligand N (epsilon)-(Carboxymethyl)lysine (CML), the receptor itself and N-(kappa)B in sural nerve biopsies of 4 patients with IGT-related PNP. Biopsies of either 4 patients with diabetic PNP and with Charcot-Marie-Tooth disease (CMT) I and II served as positive and negative controls, respectively. In IGT-related PNP and diabetic PNP, CML, RAGE, and NF-(kappa)B was found in the perineurium, epineurial vessels and in part in endoneurial vessels. CMT patients showed, if any, only weak staining for one or the other antigen. These data suggest that activation of the RAGE pathway may be one of the first steps in the pathogenesis of PNP even before chronic hyperglycemia occurs.

[Optical Rhinometry. Continuous, direct measurement of swelling of the nasal mucosa with allergen provocation. Real-time monitoring of the nasal provocation test using optical rhinometry]

BACKGROUND

Various methods exist for measuring swelling of the nasal mucosa. This is necessary in order to make the nasal provocation test objective. With the new method of optical rhinometry, it is possible to measure swelling of the mucosa directly from outside of the nose in real-time. The measurement is carried out with monochromatic near-infrared light of different wavelengths, the intensity change of which are recorded and displayed during the swelling.

MATERIALS AND METHODS

With the help of a specially developed prototype of an optical rhinometer, we carried out measurements on 15 subjects having positive nasal provocation tests with histamine and allergens, negative provocation tests with allergens in non-allergics, negative provocation tests with control solution, and decongestion with xylometazoline.

RESULTS

We found significant differences between positive and negative provocation tests ( P<0.01). Decongestion was different from all other groups ( P<0.01). Nasal congestion subjectively reported by the subject always correlated with the optical rhinometry findings.

CONCLUSION

The objective assessment of nasal swelling using optical rhinometry seems reliable. The course of the endonasal swelling can thereby be monitored in real-time. The measurement is largely independent of the cooperation of the patient. The swelling is measured directly and not indirectly via air flow resistance.

Optical measurement of nasal swellings

We introduce a new optical method to noninvasively and continuously measure the swelling process of the nasal mucosa whereby we use light of different wavelengths in the red and near-infrared range which is transilluminated through the nasal tissue and whose extinction is recorded as a function of time. From the temporal and spectral extinction data, we are able to extract characteristic parameters that describe the swelling process quantitatively by means of a regression-type parameter estimation algorithm. The method has been applied to the nasal allergen provocation test and verified on a limited number of volunteers.

A 63bp Deletion in the Promoter of RAGE Correlates with a Decreased Risk for Nephropathy in Patients with Type 2 Diabetes

Several polymorphisms have been identified in the RAGE-promoter region that might modulate the outcome of disease. Here we analyse the association of a 63bp deletion (delta63) spanning from bp - 407 to bp - 345 with diabetic nephropathy. The deletion was determined using the polymerase chain reaction (PCR) in a cross-sectional study with 1087 patients with type 1 diabetes (n = 559) and type 2 diabetes (n = 528). 475 patients with osteoporosis served as disease independent control. The prevalence of the heterozygous genotype did not significantly differ between the three groups (type 1: 2.15 %, type 2: 2.27 %, controls: 1.47 %), indicating that heterozygous delta63 is not related to the manifestation of diabetes. Homozygous carriers were not identified in this study. The heterozygous delta63 genotype, was associated with a reduced prevalence of diabetic nephropathy in patients with type 2 diabetes (OR = 0.06; 95 % CI: [0.05, 0.07]), but not in patients with type 1 (OR = 1.49; 95 % CI: [1.14, 1.94]). We conclude, that patients with type 2 diabetes and the 63bp deletion in the promoter of RAGE seem to be protected from diabetic nephropathy. The observed difference between type 1 and type 2 diabetes might point to diverse pathomechanisms of nephropathy in both types of diabetes.

Glimepiride reduces mononuclear activation of the redox-sensitive transcription factor nuclear factor-kappa B

AIMS

Glimepiride has the lowest ratio of insulin release to glucose decrease compared with other sulphonylureas. This prompted us to study in vitro and in vivo in a placebo-controlled study the effect of glimepiride on the redox-sensitive transcription factor nuclear factor-kappa B (NF-kappaB).

METHODS

Fifteen patients with type 2 diabetes on glibenclamide with a stable HbA1c over the last 6 months were included. After sampling for determination of baseline values, 10 patients were changed to an equivalent dose of glimepiride, while the placebo group was maintained at glibenclamide plus placebo. The glimepiride dose in these patients was adjusted so that no change in glucose control occurred, allowing for direct comparison. The others were kept on glibenclamide and received additional placebo. After 4 weeks of glimepiride or glibenclamide plus placebo, a second blood sample was taken. Mononuclear cells were isolated and assayed in a tissue-culture-independent electrophoretic mobility shift assay (EMSA)-based detection system for NF-kappaB binding activity, and by Western Blot for nuclear localization of NF-kappaB-p65, the cytoplasmic content of IkappaBalpha and the NF-kappaB-controlled haemoxygenase-1. Glimepiride dose-dependent inhibition of carboxymethyllysin (CML) albumin or tumour necrosis factor alpha (TNFalpha)- and H2O2-induced activation of NF-kappaB binding were determined, using isolated peripheral blood mononuclear cells from healthy volunteers, and transcriptional activity of bovine aortic endothelial cells either left untreated or induced with CML albumin incubated with or without glimepiride. Furthermore, in-vitro studies were implemented to demonstrate radical quenching properties of glimepiride in the cell-free 2,2'-azo-bis(2-aminopropane)-dihydrochloride system.

RESULTS

Baseline glucose and HbA1c remained stable in the patients switched from glibenclamide to a corresponding dose of glimepiride or kept on glibenclamide plus placebo. While in the group of patients only taking glibenclamide plus placebo the NF-kappaB binding activity did not change significantly (p = 0.58), the NF-kappaB binding activity in the group of patients taking glimepiride was reduced from 19.3 relative NF-kappaB-p65-equivalents to 15.5 relative NF-kappaB-p65-equivalents (p = 0.04). The nuclear translocation of NF-kappaB-p65 was reduced from 100% at baseline to 58% after 4 weeks (p = 0.04); the cytoplasmic localization of NF-kappaB-p65 increased from 100% to 129% (p = 0.03) and the cytoplasmic content of IkappaBalpha increased from 100% to 109% (p = 0.06). The redox-sensitive haemoxygenase-1 antigen was reduced from 100% to 82% (p = 0.04). To prove directly that glimepiride reduces NF-kappaB activation, we isolated peripheral blood mononuclear cells (PBMC) from healthy volunteers. In vitro, glimepiride reduced TNFalpha-(1 nmol/l) and CML albumin (800 nmol/l)-induced NF-kappaB activation dose dependently, being half maximal at 120 micromol/l. H2O2-mediated NF-kappaB activation was only partially reduced. In addition, glimepiride reduced NF-kappaB-dependent gene expression using a NF-kappaB-driven luciferase reporter system. Finally, a cell-free detection system showed that glimepiride has radical quenching properties.

CONCLUSION

Glimepiride can affect the activation of the redox-sensitive transcription factor NF-kappaB in vitro and in vivo.

[Determination of tissue optical parameters using HF modulation spectroscopy]

Radio frequency modulation spectroscopy is a capable method to determine tissue optical parameters in-vivo. For the eventual purpose of clinical measurements we have developed and tested an rf laser spectroscopy device which enables a measurement of the spatial amplitude and phase shift profiles of backscattered modulated laser light. Spectral absorption and scattering coefficients are computed by inverse formulas derived from analytical solutions of the diffusion model of light transport in a semi-infinite geometry.

[Modeling light distribution in nasal tissue structures]

There are different applications in the field of optical diagnostics in which the theories explaining the light transport in tissue do not lead to simple solutions for complicate geometric conditions. In these cases the Monte Carlo method provides a powerful tool to solve this problem statistically. In order to simulate the light transport in the nasal region a model was created which includes the structure depending on the swelling of the mucous membrane as well as the Monte Carlo model. Using this model it is possible to evaluate the measured values qualitatively. However, due to the long distance between light source and detector the statistical error becomes a major problem for reliable statements.