Genetische Faktoren bei Adipositas

Molekular-genetische Studien konnten bislang nur einen kleinen Anteil der interindividuellen Variabilität des Körpergewichts erklären, obwohl die Erblichkeit hoch ist. Bei den sehr wenigen bislang bekannten monogenen Formen der Adipositas führt der Ausfall eines einzelnen Genproduktes meist zu einer extremen Adipositas. Der größere Teil der Streubreite des Körpergewichts wird mutmaßlich durch das Zusammenspiel vieler einzelner Genvarianten erklärt, wobei jeder einzelnen Variante nur ein geringer Effekt zugeschrieben werden kann (polygene Adipositas). Mittels einer großen Meta-Analyse mit etwa 250 000 Personen europäischer Herkunft wurde eine Vielzahl von genetischen Varianten (so genannten Einzelnukleotidaustauschen) identifiziert, die für die Adipositas relevant sind. Die Effektstärken dieser Varianten auf das Körpergewicht sind zumeist klein, so dass sie insgesamt nur circa 1–2 % der Varianz des Body-Mass-Indexes (BMI) erklären. Neuere Studien beschäftigen sich mit den Wechselwirkungen von genetischen Faktoren und Umweltfaktoren (z.B. Lebensstil) und zeigen, dass einer genetischen Prädisposition z.B. mittels körperlicher Aktivität entgegengewirkt werden kann.

Es gibt momentan keine Konsensuserklärung, weshalb die identifizierten genetischen Faktoren die Erblichkeit bei komplexen Erkrankungen nicht vollständig erklären können. Auch die biologischen und vor allem klinischen Konsequenzen der identifizierten genetischen Varianten sind bislang unklar. Es bleibt weiterhin aktueller Forschungsgegenstand, die Funktionalität einzelner genetischer Bereiche zu untersuchen. Mutmaßlich werden in den nächsten Jahren einige funktionelle Varianten aufgeklärt, wodurch letztendlich ihr vermuteter therapeutischer Nutzen deutlicher warden kann.

Association of proton density fat fraction in adipose tissue with imaging-based and anthropometric obesity markers in adults

Background/Objectives:

The purpose of this study was to examine the relationship of the proton density fat fraction (PDFF), measured by magnetic resonance imaging (MRI), of supraclavicular and gluteal adipose tissue with subcutaneous and visceral adipose tissue (SAT and VAT) volumes, liver fat fraction and anthropometric obesity markers. The supraclavicular fossa was selected as a typical location where brown adipocytes may be present in humans and the gluteal region was selected as a typical location enclosing primarily white adipocytes.

Subjects/Methods:

In this cross-sectional study, 61 adults (44 women, median age 29.3 years, range 21–68 years) underwent an MRI examination of the neck and the abdomen/pelvis (3T, Ingenia, Philips Healthcare). PDFF maps of the supraclavicular and gluteal adipose tissue and the liver were generated. Volumes of SAT and VAT were calculated and supraclavicular and subcutaneous fat were segmented using custom-built post-processing algorithms. Body mass index (BMI), waist circumference and waist-to-height ratio were recorded. Statistical analysis was conducted using the Student's t-test and Pearson correlation analysis.

Results:

Mean supraclavicular PDFF was 75.3±4.7% (range 65.4–83.8%) and mean gluteal PDFF was 89.7±2.9% (range 82.2-94%), resulting in a significant difference (P<0.0001). Supraclavicular PDFF was positively correlated with VAT (r=0.76, P<0.0001), SAT (r=0.73, P<0.0001), liver PDFF (r=0.42, P=0.0008) and all measured anthropometric obesity markers. Gluteal subcutaneous PDFF also correlated with VAT (r=0.59, P<0.0001), SAT (r=0.63, P<0.0001), liver PDFF (r=0.3, P=0.02) and anthropometric obesity markers.

Conclusions:

The positive correlations between adipose tissue PDFF and imaging, as well as anthropometric obesity markers suggest that adipose tissue PDFF may be useful as a biomarker for improving the characterization of the obese phenotype, for risk stratification and for selection of appropriate treatment strategies.

Changes in physical activity during a weight loss intervention and follow-up: a randomized controlled trial

Physical activity is an important component in weight loss treatment and weight maintenance. We evaluated the physical activity component of two weight loss programmes, either standard care (SC) as defined by national guidelines, or a commercial programme (CP; Weight Watchers) over the period of weight loss and follow-up. 772 adults (mean body mass index: 31.4 ± 2.6 kg m(-2)) were recruited by primary care practices in Australia, the United Kingdom, and Germany, and randomly assigned to 12 months SC, or the CP. They were then followed up at 24 months. Change in physical activity levels were assessed by the International Physical Activity Questionnaire (IPAQ)-short form, and pedometer recordings. Both groups reported increases in physical activity using the IPAQ from baseline to 12 months and 24 months (within groups P < 0.0001) and in pedometer steps from baseline to 12 months only (within groups P < 0.0001). Differences between groups with both methods of assessment were not significant. There was a significant difference in weight loss between the groups at 12 months favouring the CP group; however, this statistical difference was not maintained at 24 months. In conclusion, despite similar increases in reported activity, there were significant differences in weight loss and regain between groups. Therefore, greater weight loss seen with the CP is unlikely to be due to increases in physical activity. Trends in pedometer steps mirrored changes in weight over time more closely than the IPAQ; however, both assessment tools have limitations. Better activity assessment measures are needed to more accurately gauge changes in physical activity during weight loss interventions.

The challenge of a 2-year follow-up after intervention for weight loss in primary care

BACKGROUND

Many weight loss programmes show short-term success, but long-term data in larger studies are scarce, especially in community settings. Attrition is common and complicates the interpretation of long-term outcomes.

OBJECTIVE

To investigate 2-year outcomes and explore issues of attrition and missing data.

SUBJECTS

A total of 772 overweight and obese adults recruited by primary care practices in Australia, Germany and the UK and randomised to a 12-month weight loss intervention delivered in a commercial programme (CP) or in standard care (SC).

MEASUREMENT

Weight change from 0-24 and 12-24 months including measured weights only and measured and self-reported weights, using last observation carried forward (LOCF), baseline observation carried forward (BOCF), completers-only and missing-at-random (MAR) analyses.

RESULTS

A total of 203 participants completed the 24-month visit. Using measured weights only, there was a trend for greater 24-month weight loss in CP than in SC, but the difference was only statistically significant in the LOCF and BOCF analyses: LOCF: -4.14 vs -1.99 kg, difference adjusted for centre -2.08 kg, P<0.001; BOCF: -1.33 vs -0.74 kg, adjusted difference -0.60 kg, P=0.032; completers: -4.76 vs -2.99 kg, adjusted difference -1.53 kg, P=0.113; missing at random: -3.00 vs -1.94 kg, adjusted difference -1.04 kg, P=0.150. Both groups gained weight from 12-24 months and weight regain was significantly (P<0.001) greater for CP than for SC in all analysis approaches. Inclusion of self-reported weights from a further 138 participants did not change the interpretation of the findings.

CONCLUSION

Initial weight loss was poorly maintained during the no-intervention follow-up, but both groups did have lower weight over the 24 months. Attrition was high in both groups, and assumptions about missing data had considerable impact on the magnitude and statistical significance of treatment effects. It is vital that trials on weight loss interventions consider the plausibility of these differences in an analytical approach when interpreting research findings and comparing data between studies.

[Weight reduction: evaluation of the possibilities in primary care and patient satisfaction. Results from a weight reduction trial]

BACKGROUND

Commercial weight loss programs offer support to overweight and obese patients to reduce excess bodyweight. Many patients seek advice for weight loss from their general practitioners.

PATIENTS AND METHODS

In the framework of a randomized controlled 1-year trial the effectiveness and safety of a commercial weight loss program was compared with a primary care intervention. At the end of the trial the participating general practitioners and study participants were asked to answer specific questions about their offered weight loss management. This paper relates to the German study part (268 participants, 40 general practitioners).

RESULTS

More than half of the general practitioners reported to offer a dietary concept which varied strongly across general practitioners. About one third of the general practitioners considered commercial weight loss programs as an alternative to support weight reduction. Participants reported that they considered weight loss advice by their general practitioners as helpful. But patients in the commercial weight loss program assessed the advice as more positive and achieved twice as much weight loss as patients in the primary care intervention.

CONCLUSION

Evaluated commercial weight loss programs can be effective and safe alternatives for general practitioners to achieve weight loss in overweight and obese patients.

[Weight maintenance after weight loss - how the body defends its weight]

Mean weight loss of most conservative therapeutic weight loss programmes is about five to six kilograms after one year. In our "obesogenic" environment it is difficult for persons to maintain the new weight. Also continuation of the programme cannot prevent a moderate weight increase in the follow-up year. The reasons for this are not clear: individual lifestyle, environmental and genetic factors may play a role, but also the complex regulatory system of the body "to defend its weight". Nevertheless, for weight maintenance a lifelong change of lifestyle is of critical importance. Concerning nutrition a fat-reduced diet with a decrease of energy density together with regular eating habits and adequate portion size promises the greatest benefit and is likely to allow sufficient satiety.

Combining FIB milling and conventional Argon ion milling techniques to prepare high-quality site-specific TEM samples for quantitative EELS analysis of oxygen in molten iron

This paper reports a procedure to combine the focused ion beam micro-sampling method with conventional Ar-milling to prepare high-quality site-specific transmission electron microscopy cross-section samples. The advantage is to enable chemical and structural evaluations of oxygen dissolved in a molten iron sample to be made after quenching and recovery from high-pressure experiments in a laser-heated diamond anvil cell. The evaluations were performed by using electron energy-loss spectroscopy and high-resolution transmission electron microscopy. The high signal to noise ratios of electron energy-loss spectroscopy core-loss spectra from the transmission electron microscopy thin foil, re-thinned down to 40 nm in thickness by conventional Argon ion milling, provided us with oxygen quantitative analyses of the quenched molten iron phase. In addition, we could obtain lattice-fringe images using high-resolution transmission electron microscopy. The electron energy-loss spectroscopy analysis of oxygen in Fe(0.94)O has been carried out with a relative accuracy of 2%, using an analytical procedure proposed for foils thinner than 80 nm. Oxygen K-edge energy-loss near-edge structure also allows us to identify the specific phase that results from quenching and its electronic structure by the technique of fingerprinting of the spectrum with reference spectra in the Fe-O system.

TEM foil preparation of sub-micrometre sized individual grains by focused ion beam technique

Analysis of presolar silicate grains provides new knowledge on interstellar and circumstellar environments and can be used to test models of the Galactic chemical evolution. However, structural information of these grains is rare because sample preparation for transmission electron microscopy is very difficult due to the small dimensions of these grains (<0.5 mum). With the use of the focused ion beam technique thin foils from these grains for transmission electron microscopy analysis can be prepared. Nevertheless, reaching the required precision of some tens of nanometres for the preparation of the transmission electron microscopy foil in the place of interest is not trivial. Furthermore, in the current samples, the grain of interest can only be identified by its different isotopic composition; i.e. there is no contrast difference in scanning electron microscopy or transmission electron microscopy images which allow the identification of the grain. Therefore, the grain has to be marked in some way before preparing the transmission electron microscopy foil. In the present paper, a method for transmission electron microscopy foil preparation of grains about 200 to 400 nm in diameter is presented. The method utilizes marking of the grain by Pt deposition and milling of holes to aid in the exact orientation of the transmission electron microscopy foil with respect to the grain. The proposed method will be explained in detail by using an example grain.

Genetic variants in the USF1 gene are associated with low-density lipoprotein cholesterol levels and incident type 2 diabetes mellitus in women: results from the MONICA/KORA Augsburg case-cohort study, 1984-2002

OBJECTIVE

Upstream transcription factor 1 (USF1) regulates genes of glucose and lipid metabolism. Polymorphisms in the USF1 gene showed association with familial combined hyperlipidemia and lipid parameters. The aim of our study was to examine the associations between USF1 polymorphisms and lipid parameters as well as incident type 2 diabetes mellitus (T2DM) in German Caucasians.

DESIGN

We genotyped eight polymorphisms in the USF1 gene in 2067 middle-aged (35-74 years) individuals including 498 incident T2DM cases and 1569 non-cases of the population-based case-cohort study from the MONICA/KORA Augsburg project.

METHODS

Six polymorphisms and their haplotypes were analyzed using multivariable linear regression and Cox proportional hazards models.

RESULTS

Polymorphism rs3737787 was inversely associated with incident T2DM in women with decreased risk for female heterozygotes compared with women homozygous for the major allele (Hazard ratio=0.57; 95% confidence intervals: 0.38-0.87; P=0.008). After correction for multiple testing, significance remained. Polymorphisms rs3813609 and rs1556259 were significantly associated with reduction in low-density lipoprotein (LDL) cholesterol (p(NOM)=0.001; p(NOM)=0.00002) in women. Analyses also indicated associations of haplotypes with LDL cholesterol in women, but the association lost statistical significance after correction for multiple testing. Total serum cholesterol (TC) and high-density lipoprotein (HDL) cholesterol were weakly associated (P<0.05) with USF1 polymorphisms in women. No significant associations were found in men.

CONCLUSIONS

In this large population-based study, statistically significant associations of USF1 polymorphisms with incident T2DM and LDL cholesterol were found in women, but not in men. Genetic variants in the USF1 gene showed weak or no associations with TC and HDL cholesterol.

Genetic variants in the leukemia-associated Rho guanine nucleotide exchange factor (ARHGEF12) gene are not associated with T2DM and related parameters in Caucasians (KORA study)

OBJECTIVE

The aim of our study was to determine the variant pattern of the leukemia-associated Rho guanine nucleotide exchange factor (LARG, or ARHGEF12) gene and investigate whether LARG variants are associated with diabetes mellitus type 2 (T2DM), the metabolic syndrome (MetS), or related parameters such as insulin sensitivity in German Caucasians.

DESIGN

We analyzed single nucleotide polymorphisms (SNPs) in the LARG gene in the 55-74-year-old individuals of the population-based German Caucasian Cooperative Health Research in the region of Augsberg (KORA) survey 4 (S4).

METHODS

Sequencing of Tyr1306Cys, which was of functional relevance in Pima Indians, in 48 randomly selected individuals and genotyping of 11 additional LARG SNPs in 1653 subjects were performed. Four linkage disequilibrium (LD) blocks (r(2)> or =0.8) were established and each block was statistically analyzed for association with metabolic traits. The association with T2DM and the MetS was analyzed by logistic regression in 1462 subjects, and HOMA-IR (homeostasis model assessment of insulin resistance) as a measure of insulin sensitivity was analyzed by the Kruskal-Wallis test in 1346 fasting subjects.

RESULTS

The polymorphism Tyr1306Cys, which was significantly associated with insulin sensitivity in Pima Indians, was not found in the KORA S4 population. Statistical analysis yielded no significant associations (P>0.05) between the analyzed LARG variants and T2DM, the MetS, or related parameters such as insulin sensitivity.

CONCLUSIONS

Caucasian individuals and Pima Indians differ in their genetic variance pattern in the LARG gene region. There is no evidence in the Caucasian KORA study that variants of the LARG gene confer susceptibility for T2DM, insulin sensitivity, or the MetS.

Site-specific structural investigations of oxidized nickel samples modified by plasma erosion processes

A focused ion beam was employed for local target preparation for EBSD analysis. The volume of the ion-solid interaction is well below 50 nm at glancing incidence for metallic and transition metal oxide samples. Therefore, focused ion beam can successfully be used for electron backscatter diffraction (EBSD) sample preparation. The sample investigated consists of Ni covered with a NiO layer of approximately 5 microm thickness. Focused ion beam cross-sectioning of these layers and subsequent electron imaging in addition to EBSD maps shows a bimodal structure of the oxide layer. In order to test the potential of such oxidized samples as electrode materials, single spark erosion experiments were performed. The erosion craters have diameters up to 40 microm and have a depth corresponding to the thickness of the oxide layer. In addition, a deformation zone produced by thermoshock accompanies the formation of the crater. This deformation zone was further investigated by EBSD analysis using a new way of sample preparation employing the focused ion beam technology. This target preparation routine is called Volume of Interest Transfer and has the potential of providing a full three-dimensional characterization.

Progressive multifokale Leukoenzephalopathie (PML) bei chronisch lymphatischer Leukämie (CLL) Literaturübersicht und Fallbeschreibung

Progressive multifocal leukoencephalopathy (PML) is an infectious disease of the central nervous system caused by the JC virus. Progressive multifocal leukoencephalopathy represents a reactivation of the JC virus after long-standing immunosuppression. Also, PML plays an important role as an opportunistic infection in patients with AIDS. The average time of survival in patients with PML in combination with chronic lymphatic leukemia (CLL) (n = 17 in the literature) is 4.3 months, and therapeutic options are not established. We report the case of a patient with CLL and PML. Clinical symptoms are slight hemiparesis of the right side, mainly appearing as a disturbance of motor function. In MRI, a typical subcortical lesion was shown, and JC virus DNA was positive in the CSF by PCR. Because of first positive results in treatment of PML in patients with AIDS, therapy with cidofovir was started. After treatment for 16 months, symptoms are stable, the PML-induced lesions in MRI are in regression, and JC virus DNA is not detectable in the CSF.

Reliability and validity of Kasahara's scale of melancholic type of personality (Typus melancholicus) in a German sample population

We explored the reliability and validity of Kasahara's scale of melancholic type of personality (KMT) in a German sample population. Subjects comprised 66 patients diagnosed with an affective disorder (F3, ICD-10) and 94 controls. Concerning reliability, KMT scores showed internal consistency with Cronbach's alpha coefficients of 0.65 for patients and 0.67 for controls. The KMT items, except for number 13 in controls, showed significant item-total correlations. In a test-retest procedure, the KMT total score and individual item scores were statistically similar and correlated. These results indicate reliability of the KMT. Concerning validity, KMT scores were significantly higher in patients than in controls. By controlling the effects of age and sex, partial correlation coefficients in a comparison of KMT and Zerssen's F-List (F-List) scores were 0.40 in patients and 0.53 in controls. These results show both the constructive and concurrent validity of the KMT. Sufficient reliability and validity of the KMT were shown in this German sample population to encourage cross-cultural investigation of Typus melancholicus.

Rotation of cells in an alternating electric field: theory and experimental proof

Protoplasts of Avena sativa rotate in an alternating electric field provided that at least two cells are located close to each other. An optimum frequency range (20 to 30 kHz) exists where rotation of all cells exposed to the field is observed. Below and above this frequency range, rotation of some cells is only occasionally observed. The angular velocity of rotation depends on the square of the electric field strength. At field strengths above the value leading to electrical breakdown of the cell membrane, rotation is no longer observed due to deterioration of the cells. The absolute value of the angular velocity of rotation at a given field strength depends on the arrangement of the cells in the electric field. A maximum value is obtained if the angle between the field direction and the line connecting the two cells is 45 degrees. With increasing distance between the two cells the rotation speed decreases. Furthermore, if two cells of different radii are positioned close to each other the cell with the smaller radius will rotate with a higher speed than the larger one. Rotation of cells in an alternating electric field is described theoretically by interaction between induced dipoles in adjacent cells. The optimum frequency range for rotation is related to the relaxation of the polarization process in the cell. The quadratic dependence of the angular velocity of rotation on the field strength results from the fact that the torque is the product of the external field and the induced dipole moment which is itself proportional to the external field. The theoretical and experimental results may be relevant for cyclosis (rotational streaming of cytoplasm) in living cells.

Electrical hemolysis of human and bovine red blood cells

The external electric field strength required for electrical hemolysis of human red blood cells depends sensitively on the composition of the external medium. In isotonic NaCl und KCl solutions the onset of electrical hemolysis is observed at 4 kV per cm and 50 per cent hemolysis at 6 kV per cm, whereas increasing concentrations of phosphate, sulphate, sucrose, inulin and EDTA shift the onset and the 50 per cent hemolysis-value to higher field strengths. The most pronounced effect is observed for inulin and EDTA. In the presence of these substances the threshold value of the electric field strength is shifted to 14 kV per cm. This is in contrast to the dielectric breakdown voltage of human red blood cells which is unaltered by these substances and was measured to be approximately 1 V corresponding in the electrolytical discharge chamber to an external electric field strength of 2 to 3 kV per cm. On the other hand, dielectric breakdown of bovine red blood cell membranes occurs in NaCl solution at 4 to 5 kV per cm and is coupled directly with hemoglobin release. The electrical hemolysis of cells of this species is unaffected by the above substances with exception of inulin. Inulin suppressed the electrical hemolysis up to 15 kV per cm. The data can be explained by the assumption that the reflection coefficients of the membranes of these two species to bivalent anions and uncharged molecules are field-dependent to a different extent. This explanation implies that electrical hemolysis is a secondary process of osmotic nature induced by the reversible permeability change of the membrane (dielectric breakdown) in response to an electric field. This view is supported by the observation that the mean volumes of ghost cells obtained by electrical hemolysis can be changed by changing the external phosphate concentration during hemolysis and resealing, or by subjecting the cells to a transient osmotic stress immediately after the electrical hemolysis step. An interesting finding is that the breakdown voltage, although constant throughout each normally distributed ghost size distribution, increases with increasing mean volume of the ghost populations.