Diet-resistant obesity is characterized by a distinct plasma proteomic signature and impaired muscle fiber metabolism.

BACKGROUND/OBJECTIVES: Inter-individual variability in weight loss during obesity treatment is complex and poorly understood. Here we use whole body and tissue approaches to investigate fuel oxidation characteristics in skeletal muscle fibers, cells and distinct circulating protein biomarkers before and after a high fat meal (HFM) challenge in those who lost the most (obese diet-sensitive; ODS) vs the least (obese diet-resistant; ODR) amount of weight in a highly controlled weight management program. SUBJECTS/METHODS: In 20 weight stable-matched ODS and ODR women who previously completed a standardized clinical weight loss program, we analyzed whole-body energetics and metabolic parameters in vastus lateralis biopsies and plasma samples that were obtained in the fasting state and 6 h after a defined HFM, equivalent to 35% of total daily energy requirements. RESULTS: At baseline (fasting) and post-HFM, muscle fatty acid oxidation and maximal oxidative phosphorylation were significantly greater in ODS vs ODR, as was reactive oxygen species emission. Plasma proteomics of 1130 proteins pre and 1, 2, 5 and 6 h after the HFM demonstrated distinct group and interaction differences. Group differences identified S-formyl glutathione hydratase, heat shock 70 kDA protein 1A/B (HSP72), and eukaryotic translation initiation factor 5 (eIF5) to be higher in ODS vs ODR. Group-time differences included aryl hydrocarbon interacting protein (AIP), peptidylpropyl isomerase D (PPID) and tyrosine protein-kinase Fgr, which increased in ODR vs ODS over time. HSP72 levels correlated with muscle oxidation and citrate synthase activity. These proteins circulate in exosomes; exosomes isolated from ODS plasma increased resting, leak and maximal respiration rates in C2C12 myotubes by 58%, 21% and 51%, respectively, vs those isolated from ODR plasma. CONCLUSIONS: Findings demonstrate distinct muscle metabolism and plasma proteomics in fasting and post-HFM states corresponding in diet-sensitive vs diet-resistant obese women.

A new highly penetrant form of obesity due to deletions on chromosome 16p11.2.

Obesity has become a major worldwide challenge to public health, owing to an interaction between the Western 'obesogenic' environment and a strong genetic contribution. Recent extensive genome-wide association studies (GWASs) have identified numerous single nucleotide polymorphisms associated with obesity, but these loci together account for only a small fraction of the known heritable component. Thus, the 'common disease, common variant' hypothesis is increasingly coming under challenge. Here we report a highly penetrant form of obesity, initially observed in 31 subjects who were heterozygous for deletions of at least 593 kilobases at 16p11.2 and whose ascertainment included cognitive deficits. Nineteen similar deletions were identified from GWAS data in 16,053 individuals from eight European cohorts. These deletions were absent from healthy non-obese controls and accounted for 0.7% of our morbid obesity cases (body mass index (BMI) >or= 40 kg m(-2) or BMI standard deviation score >or= 4; P = 6.4 x 10(-8), odds ratio 43.0), demonstrating the potential importance in common disease of rare variants with strong effects. This highlights a promising strategy for identifying missing heritability in obesity and other complex traits: cohorts with extreme phenotypes are likely to be enriched for rare variants, thereby improving power for their discovery. Subsequent analysis of the loci so identified may well reveal additional rare variants that further contribute to the missing heritability, as recently reported for SIM1 (ref. 3). The most productive approach may therefore be to combine the 'power of the extreme' in small, well-phenotyped cohorts, with targeted follow-up in case-control and population cohorts.

Protein nanopatterns for improved immunodetection sensitivity.

In this work, we clearly demonstrate the capability of protein nanopatterns of improving the quality factors of immunosensing devices, such as lowering of the limit of detection and increase of sensitivity. This beneficial effect is obtained by the formation on the sensor's surface of bioadhesive domains of nanometric dimensions in a nonadhesive matrix by means of colloidal lithography.

Formation of viscoelastic protein droplets on a chemically functionalized surface.

Droplet formation during adsorption of the protein lactoferrin from an aqueous solution on a surface functionalized by plasma deposited poly(acrylic acid) is studied using quartz crystal microbalance and atomic force microscopy. The formation of protein droplets is particularly favored at pH values close to the isoelectric point of lactoferrin, where the molecules carry little excess charge and intermolecular attraction exceeds the molecule-surface interaction. By combining topographic data with information on the system dynamics, it is possible to describe the viscoelastic properties of the adsorbate within a quantitative model for nonhomogeneous layers.

Tailoring surface properties of biomedical polymers by implantation of Ar and He ions.

Ion implantation at 25 and 100 keV has been used as a tool for the modification of the surface properties of two biomedical polymers. The modulation induced by the different energy dispersion mechanisms of Ar and He have allowed satisfactory modifications for both the activation of the surfaces of chemically functional polycaprolactone (PCL) and the stabilization of anti-fouling poly(ethylene glycol) (PEG). In both cases the implantations have been performed at doses of 10(14) cm(-2) by taking into account the effect of different current densities, which are shown to distinctly influence the fragmentation-crosslinking of the target polymers. The resultant films were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, time of flight secondary ion mass spectroscopy and atomic force microscopy. Both shifts in zeta potential versus pH curves and the alteration of the polar components of the surface free energy (contact angle measurements) were correlated with the composition analysis. The response of the modified surfaces towards biomolecular interaction is demonstrated by the induction of preferential adsorption on irradiated PCL and the inhibited adsorption onto implanted PEG regions for selected oligopeptides and proteins.

Use of nanopatterned surfaces to enhance immunoreaction efficiency.

In this work, we compare the immunoreaction efficiency between uniformly functionalized surface and chemically nanopatterned surfaces when applied as platforms for antigen/antibody interactions with and without the use of protein A as orienting protein. On the nanopatterned platform, the immunoreaction efficiency is higher than all the other cases with no protein A pretreatment of the surface, providing evidence of the capability of the adhesive/antiadhesive nanopatterned surface to immobilize the molecules in a reactive state, increasing their possibility to form complexes.

Poly(N-isopropylacrylamide) grafted on plasma-activated poly(ethylene oxide): thermal response and interaction with proteins.

Thermoresponsive polymer layers offer the possibility of preparing smart surfaces with properties that are switchable through a phase transition, usually close to the lower critical solution temperature of the polymer. In particular, poly( N-isopropylacrylamide) (pNIPAM) has gained a great deal of attention because it has such a phase transition in a physiologically interesting temperature range. We have prepared ultrathin thermoresponsive coatings by grafting pNIPAM on a plasma-CVD-deposited, poly(ethylene oxide)-like polymer substrate that was activated in an Ar plasma discharge to initiate the grafting. The presence and integrity of pNIPAM was verified by XPS and ToF-SIMS, and a dramatic change in the wettability during the phase transition was identified by temperature-dependent contact angle measurements. The transition from the hydrated to the collapsed conformation was analyzed by temperature-dependent QCM measurements and by AFM. An unusual, reversible behavior of the viscoelastic properties was seen directly at the phase transition from the swollen to the collapsed state. The phase transition leads to a switching from protein repulsion to a state that allows the adsorption of proteins.

Fabrication and characterization of plasma processed surfaces with tuned wettability.

Engineered surfaces with controlled hydrophilic/ hydrophobic character have been fabricated by tailoring the substrate topography and chemistry. In this method, the substrate to be treated was first coated by a photoresist, which was then surface-roughened using SF6 plasma etching. The resulting rough texture was then transferred to the underlying silicon surface by over-etching of the photoresist. At this point, the topographically modified surface was modified chemically by controlled deposition of a thin polymer layer using plasma processing. In this way, both the surface texture and the surface chemistry could be varied independently, producing surfaces with variable wetting character, including super-hydrophilicity and super-hydrophobicity, depending on the choice of plasma polymer deposited. Chemical characterization demonstrates a correlation between the surface chemistry and the wettability of the samples after etching. The surface elementary composition contained more C-F groups as the measured contact angle increased, indicating that the change of wettability is due to both the roughness and the surface energy of the deposited photoresist. In the case of materials deposited on the plasma-treated rough surfaces, the strengthening of the wetting character is only due to the created surface roughness, as XPS analyses showed no significant chemical difference as compared to the flat polymer.

Micro-spot, UV and wetting patterning pathways for applications of biofunctional aminosilane-titanate coatings.

The micropatterning of functional films for biomedical applications is a key part of the process leading to a precise application. In the present work we present three different methodologies to micro-design biofunctional aminosilane-titanate coatings. The chemical functionality of the surface immobilized amino groups was initially tested by surface characterization techniques. X-ray photoelectron spectroscopy was used to analyze the films before and after derivatization with Trifluoromethylbenzaldehyde while atomic force microscopy was used to study the adsorption kinetics onto these hybrid films. The three micropatterning pathways were selected for three different kinds of applications: (1) 300 microm spots were satisfactorily used for oligonucleotide immobilization, (2) Masked regions protected from UV irradiation were intensively coated by colloidal gold nanoparticles creating a drastic contrast with respect to the UV exposed areas, and (3) radial micro stripes, used afterwards for culturing cells, were created onto Si substrates by wetting from modified precursor solutions. The results are a clear indication of the versatility of hybrid aminosilane-titanate coatings for biomedical applications requiring micropatterned biofunctional surfaces.

Combination of ion beam stabilisation, plasma etching and plasma deposition for the development of tissue engineering micropatterned supports.

The performance of biomedical assays at both molecular and cellular level depends greatly on the ability to design new polymer surfaces. Patterns can be created by using materials with contrasted surface properties. In this work we describe in detail the preparation of micropatterned surfaces to be used as tissue engineering supports. Poly(ethylene glycol) (PEG) was used as the 'anti-fouling' polymer in opposition to functional regions covered by acrylic acid (AAc). Since spin-casted PEG films are unstable, ion beam stabilization (IBS) treatment was applied in order to render it insoluble. On the other hand, AAc films were deposited by low-power plasma chemical vapour deposition. Chemical properties of both polymers were monitored by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy while topographic features were followed by atomic force microscopy. Finally, a micropattern was produced by using a mask, which isolated the IBS-PEG from the AAc-deposited regions. Endothelial cells cultured on the surface were observed to follow the micropatterns. In fact, for a certain surface density it was observed that the cells present tensile or compressive stresses when forced to remain in the anti-fouling or the functionalised regions, respectively.