In the present study, the effect of a high fat diet on the expression of proteins in insulin target tissues was analyzed using a proteomic approach. Gastrocnemius muscle, white and brown adipose tissue, and liver were taken from C57BL/6 mice either fed on a high-fat or a chow diet. Expression levels of approximately 10 000 polypeptides for all the four tissues were assessed by two-dimensional gel electrophoresis (2-DE). Computer-assisted image analysis allowed the detection of 50 significantly (p < 0.05) differentially expressed proteins between obese and lean mice. Interestingly, more than half of these proteins were detected in the brown adipose tissue. The differentially expressed proteins were identified by tandem mass spectrometry. Several stress and redox proteins were modulated in response to the high-fat diet. A key glycolytic enzyme was found to be downregulated in adipose tissues and muscle, suggesting that at elevated plasma fatty acid concentrations, fatty acids compete with glucose as an oxidative fuel source. Furthermore, in brown adipose tissue there were significant changes in mitochondrial enzymes involved in the Krebs tricarboxylic acid (TCA) cycle and in the respiratory chain in response to the high-fat diet. The brown adipose tissue is an energy-dissipating tissue. Our data suggest that the high-fat diet treated mice were increasing energy expenditure to defend against weight gain.

The insulin sensitizer drug, rosiglitazone, has been shown to have a protective effect on pancreatic islet cell structure and function in animal models of type 2 diabetes. The identification of new molecular targets associated both with islet cell dysfunction and protection is a crucial research goal. In the present study, a proteomics approach has been used to identify such targets. Obese C57Bl/6J lep/lep mice and lean littermates were given the insulin sensitizer drug BRL49653, rosiglitazone. It normalized the impaired glucose tolerance in lep/lep mice but had no significant effect on glucose tolerance in the lean mice. Pancreatic islet polypeptides were arrayed by a two-dimensional gel electrophoresis system that separated more than 2500 individual spots. Three overexpressed and six underexpressed proteins were significant (p < 0.05) between lep/lep and lean mice, and four were modulated significantly (p < 0.05) by the rosiglitazone treatment of the obese mice. The identity of these differentially expressed proteins was made using mass spectrometric analysis and provided evidence that differential expression of actin-binding proteins may be an important aspect of defective islet function. Rosiglitazone increased carboxypeptidase B expression in both lep/lep and normal mice suggesting that this might be an independent effect of rosiglitazone that contributes to improved insulin processing.

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Peroxisome proliferator-activated receptors (PPARs) participate in the molecular mechanism of pathologies with altered lipid homeostasis such as type 2 diabetes or obesity. The insulin sensitizer drug, rosiglitazone, has been shown to bind and activate PPAR-gamma1 in adipocytes and PPAR-gamma2 in hepatocytes. The identification of new molecular targets associated with fatty acid oxidation and PPAR-gamma nuclear receptor regulation in insulin resistance tissues is a key research goal. In the present study, we have used a proteomic approach to identify such targets. Lean and obese C57 Bl/6J lep/lep mice were given BRL49653, rosiglitazone, 10 mg/kg diet, by dietary admixture for 7 days. Rosiglitazone normalized the impaired glucose tolerance and dyslipidemia in lep/lep mice but had no significant effect in the lean mice. Samples of liver, white and brown adipose tissue, and muscle proteins were obtained and 100 microg of proteins was arrayed by two-dimensional gel electrophoresis. Thirty-four polypeptides were differentially expressed (p < 0.05) between lep/lep and lean mice and eleven were significantly (p < 0.05) modulated by rosiglitazone treatment of the obese mice. None of the proteins was modulated by rosiglitazone treatment of the lean mice. The identity of these differentially expressed proteins was made using tandem mass spectrometric analysis and revealed components of fatty acid and carbohydrate metabolism as well as proteins with unknown function.

An electric analog of an electrochemical cell is assumed to consist of a constant ohmic resistance, representing the bulk electrolyte, and a parallel combination of resistance and differential capacity, representing one interface. The response of the model to a rectangular current-time function is given in terms of circuit components. The interface parameters are not assumed to be constant and the equations yield instantaneous values for each of them. A pulse generator is described, which is capable of closely approximating the required current-time function. Results of measurements made on Pt and dropping Hg are presented.

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In 1N HClO4 and in 2N H2SO4 , “oxygen” uptake on Au electrodes begins at 1.25V vs. NHE. Using a roughness factor of 1.4, monolayer coverage (600 µcoul/cm2) is reached at 1.45V; a second monolayer is completed at 1.75V. Oxygen, once adsorbed, is removed at approximately 1.3V. Thus, the kinetic parameters of the Ce(III)/Ce(IV) reaction in 1N HClO4 and in 2N H2SO4 can be obtained at oxygen coverages θ=1.5–2.0 and θ=0.7–2.0 , respectively. Apparent exchange current densities, ioa , were obtained from low overvoltage data false(≤10 normalmVfalse) . The charge transfer coefficient, α=0.65±0.06 , was determined from the slope of plots of log ioa vs. equilibrium potential. It is independent of oxygen coverage in the range indicated. The apparent rate constant, koa , was calculated from ioa and α normalto be koa≈3×10−4 normalcm/sec in the range 1≤θ≤2 false(1.5≤θ≤2.0 in HClO4false) . Extrapolation of the data to θ=0 yields koa≈12×10−4 normalcm/sec . This change in koa can be interpreted as a change in the potential across the inner double layer which appears as a change in φ2 , normalΔφ2=7.9 normalmV . It appears that up to θ=1 , oxygen adsorbs uniformly and is an excellent electronic conductor which simply serves as an extension of the electrode surface. The constancy of koa normalat 1≤θ=2 indicates no changes in the over‐all structure of the interface in this region.