PPARgamma agonist induced cardiac enlargement is associated with reduced fatty acid and increased glucose utilization in myocardium of Wistar rats.

In toxicological studies, high doses of peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists cause cardiac enlargement. To investigate whether this could be explained by a large shift from free fatty acid to glucose utilization by the heart, Wistar rats were treated for 2-3 weeks with a potent, selective PPARgamma agonist (X334, 3 micromol/kg/d), or vehicle. X334 treatment increased body-weight gain and ventricular mass. Treatment lowered plasma triglycerides by 61%, free fatty acid levels by 72%, insulin levels by 45%, and reduced total plasma protein concentration by 7% (indicating plasma volume expansion) compared to vehicle animals. Fasting plasma glucose levels were unaltered. To assess cardiac free fatty acid and glucose utilization in vivo we used simultaneous infusions of non-beta-oxidizable free fatty acid analogue, [9,10-(3)H](R)-2-bromopalmitate and [U-(14)C]2-deoxy-d-glucose tracers, which yield indices of local free fatty acid and glucose utilization. In anesthetized, 7 h fasted animals, left ventricular glucose utilization was increased to 182% while free fatty acid utilization was reduced by 28% (P<0.05) compared to vehicle. In separate studies we attempted to prevent the X334-induced hypolipidemia. Various dietary fat supplements were unsuccessful. By contrast, restricting the time during which the treated animals had access to food (promoting endogenous lipolysis), restored plasma free fatty acid from 27% to 72% of vehicle control levels and prevented the cardiac enlargement. Body-weight gain in these treated-food restricted rats was not different from vehicle controls. In conclusion, the cardiac enlargement caused by intense PPARgamma activation in normal animals is associated with marked changes in free fatty acid/glucose utilization and the enlargement can be prevented by restoring free fatty acid availability.

Beyond lipids, pharmacological PPARalpha activation has important effects on amino acid metabolism as studied in the rat.

PPARalpha agonists have been characterized largely in terms of their effects on lipids and glucose metabolism, whereas little has been reported about effects on amino acid metabolism. We studied responses to the PPARalpha agonist WY 14,643 (30 micromol x kg(-1) x day(-1) for 4 wk) in rats fed a saturated fat diet. Plasma and urine were analyzed with proton NMR. Plasma amino acids were measured using HPLC, and hepatic gene expression was assessed with DNA arrays. The high-fat diet elevated plasma levels of insulin and triglycerides (TG), and WY 14,643 treatment ameliorated this insulin resistance and dyslipidemia, lowering plasma insulin and TG levels. In addition, treatment decreased body weight gain, without altering cumulative food intake, and increased liver mass. WY 14,643 increased plasma levels of 12 of 22 amino acids, including glucogenic and some ketogenic amino acids, whereas arginine was significantly decreased. There was no alteration in branched-chain amino acid levels. Compared with the fat-fed control animals, WY 14,643-treated animals had raised plasma urea and ammonia levels as well as raised urine levels of N-methylnicotinamide and dimethylglycine. WY 14,643 induced changes in a number of key genes involved in amino acid metabolism in addition to expected effects on hepatic genes involved in lipid catabolism and ketone body formation. In conclusion, the present results suggest that, in rodents, effects of pharmacological PPARalpha activation extend beyond control of lipid metabolism to include important effects on whole body amino acid mobilization and hepatic amino acid metabolism.

PPARalpha and PPARgamma regulation of liver and adipose proteins in obese and dyslipidemic rodents.

Zucker fatty rats and ob/ob mice are both frequently used hyperlipidemic and insulin-resistant spontaneous genetic models of obesity. We used them to study the effect of PPAR agonists on the protein-expression level in liver and white adipose tissue. PPARalpha-agonist treatments of the rats resulted in that 27% of the quantified hepatic proteins were altered; implicating pronounced peroxisome proliferation and increase in capacity for beta-oxidation of fatty acids although no correction of plasma triglycerides were obtained. On treatment with PPARgamma agonists, adipose proteins were regulated to a much larger extent in the rats compared to mice, 18% and 2%, respectively.

Protein staining influences the quality of mass spectra obtained by peptide mass fingerprinting after separation on 2-d gels. A comparison of staining with coomassie brilliant blue and sypro ruby.

When separating protein mixtures on 2-D gels for proteomics purposes, fluorescent staining is superior in sensitivity and linear response as compared to Coomassie Brilliant Blue (CBB) and silver staining, respectively. We have compared the quality of mass spectra for proteins obtained from gels stained with CBB and SYPRO Ruby (SR) and found significant differences. These differences can be seen both in inferior signal/noise ratios and number of peptides detected with the fluorescent stain.

Novel binding epitope for Helicobacter pylori found in neolacto carbohydrate chains: structure and cross-binding properties.

Helicobacter pylori is a bacterium that colonizes the stomach of a majority of the global human population causing common gastric diseases like ulcers and cancer. It has an unusually complex pattern of binding to various host glycoconjugates including interaction with sialylated, sulfated, and fucosylated sequences. The present study describes an additional binding epitope comprising the neolacto internal sequence of GlcNAcbeta3-Galbeta4GlcNAcbeta. The binding was detected on TLC plates as an interaction with a seven-sugar ganglioside of rabbit thymus. The glycolipid was purified and characterized as Neu5Gcalpha3Galbeta4GlcNAcbeta3Galbeta4GlcNAcbeta3-Galbeta4Glcbeta1Cer with less than 10% of the fraction carrying a repeated lacto (type-1) core chain, Galbeta3Glc-NAcbeta3Galbeta3GlcNAcbeta. After stepwise chemical and enzymatic degradation and structural analysis of products the strongest binder was found to be the pentaglycosylceramide GlcNAcbeta3Galbeta4GlcNAcbeta3Galbeta4Glcbeta1-Cer, whereas the hexa- and tetraglycosylceramides were less active, and the trihexosylceramide was inactive. Further studies revealed that the terminal GlcNAcbeta of the pentaglycosylceramide may be exchanged for either GalNAcbeta3, GalNAcalpha3, or Galalpha3 without loss of the activity. Calculated minimum energy conformers of these four isoreceptors show a substantial topographical similarity suggesting that this binding is a result of a molecular mimicry. Although the glycoconjugate composition of human gastric epithelial cells is not known in detail it is proposed that repeating N-acetyllactosamine units of glycoconjugates may serve as bacterial attachment sites in the stomach.