Peroxins 5 and 7 are receptors for protein import into the peroxisomal matrix. We studied the involvement of these peroxins in the biogenesis of glycosomes in the protozoan parasite Trypanosoma brucei. Glycosomes are peroxisome-like organelles in which a major part of the glycolytic pathway is sequestered. We here report the characterization of the T. brucei homologue of PEX7 and provide several data strongly suggesting that it can bind to PEX5. Depletion of PEX5 or PEX7 by RNA interference had a severe effect on the growth of both the bloodstream-form of the parasite, that relies entirely on glycolysis for its ATP supply, and the procyclic form representative of the parasite living in the tsetse-fly midgut and in which also other metabolic pathways play a prominent role. The role of the two receptors in import of glycosomal matrix proteins with different types of peroxisome/glycosome-targeting signals (PTS) was analyzed by immunofluorescence and subcellular fractionation studies. Knocking down the expression of either receptor gene resulted, in procyclic cells, in the mislocalization of proteins with both a type 1 or 2 targeting motif (PTS1, PTS2) located at the C- and N-termini, respectively, and proteins with a sequence-internal signal (I-PTS) to the cytosol. Electron microscopy confirmed the apparent integrity of glycosomes in these procyclic cells. In bloodstream-form trypanosomes, PEX7 depletion seemed to affect only the subcellular distribution of PTS2-proteins. Western blot analysis suggested that, in both life-cycle stages of the trypanosome, the levels of both receptors are controlled in a coordinated fashion, by a mechanism that remains to be determined. The observation that both PEX5 and PEX7 are essential for the viability of the parasite indicates that the respective branches of the glycosome-import pathway in which each receptor acts might be interesting drug targets.

18 F-FDG PET/CT can be used to detect arterial atherosclerotic plaque inflammation. However, avid myocardial glucose uptake may preclude its use for visualizing coronary plaques. Fatty acid loading or calcium channel blockers could decrease myocardial 18 F-FDG uptake, thus assisting coronary plaque inflammation identification. The present prospective randomized trial compared the efficacies of different interventions for suppressing myocardial 18 F-FDG uptake. We also investigated whether circulating free fatty acid (cFFA) levels predicted the magnitude of myocardial 18 F-FDG uptake. Methods: Thirty-six volunteers ate a high-fat low-carbohydrate meal, followed by a 12-h fasting period. They were then randomized to 1 of 4 intervention groups. Group 1 received no additional preparation and served as a reference. Groups 2 and 3, respectively, received a commercial high-fat solution containing 43.8 g of lipids or 50 mL of olive oil 1 h before 18 F-FDG injection to evaluate the impact of fatty acid loading on myocardial 18 F-FDG uptake. Group 4 received verapamil to evaluate the effect of calcium channel blockers. Cardiac PET/CT was performed after administration of 370 MBq of 18 F-FDG. Myocardial uptake suppression was assessed using a qualitative visual scale and by measuring the myocardial maximum standardized uptake value (SUV max ). Insulin, glucose, and cFFA were serially measured. Results: The qualitative visual scale showed good myocardial 18 F-FDG uptake suppression in 8 of 9, 5 of 9, 4 of 9, and 8 of 9 subjects of groups 1, 2, 3, and 4, respectively (P 5 0.09). SUV max did not significantly differ between groups (P 5 0.17). Interestingly, cFFA levels were higher in volunteers with good suppression (0.80 ± 0.31 mmol/L) than in those with poor suppression (0.53 ± 0.15 mmol/L; P 5 0.011). We found an inverse correlation between cFFA level (measured at 18 F-FDG injection) and the SUV max (R 5 0.61). Receiver-operating-characteristic curve analysis identified 0.65 mmol/L cFFA as the best cutoff value to predict adequate 18 F-FDG uptake suppression (positive predictive value, 89%). Conclusion: A high-fat low-carbohydrate meal followed by a 12-h fasting period effectively suppressed myocardial 18 F-FDG uptake in most subjects. Neither complementary fatty acid loading nor verapamil administered 1 h before 18 F-FDG injection conferred any additional benefit. Myocardial 18 F-FDG uptake was inversely correlated with cFFA level, representing an interesting way to predict myocardial 18 F-FDG uptake suppression.

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Background— Inflammation and intraplaque neovascularization are acknowledged to be 2 features of plaque vulnerability, although their temporal expression and their respective value in predicting clinical events are poorly understood. To determine their respective temporal associations, we conducted a comprehensive assessment of inflammation and intraplaque neovascularization in the carotid plaque of symptomatic and asymptomatic patients. Methods and Results— Thirty patients with severe carotid stenosis underwent 18 F-fluorodeoxyglucose-positron emission tomography/computed tomographic imaging. Plaque 18 F-fluorodeoxyglucose-uptake, indicative of inflammation, was measured by calculating the target:background ratio. The presence of intraplaque neovascularization during contrast-enhanced ultrasound was judged semiquantitatively; low-grade contrast enhancement (CE) suggested its absence, and high-grade CE, the presence of neovascularization. Carotid surgery was performed 1.6±1.8 days after completing both imaging modalities in all patients, and the presence of macrophages and neovessels was quantified by immunohistochemistry. We identified a significant correlation between the target:background ratio and macrophage quantification ( R =0.78; P <0.001). The number of vessels was also significantly higher in carotid plaque with high-CE ( P <0.001). Surprisingly, immunohistochemistry showed that high-CE and vessel number were neither associated with an elevated target:background ratio ( P =0.28 and P =0.60, respectively) nor macrophage infiltration ( P =0.59 and P =0.40, respectively). Finally, macrophage infiltration and target:background ratio were higher in the carotid plaque of symptomatic patients ( P =0.021 and P =0.05, respectively), whereas CE grade and the presence of neovessels were not. Conclusions— Inflammation and intraplaque neovascularization are not systematically associated in carotid plaques, suggesting a temporal separation between the 2 processes. Inflammation seems more pronounced when symptoms are present. These data highlight the challenges that face any imaging strategy designed to assess plaque vulnerability.