Nutritional state (e.g. fasted vs. fed) and different food stimuli (e.g. high‐calorie vs. low‐calorie, or appetizing vs. bland foods) are both recognized to change activity in brain reward systems. ...Using functional magnetic resonance imaging, we have studied the interaction between nutritional state and different food stimuli on brain food reward systems. We examined how blood oxygen level‐dependent activity within a priori regions of interest varied while viewing pictures of high‐calorie and low‐calorie foods. Pictures of non‐food household objects were included as control stimuli. During scanning, subjects rated the appeal of each picture. Twenty non‐obese healthy adults body mass index 22.1 ± 0.5 kg/m2 (mean ± SEM), age range 19–35 years, 10 male were scanned on two separate mornings between 11:00 and 12:00 h, once after eating a filling breakfast (‘fed’: 1.6 ± 0.1 h since breakfast), and once after an overnight fast but skipping breakfast (‘fasted’: 15.9 ± 0.3 h since supper) in a randomized cross‐over design. Fasting selectively increased activation to pictures of high‐calorie over low‐calorie foods in the ventral striatum, amygdala, anterior insula, and medial and lateral orbitofrontal cortex (OFC). Furthermore, fasting enhanced the subjective appeal of high‐calorie more than low‐calorie foods, and the change in appeal bias towards high‐calorie foods was positively correlated with medial and lateral OFC activation. These results demonstrate an interaction between homeostatic and hedonic aspects of feeding behaviour, with fasting biasing brain reward systems towards high‐calorie foods.
Abstract The rising use of plastic results in an appalling amount of waste which is scattered into the environment. One of these plastics is PET which is mainly used for bottles. We have identified ...and characterized an esterase from Streptomyces , annotated as LipA, which can efficiently degrade the PET-derived oligomer BHET. The Streptomyces coelicolor Sc LipA enzyme exhibits varying sequence similarity to several BHETase/PETase enzymes, including Is PETase, Tf Cut2, LCC, PET40 and PET46. Of 96 Streptomyces strains, 18% were able to degrade BHET via one of three variants of LipA, named Sc LipA , S2 LipA and S92 LipA. SclipA was deleted from S. coelicolor resulting in reduced BHET degradation. Overexpression of all LipA variants significantly enhanced BHET degradation. All variants were expressed in E. coli for purification and biochemical analysis. The optimum conditions were determined as pH 7 and 25 °C for all variants. The activity on BHET and amorphous PET film was investigated. S 2LipA efficiently degraded BHET and caused roughening and indents on the surface of PET films, comparable to the activity of previously described Tf Cut2 under the same conditions. The abundance of the S2 LipA variant in Streptomyces suggests an environmental advantage towards the degradation of more polar substrates including these polluting plastics.
