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- Kerem, L., et al.
(författare)
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Oxytocin reduces the functional connectivity between brain regions involved in eating behavior in men with overweight and obesity
- 2020
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 0307-0565 .- 1476-5497. ; 44, s. 980-989
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Tidskriftsartikel (refereegranskat)abstract
- Background: Oxytocin (OXT), shown to decrease food intake in animal models and men, is a promising novel treatment for obesity. We have shown that in men with overweight and obesity, intranasal (IN) OXT reduced the functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent signal in the ventral tegmental area (VTA), the origin of the mesolimbic dopaminergic reward system, in response to high-calorie food vs. nonfood images. Here, we employed functional connectivity fMRI analysis, which measures the synchrony in activation between neural systems in a context-dependent manner. We hypothesized that OXT would attenuate the functional connectivity of the VTA with key food motivation brain areas only when participants viewed high-calorie food stimuli. Methods: This randomized, double-blind, and placebo-controlled crossover study of 24 IU IN OXT included ten men with overweight or obesity (mean ± SEM BMI: 28.9 ± 0.8 kg/m2). Following drug administration, subjects completed an fMRI food motivation paradigm including images of high and low-calorie foods, nonfood objects, and fixation stimuli. A psychophysiological interaction analysis was performed with the VTA as seed region. Results: Following OXT administration, compared with placebo, participants exhibited significantly attenuated functional connectivity between the VTA and the insula, oral somatosensory cortex, amygdala, hippocampus, operculum, and middle temporal gyrus in response to viewing high-calorie foods (Z ≥ 3.1, cluster-corrected, p < 0.05). There was no difference in functional connectivity between VTA and these brain areas when comparing OXT and placebo for low-calorie food, nonfood, and fixation images. Conclusion: In men with overweight and obesity, OXT attenuates the functional connectivity between the VTA and food motivation brain regions in response to high-calorie visual food images. These findings could partially explain the observed anorexigenic effect of OXT, providing insight into the mechanism through which OXT ameliorates food cue-induced reward anticipation in patients with obesity. Additional studies are ongoing to further delineate the anorexigenic effect of OXT in obesity. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.
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| 3. |
- Song, S., et al.
(författare)
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Top-down constraints on atmospheric mercury emissions and implications for global biogeochemical cycling
- 2015
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 15:12, s. 7103-7125
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Tidskriftsartikel (refereegranskat)abstract
- We perform global-scale inverse modeling to constrain present-day atmospheric mercury emissions and relevant physiochemical parameters in the GEOS-Chem chemical transport model. We use Bayesian inversion methods combining simulations with GEOS-Chem and ground-based Hg-0 observations from regional monitoring networks and individual sites in recent years. Using optimized emissions/parameters, GEOS-Chem better reproduces these ground-based observations and also matches regional over-water Hg-0 and wet deposition measurements. The optimized global mercury emission to the atmosphere is 5.8 Gg yr(-1). The ocean accounts for 3.2 Gg yr(-1) (55 % of the total), and the terrestrial ecosystem is neither a net source nor a net sink of Hg-0. The optimized Asian anthropogenic emission of Hg-0 (gas elemental mercury) is 650-1770 Mg yr(-1), higher than its bottom-up estimates (550-800 Mg yr(-1)). The ocean parameter inversions suggest that dark oxidation of aqueous elemental mercury is faster, and less mercury is removed from the mixed layer through particle sinking, when compared with current simulations. Parameter changes affect the simulated global ocean mercury budget, particularly mass exchange between the mixed layer and subsurface waters. Based on our inversion results, we re-evaluate the long-term global biogeochemical cycle of mercury, and show that legacy mercury becomes more likely to reside in the terrestrial ecosystem than in the ocean. We estimate that primary anthropogenic mercury contributes up to 23 % of present-day atmospheric deposition.
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