Fasting leptin is a metabolic determinant of food reward in overweight and obese individuals during chronic aerobic exercise training

Changes in food reward have been implicated in exercise-induced compensatory eating behaviour. However, the underlying mechanisms of food reward, and the physiological correlates of exercise-induced changes in food reward, are unknown. Methods. Forty-six overweight and obese individuals completed 12 weeks of aerobic exercise. Body composition, food intake, and fasting metabolic-related hormones were measured at baseline, week six, and postintervention. On separate days, the reward value of high-and-low-fat food (explicit liking and implicit wanting) was also assessed at baseline, week six, and postintervention. Results. Following the intervention, FM, FFM, and V O 2 peak improved significantly, while fasting leptin decreased. However, food intake or reward did not change significantly. Cross-sectional analyses indicated that FM (P = 0.022) and FFM (P = 0.046) were associated with explicit liking for high-fat food, but implicit wanting was associated with FM only (P = 0.005). Fasting leptin was associated with liking (P = 0.023) and wanting (P = 0.021) for high-fat food. Furthermore, a greater exercise-induced decline in fasting leptin was associated with increased liking (P = 0.018). Conclusion. These data indicate that food reward has a number of physiological correlates. In particular, fasting leptin appears to play an active role in mediating food reward during exercise-induced weight loss. © 2014 Mark Hopkins et al

Polychaete invader enhances resource utilization in a species-poor system

Ecosystem consequences of biodiversity change are often studied from a species loss perspective, while the effects of invasive species on ecosystem functions are rarely quantified. In this experimental study, we used isotope tracers to measure the incorporation and burial of carbon and nitrogen from a simulated spring phytoplankton bloom by communities of one to four species of deposit-feeding macrofauna found in the species-poor Baltic Sea. The recently invading polychaete Marenzelleriaarctia, which has spread throughout the Baltic Sea, grows more rapidly than the native species Monoporeia affinis, Pontoporeia femorata (both amphipods) and Macoma balthica (a bivalve), resulting in higher biomass increase (biomass production) in treatments including the polychaete. Marenzelleria incorporated and buried bloom material at rates similar to the native species. Multi-species treatments generally had higher isotope incorporation, indicative of utilization of bloom material, than expected from monoculture yields of the respective species. The mechanism behind this observed over-yielding was mainly niche complementarity in utilization of the bloom input, and was more evident in communities including the invader. In contrast, multi-species treatments had generally lower biomass increase than expected. This contrasting pattern suggests that there is little overlap in resource use of freshly deposited bloom material between Marenzelleria and the native species but it is likely that interference competition acts to dampen resulting community biomass. In conclusion, an invasive species can enhance incorporation and burial of organic matter from settled phytoplankton blooms, two processes fundamental for marine productivity

Impact of oil on bacterial community structure in bioturbated sediments

Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions - with tidal cycles and natural seawater - was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g21 wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by Gammaproteobacteria and Deltaproteobacteria. In the oiled-microcosms, the addition of H. diversicolor reduced the phylotype-richness, sequences associated to Actinobacteria, Firmicutes and Plantomycetes were not detected. These observations highlight the influence of the bioturbation on the bacterial community structure without affecting the biodegradation capacities

Characterization of Obese Individuals who Claim to Detect no Relationship between their Eating Pattern and Sensations of Hunger or Fullness

OBJECTIVE: To study the phenomenon that obese subjects show considerable individual variability in their reported relationships between eating and sensations of hunger and fullness. DESIGN: A laboratory study of the relationship between eating behaviour traits and the episodic oscillations in sensations of hunger and fullness in response to obligatory, fixed energy breakfast (481 kcal) and lunch (675 kcal) meals. SUBJECTS: Obese subjects were divided into two groups based on their responses to four 'screening' questions associated with their habitual experience of hunger and fullness sensations before and after eating: those who experienced sensations of hunger and fullness related to eating (Related-R; n=20, body mass index (BMI)=42.4 kg/m(2)) and those for whom eating was not related to hunger or fullness sensations (Unrelated - UR; n=19, BMI=41.3 kg/m(2)). In addition, a control, lean group (Control - C; n=14, BMI=22.6 kg/m(2)) who experienced sensations of hunger and fullness related to eating was studied. MEASUREMENTS: The Three-Factor Eating Questionnaire (TFEQ) was used to measure the eating behaviour traits, disinhibition, restraint and hunger. Profiles of subjective appetite sensations were continuously monitored across the day using visual analogue scales. RESULTS: All groups displayed clear meal-related oscillations in subjective sensations of hunger, fullness, desire to eat and prospective consumption. In contrast, the TFEQ disinhibition and hunger scores (but not restraint scores) were significantly different (P<0.05) between the groups ((UR; D=13.5+/-0.5, H=10.0+/-0.5), R (D 7.5+/-0.6, H 6.1+/-0.4), C(D 3.7+/-0.5, H 3.7+/-0.5)). In addition, analysis of the intra-meal changes in subjective appetite sensations revealed that the UR group displayed a smaller meal-induced suppression of hunger and elevation of fullness. CONCLUSION: These data indicate that the reported relationship between eating and hunger/fullness was associated with obese individuals showing high or low disinhibition scores. In addition, the data suggest that the processes underlying disinhibition may be associated with a modulation of the recognition of meal-related satiety sensations