Track topics on Twitter Track topics that are important to you
Aim of study:
Bariatric surgery mediates weight-loss via one or several mechanisms inherent to each technique used. Surgical restriction is the "lowest common denominator" shared, to various extent, by all procedures. Different degrees of malabsorption are utilized in "bypass procedures" such as Roux-Y gastric bypass (GBP), biliopancreatic diversion (BPD) and biliopancreatic diversion with duodenal switch (BPD-DS). These surgical options differ, also, in the degree of weight loss they promote. This difference is due to several factors including the extent of appetite suppression, increase in energy expenditure and degree of malabsorption achieved by the different procedures.
A post-operative change in the gut-brain hormonal axis is a component that has recently drawn much attention and research but is still ill defined. It is an effect, presumably mediated by a change in a myriad of peptides and hormones originating mostly from the intestinal tract, eliciting a change in hunger and satiety feelings as well as a change in the drive to eat. Generally speaking, patients after sleeve gastrectomy (SG) and the bypass procedures mentioned, have a decreased appetite and report a reduced drive to seek food, which presumably contributes to their weight loss.
Functional magnetic resonance imaging (fMRI) is an imaging modality which measures the hemodynamic response (change in blood flow) related to neural activity in the brain, therefore allowing mapping of areas in the brain which become active due to discrete stimuli.
Recent studies utilizing fMRI to study neural response to hunger and satiety states, as well as to food anticipation and ingestion, have mapped discrete areas in the brain which respond to these stimuli. Fuhrer and colleagues found that during hunger, significantly enhanced brain activity is found in the left striate and extrastriate cortex, the inferior parietal lobe, and the orbitofrontal cortices. Stimulation with food images was associated with increased activity in both insulae, the left striate and extrastriate cortex, and the anterior midprefrontal cortex. Nonfood images were associated with enhanced activity in the right parietal lobe and the left and right middle temporal gyrus1. Stice and colleagues reported brain imaging studies which suggested that obese relative to lean individuals show greater activation of the gustatory cortex (insula/frontal operculum) and oral somatosensory regions (parietal operculum and Rolandic operculum) in response to anticipated intake and consumption of palatable foods.
Ghrelin is an orexigenic (appetite stimulating) peptide secreted by the foregut prior to meals and is therefore considered a "meal initiator". Obese patients have low ghrelin levels but maintain a normal diurnal variation of this peptide, while patients after GBP, have reduced ghrelin levels which remain low throughout the day 3. Malik and co-workers demonstrated that when ghrelin was administered intravenously to healthy volunteers during fMRI the neural response to food pictures was affected. The neural effects of ghrelin were correlated with self-rated hunger ratings.
Leptin is an adipocyte-derived circulating hormone that provides information to the brain regarding energy stores. The brain's response to leptin involves changes in energy expenditure and food intake. Farooqi and co-workers reported data suggesting that leptin acts on neural circuits governing food intake to diminish perception of food reward while enhancing the response to satiety signals generated during food consumption.
Peptide YY3-36 (PYY) is a gut-derived satiety signal whose levels increase after meal ingestion. Intravenous infusion of PYY to human volunteers has been shown to cause a decrease in food consumption and self-reported feelings of hunger. It has also been able to alter neuronal activity in within both corticolimbic and higher-cortical areas as well as homeostatic brain regions. Levels of PYY are low in obese subjects, and have has been shown to gradually increase as early as 2 days after GBP, perhaps contributing to the success of this procedure in terms of appetite control.
GLP-1 (glucagons-like peptide 1), like PYY, is an anorexigenic (appetite suppressing) signal. It is secreted from the gut after meals and reduces food intake by an effect on the brain-stem, as well as by decreasing the rate of gastric emptying which adds to the feeling of fullness after a meal. Like PYY, GLP-1 levels are low in obese patients and increase dramatically following GBP, contributing both to the weight loss as well as to the improvement in glucose tolerance after this operation.
Several correlations will be assessed:
1. Correlation between subjective reporting of hunger/satiety and fMRI images.
2. Change in neural response to food-neutral and food-related pictures, following the operation (before vs. 1m and vs. 6m after the procedure).
3. Difference between the two surgical procedures (SG vs.GBP) in regard to the neural response to food images.
4. Correlation between gut-derived appetite-regulating hormone blood levels to subjective reporting of hunger/satiety and fMRI images at the different time points.
5. Correlation of measured parameters to changes in weight, BMI and excess weight loss.
Allocation: Non-Randomized, Intervention Model: Single Group Assignment, Masking: Single Blind (Investigator)
fMRI imaging following visual stimulation of food and non-food images
Sheba Medical Center
Not yet recruiting
Sheba Medical Center
Published on BioPortfolio: 2014-08-27T03:13:02-0400
Functional Magnetic resonance study on the effect of cognitive context variables on the perception and valuation of food odorants and flavor. The study is composed of two experiments; in a...
Identification of the cerebral fMRI phenotype of obese patients with FA in cognitive task context based on food choice making
This study plans to learn more about how age and weight impact appetite and food intake. Specifically, this study is being done to see whether age and obesity impact appetite and the brain...
The aim is to profile and elucidate the hormonal and neurological system interaction to food related behavior. The stimulus used will include visual and taste (gustatory) stimuli. The stud...
In this functional magnetic resonance imaging study, effects of different information of fat content of high or low fat will be examined in FD patients and healthy volunteers (n=30, respec...
In western cultures, we are surrounded by appealing visual food cues that stimulate our desire to eat, overeating and subsequent weight gain. Cognitive control of appetite (reappraisal) requires subst...
Previous research showed that human brain regions involved in reward and cognitive control are responsive to visually presented food stimuli, in particular high-energy foods. However, it is still to b...
Defining the neural basis of perceptual categorization in a rapidly changing natural environment with low-temporal resolution methods such as functional magnetic resonance imaging (fMRI) is challengin...
We used functional magnetic resonance imaging (fMRI) to assess brain regions associated with food choices between appetizing (i.e., high sugar, high fat) and plain food in adolescents with excess weig...
To examine whether subscales of Food Craving Inventory (FCI) and Three-factor Eating Questionnaire (TFEQ) correlate with brain functional magnetic resonance imaging food-cue reactivity (fMRI-FCR) in t...
The presence of parasites in food and food products. For the presence of bacteria, viruses, and fungi in food, FOOD MICROBIOLOGY is available.
Exposure of FOOD to radioactive substances, distinguishable from FOOD IRRADIATION, a food preservation technique.
Any food that has been supplemented with essential nutrients either in quantities that are greater than those present normally, or which are not present in the fortified food. The supplementation of cereals with iron and vitamins is an example of fortified food. Fortified food includes also enriched food to which various nutrients have been added to compensate for those essential nutrients removed by refinement or processing. (From Segen, Dictionary of Modern Medicine, 1992)
A reference measure of food used to identify the calorie and nutrient content in a particular amount of that food. It is defined by an authoritative source, such as the Food Guide Pyramid devised by the UNITED STATES DEPARTMENT OF AGRICULTURE. It is different from PORTION SIZE, which is the amount of food one chooses to eat at a single meal.
The electric response evoked in the cerebral cortex by visual stimulation or stimulation of the visual pathways.
Obesity is the condition in which excess fat has accumulated in the body (mostly in subcutaneous tissues). clinical obesity is considered to be present when a person has a BMI of over 30 (Oxford Dictionary of Medicine). It is becoming increasing common i...
Diabetes Diabetes Endocrine Obesity Oxycontin Renal Disease Thyroid Disorders Endocrinology is the study of the endocrine glands and the hormones that they secrete (Oxford Medical Dictionary). There are several groups of h...