Does intervention with GLP-1 receptor agonist semaglutide modulate perception of sweet taste in women with obesity: study protocol of a randomized, single-blinded, placebo-controlled clinical trial

Background Preclinical studies demonstrated that glucagon-like peptide 1 (GLP-1) is locally synthesized in taste bud cells and that GLP-1 receptor exists on the gustatory nerves in close proximity to GLP-1-containing taste bud cells. This local paracrine GLP-1 signalling seems to be specifically involved in the perception of sweets. However, the role of GLP-1 in taste perception remains largely unaddressed in clinical studies. Whether any weight-reducing effects of GLP-1 receptor agonists are mediated through the modulation of taste perception is currently unknown. Methods and analysis This is an investigator-initiated, randomized single-blind, placebo-controlled clinical trial. We will enrol 30 women with obesity and polycystic ovary syndrome (PCOS). Participants will be randomized in a 1:1 ratio to either semaglutide 1.0 mg or placebo for 16 weeks. The primary endpoints are alteration of transcriptomic profile of tongue tissue as changes in expression level from baseline to follow-up after 16 weeks of treatment, measured by RNA sequencing, and change in taste sensitivity as detected by chemical gustometry. Secondary endpoints include change in neural response to visual food cues and to sweet-tasting substances as assessed by functional MRI, change in body weight, change in fat mass and change in eating behaviour and food intake. Discussion This is the first study to investigate the role of semaglutide on taste perception, along with a neural response to visual food cues in reward processing regions. The study may identify the tongue and the taste perception as a novel target for GLP-1 receptor agonists. Ethics and disseminations The study has been approved by the Slovene National Medical Ethics Committee and will be conducted in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines. Results will be submitted for publication in an international peer-reviewed scientific journal. Trial registration ClinicalTrials.govNCT04263415. Retrospectively registered on 10 February 2020

The processing of visual food cues during bitter aftertaste perception in females with high vs. low disgust propensity: an fMRI study

An extremely bitter taste can signal food spoilage, and therefore typically elicits disgust. The present cross-modal functional magnetic resonance imaging experiment investigated whether the personality trait ‘disgust propensity’ (DP; temporally stable tendency to experience disgust across different situations) has an influence on the processing of visual food cues during bitter aftertaste perception. Thirty females with high DP and 30 females with low DP viewed images depicting sweet food (e.g., cakes, ice cream) and vegetables, once in combination with an extremely bitter aftertaste (concentrated wormwood tea), and once with a neutral taste (water). Females highly prone to disgust (compared to low disgust-prone females) showed increased activity in the anterior cingulate cortex (ACC) and increased mPFC-insula connectivity when presented with the mismatch of a bitter aftertaste and visual cues of sweet food. The ACC is involved in conflict monitoring and is strongly interconnected with insular areas. This connection plays a critical role in awareness of changes in homeostatic states. Our findings indicate that the personality trait DP is associated with cross-modal integration processes of disgust-relevant information. Females high in DP were more alert to food-related sensory mismatch (pleasant visual features, aversive taste) than females low in DP.

Acute diet soda consumption alters brain responses to food cues in humans: A randomized, controlled, cross-over pilot study

Background: Diet soda consumption has frequently been linked to obesity and its comorbidities in epidemiological studies. Whether this link is causal and a potential mechanism remains to be determined. Aim/Methods: This randomized, cross-over, controlled pilot study sought to determine whether there may be changes in reward-related brain activations to visual food cues after acute consumption of diet soda versus regular soda or carbonated water using functional magnetic resonance imaging. Results: Diet soda as compared to carbonated water consumption increased activation of reward-related caudate to highly versus less desirable food cues. Diet soda as compared to regular soda increased reward-related insula and decreased activation of cognitive control-related dorsolateral prefrontal cortex to food cues versus non-food cues. No changes in ratings of hunger an hour after beverage consumption were observed. Conclusions: These results may suggest a potential mechanism for diet soda to increase food palatability through activation of the reward system and suppression of inhibitory control that remains to be confirmed by future studies.

Exercise Shifts Hypothetical Food Choices toward Greater Amounts and More Immediate Consumption

Although exercise modulates appetite regulation and food intake, it remains poorly understood how exercise impacts decision-making about food. The purpose of the present study was to assess the impact of an acute exercise bout on hypothetical choices related to the amount and timing of food intake. Forty-one healthy participants (22.0 ± 2.6 years; 23.7 ± 2.5 kg/m2, 56% female) completed 45 min of aerobic exercise and a resting control condition in randomized order. Food amount preferences and intertemporal food preferences (preference for immediate vs. delayed consumption) were assessed using electronic questionnaires with visual food cues. Compared to rest, exercise resulted in a greater increase in the food amount selected, both immediately post-exercise (+25.8 ± 11.0 vs. +7.8 ± 11.0 kcal/item, p = 0.02) and 30 min post-exercise (+47.3 ± 12.4 vs. +21.3 ± 12.4 kcal/item, p = 0.005). Exercise further resulted in a greater increase in the preference for immediate consumption immediately post-exercise (+0.23 ± 0.10 vs. +0.06 ± 0.10; p = 0.03) and 30 min post-exercise (+0.30 ± 0.12 vs. +0.08 ± 0.12; p = 0.01). Our findings demonstrate that a single bout of aerobic exercise shifts hypothetical food choices toward greater amounts and more immediate consumption, highlighting the importance of the timing of food choices made in the exercise context.

Face the food: Food plating with facial patterns influences appetite and event-related brain potentials

The presentation of visual food cues (e.g., food plating) can affect our appetite and leads to characteristic changes of early as well as late positivity in the electroencephalogram. The present event-related potential (ERP) study attempted to change ERPs and affective ratings for food pictures by rearranging the components of a depicted meal (conventional presentation) as a smiley or frowny. The images were presented to 68 women (mean age = 24 years), who rated the wanting and liking of the meals. Compared to conventional food plating, smiley and frowny meals elicited enhanced amplitudes of the P200, P300, and late positive potential (LPP) in a large occipito-parietal cluster. Frowny meals were rated as less appetizing than conventional food presentations. The mentioned ERP components are concomitants of face configuration processing (P200), automatic attention/novelty detection (P300), and voluntary attention/assignment of emotional meaning (LPP). Thus, the combination of two affective cues (food, face) in one stimulus changed the activation in motivational circuits of the brain. Also, serving a meal as a frowny could help to regulate appetite.