On the relationship between sweet taste and seasonal body weight changes in a primate (Microcebus murinus)

The relationship between obesity and taste, especially sweet taste, has been and is of interest. From this point of view of a small primate, the lesser mouse lemur (Microcebus murinus), is of particular interest. It goes through a yearly cycle of physiological changes, one of which is an extreme variation in body weight of up to 100%. This occurs concomitantly with significant changes of the animal's liking for sucrose; measured by two-bottle preference tests, the threshold for sucrose changes from 28-45 in lean to 77-105 mM in obese animals. It is possible that a change in peripheral taste sensitivity might be the cause for these preference changes. To test this possibility we studied the ability of M.murinus to taste sucrose with electrophysiological and conditioned taste aversion techniques. The electrophysiological recordings were obtained from the chorda tympani proper nerve in two heavy and three lean animals. We did not record any difference between the two groups in their neural response to a series of sucrose concentrations. Conditioned taste aversion experiments with 200 mM sucrose as conditioning stimulus and 50 and 200 mM sucrose as test stimuli gave similar results. No difference was found between three heavy and four lean animals; both groups rejected the sucrose concentrations. The results support the notion that the seasonal variations in preference threshold to sucrose were unrelated to the ability of M.murinus to taste sucros

Effects of hunger state on flavour pleasantness conditioning at home: flavour-nutrient learning vs. flavour-flavour learning

This study examined acquired liking of flavour preferences through flavour-flavour and flavour-nutrient learning under hungry or sated conditions in a naturalistic setting. Each participant consumed one of three versions of a test drink at home either before lunch or after lunch: minimally sweetened (CONTROL: 3% sucrose, 40kcal), artificially sweetened (3% sucrose 40kcal plus artificial sweeteners ASPARTAME) and sucrose-sweetened (SUCROSE: 9.9% sugar, 132kcal). The test drink was an uncarbonated peach-flavoured iced tea served in visually identical drink cans (330ml). Participants preselected as "sweet likers" evaluated the minimally sweetened flavoured drink (conditioned stimulus, CS) in the same state (hungry or sated) in which they consumed the test drink at home. Overall, liking for the CS flavour increased in participants who consumed the SUCROSE drink, however, this increase in liking was significantly larger when tested and trained hungry than sated, consistent with a flavour-nutrient model. Overall increases in pleasantness for the CS flavour in participants who consumed the SUCROSE drink when sated or the ASPARTAME drink independent of hunger state, suggest that flavour-flavour learning also occurred. These results are discussed in light of current learning models of flavour preference

Pengaruh Penambahan Sari Pala (Myristica Fragrans) dan Cengkeh (Eugenia Carryophyllus) terhadap Tingkat Kesukaan Minuman Serbuk Berbasis Lemon Cui (Citrus Microcarpa)

Lemon cui, nutmeg meat and clove leaf contain antioxidants which can be added to powder drinks. The purpose of this study was to obtain the most preferred formula of lemon cui based instant powder drinks with the addition of nutmeg and clove leaf juice. This research uses descriptive method with experimental design that is Complete Random Design (CRD) with the treatment of the type of addition of nutmeg and clove leaf juice as antioxidants, as many as six levels of treatment made in the following formulations: (A) 50% sucrose: lemon cui juice 30%: water 20%; (B) 50% sucrose: 30% lemon cui juice: 0% nutmeg juice: clove juice 20%; (C) 50% sucrose: 30% lemon cui juice: 5% nutmeg juice: clove juice 15%; (D) 50% sucrose: 30% lemon cui juice: 10% nutmeg juice: clove juice 10%; (E) 50% sucrose: 30% lemon cui juice: 15% nutmeg juice: clove juice 5%; (F) 50% sucrose: 30% lemon cui juice: nutmeg juice 20%: clove juice 0%. The results showed that the percentage of panelists' preference based on indicators of color, odour and taste of lemon cui based powder drinks ranged from 57 to 67%, with preference level criteria being neutral. The organoleptic test results showed that the level of preference for color (2.76-3.68), odour (2.70-3.12) and taste (2.54-3.24) with criteria of liking. Based on the results of the study, it was concluded that the panelists' preferred level of the best lemon cui based instant powder drink was formula B

Changes in Food Preference and Taste Responses after Roux-en-Y Gastric Bypass

Currently, the most powerful therapy for obesity is bariatric surgery both in terms of significant weight loss and long-term efficacy. Most surgeons regard the Roux-en-Y gastric bypass (gastric bypass) operation as “gold standard” for obesity treatment. However, underlying mechanisms by which gastric bypass induces and sustains weight loss are not fully understood, but include reduced hunger, increased satiety, increased energy expenditure, altered taste, as well as reduced preference for foods with a high fat and sugar content. In fact, gastric patients often report idiosyncratic changes in taste perception that involves “sweet” taste and a calorie-dense food. I herein aimed to investigate how gastric bypass reduces intake of and preference for food high in fat and sugar in rats and humans. I found that the proportion of dietary fat in gastric bypass patients was significantly reduced six years after surgery compared with patients after vertical-banded gastroplasty. In addition, gastric bypass patients had an increased sucrose detection sensitivity compared with before surgery and controls, but hedonic taste ratings of sucrose in bypass patients remained unchanged. Rats after gastric bypass exhibit a shift away from high to low fat food. When compared to sham-operated rats, gastric bypass rats did not prefer high sucrose and fat concentrations in a two bottle preference test, but preoperative sucrose exposure reduced this effect. There was no difference in appetitive or consumatory behaviour in the brief access test between the sham-operated and gastric bypass rats. An oral gavage of 1 ml corn oil in gastric bypass rats induced conditioned taste aversion which was also demonstrated after exogenous administration of the GLP-1 receptor agonist exendin-4 (2 μg/kg intraperitoneal) in unoperated rats. These findings suggest that an altered food preference may contribute to long-term maintained weight loss after gastric bypass. Postingestive effects resulting in conditioned taste aversion may partially explain this observation

Decrease of vanillin sucrose intake by victorious and defeated mice: development of anhedonia?

Hedonic reactions to various rewards play a key role in various forms of motivated behavior. The influence of repeated experience of social victories or defeats in daily agonistic interactions between male mice on voluntary consumption of vanillin sucrose solution used as hedonic reinforcer was studied. Intake of vanillin sucrose solution was shown to decrease in the winners and losers exposed to social confrontations as compared with the controls. Three days of deprivation failed to restore the intake of vanillin sucrose solution to the control level in the losers and did so in the winners. The results obtained imply that similar reaction of animals to a hedonic non-drug reinforcer may have different motivational origin depending on positive or negative social experience

Female and male Wistar rats (Rattus norvegicus) discriminate diets according to energetic quantity

The food choice of animals is influenced by several factors including the quantity and nutrients available. It is not known, however, whether faced with alternatives that present the same amount of food, with similar flavor and obtained with the same response cost, rats would discriminate between diets with different energetic quantities. The aim was to verify whether female and male Wistar rats (Rattus norvegicus) discriminate between three types of food that differ in their energetic content (whether or not they prefer one) and whether the flavor could affect the choice between two diets with equal energetic quantities. Twelve Wistar rats (six of each sex) underwent tests of choice between pairs of diets of different energetic values. After the tests, the animals had at their disposal, in the home cage, two diets with the same energetic content, which differed in flavor (one contained sucrose) - Flavor test. The consumption of each diet was measured for five consecutive days. All the subjects demonstrated a preference for the more energetic alternative, regardless of the combination of diets presented. In the Flavor test the animals did not show significant preference for any diet, i.e., the consumption of both the S and N diets were statistically equal for all subjects. It was concluded that the animals, regardless of sex, discriminated between the diets with different energetic values and that the flavor did not seem to be a determinant variable in the food choice.

Opiate Drug Seeking and Addiction: The Influence of Sucrose Consumption on the Acquisition and Expression of Morphine-induced Conditioned Place Preferences (CPP)

Sucrose intake may lead to changes in brain and behavior similar to the effects of abused drugs. For example, sucrose may agonize endogenous opiate systems and modulate opiate-seeking behavior. Previous research reported equivocal outcomes where sucrose may either enhance (i.e., cross-sensitization) or attenuate (i.e., cross-tolerance) drug seeking as measured by morphine-induced CPP. The present experiment extends from past work and evaluated the impact of sucrose administered prior to place conditioning. Additionally, unique groups received sucrose prior to tests for CPP to measure sucrose influences on CPP expression. Sprague-Dawley rats (n=24) were assigned to sucrose (15% w/v) or water pre-exposure conditions. Subsequently, subjects received morphine place conditioning where morphine (10mg/kg) was administered on the initially non-preferred side of the apparatus. Three post-tests were conducted and, prior to each test, animals within each pre-exposure group (sucrose or water) received either sucrose or water. Factorial ANOVA was used to analyze data. Results showed robust morphine-induced CPP. Although animals in the sucrose pre-exposure condition displayed enhanced CPP, the outcomes were not statistically significant. The present findings support the value of CPP techniques to measure opiate drug-seeking behavior. Future work may discover the sufficient conditions for detecting sucrose cross-sensitization of morphine CPP

Tumor Growth Increases Neuroinflammation, Fatigue and Depressive-like Behavior Prior to Alterations in Muscle Function

Cancer patients frequently suffer from fatigue, a complex syndrome associated with loss of muscle mass, weakness, and depressed mood. Cancer-related fatigue (CRF) can be present at the time of diagnosis, during treatment, and persists for years after treatment. CRF negatively influences quality of life, limits functional independence, and is associated with decreased survival in patients with incurable disease. Currently there are no effective treatments to reduce CRF. The aim of this study was to use a mouse model of tumor growth and discriminate between two main components of fatigue: loss of muscle mass/function and altered mood/motivation. Here we show that tumor growth increased fatigue- and depressive-like behaviors, and reduced body and muscle mass. Decreased voluntary wheel running activity (VWRA) and increased depressive-like behavior in the forced swim and sucrose preference tests were evident in tumor-bearing mice within the first two weeks of tumor growth and preceded the loss of body and muscle mass. At three weeks, tumor-bearing mice had reduced grip strength but this was not associated with altered expression of myosin isoforms or impaired contractile properties of muscles. These increases in fatigue and depressive-like behaviors were paralleled by increased expression of IL-1β mRNA in the cortex and hippocampus. Minocycline administration reduced tumor-induced expression of IL-1β in the brain, reduced depressive-like behavior, and improved grip strength without altering muscle mass. Taken together, these results indicate that neuroinflammation and depressed mood, rather than muscle wasting, contribute to decreased voluntary activity and precede major changes in muscle contractile properties with tumor growth

Perceptual learning in flavor preference conditioning: restricting generalization of acquired preferences between flavors

Two experiments with rats investigated perceptual learning using a conditioned preference procedure. Experiment 1 used a between-subject procedure in which rats received either intermixed preexposure (AX, BX, AX, BX…) or blocked preexposure (AX, AX…, BX, BX…) to flavor compounds before a conditioned preference was established to AX by pairing it with sucrose. During a test, rats given intermixed preexposure showed a greater preference for AX over BX than those given blocked preexposure. Experiment 2 showed that after intermixed preexposure to AX and BX, and a block of preexposure to CX, a preference established to AX was less likely to generalize to BX than to CX. These results represent the first demonstration of the impact of the schedule of preexposure on perceptual learning using a flavor preference procedure, and they parallel those previously observed using flavor aversion procedures