Differential Effects of Acute and Chronic Antagonist And An Irreversible Antagonist Treatment On Cocaine Self-Administration Behavior in Rats

According to pharmacological theory, the magnitude of an agonist-induced response is related to the number of receptors occupied. If there is a receptor reserve, when the number of receptors is altered the fractional occupancy required to maintain this set number of receptors will change. Therefore, any change in dopamine receptor number will result in a change in the concentration of cocaine required to induce the satiety response. Rats that self-administered cocaine were treated with the irreversible monoamine receptor antagonist, EEDQ, or were infused continuously for 14 days with the D1-like antagonist, SCH23390, treatments known to decrease or increase, respectively, the number of dopamine receptors with a concomitant decrease or increase in response to dopaminergic agonists. The rate of maintained cocaine self-administration increased or decreased in rats treated with EEDQ or withdrawn from chronic SCH23390 infusion, respectively. After EEDQ treatment, the effect ratio of a single dose of SCH23390 or eticlopride were unchanged, indicating that the same dopamine receptor populations mediated the accelerated cocaine self-administration. The satiety threshold likely corresponds to a specific number of activated dopamine receptors. Changing the receptor reserve is a key determinant of the rate of cocaine self-administration because the resulting increased or decreased concentration of cocaine results in an accelerated or decelerated rate of cocaine elimination as dictated by first-order kinetics. Changes in dopamine receptor number that may occur after continuous treatment with antagonists may account for the apparent lack of efficacy of these antagonists in clinical trials for cocaine use disorder.

Hibiscus sabdariffa tea affects diet-induced thermogenesis and subjective satiety responses in healthy men, but not in women: a randomized crossover trial

The aim of this study was to investigate the effect of Hibiscus sabdariffa tea on energy expenditure, satiety response and food intake. This is an open-label, crossover, randomized clinical trial (RBR-5HZ86T), including 21 subjects (11 women, 10 men). The individuals were evaluated at acute moments (fasting and after eating standardized breakfast accompanied by water or Hibiscus sabdariffa tea). Resting energy expenditure was measured by indirect calorimetry, subjective satiety responses were evaluated with a visual analogue scale and food intake was assessed by using food records. The volunteers who drank the Hibiscus sabdariffa tea had lower perception of hunger (p=0.002) and greater feeling of satiety (p=0.010) and fullness (p=0.009) compared to control. Men who ingested the Hibiscus sabdariffa tea had an increase in nitrogen energy expenditure (water: 1501±290.7kcal, Hibiscus sabdariffa tea: 1619±288.9kcal; p=0.029). In comparison to control, men presented less perception of hunger (p=0.003) and desire to eat (p=0.016), increased satiety (p=0.021) and fullness (p=0.010), and women oxidized more fat (p=0.034) when they drank Hibiscus sabdariffa tea. There was no difference between treatments regarding the energy and macronutrient intake from the first meal and throughout the day (p>0.050) for all participants. The Hibiscus sabdariffa tea only affected energy expenditure and satiety responses in men. Clinical trial registry: ReBEC Platform of the Brazilian Clinical Trials Registry - RBR-5HZ86T Novelty bullets • Hibiscus sabdariffa tea promoted an increase in energy expenditure and caused less perception of hunger/desire to eat in men. • Hibiscus sabdariffa tea intake increased postprandial fat oxidation in women.

Both Isocarbohydrate and Hypercarbohydrate Fruit Preloads Curbed Postprandial Glycemic Excursion in Healthy Subjects

This study aimed to investigate the impact of fruit preloads on the acute postprandial glycemic response (PGR) and satiety response of a rice meal in healthy female subjects based on iso-carbohydrate (IC) and hyper-carbohydrate (HC) contents, respectively. The IC test meals including (1) rice preload (R + 35R), (2) orange preload (O + 35R), (3) apple preload (A + 35R) and (4) pear preload (P + 35R), contained 50.0 g available carbohydrates (AC) where the preload contributed 15.0 g and rice provided 35.0 g. The HC meals included (1) orange preload (O + 50R), (2) apple preload (A+50R) and (3) pear preload (P + 50R), each containing 65.0 g AC, where the fruits contributed 15.0 g and rice provided 50.0 g. Drinking water 30 min before the rice meal was taken as reference (W + 50R). All the preload treatments, irrespective of IC or HC meals, resulted in remarkable reduction (p < 0.001) in terms of incremental peak glucose (IPG) and the maximum amplitude of glycemic excursion in 180 min (MAGE0–180), also a significant decrease (p < 0.05) in the area of PGR contributed by per gram of AC (AAC), compared with the W + 50R. Apple elicited the lowest PGR among all test meals, as the A + 35R halved the IPG and slashed the incremental area under the curve in 180 min (iAUC0–180) by 45.7%, while the A + 50R reduced the IPG by 29.7%, compared with the W + 50R. All the preload meals and the reference meal showed comparable self-reported satiety in spite of the difference in AC. In conclusion, pre-meal consumption of three fruits effectively curbed post-meal glycemia even in the case of a 30% extra carbohydrate load.

A hindbrain dopaminergic neural circuit prevents weight gain by reinforcing food satiation

The neural circuitry mechanism that underlies dopaminergic (DA) control of innate feeding behavior is largely uncharacterized. Here, we identified a subpopulation of DA neurons situated in the caudal ventral tegmental area (cVTA) directly innervating DRD1-expressing neurons within the lateral parabrachial nucleus (LPBN). This neural circuit potently suppresses food intake via enhanced satiation response. Notably, this cohort of DAcVTA neurons is activated immediately before the cessation of each feeding bout. Acute inhibition of these DA neurons before bout termination substantially suppresses satiety and prolongs the consummatory feeding. Activation of postsynaptic DRD1LPBN neurons inhibits feeding, whereas genetic deletion of Drd1 within the LPBN causes robust increase in food intake and subsequent weight gain. Furthermore, the DRD1LPBN signaling manifests the central mechanism in methylphenidate-induced hypophagia. In conclusion, our study illuminates a hindbrain DAergic circuit that controls feeding through dynamic regulation in satiety response and meal structure.

Two to Tango? The Dance of Maternal Authority and Feeding Practices with Child Eating Behavior

The purpose of this study was to elucidate the relationship between maternal feeding practices and children’s eating problems. Mothers of 292 children aged 5.9 ± 1.1, 50% boys, reported online on parental authority, overt and covert control of the child’s food choices, child feeding practices, and their child’s problematic eating behavior. Structural equation modelling yielded a model with excellent indices of fit (χ(2)(52) = 50.72, p = 0.56; normed fit index (NFI) = 0.94; root mean square error of approximation (RMSEA) = 0.001). The model showed that an authoritarian maternal authority style was associated with overt control, which was associated with maternal tendency to pressure children to eat and with maternal restriction of highly processed or calorie-rich snack foods. These, in turn, were positively associated with the child’s satiety response, food fussiness, and slow eating, and negatively with the child’s enjoyment of food. In contrast, a permissive maternal authority style was associated with covert control of the child’s eating, concern over the child being overweight, and the restriction of highly processed and calorie-rich snack foods, which were in turn positively associated with the child’s emotional overeating and the child’s food responsiveness. The model seems to tap into two distinct patterns of mother-child feeding and eating dynamics, apparently related to children with opposing appetitive tendencies.

Effects of Saccharin Consumption on Operant Responding for Sugar Reward and Incubation of Sugar Craving in Rats

Repeated experience with artificial sweeteners increases food consumption and body weight gain in rats. Saccharin consumption may reduce the conditioned satiety response to sweet-tasting food. Rats were trained to press a lever to obtain sucrose for five days. A compound cue (tone + light) was presented with every sucrose delivery. On the following day, each lever press produced only the compound cue (cue-reactivity test). Subjects were then provided with yogurt for three weeks in their home cages. The rats were divided into two groups. Rats in the saccharin group received yogurt sweetened with saccharin on some days and unsweetened yogurt on others. For the plain group, only unsweetened plain yogurt was provided. Subsequently, the cue-reactivity test was conducted again. On the following day, the rats underwent a consumption test in which each lever press was reinforced with sucrose. Chow consumption and body weight gain were larger in the saccharin group than in the plain group. Lever responses increased from the first to the second cue-reactivity tests (incubation of craving) in both groups. During the consumption test, lever responses were higher in the saccharin group than in the plain group, suggesting that the conditioned satiety response was impaired in the saccharin group.

The Impact of the Use of Glycomacropeptide on Satiety and Dietary Intake in Phenylketonuria

Protein is the most satiating macronutrient, increasing secretion of gastrointestinal hormones and diet induced thermogenesis. In phenylketonuria (PKU), natural protein is restricted with approximately 80% of intake supplied by a synthetic protein source, which may alter satiety response. Casein glycomacropeptide (CGMP-AA), a carbohydrate containing peptide and alternative protein substitute to amino acids (AA), may enhance satiety mediated by its bioactive properties. Aim: In a three-year longitudinal; prospective study, the effect of AA and two different amounts of CGMP-AA (CGMP-AA only (CGMP100) and a combination of CGMP-AA and AA (CGMP50) on satiety, weight and body mass index (BMI) were compared. Methods: 48 children with PKU completed the study. Median ages of children were: CGMP100; (n = 13), 9.2 years; CGMP50; (n = 16), 7.3 years; and AA (n = 19), 11.1 years. Semi-quantitative dietary assessments and anthropometry (weight, height and BMI) were measured every three months. Results: The macronutrient contribution to total energy intake from protein, carbohydrate and fat was similar across the groups. Adjusting for age and gender, no differences in energy intake, weight, BMI, incidence of overweight or obesity was apparent between the groups. Conclusion: In this three-year longitudinal study, there was no indication to support a relationship between CGMP and satiety, as evidenced by decreased energy intake, thereby preventing overweight or obesity. Satiety is a complex multi-system process that is not fully understood.

A Fatty Acid Mouth Rinse Decreases Self-Reported Hunger and Increases Self-Reported Fullness in Healthy Australian Adults: A Randomized Cross-Over Trial

Fatty acid (FA) chemoreception in the oral cavity, known as fat taste, may trigger a satiety response that is homologous to FA chemoreception in the gastrointestinal tract. In addition, individuals with an impaired fat taste sensitivity are more likely to have an impaired satiety response. This study aimed to assess the effect of an FA mouth rinse on self-reported appetite, and to determine if the effect is modified by fat taste sensitivity. Thirty-one participants (age, 32.0 ± 8.4 y; body mass index (BMI), 26.1 ± 8.1 kg/m2) were studied on four separate days to evaluate the effect of a 20 mM oleic acid (OA) mouth rinse (in duplicate) compared to a control (in duplicate) on self-reported appetite by using a visual analogue scale (VAS) every 30 min for three hours following a standardized low-fat breakfast. The area under the curve ratings for fullness were greater (p = 0.003), and those for hunger were lower (p = 0.002) following the OA rinse compared to the control. The effect of the OA rinse was greater in individuals who were hypersensitive to fat taste compared to moderately sensitive and hyposensitive individuals for fullness (p < 0.010) and hunger (p < 0.010) ratings. In summary, an OA mouth rinse decreases self-reported hunger and increases self-reported fullness, particularly in those who are more sensitive to fat taste. FA receptors in the oral cavity may be potential targets to regulate appetite.

Plasma Glucagon-Like Peptide-1 and Cholecystokinin Responses to Fast Food in Healthy-Weight and Obese Men

<p>Satiety hormones play a role in obesity metabolism. The satiety response to similar nutrients in food in healthy and obese men remains undefined. The research was aimed to determine the satiety response differences by comparing the effect of isocaloric fast-food consumption on reducing appetite-related gut hormones, such as glucagon-like fullness ratings and both GLP-1 and CCK among healthy and obese men. Respondents were given an isocaloric fast food, then GLP-1 and CCK levels were measured using enzyme-linked immunosorbent assay (ELISA). Visual analogue scale (VAS) form was used for hunger and fullness ratings of the subjects. The difference level of GLP-1, CCK, and VAS between groups were measured by t-test. The correlation between VAS hunger and fullness rating was measured by Pearson. Plasma hormone levels in 16 obese and 16 healthy-weight respondents were assessed before eating and at 30, 60, and 120 minutes after consumption. In obese men, GLP-1 levels were significantly higher than those in healthy-weight men at 60 and 120 minutes, while healthy-weight men had significantly higher CCK levels than those of obese men over time (all p&lt;0.05). The total area under the curve (AUC) for GLP-1 was significantly higher for obese men than for healthy-weight men, while the AUC for CCK was significantly higher for healthy-weight men than for obese men. Obese men have higher plasma GLP-1 levels and lower plasma CCK than healthy men indicates that those respondents were experiencing glucose intolerance and leptin alteration. The hormonal systems that may contribute to the development of obesity need further investigation.</p>

Thylakoids: A Novel Food-Derived Supplement for Obesity – A Mini-Review

Nowadays, overweight and obesity are major epidemic health problems that can bring about some other health issues such as cardiovascular disease which is the first cause of mortality worldwide. Thylakoids are disc-like membranes responsible for photosynthetic light reactions in chloroplasts of green plants. Although only a few animal and human studies have been conducted regarding the impact of thylakoids on overweight- and obesity-related factors, all of them have resulted in positive outcomes. These outcomes are as follows: increment of satiety response; suppression of hunger sensations, particularly hedonic hunger; reduction of body weight and fat; promotion of glucose homeostasis; decrease in serum lipids; attenuation of oxidative stress and inflammation; and modulation of gut microbiota, notably by increasing some helpful bacteria such as Lactobacillus reuteri. It seems that some of these useful effects are related to retarded absorption of dietary fat and carbohydrate caused by thylakoids. There is still a need for more well-designed studies.