The Association between Fat Taste Sensitivity, Eating Habits, and Metabolic Health in Menopausal Women

The aim of our study was to evaluate the associations between sensitivity to fat taste, eating habits and BMI value in a sample of menopausal Polish women. In a population of 95 women, fat taste thresholds with oleic acid were determined, allowing us to classify each woman as a hypersensitive or hyposensitive taster. Eating habits were assessed using a validated KomPAN questionnaire for food frequency. Dietary intake was evaluated based on a food diary. Selected biochemical parameters were measured using a Konelab20i biochemical analyzer. Anthropometric parameters and blood pressure were also measured. Twenty-two menopausal women were classified as hyposensitive to fat taste and 73 as hypersensitive. The hyposensitive tasters were significantly older (p = 0.006), with the majority of them (92%) being postmenopausal (p < 0.001); this group had significantly higher BMI values (p < 0.001) and other adiposity indicators compared to their hypersensitive counterparts. The hyposensitive tasters had higher blood pressure (systolic blood pressure; SBP p = 0.030; diastolic blood pressure; DBP p = 0.003), glucose (p = 0.011) and triacylglycerols levels than the hypersensitive tasters (p = 0.031). Almost half of them had diagnosed metabolic syndrome. Daily eating occasions were associated with low oral fatty acid sensitivity, irrespective of age (p = 0.041) and BMI value (p = 0.028). There were also significant associations between frequency of consumption of meats and eggs, as well as snacks and fast foods and low oral fatty acid sensitivity before adjustment for potential confounders (both associations p < 0.05), which remained after adjustment for age (both associations p < 0.05), but not after adjustment for BMI. A multivariate logistic regression analysis showed that higher BMI value (p = 0.003), along with postmenopausal status (p = 0.003), were associated with low fat taste sensitivity irrespective of age and consumed percentage energy from fat. Postmenopausal status and BMI are associated with low fat taste sensitivity. Fat hyposensitivity may also play a role in eating habits, leading to increased eating occasions and favoring certain types of food. These eating habits may determine increased body weight and the occurrence of metabolic syndrome in mid-life women, especially those who have undergone menopause and have been exposed to the physiological changes which are conducive to these relationships.

Increased Fat Taste Preference in Progranulin-Deficient Mice

Progranulin deficiency in mice is associated with deregulations of the scavenger receptor signaling of CD36/SCARB3 in immune disease models, and CD36 is a dominant receptor in taste bud cells in the tongue and contributes to the sensation of dietary fats. Progranulin-deficient mice (Grn−/−) are moderately overweight during middle age. We therefore asked if there was a connection between progranulin/CD36 in the tongue and fat taste preferences. By using unbiased behavioral analyses in IntelliCages and Phenomaster cages we showed that progranulin-deficient mice (Grn−/−) developed a strong preference of fat taste in the form of 2% milk as opposed to 0.3% milk, and for diluted MCTs versus tap water. The fat preference in the 7d-IntelliCage observation period caused an increase of 10% in the body weight of Grn−/− mice, which did not occur in the wildtype controls. CD36 expression in taste buds was reduced in Grn−/− mice at RNA and histology levels. There were no differences in the plasma or tongue lipids of various classes including sphingolipids, ceramides and endocannabinoids. The data suggest that progranulin deficiency leads to a lower expression of CD36 in the tongue resulting in a stronger urge for fatty taste and fatty nutrition.

Additive Effects of L-Ornithine on Preferences to Basic Taste Solutions in Mice

In addition to the taste receptors corresponding to the six basic taste qualities—sweet, salty, sour, bitter, umami, and fatty—another type of taste receptor, calcium-sensing receptor (CaSR), is found in taste-bud cells. CaSR is called the ‘kokumi’ receptor because its agonists increase sweet, salty and umami tastes to induce ‘koku’, a Japanese word meaning the enhancement of flavor characters such as thickness, mouthfulness, and continuity. Koku is an important factor for enhancing food palatability. However, it is not well known whether other kokumi-receptors and substances exist. Here, we show that ornithine (L-ornithine but not D-ornithine) at low concentrations that do not elicit a taste of its own, enhances preferences to sweet, salty, umami, and fat taste solutions in mice. Increased preference to monosodium glutamate (MSG) was the most dominant effect. Antagonists of G-protein-coupled receptor family C group 6 subtype A (GPRC6A) abolished the additive effect of ornithine on MSG solutions. The additive effects of ornithine on taste stimuli are thought to occur in the oral cavity, and are not considered post-oral events because ornithine’s effects were confirmed in a brief-exposure test. Moreover, the additive effects of ornithine and the action of the antagonist were verified in electrophysiological taste nerve responses. Immunohistochemical analysis implied that GPRC6A was expressed in subsets of type II and type III taste cells of mouse circumvallate papillae. These results are in good agreement with those reported for taste modulation involving CaSR and its agonists. The present study suggests that ornithine is a kokumi substance and GPRC6A is a newly identified kokumi receptor.

High Endocannabinoid Tone In LFABP -/- Mice Drives Fat Intake and Preference

Objectives Our objective was to understand if LFABP -/- mice display a higher preference for a high fat, high palatable food over Wild-type (WT) mice and if this preference is due to alteration of oral fatty acid detection thresholds by endocannabinoids. Methods For the first experiment, 6 mice (3 WT and 3 LFABP -/-) were given access to a high-fat cake frosting (Crisco/sugar mixture) for 5 minutes and frosting intake was recorded. This was done at the same time each day and repeated 3 times. For the second experiment, we conducted a 24-hour 2 bottle preference test of a control versus stearic acid solution in 5 WT and 5 LFABP -/- mice. The 2 bottles were switched at 12 hours to minimize side-preference. Preference was defined as the percentage of intake of fatty acid solution over total intake. Results Our preliminary results showed that 1) the LFABP KO mice consumed more high-fat frosting during a brief access test and 2) the WT mice significantly preferred the control over the stearic acid solution, whereas the LFABP -/- mice showed no difference in preference between the two bottles. Conclusions These results suggest that elevated endocannabinoid tone contributes to preference for frosting, in part, by modulating oral fatty acid detection thresholds. Changes in oral detection thresholds of taste stimuli are known to affect consumption of the stimuli; the present data support this idea for ‘fat-taste’ as well. This has important implications for the overconsumption of highly palatable food in our society. Funding Sources This research was supported by NIH NIDCD R01 014286 to PASB Co-PI, USDA NJ Hatch NJ14120 to PASB and NIH NIDDK R01 38389 and USDA NJ Hatch NJ14115 to JS.

The Tryptophan/Kynurenine Pathway: A Novel Cross-Talk between Nutritional Obesity, Bariatric Surgery and Taste of Fat

Diet-induced obesity (DIO) reduces the orosensory perception of lipids in rodents and in some humans. Although bariatric surgery partially corrects this alteration, underlying mechanisms remain poorly understood. To explore whether metabolic changes might explain this fat taste disturbance, plasma metabolome analyses, two-bottle choice tests and fungiform papillae (Fun) counting were performed in vertical sleeve gastrectomized (VSG) mice and sham-operated controls. An exploratory clinic study was also carried out in adult patients undergone a VSG. In mice, we found that (i) the VSG reduces both the plasma neurotoxic signature due to the tryptophan/kynurenine (Trp/Kyn) pathway overactivation and the failure of fat preference found in sham-operated DIO mice, (ii) the activity of Trp/Kyn pathway is negatively correlated to the density of Fun, and (iii) the pharmacological inhibition of the Kyn synthesis mimics in non-operated DIO mice the positive effects of VSG (i.e., decrease of Kyn synthesis, increase of Fun number, improvement of the fat taste perception). In humans, a reduction of the plasma Kyn level is only found in patients displaying a post-surgery improvement of their fat taste sensitivity. Altogether these data provide a plausible metabolic explanation to the degradation of the orosensory lipid perception observed in obesity.

Macronutrient Sensing in the Oral Cavity and Gastrointestinal Tract: Alimentary Tastes

There are numerous and diverse factors enabling the overconsumption of foods, with the sense of taste being one of these factors. There are four well established basic tastes: sweet, sour, salty, and bitter; all with perceptual independence, salience, and hedonic responses to encourage or discourage consumption. More recently, additional tastes have been added to the basic taste list including umami and fat, but they lack the perceptual independence and salience of the basics. There is also emerging evidence of taste responses to kokumi and carbohydrate. One interesting aspect is the link with the new and emerging tastes to macronutrients, with each macronutrient having two distinct perceptual qualities that, perhaps in combination, provide a holistic perception for each macronutrient: fat has fat taste and mouthfeel; protein has umami and kokumi; carbohydrate has sweet and carbohydrate tastes. These new tastes can be sensed in the oral cavity, but they have more influence post- than pre-ingestion. Umami, fat, kokumi, and carbohydrate tastes have been suggested as an independent category named alimentary. This narrative review will present and discuss evidence for macronutrient sensing throughout the alimentary canal and evidence of how each of the alimentary tastes may influence the consumption of foods.