The Obese Taste Bud study: Objectives and study design.

AIMS: Taste modifies eating behaviour, impacting body weight and potentially obesity development. The Obese Taste Bud (OTB) Study is a prospective cohort study launched in 2020 at the University of Leipzig Obesity Centre in cooperation with the HI-MAG Institute. OTB will test the hypothesis that taste cell homeostasis and taste perception are linked to obesity. Here, we provide the study design, data collection process and baseline characteristics. MATERIALS AND METHODS: Participants presenting overweight, obesity or normal weight undergo taste and smell tests, anthropometric, and taste bud density (TBD) assessment on Day 1. Information on physical and mental health, eating behaviour, physical activity, and dental hygiene are obtained, while biomaterial (saliva, tongue swap, blood) is collected in the fasted state. Further blood samples are taken during a glucose tolerance test. A stool sample is collected at home prior to Day 2, on which a taste bud biopsy follows dental examination. A subsample undergoes functional magnetic resonance imaging while exposed to eating-related cognitive tasks. Follow-up investigations after conventional weight loss interventions and bariatric surgery will be included. RESULTS: Initial results show that glycated haemoglobin levels and age are negatively associated with TBD, while an unfavourable metabolic profile, current dieting, and vegan diet are related to taste perception. Olfactory function negatively correlates with age and high-density lipoprotein cholesterol. CONCLUSION: Initial findings suggest that metabolic alterations are relevant for taste and smell function and TBD. By combining omics data from collected biomaterial with physiological, metabolic and psychological data related to taste perception and eating behaviour, the OTB study aims to strengthen our understanding of taste perception in obesity.

The role of the oral microbiome in obesity and metabolic disease: potential systemic implications and effects on taste perception.

Obesity and its metabolic sequelae still comprise a challenge when it comes to understanding mechanisms, which drive these pandemic diseases. The human microbiome as a potential key player has attracted the attention of broader research for the past decade. Most of it focused on the gut microbiome while the oral microbiome has received less attention. As the second largest niche, the oral microbiome is associated with a multitude of mechanisms, which are potentially involved in the complex etiology of obesity and associated metabolic diseases. These mechanisms include local effects of oral bacteria on taste perception and subsequent food preference as well as systemic effects on adipose tissue function, the gut microbiome and systemic inflammation. This review summarizes a growing body of research, pointing towards a more prominent role of the oral microbiome in obesity and associated metabolic diseases than expected. Ultimately, our knowledge on the oral microbiome may support the development of new patient oriented therapeutic approaches inevitable to relieve the health burden of metabolic diseases and to reach long-term benefits in patients´ lives.

Association of Salty and Sweet Taste Recognition with Food Reward and Subjective Control of Eating Behavior.

Sweet and salty tastes are highly palatable and drive food consumption and potentially uncontrolled eating, but it remains unresolved whether the ability to recognize sweet and salty affects food reward and uncontrolled eating. We investigate the association of sweet and salty taste recognition with liking and wanting and uncontrolled eating. Thirty-eight, mainly female (68%) participants of the Obese Taste Bud study, between 22 and 67 years old, with a median BMI of 25.74 kg/m2 (interquartile range: 9.78 kg/m2) completed a taste test, the Leeds Food Preference Questionnaire to assess food reward, the Power of Food Scale (PFS) and the Three-Factor Eating Questionnaire to assess different aspects of uncontrolled eating. Better salty taste recognition predicted greater implicit wanting for high-fat savory foods (ß = 0.428, p = 0.008) and higher PFS total (ß = 0.315; p = 0.004) and PFS present subscale scores (ß = 0.494, p = 0.002). While neither sweet nor salty taste recognition differed between lean individuals and individuals with obesity, those with greater trait uncontrolled eating showed significantly better salty taste recognition (U = 249.0; p = 0.009). Sweet taste recognition did not associate with food reward or uncontrolled eating. Better salty but not sweet taste recognition associates with a greater motivation for, but not liking of, particularly savory high-fat foods and further relates to greater loss of control over eating. Salty taste perception, with taste recognition in particular, may comprise a target to modulate food reward and uncontrolled eating.

The Concentration of Salivary Extracellular Vesicles Is Related to Obesity.

BACKGROUND AND AIMS: Saliva is essential for the proper dilution and distribution of taste molecules on the tongue. It harbors extracellular vesicles (EVs), which mediate cell-cell communication. Changes in the composition of salivary EVs may arise under obese conditions and may potentially be involved in taste sensation and dysregulated eating behavior. Therefore, this study addresses the relationship between the size and concentration of salivary EVs and metabolic shifts in obesity or factors of taste sensation. MATERIALS AND METHODS: A total of 119 participants in the Obese Taste Bud (OTB) Study were included, who performed a standardized taste test, underwent taste bud density assessment, and were phenotypically characterized for anthropometrics, blood- and saliva adipokine levels, and various metabolic factors. Utilizing size exclusion chromatography followed by ultrafiltration, EVs were extracted from 2 mL of actively secreted saliva. EVs were characterized using nanoparticle tracking analyses, Western blot, and scanning transmission electron microscopy. Finally, group comparisons and bivariate correlation analyses were conducted. RESULTS: Among the total cohort, the median size of salivary EVs was 190.05 nm, and the overall concentration ranged from 1.4 × 107 to 1.76 × 109 per mL of saliva. The size range and concentration of EVs per mL are negatively correlated (p = 0.0002, r = -0.264). Comparing lean participants (mean rank of 45.98) with those presenting obesity (mean rank of 34.46), a significant difference in the salivary EV content was observed (p = 0.029). Body weight, BMI, arm and calf circumferences, as well as the percentage of body fat were all negatively related to the concentration of EVs in all study participants (all p < 0.05, r > -0.2). No associations were found between the EV parameters and taste perception but serum alkaline phosphatase levels were negatively correlated (p = 0.007, r = -0.284) and adiponectin serum levels were positively correlated to the EV concentration (p = 0.036, r = 0.208). CONCLUSION: The current study provides evidence for the relation between salivary EVs and anthropometric as well as metabolic parameters of obesity. This can provide the basis for further research on the cargo of salivary EVs and how they may influence taste sensation, and may elucidate their potential connection to altered eating habits in obesity.

The Effect of FGF21 and Its Genetic Variants on Food and Drug Cravings, Adipokines and Metabolic Traits.

Fibroblast growth factor 21 (FGF21) is a regulator of addictive behavior. Increasing evidence suggests an impact of FGF21 on eating behavior, food and drug cravings and on other adipokines like insulin-like growth factor 1 (IGF-1) or adiponectin. We investigated the association of serum FGF21 and genetic variants with aspects of food and drug craving and obesity related metabolic parameters including serum adipokine levels. Standardized questionnaires, blood samples and anthropometric data of the Sorbs cohort (n = 1046) were analyzed using SPSS. For genetic analyses, the FGF21-locus ±10 kb was genotyped and analyzed using PLINK. Validation was conducted in a second independent cohort (n = 704). FGF21 was significantly associated with alcohol and coffee consumption, smoking and eating behavior (disinhibition). We confirmed correlations of FGF21 serum levels with IGF-1, adiponectin, pro-enkephalin, adipocyte fatty-acid-binding protein, chemerin and progranulin. FGF21 genetic variants were associated with anthropometric and metabolic parameters, adipokines, food and drug craving while strongest evidence was seen with low-density lipoprotein cholesterol (LDL-C). We highlight the potential role of FGF21 in food and drug cravings and provide new insights regarding the link of FGF21 with other adipokines as well as with metabolic traits, in particular those related to lipid metabolism (LDL-C).

Adiponectin and negative mood in healthy premenopausal and postmenopausal women.

Negative mood and stress are associated with cardiovascular and metabolic disease. There are likely many physiological mechanisms underlying the poor health outcomes. The relationship of psychological states (negative mood, life stress, and stress-responsive hormones) and adiponectin, an adipokine that promotes insulin sensitivity, was investigated in two separate studies. The two groups of participants included 52 healthy, premenopausal women, and 63 postmenopausal women with a range of stress levels. The relationship between adiponectin and psychological state (perceived stress and negative mood) was examined cross-sectionally in both groups of participants, but also prospectively (1 year later) in the group of postmenopausal women. In premenopausal women, negative mood and nocturnal urinary epinephrine were significantly related to adiponectin, independent of BMI. In postmenopausal women, negative mood was not associated with adiponectin cross-sectionally, but negative mood was a significant predictor for lower levels of adiponectin 1 year later, independent of initial adiponectin concentrations and changes in body mass index. Lastly, having a depressive disorder was related to lower adiponectin. As adiponectin levels are associated with insulin resistance, obesity, and diabetes mellitus, these findings suggest there may be an adiponectin-mediated pathway explaining in part how negative mood affects metabolic health. Mechanistic studies are needed to explore this potential relationship further.

Consequences of Obesity on the Sense of Taste: Taste Buds as Treatment Targets?

Premature obesity-related mortality is caused by cardiovascular and pulmonary diseases, type 2 diabetes mellitus, physical disabilities, osteoarthritis, and certain types of cancer. Obesity is caused by a positive energy balance due to hyper-caloric nutrition, low physical activity, and energy expenditure. Overeating is partially driven by impaired homeostatic feedback of the peripheral energy status in obesity. However, food with its different qualities is a key driver for the reward driven hedonic feeding with tremendous consequences on calorie consumption. In addition to visual and olfactory cues, taste buds of the oral cavity process the earliest signals which affect the regulation of food intake, appetite and satiety. Therefore, taste buds may play a crucial role how food related signals are transmitted to the brain, particularly in priming the body for digestion during the cephalic phase. Indeed, obesity development is associated with a significant reduction in taste buds. Impaired taste bud sensitivity may play a causal role in the pathophysiology of obesity in children and adolescents. In addition, genetic variation in taste receptors has been linked to body weight regulation. This review discusses the importance of taste buds as contributing factors in the development of obesity and how obesity may affect the sense of taste, alterations in food preferences and eating behavior.

Inflammatory markers are associated with cardiac autonomic dysfunction in recent-onset type 2 diabetes.

OBJECTIVE: Cardiovascular autonomic neuropathy is a common but underestimated diabetes-related disorder. Associations between cardiovascular autonomic dysfunction and subclinical inflammation, both risk factors of diabetic comorbidities and mortality, have been proposed in non-diabetic populations, while data for type 1 and type 2 diabetes are conflicting. Our aim was to investigate associations between inflammation-related biomarkers and cardiac autonomic dysfunction in patients with diabetes. METHODS: We characterised the associations between seven biomarkers of subclinical inflammation and cardiac autonomic dysfunction based on heart rate variability and cardiovascular autonomic reflex tests (CARTs) in 161 individuals with type 1 and 352 individuals with type 2 diabetes (time since diagnosis of diabetes <1 year). Analyses were adjusted for age, sex, anthropometric, metabolic and lifestyle factors, medication and cardiovascular comorbidities. RESULTS: In individuals with type 2 diabetes, higher serum interleukin (IL)-18 was associated with lower vagal activity (p≤0.015 for association with CARTs), whereas higher levels of total and high-molecular-weight adiponectin showed associations with very low frequency power, an indicator of reduced sympathetic activity (p≤0.014). Higher levels of soluble intercellular adhesion molecule-1 were associated with indicators of both lower vagal (p=0.025) and sympathetic (p=0.008) tone, soluble E-selectin with one indicator of lower vagal activity (p=0.047). Serum C-reactive protein and IL-6 were also related to cardiac autonomic dysfunction, but these associations were explained by confounding factors. No consistent associations were found in individuals with type 1 diabetes. CONCLUSIONS: Biomarkers of inflammation were differentially associated with diminished cardiac autonomic dysfunction in recent-onset type 2 diabetes.

Adiponectin, markers of subclinical inflammation and nerve conduction in individuals with recently diagnosed type 1 and type 2 diabetes.

OBJECTIVE: Subclinical inflammation has been implicated in the development of diabetic sensorimotor polyneuropathy (DSPN), but studies using electrophysiological assessment as outcomes are scarce. Therefore, we aimed to investigate associations of biomarkers reflecting different aspects of subclinical inflammation with motor and sensory nerve conduction velocity (NCV) in individuals with diabetes. DESIGN AND METHODS: Motor and sensory NCV was assessed in individuals with recently diagnosed type 2 (n=352) or type 1 diabetes (n=161) from the baseline cohort of the observational German Diabetes Study. NCV sum scores were calculated for median, ulnar and peroneal motor as well as median, ulnar and sural sensory nerves. Associations between inflammation-related biomarkers, DSPN and NCV sum scores were estimated using multiple regression models. RESULTS: In type 2 diabetes, high serum interleukin (IL)-6 was associated with the presence of DSPN and reduced motor NCV. Moreover, higher levels of high-molecular weight (HMW) adiponectin, total adiponectin and their ratio were associated with prevalent DSPN and both diminished motor and sensory NCV, whereas no consistent associations were observed for C-reactive protein, IL18, soluble intercellular adhesion molecule-1 and E-selectin. In type 1 diabetes, only HMW and total adiponectin showed positive associations with motor NCV. CONCLUSIONS: Our results point to a link between IL6 and both DSPN and slowed motor NCV in recently diagnosed type 2 diabetes. The reverse associations between adiponectin and NCV in type 1 and type 2 diabetes are intriguing, and further studies should explore whether they may reflect differences in the pathogenesis of DSPN in both diabetes types.

Leptin concentrations in response to acute stress predict subsequent intake of comfort foods.

Both animals and humans show a tendency toward eating more "comfort food" (high fat, sweet food) after acute stress. Such stress eating may be contributing to the obesity epidemic, and it is important to understand the underlying psychobiological mechanisms. Prior investigations have studied what makes individuals eat more after stress; this study investigates what might make individuals eat less. Leptin has been shown to increase following a laboratory stressor, and is known to regulate satiety. This study examined whether leptin reactivity accounts for individual differences in stress eating. To test this, we exposed forty women to standardized acute psychological laboratory stress (Trier Social Stress Test) while blood was sampled repeatedly for measurements of plasma leptin. We then measured food intake after the stressor. Increasing leptin during the stressor predicted lower intake of comfort food. These initial findings suggest that acute changes in leptin may be one of the factors modulating down the consumption of comfort food following stress.