Intense Sweeteners, Taste Receptors and the Gut Microbiome: A Metabolic Health Perspective

Sucralose-Enhanced Adipogenesis on Preadipocyte Human Cell Line During Differentiation Process

Sucralose, a commonly nonnutritive sweetener used in daily products of habitual diet, is related to impairing the gut microbiome by disrupting inflammatory response, promoting weight gain by increasing adipose tissue and promoting chronic inflammatory processes. Considering the impact of sucralose in the development of metabolic diseases, in this work, we focused on the impact of sucralose on the adipocyte differentiation process to determine if sucralose can promote adipogenesis and increase adipose tissue depots in PCS 210 010 human preadipocytes cell line. Sucralose at 25 (S25) and 100 ng/µL (S100) concentrations were tested against control with no edulcorant (NS) during the adipocyte differentiation process at 48 h and 96 h. The genetic expression of adipogenesis markers such as CEBP-α, PPARγ, EBF-2, UCP-1, and lipogenesis regulator ACC was determined by qPCR. A panel of human cytokines related to inflammatory response was measured by a flow cytometer using the kit Legend Plex Human Cytokine panel of BIOLUMINEX. Our results indicate that sucralose increased the expression of white adipocyte differentiation marker CEBP-α and lipogenesis regulator ACC at 96 h before complete differentiation. Also, sucralose triggers an inflammatory response by synthesizing adiponectin, resistin, IL-6, IL-8, and Il-1B. To summarize, sucralose stimulates the expression of genes related to adipogenesis and negatively affects the secretion of inflammatory cytokines and adipokines during preadipocyte differentiation.

Bitter taste receptors: Key target to understand the effects of polyphenols on glucose and body weight homeostasis. Pathophysiological and pharmacological implications

Experimental and clinical research has reported beneficial effects of polyphenol intake on high prevalent diseases such as type 2 diabetes and obesity. These phytochemicals are ligands of taste 2 receptors (T2Rs) that have been recently located in a variety of organs and extra-oral tissues. Therefore, the interaction between polyphenol and T2Rs in brain structures can play a direct effect on appetite/satiety regulation and food intake. T2Rs are also expressed along the digestive tract, and their interaction with polyphenols can induce the release of gastrointestinal hormones (e.g., ghrelin, GLP-1, CCK) influencing appetite, gastrointestinal functionally, and glycemia control. Intestinal microbiota can also influence on network effects of polyphenols-T2Rs interaction and vice versa, impacting innate immune responses and consequently on gut functionally. Furthermore, polyphenols binding to T2Rs present important effects on adipose tissue metabolism. Interestingly, T2R polymorphism could, at least partially, explain the inter-individual variability of the effects of polyphenols on glucose and body weight homeostasis. Together, these factors can contribute to understand the beneficial effects of polyphenol-rich diets but also might aid in identifying new pharmacological pathway targets for the treatment of diabetes and obesity.

Integrating Computational and Experimental Methods to Identify Novel Sweet Peptides from Egg and Soy Proteins

Sweetness in food delivers a delightful sensory experience, underscoring the crucial role of sweeteners in the food industry. However, the widespread use of sweeteners has sparked health concerns. This underscores the importance of developing and screening natural, health-conscious sweeteners. Our study represents a groundbreaking venture into the discovery of such sweeteners derived from egg and soy proteins. Employing virtual hydrolysis as a novel technique, our research entailed a comprehensive screening process that evaluated biological activity, solubility, and toxicity of the derived compounds. We harnessed cutting-edge machine learning methodologies, specifically the latest graph neural network models, for predicting the sweetness of molecules. Subsequent refinements were made through molecular docking screenings and molecular dynamics simulations. This meticulous research approach culminated in the identification of three promising sweet peptides: DCY(Asp-Cys-Tyr), GGR(Gly-Gly-Arg), and IGR(Ile-Gly-Arg). Their binding affinity with T1R2/T1R3 was lower than -15 kcal/mol. Using an electronic tongue, we verified the taste profiles of these peptides, with IGR emerging as the most favorable in terms of taste with a sweetness value of 19.29 and bitterness value of 1.71. This study not only reveals the potential of these natural peptides as healthier alternatives to traditional sweeteners in food applications but also demonstrates the successful synergy of computational predictions and experimental validations in the realm of flavor science.

Consumption of the Non-Nutritive Sweetener Stevia for 12 Weeks Does Not Alter the Composition of the Human Gut Microbiota

The use of non-nutritive sweeteners (NNSs) as an alternative to caloric sugars has increased in recent years. Stevia is an NNS that has demonstrated beneficial effects on appetite and energy intake. However, the impact on the gut microbiota is not well understood. Therefore, we investigated how regular consumption of stevia, for up to 12 weeks, impacts the human gut microbiota. Healthy subjects with a normal body mass index participated in our study; the stevia group (n = 14) was asked to consume five drops of stevia twice daily, compared to control participants (n = 13). Faecal samples collected before and after treatment were analysed by 16S rRNA gene sequencing. Stevia did not cause significant changes in the alpha or beta diversity when compared to the control groups. When the relative abundances of taxa were investigated, no clear differences were detected. Conversely, a random forest analysis correctly associated the gut microbiome with the control and stevia groups with an average of 75% accuracy, suggesting that there are intrinsic patterns that could discriminate between control and stevia use. However, large-scale changes in the gut microbiota were not apparent in this study, and, therefore, our data suggest that stevia does not significantly impact the gut microbiota.

Distinct microbiome of tongue coating and gut in type 2 diabetes with yellow tongue coating

The gut microbiome plays a critical role in the pathogenesis of type 2 diabetes mellitus (T2DM). However, the inconvenience of obtaining fecal samples hinders the clinical application of gut microbiome analysis. In this study, we hypothesized that tongue coating color is associated with the severity of T2DM. Therefore, we aimed to compare tongue coating, gut microbiomes, and various clinical parameters between patients with T2DM with yellow (YC) and non-yellow tongue coatings (NYC). Tongue coating and gut microbiomes of 27 patients with T2DM (13 with YC and 14 with NYC) were analyzed using 16S rDNA gene sequencing technology. Additionally, we measured glycated hemoglobin (HbA1c), random blood glucose (RBG), fasting blood glucose (FBG), postprandial blood glucose (PBG), insulin (INS), glucagon (GC), body mass index (BMI), and homeostasis model assessment of β-cell function (HOMA-β) levels for each patient. The correlation between tongue coating and the gut microbiomes was also analyzed. Our findings provide evidence that the levels of Lactobacillus spp. are significantly higher in both the tongue coating and the gut microbiomes of patients with YC. Additionally, we observed that elevated INS and GC levels, along with decreased BMI and HOMA-β levels, were indicative of a more severe condition in patients with T2DM with YC. Moreover, our results suggest that the composition of the tongue coating may reflect the presence of Lactobacillus spp. in the gut. These results provide insights regarding the potential relationship between tongue coating color, the gut microbiome, and T2DM.

The Effects of Artificial Sweeteners on Intestinal Nutrient-Sensing Receptors: Dr. Jekyll or Mr. Hyde?

The consumption of artificial and low-calorie sweeteners (ASs, LCSs) is an important component of the Western diet. ASs play a role in the pathogenesis of metabolic syndrome, dysbiosis, inflammatory bowel diseases (IBDs), and various inflammatory conditions. Intestinal nutrient-sensing receptors act as a crosstalk between dietary components, the gut microbiota, and the regulation of immune, endocrinological, and neurological responses. This narrative review aimed to summarize the possible effects of ASs and LCSs on intestinal nutrient-sensing receptors and their related functions. Based on the findings of various studies, long-term AS consumption has effects on the gut microbiota and intestinal nutrient-sensing receptors in modulating incretin hormones, antimicrobial peptides, and cytokine secretion. These effects contribute to the regulation of glucose metabolism, ion transport, gut permeability, and inflammation and modulate the gut-brain, and gut-kidney axes. Based on the conflicting findings of several in vitro, in vivo, and randomized and controlled studies, artificial sweeteners may have a role in the pathogenesis of IBDs, functional bowel diseases, metabolic syndrome, and cancers via the modulation of nutrient-sensing receptors. Further studies are needed to explore the exact mechanisms underlying their effects to decide the risk/benefit ratio of sugar intake reduction via AS and LCS consumption.

Sweet Taste Receptors and Associated Sweet Peptides: Insights into Structure and Function

Long-term consumption of a high-sugar diet may contribute to the pathogenesis of several chronic diseases, such as obesity and type 2 diabetes. Sweet peptides derived from a wide range of food sources can enhance sweet taste without compromising the sensory properties. Therefore, the research and application of sweet peptides are promising strategies for reducing sugar consumption. This work first outlined the necessity for global sugar reduction, followed by the introduction of sweet taste receptors and their associated transduction mechanisms. Subsequently, recent research progress in sweet peptides from different protein sources was summarized. Furthermore, the main methods for the preparation and evaluation of sweet peptides were presented. In addition, the current challenges and potential applications are also discussed. Sweet peptides can stimulate sweetness perception by binding sweet taste receptors T1R2 and T1R3 in taste buds, which is an effective strategy for reducing sugar consumption. At present, sweet peptides are mainly prepared artificially by synthesis, hydrolysis, microbial fermentation, and bioengineering strategies. Furthermore, sensory evaluation, electronic tongues, and cell models have been used to assess the sweet taste intensity. The present review can provide a theoretical reference for reducing sugar consumption with the aid of sweet peptides in the food industry.

Comparing the effects of dietary sugars on cognitive performance and reaction time: A randomized, placebo- controlled and double-blind experimental trial

The aim of the study was to compare the effects of acute intake dietary sugars on cognitive performance and reaction time. This study was, randomized, placebo-controlled, double-blind experimental design, conducted with 75 healthy adults. At the beginning of the study, the participants (36 male, 39 female; 21.6 ± 1.3 years of age; body mass index: 21.59 ± 1.94 kg/m²) were randomly divided into equal five groups (n:15) (glucose (10 g), fructose (10 g), sucrose (10 g), saccharin (0.24 g), placebo), and received dietary sugars dissolved in 200 mL of water. Cognitive performance was determined with Cancelation Test, and the Simple Response Time and Ruler Drop Tests were used in order to response and reaction time of participants, respectively. General score of cognitive performance (0.93 ± 0.1), reaction (295 ± 20 ms), and response (204 ms) were highest in glucose and lowest in placebo (0.63 ± 0.1; 368 ± 22 ms; 251 ms, respectively) (p < .001). Saccharin groups had a higher reaction (312 ± 22 ms) and response (216 ms) time score compared to consumed fructose (316 ± 39; 227 ms), sucrose (354 ± 26; 246 ms), and placebo (368 ± 22; 251 ms) groups, respectively (p < .001). These findings show that differences in the absorption pattern and sweetness levels of sugar types may have different effects on cognitive performance and reaction time.

Influences of Microbial Symbionts on Chemoreception of Their Insect Hosts

Chemical communication is widespread among insects and exploited to adjust their behavior, such as food and habitat seeking and preferences, recruitment, defense, and mate attraction. Recently, many studies have revealed that microbial symbionts could regulate host chemical communication by affecting the synthesis and perception of insect semiochemicals. In this paper, we review recent studies of the influence of microbial symbionts on insect chemoreception. Microbial symbionts may influence insect sensitivity to semiochemicals by regulating the synthesis of odorant-binding proteins or chemosensory proteins and olfactory or gustatory receptors and regulating host neurotransmission, thereby adjusting insect behavior. The manipulation of insect chemosensory behavior by microbial symbionts is conducive to their proliferation and dispersal and provides the impetus for insects to change their feeding habits and aggregation and dispersal behavior, which contributes to population differentiation in insects. Future research is necessary to reveal the material and information exchange between both partners to improve our comprehension of the evolution of chemoreception in insects. Manipulating insect chemoreception physiology by inoculating them with microbes could be utilized as a potential approach to managing insect populations.

Obesity, Diabetes Mellitus, and Vascular Impediment as Consequences of Excess Processed Food Consumption

Regular intake of ready-to-eat meals is related to obesity and several noninfectious illnesses, such as cardiovascular diseases, hypertension, diabetes mellitus (DM), and tumors. Processed foods contain high calories and are often enhanced with excess refined sugar, saturated and trans fat, Na⁺ andphosphate-containing taste enhancers, and preservatives. Studies showed that monosodium glutamate (MSG) induces raised echelons of oxidative stress, and excessive hepatic lipogenesis is concomitant to obesity and type 2 diabetes mellitus (T2DM). Likewise, more than standard salt intake adversely affects the cardiovascular system, renal system, and central nervous system (CNS), especially the brain. Globally, excessive utilization of phosphate-containing preservatives and additives contributes unswervingly to excessive phosphate intake through food. In addition, communities and even health experts, including medical doctors, are not well-informed about the adverse effects of phosphate preservatives on human health. Dietary phosphate excess often leads to phosphate toxicity, ultimately potentiating kidney disease development. The mechanisms involved in phosphate-related adverse effects are not explainable. Study reports suggested that high blood level of phosphate causes vascular ossification through the deposition of Ca²⁺ and substantially alters fibroblast growth factor-23 (FGF23) and calcitriol.

Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance

Non-nutritive sweeteners (NNS) are commonly integrated into human diet and presumed to be inert; however, animal studies suggest that they may impact the microbiome and downstream glycemic responses. We causally assessed NNS impacts in humans and their microbiomes in a randomized-controlled trial encompassing 120 healthy adults, administered saccharin, sucralose, aspartame, and stevia sachets for 2 weeks in doses lower than the acceptable daily intake, compared with controls receiving sachet-contained vehicle glucose or no supplement. As groups, each administered NNS distinctly altered stool and oral microbiome and plasma metabolome, whereas saccharin and sucralose significantly impaired glycemic responses. Importantly, gnotobiotic mice conventionalized with microbiomes from multiple top and bottom responders of each of the four NNS-supplemented groups featured glycemic responses largely reflecting those noted in respective human donors, which were preempted by distinct microbial signals, as exemplified by sucralose. Collectively, human NNS consumption may induce person-specific, microbiome-dependent glycemic alterations, necessitating future assessment of clinical implications.

Is There an Academic Bias against Low-Energy Sweeteners?

This perspective considers evidence of a common academic bias against low-energy sweeteners (LES). The core proposition is that this bias is manifested in research and reporting focused on generating and placing a negative spin on LESs, largely through selective citation, interpretation and reporting. The evidence centres on three inter-related points, which together may generate a misleading impression of the balance of evidence: (1) basic and mechanistic research on LES perpetuates “explanations” for unsubstantiated adverse effects of LES; (2) the literature on LES—particularly narrative reviews and commentaries—continually reprises hypotheses of adverse effects without acknowledging where these hypotheses have been rigorously tested and rejected; and (3) negative interpretations of the effects of LES largely rely upon selectively emphasising lower-quality research whilst ignoring or dismissing higher-quality evidence. The expert community should consider these issues in assuring scientific integrity and balance in the academic discourse on LES, and how this is translated into messages for public health and consumers.

Fueling Gut Microbes: A Review of the Interaction between Diet, Exercise, and the Gut Microbiota in Athletes

The athlete's goal is to optimize their performance. Towards this end, nutrition has been used to improve the health of athletes' brains, bones, muscles, and cardiovascular system. However, recent research suggests that the gut and its resident microbiota may also play a role in athlete health and performance. Therefore, athletes should consider dietary strategies in the context of their potential effects on the gut microbiota, including the impact of sports-centric dietary strategies (e.g., protein supplements, carbohydrate loading) on the gut microbiota as well as the effects of gut-centric dietary strategies (e.g., probiotics, prebiotics) on performance. This review provides an overview of the interaction between diet, exercise, and the gut microbiota, focusing on dietary strategies that may impact both the gut microbiota and athletic performance. Current evidence suggests that the gut microbiota could, in theory, contribute to the effects of dietary intake on athletic performance by influencing microbial metabolite production, gastrointestinal physiology, and immune modulation. Common dietary strategies such as high protein and simple carbohydrate intake, low fiber intake, and food avoidance may adversely impact the gut microbiota and, in turn, performance. Conversely, intake of adequate dietary fiber, a variety of protein sources, and emphasis on unsaturated fats, especially omega-3 (ɷ-3) fatty acids, in addition to consumption of prebiotics, probiotics, and synbiotics, have shown promising results in optimizing athlete health and performance. Ultimately, while this is an emerging and promising area of research, more studies are needed that incorporate, control, and manipulate all 3 of these elements (i.e., diet, exercise, and gut microbiome) to provide recommendations for athletes on how to "fuel their microbes."

Artificial Sweeteners: History and New Concepts on Inflammation

Since the introduction of artificial sweeteners (AS) to the North American market in the 1950s, a growing number of epidemiological and animal studies have suggested that AS may induce changes in gut bacteria and gut wall immune reactivity, which could negatively affect individuals with or susceptible to chronic inflammatory conditions such as inflammatory bowel disease (IBD), a disorder that has been growing exponentially in westernized countries. This review summarizes the history of current FDA-approved AS and their chemical composition, metabolism, and bacterial utilization, and provides a scoping overview of the disease mechanisms associated with the induction or prevention of inflammation in IBD. We provide a general outlook on areas that have been both largely and scarcely studied, emerging concepts using silica, and describe the effects of AS on acute and chronic forms of intestinal inflammation.

Oral, Tongue-Coating Microbiota, and Metabolic Disorders: A Novel Area of Interactive Research

Interactions between colonizing microbiota and the host have been fully confirmed, among which the tongue-coating microbiota have a moderate rate of renewal and disease sensitivity and are easily obtained, making them an ideal research subject. Oral microbiota disorders are related to diabetes, obesity, cardiovascular disease, cancer, and other systemic diseases. As an important part of the oral cavity, tongue-coating microbiota can promote gastritis and digestive system tumors, affecting the occurrence and development of multiple chronic diseases. Common risk factors include diet, age, and immune status, among others. Metabolic regulatory mechanisms may be similar between the tongue and gut microbiota. Tongue-coating microbiota can be transferred to the respiratory or digestive tract and create a new balance with local microorganisms, together with the host epithelial cells forming a biological barrier. This barrier is involved in the production and circulation of nitric oxide (NO) and the function of taste receptors, forming the oral-gut-brain axis (similar to the gut-brain axis). At present, the disease model and mechanism of tongue-coating microbiota affecting metabolism have not been widely studied, but they have tremendous potential.

Do Gut Microbes Taste?

Gut microbiota has emerged as a major metabolically active organ with critical functions in both health and disease. The trillions of microorganisms hosted by the gastrointestinal tract are involved in numerous physiological and metabolic processes including modulation of appetite and regulation of energy in the host spanning from periphery to the brain. Indeed, bacteria and their metabolic byproducts are working in concert with the host chemosensory signaling pathways to affect both short- and long-term ingestive behavior. Sensing of nutrients and taste by specialized G protein-coupled receptor cells is important in transmitting food-related signals, optimizing nutrition as well as in prevention and treatment of several diseases, notably obesity, diabetes and associated metabolic disorders. Further, bacteria metabolites interact with specialized receptors cells expressed by gut epithelium leading to taste and appetite response changes to nutrients. This review describes recent advances on the role of gut bacteria in taste perception and functions. It further discusses how intestinal dysbiosis characteristic of several pathological conditions may alter and modulate taste preference and food consumption via changes in taste receptor expression.

Expression of Jejunal Taste Receptors in Women with Morbid Obesity

Nutrient sensing plays important roles in promoting satiety and maintaining good homeostatic control. Taste receptors (TAS) are located through the gastrointestinal tract, and recent studies have shown they have a relationship with metabolic disorders. The aim of this study was to analyze the jejunal expression of TAS1R2, TAS1R3, TAS2R14 and TAS2R38 in women with morbid obesity, first classified according to metabolic syndrome presence (MetS; n = 24) or absence (non-MetS; n = 45) and then classified according to hepatic histology as normal liver (n = 28) or nonalcoholic fatty liver disease (n = 41). Regarding MetS, we found decreased expression of TAS2R14 in MetS patients. However, when we subclassified patients according to liver histology, we did not find differences between groups. We found negative correlations between glucose levels, triglycerides and MetS with TAS1R3 expression. Moreover, TAS2R14 jejunal expression correlated negatively with the presence of MetS and ghrelin levels and positively with the jejunal Toll-like receptor (TLR)4, peroxisome proliferator-activated receptor (PPAR)-γ, and interleukin (IL)-10 levels. Furthermore, TAS2R38 expression correlated negatively with TLR9 jejunal expression and IL-6 levels and positively with TLR4 levels. Our findings suggest that metabolic dysfunctions such as MetS trigger downregulation of the intestinal TASs. Therefore, taste receptors modulation could be a possible therapeutic target for metabolic disorders.

An Overview of Current Knowledge of the Gut Microbiota and Low-Calorie Sweeteners

This review provides an overview of the interrelationships among the diet, gut microbiota and health status, and then focuses specifically on published research assessing the relationship of low/no-calorie sweeteners (LNCS) to selected aspects of the gut microbiota. Microbiome research is expanding as new data on its role in health and disease vulnerability emerge. The gut microbiome affects health, digestion, and susceptibility to disease. In the last 10 years, investigations of LNCS effects on the gut microbiota have proliferated, though results are conflicting and are often confounded by differences in study design such as study diet, the form of the test article, dosage, and study population. Staying current on microbiome research and the role of dietary inputs, like LNCS, will allow healthcare and nutrition practitioners to provide evidenced-based guidance to the individuals they serve.

Diet Sugar-Free Carbonated Soda Beverage, Non-Caloric Flavors Consumption, and Diabetic Retinopathy: Any Linkage

PURPOSE

Assessing diabetic retinopathy (DR) risk factors and daily nutrition habits are vital for prevention. This study aims to evaluate the relationship between diet soda cans, non-nutritive sweetener consumption, and diabetic retinopathy.

PATIENTS AND METHODS

A cross-sectional study was conducted among 200 patients attending a diabetes center in Tabuk City, Saudi Arabia, from September 2019 to July 2020. A structured questionnaire was used to collect patients' demographic factors, and DR risk factors including the use of diet soda, non-nutritive sweeteners, and exercise habits. Dilated fundus eye examination was done to detect any diabetic retinopathy. A blood sample was taken for measuring glycated hemoglobin to assess the degree of glycemic control.

RESULTS

The participant's age was 50.74 ±13.51 years, and the duration since the diagnosis of diabetes was 9.99 ±6.97 years, body mass index was 27.28 ±4.68, and HbA1c %, 8.50 ±1.61), the patients used to consume 1.31 ±1.57 diet soda cans/week, and 1.06±1.39 artificial sweeteners/sachet/day. DR was found in 33%. Diet sugar-free carbonated soda beverage was associated with poor glycemic control and retinopathy, while non-caloric flavor consumption was associated with obesity (P-value<0.05). No association was evident regarding other factors (P-value>0.05).

CONCLUSION

Diet sugar-free carbonated soda beverage was associated with higher HbA1c and retinopathy, while non-caloric flavor consumption was associated with obesity. No association was evident regarding other factors. Further larger multicenter studies are needed.