Salivary α-Amylase Activity and Starch-Related Sweet Taste Perception in Humans

Effect of sweetened beverages intake on salivary aspartame, insulin and alpha-amylase levels: A single-blind study

The objective was to assess aspartame excretion in saliva and the salivary insulin, total protein (TP), and alpha-amylase (AMI) levels in response to the ingestion of sweetened beverages (sodium cyclamate, aspartame, acesulfame, and sucrose). Fifteen healthy participants were included in a single-blinded trial with the intake of Diet soft drink, Regular soft drink, Water + sweeteners, Low sucrose content (3.5 g), and Water (blank) in 5 different days. In each day, saliva was collected at T0 (fasting), T1 (15 min after test-drink intake), T2 (30 min), T3 (60 min), and T4 (120 min) for the measurement of salivary aspartame (HPLC), TP, AMI (ELISA assays) and insulin levels (chemiluminescence). Chi-square, Friedman, ANOVA and Spearman correlation tests were applied. The late-perceived sweet/sour residual flavor was reported at a frequency of 80%, 60% and 20% after ingestion of artificially sweetened drinks, beverages with sucrose, and plain water, respectively (p < 0.05). Aspartame was detected in saliva after artificially sweetened drinks intake, with highest area under the peak for the Diet soft drink (p = 0.014). No change was observed for TP and AMI levels during the 120 min. Insulin levels increased 1 h after soft-drinks ingestion (regular and diet), while the levels did not change for Low sucrose content and Water + sweeteners test-drinks. Salivary aspartame correlated with insulin levels only after Diet soft drink intake (rho ≥ 0.7; p < 0.05). As aspartame can be detected in saliva and swallowed again until completely excreted, these results contribute to the knowledge of the biological fate of artificial sweeteners and the study of health outcomes.

Oral stimulation with maltodextrin: Effect on cephalic phase insulin release

Cephalic phase insulin release (CPIR) occurs following sensory stimulation with food-related stimuli, and has been shown to limit postabsorptive hyperglycemia. While the specific stimuli that elicit CPIR in humans have not been clearly defined, previous research points to sugars as having potential importance. Maltodextrins are a starch-derived food ingredient commonly found in a variety of processed food products. When consumed, salivary α-amylase rapidly cleaves its component saccharides into smaller units, leading to the production of sugars in the mouth. Here, we investigated whether humans elicit CPIR after tasting but not swallowing maltodextrin, and whether the degree of CPIR exhibited is affected by individuals' salivary α-amylase activity. We found that a gelatin-based stimulus containing 22% w/v maltodextrin elicited CPIR in healthy individuals (N = 22) following a modified sham-feeding protocol using both insulin and c-peptide as indices of the response. However, the degree of CPIR measured did not differ across three groupings (low, medium, or high) of effective α-amylase activity by either index. In a follow-up experiment, a subset of participants (N = 14) underwent the same protocol using a gelatin stimulus without maltodextrin, and no observable CPIR ensued. These findings suggest that oral stimulation with maltodextrin elicits CPIR in humans, but that individual differences in effective salivary α-amylase activity may not necessarily be predictive of the degree of CPIR.

Pre-harvest Nitrogen Limitation and Continuous Lighting Improve the Quality and Flavor of Lettuce (Lactuca sativa L.) under Hydroponic Conditions in Greenhouse

Short-term nitrogen limitation and continuous lighting (red/blue = 3:1) were applied individually and in combination to butterhead and red oak leaf lettuce for 1, 2, or 3 days before harvest to assess their effects on improving the nutritional value and sweet taste and reducing nitrate content and bitterness of lettuce. The results suggested that a 3-day nitrogen limitation combined with continuous lighting reduced the lettuce content of nitrate and sesquiterpene lactones and improved the quantities of soluble sugar, soluble protein, anthocyanins, and phenolic compounds without reducing the fresh weight of lettuce. In addition, in vitro simulated digestion results suggested that the 3-day nitrogen limitation combined with continuous lighting significantly improved the sweetness and reduced the bitterness of lettuce compared to the control. In conclusion, nitrogen limitation combined with continuous lighting for 3 days before harvest effectively enhanced the quality and taste of lettuce, showing great potential for its use in hydroponic lettuce production.

Association of total and pancreatic serum amylase enzymatic activity with insulin resistance and the glucose and insulin responses to oral starch test in Mexican children

BACKGROUND/OBJECTIVES

Little is known about the effect of serum amylase enzymatic activity on glucose metabolism. We investigated the association of serum amylase enzymatic activity with fasting plasma glucose, insulin resistance (IR), and the plasma glucose and insulin response to an oral starch test (OST) in Mexican children.

METHODS

Anthropometric data, glucose and insulin levels, and the serum enzymatic activity of total (AMYt), salivary (AMY1), and pancreatic (AMY2) amylase were analysed in 764 children (N_{normal weight}  = 427/N_obesity  = 337). After categorization into low (LA) and high (HA) AMYt, an OST with commercial white bread was performed in 39 children (N_{normal weight}  = 17/N_obesity  = 22).

RESULTS

A positive association between serum enzymatic activity of AMY2 and IR was observed in children with obesity (p = 0.018). Children with normal weight had lower plasma glucose and insulin response to OST than children with obesity (P_glucose  = 4.1 × 10^-12 ; P_insulin  = 2.1 × 10^-15 ). Compared with the LA group, children with HA showed lower plasma glucose and insulin response to OST (P_glucose  ≤ 0.040; P_insulin  ≤ 0.015).

CONCLUSION

Our results suggest that AMY2 is positively associated with IR. A high level of AMYt is related to lower glucose and insulin responses to OST in Mexican children, regardless of their weight status.

A secret of salivary secretions: Multimodal effect of saliva in sensory perception of food

Saliva plays multifunctional roles in oral cavity. Even though its importance for the maintenance of oral health has long been established, the role of saliva in food perception has attracted increasing attention in recent years. We encourage researchers to discover the peculiarity of this biological fluid and aim to combine the data concerning all aspects of the saliva influence on the sensory perception of food. This review presents saliva as a unique material, which modulates food perception due to constant presence of saliva in the mouth and thanks to its composition. Therefore, we highlight the salivary components that contribute to these effects. Moreover, this review is an attempt to structure the effects of saliva on perception of different food categories, where the mechanisms of salivary impact in perception of liquid, semi-solid, and solid foods are revealed. Finally, we emphasize that the large inter-individual variability in salivary composition and secretion appear to contribute to the fact that everyone experiences food in their own way. Therefore, the design of the sensory studies should consider the properties of volunteers' saliva and also carefully monitor the experimental conditions that affect salivary composition and flow rate.

Ethnic-specific association of amylase gene copy number with adiposity traits in a large Middle Eastern biobank

Studies assessing the impact of amylase genes copy number (CN) on adiposity report conflicting findings in different global populations, likely reflecting the impact of ancestral and ethnic-specific environment and lifestyle on selection at the amylase loci. Here, we leverage population size and detailed adiposity measures from a large population biobank to resolve confounding effects and determine the relationship between salivary (AMY1) and pancreatic (AMY2A) amylase genes CN and adiposity in 2935 Qatari individuals who underwent whole-genome sequencing (WGS) as part of the Qatar Genome Programme. We observe a negative association between AMY1 CNs and trunk fat percentage in the Qatari population (P = 7.50 × 10^-3) and show that Qataris of Arab descent have significantly lower CN at AMY1 (P = 1.32 × 10^-10) as well as less favorable adiposity and metabolic profiles (P < 1.34 × 10^-8) than Qataris with Persian ancestry. Indeed, lower AMY1 CN was associated with increased total and trunk fat percentages in Arabs (P < 4.60 × 10^-3) but not in Persians. Notably, overweight and obese Persians reported a significant trend towards dietary restraint following weight gain compared to Arabs (P = 4.29 × 10^-5), with AMY1 CN showing negative association with dietary self-restraint (P = 3.22 × 10^-3). This study reports an association between amylase gene CN and adiposity traits in a large Middle Eastern population. Importantly, we leverage rich biobank data to demonstrate that the strength of this association varies with ethnicity, and may be influenced by population-specific behaviors that also contribute to adiposity traits.

A stepwise approach investigating salivary responses upon multisensory food cues

Exposure to sensory food cues such as smell, vision, taste and/or texture may trigger anticipatory physiological responses such as salivation, participating on adequate metabolism of the signaled food. However, the individual contribution of each sensory modality as well as the impact of particular food products on salivation and salivary composition remains unclear. Therefore, by systematically varying sensory modalities and nutrient content of food stimuli, we investigated their effect on saliva secretion, α-amylase activity and other salivary characteristics (pH level, buffering capacity, MUC5B concentration, and total protein content). Over 3 sessions, 46 normal-weight healthy participants were exposed to 12 conditions, consisting of 4 levels of sensory stimulation (odor, odor + vision, odor + vision + taste, and odor + vision + taste + mastication) and 3 types of stimuli (bread, high-in-starch; cucumber, low-in-starch; and parafilm as non-food control) during which saliva was collected. Linear mixed models showed a significant increase in salivation with increasing levels of sensory stimulation. α-amylase secretion rate increased upon the highest level of stimulation, which involved mastication, compared to odor and odor + visual level of stimulation. Other salivary characteristics varied with the level of sensory stimulation, which might be related to the total volume of salivation. The type of stimuli did not influence the saliva composition (α-amylase concentration nor other salivary components). Our findings indicate that cumulative sensory information, rather than specific (food) product, play a vital role in anticipatory salivary responses.

A standardised semi-dynamic in vitro digestion method suitable for food – an international consensus

Standardised recommendations for a physiologically relevant, semi-dynamic in vitro simulation of upper GI tract digestion.

Review: Chemosensing of nutrients and non-nutrients in the human and porcine gastrointestinal tract

The gastrointestinal tract (GIT) is an interface between the external and internal milieus that requires continuous monitoring for nutrients or pathogens and toxic chemicals. The study of the physiological/molecular mechanisms, mediating the responses to the monitoring of the GIT contents, has been referred to as chemosensory science. While most of the progress in this area of research has been obtained in laboratory rodents and humans, significant steps forward have also been reported in pigs. The objective of this review was to update the current knowledge on nutrient chemosensing in pigs in light of recent advances in humans and laboratory rodents. A second objective relates to informing the existence of nutrient sensors with their functionality, particularly linked to the gut peptides relevant to the onset/offset of appetite. Several cell types of the intestinal epithelium such as Paneth, goblet, tuft and enteroendocrine cells (EECs) contain subsets of chemosensory receptors also found on the tongue as part of the taste system. In particular, EECs show specific co-expression patterns between nutrient sensors and/or transceptors (transport proteins with sensing functions) and anorexigenic hormones such as cholecystokinin (CCK), peptide tyrosine tyrosine (PYY) or glucagon-like peptide-1 (GLP-1), amongst others. In addition, the administration of bitter compounds has an inhibitory effect on GIT motility and on appetite through GLP-1-, CCK-, ghrelin- and PYY-labelled EECs in the human small intestine and colon. Furthermore, the mammalian chemosensory system is the target of some bacterial metabolites. Recent studies on the human microbiome have discovered that commensal bacteria have developed strategies to stimulate chemosensory receptors and trigger host cellular functions. Finally, the study of gene polymorphisms related to nutrient sensors explains differences in food choices, food intake and appetite between individuals.