Barbara Lieder

A 12-week intervention with nonivamide, a TRPV1 agonist, prevents a dietary-induced body fat gain and increases peripheral serotonin in moderately overweight subjects.

Scope: A bolus administration of 0.15 mg nonivamide has previously been demonstrated to reduce energy intake in moderately overweight men. This 12‐week intervention investigated whether a daily consumption of nonivamide in a protein‐based product formulation promotes a reduction in body weight in healthy overweight subjects and affects outcome measures associated with mechanisms regulating food intake, e.g. plasma concentrations of (an)orexigenic hormones, energy substrates as well as changes in fecal microbiota. Methods and results: Nineteen overweight subjects were randomly assigned to either a control (C) or a nonivamide (NV) group. Changes in the body composition and plasma concentrations of satiating hormones were determined at fasting and 15, 30, 60, 90, and 120 min after a glucose load. Participants were instructed to consume 0.15 mg nonivamide per day in 450 mL of a milk shake additionally to their habitual diet. After treatment, a group difference in body fat mass change (–0.61 ± 0.36% in NV and +1.36 ± 0.38% in C) and an increase in postprandial plasma serotonin were demonstrated. Plasma metabolome and fecal microbiome read outs were not affected. Conclusions: A daily intake of 0.15 mg nonivamide helps to support to maintain a healthy body composition.

Nonivamide, a capsaicin analogue, exhibits anti‐inflammatory properties in peripheral blood mononuclear cells and U‐937 macrophages

SCOPE Inflammation-related diseases are a worldwide problem. The counteraction of inflammation with compounds activating the trigeminal nerve is one strategy to fight these diseases. Known trigeminally active compounds found in black or red pepper are the tingling t-pellitorine, the pungent capsaicin, and the less pungent nonivamide. The presented study compares the anti-inflammatory potential of nonivamide to the two known anti-inflammatory compounds, elucidating the mechanism of action and the role of transient receptor protein (TRP) channels. METHODS AND RESULTS Primary peripheral blood mononuclear cells (PBMCs) and U-937 macrophages were stimulated with 1 μg/mL LPS from Escherichia coli (EC-LPS) to induce inflammation. Nonivamide attenuated the EC-LPS induced release of IL-6 and TNF-α in PBMCs and U-937 macrophages determined by magnetic bead kit analysis. This anti-inflammatory mechanism was independent from nuclear factor-kappa B pathway but mitogen-activated protein kinase (MAPK) pathway may be involved. In addition, cotreatment of U-937 with the trigeminally active compound and an antagonist of TRPV1 or TRPA1 abolished the anti-inflammatory activity. CONCLUSIONS Nonivamide possessed similar anti-inflammatory potential as capsaicin and t-pellitorine. In U-937 macrophages, the tested compounds exploited an anti-inflammatory effect by inhibiting the EC-LPS induced activation of the MAPK pathway. In addition, the TRP channel activation plays a role in the anti-inflammatory capacity of capsaicin and nonivamide.

Nϵ-Carboxymethyllysine Increases the Expression of miR-103/143 and Enhances Lipid Accumulation in 3T3-L1 Cells

Advanced glycation endproducts, formed in vivo, but also by the Maillard reaction upon thermal treatment of foods, have been associated with the progression of pathological conditions such as diabetes mellitus. In addition to the accumulation with age, exogenous AGEs are introduced into the circulation from dietary sources. In this study, we investigated the effects of addition of free Nϵ‐carboxymethyllysine (CML), a well‐characterized product of the Maillard reaction, on adipogenesis in 3T3‐L1 preadipocytes. Treatment with 5, 50, or 500 μM CML resulted in increased lipid accumulation to similar extents, by 11.5 ± 12.6%, 12.9 ± 8.6%, and 12.8 ± 8.5%, respectively. Long‐term treatment with 500 μM CML during adipogenesis resulted in increases in miR‐103 and miR‐143 levels, two miRNAs described to be involved in impaired glucose homeostasis and increased lipid accumulation. Furthermore, the expression of genes associated with these miRNAs, consisting of Akt1, PI3k, and Cav1 was regulated by CML. Short‐term treatment of mature 3T3‐L1 adipocytes with CML resulted in decreased basal glucose uptake. These results, indicate that the addition of protein‐free CML to 3T3‐L1 cells influence parameters associated with adipogenesis and glucose homeostasis at transcriptional, and functional level; this indicates that free CML derived from exogenous sources, in addition to protein‐bound CML may be relevant in this context. J. Cell. Biochem. 117: 2413–2422, 2016.

The flavanone homoeriodictyol increases SGLT-1-mediated glucose uptake but decreases serotonin release in differentiated Caco-2 cells

Flavanoids and related polyphenols, among them hesperitin, have been shown to modulate cellular glucose transport by targeting SGLT-1 and GLUT-2 transport proteins. We aimed to investigate whether homoeriodictyol, which is structurally related to hesperitin, affects glucose uptake in differentiated Caco-2 cells as a model for the intestinal barrier. The results revealed that, in contrast to other polyphenols, the flavanon homoeriodictyol promotes glucose uptake by 29.0 ± 3.83% at a concentration of 100 μM. The glucose uptake stimulating effect was sensitive to phloridzin, but not to phloretin, indicating an involvement of the sodium-coupled glucose transporter SGLT-1, but not of sodium-independent glucose transporters (GLUT). In addition, in contrast to the increased extracellular serotonin levels by stimulation with 500 mM D-(+)-glucose, treatment with 100 μM homoeriodictyol decreased serotonin release by –48.8 ± 7.57% in Caco-2 cells via a phloridzin-sensitive signaling pathway. Extracellular serotonin levels were also reduced by –57.1 ± 5.43% after application of 0.01 μM homoeriodictyol to human neural SH-SY5Y cells. In conclusion, we demonstrate that homoeriodictyol affects both the glucose metabolism and the serotonin system in Caco-2 cells via a SGLT-1-meditated pathway. Furthermore, the results presented here support the usage of Caco-2 cells as a model for peripheral serotonin release. Further investigations may address the value of homoeriodictyol in the treatment of anorexia and malnutrition through the targeting of SGLT-1.

The advanced glycation end product Nϵ-carboxymethyllysine and its precursor glyoxal increase serotonin release from Caco-2 cells

Advanced glycation end products (AGEs), comprising a highly diverse class of Maillard reaction compounds formed in vivo and during heating processes of foods, have been described in the progression of several degenerative conditions such as Alzheimers disease and diabetes mellitus. Nϵ‐Carboxymethyllysine (CML) represents a well‐characterized AGE, which is frequently encountered in a Western diet and is known to mediate its cellular effects through binding to the receptor for AGEs (RAGE). As very little is known about the impact of exogenous CML and its precursor, glyoxal, on intestinal cells, a genome‐wide screening using a customized microarray was conducted in fully differentiated Caco‐2 cells. After verification of gene regulation by qPCR, functional assays on fatty acid uptake, glucose uptake, and serotonin release were performed. While only treatment with glyoxal showed a slight impact on fatty acid uptake (P < 0.05), both compounds reduced glucose uptake significantly, leading to values of 81.3% ± 22.8% (500 μM CML, control set to 100%) and 68.3% ± 20.9% (0.3 μM glyoxal). Treatment with 500 μM CML or 0.3 μM glyoxal increased serotonin release (P < 0.05) to 236% ± 111% and 264% ± 66%, respectively. Co‐incubation with the RAGE antagonist FPS‐ZM1 reduced CML‐induced serotonin release by 34%, suggesting a RAGE‐mediated mechanism. Similarly, co‐incubation with the SGLT‐1 inhibitor phloridzin attenuated serotonin release after CML treatment by 32%, hinting at a connection between CML‐stimulated serotonin release and glucose uptake. Future studies need to elucidate whether the CML/glyoxal‐induced serotonin release in enterocytes might stimulate serotonin‐mediated intestinal motility.

Caffeine induces gastric acid secretion via bitter taste signaling in gastric parietal cells

Significance This study shows that caffeines effect on gastric acid secretion (GAS) is more complex than has been previously thought. Oral and gastric bitter taste receptors are involved in the regulation of GAS in humans. This regulatory process can be modified by the bitter-masking compound homoeriodictyol. Practical applications of the results may include treatment of gastroesophageal reflux disease or peptic ulcer by manipulating gastric pH by means of bitter tastants and inhibitors. Caffeine, generally known as a stimulant of gastric acid secretion (GAS), is a bitter-tasting compound that activates several taste type 2 bitter receptors (TAS2Rs). TAS2Rs are expressed in the mouth and in several extraoral sites, e.g., in the gastrointestinal tract, in which their functional role still needs to be clarified. We hypothesized that caffeine evokes effects on GAS by activation of oral and gastric TAS2Rs and demonstrate that caffeine, when administered encapsulated, stimulates GAS, whereas oral administration of a caffeine solution delays GAS in healthy human subjects. Correlation analysis of data obtained from ingestion of the caffeine solution revealed an association between the magnitude of the GAS response and the perceived bitterness, suggesting a functional role of oral TAS2Rs in GAS. Expression of TAS2Rs, including cognate TAS2Rs for caffeine, was shown in human gastric epithelial cells of the corpus/fundus and in HGT-1 cells, a model for the study of GAS. In HGT-1 cells, various bitter compounds as well as caffeine stimulated proton secretion, whereby the caffeine-evoked effect was (i) shown to depend on one of its cognate receptor, TAS2R43, and adenylyl cyclase; and (ii) reduced by homoeriodictyol (HED), a known inhibitor of caffeine’s bitter taste. This inhibitory effect of HED on caffeine-induced GAS was verified in healthy human subjects. These findings (i) demonstrate that bitter taste receptors in the stomach and the oral cavity are involved in the regulation of GAS and (ii) suggest that bitter tastants and bitter-masking compounds could be potentially useful therapeutics to regulate gastric pH.

Cinnamyl Isobutyrate Decreases Plasma Glucose Levels and Total Energy Intake from a Standardized Breakfast: A Randomized, Crossover Intervention

Scope Cinnamon is associated with anti‐obesity effects, regulating food intake, improving plasma glucose levels and lipid profiles in vivo. In the present study, the impact of cinnamyl isobutyrate (CIB), one constituent of cinnamon, on ad libitum food intake from a standardized breakfast and outcome measures of hormonal regulation of appetite were investigated. Methods and results In this randomized, short‐term crossover intervention study, a 75 g per 300 mL glucose solution solely (control) or supplemented with 0.45 mg CIB was administered to 26 healthy volunteers. Prior to and 2 h after receiving control or CIB treatment, subjective hunger perceptions were rated using a visual analog scale. Food intake from a standardized breakfast was assessed 2 h after treatments. Plasma peptide YY3–36, glucagon‐like‐peptide1, ghrelin, and serotonin as well as plasma glucose and insulin were measured in blood samples drawn at fasting and 15, 30, 60, 90, and 120 min after treatment. CIB administration decreased total energy intake and delta area under curve plasma glucose by 4.64 ± 3.51% and 49.3 ± 18.5% compared to control treatment, respectively. Conclusions CIB, administered at a 0.45 mg bolus in 75 g glucose–water solution, decreased ad libitum energy intake from a standardized breakfast and postprandial plasma glucose levels.

Noncaloric Sweeteners Induce Peripheral Serotonin Secretion via the T1R3-Dependent Pathway in Human Gastric Parietal Tumor Cells (HGT-1)

The role of sweet taste in energy intake and satiety regulation is still controversial. Noncaloric artificial sweeteners (NCSs) are thought to help reduce energy intake, although little is known about their impact on the satiating neurotransmitter serotonin (5-HT). In the gastrointestinal (GI) tract, 5-HT regulates gastric acid secretion and gastric motility, both part of the complex network of mechanisms regulating food intake and satiety. This study demonstrated a stimulating impact compared to controls (100%) on 5-HT release in human gastric tumor cells (HGT-1) by the NCSs cyclamate (50 mM, 157% ± 6.3%), acesulfame potassium (Ace K, 50 mM, 197% ± 8.6%), saccharin (50 mM, 147% ± 6.7%), sucralose (50 mM, 194% ± 11%), and neohesperidin dihydrochalcone (NHDC, 1 mM, 201% ± 13%). Although these effects were not associated with the sweet taste intensity of the NCSs tested, involvement of the sweet receptor subunit T1R3 in the NCS-evoked response was demonstrated by mRNA expression of TAS1R3, co-incubation experiments using the T1R3 receptor antagonist lactisole, and a TAS1R3 siRNA knockdown approach. Analysis of the downstream signaling revealed activation of the cAMP/ERK/Ca2+ cascade. Co-treatment experiments with 10 mM glucose enhanced the 5-HT release induced by cyclamate, Ace K, saccharin, and sucralose, thereby supporting the enhancing effect of glucose on a NCS-mediated response. Overall, the results obtained identify NCSs as potent inducers of 5-HT release via T1R3 in human gastric parietal cells in culture and warrant in vivo studies to demonstrate their efficacy.

The Alkamide trans-Pellitorine Targets PPARγ via TRPV1 and TRPA1 to Reduce Lipid Accumulation in Developing 3T3-L1 Adipocytes

Adipose tissue is an important endocrine organ in the human body. However, pathological overgrowth is associated with chronic illness. Regulation of adipogenesis and maturation of adipocytes via bioactive compounds in our daily diet has been in focus of research in the past years and showed promising results for agonists of the ion channels transient receptor potential channel (TRP) V1 and A1. Here, we investigated the anti-adipogenic potential and underlying mechanisms of the alkamide trans-pellitorine present in Piper nigrum via TRPV1 and TRPA1 in 3T3-L1 cells. trans-pellitorine was found to suppress mean lipid accumulation, when applied during differentiation and maturation, but also during maturation phase solely of 3T3-L1 cells in a concentration range between 1 nM and 1 μM by up to 8.84 ± 4.97 or 7.49 ± 5.08%, respectively. Blockage of TRPV1 using the specific inhibitor trans-tert-butyl-cyclohexanol demonstrated that the anti-adipogenic activity of trans-pellitorine depends on TRPV1. In addition, blockage of the TRPA1 channel using the antagonist AP-18 showed a TRPA1-dependent signaling in the early to intermediate stages of adipogenesis. On a mechanistic level, treatment with trans-pellitorine during adipogenesis led to reduced PPARγ expression on gene and protein level via activation of TRPV1 and TRPA1, and increased expression of the microRNA mmu-let-7b, which has been associated with reduced PPARγ levels. In addition, cells treated with trans-pellitorine showed decreased expression of the gene encoding for fatty acid synthase, increased expression of microRNA-103 and a decreased short-term fatty acid uptake on the functional level. In summary, these data point to an involvement of the TRPV1 and TRPA1 cation channels in the anti-adipogenic activity of trans-pellitorine via microRNA-let7b and PPARγ. Since trans-pellitorine does not directly activate TRPV1 or TRPA1, an indirect modulation of the channel activity is assumed and warrants further investigation.