Gastric Serotonin Biosynthesis and Its Functional Role in L-Arginine-Induced Gastric Proton Secretion.

Among mammals, serotonin is predominantly found in the gastrointestinal tract, where it has been shown to participate in pathway-regulating satiation. For the stomach, vascular serotonin release induced by gastric distension is thought to chiefly contribute to satiation after food intake. However, little information is available on the capability of gastric cells to synthesize, release and respond to serotonin by functional changes of mechanisms regulating gastric acid secretion. We investigated whether human gastric cells are capable of serotonin synthesis and release. First, HGT-1 cells, derived from a human adenocarcinoma of the stomach, and human stomach specimens were immunostained positive for serotonin. In HGT-1 cells, incubation with the tryptophan hydroxylase inhibitor p-chlorophenylalanine reduced the mean serotonin-induced fluorescence signal intensity by 27%. Serotonin release of 147 ± 18%, compared to control HGT-1 cells (set to 100%) was demonstrated after treatment with 30 mM of the satiating amino acid L-Arg. Granisetron, a 5-HT3 receptor antagonist, reduced this L-Arg-induced serotonin release, as well as L-Arg-induced proton secretion. Similarly to the in vitro experiment, human antrum samples released serotonin upon incubation with 10 mM L-Arg. Overall, our data suggest that human parietal cells in culture, as well as from the gastric antrum, synthesize serotonin and release it after treatment with L-Arg via an HTR3-related mechanism. Moreover, we suggest not only gastric distension but also gastric acid secretion to result in peripheral serotonin release.

TRPA1 Agonist Cinnamaldehyde Decreases Adipogenesis in 3T3-L1 Cells More Potently than the Non-agonist Structural Analog Cinnamyl Isobutyrate.

The cinnamon-derived bioactive aroma compound cinnamaldehyde (CAL) has been identified as a promising antiobesity agent, inhibiting adipogenesis and decreasing lipid accumulation in vitro as well as in animal models. Here, we investigated the antiadipogenic effect of cinnamyl isobutyrate (CIB), another cinnamon-derived aroma compound, in comparison to CAL in 3T3-L1 adipocyte cells. In a concentration of 30 µM, CIB reduced triglyceride (TG) and phospholipid (PL) accumulation in 3T3-L1 pre-adipocytes by 21.4 ± 2.56 and 20.7 ± 2.05%, respectively. CAL (30 µM), in comparison, decreased TG accumulation by 37.5 ± 1.81% and PL accumulation by 28.7 ± 1.83%, revealing the aldehyde to be the more potent antiadipogenic compound. The CIB- and CAL-mediated inhibition of lipid accumulation was accompanied by downregulation of essential adipogenic transcription factors PPARγ, C/EBPα, and C/EBPß on gene and protein levels, pointing to a compound-modulated effect on adipogenic signaling cascades. Coincubation experiments applying the TRPA-1 inhibitor AP-18 demonstrated TRPA1 dependency of the CAL, but not the CIB-induced antiadipogenic effect.

Identification of Cinnamaldehyde as Most Effective Fatty Acid Uptake Reducing Cinnamon-Derived Compound in Differentiated Caco-2 Cells Compared to Its Structural Analogues Cinnamyl Alcohol, Cinnamic Acid, and Cinnamyl Isobutyrate.

Naturally occurring cinnamon compounds such as cinnamaldehyde (CAL) and structurally related constituents have been associated with antiobesity activities, although studies regarding the impact on intestinal fatty acid uptake are scarce. Here, we demonstrate the effects of CAL and structural analogues cinnamyl alcohol (CALC), cinnamic acid (CAC), and cinnamyl isobutyrate on mechanisms regulating intestinal fatty acid uptake in differentiated Caco-2 cells. CAL, CALC, and CAC (3000 µM) were found to decrease fatty acid uptake by 58.0 ± 8.83, 19.4 ± 8.98, and 21.9 ± 6.55%, respectively. While CAL and CALC at a concentration of 300 µM increased serotonin release 14.9 ± 3.00- and 2.72 ± 0.69-fold, respectively, serotonin alone showed no effect on fatty acid uptake. However, CAL revealed transient receptor potential channel A1-dependency in the decrease of fatty acid uptake, as well as in CAL-induced serotonin release. Overall, CAL was identified as the most potent of the cinnamon constituents tested.

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.

High-Efficiency Reverse (5'→3') Synthesis of Complex DNA Microarrays.

DNA microarrays are important analytical tools in genetics and have recently found multiple new biotechnological roles in applications requiring free 3' terminal hydroxyl groups, particularly as a starting point for enzymatic extension via DNA or RNA polymerases. Here we demonstrate the highly efficient reverse synthesis of complex DNA arrays using a photolithographic approach. The method is analogous to conventional solid phase synthesis but makes use of phosphoramidites with the benzoyl-2-(2-nitrophenyl)-propoxycarbonyl (BzNPPOC) photolabile protecting group on the 3'-hydroxyl group. The use of BzNPPOC, with more than twice the photolytic efficiency of the 2-(2-nitrophenyl)-propoxycarbonyl (NPPOC) previously used for 5'→3' synthesis, combined with additional optimizations to the coupling and oxidation reactions results in an approximately 3-fold improvement in the reverse synthesis efficiency of complex arrays of DNA oligonucleotides. The coupling efficiencies of the reverse phosphoramidites are as good as those of regular phosphoramidites, resulting in comparable yields. Microarrays of DNA surface tethered on the 5' end and with free 3' hydroxyl termini can be synthesized quickly and with similarly high stepwise coupling efficiency as microarrays using conventional 3'→5' synthesis.