Capsaicin increases gastric emptying rate in healthy human subjects measured by 13C-labeled octanoic acid breath test

Lactational performance, enteric methane emission, and nutrient utilization of dairy cows supplemented with botanicals

The objective of this study was to evaluate lactational performance, enteric gas emissions, ruminal fermentation, nutrient use efficiency, milk fatty acid profile, and energy and inflammatory markers in blood of peak-lactation dairy cows fed diets supplemented with Capsicum oleoresin or a combination of Capsicum oleoresin and clove oil. A 10-wk randomized complete block design experiment was conducted with 18 primiparous and 30 multiparous Holstein cows. Cows were blocked based on parity, days in milk, and milk yield (MY), and randomly assigned to 1 of 3 treatments (16 cows/treatment): (1) basal diet (CON); (2) basal diet supplemented with 300 mg/cow per day of Capsicum oleoresin (CAP); and (3) basal diet supplemented with 300 mg/cow per day of a combination of Capsicum oleoresin and clove oil (CAPCO). Premixes containing ground corn (CON), CAP, or CAPCO were mixed daily with the basal diet at 0.8% of dry matter intake (DMI). Supplementation of the diet with CAP or CAPCO did not affect DMI, MY, milk components, and feed efficiency of the cows. Body weight (BW) was increased during the last 2 wk of the experiment by CAP and CAPCO, compared with CON. The botanicals improved BW gain (0.85 and 0.66 kg/d for CAP and CAPCO, respectively, compared with -0.01 kg/d for CON) and CAP enhanced the efficiency of energy utilization, compared with CON (94.5% vs. 78.4%, respectively). Daily CH4 emission was not affected by treatments, but CH4 emission yield (per kg of DMI) and intensity (per kg of MY) were decreased by up to 11% by CAPCO supplementation, compared with CON and CAP. A treatment × parity interaction indicated that the CH4 mitigation effect was pronounced in primiparous but not in multiparous cows. Ruminal molar proportion of propionate was decreased by botanicals, compared with CON. Concentrations of trans-10 C18:1 and total trans fatty acids in milk fat were decreased by CAP and tended to be decreased by CAPCO, compared with CON. Total-tract apparent digestibility of nutrients was not affected by treatments, except for a tendency for decreased starch digestibility in cows supplemented with botanicals. Blood concentrations of β-hydroxybutyrate, total fatty acids, and insulin were not affected by botanicals. Blood haptoglobin concentration was increased by CAP in multiparous but not in primiparous cows. Lactational performance of peak-lactation dairy cows was not affected by the botanicals in this study, but they appeared to improve efficiency of energy utilization and partitioned energy toward BW gain. In addition, CH4 yield and intensity were decreased in primiparous cows fed CAPCO, suggesting a potential positive environmental effect of the combination of Capsicum oleoresin and clove oil supplementation.

Feeding encapsulated pepper to dairy cows during the hot season improves performance without affecting core and skin temperature

Peppers (Capsicum spp.) contain capsaicin, an organic compound with a group of alkaloids that has shown thermoregulation properties in humans and mice, and may influence glucose and lipid metabolism in ruminants. An experiment was conducted to evaluate different doses of a feed additive containing encapsulated pepper on milk yield and composition, dry matter intake, feed sorting index, total-tract apparent digestibility of nutrients, purine derivatives excretion, and serum concentrations of urea-N and glucose, N excretion, respiration rate, rectal temperature, and skin temperature in different regions (forehead, face, and rumen). Thirty-six Holstein cows (150 ± 102.1 d in milk and 29.3 ± 5.81 kg/d milk yield) were used in a 9-wk randomized complete block (n = 12) design experiment. Following a 2-wk covariate period, cows were blocked according to parity, days in milk, and milk yield and were randomly assigned to the following treatments: 0 (CAP0), 0.75 (CAP75), or 1.5 (CAP150) g/d of a feed additive containing encapsulated pepper (1 g/kg, Capcin; NutriQuest) added to the concentrate along with minerals. Treatment differences were evaluated through orthogonal contrasts (CAP0 vs. CAP75 + CAP150 or CAP75 vs. CAP150). The average temperature-humidity index during the experiment was 72.0 ± 2.07. Dry matter intake was greater in cows fed a feed additive containing encapsulated pepper (CAP) treatments (CAP75 and CAP150) compared with CAP0. Cows fed CAP150 tended to have greater dry matter intake than those in CAP75 group. Feeding CAP decreased sorting for feed particles with size between 8 and 4 mm. An interaction effect between treatment and week was observed for crude protein digestibility whereas cows fed CAP150 had the greatest digestibility on the third week of experiment. Orthogonal contrasts did not detect differences in serum concentrations of glucose and urea-N, or purine derivatives excretion. Nitrogen excretion (as % of N intake) in milk, urine, and feces was not altered by treatments. Feeding CAP increased yields of 3.5% fat-corrected milk, fat, protein, and lactose. A tendency toward greater milk protein content was observed for cows fed CAP150 than CAP75. No differences were detected on respiration rate, rectal temperature, and skin temperature of cows. A feed additive containing encapsulated pepper fed at 0.75 or 1.5 g/d can improve yield of fat-corrected milk and milk solids by increasing feed intake without affecting nutrient digestibility and body temperature of lactating cows during the hot season.

Acute Response to Capsiate Supplementation at Rest and during Exercise on Energy Intake, Appetite, Metabolism, and Autonomic Function: A Randomized Trial

OBJECTIVE

The purpose of the present study was to examine the effect of capsiate supplementation on energy intake, self-reported appetite-related sensations, energy expenditure, fat oxidation, and autonomic parameters with and without an exercise intervention.

METHODS

Thirteen healthy men completed four randomized trials: two trials for the control condition (without exercise), one with capsiate supplementation (CTRL_cap) and one with a placebo (CTRL_pla), and two trials for the exercise condition, one with capsiate supplementation (EX_cap) and one with placebo (EX_pla). Exercise sessions were performed 150 min after the consumption of a standardized breakfast, and supplementation 115 min after consumption of breakfast. An ad libitum buffet was offered 200 min following the completion of the standardized breakfast, and energy intake (EI) and relative energy intake (REI) (relative energy intake = energy intake - energy expenditure related to exercise) were evaluated.

RESULTS

There were no significant effects on EI, self-reported appetite sensations, fat oxidation, and energy expenditure. REI was reduced in conditions involving EX when compared to CTRL. A low-frequency to high-frequency ratio for heart rate variability was higher in CTRL_cap (1.6 ± 1.1) vs. CTRL_pla (1.2 ± 0.9) (p = 0.025; d = 0.39).

CONCLUSION

Acute capsiate supplementation combined with aerobic exercise has limited effects on the examined variables (EI, REI, fat oxidation, energy expenditure, and autonomic parameters), while changes in the autonomic nervous system function in the absence of exercise may have occurred without influencing other variables.

CLINICAL TRIAL REGISTRATION

ensaiosclinicos.gov.br number, RBR-5pckyr https://ensaiosclinicos.gov.br/rg/RBR-5pckyr.

The Role of Transient Receptor Potential Vanilloid 1 in Common Diseases of the Digestive Tract and the Cardiovascular and Respiratory System

Transient receptor potential vanilloid subtype 1 (TRPV1), a member of the transient receptor potential vanilloid (TRPV) channel family, is a nonselective cation channel that is widely expressed in sensory nerve fibers and nonneuronal cells, including certain vascular endothelial cells and smooth muscle cells. The activation of TRPV1 may be involved in the regulation of various physiological functions, such as the release of inflammatory mediators in the body, gastrointestinal motility function, and temperature regulation. In recent years, a large number of studies have revealed that TRPV1 plays an important role in the physiological and pathological conditions of the digestive system, cardiovascular system, and respiratory system, but there is no systematic report on TRPV1. The objective of this review is to explain the function and effects of TRPV1 on specific diseases, such as irritable bowel syndrome, hypertension, and asthma, and to further investigate the intrinsic relationship between the expression and function of TRPV1 in those diseases to find new therapeutic targets for the cure of related diseases.

Potential Phytopharmacy and Food Applications of Capsicum spp.: A Comprehensive Review

Capsicum genus (Solanaceae) is native to the Americas. Today, it is an important agricultural crop cultivated around the world, not only due to its economic importance, but also for the nutritional value of the fruits. Among their phytochemical constituents, capsaicinoids are characteristic and responsible of the pungency of sharp-tasting cultivars. Moreover, Capsicum and capsaicinoids (mainly, capsaicin) have been largely studied because of their health benefits. Thus, this study reviews the scientific knowledge about Capsicum spp. and their phytochemicals against cancer, diabetes, gastrointestinal diseases, pain, and metabolic syndrome, as well as their antioxidant and antimicrobial activity. These bioactivities can be the basis of the formulation of functional ingredients and natural preservatives containing Capsicum extracts or isolated compounds.

l-Ornithine and l-lysine stimulate gastrointestinal motility via transient receptor potential vanilloid 1

SCOPE

The gastrointestinal (GI) tract senses and responds to intraluminal nutrients and these interactions often affect GI functions. We found that, among basic amino acids, l-ornithine (Orn) and l-lysine (Lys) stimulated but l-arginine (Arg) suppressed GI motility after oral administration (24 mmol/kg) in mice (Orn and Lys, 14.3 and 26.4% promotion; Arg, 7.7% suppression). We investigated the mechanism of the action of Orn and Lys on GI motility.

METHODS AND RESULTS

Orn-induced promotion of small intestinal transit was significantly inhibited (p<0.05) by oral administration of capsazepine, a transient receptor potential vanilloid 1 (TRPV1) antagonist. Moreover, the stimulatory effect of Orn and Lys was abolished in TRPV1-knockout mice. In TRPV1-transfected HEK293 cells, Orn and Lys (10 mM) evoked Ca²⁺ influx, which was blocked by ruthenium red, a TRP channel antagonist. These results suggest that Orn and Lys promote GI motility via activation of TRPV1. The GI motility stimulation by Orn and Lys was also blocked by atropine, a muscarinic acetylcholine receptor (mAChR) antagonist, or N^G -nitro-l-arginine methyl ester, a nitric oxide (NO) synthase inhibitor.

CONCLUSION

Orally administered Orn and Lys stimulate GI motility via TRPV1, mAChR and NO synthase in mice.

Phytochemistry and gastrointestinal benefits of the medicinal spice, Capsicum annuum L. (Chilli): a review

Dietary spices and their active constituents provide various beneficial effects on the gastrointestinal system by variety of mechanisms such as influence of gastric emptying, stimulation of gastrointestinal defense and absorption, stimulation of salivary, intestinal, hepatic, and pancreatic secretions. Capsicum annuum (Solanaceae), commonly known as chilli, is a medicinal spice used in various Indian traditional systems of medicine and it has been acknowledged to treat various health ailments. Therapeutic potential of chilli and capsaicin were well documented; however, they act as double-edged sword in many physiological circumstances. In traditional medicine chilli has been used against various gastrointestinal complains such as dyspepsia, loss of appetite, gastroesophageal reflux disease, gastric ulcer, and so on. In chilli, more than 200 constituents have been identified and some of its active constituents play numerous beneficial roles in various gastrointestinal disorders such as stimulation of digestion and gastromucosal defense, reduction of gastroesophageal reflux disease (GERD) symptoms, inhibition of gastrointestinal pathogens, ulceration and cancers, regulation of gastrointestinal secretions and absorptions. However, further studies are warranted to determine the dose ceiling limit of chilli and its active constituents for their utilization as gastroprotective agents. This review summarizes the phytochemistry and various gastrointestinal benefits of chilli and its various active constituents.

Effects of rumen-protected Capsicum oleoresin on productivity and responses to a glucose tolerance test in lactating dairy cows

The objective of this experiment was to investigate the effects of rumen-protected Capsicum oleoresin (RPC) supplementation on feed intake, milk yield and composition, nutrient utilization, fecal microbial ecology, and responses to a glucose tolerance test in lactating dairy cows. Nine multiparous Holstein cows were used in a replicated 3 × 3 Latin square design balanced for residual effects with three 28-d periods. Each period consisted of 14 d for adaptation and 14 d for data collection and sampling. Treatments were 0 (control), 100, and 200 mg of RPC/cow per day. They were mixed with a small portion of the total mixed ration and top-dressed. Glucose tolerance test was conducted once during each experimental period by intravenous administration of glucose at a rate of 0.3 g/kg of body weight. Dry matter intake was not affected by RPC. Milk yield tended to increase for RPC treatments compared to the control. Feed efficiency was linearly increased by RPC supplementation. Concentrations of fat, true protein, and lactose in milk were not affected by RPC. Apparent total-tract digestibility of dry matter, organic matter, and crude protein was linearly increased, and fecal nitrogen excretion was linearly decreased by RPC supplementation. Rumen-protected Capsicum oleoresin did not affect the composition of fecal bacteria. Glucose concentration in serum was not affected by RPC supplementation post glucose challenge. However, compared to the control, RPC decreased serum insulin concentration at 5, 10, and 40 min post glucose challenge. The area under the insulin concentration curve was also decreased 25% by RPC. Concentration of nonesterified fatty acids and β-hydroxybutyrate in serum were not affected by RPC following glucose administration. In this study, RPC tended to increase milk production and increased feed efficiency in dairy cows. In addition, RPC decreased serum insulin concentration during the glucose tolerance test, but glucose concentration was not affected by treatment.

The metabolic effects of a commercially available chicken peri-peri (African bird's eye chilli) meal in overweight individuals

A growing body of evidence suggests that capsaicin ingestion may lead to desirable metabolic outcomes; however, the results in humans are equivocal. Whether or not benefits may be gained from ingestion of capsaicin via a commercially available meal has not been determined. The objectives of this randomised, cross-over intervention study were to compare the 2 h postprandial effects of a standard commercially prepared meal containing chilli (HOT, 5·82 mg total capsaicinoids) with a similar meal with no chilli (CON, 25 kg/m2 and a waist circumference >94 cm (men) or 80 cm (women), were studied. Participants had normal glucose tolerance and were accustomed, but were not regular chilli eaters. A paired t test indicated that insulin AUC was smaller following the HOT meal (P=0·002). Similarly, there was a tendency for glucose AUC to be reduced following the HOT meal (P=0·056). No discernable effects of the HOT meal were observed on metabolic rate, core temperature, hs-CRP concentrations and endothelial-dependent microvascular reactivity. The results from this study indicate that a standard restaurant meal containing a relatively small dose of capsaicin delivered via African bird's eye chilli, which is currently available to the public, results in lower postprandial insulin concentrations in overweight individuals, compared with the same meal without chilli.

Stimulation of GLP-1 secretion downstream of the ligand-gated ion channel TRPA1

Stimulus-coupled incretin secretion from enteroendocrine cells plays a fundamental role in glucose homeostasis and could be targeted for the treatment of type 2 diabetes. Here, we investigated the expression and function of transient receptor potential (TRP) ion channels in enteroendocrine L cells producing GLP-1. By microarray and quantitative PCR analysis, we identified trpa1 as an L cell-enriched transcript in the small intestine. Calcium imaging of primary L cells and the model cell line GLUTag revealed responses triggered by the TRPA1 agonists allyl-isothiocyanate (mustard oil), carvacrol, and polyunsaturated fatty acids, which were blocked by TRPA1 antagonists. Electrophysiology in GLUTag cells showed that carvacrol induced a current with characteristics typical of TRPA1 and triggered the firing of action potentials. TRPA1 activation caused an increase in GLP-1 secretion from primary murine intestinal cultures and GLUTag cells, an effect that was abolished in cultures from trpa1(-/-) mice or by pharmacological TRPA1 inhibition. These findings present TRPA1 as a novel sensory mechanism in enteroendocrine L cells, coupled to the facilitation of GLP-1 release, which may be exploitable as a target for treating diabetes.

Orally given gastroprotective capsaicin does not modify aspirin-induced platelet aggregation in healthy male volunteers (human phase I examination)

Capsaicin is a well-known component of red pepper. Recent studies have shown that capsaicin could prevent gastric ulcer provoked by various NSAID-s like acetylsalicylic acid (ASA). Primary objective of this human clinical phase I trial was to investigate whether two different doses of capsaicin co-administered with ASA could alter the inhibitory effect of ASA on platelet aggregation. 15 healthy male subjects were involved in the study and treated orally with 400 μg capsaicin, 800 μg capsaicin, 500 mg ASA, 400 μg capsaicin+500 mg ASA and 800 μg capsaicin+500 mg ASA. Blood was drawn before and 1, 2, 6 and 24 hours after the drug administration. After that epinephrine induced platelet aggregation was measured by optical aggregometry. Between treatments, volunteers had a 6-day wash-out period. Our results showed that capsaicin had no effect on platelet aggregation, while as expected, ASA monotherapy resulted in a significant and clinically effective platelet aggregation inhibition (p ≤ 0.001). The combined ASA-capsaicin therapies reached equivalent effectiveness in platelet aggregation inhibition as ASA monotherapy. Our investigation proved that capsaicin did not influence the inhibitory effect of ASA on platelet aggregation, thus the capsaicin-ASA treatment would combine the antiplatelet effect of ASA with the possible gastroprotection of capsaicin.

Dynamic carbon 13 breath tests for the study of liver function and gastric emptying

In gastroenterological practice, breath tests (BTs) are diagnostic tools used for indirect, non-invasive assessment of several pathophysiological metabolic processes, by monitoring the appearance in breath of a metabolite of a specific substrate. Labelled substrates originally employed radioactive carbon 14 (¹⁴C) and, more recently, the stable carbon 13 isotope (¹³C) has been introduced to label specific substrates. The ingested ¹³C-substrate is metabolized, and exhaled ¹³CO₂ is measured by mass spectrometry or infrared spectroscopy. Some ¹³C-BTs evaluate specific (microsomal, cytosolic, and mitochondrial) hepatic metabolic pathways and can be employed in liver diseases (i.e. simple liver steatosis, non-alcoholic steato-hepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug and alcohol effects).

Another field of clinical application for ¹³C-BTs is the assessment of gastric emptying kinetics in response to liquids (¹³C-acetate) or solids (¹³C-octanoic acid in egg yolk or in a pre-packed muffin or the ¹³C-Spirulina platensis given with a meal or a biscuit). Studies have shown that ¹³C-BTs, used for gastric emptying studies, yield results that are comparable to scintigraphy and can be useful in detecting either delayed- (gastroparesis) or accelerated gastric emptying or changes of gastric kinetics due to pharmacological effects. Thus, ¹³C-BTs represent an indirect, cost-effective and easy method of evaluating dynamic liver function and gastric kinetics in health and disease, and several other potential applications are being studied.

Capsaicin as new orally applicable gastroprotective and therapeutic drug alone or in combination with nonsteroidal anti-inflammatory drugs in healthy human subjects and in patients

BACKGROUND

Capsaicin is a specific compound acting on capsaicin-sensitive afferent nerves.

AIM

Capsaicin was used to study the different events of human gastrointestinal physiology, pathology, and clinical pharmacology, and possible therapeutic approaches to enhance gastrointestinal mucosal defense in healthy human subjects and in patients with various different gastrointestinal disorders as well as its use with nonsteroidal anti-inflammatory drugs (NSAIDs) in healthy subjects and in patients.

MATERIALS AND METHODS

The observations were carried out in 198 healthy human subjects and in 178 patients with different gastrointestinal (GI) diseases (gastritis, erosions, ulcer, polyps, cancer, inflammatory bowel diseases, colorectal polyps, cancers), and in 69 patients with chronic (Helicobacter pylori positive and negative) gastritis (before and after eradication treatment). The gastric secretory responses and their chemical composition, gastric emptying, sugar loading test, gastric transmucosal potential difference (GTPD) with application of capsaicin alone, after ethanol alone and with capsaicin, indomethacin-induced gastric mucosal microbleeding without and with capsaicin were studied. The immunohistochemical examinations of the capsaicin receptor (TRVP1), calcitonin gene- related peptide (CGRP), and substance P (SP) were carried out in gastrointestinal tract, and especially in patients with chronic gastritis (with and without Helicobacter infection, before and after classical eradication treatment). Classical molecular pharmacological methods were applied to study the drugs inhibiting the gastric basal acid output.

RESULTS

Capsaicin decreased the gastric basal output, enhanced the "non-parietal" (buffering) component of gastric secretory responses, and gastric emptying, and the release of glucagon. Capsaicin prevented the indomethacin- and ethanol-induced gastric mucosal damage; meanwhile capsaicin itself enhanced (GTPD). Capsaicin prevented the indomethacin-induced gastric mucosal microbleeding. The expression of TRVP1 and CGRP increased in the gastric mucosa of patients with chronic gastritis (independently of the presence of Helicobacter pylori infection), and the successfully carried out eradication treatment. The human first phase examinations (the application of acetylsalicylic acid (ASA), diclqfenac, and naproxen together with capcaicinoids) (given in doses that stimulate capsaicin-sensitive afferent vagal nerves) showed no change in the pharmacokinetic parameters of ASA and diclofenac and the ASA and diclofenac-induced platelet aggregation.

CONCLUSIONS

Capsaicin represents a new orally applicable gastroprotective agent in healthy human subjects and in patients with different chemical and Helicobacter pylori-induced mucosal damage and in many other diseases requiring treatment with NSAIDs.

Transient receptor potential channels and energy homeostasis

Transient receptor potential (TRP) channels are members of an ancient class of ion channels that are present in most mammalian tissues. Consistent with their wide tissue distribution, TRPs are capable of influencing diverse physiological processes including adipocyte function, energy intake and energy expenditure. TRPs function as transduction channels downstream of G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases, and some can also be direct sensors of chemical irritants that influence food intake or regulate body temperature and thermogenesis. TRP agonists were shown to reduce body weight and adiposity, suggesting that they might be exploited as therapeutic targets. In this review I discuss the current knowledge of how TRP channels influence energy balance.

Herb-drug pharmacokinetic interactions reviewed

IMPORTANCE OF THE FIELD

the global increase in the popularity of alternative medicines has raised renewed concerns regarding herb-drug interactions. These interactions are especially important for drugs with narrow therapeutic indices and may either be pharmacodynamic or pharmacokinetic in nature.

AREAS COVERED IN THIS REVIEW

pharmacokinetic interactions which may exist between herbs and drugs, and the mechanisms of these interactions with appropriate examples based on primary and secondary data in publications are discussed. The mechanisms covered include those that affect oral drug absorption (e.g., modulation of efflux and uptake transporters, complex formation, gastrointestinal motility and pH) and drug biotransformation (e.g., inhibition or induction of enzymes).

WHAT THE READER WILL GAIN

knowledge on the mechanisms of herb-drug pharmacokinetic interactions supported by an extended list of these types of interactions for quick reference. A critical evaluation of certain herb-drug pharmacokinetic interactions reported in the scientific literature.

TAKE HOME MESSAGE

as the incidence and severity of herb-drug pharmacokinetic interactions increase due to a worldwide rise in the use of herbal preparations, more clinical data regarding herb-drug pharmacokinetic interactions are needed to make informed decisions regarding patient safety.

A two-component nonlinear mixed effects model for longitudinal data, with application to gastric emptying studies

Gastric emptying studies are of great interest in human and veterinary medical research to evaluate effects of medications or diets for promoting gastrointestinal motility and to examine unintended side-effects of new or existing medications, diets, or procedures. Summarizing gastric emptying data is important to allow easier comparison between treatments or groups of subjects and comparisons of results among studies. The standard method for assessing gastric emptying is by using scintigraphy and summarizing the nonlinear emptying of the radioisotope. A popular model for fitting gastric emptying data is the power exponential model. This model can only describes a globally decreasing pattern and thus has the limitation of poorly describing localized intragastric events that can occur during emptying. Hence, we develop a new model for gastric emptying studies to improve population and individual inferences using a mixture of nonlinear mixed effects models. One mixture component is based on a power exponential model which captures globally decreasing patterns. The other is based on a locally extended power exponential model which captures both local bumping and rapid decay. We refer to this mixture model as a two-component nonlinear mixed effects model. The parameters in our model have clear graphical interpretations that provide a more accurate representation and summary of the curves of gastric emptying pattern. Two methods are developed to fit our proposed model: one is the mixture of an Expectation Maximization algorithm and a global two-stage method and the other is the mixture of an Expectation Maximization algorithm and the Monte Carlo Expectation Maximization algorithm. We compare our methods using simulation, showing that the two approaches are comparable to one another. For estimating the variance and covariance matrix, the second approach appears approximately more efficient and is also numerically more stable in some cases. Our new model and approaches are applicable for assessing gastric emptying in human and veterinary medical research and in many other biomedical fields such as pharmacokinetics, toxicokinetics, and physiological research. An example of gastric emptying data from equine medicine is used to demonstrate the advantage of our approaches.

Interdisciplinary review for correlation between the plant origin capsaicinoids, non-steroidal antiinflammatory drugs, gastrointestinal mucosal damage and prevention in animals and human beings

BACKGROUND

The plant origin capsaicinoids (capsaicin, dihydrocapsaicin, norcapsaicin, dihydrocapsaicin, homocapsaicin, homodihydrocapsaicin) are well known and used as nutritional additive agents in the every day nutritional practice from the last 9,500 years; however, we had have a very little scientifically based knowledge on their chemistry, physiology and pharmacology in animal observations, and in humans up to the mid-twentieth century. Our knowledge about their chemistry, physiology, pharmacology entered to be scientifically based evidence from the year 1980, dominantly in animal observations. The human observations with capsaicin (capsaicinoids), in terms of good clinical practice, have been started only in the last 10-year period (from 1997) in randomized, prospective, multiclinical studies. The name of "capsaicin" used only in the physiological and pharmacological research both in animal experiments and in human observation. The "capsaicin" (as a "chemically" used natural compound) modifies the so-called capsaicin-sensitive afferent nerves depending on their applied doses.

AIMS

The specific action of capsaicin (capsaicinoids) on sensory afferent nerves modifying gastrointestinal (GI) function (under very specific conditions) offers a possibility for the production of an orally applicable drug or for other drug combinations, which can be used in the human medical therapy. The production of new drug is based on the critical interdisciplinary review of the results obtained with capsaicinoids.

MATERIALS AND METHODS

This paper gives an interdisciplinary and critical overview on the chemical, physiological, pharmacological and toxicological actions of the natural origin capsaicinoids (from the point of drug production) under conditions of acute, subacute and chronic administration in animal experiments and human observations, toxicology, pharmacokinetics). This interdisciplinary review covers the following main chapters: (1) physiological and pharmacological research tool by capsaicin in the animals and human beings, (2) capsaicin research in animals (including the acute, subacute toxicology and chronic toxicology metabolism, genotoxicology), (3) capsaicin observation with capsaicin in human beings.

CONCLUSION

(1) The capsaicin used in the physiological and pharmacological observations (in animals and human beings) chemically represents different chemical compounds, which can be obtained from the plants (paprika, chilli, etc.), (2) capsaicinoids are able to modify the capsaicin-sensitive afferent nerves, which have principle roles in the defence of different organs (including the gastrointestinal tract [against the different chemicals, heat, strech, chemical millieu-induced damage], (3) the application of capsaicin (capsaicinoids) can be repeated for the beneficial effects on the gastrointestinal tract as those in animal experiments. After this interdisciplinary and critical review, this paper demonstrates the well-planned research pathways of the discoveries of capsaicinoids from plant chemistry, via physiology, pharmacology and toxicology in animal experiments and human observations.

The effects of capsaicin on gastrin secretion in isolated human antral glands: before and after ingestion of red chilli

BACKGROUND

Capsaicin is known to have regulatory effects on gastrointestinal functions via the vanilloid receptor (VR1). We reported previously that endocrine-like cells in the human antrum express VR1.

AIM

To identify VR1-expressing endocrine-like cells in human antral glands and to examine whether stimulation with capsaicin causes release of gastrin, somatostatin, and serotonin. Further, to investigate the effects of a chilli-rich diet.

METHODS

Gastroscopic biopsies were received from 11 volunteers. Seven of the 11 subjects agreed to donor gastric biopsies a second time after a 3-week chilli-rich diet containing 1.4-4.2 mg capsaicin/day. VR1-immunoreactive cells were identified by double-staining immunohistochemistry against gastrin, somatostatin, and serotonin. For the stimulation studies, we used an in vitro method where antral glands in suspension were stimulated with 0.01 mM capsaicin and physiological buffer was added to the control vials. The concentrations of secreted hormones were detected and calculated with radioimmunoassay (RIA). Results The light microscopic examination revealed that VR1 was localized in gastrin cells. The secretory studies showed an increase in release of gastrin and somatostatin compared to the control vials (P = 0.003; P = 0.013). Capsaicin-stimulation caused a consistent raise of the gastrin concentrations in the gland preparations from all subjects. A chilli-rich diet had an inhibitory effect on gastrin release upon stimulation compared to the results that were obtained before the start of the diet.

CONCLUSION

This study shows that capsaicin stimulates gastrin secretion from isolated human antral glands, and that a chilli-rich diet decreases this secretion.

The acute effects of a lunch containing capsaicin on energy and substrate utilisation, hormones, and satiety

Background

Addition of capsaicin to the diet has been shown to increase satiety and thermogenesis. The effects of capsaicin on ghrelin, peptide YY (PYY) and glucagon-like peptide 1 (GLP-1), in relation to changes in hunger and satiety are unknown.

Aim

To test the acute effects of a lunch containing capsaicin on gut derived hormones (GLP-1, ghrelin, and PYY), energy expenditure (EE), substrate oxidation and satiety at lunch in the postprandial state.

Methods

Thirty subjects (age: 31 ± 14 years, BMI: 23.8 ± 2.8 kg/m²) were studied twice in a crossover design. After 30 min resting on a bed, resting metabolic rate was measured by a ventilated hood system. Subsequently lunch (35% of daily energy intake) was served. The two lunch conditions were: (1) lunch without capsaicin and (2) lunch with capsaicin (CAPS). The macronutrient composition (energy percentage) of the lunches was 60% carbohydrates, 10% protein and 30% fat. During 3 h after the lunch diet-induced thermogenesis was measured. Furthermore, anchored 100 mm visual analogue scales on the appetite profile were collected (t = 0, 30, 60, 120, 150, 180 and 240) and blood samples were taken for analysis of GLP-1, PYY, and ghrelin concentrations (t = 0, 45, 60, 120, and 180).

Results

Satiety and EE were not different after CAPS lunch as compared to the control lunch. Fifteen minutes after lunch CAPS lunch increased GLP-1 (p < 0.05) and tended to decrease ghrelin (p = 0.07) as compared to the control lunch. PYY responses were not different between the CAPS lunch and the control lunch.

Conclusions

An acute lunch containing capsaicin had no effect on satiety, EE, and PYY, but increased GLP-1 and tended to decrease ghrelin.

Capsaicin and gastric ulcers

In recent years, infection of the stomach with the organism Helicobacter Pylori has been found to be the main cause of gastric ulcers, one of the common ailments afflicting humans. Excessive acid secretion in the stomach, reduction in gastric mucosal blood flow, constant intake of non-steroid anti-inflammatory drugs (NSAIDS), ethanol, smoking, stress etc. are also considered responsible for ulcer formation. The prevalent notion among sections of population in this country and perhaps in others is that "red pepper" popularly known as "Chilli," a common spice consumed in excessive amounts leads to "gastric ulcers" in view of its irritant and likely acid secreting nature. Persons with ulcers are advised either to limit or avoid its use. However, investigations carried out in recent years have revealed that chilli or its active principle "capsaicin" is not the cause for ulcer formation but a "benefactor." Capsaicin does not stimulate but inhibits acid secretion, stimulates alkali, mucus secretions and particularly gastric mucosal blood flow which help in prevention and healing of ulcers. Capsaicin acts by stimulating afferent neurons in the stomach and signals for protection against injury causing agents. Epidemiologic surveys in Singapore have shown that gastric ulcers are three times more common in the "Chinese" than among Malaysians and Indians who are in the habit of consuming more chillis. Ulcers are common among people who are in the habit of taking NSAIDS and are infected with the organism "Helicobacter Pylori," responsible for excessive acid secretion and erosion of the mucosal layer. Eradication of the bacteria by antibiotic treatment and avoiding the NSAIDS eliminates ulcers and restores normal acid secretion.

Capsaicin and glucose absorption and utilization in healthy human subjects

Although many animal experiments (under different experimental circumstances) have been performed, however, to date there have been no human studies of the role of capsaicin-sensitive afferent nerves in carbohydrate metabolism. The glucose loading test (administration of 75 g orally given glucose) was evaluated in 14 human healthy subjects by the simultaneous measurement of plasma level of glucose, C-peptide and glucagon every 15 min for 4 h without and with (ED50) oral application of capsaicin. The plasma level of glucose increased significantly from 30 to 150 min, and the plasma glucagon level increased from 90 to 180 min after the glucose loading when capsaicin administered. The plasma levels of insulin and C-peptide increased from 90 to 165 min after glucose loading but there were no significant difference between the results obtained without and with capsaicin administration. It is concluded that the capsaicin increases the glucose absorption from the gastrointestinal tract and increases the glucagon release (independently of the hormonal antagonist regulation by insulin released after glucose) loading during glucose loading tests carried out in human healthy subjects.

Facilitation and inhibition by capsaicin of cholinergic neurotransmission in the guinea-pig small intestine

The effects of capsaicin on [3H]acetylcholine release and muscle contraction were studied on the myenteric plexus-longitudinal muscle preparation of the guinea-pig ileum preincubated with [3H]choline. Capsaicin concentration-dependently increased both basal [3H]acetylcholine release (pEC50 7.0) and muscle tone (pEC50 6.1). The facilitatory effects of capsaicin were antagonized by 1 microM capsazepine (pK (B) 7.0 and 7.6), and by the combined blockade of NK1 and NK3 tachykinin receptors with the antagonists CP99994 plus SR142801 (each 0.1 microM). This suggests that stimulation by capsaicin of TRPV1 receptors on primary afferent fibres causes a release of tachykinins which, in turn, mediate via NK1 and NK3 receptors an increase in acetylcholine release. The capsaicin-induced acetylcholine release was significantly enhanced by the NO synthase inhibitor L-NG-nitroarginine (100 microM). This indicates that tachykinins released from sensory neurons also stimulate nitrergic neurons and thus lead, via NO release, to inhibition of acetylcholine release. Capsaicin concentration-dependently reduced the electrically-evoked [3H]acetylcholine release (pEC50 6.4) and twitch contractions (pEC50 5.9). The inhibitory effects were not affected by either capsazepine, NK1 and NK3 receptor antagonists, the cannabinoid CB1 antagonist SR141716A or by L-NG-nitroarginine. Desensitization of TRPV1 receptors by a short exposure to 3 microM capsaicin abolished the facilitatory responses to a subsequent administration, but did not modify the inhibitory effects. In summary, capsaicin has a dual effect on cholinergic neurotransmission. The facilitatory effect is indirect and involves tachykinin release and excitation of NK1 and NK3 receptors on cholinergic neurons. The inhibition of acetylcholine release may be due to a decrease of Ca2+ influx into cholinergic neurons.

Gastroprotection induced by capsaicin in healthy human subjects

AIM: To evaluate the gastro-protective effect of capsaicin against the ethanol- and indomethacin (IND)-induced gastric mucosal damage in healthy human subjects.

METHODS: The effects of small doses (1-8 μg/mL, 100 mL) of capsaicin on the gastric acid secretion basal acid output (BAO) and its electrolyte concentration, gastric transmucosal potential difference (GTPD), ethanol- (5 mL 300 mL/L i.g.) and IND- (3×25 mg/d) induced gastric mucosal damage were tested in a randomized, prospective study of 84 healthy human subjects. The possible role of desensitization of capsaicin-sensitive afferents was tested by repeated exposures and during a prolonged treatment.

RESULTS: Intragastric application of capsaicin decreased the BAO and enhanced “non-parietal” component (GTPD) in a dose-dependent manner. The decrease of GTPD evoked by ethanol was inhibited by the capsaicin application, which was reproducible. Gastric microbleeding induced by IND was inhibited by co-administration with capsaicin, but was not influenced by two weeks pretreatment with a daily capsaicin dose of 3×400 μg i.g.

CONCLUSION: Capsaicin in low concentration range protects against gastric injuries induced by ethanol or IND, which is attributed to stimulation of the sensory nerve endings.

Calcitonin gene-related peptide released by capsaicin suppresses myoelectrical activity of gastric smooth muscle

BACKGROUND

It is widely accepted that the inhibition of gastric motor activity as well as the maintenance of gastric mucosal blood flow and mucous secretion are important for the homeostasis of the gastric mucosa. The present study was performed to ascertain whether or not capsaicin, which can protect the stomach from noxious stimuli, affects gastric motor activity.

METHODS

Male Sprague-Dawley rats were anesthetized with urethane, and the stomach was cannulated by two catheters from esophageal and duodenal sides. A biopolar electrode was fixed to the serosal surface of the antrum and myoelectrical activity was recorded during the instillation of a small volume of solutions.

RESULTS

The myoelectrical activity of rat gastric smooth muscle was increased at intragastric pressures of >2 cmH(2)O. Replacement of intragastric physiological saline with 1.6 mmol/L capsaicin solution significantly suppressed this myoelectrical activity by 50%. Intragastric capsaicin administration caused a significant release of substance P (SP) and calcitonin gene-related peptide (CGRP). The maximum released levels of CGRP in the gastric perfusates were 100-fold those of SP. The myoelectrical activity observed at an intragastric pressure of 2 cmH(2)O was avoided by continuous infusion of CGRP (0.1-3.0 nmol/kg per min) into the gastric artery in a dose-dependent manner, but not by that of SP (1.0 nmol/kg per min). Continuous CGRP-(8-37) infusion into the gastric artery completely blocked the reduction by intragastric capsaicin of myoelectrical activity.

CONCLUSION

These results suggest that the suppression of the myoelectrical activity of gastric smooth muscle by capsaicin is attributable to the endogenous CGRP released.

Effects of capsaicin on the sensorimotor function of the proximal stomach in humans

BACKGROUND

Capsaicin-sensitive afferents have been implicated in the control of visceral sensorimotor functions.

AIM

To study the effects of capsaicin on the sensorimotor function of the proximal stomach in humans.

METHODS

In 10 healthy subjects, a gastric barostat was used to study the effect of saline or capsaicin-containing red pepper sauce on the sensitivity to gastric distension and on gastric accommodation to a meal.

RESULTS

The administration of capsaicin was accompanied by a relaxation of the proximal stomach. After capsaicin, the compliance of the proximal stomach was increased and higher perception scores were reached for the same distending pressures. Dosing with capsaicin significantly decreased the pressures and corresponding wall tensions at the discomfort threshold. Gastric accommodation to a meal was not altered by capsaicin.

CONCLUSION

The acute administration of capsaicin decreases proximal gastric tone, inhibits phasic contractility of the proximal stomach and increases sensitivity to proximal gastric distension. These data suggest the involvement of vanilloid receptor 1 in the modulation of gastric sensorimotor function in humans.

The treatment of functional dyspepsia with red pepper

AIM

: To decrease the intensity of dyspeptic symptoms by impairing the visceral nociceptive C-type fibres with capsaicin, contained in red pepper powder.

METHODS

: The study was performed on 30 patients with functional dyspepsia and without gastro-oesophageal reflux disease and irritable bowel syndrome. After a 2-week washout period, 15 patients received, before meals randomly and in a double-blind manner, 2.5 g/day of red pepper powder for 5 weeks, and 15 patients received placebo. A diary sheet was given to each patient to record, each day, the scores of individual and overall symptom intensity, which subsequently were averaged weekly and over the entire treatment duration.

RESULTS

: The overall symptom score and the epigastric pain, fullness and nausea scores of the red pepper group were significantly lower than those of the placebo group, starting from the third week of treatment. The decrease reached about 60% at the end of treatment in the red pepper group, whilst placebo scores decreased by less than 30%.

CONCLUSIONS

: Red pepper was more effective than placebo in decreasing the intensity of dyspeptic symptoms, probably through a desensitization of gastric nociceptive C-fibres induced by its content of capsaicin. It could represent a potential therapy for functional dyspepsia.

Four response stages of capsaicin-sensitive primary afferent neurons to capsaicin and its analog: gastric acid secretion, gastric mucosal damage and protection

Capsaicin is the active component of red hot peppers, which modifies specifically the capsaicin-sensitive sensory afferent nerves. The action of capsaicin is an initial short-lasting stimulation, which is followed by desensitization to capsaicin itself, and to other stimuli of afferent sensory nerves. Four response stages of capsaicin-sensitive primary afferents exist to capsaicin, depending on the dose and duration of exposure to the drug. These are excitation, a sensory blocking effect, long-term selective neurotoxic impairment, and irreversible cell destruction. The possible roles of four stages of capsaicin-sensitive primary afferents can be evaluated in relation to gastric acid secretion, and to the details of the defensive side of gastric mucosa against different chemicals, physical agents, drugs and other pathological stress. Capsaicin inhibited the gastric acid secretion in pylorus-ligated rats when it was given intragastrically at a dose of 0.4-1.8 microg/kg. Small doses of capsaicin (up to 800 microg, i.g.) produced a dose-dependent inhibition (ID50 = 400 microg), and its inhibitory effect was exerted for 1 h in healthy human subjects. While a small dose (5 microg/kg) of capsaicin caused inhibition, a high dose (50-100 mg/kg) enhanced the gastric mucosal lesions productivity by causing hyperacidity in pylorus-ligated animals. Capsaicin and its analog inhibited the development of different chemically induced gastric mucosal damage in various experimental models if they were given intragastric doses (microg/kg). The final effects of capsaicin depend on the dosage and timing. The different effects are excitation, a sensory-blocking effect, long-term selective neurotoxic impairment and irreversible cell destruction.

Capsaicin-sensitive afferents and their role in gastroprotection: an update

The pivotal role of capsaicin-sensitive peptidergic sensory fibers in the maintenance of gastric mucosal integrity against injurious interventions was suggested by the authors 20 years ago. Since then substantial evidence has accumulated for the local sensory-efferent function of the released CGRP, tachykinins and NO in this gastroprotective mechanism. This overview outlines some recent achievements which shed light on new aspects and further horizons in this field. (1) Cloning the capsaicin VR-1 receptor (an ion channel-coupled receptor) and raising the VR-1 knockout mice provided a definite molecular background for the existence of capsaicin-sensitive afferents with both sensory and mediator releasing functions in the stomach. This cation channel is also sensitive to hydrogen ions. (2) VR-1 agonists (capsaicin, resiniferatoxin, piperine) protect against gastric ulcer of the rat parallel with their sensory stimulating potencies. (3) Antidromic stimulation of capsaicin-sensitive vagal and somatic afferents results in the release of CGRP, tachykinins, NO and somatostatin. Somatostatin with gastroprotective effect is released from D cells and sensory nerve endings. (4) The recent theory for the existence of spinal afferents without sensory function [P. Holzer, C.A. Maggi, Dissociation of dorsal root ganglion neurons into afferent and efferent-like neurons, Neuroscience 86 (1998) 389-398] is discussed. Data proposed to support this theory are interpreted here on the basis of a dual sensory-efferent function of VR-1 positive afferents, characterized by a frequency optimum of discharges for release vasodilatory neuropeptides below the nociceptive threshold. (5) Recent data on the effect of capsaicin in healthy human stomach are summarized. These results indicate that the gastroprotective effect of capsaicin in the human stomach involves additional mechanisms to those already revealed in the rat.

Small doses of capsaicin given intragastrically inhibit gastric basal acid secretion in healthy human subjects

Although the direct inhibitory effect of small dose of capsaicin on gastric secretory responses was proved in animal observations, the role of capsaicin-sensitive afferent nerves (CSAN) and the effect of capsaicin applied in small and high doses on gastric secretion in human has not been clarified yet. In this study we investigated the influence of different small doses (100-800 microg) of capsaicin given intragastrically through an orogastric tube on gastric basal secretory responses in 10 healthy human subjects. Gastric basal secretory responses (volume, H+-concentration, H+-output) were measured from the suctions of gastric juice for a 1-h period. It has been found that: a) capsaicin dose-dependently inhibited the volume and H+-output of gastric juice; b) ID50 was found to be about 400 microg for capsaicin on gastric acid secretion; c) the time interval for capsaicin-induced gastric inhibition existed for about 1 h indifferently from the higher dose (800 microg) of capsaicin given after. It has been concluded that the capsaicin (given in small doses) inhibits the gastric basal acid output via stimulation of the inhibition of capsaicin sensitive afferent nerves.