Gastric administration of garlic powder containing the trpa1‐ agonist allicin induces specific epigastric symptoms and gastric relaxation in healthy subjects

Abstract

Background TRPA1 is an excitatory ion channel and is involved in sensory processes including thermal nociception and inflammatory pain. The allicin in garlic is a strong activator of the TRPA1 channel. Aim To evaluate the effect of intragastric garlic powder containing allicin on perception, gastric tone, and mechanosensitivity. Methods An infusion‐barostat balloon assembly was used for infusion of test solutions, for distension, and to measure proximal gastric compliance and tone. After an initial open label dose finding with 1 g, 2 g, 3.75 g, and 7.5 g commercially available garlic powder, a bolus of 2 g garlic powder (11 mg allicin)/60 mL H2O was considered to induce moderate but constant sensation and was used hereafter in a placebo‐controlled, single‐dose, double‐blind, randomized study in 7 volunteers to evaluate gastric sensation, tone, and mechanosensitivity. Key Results Bolus injection of garlic caused immediate epigastric symptoms, mean aggregate symptom scores (AUC in 15 minutes) were 106 ± 49 vs. 35 ± 30 after placebo (P = 0.01). Garlic induced significant epigastric pressure, stinging, and warmth (P < 0.01 vs. placebo), while intensity of cramps, satiety, nausea, and pain was not significantly different to placebo (P > 0.05). Garlic induced an immediate, short lived fundic relaxation (balloon volume 627 ± 349 mL vs. −145 ± 120 mL; P < 0.02). No effect of allicin on proximal gastric mechanosensitivity and compliance was observed (NS). Conclusion and Inferences Garlic containing allicin induces immediate epigastric symptoms of pressure, stinging, and warmth and induces fundic relaxation but does not influence mechanosensitivity or compliance. TRPA1 is a receptor that is involved in gastric sensation and motility.

Mammalian Transient Receptor Potential TRPA1 Channels: From Structure to Disease

“…Additionally, a decreased adrenal sympathetic nerve activity upon gastric application of ␤-eudesmol is only observed in WT but not in Trpa1 KO rats (621,623). In this context, garlic powder, containing the TRPA1 agonist allicin, induces gastric relaxation and epigastric symptoms of pressure and warmth in healthy subjects (257). Nonetheless, the TRPA1 contribution to the regulation of the GI motility is not restricted to ENS intrinsic and extrinsic afferent pathways.…”

“…It must be noted that allicin and its derivatives also activate TRPV1, although with lower potency than for TRPA1 and with a lower efficacy compared with capsaicin (412,492). Nevertheless, this unspecificity should be taken into account when extracting conclusions over the role of TRPA1 in visceral sensitivity and motility from experiments based on the use of garlic (and allicin) as agonist of this channel (257). Interestingly, allicin-induced activation of TRPV1 is mediated by a single cysteine residue in the NH 2 terminus of the channel, suggesting for a similarity with the mechanisms of action operating in TRPA1 (706).…”

Potential Interplay between Nrf2, TRPA1, and TRPV1 in Nutrients for the Control of COVID-19

“…TRPA1 is expressed in both dorsal root ganglions and nodose ganglion neurons innervating the stomach, as well as in nerve fibers of the gastric wall. Gastric administration of garlic powder containing the TRPA1-agonist allicin induces specific epigastric symptoms and gastric relaxation in healthy subjects [60]. Capsaicin can induce gastroesophageal and abdominal pain, heartburn, bloating, and/or dyspepsia through TRPV1 [61][62][63].…”

TRP (transient receptor potential) ion channel family: structures, biological functions and therapeutic interventions for diseases

“…Symptoms of COVID-19 associated with TRPA1/TRPV1 include the following: cough, 368 smell, and taste disturbances, 369 – 372 loss of appetite, 373 nausea, 374 vomiting, 375 inflammatory responses, and pain. 40 However, several clinical studies targeted TRP channels for the treatment of COVID-19.…”