[6]-Gingerol Induces Electrogenic Sodium Absorption in the Rat Colon via the Capsaicin Receptor TRPV1

Ion channels and transporters regulate nutrient absorption in health and disease

Ion channels and transporters are ubiquitously expressed on cell membrane, which involve in a plethora of physiological process such as contraction, neurotransmission, secretion and so on. Ion channels and transporters is of great importance to maintaining membrane potential homeostasis, which is essential to absorption of nutrients in gastrointestinal tract. Most of nutrients are electrogenic and require ion channels and transporters to absorb. This review summarizes the latest research on the role of ion channels and transporters in regulating nutrient uptake such as K+ channels, Ca2+ channels and ion exchangers. Revealing the mechanism of ion channels and transporters associated with nutrient uptake will be helpful to provide new methods to diagnosis and find potential targets for diseases like diabetes, inflammatory bowel diseases, etc. Even though some of study still remain ambiguous and in early stage, we believe that ion channels and transporters will be novel therapeutic targets in the future.

Ca2+-Permeable Channels/Ca2+ Signaling in the Regulation of Ileal Na+/Gln Co-Transport in Mice

Oral glutamine (Gln) has been widely used in gastrointestinal (GI) clinical practice, but it is unclear if Ca²⁺ regulates intestinal Gln transport, although both of them are essential nutrients for mammals. Chambers were used to determine Gln (25 mM)-induced I_sc through Na⁺/Gln co-transporters in the small intestine in the absence or the presence of selective activators or blockers of ion channels and transporters. Luminal but not serosal application of Gln induced marked intestinal I_sc, especially in the distal ileum. Lowering luminal Na⁺ almost abolished the Gln-induced ileal I_sc, in which the calcium-sensitive receptor (CaSR) activation were not involved. Ca²⁺ removal from both luminal and serosal sides of the ileum significantly reduced Gln- I_sc. Blocking either luminal Ca²⁺ entry via the voltage-gated calcium channels (VGCC) or endoplasmic reticulum (ER) release via inositol 1,4,5-triphosphate receptor (IP₃R) and ryanodine receptor (RyR) attenuated the Gln-induced ileal I_sc, Likewise, blocking serosal Ca²⁺ entry via the store-operated Ca²⁺ entry (SOCE), TRPV1/2 channels, and Na⁺/Ca²⁺ exchangers (NCX) attenuated the Gln-induced ileal I_sc. In contrast, activating TRPV1/2 channels enhanced the Gln-induced ileal I_sc. We concluded that Ca²⁺ signaling is critical for intestinal Gln transport, and multiple plasma membrane Ca²⁺-permeable channels and transporters play roles in this process. The Ca²⁺ regulation of ileal Na⁺/Gln transport expands our understanding of intestinal nutrient uptake and may be significant in GI health and disease.

[6]-Gingerol Induces Amiloride-Sensitive Sodium Absorption in the Rat Colon via the Capsaicin Receptor TRPV1 in Colonic Mucosa

[6]-Gingerol possesses various beneficial pharmacological and therapeutic properties, including anti-carcinogenic and anti-inflammatory properties and the ability to regulate intestinal contraction. Recently, our group observed that the serosal administration of [6]-gingerol stimulated electrogenic sodium absorption in the rat colon via the capsaicin receptor, TRPV1. TRPV1 is known to be expressed in both the mucosal epithelium and the muscle layers in the colon. In the present study, we assessed whether [6]-gingerol stimulated sodium absorption via TRPV1 in the colonic mucosal epithelium. We compared the effect of [6]-gingerol on TRPV1-dependent colonic sodium absorption in the colon preparation with or without muscle layer. All experiments were performed by measuring the transmural potential difference (ΔPD) in an Ussing chamber system. [6]-Gingerol induced positive ΔPD when administered to the serosal side of the colon, and this effect was significantly larger in the colon preparation without muscle layer than in that with the muscle layer. In the colon preparation without muscle layer, the [6]-gingerol-dependent induction of ΔPD was markedly suppressed by mucosal addition of amiloride, a selective inhibitor of epithelial sodium channel. ΔPD induction by [6]-gingerol was considerably diminished by capsazepine, an inhibitor of the capsaicin receptor TRPV1, but not by AP-18, an inhibitor of TRPA1. These results suggest that [6]-gingerol induces amiloride-sensitive electrogenic sodium absorption in the rat colon via TRPV1 expressed in the colonic mucosal epithelium, and that this effect is independent of TRPV1 in the colonic muscle layer.

Ginger Extract-Loaded Solid Dispersion System with Enhanced Oral Absorption and Antihypothermic Action

The aim of this study is to enhance the antihypothermic action of ginger extract (GE) employing a solid dispersion (SD) approach. The prepared SD of GE (GE/SD) was characterized in terms of physicochemical and pharmacokinetic properties. The antihypothermic action of GE samples was evaluated in a rat model of hypothermia. GE/SD exhibited improved dissolution behavior of the major active ingredients in GE, 6-gingerol (6G) and 8-gingerol (8G), with levels of dissolution 12- and 31-fold higher than that of GE, respectively. Even after storage under accelerated conditions, limited degradations of 6G and 8G were observed in GE/SD, although 6G and 8G were slightly degraded in GE. After oral administration of GE (300 mg/kg) and GE/SD (100 mg of GE/kg), the relative bioavailabilities of 6G and 8G in GE/SD were 5.0- and 5.8-fold higher than those in GE, respectively. Orally administered GE/SD (30 mg of GE/kg) inhibited ethanol-evoked hypothermia because of improved oral absorption of 6G and 8G. From these observations, the SD approach might be efficacious for enhancing the nutraceutical potentials of GE.

Effects of Salmon Nasal Cartilage Proteoglycan on Plasma Glucose Concentration and Active Glucose Transport in the Small Intestine

Recently, proteoglycan was purified from the nasal cartilage of salmon. Although several physiological effects have been reported, the effect of salmon nasal cartilage proteoglycan (salmon PG) on glucose metabolism remains unclear. We studied the effect of salmon PG on rat plasma glucose levels. Oral administration of 1% salmon PG significantly attenuated the increase in portal plasma glucose levels following an oral glucose tolerance test (OGTT). Additionally 1% salmon PG delayed the increase in peripheral glucose concentration induced by the OGTT. Mucosal administration of 1% salmon PG significantly decreased active glucose transport using the everted jejunal sac method. Furthermore, transmural potential difference (ΔPD) measurements using the everted jejunum revealed that 1% salmon PG significantly decreased glucose-dependent and phlorhizin (inhibitor of sodium-glucose co-transporter 1; SGLT1)-sensitive ΔPD. These results suggest that salmon PG decreases glucose absorption via SGLT1 in the jejunum, thereby attenuating the increase in portal and peripheral plasma glucose levels in rats.

6-Gingerol modulates proinflammatory responses in dextran sodium sulfate (DSS)-treated Caco-2 cells and experimental colitis in mice through adenosine monophosphate-activated protein kinase (AMPK) activation

6-Gingerol suppressed up-regulated production of proinflammatory cytokine in DSS-treated Caco-2 cells.