Aldioxa improves delayed gastric emptying and impaired gastric compliance, pathophysiologic mechanisms of functional dyspepsia

Abstract

Delayed gastric emptying and impaired gastric accommodation (decreased gastric compliance) play important roles in functional dyspepsia (FD). Here we screen for a clinically used drug with an ability to improve delayed gastric emptying in rats. Oral administration of aldioxa (dihydroxyaluminum allantoinate) partially improved clonidine- or restraint stress-induced delayed gastric emptying. Administration of allantoin, but not aluminium hydroxide, restored the gastric emptying. Both aldioxa and allantoin inhibited clonidine binding to the α-2 adrenergic receptor, suggesting that antagonistic activity of the allantoin moiety of aldioxa on this receptor is involved in the restoration of gastric emptying activity. Aldioxa or aluminium hydroxide but not allantoin restored gastric compliance with restraint stress, suggesting that aluminium hydroxide moiety is involved in this restoration. We propose that aldioxa is a candidate drug for FD, because its safety in humans has already been confirmed and its ameliorating effect on both of delayed gastric emptying and impaired gastric compliance are confirmed here.

Figure 1. Effect of aldioxa on clonidine-induced delayed gastric emptying.

Mice fasted for 18 h were orally administered indicated dose (a) or 200 mg kg⁻¹ (b,c) of aldioxa, indicated dose of cisapride (a) or vehicle (1% methylcellulose) (a–c). Fifty-five (a) or forty-five (b,c) minutes after each drug administration, delayed gastric emptying was induced by the subcutaneous administration of clonidine (100 (a) or 30 (b,c) μg kg⁻¹). Control mice were subcutaneously administered saline (a–c). Gastric emptying was measured using the phenol red method (a) or the [¹³C]-labeled acetic acid breath test (b,c) and gastric emptying (a), Δ¹³CO₂ (%) (b) and T_1/2 (c) were calculated as described in the Methods. Values are mean ± s.e.m. *P < 0.05; **P < 0.01 (Tukey test). Experiments were replicated at least two times.

Figure 2. Effect of gastroprotective drugs on clonidine-induced delayed gastric emptying.

Mice fasted for 18 h were orally administered indicated dose of aldioxa, geranylgeranylacetone (GGA) or sucralfate. One hour later, 20 mg kg⁻¹ of indomethacin was orally administered and 8 h later, stomachs were removed and gastric mucosal lesions were measured (a). The effect of GGA or sucralfate at indicated dose on clonidine-induced delayed gastric emptying was examined using the phenol red method as described in the legend of Fig. 1 (b). Values are mean ± s.e.m. *P < 0.05; **P < 0.01 (Tukey test). n.s., not significant. Experiments were replicated at least two times.

Figure 3. Effect of allantoin or aluminium hydrate on clonidine-induced delayed gastric emptying.

Mice fasted for 18 h were orally administered aldioxa (200 mg kg⁻¹), allantoin (145 mg kg⁻¹), aluminium hydrate (Al(OH)₃) (72 mg kg⁻¹) or vehicle (1% methylcellulose). Clonidine-induced delayed gastric emptying was induced and measured using the phenol red method as described in the legend of Fig. 1. Values are mean ± s.e.m. *P < 0.05 (Tukey test). n.s., not significant. Experiments were replicated at least two times.

Figure 4. Effect of aldioxa on restraint stress-induced delayed gastric emptying and normal gastric emptying.

Mice fasted for 18 h were orally administered aldioxa (200 mg kg⁻¹) (a–d), mosapride (7.7 mg kg⁻¹) (a–d), cisapride (5 mg kg⁻¹) (d) or vehicle (1% methylcellulose) (a–d) and delayed gastric emptying was induced by restraint stress (RS) (a–c). One hour after the administration of each test compound, gastric emptying was measured using the phenol red method (a,d) or the [¹³C]-labeled acetic acid breath test (b,c) as described in the legend of Fig. 1. Values are mean ± s.e.m. *P < 0.05; **P < 0.01 (Tukey test). n.s., not significant. Experiments were replicated at least two times.

Figure 5. Stimulatory effect of aldioxa on gastric emptying was independent of 5-HT₄ and D₂ receptors.

Mice fasted for 18 h were orally administered aldioxa (200 mg kg⁻¹) (a,b), cisapride (5 mg kg⁻¹) (a), itopride (200 mg kg⁻¹) (b) or vehicle (1% methylcellulose) (a,b). GR113808 (10 mg kg⁻¹), a selective 5-HT₄ antagonist, was administered 5 min before each drug administration (a). Forty-five (a) or thirty (b) minutes after each drug administration, delayed gastric emptying was induced by administration of clonidine (100 μg kg⁻¹) (a) or apomorphine (5 mg kg⁻¹) (b) and examined using the phenol red method as described in the legend of Fig. 1. Values are mean ± s.e.m. *P < 0.05; **P < 0.01 (Tukey test). n.s., not significant. Experiments were replicated at least two times.

Figure 6. Involvement of α-2 adrenergic receptor in stimulatory effect of aldioxa on gastric emptying.

SH-SY5Y cells were incubated with indicated concentration of aldioxa, yohimbine, allantoin or aluminium hydrate (Al(OH)₃) in the presence of 100 μM clonidine, 5 μM forskolin and 1 mM IBMX for 30 min at 37 °C. Control cells were incubated with 5 μM forskolin and 1 mM IBMX in the presence ( + ) or absence (−) of 100 μM clonidine. Intracellular cAMP levels were determined by ELISA and expressed relative to control (a). Membrane fractions prepared from cells expressing human α-2 adrenergic receptor (b) or human muscarinic M3 receptor (c) were incubated with [³H]-clonidine (20 nM) (b) or [³H]-NMS (2 nM) (c), respectively, in the presence of indicated concentrations of aldioxa, allantoin, aluminium hydrate (Al(OH)₃), L-(-)-norepinephrine or yohimbine for 2 h and clonidine- (b) or NMS- (c) binding was determined by the filter-binding assay. Effect of indicated dose of yohimbine on restraint stress (RS)- (d) or clonidine- (e) induced delayed gastric emptying was examined using the phenol red method as described in the legends of Figs 1 and 4. Values are mean ± s.e.m. *P < 0.05; **P < 0.01 (Tukey test). Experiments were replicated at least two times.

Figure 7. Effect of aldioxa on gastric compliance in rats.

Rats fasted for 18 h were orally administered indicated dose of aldioxa (mg kg⁻¹) (a,c), acotiamide (100 mg kg⁻¹) (a,c), allantoin (145 mg kg⁻¹) (d), aluminium hydrate (Al(OH)₃) (72 mg kg⁻¹) (d), yohimbine (1 mg kg⁻¹) (e), sucralfate (56 mg kg⁻¹) (e) or vehicle (1% methylcellulose) (a,c–e). Rats were subjected to wrap restraint stress (WRS) for 1 h (b–e). Gastric compliance was measured one hour after the administration of each drug. Values are mean ± s.e.m. *P < 0.05; **P < 0.01 (Tukey test) (versus vehicle (a), versus control (b), versus WRS (c–e). Experiments were replicated at least two times.