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Mineralocorticoid activity of carbenoxolone: contrasting effects of carbenoxolone and liquorice on 11 beta-hydroxysteroid dehydrogenase activity in man.

1. 11-beta-Hydroxysteroid dehydrogenase is an enzyme complex consisting of 11 beta-dehydrogenase and 11-oxoreductase responsible for the interconversion of cortisol to cortisone in man. Inhibition of 11 beta-dehydrogenase (e.g. after liquorice ingestion) results in cortisol acting as a potent mineralocorticoid. We have evaluated the effect of the synthetic liquorice derivative, carbenoxolone, on this enzyme complex. 2. Carbenoxolone given to six volunteers in metabolic balance produced sodium retention with suppression of the renin-angiotensin-aldosterone system. Plasma potassium fell, although there was no kaliuresis. This was associated with inhibition of 11 beta-dehydrogenase (as measured by a rise in the plasma half-life of [11 alpha-3H]cortisol). Unlike liquorice, however, carbenoxolone also inhibited 11-oxoreductase (as measured by the generation of cortisol after oral cortisone acetate). 3. The mineralocorticoid activity of carbenoxolone, like liquorice, is mediated via cortisol by inhibition of 11 beta-dehydrogenase. Carbenoxolone, however, also inhibits 11-oxoreductase activity and this may relate to its effect on renal potassium excretion.

11-beta-Hydroxysteroid Dehydrogenases↗

Effect of carbenoxolone on prostaglandin synthesizing and metabolizing enzymes and correlation with gastric mucosal carbenoxolone concentrations.

Carbenoxolone in a dose dependent manner inhibits the activity of the prostaglandin (PG) metabolizing enzymes 15-hydroxy-PG-dehydrogenase and delta 13-PG-reductase in vitro, while this drug in the same dose range does not influence gastric mucosal PG synthesis by a microsomal cell fraction. Using a radioimmunoassay for carbenoxolone determination, we could show that during absorption high levels of the drug are reached within the gastric mucosa of human volunteers and gastric ulcer patients. From the tissue levels reached it seems possible that carbenoxolone inhibits PG inactivating enzymes of gastric mucosa in vivo as it does in vitro. Thus, decreased inactivation cytoprotective PG synthesized within the gastric mucosa, might contribute to the ulcer healing effect of carbenoxolone.

15-Oxoprostaglandin 13-Reductase↗

Carbenoxolone damages endothelium and enhances vasoconstrictor action in aortic rings.

Carbenoxolone causes hypertension indirectly by inhibition of 11beta-hydroxysteroid dehydrogenase and consequent elevation of intracellular glucocorticoid levels and enhancement of vasoconstrictor action. We performed the present study to determine whether carbenoxolone also enhances vascular tone directly by mechanisms independent of glucocorticoids and other systemic influences. Exposure of rat aortic rings to 10 to 100 micromol/L carbenoxolone in aerated Krebs-Henseleit buffer for 24 hours resulted in concentration-dependent increases in angiotensin II (Ang II) (100 nmol/L)-stimulated contractions and significant shifting of the phenylephrine cumulative contraction curve to the left but not increases in KCI (120 mmol/L)-stimulated contractions. Maximal enhancement of Ang II contraction was 39 percent. In contrast, brief (15-minute) exposure to 100 micromol/L carbenoxolone did not alter Ang II contractions. Mechanical denudation of the endothelium obviated enhancement of Ang II contractions by carbenoxolone, suggesting interaction of carbenoxolone with the endothelium. Endothelium-dependent relaxation of precontracted rings to acetylcholine or ATP was reduced by more than 90 percent by 24-hour pretreatment with 100 micromol/L carbenoxolone but not with 100 micromol/L deoxycorticosterone acetate (a mineralocorticoid) or 100 mu mol/L glycyrrhizic acid (a natural 11beta-hydroxysteroid dehydrogenase inhibitor). Vascular smooth muscle relaxation with sodium nitroprusside was not inhibited by carbenoxolone. Incubation of cultured endothelial cells with 100 mu mol/L carbenoxolone for 24 hours did not inhibit nitric oxide synthase activity, as measured by conversion of [3H]L-arginine to [3H]L-citrulline. Electron micrography demonstrated that endothelial cell ultrastructure but not vascular smooth muscle cell ultrastructure was abnormal after incubation of rings for 24 hours with 100 micromol/L carbenoxolone. These studies suggest that carbenoxolone concentrations higher than 10 micromol/L enhance vasoconstrictor action via selective toxicity to the endothelium and elimination of endothelium-dependent relaxation.

Angiotensin II↗

Influence of carbenoxolone on the anticonvulsant efficacy of conventional antiepileptic drugs against audiogenic seizures in DBA/2 mice.

Carbenoxolone, the succinyl ester of glycyrrhetinic acid, is an inhibitor of 11beta-hydroxy steroid dehydrogenase and gap junctional intercellular communication. It is currently used in clinical treatment of ulcer diseases. Systemic administration of carbenoxolone (1-40 mg/kg, intraperitoneally (i.p.)) was able to produce a dose-dependent decrease in DBA/2 audiogenic seizure severity score. Glycyrrhizin, an analogue of carbenoxolone inactive at the gap-junction level, was unable to affect audiogenic seizures at doses up to 30 mg/kg. In combination with conventional antiepileptic drugs, carbenoxolone, 0.5 mg/kg, i.p., which per se did not significantly affect the occurrence of audiogenic seizures in DBA/2 mice, potentiated the anticonvulsant activity of carbamazepine, diazepam, felbamate, gabapentin, lamotrigine, phenytoin, phenobarbital and valproate against sound-induced seizures in DBA/2 mice. This effect was not observed after the combination of glycyrrhizin (10 mg/kg, i.p.) with some conventional antiepileptic drugs. The degree of potentiation induced by carbenoxolone was greater for diazepam, felbamate, gabapentin, phenobarbital and valproate, less for lamotrigine, phenytoin and carbamazepine. This increase was associated with a comparable impairment in motor activity; however, the therapeutic index of combined treatment of antiepileptic drugs with carbenoxolone was more favourable than the combination with glycyrrhizin or saline. Since carbenoxolone did not significantly influence the total and free plasma levels of diazepam, felbamate, gabapentin, lamotrigine, phenytoin, phenobarbital, valproate and carbamazepine, pharmacokinetic interactions are not likely. However, the possibility that carbenoxolone can modify the brain clearance of the anticonvulsant drugs studied may not be excluded. In addition, carbenoxolone did not significantly affect the hypothermic effects of the anticonvulsants tested. In conclusion, carbenoxolone showed an additive anticonvulsant effect when administered in combination with some classical anticonvulsants, most notably diazepam, felbamate, gabapentin, phenobarbital, and valproate, implicating a possible therapeutic relevance of such drug combinations.

Acoustic Stimulation↗

Effect of carbenoxolone on the plasma renin activity and hypothalamic-pituitary-adrenal axis in congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

OBJECTIVE: To test the hypothesis that carbenoxolone, an inhibitor of 11beta-hydroxysteroid dehydrogenase, might augment the ACTH-suppressing and mineralocorticoid activities of hydrocortisone without a corresponding increase in peripheral hydrocortisone effects, we assessed the effects of carbenoxolone in patients with congenital adrenal hyperplasia. DESIGN AND PATIENTS: Six patients with classic 21-hydroxylase deficiency (5 salt-losing, 1 nonsalt-losing) were enrolled in this study. The study protocol involved 3 treatment periods (except for patient 3): phase 1, hydrocortisone and fludrocortisone; phase 2, hydrocortisone, fludrocortisone and carbenoxolone; phase 3, hydrocortisone and carbenoxolone. Patient 3 was not treated with fludrocortisone at baseline, so she participated only in phase 1 (hydrocortisone only) and phase 2 (hydrocortisone and carbenoxolone). Hydrocortisone and fludrocortisone dosages were kept the same during the study except for the discontinuation of fludrocortisone during phase 3. MEASUREMENTS: Plasma adrenal androgens or their precursors (androstenedione, 17-hydroxyprogesterone, and testosterone, and urine pregnanetriol); plasma cortisol, cortisol-binding globulin, ACTH, apparent cortisol metabolic clearance, 24-h urine 17-hydroxysteroids, and urine free cortisol; mineralocorticoid activity, as measured by plasma renin activity, body weight, plasma potassium, and mean blood pressure; fasting insulin/glucose ratio, protein balance, % eosinophils in peripheral blood, and total urine pyridinoline and deoxypyridinoline; TRH stimulation of TSH and pyridostigmine/GHRH stimulation of growth hormone. RESULTS: Compared to phase 1, the addition of carbenoxolone (with or without concurrent fludrocortisone administration) produced statistically significant decreases of 20-50% in mean plasma 17-hydroxyprogesterone, androstenedione, and renin activity. Since carbenoxolone also decreased the apparent metabolic clearance rate of cortisol by 20%, other measures of systemic glucocorticoid activity were examined. Carbenoxolone did not produce a cushingoid appearance or increase body weight, blood pressure, blood glucose or plasma insulin levels. Carbenoxolone also did not suppress stimulated GH levels, but did decrease TRH-stimulated TSH levels by approximately 20% (P < 0.05). CONCLUSION: Carbenoxolone can augment the adrenal androgen-suppressing activity of hydrocortisone in patients with 21-hydroxylase deficiency. These observations support the hypothesis that selective inhibition of enzymes that metabolize cortisol may lead to new approaches to improve the treatment of congenital adrenal hyperplasia.

11-beta-Hydroxysteroid Dehydrogenases↗

Anticonvulsant, sedative and muscle relaxant effects of carbenoxolone in mice.

BACKGROUND: Carbenoxolone, as an antiulcer medicine, has some pharmacological properties such as: the inhibition of gap junctional (GJ) intercellular communication. In vitro studies have shown, carbenoxolone to abolish the generation of full or partial ectopic spike generation, by 4-aminopyridine, as well as spontaneous epileptiform activity in CA3 or CA1 regions of the rat hippocampal slices via closing GJ channels. Thus, we considered the possible anticonvulsant effects of carbenoxolone in animal seizure models. RESULTS: ED50 values of diazepam and carbenoxolone in the pentylenetetrazole model were 1.13 mg/kg and 283.3 mg/kg, respectively. In this model, carbenoxolone in doses of 200 and 300 mg/kg prolonged the onset time of seizure and decreased the duration of seizures. In the maximal electroshock model, carbenoxolone in a dose of 400 mg/kg decreased the duration of seizure producing protection against seizure but failing to protect against mortality in comparison with diazepam. In the potentiation of pentobarbitone sleep test, carbenoxolone significantly increased sleeping time and decreased latency in doses of 100, 200 and 300 mg/kg in mice dose dependently. In the traction test, carbenoxolone (400 mg/kg) showed muscle relaxant activity and in the accelerated rotarod test, carbenoxolone in doses of 200 and 300 mg/kg showed a decline in motor coordination. CONCLUSION: It can be concluded that carbenoxolone possesses anticonvulsant, muscle relaxant and hypnotic effects, which could contribute to the control of petit mal and grand mal seizures.

Animals↗

Effect of carbenoxolone on the biological activity of nitric oxide: relation to gastroprotection.

1. The interactions between carbenoxolone and nitric oxide (NO) were examined by investigating their effects on human platelet aggregation, on rat aortic strips precontracted by phenylephrine and on protection of rat gastric mucosa against ethanol-induced injury. 2. Carbenoxolone (100-300 microM) caused a significant and concentration-dependent potentiation of rat peritoneal neutrophil (RPN)- 3-morpholino-syndnonimine (SIN-1)- or iloprost-induced inhibition of platelet aggregation. Higher concentrations (500 microM) of carbenoxolone alone markedly inhibited platelet aggregation. Pretreatment with carbenoxolone (100-300 microM) antagonized the reversal of the RPN- or SIN-1-induced antiaggregatory effect by oxyhaemoglobin (10 microM). 3. Rat aortic strips with intact endothelium precontracted by phenylephrine (0.1-0.3 microM) were relaxed by carbenoxolone (100-300 microM) in a concentration-dependent manner. Relaxations were abolished by mechanical removal of the endothelium or by incubation with methylene blue (10 microM) or NG-nitro-L-arginine (L-NNA, 100 microM). Sodium nitroprusside (10 nM)-induced relaxations of endothelium-denuded rat aortic strips were potentiated by carbenoxolone (100 microM). . The carbenoxolone (200 mg kg-1, p.o.)-induced gastroprotection against ethanol was antagonized by L-NNA (5-40 mg kg-1) in a dose-dependent manner. Pretreatment of rats with indomethacin (10 mg kg-1, s.c.) increased the effect of L-NNA. 5. The results suggest that the activity of carbenoxolone in the experimental systems tested is due to phosphodiesterase inhibition, although radical scavenging properties of the drug could contribute to some of the effects observed. In the rat gastric mucosa both increased prostaglandin levels and effects on the NO system could contribute to the protective action of carbenoxolone.

Animals↗

Direct and indirect effects of carbenoxolone on responses to glucocorticoids and noradrenaline in rat aorta.

BACKGROUND: In the kidney carbenoxolone impairs inactivation of glucocorticoids and facilitates their access to mineralocorticoid receptors by inhibiting 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD). 11 beta-OHSD is also expressed in vascular smooth muscle, and, in humans, carbenoxolone potentiates vasoconstrictor sensitivity to cortisol and noradrenaline. OBJECTIVE: To establish in vitro whether the vascular effects of carbenoxolone are mediated by inhibition of 11 beta-OHSD. METHODS: Noradrenaline-induced vasoconstriction was measured in helical de-endothelialized rat aortic strips following 2-5 h exposure to one or more of: carbenoxolone, corticosterone, a mineralocorticoid-receptor antagonist (spironolactone) and a glucocorticoid- and progesterone-receptor antagonist (RU 38486). RESULTS: Carbenoxolone potentiated noradrenaline-induced vasoconstriction in aortae from adrenalectomized rats, an effect which was prevented by spironolactone but not by RU 38486. By contrast, when corticosterone was added or when aortae from non-adrenalectomized rats were studied, carbenoxolone attenuated noradrenaline-induced vasoconstriction. CONCLUSIONS: Carbenoxolone has a direct effect, independent of 11 beta-OHSD, which potentiates noradrenaline-induced vasoconstriction and might be mediated by activation of mineralocorticoid receptors. Carbenoxolone also has an indirect effect, attenuating noradrenaline-induced vasoconstriction dependent on corticosterone and, therefore, mediated by inhibition of 11 beta-OHSD. Although experiments with carbenoxolone must be interpreted with caution because of its direct effect, the present data confirm that 11 beta-OHSD modulates vascular sensitivity to glucocorticoids and noradrenaline. Therefore, 11 beta-OHSD activity might influence blood pressure by effects in both the kidney and the vasculature.

Adrenalectomy↗

Metabolic effects of carbenoxolone in rat liver.

The action of carbenoxolone on hepatic energy metabolism was investigated in the perfused rat liver and isolated mitochondria. In perfused livers, carbenoxolone (200-300 microM) increased oxygen consumption, glucose production and glycolysis from endogenous glycogen. Gluconeogenesis from lactate or fructose, an energy-dependent process, was inhibited. This effect was already evident at a concentration of 25 microM. The cellular ATP levels and the adenine nucleotide content were decreased by carbenoxolone, whereas the AMP levels were increased. In isolated mitochondria, carbenoxolone stimulated state IV respiration and decreased the respiratory coefficient with the substrates beta-hydroxybutyrate and succinate. The ATPase of intact mitochondria was stimulated, the ATPase of uncoupled mitochondria was inhibited, and the ATPase of disrupted mitochondria was not altered by carbenoxolone. These results indicate that carbenoxolone acts as an uncoupler of oxidative phosphorylation and, possibly, as an inhibitor of the ATP/ADP exchange system. The inhibitory action of carbenoxolone on mitochondrial energy metabolism could be contributing to induce the mitochondrial permeability transition (MPT), a key phenomenon in apoptosis. The results of the present study can explain, partly at least, the in vivo hepatotoxic actions of carbenoxolone that were found in a previous clinical evaluation.

Adenosine Triphosphate↗

In vivo and in vitro effects of carbenoxolone on glucocorticoid receptor binding and glucocorticoid activity.

Carbenoxolone potentiates the mineralocorticoid activity of endogenous glucocorticoid hormones by inhibiting the enzyme 11 beta-hydroxysteroid dehydrogenase, which converts cortisol and corticosterone to inactive 11-oxo-derivatives. We addressed the question of whether glucocorticoid activity is also affected by carbenoxolone. Using a rat model involving low dose corticosterone treatment, we found that carbenoxolone neither potentiated nor inhibited the modest increases in blood pressure or reductions in weight gain caused by steroid treatment. Other indices of glucocorticoid activity including white blood cell number, thymus weight, and down regulation of the glucocorticoid receptor were unaffected. In vitro studies with liver and kidney cytosol preparations indicated that carbenoxolone did compete for 3H-dexamethasone binding sites. Carbenoxolone was 5-10 times more effective than glycyrrhetinic acid, 20-30 thousand times less effective than dexamethasone, and is therefore, approximately 1000 times less effective than corticosterone. Analysis of dexamethasone-binding curves indicated a single class of receptor. We conclude that carbenoxolone at the dose tested does not have intrinsic glucocorticoid activity in vivo, nor does it modulate the activities of corticosterone. Carbenoxolone binds weakly to the glucocorticoid receptor. It is not clear whether this weak affinity accounts for some or any of the direct in vitro effects of high concentrations of carbenoxolone that others have described.

Animals↗

Carbenoxolone inhibits DNA synthesis and collagen gene expression in rat hepatic stellate cells in culture.

BACKGROUND/AIMS: This study using primary-cultured rat hepatic stellate cells (HSCs) was aimed to reveal the effect of carbenoxolone and the other gap-junction blockers on the proliferation and activation of HSCs. METHODS: HSC morphology was microscopically evaluated. DNA synthesis was determined by [3H]thymidine incorporation. Expression of HSC activation markers and cell cycle-related proteins was evaluated by Western blot. Collagen alpha1(I) mRNA expression was evaluated by quantitative reverse transcription polymerase chain reaction. RESULTS: Carbenoxolone triggered the morphological change of activated HSCs without inducing apoptosis. Culture-induced DNA synthesis was suppressed to 22.6 and 8.51%, respectively, by 40 and 80 microM carbenoxolone. The other gap-junction blockers failed to affect the morphology and the DNA synthesis of activated HSCs. Carbenoxolone decreased the expression of cyclins D1/2 and cyclin-dependent kinases 4/6. Platelet-derived growth factor (PDGF)-BB-elicited DNA synthesis was reduced to 45.6 and 3.27%, respectively, by 40 and 80 microM carbenoxolone. Phosphorylation of c-Raf, MEK and mitogen-activated protein kinase, but not PDGF receptor beta, under PDGF-BB stimulation was attenuated by carbenoxolone. Collagen alpha1(I) mRNA expression was significantly reduced. In addition, carbenoxolone suppressed the activation process of quiescent HSCs. CONCLUSIONS: Carbenoxolone reduced the DNA synthesis and the expression of collagen alpha1(I) mRNA in activated HSCs independently of its pharmacological action as gap-junction blocker.

Animals↗

Carbenoxolone: a review of its pharmacological properties and therapeutic efficacy in peptic ulcer disease.

Carbenoxolone sodium has been shown to accelerate the rate of healing of both gastric and duodenal ulcers, but its overall value in duodenal ulcer is probably less because of the high rate of natural remission of duodenal ulcers. Further studies are required to decide whether it should be used prophylactically to delay ulcer recurrence. Carbenoxolone may act by affecting both the proliferative activity of gastric epithelium and the differentiation of the epithelial cells to produce mucus (as well as favourably altering the physicochemical properties of mucus and by reducing peptic activity), factors which may be relevant ot the prevention of acute gastric ulcers. Some studies suggest that carbenoxolone adds to the effect of hospitalisation and bed rest on ulcer healing. Whether bed rest confers additional benefit to the drug's ulcer healing effect in outpatients is also uncertain. There is no evidence that accelerated healing by carbenoxolone is associated with improved overall prognosis. Carbenoxolone is of greatest benefit in accelerating the healing of gastric ulcers in patients for whom hospitalisation is not possible or desirable, but it should only be used in the ambulatory patient when careful and regular observation of serum electrolytes (particularly potassium), blood pressure and weight is possible and when it is known that the patient will attend regular follow-up. Patient must be educated in the proper use of the drug. If severe mineralocorticoid-like toxic effects such as sodium and water retention and hypokalaemia appear, as they do in a variable proportion of patients but most frequently in those receiving excessive doses, carbenoxolone should be stopped and the complication treated; they respond to thiazide diuretics and potassium supplements, and probably to amiloride given in conjunction with a low dose of a thiazide diuretic. Treatment with carbenoxolone can continue with concurrent diuretic therapy in patients with less severe side-effects. Optimum therapeutic effect in gastric ulcer with the least side-effects is achieved with a dosage of 100mg carbenoxolone tablets 3 times daily for the first week followed by 50mg 3 times daily thereafter, best taken before meals. A lower dosage is desirable in the elderly and in those with liver, cardiac or renal disease. Barium meal or preferably endoscopic examinations should be performed regularly and therapy continued until the ulcer is healed. Dosage for duodenal ulcer is 50mg 4 times daily, in special positioned-release capsules. These are best taken about 20 minutes before meals.

Adult↗

A double-blind trial of carbenoxolone sodium capsules in the treatment of duodenal ulcer.

A controlled trial of carbenoxolone sodium positioned-release capsules (Duogastrone) was carried out on a randomized series of 100 unselected male Service personnel with symptoms of active duodenal ulceration and supporting radiological evidence. Fifty-seven patients completed the trial, 29 in the carbenoxolone group and 28 in the control group. The carbenoxolone group was given capsules containing 50 mg carbenoxolone four times a day for 12 weeks while the controls received a capsule identical in every respect except that it did not contain carbenoxolone. All patients were assessed at fortnightly intervals and had clinical and radiological reassessments three and six months after commencing treatment. Review at three months and at six months revealed a slight but clinically insignificant trend in favour of the carbenoxolone group. As a corollary to this controlled trial, those patients (38 in all) who did not have an early remission of symptoms were removed from the trial and placed on capsules known to contain carbenoxolone. Subsequently these patients did not show an advantage for carbenoxolone.

Clinical Trials as Topic↗

Effects of carbenoxolone on alveolar fluid clearance and lung inflammation in the rat.

OBJECTIVES: 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), which requires oxidized nicotinamide adenine dinucleotide as a cofactor, metabolizes endogenous glucocorticoids. Since 11beta-HSD2 has been detected in lung epithelial cells, we examined whether carbenoxolone, a potent inhibitor of 11beta-HSD, would enhance endogenous glucocorticoid action on lung fluid balance and inflammation. DESIGN: Controlled laboratory study. SETTING: University research laboratory. SUBJECTS: Adult Sprague-Dawley rats (n = 66). INTERVENTIONS: Rats were intraperitoneally injected with carbenoxolone (2 x 10 mg.kg(-1).day(-1) for 3 days) and allowed free access to water and food. Rats were further challenged with endotoxin instillation (1 mg/kg). MEASUREMENTS AND MAIN RESULTS: We discovered that carbenoxolone significantly increased messenger RNA expression of all three epithelial sodium channel subunits in distal lung tissues (two-fold increase of alpha-subunit, four-fold increase of beta-subunit, and two-fold increase of gamma-subunit) as well as in trachea. Carbenoxolone increased the amiloride-sensitive alveolar fluid clearance significantly. When rats were further challenged by endotoxin instillation (1 mg/kg), pretreatment with carbenoxolone significantly inhibited endotoxin-induced increase in lung neutrophils as well as tumor necrosis factor-alpha and cytokine-induced neutrophil chemoattractant-1 concentrations in serum and bronchoalveolar lavage fluid. CONCLUSIONS: These beneficial effects of carbenoxolone on lung fluid balance and inflammation are very similar to those expected when glucocorticoids are introduced exogenously. We conclude that carbenoxolone increased the actions of endogenous bioactive glucocorticoids on lung cells by reducing local steroid breakdown.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗

The effect of an aldosterone antagonist on the protective action of carbenoxolone on the gastric mucosal barrier.

The effect of an aldosterone antagonist on the protective action of carbenoxolone sodium on the gastric mucosal barrier has been studied in three dogs with Heidenhain pouches. The net fluxes of hydrogen ion and sodium ion were measured before, during, and after contact with a 10 mM bile acid solution at pH 2, in pouches which had not been treated with drugs, in pouches treated with carbenoxolone sodium and in pouches treated with both carbenoxolone sodium and the aldosterone antagonist, spironolactone. Hydrogen ion back diffusion from, and sodium ion gain by the untreated pouch was increased by 10 mM bile acid solution. Addition to the pouches of either carbenoxolone sodium alone or carbenoxolone sodium and spironolactone reduced the hydrogen ion back diffusion after exposure to the bile acid solution. The spironolactone did not change the protective effect of carbenoxolone on the gastric mucosal barrier. Carbenoxolone did not change the increased sodium ion diffusion caused by bile.

Animals↗

Is 11beta-hydroxysteroid dehydrogenase type 1 a therapeutic target? Effects of carbenoxolone in lean and obese Zucker rats.

In liver and adipose tissue, 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) regenerates glucocorticoids from inactive 11-keto metabolites. Pharmacological inhibition or transgenic disruption of 11beta-HSD1 attenuates glucocorticoid action and increases insulin sensitivity. Increased adipose 11beta-HSD1 may also contribute to the metabolic complications of obesity. Here, we examine the effects of inhibition of 11beta-HSDs with carbenoxolone in obese insulin-resistant Zucker rats, a strain in which tissue-specific dysregulation of 11beta-HSD1 (increased in adipose, decreased in liver) mirrors changes in human obesity. Six-week-old male rats were treated orally with carbenoxolone (50 mg/kg/day) or water (1 ml/kg/day) for 3 weeks. Carbenoxolone inhibited 11beta-HSD1 activity in liver (25 +/- 3 versus 52 +/- 2% conversion in lean; 18 +/- 3 versus 35 +/- 3% in obese; p < 0.01) but not in adipose tissue or skeletal muscle. Carbenoxolone had no effect on weight gain or food intake, did not affect plasma glucose during an oral glucose tolerance test, and increased the plasma insulin response to glucose. However, high-density lipoprotein cholesterol was increased by carbenoxolone in obese animals (1.52 +/- 0.24 versus 1.21 +/- 0.26 mM; p < 0.03). Carbenoxolone did not inhibit hepatic inactivation of glucocorticoid by 5beta-reductase and had no significant effect on plasma corticosterone levels. In conclusion, carbenoxolone provides a model for liver-specific inhibition of 11beta-HSD1, which results in improved lipid profile, in Zucker obese rats. Failure to inhibit 11beta-HSD1 in adipose tissue and/or skeletal muscle may explain the lack of effect on glucose tolerance and obesity. Inhibition of adipose 11beta-HSD1 is probably necessary to gain the maximum benefit of an 11beta-HSD1 inhibitor.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗