Glycyrrhetinic acid food supplementation lowers serum potassium concentration in chronic hemodialysis patients

Steroid and bioactive molecule conjugates: Improving therapeutic approaches in disease management

Conjugates of steroids and other natural bioactive molecules (such as amino acids or carbohydrates) have proven promising compounds with diverse biological effects. This literature review summarises the importance of steroid conjugates in a broad spectrum of therapeutic applications. Steroid conjugates exhibit improved pharmacokinetic properties, improved target specificity, and reduced side effects compared to the parent compounds. This increases their clinical usefulness. Their versatility extends to drug delivery systems, enabling precise modulation of drug release kinetics and bioavailability. Moreover, steroid conjugates are vital in treating inflammatory and neurodegenerative diseases, hormonal disorders, cancer therapy, and combating microbial infections. The review presents the current state of research on steroid conjugates, highlighting the crucial role of steroid conjugates in modern medicine and their potential to revolutionise therapeutic paradigms and improve patient outcomes. Steroid compounds are excellent for developing agents with better bioavailability and are used as drug carriers or hydrogelators.

18β-glycyrrhetinic acid suppresses Lewis lung cancer growth through protecting immune cells from ferroptosis

PURPOSE

18β-glycyrrhetinic acid (GA), the main metabolite of glycyrrhizic acid extracted from the root of licorice, has been reported to possess anti-cancer and immunomodulatory activity, but the mechanisms are not well understood. Recent studies have shown that ferroptosis of immune cells is involved in tumor-associated immune suppression. The purpose of this study was to investigate whether the enhanced immune response via inhibiting immune cell ferroptosis contributed to the anticancer effect of 18β-GA.

METHODS

Lewis Lung carcinoma mouse model and Murine CD8 + T cell culture model were used to examine the changes of immune response and ferroptosis of immune cells.

RESULTS

We found that 18β-GA was effective against lung cancer accompanied by enhanced activation of tumor-infiltrating CD8+ T cells in Lewis Lung carcinoma mouse model. Furthermore, we demonstrated that the boosted immune response by GA was attributed to its ability to inhibit arachidonic acid (AA)-mediated CD8+ T ferroptosis via suppressing CD36 expression.

CONCLUSION

The findings of the present study unraveled a novel mechanism underlying the anti-cancer and immunomodulatory activity of 18β-GA and support that 18β-GA holds potential to be used as an immune enhancer for lung cancer prevention or treatment.

Pathophysiology and clinical management of hyperkalemia in chronic kidney disease

Adaptive increases in kidney and gastrointestinal excretion of K+ help to prevent hyperkalemia in patients with chronic kidney disease (CKD) as long as the glomerular filtration rate (GFR) remains >15-20 mL/min. K+ balance is maintained by increased secretion per functioning nephron, which is mediated by elevated plasma K+ concentration, aldosterone, increased flow rate, and enhanced Na+-K+-ATPase activity. Fecal losses of potassium also increase in CKD. These mechanisms are effective in preventing hyperkalemia if urine output is in excess of 600 mL/day and the GFR exceeds 15 mL/min. Development of hyperkalemia with only mild to moderate reductions in GFR should prompt a search for intrinsic disease of the collecting duct, disturbances in mineralocorticoid activity, and/or decreased delivery of sodium to the distal nephron. The initial approach to treatment is to review the patient's medication profile and whenever possible discontinue drugs that impair kidney K+ excretion. Patients should be educated on sources of K+ in the diet and should be strongly encouraged to avoid the use of K+ containing salt substitutes as well as herbal remedies since herbs may be a hidden source of dietary K+. Effective diuretic therapy and correction of metabolic acidosis are effective strategies to minimize the potential for hyperkalemia. Discontinuation or use of submaximal doses of renin-angiotensin blockers should be discouraged given the cardiovascular protective effect these drugs provide. Potassium binding drugs can be useful to enable use of these drugs and potentially allow liberalization of the diet in CKD patients.

Ethnobotanical, pharmacological, phytochemical, and clinical investigations on Moroccan medicinal plants traditionally used for the management of renal dysfunctions

ETHNOPHARMACOLOGICAL RELEVANCE

Renal disease is a significant public health concern that affects people all over the world. The main limitations of conventional therapy are the adverse reaction on human health and the expensive cost of drugs. Indeed, it is necessary to develop new therapeutic strategies that are less expensive and have fewer side effects. As a consequence of their natural compounds, medicinal plants can be used as an alternative therapy to cure various ailments including kidney diseases.

OBJECTIVE

of the study: This review paper has two principal goals: (1) to inventory and describe the plants and their ancestral use by Moroccan society to cure renal problems, (2) to link traditional use with scientific confirmations (preclinical and clinical).

METHODS

To analyze pharmacological effects, phytochemical, and clinical trials of plants, selected for renal therapy, a bibliographical search was undertaken by examining ethnobotanical investigations conducted in Morocco between 1991 and 2019 and consulting peer-reviewed papers from all over the world.

RESULTS

Approximately 290 plant species, spanning 81 families and 218 genera have been reported as being utilized by Moroccans to manage renal illness. The most frequently mentioned species in Morocco were Herniaria hirsuta subsp. cinerea (DC.), Petroselinum crispum (Mill.) Fuss and Rosmarinus officinalis L. The leaves were the most frequently used plant parts, followed by the whole plant. Decoction and infusion were the most popular methods of preparation. A record of 71 plant species was studied in vitro and/or in vivo for their therapeutic efficacy against kidney disorders, including 10 plants attempting to make it to the clinical stage. Twenty compounds obtained from 15 plants have been studied for the treatment of kidney diseases.

CONCLUSION

Medicinal herbs could be a credible alternative therapy for renal illness. However, additional controlled trials are required to confirm their efficiency in patients with kidney failure. Overall, this work could be used as a database for future exploration.

Excipient-free nanodispersions dominated by amphiphilic glycosides for bioavailability enhancement of hydrophobic aglycones, a case of glycyrrhetinic acid with diammonium glycyrrhizinate

Natural aglycones, a major ingredient accompanied by glycosides in plants, have played an important role in the treatment of various diseases. However, their bioavailability is limited by their poor water solubility. In contrast to previous efforts that required the use of new exotic materials which may raise concerns about biocompatibility, we report the first case of excipient-free nanodispersions in which an insoluble glycyrrhetinic acid (GA) assembled with its amphiphilic parent drug diammonium glycyrrhizinate (DG) into water-dispersible nanodispersions (130.8 nm for particle size and 91.74% for encapsulation efficiency). This strategy largely increased GA's water apparent solubility by hundreds of times to 549.0 μg/mL with a high cumulative dissolution percentage in vitro greater than 80% in 5 min. The study on the formation mechanism showed that the OH, C-O and C=O group stretching peaks shifted in the FTIR spectra of GA-DG nanodispersions, while the COOH peak (δ _COOH 12.19 ppm) disappeared in the ¹H NMR spectrum of GA-DG nanodispersions, indicating that carboxyl groups on GA may interact with the hydroxyl groups of DG in solution. Molecular dynamics simulations suggested that both hydrophobic interactions and hydrogen-bond interactions contribute to the coassembly of GA and DG molecules in aqueous solution. Oral pharmacokinetic studies in rats demonstrated that such nanodispersions have a significant increase in C_max and AUC_0-t of 2.45- and 3.45-fold compared with those for GA, respectively. Therefore, this strategy, employing amphiphilic glycosides as excipients to prepare nanodispersions, not using new materials, paves the way for the further application of hydrophobic aglycone drugs.

Cortisol excess in chronic kidney disease - A review of changes and impact on mortality

Chronic kidney disease (CKD) describes the long-term condition of impaired kidney function from any cause. CKD is common and associated with a wide array of complications including higher mortality, cardiovascular disease, hypertension, insulin resistance, dyslipidemia, sarcopenia, osteoporosis, aberrant immune function, cognitive impairment, mood disturbances and poor sleep quality. Glucocorticoids are endogenous pleiotropic steroid hormones and their excess produces a pattern of morbidity that possesses considerable overlap with CKD. Circulating levels of cortisol, the major active glucocorticoid in humans, are determined by a complex interplay between several processes. The hypothalamic-pituitary-adrenal axis (HPA) regulates cortisol synthesis and release, 11β-hydroxysteroid dehydrogenase enzymes mediate metabolic interconversion between active and inactive forms, and clearance from the circulation depends on irreversible metabolic inactivation in the liver followed by urinary excretion. Chronic stress, inflammatory states and other aspects of CKD can disturb these processes, enhancing cortisol secretion via the HPA axis and inducing tissue-resident amplification of glucocorticoid signals. Progressive renal impairment can further impact on cortisol metabolism and urinary clearance of cortisol metabolites. Consequently, significant interest exists to precisely understand the dysregulation of cortisol in CKD and its significance for adverse clinical outcomes. In this review, we summarize the latest literature on alterations in endogenous glucocorticoid regulation in adults with CKD and evaluate the available evidence on cortisol as a mechanistic driver of excess mortality and morbidity. The emerging picture is one of subclinical hypercortisolism with blunted diurnal decline of cortisol levels, impaired negative feedback regulation and reduced cortisol clearance. An association between cortisol and adjusted all-cause mortality has been reported in observational studies for patients with end-stage renal failure, but further research is required to assess links between cortisol and clinical outcomes in CKD. We propose recommendations for future research, including therapeutic strategies that aim to reduce complications of CKD by correcting or reversing dysregulation of cortisol.

Promoting Plant-Based Therapies for Chronic Kidney Disease

Chronic kidney disease (CKD) is debilitating, increasing in incidence worldwide, and a financial and social burden on health systems. Kidney failure, the final stage of CKD, is life-threatening if untreated with kidney replacement therapies. Current therapies using commercially-available drugs, such as angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers and calcium channel blockers, generally only delay the progression of CKD. This review article focuses on effective alternative therapies to improve the prevention and treatment of CKD, using plants or plant extracts. Three mechanistic processes that are well-documented in CKD pathogenesis are inflammation, fibrosis, and oxidative stress. Many plants and their extracts are already known to ameliorate kidney dysfunction through antioxidant action, with subsequent benefits on inflammation and fibrosis. In vitro and in vivo experiments using plant-based therapies for pre-clinical research demonstrate some robust therapeutic benefits. In the CKD clinic, combination treatments of plant extracts with conventional therapies that are seen as relatively successful currently may confer additive or synergistic renoprotective effects. Therefore, the aim of recent research is to identify, rigorously test pre-clinically and clinically, and avoid any toxic outcomes to obtain optimal therapeutic benefit from medicinal plants. This review may prove to be a filtering tool to researchers into complementary and alternative medicines to find out the current trends of using plant-based therapies for the treatment of kidney diseases, including CKD.

The effect of hyperkalemia and long inter-dialytic interval on morbidity and mortality in patients receiving hemodialysis: a systematic review

BACKGROUND

Patients with chronic kidney disease, especially those receiving hemodialysis (HD), are at risk of hyperkalemia (HK). This systematic review aimed to evaluate the prevalence of HK in patients with renal disease receiving HD and collate evidence on the effect of HK and differing HD patterns (i.e., long vs. short inter-dialytic intervals [LIDI and SIDI, respectively] in a thrice weekly schedule) on mortality.

METHODS

Comprehensive searches were conducted across six databases and selected conference proceedings by two independent reviewers up to September 2020. A hundred and two studies reporting frequency of HK, mortality, or cardiovascular (CV) outcomes in adult patients with acute, chronic or end-stage renal disease in receipt of HD were included. Narrative synthesis of results was undertaken with key findings presented in tables and figures.

RESULTS

Median prevalence of HK in patients with renal disease receiving HD was 21.6% and increased in patients receiving concomitant medications - mainly renin-angiotensin-aldosterone system inhibitors and potassium-sparing diuretics. Associations between elevated potassium levels and increased risk of both all-cause and CV mortality in the HD population were consistent across the included studies. In addition, there was a rise in all-cause and CV mortality on the day following LIDI compared with the day after the two SIDIs in patients on HD.

CONCLUSIONS

Evidence identified in this systematic review indicates a relationship between HK and LIDI with mortality in patients with renal disease receiving HD, emphasizing the need for effective monitoring and management to control potassium levels both in emergency and chronic HD settings.

Comparative risk of new-onset hyperkalemia for antihypertensive drugs in patients with diabetic nephropathy: A Bayesian network meta-analysis

Several randomised controlled trials (RCTs) have evaluated the risk of hyperkalemia of antihypertensive drugs on diabetic nephropathy, yet the results are conflicting. We searched MEDLINE, Embase, The Cochrane Library, and Web of Science for RCTs investigating the risk of antihypertensive drugs on hyperkalemia in diabetic nephropathy from inception to May 31, 2020. Direct comparative meta-analysis showed that the proportion of patients with hyperkalemia was significantly higher in the ARB, aldosterone antagonist, renin inhibitor group than in the placebo group. Moreover, the risk of hyperkalemia in the ARB group was higher than that in the CCB group. Network meta-analysis showed the risk of hyperkalemia in the ARB, aldosterone antagonist, and renin inhibitor group was higher than in the placebo group, but there was no statistical difference between the CCB, ACEI, β blocker, endothelin inhibitor, and diuretic groups than in the placebo group. The possibility of antihypertensive drugs in risk of hyperkalemia being the worst treatment was aldosterone antagonist (98.8%), followed by ARB (73.8%), renin inhibitor (63.8%), diuretic (53.1%), ACEI (46.9%), β blocker (36.8%), endothelin inhibitor (35.2%), placebo (27.1%), and finally CCB (14.3.1%). Therefore, aldosterone antagonist seems worse than other antihypertensive drugs in the risk of hyperkalemia in patients with diabetic nephropathy.

Severe asymptomatic hypokalemia associated with prolonged licorice ingestion: A case report

RATIONALE

Excessive ingestion of licorice can cause pseudohyperaldosteronism. A few case reports in the available literature have described significant hypokalemia secondary to licorice consumption with clinical manifestations of muscle weakness, paralysis, or severe hypertension. To our knowledge, no report has discussed severe asymptomatic hypokalemia associated with licorice consumption.

PATIENT CONCERNS

A 79-year-old man presented to the urology clinic with a several-month history of urinary frequency and a weak stream. Routine laboratory investigations revealed serum potassium (K) level of 1.8 mmol/L, and he was immediately admitted to the nephrology department.

DIAGNOSES

He was in a good state of health, and systemic and neurological examinations were unremarkable. However, laboratory investigations revealed severe hypokalemia and metabolic alkalosis accompanied with renal K wasting and hypertension, suggesting a state of mineralocorticoid excess. Hormonal studies revealed low serum renin and aldosterone but normal serum cortisol levels. Detailed history taking revealed that he had used licorice tea daily during the preceding 18 months.

INTERVENTIONS AND OUTCOME

The patient's serum K returned to normal levels after vigorous K replacement and discontinuation of licorice intake. He was also diagnosed with benign prostatic hyperplasia during hospitalization and was treated.

LESSONS

Chronic licorice ingestion can precipitate severe hypokalemia, although patients may remain asymptomatic. This case report indicates that the severity of a patient's clinical presentation depends on individual susceptibility, as well as the dose and duration of licorice intake.

18 beta-glycyrrhetinic acid ameliorates the cognitive functions and decreases the recurrence rate of pituitary adenomas patients

Pituitary adenomas, the most common tumors of all intracranial neoplasms, may cause either symptoms of mass effect or symptoms of hormone abnormal production. Besides physical damages, patients with pituitary adenomas always suffer from cognitive impairments, mainly in memory and executive functions. 18 beta-glycyrrhetinic acid (GA) has been found to exhibit anti-tumor effects in rat pituitary adenoma-derived cells. The aim of this paper was to investigate the effect of GA in postoperative clinical application. In this study, we recruited 647 patients with pituitary adenoma and 135 patients who dropped out were excluded from analysis. Thus, altogether 512 patients with pituitary adenoma completed the study, of whom 268 were treated with GA, and 244 were treated with placebo. Cognitive assessments, eyesight, tumor size, and hormone secretion levels were examined before and after surgery in both groups. All patients underwent surgeries by single-nostril transsphenoidal approach for their first-time medical treatment. Hormone secretion levels were measured by blood samples and Magnetic resonance imaging (MRI) was used for examining the status of tumor excision. Compared with placebo group, the scores in orientation, language (expression), memory (recall), practice, abstract thinking, and MiniMental State Examination (MMSE) were significantly improved (p < 0.05) in GA treated group after one month of surgery. After six months, there was still a significant increase in abstract thinking scores. Moreover, GA did not impact the overall survival percentage of patients enrolled during our five-year follow-up, but significantly reduced the recurrence rate than that of the placebo group. GA significantly improved the cognitive functions at the early stage after surgery and had a long-termed efficacy on abstract thinking. Notably, GA inhibited the five-year recurrence rate of the recruited pituitary adenomas patients.

Glycyrrhiza glabra

Liquorice foliage

The mechanism of hydrothermal hydrolysis for glycyrrhizic acid into glycyrrhetinic acid and glycyrrhetinic acid 3-O-mono-β-D-glucuronide in subcritical water

To improve the bioactivity and sweetness properties of glycyrrhizic acid (GL), the hydrothermal hydrolysis of GL into glycyrrhetinic acid (GA) and glycyrrhetinic acid 3-O-mono-β-D-glucuronide (GAMG) in subcritical water was investigated. The effects of temperature, time and their interaction on the conversion ratios were analyzed and the reactions were elaborated with kinetics and thermodynamics. The results showed that GL hydrothermal hydrolysis was significantly (P < 0.05) affected by reaction time and temperature, as well as their interaction, and could be fitted into first-order kinetics. The thermodynamic analysis indicated that the hydrolysis of GL was endergonic and non-spontaneous. The hydrolytic pathways were composed of complex consecutive and parallel reactions. It was concluded that subcritical water may be a potential medium for producing GAMG and GA.

Properties and structures of β-glucuronidases with different transformation types of glycyrrhizin

Substrate recognition mechanisms of three fungi β-glucuronidases with different types of GL hydrolysis were analyzed.

Pharmacophore Model Refinement for 11β-Hydroxysteroid Dehydrogenase Inhibitors: Search for Modulators of Intracellular Glucocorticoid Concentrations

11β-Hydroxysteroid dehydrogenases (11β-HSD) control the intracellular concentrations of glucocorticoids: 11β-HSD1 converts the inactive cortisone to the active cortisol, and 11β-HSD2 is responsible for the opposite reaction. Inhibition of 11β-HSD1 is beneficial in the treatment of metabolic syndrome, whereas 11β-HSD2 inhibition leads to hypertension. Therefore, 11β-HSD1 inhibitors should be selective over 11β-HSD2. To support drug discovery and toxicological studies, we have previously reported pharmacophore models for 11β-HSD1 and 2 inhibition. These models represent the common chemical features of 11β-HSD inhibitors, which were used as virtual screening filter. Since new inhibitors are constantly discovered, the quality of the pharmacophore models has to be evaluated in order to maintain a good predictive power. In this study, we report a systematic evaluation and refinement of our pharmacophore model collection. We employed our models for virtual screening, especially focusing on the 11β-HSD2 inhibition. In total, 42 compounds were biologically evaluated and among these we discovered 17 11β-HSD inhibitors that decreased the residual enzyme activity to 50% or less at the concentration of 20 µM. The experimental 11β-HSD1 and 2 readouts from these compounds were used for further model refinement. Evaluation metrics were applied for a quantitative comparison of the old and newly generated models which resulted in a set of improved pharmacophore models offering reliable in silico tools for the identification of novel and selective 11β-HSD inhibitors.

Isolation and characterization of three fungi with the potential of transforming glycyrrhizin

Three fungi with different types of transformation of glycyrrhizin (GL) were isolated from the soil samples of glycyrrhiza glabra planting area in China. According to their morphologies and 18 S rDNA gene sequence analysis, the three fungi were identified and named as Penicillium purpurogenum Li-3, Aspergillus terreus Li-20 and Aspergillus ustus Li-62. Transforming products analysis by TLC and HPLC-MS indicated that P. purpurogenum Li-3, A. terreus Li-20 and A. ustus Li-62 could stably transform GL into GAMG, GAMG and GA, and GA, respectively. P. purpurogenum Li-3 was especially valuable to directly prepare GAMG for applications in the pharmaceutical industry.

The effect of glycyrrhetinic acid on pharmacokinetics of cortisone and its metabolite cortisol in rats

The purpose of this paper is to study pharmacokinetics of cortisone (E) and its metabolite cortisol (F) in rats after administration of glycyrrhetinic acid (GA) and cortisone. Healthy male SD rats were randomized to be given 20 mg/kg E or E combined with 10 mg/kg GA. Blood samples were collected at 5, 10, 20, 40, 60, 90, 120, 150, 180, and 240 min after administration. The serum concentrations of E and F were determined by HLPC and pharmacokinetic parameters were calculated using DASver2.0 software. The parameters of AUC_(0−t), AUC_(0−∞), and C_max for E in the group of E + GA were significantly higher than those in the group of E (P < 0.01); the half-time (t_1/2β) was extended compared to E (P < 0.05) and CL/F was dropped obviously (P < 0.01). The rise in AUC_(0−t), AUC_(0−∞), and C_max for cortisol in the group of E + GA was significantly compared to the group of E (P < 0.01). CL/F was lower than E (P < 0.01) and the half-time (t_1/2β) was slightly extended. In this study, we find that GA restrains the metabolism of E and F and thus increases AUC, t_1/2β, and C_max of E and F, which may be related to its inhibition effect on 11β-hydroxysteroid dehydrogenase (11β-HSD).

Born to yawn? Understanding yawning as a warning of the rise in cortisol levels: randomized trial

BACKGROUND

Yawning consistently poses a conundrum to the medical profession and neuroscientists. Despite neurological evidence such as parakinesia brachialis oscitans in stroke patients and thermo-irregulation in multiple sclerosis patients, there is considerable debate over the reasons for yawning with the mechanisms and hormonal pathways still not fully understood. Cortisol is implicated during yawning and may link many neurological disorders. Evidence was found in support of the Thompson cortisol hypothesis that proposes cortisol levels are elevated during yawning just as they tend to rise during stress and fatigue.

OBJECTIVES

To investigate whether saliva cortisol levels rise during yawning and, therefore, support the Thompson cortisol hypothesis.

METHODS

We exposed 20 male and female volunteers aged between 18 and 53 years to conditions that provoked a yawning response in a randomized controlled trial. Saliva samples were collected at the start and again after the yawning response, or at the end of the stimuli presentations if the participant did not yawn. In addition, we collected electromyographic data of the jaw muscles to determine rest and yawning phases of neural activity. Yawning susceptibility scale, Hospital Anxiety and Depression Scale, General Health Questionnaire, and demographic and health details were also collected from each participant. A comprehensive data set allowed comparison between yawners and nonyawners, as well as between rest and yawning phases. Collecting electromyographic data from the yawning phase is novel, and we hope this will provide new information about neuromuscular activity related to cortisol levels. Exclusion criteria included chronic fatigue, diabetes, fibromyalgia, heart conditions, high blood pressure, hormone replacement therapy, multiple sclerosis, and stroke. We compared data between and within participants.

RESULTS

In the yawning group, there was a significant difference between saliva cortisol samples (t10 = -3.071, P = .01). Power and effect size were computed based on repeated-measures t tests for both the yawning and nonyawning groups. There was a medium effect size for the nonyawners group (r = .467) but low power (36%). Results were similar for the yawners group: medium effect size (r = .440) and low power (33%).

CONCLUSIONS

There was significant evidence in support of the Thompson cortisol hypothesis that suggests cortisol levels are elevated during yawning. A further longitudinal study is planned to test neurological patients. We intend to devise a diagnostic tool based on changes in cortisol levels that may assist in the early diagnosis of neurological disorders based on the data collected.

TRIAL REGISTRATION

International Standard Randomized Controlled Trial Number (ISRCTN): 61942768; http://www.controlled-trials.com/ISRCTN61942768/61942768 (Archived by WebCite at http://www.webcitation.org/6A75ZNYvr).

Licorice abuse: time to send a warning message

Licorice extract has always been recognized as a sweetener and a thirst quencher. Its nutritive value is overrated by many who consume significant amounts and are prone to complications. Glycyrrhetic acid, the active metabolite in licorice, inhibits the enzyme 11-ß-hydroxysteroid dehydrogenase enzyme type 2 with a resultant cortisol-induced mineralocorticoid effect and the tendency towards the elevation of sodium and reduction of potassium levels. This aldosterone-like action is the fundamental basis for understanding its health benefits and the wide spectrum of adverse effects. Herein, we present a comprehensive review of licorice along with the reported complications related to excess intake. Despite its apparent use in a few clinical scenarios, the daily consumption of licorice is never justified because its benefits are minor compared to the adverse outcomes of chronic consumption. The review highlights the importance of investigating the dietary habits and herbal remedies which are being used worldwide on cultural and habitual bases rather than reliable scientific evidence. Licorice is a US Food and Drug Administration (FDA) approved food supplement used in many products without precise regulations to prevent toxicity. Increased awareness among the public is required through TV commercials, newspapers, internet sites, magazines and product labels regarding the upper limit of ingestion and health hazards associated with excess intake. We hope that this review will serve as a warning message that should be transmitted from physicians to patients to avoid excessive licorice intake as well as a message to the FDA to start regulating the use of this substance.

Outcomes after the long interdialytic break: implications for the dialytic prescription

A thrice-weekly schedule dominates hemodialysis practice today. Inherent in such a schedule is a 72-hour interweek break over the weekend. A growing body of evidence suggests that this break may be associated with increased cardiovascular morbidity and mortality. Five recent studies have linked dialysis session timing to higher cardiovascular event rates, and have shed light on possible underlying physiologic mechanisms. We reviewed outcome data linking the "long break" to cardiovascular outcomes, and suggest physiologic rationale for this relationship while identifying knowledge gaps that require further study to inform discussions regarding the application and composition of individualized dialysis prescriptions. Further work is needed to determine the relative importance of electrolyte perturbations and hemodynamic shifts in the relationship between the long break and cardiovascular mortality. The evidence suggests that at least in some at-risk patients, an individualized approach to the dialytic schedule and prescription is warranted.

High salt intake down-regulates colonic mineralocorticoid receptors, epithelial sodium channels and 11β-hydroxysteroid dehydrogenase type 2

Besides the kidneys, the gastrointestinal tract is the principal organ responsible for sodium homeostasis. For sodium transport across the cell membranes the epithelial sodium channel (ENaC) is of pivotal relevance. The ENaC is mainly regulated by mineralocorticoid receptor mediated actions. The MR activation by endogenous 11β-hydroxy-glucocorticoids is modulated by the 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). Here we present evidence for intestinal segment specific 11β-HSD2 expression and hypothesize that a high salt intake and/or uninephrectomy (UNX) affects colonic 11β-HSD2, MR and ENaC expression. The 11β-HSD2 activity was measured by means of 3H-corticosterone conversion into 3H-11-dehydrocorticosterone in Sprague Dawley rats on a normal and high salt diet. The activity increased steadily from the ileum to the distal colon by a factor of about 3, an observation in line with the relevance of the distal colon for sodium handling. High salt intake diminished mRNA and protein of 11β-HSD2 by about 50% (p<0.001) and reduced the expression of the MR (p<0.01). The functionally relevant ENaC-β and ENaC-γ expression, a measure of mineralocorticoid action, diminished by more than 50% by high salt intake (p<0.001). The observed changes were present in rats with and without UNX. Thus, colonic epithelial cells appear to contribute to the protective armamentarium of the mammalian body against salt overload, a mechanism not modulated by UNX.

Pharmacophore-based discovery of FXR agonists. Part I: Model development and experimental validation

The farnesoid X receptor (FXR) is involved in glucose and lipid metabolism regulation, which makes it an attractive target for the metabolic syndrome, dyslipidemia, atherosclerosis, and type 2 diabetes. In order to find novel FXR agonists, a structure-based pharmacophore model collection was developed and theoretically evaluated against virtual databases including the ChEMBL database. The most suitable models were used to screen the National Cancer Institute (NCI) database. Biological evaluation of virtual hits led to the discovery of a novel FXR agonist with a piperazine scaffold (compound 19) that shows comparable activity as the endogenous FXR agonist chenodeoxycholic acid (CDCA, compound 2).

Characterization of activity and binding mode of glycyrrhetinic acid derivatives inhibiting 11β-hydroxysteroid dehydrogenase type 2

Modulation of intracellular glucocorticoid availability is considered as a promising strategy to treat glucocorticoid-dependent diseases. 18β-Glycyrrhetinic acid (GA), the biologically active triterpenoid metabolite of glycyrrhizin, which is contained in the roots and rhizomes of licorice (Glycyrrhiza spp.), represents a well-known but non-selective inhibitor of 11β-hydroxysteroid dehydrogenases (11β-HSDs). However, to assess the physiological functions of the respective enzymes and for potential therapeutic applications selective inhibitors are needed. In the present study, we applied bioassays and 3D-structure modeling to characterize nine 11β-HSD1 and fifteen 11β-HSD2 inhibiting GA derivatives. Comparison of the GA derivatives in assays using cell lysates revealed that modifications at the 3-hydroxyl and/or the carboxyl led to highly selective and potent 11β-HSD2 inhibitors. The data generated significantly extends our knowledge on structure-activity relationship of GA derivatives as 11β-HSD inhibitors. Using recombinant enzymes we found also potent inhibition of mouse 11β-HSD2, despite significant species-specific differences. The selected GA derivatives potently inhibited 11β-HSD2 in intact SW-620 colon cancer cells, although the rank order of inhibitory potential differed from that obtained in cell lysates. The biological activity of compounds was further demonstrated in glucocorticoid receptor (GR) transactivation assays in cells coexpressing GR and 11β-HSD1 or 11β-HSD2. 3D-structure modeling provides an explanation for the differences in the selectivity and activity of the GA derivatives investigated. The most potent and selective 11β-HSD2 inhibitors should prove useful as mechanistic tools for further anti-inflammatory and anti-cancer in vitro and in vivo studies. Article from the Special issue on Targeted Inhibitors.