Acute myopathy associated with chronic licorice ingestion: reversible loss of myoadenylate deaminase activity

Glycyrrhiza glabra (Licorice): A Comprehensive Review on Its Phytochemistry, Biological Activities, Clinical Evidence and Toxicology

There are more than 30 species of Glycyrrhiza genus extensively spread worldwide. It was the most prescribed herb in Ancient Egyptian, Roman, Greek, East China, and the West from the Former Han era. There are various beneficial effects of licorice root extracts, such as treating throat infections, tuberculosis, respiratory, liver diseases, antibacterial, anti-inflammatory, and immunodeficiency. On the other hand, traditional medicines are getting the attraction to treat many diseases. Therefore, it is vital to screen the medicinal plants to find the potential of new compounds to treat chronic diseases such as respiratory, cardiovascular, anticancer, hepatoprotective, etc. This work comprehensively reviews ethnopharmacological uses, phytochemistry, biological activities, clinical evidence, and the toxicology of licorice, which will serve as a resource for future clinical and fundamental studies. An attempt has been made to establish the pharmacological effect of licorice in different diseases. In addition, the focus of this review article is on the molecular mechanism of licorice extracts and their four flavonoids (isoliquiritigenin, liquiritigenin, lichalocone, and glabridin) pharmacologic activities. Licorice could be a natural alternative for current therapy to exterminate new emerging disorders with mild side effects. This review will provide systematic insights into this ancient drug for further development and clinical use.

Glycyrrhiza glabra

Liquorice foliage

Potassium dependent rescue of a myopathy with core-like structures in mouse

Myopathies decrease muscle functionality. Mutations in ryanodine receptor 1 (RyR1) are often associated with myopathies with microscopic core-like structures in the muscle fiber. In this study, we identify a mouse RyR1 model in which heterozygous animals display clinical and pathological hallmarks of myopathy with core-like structures. The RyR1 mutation decreases sensitivity to activated calcium release and myoplasmic calcium levels, subsequently affecting mitochondrial calcium and ATP production. Mutant muscle shows a persistent potassium leak and disrupted expression of regulators of potassium homeostasis. Inhibition of KATP channels or increasing interstitial potassium by diet or FDA-approved drugs can reverse the muscle weakness, fatigue-like physiology and pathology. We identify regulators of potassium homeostasis as biomarkers of disease that may reveal therapeutic targets in human patients with myopathy of central core disease (CCD). Altogether, our results suggest that amelioration of potassium leaks through potassium homeostasis mechanisms may minimize muscle damage of myopathies due to certain RyR1 mutations.

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.

Hypokaliemic rhabdomyolysis associated with liquorice ingestion: report of an atypical case

We here present an unusual case of hypokaliemic rhabdomyolysis, characterised by a sthenic deficit exclusively involving the distal muscles of the upper limbs and secondary to chronic glycyrrhizic acid intoxication, and by the absence of even ictal arterial hypertension. We discuss the etiopathogenetic bases and the risks related to the development of this secondary hypokaliemic syndrome, also in relation to other concomitant risk factors such as prolonged physical exercise and exposure to low temperatures.