Tibolone: the way to beat many a postmenopausal ailments

Effects of Human Sulfotransferase 2A1 Genetic Polymorphisms 3 on the Sulfation of Tibolone

BACKGROUND AND OBJECTIVES

Previous studies have demonstrated the metabolism of tibolone through sulfation, with the cytosolic sulfotransferase (SULT) SULT2A1 as the major responsible enzyme. The current study aimed to investigate how SULT2A1 genetic polymorphisms may affect the dehydroepiandrosterone (DHEA)- and tibolone-sulfating activity of SULT2A1.

METHODS

Site-directed mutagenesis was employed to generate cDNAs encoding ten different SULT2A1 allozymes. Recombinant SULT2A1 allozymes were expressed in BL21 E. coli cells, and purified using glutathione-sepharose affinity chromatography. An established sulfotransferase assay was used to analyze DHEA- and tibolone-sulfating activity of the purified SULT2A1 allozymes.

RESULTS

The nine human SULT2A1 allozymes plus the wild-type SULT2A1 were found to display differential sulfating activity toward DHEA and tibolone. Kinetic analysis revealed that different SULT2A1 allozymes exhibited differential substrate affinity and catalytic efficiency toward the two substrates tested.

CONCLUSION

The results obtained provided useful information concerning the differential metabolism of tibolone through sulfation in individuals with different SULT2A1 genotypes.

[Pharmacologic treatment of osteoporosis--2011]

Osteoporosis affects approximately 9% of the population in Hungary resulting in about 100 000 osteoporotic fractures annually. Thirty-five percent of patients with hip fractures due to osteoporosis will die within 1 year. Direct costs of osteoporosis exceed 25 billion forints per year. Apparently, cost-effective reduction of bone loss and consequent fracture risk will add up to not only financial savings but improvement in quality of life, as well. A number of pharmacological modalities are available for this purpose. The mainstay of the treatment of osteoporosis is the bisphosphonate group that includes effective anti-resorptive compounds mitigating bone loss and fragility. The recently registered denosumab exhibits similar efficacy by neutralizing RANK ligand, however, marked differences can be observed between the two drug classes. Strontium has a unique mechanism of action by rebalancing bone turnover, and thus, providing an efficient treatment option for the not fast bone losers who are at high fracture risk. The purely anabolic teriparatide is available for the extremely severe osteoporotic patients and for those who do not respond to other types of therapy. Older treatment options such as hormone replacement therapy, raloxifene, tibolone or calcitonin may also have a restricted place in the management of osteoporosis.

Herb-drug interactions with St John's wort (Hypericum perforatum): an update on clinical observations

St John's wort (SJW) extracts, prepared from the aerial parts of Hypericum perforatum, contain numerous pharmacologically active ingredients, including naphthodianthrones (e.g., hypericin and its derivatives), phloroglucinols derivatives (e.g., hyperforin, which inhibits the reuptake of a number of neurotransmitters, including serotonin), and flavonoids. Such extracts are widely used for the treatment of mild-to-moderate depression. As a monotherapy, SJW has an encouraging safety profile. However, relevant and, in some case, life-threatening interactions have been reported, particularly with drugs which are substrate of cytochrome P450 and/or P-glycoprotein. Well-documented SJW interactions include (1) reduced blood cyclosporin concentration, as suggested by multiple case reports as well as by clinical trials, (2) serotonin syndrome or lethargy when SJW was given with serotonin reuptake inhibitors, (3) unwanted pregnancies in women while using oral contraceptives and SJW, and (4) reduced plasma drug concentration of antiretroviral (e.g., indinavir, nevirapine) and anticancer (i.e., irinotecan, imatinib) drugs. Hyperforin, which is believed to contribute to the antidepressant action of St John's wort, is also strongly suspected to be responsible of most of the described interactions.