The comparative effect of teriparatide and denosumab on activins, follistatins, and inhibins in women with postmenopausal osteoporosis.

ABSTRACT

The activins-follistatins-inhibins (AFI) hormonal system affects bone metabolism. Treatments that alter bone metabolism may also alter the AFI molecules. In this non-randomized, open-label, head-to-head comparative study, circulating levels of the AFI system were evaluated in postmenopausal women with osteoporosis treated for 12 mo with either teriparatide (n = 23) or denosumab (n = 22). Τeriparatide treatment increased activin B (P=.01) and activin AB (P=.004) and the ratios activin A/follistatin (P=.006), activin B/follistatin (P=.007), activin AB/follistatin (P<.001), and activin AB/ follistatin-like 3 (FSTL3) (P=.034). The significant P for trend in group × time interactions of activins B and AB and of the ratio activin AB/FSTL3 remained robust after adjustment for BMI and LS BMD but it was lost for activin B after adjustment for previous antiresorptive treatment. The effect of teriparatide on BMD was attenuated when it was adjusted for baseline activins levels or their 12-mo changes. No changes were observed after denosumab treatment. In conclusion, activins B and AB, as well as the ratios of all activins to follistatin and of activin AB to FSTL3 increased with teriparatide treatment, possibly in a compensatory manner. Future studies are needed to study the potentially important role activins may play in bone biology and any associations with the effect of teriparatide on BMD. Clinical Trials identifier NCT04206618. ClinicalTrials.gov  https//clinicaltrials.gov/search?term=NCT04206618.

Bone and the muscle comprise 2 tissues that are considered to interact with each other, not only through mechanical but also through endocrine signals. Several components of the activins­follistatins­inhibins (AFI) hormonal system have been shown to be secreted by the muscle and affect the bone possibly contributing to this interplay. We have previously investigated the levels of the AFI molecules in case­control studies and reported differences between osteoporotic vs osteopenic vs postmenopausal and premenopausal women with normal BMD. In this 12-mo, non-randomized, open-labeled, head-to-head comparative study, we prospectively compared the effect of antiosteoporotic agents with opposite effect on bone metabolism, that is, teriparatide vs denosumab, on the circulating concentrations of all known molecules of the AFI system in postmenopausal women with osteoporosis. We observed increases of activins after teriparatide treatment, but no effect after denosumab treatment on any of the AFI molecules studied. Since activins are mainly acting in an autocrine way and since activin B and AB have not been extensively studied, further studies in the basic research, preclinical, and clinical research fields are required to expand these observations and fully elucidate physiology and any therapeutic potential.