Comparison of Naringenin and Alendronate in the Attenuation of Ovariectomy-Induced Osteoporosis by Modulating Autophagy, Apoptosis, and Oxidative Stress in Rats.

BACKGROUND: Estrogen deficiency after menopause is a major driver of osteoporosis and has been increasingly linked to dysregulated cellular stress responses, including autophagy and apoptosis, that affect bone remodeling and microarchitecture. OBJECTIVES: This study aimed to evaluate the therapeutic effects of naringenin (NA) and alendronate (AL) on ovariectomy (OVX)-induced osteoporosis in rats, with emphasis on autophagy- and apoptosis-related molecular signatures. METHODS: Female Sprague-Dawley rats were assigned to sham-operated (SH), OVX, OVX+NA (50 mg/kg/day), or OVX+AL (5 µg/kg/day) groups (n = 10/group) and were treated by oral gavage for 10 weeks. Bone health markers, including bone cell numbers and trabecular weight and volume, were assessed using stereology. Serum estradiol and osteocalcin levels were assayed by enzyme-linked immunosorbent assay. Oxidative markers, including catalase (CAT) and glutathione reductase (GR) activities, were measured using spectrophotometric assays. Femoral mRNA expression of microtubule-associated protein 1 light chain 3 (LC3), beclin 1 (BECN1), autophagy-related 5 (ATG5), caspase 9 (CASP9), and B-cell lymphoma 2 (BCL2) was quantified by reverse transcription quantitative polymerase chain reaction. RESULTS: Ovariectomy reduced estradiol levels compared with SH, and estradiol was not restored by NA or AL. Both treatments mitigated OVX-associated changes in osteocalcin and improved femoral stereological/histomorphometric outcomes, with AL exerting a greater effect across multiple structural and molecular outcomes. NA, but not AL, significantly increased CAT and GR activities relative to OVX. Ovariectomy increased CASP9 and autophagy markers and decreased BCL2; both treatments shifted these transcripts toward SH values, with a stronger effect for AL. CONCLUSIONS: Naringenin and AL mitigated OVX-associated osteoporotic changes without restoring systemic estradiol levels, and these effects were accompanied by shifts in apoptosis- and autophagy-related gene expression. These findings suggest that the beneficial effects of AL and NA may be associated with the modulation of oxidative stress and apoptosis- and autophagy-related mechanisms.