Geranylgeraniol as a Modulator of Mevalonate Pathway Disruption: A Scoping Review of Cellular Mechanisms and Skeletal Outcomes in Osteoporosis Models.

Background/

Objectives

Geranylgeraniol (GGOH), an isoprenoid intermediate of the mevalonate pathway, regulates bone cell viability and function, particularly by mitigating cellular toxicity induced by nitrogen-containing bisphosphonates (N-BPs). Despite this, its role in osteoporosis remains underexplored. This scoping review synthesises evidence on the effects of GGOH in in vitro and in vivo models of osteoporosis.

Methods

PubMed, Scopus, and Ovid were searched using GGOH- and osteoporosis-related terms. Primary studies evaluating GGOH exposure in cellular or animal osteoporosis models were eligible. Twenty-nine studies met the inclusion criteria.

Results

In vitro findings demonstrate that GGOH reverses N-BP-induced depletion of geranylgeranyl pyrophosphate, restoring protein prenylation which is essential for osteoclast and osteoblast survival, cytoskeletal organisation, and differentiation. GGOH reduced osteoclast apoptosis, restored nuclear factor of activated T-cells 1 and carbonic anhydrase II expression, and prevented N-BP-associated suppression of bone resorption. In osteoblasts and mesenchymal stem cells, GGOH improved viability, upregulated osteogenic markers including runt-related transcription factor 2, alkaline phosphatase, collagen type I, and bone morphogenetic proteins, and rescued mineralisation impaired by alendronate or zoledronate. Independent of N-BPs, GGOH exerted divergent effects on osteoclasts, by inhibiting osteoclastogenesis or promoting retinoic acid receptor-mediated bone resorption and attenuating zoledronate protection in vascular calcification settings in a model-specific manner. In vivo, dietary GGOH supplementation improved trabecular and cortical bone parameters and reduced serum C-terminal telopeptide of type I collagen in obese mice, indicating suppression of bone resorption.

Conclusions

Overall, although GGOH shows osteoprotective potential, its capacity to antagonise N-BP efficacy limits systemic co-administration. Current evidence suggests that local delivery may warrant future investigation as a strategy to mitigate N-BP-induced skeletal toxicity. However, studies evaluating bone tissue exposure, pharmacokinetics, and clinically achievable concentrations are required before this approach can be translated.