Age- and sex-associated effects of C18 ceramide sphingolipids on osteoclastogenesis in experimental models of Gulf War Illness

Approximately 60 % of Gulf War Illness (GWI) cases are correlated with toxic exposure to permethrin (PER) and pyridostigmine bromide (PB) in Veterans. Among the known hallmarks of GWI, pathological changes in bone of Veterans with GWI are poorly understood due to the lack of relevant experimental models of osteoclastogenesis. Emerging metabolomic studies have reported that GWI symptoms are positively correlated with the accelerated prevalence of ceramide sphingolipids in the serum. According to a secondary analysis of publicly available targeted metabolomic datasets, the area under the curve (AUC) value of C18:0 ceramide was significantly elevated by more than 56 % in the serum of male GWI Veterans compared to non-veteran healthy controls. Using mouse bone marrow-derived osteoclast precursors from young (2-month-old) and aged (22-month-old) mice, our observational studies confirmed that C18:0 and C18:1 significantly accelerated RANKL-primed osteoclastogenesis in vitro. Furthermore, C18:0 ceramide increased RANKL-primed osteoclast formation in aged, but not young male osteoclast precursors exposed to PB or PER in vitro. In contrast, a mixture of C18:0 and C18:1 with PB reduced the number of osteoclasts from young female mice in vitro. In addition, C18:1 diminished RANKL-primed osteoclastogenesis in young male as well as young and aged female mouse osteoclast precursors in the presence of PER in vitro. As Veterans with GWI rapidly approach the senior 65+ age range, further studies are warranted to evaluate the potential link between Gulf War toxic exposure and ceramide sphingolipids in age- and sex-associated osteoclastogenesis.