Clinical evidence indicates that fat is inversely proportional to bone mass in elderly obese women. However, it remains unclear whether obesity accelerates bone loss. In this report we present evidence that increased visceral fat leads to inflammation and subsequent bone loss in 12-monthold C57BL/6J mice that were fed 10% corn oil (CO)-based diet and a control lab chow (LC) for 6 months. As expected from our previous work, CO-fed mice demonstrated increased visceral fat and enhanced total body fat mass compared to LC. The adipocyte-specific PPARγ and bone marrow (BM) adiposity were increased in CO-fed mice. In correlation with those modifications, inflammatory cytokines (IL-1β, IL-6, TNF-α) were significantly elevated in COfed mice compared to LC-fed mice. This inflammatory BM microenvironment resulted in increased superoxide production in osteoclasts and undifferentiated BM cells. In CO-fed mice, the increased number of osteoclasts per trabecular bone length and the increased osteoclastogenesis assessed exvivo suggest that CO diet induces bone resorption. Additionally, the up-regulation of osteoclastspecific cathepsin k and RANKL expression and down-regulation of osteoblast-specific RUNX2/ Cbfa1 supports this bone resorption in CO-fed mice. Also, COfed mice exhibited lower trabecular bone volume in the distal femoral metaphysis and had reduced OPG expression. Collectively, our results suggest that increased bone resorption in mice fed a CO-enriched diet is possibly due to increased inflammation mediated by the accumulation of adipocytes in the BM microenvironment. This inflammation may consequently increase osteoclastogenesis, while reducing osteoblast development in CO-fed mice.

We investigated the mechanism of H 2 O 2 activation of the Ca 2+ -regulated NADPH oxidase NOX5. H 2 O 2 induced a transient, dose-dependent increase in superoxide production in K562 cells expressing NOX5. Confocal studies demonstrated that the initial calcium influx generated by H 2 O 2 is amplified by a feedback mechanism involving NOX5-dependent superoxide production and H 2 O 2 . H 2 O 2 -NOX5 activation was inhibited by extracellular Ca2+ chelators, a pharmacological inhibitor of cAbl, and over-expression of kinase-dead c-Abl.Transfected kinase-active GFP-c-Abl co-localized with vesicular sites of superoxide production in a Ca 2+ -dependent manner. In contrast to H 2 O 2 , the Ca2+ ionophore ionomycin induced NOX5 activity independently of c-Abl. Immunoprecipitation of cell lysates revealed that active GFP-c-Abl formed oligomers with endogenous c-Abl and that phosphorylation of both proteins was increased by H 2 O 2 treatment. Furthermore, H 2 O 2 -induced NOX5 activity correlated with increased localization of c-Abl to the membrane fraction, and NOX5 proteins could be co-immunoprecipitated with GFP-Abl proteins.Our data demonstrate for the first time that NOX5 is activated by c-Abl through a Ca 2+ -mediated, redox-dependent signaling pathway and suggest a functional association between NOX5 NADPH oxidase and c-Abl.

Background:The role and source of ROS in insulin resistance induced by a high fat diet remain uncertain. Results: Insulin resistance induced by a high fat diet, palmitate, or a high concentration of glucose is mitigated in the absence of Nox2. Conclusion: Nox2 mediates insulin resistance in skeletal muscle. Significance: Nox2 represents a new target for the treatment of metabolic syndrome and its associated complications.

Background:The identity of the reactive oxygen species (ROS)-producing enzyme(s) in human spermatozoa remains uncertain. Results: NOX5 NADPH oxidase, but not NOX1/2/4, is expressed in human spermatozoa and produces superoxide. Inhibition of NOX5 activity reduces spermatozoa motility. Conclusion: NOX5 is the main source of superoxide and is implicated in human spermatozoa motility. Significance: NOX5 might control the numerous ROS-dependent (patho)physiological processes in human spermatozoa.

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