Highly hydroxylated fullerene localizes at the cytoskeleton and inhibits oxidative stress in adipocytes and a subcutaneous adipose-tissue equivalent

Adipose tissue is a crucial site for pathologic changes in obesity/metabolic syndrome-related diseases. Interaction between adipogenesis and reactive oxygen species (ROS) in adipose tissue involving chronic low-grade inflammation is postulated to be causal in the development of insulin resistance and other metabolic consequences. We used different culture systems to investigate the relationship between ROS and adipogenesis at three levels: within adipocytes, during adipocyte-monocyte interactions, and in a subcutaneous adipose tissue model. The effects of highly hydroxylated fullerene (HHF; C60(OH)36) on adipogenesis-accompanying oxidative stress and inflammatory changes were examined using these three systems. We demonstrated that H2O2 stimulates lipid accumulation in 3T3-L1 preadipocytes, and lipid uptake causes ROS generation in OP9 preadipocytes, both of which were then markedly suppressed with HHF treatment. HHF significantly inhibited the adipogenic stimulant insulin-rich serum replacement (SR)-induced triacylglycerol accumulation, ROS production, and macrophage activation in cultured OP9 cells and an OP9-U937 monocyte-like cell coculture system. H2O2-induced intracellular ROS production in OP9 adipocytes was also notably inhibited by HHF. We developed a three-dimensional subcutaneous adipose-tissue equivalent (SATE) consisting of air-exposed cultures of HaCaT keratinocytes on an OP9 adipocyte-populated collagen gel in a culture insert. With SR stimulation and under suitable conditions, fat accumulation, ROS generation, and macrophage infiltration were observed in the SATE and significantly inhibited by HHF. By western blotting, we demonstrated that HHF localized at the cytoskeleton, which controls the transport of lipids. In conclusion, HHF is able to inhibit oxidative stress in adipocytes and adipogenesis-related macrophage activation in adipose tissues through its antioxidation.