C20Sphingomyelin is a naturally occurring sphingolipid. Levels of C20sphingomyelin are upregulated in the hippocampus of rats with diabetes induced by streptozotocin and in human plasma where it is positively correlated with insulin resistance in obese humans. C20sphingomyelin is also upregulated in the liver of a mouse model of Niemann-Pick type C1 disease, a neurodegenerative cholesterol-sphingolipid lysosomal storage disorder. The plasma concentration of C20sphingomyelin is decreased in men with prostate cancer.