Although the molecular basis for the correlation between NKT cell activation and altered PHL levels in obese subjects remains unclear, some PHLs may affect NKT cell biology, based on the observations that the concentration of Cer species (C18:0, C20:0, and C24:1) and total Cer level was higher in type 2 diabetes; insulin sensitivity was inversely correlated with C18:0, C20:0, C24:1, C24:0, and total Cer levels; and increased tumor necrosis factor (TNF)-α concentration was correlated with the levels of C18:1 and C18:0 ceramide (80). The gene discussed is TNF; the disease is type 2 diabetes mellitus.