Gender-Specific Differences in Serum Sphingomyelin Species in Patients with Hepatitis C Virus Infection-Sphingomyelin Species Are Related to the Model of End-Stage Liver Disease (MELD) Score in Male Patients

Hepatitis C virus (HCV) replication depends on cellular sphingomyelin (SM), but serum SM composition in chronic HCV infection has been hardly analyzed. In this work, 18 SM species could be quantified in the serum of 178 patients with chronic HCV infection before therapy with direct-acting antivirals (DAAs) and 12 weeks later, when therapy was completed. Six SM species were higher in the serum of females than males before therapy and nine at the end of therapy; thus, sex-specific analysis was performed. Type 2 diabetes was associated with lower serum levels of SM 36:2;O2 and 38:2;O2 in men. Serum SM species did not correlate with the viral load in both sexes. Of note, three SM species were lower in males infected with HCV genotype 3 in comparison to genotype 1 infection. These SM species normalized after viral cure. SM 38:1;O2, 40:1;O2, 41:1;O2, and 42:1;O2 (and, thus, total SM levels) were higher in the serum of both sexes at the end of therapy. In males, SM 39:1;O2 was induced in addition, and higher levels of all of these SM species were already detected at 4 weeks after therapy has been started. Serum lipids are related to liver disease severity, and in females 15 serum SM species were low in patients with liver cirrhosis before initiation of and after treatment with DAAs. The serum SM species did not correlate with the model of end-stage liver disease (MELD) score in the cirrhosis and the non-cirrhosis subgroups in females. In HCV-infected male patients, nine SM species were lower in the serum of patients with cirrhosis before DAA treatment and eleven at the end of the study. Most of the SM species showed strong negative correlations with the MELD score in the male cirrhosis patients before DAA treatment and at the end of therapy. Associations of SM species with the MELD score were not detected in the non-cirrhosis male subgroup. In summary, the current analysis identified sex-specific differences in the serum levels of SM species in HCV infection, in liver cirrhosis, and during DAA therapy. Correlations of SM species with the MELD score in male but not in female patients indicate a much closer association between SM metabolism and liver function in male patients.