Serum sulfatide abnormality is associated with increased oxidative stress in hemodialysis patients.

Sulfatides are major glycosphingolipids of lipoproteins that influence atherosclerosis and blood coagulation. Our previous cross-sectional study of hemodialysis patients showed that serum sulfatide levels decreased markedly with increasing duration of hemodialysis treatment, which may contribute to the development of cardiovascular disease. However, this past study could not demonstrate the time-dependent change in serum sulfatide levels in each patient, and the underlying mechanism is unknown. To confirm the time-dependent aggravation of serum sulfatide abnormality, 95 stable hemodialysis outpatients were followed up for 3 years. To show the underlying mechanisms, we statistically analyzed correlations between serum sulfatide levels and clinical factors, including an oxidative stress marker, malondialdehyde. Serum sulfatides were quantified by mass spectrometry after conversion to lysosulfatides. Malondialdehyde was measured using a colorimetric assay. The results showed a time-dependent decrease in serum sulfatide levels associated with increased malondialdehyde levels, although the absolute level of serum malondialdehyde does not determine the baseline level of serum sulfatides. Multiple linear regression analysis showed a significant correlation only between the time-dependent change in serum sulfatide levels and the time-dependent change in serum malondialdehyde levels. This study demonstrated, for the first time, a time-dependent aggravation of serum sulfatide abnormality in hemodialysis patients, as well as the potential relationship between serum sulfatide abnormality and increasing oxidative stress. These findings suggest that oxidative stress might be an aggravating factor in serum sulfatide abnormality. As continuation of hemodialysis treatment hardly improves abnormal serum sulfatide levels or increased oxidative stress, development of novel therapeutic strategies may be important.

Peroxisome proliferator-activated receptor α mediates enhancement of gene expression of cerebroside sulfotransferase in several murine organs.

Sulfatides, 3-O-sulfogalactosylceramides, are known to have multifunctional properties. These molecules are distributed in various tissues of mammals, where they are synthesized from galactosylceramides by sulfation at C3 of the galactosyl residue. Although this reaction is specifically catalyzed by cerebroside sulfotransferase (CST), the mechanisms underlying the transcriptional regulation of this enzyme are not understood. With respect to this issue, we previously found potential sequences of peroxisome proliferator-activated receptor (PPAR) response element on upstream regions of the mouse CST gene and presumed the possible regulation by the nuclear receptor PPARα. To confirm this hypothesis, we treated wild-type and Ppara-null mice with the specific PPARα agonist fenofibrate and examined the amounts of sulfatides and CST gene expression in various tissues. Fenofibrate treatment increased sulfatides and CST mRNA levels in the kidney, heart, liver, and small intestine in a PPARα-dependent manner. However, these effects of fenofibrate were absent in the brain or colon. Fenofibrate treatment did not affect the mRNA level of arylsulfatase A, which is the key enzyme for catalyzing desulfation of sulfatides, in any of these six tissues. Analyses of the DNA-binding activity and conventional gene expression targets of PPARα has demonstrated that fenofibrate treatment activated PPARα in the kidney, heart, liver, and small intestine but did not affect the brain or colon. These findings suggest that PPARα activation induces CST gene expression and enhances sulfatide synthesis in mice, which suggests that PPARα is a possible transcriptional regulator for the mouse CST gene.