Secretory Acid Sphingomyelinase in Children and Adolescents With Type 1 Diabetes

The activity of acid sphingomyelinase (ASMase), a key enzyme in sphingolipid metabolism, has been found to be increased in a variety of human diseases. Studies conducted on animal and cellular models showed that sphingolipids and ASMase play a central role in the pathogenesis of type 1 diabetes (T1D) and T1D-related vascular damage. Currently, no studies have investigated the role of ASMase activity in pediatric patients with T1D. Therefore, we conducted a cross-sectional study to evaluate the activity of the secretory form of ASMase (S-ASMase) in the serum of patients with T1D aged 2-16 years in comparison with a control group (healthy subjects matched for age, gender, and pubertal stage).

We recruited children and adolescents affected by T1D (including patients with new-onset and established T1D) aged 2-16 years and healthy normal-weight subjects with normal timing of puberty (matched for age, gender, and pubertal stage), who were consecutively admitted-as outpatients-to our institution for screening purposes. Serum lipid profile, glycated hemoglobin (HbA1c), and urine albumin-creatinine ratio (uACR) were assessed in all T1D patients. S-ASMase activity was measured in all study participants through a colorimetric assay.

In total, 68 T1D patients and 51 healthy controls were recruited in this study. None of the T1D patients had T1D-related complications. No difference in S-ASMase activity was observed between subjects with T1D and healthy controls. However, when T1D patients were stratified according to the duration of diabetes, we found a significantly higher activity of S-ASMase in patients with new-onset T1D (recruited within 1 week after the disease diagnosis) as compared to that observed in patients with established T1D. In all patients with T1D, S-ASMase activity correlated positively with HbA1c and triglyceride levels, while it correlated negatively with total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) levels. However, there were no significant differences in S-ASMase activity between T1D patients with new-onset disease who presented with diabetic ketoacidosis (DKA; n = 12) and T1D patients with new-onset disease who did not present with DKA (n = 13).

Our study evaluated, for the first time, the in vivo activity of S-ASMase in a pediatric cohort of patients with T1D. In pediatric patients with new-onset T1D, we found a significantly higher S-ASMase activity as compared to that observed in patients with established T1D. In all T1D patients, the positive correlation between S-ASMase activity, HbA1c, and triglyceride levels, as well as the negative correlation between S-ASMase activity and HDL-C levels, suggests a potential role played by sphingolipids in T1D pathophysiology. Further mechanistic studies are needed to better elucidate the role of S-ASMase in patients with T1D at different stages of the disease.