Ceramides and other sphingolipids as predictors of incident dysglycemia (CASPID): Design, methods, and baseline characteristics.

The Ceramides and other Sphingolipids as Predictors of Incident Dysglycemia (CASPID) study tests the overall hypothesis that sphingolipids are pathophysiologic mediators of transition from normal glucose regulation (NGR) to prediabetes, type 2 diabetes (T2DM), and associated complications. The CASPID study utilizes two longitudinal cohorts - the Pathobiology of Prediabetes in a Biracial Cohort (POP-ABC)/Pathobiology and Reversibility of Prediabetes in a Biracial Cohort (PROP-ABC) and the Diabetes Prevention Program (DPP)/DPP Outcomes Study (DPPOS). Normoglycemic POP-ABC/PROP-ABC were followed for 10 years for progression to prediabetes and offered lifestyle intervention to reverse prediabetes. The DPP/DPPOS participants had prediabetes at enrollment, were randomized to placebo, lifestyle intervention, or metformin treatment, and followed for 11 years for progression to T2DM. Using a case-control design, we analyze 76 targeted plasma sphingolipids as predictors of progression from NGR to prediabetes (Aim 1), prediabetes to T2DM (Aim 2), response to interventions (Aim 3), and development of diabetes complications (Aim 4). A sample size of 600 subjects provides >80% power to detect a 20% difference in sphingolipid profiles between comparison groups (alpha = 0.01). At enrollment, POP-ABC participants had a mean age of 47.7 ± 9.00 years, body mass index (BMI) 30.4 ± 6.10 kg/m2, fasting glucose 92.9 ± 6.90 mg/dL, and 2-h glucose 130 ± 28.8 mg/dL; DPP participants had a mean age of 51.9 ± 9.44 years, BMI 33.7 ± 6.33 kg/m2, fasting glucose 106 ± 7.88 mg/dL, and 2-h glucose 164 ± 16.9 mg/dL. Among normoglycemic participants, those with parental history of T2DM had significantly higher baseline levels of total sphingomyelins, and lower levels of total ceramides and sphingosine, compared with control subjects without familial diabetes history. As the first such study in longitudinal human cohorts, CASPID will elucidate the role of sphingolipids in the pathogenesis of dysglycemia and facilitate the discovery of novel predictive and prognostic biomarkers.