Continuous glucose monitoring (CGM) is frequently used to assess glucose abnormalities in cystic fibrosis (CF) prior to frank diabetes, yet the biological significance of various CGM measures is unclear. Our aim is to identify CGM measures correlated with β-cell function decline in youth with CF. CGM and 2 hour oral glucose tolerance testing (OGTT) were collected in youth with CF and healthy controls (HC). Glucose and insulin were measured at baseline and 30 minutes on OGTT. Insulinogenic index [IGI=(insulin30-insulin0)/(Glucose30-Glucose0)] was used to estimate β-cell function. Eighty-one participants were included in the analysis [15 HC, 13 CF normal glucose tolerance (NGT), 41 CF abnormal glucose tolerance, and 12 CF related diabetes by OGTT]. There were no differences in age (13.6±3.5 years), sex, race, nor BMI z-score among groups. IGI was significantly lower in all CF groups, even CF NGT, compared to HC (p<0.0001). Table 1 presents correlations between CGM measures and IGI. Youth with CF, despite NGT by OGTT, have impairments in insulin secretion. Greater peak glucose, %time >140 mg/dl, and glucose variability (SD and MAGE), but not measures of average nor low glucose, on CGM correlate with declines in β-cell function. Further studies are needed to determine whether these CGM measures predict clinical decline in CF.
C.L. Chan: None. T.B. Vigers: None. L. Pyle: None. P. Zeitler: Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Janssen Research & Development, Merck & Co., Inc., Novo Nordisk Inc. K.J. Nadeau: None.
Cystic Fibrosis Foundation (CHAN16A0, CHAN16GE0); National Institutes of Health (DK094712-04)