title: Indices of insulin secretion during a liquid mixed-meal test in obese youth with diabetes.
abstract: OBJECTIVE
  To compare indices of insulin secretion, insulin sensitivity (IS), and oral disposition index (oDI) during the liquid mixed-meal test in obese youth with clinically diagnosed type 2 diabetes mellitus (T2DM) and negative autoantibodies (Ab(-)) versus those with T2DM and positive autoantibodies (Ab(+)) to examine whether differences in β-cell function can be detected between the 2 groups.
  
  
  METHODS
  Twenty-seven youth with Ab(-) and 15 youth with Ab(+) clinically diagnosed T2DM underwent a mixed-meal test (Boost; 55% carbohydrate, 25% protein, and 20% fat). Fasting and mixed-meal-derived insulin and C-peptide indices of IS, secretion (30-minute insulinogenic [ΔI(30)/ΔG(30)] and C-peptide [ΔC(30)/ΔG(30)]), and oDI were calculated.
  
  
  RESULTS
  Indices of insulin secretion were ~40%-50% lower in patients with Ab(+) T2DM compared with those with Ab(-) T2DM. After controlling for body mass index, ΔI(30)/ΔG(30), ΔC(30)/ΔG(30), C-peptide area under the curve (AUC)/glucose AUC, and insulin AUC/glucose AUC were significantly (P < .05) lower in the Ab(+) group compared with the Ab(-) group. Sensitivity indices were significantly higher in the Ab(+) group. The oDI, 1/fasting insulin × ΔI(30)/ΔG(30) (0.04 ± 0.02 vs 0.12 ± 0.02 mg/dL(-1); P = .005), and 1/fasting C-peptide × ΔC(30)/ΔG(30) (0.02 ± 0.009 vs 0.05 ± 0.006 mg/dL(-1); P = .018) were lower in the Ab(+) group. Receiver operating characteristic curve analyses revealed that fasting C-peptide <3.2 ng/mL had 87% sensitivity and 74% specificity and ΔC(30)/ΔG(30) <0.075 ng/mL per mg/dL had 93% sensitivity and 80% specificity for identifying youth with Ab(+) T2DM.
  
  
  CONCLUSIONS
  During a liquid mixed-meal test, indices of β-cell function were lower and IS was higher in patients with Ab(+) T2DM versus those with Ab(-) T2DM, with high sensitivity and specificity for fasting and stimulated C-peptide as markers of Ab(+) status. Indices of insulin secretion during this standardized mixed-meal test could be used to assess β-cell function in therapeutic trials of β-cell restoration in youth with T2DM.
authors.affiliation: Division of Weight Management and Wellness, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA, USA. fbacha@bcm.edu
authors.forename: Fida
authors.initials: F
authors.lastname: Bacha
authors.forename: Neslihan
authors.initials: N
authors.lastname: Gungor
authors.forename: Sojung
authors.initials: S
authors.lastname: Lee
authors.forename: Javier
authors.initials: J
authors.lastname: de las Heras
authors.forename: Silva
authors.initials: S
authors.lastname: Arslanian
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000032:analysis*; D002096:C-Peptide / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D000078790:Insulin Secretion; D008297:Male; D062407:Meals; D009765:Obesity / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin