title: Effect of low- and high-glycemic load on circulating incretins in a randomized clinical trial.
abstract: OBJECTIVE
  Low-glycemic load diets lower post-prandial glucose and insulin responses; however, the effect of glycemic load on circulating incretin concentrations is unclear. We aimed to assess effects of dietary glycemic load on fasting and post-prandial glucose, insulin and incretin (i.e., glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1)) concentrations and to examine for effect modification by adiposity.
  
  
  METHODS
  We conducted a single-center, randomized controlled crossover feeding trial in which a subset of participants had post-prandial testing. Participants were recruited from the local Seattle area. We enrolled 89 overweight-obese (BMI 28.0-39.9 kg/m(2)) and lean (BMI 18.5-25.0 kg/m(2)) healthy adults. Participants consumed two 28-day, weight-maintaining high- and low-glycemic load controlled diets in random order. Primary outcome measures were post-prandial circulating concentrations of glucose, insulin, GIP and GLP-1, following a test breakfast.
  
  
  RESULTS
  Of the 80 participants completing both diet interventions, 16 had incretin testing and comprise the group for analyses. Following each 28-day high- and low-glycemic load diet, mean fasting concentrations of insulin, glucose, GIP and GLP-1 were not significantly different. Mean integrated post-prandial concentrations of glucose, insulin and GIP were higher (1504±476 mg/dL/min, p<0.01; 2012±644 μU/mL/min, p<0.01 and 15517±4062 pg/mL/min, p<0.01, respectively) and GLP-1 was lower (-81.6±38.5 pmol/L/min, p<0.03) following the high-glycemic load breakfast as compared to the low-glycemic load breakfast. Body fat did not significantly modify the effect of glycemic load on metabolic outcomes.
  
  
  CONCLUSIONS
  High-glycemic load diets in weight-maintained healthy individuals lead to higher post-prandial GIP and lower post-prandial GLP-1 concentrations. Future studies evaluating dietary glycemic load manipulation of incretin effects would be helpful for establishing diabetes nutrition guidelines.
authors.affiliation: Department of Medicine, Division of Endocrinology, Metabolism and Nutrition, University of Washington, Seattle, WA 98195, USA.
authors.forename: Shauna S
authors.initials: SS
authors.lastname: Runchey
authors.forename: Liisa M
authors.initials: LM
authors.lastname: Valsta
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Schwarz
authors.forename: Chiachi
authors.initials: C
authors.lastname: Wang
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Song
authors.forename: Johanna W
authors.initials: JW
authors.lastname: Lampe
authors.forename: Marian L
authors.initials: ML
authors.lastname: Neuhouser
mesh_terms: D050154:Adiposity / Q000502:physiology; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D062408:Breakfast; D018592:Cross-Over Studies; D004032:Diet; D005260:Female; D005749:Gastric Inhibitory Polypeptide / Q000097:blood / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1 / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism; D008297:Male; D009765:Obesity / Q000097:blood / Q000378:metabolism*; D019518:Postprandial Period; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1