title: Relationship between whole-body macronutrient oxidative partitioning and pancreatic insulin secretion/β-cell function in non-diabetic humans.
abstract: BACKGROUND
  Glucose-stimulated insulin secretion correlates inversely with the degree of whole-body insulin sensitivity suggesting a crosstalk between peripheral organs and pancreas. Such sensing mechanism could be mediated by changes in glucose flux (uptake, oxidation or storage) in peripheral tissues that may drive insulin secretion.
  
  
  OBJECTIVE
  To relate whole-body non-protein respiratory quotient (npRQ), an index of macronutrient oxidative partitioning, with insulin secretion and β-cell function in non-diabetic individuals.
  
  
  METHODS
  Macronutrient oxidation was measured after an overnight fast and for 4h after a 75-g oral glucose tolerance test (OGTT) in 30 participants (15/15 males/females; 35±12y; 27±4kg/m(2)). Furthermore, npRQ was assessed for 24h in a metabolic chamber. Insulin secretion was estimated by deconvolution of serum C-peptide concentration (fasting and 4-h OGTT) and from 24-h urinary C-peptide excretion corrected for energy intake (metabolic chamber). β-Cell function parameters were obtained by mathematical modeling, while insulin sensitivity was determined by a euglycemic-hyperinsulinemic clamp (120mU·m(-2)·min(-1)).
  
  
  RESULTS
  Insulin secretion (from 24-h urinary C-peptide) correlated inversely with 24-h npRQ (r=-0.61; p=0.001), even after controlling for insulin sensitivity, energy balance, age and body mass index (r=-0.52; p=0.01). In turn, insulin secretion (from serum C-peptide) was not associated with fasting or OGTT npRQ. However, fasting npRQ was positively correlated with rate sensitivity (r=0.40; p<0.05) and marginally with glucose sensitivity (r=0.34; p=0.08).
  
  
  CONCLUSIONS
  Macronutrient oxidative partitioning, specifically glucose oxidation, might play a role on the regulation of insulin secretion. Further studies should aim at identifying the signals linking these processes.
authors.affiliation: Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile; UDA-Ciencias de la Salud, Carrera de Nutrición y Dietética, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. Electronic address: jgalgani@uc.cl.
authors.forename: Jose E
authors.initials: JE
authors.lastname: Galgani
authors.affiliation: Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Maria L
authors.initials: ML
authors.lastname: Mizgier
authors.affiliation: Istituto di Ingegneria Biomedica, Consiglio Nazionale delle Ricerche, Padova, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Mari
authors.affiliation: Pennington Biomedical Research Center, Baton Rouge, LA, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Ravussin
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009752:Nutritional Status; D010084:Oxidation-Reduction
chemical_list: D007328:Insulin
keywords: Glucose flux; Insulin resistance; Respiratory quotient; Skeletal muscle