title: Urinary C-peptide excretion: a novel alternate measure of insulin sensitivity in physiological conditions.
abstract: Insulin sensitivity (IS) is measured by the euglycemic-hyperinsulinemic clamp under a nonphysiological condition. Daily C-peptide urinary excretion may be a physiological index of IS, because C-peptide is co-secreted with insulin as a function of nutrient intake and IS. The amount of (2)H(2)O released from glycolytic glucose metabolism after [6,6-(2)H(2)]-glucose ingestion was recently proposed as a physiological measure of IS. We compared these IS surrogates to the gold standard (euglycemic-hyperinsulinemic clamp). Thirty (15 male/15 female) sedentary, nondiabetic participants (27.2 +/- 4.0 (s.d.) kg/m(2), 35 +/- 12 years) were admitted for 3 days to our in-patient unit. After a 10-h fast, they received 60 g of glucose and 15 g of [6,6-(2)H(2)]-glucose. Before glucose ingestion and hourly thereafter for 4 h, plasma glucose and insulin concentrations, and plasma deuterium enrichment were determined. Plasma (2)H(2)O production divided by insulin response was used as the glycolytic index. On day 2, subjects spent 23 h in a metabolic chamber (eucaloric diet, 50% carbohydrate, 30% fat). Urinary C-peptide excretion was divided by energy intake yielding the C-peptide to energy intake ratio (CPEP/EI). After leaving the chamber (day 3, 10-h fast), IS was measured by a 2-h clamp (120 mU/m(2)/min). Average IS (clamp) was 7.3 +/- 2.6 mg glucose/kg estimated metabolic body size/min (range: 3.6-13.2). These values were inversely correlated with CPEP/EI (r = -0.62; P < 0.01) and positively with the glycolytic rate (r = 0.60; P < 0.01). In nondiabetic subjects, two novel estimates of IS--daily urinary C-peptide urinary excretion and glycolytic rate during an oral glucose tolerance test --were related to IS by a clamp.
authors.affiliation: Pennington Biomedical Research Center, Baton Rouge, Louisiana, USA.
authors.forename: Jose E
authors.initials: JE
authors.lastname: Galgani
authors.forename: Lilian
authors.initials: L
authors.lastname: de Jonge
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Rood
authors.forename: Steven R
authors.initials: SR
authors.lastname: Smith
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Young
authors.forename: Eric
authors.initials: E
authors.lastname: Ravussin
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000652:urine; D002096:C-Peptide / Q000652:urine*; D003903:Deuterium / Q000032:analysis; D004032:Diet; D002149:Energy Intake; D005215:Fasting; D005260:Female; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D006019:Glycolysis / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance / Q000502:physiology*; D007553:Isotope Labeling; D008297:Male; D008875:Middle Aged; D057185:Sedentary Behavior; D014867:Water / Q000032:analysis; D055815:Young Adult
chemical_list: D015415:Biomarkers; D002096:C-Peptide; D007328:Insulin; D014867:Water; D003903:Deuterium; D005947:Glucose