title: Dietary proteins contribute little to glucose production, even under optimal gluconeogenic conditions in healthy humans.
abstract: Dietary proteins are believed to participate significantly in maintaining blood glucose levels, but their contribution to endogenous glucose production (EGP) remains unclear. We investigated this question using multiple stable isotopes. After overnight fasting, eight healthy volunteers received an intravenous infusion of [6,6-²H₂]-glucose. Two hours later, they ingested four eggs containing 23 g of intrinsically, uniformly, and doubly [¹⁵N]-[¹³C]-labeled proteins. Gas exchanges, expired CO₂, blood, and urine were collected over the 8 h following egg ingestion. The cumulative amount of dietary amino acids (AAs) deaminated over this 8-h period was 18.1 ± 3.5%, 17.5% of them being oxidized. The EGP remained stable for 6 h but fell thereafter, concomitantly with blood glucose levels. During the 8 h after egg ingestion, 50.4 ± 7.7 g of glucose was produced, but only 3.9 ± 0.7 g originated from dietary AA. Our results show that the total postprandial contribution of dietary AA to EGP was small in humans habituated to a diet medium-rich in proteins, even after an overnight fast and in the absence of carbohydrates from the meal. These findings question the respective roles of dietary proteins and endogenous sources in generating significant amounts of glucose in order to maintain blood glucose levels in healthy subjects.
authors.affiliation: Institut National de Recherche Agronomique, Centre de Recherche en Nutrition Humaine d'Ile-de-France, UMR914 Nutrition Physiology and Ingestive Behaviour, Paris, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Fromentin
authors.forename: Daniel
authors.initials: D
authors.lastname: Tomé
authors.forename: Françoise
authors.initials: F
authors.lastname: Nau
authors.forename: Laurent
authors.initials: L
authors.lastname: Flet
authors.forename: Catherine
authors.initials: C
authors.lastname: Luengo
authors.forename: Dalila
authors.initials: D
authors.lastname: Azzout-Marniche
authors.forename: Pascal
authors.initials: P
authors.lastname: Sanders
authors.forename: Gilles
authors.initials: G
authors.lastname: Fromentin
authors.forename: Claire
authors.initials: C
authors.lastname: Gaudichon
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000032:analysis* / Q000096:biosynthesis; D002247:Carbon Isotopes; D003641:Deamination; D003903:Deuterium; D050528:Diet, Carbohydrate-Restricted; D004038:Diet, Reducing; D004044:Dietary Proteins / Q000378:metabolism*; D004527:Egg Proteins / Q000378:metabolism; D005260:Female; D005943:Gluconeogenesis; D050261:Glycogenolysis; D006801:Humans; D008099:Liver / Q000378:metabolism; D008297:Male; D009587:Nitrogen Isotopes; D019518:Postprandial Period; D059748:Proteolysis; D055815:Young Adult
chemical_list: D000596:Amino Acids; D001786:Blood Glucose; D002247:Carbon Isotopes; D004044:Dietary Proteins; D004527:Egg Proteins; D009587:Nitrogen Isotopes; D003903:Deuterium