Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/131067
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Type: Journal article
Title: Effects of intragastric administration of L-tryptophan on the glycaemic response to a nutrient drink in men with type 2 diabetes - impacts on gastric emptying, glucoregulatory hormones and glucose absorption
Author: Hajishafiee, M.
Elovaris, R.A.
Jones, K.L.
Heilbronn, L.K.
Horowitz, M.
Poppitt, S.D.
Feinle-Bisset, C.
Citation: Nutrition and Diabetes, 2021; 11(1):3-3
Publisher: Nature Publishing Group
Issue Date: 2021
ISSN: 2044-4052
2044-4052
Statement of
Responsibility: 
Maryam Hajishafiee, Rachel A. Elovaris, Karen L. Jones, Leonie K. Heilbronn, Michael Horowitz, Sally D. Poppitt and Christine Feinle-Bisset
Abstract: BACKGROUND: The rate of gastric emptying and glucoregulatory hormones are key determinants of postprandial glycaemia. Intragastric administration of L-tryptophan slows gastric emptying and reduces the glycaemic response to a nutrient drink in lean individuals and those with obesity. We investigated whether tryptophan decreases postprandial glycaemia and slows gastric emptying in type 2 diabetes (T2D). METHODS: Twelve men with T2D (age: 63 ± 2 years, HbA1c: 49.7 ± 2.5 mmol/mol, BMI: 30 ± 1 kg/m2) received, on three separate occasions, 3 g ('Trp-3') or 1.5 g ('Trp-1.5') tryptophan, or control (0.9% saline), intragastrically, in randomised, double-blind fashion, 30 min before a mixed-nutrient drink (500 kcal, 74 g carbohydrates), containing 3 g 3-O-methyl-D-glucose (3-OMG) to assess glucose absorption. Venous blood samples were obtained at baseline, after tryptophan, and for 2 h post-drink for measurements of plasma glucose, C-peptide, glucagon and 3-OMG. Gastric emptying of the drink was quantified using two-dimensional ultrasound. RESULTS: Tryptophan alone stimulated C-peptide (P = 0.002) and glucagon (P = 0.04), but did not affect fasting glucose. In response to the drink, Trp-3 lowered plasma glucose from t = 15-30 min and from t = 30-45 min compared with control and Trp-1.5, respectively (both P < 0.05), with no differences in peak glucose between treatments. Gastric emptying tended to be slower after Trp-3, but not Trp-1.5, than control (P = 0.06). Plasma C-peptide, glucagon and 3-OMG increased on all days, with no major differences between treatments. CONCLUSIONS: In people with T2D, intragastric administration of 3 g tryptophan modestly slows gastric emptying, associated with a delayed rise, but not an overall lowering of, postprandial glucose.
Keywords: Humans
Diabetes Mellitus, Type 2
Obesity
Glucagon
Insulin
C-Peptide
3-O-Methylglucose
Glucose
Blood Glucose
Tryptophan
Drug Administration Routes
Double-Blind Method
Gastric Emptying
Intestinal Absorption
Postprandial Period
Beverages
Aged
Middle Aged
Male
Nutrients
Description: Published: 05 January 2021
Rights: © The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any mediumor format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changesweremade. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
DOI: 10.1038/s41387-020-00146-9
Grant ID: http://purl.org/au-research/grants/nhmrc/1158296
http://purl.org/au-research/grants/nhmrc/1103020
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