Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/126451
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Type: Journal article
Title: Effects of L-phenylalanine on energy intake and glycaemia–impacts on appetite perceptions, gastrointestinal hormones and gastric emptying in healthy males
Author: Fitzgerald, P.C.E.
Manoliu, B.
Herbillon, B.
Steinert, R.E.
Horowitz, M.
Feinle-Bisset, C.
Citation: Nutrients, 2020; 12(6):1788-1-1788-17
Publisher: MDPI
Issue Date: 2020
ISSN: 2072-6643
2072-6643
Statement of
Responsibility: 
Penelope C.E. Fitzgerald, Benoit Manoliu, Benjamin Herbillon, Robert E. Steinert, Michael Horowitz, and Christine Feinle-Bisset
Abstract: In humans, phenylalanine stimulates plasma cholecystokinin (CCK) and pyloric pressures, both of which are important in the regulation of energy intake and gastric emptying. Gastric emptying is a key determinant of postprandial blood glucose. We evaluated the effects of intragastric phenylalanine on appetite perceptions and subsequent energy intake, and the glycaemic response to, and gastric emptying of, a mixed-nutrient drink. The study consisted of two parts, each including 16 healthy, lean males (age: 23 ± 1 years). In each part, participants received on three separate occasions, in randomised, double-blind fashion, 5 g (Phe-5 g) or 10g ('Phe-10 g) L-phenylalanine, or control, intragastrically, 30 min before a standardised buffet-meal (part A), or a standardised mixed-nutrient drink (part B). In part A, plasma CCK and peptide-YY (PYY), and appetite perceptions, were measured at baseline, after phenylalanine alone, and following the buffet-meal, from which energy intake was assessed. In part B, plasma glucose, glucagon-like peptide-1 (GLP-1), insulin and glucagon were measured at baseline, after phenylalanine alone, and for 2 h following the drink. Gastric emptying of the drink was also measured by ¹³C-acetate breath-test. Phe-10 g, but not Phe-5 g, stimulated plasma CCK (p = 0.01) and suppressed energy intake (p = 0.012); energy intake was correlated with stimulation of CCK (r = -0.4, p = 0.027), and tended to be associated with stimulation of PYY (r = -0.31, p = 0.082). Both Phe-10 g and Phe-5 g stimulated insulin and glucagon (all p < 0.05), but not GLP-1. Phe-10 g, but not Phe-5 g, reduced overall plasma glucose (p = 0.043) and peak plasma glucose (p = 0.017) in response to the mixed-nutrient drink. Phenylalanine had no effect on gastric emptying of the drink. In conclusion, our observations indicate that the energy intake-suppressant effect of phenylalanine is related to the stimulation of CCK and PYY, while the glucoregulatory effect may be independent of stimulation of plasma GLP-1 or slowing of gastric emptying.
Keywords: Food intake; appetite regulation; blood glucose control; postprandial; amino acid; cholecystokinin; peptide YY; glucagon-like peptide-1; insulin; gastric motility; humans
Rights: © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
DOI: 10.3390/nu12061788
Grant ID: http://purl.org/au-research/grants/nhmrc/1158296
http://purl.org/au-research/grants/nhmrc/1103020
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