The nutritional control of ghrelin secretion in humans: the effects of enteral vs. parenteral nutrition.
BACKGROUND
The nutritional control of ghrelin has not been fully clarified yet. Particularly, the influence of aminoacids and lipids is controversial and, moreover, whether the intraluminal gastric contact with nutrients is required or if the modulatory action of nutrients on ghrelin secretion is mediated by insulin is still matter of debate.


OBJECTIVE
To clarify the role of nutrients in the control of ghrelin secretion evaluating the effects of intravenous and oral lipids and aminoacids compared with glucose and fructose load in healthy subjects.


METHODS
A total of 6 healthy overnight-fasted volunteers underwent the following testing sessions: (a) iv arginine (ARG, 0.5 g/kg); (b) oral protein load (PRO, 50 g); (c) iv lipid-heparin infusion (Li He, Intralipid 10% 250 ml); (d) oral fat load (OIL, soy oil 40 g); (e) oral glucose load (OGL, 100 g); (f) oral fructose load (OFL, 100 g); (g) iv saline (SAL, 3 ml); (h) oral water load (WL, 200 ml). Total ghrelin, insulin, and glucose were assayed every 15 min from 0 up to +180 min.


RESULTS
WL and SAL did not modify insulin, glucose and ghrelin. ARG induced a prompt but transient increase (P < 0.05) of insulin and glucose (P < 0.01), without modifying ghrelin secretion. PRO induced a mild but sustained increase of insulin secretion (P < 0.05) without affecting glucose and ghrelin. Li-He progressively increased circulating glucose (P < 0.01) without modifying insulin and ghrelin secretion. No significant variations in circulating glucose, insulin, and ghrelin occurred after OIL. OGL significantly (P < 0.01) increased insulin and glucose levels and progressively decreased (P < 0.05) ghrelin levels. OFL induced a mild (P < 0.05) increase of insulin without modifying glucose levels. Similarly, OFL was followed by a milder decrease (P < 0.05) of ghrelin levels.


CONCLUSIONS
Differently from carbohydrates and independently from their modulatory effect on insulin secretion and glucose levels, both lipids and aminoacids play a negligible role in the acute control of ghrelin secretion either after acute enteral and parenteral administration.
Prodam
Flavia
F
Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Turin, c.so Dogliotti, 14 Turin, Italy.
Me
Elisa
E
Riganti
Fabrizio
F
Gramaglia
Elena
E
Bellone
Simonetta
S
Baldelli
Roberto
R
Rapa
Anna
A
van der Lely
Aart Jan
AJ
Bona
Gianni
G
Ghigo
Ezio
E
Broglio
Fabio
F
D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage / Q000378:metabolism; D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism*; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism; D004750:Enteral Nutrition; D005217:Fat Emulsions, Intravenous / Q000008:administration & dosage / Q000378:metabolism; D054439:Ghrelin; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D009747:Nutritional Physiological Phenomena / Q000502:physiology*; D010288:Parenteral Nutrition; D036361:Peptide Hormones / Q000378:metabolism*
D000596:Amino Acids; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005217:Fat Emulsions, Intravenous; D054439:Ghrelin; D007328:Insulin; D036361:Peptide Hormones