Carbohydrates modulate opiate receptor mediated mechanisms during postprandial endocrine function

Area of Science:

• Gastroenterology
• Endocrinology
• Neuroscience

Background:

• Endogenous opiates play a role in regulating gastrointestinal hormone release.
• The influence of carbohydrates on opiate receptor-mediated hormonal responses is not fully understood.

Purpose of the Study:

• To investigate the role of carbohydrates in naloxone-induced opiate receptor blockade.
• To determine the effect of carbohydrates on postprandial somatostatin, insulin, and pancreatic polypeptide levels in response to protein and fat meals.

Main Methods:

• Conscious dogs were fed test meals containing protein (liver extract) or fat (corn oil) with or without carbohydrates (sucrose or intravenous glucose).
• Naloxone (an opiate receptor antagonist) or saline was administered with the test meals.
• Plasma levels of somatostatin, insulin, and pancreatic polypeptide were measured postprandially.

Main Results:

• Carbohydrates abolished naloxone's inhibitory effect on postprandial somatostatin in protein meals but stimulated somatostatin in fat meals.
• Naloxone augmented insulin secretion when carbohydrates were given with fat meals.
• Pancreatic polypeptide release was enhanced by naloxone when carbohydrates were combined with either protein or fat meals.

Conclusions:

• Oral or intravenous carbohydrates modulate the effects of endogenous opiates on postprandial somatostatin, insulin, and pancreatic polypeptide release in dogs.
• Carbohydrates appear to induce inhibitory mechanisms mediated via endogenous opiate receptors in this context.