Nutritional implications of cephalic phase thermogenic responses

Area of Science:

• Physiology
• Neuroendocrinology

Background:

• Feeding initiates a cephalic phase response, involving thermogenesis and hormonal changes.
• Sensory aspects of feeding, not just nutrient intake, stimulate this response.

Purpose of the Study:

• To investigate the neural and hormonal mechanisms underlying the cephalic thermogenic response to feeding.
• To elucidate the roles of the vagus nerve, insulin, catecholamines, and glucagon in this response.

Main Methods:

• Sham feeding and tube feeding were used to differentiate sensory from nutrient stimuli.
• Pharmacological interventions included vagal denervation, atropine, and adrenergic blockers.
• Hormonal levels (insulin, catecholamines, glucagon) and thermogenic response were measured.

Main Results:

• Sensory feeding and sham feeding elicited a thermogenic response with increased insulin, catecholamines, and glucagon.
• Vagal denervation or atropine blocked initial insulin release and reduced thermogenesis and norepinephrine release.
• Adrenergic blockers also reduced the response, but combined atropine and beta-blocker did not, suggesting a role for glucagon.

Conclusions:

• The cephalic thermogenic response to feeding is mediated by vagal and adrenergic pathways.
• Both sensory stimulation and hormonal factors like insulin, catecholamines, and potentially glucagon are involved.
• The interplay between cholinergic, adrenergic, and potentially glucagon pathways explains the complex thermogenic response.