Hormonal and metabolic responses to fasting and refeeding

Area of Science:

• Physiology
• Metabolism
• Neuroendocrinology

Background:

• Understanding the metabolic and neural regulation of feeding responses is crucial for metabolic health.
• The immediate post-prandial metabolic effects of refeeding after fasting are not fully elucidated.

Purpose of the Study:

• To define the sequential neural, humoral, and metabolic responses to a single meal in fasted rats.
• To investigate the mechanisms underlying the delayed metabolic response to refeeding.

Main Methods:

• Development of an experimental model involving refeeding 3-day fasted rats.
• Measurement of resting oxygen consumption as a metabolic endpoint.
• Utilizing pharmacological and endocrinological techniques to analyze hormonal and neural factors.

Main Results:

• Refeeding fasted rats induced a marked 24-hour delay in the post-prandial rise of resting oxygen consumption.
• This delay was attributed to a complex interplay of blood glucose, insulin, thyroid hormones, sympathetic activity, and brown fat function.
• Genetically obese rats failed to exhibit a post-prandial rise in oxygen consumption, linked to insulin insensitivity.

Conclusions:

• The metabolic response to refeeding after fasting is significantly delayed and involves intricate neuro-hormonal regulation.
• Insulin insensitivity plays a critical role in the blunted metabolic response observed in genetically obese rats.
• The ventromedial hypothalamus may be involved in mediating these post-prandial events.