Estradiol replacement enhances sweet taste preference in ovariectomized Rats: Interaction with energy intake...

Area of Science:

• Neuroendocrinology
• Behavioral Neuroscience
• Obesity Research

Background:

• Estrogens are known for homeostatic regulation of appetite and body weight.
• The influence of estrogens on hedonic (pleasure-driven) eating, especially sweet taste preference, is not well understood.

Purpose of the Study:

• To investigate the effect of estradiol replacement on the consumption of sweet solutions and overall energy intake in ovariectomized rats.
• To explore the role of micro-opioid receptors in mediating estrogen's effects on sweet taste preference and ingestive behavior.

Main Methods:

• Ovariectomized rats received estradiol replacement (E2 (+)) or no replacement (E2 (-)).
• Intake of sweetened solutions (artificial and natural sugars), water, and chow was measured.
• Naltrexone (NTX), a micro-opioid receptor antagonist, was administered to assess its impact.
• c-Fos expression in the nucleus accumbens shell was analyzed.

Main Results:

• Estradiol replacement increased the intake of various sweetened solutions, including non-caloric and caloric sweeteners.
• Food intake was reduced in the estradiol-replaced group, but total energy intake was only reduced with water, sucralose, and fructose (not glucose or sucrose).
• Naltrexone attenuated sucrose intake in the estradiol-replaced group and reduced food intake in the non-replaced group, suggesting differential roles of micro-opioid receptors.

Conclusions:

• Estrogen enhances sweet taste preference, potentially through micro-opioid pathways.
• The presence of palatable sugars like glucose or sucrose can diminish estrogen's effect on attenuating homeostatic energy intake.
• Micro-opioid receptors appear crucial for estrogen's enhancement of hedonic sweet preference and for homeostatic intake regulation in the absence of estrogen.