Gonadal hormones influence core body temperature during calorie restriction

Area of Science:

• Endocrinology
• Metabolic Physiology
• Neuroendocrinology

Background:

• Calorie restriction (CR) triggers physiological adjustments in endotherms, including decreased core body temperature (T_b) and reduced energy expenditure.
• Previous research indicated a sex-dependent regulation of CR-induced hypothermia linked to central insulin-like growth factor receptor signaling.

Purpose of the Study:

• To investigate the specific contribution of sex hormones to the regulation of core body temperature during calorie restriction in wild-type mice.
• To determine the effects of gonadectomy and subsequent hormonal replacement (progesterone, 17-ß estradiol, 5-α dihydrotestosterone) on CR-induced hypothermia.

Main Methods:

• Core body temperature (T_b) was measured in gonadectomized (GNX) and hormone-replaced male and female C57BL6 mice under calorie restriction (CR).
• Hormonal replacement included progesterone (P4), 17-ß estradiol (E2), a combination of both (P4 + E2) in females, and 5-α dihydrotestosterone (5-α DHT) in males.

Main Results:

• Gonadectomy led to an earlier and more pronounced CR-induced hypothermia in both sexes.
• In females, 17-ß estradiol (E2) replacement fully prevented the hypothermic effects of CR, while progesterone (P4) had minimal impact alone or in combination with E2.
• In males, 5-α dihydrotestosterone (5-α DHT) showed only minor and transient effects in preventing T_b reduction during CR in gonadectomized mice.

Conclusions:

• Gonadal hormones play a crucial role in the sex-specific regulation of core body temperature and energy expenditure during periods of scarce nutrient availability.
• 17-ß estradiol is a key hormone in mediating female resistance to CR-induced hypothermia, whereas the role of androgens in males appears less significant.