Hyperprolactinemia prevents short photoperiod-induced changes in brown fat

Area of Science:

• Endocrinology
• Metabolic Physiology
• Chronobiology

Background:

• Short photoperiod exposure is known to decrease prolactin levels.
• Changes in brown adipose tissue (BAT) and body composition are associated with photoperiod shifts.

Purpose of the Study:

• To investigate if decreased prolactin levels mediate the effects of short photoperiods on brown fat mass, thermogenic capacity, and carcass composition in golden hamsters.
• To determine the necessity of prolactin reduction for photoperiod-induced metabolic adaptations.

Main Methods:

• Male golden hamsters were exposed to short (10L:14D) or long (14L:10D) photoperiods for 4 or 10 weeks.
• Groups included sham-operated controls and hamsters with exogenous pituitary implants to manipulate prolactin levels (hyperprolactinemia).
• Measurements included circulating prolactin, brown fat mass, protein content, thermogenic capacity, and carcass composition (lipid content).

Main Results:

• After 4 weeks, short photoperiods increased carcass lipid content, an effect blunted by induced hyperprolactinemia.
• After 10 weeks, short photoperiods significantly reduced prolactin and increased brown fat mass, protein content, thermogenic capacity, and carcass fat.
• These 10-week short-photoperiod-induced metabolic changes were prevented or attenuated in hyperprolactinemic hamsters.

Conclusions:

• Decreased prolactin levels are a necessary mediator of short-photoperiod-induced increases in brown fat mass, protein content, and thermogenic capacity in golden hamsters.
• The results highlight the critical role of prolactin regulation in seasonal metabolic adaptations to photoperiod.