Constant light during lactation programs circadian and metabolic systems

Area of Science:

• Chronobiology
• Developmental Biology
• Metabolic Health

Background:

• Circadian disruption from light at night is a risk factor for metabolic disease in adults.
• The developing circadian system is particularly vulnerable to light exposure, potentially leading to long-term programming effects.
• Lactation represents a critical developmental window where light-dark cycle disruptions may have lasting consequences.

Purpose of the Study:

• To investigate the short- and long-term effects of constant light (LL) exposure during lactation on the developing circadian system and metabolism in pups.
• To determine if disrupted light-dark cycles during early development can program long-term metabolic disorders.

Main Methods:

• Pups were exposed to constant light (LL) during lactation.
• Short-term effects on suprachiasmatic nucleus (SCN) cell populations (VIP, AVP, PER1) and physiological rhythms (activity, glucose, triglycerides) were assessed.
• Long-term effects were evaluated after pups were returned to standard light-dark (LD) conditions, assessing rhythmicity and metabolic parameters.

Main Results:

• Short-term LL exposure during lactation disrupted SCN rhythmicity and reduced VIP, AVP, and PER1 immunopositive cells.
• LL exposure led to immediate body weight gain and disrupted daily rhythms in activity, glucose, and triglycerides.
• Long-term, even after returning to LD cycles, disrupted rhythms in glucose and triglycerides persisted, with significantly increased mean triglyceride levels.

Conclusions:

• The light-dark cycle during early development plays a critical programming role in the maturation of the circadian system and metabolic regulation.
• Exposure to altered light environments during lactation poses a significant risk for long-term metabolic dysfunction in offspring.
• These findings highlight the importance of appropriate light-dark cycles for infant health, particularly in environments like neonatal intensive care units (NICUs).