Monosodium L-glutamate affects orthodontic outcomes by inhibiting hypothalamic-pituitary-gonadal axis function

Area of Science:

• Endocrinology
• Orthodontics
• Bone Biology

Background:

• Orthodontic treatment relies on bone remodeling regulated by the Osteoprotegerin (OPG)/Receptor Activator of nuclear factor Kappa-B Ligand (RANKL)/Receptor activator of nuclear factor Kappa-B (RANK) pathway.
• Monosodium L-glutamate (MSG) is known to disrupt the hypothalamic-pituitary-gonadal (HPG) axis and potentially affect bone metabolism.

Purpose of the Study:

• To investigate the impact of MSG-induced HPG axis disruption on orthodontic tooth movement and bone remodeling in a neonatal rat model.
• To assess hormonal changes, inflammatory markers, and bone structural alterations following MSG exposure.

Main Methods:

• Neonatal rats received MSG or saline injections.
• Hormone levels (GnRH, FSH, LH, estradiol, testosterone) and inflammatory cytokines (IL-6, IL-1β, TNF-α) were measured.
• Orthodontic tooth movement was induced, and OPG/RANKL ratio, osteoclast counts, and bone structure (Micro-CT) were analyzed.

Main Results:

• MSG significantly decreased sex hormone levels and the OPG/RANKL ratio, while increasing osteoclast numbers and cytokine expression, indicating heightened bone resorption.
• MSG-treated rats exhibited increased periodontal space, reduced bone volume fraction, and greater inter-molar distance, signifying accelerated tooth movement.
• HPG axis disruption by MSG demonstrably impacts bone metabolism and orthodontic outcomes.

Conclusions:

• MSG-induced HPG axis disruption alters bone metabolism and accelerates orthodontic tooth movement in rats.
• Hormonal imbalances play a critical role in modulating bone metabolism and tooth movement during orthodontic interventions.
• These findings suggest potential implications for managing orthodontic treatment in individuals with hormonal disruptions.