Leptin-sensitive sensory nerves innervate white fat

Area of Science:

• Neuroscience
• Endocrinology
• Adipose Tissue Biology

Background:

• Leptin, a key adipokine from white adipose tissue (WAT), is traditionally viewed as a systemic signal of lipid reserves to the brain.
• White adipose tissue exhibits fat pad-specific (FPS) responses, questioning the capacity of systemic signals like leptin to convey localized information.
• Sensory innervation of WAT suggests a potential pathway for transmitting localized physiological data.

Purpose of the Study:

• To investigate whether leptin acts as a paracrine factor activating sensory nerves within white adipose tissue.
• To determine if leptin signaling in WAT can provide the brain with fat pad-specific information.

Main Methods:

• Immunohistochemical detection of the long-form leptin receptor (Ob-Rb) on dorsal root ganglia (DRG) neurons retrogradely labeled from inguinal WAT (IWAT).
• Measurement of nerve spike rate in IWAT following intra-IWAT leptin injections.
• Assessment of c-Fos immunoreactivity (ir) in DRG neurons after leptin administration.

Main Results:

• The long form of the leptin receptor (Ob-Rb) was found on sensory neurons innervating IWAT.
• Leptin injections into IWAT significantly increased nerve spike rate within minutes.
• Intra-IWAT leptin induced c-Fos immunoreactivity in sensory neurons, indicating neural activation.
• Systemic leptin injection did not activate central targets (DRG, arcuate nucleus).

Conclusions:

• Endogenous leptin acts as a paracrine factor within white adipose tissue.
• Leptin activates spinal sensory nerves innervating WAT, suggesting a local signaling role.
• This paracrine leptin action may convey fat pad-specific information via sensory pathways.