Microglia dictate the impact of saturated fat consumption on hypothalamic inflammation and neuronal function

Area of Science:

• Neuroscience
• Immunology
• Metabolism

Background:

• Diets high in saturated fats trigger inflammation, gliosis, and neuronal stress in the mediobasal hypothalamus (MBH).
• The specific cellular mechanisms and mediators of this hypothalamic response to saturated fatty acids (SFAs) remain unclear.

Purpose of the Study:

• To investigate the role of microglia in mediating diet-induced inflammation and neuronal stress in the MBH.
• To determine if microglia are the primary responders to SFAs in the hypothalamus and if their depletion impacts SFA-induced effects.

Main Methods:

• Mice were fed diets rich in saturated fatty acids (SFAs).
• Microglia and astrocytes in the MBH were analyzed for activation and accumulation.
• Enteric gavage with SFAs was used to mimic dietary effects.
• Primary microglial and astrocyte cultures were treated with SFAs.
• Microglia depletion was performed in vivo and in hypothalamic slices.
• Leptin signaling and food intake were measured after microglial depletion.

Main Results:

• High SFA diets led to microglial inflammatory activation and SFA accumulation in the MBH, alongside neuronal stress.
• Enteric SFA gavage reproduced microglial activation and neuronal stress; SFAs activated microglia but not astrocytes in culture.
• Depleting microglia abolished SFA-induced inflammation in hypothalamic slices and in vivo, reduced neuronal stress, enhanced leptin signaling, and decreased food intake.

Conclusions:

• Microglia are key mediators of inflammation and neuronal stress in the MBH in response to high saturated fat consumption.
• Microglia sense SFAs and orchestrate a hypothalamic inflammatory response that impairs neuronal function and alters appetite regulation.
• Targeting microglial activation in the MBH may offer therapeutic strategies for metabolic disorders associated with high-fat diets.