Leptin responsiveness in mice that ectopically express agouti protein

Area of Science:

• Endocrinology
• Neuroscience
• Obesity Research

Background:

• Agouti protein antagonizes melanocortin receptors (MCR3, MCR4), key in leptin's appetite regulation.
• Leptin signaling is crucial for controlling food intake and body weight.
• Agouti protein overexpression in BAPa mice causes obesity and diabetes, more severe in males.

Purpose of the Study:

• To investigate leptin's effects on energy balance in mice with ectopic agouti protein expression.
• To determine if leptin's action is dependent on the melanocortin system.

Main Methods:

• Administered leptin peripherally (intraperitoneal) and centrally (intracerebroventricular) to wild-type and BAPa mice.
• Monitored body weight, food intake, and energy expenditure.
• Compared responses between male and female mice, and between wild-type and BAPa genotypes.

Main Results:

• Peripheral leptin caused weight loss and reduced food intake in wild-type mice, with greater effects in males.
• Male BAPa mice showed resistance to peripheral leptin, while females lost weight.
• Central leptin injection induced body weight loss in all mice, with a more pronounced effect in female BAPa mice.
• Food intake suppression was delayed and recovered faster in BAPa mice compared to wild-type males, suggesting leptin impacts energy expenditure independently of the melanocortin system.

Conclusions:

• Leptin's effects on energy balance are not solely mediated by the melanocortin system.
• Agouti protein influences leptin sensitivity and energy expenditure.
• Sex differences exist in leptin's efficacy and the role of agouti protein.