An underexpression or knockout of the hormone leptin would most likely lead to which of the following outcomes?

• A. Enhanced insulin sensitivity
• B. Decreased appetite and weight loss
• C. Increased appetite and weight gain
• D. Increased metabolic rate

Answer: (C)

Verified step by step guidance

1. Understand the role of leptin: Leptin is a hormone primarily produced by adipose (fat) tissue. It plays a key role in regulating energy balance by inhibiting hunger, which in turn helps to regulate body weight.
2. Consider the effects of leptin underexpression or knockout: If leptin levels are reduced or absent, the body's ability to signal satiety (feeling full) is impaired. This can lead to increased hunger and food intake.
3. Relate leptin deficiency to weight gain: With increased appetite and food consumption, the body is likely to store more energy as fat, leading to weight gain over time.
4. Evaluate metabolic rate: Leptin also influences metabolic rate. A deficiency in leptin may reduce the body's ability to maintain a higher metabolic rate, further contributing to weight gain.
5. Rule out incorrect options: Enhanced insulin sensitivity and decreased appetite are inconsistent with leptin underexpression. Increased metabolic rate is also unlikely, as leptin deficiency typically lowers metabolic activity.