Ghrelin and Leptin: Key Regulators of Appetite and Energy Balance - Hunger Hormone

By SWA

Ghrelin:

  • Role: Ghrelin, often called the "hunger hormone," is produced in the stomach and signals the brain to increase appetite.
  • Mnemonic: "GhRelin—— GROW big" reminds us of its role in stimulating hunger and promoting food intake.

Leptin:

  • Role: Leptin, known as the "satiety hormone," is produced by adipose (fat) cells and signals the brain to reduce appetite.
  • Mnemonic: "LepTin—-Thin" highlights its function in suppressing hunger and maintaining a healthy body weight.

The Paradox of Leptin Resistance

Leptin Resistance:

  • Definition: Leptin resistance occurs when the brain does not respond effectively to leptin signals despite high levels of the hormone, commonly seen in obesity.
  • Effect: The brain continues to signal hunger, leading to increased food intake and weight gain despite adequate or excessive fat stores.
  • Paradox: Despite high leptin levels (which should promote satiety and reduce appetite), individuals with leptin resistance continue to feel hungry and overeat, leading to further weight gain.

Related Hormones and Their Interactions

1. Insulin:

  • Role: Regulates blood sugar levels by facilitating glucose uptake into cells.
  • Interaction: Chronic high insulin levels can contribute to leptin resistance. Insulin resistance often coexists with leptin resistance, exacerbating appetite regulation issues.

2. Adiponectin:

  • Role: Enhances insulin sensitivity, reduces inflammation, and protects against cardiovascular disease.
  • Interaction: Lower levels in obese individuals, inversely correlated with body fat. High adiponectin is associated with improved metabolic profiles, contrasting with leptin resistance.

3. Cortisol:

  • Role: Regulates metabolism, stress responses, and immune function.
  • Interaction: Elevated cortisol levels increase ghrelin levels and affect leptin sensitivity, contributing to weight gain and leptin resistance.

4. Peptide YY (PYY):

  • Role: Reduces appetite by signaling satiety to the brain.
  • Interaction: PYY levels increase post-meal, counteracting ghrelin’s effects and working synergistically with leptin. Blunted PYY response in obesity contributes to appetite regulation difficulties.

5. Glucagon-Like Peptide-1 (GLP-1):

  • Role: Enhances insulin secretion, inhibits glucagon release, and slows gastric emptying, promoting satiety.
  • Interaction: Reduces appetite, complementing leptin's role. GLP-1 analogs are used to treat type 2 diabetes and obesity due to their appetite-suppressing effects.

6. Cholecystokinin (CCK):

  • Role: Promotes satiety in response to food intake, especially fats and proteins.
  • Interaction: Signals the brain to reduce appetite and suppresses ghrelin secretion, working with leptin to regulate short-term food intake.

Summary

The regulation of appetite and energy balance is a complex interplay between multiple hormones. Ghrelin and leptin are central to this system, with ghrelin stimulating hunger and leptin promoting satiety. However, in conditions like leptin resistance, this balance is disrupted, leading to increased appetite and weight gain despite high leptin levels. Understanding these hormonal interactions provides insight into potential treatments for obesity and metabolic disorders, aiming to restore normal hormonal function.

Reference

For further reading on the interactions between these hormones and their role in energy balance, see the following sources:

  • Friedman, J. M., & Halaas, J. L. (1998). Leptin and the regulation of body weight in mammals. Nature, 395(6704), 763-770.
  • Kojima, M., Hosoda, H., Date, Y., Nakazato, M., Matsuo, H., & Kangawa, K. (1999). Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature, 402(6762), 656-660.
  • Ahima, R. S., & Flier, J. S. (2000). Leptin. Annual Review of Physiology, 62(1), 413-437.
  • Rosenbaum, M., & Leibel, R. L. (2014). 20 years of leptin: Role of leptin in energy homeostasis in humans. The Journal of Endocrinology, 223(1), T83-T96.
  • Tschöp, M., Smiley, D. L., & Heiman, M. L. (2000). Ghrelin induces adiposity in rodents. Nature, 407(6806), 908-913.

These references provide a foundational understanding of the roles and interactions of ghrelin, leptin, and related hormones in the regulation of appetite and body weight.

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