In life-threatening starvation, the kidneys synthesize glucose by
Multiple Choice
contributing to calcium homeostasis
producing uric acid
secreting erythropoietin
secreting renin
deaminating amino acids
The Correct Answer and Explanation is:
Correct Answer: Deaminating amino acids
Explanation:
In situations of life-threatening starvation, the body must find alternative energy sources to maintain essential functions, particularly for organs like the brain that rely heavily on glucose. During prolonged starvation, the body’s glycogen stores are depleted within 24 hours, and gluconeogenesis (the process of generating glucose from non-carbohydrate sources) becomes the primary way to maintain blood glucose levels.
The kidneys play an important role in gluconeogenesis during prolonged fasting or starvation, second only to the liver. One of the key processes involved in gluconeogenesis in the kidney is the deamination of amino acids.
What is Deamination?
Deamination is the removal of the amino group (-NH₂) from amino acids. This process occurs in the liver and kidneys, producing ammonia (which is then converted to urea and excreted) and a carbon skeleton. The remaining carbon backbone can then be converted into glucose through the gluconeogenic pathway.
For example:
- The amino acid alanine can be deaminated and converted into pyruvate, which then enters the gluconeogenesis pathway to produce glucose.
- Glutamine, an abundant amino acid in the bloodstream during starvation, is taken up by the kidneys, deaminated, and used for gluconeogenesis.
Why is this Critical During Starvation?
During life-threatening starvation:
- Protein catabolism increases, releasing amino acids into circulation.
- The kidneys increase gluconeogenesis to help sustain blood glucose levels, especially for the brain and red blood cells, which require glucose.
- This helps prevent hypoglycemia and maintains acid-base balance, since the kidneys can also excrete the resulting ammonium (NH₄⁺), aiding in pH regulation.
Why the Other Options Are Incorrect:
- Contributing to calcium homeostasis: Important but not related to glucose synthesis.
- Producing uric acid: A waste product of purine metabolism, not involved in glucose production.
- Secreting erythropoietin: Stimulates red blood cell production, not gluconeogenesis.
- Secreting renin: Regulates blood pressure, not glucose synthesis.
Conclusion:
The kidneys contribute to glucose synthesis in starvation by deaminating amino acids, allowing for the generation of glucose to support vital organs.