Question

Essential fructosuria is a defect in fructokinase whereas fructose intolerance is a defect in fructose 1 -phosphate aldolase. Which of these two diseases leads to severe hypoglycemia after ingestion of fructose, and why?

Short answer

Answer: Fructose intolerance leads to severe hypoglycemia after the ingestion of fructose because the deficiency in the enzyme fructose-1-phosphate aldolase causes the accumulation of fructose-1-phosphate in the liver. This accumulation leads to a decrease in available inorganic phosphate and glucose production, resulting in hypoglycemia. Essential fructosuria, on the other hand, is considered a benign condition and does not cause hypoglycemia.

Step-by-step solution

Understanding Essential Fructosuria

Essential fructosuria is a rare genetic disorder caused by a deficiency in the enzyme fructokinase, which is responsible for converting fructose to fructose-1-phosphate in the liver. Due to this enzyme deficiency, fructose is excreted in the urine instead of being utilized by the body for energy. This disorder is generally considered benign, as it does not lead to any serious health consequences. The individuals affected by essential fructosuria usually do not experience any symptoms or complications when they consume fructose.

Understanding Fructose Intolerance

Fructose intolerance, also known as hereditary fructose intolerance (HFI), is a genetic disorder caused by a deficiency in the enzyme fructose-1-phosphate aldolase. Unlike essential fructosuria, fructose intolerance can have severe consequences for the affected individual. When a person with fructose intolerance consumes fructose, it is still converted to fructose-1-phosphate in the liver, but due to the deficiency in fructose-1-phosphate aldolase, it cannot be further metabolized. As a result, fructose-1-phosphate accumulates in the liver, leading to a decrease in available inorganic phosphate and a subsequent decrease in glucose production.

Hypoglycemia in Fructose Intolerance

The decrease in available inorganic phosphate and glucose production caused by excessive fructose-1-phosphate in the liver can lead to severe hypoglycemia after the ingestion of fructose in individuals with fructose intolerance. Hypoglycemia is a condition characterized by low blood sugar levels, which can cause a range of symptoms such as dizziness, confusion, sweating, shaking, and even unconsciousness in severe cases.

Conclusion

Among the two diseases, essential fructosuria and fructose intolerance, it is fructose intolerance that leads to severe hypoglycemia after ingestion of fructose. This is because the deficiency in the enzyme fructose-1-phosphate aldolase causes the accumulation of fructose-1-phosphate in the liver, which in turn leads to a decrease in available inorganic phosphate and glucose production, resulting in hypoglycemia. On the other hand, essential fructosuria is considered a benign condition, as the deficiency in fructokinase only leads to the excretion of fructose in the urine without causing any serious health consequences or symptoms related to hypoglycemia.