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Why is there Lactic acidosis and Hyperuricemia in Glycogen storage disease?

Asked by Turco 

Glucose-6-Phosphate that accumulates is diverted to HMP shunt, leading to increased synthesis of ribose phosphates which increase the cellular levels of phosphoribosyl pyrophosphate and enhance the metabolism of purine nucleotides to uric acid.

Lactic acidosis arises from impairment of gluconeogenesis. Lactic acid is generated both in the liver and muscle and is oxidized by NAD+ to pyruvic acid and then converted via the gluconeogenic pathway to G6P. Accumulation of G6P inhibits conversion of lactate to pyruvate. The lactic acid level rises during fasting as glucose falls.

Uric acid competes with lactic acid and other organic acids for renal excretion in the urine. Diminished urine excretion due to higher lactic acid is another mechanism of hyperuricemia.