The human disease beriberi is caused by a deficiency of thiamine in the diet. People with severe beriberi have higher than normal levels of pyruvate in their blood and urine. Explain this observation in terms of specific enzymatic reaction(s).

Thiamine also known as Vitamin B1 is essential for the synthesis of the cofactor thiamine pyrophosphate (TPP)
Pyruvate decarboxylation occurs in matrix of mitochondria and is an irreversible reaction catalysed by a multienzyme complex called pyruvate dehydogenase (PDH) complex
PDH complex consists of three different enzymes and require five coenzymes
TPP is the coenzyme of pyruvate dehydrogenase, which is concerned with the oxidative decarboxylation of pyruvate and generation of acetyl CoA
CoA and lipoic acid are coenzymes of dihydrolipoyl transacetylase or transferase which is concerned with condensation of acetyl group with coenzyme A and produce acetyl CoA
NAD+ and FAD are coenzymes of dihydrolipoyl dehydrogenase which is concerned with oxidation of lipoic acid and transfer electrons from lipoic acid to NAD+ via FAD
Without TPP pyruvate dehydrogenase complex cannot convert pyruvate into acetyl-CoA, so the pyruvate produced by glycolysis accumulates