
The primary substrates for ketone body formation are free fatty acids from adipose store. Increased hepatic ketone production and decreased peripheral tissue metabolism lead to acetoacetate accumulation in the blood. A small part is converted to acetone by spontaneous decarboxylation, but most is converted to 3-HB. Diabetes and alcohol consumption are the common causes of ketoacidosis. It has recently been shown that acetoacetate/3-hydroxybutyrate ratio in arterial blood reflects stages of liver failure.
When a sample is mixed with 3-HB R1, AcAc in the sample is broken down to acetone by acetoacetate decarboxylase (AADC). Upon addition of 3-HB R2, 3-HB in the sample is oxidized in the presence of 3-HBDH and Thio-NAD. This oxidation triggers the above cyclic reactions. Since the original AcAc in the sample has been removed, only 3-HB is assayed by measuring the rate of Thio-NADH production spectrophotometrically.
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Keywords: diabetes, alcoholism