Clinical meaning
Understanding the detailed biochemistry of ketogenesis and osmotic diuresis is essential for the NP to anticipate clinical findings, guide management decisions, and recognize treatment complications. KETOGENESIS IN DKA: In the absence of insulin, hormone-sensitive lipase in adipose tissue is uninhibited, releasing massive quantities of free fatty acids (FFAs) into the bloodstream. FFAs are transported to hepatic mitochondria where they undergo beta-oxidation, producing acetyl-CoA. Normally, acetyl-CoA enters the citric acid cycle (TCA cycle), but in DKA, the TCA cycle is overwhelmed because oxaloacetate is diverted to gluconeogenesis (insulin deficiency de-represses PEPCK). The excess acetyl-CoA is shunted into the ketogenic pathway: 1. Two acetyl-CoA molecules condense to form acetoacetyl-CoA 2. HMG-CoA synthase (rate-limiting enzyme of ketogenesis, upregulated by glucagon and downregulated by insulin) converts acetoacetyl-CoA to HMG-CoA 3. HMG-CoA lyase cleaves HMG-CoA to acetoacetate (the first ketone body) 4. Acetoacetate is reversibly reduced to beta-hydroxybutyrate (the predominant ketone body, ratio 3:1 to 10:1 in DKA) or spontaneously decarboxylated to acetone (volatile — exhaled through the lungs, producing fruity breath) Beta-hydroxybutyrate and acetoacetate are strong organic acids (pKa ~4.7) that dissociate completely at...