Ketogenesis and hyperketonemia

The Computational Acid-Base Chemistry of Hepatic Ketoacidosis

Opposing evidence exists for the source of the hydrogen ions (H⁺) during ketoacidosis. Organic and computational chemistry using dissociation constants and alpha equations for all pertinent ionizable metabolites were used to (1) document the atomic changes in the chemical reactions of ketogenesis and ketolysis and (2) identify the sources and quantify added fractional (~) H⁺ exchange (~H⁺e). All computations were performed for pH conditions spanning from 6.0 to 7.6. Summation of the ~H⁺e for given pH conditions for all substrates and products of each reaction of ketogenesis and ketolysis resulted in net reaction and pathway ~H⁺e coefficients, where negative revealed ~H⁺ release and positive revealed ~H⁺ uptake. Results revealed that for the liver (pH = 7.0), the net ~H⁺e for the reactions of ketogenesis ending in each of acetoacetate (AcAc), β-hydroxybutyrate (β-HB), and acetone were -0.9990, 0.0026, and 0.0000, respectively. During ketogenesis, ~H⁺ release was only evident for HMG CoA production, which is caused by hydrolysis and not ~H⁺ dissociation. Nevertheless, there is a net ~H⁺ release during ketogenesis, though this diminishes with greater proportionality of acetone production. For reactions of ketolysis in muscle (pH = 7.1) and brain (pH = 7.2), net ~H⁺ coefficients for β-HB and AcAc oxidation were -0.9649 and 0.0363 (muscle), and -0.9719 and 0.0291 (brain), respectively. The larger ~H⁺ release values for β-HB oxidation result from covalent ~H⁺ release during the oxidation-reduction. For combined ketogenesis and ketolysis, which would be the metabolic condition in vivo, the net ~H⁺ coefficient depends once again on the proportionality of the final ketone body product. For ketone body production in the liver, transference to blood, and oxidation in the brain and muscle for a ratio of 0.6:0.2:0.2 for β-HB:AcAc:acetone, the net ~H⁺e coefficients for liver ketogenesis, blood transfer, brain ketolysis, and net total (ketosis) equate to -0.1983, -0.0003, -0.2872, and -0.4858, respectively. The traditional theory of ketone bodies being metabolic acids causing systemic acidosis is incorrect. Summation of ketogenesis and ketolysis yield H⁺ coefficients that differ depending on the proportionality of ketone body production, though, in general, there is a small net H⁺ release during ketosis. Products formed during ketogenesis (HMG-CoA, acetoacetate, β-hydroxybutyrate) are created as negatively charged bases, not acids, and the final ketone body, acetone, does not have pH-dependent ionizable groups. Proton release or uptake during ketogenesis and ketolysis are predominantly caused by covalent modification, not acid dissociation/association. Ketosis (ketogenesis and ketolysis) results in a net fractional H⁺ release. The extent of this release is dependent on the final proportionality between acetoacetate, β-hydroxybutyrate, and acetone.

Measurement of the respiratory metabolism of the fowl

1. The occurrence of low respiratory quotients (RQ) in fowls and the reliability of oxygen consumption, carbon dioxide output and heat production data in indirect calorimetry were studied. 2. The RQ data from the gravimetric and the combined gravimetric-volumetric systems were essentially the same, while differences in O2 and CO2 between the systems were primarily due to variations in environmental temperature. 3. Fasting RQ was never less than 0.70 in these systems. 4. In the volumetric system the O2, CO2 and RQ data from the diaferometer were significantly different from the infra-red and paramagnetic analyses. 5. The CO2 values from the diaferometer were correct, but the O2 values were too low. In the specific analysers the reverse was seen, the paramagnetically-determined O2 values being correct and the CO2 values from infra-red analysis being too low. 6. Thus the fasting RQ values from the diaferometer were too high (0.762) and from the specific analysers too low (0.683).

[Metabolic differences between males and females and between normal and obese subjects during total fast]

In 24 normal and 24 obese subjects of both sexes circulating substrates (blood sugar, free fatty acids, ketone bodies) and hormones (insulin, growth hormone, pancreatic glucagon) were determined during 6 days of total fast. In normals the blood sugar fell to lower levels than in the obese. Plasma free fatty acids and ketone concentrations rose faster in normal than in obese subjects, and faster in females than in males. Plasma insulin concentrations declined to a greater extent in obese than in normal subjects. In all groups studied a significant increase of the pancreatic glucagon level within 1-3 days of fasting was observed, however, its rise occurred faster in normal females than in males. Growth hormone (GH) rose significantly in normal males but not in obese males. Following high overnight fasting values in some normal females showed no significant increase in GH levels but significantly higher GH values than obese females after 1-6 days of fasting. After summarizing starvation-induced metabolic changes common to all study groups the respective differences found between males and females and between normal and obese subjects are discussed.

Ketotic (idiopathic glucagon unresponsive) hypoglycaemia: diazoxide effects

Glucagon unresponsiveness in the fasting state characterizes a variety of hypoglycaemia with infrequent episodes usually occurring in the early morning with good health between attacks. Vomiting commonly accompanies the episodes. This variety of idiopathic hypoglycaemia has been called `ketotic hypoglycaemia', but ketonuria may be an inconsistent finding. 13 patients were compared to 8 contrast subjects with other varieties of hypoglycaemia and to 7 children without hypoglycaemia to confirm the abnormality of response to glucagon in the fasting state. 9 children were studied before and after treatment with diazoxide, 15 mg/kg per day for 3 days. 6 subjects experienced restoration of fasting glucagon response with diazoxide. The difference between responding and nonresponding subjects could either be due to variability in expression of the same metabolic defect or represent different defects in fasting energy metabolism.