Model of the kinetics of ketone bodies in humans

1982 ◽  
Vol 243 (1) ◽  
pp. R7-R17 ◽  
Author(s):  
C. Cobelli ◽  
R. Nosadini ◽  
G. Toffolo ◽  
A. McCulloch ◽  
A. Avogaro ◽  
...  
Keyword(s):  
Ketone Body ◽  
Specific Activity ◽  
Ketone Bodies ◽  
Mathematical Representation ◽  
Parameter Estimates ◽  
Extrahepatic Tissues ◽  
Body Compartments ◽  
Body Production ◽  
Kinetics Of

The kinetics of ketone bodies was studied in normal humans by giving a combined bolus intravenous injection of labeled acetoacetate ([14C]AcAc) and D(--)-beta-hydroxybutyrate (beta-[14C]-OHB) to seven subjects after an overnight fast, on two different occasions, and by collecting frequent blood samples for 100 min. Kinetic data were analyzed with both noncompartmental and compartmental modeling techniques. A four-compartment model, representing AcAc and beta-OHB in blood and two equilibrating ketone body compartments, inside the liver and extrahepatic tissues, was chosen as the most reliable mathematical representation; it is physiologically plausible and was able to accurately fit the data. The model permitted evaluation of the in vivo rate of ketone body production in the liver, the individual plasma clearance rates of AcAc and beta-OHB, their initial volumes of distribution, and the transfer rate parameters among the four ketone body compartments. Moreover, the model provided estimates of the components of the rates of appearance of AcAc and beta-OHB in plasma due to newly synthesized ketone body from acetyl-CoA in the liver, and to interconversion and recycling in the liver and extrahepatic tissues. The model also was used to evaluate other methodologies currently employed in the analysis of ketone body turnover data: the conventional approach based on use of the combined specific activity of AcAc and beta-OHB required assumptions not satisfied in vivo, leading to substantial errors in key parameter estimates.

Pseudoketogenesis in hepatectomized dogs

1990 ◽  
Vol 258 (3) ◽  
pp. E519-E528 ◽  
Author(s):  
C. Des Rosiers ◽  
J. A. Montgomery ◽  
M. Garneau ◽  
F. David ◽  
O. A. Mamer ◽  
...  
Keyword(s):  
Bolus Injection ◽  
Specific Activity ◽  
Ketone Bodies ◽  
Gas Chromatography Mass Spectrometry ◽  
Selected Ion Monitoring ◽  
Coa Transferase ◽  
Net Uptake ◽  
Extrahepatic Tissues ◽  
Molar Percent

Overestimation of ketone body turnover in vivo, measured by tracer kinetics, could occur if specific activity or molar percent enrichment is diluted in extrahepatic tissues by label exchange via reversal of 3-oxoacid-CoA transferase, a process we call pseudoketogenesis. To test this hypothesis, euglycemic hepatectomized dogs were injected with a bolus of acetoacetate (0.8 mmol/kg), 32% enriched in [3,4-13C2]acetoacetate. Concentrations and labeling patterns of blood acetoacetate and R-3-hydroxybutyrate were measured by selected ion-monitoring gas chromatography-mass spectrometry. During the 60 min after bolus injection of [3,4-13C2]acetoacetate, the molar percent enrichment of blood [3,4-13C2]acetoacetate decreased to 73 +/- 3% (n = 5) in controls and to 11.5 +/- 0.8% (n = 3) during infusion of dichloroacetate, an activator of pyruvate dehydrogenase. The enrichment of R-3-hydroxy-[3,4-13C2]butyrate followed closely that of [3,4-13C2]acetoacetate. These dilutions occurred despite a net uptake of ketone bodies. Concomitantly, 10.6 +/- 2.2 (n = 5) and 6.0 +/- 2.9% (n = 3) of [13C]acetoacetate molecules were labeled on all four carbons in control and dichloroacetate-treated dogs, respectively. This uniformly labeled acetoacetate arises from partial equilibration between [3,4-13C2]acetoacetate and [1,2-13C2]acetyl-CoA via the reactions catalyzed by 3-oxoacid-CoA transferase and acetoacetyl-CoA thiolase. Our data demonstrate the reversibility of the 3-oxoacid-CoA transferase in intact extrahepatic tissues and support the concept of pseudoketogenesis. This phenomenon has been quantitated by kinetic analysis of the data.

scholarly journals A double-isotope method for the measurement of ketone-body turnover in the rat. Effect of l-alanine

1984 ◽  
Vol 219 (1) ◽  
pp. 15-24 ◽  
Author(s):  
W D Reed ◽  
P J Baab ◽  
R L Hawkins ◽  
P T Ozand
Keyword(s):  
Amino Acids ◽  
Ketone Body ◽  
Ketone Bodies ◽  
Isotope Method ◽  
Significant Change ◽  
Kinetics Of ◽  
Double Isotope

The synthesis of 4-3H-labelled ketone bodies, and their use along with 14C-labelled ketone-body precursors, is employed using an ‘in vivo’ rat infusion model to measure ketone-body turnover. The use of two isotopes is necessary to measure ketone-body turnover when ketogenesis may occur from more than one precursor such as glucose and fatty or amino acids. Requirements of isotopic equivalence in terms of metabolic similarity, valid stoichiometry and the lack of differences in the kinetics of relevant enzymes is demonstrated for the 4-3H- and 14C-labelled ketone bodies. The hypoketonaemic effect of L-alanine is shown by two distinct phases after the administration of L-alanine. During the first 12 min after alanine administration ther was a 50% decrease in acetoacetate and a 30% decrease in 3-hydroxybutyrate production, with no significant change in the utilization of either compound. The hypoketonaemic action of alanine during the following 16 min was primarily associated with an uptake of 3-hydroxybutyrate that was somewhat greater than the increase in its production. There were essentially equivalent decreases in production and utilization of acetoacetate, resulting in no significant net change in the level of this ketone body in the blood.

Validation of two-pool model for in vivo ketone body kinetics

1990 ◽  
Vol 258 (5) ◽  
pp. E850-E855 ◽  
Author(s):  
J. W. Bailey ◽  
M. W. Haymond ◽  
J. M. Miles
Keyword(s):  
Ketone Body ◽  
Ketone Bodies ◽  
Accurate Estimate ◽  
Isotope Data ◽  
Pool Model ◽  
Body Production ◽  
Beta Hydroxybutyrate

Previous studies have indicated that simultaneous infusions of two ketone body tracers ([13C]acetoacetate and [14C]beta-hydroxybutyrate) provide accurate estimates of exogenous ketone body inflow when an open two-pool model is employed. In the present studies, net hepatic ketone body production was determined from surgically placed arterial, portal venous, and hepatic venous catheters in conscious diabetic (n = 6) and 4-day fasted (n = 7) dogs. [13C]acetoacetate and [14C]beta-hydroxybutyrate were infused simultaneously, and ketone body production was calculated from either acetoacetate (AcAc) single-isotope data, beta-hydroxybutyrate (beta-OHB) single-isotope data, the sum of individual fluxes, or the two-pool model. In fasted animals, both the AcAc single-isotope calculation and the sum of individual fluxes overestimated net hepatic production by approximately 50% (P less than 0.05), whereas the beta-OHB single-isotope calculation and the two-pool model gave accurate estimates. In the diabetic animals, the beta-OHB single-isotope calculation underestimated net hepatic production by approximately 30% (P less than 0.05). The sum of individual fluxes overestimated net hepatic production by approximately 46% (P less than 0.05), whereas both the AcAc single-isotope calculation and the two-pool model gave accurate estimates. In conclusion, single-isotope methods give erroneous estimates of net hepatic production of ketone bodies. In contrast, a two-pool model provided an accurate estimate of net hepatic production and thus appears to be suitable for determination of ketone body kinetics in humans.

Validation of a tracer technique to determine nonsteady-state ketone body turnover rates in man

1981 ◽  
Vol 240 (3) ◽  
pp. E253-E262 ◽  
Author(s):  
U. Keller ◽  
G. E. Sonnenberg ◽  
W. Stauffacher
Keyword(s):  
Ketone Body ◽  
Specific Activity ◽  
Ketone Bodies ◽  
Compartment Model ◽  
Volume Of Distribution ◽  
Turnover Rates ◽  
Production Rates ◽  
Nonsteady State ◽  
Body Production ◽  
Beta Hydroxybutyrate

The features of a single-compartment model of total ketone bodies were evaluated using primed constant infusions of [3-14C]acetoacetate (AcAc) and of D-[3-14C]beta-hydroxybutyrate (beta OHB) in 12 postabsorptive subjects. The volume of distribution (VD) of AcAc was 0.18 +/- 0.01 liter/kg (n = 9), and that of beta OHB was similar, 0.18 +/- 0.02 liter/kg (n = 3). The production rate of total ketone bodies was calculated using the combined specific activity of AcAc and of beta OHB. The mean basal total ketone body production rates were similar using either [14C]AcAc (6.5 mumol . kg-1 . min-1) or [14C]beta OHB (6.8 mumol . kg-1 . min-1). To determine the pool fraction that was rapidly mixed during nonsteady state of ketone body inflow, unlabeled AcAc was infused with stepwise increasing and decreasing rates between 5 and 25 mumol . kg-1 . m-1 to mimic nonsteady-state ketone body production rates. The "functional" pool fraction P was determined as the pool fraction that provided the best match between tracer-determined rates of ketone production and rates of AcAc infusion. P of total ketone bodies was almost equal to 1 using either [14C]AcAc (1.05 +/- 0.16) or [14C]beta OHB (1.00 +/- 0.06), suggesting rapid mixing of ketone bodies throughout the entire pool. The described pool model may be used to determine total ketone body kinetics during acute perturbations of the steady state.

A dual-isotope technique for determination of in vivo ketone body kinetics

1986 ◽  
Vol 251 (2) ◽  
pp. E185-E191 ◽  
Author(s):  
J. M. Miles ◽  
W. F. Schwenk ◽  
K. L. McClean ◽  
M. W. Haymond
Keyword(s):  
Ketone Body ◽  
Specific Activity ◽  
Ketone Bodies ◽  
Turnover Rates ◽  
Dual Isotope ◽  
Pool Model ◽  
Isotope Technique ◽  
Beta Hydroxybutyrate

"Total ketone body specific activity" has been widely used in studies of ketone body metabolism to circumvent so-called "isotope disequilibrium" between the two major ketone body pools, acetoacetate and beta-hydroxybutyrate. Recently, this approach has been criticized on theoretical grounds. In the present studies, [13C]acetoacetate and beta-[14C]hydroxybutyrate were simultaneously infused in nine mongrel dogs before and during an infusion of either unlabeled sodium acetoacetate or unlabeled sodium beta-hydroxybutyrate. Ketone body turnover was determined using total ketone body specific activity, total ketone body moles % enrichment, and an open two-pool model, both before and during the exogenous infusion of unlabeled ketone bodies. Basal ketone body turnover rates were significantly higher using [13C]acetoacetate than with either beta-[14C]hydroxybutyrate alone or the dual-isotope model (3.6 +/- 0.5 vs. 2.2 +/- 0.2 and 2.7 +/- 0.2 mumol X kg-1 X min-1, respectively, P less than 0.05). During exogenous infusion of unlabeled sodium acetoacetate, the dual-isotope model provided the best estimate of ketone body inflow, whereas 14C specific activity underestimated the known rate of acetoacetate infusion by 55% (P less than 0.02). During sodium beta-hydroxybutyrate infusion, [13C]-acetoacetate overestimated ketone body inflow by 55% (P = NS), while better results were obtained with 14C beta-hydroxybutyrate alone and the two-pool model. Ketone body interconversion as estimated by the dual-isotope technique increased markedly during exogenous ketone body infusion. In conclusion, significant errors in estimation of ketone body inflow were made using single-isotope techniques, whereas a dual-isotope model provided reasonably accurate estimates of ketone body inflow during infusion of exogenous acetoacetate and beta-hydroxybutyrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphatidylethanolamine in Liver Mitochondria and Endoplasmic Reticulum; Molecular Species Distribution and Turnover

1975 ◽  
Vol 53 (6) ◽  
pp. 698-705 ◽  
Author(s):  
J. G. Parkes ◽  
W. Thompson
Keyword(s):  
Endoplasmic Reticulum ◽  
Fatty Acid ◽  
Specific Activity ◽  
Liver Mitochondria ◽  
Relative Activity ◽  
Layer Chromatography ◽  
Kinetics Of ◽  
Fatty Acid Compositions

Phosphatidylethanolamine from mitochondria and microsomes of guinea pig liver was separated by thin-layer chromatography into eight different classes differing in degree of unsaturation. The fatty acid compositions and molar proportions of each class isolated from microsomes were very similar to the corresponding class in mitochondria. In both organelles about half of the total was dienoic species while tetraenes comprised approximately 20%. Stearic acid was the major saturated fatty acid and in each membrane a greater selectivity for stearate over palmitate was found in each sub-class of phosphatidylethanolamine, when compared with the corresponding class of phosphatidylcholine.Following the intraperitoneal injection of [2-3H]glycerol, the labelling of each molecular class of phosphatidylethanolamine showed very similar progressions in microsomes and mitochondria over a 3 h interval. In both organelles the highest relative specific activity was attained by penta-plus hexaenoic classes, while the large dienoic class had the lowest relative activity, which, however, increased with time. Analysis of the dienoic class of phosphatidylethanolamine from whole liver showed it to be constituted by a rapidly turning over palmitoyl–linoleoyl fraction and a slowly labelled stearoyl–linoleoyl fraction, a pattern also exhibited by dienoic phosphatidylcholines.The similarities in profile of molecular classes of phosphatidylethanolamine and in the kinetics of labelling in vivo point to a close metabolic relation between the lipids of both organelles, suggestive of a transfer of different molecular classes at comparable rates from the endoplasmic reticulum, the site of synthesis, to the mitochondria. This is consistent with numerous other studies in vitro that have demonstrated inter-organelle exchange of lipids.

Stimulatory effect of norepinephrine on ketogenesis in normal and insulin-deficient humans

1984 ◽  
Vol 247 (6) ◽  
pp. E732-E739 ◽  
Author(s):  
U. Keller ◽  
P. P. Gerber ◽  
W. Stauffacher
Keyword(s):  
Ketone Body ◽  
Ketone Bodies ◽  
Plasma Free Fatty Acid ◽  
Normal Subjects ◽  
Plasma Norepinephrine ◽  
Metabolic Clearance ◽  
Insulin Deficiency ◽  
Norepinephrine Infusion ◽  
Normal Humans ◽  
Body Production

Elevation of plasma norepinephrine concentrations to stress levels (1,800 pg/ml) resulted in normal subjects in a significant increase in ketone body production by 155% (determined by use of [14C]acetoacetate infusions), in a decrease of the metabolic clearance rate by 38%, hyperketonemia, and in increased plasma free fatty acid (FFA) levels by 57% after 75 min. Norepinephrine infusion during somatostatin-induced insulin deficiency resulted in an augmented and sustained increase in ketone body concentrations due to increased production and decreased peripheral clearance of ketone bodies. Norepinephrine's stimulatory effect on lipolysis waned with time, and its effect on ketogenesis in normal subjects was greater than its influence on plasma FFA levels, and thus presumably on hepatic FFA uptake, suggesting a direct stimulatory effect on hepatic ketogenesis. The data demonstrate that in normal humans the hyperketonemic effect of elevated plasma norepinephrine concentrations results from a combination of three factors: increased ketone body production from augmented FFA supply to the liver; accelerated hepatic ketogenesis; and modestly decreased metabolic clearance of ketone bodies. Acute insulin deficiency augments all these effects and results in progressive ketosis.

Proteomics analysis reveals diabetic kidney as a ketogenic organ in type 2 diabetes

2011 ◽  
Vol 300 (2) ◽  
pp. E287-E295 ◽  
Author(s):  
Dongjuan Zhang ◽  
Hang Yang ◽  
Xiaomu Kong ◽  
Kang Wang ◽  
Xuan Mao ◽  
...  
Keyword(s):  
Ketone Body ◽  
Molecular Mechanisms ◽  
Transforming Growth Factor ◽  
Ketone Bodies ◽  
Proximal Tubule Cell ◽  
Diabetic Kidney ◽  
Mesenchymal Transition ◽  
Proteomic Approach ◽  
Body Production

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. To date, the molecular mechanisms of DN remain largely unclear. The present study aimed to identify and characterize novel proteins involved in the development of DN by a proteomic approach. Proteomic analysis revealed that 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase 2 (HMGCS2), the key enzyme in ketogenesis, was increased fourfold in the kidneys of type 2 diabetic db/db mice. Consistently, the activity of HMGCS2 in kidneys and 24-h urinary excretion of the ketone body β-hydroxybutyrate (β-HB) were significantly increased in db/db mice. Immunohistochemistry, immunofluorescence, and real-time PCR studies further demonstrated that HMGCS2 was highly expressed in renal glomeruli of db/db mice, with weak expression in the kidneys of control mice. Because filtered ketone bodies are mainly reabsorbed in the proximal tubules, we used RPTC cells, a rat proximal tubule cell line, to examine the effect of the increased level of ketone bodies. Treating cultured RPTC cells with 1 mM β-HB significantly induced transforming growth factor-β1 expression, with a marked increase in collagen I expression. β-HB treatment also resulted in a marked increase in vimentin protein expression and a significant reduction in E-cadherin protein levels, suggesting an enhanced epithelial-to-mesenchymal transition in RPTCs. Collectively, these findings demonstrate that diabetic kidneys exhibit excess ketogenic activity resulting from increased HMGCS2 expression. Enhanced ketone body production in the diabetic kidney may represent a novel mechanism involved in the pathogenesis of DN.

scholarly journals Fatty acid metabolism in the perfused rat liver

1970 ◽  
Vol 119 (3) ◽  
pp. 525-533 ◽  
Author(s):  
H. A. Krebs ◽  
R. Hems
Keyword(s):  
Fatty Acids ◽  
Rat Liver ◽  
Ketone Body ◽  
Unsaturated Fatty Acids ◽  
Ketone Bodies ◽  
Saturated Fatty Acids ◽  
Perfused Rat Liver ◽  
Body Formation ◽  
Body Production ◽  
Chain Fatty Acids

1. The formation of acetoacetate, β-hydroxybutyrate and glucose was measured in the isolated perfused rat liver after addition of fatty acids. 2. The rates of ketone-body formation from ten fatty acids were approximately equal and independent of chain length (90–132μmol/h per g), with the exception of pentanoate, which reacted at one-third of this rate. The [β-hydroxybutyrate]/[acetoacetate] ratio in the perfusion medium was increased by long-chain fatty acids. 3. Glucose was formed from all odd-numbered fatty acids tested. 4. The rate of ketone-body formation in the livers of rats kept on a high-fat diet was up to 50% higher than in the livers of rats starved for 48h. In the livers of fat-fed rats almost all the O2 consumed was accounted for by the formation of ketone bodies. 5. The ketone-body concentration in the blood of fat-fed rats rose to 4–5mm and the [β-hydroxybutyrate]/[acetoacetate] ratio rose to 11.5. 6. When the activity of the microsomal mixed-function oxidase system, which can bring about ω-oxidation of fatty acids, was induced by treatment of the rat with phenobarbitone, there was no change in the ketone-body production from fatty acids, nor was there a production of glucose from even-numbered fatty acids. The latter would be expected if ω-oxidation occurred. Thus ω-oxidation did not play a significant role in the metabolism of fatty acids. 7. Arachidonate was almost quantitatively converted into ketone bodies and yielded no glucose, demonstrating that gluconeogenesis from poly-unsaturated fatty acids with an even number of carbon atoms does not occur. 8. The rates of ketogenesis from unsaturated fatty acids (sorbate, undecylenate, crotonate, vinylacetate) were similar to those from the corresponding saturated fatty acids. 9. Addition of oleate together with shorter-chain fatty acids gave only a slightly higher rate of ketone-body formation than oleate alone. 10. Glucose, lactate, fructose, glycerol and other known antiketogenic substances strongly inhibited endogenous ketogenesis but had no effects on the rate of ketone-body formation in the presence of 2mm-oleate. Thus the concentrations of free fatty acids and of other oxidizable substances in the liver are key factors determining the rate of ketogenesis.

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