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PubMed1977

Hypoketonaemic effect of L-alamine. Specific decrease in blood concentrations of 3-hydroxybutyrate in the rat.

1. The injection of L-alanine (50-100 mg/kg) into 35-day-old rats that had been starveed for 48 h increased blood L-alanine concentration to values observed in fed animals and lowered the blood concentration of 3-hydroxybutyrate within 2 min. 2. This hypoketon aemic action of L-alanine was specific for 3-hydroxybutyrate, since the acetoacetate concentrations did not change significantly. 3. The decrease in 3-hydroxybutyrate elicited by L-alanine was not related to changes in the blood concentrations of insulin, glucagon, growth hormone, glucose, unesterified fatty acids, lactate or pyruvate. 4. The injection of L-alanine resulted in a decrease in total ketones that was apparently unrelated to their increased peripheral utilization. These results are interpreted as an anti-ketogenic action of L-alanine. 5. The data suggest that L-alamine lowers ketone-body formation in starved rats, possibly via an alteration in hepatic redox equilibrium.

Acetates↗

PubMed1978

Effect of alloxan-diabetes on gluconeogenesis and ureogenesis in isolated rabbit liver cells.

1. Neither alloxan-diabetes nor starvation affected the rate of glucose production in hepatocytes incubated with lactate, pyruvate, propionate or fructose as substrates. In contrast, glucose synthesis with either alanine or glutamine was increased nearly 3- and 12-fold respectively, in comparison with that in fed rabbits. 2. The addition of amino-oxyacetate resulted in about a 50% decrease in glucose formation from lactate in hepatocytes isolated from fed, alloxan-diabetic and starved rats, suggesting that both mitochondrial and cytosolic forms of rabbit phosphoenolpyruvate carboxykinase function actively during gluconeogenesis. 3. Alloxan-diabetes resulted in about 2-3-fold stimulation of urea production from either amino acid studied or NH4Cl as NH3 donor, whereas starvation caused a significant increase in the rate of ureogenesis only in the presence of alanine as the source of NH3. 4. As concluded from changes in the [3-hydroxybutyrate]/[acetoacetate] ratio, in hepatocytes from diabetic animals the mitochondrial redox state was shifted toward oxidation in comparison with that observed in liver cells isolated from fed rabbits.

Acetoacetates↗

PubMed1982

Regulation of 3-hydroxybutyrate formation and secretion of very-low-density-lipoprotein triacylglycerol by perfused livers from fed and starved rats.

Acetoacetate was the sole ketone body formed when livers from starved rats were perfused with minimal concentrations of non-esterified fatty acid. Absence of 3-hydroxybutyrate was related to a low substrate potential, which caused a more oxidized redox state and a decreased [ATP]/[ADP] ratio. Only under conditions of comparable non-esterified fatty acid uptake was lipoprotein triacylglycerol production inversely related to ketogenesis.

3-Hydroxybutyric Acid↗

PubMed1983

Initial-velocity kinetics of succinoyl-coenzyme A-3-oxo acid coenzyme A-transferase from sheep kidney.

The initial-velocity kinetics of sheep kidney CoA-transferase are consistent with a Ping Pong mechanism. A KAcAc-CoA of 2.7 X 10(-5) M, KSucc-CoA of 1.6 X 10(-4) M, KSucc of 5.6 X 10(-3) M and KAcAc of 6.7 X 10(-5) M were determined by using a direct assay system that monitors the concentration of magnesium acetoacetyl-CoA enolate. However, product-inhibition kinetics of sheep kidney CoA-transferase are inconsistent with a Ping Pong mechanism. The possible involvement of separate binding sites for succinate and acetoacetate are discussed.

Acetoacetates↗

PubMed1983

The control of fatty acid metabolism in liver cells from fed and starved sheep.

Isolated liver cells prepared from starved sheep converted palmitate into ketone bodies at twice the rate seen with cells from fed animals. Carnitine stimulated palmitate oxidation only in liver cells from fed sheep, and completely abolished the difference between fed and starved animals in palmitate oxidation. The rates of palmitate oxidation to CO2 and of octanoate oxidation to ketone bodies and CO2 were not affected by starvation or carnitine. Neither starvation nor carnitine altered the ratio of 3-hydroxybutyrate to acetoacetate or the rate of esterification of [1-14C]palmitate. Propionate, lactate, pyruvate and fructose inhibited ketogenesis from palmitate in cells from fed sheep. Starvation or the addition of carnitine decreased the antiketogenic effectiveness of gluconeogenic precursors. Propionate was the most potent inhibitor of ketogenesis, 0.8 mM producing 50% inhibition. Propionate, lactate, fructose and glycerol increased palmitate esterification under all conditions examined. Lactate, pyruvate and fructose stimulated oxidation of palmitate and octanoate to CO2. Starvation and the addition of gluconeogenic precursors stimulated apparent palmitate utilization by cells. Propionate, lactate and pyruvate decreased cellular long-chain acylcarnitine concentrations. Propionate decreased cell contents of CoA and acyl-CoA. It is suggested that propionate may control hepatic ketogenesis by acting at some point in the beta-oxidation sequence. The results are discussed in relation to the differences in the regulation of hepatic fatty acid metabolism between sheep and rats.

3-Hydroxybutyric Acid↗

PubMed1984

Metabolism of ketone bodies, oleate and glucose in lymphocytes of the rat.

Isolated incubated lymphocytes utilized acetoacetate, 3-hydroxybutyrate or oleate at about 0.5 mumol/min per g dry wt. These rates were not markedly affected by concanavalin A or by starvation of the donor animal. When ketone bodies replaced glucose in the culture medium, they could not support lymphocyte proliferation when cells were cultured for 48 h. Addition of oleate (0.5 mM) to isolated lymphocytes increased the rate of O2 consumption markedly, suggesting that it could contribute about 30% to O2 consumption. The rate of oleate uptake and the stimulated rate of O2 consumption were maximal at 0.5 M-oleate; this is in contrast with the effect in some other tissues, in which the rate of fatty acid oxidation is linear with concentration up to about 2 mM. Since the normal plasma concentration of fatty acid in the fed state is about 0.5 mM, this suggests that lymphocytes can utilize fatty acids at a maximal rate in the fed state. Ketone bodies or oleate decreased the rate of glucose utilization by incubated lymphocytes; ketone bodies decreased the rate of pyruvate oxidation and increased the intracellular concentration of hexose monophosphate and citrate, suggesting that 6-phosphofructokinase is inhibited by citrate, and hexokinase by glucose 6-phosphate. These effects may be important not so much in conserving glucose in the whole animal but in maintaining the concentrations of glycolytic intermediates necessary for biosynthetic processes during proliferation.

Acetoacetates↗

PubMed1985

Monoacetoacetin and protein metabolism during parenteral nutrition in burned rats.

The effect of intravenous infusion of monoacetoacetin (glycerol monoacetoacetate) as a non-protein energy source was evaluated in burned rats. During 3 days of parenteral nutrition, in which animals received 14 g of amino acids/kg body wt. per day exclusively (group I) or with the addition of isoenergetic amounts (523 kJ/kg per day) of dextrose (group II), a 1:1 mixture of dextrose and monoacetoacetin (group III) or monoacetoacetin (group IV), significant decreases in urinary nitrogen excretion and whole-body leucine oxidation were observed in the three groups given additional non-protein energy as compared with group I. Serum ketone bodies (acetoacetate and 3-hydroxybutyrate) were decreased in rats given dextrose, whereas glucose and insulin increased significantly. Monoacetoacetin-infused animals (group IV) had high concentrations of ketone bodies without changes in glucose and insulin, whereas animals infused with both monoacetoacetin and glucose (group III) showed intermediate values. On day 4 of nutritional support, whole-body L-leucine kinetics were measured by using a constant infusion of L-[1-14C]leucine. In comparison with group I, the addition of dextrose or monoacetoacetin produced a significant decrease in plasma leucine appearance and release from whole-body protein breakdown. Gastrocnemius-muscle protein-synthesis rates were also higher in the three groups receiving additional non-protein energy. These findings suggest that monoacetoacetin can effectively replace dextrose as an intravenous energy source in stressed rats. Both fuels are similar in decreasing weight loss, nitrogen excretion, leucine release from whole-body protein breakdown and oxidation, in spite of differences in energy substrate and insulin concentrations.

Acetoacetates↗

PubMed1985

Gluconeogenesis from acetone in starved rats.

To non-anaesthetized rats starved for 3 days, [U-14C]acetone, NaH14CO3, L-[U-14C]lactate, [2-14C]acetate or D-[U-14C]- plus D-[3-3H]-glucose was injected intravenously. From the change in the plasma concentration of labelled acetone versus time after the injection, the metabolic clearance rate of acetone was calculated as 2.25 ml/min per kg body wt., and its rate of turnover as 0.74 mumol/min per kg. The extent and time course of the labelling of plasma glucose, lactate, urea and acetoacetate were followed and compared with those observed after the injection of labelled lactate, acetate and NaHCO3. The labelling of plasma lactate was rapid and extensive. Some 1.37% of the 14C atoms of circulating glucose originated from plasma acetone, compared with 44% originating from lactate. By deconvolution of the Unit Impulse Response Function of glucose, it was shown that the flux of C atoms from acetone to glucose reached a peak at about 100 min after injection of labelled acetone. In comparable experiments the transfer from lactate reached a peak at 14 min after the injection of labelled lactate. It was concluded that acetone is converted into lactate to a degree sufficient to account for the labelling of plasma glucose and is thus a true, albeit minor, substrate of glucose synthesis in starved rats.

Acetoacetates↗

PubMed1986

The metabolic route by which oleate is converted into cholesterol in rat hepatocytes.

The effect of (-)-hydroxycitrate on the conversion of [1-14C]oleate into cholesterol was dependent on the time of day at which the cells were prepared and on the extracellular oleate concentration. In hepatocytes prepared during the light phase of the diurnal cycle (L2-hepatocytes), (-)-hydroxycitrate inhibited the conversion of L-[U-14C]lactate (2 mM) and of 0.13 mM-[1-14C]oleate into cholesterol. However, when [1-14C]oleate was present at 1.3 mM, most of the sterol carbon was derived from this source, and under these conditions (-)-hydroxycitrate had no inhibitory effect on [14C]cholesterol formation. In these cells, non-radioactive acetoacetate blocked the conversion of 1.3 mM-[1-14C]oleate, but not of 0.13 mM-[1-14C]oleate, into cholesterol. In cells prepared during the dark phase of the diurnal cycle (D6-hepatocytes), irrespective of the concentration of [1-14C]oleate, (-)-hydroxycitrate decreased its conversion into cholesterol. In both types of cell preparation, the inhibitory effect of (-)-hydroxycitrate on the conversion of L-[U-14C]lactate into cholesterol was greater than that on the overall rate of cholesterol production from all endogenous sources. These results provide evidence for the following. (1) The major metabolic route by which oleate is converted into cholesterol is dependent on its extracellular concentration. (2) When oleate is the major source of hepatic sterol carbon, the flux of substrate through citrate into cholesterol is dependent on the nutritional state of the animal. (3) When endogenous substrates are the sole source of sterol carbon, a substantial proportion of the carbon enters the cholesterol pathway through routes not involving citrate cleavage.

Acetoacetates↗

PubMed1997

Heart failure ketosis.

OBJECTIVE: To assess whether blood ketone bodies are increased in congestive heart failure (CHF). METHODS: Thirteen patients with CHF and 11 cardiac patients without CHF took part in the study. Blood acetoacetate and b-hydroxybutyrate levels and the pertinent metabolic and hormonal milieu were measured during 20 h fast and after 2 h glucose infusion. RESULTS: The averaged blood ketone body and free fatty acid levels were significantly higher during the fast and also remained higher after glucose infusion in patients with CHF than in the control group. The areas under ketone body concentration time curve over the last 8 h of the fast were 3522 +/- 662 mumol L-1 h-1 (SE) and 1789 +/- 192 mumol L-1 h-1 in patients with and without CHF, respectively (P = 0.022). Circulating noradrenaline and growth hormone were higher but glucagon lower in patients with CHF than in the controls (P < 0.05 for all differences) whereas the glucose and insulin concentrations were comparable in the study groups. At the time of peak ketonaemia the glucagon-to-insulin ratio was lower in patients with CHF than in patients without CHF (P = 0.04). CONCLUSIONS: These data suggest that severe CHF is a ketosis-prone state. Augmented supply of free fatty acids for ketogenesis due to increased stress hormone-related lipolysis is one likely mechanism.

3-Hydroxybutyric Acid↗

PubMed2001

Fasting medium chain acyl-coenzyme A dehydrogenase--deficient children can make ketones.

Medium chain acyl-coenzyme A dehydrogenase (MCAD) deficiency classically presents as hypoketotic hypoglycemia. Under-production of ketones has been presumed to be the cause of hypoketosis, but this has never been proven. Stable isotope dilution studies of ketone kinetics were performed on three well children with homozygous 985G MCAD deficiency using 1,3-13C2 sodium acetoacetate and 1,2,3,4-13C4 sodium 3-hydroxybutyrate to ascertain the rates of ketone production, interconversion, and use. All children were fasted for 9 to 11.5 hours before the beginning of the study period. Euglycemia was maintained in all cases. Ketone kinetics were calculated using a two-accessible pool model and showed normal ketone production in all three children compared with published control data from children fasted for a similar length of time. There is no evidence for underproduction or overuse of ketones in these MCAD-deficient children, at least when they are well. We propose that another factor, such as fever, may be required to reduce ketone production and result in the biochemical phenotype recognized in unwell children.

3-Hydroxybutyric Acid↗

PubMed1979

Effect of metaproterenol on ketone body metabolism of the forearm in healthy and diabetic subjects.

Muscular ketone body metabolism was studied by the registration of arterial-deepvenous concentration differences of glycerol, beta-hydroxybutyrate and acetoacetate, and of muscular blood flow in 53 healthy volunteers and 23 juvenile diabetics. In six subjects of each group substrate metabolism was also investigated during the intrabrachial arterial infusion of metaproterenol (0.4 microgram/min). Identical rates of muscular glycerol release and ketone's fractional extraction were obtained in healthy and diabetic subjects during the basal period. A significant correlation between muscular ketone extraction and arterial ketone concentration was calculated in both groups. During the infusion of metaproterenol the diabetics, unlike the controls, revealed enhanced muscular glycerol output and reduced fractional extraction of beta-hydroxybutyrate. These findings are in line with the present view that the impairment of muscular ketone body utilisation in diabetic ketoacidosis may at least partly be due to enhanced muscular lipolysis.

Acetoacetates↗

PubMed1992

Adrenergic mechanism in hyperketonemia in thyrotoxic and starved rats.

To evaluate the possible role of the adrenergic mechanism in hyperketonemia in hyperthyroidism and starvation, the plasma concentrations of FFA, acetoacetate (AcAc), and beta-hydroxybutyrate (BOHB) were measured in thyrotoxic and starved rats for 96 hours. Thyrotoxemia was induced in rats by a daily subcutaneous thyroxine (100 micrograms/kg/day) injection carried out for 7 days. Some of the thyrotoxic and starved rats were administered subcutaneous phentolamine (2 mg/kg, twice daily) or propranolol (0.1 mg/kg, twice daily). Plasma levels of FFA, AcAc, and BOHB were significantly increased in thyrotoxic and starved rats compared with the control rats. Phentolamine and propranolol administration did not alter plasma levels of FFA, AcAc, and BOHB in thyrotoxic rats. In starved rats, propranolol did not alter plasma levels of FFA, AcAc, and BOHB, however, phentolamine did increase plasma levels of FFA, AcAc, and BOHB. These results indicate that the adrenergic mechanism may not contribute to the hyperketonemia in thyrotoxic rats, but may have a slight inhibitory effect on ketogenesis in starvation probably due to alpha-antilipolytic action.

3-Hydroxybutyric Acid↗

PubMed2004

[Effects of ovarian stimulation on serum concentrations of lipids and ketone bodies in patients undergoing IVF/ICSI treatment].

OBJECTIVE: The ovarian stimulation increase the estradiol concentration in comparison to the one observed in the menstrual cycle. The aim of the study was to determine the influence of ovarian stimulation on serum concentrations of lipids and ketone bodies in patients undergoing IVF/ICSI treatment. PATIENTS AND METHODS: 50 patients were included in this study. All patients underwent an ovarian stimulation either with recombinant follicle stimulating Hormone (Gonal-F, n = 28) or human menopausal gonadotropin (Menogon, n = 22) after pituitary down-regulation with Goserelin or Triptorelin. Five blood samples were taken: before treatment, at the beginning of ovarian stimulation, on the day of HCG injection for the ovulation induction, on the day of follicle aspiration and 14 days after embryo transfer. Afterwards, the samples were analysed with regard to the concentrations of triglyceride, total-cholesterol, HDL-/LDL-cholesterol, acetoacetate, beta-hydroxybutyrate and alpha-ketoglutarate. RESULTS: During the ovarian stimulation, total-cholesterol andA'LDL-cholesterol decreased significantly (p(Chol) < or = 0.001; p(LDL) < or = 0.001), whereas the concentration of HDL-cholesterol increased significantly (p(HDL) < or = 0.001). Furthermore, a significant increase of beta-hydroxybutyrate and alpha-ketoglutarate has been detected (p(HBS) = 0.039; p (KG) = 0.023). CONCLUSIONS: The observed changes in serum concentrations of lipids and ketone bodies began with the application of gonadotrophins for stimulation and persisted until the end of the treatment. Therefore, the increase of estradiol, stimulated by gonadotrophins, seems to be responsible for the changes in the serum concentrations of lipids and ketone bodies. All women undergoing ovarian stimulation should be monitored for long-term thrombogenic and atherogenic risks.

3-Hydroxybutyric Acid↗

PubMed1988

Inhibition of muscular ketone extraction by lipid infusion in man.

Using the forearm technique, muscular ketone body metabolism was investigated in 12 healthy volunteers during an i.v. infusion of lipid emulsions containing long chain triglycerides (LCT) or a mixture of medium- and long chain triglycerides (MCT/LCT). During the basal period, arterial concentrations and muscular extraction of beta-hydroxybutyrate and acetoacetate were linearly correlated as expected. This relationship was abolished during the infusion of both lipid emulsions. In addition, fractional extraction rates of ketone bodies were reduced. These changes were most probably mediated by elevated levels of free fatty acids and triglycerides as well.

3-Hydroxybutyric Acid↗

PubMed1981

Ketone kinetics in man.

1. Five normal volunteers after an overnight fast were given an injection of DL-beta hydroxybutyrate on one occasion, and an injection of acetoacetate (AcAc) on another occasion. The concentrations of D-(--)-beta-hydroxybutyrate (D-beta-OHB) and AcAc were measured every 5 minutes for 40 minutes after each injection. 2. The rate constant of disappearance (K), the volume of distribution (V) and the metabolic clearance (MCR) were calculated for the injected ketone. The values were similar for the two ketones, and therefore these values can be taken as estimates for total ketones. 3. The metabolic clearance rate of total ketones (beta-OHB plus AcAc) was also calculated from the changes in total ketone body concentration after the injection of DL-beta-OHB or AcAc which are the methods used previously. The values obtained by these methods were only 50% of that calculated from the kinetics of the injected ketone. This difference is entirely due to the differences in the apparent volume of distribution. 4. It is suggested that the best estimate of total ketone body production rate is the product of the MCR of the injected ketone and the basal concentration of total ketone bodies.

Acetoacetates↗

PubMed1981

Effects of oxaloacetate and beta-hydroxybutyrate on rat liver mitochondrial calcium flow during starvation.

Rat liver mitochondria accumulate calcium from the incubation medium both in the presence of ATP and of succinate with rotenone. Lowering free calcium concentration by means of EGTA leads to a reduction of maximum transport capacity to less than 25% of the total added calcium. Under these conditions addition of oxaloacetate inhibits calcium uptake, an effect which is blocked by equimolar concentrations of beta-hydroxybutyrate. Oxaloacetate and acetoacetate induce an efflux of previously accumulated mitochondrial calcium. These effects appear to be independent of free calcium concentration and of whether the mitochondria were obtained from fed rats or rats fasted for 16 h or 4 days.

Acetoacetates↗

PubMed1975

Nitrogen-sparing intravenous fluids in postoperative patients.

Improved nitrogen sparing was demonstrated in 20 patients undergoing either head-and-neck operations or abdominal explorations, who were randomized to receive intravenously either 3 per cent amino acids or 5 per cent dextrose. Infusions were started immediately after operation and continued for a minimum of six days. In patients receiving amino acids, as compared with those receiving dextrose, mean cumulative six-day nitrogen losses were significantly lower (42 plus or minus 5 g [S.E.M.] and 74 plus or minus 7 g, respectively--P smaller 0.005), as were serum glucose and insulin levels, but beta-hydroxybutyrate, acetoacetate and blood urea nitrogen were significantly elevated. No adverse effects of the amino acid solution were observed. The presumed mechanism for improved nitrogen sparing is a decrease in serum glucose and insulin levels, allowing greater endogenous fat mobilization and utilization, thus sparing lean body mass.

Acetoacetates↗